2024/02/28 更新

写真a

スズキ トオル
鈴木 達
所属
理工学術院 大学院先進理工学研究科
職名
教授(任期付)
学位
博士(工学)

経歴

  • 2023年04月
    -
    継続中

    国立研究開発法人物質・材料研究機構   電子・光機能材料研究センター 高機能光学セラミックスグループ   グループリーダー

  • 2016年04月
    -
    2023年03月

    国立研究開発法人物質・材料研究機構   機能性材料研究拠点セラミックスプロセッシンググループ   グループリーダー

  • 2012年04月
    -
    2016年03月

    独立行政法人 物質・材料研究機構   先端材料プロセスユニット セラミック材料グループ   主席研究員

  • 2002年04月
    -
    2012年03月

    独立行政法人物質・材料研究機構   材料研究所 微粒子プロセスグループ   主任研究員

  • 1996年04月
    -
    2002年03月

    科学技術庁金属材料技術研究所   研究員

  • 1995年04月
    -
    1996年03月

    早稲田大学   各務記念材料技術研究所   助手

  • 1994年04月
    -
    1995年03月

    早稲田大学   理工学部   助手

▼全件表示

学歴

  •  
     
     

    早稲田大学理工学部材料工学科  

  •  
     
     

    早稲田大学大学院理工学研究科資源及び材料工学専攻博士課程  

所属学協会

  •  
     
     

    無機マテリアル学会

  •  
     
     

    日本磁気科学会

  •  
     
     

    粉体工学会

  •  
     
     

    American Ceramic Society

  •  
     
     

    日本セラミックス協会

  •  
     
     

    粉体粉末冶金協会

  •  
     
     

    日本金属学会

▼全件表示

研究分野

  • 無機材料、物性

研究キーワード

  • 透光性セラミックス

  • 焼結

  • セラミックス

  • 強磁場プロセス

  • 結晶配向

  • 粉体プロセス

  • 材料強度

▼全件表示

受賞

  • 学術賞

    2022年06月   無機マテリアル学会  

    受賞者: 鈴木達

  • 米国セラミックス協会フェロー表彰

    2021年11月   米国セラミックス協会  

    受賞者: 鈴木達

  • 日本セラミックス協会フェロー表彰

    2020年06月   日本セラミックス協会  

    受賞者: 鈴木達

  • Global Star Award

    2017年01月   米国セラミックス協会エンジニアリングセラミックス部会  

    受賞者: 鈴木 達

  • 学術賞

    2015年06月   日本セラミックス協会  

    受賞者: 鈴木 達

  • JCerSJ優秀論文賞

    2012年06月   日本セラミックス協会  

  • 学術写真賞 優秀賞

    2010年03月   日本セラミックス協会  

  • 研究進歩賞

    2005年05月   粉体粉末冶金協会  

  • 論文賞

    2001年05月   粉体粉末冶金協会  

  • 研究進歩賞

    1998年05月   粉体粉末冶金協会  

▼全件表示

 

論文

  • Strontium fluorapatite (S-FAP) nano-grained laser ceramics

    Hiroaki Furuse, Yuki Mochizuki, Daichi Kato, Koji Morita, Byung-Nam Kim, Tohru S. Suzuki

    Scripta Materialia   241   115881 - 115881  2024年03月

    DOI

    Scopus

  • CNT–MXene ultralight membranes: fabrication, surface nano/microstructure, 2D–3D stacking architecture, ion-transport mechanism, and potential application as interlayers for Li–O2 batteries

    Mehdi Estili, Shoichi Matsuda, Lulu Jia, Nobuyuki Sakai, Renzhi Ma, Tohru S. Suzuki, Kohei Uosaki

    Nanoscale   15 ( 18 ) 8289 - 8303  2023年05月  [査読有り]

     概要を見る

    This study aims to control the structure of MXene macrostructures using individually dispersed MWCNTs to allow for scalability for various energy-related applications.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Reactive consolidation of tough, deformation resistant tantalum monoboride

    D. Demirskyi, K. Yoshimi, T.S. Suzuki, O. Vasylkiv

    Scripta Materialia   229   115383 - 115383  2023年05月

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Orientation Dependence of High Temperature Compressive Behavior of Textured Ti<sub>3</sub>SiC<sub>2</sub>

    Yuji Shirakami, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka

    MATERIALS TRANSACTIONS   64 ( 4 ) 805 - 812  2023年04月

    DOI

  • Orientation Dependence of Plastic Deformation Behavior and Fracture Energy Absorption Mechanism around Vickers Indentation of Textured Ti<sub>3</sub>SiC<sub>2</sub> Sintered Body

    Yuji Shirakami, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka

    MATERIALS TRANSACTIONS   64 ( 3 ) 650 - 656  2023年03月

    DOI

  • Dual-phase oxygen separation membrane composed of Y2O3-doped ZrO2 and stainless steel

    Aunsaya Eksatit, Kento Ishii, Kiyoshi Kobayashi, Thi Kim Ngan Nguyen, Koji Morita, Tohru S. Suzuki, Tetsuo Uchikoshi

    Journal of the Ceramic Society of Japan   131 ( 2 ) 22 - 26  2023年02月

    DOI

    Scopus

  • Characterization of Transparent Fluorapatite Ceramics Fabricated by Spark Plasma Sintering

    Hiroaki Furuse, Daichi Kato, Koji Morita, Tohru S. Suzuki, Byung-Nam Kim

    Materials   15 ( 22 ) 8157 - 8157  2022年11月

     概要を見る

    Highly optically transparent polycrystalline fluorapatite ceramics with hexagonal crystal structures were fabricated via a liquid-phase synthesis of fluorapatite powder, followed by spark plasma sintering (SPS). The effect of sintering temperature, as observed using a thermopile, on the optical transmittance and microstructure of the ceramics was investigated in order to determine suitable sintering conditions. As a result, high optical transmittance was obtained in the SPS temperature range of 950–1100 °C. The highest optical transmittance was obtained for the ceramic sample sintered at 1000 °C, and its average grain size was evaluated at only 134 nm. The grain size dramatically increased with temperature, and the ceramics became translucent at SPS temperatures above 1200 °C. The mechanical and thermal properties of the ceramics were measured to evaluate the thermal shock parameter, which was found to be comparable to or slightly smaller than that of single-crystal fluorapatite. This transparent polycrystalline fluorapatite ceramic material should prove useful in a wide range of applications, for example as a biomaterial or optical/laser material, in the future. Furthermore, the knowledge obtained in this study should help to promote the application of this ceramic material.

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • High‐temperature reactive synthesis of the Zr–Ta multiboride with a supercomposite structure

    Dmytro Demirskyi, Tohru S. Suzuki, Kyosuke Yoshimi, Oleg Vasylkiv

    Journal of the American Ceramic Society   105 ( 11 ) 6989 - 7002  2022年11月

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • Consolidation and high‐temperature properties of ceramics in the TaC–NbC system

    Dmytro Demirskyi, T. Nishimura, T. S. Suzuki, K. Yoshimi, Oleg Vasylkiv

    Journal of the American Ceramic Society   105 ( 12 ) 7567 - 7581  2022年07月

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Reactive consolidation and high-temperature strength of HfB2–SiB6

    D. Demirskyi, T. Nishimura, T.S. Suzuki, K. Yoshimi, O. Vasylkiv

    Journal of the European Ceramic Society    2022年05月

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Anisotropic thermal expansion and ionic conductivity of a crystal-oriented, Mg2+-conducting NASICON-type solid electrolyte

    Cem E. Özbilgin, Kiyoshi Kobayashi, Shinji Tamura, Nobuhito Imanaka, Tohru S. Suzuki

    Ceramics International   48 ( 8 ) 10733 - 10740  2022年04月

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Effect of CNT addition and its orientation on thermal shock resistance of B4C/CNT composites fabricated by hot-pressing

    Ryosuke S. S. Maki, Fajar Muhammad, Jelena Maletaskic, Anna Gubarevich, Katsumi Yoshida, Toyohiko Yano, Tohru S. Suzuki, Tetsuo Uchikoshi

    JOURNAL OF ASIAN CERAMIC SOCIETIES    2022年04月

     概要を見る

    This paper describes the synthesis of B4C/carbon nanotube (CNT) composite by hot-pressing and shows the details for the effectiveness of CNT addition, additive amount and its orientation on the thermal shock resistance. CNTs tend to array perpendicular to the hot-pressing direction, which caused anisotropic mechanical and thermal properties of B4C/CNT composite. We investigated the residual bending strength of thermally shocked B4C/CNT composites and determined the critical temperature Delta T-C that causes precipitous strength drop. In the case of B4C/15 vol% CNT composite, the residual bending strength almost unchanged at similar to 450 degrees C; Delta T-C increased by 150 degrees C or more than that of monolithic B4C. Based on the thermal stress fracture-resistance parameter R' of the composites, it was clarified that the excellent R' is mainly due to the higher thermal conductivity and lower elastic modulus. The numerical results showed that CNT addition has a pronounced effect on the thermal shock residual bending strength and thermal stress fracture-resistance of B4C/CNT composite.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Ultra-high temperature flexure and strain driven amorphization in polycrystalline boron carbide bulks

    D. Demirskyi, H. Sepehri-Amin, T.S. Suzuki, K. Yoshimi, O. Vasylkiv

    Scripta Materialia   210   114487 - 114487  2022年03月

     概要を見る

    The temperature dependence of the flexural strength of sintered boron carbide was studied. At temperatures above 2000 °C, B4C showed an ultrahigh flexural strength exceeding 1 GPa which was accompanied by a change in the deformation mechanism from brittle fracture to plastic deformation. Scanning transmission electron microscopy (STEM) observations revealed that the amorphization can be of microstructural origin for the observed plasticity in B4C at temperatures above 2000 °C and a strain rate of 3•10−3 s−1. The amorphization occurs inside of the severely deformed grains. Flexural tests below 2000 °C provided evidence for the formation of stacking faults or dislocations, which are ordinary defects after the flexural tests. The results at 2000 °C suggest that the magnitude of the tensile stresses imposed on the B4C grains during deformation in flexure and the total strain transferred to a ceramic during the deformation process play the dominant role in the crystalline-amorphous transformation.

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • Improvement of Thermoelectric Properties via Texturation Using a Magnetic Slip Casting Process-The Illustrative Case of CrSi2

    Sylvain Le Tonquesse, Wenhao Zhang, Bhuvanesh Srinivasan, Bruno Fontaine, Takanobu Hiroto, Takao Mori, Jean-Francois Halet, David Berthebaud, Tohru S. Suzuki

    CHEMISTRY OF MATERIALS   34 ( 3 ) 1143 - 1156  2022年02月

     概要を見る

    Transition metal silicides constitute a promising class of inexpensive and nontoxic thermoelectric materials showing competitive properties. This article reports an efficient process to synthesize highly textured polycrystalline CrSi2 by performing slip casting under a strong magnetic field. The crystallographic texture of spark plasma sintered samples, characterized by electron backscattered and X-ray diffraction techniques, showed a fiber texture symmetry with the c-axis of hexagonal CrSi2 aligning preferentially along the magnetic field direction. The thermoelectric properties measured both parallel and perpendicular to the c-axis texture direction showed a large anisotropy. In particular, a significantly higher Seebeck coefficient was measured,.c, reaching a maximum value of 200 mu V K-1 at 650 K, inducing a power factor.c twice higher than.c with an average value of 2.2 mW m(-1) K-2. Density functional theory and transport property calculations revealed that an anisotropic two-band model can explain the higher thermoelectric property along the c-axis direction, which can be traced to Cr-Cr bonding interactions along this direction. The estimated thermoelectric figure of merit ZT. c was improved to 0.20 at 773 K. This is 50% higher than that measured for randomly oriented samples and comparable to that observed for single crystals. Such a performance boost can certainly be reiterated for other types of thermoelectric materials using the efficient magnetic slip-casting process reported in this article.

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • pH-controlled synthesis and spark plasma sintering of fine and homogeneous MgZr4(PO4)6 powder

    Kenta Fukushima, Tohru S. Suzuki, Cem Eren ?zbilgin, Kiyoshi Kobayashi, Hiroya Abe, Yoshikazu Suzuki

    Journal of the Ceramic Society of Japan   130 ( 2 ) 243 - 248  2022年02月  [査読有り]

    DOI

  • Fabrication of Textured Porous Ti3SiC2 by Slip Casting under High Magnetic Field and Microstructural Evolution through High Temperature Deformation

    Nana Hashimoto, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka

    MATERIALS TRANSACTIONS   63 ( 2 ) 133 - 140  2022年02月

    DOI

  • Consolidation and high‐temperature strength of monolithic lanthanum hexaboride

    Dmytro Demirskyi, Tohru S. Suzuki, Kyosuke Yoshimi, Oleg O. Vasylkiv

    Journal of the American Ceramic Society    2022年01月

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Deformation‐resistant Ta 0.2 Hf 0.8 C solid‐solution ceramic with superior flexural strength at 2000°C

    Dmytro Demirskyi, Hanna Borodianska, Toshiyuki Nishimura, Tohru S. Suzuki, Kyosuke Yoshimi, Oleg Vasylkiv

    Journal of the American Ceramic Society   105 ( 1 ) 512 - 524  2022年01月

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • Enhanced ionic conductivity of aluminum tungstate by crystallographic orientation in a strong magnetic field

    Cem E. Özbilgin, Kiyoshi Kobayashi, Shinji Tamura, Nobuhito Imanaka, Tohru S. Suzuki

    Journal of the American Ceramic Society    2021年07月

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Fabrication of Textured Porous Ti3SiC2 by Slip Casting under High Magnetic Field and Microstructural Evolution through High Temperature Deformation

    Nana Hashimoto, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka

    Journal of the Japan Institute of Metals and Materials   85 ( 7 ) 256 - 263  2021年07月

    DOI

  • Production of crystal-oriented lanthanum silicate oxyapatite ceramics with anisotropic electrical conductivity and thermal expansion

    Kiyoshi Kobayashi, Kenya Hirai, Tetsuo Uchikoshi, Yoshio Sakka, Takaya Akashi, Tohru S. Suzuki

    Open Ceramics   6   100100 - 100100  2021年06月

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • Fabrication of textured B4C ceramics with oriented tubal pores by strong magnetic field-assisted colloidal processing

    Shota Azuma, Tetsuo Uchikoshi, Katsumi Yoshida, Tohru S. Suzuki

    Journal of the European Ceramic Society    2021年04月

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • Elastic isotropy originating from heterogeneous interlayer elastic deformation in a Ti<inf>3</inf>SiC<inf>2</inf> MAX phase with a nanolayered crystal structure

    Ruxia Liu, Masakazu Tane, Hajime Kimizuka, Yuji Shirakami, Ken ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka, Lianmeng Zhang, Tohru Sekino

    Journal of the European Ceramic Society   41 ( 4 ) 2278 - 2289  2021年04月

     概要を見る

    The elastic properties of a single-crystalline Ti SiC MAX phase with a nanolayered crystal structure, comprising Ti-Si and two distinct Ti-C bonding layers, that had remained unclear because of the difficulty in growing large single crystals, were studied. Rather than unavailable large single crystals, polycrystalline samples with a crystallographic texture were prepared. By analyzing the polycrystalline elastic constants on the basis of an inverse Voigt–Reuss–Hill approximation, the elastic properties of a single crystal Ti SiC with a hexagonal symmetry were determined. This revealed that the single-crystalline Young's modulus was almost isotropic despite its highly anisotropic layered structure. The shear modulus for (0001)〈112¯0〉 was higher than that for {112¯0}[0001] in contrast to the basal slip-dominated plastic deformation reflecting the layered structure. Furthermore, first-principles calculations revealed that heterogeneous interlayer elastic deformation caused by the stabilization of Ti-Si bonding is the origin of the elastic isotropy in a Ti SiC MAX phase. 3 2 3 2 3 2

    DOI

    Scopus

    7
    被引用数
    (Scopus)
  • Free Analysis and Visualization Programs for Electrochemical Impedance Spectroscopy Coded in Python

    Kiyoshi KOBAYASHI, Tohru S. SUZUKI

    Electrochemistry   89 ( 2 ) 218 - 222  2021年03月

    DOI

    Scopus

    14
    被引用数
    (Scopus)
  • Effect of volume ratio on optical and mechanical properties of Y2O3-MgO composites fabricated by spark-plasma-sintering process

    Lihong Liu, Koji Morita, Tohru S. Suzuki, Byung-Nam Kim

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   41 ( 3 ) 2096 - 2105  2021年03月

     概要を見る

    The effect of Y2O3:MgO ratio on the microstructures, optical and mechanical properties of the Y2O3:MgO composites were investigated. Although the dense Y2O3:MgO composites were successfully fabricated in various Y2O3:MgO ratios using the spark-plasma-sintering (SPS) technique, the Y2O3:MgO ratio significantly influenced the microstructures and the optical/mechanical properties of the composites. Fine grain size was obtained in the composite with Y2O3:MgO = 50:50 owing to the effective pinning force caused by the homogenous two phase microstructure. The SPSed dense composites showed good transmittance in the wide wavelength range from visible to infrared (IR). The monolithic Y2O3 polycrystal, that is Y2O3:MgO = 100:0, showed the highest transmittance of 62.3 % at 600 nm and 84.3 % at 5 mu m. Although the IR transmittance is independent of the Y2O3:MgO ratio, the visible transmittance decreased with the MgO particle dispersion. Among the Y2O3:MgO composites, the higher visible transmittance was obtained in the composite with Y2O3:MgO = 50:50 than those of the other two composites with Y2O3:MgO = 30:70 and 70:30 due to its smallest grain size. In contrast to the transmittance, the hardness H-v and toughness K-IC tend to increase with increasing the MgO fraction irrespective of the grain size; both H v and K ic increased from 9.6 GPa and 1.1 MPa m(1/2) for the monolithic Y2O3 to 12.7 GPa and 2.5 MPa m(1/2) for the composite with Y2O3:MgO = 30:70, respectively. The enhanced hardness and toughness of the composite can be interpreted dominantly by the mixture rule as a function of the volume fraction of the MgO phase.

    DOI

    Scopus

    19
    被引用数
    (Scopus)
  • Effect of the Heating Rate on the Spark-Plasma-Sintering (SPS) of Transparent Y2O3 Ceramics: Microstructural Evolution, Mechanical and Optical Properties

    Lihong Liu, Koji Morita, Tohru S. Suzuki, Byung-Nam Kim

    Ceramics   4 ( 1 ) 56 - 69  2021年02月

     概要を見る

    High strength transparent Y2 O3 ceramics were fabricated from commercial powders using spark plasma sintering (SPS) technique by optimizing the heating rate. The heating rate significantly influenced the microstructures and the optical/mechanical properties of the Y2 O3 ceramics. Grain growth was limited accordingly with increasing the heating rate. The ball milling process of the commercial Y2 O3 powders is likely to further enhance the sinterability during the SPS processing. The dense Y2 O3 ceramics, which were sintered by SPS with 100◦ C/min, showed good transmittance range from visible to near infrared (IR). For a high heating rate of 100◦ C/min, the in-line transmittance at a visible wavelength of 700 nm was 66%, whereas for a slow heating rate of 10◦ C/min, it reduced to 46%. The hardness Hv tends to increase with increasing the heating rate and rigorously followed the Hall–Petch relationship; that is, it is enhanced with a reduction of the grain size. The toughness KIC, on the other hand, is less sensitive to both the heating rate and the grain size, and takes a similar value. This research highlighted that the high heating rate SPS processing can fabricate fully dense fine-grained Y2 O3 ceramics with the excellent optical and mechanical properties.

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Preparation and investigation of hexagonal-tetragonal BaTiO3 powders

    Hari Shankar MALLIK, Ichiro FUJII, Yoshio MATSUI, Gopal Prasad KHANAL, Sangwook KIM, Shintaro UENO, Tohru S. SUZUKI, Satoshi WADA

    Journal of the Ceramic Society of Japan   129 ( 2 ) 91 - 96  2021年02月

    DOI

    Scopus

    6
    被引用数
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  • Effect of Powder Calcination Conditions on IR Transmission in Y<inf>2</inf>O<inf>3</inf>-MgO Nanocomposites Fabricated by Pulsed Electric Current Sintering Technique

    Lihong Liu, Koji Morita, Tohru S. Suzuki, Byung Nam Kim

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   68 ( 11 ) 500 - 506  2021年

     概要を見る

    In order to improve IR transparency of the Y2O3-MgO composite, the effect of powder calcination conditions was investigated. The absorption intensity of carbonate peaks sensitively changes with the powder calcination conditions, such as temperature and time, before the pulsed electric current sintering (PECS). The calcination at 1150°C for 8 h can eliminate the contamination of the carbonate groups pre-existing in the starting Y2O3 and MgO powders. The composites fabricated from the powders, which were calcinated at the optimum conditions, can attain high IR transparency with maintaining the fine and dense microstructures. This indicates that the pre-calcination of the powders is an effect method to remove the carbonate contamination without causing significant powder coarsening and agglomeration in the Y2O3-MgO composites. During the PECS processing, however, a small amount of carbon contaminations occurs additionally from the graphite die/paper and remains even in the post-annealed Y2O3-MgO composite. It can be concluded that for the Y2O3-MgO composites, although the carbonate related contaminations are succeeded to remove from the starting power mixture, the carbon contamination occurs additionally from the graphite die/paper during the PECS processing and degrades the IR transparency.

    DOI

    Scopus

  • Simulation of densification behavior of nano-powder in final sintering stage: Effect of pore-size distribution

    Byung-Nam Kim, Koji Morita, Tohru S. Suzuki, Ji-Guang Li, Hideaki Matsubara

    Journal of the European Ceramic Society   41 ( 1 ) 625 - 634  2021年01月

    DOI

    Scopus

    6
    被引用数
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  • structure and high temperature X-ray diffraction study of thermoelectric chimney-ladder FeGe gamma (gamma approximate to 1.52)

    Sylvain Le Tonquesse, Christopher Hassam, Yuichi Michiue, Yoshitaka Matsushita, Mathieu Pasturel, Takao Mori, Tohru S. Suzuki, David Berthebaud

    JOURNAL OF ALLOYS AND COMPOUNDS   846  2020年12月

     概要を見る

    The crystal structure of Nowotny chimney-ladder phase FeGe gamma with gamma approximate to 1.52 was studied by X-ray diffractometry from 300 K to 850 K. The diffraction patterns were fitted by Rietveld refinement considering an incommensurate composite crystal structure. The refined crystal structure of FeGe gamma is described in details and compared to MnSi gamma, a thermoelectric material with gamma = 1.74. The lattice parameters a, c(Fe) and c(Ge) were found to increase with the temperature following a polynomial law, while the modulation vector component gamma remained constant up to the peritectoid decomposition into FeGe and FeGe2. Within the temperature range considered, the linear and volumetric thermal expansion parameters increased from about 3 x 10(-6) K-1 to 10 x 10(-6) K-1 and from 9.6 x 10(-6) K-1 to 31.5 x 10(-6) K-1, respectively. (C) 2020 Elsevier B.V. All rights reserved.

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Orientation dependence of plastic deformation behavior and fracture energy absorption mechanism around vickers indentation of textured Ti<inf>3</inf>SiC<inf>2</inf>sintered body

    Yuji Shirakami, Ken Ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   67 ( 11 ) 607 - 614  2020年11月

     概要を見る

    In order to clarify plastic deformation behavior and mechanism of fracture energy absorption of Ti3SiC2, Vickers indentation tests were conducted for Ti3SiC2 sintered bodies with various textured orientations. Textured Ti3SiC2 sintered bodies were fabricated by slip casting in a strong magnetic field and spark plasma sintering (SPS), and their orientation distribution were analyzed by SEM/EBSD. It was found that for the textured Ti3SiC2, the plastic deformation behavior around Vickers indents such as an indent shape and a grain pile-up were strongly affected by basal slip and kink deformation. Furthermore, the fracture energy absorption mechanism around the indents also depended on the texture orientations. From our results, it is concluded that the most effective factor for suppressing the crack propagation was the grain pile-up, and the second one was crack deflections.

    DOI

    Scopus

  • Synthesis of medium-entropy (Zr1/3Hf1/3Ta1/3)B2 using the spark plasma consolidation of diboride powders

    Dmytro DEMIRSKYI, Tohru S. SUZUKI, Kyosuke YOSHIMI, Oleg VASYLKIV

    Journal of the Ceramic Society of Japan   128 ( 11 ) 977 - 980  2020年11月

     概要を見る

    In this study, we introduce a simple and effective method for producing a ternary solid-solution of diborides, a medium-entropy Zr1/3Hf1/3Ta1/3B2. Using commercially available diboride powders with equimolar ratio and performing spark plasma consolidation at 1927°C we demonstrate that single-phase medium-entropy ceramic can be consolidated using an hour-long procedure. The flexural strength and fracture toughness at room temperature were 318 ?14MPa and 2.9MPam1/2, respectively. ?020 The Ceramic Society of Japan.

    DOI

    Scopus

    6
    被引用数
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  • Evolution of microstructure, mechanical, and optical properties of Y2O3-MgO nanocomposites fabricated by high pressure spark plasma sintering

    Lihong Liu, Koji Morita, Tohru S. Suzuki, Byung-Nam Kim

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   40 ( 13 ) 4547 - 4555  2020年10月

     概要を見る

    A high-pressure spark plasma sintering (SPS) process was applied for consolidating Y2O3-MgO nanocomposites. This approach enabled to fabricate a fully dense infrared (IR) transparent nanocomposites, which possess an average grain size of similar to 70 nm and high hardness, at a relatively low sintering temperature of 1130 degrees C under a high pressure of 300 MPa. The light transmittance was improved with increasing pressure and reached to the maximum transmittance of 64.5% at a wavelength of 0.2-1.6 mu m owing to the fine-grained microstructure. The Vickers hardness exhibited 16.6 +/- 0.7 GPa for the grain size of 74 nm, which is significantly higher than that of the sub-micro grains obtained at a conventional sintering pressure of 70 MPa (11.9 +/- 0.8 GPa). The hardness rigorously followed the Hall-Petch relationship, that is, it is enhanced with a reduction of the grain size. Successful fabrication of the high-performance Y2O3-MgO nanocomposites indicates that the nanopowder processing followed by the high-pressure sintering process can be applied for fabricating fully dense fine-grained nanocomposites with excellent optical and mechanical properties.

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  • Synthesis and high-temperature properties of medium-entropy (Ti,Ta,Zr,Nb)C using the spark plasma consolidation of carbide powders

    D. Demirskyi, T.S. Suzuki, K. Yoshimi, O. Vasylkiv

    Open Ceramics   2   100015 - 100015  2020年07月  [査読有り]

     概要を見る

    In this study, we explore a simple and effective method for producing a quaternary solid-solution of carbides, a medium-entropy (Ti1/4Ta1/4Zr1/4Nb1/4)C. Using commercially-available carbide powders with an equimolar ratio and performing spark plasma consolidation at 1927 ​°C and 1977 ​°C, we demonstrated that the phase formation and high-temperature flexural strength can be controlled using the processing conditions. The flexural strength and fracture toughness at room temperature were reached an average of 560 ​MPa and 3.2 ​MPa ​m1/2, respectively. The high-temperature performance of these ceramics was analyzed and compared with the available data for the group IV and V transition metal carbide monoliths.

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    26
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  • Theoretical modelling of electrode overvoltage for an all-solid-state electrochemical device

    Kiyoshi Kobayashi, Tohru S. Suzuki

    Japanese Journal of Applied Physics   59 ( SI ) SIIG04 - SIIG04  2020年06月

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    4
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  • Synthesis of highly-infrared transparent Y2O3-MgO nanocomposites by colloidal technique and SPS

    Lihong Liu, Koji Morita, Tohru S. Suzuki, Byung-Nam Kim

    CERAMICS INTERNATIONAL   46 ( 9 ) 13669 - 13676  2020年06月

     概要を見る

    Infrared (IR) transparent Y2O3-MgO nanocomposites with a volume ratio of 50:50 were synthesized by combining colloidal and spark-plasma-sintering (SPS) techniques. In order to attain well-dispersed and homogeneous starting Y2O3-MgO nanopowder mixture, the effects of the pH value and the amount of polyetherimide (PEI) dispersant on the suspension stability were studied. Rheological measurement reveals that highly-dispersed and stable suspension was obtained at 7 wt% of PEI dispersant under pH = 10.6. The obtained nanopowders with particle size of 20-30 nm were densified using SPS at several sintering temperatures. The sintered composites show fine grains, narrow grain size distribution and uniform microstructure. The nanocomposite sintered at 1250 degrees C showed the maximum IR transmittance of 84% at a wavelength range of 2.5-6 mu m. The Vickers hardness of the nanocomposite was about 11.9 +/- 0.3 GPa, which is significantly higher than those of single phase MgO or Y2O3. Successful fabrication of the high-performance Y2O3-MgO nanocomposite indicates that i) the colloidal technique is an effect method to obtain highly dispersed and homogeneous nanopowders and ii) the SPS technique is a powerful tool to fabricate fine-grained dense transparent ceramics, which are suitable for fabricating IR transparent Y2O3-MgO composite ceramics from commercial starting powders.

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    21
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  • Fabrication and Anisotropic Electrical Property for Oriented Ceramic of Li-(Nb,Ta)-Ti-O System under High-magnetic Field

    Hiromi NAKANO, Tohru SUZUKI, Akinori KAN

    Journal of the Japan Society of Powder and Powder Metallurgy   67 ( 4 ) 208 - 212  2020年04月

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  • Vickers indentation tests on olivine: size effects

    Sanae Koizumi, Takehiko Hiraga, Tohru S. Suzuki

    Physics and Chemistry of Minerals   47 ( 2 )  2020年02月  [査読有り]

     概要を見る

    © 2020, Springer-Verlag GmbH Germany, part of Springer Nature. We conducted Vickers indentation tests on Fe-free (Mg2SiO4) and Fe-bearing (Mg1.8Fe0.2SiO4) olivine single crystals and high-density polycrystalline material with average grain sizes ranging from 170 to 890 nm. The Vickers microhardness (Hv) of the Fe-free polycrystalline material with the finest grain size is ~ 17 GPa at a load of 0.1 N, while that of the Fe-bearing single crystal is ~ 8 GPa at the largest load applied. Overall, Hv decreases with increasing grain size, load (indentation depth), and the presence of Fe. For each grain size, Hv is well characterized by a power law of the form Hv/Hv0∝l-x, where Hv0 is the depth-independent value of Hv, l represents either grain size or indentation depth, and x is 0.09. Despite the small exponent value for each size effect, the nonlinear interaction of the two size effects results in large variations of Hv in our samples. We show that our semi-empirically derived relationship as a function of grain size and indentation depth explains the Hv of both polycrystalline and single-crystal olivine at any indentation conditions. Indentation fracture toughness of the finest-grained material is 0.8 MPam1/2, which increases slightly to 1.1 MPam1/2 with increasing grain size, while the toughness of the single crystals varies from 0.5 to 0.8 MPam1/2 depending on the crystallographic orientation of the fracture planes.

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    9
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  • 12
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  • High-temperature toughening in ternary medium-entropy (Ta<inf>1/3</inf>Ti<inf>1/3</inf>Zr<inf>1/3</inf>)C carbide consolidated using spark-plasma sintering

    D. Demirskyi, T. Nishimura, T. S. Suzuki, Y. Sakka, O. Vasylkiv, K. Yoshimi

    Journal of Asian Ceramic Societies   8 ( 4 ) 1262 - 1270  2020年

     概要を見る

    We report for the first time the effect of temperature on the mechanical properties of (Ta1/3Ti1/3Zr1/3)C carbide. Flexural strength and fracture toughness were investigated using the three-point bending technique in argon. Using commercially available carbide powders with an equimolar ratio and performing spark plasma consolidation at 1973°C, we obtained a bulk single-phase medium-entropy carbide ceramic with the lattice parameter a= 4.458 Å. The flexural strength and fracture toughness at room temperature reached on average 700 MPa and 3.2 MPa m1/2, respectively. At 1800°C, local decomposition of the medium-entropy carbide took place as a structure with a local chemical gradient was observed after high-temperature tests, which increased fracture toughness by 30% (to 4.4 MPa m1/2).

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    16
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  • Fabrication of <111>-Oriented BaTiO3 Ceramics by High Magnetic Field Electrophoretic Deposition using Hexagonal-Tetragonal Co-existing BaTiO3 Powder”

    Hari Shankar Mallik, Ichiro Fujii, Gopal Parasad Khanal, Sangwook Kim, Shintaro Ueno, Tohru S. Suzuki, Satoshi Wada

    Journal of the Ceramic Society of Japan     in press  2020年  [査読有り]

  • Bulks of Al-B-C obtained by reactively spark plasma sintering and impact properties by Split Hopkinson Pressure Bar

    O. Vasylkiv, H. Borodianska, D. Demirskyi, P. Li, T. S. Suzuki, M. A. Grigoroscuta, I. Pasuk, A. Kuncser, P. Badica

    Scientific Reports   9 ( 1 )  2019年12月

     概要を見る

    Mixtures of B4C, α-AlB12 and B powders were reactively spark plasma sintered at 1800 °C. Crystalline and amorphous boron powders were used. Samples were tested for their impact behavior by the Split Hopkinson Pressure Bar method. When the ratio R = B4C/α-AlB12 ≥ 1.3 for a constant B-amount, the major phase in the samples was the orthorhombic AlB24C4, and when R < 1 the amount of AlB24C4 significantly decreased. Predictions that AlB24C4 has the best mechanical impact properties since it is the most compact and close to the ideal cubic packing among the Al-B-C phases containing B12-type icosahedra were partially confirmed. Namely, the highest values of the Vickers hardness (32.4 GPa), dynamic strength (1323 MPa), strain and toughness were determined for the samples with R = 1.3, i.e., for the samples with a high amount of AlB24C4. However, the existence of a maximum, detectable especially in the dynamic strength vs. R, indicated the additional influence of the phases and the composite’s microstructure in the samples. The type of boron does not influence the dependencies of the indicated mechanical parameters with R, but the curves are shifted to slightly higher values for the samples in which amorphous boron was used.

    DOI PubMed

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  • Effect of Al2O3 addition on texturing in a rotating strong magnetic field and densification of B4C

    Muhammad Fajar, Anna Gubarevich, Ryosuke S. S. Maki, Tetsuo Uchikoshi, Tohru S. Suzuki, Toyohiko Yano, Katsumi Yoshida

    CERAMICS INTERNATIONAL   45 ( 15 ) 18222 - 18228  2019年10月  [査読有り]

     概要を見る

    The properties of ceramics can be improved by controlling the microstructure through texturing ceramics in a strong magnetic field. Fabricating dense boron carbide (B4C) requires high temperature sintering, therefore sintering additives are often used in order to densify B4C ceramics at lower temperatures. However, combined effect of texturing and sintering additives on densification of B4C has not been made clear yet. Here we report the effect of alumina (Al2O3) sintering additive on texturing in a strong magnetic field and densification of B4C. Texturing was performed by rotating superconducting magnet at 12 T during slip casting process. Electron backscatter diffraction (EBSD) was used to observed the texturing projection. {0001} plane is clearly oriented in the plane parallel to rotating magnetic field. In addition, Lotgering factor was also calculated as quantitatively evaluation of texturing degree. Results on densification showed that addition of Al2O3 successfully increased density of B4C sintered by spark plasma sintering (SPS) at 1800 degrees C to 97.8%. Formation of aluminum borate (Al5BO9) as secondary phase was detected by X-Ray diffraction (XRD). It is considered that the generation of Al5BO9 assisted finer densification of B4C ceramic. Textured B4C sintered at 1700 degrees C by SPS without alumina addition exhibited the highest orientation of c-axis. Addition of alumina caused decrease in degree of orientation of c-axis.

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    9
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  • Anisotropic Electric Conductivity and Battery Performance in C-axis Oriented Lanthanum Silicate Oxyapatite Prepared by Slip Casting in a Strong Magnetic Field

    Tohru S. Suzuki, Satoshi Takahashi, Tetsuo Uchikoshi, Kiyoshi Kobayashi

    MATERIALS TRANSACTIONS   60 ( 9 ) 1949 - 1953  2019年09月  [査読有り]

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    4
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  • Growth of small GeO2 single crystals on a polyvinyl chloride substrate at room temperature using oversaturate aqueous solution

    KOBAYASHI Kiyoshi, Tohru S. Suzuki

    Electronics and Communications in Japan   102 ( 7 ) 12 - 16  2019年07月  [査読有り]

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    1
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  • Optimization of preparation conditions of highly textured piezoelectric (Bi0.5K0.5)TiO3 ceramics

    Gopal Prasad Khanal, Ichiro Fujii, Sangwook Kim, Shintaro Ueno, Tohru S. Suzuki, Satoshi Wada

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   127 ( 6 ) 362 - 368  2019年06月  [査読有り]

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    5
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  • Effect of oxygen partial pressure during sintering on electric properties of BiFeO3-based piezoelectric ceramics

    Tomoya Aizawa, Ichiro Fujii, Shintaro Ueno, Tohru S. Suzuki, Satoshi Wada

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   127 ( 6 ) 383 - 387  2019年06月  [査読有り]

    DOI

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    2
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  • Microstructure and flexural strength of hafnium diboride via flash and conventional spark plasma sintering

    D. Demirskyi, T.S. Suzuki, S. Grasso, O. Vasylkiv

    Journal of the European Ceramic Society   39 ( 4 ) 898 - 906  2019年04月

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    10
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  • Theoretical analysis of experimental densification kinetics in final sintering stage of nano-sized zirconia

    Byung-Nam Kim, Tohru S. Suzuki, Koji Morita, Hidehiro Yoshida, Ji-Guang Li, Hideaki Matsubara

    Journal of the European Ceramic Society   39 ( 4 ) 1359 - 1365  2019年04月  [査読有り]

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    6
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  • High-temperature flexural strength performance of ternary high-entropy carbide consolidated via spark plasma sintering of TaC, ZrC and NbC

    Scripta Materialia   164   12 - 16  2019年04月  [査読有り]

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    111
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  • 室温過飽和水溶液を用いたポリ塩化ビニル基板上への微小二酸化ゲルマニウム単結晶の育成

    小林 清, 鈴木 達

    電気学会論文誌C(電子・情報・システム部門誌)   139 ( 3 ) 203 - 206  2019年03月  [査読有り]

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  • Evaluation of thermal shock fracture resistance of B4C/CNT composites with a high-frequency induction-heating furnace

    R.S.S. Maki, M. Fajar, J. Maletaskic, A.V. Gubarevich, K. Yoshida, T. Yano, T.S. Suzuki, T. Uchikoshi

    Materials Today: Proceedings   16   137 - 143  2019年  [査読有り]

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    3
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  • Fabrication of translucent AlN ceramics with MgF2 additive by spark plasma sintering

    Son, Hyoung-Won, Kim, Byung-Nam, Suzuki, Tohru S, Suzuki, Yoshikazu

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   101 ( 10 ) 4430 - 4433  2018年10月  [査読有り]

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    17
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  • Distribution of Relaxation Time Analysis for Non-ideal Immittance Spectrum: Discussion and Progress

    Kiyoshi Kobayashi, Tohru S. Suzuki

    Journal of the Physical Society of Japan   87 ( 9 ) 094002  2018年09月  [査読有り]

     概要を見る

    The problem regarding the distribution of relaxation times (DRT) is revisited and discussed from the point of view of mathematics and computing algorithms. Although the algorithm in conventional DRT analysis software involves an implicit hypothesis that DRT is a continuous real function with continuous relaxation time, this hypothesis is not a principle of nature but a demand by a mathematical equation used for analysis. It is to be noted that the DRT calculated using the conventional algorithm is a continuous distribution of relaxation times (CDRT). As per the CDRT hypothesis, DRT is a set of discrete values. On the other hand, there is a model that involves the discrete distribution of relaxation times (DDRT). Thus, the fundamental difference between the CDRT and DDRT models originates f

    DOI

  • Effect of texture on oxidation resistance of Ti3AlC2

    Ludi Xu, Degui Zhu, Yunlong Liu, Tohru S. Suzuki, Byung-nam Kim, Yoshio Sakka, Salvatore Grasso, Chunfeng Hu

    Journal of the European Ceramic Society   38 ( 10 ) 3417 - 3423  2018年08月  [査読有り]

     概要を見る

    Oxidation resistance of textured Ti3AlC2 ceramics was measured in the temperature range 1273–1573 K. It was found that the oxidation was markedly anisotropic and the samples exhibited a better oxidation resistance when tested along a direction transverse to the c-axis. This behavior was attributed to the rapid diffusion of Al within its basal planes to form a passivating Al2O3 scale and it respected Ellingham diagrams. The scales formed had different compositions depending on the testing direction
    this response was clearly resulting from the crystallographic orientation. Even at 1473 K after 20 h exposure, the samples tested in a direction transverse to the c-axis showed a reduced weight gain which was 45 times lower than one seen on a basal plane.

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    33
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  • Effect of ball-milling time and surfactant content for fabrication of 0.85(Bi0.5Na0.5)TiO3:0.15BaTiO3 green ceramics by electrophoretic deposition

    Minsu Kim, Piyush Sapkota, Gopal, Prasad Khanal, Sangwook Kim, Ichiro Fujii, Shintaro Ueno, Takahiro Takei, Tohru S. Suzuki, Tetsuo Uchikoshi, Satoshi Wada

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   126 ( 7 ) 542 - 546  2018年07月  [査読有り]

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    4
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  • Effect of crystallographic orientation on transparency of alumina prepared using magnetic alignment and SPS

    Takaharu Ashikaga, Byung-Nam Kim, Hajime Kiyono, Tohru S. Suzuki

    Journal of the European Ceramic Society   38 ( 7 ) 2735 - 2741  2018年07月  [査読有り]

     概要を見る

    Transparent polycrystalline alumina was developed over many years because its attractive properties are expected to find applications in many fields. Crystallographic orientation is one of the effective ways to improve transparency in birefringent ceramics such as alumina, because birefringence at grain boundaries can be suppressed by the alignment of optical axis. Fabrication of high-transparency alumina with an oriented c-axis and fine microstructure can be attained by slip casting in a strong magnetic field, followed by spark plasma sintering at 1150 °C for 20 min. The real in-line transmittance of the textured alumina with a thickness of 0.80 mm was 70% at λ = 640 nm, which was higher than that of randomly-oriented alumina. The c-axis orientation reduced the actual difference of the refractive index and suppressed remarkably the birefringence.

    DOI

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    26
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  • SLFC(Sr3-xLaxFe2-yCoyO7-z)系層状ペロブスカイト型混合伝導体の配向制御と異方性評価

    矢野広将, 打越哲郎, 小林 清, 鈴木 達, 明石孝也, 松田元秀

    粉体および粉末冶金   65   114 - 120  2018年02月  [査読有り]

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  • Transparent ultrafine Yb3+:Y2O3 laser ceramics fabricated by spark plasma sintering

    Hiroaki Furuse, Shunsuke Nakasawa, Hidehiro Yoshida, Koji Morita, Tohru S. Suzuki, Byung-Nam Kim, Yoshio Sakka, Keijiro Hiraga

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   101 ( 2 ) 694 - 702  2018年02月  [査読有り]

     概要を見る

    Conventional ceramic processing techniques do not produce ultrafine-grained materials. However, since the mechanical and optical properties are highly dependent on the grain size, advanced processing techniques are needed to obtain ceramics with a grain size smaller than the wavelength of visible light for new laser sources. As an empirical study for lasing from an ultrafine-grained ceramics, transparent Yb3+:Y2O3 ceramics with several doping concentrations were fabricated by spark plasma sintering (SPS) and their microstructures were analyzed, along with optical and spectroscopic properties. Laser oscillation was verified for 10at.% Yb3+:Y2O3 ceramics. The laser ceramics in our study were sintered without sintering additives, and the SPS produced an ultrafine microstructure with an average grain size of 261nm, which is about one order of magnitude smaller than that of ceramics sintered by conventional techniques. A load was applied during heating to enhance densification, and an in-line transmittance near the theoretical value was obtained. An analysis of the crystal structure confirmed that the Yb3+:Y2O3 ceramics were in a solid solution. To the best of our knowledge, this study is the first report verifying the lasing properties of not only ultrafine-grained but also Yb-doped ceramics obtained by SPS.

    DOI

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    36
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  • Fabrication of lead-free piezoelectric (Bi0.5Na0.5)TiO3–BaTiO3 ceramics using electrophoretic deposition

    Minsu Kim, Ryo Ito, Sangwook Kim, Gopal Prasad Khanal, Ichiro Fujii, Tohru S. Suzuki, Tetsuo Uchikoshi, Chikako Moriyoshi, Yoshiro Kuroiwa, Satoshi Wada

    Journal of Materials Science   53 ( 4 ) 2396 - 2404  2018年02月  [査読有り]

     概要を見る

    EPD process has certain advantages such as it can be applied for a mass production and also can be combined with magnetic crystal alignment technique. In this work, we prepared lead-free 85(Bi0.5 Na0.5)TiO3&amp;#8211;15BaTiO3 (85BNT&amp;#8211;15BT) piezoelectric ceramics by conventional uniaxial pressing and EPD process. 85BNT&amp;#8211;15BT ceramics prepared using EPD process revealed the Curie temperature of about 250C, coercive field of about 30 kV/cm, and piezoelectric constant (d33) of 75 pC/N. This study lays a foundation on the fabrication of Bi-based lead-free piezoelectric ceramics by an alternative route other than the conventionally practiced solid-state reaction method maintaining the similar chemical composition, moreover, leaving a large space to explore more in the future.

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    15
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  • Stabilization of the high-temperature phase and total conductivity of yttrium-doped lanthanum germanate oxyapatite

    Kiyoshi Kobayashi, Yukihito Igarashi, Noriko Saito, Tohru Higuchi, Yoshio Sakka, Tohru S. Suzuki

    Journal of the Ceramic Society of Japan   126 ( 2 ) 91 - 98  2018年02月  [査読有り]

     概要を見る

    The high-temperature phase of lanthanum germanate is useful due to its high oxide ion conductivity. While the transition from the high- to low-temperature phase could be suppressed by yttrium substitution in lanthanum sites, full stabilization of the high-temperature phase was difficult to achieve by yttrium substitution under conditions of different lanthanum-deficient compositions, as some X-ray diffraction (XRD) peaks were broadened after annealing at 873 K. With lattice constant analysis using the XRD peaks, the degree of lattice asymmetry for the low-temperature phase with triclinic lattice was found to decrease with increases in the deficiency of the lanthanum site and yttrium concentration. Formation of the low-temperature phase was difficult to detect even from Raman shift spectra. On the other hand, Raman shift spectra showed high sensitivity to detection of the La2GeO5 impurity phase. The influence of the total conductivity on the phase transition showed different trends with increases in the lanthanum deficiency and yttrium concentration. With tuning of the composition, the highest conductivity was observed in La8.51Y0.96(GeO4)6O2.205. This conductivity (6.12 © 1011 S/m11 at 873 K) is higher than that of yttria-stabilized zirconia at the same temperature.

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    4
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  • Inherent anisotropy in transition metal diborides and microstructure/property tailoring in ultra-high temperature ceramics—A review

    Guo-Jun Zhang, De-Wei Ni, Ji Zou, Hai-Tao Liu, Wen-Wen Wu, Ji-Xuan Liu, Tohru S. Suzuki, Yoshio Sakka

    Journal of the European Ceramic Society   38 ( 2 ) 371 - 389  2018年02月  [査読有り]

     概要を見る

    This is the first comprehensive review on inherent anisotropic features of transition metal diboride (MB2) and their implementation for tailoring the microstructure and properties of MB2-based Ultra-high temperature Ceramics (UHTCs). The emphasis is on the processing approaches, microstructures, and properties of self-reinforced and/or textured MB2-based composites with elongated MB2 grains.

    DOI

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    87
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  • Anisotropic electronic conductivity and battery performance in c-axis oriented lanthanum silicate oxyapatite prepared by slip casting in a strong magnetic field

    Tohru S. Suzuki, Satoshi Takahashi, Tetsuo Uchikoshi, Takamasa Ishigaki, Kiyoshi Kobayashi

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   65 ( 2 ) 121 - 126  2018年02月  [査読有り]

     概要を見る

    Lanthanum silicate oxyapatite (LSO) has superior features for application of solid electrolyte in solid oxide fuel cells. Because LSO has a higher oxygen-ion conductivity compared with yttria stabilized zirconia at temperatures below 600°C. Textured LSO bulk ceramics were fabricated by using a magnetic field-assisted colloidal processing technique. The c-axis of LSO was aligned parallel to the applied magnetic field. The anisotropic electric conductivity of the textured bulk ceramics was evaluated by the complex impedance method. It was demonstrated that the conductivity was very high along the c-axis. Battery performance was higher in the textured LSO compared with the random LSO.

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  • 強磁場と電場を利用した配向積層制御装置

    鈴木 達, 打越 哲郎

    コロイドおよび界面化学部会『C&I Commun』   43 ( 1 ) 5 - 6  2018年01月

     概要を見る

    セラミックスの創製において、成形過程で強磁場を印加することにより常磁性、反磁性セラミックスであっても結晶配向制御を可能とするプロセスと、さらに積層構造を造り込むことを可能にする電気泳動堆積法の二つのプロセスを重畳させることで配向積層セラミックスの創製を可能とした。このセラミックスの配向積層構造を造り込むための装置を紹介する。

  • Development of an algorithm for automatic analysis of the impedance spectrum based on a measurement model

    Kiyoshi Kobayashi, Tohru S. Suzuki

    Journal of the Physical Society of Japan   87 ( 3 ) 034004  2018年  [査読有り]

     概要を見る

    A new algorithm for the automatic estimation of an equivalent circuit and the subsequent parameter optimization is developed by combining the data-mining concept and complex least-squares method. In this algorithm, the program generates an initial equivalent-circuit model based on the sampling data and then attempts to optimize the parameters. The basic hypothesis is that the measured impedance spectrum can be reproduced by the sum of the partial-impedance spectra presented by the resistor, inductor, resistor connected in parallel to a capacitor, and resistor connected in parallel to an inductor. The adequacy of the model is determined by using a simple artificial-intelligence function, which is applied to the output function of the Levenberg-Marquardt module. From the iteration of model modifications, the program finds an adequate equivalent-circuit model without any user input to the equivalent-circuit model.

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    5
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  • Fabrication and mechanical properties of textured Ti3SiC2 systems using commercial powder

    Yuichi Uchida, Koji Morita, Tohru S. Suzuki, Toshiyuki Nishimura, Kenjiro Fujimoto, Yoshio Sakka

    Materials Transactions   59 ( 5 ) 829 - 834  2018年  [査読有り]

     概要を見る

    Ti3SiC2 is a typical Mn+1AXn (MAX) phase ceramic and exhibits both metal-like and ceramic-like properties. To improve these properties, texturing and Al2O3 addition were performed. The commercial Ti3SiC2 powder used contained approximately 10 mass% TiC phase. Textured Ti3SiC2 was prepared by slip casting in a strong magnetic field (MF) followed by spark plasma sintering (SPS) at 1623 K under a pressure of 40 MPa for 5 min. The Lotgering orientation factor of the (00l) peaks of Ti3SiC2 prepared under an MF was 0.96, and the relative density of samples exceeded 99%. The bending strength and fracture toughness of Ti3SiC2 were improved by texturing. The textured Ti3SiC2 exhibited an excellent bending strength of 978 MPa, but Al2O3 addition, reduced the bending strength and fracture toughness. The textured Ti3SiC2 showed the plastic deformation at a temperature of approximately 1173 K.

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  • 高校生を対象としたNIMSにおける見学と体験学習

    鈴木 達, 打越 哲郎

    セラミックス   52 ( 11 ) 768 - 771  2017年11月

     概要を見る

    NIMSでは毎年4月中旬の科学技術週間に合わせて研究所一般公開を行い、土曜日には小学生、中学生向けに青少年企画を実施している。この時にミネラルファンデーション作製体験を実施しており、小学生から主婦まで幅広い層から人気を得ている。また、日本全国からの高校生の研究所見学、体験学習も随時受け付けており、その受け入れ人数は年に2000人を超えている。NIMSでは3〜4箇所の実験施設を20分〜30分程度ずつで見学するコースと、一つのテーマで2時間程度の体験実験をしながら学習を行うコースとで種々のテーマを用意している。その中でも、著者らが中心となって行っている強磁場の見学、ファンデーションの作製、CIPを用いた実験による圧力の体験学習を行っており、本記事ではこれらについて紹介する。

  • Fabrication of 〈110〉 grain-oriented 0.15BaTiO3–0.85(Bi0.5Na0.5)TiO3 ceramics by a reactive templated grain growth method

    Shintaro Ueno, Ryo Itou, Tohru S. Suzuki, Satoshi Wada, Ichiro Fujii

    Japanese Journal of Applied Physics   56 ( 10 ) 10PD06  2017年10月  [査読有り]

     概要を見る

    &amp;lt;110&amp;gt; grain-oriented ceramics with the composition of 0.15BaTiO3-0.85(Bi0.5Na0.5)TiO3 with a high Curie temperature of ~300 &amp;#730;C were successfully fabricated by reactive templated grain growth of layered hydrogen titanate platelets with (Bi0.5Na0.5)TiO3 and BaCO3 matrix powders. A large degree of &amp;lt;110&amp;gt; orientation F110 = 84% was achieved by decrease in green sheet thickness and application of pressure on a compact during sintering. As a consequence, improved remanent polarization was observed compared with randomly-oriented ceramics. A piezoelectric constant d33 of 103 pC/N and an electromechanical coupling factor k33 of 0.44 were obtained for &amp;lt;110&amp;gt; grain-oriented ceramics.

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  • Fabrication and mechanical properties of textured T3SiC2 systems using commercial powders

    Yuichi Uchida, Koji Morita, Tohru S. Suzuki, Toshiyuki Nishimura, Kenjiro Fujimoto, Yoshio Sakka

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   64 ( 10 ) 552 - 557  2017年10月  [査読有り]

     概要を見る

    T3SiC2 is a typical Mn+1AXn (MAX) phase ceramics and shows unique metallic-like and ceramic-like properties. To improve these properties, texturing and Al2O3 addition have been conducted. The commercial T3SiC2 powder used contains approximately 10 wt% TiC phase. Textured T3SiC2 was prepared by slip cast in strong magnetic fields followed by spark plasma sintering (SPS) at 1350°C under 40 MPa for 5 min. The Lotgering orientation factor of (00l) peaks of T3SiC2 with magnetic field (MF) was 0.96, and relative density of samples was beyond 99%. The bending strength and fracture toughness of T3SiC2 were improved by texturing. T3SiC2 with magnetic field showed excellent value of bending strength of 978 MPa, but Al2O3 addition caused deterioration of bending strength and fracture toughness. T3SiC2 with MF showed the plastic deformation at temperature at around 900°C.

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  • Fabrication and anisotropic electronic property for oriented Li 1+ x − y Nb 1− x −3 y Ti x +4 y O 3 solid solution by slip casting in a high magnetic field

    Hiromi Nakano, Shohei Furuya, Motohiro Yuasa, Tohru S. Suzuki, Hitoshi Ohsato, Nakano Hiromi, Furuya Shohei, Yuasa Motohiro, Osato Hitoshi

    ADVANCED POWDER TECHNOLOGY   28 ( 9 ) 2373 - 2379  2017年09月  [査読有り]

     概要を見る

    In the Li2O-Nb2O5-TiO2 system, a unique structure appeared in the Li1+x-yNb1-x-3yTix+4yO3 (0.06 &amp;#61603; x &amp;#61603; 0.33, 0 &amp;#61603; y &amp;#61603; 0.09) (LNT) form as a superstructure. In this work, we fabricated an oriented LNT balk ceramic by slip casting in a strong magnetic field of 12 T. The direction of the magnetic field was parallel or perpendicular to the casting direction The compact was densified by cold isostatic pressing and then heated at 1373 K. The c-axis of the LNT powders was aligned parallel to the magnetic field. Consequently, we found anisotropic and unique electric properties and the mechanism appeared in the oriented LNT due to a superstructure with intergrowth layers of corundum-type [Ti2O3]2+. The Qf value along c-axis was five times greater than that of perpendicu

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  • Effect of texture microstructure on tribological properties of tailored Ti3AlC2 ceramic

    Ludi Xu, Degui Zhu, Salvatore Grasso, Tohru S. Suzuki, Akira Kasahara, Masahiro Tosa, Byung-nam Kim, Yoshio Sakka, Minhao Zhu, Chunfeng Hu

    JOURNAL OF ADVANCED CERAMICS   6 ( 2 ) 120 - 128  2017年06月  [査読有り]

     概要を見る

    Tribological property of c-axis textured shell-like Ti3AlC2 ceramic was investigated using reciprocating sliding balls (SUS304) under loads of 1, 5, and 9 N. It was found that the textured top surface (TTS), corresponding to the (000l) plane, shows the lowest mean coefficient of friction in comparison with those measured on the textured side surface (TSS), where the sliding directions are parallel (TSS-1) and perpendicular (TSS-2) to c axis, under the same load. Among all the tested orientations, the TSS-2 exhibited the lowest wear rate of 1.51x10(-3) mm(3)/(N.m) under the load of 9 N. The worn mechanisms on the TTS and TSS-1 were delamination, grain fracture, and grain spalling-off. On the TSS-2, plowing effect against balls was the dominating mechanism. This work suggests the criteria to maximize the wear resistance in the load range of 1-9 N.

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  • Evaluation of densification and grain-growth behavior during isothermal sintering of zirconia

    Byung-Nam Kim, Tohru S. Suzuki, Koji Morita, Hidehiro Yoshida, Ji-Guang Li, Hideaki Matsubara

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   125 ( 4 ) 357 - 363  2017年04月  [査読有り]

     概要を見る

    The densification behavior during the isothermal sintering of 7.8 mol% Y2O3-stabilized zirconia was examined in the intermediate and final stages of sintering. In the intermediate stage, it is shown that the relationship between the grain size and the relative density is not invariant, but is temperature dependent. The relationship is combined with the measured densification rate to evaluate the grain size exponent, the activation energy and an unspecified function of density. The evaluation of the characteristic parameters indicates that the densification and the grain growth are related to a mechanism of grain-boundary diffusion and sliding. The densification rate predicted with the evaluated parameters shows a good consistence to the measured rate. In the final stage, the densification rate is inversely proportional to the grain size, and the kinetics is well explained by using the diffusive model modified with a gas pressure in closed pores. (C) 2017 The Ceramic Society of Japan. All rights reserved.

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  • 結晶磁気異方性を利用したモルデナイト配向膜の作製

    松永知佳, 打越 哲郎, 鈴木 達, 目 義雄, 松田元秀

    セラミックス   52 ( 1 ) 26 - 30  2017年01月  [査読有り]

     概要を見る

    我々は、セラミックス粒子の配向を高度に制御できる方法として、強磁場を利用した配向プロセスに着目してきた。これまでの知見を基に、個々のゼオライトの結晶磁気異方性に基づき、種結晶の配向挙動を制御できれば、それぞれのゼオライトに適した配向状態が実現できると考えた。しかしながら、ゼオライトの磁気的性質を調査した報告例は無く、強磁場を用いたゼオライト配向膜の作製はまさに未踏の分野である。本報では、結晶磁気異方性に基づく種結晶の磁場配向制御を検討し、磁場配向制御で製膜された種結晶配向層の水熱固化からゼオライトの緻密配向膜を得る手法について紹介した。

    CiNii

  • Development of functional properties in ceramics by microstructure control using a magnetic field

    Tohru S. Suzuki

    Journal of the Society of Powder Technology, Japan   54 ( 1 ) 41 - 45  2017年

     概要を見る

    Tailoring the crystallographic orientation in ceramics is very useful for improving their properties. A magnetic field is shown to be very effective in controlling the crystallographic orientation in bulk ceramics. The particles were rotated to an angle minimizing the system energy by a magnetic torque generated from the interaction between the magnetic anisotropy and the applied magnetic field. This processing was applied to control the microstructure in lanthanum silicate oxyapatite (LSO) for SOFC and LiCoO2 for Li ion secondary battery. Electric conductivity parallel to the c-axis in the c-axis oriented LSO was higher than that perpendicular to the c-axis. The battery performance of the ideal textured cell fabricated using a rotating magnetic field has a significantly higher performance than a oriented cell prepared by a static magnetic field.

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  • Electrophoretic fabrication of a-b plane oriented La2NiO4 cathode onto electrolyte in strong magnetic field for low-temperature operating solid oxide fuel cell

    Motohide Matsuda, Miwa Hashimoto, Chika Matsunaga, Tohru S. Suzuki, Yoshio Sakka, Tetsuo Uchikoshi

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   36 ( 16 ) 4077 - 4082  2016年12月  [査読有り]

     概要を見る

    An oriented La2NiO4 cathode was successfully fabricated on a dense Gd2O3-doped CeO2 electrolyte pre-coated with conducting polypyrrole by electrophoretic deposition in a static magnetic field of 12 T for use in low-temperature operating solid oxide fuel cell. The orientation of La2NiO4 was based on an anisotropic magnetic property in its crystal structure. Firm adhesion of the La2NiO4 cathode to an electrolyte was made by the co-deposition of starch added as a pore former. The La2NiO4 cathode with the preferential orientation of the a-b plane perpendicular to the surface of the electrolyte showed a polarization loss lower than that with a random orientation, leading to an enhancement in the cell performance at 500 degrees C. (C) 2016 Elsevier Ltd. All rights reserved.

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  • Ti3SiC2系MAX相セラミックス配向体の作製とその力学特性

    打田 雄一, 武舎 翔太郎, 森田 孝治, 鈴木 達, 西村 聡之, 藤本 憲次郎, 目 義雄

    Journal of the Japan Society of Powder and Powder Metallurgy   63 ( 11 ) 970 - 975  2016年10月  [査読有り]

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  • Development of an electrochemical impedance analysis program based on the expanded measurement model

    Kiyoshi Kobayashi, Yoshio Sakka, Tohru S. Suzuki

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   124 ( 9 ) 943 - 949  2016年09月  [査読有り]

     概要を見る

    A new program for electrochemical impedance analysis has been developed based on the expanded measurement model. The main feature of this program is that it allows the user to easily estimate the equivalent circuit, as well as an initial guess of the fitting parameters, through a graphic user interface (GUI). The function to illustrate the partial impedance spectra is implemented in the graphs of log f-Z(real) and log f-Z(imag). In this context, f represents the alternating current frequency applied to the sample; Z(real) and Z(imag) represent the real and imaginary components of the impedance, respectively. By employing the GUI supporting function, the impedance spectrum can be analyzed without the use of a pseudo-element such as a constant phase element and with an empirical parameter in the Warburg and Gerischer impedance. Based on the results, it is possible to calculate a discrete distribution of the relaxation times from the optimized parameters. (C) 2016 The Ceramic Society of Japan. All rights reserved.

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    19
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  • Triaxial Crystalline Orientation of MgTi2O5 Achieved Using a Strong Magnetic Field and Geometric Effect

    Tohru S. Suzuki, Yoshikazu Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   99 ( 6 ) 1852 - 1854  2016年06月  [査読有り]

     概要を見る

    Tailoring the crystallographic orientation in ceramics is very useful for improving their properties. We reported that the colloidal processing in a strong magnetic field was able to control the crystallographic orientation even in diamagnetic ceramics. In this process, a strong magnetic field is applied to the particles in a stable suspension. The orientation of the crystal depends on the axis having easy magnetization and one-dimensional orientation can be controlled. In this study, our concept is that control of multiaxial crystalline orientation in ceramics by using both anisometric particles and a magnetic field. The control of the triaxial orientation was achieved by tape casting of rod-like MgTi2O5 particle in a magnetic field. The b-axis was aligned by the magnetic field, and the a-axis was aligned by the geometric effect and shear stress during tape casting.

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  • Densification kinetics during isothermal sintering of 8YSZ

    Byung-Nam Kim, Tohru S. Suzuki, Koji Morita, Hidehiro Yoshida, Yoshio Sakka, Hideaki Matsubara

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   36 ( 5 ) 1269 - 1275  2016年04月  [査読有り]

     概要を見る

    The densification behavior during the isothermal sintering of 8YSZ was examined in the initial and intermediate stages of sintering. In the initial stage, a difficulty in evaluating the densification behavior arises from the transition of the stable pore structure and the limitation of the theoretical two-sphere model. In the intermediate stage, a linear relationship with a slope of -1/2 is observed between the densification rate and the time. An empirical equation of the densification kinetics is proposed and found to be valid in a wide density range. At a relative density of 0.6-0.73, the activation energy is 688 kJ/mol. Rapid grain growth is observed at a relative density of 0.73-0.8 and &gt;0.9 for the isothermal sintering at 1200-1300 degrees C and 1400-1500 degrees C, respectively. The rapid grain growth reduced significantly the densification rate. The densification mechanism and grain growth behavior are also discussed. (C) 2015 Elsevier Ltd. All rights reserved.

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    21
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  • Magnetic field alignment in highly concentrated suspensions for gelcasting process

    Agnieszka Szudarska, Yoshio Sakka, Tohru S. Suzuki, Tadeusz Mizerski, Mikolaj Szafran

    CERAMICS INTERNATIONAL   42 ( 1 ) 294 - 301  2016年01月  [査読有り]

     概要を見る

    The aim of the current paper is to present the development of the method used for fabricating highly textured a-alumina elements. The experimental procedure described is based on a combination of two techniques: gelcasting is used in tandem with high magnetic field exposure. In the element shaping process, a new, low-toxic and environmentally friendly gelating system was implemented that is based on in situ polymerisation of an acryloyl derivative of galactose. Here, care was taken to achieve a highly textured structure of elements gelcast from the ceramic slurries of high solid contents (45-50 vol%), which have not been processed successfully for magnetic field alignment before. A secondary aim of the study was to investigate the combined effect of magnetic field exposure duration and the idle time of polymerisation on the effectiveness of the alignment. In the course of the experiment, high degrees of crystalline orientation of the gelcast samples were obtained ranging from 0.92 to 0.96, developed after the subsequent sintering at 1600 degrees C (the parameters were calculated on the basis of XRD pattern of the surface perpendicular to the magnetic field direction). The microstructures of the obtained elements are described in detail at the end of the paper, in a stereological analysis. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

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  • Synthesis of crystallographically oriented olivine aggregates using colloidal processing in a strong magnetic field

    Koizumi, S., Suzuki, T.S., Sakka, Y., Yabe, K., Hiraga, T.

    Physics and Chemistry of Minerals   43 ( 10 ) 689 - 706  2016年  [査読有り]

     概要を見る

    This study develops a fabrication technique to obtain Fe-free and Fe-bearing (Fe:Mg = 1:9) olivine aggregates not only with high density and fine grain size but with crystallographic preferred orientation (CPO). A magnetic field is applied to synthetic, fine-grained, olivine particles dispersed in solvent. We find that (1) preparation of fully reacted olivine particles, with less propensity to coalesce; (2) preparation of a suspension with highly dispersed particles; and (3) application of a certain strength of the magnetic field are essential to obtain well sintered and well-aligned aggregates. High density and fine grain size Fe-free and Fe-bearing olivine aggregates were successfully synthesized with uniaxially aligned a- and c-axes, respectively.

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  • 強磁場を用いたセラミックスの配向制御

    鈴木 達

    材料の科学と工学   52 ( 5 ) 161 - 164  2015年10月

     概要を見る

    金属材料だけでなくセラミックスにおいても,その材料特性を改善させるためには,微構造制御が有効で有り,その中でも結晶配向制御は有望な方法として挙げられる.金属では集合組織の制御が精緻に行われているが,セラミックスにおいては,その制御手法も限られる.しかしながら,強磁場を用いることで反磁性セラミックスであっても結晶配向制御することが可能になり,近年ではさらに反応焼結や,相変態,形状異方性粒子などの他のプロセス技術を組み合わせることにより,さらにその展開が広がっている.ここでは,最近での強磁場によるセラミックスの配向制御の展開について紹介する.

    CiNii

  • Densification, microstructure evolution and mechanical properties of WC doped HfB2–SiC ceramics

    Ji-Xuan Liu, Guo-Jun Zhang, Fang-Fang Xu, Wen-Wen Wu, Hai-Tao Liu, Yoshio Sakka, Toshiyuki Nishimura, Tohru S. Suzuki, De-Wei Ni, Ji Zou

    Journal of the European Ceramic Society   35 ( 10 ) 2707 - 2714  2015年09月  [査読有り]

     概要を見る

    Despite of good oxidation resistance and ablation resistance, challenge to densify and tendency to loss high temperature (H.T.) strength have limited its potential applications in aerospace for HfB2-SiC ceramic. In this work, dense HfB2-SiC ceramic with improved H.T. flexural strength was prepared using WC as sintering aid.

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  • Fabrication of (111)-oriented Tetragonal BaTiO3 Ceramics by an Electrophoretic Deposition in a High Magnetic Field

    Eigo Kobayashi, Shintaro Ueno, Kouichi Nakashima, Nobuhiro Kumada, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka, Ichiro Fujii, Satoshi Wada

    Transactions of the Materials Research Society of Japan   40 ( 3 ) 223 - 226  2015年08月  [査読有り]

     概要を見る

    (111)-oriented tetragonal barium titante (BaTiO3, BT) ceramics with the degree of (111) orientation of 100 % were fabricated by sintering (001)-oriented hexagonal BT accumulations prepared by a magnetic field assisted electrophoretic deposition (EPD) method. Apparent piezoelectric constant d33* value calculated from the slope of a unipolar strain vs. electric field curve of the (111)-oriented tetragonal BT ceramics was 597 pm/V, which was larger than that of randomly oriented ceramics (d33* = 460 pm/V). This enhancement was associated with an electric field induced phase transition.

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  • Effects of Gd Substitution on Sintering and Optical Properties of Highly Transparent (Y 0.95− x Gd x Eu 0.05

    Bin Lu, Ji‐Guang Li, Tohru S. Suzuki, Hidehiko Tanaka, Xudong Sun, Yoshio Sakka

    Journal of the American Ceramic Society   98 ( 8 ) 2480 - 2487  2015年08月  [査読有り]

     概要を見る

    Highly transparent (Y0.95-xGdxEu0.05)2O3 (x=0.15-0.55) ceramics have been fabricated by vacuum sintering at the relatively low temperature of 1700 。&amp;#65533; for 4 h with the in-line ransmittances of 73.6-79.5% at the Eu3+ emission wavelength of 613 nm (&amp;#8764;91.9-99.3% of the theoretical transmittance of Y1.34Gd0.6Eu0.06O3 single crystal), while the x=0.65 ceramic undergoes a phase transformation at 1650 。&amp;#65533; and has a transparency of 53.4% at the lower sintering temperature of 1625 。&amp;#65533;. The effects of Gd3+ substitution for Y3+ on the particle properties, sintering kinetics and optical performances of the materials were systematically studied.

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  • Highly anisotropic single crystal-like La2Ti2O7 ceramic produced by combined magnetic field alignment and templated grain growth

    Zhipeng Gao, Tohru S. Suzuki, Salvatore Grasso, Yoshio Sakka, Mike J. Reece

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   35 ( 6 ) 1771 - 1776  2015年06月  [査読有り]

     概要を見る

    Highly anisotropic single crystal-like ceramic of La2Ti2O7 was successfully prepared by an effective 2-D grain alignment using both seed crystals and magnetic field alignment during slip casting followed by templated grain growth (TGG). It was found that the highest magnetic susceptibility is in the [0 0 l] direction of LTO. The grain orientation factors of the three directions for the textured ceramic were calculated as 0.76, 0.71, and 0.73, respectively. The dielectric and ferroelectric properties of the textured ceramic were found to be single crystal like. The dielectric permittivity of the aligned ceramic in the different directions is higher than for single crystal due to contributions from domain walls and grain boundaries. Crown Copyright (C) 2014 Published by Elsevier Ltd. All rights reserved.

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  • Controlled Synthesis of Layered Rare-Earth Hydroxide Nanosheets Leading to Highly Transparent (Y0.95Eu0.05)(2)O-3 Ceramics

    Bin Lu, Ji-Guang Li, Tohru S. Suzuki, Mehdi Estili, Weigang Liu, Xudong Sun, Yoshio Sakka

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   98 ( 5 ) 1413 - 1422  2015年05月  [査読有り]

     概要を見る

    Chemical precipitation at the freezing temperature of similar to 4 degrees C has directly yielded layered rare-earth hydroxide [LRH, Ln(2)(OH)(5)-NO3 center dot nH(2)O, Ln = Y0.95Eu0.05] nanosheets (up to 7 nm thick) for the Y/Eu binary system, with the interlayer NO3- exchangeable with SO42-. Calcining the sulfate derivative at 1100 degrees C for 4 h produces well-dispersed and readily sinterable Ln(2)O(3) red phosphor powders (similar to 14.8 m(2)/g) that can be densified into highly transparent ceramics via optimized vacuum sintering at the relatively low temperature of 1700 degrees C for 4 h (average grain size similar to 14 mu m; in-line transmittance similar to 80% at the 613 nm Eu3+ emission or similar to 99% of the theoretical transmittance of Y2O3 single crystal). Our systematic studies also found that (1) the extent of SO42 - exchange and the interlayer distance of LRH are both affected by the SO42-/Ln(3)(+) molar ratio (R), and an almost complete exchange is achievable at R = 0.25 as expected from the chemical formula (one SO42- replaces two NO3- for charge balance). The optimal R value for sintering, however, was found to be 0.03; (2) The Ln(3+) concentration for LRH synthesis substantially affects properties of the resultant oxides, and hard agglomeration has been significantly reduced at the optimized Ln(3+) concentration of 0.05-0.075 mol/L; (3) Sulfate exchange significantly alters the thermal decomposition pathway of LRH, and was found essential to produce well-dispersed and highly sinterable oxide powders; (4) Both the oxide powders and transparent ceramics exhibit the typical red emission of Eu3+ at similar to 613 nm (the D-5(0) -&gt; F-7(2) transition) under charge-transfer (CT) excitation. Red-shifted CT band center, stronger excitation/emission, and shorter fluorescence lifetime were, however, observed for the transparent ceramics.

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  • Processing and enhanced piezoelectric properties of highly oriented compositionally modified Pb(Zr,Ti)O-3 ceramics fabricated by magnetic alignment

    Yasunari Miwa, Shinichiro Kawada, Masahiko Kimura, Suetake Omiya, Noriyuki Kubodera, Akira Ando, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    APPLIED PHYSICS EXPRESS   8 ( 4 ) 041501  2015年04月  [査読有り]

     概要を見る

    Highly oriented compositionally modified Pb(Zr, Ti)O-3 (PZT) ceramics were successfully obtained by slip casting in a high magnetic field. PZT is a well-known superior ceramic with the highest piezoelectric properties, and these properties have been expected to be further improved through crystalline orientation. However, highly oriented PZT ceramics fabricated by slip casting in a high magnetic field have never been reported. We obtained oriented ceramics using compositionally modified PZT with Pb(Ni, Nb)O-3, and their Lotgering factor was 0.77. The electromechanical coupling coefficient (k(31)) increased by 30%, and an extremely high value of 0.44 was achieved for the oriented ceramics. (C) 2015 The Japan Society of Applied Physics

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  • Sinterable powder fabrication of lanthanum silicate oxyapatite based on solid-state reaction method

    Kiyoshi Kobayashi, Kenya Hirai, Tohru S. Suzuki, Tetsuo Uchikoshi, Takaya Akashi, Yoshio Sakka

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   123 ( 1436 ) 274 - 279  2015年04月  [査読有り]

     概要を見る

    Sinterable lanthanum silicate oxyapatite (LSO) powders were prepared by the combination of solid-state reaction synthesis and particle size control via planetary ball-milling. We successfully fabricated the LSO ceramics with relative densities exceeding 94% at 1773K even though it was suggested that the densified LSO ceramics could not be obtained below 1923K using a powder synthesized by a solid-state reaction. Impurity phases resulting from contamination due to the ball and pod during the planetary ball milling were, in some cases, detected by the X-ray diffraction analysis of the sintered ceramics. The planetary ball-milling conditions were deemed important for the successful fabrication of the sinterable LSO powder. (C) 2015 The Ceramic Society of Japan. All rights reserved.

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    8
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  • Dense SiC containing strongly aligned plate-like grains by magnetic treatment

    S. H. Lee, L. Feng, J. Yin, J. S. Lee, X. Zhu, T. S. Suzuki, Y. Sakka, H. Tanaka

    CERAMICS INTERNATIONAL   41 ( 3 ) 5079 - 5084  2015年04月  [査読有り]

     概要を見る

    Dense SiC having strongly aligned plate-like grains was prepared by slip casting under strong magnetic field and subsequent densification using Al3BC3 additive. Irregular-shaped 6H-SiC powders in the green body were strongly aligned by the magnetic treatment. Subsequently, Al3BC3 additive induced the formation of aligned plate-like SiC grains during densification. The hardness of SiC could be tailored up to 11% by the strong alignment of the grains. Crack deflection was also strongly affected by the direction of the aligned plate-like grains. As a result, the length of the cracks which propagated parallel to the elongated grains was 18.6% shorter compared to that formed perpendicular to the grains. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

    DOI

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    11
    被引用数
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  • Tailoring Ti3AlC2 ceramic with high anisotropic physical and mechanical properties

    H. B. Zhang, C. F. Hu, K. Sato, S. Grasso, M. Estili, S. Q. Guo, K. Morita, H. Yoshida, T. Nishimura, T. S. Suzuki, M. W. Barsoum, B. N. Kim, Y. Sakka

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   35 ( 1 ) 393 - 397  2015年01月  [査読有り]

     概要を見る

    Textured Ti3AlC2 ceramic was successfully fabricated by a strong magnetic field alignment (SMFA) technique followed by spark plasma sintering (SPS). About 15 vol.% Al2O3 particles were formed in situ during the process. The unique combination of excellent bending strength of 1261 MPa (//c axis) and fracture toughness of 14.6 MPa m(1/2) (perpendicular to c axis) was achieved. Also, the high electrical and thermal conductivities were determined as 1.0 x 10(6) Omega(-1) m(-1) (//c axis) and 25.3 W (mK)(-1) (perpendicular to c axis), respectively. (C) 2014 Elsevier Ltd. All rights reserved.

    DOI

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    48
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  • Fabrication of c-axis-oriented zeolite L seed layer on porous zirconia substrate by electrophoretic deposition in strong magnetic field

    Chika Matsunaga, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Motohide Matsuda

    Key Engineering Materials   654   274 - 279  2015年  [査読有り]

     概要を見る

    Orientation technique based on the magneto-scientific crystal alignment phenomenon combined with electrophoretic deposition (EPD) technique was applied for the seeding process of zeolite L particles. Well-dispersed, ethanol-based zeolite L suspension was prepared and then consolidated on porous zirconia substrates by EPD. Conducting polypyrrole film synthesized on the zirconia substrate was used as an anodic substrate for the EPD process. The EPD was performed in a superconducting magnet with applying 12 T strong magnetic field to the suspension. The degree of orientation was characterized by XRD and compared with that of the zeolite L layer prepared by slip casting in a 12 T strong magnetic field using the same suspension.

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  • Surface modification of complex oxide powder with polyelectrolyte layers improving EPD characteristics

    Tetsuo Uchikoshi, Eiji Eto, Harue T. Suzuki, Chika Matsunaga, Kiyoshi Kobayashi, Tohru S. Suzuki, Hiroyuki Muto, Atsunori Matsuda

    Key Engineering Materials   654   255 - 260  2015年  [査読有り]

     概要を見る

    The surface modification of Gd doped ceria (GDC) and Sr- and Mg-codoped lanthanum gallate (LSGM) powders with cationic and anionic polyelectrolytes, Poly(diallyldimethylammonium chloride) (PDDA) and poly(2 -acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS), respevtively, was performed by the Layer by Layer (LbL) adsorption method to improve the surface-charging uniformity. The tri-layer of GDC/LSGM/GDC was deposited on a polypyrrole coated porous NiO-YSZ substrate by sequential EPD using the ethanol-based suspensions of the surface-modified powders. The topcoating of hydroxyl-propyl cellulose (HPC) on the deposited layers was conducted to control the drying rate with suppressing the cracking and peeling-off of the deposits. The advantage of the use of those polymers for the EPD process including the drying technique was demonstrated.

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  • Fabrication of textured alumina by magnetic alignment via gelcasting based on low-toxic system

    Agnieszka Szudarska, Tadeusz Mizerski, Yoshio Sakka, Tohru S. Suzuki, Mikolaj Szafran

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   34 ( 15 ) 3841 - 3848  2014年12月  [査読有り]

     概要を見る

    The controlled development of texture in ceramics allows to improve some electrical, piezoelectric and mechanical properties of advanced ceramics materials by tailoring the microstructure. A highly textured microstructure of undoped dense alumina was attained by applying a novel combination of gelcasting techniques with magnetic alignment followed by sintering. A newly synthesized low-toxic acrylic monomer based on galactose was introduced to the gelcasting procedure. Thermal analysis of the gelcast has been performed to examine decomposition process of the new binder and match appropriate sintering rate. The effectiveness of the proposed procedure has been related to rheological properties of the suspension by clarifying the influence of the powder and the dispersant content. It has been also related to the idle time of polymerization by clarifying the influence of the initiator content. The new method is compared to slip casting in high magnetic field that has been used widely so far. (C) 2014 Elsevier Ltd. All rights reserved.

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    20
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  • 磁場中スリップキャストとパルス通電焼結によるTi2AlN 配向体の創製

    武舍 翔太郎, 佐藤 仁俊, 鈴木 達, 藤本 憲次郎, 目 義雄

    Journal of the Japan Society of Powder and Powder Metallurgy   61 ( 11 ) 538 - 543  2014年11月  [査読有り]

  • Fabrication of textured Ti2AIN Ceramic by slip casting in a strong magnetic field and spark plasma sintering

    Shotaro Musha, Kimitoshi Sato, Tohru S. Suzuki, Kenjiro Fujimoto, Yoshio Sakka

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   61 ( 11 ) 538 - 543  2014年11月  [査読有り]

     概要を見る

    MAX phase materials are known to show unique properties with the combination of metallic and ceramic properties. Recently textured MAX phase materials have been expected to show excellent properties. Here Ti2AlN powders were synthesized from Ti, Al and TiN powders, or Ti and A1N powders heating at 1573 K-1773 K. Then highly textured Ti2AlN was fabricated by slip casting in a strong magnetic field and spark plasma sintering at 1473 K - 1773 K and the relative density was nearly 91%. The c-axis of the Ti2AlN grains were oriented parallel direction of the magnetic field, the lotgering orientation factor was determined 0.96. The nacre like structure was observed in the side surface of the textured sample.

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    5
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  • Fabrication of textured Ti3SiC2 ceramic by slip casting in a strong magnetic field and pressureless sintering

    Kimitoshi Sato, Mrinalini Mishra, Hiroto Hirano, Tohru S. Suzuki, Yoshio Sakka

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   122 ( 1429 ) 817 - 821  2014年09月  [査読有り]

     概要を見る

    Sinterable Ti3SiC2 powder was synthesized from a powder mixture with a molar ratio of 1.0Ti:0.3Al:1.2Si:2.0TiC by heating at 1200 degrees C in Ar flow. Almost single-phase peaks of Ti3SiC2 were observed in X-ray diffraction patterns. The powder was dispersed in ethanol using polyethylenimine (PEI) as the polymer dispersant. Textured dense Ti3SiC2 ceramics were successfully fabricated by slip casting in a strong magnetic field followed by pressureless sintering at 1400 degrees C for 2 h. The relative density of these Ti3SiC2 ceramics was 99.4%, and the bending strength, fracture toughness and electrical resistivity were 623 +/- 9 MPa, 5.9 +/- 0.1 MPa.m(1/2) and 0.31 mu Omega.mu, respectively. Compared with those of nontextured pressureless sintered samples of almost full density, the bending strength and fracture toughness of the textured Ti3SiC2 ceramics were increased by factors of 1.6 and 1.4, respectively. (C) 2014 The Ceramic Society of Japan. All rights reserved.

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    18
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  • Transparent ZnAl2O4 ceramics fabricated by spark plasma sintering

    Byung-Nam Kim, Keijiro Hiraga, Ahrong Jeong, Chungfeng Hu, Tohru S. Suzuki, Jon-Do Yun, Yoshio Sakka

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   122 ( 1429 ) 784 - 787  2014年09月  [査読有り]

     概要を見る

    Highly transparent zinc aluminate ceramics were fabricated by the solid-state reaction using a spark plasma sintering machine. The sintered body exhibited a microstructure consisting of submicron-sized grains and extremely low porosities. Annealing of the sintered body in air improved the transmission close to the theoretical limit in a wavelength range of 1-5 mu m. The band gap energy estimated from the absorption coefficient was 4.3 eV. The Young's modulus and the bulk modulus measured for the fully dense zinc aluminates were 282 and 211 GPa, respectively. (C) 2014 The Ceramic Society of Japan. All rights reserved.

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    24
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  • Fabrication of Textured Ceramics Using Mn and Nb-doped Hexagonal BaTiO3 by an Electrophoretic Deposition in a High Magnetic Field

    Eigo Kobayashi, Shintaro Ueno, Kouichi Nakashima, Nobuhiro Kumada, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka, Yasunari Miwa, Shinichiro Kawada, Suetake Omiya, Noriyuki Kubodera, Ichiro Fujii, Satoshi Wada

    Transactions of the Materials Research Society of Japan   39 ( 2 ) 199 - 202  2014年08月  [査読有り]

     概要を見る

    (111)-oriented Mn and Nb-doped barium titanate (BaTiO3, BT) ceramics with fine grains were fabricated with an electrophoretic deposition (EPD) method in a high magnetic field and a topotactic phase transition. Initially, accumulations of (0001)-oriented hexagonal Ba(Ti0.95Mn0.05)O3 particles added with 2.5 mol%-Nb2O5 powder were prepared by the EPD method in the high magnetic field of 12 T. Then, the (111)-oriented, Mn and Nb-doped pseudo-cubic BT ceramics with fine grains of ~0.4 μm in diameter were obtained via the topotactic phase transition, with the degree of the (111) orientation being as high as 79 %. The piezoelectric properties of the oriented ceramics were also studied.

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  • Dispersion/Coagulation and Colloidal Processing of Ceramic Particles

    Tetsuo Uchikoshi, Tohru S. Suzuki

    Journal of the Society of Powder Technology, Japan   51 ( 6 ) 462 - 472  2014年06月  [査読有り]

     概要を見る

    直径が10-7〜10-9 m程度の大きさの粒子が気体や液体に分散している状態をコロイドという。サブミクロン〜ナノサイズのセラミックスの粒子も、水や非水溶媒などの液体に分散すると、通常のコロイド粒子と全く同じ性質を示す。コロイド粒子のサスペンションから、粒子を適当な方法で凝集させると、緻密な固化成形体を得ることができる。スラリーを経由する粉体成形法はコロイドプロセスと呼ばれ、複雑形状のセラミックス製品を製造する方法として注目されている。本稿では、セラミックスを中心にコロイド粒子の分散、凝集についてまず概説し、次いでコロイドプロセスにおけるサスペンション調製の注意点について、例をあげて紹介する。

    DOI

  • Preparation of Textured Li1+x-yNb1-x-3yTix+4yO3 Solid Solution in a High Magnetic Field

    Hiromi Nakano, Shiho Suehiro, Tohru S. Suzuki

    Materials Science Forum   783-786   2480 - 2484  2014年05月  [査読有り]

     概要を見る

    In the Li2O-Nb2O5-TiO2 system, Li1+x-yNb1-x-3yTix+4yO3 (0.06 &amp;#61603; x &amp;#61603; 0.33, 0 &amp;#61603; y &amp;#61603; 0.09) (LNT) forms with a superstructure, and this is so-called M-phase. The superstructure of the M-phase is formed by periodical insertion of an intergrowth layer in a matrix having a trigonal structure. As an application of the unique qualities of an electro-ceramic with an anisotropy structure, we prepared an oriented LNT ceramic by slip casting in a high magnetic field (12 T). Consequently, c-axis of the LNT powder was aligned parallel to the magnetic field. The orientation degree was determined using a Lotgering factor and high orientation degrees (over 90 %) were achieved.

    DOI

  • Magnesium ion distribution and defect concentrations of MgO-doped lanthanum silicate oxyapatite

    Kiyoshi Kobayashi, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    SOLID STATE IONICS   258   24 - 29  2014年05月  [査読有り]

     概要を見る

    The distribution of magnesium ions at the lanthanum and silicon sites in MgO-doped lanthanum silicate oxyapatite as well as the concentration of neutral lanthanum vacancies were determined using densities and chemical compositions of the doped samples. On the basis of the density data, it was found that magnesium ions are substituted at the silicon site as well as the lanthanum sites in the oxyapatite phase. Owing to the existence of neutral lanthanum vacancies, it was difficult to evaluate the number of the oxygen ions present, Which are related to the oxygen ion conductivity of the compound, from the chemical compositions of the samples alone. Further, it was found that the fact that the total conductivity of MgO-doped lanthanum silicate oxyapatite depends on the MgO concentration as well as that of other defects could not be explained on the basis of conventional defect chemistry. (c) 2014 Elsevier B.V. All rights reserved.

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    5
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  • 静電吸着法により設計された粉末均一混合体からのランタンシリケートオキシアパタイトセラ ミックスの作製

    高橋 聡志, 打越 哲郎, 小林 清, 鈴木 達, 目 義雄, 石垣隆正

    JOURNAL OF THE SOCIETY OF INORGANIC MATERIALS,JAPAN   21 ( 370 ) 155 - 161  2014年05月  [査読有り]

     概要を見る

    La(OH)3,SiO2粉末を出発原料とした固相反応により,ランタンシリケートオキシアパタイトセラミックスの緻密体を作製した.水溶媒中で正に帯電したLa(OH)3粒子と,負に帯電したSiO2粒子をヘテロ凝集させることで両粉末の均一混合凝集粉を得た。このとき,La(OH)3については,ポリカチオン(poly-diallyldimethylammonium chloride)とポリアニオン(poly-sodium 4-styrenesulfonate)をLayer-by-Layer法を適用して,交互に吸着させることにより,正のゼータ電位を向上させた.得られたヘテロ凝集粉は,スリップキャストにより成形し,大気中で1600 ℃,10 時間焼成した.この焼成体がランタンシリケートオキシアパタイトの単相よりなることがXRDにより確かめられた.また,焼成体の相対密度は97 %であった.

  • Fabrication of Textured Ti3SiC2 Ceramics by Slip Casting in a Magnetic Field and Pulsed Electric Current Sintering

    Kimitoshi Sato, Hiroto Hirano, Tohru Suzuki, Takamasa Ishigaki, Yoshio Sakka

    Journal of the Society of Powder Technology, Japan   51 ( 3 ) 163 - 168  2014年04月  [査読有り]

     概要を見る

    本研究では、MAX相セラミックスの中で、最も検討されているTi3SiC2を用いて、薄くて大きな板状粒子どうしの結合力を低くして、破壊される際の粒子引き抜く効果を高め、高強度でありながら、高靱性で、壊れにくい材料の創製を目的とした。

    DOI

  • Effect of Ultrasonication on Colloidal Dispersion of Al2O3 and ZrO2 Powders in pH Controlled Suspension

    Tohru S. Suzuki, Yoshio Sakka, Keishi Nakano, Keijiro Hiraga

    Materials Transactions, JIM   39 ( 6 ) 689 - 692  2014年03月

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    34
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  • Microstructure and Anisotropic Properties of Textured ZrB2and ZrB2-MoSi2 Ceramics Prepared by Strong Magnetic Field Alignment

    Wen-Wen Wu, Yoshio Sakka, Tohru S. Suzuki, Guo-Jun Zhang

    International Journal of Applied Ceramic Technology   11 ( 2 ) 218 - 227  2014年03月  [査読有り]

     概要を見る

    Dense highly textured ZrB2 and ZrB2-MoSi2 ceramics were fabricated via strong magnetic field alignment method during slip casting, followed by spark plasma sintering, using ZrB2 and MoSi2 as starting powders. The alignment of MoSi2 in the same direction of ZrB2 enhanced the degree of orientation of ZrB2, decreased the grain size but increased the aspect ratio of platelet-like ZrB2 grains. Mechanical property measurements revealed higher Vickers hardness, flexural strength but lower Young’s modulus in c-axis direction than a, b-axis direction. Oxidation resistance was obviously better on the surface of c-axis direction.

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    26
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  • Reactive spark plasma sintering of binderless WC ceramics at 1500°C

    Shi-Kuan Sun, Guo-Jun Zhang, Wen-Wen Wu, Ji-Xuan Liu, Ji Zou, Tohru Suzuki, Yoshio Sakka

    International Journal of Refractory Metals and Hard Materials   43   42 - 45  2014年03月  [査読有り]

     概要を見る

    Binderless WC ceramicswere prepared by reactive spark plasma sintering, using tungsten trioxide, tungsten and carbon black as the starting materials. Phase assemblages and microstructure of the as-sintered ceramics were investigated. It was found that graphite existed as an impurity phase due to the volatilization of WO3, and Wcould compensate for the WO3 loss to form WC with a single phase. Benefiting from the enhanced sinterability,WC ceramics with high relative density and good hardness could be obtained at temperature as low as 1500℃

    DOI

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    30
    被引用数
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  • Densification of SiC by colloidal processing and SPS without sintering additives

    T. S. Suzuki, T. Uchikoshi, Y. Sakka

    ADVANCES IN APPLIED CERAMICS   113 ( 2 ) 85 - 88  2014年02月  [査読有り]

     概要を見る

    Silicon carbide is one of the most important ceramics used as structural and functional materials in a wide variety of applications. Many studies have reported the densification of SiC using oxide and nonoxide additives such as the Al2O3, B4C and Al-B-C system. However, it is difficult to densify SiC at temperatures below 2000 degrees C without sintering additives even if spark plasma sintering (SPS) is used. The authors attempted to densify SiC using colloidal processing and SPS without sintering additives. A commercially available SiC powder with the average particle size of 0.55 mm was used as the starting material. The densities of the green body prepared by slip casting and the sintered body by SPS were 65.5 and 98.7% respectively.

    DOI

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    13
    被引用数
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  • Microstructure and high-temperature strength of textured and non-textured ZrB2 ceramics

    Wen-Wen Wu, Yoshio Sakka, Mehdi Estili, Tohru S. Suzuki, Toshiyuki Nishimura, Guo-Jun Zhang

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   15 ( 1 ) 014202  2014年02月  [査読有り]

     概要を見る

    Zirconium diboride (ZrB2) ceramic possesses a unique combination of nice mechanical performance, high melting point (&gt; 3000 degrees C) and great high-temperature oxidation resistance (up to 1600 degrees C), which makes it a promising material system for ever-increasing ultra-high temperature (UHT) applications. However, ZrB2 suffers from poor mechanical performance at UHTs, which could strongly limit its applications at UHT. Here, we successfully demonstrate that texturing is an effective strategy to greatly enhance the flexural strength of monolithic ZrB2, reaching a high value of 810 +/- 60 MPa at 1600 degrees C when loaded in c-axis direction. We thoroughly discuss the strengthening mechanism by in-depth microstructural observations and analysis. Our discovery has technological and scientific implications for other UHT ceramic systems, especially those using ZrB2 as a matrix.

    DOI

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    45
    被引用数
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  • Preparation of Barium Titanate Nanoperticles with Necking structure/Polymer Complex and Their Dielectric Properties

    Shuhei Tsukamoto, Ichiro Fujii, Kouichi Nakashima, Takahiro Takei, Nobuhiro Kumada, Satoshi Wada, Tohru Suzuki, Tetsuro Uchikoshi, Yoshio Sakka

    ELECTROCERAMICS IN JAPAN XVI   582   23 - +  2014年  [査読有り]

     概要を見る

    Barium titanate (BaTiO3) nanoparticles were prepared by a 2-step thermal decomposition method using nano oxalate particles. BaTiO3 nanoparticles were characterized using various methods. Accumulations were prepared by electrophoresis deposition method using the obtained BaTiO3 nanoparticles. They were performed necking structure by a solvothermal method. Polymer was infiltrated into the accumulations in vacuum to prepare a polymer film capacitor.

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  • Preparation of Barium Titanate Grain-oriented Ceramics by Electrophoresis Deposition Method under High Magnetic Field using Single-domain Nanoparticles

    Satoshi Wada, Tatsuya Kita, Ichiro Fujii, Kouichi Nakashima, Takahiro Takei, Nobuhiro Kumada, Toru Suzuki, Tetsuro Uchikoshi, Yoshio Sakka, Yasunari Miwa, Shinichiro Kawada, Masahiko Kimura, Yoshihiro Kuroiwa

    ELECTROCERAMICS IN JAPAN XVI   582   27 - +  2014年  [査読有り]

     概要を見る

    Barium titanate (BaTiO3, BT) gain-oriented ceramics were prepared by electrophoresis deposition (EPD) method under high magnetic field (HM-EPD) of 12 T. For this objective, the BT single-domain nanoparticles with high c/a ratio of 1.008 and size of 103 nm were prepared by two-step thermal decomposition method. Using the BT nanoparticle slurry, BT nanoparticle accumulations were prepared by EPD or slipcasting (SC) methods with/without high magnetic field. After binder burnout, these accumulations were sintered at 1350 degrees C and it was revealed that only the BT ceramics prepared by the HM-EPD method was assigned to grain-oriented ceramics with weak preferential crystallographic orientation along [110] direction.

    DOI

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    3
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  • Analysis of abnormal grain growth of oriented LiCoO2 prepared by slip casting in a strong magnetic field

    Hideto Yamada, Tohru S. Suzuki, Tetsuo Uchikoshi, Masato Hozumi, Toshiya Saito, Yoshio Sakka

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   33 ( 15-16 ) 3059 - 3064  2013年12月  [査読有り]

     概要を見る

    The relationship between the development of the crystallographic orientation and the grain growth behavior were studied. The degree of orientations of the green compacts and sintered samples were evaluated by the Lotgering factor. The f(0 0 l) of all the samples were drastically increased with the increasing applied magnetic field strength. The f(0 0 l) of the samples sintered at 1223 K were improved in comparison to those of the green compacts. However, the f(0 0 l) value of the samples sintered at 1273 K were not increased at 4 T or lower. To characterize the grain growth process, these samples were analyzed using electron backscatter diffraction (EBSD). The sintered samples prepared in the magnetic field at 4 T or lower showed abnormal grain growth. The samples with an applied magnetic field of 8 T or higher had no abnormal grain growth. It was revealed that the orientation angle of the particles has an effect on the grain growth. (C) 2013 Elsevier Ltd. All rights reserved.

    DOI

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  • AAO-template assisted synthesis and size control of one-dimensional TiO2 nanomaterials

    Kazufumi Aisu, Tohru S. Suzuki, Eri Nakamura, Hiroya Abe, Yoshikazu Suzuki

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   121 ( 1418 ) 915 - 918  2013年10月  [査読有り]

     概要を見る

    Anodic aluminum oxide (AAO)-template method is a synthesis process that AAO film with uniform pores is used as a template for 1-D nanostructure. In this study, we have synthesized well-defined TiO2 nanorods or nanowires using AAO-template method. As for the first method, AAO template was immersed for 1 min in the Ti precursor solution with slightly decompressed atmosphere (Immersion setting, IS). As for the second method, AAO template was put on the filtering flask as a cover plate. Precursor solution was dropped on the AAO template for 1 min with vacuuming from the bottom part of AAO template (Vacuum and drop setting, VDS). With the calcination and HCl treatment to remove AAO, polycrystalline TiO2 anatase nanorods and nanowires were successfully fabricated, just by changing the sample setting, viz., IS and VDS, respectively. (C) 2013 The Ceramic Society of Japan. All rights reserved.

    DOI

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    11
    被引用数
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  • Hydrothermal transformation of magnetically orientation-controlled seed layer into orientation-retained dense, continuous film in clear reaction solution

    Chika Matsunaga, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Motohide Matsuda

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   121 ( 1415 ) 550 - 554  2013年07月  [査読有り]

     概要を見る

    Randomly-oriented and b-axis oriented mordenite seed layers, which were pre-fabricated out of and in a strong 12T magnetic field, were hydrothermally treated in clear reaction solutions with molar ratios of 6Na(2)O:Al2O3:30SiO(2):xH(2)O ( x = 1500, 3500 and 10000). Crystal growth of the seed particles only slightly occurred in the solution of x = 10000, but occurred in the solutions of x = 1500 and 3500, giving rise to densified films. However, the films treated with x = 1500 were composed of two layers with different morphologies; i.e., the precipitation of crystals from the solution was considered to induce the upper layer in the bi-layered films. Homogenized films were formed in the solutions of x = 3500. The initial orientation of the seed layer was retained in the continuous films treated at x = 3500. Thus, dense, continuous mordenite films with random and b-axis orientations were successfully fabricated from random and b-axis oriented seed layers by hydrothermal treatment in the clear reaction solutions at the molar ratio of 6Na(2)O:Al2O3:30SiO(2):3500H(2)O. (C)2013 The Ceramic Society of Japan. All rights reserved.

    DOI

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    被引用数
    (Scopus)
  • Reactive spark plasma sintering of ZrC and HfC ceramics with fine microstructures

    Shi-Kuan Sun, Guo-Jun Zhang, Wen-Wen Wu, Ji-Xuan Liu, Tohru Suzuki, Yoshio Sakka

    Scripta Materialia   69 ( 2 ) 139 - 142  2013年07月  [査読有り]

     概要を見る

    Zirconium carbide and hafnium carbide ceramics were prepared by reactive spark plasma sintering, using oxides and carbon black as the raw materials. The phase and microstructure evolution during the sintering process was investigated. It was found that ZrC and HfC powder intermediates were formed at 1750 and 1800 °C, respectively. Due to the high sinterability of the in situ formed carbide particles, samples with a fine microstructure could be densified at a relatively low temperature. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI

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    51
    被引用数
    (Scopus)
  • Anisotropy in activation energy of textured LiCoO2 for the initial stage of sintering

    H. Yamada, T. S. Suzuki, T. Uchikoshi, M. Hozumi, T. Saito, Y. Sakka

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   33 ( 5 ) 1037 - 1044  2013年05月  [査読有り]

     概要を見る

    The anisotropic initial sintering of oriented LiCoO2 green compacts prepared by slip casting in a strong magnetic field was studied. The activation energy and the mechanism of the initial stage of sintering were analyzed in order to understand the effect of the orientation. The analysis was carried out using constant rate heating (CRH). The activation energy of the initial stages of sintering for random, a, b-axes and c-axis direction was evaluated from the Arrhenius plots of the dilatometric measurements. It was confirmed that the activation energy of the c-axis direction was larger than that of the a, b-axes direction at the initial stage of sintering. The anisotropic shrinkage was attributed to the differences in the surface energies. (C) 2012 Elsevier Ltd. All rights reserved.

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • Two-dimensional orientation in Bi4 Ti3 O12 prepared using platelet particles and a magnetic field

    Tohru S. Suzuki, Yasunari Miwa, Shinichiro Kawada, Masahiko Kimura, Tetsuo Uchikoshi, Yoshio Sakka

    Journal of the American Ceramic Society   96 ( 4 ) 1085 - 1089  2013年04月  [査読有り]

     概要を見る

    Tailoring the crystallographic orientation in piezoelectric ceramics is very useful for improving their properties. Orientation in ceramics can be controlled by templated grain growth, hot forging, etc. We have focused on using a strong magnetic field for the crystallographic orientation even in diamagnetic ceramics. In a previous study, although only a one-directional orientation could be controlled by these methods, it was difficult to control the multi-axis orientation in the ceramics. In this study, we demonstrated that alignments of the c-axis and the &lt
    100&gt
    axis in Bi4Ti 3O12 piezoelectric ceramics were controlled by using a strong magnetic field as well as platelet particles. We also estimated the degree of orientation by an electron back scattering diffraction analysis. When the magnetic field was applied to the platelet particles, appropriately 80% of the grains were aligned with the tilt angle made by the c-axis and the vertical direction less than 10° and 73% of grains were oriented with the angle between the &lt
    100&gt
    axis and the magnetic field less than 10°. © 2013 The American Ceramic Society.

    DOI

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    14
    被引用数
    (Scopus)
  • 多孔質セラミックス基板への配向制御されたL型ゼオライト層の電気泳動堆積

    UCHIKOSHI, Tetsuo, MATSUNAGA, Chika, SUZUKI, Tohru, SAKKA, Yoshio, MotohideMATSUDA

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   121 ( 1412 ) 370 - 372  2013年04月  [査読有り]

     概要を見る

    Magneto-scientific technique combined with colloidal processing was applied to obtain crystalline-oriented zeolite L seed layers. Well-dispersed non-aqueous suspensions of the zeolite L were prepared for the fabrication of thin seed layers on porous substrates by electrophoretic deposition (EPD) in a superconducting magnet. The c-axis oriented seed layers of the zeolite L was successfully obtained on porous YSZ substrates by EPD under the magnetic field.

    DOI

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    4
    被引用数
    (Scopus)
  • Fabrication of Textured BaTiO3 Ceramics by Electrophoretic Deposition in A High Magnetic Field using Single-domain Particles

    Ichiro Fujii, Tatsuya Kita, Kouichi Nakashima, Takahiro Takei, Nobuhiro Kumada, Tohru S. Suzuki, Tetsuro Uchikoshi, Yoshio Sakka, Yasunari Miwa, Shinichiro Kawada, Masahiko Kimura, Yoshihiro Kuroiwa, Satoshi Wada

    Transactions of Materials Research Society of Japan   38   41 - 44  2013年  [査読有り]

    DOI

  • Fabrication of textured alpha-alumina in high magnetic field via gelcasting with the use of glucose derivative

    Paulina Wiecinska, Yoshio Sakka, Tohru S. Suzuki, Tetsuo Uchikoshi, Tadeusz Mizerski, Mikolaj Szafran

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   121 ( 1409 ) 89 - 94  2013年01月  [査読有り]

     概要を見る

    Textured ceramic materials arouse recently great interest due to the effective improvement of their physical and mechanical properties compared to those not crystalline oriented. Feeble magnetic ceramics, such as alumina can be textured under high magnetic field of 12T during shaping process. The connection between shaping by gelcasting method and crystalline orientation of alpha-alumina in high magnetic field is reported in this paper. Gelcasting allows obtaining high-quality complex-shaped elements with small quantities of organic binders. A new environmentally friendly compound on the basis of glucose (3-O-acryloyl-D-glucose) was synthesized and applied as a monomer in gelcasting process. The ceramic slurries of solid loading 30-50 vol % have been exposed to high magnetic field at the time of consolidation through an in situ polymerization of used monomer. The degree of crystalline orientation of sintered at 1600 degrees C bodies was evaluated by X-ray diffraction (XRD). (C)2013 The Ceramic Society of Japan. All rights reserved.

    DOI

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    7
    被引用数
    (Scopus)
  • Fabrication of the c-axis oriented zeolite L compacts using strong magnetic field

    Chika Matsunaga, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Motohide Matsuda

    Materials Letters   93   408 - 410  2013年  [査読有り]

     概要を見る

    Preferentially oriented thick and thin compacts of zeolite L with a large anisotropy in their crystal structures were successfully prepared by colloidal processes in a strong 12 T magnetic field. The orientation along the direction of the applied magnetic field was characterized by XRD using slip-cast compacts. In the present experiments, it was revealed that the c-axis of zeolite L was an easy-magnetization axis. The c-axis oriented zeolite L layer with a thickness of ca. 3 μm was formed on a porous ceramics substrate via electrophoretic deposition in a strong magnetic field applied perpendicular to the surface of the substrate. © 2012 Elsevier B.V.

    DOI

    Scopus

    10
    被引用数
    (Scopus)
  • Fabrication of textured Ti3AlC2 by spark plasma sintering and their anisotropic mechanical properties

    Yutaka Mizuno, Kimitoshi Sato, Mishra Mrinalini, Tohru S. Suzuki, Yoshio Sakka

    Journal of the Ceramic Society of Japan   121 ( 1412 ) 366 - 369  2013年  [査読有り]

     概要を見る

    Textured, dense, polycrystalline Ti3AlC2 ceramics was fabricated by spark plasma sintering (SPS) of plate-like Ti3AlC 2 powder nsynthesized by a reactive SPS-heat treatment of elemental Ti, Al and carbon black powders. The relative density was found to nexceed 99% for samples sintered at 1573 K. The Lotgering orientation factor was determined to be f(00l) = 0.69. The crack npropagation behavior near the indentation marks formed by a force of 49N was observed. On the surface parallel to the SPSloading ndirection, the toughening mechanism of crack deflection was observed. n©2013 The Ceramic Society of Japan. All rights reserved.

    DOI

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    24
    被引用数
    (Scopus)
  • Microstructure control of potassium niobate porous ceramics and their sensor properties

    Kazuki Maeda, Kenta Yamashita, Ichiro Fujii, Kouichi Nakashima, Tohru S. Suzuki, Yoshihiro Kuroiwa, Satoshi Wada

    ELECTROCERAMICS IN JAPAN XV   566   241 - 244  2013年  [査読有り]

     概要を見る

    Porous potassium niobate (KNbO3, KN) system ceramics were prepared by spark plasma sintering (SPS) method using carbon black (CB, 5 mu m). First, the powders of raw materials were mixed in ethanol by ball milling, and then calcined. Obtained KN powders with CB were sintered by SPS in argon atmosphere. Their piezoelectric properties were measured and a relationship between porosity, pore size, and sensor properties was studied. It was found that d(33) increased as pore size decreased. Thus, pore size was important for the improvement of value of g(33)/rho.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Preparation of Ceramics/Polymer Film Capacitor using Barium Titanate Nanoparticles with High Dielectric Property and Their Dielectric Property

    Tatsuya Kita, Shuhei Kondo, Shuhei Tsukamoto, Takahiro Takei, Nobuhiro Kumada, Kouichi Nakashima, Ichiro Fujii, Toru Suzuki, Tetsuro Uchikoshi, Yoshio Sakka, Satoshi Wada

    ELECTROCERAMICS IN JAPAN XV   566   54 - 58  2013年  [査読有り]

     概要を見る

    Barium titanate (BaTiO3, BT) nanoparticle accumulations were prepared by an electrophoresis deposition (EPD) method, and their dielectric properties were measured. The BTKK accumulation exhibited high dielectric constant of 100. To prepare the BT ceramic/polymer film capacitors, the polymer was injected into the accumulations in vacuum. Finally, dielectric properties were measured, and it was clarified that the dielectric constant of the ceramic/polymer film capacitors became smaller than those of the accumulation because of surfactant used as particle dispersion.

    DOI

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  • Effect of Hydrothermal Treatment on the Piezoelectric Response of Oriented Barium Titanate Ceramics

    Ichiro Fujii, Rintaro Mori, Kouichi Nakashima, Hiroshi Hayashi, Yoshitaka Nagamori, Yuichi Yamamoto, Tohru S. Suzuki, Satoshi Wada

    ELECTROCERAMICS IN JAPAN XV   566   45 - 49  2013年  [査読有り]

     概要を見る

    The piezoelectric response of [110]-oriented, fine-grained BaTiO3 ceramics was investigated. It was found that an exposure of the BaTiO3 compacts to high-pressure, high-temperature steam in an autoclave promoted the orientation of the sintered ceramics. As temperature in the autoclave increased, the orientation increased. A large small-field piezoelectric constant of d3(3) = 517 pC/N was observed for the oriented BaTiO3 ceramics with the grain size of 1.76 and the Lotgering factor of 85.3 %.

    DOI

    Scopus

  • Ideal design of textured LiCoO2 sintered electrode for Li-ion secondary battery

    Hideto Yamada, Tohru S. Suzuki, Tetsuo Uchikoshi, Masato Hozumi, Toshiya Saito, Yoshio Sakka

    APL Materials   1 ( 4 ) 042110  2013年  [査読有り]

     概要を見る

    To improve the energy density and practical realization of the all-solid-state Li-ion secondary battery, the principal requirement is a high electric conductivity in the densely sintered positive electrode. To accomplish this task, we focused on the anisotropic Li-ion and electron conductivities of the LiCoO2. As a result of our work, the ideal design of the texturing, perpendicular alignment of the c-plane and horizontal but random orientation of the c-axis on the electrode, was proposed. The battery performance of the ideal textured cell fabricated using a rotating strong magnetic field has a significantly higher performance than a randomly oriented cell. © 2013 Author(s).

    DOI

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    20
    被引用数
    (Scopus)
  • Orientation Control of Layered Perovskite La2NiO4 Using Strong Magnetic Field for High Performance Cathode of SOFC

    Chunxi Hai, Miwa Hashimoto, Chika Matsunaga, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Motohide Matsuda

    SOLID OXIDE FUEL CELLS 13 (SOFC-XIII)   57 ( 1 ) 1969 - 1978  2013年  [査読有り]

     概要を見る

    Aiming at designing a high performance cathode for solid oxide fuel cells (SOFC), orientation of the La2NiO4 (LNO) with layered structure was controlled by slip casing in a strong magnetic field. The oriented LNO compact along a, b-axes was successfully fabricated in a static magnetic field. The c-axis oriented one was managed by applying a rotating magnetic field perpendicular to the slip casting direction. Enhanced conductivities were valid along a,b-axes orientation which resulted in the accelerated mobility of conducive carriers. From those results, it is clearly expected that the orientation control of LNO brings about high performance in the cathode of SOFC.

    DOI

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    3
    被引用数
    (Scopus)
  • Uniformly Porous MgTi2O5 with Narrow Pore-Size Distribution: XAFS Study, Improved In Situ Synthesis, and New In Situ Surface Coating

    Yoshikazu Suzuki, Tohru S. Suzuki, Yutaka Shinoda, Katsumi Yoshida

    ADVANCED ENGINEERING MATERIALS   14 ( 12 ) 1134 - 1138  2012年12月  [査読有り]

     概要を見る

    Porous MgTi2O5 ceramics with pseudobrookite-type structure have been prepared by in situ processing (viz. reactive sintering). In this communication, further studies have been carried out in order to evolve the porous MgTi2O5, viz., (1) X-ray absorption fine structure (XAFS) study of porous MgTi2O5, (2) improved in situ synthesis (i.e., more precise stoichiometric control), and (3) new in situ surface coating, which enables in situ MgTi2O5 synthesis, in situ uniform pore formation, and in situ surface coating in only one-step heating.

    DOI

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    22
    被引用数
    (Scopus)
  • Fabrication and Analysis of the Oriented LiCoO2 by Slip Casting in a Strong Magnetic Field

    Hideto Yamada, Tohru S. Suzuki, Tetsuo Uchikoshi, Masato Hozumi, Keiichi Kohama, Yoshio Sakka

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   95 ( 11 ) 3428 - 3433  2012年11月  [査読有り]

     概要を見る

    We attempted to fabricate the oriented bulk LiCoO2 using slip casting in a strong magnetic field. The shrinkage of the oriented green compact was measured using a dilatometer. It was confirmed that the oriented green compact undergoes anisotropic shrinkage. The shrinkage in the c-plane direction of the oriented LiCoO2 was greater than that in the c-axis direction. The degree of orientation in the bulk LiCoO2 was analyzed using XRD and electron backscatter diffraction; the c-axis of LiCoO2 was oriented parallel to the magnetic field. Moreover, the orientation parameter, r, was 0.234, indicating that 92% of the grains was aligned with a tilt angle less than 10 degrees between the c-axis and the magnetic field direction. The texturing led LiCoO2 to anisotropy in the electric conductivity between the c-plane and c-axis directions. It was concluded that the magneto-scientific technique is a powerful method to fabricate highly oriented bulk LiCoO2.

    DOI

    Scopus

    10
    被引用数
    (Scopus)
  • Textured Ti3SiC2 by gelcasting in a strong magnetic field

    Mrinalini Mishra, Yoshio Sakka, Agneiska Szudarska, Mikolaj Szafran, Tohru S. Suzuki, Uchikoshi Tetsuo

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   120 ( 1407 ) 544 - 547  2012年11月  [査読有り]

     概要を見る

    We present a novel application of gelcasting in a strong magnetic field for texture development in the ternary MAX phase carbide-Ti3SiC2. The applicability of a low-toxic and water soluble monomer-glycerol monoacrylate for gelcasting Ti3SiC2 has been shown. Textured green bodies of Ti3SiC2 with a,b-axis oriented along the direction parallel to the applied magnetic field could be fabricated. The relative green density was found to increase from 34 to 58% with increasing solid-loading (30 to 55 vol %) of the suspension but at the cost of the degree of orientation. The Lotgering's orientation factor- f(L(001)) - on the textured top surfaces varied from 0.81 to 0.2 as the solid-loading increased from 30 to 55 vol %. (C)2012 The Ceramic Society of Japan. All rights reserved.

    DOI

    Scopus

    10
    被引用数
    (Scopus)
  • 直流パルス電場を用いた電気泳動堆積プロセスとその特徴

    打越 哲郎, 鈴木 達, 目 義雄

    MATERIALS INTEGRATION   25 ( 11 ) 34 - 39  2012年11月

     概要を見る

    最近、我々は、水系スラリーのEPDにおいて、通常の連続通電場ではなくDCパルス電場(矩形波)を印加すると、気泡発生のない良好な膜質の堆積層が形成される場合があることを見出し、粒子堆積速度や気泡生成・抑止に及ぼす条件を系統的に検討してきた。この方法は、印加する電場のパルス電圧・電流やON/OFF時間の制御だけで、電極基板の材質によらず、また、カソードでポジション、アノードでポジションのいずれのケースにおいても適用できる。本稿では、直流パルス電場を用いたEPDプロセスとその特徴について、最近のデータを紹介して解説する。

    CiNii

  • 強磁場と板状粒子を用いたBi3TiNbO9圧電セラミックスの2軸配向制御

    鈴木 達, 打越 哲郎, 目 義雄, 三輪 恭也, 川田 慎一郎, 木村 雅彦

    マチリアルインテグレーション   25 ( 11 ) 29 - 33  2012年11月

     概要を見る

    現在のセラミックスにおける磁場配向技術では、そのほとんどが結晶軸の一軸のみの配向制御にとどまっているが、組織制御としては配向の多軸化へとその高度化が望まれる。上記のように様々な材料への展開が可能なTGGプロセスおよび磁場プロセスを組み合わせたセラミックスプロセスを新規に提案することで、より精緻な配向構造を制御できると期待できる。そこで、本報においては、この配向方位の多軸化の取り組みとして、板状粒子と強磁場を組み合わせた組織制御による2軸配向を試みたので紹介する。

    CiNii

  • Fabrication of ceria- and lanthanium gallate-based solid electrolyte layers on porous NiO-YSZ by sequential electrophoretic deposition process

    Harae T. Suzuki, Tetsuo Uchikoshi, Kiyoshi Kobayashi, Kenji Furuya, Tohru S. Suzuki, Yoshio Sakka, Fumio Munakata

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   59 ( 11 ) 626 - 630  2012年11月  [査読有り]

     概要を見る

    The microstructure control of NiO-YSZ for SOFC anode was performed using rice starch as pore former. Positively-charged NiO-YSZ slurry and negatively-charge rice starch slurry were heterocoaglated and then filtrated to prepare green plates. The rice starch was burnt out by sintering in air and porous NiO-YSZ electrode was obtained. The surface of NiO-YSZ substrate was coated with conductive polypyrrole to give electric conduction that is essential for EPD processing. The GDC/LSGM/GDC laminar coating was conducted by sequential deposition on the same substrate. The electrolyte layers were easily sintered together on the anode without cracking and peering-off at the interfaces.

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • 全固体二次電池の開発に向けたLiCoO2配向バルク体の創製

    山田 英登, 鈴木 達, 打越 哲郎, 穂積正人, 小谷幸成, 目 義雄

    MATERIALS INTEGRATION   25 ( 10 ) 61 - 66  2012年10月

     概要を見る

    We attempted to fabricate the oriented bulk LiCoO2 using slip casting in a strong magnetic field. The degree of orientation in the bulk LiCoO2 was analyzed using electron backscatter diffraction; the c-axis of LiCoO2 was oriented parallel to the magnetic field. Moreover, the orientation parameter, r, was 0.234, indicating that 92% of the grains was aligned with a tilt angle less than 10° between the c-axis and the magnetic field direction. The texturing led LiCoO2 to anisotropy in the electric conductivity between the c-plane and c-axis directions. It was concluded that the magneto-scientific technique is a powerful method to fabricate highly oriented bulk LiCoO2.

    CiNii

  • Electrophoretic Deposition of Ti3SiC2 and Texture Development in a Strong Magnetic Field

    Mrinalini Mishra, Yoshio Sakka, Chungfeng Hu, Tohru S. Suzuki, Tetsuo Uchikoshi, Laxmidhar Besra

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   95 ( 9 ) 2857 - 2862  2012年09月  [査読有り]

     概要を見る

    In this study,we have shown the applicability of electrophoretic deposition (EPD) for shape-forming in Ti3SiC2-a representative MAX phase; and viability of texture development thereof by application of a strong magnetic field (12 T). The dispersion characteristics of Ti3SiC2 suspension were investigated in terms of surface charge, rheological measurement, and adsorption study. Polyethyleneimine has been used as dispersant to stabilize the suspension. It was found that the iso-electric point (IEP) of Ti3SiC2 powder was pHIEP 4. The surface charge of powder changed in presence of the Polyethyleneimine dispersant and IEP shifted significantly towards basic pH 10. The shift in IEP has been quantified in terms of ?G0SP, the specific free energy of adsorption between the surface sites and the adsorbing polyelectrolyte (PEI) (The value of ?G0SP obtained is -9.521 RT units). The optimized suspension parameters for EPD were determined as 10 vol% Ti3SiC2 and 1 dwb PEI in 50% ethanolic water at pH similar to 7. X-ray diffraction analysis of the textured samples developed, revealed that the preferred orientation of Ti3SiC2 grains parallel to the magnetic field direction was along the a, b-axis (The Lotgering orientation factors on the textured top surface and textured side surface were determined as fL(hk0) = 0.35 and fL(00l) = 0.75, respectively).

    DOI

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    29
    被引用数
    (Scopus)
  • バルクセラミックスにおける異方性工学の進展と今後の展望

    鈴木 達, 打越 哲郎, 目 義雄

    セラミックス   47 ( 4 ) 243 - 248  2012年04月  [査読有り]

     概要を見る

    異方性工学研究会では、「新しい有用人工物を生み出すために、物質や材料の持つ異方的な性質を解明する、または創造する、または積極的に利用する科学と技術」を「異方性工学」と定義している。これらの定義から言えば、形状や異方的な特性をもつ物質と材料そのものについてと、その異方的な特性を付与することと微構造を制御するプロセスとについても異方性工学として扱うことになる。異方性というキーワードで俯瞰した場合には、気体と液体を除くほぼすべての材料が当てはまり広範にわたるため、ここでは形状や結晶方位などの異方性を揃える、また、異方性を組み合わせるデザインをすることで特性を引き出された材料とそれらの材料を創製するプロセスについてバルクセラミックスを中心として総説を述べる。

    CiNii

  • Hydrogen generation from water using Mg nanopowder produced by arc plasma method

    Masahiro Uda, Hideo Okuyama, Tohru S. Suzuki, Yoshio Sakka

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   13 ( 2 ) 025009  2012年04月  [査読有り]

     概要を見る

    We report that hydrogen gas can be easily produced from water at room temperature using a Mg nanopowder (30-1000 nm particles, average diameter 265 nm). The Mg nanopowder was produced by dc arc melting of a Mg ingot in a chamber with mixed-gas atmosphere (20% N-2-80% Ar) at 0.1MPa using custom-built nanopowder production equipment. The Mg nanopowder was passivated with a gas mixture of 1% O-2 in Ar for 12 h in the final step of the synthesis, after which the nanopowder could be safely handled in ambient air. The nanopowder vigorously reacted with water at room temperature, producing 110 ml of hydrogen gas per 1 g of powder in 600 s. This amount corresponds to 11% of the hydrogen that could be generated by the stoichiometric reaction between Mg and water. Mg(OH)(2) flakes formed on the surface of the Mg particles as a result of this reaction. They easily peeled off, and the generation of hydrogen continued until all the Mg was consumed.

    DOI

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    32
    被引用数
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  • Orientation control of mordenite zeolite in strong magnetic field

    Chika Matsunaga, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Motohide Matsuda

    MICROPOROUS AND MESOPOROUS MATERIALS   151   188 - 194  2012年03月  [査読有り]

     概要を見る

    Oriented compacts of mordenite zeolite with an orthorhombic structure were successfully fabricated in a strong magnetic field up to 12 T by a slip casting process. The magnetic orientation was achieved by removing the large agglomerated particles from the suspensions prior to the slip casting. The b-axis oriented compacts of mordenite were fabricated in a static magnetic field. On the other hand, the c-axis orientation was made in a rotating magnetic field which was artificially produced by rotating a vessel put on a turntable in a horizontally-placed magnet. The c-axis was preferentially aligned perpendicular to the plane on which the magnetic field was rotated. The controlled orientation of mordenite was based on the anisotropic magnetic properties in the orthorhombic mordenite crystals. (c) 2011 Elsevier Inc. All rights reserved.

    DOI

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    16
    被引用数
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  • 強磁場を用いたゼオライト細孔の一軸配向

    鈴木 達, 打越 哲郎, 目 義雄, 松永 知佳, 松田 元秀

    MATERIALS INTEGRATION(マテリアルインテグレーション)   25 ( 3 ) 51 - 56  2012年03月  [査読有り]

     概要を見る

    ゼオライトはアルミノケイ酸塩のなかで結晶構造中に比較的大きな空隙を持つものの総称であり、ナノサイズの細孔や取り込まれたカチオンの種類がゼオライトの様々な機能性を発現させる要因となり、分子ふるい、触媒、吸着材として利用されている。ランダムに配列した細孔を用いた場合には、これらの機能が相殺されてしまったり、十分にその特性を引き出すことが出来ないこともある。その場合、細孔を一方向に配列させることで、光学、電気機能だけでなく分子ふるい等の機能においても、その特性を効果的に利用することが期待できる。例えば、モルデナイトは、b軸とc軸に径が異なる細孔を持つため、それぞれの細孔の向きを揃えることで、精緻に細孔を使用することができるようになると期待される。ここでは、それぞれの細孔を使い分けするために結晶磁気異方性を用いて直径1nm以下の細孔の方向制御を行うことを試みた結果を紹介する。

    CiNii

  • Orientation Control of Hematite via Transformation of Textured Goethite Prepared by EPD in a Strong Magnetic Field

    Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka

    ELECTROPHORETIC DEPOSITION: FUNDAMENTALS AND APPLICATIONS IV   507   227 - 231  2012年  [査読有り]

     概要を見る

    Fabrication of textured hematite was achieved from paramagnetic goethite by electrophoretic deposition in a strong magnetic field followed by thermal treatment via topotactic phase transformation. The textured microstructure of the hematite was characterized by XRD and SEM observations. It was confirmed that the a,b-axes of the goethite were taken over the c-axis of the hematite through the topotactic phase transformation The magnetization vs magnetic field measurement using a VSM revealed that the textured hematite showed an anisotropic magnetic property depending on the direction of the crystalline orientation.

    DOI

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    2
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  • Textured Ti3SiC2 by EPD in a Strong Magnetic Field

    Mrinalini Mishra, Yoshio Sakka, Chungfeng Hu, Tohru S. Suzuki, Tetsuo Uchikoshi, Laxmidhar Besra

    ELECTROPHORETIC DEPOSITION: FUNDAMENTALS AND APPLICATIONS IV   507   15 - +  2012年  [査読有り]

     概要を見る

    We present a method for fabrication of textured MAX phase ceramics, particularly, Ti3SiC2; by EPD in a strong magnetic field (12T). Ti3SiC2 was dispersed in cationic polyelectrolyte-Polyethylenimine (PEI). Addition of 0.3-1dwb PEI resulted in high zeta potential values and suspension was found to be stable and of good fluidity. The optimized suspension parameters for EPD were determined as 10vol% Ti3SiC2 and 1dwb PEI in 50 % ethanolic water at pH similar to 7. X-ray diffraction analysis of the textured samples revealed that the preferred orientation of Ti3SiC2 grains parallel to the magnetic field direction was along the a,b-axis. The Lotgering orientation factors on the textured top surface and textured side surface were determined as f ((hk0)) = 0.35 and f ((001)) = 0.75, respectively.

    DOI

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    2
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  • Low-temperature formation of Ln silicate oxyapatite (Ln=La and Nd) by the water-based sol–gel method

    Kiyoshi Kobayashi, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    Solid State Ionics   204   91 - 96  2011年12月  [査読有り]

     概要を見る

    Oxyapatite phase formation was found at about 1073 K in the case of lanthanum silicate and at about 1273 K in the case of neodymium silicate―temperatures much lower than those for a conventional solid-state reaction method. In each system, the oxyapatite phase was formed after decomposition of the lanthanoid oxycarbonate or metastable lanthanoid oxide. In particular, decomposition of lanthanum oxycarbonate was found to play an important role in lanthanum silicate oxyapatite formation. We hypothesize an in-situ chemical pulverization process due to the delamination of lanthanoid oxide by carbon dioxide dissociation.

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    11
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  • Fabrication of the oriented CoO2 sheet using a strong magnetic field

    Hideto Yamada, Tohru S. Suzuki, Tetsuo Uchikoshi, Masato Hozumi, Keiichi Kohama, Yoshio Sakka

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   119 ( 1393 ) 701 - 705  2011年09月  [査読有り]

     概要を見る

    LiCoO2 is a popular positive electrode material for Li-ion secondary batteries. The perpendicular alignment of the interlayer of the LiCoO2 lattice on the electrode contributes to easy access of Li-ions. In this study, we report the preparation of an oriented LiCoO2 sheet using the conventional coating method followed by drying in a maximum 12 T strong magnetic field. We discuss the effect of the particle shape and viscosity of the paste on the degree of orientation. As a result, when the sheets are dried in a strong horizontal magnetic field, the electrochemical active planes of the LiCoO2 are aligned perpendicular to the sheet surface. (C) 2011 The Ceramic Society of Japan. All rights reserved.

    DOI

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    9
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  • Texture development of surface-modified SiC prepared by EPD in a strong magnetic field

    Tohru S. Suzuki, Tetsuo Uchikoshi, Saki Sakakibara, Hiroyuki Muto, Atsunori Matsuda, Yoshio Sakka

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   119 ( 1392 ) 667 - 671  2011年08月  [査読有り]

     概要を見る

    Silicon carbide is a very important material for various applications and its properties are expected to be improved by controlling the crystallographic orientation. It was difficult to simultaneously consolidate SiC powder and sintering additives by electrophoretic deposition (EPD) because of the Afferent electrophoretic mobility. When using the alumina-coated SiC by the sol-gel method, it is possible to deposit SiC and sintering additives by EPD at the same time.
    In this study, we demonstrated that the c-axis alignment of SiC was controlled by EPD and a strong magnetic field, and we investigated the effect of the surface-modification on the microstructure and the degree of orientation. The dilute solution and the large number of repeated coating times prevent the oxide phase from precipitating at the multiple grain junctions and enhance grain growth. The grain growth promoted the degree of orientation in the textured SiC prepared by EPD in a strong magnetic field. (C) 2011 The Ceramic Society of Japan. All rights reserved.

    DOI

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    5
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  • Pulverization Phenomenon of Nb-Zr-Fe Alloys by Absorbing a Hydrogen Gas

    Hideo Okuyama, Masahiro Uda, Tetuo Uchikoshi, Touru Suzuki, Yoshio Sakka

    Journal of the Japan Society of Powder and Powder Metallurgy   50 ( 10 ) 792 - 797  2011年06月  [査読有り]

     概要を見る

    アーク溶解法によるNb精錬過程で表面清浄なNb(Zr)‐Fe 系合金は,室温,大気圧下で水素と接触させることにより,合金が粉化することが判明した.この事実を基に各種Nb-Zr-Fe 合金の粉化を試みるとともにその領域を探索した.合金が粉化する様子をビデオカメラで観察し,粉化時に生ずる気流の駆動力の成因について考察した. 各種組成のNb, Zr, Fe 三元合金(35種類)を作製して水素による粉化する領域を探索し.極めて広範囲の組成域が粉化することが判明した.合金組成により粉化の特性は異なるが,微細粉を作るとの観点よりすればFe 濃度を15 〜 30at% に固定してNbとZr 割合が同量付近の組成が最適であった.一例として45Nb40Zr15Fe合金の微細粉の粒径は0.6ミクロン(比表面積測定)で,その水素吸収濃度は1.8wt%, 水素放出の最大ピーク温度は473K〜503Kであった.Nb-Zr-Fe三元合金が微粉化する条件は,適量のFe が合金中に含有されることであると考えられる.

    DOI

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  • Texture development in anatase and rutile prepared by slip casting in a strong magnetic field

    Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   119 ( 1389 ) 334 - 337  2011年05月  [査読有り]

     概要を見る

    Titania is a very important material for various applications and its properties are expected to be improved by controlling the crystallographic orientation. In this study, we demonstrated that the c-axes of both rutile and anatase were aligned parallel to a magnetic field and we investigated the effect of the orientation on the microstructure development and the effect of the transformation from anatase to ruffle on the orientation during heating. When using rutile as the starting material, the c-axis was aligned and the elongated grains were aligned after sintering. When using anatase as the starting material, the c-axis of anatase was aligned parallel to the magnetic field. However, after transformation, the rutile had a tilt and the anisotropic grain growth was suppressed. (C) 2011 The Ceramic Society of Japan. All rights reserved

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    15
    被引用数
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  • Tailoring Ti3SiC2 Ceramic via a Strong Magnetic Field Alignment Method Followed by Spark Plasma Sintering

    Chunfeng Hu, Yoshio Sakka, Salvatore Grasso, Tohru Suzuki, Hidehiko Tanaka

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   94 ( 3 ) 742 - 748  2011年03月  [査読有り]

     概要を見る

    Highly textured Ti3SiC2 ceramic was successfully fabricated by slip casting in a 12 T strong magnetic field followed by spark plasma sintering. The optimized suspension parameters for slip casting were determined as 20 vol% Ti3SiC2 and 1.5 wt% polyethyleneimine dispersant of powder in deionized water. After texturing in the 12 T strong magnetic field and then cold isostatic pressing, the relative densities of green bodies were 51.4% and 63.8%, respectively. X-ray diffraction analysis revealed that the preferred orientation of Ti3SiC2 grains perpendicular to the magnetic field direction was along the c-axis. After sintering at 1100 degrees and 1000 degrees C under the pressure of 120 and 500 MPa, respectively, the relative density of Ti3SiC2 reached 88.2% and 98.6%. The Lotgering orientation factors on the textured top surface and textured side surface were determined as f((00l))=0.95 and f((hk0))=0.31, respectively. The textured microstructure contributed to the anisotropic mechanical property tested by Vickers indentation.

    DOI

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    52
    被引用数
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  • コロイドプロセスの高度化による高次構造セラミックスの創製

    目 義雄, 鈴木 達, 打越 哲郎

    粉砕   ( 54 ) 28 - 35  2011年03月  [査読有り]

     概要を見る

    ナノセラミックスセンターでは,光,電磁機能,耐熱性や高強度といった基本的特性の先鋭化に加えて,これらの特性を意図的に重畳あるいは洗練させた多機能性のイノベイティブセラミックスを創製すること目指している。本総説では,外場を作用させたコロイドプロセスを中心とした研究を紹介する。

    CiNii

  • High-hardness B4C textured by a strong magnetic field technique

    Salvatore Grasso, Chunfeng Hu, Oleg Vasylkiv, Tohru S. Suzuki, Shuqi Guo, Toshiyuki Nishimura, Yoshio Sakka

    SCRIPTA MATERIALIA   64 ( 3 ) 256 - 259  2011年02月  [査読有り]

     概要を見る

    High-hardness B4C was prepared by sintering samples textured by a strong magnetic field alignment technique (12 T). The c-axis was highly oriented perpendicular to the applied magnetic field. The hardnesses measured on the surface perpendicular and parallel to c-axis were 38.86 +/- 2.13 and 31.31 +/- 0.79 GPa, respectively. The high values of hardness and elastic modulus were in agreement with those reported for B4.38C monocrystal. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI

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    51
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  • Preparation and Characterization of Grain-Oriented Barium Titanate Ceramics using Electrophoresis Deposition Method under a High Magnetic Field

    Tatsuya Kita, Shuhei Kondo, Takahiro Takei, Nobuhiro Kumada, Kouichi Nakashima, Ichiro Fujii, Satoshi Wada, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka, Yasunari Miwa, Shinichiro Kawada, Masahiko Kimura

    ELECTROCERAMICS IN JAPAN XIV   485   313 - +  2011年  [査読有り]

     概要を見る

    Grain-oriented Barium titanate (BaTiO3) ceramics were prepared using an electrophoresis deposition (EPD) method under high magnetic field of 12 T and sintering at 1350 degrees C. It was found that BT03 and BTKK nanoparticles were necessary to synthesize the grain-oriented BT ceramics. The grain orientation was correlated with particles size and c/a ratio of lattice constants. The reason why the grain-oriented BT ceramics using the BT03 and BTKK were prepared was having the large values of the particles size and the c/a ration of lattice constants.

    DOI

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    2
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  • Microstructure Control of Barium Titanate - Potassium Niobate Solid Solution System Ceramics by MPB Engineering and Their Piezoelectric Properties

    Shigehito Shimizu, Nobuhiro Kumada, Kouichi Nakashima, Ichiro Fujii, Daisuke Tanaka, Masahito Furukawa, Yoshihiro Kuroiwa, Tohru Suzuki, Tetsuo Uchikoshi, Yoshio Sakka, Satoshi Wada

    ELECTROCERAMICS IN JAPAN XIV   485   89 - +  2011年  [査読有り]

     概要を見る

    Effect of the microstructural homogeneity of 0.5 BaTiO3 - 0.5 KNbO3 (0.5BT-0.5KN) solid solution ceramics on the dielectric and piezoelectric properties was investigated. Microstructure of a sample prepared by a conventional sintering method was homogenous, and the room temperature crystal structure was assigned to cubic Pm3m symmetry and therefore the sample was paraelectric. On the other hand, microstructure of samples prepared by a two-step sintering method was inhomogeneous, that is, it was made of BT and KN grains. The large electric field piezoelectric constant d(33)* increased with increasing interface area.

    DOI

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    7
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  • Textured lead titanate ceramics fabricated by slip casting under a high magnetic field

    Yasunari Miwa, Shinichiro Kawada, Masahiko Kimura, Takehiro Konoike, Hiroshi Takagi, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   119 ( 1385 ) 60 - 64  2011年01月  [査読有り]

     概要を見る

    Oriented PbTiO3 ceramics were obtained by slip casting under a high magnetic field, and the orientation factor was 90%. Such highly oriented perovskite ceramics by slip casting under a high magnetic field have never been reported as far as we know. It was thought that dispersibility and crystallinity of the powder were important for orientation by slip casting under a high magnetic field. In this study, we controlled the dispersibility and crystallinity of powder by calcination temperature. As a result, the sample obtained from the powder calcined at 1100 degrees C was oriented, but the one obtained from the powder calcined at 900 degrees C was not. The powder calcined at 900 degrees C is more aggregated than that at 1100 degrees C and the crystallinity of the powder calcined at 1100 degrees C is higher than that of the powder calcined at 900 degrees C. It became clear that highly oriented PbTiO3 ceramics can be fabricated from the powder with high dispersibility and high crystallinity by slip casting under a high magnetic field. (c) 2011 The Ceramic Society of Japan. All rights reserved.

    DOI

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    8
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  • Microstructure Control of Barium Titanate – Potassium Niobate Solid Solution System Ceramics by MPB Engineering and their Piezoelectric Properties

    Shigehito Shimizu, Nobuhiro Kumada, Kouichi Nakashima, Ichiro Fujii, Daisuke Tanaka, Masahito Furukawa, Yoshihiro Kuroiwa, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka, Satoshi Wada

    Key Engineering Materials   18   89 - 92  2011年  [査読有り]

     概要を見る

    現在、環境に優しくかつ高性能な圧電材料が求められており、その候補の1つとして、チタン酸バリウム(BT)−ニオブ酸カリウム(KN)系セラミックスが報告されている。このBT-KN系セラミックスは、0.5BT-0.5KNにおいて誘電率と圧電定数が高いが、これはこの組成で斜方晶と正方晶構造の2相共存であり、この界面領域が誘電率、圧電定数に影響を与えていると考えられている。これまでに我々は0.5BT-0.5KNセラミックスに対してMPBエンジニアリングを行うことにより微構造を制御し、圧電定数が向上することを報告した。本研究では、0.5BT-0.5KNセラミックスの焼結方法を変更して試料を作製することで、微構造を制御し、その圧電特性を調査した。

    DOI

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    2
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  • Preparation and Dielectric Properties of Dense Barium Titanate Nanoparticle Accumulations by Electrophoresis Deposition Method

    Satoshi Wada, Shuhei Kondo, Tatsuya Kita, Risa Nakata, Ichiro Fujii, Koichi Nakashima, Naoya Miyajima, Thoru S. Suzuki, Tetsuro Uchikoshi, Yoshio Sakka, Takahiro Takei, Nobuhiro Kumada

    ELECTROCERAMICS IN JAPAN XIV   485   35 - +  2011年  [査読有り]

     概要を見る

    Dense barium titanate (BaTiO3, BT) nanoparticle accumulations were prepared by an electrophoresis deposition (EPD) method using three kinds of BT nanoparticles with different particles sizes and tetragonality. First, the BT particles were dispersed into ethanol using ball-milling technique, and an optimum milling condition was investigated. As the results, it was confirmed that ball-milling led to a formation of mixture between single-dispersed nanoparticles and aggregated particles. Thus, the aggregated particles in the slurry were removed by a centrifuge in order to obtain narrow the size distribution. Using well-dispersed slurry, BT nanoparticle accumulations were deposited on paradigm electrode by the EPD method. Despite various BT nanoparticles, the dense BT nanoparticle accumulations were obtained at relative densities of around 60%. Mier gold electrode deposition on the both surfaces of the accumulations by spattering method, dielectric properties were measured at 20 degrees C, the highest dielectric constants of around 160 was measured at 10 MHz.

    DOI

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    2
    被引用数
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  • Preparation and characterization of Grain-Oriented Barium Titanate Ceramics Using Electrophoresis Deposition Method under A High Magnetic Field

    T. Kita, S. Kondo, T. Takei, N. Kumada, K. Nakashima, I. Fujii, S. Wada, T. S. Suzuki, T. Uchikoshi, Y. Sakka, Y. Miwa, S. Kawada, M. Kimura

    3RD INTERNATIONAL CONGRESS ON CERAMICS (ICC3): ADVANCES IN ELECTRO CERAMICS   18   313 - 316  2011年  [査読有り]

     概要を見る

    Barium titanate (BaTiO3) grain-oriented ceramics were prepared using electrophoresis deposition (EPD) method under high magnetic field of 12 T. First, BaTiO3 nanoparticles with high c/a ratio of 1.008 and size of 84 nm were prepared by two-step thermal decomposition method with barium titanyl oxalate nanoparticles. Using the BaTiO3 slurry, BaTiO3 nanoparticle accumulations were prepared by EPD method under high magnetic field. After binder burnout, the accumulations were sintered and BaTiO3 grain-oriented ceramics were prepared. Moreover, dielectric properties of their ceramics were investigated

    DOI

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  • Microstructure Control of Barium Titanate - Potassium Niobate Solid Solution System Ceramics by MPB Engineering and Their Piezoelectric Properties

    Shigehito Shimizu, Nobuhiro Kumada, Kouichi Nakashima, Ichiro Fujii, Daisuke Tanaka, Masahito Furukawa, Yoshihiro Kuroiwa, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka, Satoshi Wada

    3RD INTERNATIONAL CONGRESS ON CERAMICS (ICC3): ADVANCES IN ELECTRO CERAMICS   18 ( 9 ) 092058  2011年  [査読有り]

     概要を見る

    KBaTiNbO6, i.e., 0.5BT-0.5KN complete solid solution ceramics and barium titanate (BaTiO3, BT) - potassium niobate (KNbO3, KN) system (0.5BT-0.5KN) ceramics with various microstructures were prepared by conventional sintering method and two-step sintering method. The 0.5BT-0.5KN with diffusion of BT and KN completely were paraelectrics. Their microstructures were investigated using X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM). KBaTiNbO6 at room temperature was assigned to cubic Pm3m symmetry. For the 0.5BT-0.5KN patially solid solution system ceramics, the control of the interface area between two phases was important to enhance piezoelectric property. Their piezoelectric property was measured, and the apparent piezoelectric constant d(33)* increased with increasing interface area.

    DOI

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    2
    被引用数
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  • Control of Interfacial Structure of Potassium Niobate-Barium Titanate Ceramics and Their Dielectric Properties

    K. Yamashita, S. Shimizu, I. Fujii, K. Nakashima, N. Kumada, T. Tsukada, T. S. Suzuki, T. Uchikoshi, Y. Sakka, S. Wada

    3RD INTERNATIONAL CONGRESS ON CERAMICS (ICC3): ADVANCES IN ELECTRO CERAMICS   18 ( 9 ) 092065  2011年  [査読有り]

     概要を見る

    ANbO(3) - BaTiO3 (A=K, Na, or K0.5Na0.5) system ceramics were prepared using a conventional sintering method, and their dielectric properties were investigated. It was found that the dielectric constant of KNbO3-BaTiO3 system ceramics did not strongly depend on temperature between 20 and 400 degrees C, making them useful for capacitor application. However, the dielectric constant of KNbO3-BaTiO3 system ceramics was low. The high dielectric constant is attributable to a large area of interfaces between KN and BT grains. Ceramics sintered by spark plasma sintering (SPS) are expected to suppress a grain growth, increasing area of the interfacial layer. In this study, SPS method was employed to achieve a large area of the interfaces and to see how the dielectric properties change with the interfacial structure. The structure was controlled by changing sintering temperatures and time of the spark plasma sintering. As a result, X-ray diffraction patterns showed that perovskite single phase and their relative densities were greater than 97%. By contrast, the dielectric constant was decreased.

    DOI

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    1
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  • Hybrid processing and anisotropic sintering shrinkage in textured ZnO ceramics

    Kahraman Keskinbora, Tohru S. Suzuki, I. Ozgur Ozer, Yoshio Sakka, Ender Suvaci

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   11 ( 6 ) 065006  2010年12月  [査読有り]

     概要を見る

    We have studied the combined effects of the templated grain growth and magnetic alignment processes on sintering, anisotropic sintering shrinkage, microstructure development and texture in ZnO ceramics. Suspensions of 0-10 vol % ZnO template particles were slip cast in a 12 T rotating magnetic field. Sintering and texture characteristics were investigated via thermomechanical analysis and electron backscatter diffraction, respectively. Sintering as well as texture characteristics depend on template concentration. For the studied ZnO system, there is a critical template concentration (2 vol % in this study) above which densification is limited by the templates owing to constrained sintering. Below this limit, the densification is enhanced and the anisotropic shrinkage is reduced, which is attributed to densifying characteristics of the templates.

    DOI

  • Effect of sintering conditions on microstructure orientation in α-SiC prepared by slip casting in a strong magnetic field

    Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    Journal of the European Ceramic Society   30 ( 14 ) 2813 - 2817  2010年10月  [査読有り]

     概要を見る

    Tailoring the crystallographic texture in ceramics is one way of effectively improving their properties. On the other hand, recently, superconducting magnet technologies have been developed and used for various applications, and we reported that the successful control of the development of a textured microstructure even in diamagnetic ceramics was achieved by a colloidal processing in a strong magnetic field and the crystalline orientation was seemed to be closely related with the microstructure. In this presentation, we report the relationship between the development of the crystallographic orientation during consolidation and the microstructure in ceramics prepared by consolidation of colloidal suspensions in a strong magnetic field.

    DOI

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    44
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  • Sedimentation classification treatment effect of starting powders in slip casting on magneto-orientation of mordenite zeolite

    C. Matsunaga, T. Uchikoshi, T. S. Suzuki, Y. Sakka, M. Matsuda

    Trans. of the Mater. Res. Soc., Jpn.   35 ( 3 ) 701 - 703  2010年09月  [査読有り]

    DOI

  • アルミナセラミックスの強磁場配向

    目 義雄, 鈴木 達, 打越 哲郎

    金属   80 ( 80 ) 385 - 390  2010年05月

     概要を見る

    優れた特性を発現させる手法として,組織の配向制御が注目されている.従来,反磁性体や常磁性体は,非磁性体として扱われてきたが,10Tを超える強磁場では結晶磁気異方性を利用した配向制御が可能になった.ここでは,アルミナを例として,コロイドプロセスによる配向制御の概要と配向制御に必要なプロセス因子の要件,またその適用例を紹介する.

  • 高校におけるセラミックス教育の現場から

    鈴木 義和, 鈴木 達

    セラミックス   45 ( 4 ) 297 - 302  2010年04月

     概要を見る

    先端科学技術としてのファインセラミックス分野,また,伝統工芸を含む広義のセラミックス産業を今後発展させていくためには,若手人材の育成がますます重要な課題となっている.本稿では,日本セラミックス協会年会などに毎回優れた作品を出展している,大阪市立泉尾工業高校,愛知県立瀬戸窯業高校,佐賀県立有田工業高校,愛知県立常滑高校,岐阜県立多治見工業高校を訪問し,高校におけるセラミックス教育の現場をレポートした。

    CiNii

  • Determination of Easy Magnetization Axis of Mordenite Zeolite

    Chika Matsunaga, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Motohide Matsuda

    CHEMISTRY LETTERS   39 ( 4 ) 347 - 349  2010年04月  [査読有り]

     概要を見る

    The easy-magnetization axis of mordenite zeolite was determined using commercially available mordenite powder. The well-dispersed suspension of the powder was consolidated by slip casting in a 12-T static magnetic field. The thick bulk deposit was cut into a dice in order to investigate the XRD patterns from the mutually orthogonal surfaces of the consolidated mordenite compacts, the normal lines of which surfaces were parallel and perpendicular to the applied magnetic field. The easy-magnetization axis of mordenite was determined to be the b axis based on the XRD measurements.

    DOI

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  • Experimental verification of pH localization mechanism of particle consolidation at the electrode/solution interface and its application to pulsed DC electrophoretic deposition (EPD)

    Laxmidhar Besra, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   30 ( 5 ) 1187 - 1193  2010年03月  [査読有り]

     概要を見る

    Experimental measurement and verification of the pH localization at the electrode/solution interface was conducted during continuous and pulsed DC electrophoretic deposition (EPD) from aqueous solution. Application of pulsed DC enabled controlling bubble incorporation and obtaining bubble-free deposits during electrophoretic deposition (EPD) from aqueous suspension. The pH localization at the electrode/solution interface on application of electric field was attributed as the underlying mechanism of particle consolidation during continuous as well as Pulsed EPD. The Suspension pH tends to shift towards isoelectric point (i.e.p.) leading to spontaneous coagulation of particles at the electrode. Application of continuous DC tends to attain the i.e.p. faster and closer compared to pulse DC leading to maximum deposit yield. The kinetics and closeness of attainment of pH towards i.e.p. decreased progressively with decreasing Pulse size resulting in a corresponding decrease in deposit yield. (C) 2009 Elsevier Ltd. All rights reserved.

    DOI

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    68
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  • Fabrication of c-axis oriented zinc oxide by electrophoretic deposition in a rotating magnetic field

    Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   30 ( 5 ) 1171 - 1175  2010年03月  [査読有り]

     概要を見る

    The fabrication of c-axis oriented zinc oxide was attempted by electrophoretic deposition (EPD) in a rotating magnetic field. The EPD was conducted in a small container which was placed on a turntable arranged in a Superconducting magnet. The suspension was rotated at 0-90 rpm in a 12 T magnetic field during the deposition. The deposits were dried and then sintered at 1400 degrees C for 2 h. The degree of the c-axis orientation was evaluated by the Lotgering factor calculated from the X-ray diffraction data. (C) 2009 Elsevier Lid. All rights reserved.

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    12
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  • Kinetics of dehydrogenation in Ti600, TC21 and Ti40 alloys

    Xiaoli Wang, Yongqing Zhao, Masuo Hagiwara, Hongliang Hou, Tohru Suzuki

    JOURNAL OF ALLOYS AND COMPOUNDS   490 ( 1-2 ) 531 - 536  2010年02月  [査読有り]

     概要を見る

    The dehydrogenation kinetics of Ti600, TC21 and Ti40 alloys has been studied using a tubular thermohydrogen processing furnace and simultaneous DTA-TG apparatus. The results show that the initial dehydrogenation temperatures in Ti600, TC21 and Ti40 alloys were 580 degrees C, 600 degrees C and 540 degrees C, respectively. At the initial stage of dehydrogenation, the passive layer on the alloy surface was the barrier to enhance the diffusion activation energy. Therefore, activation energy decreased with the increase of reacted fraction. At the initial stage, values of activation energy for the three alloys were 255 kJ/mol, 322 kJ/mol and 177 kJ/mol, respectively. After incubation period, the dehydrogenation average values of activation energy were 200 +/- 5 kJ/mol, 240 +/- 5 kJ/mol and 155 +/- 5 kJ/mol, respectively. (C) 2009 Elsevier B.V. All rights reserved.

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    13
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  • コロイド粒子の電気泳動現象を用いたナノ粒子集積技術

    打越 哲郎, 鈴木 達

    セラミックス   45 ( 2 ) 88 - 92  2010年02月  [査読有り]

     概要を見る

    Electrophoretic Deposition(EPD)法は、セラミックスなどの粒子を液中で帯電、分散させ、そのサスペンションに電場を印加し粒子をその表面電荷と正負の異なる電極方向に電気泳動させて、基材上に粒子堆積層を形成させる固化成形法である。電気泳動堆積法、泳動電着法または単に電気泳動法などとも呼ばれ、比較的均一な粒子堆積膜が低コストかつ短時間で得られる簡便な方法として注目されている。本稿では、電気泳動プロセスの概略を解説し、ナノ粒子集積技術としての電気泳動プロセスの利点について紹介する。

    CiNii

  • Textured PbTiO3 Based Ceramics Fabricated by Slip Casting in a High Magnetic Field

    Yasunari Miwa, Shinichiro Kawada, Masahiko Kimura, Yukio Higuchi, Hiroshi Takagi, Tohru S. Suzuki, Tetsuo Uchikoshi, Yosio Sakka

    ASIAN CERAMIC SCIENCE FOR ELECTRONICS III AND ELECTROCERAMICS IN JAPAN XII   421-422   395 - +  2010年  [査読有り]

     概要を見る

    Textured PbTiO3 (PT) ceramics were fabricated by slip casting in a high magnetic field of 12 T. The sample obtained from the powder calcined at 1100 degrees C was (100), (010), and (001)-oriented, and the orientation factor was 90 %. On the other hand, the sample obtained from the powder calcined at 900 degrees C was not oriented. Aggregability and crystallinity of powder are an important factor when textured ceramics are fabricated by slip casting in a high magnetic field.

    DOI

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    2
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  • Synthesis, Microstructure and Mechanical Properties of ZrB(2) Ceramic Prepared by Mechanical Alloying and Spark Plasma Sintering

    Chun Feng Hu, Yoshio Sakka, Tetsuo Uchikoshi, Tohru S. Suzuki, Byung Koog Jang, Salvatore Grasso, Gustavo Suarez

    HIGH-PERFORMANCE CERAMICS VI   434-435   165 - 168  2010年  [査読有り]

     概要を見る

    Dense bulk ZrB(2) ceramic was synthesized by mechanical alloying (MA) and followed spark plasma sintering (SPS) using zirconium and boron as initial materials. It was found that MA process was effective to fragment the coarse metal zirconium particles from 45 mu m to less than 1 mu m within 20 hours. In comparison with the commercial ZrB(2) powder, the as-obtained zirconium and boron mixture powders showed higher sinterability. When the sintering was carried out at 1800 degrees C, the relative density of synthesized ZrB(2) samples using mixture powder was above 95%, higher than that of ZrB(2) sample prepared using commercial powder (73%). Vickers hardness of those ZrB(2) samples was at the same level of 15 GPa. However, the fracture toughness of ZrB(2) samples seemed to depend on the heating rate of the SPS process. Corresponding to the heating rates of 10, 50, and 100 degrees C/min, the fracture toughness of as-prepared ZrB(2) samples were 3.83, 3.19, and 2.74 MPa.m(1/2), respectively.

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    4
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  • EPD of LDC/LSGM/LDC Tri-layers on NiO-YSZ for Anode-supported SOFC

    SUZUKI Harue, UCHIKOSHI, Tetsuo KOBAYASHI, Kiyoshi, SUZUKI, Tohru, Tatuo Sugiyama, Kenji Furuya, motohide Matsuda, SAKKA Yoshio, Fumio Munakata

    TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN   35 ( 3 ) 723 - 725  2010年  [査読有り]

    DOI

  • The c-axis texturing of seeded Si3N4 with β-Si3N4 whiskers by slip casting in a rotating magnetic field

    X.W. Zhu, Y. Sakka, T.S. Suzuki, T. Uchikoshi, S. Kikkawa

    Acta Materialia   58 ( 1 ) 146 - 161  2010年01月  [査読有り]

     概要を見る

    The c-axis texture development in seeded Si3N4 with b-Si3N4 whiskers by slip casting in a rotating magnetic field was investigated.The resultant c-axis textured Si3N4 exhibits thermal anisotropy as high as 55%, slightly lower than the intrinsic thermal anisotropy (62%) of b-Si3N4. A theoretical analysis is performed to help understand the key factors affecting the orientation of b-Si3N4 whiskers by slip casting in the rotating magnetic field. The formation mechanisms of the nonuniform texture were discussed.

    DOI

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    53
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  • Enhanced Piezoelectric Properties of Barium Titanate-Potassium Niobate Solid Solution System Ceramics by MPB Engineering

    Shigehito Shimizu, Petr Pulpan, Nobuhiro Kumada, Daisuke Tanaka, Masahito Furukawa, Yoshihiro Kuroiwa, Tohru Suzuki, Tetsuo Uchikoshi, Satoshi Wada

    ELECTROCERAMICS IN JAPAN XIII   445   11 - +  2010年  [査読有り]

     概要を見る

    Barium titanate (BaTiO3, BT) - potassium niobate (KNbO3, KN) solid solution system (0.5BT-0.5KN) ceramics with various microstructures were prepared by conventional sintering method and two-step sintering method using BT and KN nanoparticles. Their microstructures were investigated using X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM), and it was confirmed that two ferroelectric phases, i.e., BT-rich tetragonal and KN-rich orthorhombic phases, always coexisted for all ceramics, which suggested that 0.5BT-0.5KN ceramics had "pseudo-morphotropic phase boundary (MPB)" structure. Thus, the control of the interface area between two phases was important to enhance piezoelectric property. Finally, their piezoelectric property was measured, and the apparent piezoelectric constant d(33)* increased with increasing interface area.

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    6
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  • Preparation of Barium Titanate Grain-oriented Ceramics and Their Piezoelectric Properties

    Rintaro Mori, Petr Pulpan, Hiroshi Hayashi, Yoshitaka Nagamori, Yuichi Yamamoto, Tethuo Uchikoshi, Thoru Suzuki, Satoshi Wada

    ELECTROCERAMICS IN JAPAN XIII   445   3 - +  2010年  [査読有り]

     概要を見る

    Barium titanate (BaTiO3, BT) grain-oriented ceramics along [110] direction were prepared by a templated grain growth (TGG) method. The [110] oriented BT platelike particles (t-BT) were used as template particles. BT grain-oriented ceramics with higher relative density (D-rel) over 95 %, high degree of orientation along [110] direction (F-110) over 80% and grain sizes around 30 mu m were successfully prepared using only the template particles. The relationship between microstructures and piezoelectric constant (d(33)) was investigated. The higher F-110 was, the higher D-rel and the smaller grain size were required for enhancement of the piezoelectric properties.

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  • Fabrication of GDC/LSGM/GDC tri-layers on polypyrrole-coated NiO-YSZ by electrophoretic deposition for anode-supported SOFC

    Harue T. Suzuki, Tetsuo Uchikoshi, Kiyoshi Kayashi, Tohru S. Suzuki, Tatsuo Sugiyama, Kenji Furuya, Motohide Matsuda, Yoshio Sakka, Fumio Munakata

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   117 ( 1371 ) 1246 - 1248  2009年11月  [査読有り]

     概要を見る

    The formation of thin tri-layers of Sr- and Mg-doped lanthanum gallate (LSGM) and Gd-doped ceria (GDC) solid electrolytes was performed by electrophoretic deposition (EPD) on a Ni-YSZ anode for use in solid oxide fuel cell (SOFC) applications. The surface of the NiO-YSZ substrate was coated with a conductive polypyrrole to provide electric conduction, which is essential for the EPD processing. The GDC/LSGM8282/GDC laminar coating was performed by sequential deposition on the same substrate. The electrolyte layers were easily sintered together on the anode without cracking and peering-off at the interfaces. (C) 2009 The Ceramic Society of Japan. All rights reserved.

    DOI

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    25
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  • 強磁場を利用した新規セラミックス配向制御

    鈴木 達, 打越 哲郎, 目 義雄

    セラミックデータブック (2009年版)   37 ( 91 ) 117 - 120  2009年10月

     概要を見る

    配向(集合)組織制御は、多結晶材料の諸特性を最大限まで高める有効手段として研究されている。金属材料では、加工・再結晶等の手法により比較的容易にその形成・制御が可能であるのに対し、脆性なセラミックスでは高機能化に向けた配向制御手法の開発が課題となっていた。近年、著者により磁場(外場)を用いた新規配向制御プロセスが開発され、種々のセラミックスに応用可能であること、また、特性向上が期待できることが確認されれてきている。そこで、磁場配向プロセスの原理からセラミックスの高・多機能化の例について紹介し、セラミックスにおける配向制御の有効性について解説した。

  • Effect of sintering additive on crystallographic orientation in AlN prepared by slip casting in a strong magnetic field

    Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   29 ( 12 ) 2627 - 2633  2009年09月  [査読有り]

     概要を見る

    The preparation of oriented AlN bulk ceramics with and without additives was achieved by slip casting in a high magnetic field. The a and b axes of the AlN were aligned parallel to the direction of the magnetic field. The degree of crystallographic orientation was controlled by the viscosity of the slurry and the grain growth during sintering attributed to the sintering additives. The mechanical properties of the textured AlN depended on the direction of the crystallographic orientation. (C) 2009 Elsevier Ltd. All rights reserved.

    DOI

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  • Texture development in 3 mol% yttria-stabilized tetragonal zirconia

    Gustavo Suarez, Yoshio Sakka, Tohru Suzuki, Tetsuo Uchikoshi, Esteban F. Aglietti

    MATERIALS RESEARCH BULLETIN   44 ( 8 ) 1802 - 1805  2009年08月  [査読有り]

     概要を見る

    We have developed a method of forming textured tetragonal zirconia. A suspension containing 10 vol% solid loading of monoclinic ZrO(2) mixed with 3 mol% Y(2)O(3) was prepared, and then a bead-milling process was performed using 50 mu m diameter zirconia beads resulting in a well-dispersed suspension. The mixture suspension of monoclinic zirconia and yttria nanoparticles was slip cast under a magnetic field of 12 T to produce oriented monoclinic zirconia with yttria. The reaction sintering between yttria and the oriented monoclinic zirconia produces a final 3 mol% Y(2)O(3) doped tetragonal zirconia that remains oriented. (C) 2009 Elsevier Ltd. All rights reserved.

    DOI

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    15
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  • Application of constant current pulse to suppress bubble incorporation and control deposit morphology during aqueous electrophoretic deposition (EPD)

    L. Besra, T. Uchikoshi, T. S. Suzuki, Y. Sakka

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   29 ( 10 ) 1837 - 1845  2009年07月  [査読有り]

     概要を見る

    Electrophoretic deposition (EPD) from aqueous suspension generally forms deposits containing enormous pores because of evolution of hydrogen gas at cathode and oxygen at anode due to electrolysis of water on application of DC electric field. We have demonstrated through this investigation on aqueous EPD of alumina suspension as an example that application of pulsed DC instead of the conventionally used continuous DC is a convenient and effective way to control and suppress the amount of bubble incorporation in the deposit. Bubble-free deposits of reasonable yield were obtained at suitable pulse widths and/or duty cycle. The deposit yield and bubble incorporation decreased progressively with decrease in the pulse width and duty cycle of the applied pulse current. A characteristic deposition window was found in the current vs. pulse width plot within which smooth and bubble-free deposits are obtained. The window is wider at low-applied currents compared to that at higher currents implying that it is easier to control the pulsed EPD at lower applied currents. No deposition occurred below the window whereas deposits with incorporated bubbles formed above the window. Possible mechanisms involved in pulsed EPD have been advocated on the basis of amount of hydrogen evolved/pulse due to the electrolysis of water. The discrete amount of H(2) evolved/pulse was higher for larger pulse widths leading to incorporation of more bubbles and vice versa. This was verified by monitoring the gain in weight of palladium (Pd) electrode used as cathode for electrolysis experiment since it is known to absorb hydrogen. (C) 2009 Published by Elsevier Ltd.

    DOI

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    65
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  • 3-dimensional grain orientation of Re-Ba-Cu-O superconductors using a modulated oval magnetic field

    T. Fukushima, S. Horii, T. Uchikoshi, H. Ogino, A. Ishihara, T.S. Suzuki, Y. Sakka, J.-I. Shimoyama, K. Kishio

    IEEE Transactions on Applied Superconductivity   19 ( 3 ) 2961 - 2964  2009年06月  [査読有り]

    DOI

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    16
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  • Elucidation of crystal-chemical determination factor of magnetic anisotropy in htsc

    A. Ishihara, S. Horii, T. Uchikoshi, T.S. Suzuki, Y. Sakka, H. Ogino, J.-I. Shimoyama, K. Kishio

    IEEE Transactions on Applied Superconductivity   19 ( 3 ) 2965 - 2969  2009年06月  [査読有り]

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  • 強磁場を用いた反磁性セラミックスの配向制御

    鈴木 達, 打越 哲郎, 目 義雄

    まてりあ   48 ( 6 ) 321 - 326  2009年06月

     概要を見る

    配向(集合)組織制御は、多結晶材料の諸特性を最大限まで高める有効手段として研究されています。金属材料では、加工・再結晶等の手法により比較的容易にその形成・制御が可能であるのに対し、脆性なセラミックスでは高機能化に向けた配向制御手法の開発が課題となっていました。 近年、著者により磁場(外場)を用いた新規配向制御プロセスが開発され、種々のセラミックスに応用可能であること、また、特性向上が期待できることが確認されました。そこで、磁場配向プロセスの原理からセラミックスの高・多機能化の例について紹介し、セラミックスにおける配向制御の有効性について解説します。

    DOI CiNii

  • Neutron diffraction texture analysis for α-Al2O3oriented by high magnetic field and sintering

    N Terada, H S Suzuki, T S Suzuki, H Kitazawa, Y Sakka, K Kaneko, N Metoki

    Journal of Physics D: Applied Physics   42 ( 10 ) 105404  2009年05月  [査読有り]

     概要を見る

    We have performed neutron diffraction experiments on highly oriented α-Al2 O3 , obtained by slip casting under a magnetic &amp;#64257;eld and sintering. In order to investigate the magnetic &amp;#64257;eld, B, and sintering temperature, Tsint , dependence of the degree of alignment of the orientation, we used samples treated with systematically varied B up to 12 T and Tsint up to 1600 &amp;#9702; C.

    DOI

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    18
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  • Effect of bead-milling treatment on the dispersion of tetragonal zirconia nanopowder and improvements of two-step sintering

    Gustavo Suarez, Yoshio Sakka, Tohru S. Suzuki, Tetsuo Uchikoshi, Esteban F. Aglietti

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   117 ( 1364 ) 470 - 474  2009年04月  [査読有り]

     概要を見る

    The advantages of a good colloidal processing of tetragonal zirconia for achieving a full densification and a small grain size were determined in this study. The optimization of slurry preparation was studied to obtain well-dispersed suspensions. A deagglomeration technique was applied by bead-milling using grinding media of 50 mu m diameter and initial particle size and green density were improved. Colloidal processing was considered responsible for the improvements of particle packing that increase the green density. A conventional sintering at low temperatures and two-step sintering were observed to be more effective with the final bead-milling treatment. (C) 2009 The Ceramic Society of Japan. All rights reserved.

    DOI

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    15
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  • Effect of starting powders on the sintering of nanostructured ZrO2 ceramics by colloidal processing

    Gustavo Suarez, Yoshio Sakka, Tohru S. Suzuki, Tetsuo Uchikoshi, Xinwen Zhu, Esteban F. Aglietti

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   10 ( 2 ) 025004  2009年04月  [査読有り]

     概要を見る

    The effect of starting powders on the sintering of nanostructured tetragonal zirconia was evaluated. Suspensions were prepared with a concentration of 10 vol.% by mixing a bicomponent mixture of commercial powders (97 mol.% monoclinic zirconia with 3 mol.% yttria) and by dispersing commercially available tetragonal zirconia (3YTZ, Tosoh). The preparation of the slurry by bead-milling was optimized. Colloidal processing using 50 mu m zirconia beads at 4000 rpm generated a fully deagglomerated suspension leading to the formation of high-density consolidated compacts (62% of the theoretical density (TD) for the bicomponent suspension). Optimum colloidal processing of the bicomponent suspension followed by the sintering of yttria and zirconia allowed us to obtain nanostructured tetragonal zirconia. Three different sintering techniques were investigated: normal sintering, two-step sintering and spark plasma sintering. The inhibition of grain growth in the bicomponent mixed powders in comparison with 3YTZ was demonstrated. The inhibition of the grain growth may have been caused by inter-diffusion of cations during the sintering.

    DOI

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    31
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  • Magnetic orientation and magnetic anisotropy in paramagnetic layered oxides containing rare-earth ions

    Shigeru Horii, Atsushi Ishihara, Takayuki Fukushima, Tetsuo Uchikoshi, Hiraku Ogino, Tohru S. Suzuki, Yoshio Sakka, Jun-ichi Shimoyama, Kohji Kishio

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   10 ( 1 ) 014604  2009年03月  [査読有り]

     概要を見る

    The magnetic anisotropies and easy axes of magnetization at room temperature were determined, and the effects of rare-earth (RE) ions were clarified for RE-based cuprates, RE-doped bismuth-based cuprates and RE-doped Bi-based cobaltite regarding the grain orientation by magnetic field. The easy axis, determined from the powder orientation in a static field of 10 T, depended qualitatively on the type of RE ion for all three systems. On the other hand, the magnetization measurement of the c-axis oriented powders, aligned in static or rotating fields, revealed that the type of RE ion strongly affected not only the directions of the easy axis but also the absolute value of magnetic anisotropy, and an appropriate choice of RE ion is required to minimize the magnetic field used for grain orientation. We also studied the possibility of triaxial grain orientation in high-critical-temperature superconductors by a modulated oval magnetic field. In particular, triaxial orientation was attempted in a high-oxygen-pressure phase of orthorhombic RE-based cuprates Y2Ba4Cu7Oy. Although the experiment was performed in epoxy resin, which is not practical, in-plane alignment within 3 degrees was achieved.

    DOI

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    33
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  • Preparation of Highly Oriented Transparent (Sr,Ba)Nb2O6 Ceramics and Their Ferroelectric Properties

    Teppei Kubota, Nobuhiko Tanaka, Keisuke Kageyama, Hiroshi Takagi, Yukio Sakabe, Tohru S. Suzuki, Yoshio Sakka

    JAPANESE JOURNAL OF APPLIED PHYSICS   48 ( 3 ) 031405  2009年03月  [査読有り]

     概要を見る

    Highly oriented transparent (Sr,Ba)Nb2O6 (SBN) ceramics were prepared to obtain excellent electrooptic properties and a high spontaneous polarization, such as those observed in a Sr0.75Ba0.25Nb2O6 (SBN75) single crystal. As a result of slip casting at a high magnetic field of 12T and firing at 1460 degrees C for 48 h in an oxygen atmosphere, highly oriented ceramics and strong ferroelectric properties were observed. The spontaneous polarization of highly oriented SBN ceramics was above 15 mu C/cm(2), which was close to that of the SBN75 single crystal (17 mu C/cm(2)). (C) 2009 The Japan Society of Applied Physics

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    16
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  • Pulsed-DC Electrophoretic deposition (EPD) of aqueous alumina suspension for controlling bubble incorporation and deposit microstructure

    Laxmidhar Besra, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka

    ELECTROPHORETIC DEPOSITION: FUNDAMENTALS AND APPLICATIONS III   412   39 - 44  2009年  [査読有り]

     概要を見る

    Electrophoretic deposition (EPD) from aqueous suspension generally forms deposit containing incorporated bubbles because of evolution of gases at electrodes due to electrolysis of water. We have demonstrated here that application of pulsed voltage /current instead of continuous DC enables controlling the amount of bubble incorporation and obtain bubble-free deposits during EPD of aqueous suspension. The yield and bubble incorporation decreased progressively with decrease in size of the applied pulse. A characteristic band of deposition window was found in the plot of voltage/current vs. pulse width within which smooth and bubble-free deposits are obtained. The window is wider at low applied voltages/currents than at higher voltages/currents implying that it is more easier to control the pulsed EPD at lower applied voltages and/currents. No deposition occurred below the window whereas deposits with incorporated bubbles formed above the window. Suppression of bubbles with decreasing pulse size was attributed to decrease in the amount of hydrogen evolved per pulse and verified by monitoring the gain in weight of palladium (Pd) electrode used as cathode during electrolysis of water.

  • Formation of Crystalline-Oriented Titania Thin Films on ITO Glass Electrodes by EPD in a Strong Magnetic Field

    Mamiko Kawakita, Tetsuo Uchikoshi, Laxmidhar Besra, Tohru S. Suzuki, Jin Kawakita, Yoshio Sakka

    ELECTROPHORETIC DEPOSITION: FUNDAMENTALS AND APPLICATIONS III   412   143 - +  2009年  [査読有り]

     概要を見る

    Crystal-oriented and crack-free thin TiO2 films with a good interfacial adhesion on indium-tin oxide (ITO) glass substrates for photoelectrodes were fabricated by the electrophoretic, deposition (EPD) method in a 12 T strong magnetic field. A binder-free suspension for the EPD was prepared by dispersing TiO2 in the mixture of 2-propanol and 2,4-pentanedione. The electrophoretic mobility and the sedimentation rate were measured at various ratios of the mixed solution. The optimized state of the suspension exhibiting the highest surface charge potential and producing deposits with the highest green density was obtained at the 50:50 mixing ratio. The TiO2 films were characterized by XRD and SEM analyses. The photo-current measurement was also conducted to investigate the relation between the photo-anode characteristics of a dye-sensitized solar cell and the plane orientation of the TiO2 films.

  • Control of Residual Stress in Multilayered Alumina Composites Prepared Using EPD in a Strong Magnetic Field

    Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    ELECTROPHORETIC DEPOSITION: FUNDAMENTALS AND APPLICATIONS III   412   233 - 236  2009年  [査読有り]

     概要を見る

    The mechanical properties of ceramics materials can be tailored by designing their micro structures. Residual stress is one of the important factors for controlling the crack propagation and consequently improving the mechanical properties. On the other hand, development of the crystallographic orientation even in a diamagnetic ceramic can be controlled by colloidal processing in a strong magnetic field. In this study, alumina/alumina laminar composites with different crystalline-oriented layers were fabricated by EPD in a strong magnetic field in order to control the residual stress using the difference in the thermal expansion of each layer.

  • Fabrication of multi-layered thermoelectric thick films and their thermoelectric performance

    S. Horii, M. Sakurai, T. Uchikoshi, R. Funahashi, T.S. Suzuki, Y. Sakka, H. Ogino, J.-I. Shimoyama, K. Kishio

    Key Engineering Materials   412   291 - 296  2009年  [査読有り]

     概要を見る

    We report the fabrication of p- and n-type thermoelectric oxide thick films laminated by insulating alumina using electrophoretic deposition and their thermoelectric performance. From the experimental studies performed for optimization of the thermoelectric performance in the p- and n-type mono-layers, the control of sintering temperature for densification and the usage of fine powder were effective for reducing the electrical resistivity of thermoelectric layers. These findings could be applicable also to the triple-layered thick films. When one assumes that two triple-layered films of p- and n-type thermoelectric materials are combined as unicouple of thermoelectric module, an estimated maximum output power was 20 times higher than a measured maximum output power of a previously reported multi-layered thermoelectric module. It was found that precise control of the microstructure in the thermoelectric layers is indispensable for development of the thermoelectric modules based on the electrophoretic deposition.

    DOI

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  • Surface modification of SiC powder for use in electrophoretic deposition

    Sakakibara S, Suzuki T, Matsuda A, Uchikoshi T

    Key Engineering Materials   412   287 - 290  2009年  [査読有り]

    DOI

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    5
    被引用数
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  • Aqueous Dispersions of Carbon Nanotubes Stabilized by Zirconium Acetate

    Seiichi Furumi, Tetsuo Uchikoshi, Naoto Shirahata, Tohru S. Suzuki, Yoshio Sakka

    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY   9 ( 1 ) 662 - 665  2009年01月  [査読有り]

     概要を見る

    This report describes a simple strategy for preparing dispersion of multi-walled carbon nanotubes (MWCNTs) in water. Zirconium acetate (ZrAc3) was used as a dispersant for the MWCNTs in water. Interestingly, an aqueous dispersion of MWCNTs was stabilized by adding an extremely small amount of ZrAc3, followed by ultrasonic agitation. The resultant MWCNT dispersion was durably retained even after storing at room temperature over 6 months. The dispersion state of MWCNTs on a substrate was observed by means of reflection optical and scanning electron microscopes. Furthermore, we demonstrated the effect of external high magnetic field on the orientation of MWCNTs on the substrate surface from the aqueous dispersion.

    DOI

    Scopus

    8
    被引用数
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  • Anelastic behavior of 8Y-FSZ/Al2O3 composite

    Rumi Kitazawa, Susumu Horibe, Tohru S. Suzuki

    JOURNAL OF MATERIALS SCIENCE   43 ( 21 ) 6834 - 6839  2008年11月  [査読有り]

     概要を見る

    This paper has clarified the anelasticity of 8Y-FSZ/alpha-alumina composites wherein the 8Y-FSZ phases are dispersed like islands. The amount of anelastic strain generated and the manner of anelastic deformation were compared to those of monolithic 8Y-FSZ. The anelastic strains of six kinds of 8Y-FSZ/alpha-alumina, as well as of monolithic 8Y-FSZ and monolithic alpha-alumina, were measured. The results showed that the anelastic strain was produced even in the composite where 8Y-FSZ phases existed as islands, and that the more the anelastic strain produced, the higher the volume fraction of 8Y-FSZ. In addition, the composition with a fully densified alumina phase had the effect of inhibiting anelastic strain in the 8Y-FSZ phase.

    DOI

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  • Tri-axial Grain Orientation of Y2Ba4Cu7Oy Achieved by the Magneto-science Method

    Takayuki Fukushima, Shigeru Horii, Hiraku Ogino, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Atsushi Ishihara, Jun-ichi Shimoyama, Kohji Kishio

    APPLIED PHYSICS EXPRESS   1 ( 11 ) 111701-1 - 111701-3  2008年11月  [査読有り]

     概要を見る

    Tri-axial orientation of orthorhombic and twin-free Y2Ba4Cu7Oy (Y247) powders was attempted using a rotating magnetic field with modulated rate. Although magnetic anisotropy of paramagnetic Y247 originated only from the two-dimensional CuO2 and one-dimensional Cu-O chain structures are small, strong tri-axial grain orientation with misorientation angles below 1.5 degrees was successfully achieved during the solidification process of epoxy resin. Our present results indicate the possibility of fabrication of tri- or bi-axial grain-orierited bulk and thick films without applying epitaxial methods, such as melt-solidification or thin film deposition, and that the modulated-rotation magnetic field is applicable not only to RE247 compounds but also to orthorhombic high critical temperature cuprate superconductors, including practical REBa2Cu3Oy, in principle. (C) 2008 The Japan Society of Applied Physics

    DOI

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    21
    被引用数
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  • Bubble-Free Aqueous Electrophoretic Deposition (EPD) by Pulse-Potential Application

    Laxmidhar Besra, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   91 ( 10 ) 3154 - 3159  2008年10月  [査読有り]

     概要を見る

    A novel method based on the application of a square-wave pulse potential of 50% duty cycle has been demonstrated to obtain dense bubble-free deposits of alumina by constant voltage electrophoretic deposition (EPD) from an aqueous suspension. Application of continuous dc voltage invariably resulted in the incorporation of bubbles in the deposits. Bubbles in the deposit decreased progressively with decrease in the size of pulse width during the pulse potential EPD. A unique and narrow band of pulse width exists for each voltage within which a bubble-free deposit is obtained. The band is wider at low applied voltages than at higher voltages. Such bands of pulse width were found to be independent of substrate material and occurred at the same range for stainless steel and nickel substrates, suggesting that the process may be generic and applicable to any conductive substrate. The green density of deposits obtained by pulse EPD has been found to be the same as those obtained by continuous dc voltage EPD. The cathodic pulse EPD produced uniform and homogeneous deposits and was more convenient and amenable to better control than anodic pulse EPD.

    DOI

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    73
    被引用数
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  • Conductive polymer coating on nonconductive ceramic substrates for use in the electrophoretic deposition process

    Tetsuo Uchikoshi, Seiichi Furumi, Naoto Shirahata, Tohru S. Suzuki, Yoshio Sakka

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   91 ( 5 ) 1674 - 1677  2008年05月  [査読有り]

     概要を見る

    Uniform coating and line patterning of a conductive polypyrrole (Ppy) film on nonconductive ceramic materials were performed for use as substrates in the electrophoretic deposition (EPD) process. The Ppy was synthesized by chemical oxidation in the pyrrole solution. Direct shaping or line patterning of alumina or zirconia particles by EPD was carried out using the Ppy films as cathodes.

    DOI

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    25
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  • Rare-earth-dependent magnetic Anisotropy in REBa2Cu3Oy

    Atsushi Ishihara, Shigeru Horii, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Hiraku Ogino, Jun-chi Shimoyama, Kohji Kishio

    APPLIED PHYSICS EXPRESS   1 ( 3 ) 031701-1 - 031701-3  2008年03月  [査読有り]

     概要を見る

    We report magnetic anisotropies (Delta chi) depending on rare earth (RE) element in the paramagnetic REBa2CU3Oy (RE123) system as an important finding of magneto-scientific grain-orientation. The c-axis-oriented RE123 powder samples using static or rotating magnetic fields were fabricated at room temperature to clarify Delta chi. Their easy axes of magnetization were mainly dominated by second-order Stevens factors, whereas vertical bar Delta chi vertical bar largely depended on y and RE elements. Especially for heavy RE elements, vertical bar Delta chi vertical bar reached the order of 10(-4), indicating that appropriate choice of RE directly leads to a drastic reduction of required magnetic fields for grain-orientation of RE123. (C) 2008 The Japan Society of Applied Physics.

    DOI

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    11
    被引用数
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  • In situ neutron diffraction study of aligning of crystal orientation in diamagnetic ceramics under magnetic fields

    N. Terada, H. S. Suzuki, T. S. Suzuki, H. Kitazawa, Y. Sakka, K. Kaneko, N. Metoki

    APPLIED PHYSICS LETTERS   92 ( 11 ) 112507  2008年03月  [査読有り]

     概要を見る

    We have first studied the orientation process of alpha-Al(2)O(3) fine particles, using in situ neutron diffraction measurements on the particles in a liquid solvent under magnetic fields. The neutron diffraction intensity of 006 and 116 reflections is significantly reduced by the vertical magnetic field up to 100 kOe, while the 113 and 204 reflections remain unchanged within the experimental accuracy. The energy balance between the magnetic anisotropic energy and the thermal fluctuation following the Boltzmann distribution is important for the crystal orientation of the alpha-Al(2)O(3) particles in suspension. Comparing the experimental data with the theoretical equation, we find that the magnetic field, where the particles are fully oriented, is above 200 kOe. Our obtained data prove that the in situ neutron diffraction measurement is a powerful tool for investigating the alignment of the crystal orientation under magnetic fields. (c) 2008 American Institute of Physics.

    DOI

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    25
    被引用数
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  • Highly Texturing β-Sialon Via Strong Magnetic Field Alignment

    Xinwen Zhu, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    Journal of the American Ceramic Society   91 ( 2 ) 620 - 623  2008年02月  [査読有り]

     概要を見る

    This paper reports the texturing behavior of b-Sialon by strong magnetic field alignment (SMFA) during slip casting, followed by reaction pressureless sintering, using either a or b-Si3N4, Al2O3 and AlN as starting materials. It is found that the b-Si3N4 crystal exhibits substantially stronger orientation ability than the a-Si3N4 crystal regardless of the Si3N4 raw powders in the magnetic field of 12 T. The results indicate that the use of the &amp;#61538;-raw powder is more efficient for producing highly textured b-Sialon via SMFA than that of the &amp;#61537;-raw powder as well as the prolonged sintering.

    DOI

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    17
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  • Texture development of hydroxyapatite ceramics by colloidal processing in a high magnetic field followed by sintering

    Yoshio Sakka, Kazuya Takahashi, Tohru S. Suzuki, Shigeru Ito, Nobuyuki Matsuda

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   475 ( 1-2 ) 27 - 33  2008年02月  [査読有り]

     概要を見る

    Hydroxyapatite (HAP, Ca-10(PO4)(6)(OH)(2)) is a main component in the human body and teeth, and a specific crystal orientation is required because of the different properties for each crystal plane. In this study, two types of hydroxyapatite powders were used for the fabrication of a textured HAP. The effects of the processing parameters on the orientation, such as de-agglomeration by ultrasonication and milling procedures, applied magnetic field and sintering temperatures, were examined. Using the de-agglomerated particle by a milling procedure, it is possible to control the particle orientation, but when using heavily agglomerated particles, it was impossible to control the particle orientation by applying a high magnetic field. Highly textured HAP can be fabricated by slip casting using a well-dispersed suspension in a high magnetic field followed by sintering above 1373 K. (C) 2007 Elsevier B.V. All rights reserved.

    DOI

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    22
    被引用数
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  • Texturing of Si3N4 ceramics via strong magnetic field alignment

    Xinwen Zhu, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    HIGH-PERFORMANCE CERAMICS V, PTS 1 AND 2   368-372   871 - 874  2008年  [査読有り]

     概要を見る

    This paper reports the texture development in Si3N4 by strong magnetic field alignment (SMFA), using slip casting of alpha-Si3N4 raw powder (SN-E10) and pressureless sintering. The texture of beta-Si3N4 in the green and sintered bodies was characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The a, b-axis and c-axis aligned beta-Si3N4 has been obtained by the static and rotating magnetic field of 12 T, respectively. The beta-seed addition and prolonged sintering both enhance the texture, but the former is more efficient. This work suggests an efficient SMFA strategy of producing highly textured beta-Si3N4, particularly the unidirectionally c-axis aligned beta-Si3N4 by seeding the alpha-raw powder using the less-agglomerated beta-phase particles.

  • Texturing behavior in sintered reaction-bonded silicon nitride via strong magnetic field alignment

    Xinwen Zhu, Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   28 ( 5 ) 929 - 934  2008年  [査読有り]

     概要を見る

    An attempt has been made to study the texture behavior in sintered reaction-bonded silicon nitride by strong magnetic field alignment, using slip casting of Si-powder without and with beta-Si3N4 Particle addition. It is shown that the a, b-axis aligned texture, parallel to the magnetic field, develop in the resultant SRBSN with P-seed addition, whereas no texture develops in those SRBSN without beta-seed addition. The degree of orientation of beta-Si3N4 is found to decrease with the formation of new beta-phase during the nitridation, regardless of the nitriding conditions, suggesting that the initially oriented beta-seed dose not promote the formation of newly oriented beta-Si3N4. Compared to the nitridation, the degree of texture is enhanced by the post-sintering, but the nitridation condition has little effect on the texture development during the post-sintering. The present work implies that the texture development in SRBSN is governed by the initial orientation Of beta-Si3N4 seed and the post-sintering. (c) 2007 Elsevier Ltd. All rights reserved.

    DOI

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    12
    被引用数
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  • Fabrication and some properties of textured alumina-related compounds by colloidal processing in high-magnetic field and sintering

    Yoshio Sakka, Tohru S. Suzuki, Tetsuo Uchikoshi

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   28 ( 5 ) 935 - 942  2008年  [査読有り]

     概要を見る

    Recently to improve properties, highly microstructure controlled ceramics such as fine-grained, textured and laminated structures are required. We have demonstrated a new processing of textured ceramics with a feeble magnetic susceptibility by colloidal processing in a high-magnetic field and subsequent heating. As colloidal processing, slip casting and electrophoretic deposition (EPD) have been conducted successfully. Colloidal processing is known to be a powerful method for consolidating fine particles with a high density and homogeneous microstructure. Crystalline-textured controlled laminated alumina can be fabricated using EPD by varying the angle between the vectors of electric field and magnetic field. Also textured ceramics with complicated structure such as P-alumina and alumina-based nanocomposite can be fabricated by reaction sintering. The textured alumina-related compounds showed anisotropic properties depending on the crystal plane. The colloidal processing in a high-magnetic field confers several advantages and can be applied to many non-cubic ceramics. (c) 2007 Elsevier Ltd. All rights reserved.

    DOI

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    54
    被引用数
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  • Magnetic tri-axial orientation in rare-earth-based cuprate superconductors

    S. Horii, T. Fukushima, S. Sato, T. Uchikoshi, T. S. Suzuki, Y. Sakka, H. Ogino, J. Shimoyama, K. Kishio

    IUMRS-ICA 2008 SYMPOSIUM AA. RARE-EARTH RELATED MATERIAL PROCESSING AND FUNCTIONS   1  2008年  [査読有り]

     概要を見る

    We report the development of a new high oxygen pressure synthesis method of orthorhombic and twin-free RE2Ba4Cu7Oy (RE247, RE = rare earth elements) superconductors and their tri-axial orientation using by a modulated rotation magnetic field. By the new synthesis method using quartz ampoule and a chemical reaction generating additional source of oxygen pressure in it, we have successfully fabricated RE247 (RE=Y, Er) polycrystals in the almost same synthesis conditions with those using a high oxygen pressure furnace. Furthermore, tri-axial orientation of these RE247 powders has been successfully accomplished using a modulated rotation magnetic field. Although our experimental studies on the magnetic orientation were performed in epoxy resin, high degrees of in-plane orientation less than 6 degrees were achieved. Especially for RE=Y, the degree of in-plane orientation was found to be less than 1.5, and high effectiveness of this tri-axial orientation technique was shown in principle.

    DOI

  • Thermoelectric properties and magnetic anisotropies of magnetically grain-oriented Sr- or Bi-doped Ca3Co4O9 thick films

    Shigeru Horii, Yuhya Yamasaki, Masayuki Sakurai, Ryoji Funahashi, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Hiraku Ogino, Jun-ichi Shimoyama, Kohji Kishio

    THERMOELECTRIC POWER GENERATION   1044   363 - +  2008年  [査読有り]

     概要を見る

    We report magnetic properties of [Ca2CoO3-delta](0.62)COO2 (Ca349) powders with various average size and the Bi- and Sr-doping effects on thermoelectric properties for the magnetically grain-aligned and densified Ca349 thick films. Magnetic anisotropy at 300 K depended on the initial average size of Ca349 powders and decreased with the decrease in the size. This presumably suggests that distortion of crystal structure was induced by a ball-milling process and led to the change of magnetic anisotropy. On the Bi- and Sr-doping effects, an obvious enhancement of thermoelectric properties did not emerge in the case of the Sr-doping, whereas the enhancement was observed for the Bi-doped Ca349 thick films. However, a drastic decrease of magnetic anisotropy was caused by the Bi-doping. For usage of the p-type layer in multilayered thermoelectric module, tuning of the Bi-doping levels in which both enhancement of thermoelectric properties and a certain level of magnetic anisotropy are achieved is required.

  • Improvement of thermoelectric properties of p- and n-types oxide thick films fabricated by electrophoretic deposition

    Sakurai Masayuki, Horii Shigeru, Funahashi Ryoji, Uchikoshi Tetsuo, Suzuki Tohru, Sakka Yoshio, Ogino Hiraku, Shimoyama Jun-ichi, Kishio Kohji

    THERMOELECTRIC POWER GENERATION   1044   357 - +  2008年  [査読有り]

  • Low temperature crystallization of TiO2 in layer-by-layer assembled thin films formed from water-soluble Ti-complex and polycations

    Katagiri K, Suzuki T, Muto H, Sakai M, Matsuda A

    Colloids and Surfaces A: Physicochemical and Engineering Aspects   321 ( 1-3 ) 233 - 237  2008年  [査読有り]

    DOI

  • Effect of milling treatment on texture development of hydroxyapatite ceramics by slip casting in high magnetic field

    Yoshio Sakka, Kazuya Takahashi, Nobuyuki Matsuda, Tohru S. Suzuki

    MATERIALS TRANSACTIONS   48 ( 11 ) 2861 - 2866  2007年11月  [査読有り]

     概要を見る

    Hydroxyapatite (HAP, Ca-10(PO4)(6)(OH)(2)) is a main component of bones and teeth, and a specific crystal orientation is required for biomaterial application. In this study, the effects of the processing parameters on the orientation, such as de-agglomeration by milling procedure, applied magnetic field and sintering temperatures, were examined. Using the de-agglomerated particle by a milling procedure, it is possible to control the particle orientation, but when using heavily agglomerated particles, it was impossible to control the particle orientation by applying a high magnetic field. Highly-textured HAP can be fabricated by slip casting using a well-dispersed suspension in a high magnetic field (above 4 T) followed by sintering above 1373 K.

    DOI

    Scopus

    21
    被引用数
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  • Fabrication of textured alpha-SiC using colloidal processing and a strong magnetic field

    Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    MATERIALS TRANSACTIONS   48 ( 11 ) 2883 - 2887  2007年11月  [査読有り]

     概要を見る

    In general, the mechanical and physical properties of a crystal depend on the direction of the crystal axis. The controlled development of the crystallographic texture in ceramics is very useful for improvement of their properties. The preparation of the textured SiC polycrystal was achieved by colloidal processing in a strong magnetic field. The c-axis of the SiC was parallel to the direction of the applied magnetic field. The bending strength of the textured SiC depends on the crack-growth direction.

    DOI

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    19
    被引用数
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  • Texturing Ca-α-Sialon Via Strong Magnetic Field Alignment

    Xinwen ZHU, Tohru S. SUZUKI, Tetsuo UCHIKOSHI, Yoshio SAKKA

    Journal of the Ceramic Society of Japan   115 ( 1347 ) 701 - 705  2007年11月  [査読有り]

     概要を見る

    This paper reports a dense textured single Ca-&amp;#61537;-sialon fabricated by strong magnetic field alignment (SMFA) during non-aqueous slip casting of a-Si3N4, CaCO3, Al2O3 and AlN starting powders, followed by reaction pressureless sintering at 1800 oC. XRD analysis reveals that the orientation of the &amp;#61537;-Si3N4 crystals occurs with the c-axis perpendicular to the magnetic field during slip casting. It is shown that the formation of the single Ca-&amp;#61537;-sialon is complete within 5 min and nearly complete densification is achieved within 60 min. SEM observation reveals that the texture Ca-&amp;#61537;-sialon is featured by the long-axis (c-axis) of large elongated grains perpendicular to the magnetic field. The texturing mechanism is attributed to the heterogeneous nucleation and epitaxia

    DOI

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    6
    被引用数
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  • High-strain-rate superplasticity in oxide ceramics

    Keijiro Hiraga, Byung-Nam Kim, Koji Morita, Hidehiro Yoshida, Tohru S. Suzuki, Yoshio Sakka

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   8 ( 7-8 ) 578 - 587  2007年10月  [査読有り]

     概要を見る

    Factors limiting the strain rate of superplastic deformation in ceramic materials are discussed on the basis of existing models and experimental results concerning high-temperature plastic deformation, intergranular cavitation and dynamic grain growth. From the discussion, it is indicated that simultaneously fulfilling the following conditions is essential for attaining high-strain-rate superplasticity (HSRS) in ceramic materials: reduction in the initial grain size, enhanced diffusivity, suppressed dynamic grain growth, a homogeneous microstructure and a reduced number of residual defects. In the light of these conditions, explanations are given for HSRS attained in earlier studies on some oxide materials. It is also shown that HSRS can be intentionally attained in doped yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and composites synthesized from ZrO2, Al2O3 and MgO2; the tensile ductility of these composites reached 300-2500% at a strain rate of 0.01-1.0 s(-1). The postdeformation microstructure indicates that some secondary phases may suppress cavitation damage and thereby enhance HSRS. (C) 2007 NIMS and Elsevier Ltd. All rights reserved.

    DOI

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    38
    被引用数
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  • Improvement of thermoelectric performance in magnetically c-axis-oriented bismuth-based cobaltites

    Shigeru Horii, Toshiaki Kumagai, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Jun-ichi Shimoyama, Kohji Kishio

    SCRIPTA MATERIALIA   57 ( 4 ) 333 - 336  2007年08月  [査読有り]

     概要を見る

    Fabrication of thermoelectric Bi-based cobaltites with large magnetic anisotropy (Delta chi = chi c - chi ab) and relatively low resistivity using a crystallochernical process is reported. Doping of various rare earth (RE) ions into the Ca site in [(Bi0.5Pb0.5)(2)Ca2O4](y)CoO2 [(Bi,Pb)Ca222] enhanced Delta chi comparable to that of [Ca2CoO3-delta](0.62)CoO2. Tailoring of the Sr-doping level in Dy-doped (Bi,Pb)Ca222 enabled the resistivity to be reduced without decreasing Ay. The magnetically c-axis-oriented (Sr,Dy)-doped (Bi,Pb)Ca222 bulk exhibited improved thermoelectric performance compared with the Sr-free RE-doped BiCa222 and a-axis grain-oriented [(Bi0.5Pb0.5)(2)Sr2O4](similar to 0.55) CoO2. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI

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    6
    被引用数
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  • 強磁場中電気泳動法による配向積層アルミナの作製

    鈴木 達, 打越 哲郎, 目 義雄

    化学工業   58 ( 6 ) 439 - 444  2007年06月

     概要を見る

    強磁場中での成形によるセラミックスの配向制御と電気泳動堆積法について概説し、電場と強磁場を重畳作用する強磁場中電気泳動堆積法についての解説を行なう。さらに磁場と電場のなす角を制御することにより多層セラミックスにおいて各層での結晶方位制御が可能であることを述べ、実際にアルミナについて適用した例を紹介する。

    CiNii

  • Layer structure of textured CaBi4Ti4O15 ceramics fabricated by slip casting in high magnetic field

    Masahiko Kimura, Kosuke Shiratsuyu, Akira Ando, Tohru S. Suzuki, Yoshio Sakka

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   90 ( 5 ) 1463 - 1466  2007年05月  [査読有り]

     概要を見る

    Textured CaBi4Ti4O15 (CBT) ceramics were fabricated by slip casting in a high magnetic field of 12 T, and a layer structure was obtained by co-firing with the textured CBT ceramics and a metal internal electrode. The crystalline a(b)-axis of CBT was aligned parallel to the magnetic field, and highly a(b)-axis textured ceramics were obtained. The orientation degree of the textured ceramics was 0.82, and the electromechanical coupling coefficient of thickness extensional (TE) vibration was about 1.5 times larger than that of the randomly oriented ceramics. The second harmonic TE vibration was successfully generated in the layer structure specimens, which contained two layers of the textured ceramics and an internal electrode. Therefore, it was recognized that the layer structure was satisfactorily fabricated.

    DOI

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    17
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  • Effect of polyethylenimine on hydrolysis and dispersion properties of aqueous Si3N4 suspensions

    Xinwen Zhu, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   90 ( 3 ) 797 - 804  2007年03月  [査読有り]

     概要を見る

    The roles of polyethylenimine (PEI) in the hydrolysis and dispersion properties of aqueous Si3N4 suspensions were studied in terms of the hydrolysis, adsorption, electrokinetic, and rheological measurements. It was found that the pH change of the suspensions in the acidic environment could be minimized in the presence of &gt;= 0.5 dwb% PEI. The ammonia and oxygen measurements suggest that this phenomenon is primarily attributed to the buffer mechanism generated by the ionized PEI, instead of the protection mechanism. The constant pH enables the suspensions to retain a better stability with time at acidic pH. The adsorption of PEI on Si3N4 is a high-affinity type at highly basic pH, but is a low-affinity type at acidic pH. As the PEI amount increases, the adsorption shifts the isoelectric point (IEP) of Si3N4 from pH 5.9 to pH similar to 11 until complete coverage is attained. The stability of Si3N4 suspensions is found to depend strongly on the saturated adsorption of PEI, which is as a function of the pH and PEI amount. Once the saturated adsorption limit is reached, the excess free PEI molecules become more detrimental to the stability with increased solid loading. The stabilization mechanisms of Si3N4 suspensions by PEI were discussed in detail.

    DOI

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    46
    被引用数
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  • コロイド粒子の電気泳動現象を利用したセラミックスの直接成形

    打越 哲郎, 鈴木 達, 古海 誓一, 三木 理子, 目 義雄

    マテリアルインテグレーション   20 ( 2 ) 82 - 86  2007年02月

     概要を見る

    電気泳動プロセスでは、蒸着やスパッタリングなどの製膜法と異なり、帯電した粒子は電極間の最短距離を直線的に泳動するわけではなく、溶媒で満たされた空間を電位勾配に従って泳動、堆積する。電極間を電気力線に沿って泳動した粒子は電極の裏側にも回り込むため、曲面や凹凸を持つ基材表面にも比較的均一な粒子堆積膜の形成が容易にできる。この特徴を積極的に利用すると、電極の極性と空間的配置を工夫し、電場のポテンシャルを3次元的に制御することにより、粒子を基材上のある特定の場所に優先的に導き堆積させることも可能である。このことは、電場の精密制御による粒子アセンブリングの可能性を示しており、電気泳動プロセスの大きなメリットの1つとも言える。本稿では、電気泳動プロセスの概略を解説し、3次元的複雑形状部材の作製に電気泳動プロセスを応用した例を紹介する。

    CiNii

  • 酸化物系高速超塑性体の材料設計と開発

    平賀 啓二郎, 金 炳男, 森田 孝治, 吉田 英弘, 鈴木 達, 目 義雄

    マテリアルインテグレーション   20 ( 2 ) 23 - 27  2007年02月  [査読有り]

     概要を見る

    著者らの研究に基づいて、酸化物多結晶体で高速超塑性を実現するための微視構造、組成、プロセシング上の必要条件を解説する。また、これらの条件を満たすことによって得られた超塑性特性について述べる。

  • コロイドプロセスによる高次構造セラミックスの作製

    目 義雄, 鈴木 達

    マテリアルインテグレーション   20 ( 2 ) 3 - 9  2007年02月  [査読有り]

     概要を見る

    Highly structure controlled ceramics were required for improving their properties. Colloidal processing using fine particles provides this required control mechanism through well-dispersed suspension or hetero-coagulate suspension. We demonstrate highly structure controlled ceramics fabricated by novel colloidal processing; (i) dense nano-sized zirconia without pressure sintering, (ii) porous ceramics with controlled pore size by hetero-coagulated suspension of ceramics and polymer, (iii) nanocomposite by reaction sintering, and (iv) textured ceramics with feeble magnetic susceptibility by colloidal processing in a high magnetic field.

  • Preparation and properties of Al2O3-mullite-SiC nano-composite by slip casting in a high magnetic field and reaction sintering

    Sho Saito, Yoshio Sakka, Tohru S. Suzuki, Takeshi Nakata

    High-Performance Ceramics IV, Pts 1-3   336-338   1133 - 1136  2007年  [査読有り]

     概要を見る

    We have demonstrated that textured Al2O3-mullite-SiC nanocomposites can be fabricated by slip casting followed by partial oxidation - reaction sintering of mixed suspensions of Al2O3 and SiC powders in a high magnetic field. The sintered density was changed by the degree of oxidation at 1200 degrees C and 1300 degrees C. The degree of orientation of alumina in the nanocomposite was examined on the basis of the X-ray diffraction patterns and scanning electron micrographs. It is confirmed that alumina-oriented nanocomposites were fabricated. The three-point bending strength at room temperature was observed for the nanocomposites.

  • Hydrogen storage properties of Nb-Zr-Fe alloys disintegrated by hydrogen gas

    Hideo Okuyama, Masahiro Uda, Tetsuo Uchikoshi, Tohru Suzuki, Yoshio Sakka

    PROGRESS IN POWDER METALLURGY, PTS 1 AND 2   534-536   73 - +  2007年  [査読有り]

     概要を見る

    The disintegration of 6 different Nb-Zr-Fe alloys and their hydrogen storage properties due to hydrogenation have been investigated. The hydrogenation was performed in a 0.1MPa hydrogen pressure held at room temperature in are melting chamber without exposure to air atmosphere. The thermal stability of hydrogen dissolved in disintegrated powder was measured in the temperature range from room temperature to 600 degrees C by using the thermal analysis equipment. Hydrogen contents in alloys were evaluated from the mass difference of TG curve and chemical determinations for hydrogen gas analysis. The values of hydrogen content are in accordance with both chemical and mass difference methods. The hydrogen contents of disintegrated alloys synthesized were in the range of 1.2-2.0 wt% which depend on the composition of alloys.

  • FABRICATION OF TEXTURED ALUMINA-MULLITE-SILICON CARBIDE NANO-COMPOSITES

    Yoshio Sakka, Sho Saito, Atsushi Honda, Tohru S. Suzuki

    CHARACTERIZATION AND CONTROL OF INTERFACES FOR HIGH QUALITY ADVANCED MATERIALS II   198   145 - 151  2007年  [査読有り]

     概要を見る

    The controlled development of microstructure such as nanocomposite or texture is a way for effectively improving physical and mechanical properties. Al(2)O(3)-mullite-SiC nanocomposites were prepared by partial oxidation of the Al(2)O(3)-SiC green body followed by reaction sintering. Recently, we reported that the crystal orientation of alumina can be controlled in a high magnetic field due to its crystal magnetic anisotropy. By the combination of both techniques we have demonstrated that textured Al(2)O(3)-mullite-SiC nanocomposites can be fabricated by slip casting of mixed suspensions of Al(2)O(3) and SiC powders in a high magnetic field followed by partial oxidation and reaction sintering of the Al(2)O(3) and SiC. The sintered density depended on the degree of dispersion and oxidation of SiC. Dense nanocomposites were prepared by suitable oxidation and reaction sintering at 1600 without pressure. The three-point bend strength was observed approximately 800 MPa for the nanocomposites. The strength depended on the textured plane and amount of mullite phase, and increased using the suspension treated by beads-milling due to the de-agglomeration of SiC powders.

  • Direct shaping of alumina ceramics by electrophoretic deposition using conductive polymer-coated ceramic substrates

    T. Uchikoshi, S. Furumi, T. S. Suzuki, Y. Sakka

    ADVANCED MATERIALS AND PROCESSING IV   29-30   227 - 230  2007年  [査読有り]

     概要を見る

    Cathodic electrophoretic deposition of bimodal alumina suspension was performed using conductive polypyrrole (Ppy) film as an electrode. The coating of the Ppy on nonconductive ceramic substrates was performed by polymerization of pyrrole (Py) in an aqueous solution. The relative green density of the deposits measured by Archimedes' method was 68 %. Alumina ceramics were obtained by sintering the deposits together with the Ppy coated ceramic substrates in air.

  • Fabrication of highly microstructure controlled ceramics by novel colloidal processing

    Yoshio Sakka, Tetsuo Uchikoshi, Tohru S. Suzuki

    HIGH-PERFORMANCE CERAMICS IV, PTS 1-3   336-338   2372 - +  2007年  [査読有り]

     概要を見る

    Highly structure controlled ceramics were required for improving their properties. Here, we demonstrate such ceramics fabricated by novel colloidal processing; (i) dense nano-sized zirconia without pressure sintering, (ii) porous ceramics with controlled pore size by hetero-coagulated suspension of ceramics and polymer, and (iii) textured ceramics with feeble magnetic susceptibility by electrophoretic deposition in a high magnetic field.

  • Fabrication and some properties of textured ceramics by colloidal processing in high magnetic field

    Yoshio Sakka, Tohru S. Suzuki, Tetsuo Uchikoshi

    INNOVATION IN CERAMICS SCIENCE AND ENGINEERING   352   101 - +  2007年  [査読有り]

     概要を見る

    Recently to improve properties, highly microstructure controlled ceramics such as fine-grained, textured and laminated structures are required. We have demonstrated a new processing of textured ceramics with a feeble magnetic susceptibility by colloidal processing in a high magnetic field and subsequent heating. As colloidal processing, slip casting and electrophoretic deposition (EPD) have been conducted successfully. Colloidal processing is known to be a powerful method for consolidating fine particles with a high density and homogeneous microstructure. The degree of orientation strongly depends on the particle dispersion and some processing factors, such as particle size, applied magnetic field, concentration of the suspension, sintering temperature, etc. Crystalline-textured controlled laminated composites can be fabricated using EPD by varying the angle between the vectors of electric field and magnetic field. Also textured ceramics with complicated structure can be fabricated by reaction sintering. The colloidal processing in a high magnetic field confers several advantages and it is possible for this type of processing to be applied to non-cubic ceramics, such as alumina, titania, zinc oxide, tin oxide, hydroxy apatite, aluminium nitride, silicon carbide, silicon nitride, etc. The textured ceramics showed anisotropic properties depending on the crystal plane.

  • Orientation control in multilayered alumina prepared using electrophoretic deposition in a strong magnetic field

    Suzuki T.S, Uchikoshi T, Morita K, Hiraga K, Sakka Y

    Advanced Materials Research   29-30   223 - 226  2007年  [査読有り]

  • Crystalline orientation of alumina ceramics prepared by electrophoretic deposition under a high magnetic field

    T. Uchikoshi, T. S. Suzuki, Y. Sakka

    JOURNAL OF MATERIALS SCIENCE   41 ( 24 ) 8074 - 8078  2006年12月  [査読有り]

     概要を見る

    Electrophoretic deposition (EPD) of alumina in a superconducting magnet was performed at various magnetic field strengths. A stable colloidal suspension of alumina appropriate for magnetic alignment was prepared in an ethanol medium by using a phosphate ester (PE) as a dispersant. The amount of PE appropriate for the stability of the alumina suspension was investigated by measuring the pH, zeta-potential and the relative density of the green compacts. The consolidation of alumina powder was performed by EPD under a magnetic field of 0-12 T. The degree of crystalline orientation of the sintered bodies was evaluated by X-ray diffraction (XRD) as a function of the applied magnetic field during deposition and the sintering temperature.

    DOI

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    31
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  • 強磁場中スリップキャストによる窒化ケイ素セラミックスの配向

    ZHU, Xinwen, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, NISHIMURA, Toshiyuki, SAKKA, Yoshio

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   114 ( 1335 ) 979 - 987  2006年11月  [査読有り]

     概要を見る

    The effects of &amp;#61537;-Si3N4 powder, &amp;#61538;-Si3N4 seed particles and sintering conditions on the texture development in Si3N4 ceramics, which were prepared by slip casting in a strong field of 12 T, followed by pressureless sintering. In the case of the replacement of the fine powder (UBE SN-E10) with the coarse powder (UBE SN-E05), no alignment of &amp;#61537;-Si3N4 crystals was observed, but the alignment of &amp;#61538;-Si3N4 crystals was observed in the green body, despite the low amount of &amp;#61538;-Si3N4 (~ 1 wt%). This suggests that the grain alignment during slip casting is predominant by the grain alignment of the minor &amp;#61538;-Si3N4 phase present in the green &amp;#61537;-Si3N4 raw powder, which is featured by the rod-like shape and less-agglomerated form.

  • 微粒子分散を利用した固化成形プロセスと組織制御

    鈴木 達

    M&E   33 ( 11 ) 164 - 165  2006年11月

     概要を見る

    ファインセラミックスの原料に用いるサブミクロン以下の微粒子は凝集しやすく、この凝集は成形体の高密度化、均質化を妨げる要因となる。微粒子の分散状態を制御して均一で高充填の成形体を作ることは、低温焼結と欠陥サイズの低減を目指すセラミックス製造技術の基本となる。セラミックス微粒子のサスペンション中における分散制御が、その後の成形、焼結における組織制御に重要であることを示し、超塑性セラミックスや配向セラミックスの作製への適用について紹介する。

  • セラミック材料における高速超塑性

    平賀 啓二郎, 金 炳男, 森田 孝治, 吉田 英弘, 鈴木 達, 目 義雄

    まてりあ   45 ( 9 ) 640 - 643  2006年09月  [査読有り]

     概要を見る

    セラミックスにおける高速超塑性現象を高速度下で発現させるために必要な材料科学的な諸条件、そのための材料創製手法、将来の応用化を見据えた今後の課題について、NIMSの最新成果を含めて論じた。

  • 強磁場中コロイドプロセスによる弱磁性セラミックス配向体の作製

    目 義雄, 鈴木 達, 打越 哲郎

    耐火物   58 ( 9 ) 490 - 497  2006年09月  [査読有り]

     概要を見る

    微粒子の分散制御とコロイドプロセスについて概説し,強磁場中でのコロイドプロセスを用いた配向セラミックスの作成について筆者らの実験結果を紹介する。特に、アルミナ微粒子分散系において、プロセスパラメーターと配向の関係を明確にし、多様な系に適用できることを示した。

    CiNii

  • Highly controlled orientation of CaBi4Ti4O15 using a strong magnetic field

    Tohru S. Suzuki, Masahiko Kimura, Kosuke Shiratsuyu, Akira Ando, Yoshio Sakka, Yukio Sakabe

    APPLIED PHYSICS LETTERS   89 ( 13 ) 132902  2006年09月  [査読有り]

     概要を見る

    The texture of feeble magnetic ceramics can be controlled by a strong magnetic field. When the magnetic susceptibility of the c axis is smaller than that of the other axes, the c axis aligns perpendicular to the magnetic field; however, the direction is randomly oriented on the plane perpendicular to the magnetic field. The authors demonstrate in this letter that a highly controlled texture in bismuth titanate, which has a c-axis susceptibility smaller than the other axes, can be achieved using a two-step magnetic field procedure. This highly controlled orientation is effective for improving the electromechanical coupling coefficient. (c) 2006 American Institute of Physics.

    DOI

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    16
    被引用数
    (Scopus)
  • 強磁場と電場の重畳作用を利用したセラミックスのコロイドプロセス

    打越 哲郎, 鈴木 達, 目 義雄, 堀井滋

    粉体と工業   38 ( 8 ) 63 - 70  2006年08月

     概要を見る

    コロイド分散系に2つの外部場である強磁場と電場を重畳作用させることにより、結晶方位と高次構造が高度に制御された配向セラミックスを作製するNIMS独自の試みについて、我々の最近の研究成果を紹介する。

    CiNii

  • Fabrication of multilayered oxide thermoelectric modules by electrophoretic deposition under high magnetic fields

    Taichi Okamoto, Shigeru Horii, Tetsuo Uchikoshi, Tohru S. Suzuki, Yoshio Sakka, Ryoji Funahashi, Naoko Ando, Masayuki Sakurai, Jun-ichi Shimoyama, Kohji Kishio

    APPLIED PHYSICS LETTERS   89 ( 8 ) 081912  2006年08月  [査読有り]

     概要を見る

    The authors report the fabrication of grain-aligned [Ca2CoO3-delta](0.62)CoO2 (Ca349) thick films and a multilayered thermoelectric unicouple of Ca349 and Ca0.9La0.1MnO3-delta (Mn113) using electrophoretic deposition (EPD) and magnetic alignment methods. Strongly c-axis-oriented Ca349 thick films were obtained by EPD performed under magnetic fields. In addition, the c axis of grains was found to always align parallel to the direction of field, independently of the EPD cell configuration. The required conditions for magnetic grain alignment of fine Ca349 powders were quantitatively discussed based on magnetization anisotropy. An alpha-Al2O3/Mn113/alpha-Al2O3/Ca349/alpha-Al2O3 multilayered thick film was successfully developed.

    DOI

    Scopus

    30
    被引用数
    (Scopus)
  • Control of the texture in feeble magnetic ceramics using colloidal processing in a strong magnetic field

    Tohru S. Suzuki, Yoshio Sakka, Koichi Kitazawa

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   53 ( 6 ) 479 - 487  2006年06月  [査読有り]

     概要を見る

    The controlled development of texture has recently become a topic of interest in ceramic processing, since it allows improved tailoring of the properties of a material. Anisotropic susceptibilities of feeble magnetic ceramics such as A12O3 and ZnO are quite small. It is generally difficult to apply a magnetic field effectively in order to rotate fine feeble magnetic particles, since fine particles tend to spontaneously agglomerate due to strong attractive interactions (van der Waals forces). It is necessary to disperse the particles in a suspension in order to effectively utilize a magnetic field to rotate the particles. Colloidal processing is a powerful technique for controlling the stability of particles in a suspension. This processing can be used for production of textured ceramics with complex shapes by near-net-shape slip casting. In addition, the direction of textured polycrystalline can be controlled by the direction of the applied magnetic field.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Control of texture in alumina by colloidal processing in a strong magnetic field

    Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   7 ( 4 ) 356 - 364  2006年05月  [査読有り]

     概要を見る

    Electrical, mechanical and other properties of ceramic materials can be controlled by designing their microstructures. It had generally been difficult to utilize a magnetic field for tailoring the microstructure, in feeble magnetic ceramics, such as Al2O3; however, the possibility of controlling the microstructure by a magnetic field occurred with the development of superconducting magnets. In this review paper, we introduce a novel processing for the microstructual design in ceramics by colloidal processing in a strong magnetic field and an electric field. We demonstrate that the textured alumina can be fabricated by slip casting in a strong magnetic field and the production of alumina/alumina laminar composites with different crystalline-oriented layers can be achieved by electrophoretic deposition in a strong magnetic field. In order to control the texture using a magnetic field, a good dispersion of powder in a suspension is necessary because a strong attractive force between the agglomerated particles prevents each particle in a suspension from rotating in the magnetic field. The degree of orientation depends on the processing factors, such as heating temperature, viscosity of suspension, etc. And the grain growth in Al2O3 matrix enhances crystallographic texture development. The bending strength of the laminar composite depended on the direction of the multilayered microstructure with alternate crystalline-oriented layers. Crack propagation and fracture mode depend on the direction of microstructure in the laminar composite with controlled crystalline orientation. (c) 2006 NIMS and Elsevier Ltd. All rights reserved.

    DOI

    Scopus

    104
    被引用数
    (Scopus)
  • 6th Pacific Rim Conference on Ceramics and Glass Technology (PAC RIM 6)に参加して

    鈴木 達

    粉体工学会誌   43 ( 2 ) 137 - 138  2006年02月

     概要を見る

    2005年9月に行われた6th Pacific Rim Conference on Ceramics and Glass Technology (PAC RIM 6)について報告し、最近のセラミックスの研究、開発動向の情報を提供する。

    DOI CiNii

  • Texture development in Si3N4 ceramics by magnetic field alignment during slip casting

    Xinwen Zhu, Tohru S. Suzuki, Tetsuo Uchikoshi, Toshiyuki Nishimura, Yoshio Sakka

    Journal of the Ceramic Society of Japan   114 ( 1335 ) 979 - 987  2006年  [査読有り]

     概要を見る

    The effects of α-Si3N4 powder, β-Si 3N4 seed particles and sintering conditions on the texture development in Si3N4 ceramics, which were prepared by slip casting in a strong field of 12 T, followed by pressureless sintering. In the case of the replacement of the fine powder (UBE SN-E10) with the coarse powder (UBE SN-E05), no alignment of α-Si3N4 crystals was observed, but the alignment of β-Si3N4 crystals was observed in the green body, despite the low amount of β-Si3N4 (∼1 wt%). This suggests that the grain alignment during slip casting is predominant by the grain alignment of the minor β-Si3N4 phase present in the α-Si 3N4 raw powder, which is featured by the rod-like shape and less-agglomerated form. The alignment of both α-Si3N 4 and β-Si3N4 crystals occurs by the c-axis of the crystals perpendicular to the magnetic field. The addition of 5 wt% β-Si3N4 particles leads to the enhanced grain orientation of the β-Si3N4 particles in the green body for both raw α-Si3N4 powders. It is shown that the crystallographic orientation of β-Si3N4 is enhanced by the substitution of SN-E10 for SN-E05 powder, the addition of β-Si3N4 particles and prolonged sintering, but the phase transformation of α to β may play a dominant role in the texture development in Si3N4 during sintering, compared to the grain growth after the complete phase transformation. Owing to the crystallographic orientation, the samples exhibited anisotropic shrinkage behavior during sintering and the anisotropy becomes strong with enhanced grain orientation. The present study suggests that the control of the alignment of β-Si3N4 is crucial for the texture development in Si3N4 by the magnetic field alignment.

    DOI

    Scopus

    43
    被引用数
    (Scopus)
  • Electrophoretic deposition of alumina on conductive polymer-coated ceramic substrates

    Tetsuo Uchikoshi, Seiichi Furumi, Tohru S. Suzuki, Yoshio Sakka

    Journal of the Ceramic Society of Japan   114 ( 1325 ) 55 - 58  2006年  [査読有り]

     概要を見る

    The coating of conductive polypyrrole (Ppy) on nonconductive ceramic substrates was performed by polymerization of pyrrole (Py) in an aqueous solution. The Ppy film was characterized by scanning electron microscopy and conductivity measurements. Electrophoretic deposition of bimodal alumina suspension prepared with a phosphate ester was performed using Ppy film as a cathode. Fabrication of alumina ceramics with irregular shapes or complicated patterns were also attempted by sintering the deposits together with the Ppy coated substrates in air.

    DOI

    Scopus

    21
    被引用数
    (Scopus)
  • Design of alumina/alumina laminate composites with crystalline-orientated layers produced by electrophoretic deposition under a high magnetic field

    Tetsuo Uchikoshi, Tohru S. Suzuki, Hideo Okuyama, Yoshio Sakka

    ELECTROPHORETIC DEPOSITON: FUNDAMENTALS AND APPLICATIONS II   314   25 - 30  2006年  [査読有り]

     概要を見る

    Highly crystalline-textured alumina ceramics were fabricated by electrophoretic deposition (EPD) in a strong magnetic field of 12 T. Preferred orientation of the bulk was controlled by changing the direction of the applied electric field E relative to the magnetic field B during the EPD. Average orientation angle of the prepared monoliths as a function of the angle between the vectors E and B, phi B-E was estimated from the X-ray diffraction analysis. Alumina/alumina laminar composites with crystalline-oriented layers were also fabricated by alternately changing the phi B-E layer by layer during EPD in a magnetic field of 12 T.

  • Control of crystalline texture in polycrystalline TiO2 (anatase) by electrophoretic deposition in a strong magnetic field

    T Uchikoshi, TS Suzuki, S Iimura, FQ Tang, Y Sakka

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   26 ( 4-5 ) 559 - 563  2006年  [査読有り]

     概要を見る

    Crystalline oriented titania (anatase) thick films have been fabricated by electrophoretic deposition in a strong 12T magnetic field. Anatase particles in an aqueous suspension are rotated due to their magnetic anisotropy and then deposited on a substrate in a dc electric field. The angle between the directions of the magnetic and electric fields phi(B-E) is fixed at specified angles (phi(B-E) = 0, M 60 and 90 degrees) during the deposition to control the dominant crystalline orientation of the deposits. The crystalline orientation characterized by the X-ray diffraction for the anatase films proves the orientation dependence of anatase upon the phi(B-E) angle during the EPD. The crystalline orientation of the anatase films can be controlled by varying the angle of E versus B. (c) 2005 Elsevier Ltd. All rights reserved.

    DOI

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    45
    被引用数
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  • Mechanical properties of textured, multilayered alumina produced using electrophoretic deposition in a strong magnetic field

    Suzuki T.S, Uchikoshi T, Okuyama H, Sakka Y, Hiraga K

    Journal of the European Ceramic Society   26 ( 4-5 ) 661 - 665  2006年  [査読有り]

    DOI

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    24
    被引用数
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  • Mechanical properties of textured alumina prepared by colloidal processing in a strong magnetic field

    Suzuki T.S, Uchikoshi T, Monta K, Hiraga K, Sakka Y

    Materials Research Society Symposium Proceedings   977   9 - 11  2006年  [査読有り]

  • Control of magnetic anisotropy in (Bi1-xPbx) 2(AE1-yREy)2Co2O z and fabrication of magnetically aligned bulks

    T. Kumagai, S. Horii, T. Okamoto, J. Shimoyama, K. Kishio, T. Uchikoshi, T.S. Suzuki, Y. Sakka, M. Mikami, R. Funahashi

    Ceramic Transactions   196   291 - 301  2006年  [査読有り]

  • Fabrication of grain-aligned thick films of thermoelectric oxides by an electrophoretic deposition method under high magnetic fields

    T. Okamoto, S. Horii, T. Kumagai, J.-I. Shimoyama, K. Kishio, T. Uchikoshi, T. Suzuki, Y. Sakka

    Ceramic Transactions   196   257 - 266  2006年  [査読有り]

  • 導電性ポリマーを被覆したセラミックス基材へのアルミナの電気泳動堆積

    UCHIKOSHI, Tetsuo, FURUMI, Seiichi, SUZUKI, Tohru, SAKKA, Yoshio

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   114 ( 1325 ) 55 - 58  2006年01月  [査読有り]

     概要を見る

    The coating of conductive polypyrrole (Ppy) on nonconductive ceramic substrates was performed by polymerization of pyrrole (Py) in an aqueous solution. The Ppy film was characterized by scanning electron microscopy and conductivity measurements. Electrophoretic deposition of bimodal alumina suspension prepared with a phosphate ester was performed using Ppy film as a cathode. Fabrication of alumina ceramics with irregular shapes or complicated patterns were also attempted by sintering the deposits together with the Ppy coated substrates in air.

  • NA

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   114 ( 1 ) 59 - 62  2006年01月  [査読有り]

     概要を見る

    Magnetic susceptibility is very small in feeble magnetic ceramics; consequently, it had been very difficult to develop a textured microstructure in these ceramics by using a magnetic field. We have demonstrated, however, that textured microstructures in alumina can be prepared by colloidal processing in a high magnetic field. We applied this processing technique to alumina based composites. The degree of crystallographic texture was small in specimen sintered at the low temperature. The degree of orientation increased rapidly with increasing sintering temperature and depended on the grain size of alumina matrix. The grain size can be controlled by the content of YTZ particle as a second phase, the kind of dopant, sintering temperature, annealing temperature and annealing time.

  • 電場と強磁場の重畳作用によるセラミックスのマテリアルデザイン

    鈴木 達, 打越 哲郎, 目 義雄

    マテリアルインテグレーション   18 ( 11 ) 26 - 30  2005年11月

     概要を見る

    コロイドプロセスにおける電場を用いた積層制御および強磁場を用いた配向制御を概説した。さらに電場と強磁場を重畳作用することによる配向積層させた構造制御についての解説を行った。アルミナについて、配向方向が層毎に90度づつ異なる積層体を実際に作製し、このプロセスの応用の一例として示した。

    CiNii

  • 水酸アパタイトの緻密化と超塑性

    Keiichiro TAGO, Kiyoshi ITATANI, SUZUKI, Tohru, SAKKA, Yoshio, Seiichiro KODA

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   113 ( 1322 ) 669 - 673  2005年10月  [査読有り]

     概要を見る

    Fabrication conditions of the high-density and fine-grained hydroxyapatite(Ca10(PO4)6(OH)2: HAp)ceramic were examined; the tensile elongation of HAp ceramic during the heating was measured in order to evaluate the superplasticity. The HAp compact was fired in air at a temperature between 1100 and 1200○C for 5 h. The relative density of HAp compact fired at 1100○C for 5 h showed a maximum (99.2%), whereas the average grain size was as small as 0.56 &amp;#61549;m. The tensile elongation of this HAp specimen was tested at a temperature between 940 and 1100○C. The tensile elongations tested at 1050 and 1100○C attained 156 and 157%, respectively; the specimen tested at 1050○C contained a limited number of cavities, whereas the specimen tested at 1100○C was observed to have a large number of

  • 強磁場電気泳動堆積法による配向セラミックスの創製

    打越 哲郎, 鈴木 達, 目 義雄

    MATERIAL STAGE   5 ( 7 ) 111 - 115  2005年10月

     概要を見る

    コロイド分散系に2つの外部場である強磁場と電場を重畳作用させることにより、結晶方位と高次構造が高度に制御された新しい配向セラミックスを作製する試みについて紹介する。

    CiNii

  • 磁場と電場の重畳印加によるセラミックスの高次構造制御

    鈴木 達, 打越 哲郎, 目 義雄

    Fine Ceramics Report   23 ( 4 ) 166 - 169  2005年10月

     概要を見る

    当グループでは反磁性セラミックスでさえも配向を可能とする強磁場プロセスを既に開発してきており、さらに、配向と積層を組み合わせることで高次な構造の創製を目指している。そのために、強磁場中での電気泳動堆積を試みており、任意の方向に配向させた層を堆積させることにより、配向と積層を組み合わせた高度な異方性制御が可能であることを見出した。磁場と電場の重畳印加による配向積層制御プロセスについて紹介する。

    CiNii

  • NA

    E. Guilmeau, D. Chateigner, SUZUKI, Tohru, SAKKA, Yoshio, C. Henrist, B. Oulanddiaf

    annual report 04, Institute Laue-Langevin     36 - 37  2005年08月  [査読有り]

     概要を見る

    The orientation distributions of alpha-alumina textured ceramics are determined from neutron di9ffraction spe3ctra. A curved position-sensitive detector coupled to a tilt angle scan allowed treatment of the whole diffraction pattern in a Rietvelt-WIMV-Popa algorithm. With increasing the sintering temperature of alumina, the texture strength is enhanced and the c-axis distribution is sharper. We se

  • 強磁場によるセラミックス結晶配向制御プロセス

    鈴木 達, 打越 哲郎, 目 義雄

    工業材料   53 ( 8 ) 60 - 63  2005年08月

     概要を見る

    アルミナ等の反磁性・常磁性セラミックスであっても強磁場とコロイドプロセスを用いれば結晶配向が可能であり、この手法が適用物質と成形法の選択の広さから汎用性が高く、高次な構造をデザインすることが可能となるプロセスでることを紹介する。

    CiNii

  • 外場制御コロイドプロセスによる高次構造セラミックスの創製

    打越 哲郎, 鈴木 達

    ANNUAL REPORT OF HOSOKAWA POWDER TECHNOLOGY FOUNDATION 2004   12   82 - 88  2005年05月

     概要を見る

    溶媒中におけるセラミックス粒子の表面帯電現象と粒子間の相互作用を利用して固化成形体の微構造制御を行う「コロイドプロセス」を、電場や磁場などの外場が印加された環境下で行うことで、より高次な組織微構造の制御が行える「外場印加コロイドプロセス」という新しい手法・概念に発展させた。本報は、I. 電気泳動堆積法における粒子堆積挙動に及ぼす諸因子の影響の解明II.強磁場中鋳込み成形法による粒子配向技術の確立と適応系の拡大III.強磁場電気泳動堆積法による結晶方位制御と積層コンポジットの作製について、ホソカワ粉体工学振興財団による助成研究の成果報告書として寄稿されたものであるが、内容・スタイルは、オリジナルな研究論文となっている。

  • Preparation of oriented bulk 5wt% Y2O3–AlN ceramics by slip casting in a high magnetic field and sintering

    Tohru S. Suzuki, Yoshio Sakka

    Scripta Materialia   52 ( 7 ) 583 - 586  2005年04月  [査読有り]

     概要を見る

    微粒子の分散を制御したサスペンションを用いて磁場中スリップキャストを行うことにより、AlNの結晶方位を配向制御可能であることを見出した。AlN六方結晶のa, b軸が磁場と平行になるように配向し、配向度は緻密化が進むほど増加する。また、配向AlN焼結体の曲げ強度、靭性、熱伝導率は配向させた方位に依存し、3っの特性が同時に改善可能であると考えられる。

    DOI

    Scopus

    66
    被引用数
    (Scopus)
  • Microstructural design for high-strain-rate superplastic oxide ceramics

    K Hiraga, BN Kim, K Morita, TS Suzuki, Y Sakka

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   113 ( 1315 ) 191 - 197  2005年03月  [査読有り]

     概要を見る

    Factors limiting the strain rate available to superplastic deformation in oxide ceramics are discussed from existing knowledge about high-temperature plastic deformation and cavitation mechanisms. Simultaneously controlling these factors is essential for attaining high-strain-rate superplasticity (HSRS). This is shown in monolithic tetragonal zirconia and composite materials consisting of zirconia, alpha-alumina and a spinel phase: at strain rates higher than 10(-2)s(-1), tensile ductility reached 300-600% in the monolithic material and 600-2500% in the composite materials. Post-deformation microstructure indicates that certain secondary phases should be effective in suppressing cavitation damage and thereby enhancing HSRS.

  • 強磁場・電場印加コロイドプロセスによる構造制御セラミックスの創製

    鈴木 達, 打越 哲郎, 奥山 秀男, 目 義雄

    セラミックス   40 ( 3 ) 168 - 172  2005年03月

     概要を見る

    従来は磁場の影響を受けないと考えられてきたアルミナのような弱磁性セラミックスでもコロイドプロセスと強磁場を用いることで、その結晶方位を制御できることを見出した。ここでは、弱磁性セラミックスの結晶磁気異方性を利用した磁場配向と、電気泳動法の高次成形プロセスを組み合わせた強磁場電気泳動法による結晶配向積層コンポジットの創製について解説する。

    CiNii

  • コロイドプロセスの高度化による高次構造耐環境セラミックスの作製に関する研究

    目 義雄, 鈴木 達, 打越 哲郎, 平賀 啓二郎, 金 炳男, 森田 孝治

    平成15年度国立機関等原子力試験研究成果報告書   44  2005年02月

     概要を見る

    コロイドプロセスの高度化を図ることにより、優れた特性を有する原子力用構造材料を作成することを目的とした。今年度は、SiCナノ粒子にポリエチレンを添加することによる水系サスペンションの安定性チタニアナノ粒子の電気泳動堆積挙動とサスペンションの安定性、およびスリップキャストによる高速超塑性の作成について報告した。

  • New processing of textured ceramics by colloidal processing under high magnetic field

    Y Sakka, TS Suzuki

    HIGH-PERFORMANCE CERAMICS III, PTS 1 AND 2   280-283   721 - 728  2005年  [査読有り]

     概要を見る

    The controlled development of texture is one of the ways for effective in improving the physical and mechanical properties. We'll demonstrate new processing of textured ceramics as an example of alumina by slip casting in a high magnetic field and subsequent heating. Susceptibility of diamagnetic alpha-alumina is very small, but the orientation energy of alumina particle by a high magnetic field becomes larger than the thermal energy. alpha-alumina of a rhombohedral structure shows anisotropic susceptibility, but this anisotropy has up to now been more or less ignored due to its very low value. However, in a high magnetic field the energy of crystal anisotropy becomes comparable to or larger than the energy of thermal motion. The degree of orientation depends on processing factors such as heating temperature, particle size, magnetic field and concentration of suspension, etc. This process technique confers several advantages and it is possible for this type of processing to be applied to other non-cubic ceramics, such as TiO2, ZnO, SnO, HAP, AlN, SiC, etc.

  • Texture of alumina by neutron diffraction and SEM-EBSD

    E Guilmeau, C Henrist, TS Suzuki, Y Sakka, D Chateigner, D Grossin, B Ouladdiaf

    ICOTOM 14: TEXTURES OF MATERIALS, PTS 1AND 2   495-497   1395 - 1400  2005年  [査読有り]

     概要を見る

    The orientation distributions of alpha-Al2O3 textured ceramics are determined from neutron diffraction and SEM-EBSD. A curved position-sensitive detector coupled to a tilt angle (chi) scan allowed the whole neutron diffraction pattern treatment in the combined Rietveld-WIMV-Popa algorithm. Analyses from neutron and electron diffraction data gave similar results if EBSD data are smoothed to account for grain statistics. Four textured alumina ceramics were prepared by slip-casting under a high magnetic field and sintered at 800 degrees C, 1300 degrees C, 1400 degrees C and 1600 degrees C. The inverse pole figures and EBSD-mapping highlights the influence of the magnetic field and sintering temperature on the texture development. The inverse pole figures calculated for the fiber direction show a major (001) component for all the samples. With the increasing sintering temperature, the texture strength is enhanced and the c-axis distribution is sharper. The effectiveness of the combined approach for determining the crystallite size is also evident. As a global trend, the calculated crystallite size and observed grain size are similar and increase with the increasing sintering temperature. The mechanism of the texture development in the sintered specimens is certainly initiated from the preferred orientation of the green body after slip-casting under a high magnetic field. The basal texture is enhanced during sintering by selective anisotropic grain growth. We evidenced here the powerfulness of the Rietveld texture analysis correlated to SEM-EBSD calculation to provide a basis for the correlation of texture, microstructural parameters and anisotropic properties.

  • 強磁場コロイドプロセスによる弱磁性セラミックスの配向

    SAKKA, Yoshio, SUZUKI, Tohru

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   113 ( 1313 ) 26 - 36  2005年01月  [査読有り]

     概要を見る

    In this review paper, we introduce a new processing of textured ceramics with a feeble magnetic susceptibility by slip casting in a high magnetic field and subsequent heating. As an example of feeble magnetic ceramics, we demonstrate the fabrication of textured alumina in details. The susceptibility of diamagnetic &amp;#61537;-alumina is very small, but the orientation energy of the alumina particle by a high magnetic field becomes greater than the thermal energy. &amp;#61537;-Alumina with a rhombohedral structure shows anisotropic susceptibility, but this anisotropy has up to now been more or less ignored due to its very low value. However, in a high magnetic field, the energy of crystal anisotropy becomes comparable to or greater than the energy of thermal motion. The degree of orientation depends on the processing factors, such as heating temperature, particle size, applied magnetic field, concentration of the suspension, etc. This process technique confers several advantages and it is possible for this type of pr

  • Rietveld texture analysis of alumina ceramics by neutron diffraction

    E Guilmeau, D Chateigner, TS Suzuki, Y Sakka, C Henrist, B Ouladdiaf

    CHEMISTRY OF MATERIALS   17 ( 1 ) 102 - 106  2005年01月  [査読有り]

     概要を見る

    The orientation distributions of alpha-Al2O3 textured ceramics are determined from neutron diffraction spectra. A curved position-sensitive detector coupled to a tilt angle (chi) scan allowed the whole diffraction pattern treatment in the combined Rietveld-WIMV-Popa algorithm. Four textured alumina ceramics were prepared by slip-casting under a high magnetic field and sintered at 800, 1300, 1400, and 1600 degreesC. The calculation of the distribution density, correlated to the representation of the normal and inverse pole figures, highlights the influence of the magnetic field and sintering temperature on the texture development. The principal pole figures show a pronounced (00l) texture: (001) pole parallel to the direction of slip-casting, and (110) pole with higher distribution density for the directions perpendicular to the expected fiber axis. The inverse pole figures calculated for the fiber direction show a major (001) component for all the samples. With the increasing sintering temperature, the texture strength is enhanced and the c-axis distribution is sharper. The effectiveness of the approach for determining the crystallite size is also evident. As a global trend, the calculated crystallite size and observed grain size are similar and increase with the increasing sintering temperature. The mechanism of the texture development in the sintered specimens is certainly initiated from the preferred orientation of the green body after slip-casting under a high magnetic field. The basal texture is enhanced during sintering by selective anisotropic grain growth. We evidenced here the powerfulness of the Rietveld texture analysis to provide a basis for the correlation of texture, microstructural parameters, and anisotropic properties.

    DOI

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    20
    被引用数
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  • Development of thermoelectric bi-based cobaltites with an easy axis of magnetization parallel to the C-axis for magnetic alignment

    T Kumagai, S Horii, T Uchikoshi, TS Suzuki, Y Sakka, T Okamoto, J Shimoyama, K Kishio

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS   44 ( 37-41 ) L1263 - L1266  2005年  [査読有り]

     概要を見る

    We report the conversion of the easy axis of magnetization from the a-axis to the c-axis in thermoelectric misfit-layered Bismuth-based cobaltites for a magnetic grain-alignment process. The conversion was accomplished by the substitution of Ca for Sr in the block layer of [(Bi0.5Pb0.5)(2)Sr2O4](0.55)CoO2. Moreover, magnetic anisotropy along the c-axis was enhanced by partial substitution of Pr for Ca in [(Bi0.5Pb0.5)(2)Ca2O4](z)CoO2. From the analysis of their crystal structures, we concluded that the doping of Pr and Ca played a role in distortion of the block layer, indirectly leading to changes in the local structure of the CoO2 layers and magnetic anisotropy. The c-axis grain-aligned bulk has been successfully fabricated by a magnetic grain-alignment method in 10T, and a drastic reduction in the resistivity perpendicular to the applied field and the grain-oriented microstructure were observed.

    DOI

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    13
    被引用数
    (Scopus)
  • The crystal orientation taking account of gravity force under high magnetic field

    CY Wu, SQ Li, K Sassa, Y Sakka, TS Suzuki, S Asai

    ISIJ INTERNATIONAL   45 ( 7 ) 997 - 1000  2005年  [査読有り]

     概要を見る

    High magnetic field is well known to have the function of crystal orientation, which is largely influenced by crystal size and shape to some extent. For crystals with large rod shape, the gravity force functions and affects the crystal orientation. In our experiment, different results were got when a high magnetic field was applied perpendicular and parallel to the gravity force. In this paper, the effect of the gravity force for crystal orientation under the high magnetic field is summarized and compared with the experiment result.

    DOI

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    11
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  • Processing-Dependent Microstructural Factors Affecting Cavitation Damage and Tensile Ductility in a Superplastic Alumina Dispersed with Zirconia

    Keijiro Hiraga, Keishi Nakano, Tohru S. Suzuki, Yoshio Sakka

    Journal of the American Ceramic Society   85 ( 11 ) 2763 - 2770  2004年12月  [査読有り]

     概要を見る

    Abstract: Superplastic tensile ductility in Al2O3-10 vol% ZrO2 (3 mol% Y2O3) exhibits processing-dependence when the grain size is reduced to 0.45 um for a given relative density of ~99.5%. The reduced grain size leads to largely enhanced ductility in a material prepared by colloidal processing, but does not in a material prepared by conventional dry processing. This result is explained from cavity-damage accumulation sensitive to rather a small variation in a few processing-dependent factors: the numerical densities of residual defects and ZrO2 particles. The rate of damage accumulation is shown to depend mainly on the former and additionally on the latter.

    DOI

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    27
    被引用数
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  • 電・磁界印加による配向チタニアの作製

    FRENGQIU, TANG, UCHIKOSHI, Tetsuo, OZAWA, Kiyoshi, SUZUKI, Tohru, SAKKA, Yoshio

    TRANSACTIONS OF THE MAGNETICS SOCIETY OF JAPAN   29 ( 8 ) 3379 - 3382  2004年12月  [査読有り]

     概要を見る

    Electrophoretic Deposition process was used to deposit titania particles on an electrode to form the thick films from an aqueous suspension, while a high magnetic field was used to align the particles at the same time. X-ray diffraction pattern and scanning electron microscope revealed that textured titania thick films were fabricated successfully, the grains in the c-axis direction were orientated along the high magnetic field even though the anisotropic susceptibility of titania is quite feeble. The suspension condition and heating temperature play important role on the alignment of the particles. The degree of crystalline texture increased with sintering temperature, and a highly dispersed suspension was also favorable for the alignment of particle direction in the high magnetic field t

  • Alignment of TiO2 particles by electrophoretic deposition in a high magnetic field

    FQ Tang, T Uchikoshi, TS Suzuki, Y Sakka

    MATERIALS RESEARCH BULLETIN   39 ( 14-15 ) 2155 - 2161  2004年12月  [査読有り]

     概要を見る

    Textured titania thick films were fabricated by applying external electrical and magnetic fields. X-ray diffraction (XRD) results and scanning electron microscopy (SEM) images revealed that the titania grains in the c-axis direction were orientated along the high magnetic field (10 T) even though the anisotropic susceptibility of titania ceramic is quite weak. (C) 2004 Elsevier Ltd. All rights reserved.

    DOI

  • Fabrication of oriented beta-alumina from porous bodies by slip casting in a high magnetic field

    Y Sakka, A Honda, TS Suzuki, Y Moriyoshi

    SOLID STATE IONICS   172 ( 1-4 ) 341 - 347  2004年08月  [査読有り]

     概要を見る

    Designing texture is one possible way for improving the electrical, chemical, mechanical and other properties of ceramics. We have reported that oriented alpha-alumina was obtained by slip casting in a high magnetic field followed by sintering. beta-Alumina is well known as sodium ion conductor used in a sodium-sulfur battery. beta-Alumina consists of spinel blocks and ion conductive planes. Since the direction of the ion conductive plane of polycrystalline beta-alumina is random, the ionic conductivity of the polycrystal is lower than that of the single crystal. The purpose of this study is to prepare oriented beta-alumina to enhance the sodium ion conductivity. Oriented beta-alumina was prepared by the following method: (1) oriented alpha-alumina green bodies were prepared by colloidal processing in a high magnetic field, (2) the oriented alpha-alumina green bodies were infiltrated with Na2O and MgO, and (3) the oriented beta-alumina bodies were synthesized by reaction sintering at 1600 and 1700 degreesC. The reaction product and orientation of the beta-alumina were confirmed by XRD. (C) 2004 Elsevier B.V. All rights reserved.

    DOI

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    32
    被引用数
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  • Effect of titania and magnesia addition to 3 mol% yttria doped tetragonal zirconia on some diffusion related phenomena

    Y Sakka, TS Suzuki, T Matsumoto, K Morita, K Hiraga, Y Moriyoshi

    SOLID STATE IONICS   172 ( 1-4 ) 499 - 503  2004年08月  [査読有り]

     概要を見る

    The 3 mol% yttria doped tetragonal zirconia (3YTZ) is known to show ionic conductivity and superplastic property. However, the application of superplasticity to the manufacturing process is limited because the strain rate is low. The purpose of this study is to fabricate high-strain rate superplastic zirconias by adding titania and magnesia to 3YTZ. Effect of titania and magnesia addition to 3YTZ on diffusion related phenomena such as sintering, grain growth, superplastic properties and ionic conductivity was investigated. Dense and fine-grained zirconia polycrystals were obtained by colloidal processing, where aqueous suspensions were prepared by dispersing 3YTZ, magnesia and titania powders by ultrasonication and adding the appropriate amount of polyelectrolyte. The grain growth was controlled by cation lattice diffusion and the grain growth rate was enhanced by adding titania and magnesia. The tensile ductility of about 216% was established for the titania and magnesia added 3YTZ at the low temperature of 1350 degreesC and high strain rate of 1.2 x 10(-2)s(-1). The ionic conductivity of 3YTZ was decreased with titania addition. (C) 2004 Elsevier B.V All rights reserved.

    DOI

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    9
    被引用数
    (Scopus)
  • Texture development in zirconia-dispersed alumina composites by slip casting in a high magnetic field

    TS Suzuki, Y Sakka, K Kitazawa

    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY   14 ( 2 ) 1584 - 1587  2004年06月  [査読有り]

     概要を見る

    Many trials have been reported for the production of textured ceramics. Recently, such processing using a high magnetic field has been developed. After the suspension was compacted in a high magnetic field, a green body with a slight degree of crystallographic orientation was obtained. The degree of texture increased with increasing temperature. After densification, grains grew to produce ceramics with a higher degree of crystallographic orientation. We were able to produce a highly textured microstructure. In this paper, we discuss the relationship between the microstructure and the crystalline orientation, and demonstrate that the crystalline orientation depends on the grain size.

    DOI

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    9
    被引用数
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  • Strain softening and hardening during superplastic-like flow in a fine-grained MgAl2O4 spinel polycrystal

    K Morita, K Hiraga, BN Kim, TS Suzuki, Y Sakka

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   87 ( 6 ) 1102 - 1109  2004年06月  [査読有り]

     概要を見る

    Superplastic-like flow in a fine-grained MgAl2O4 polycrystal exhibits strain softening and hardening, which cannot be ascribed to cavity damage and grain growth during deformation, respectively. The softening and hardening can be related to a change in the internal stress, which depends on a decrease and an increase in the density of the intragranular dislocations, respectively, whose motion contributes to the relaxation of stress concentrations exerted through the predominant deformation mechanism of grain-boundary sliding. In these two regions, the rate of deformation is controlled by the continuous recovery of the dislocations limited by lattice diffusion of the oxygen ions.

    DOI

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    15
    被引用数
    (Scopus)
  • 強磁場中コロイドプロセスを用いた弱磁性セラミックスの異方性制御

    鈴木 達, 打越 哲郎, 奥山 秀男, 目 義雄

    MATERIALS INTEGRATION(マテリアルインテグレーション)   17 ( 5 ) 32 - 38  2004年05月

     概要を見る

    従来は磁場の影響を受けないと考えられてきた弱磁性セラミックスでもコロイドプロセスと強磁場を用いることで、その配向を制御できることを見出した。ここでは、アルミナを例にとり、強磁場を用いて配向制御するためのプロセス因子を解説し、その応用として酸化チタン、酸化亜鉛なども配向制御した例を示した。

    CiNii

  • Control of crystalline texture in polycrystalline alumina ceramics by electrophoretic deposition in a strong magnetic field

    T Uchikoshi, TS Suzuki, H Okuyama, Y Sakka

    JOURNAL OF MATERIALS RESEARCH   19 ( 5 ) 1487 - 1491  2004年05月  [査読有り]

     概要を見る

    Highly crystalline-textured pure dense alumina ceramics were fabricated from spherical alumina powder without any seed particles and sintering additives by electrophoretic deposition (EPD) in a strong magnetic field of 10 T. The crystalline texture was confirmed by x-ray diffraction (XRD) for alumina ceramics deposited at 10 T followed by sintering at 1873 K. The angle between the directions of the magnetic and electric fields (phi(B-E)) was altered to control the dominant crystal faces of the alpha-alumina monoliths. The average orientation angles estimated from the XRD diagram of the samples prepared at phi(B-E) = 0degrees, 45degrees, and 90degrees were 16.52degrees, 45.15degrees, and 84.90degrees, respectively. Alumina/alumina laminar composites with different crystalline-oriented layers were also fabricated by alternately changing the phi(B-E) layer by layer during EPD in a 10 T magnetic field. It was demonstrated that by using this technique, it is possible to control the crystalline orientation by changing the angle of E versus B during the EPD.

    DOI

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    25
    被引用数
    (Scopus)
  • 電・磁界印加コロイドプロセスによる高次組織制御

    目 義雄, 鈴木 達, 打越 哲郎

    化学と工業   57 ( 4 ) 403 - 405  2004年04月

     概要を見る

    コロイドプロセスは、溶液中の微粒子の分散・凝集を制御し成形する手法で、緻密で微細粒焼結体の作製手段として注目されてきた.さらに,外界から電界・磁界を印加することにより,高度に微構造を制御するプロセスとして期待されいる.ここでは、我々の行っている超塑性微細粒セラミックスの作製と特性、電気泳動堆積法による積層体の作製、および強磁場印加コロイドプロセス―粒成長による高配向構造体の作製、について紹介する.

    CiNii

  • Fabrication of textured alumina by electrophoretic deposition in a strong magnetic field

    T Uchikoshi, TS Suzuki, H Okuyama, Y Sakka

    JOURNAL OF MATERIALS SCIENCE   39 ( 3 ) 861 - 865  2004年02月  [査読有り]

     概要を見る

    Textured alumina ceramics were fabricated by electrophoretic deposition in a strong magnetic field of 10 T (Tesla) followed by sintering. Single crystalline alpha-alumina particles dispersed in aqueous media were aligned due to their anisotropic diamagnetic susceptibility and then deposited on a cathodic substrate. The degree of crystalline orientation of the as-deposited specimen characterized by X-ray diffraction was small but highly improved by sintering in the temperature range of 1273-1873 K. Microstructural observations showed the absence of any anisotropic grain growth. (C) 2004 Kluwer Academic Publishers.

    DOI

  • Electrophoretic deposition of alumina suspension in a strong magnetic field

    T Uchikoshi, TS Suzuki, H Okuyama, Y Sakka, PS Nicholson

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   24 ( 2 ) 225 - 229  2004年  [査読有り]

     概要を見る

    Textured monolithic alumina ceramics were synthesized by electrophoretic deposition (EPD) in strong magnetic field of 10 T. Single crystalline, granular a-alumina particles in aqueous suspensions were rotated due to their anisotropic diamagnetic susceptibility and then deposited on substrate. A multilayered alumina composite of oriented and randomly oriented layers was also synthesized by the alternate EPD of alumina suspensions which were placed in and out of a superconducting magnet. It was demonstrated that the EPD in a strong magnetic field is a promising ceramic processing technique for fabricating sophisticated ceramic composites. (C) 2003 Elsevier Ltd. All rights reserved.

    DOI

    Scopus

    52
    被引用数
    (Scopus)
  • Fabrication of tailored ceramics by colloidal processing and their application

    Y Sakka, TS Suzuki, T Uchikoshi, K Hiraga, T Shibata, M Ishihara

    BASIC STUDIES IN THE FIELD OF HIGH-TEMPERATURE ENGINEERING     225 - 235  2004年  [査読有り]

     概要を見る

    Two types of tailored ceramics were prepared by colloidal processing. First, colloidal processing was applied to obtain dense and homogeneous alumina- and zirconia-based ceramics with fine-grained microstructure. Large tensile elongation exceeding 550% was achieved for 10 vol.% zirconia-dispersed Al2O3 at 1773 K and high-strain-rate (above 10(-2) s(-1)) superplastic zirconia-based ceramics were achieved by adding TiO2 and MgO. In the second process, a high magnetic field was applied during slip casting of alumina suspension to produce textured microstructure. A green body with a slight degree of crystallographic orientation was obtained and the degree of texture increased as temperature was increased. After densification, alumina grains grow to yield ceramics with textured grains and high degrees of crystallographic orientation. This processing can be applied to other ceramics having asymmetric unit cell, such as SiC, Si3N4, etc.

  • High-strain rate superplastic zirconia systems

    Y Sakka, TS Suzuki, K Morita, BN Kim, K Hiraga

    EURO CERAMICS VIII, PTS 1-3   264-268   285 - 288  2004年  [査読有り]

     概要を見る

    The purpose of this study is to fabricate high-strain fate above 10(-2) s(-1) superplastic zirconia systems. Dense, homogeneous and fine-grained zirconia systems of MgO and TiO2 added 3YTZ (3mol%Y2O3 doped tetragonal zirconia), and Al2O3 and/or Mn3O4 added 3YTZ were obtained by colloidal processing. The grain growth was controlled by cation lattice diffusion and the grain growth rate was enhanced by adding TiO2, Al2O3 and/or Mn3O4. High-strain rate superplasticity was established for the systems of 3(Y2O3, MgO) (.) 97(Zr0.95Ti0.05)O-2 and small amounts of Al2O3 and/or Mn3O4 added 3YTZ,. Such excellent superplasticity is due to the homogeneous, fine grained microstructure and enhancement of cation lattice diffusion in 3YTZ by addition of TiO2, Al2O3 and/or Mn3O4.

  • Crystalline-oriented TiO2 fabricated by the electrophoretic deposition in a strong magnetic field

    T Uchikoshi, TS Suzuki, F Tang, H Okuyama, Y Sakka

    CERAMICS INTERNATIONAL   30 ( 7 ) 1975 - 1978  2004年  [査読有り]

     概要を見る

    Electrophoretic deposition of titania (anatase) suspension was conducted in a strong magnetic field of 10 T. The direction of the electric field E relative to the magnetic field B was altered (phi(B-E) = 0, 30, 60 and 90degrees) to control the dominant crystal faces of the deposit surfaces. The crystalline orientation was investigated by the X-ray diffraction for the titania films of as-deposited, sintered at 650, 750 and 1200 degreesC as a function of the angle between the directions of B and E (phi(B-E)). It was found that changing the angle phi(B-E) during the EPD could control the crystalline orientation of the titania films. (C) 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

    DOI

    Scopus

    38
    被引用数
    (Scopus)
  • Fabrication of high-strain rate superplastic yttria-doped zirconia polycrystals by adding manganese and aluminum oxides

    Y Sakka, T Ishii, TS Suzuki, K Morita, K Hiraga

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   24 ( 2 ) 449 - 453  2004年

     概要を見る

    Conventional superplastic ceramics have been established at temperatures over 1400 degreesC with a slower deformation velocity of about 10(-4) (s(-1)). For the application of superplasticity to the manufacturing process, however, high-strain rate deformation velocity of around 10(-2)/s(-1) is necessary. We have reported that alumina addition to 3YTZ (3 mol.%Y2O3 doped ZrO2) is effective in the enhanced ductility. The purpose of this study is to fabricate high-strain rate superplastic 3YTZ by adding manganese and aluminium oxides. Dense and fine-grained 3YTZ systems were obtained by slip casting and low temperature sintering. Manganese and alminium oxides added 3YTZ showed a maximum tensile ductility of about 600% at 1450 degreesC at a strain rate of 1.2 x 10(-2)s(-1). (C) 2003 Elsevier Ltd. All rights reserved.

    DOI

    Scopus

    47
    被引用数
    (Scopus)
  • 高次構造体作製のための微粒子分散制御

    鈴木 達, 目 義雄

    粉体工学会誌 = Journal of the Society of Powder Technology, Japan   40 ( 4 ) 265 - 273  2003年04月

    DOI CiNii

  • Low-temperature and high-strain rate superplastic zirconia

    Y Sakka, T Matsumoto, TS Suzuki, K Morita, BN Kim, K Hiraga, Y Moriyoshi

    ADVANCED ENGINEERING MATERIALS   5 ( 3 ) 130 - 133  2003年03月  [査読有り]

  • Electrophoretic deposition of alpha-alumina particles in a strong magnetic field

    T Uchikoshi, TS Suzuki, H Okuyama, Y Sakka

    JOURNAL OF MATERIALS RESEARCH   18 ( 2 ) 254 - 256  2003年02月  [査読有り]

     概要を見る

    The electrophoretic deposition of single-crystalline a-alumina particles dispersed in aqueous media was performed in a strong magnetic field of 10 T. The a-alumina particles in the stable suspension were aligned due to their anisotropic diamagnetic susceptibility and then deposited on a cathodic substrate. The orientation of the a-alumina crystallites was confirmed by x-ray diffraction of the sintered specimen.

  • Pulverization Phenomenon of Nb-Zr-Fe Alloys by Absorbing a Hydrogen Gas

    Hideo Okuyama, Masahiro Uda, Tetuo Uchikoshi, Touru Suzuki, Yoshio Sakka

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   50 ( 10 ) 792 - 797  2003年  [査読有り]

     概要を見る

    In order to find a new energy-saving-powder manufacturing process, the pulverization due to hydrogenation of Nb-Zr-Fe alloys with 35 different compositions has been studied. The hydrogenation was performed under the hydrogen atmosphere of 0.1 MPa and room temperature in an arc melting chamber without exposure to air after arc-melting. Nb-Zr-Fe alloys absorb a large amount of hydrogen from 0.1 to 1.8wt%H and pulverize into powders. This pulverization is closely related to the composition of alloys. The composition which is easy to pulverize is concentrated to the ranges of 15 at%Fe in Nb-Zr-Fe alloys and 15-30 at% Fe with fixed to Nb/Zr ≒ 1/1 in Nb-Zr-Fe alloys. For an example, hydrogen absorbed powder of 45Nb-40Zr-15Fe alloy has wide size distribution from 5 to 200 micron with flake figure and with many fine cracks. The hydrogen in powder of 45Nb-40Zr-15Fe alloy is stably stable until 473 K and dehydrogenation temperature is from 473 K to 773 K. It is estimated that hydrogenation is induced by proper amount of iron element in Nb-Zr-Fe alloys and a hydrogen rich phase and a hydrogen poor phase are formed in an alloy ingot. Forming of two phases by absorbing hydrogen causes to pulverization of Nb-Zr-Fe alloys.

    DOI

    Scopus

  • Role of the initial degree of ionization of polyethylenimine in the dispersion of silicon carbide nanoparticles

    XW Zhu, FQ Tang, TS Suzuki, Y Sakka

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   86 ( 1 ) 189 - 191  2003年01月  [査読有り]

     概要を見る

    The role of the initial degree of ionization (alpha(i)) of polyethylenimine (PEI) in the dispersion of SiC nanopartilces in water was investigated by sedimentation and rheological measurements. The ionization of PEI was characterized by potentiometric titration, which indicated a pH-dependent conformational transition. The dispersion of SiC particles in the presence of PEI was found to strongly depend on the alpha(i). In the presence of 0.4% by weight PEI, the 23.8% SiC by volume (Phi(SiC) = 23.8) slurries showed a Newtonian behavior for alpha(i) = 0.12-0.4 values, whereas a shear-thinning behavior was observed for alpha(i) &gt; 0.4 in the optimal pH range of around pH 4. The rheological behavior of the slurries exhibited a strong dependence on the concentration of PEI of alpha(i) = 0.12-0.4 and the slurry showed a Newtonian behavior at an optimal concentration of 0.4% by weight. The stabilization may be dominated by an electrosteric effect arising from the adsorbed PEI of alpha(i) = 0.12-0.4. The flocculation mechanism of the slurries with PEI of alpha(i) 0.4 is also discussed.

  • Control of texture in electroceramics by slip-casting in a high magnetic field

    TS Suzuki, Y Sakka

    ELECTROCERAMICS IN JAPAN VI   248   191 - 194  2003年  [査読有り]

     概要を見る

    The control of texture in ceramics is one of the ways for effectively improving their properties. Anisotropic susceptibility is very small in ZnO and TiO2; therefore, it had been very difficult to developing the textured microstructure using a magnetic field. But we demonstrate in this paper that the textured ZnO and TiO2 can be prepared by a colloidal processing in a high magnetic field followed by heating. A green solid with a slight degree of crystallographic orientation was obtained before sintering. The degree of texture increased with increasing temperature, and crystallographic texture development accompanies the densification and grain growth in the specimens.

  • Control of texture in ZnO by slip casting in a strong magnetic field and heating

    TS Suzuki, Y Sakka

    CHEMISTRY LETTERS   ( 12 ) 1204 - 1205  2002年12月  [査読有り]

     概要を見る

    Anisotropic susceptibilities of feeble magnetic ceramics such as zinc oxide are quite small; therefore, it had been difficult to control the textured microstructures of these ceramics using a magnetic field. However, fabrication of the textured ZnO is achieved by slip casting in a strong magnetic field followed by heating. After the stable suspension of ZnO fine particles was compacted by slip casting in a strong magnetic field, a green body with a slight degree of crystalline texture was obtained. Densification and the grain growth enhanced the degree of texture during the sintering.

  • Alignment of titania whisker by colloidal filtration in a high magnetic field

    Y Sakka, TS Suzuki, N Tanabe, S Asai, K Kitazawa

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   41 ( 12A ) L1416 - L1418  2002年12月  [査読有り]

     概要を見る

    Whisker alignment is one possible way in order to improve the properties of whisker reinforced materials. Susceptibility is very small in diamagnetic ceramics such as titania and alumina, etc.; therefore, the effects of a high-magnetic field on these ceramics had been generally neglected. Recently, superconducting magnet technologies have been developed and used for applications for such feeble magnetic materials. We demonstrate that the alignment of titania whiskers can be controlled by colloidal filtration of a well-dispersed suspension of the whiskers in a high magnetic field (10T) when the direction of the magnetic field was perpendicular to the direction of the fluid.

    DOI

  • Fabrication of textured titania by slip casting in a high magnetic field followed by heating

    TS Suzuki, Y Sakka

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   41 ( 11A ) L1272 - L1274  2002年11月  [査読有り]

     概要を見る

    Anisotropic susceptibility is very small in feeble magnetic ceramics such as titania; therefore, it had been very difficult to develop a textured microstructure using a magnetic field. However, we demonstrate in this paper, that textured titania can be prepared by slip casting in a high magnetic field and heating. After the suspension was compacted by slip casting in a high magnetic field, a green solid with a slight degree of crystallographic orientation was obtained. The degree of texture increased with increasing temperature, and crystallographic texture development accompanied grain growth in the specimens.

    DOI

  • Microstructure and superplasticity in various zirconia-dispersed aluminas

    TS Suzuki, Y Sakka, K Nakano, K Hiraga

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   110 ( 10 ) 927 - 930  2002年10月  [査読有り]

     概要を見る

    High-temperature tensile ductility in alumina-based ceramics is usually limited due to dynamic grain growth. In this study, superplasticity in zirconia-dispersed alumina has been achieved by colloidal processing using monoclinic, tetragonal and cubic zirconia powders. The densities and microstructures depend on the zirconia particles used as a second phase. Differences in the static alumina grain growth in various zirconia-dispersed alumina composites were caused by differences in distribution of the zirconia particles. The tensile ductility of these materials was found to depend on the type of zirconia used. Limited superplasticity seems to be caused by the density and dynamic alumina grain growth during deformation.

    DOI

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    1
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  • Microstructure and superplasticity in various zirconia-dispersed aluminas

    Tohru S. Suzuki, Yoshio Sakka, Keishi Nakano, Keijiro Hiraga

    Journal of the Ceramic Society of Japan   110 ( 1286 ) 927 - 930  2002年  [査読有り]

     概要を見る

    High-temperature tensile ductility in alumina-based ceramics is usually limited due to dynamic grain growth. In this study, superplasticity in zirconia-dispersed alumina has been achieved by colloidal processing using monoclinic, tetragonal and cubic zirconia powders. The densities and microstructures depend on the zirconia particles used as a second phase. Differences in the static alumina grain growth in various zirconia-dispersed alumina composites were caused by differences in distribution of the zirconia particles. The tensile ductility of these materials was found to depend on the type of zirconia used. Limited superplasticity seems to be caused by the density and dynamic alumina grain growth during deformation.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Fabrication of tailored alumina-based ceramics through colloidal processing

    Y Sakka, TS Suzuki, K Hiraga

    HIGH-PERFORMANCE CERAMICS 2001, PROCEEDINGS   224-2   619 - 622  2002年  [査読有り]

     概要を見る

    Super-plastic zirconia-dispersed alumina ceramics with fine-grained microstructure and the other is highly textured alumina were prepared. Colloidal processing was applied to obtain dense and homogeneous zirconia-dispersed alumina ceramics with mean grain size of 0.45 mum. Large tensile elongation exceeding 550% was achieved for 10 vol% zirconia-dispersed Al2O3 at 1773K, High magnetic field (10T) was applied during slip casting of alumina suspension to produce textured microstructure. Green body with slight degree of crystallographic orientation was obtained and the degree of texture increased with increasing temperature. After densification, alumina grains grow to yield cerarnics with textured grains and high degrees of crystallographic orientation. This processing can be applied to other ceramics with asymmetric unit cell.

  • Colloidal processing and superplastic proprties of fine-grained zirconia-based ceramics

    Y Sakka, TS Suzuki, K Morita, K Hiraga

    EURO CERAMICS VII, PT 1-3   206-2   645 - 648  2002年  [査読有り]

     概要を見る

    Colloidal processing was applied to obtain dense and homogeneous yttria-doped tetragonal zirconia (YTZ), alumina-dispersed YTZ, and magnesia- and titania-doped YTZ. Their slurries were prepared by adding appropriate amounts of polyelectrolyte, and their fine-grained bodies were obtained through slip casting, cold isostatic pressing and low-temperature sintering. The obtained bodies show excellent superplastic properties. In particular alumina addition was found to (1) decrease the limit temperature of superplasticity in YTZ to 1573 K or lower, (2) increase the limit strain rate for large elongation exceeding 300% up to 1.2x10(-2) s(-1) at 1573 K and (3) large tensile elongation exceeding 1000% at 1.7x10(-4) s(-1). The effects of microstructure such as grain size, grain-boundary stracture and cavity density on the superplastic properties are discussed by comparison with the conventionally prepared samples. The creep parameters prepared by the colloidal processing were similar to those prepared by conventional dry processing. Their excellent superplasticities are due to the reduction of residual defects, fine-grained and homogeneous microstructures.

  • Fabrication of textured alumina through slip casting in a high magnetic field and heating

    Y Sakka, TS Suzuki, K Kitazawa

    EURO CERAMICS VII, PT 1-3   206-2   349 - 352  2002年  [査読有り]

     概要を見る

    We achieved to produce the highly textured microstructure of undoped dense alumina prepared by slip casting in a high magnetic field and subsequent heating. Well-dispersed alumina aqueous suspensions were prepared by adding appropriate amount of polyelectrolyte. After the suspension was consolidated by slip casting in high magnetic field, the green body with slight degrees of crystallographic orientation was obtained. The degree of texture increased with increasing temperature. After densification, alumina grains grow to yield ceramics with textured grains and high degrees of crystallographic orientation. This processing can be applied to other ceramics with asymmetric unit cell.

  • Electrophoretic deposition of alumina aqueous suspensions in a strong magnetic

    T Uchikoshi, TS Suzuki, H Okuyama, Y Sakka, K Kitazawa

    ELECTROPHORETIC DEPOSITION: FUNDAMENTALS AND APPLICATIONS, PROCEEDINGS   2002 ( 21 ) 9 - 14  2002年  [査読有り]

     概要を見る

    Electrophoretic deposition of single crystalline a-alumina particles dispersed in aqueous media was performed in a strong magnetic field of 10 T. The a-alumina particles in the stable suspension were aligned due to their anisotropic diamagnetic susceptibility. and then deposited. on a cathodic substrate. The orientation of the a-alumina crystallites was confirmed by X-ray diffraction of the sintered specimen.

  • Preferred orientation of the texture in the SiC whisker-dispersed Al2O3 ceramics by slip casting in a high magnetic field

    TS Suzuki, Y Sakka, K Kitazawa

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   109 ( 10 ) 886 - 890  2001年10月  [査読有り]

     概要を見る

    Developing texture is one possible way for improving the properties of ceramics. Texture in ferromagnetic materials can be tailored by a magnetic field, but it had been difficult to produce texture in diamagnetic and paramagnetic materials, such as silicon carbide and alumina, because their susceptibility is very small. A well-dispersed suspension of SiC (w) -Al2O3 was prepared and consolidated by slip casting in a high magnetic field. The Al2O3 matrix with a slight degree of orientation was observed in the green body and the degree of texture increased by annealing.

    DOI

    Scopus

    40
    被引用数
    (Scopus)
  • Orientation amplification of alumina by colloidal filtration in a strong magnetic field and sintering

    TS Suzuki, Y Sakka, K Kitazawa

    ADVANCED ENGINEERING MATERIALS   3 ( 7 ) 490 - 492  2001年07月  [査読有り]

  • Preferred orientation of the texture in the SiC whisker-dispersed Al2O3 ceramics by slip casting in a high magnetic field

    Tohru S. Suzuki, Yoshio Sakka, Koichi Kitazawa

    Journal of the Ceramic Society of Japan   109 ( 1274 ) 886 - 890  2001年  [査読有り]

     概要を見る

    Developing texture is one possible way for improving the properties of ceramics. Texture in ferromagnetic materials can be tailored by a magnetic field, but it had been difficult to produce texture in diamagnetic and paramagnetic materials, such as silicon carbide and alumina, because their susceptibility is very small. A well-dispersed suspension of SiC (w)-Al2O3 was prepared and consolidated by slip casting in a high magnetic field. The Al2O3 matrix with a slight degree of orientation was observed in the green body and the degree of texture increased by annealing.

    DOI

    Scopus

    40
    被引用数
    (Scopus)
  • Cavity formation and growth in a superplastic alumina containing zirconia particles

    K Hiraga, K Nakano, TS Suzuki, Y Sakka

    SUPERPLASTICITY IN ADVANCED MATERIALS, ICSAM-2000   357-3   193 - 198  2001年  [査読有り]

     概要を見る

    The present study on a tensile-deformed superplastic alumina reveals that the growth of cavities finer than the current grain size (fine cavities) into larger ones (large cavities) is constrained from the surrounding matrix. As a result of the constraint, the density of the large cavities becomes noticeably lower than that of the finer ones and shows non-linear dependence on strain, although the total cavity density, i.e., the sum of the fine and large cavity densities depends linearly on strain. Analysis of cavity size distributions also reveals the formation and growth laws of the large cavities.

  • Sintering and ionic conductivity of CuO-doped tetragonal ZrO<inf>2</inf> prepared by novel colloidal processing

    Sakka Y, Suzuki T.S, Ozawa K, Uchikoshi T, Hiraga K

    Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan   109 ( 1276 ) 1004 - 1009  2001年  [査読有り]

    DOI

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    6
    被引用数
    (Scopus)
  • Effect of Ultrasonication on the Microstructure and Tensile Elongation of Zirconia-Dispersed Alumina Ceramics Prepared by Colloidal Processing

    Suzuki T.S, Sakka Y, Nakano K, Hiraga K

    Journal of the American Ceramic Society   84 ( 9 ) 2132 - 2134  2001年  [査読有り]

    DOI

    Scopus

    70
    被引用数
    (Scopus)
  • Colloidal processing and superplastic properties of zirconia- and alumina-based nanocomposites

    Sakka Y, Suzuki T.S, Morita K, Nakano K, Hiraga K

    Scripta Materialia   44 ( 8-9 ) 2075 - 2078  2001年  [査読有り]

    DOI

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    47
    被引用数
    (Scopus)
  • Enhanced superplasticity in a alumina-containing zirconia prepared by colloidal processing

    TS Suzuki, Y Sakka, K Morita, K Hiraga

    SCRIPTA MATERIALIA   43 ( 8 ) 705 - 710  2000年09月  [査読有り]

    DOI

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    56
    被引用数
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  • Fabrication of silicon nitride ceramics by electrophoretic deposition

    Tetsuo Uchikoshi, Yoko Fukada, Tohru S. Suzuki, Patrick S. Nicholson

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   47 ( 9 ) 1021 - 1025  2000年  [査読有り]

     概要を見る

    Surface coating of Si3N4, powder with an alumina precursor was achieved by a sol-gel method using aluminum isopropoxide. Electrophoretic data showed the surface-coated Si3N4 powder behaved like alumina. Consolidation of the surface-coated powder was attempted by an electrophoretic deposition (EPD) technique. EPD rate was improved for the surface-coated powder. Sintering characteristics and fracture toughness were investigated for EPDed compacts. It was demonstrated that the surface coating of Si3N4 powder with alumina precursor had the advantage of not only the improvement of suspension stability, but also the addition of sintering aid.

    DOI

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    1
    被引用数
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  • Cavitation failure in a superplastic alumina with zirconia-particle dispersion

    K Hiraga, Y Sakka, TS Suzuki, K Nakano

    CREEP AND FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES   171-1   763 - 769  2000年  [査読有り]

     概要を見る

    High temperature tensile failure in a fine-grained alumina with zirconia particle dispersion is found to relate closely to the separation distance among micrometer-sized cavities Bowing from preexistent defects and from newly formed ones during deformation. As the separation distance is decreased to a certain level with an increase in both density and size of such cavities, extensive cavity interlinkage starts to cause microcracking, and the microcracking leads to the occurrence of macroscopic cracks propagating in a direction perpendicular to the tensile axis toward the final failure. The dependence of the onset strain of microcracking on temperature and grain size is also found to relate closely to the dependence of cavity formation and growth rates on these factors.

  • Synthesis of aligned alumina by slip casting in a high magnetic field and heat treatment

    Suzuki T.S, Ohtsuka H, Sakka Y, Hiraga K, Kitazawa K

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   47 ( 9 ) 1010 - 1014  2000年  [査読有り]

    DOI

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    21
    被引用数
    (Scopus)
  • Creep properties of base metal and welded joint of Hastelloy XR produced for high-temperature engineering test reactor in simulated primary coolant helium

    Y Kurata, T Tanabe, Mutoh, I, H Tsuji, K Hiraga, M Shindo, T Suzuki

    JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY   36 ( 12 ) 1160 - 1166  1999年12月  [査読有り]

     概要を見る

    Creep tests of base metal. weld metal and welded joint of Hastelloy XR, which had the same chemical composition as Hastelloy XR produced for an intermediate heat exchanger of the High-Temperature Engineering Test Reactor, were conducted in simulated primary coolant helium. The weld metal and welded joint showed almost equal to or longer rupture time than the base metal of Hastelloy XR at 850 and 900 degrees C, although they gave shorter rupture time at 950 degrees C under low stress and at 1,000 degrees C. The welded joint of Hastelloy SR ruptured at the base metal region at 850 and 900 degrees C. On the other hand, it ruptured at the weld metal region at 950 and 1,000 degrees C. The steady-state creep rate of weld metal of Hastelloy SR was lower than that of base metal at 850, 900 and 950 degrees C. The creep rupture strengths of base metal, weld metal and welded joint of Hastelloy XR obtained in this study were confirmed to be much higher than the design allowable creep-rupture stress (S-R) of. the Design Allowable Limits below 950 degrees C.

    DOI

  • Comparison of fine-grained alumina-zirconia prepared by slip casting and electrophoretic deposition

    Benjamin D. Hatton, Tohru S. Suzuki, Yoshio Sakka

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   46 ( 12 ) 1284 - 1291  1999年  [査読有り]

     概要を見る

    Al2O3-dispersed ZrO2-3mol%Y2O3 composites have been prepared by slip casting and electrophoretic deposition to compare the sinterability and microstructure, using three commercially-available Al2O3 powders. Composites were prepared by pressureless sintering at 1300 °C. The consolidated (green) density, sintered density, grain size and dispersion are compared for both colloidal techniques with the aim of improving the homogeneity and reducing the necessary temperature for sintering.

    DOI

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    2
    被引用数
    (Scopus)
  • Superplasticity in zirconia-dispersed alumina prepared by colloidal processing

    K Hiraga, TS Suzuki, Y Sakka, K Nakano

    PROGRESS IN MECHANICAL BEHAVIOUR OF MATERIALS (ICM8), VOL 3     981 - 986  1999年  [査読有り]

     概要を見る

    Substantial superplasticity, where total tensile elongation to failure exceeds 500% at 1773 K, is attained in a zirconia-dispersed alumina by grain size refinement to less than 0.5 mu m through colloidal processing. The material shows gradual strain hardening persisting up to large strains owing to gradual grain growth and damage accumulation. In contrast, the grain size refinement to 0.45 mu m through conventional dry processing is not effective in enhancing tensile ductility. From the microstructural data of these materials, the prerequisites are discussed for obtaining large tensile ductility in zirconia-dispersed alumina.

  • Superplastic tensile ductility in a zirconia-dispersed alumina produced by colloidal processing

    TS Suzuki, Y Sakka, K Nakano, K Hiraga

    TOWARDS INNOVATION IN SUPERPLASTICITY II   304-3   489 - 494  1999年  [査読有り]

     概要を見る

    Substantial superplasticity, where total tensile elongation to failure reaches 550 % at 1773 K, can be attained in a 10-vol%-ZrO2-dispersed alumina when the alumina grain size is reduced to 0.45 mu m by colloidal processing. Although the same grain size is attainable by conventional dry processing, the resultant tensile elongation stays about 260%. The examination of undeformed and deformed microstructures revealed that both homogeneous particle dispersion and reduction in the size and density of residual defects in the sintered bodies are the prerequisites for obtaining large superplastic tensile ductility in zirconia dispersed alumina.

  • Cavity damage accumulation in alumina doped with zirconia or magnesia

    K Hiraga, K Nakano, TS Suzuki, Y Sakka

    TOWARDS INNOVATION IN SUPERPLASTICITY II   304-3   431 - 436  1999年  [査読有り]

     概要を見る

    For an initial grain size of 1.0 mu m, the accumulation of damage volume in a ZrO2-dispersed alumina is shown to proceed more slowly than that in a MgO-doped alumina under a given loading condition, irrespective of higher tensile flow stress in the former than in the latter. The slower damage accumulation in the ZrO2-dispersed alumina is caused from the slower formation and growth of cavities larger than the initial grain size. Such slower cavitation is also shown to delay the onset of microcracking. The delayed microcracking leads to higher tensile ductility in the ZrO2-doped material than in the MgO-doped one.

  • Cavitation damage during high temperature tensile deformation in fine-grained alumina doped with magnesia or zirconia

    K Hiraga, K Nakano, TS Suzuki, Y Sakka

    SCRIPTA MATERIALIA   39 ( 9 ) 1273 - 1279  1998年10月  [査読有り]

    DOI

    Scopus

    19
    被引用数
    (Scopus)
  • Effect of ultrasonication on colloidal dispersion of Al2O3 and ZrO2 powders in pH controlled suspension

    TS Suzuki, Y Sakka, K Nakano, K Hiraga

    MATERIALS TRANSACTIONS JIM   39 ( 6 ) 689 - 692  1998年06月  [査読有り]

     概要を見る

    Colloidal processing is well known to be an effective method to avoid the agglomeration of particles in powder processing. In this method, particles are dispersed by the electrostatic repulsion arising from their surface charge which can be controlled by the pH-value of the suspension. Since fine particles tend to agglomerate, however, additional redispersion treatment is necessary to obtain dispersed suspension of submicrometer-sized particles. In this study was used ultrasonication such as additional re-dispersion treatment for the dispersion of fine powders. Al2O3 and ZrO2 used in this study were high-purity fine powders and their particle sizes were 0.2 and 0.07 mu m, respectively. Three types of suspensions were prepared under different conditions of mixing with ultrasonication for various treatment periods. With increasing degree of ultrasonication, the apparent viscosity of suspension decreased, the dispersion of the particles in the suspensions was promoted and the relative densities of the compacts and the sintered specimens increased, because of a decrease in both total pore volume and the pore size. The microstructure of the sintered specimen prepared from the sufficiently ultrasonicated suspension was very fine, which resulted in high superplasticity.

  • Preparation of fine-grained zirconia systems by colloidal processing

    Y Sakka, T Uchikoshi, K Ozawa, TS Suzuki, K Hiraga

    CERAMIC PROCESSING SCIENCE   83   233 - 240  1998年  [査読有り]

     概要を見る

    Slurries of monoclinic zirconia and CuO adsorbed tetragonal zirconia (3mol% Y2O3 doped tetragonal ZrO2: 3Y-TZ) were prepared. Their dense compacts were obtained by pressure filtration follwed by CIP treatment. The compacts were densified by pressureless sintering in air to &gt; 98%. Dense bodies of the undoped monoclinic zirconia and CuO doped tetragonal 3Y-TZ with average grain size under 100 nm are obtained.

  • Microstructure control and superplastic property of zirconia dispersed alumina ceramics

    Sakka Y, Suzuki T.S, Nakano K, Hiraga K

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   45 ( 12 ) 1186 - 1195  1998年  [査読有り]

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Superplastic tensile ductility enhanced by grain size refinement in a zirconia-dispersed alumina

    K Nakano, TS Suzuki, K Hiraga, Y Sakka

    SCRIPTA MATERIALIA   38 ( 1 ) 33 - 38  1997年12月  [査読有り]

  • High-temperature deformation of TiAl/Ti2AlC composites produced by reaction milling

    A Okuno, TS Suzuki, N Sasaki, Y Matsumoto, M Nagumo

    TOWARDS INNOVATION IN SUPERPLASTICITY I   233-2   295 - 302  1997年  [査読有り]

     概要を見る

    Composites of gamma-TiAl intermetallic compound and a complex carbide (Ti2AlC) have been formed by mechanical alloying of Ti-Al-heptane system followed by hot consolidation. The amount of the carbide can be controlled by the milling parameters. The composites have fine microstructures of an average grain size of a few hundreds nm. Mechanical properties at elevated temperatures have been investigated by tensile tests. At 1073K, different deformation behaviors depending on the carbon content are distinct, while the total elongation is still small. The total elongation of specimen tested at 1273K and at a strain rate of 1x10(-3) s(-1) exceeds 300%.

  • Colloidal processing for fine particles of Al <inf>2</inf>O <inf>3</inf>-15 vol% ZrO <inf>2</inf> system

    Suzuki T.S, Sakka Y, Hiraga K

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   44 ( 4 ) 356 - 361  1997年  [査読有り]

  • Metastable states during reaction milling of hcp transition metals with hydrocarbon

    M Nagumo, TS Suzuki, K Tsuchida

    METASTABLE, MECHANICALLY ALLOYED AND NANOCRYSTALLINE MATERIALS, PTS 1 AND 2   225   581 - 586  1996年  [査読有り]

     概要を見る

    The reaction process during milling of Zr and Ti with n-heptane has been investigated. Formation of a metastable intermediate phase characterized by fee-like structure has been revealed at a certain milling time. It disappears upon heating with reversible appearance of the original hcp structure. The amounts of H and C in the metal powders increase with milling time to a constant level at which stabilization of the intermediate phase takes place. The intermediate phase is presumably the stacking fault of hcp structure stabilized by H and C atoms as the precursor of the stable carbides. Dissociation of H from heptane precedes that of C. Site occupation is competitive between H and C, and stabilization of the intermediate phase during milling takes place by the increase of C content excluding H to sites with lower binding energy with H.

▼全件表示

書籍等出版物

  • サスペンション中の粒子配向制御

    目 義雄, 鈴木 達, 打越 哲郎

    2013年

     概要を見る

    我々は,粒子を溶媒中に分散させて成形するコロイドプロセスを強磁場中で行うことにより,配向性アルミナの作製に成功した3-5)。ここでは,粒子配向の原理と配向制御に必要なプロセス因子の要件を紹介し、さらにより高度な配向制御技術について紹介する。

  • セラミックス微粒子の強磁場配向制御

    鈴木 達

    2013年

     概要を見る

    固体の物質において、その特性が完全に等方的であることはまれであり、性質に異方性があることを利用して材料として用いることは有用である。例えば、圧電体材料における分極異方性の利用、繊維材の繊維方向に強度が高いという異方性を利用して編み込むことなどによる機械特性の強化、鉄鋼材料での集合組織の精緻な制御などの例を挙げることが出来る。フィラーの利用においても、その特性の異方性を有効に使うために配向制御は有用であり、無機フィラーを用いる場合には、セラミックス粉体プロセスにおける配向手法を役立てることが出来る。本章においては、無機フィラーの配向付与プロセスの一端として、セラミックス微粒子を用いた強磁場配向制御プロセスについて解説する。

  • NA

    SAITO, Sho, SAKKA, Yoshio, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, NAKATA, Seiji

    2005年

     概要を見る

    Aqueous suspensions of three types of different diameter of alpha-Si3N4 particles with sintering additives were prepared and consolidated by slip casting in 10T. They were sintered in N2 atmosphere at temperatures of 1500-1700℃. The usefulness of the processes has been confirmed through the orientation index evaluated by X-ray diffraction patterns and scanning electron microscope (SEM) images of Si3N4 crystals. The crystal a,b-axis of beta-Si3N4 grains aligned to the magnetic direction. It is also confirmed that the crystalline orientation was improved by addition of &#61538;-Si3N4 whisker.

  • 強磁場印加コロイドプロセスによるセラミックスの配向制御

    鈴木 達

    2004年

     概要を見る

    従来は磁場の影響を受けないと考えられてきた弱磁性セラミックスでもコロイドプロセスと強磁場を用いることで、その配向を制御できることを見出した。ここでは、アルミナを例にとり、強磁場を用いて配向制御するためのプロセス因子を解説し、その応用として酸化チタン、酸化亜鉛なども配向制御した例を示した。

講演・口頭発表等

  • BiFeO3系圧電セラミックスの焼結条件の検討と物性評価

    相澤朋弥, 上野慎太郎, 藤井一郎, 和田智志, 鈴木 達

    エレクトロセラミックス研究討論会  

    発表年月: 2018年11月

     概要を見る

    環境問題の観点から、Pb(Zr,Ti)O3 (PZT)系セラミックスに代わる高性能な鉛フリー圧電材料の開発が急務となっている。これまでに酸化ビスマスの揮発を抑制するため、低温・短時間で焼結が行えるスパークプラズマ焼結(SPS)法を用いて0.3BT-0.1BMT-0.6BFセラミックスを作製した。しかしながらその圧電特性に大きな改善は見られなかった。これはSPSが還元雰囲気下で行われるため、空気中でポストアニールを行った後も焼結時に生成した酸素空孔の一部が残り、これと鉄の価数変化により圧電特性が低下したためと考えられる。そこで本研究では、焼結時の酸素分圧を変えてセラミックスを作製し、微構造や電気特性を調査した。また、焼結後に空気中でポストアニールを行い、そのときの降温速度の影響も調査した。

  • 最終焼結段階における緻密化挙動のシミュレーション

    金 炳男, 鈴木 達, 森田 孝治, 吉田 英弘, 李 継光, 松原秀彰

    粉体粉末冶金協会平成30年度秋季大会  

    発表年月: 2018年10月

     概要を見る

    粉体の焼結挙動を理解するためには、緻密化速度の粒径依存性や活性化エネルギーの評価、すなわち焼結機構に対する評価も重要であるが、焼結挙動を予測・再現するためには、緻密化速度の相対密度依存性に対する評価が不可欠である。最近緻密化速度の相対密度依存性が実験的に評価できるようになったが、粉体の焼結挙動をより深く理解するためには、これら実験的な計測値を理論モデルにより解析することも必要である。しかし、従来の理論モデルは単純構造気孔の収縮を対象としており、実際の複雑構造の気孔に対しては直接適用できない。本研究では、焼結途中の多孔体における複雑な気孔構造を気孔サイズの分布を持って表した。気孔サイズに分布がある場合、緻密化に伴うサイズ分布の変化や緻密化速度に及ぼす影響などを調べることにより、実際の緻密化挙動を理解・解析することが目的である。

  • 配向制御した透光性アルミナの作製

    鈴木 達, 足利昂治, 金 炳男, 清野肇

    粉体粉末冶金協会 秋季大会  

    発表年月: 2018年10月

     概要を見る

    高強度、高耐摩耗性などの機械的特性の優れた透明性の高いアルミナを得るためには、極めて低い気孔率と小さな粒径(&lt;1 μm)が不可欠であり、SPSを用いた透光性微細粒アルミナの作製が多く報告されている。また、アルミナは異方性結晶であるため、粒界での複屈折が透光性の劣化原因となるが、結晶方位を揃える配向制御は複屈折を抑えて直線透過性の向上に有効であると示してきた。アルミナはc軸が磁化容易軸となり、磁場中成形を用いることによってc軸配向アルミナを作製可能である。コロイドプロセスを用いて微粒子の分散を制御したスラリーを磁場中スリップキャストすることにより、c軸の向きが揃ったアルミナ成形体を作製し、作製した成形体はSPS法での低速昇温焼結によって透明配向アルミナを作製することが可能である。本研究では、このときのSPS条件がアルミナ焼結体の透光性に及ぼす影響を検討した。

  • Preparing highly structured B4C control rod via magnetic field-assisted colloidal processing

    AZUMA, Shota, UCHIKOSHI, Tetsuo, Yoshida Katsumi, SUZUKI, Tohru

    The Nuclear Materials Conference  

    発表年月: 2018年10月

     概要を見る

    Random orientation B4C is usually used as the control rods in fast reactors, but cracks are easily generated during operation because of volume swelling due to the accommodation of helium gas during the neutron absorption reaction. Releasing the accumulated helium is difficult because a conventional pellet has few closed pores without specific direction. However, helium release should be achieved in similar porosity to maintain the mechanical properties. In this study, to develop the B4C control rods with long lifespan than the current one, the conditions of the strong magnetic field-assisted colloid process was optimized for fabricating highly structured materials based on B4C. This ceramic is constructed with oriented tubal pore-phase, and dense- c-axis alignment B4C phase.

  • Control of crystallographic orientation in ceramics by a strong magnetic field

    Muhammand Fajar, SUZUKI, Tohru, AZUMA, Shota, Yoshida Katsumi, Pornphatdetaudom Thanataon, Yano Toyohiko

    The Nuclear Materials Conference  

    発表年月: 2018年10月

     概要を見る

    The development of crystallographic orientation is an interesting topic in ceramics and one of the effective ways to improve their properties. Recently, we reported that the successful control of a textured microstructure even in diamagnetic ceramics was achieved by a colloidal processing in a strong magnetic field. This technique can be applied to the wide variety of ceramics as the important materials for nuclear reactor, such as, AlN, SiC and B4C. The green compacts after slip casting in a static or rotating magnetic field were isothermally sintered by SPS. The thermal conductivity and the electrical conductivity perpendicular to the c-axis of the textured SiC and AlN were higher than those parallel to the c-axis in the both textured ceramics.

  • Development of New and High-Functional Software for Electrochemical Impedance Analysis

    KOBAYASHI, Kiyoshi, SUZUKI, Tohru

    WAIM2018  

    発表年月: 2018年09月

     概要を見る

    New and highly functional analysis software for electrochemical impedance is introduced. Various functions such as conventional analysis, Kramers-Kronig transformation tests, automatic analysis using simple artificial-intelligence function will be presented.

  • Fabrication of lanthanum silicate oxyapatite ceramics with crystal orientation by slip casting in a strong magnetic field

    Takaya Akashi, SUZUKI, Tohru, Atsushi Yamazoe, KOBAYASHI, Kiyoshi, UCHIKOSHI, Tetsuo

    WAIM2018  

    発表年月: 2018年09月

     概要を見る

    Crystal oriented lanthanum silicate oxyapatite (LSO) was successfully fabricated by slip casting under a strong magnetic field. The crystal-oriented LSO showed higher oxide ion conductivity along to c-axis.

  • 高機能インピーダンス解析ソフトの開発

    小林 清, 鈴木 達

    第79回応用物理学会秋季学術講演会  

    発表年月: 2018年09月

     概要を見る

    インピーダンス・スペクトルの解析は誘電や伝導などの固体物性,電池やキャパシターにおける反応過程分離,電気回路の交流応答特性の評価など様々な領域で利用されている.既存のインピーダンス解析ソフトは解析者に対して実測スペクトルグラフを表示し,解析者は表示されたスペクトルに当てはめるべき等価回路を推定・設定すると共にモデルパラメータの初期値入力を入力後,非線形最小自乗プロセスを実行する仕様となっている.実測インピーダンス・スペクトルの多くは単純かつ理想的な形状を示さないため,解析に用いる等価回路と初期パラメータの選択は解析者に委ねられていることが解析の難しさになる.本研究では実測スペクトルグラフをインタラクティブに利用しながら逐次モデル構築と初期値設定を容易に行う新しいタイプのインピーダンス解析ソフトを開発した.

  • Effect of green sheet thickness and application of pressure on a compact during sintering in &lt;110&gt;-oriented 0.85(Bi0.5Na0.5)TiO3-0.15BaTiO3 ceramics

    Fujii Ichiro, ITO Ryo, Kawachi Kosuke, Ueno Shintaro, SUZUKI, Tohru, WADA Satoshi

    IWPMA2018  

    発表年月: 2018年09月

     概要を見る

    &lt;110&gt;-oriented ceramics with the composition of 0.85(Bi0.5Na0.5)TiO3-0.15BaTiO3 with a high Curie temperature of ~300。&#65533;C were successfully fabricated by reactive templated grain growth of layered hydrogen titanate platelets with (Bi0.5Ti0.5)TiO3 and BaCO3 matrix powders.[1] A large degree of &lt;110&gt; orientation F110 = 84% was achieved by decreasing green sheet thickness and application of pressure on a compact during sintering, as shown in Fig. 1. Consequently, improved remanent polarization was observed in the ceramics compared with randomly oriented ceramics, owing to easier polarization switching. A piezoelectric constant d33 of 103 pC/N and an electromechanical coupling factor k33 of 0.44 were obtained for the &lt;110&gt; grain-oriented ceramics.

  • 強磁場中水熱合成法を用いたZnO結晶配向制御

    小沢寛人, 清野肇, 鈴木 達

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2018年09月

     概要を見る

    ZnOナノ構造材料は気相あるいは液相から成長させることができる。気相法による合成は高温かつ高コストであるため、低温かつ穏やかな条件下で合成を行うことができる液相法への注目が高くなってきている。セラミックス材料の特性向上の要因の一つに微細組織の制御がある。多くの固体材料の特性には異方性があり、特性向上のために配向制御は重要であり、セラミックスの配向制御の方法の1つに磁場を印加する手法がある。既存の研究では磁場中でMnやCrをドープしたZnOの水熱合成を行うことでドープ量が増加したと報告され、磁場中水熱合成が有用な手法であるが、ZnO粒子の配向に及ぼす影響については未解明である。したがって、本研究では磁場中水熱合成による磁場中水熱合成が粒子配向に及ぼす影響について調査する。

  • SOFC 配向電極作製のための Nd2-xLaxNiO4の結晶磁気異方性の調査

    田島卓, 松田元秀, 鈴木 達, 中根 茂行, 名嘉 節, 打越 哲郎

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2018年09月

     概要を見る

    低温作動固体酸化物形燃料電池用カソード材として、K2NiF4 型構造からなる Nd2NiO4 (NNO)および La2NiO4 (LNO)が注目されている。その特性は結晶構造の影響で大きな異方性があり、応用に向けては配向化を含めた組織制御が求められる。我々の研究グループは、最近、磁場を用いた電極作製プロセスで、NNO および LNOの配向カソードを低温作動固体酸化物形燃料電池用電解質上に得ることに成功している[1], [2]。その検討の中で、NNO は c 軸配向性を、LNO は ab 面が磁場印加方向に沿って配列する傾向にあることを見出し、NNO とLNO では配向性に違いがあることを明らかにした。そこで本研究では、NNO と LNO に加えて、混合組成である Nd2-xLaxNiO4 (NLNO)を作製し、その結晶磁気異方性について調査を行った。

  • CNT 添加量が B4C/CNT 複合セラミックスの 熱的・機械的特性及び耐熱衝撃性に及ぼす影響

    牧涼介, Muhammad Fajar, Maletaskic Jelena, Gubarevich Anna, 吉田克己, 矢野豊彦, 鈴木 達, 打越 哲郎

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2018年09月

     概要を見る

    高速炉では、優れた熱安定性及び中性子吸収断面積を有する炭化ホウ素(B4C)が制御材として用いられている。しかしながら、中性子吸収反応に伴うヘリウムの生成や、不均一な温度分布により生じる熱応力による B4C ペレットの割れなどが問題となっており、B4C ペレットの熱的・機械的特性の向上が高速炉の安全性確保において重要な課題となっている。我々はこれまでに、カーボンナノチューブ(CNT)を添加することで熱的・機械的特性に優れた B4C 基セラミックスの作製に成功している。本研究では、CNT 添加量の異なる B4C/CNT 複合セラミックスを作製し、CNT 添加が B4C 基セラミックスの微構造、熱的・機械的特性及び耐熱衝撃性に与える影響について評価した。

  • 反応放電プラズマ焼結による透光性酸窒化アルミニウム(AlON)の作製

    川口智也, 清野肇, 鈴木 達

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2018年09月

     概要を見る

    酸窒化アルミニウムは優れた光学的特性、機械的特性および化学的安定性を有している。透光性AlONの作製方法はAlON粉末を合成してから焼結する二段工程と酸化アルミニウムと窒化アルミニウムを反応焼結する単一工程の2つある。従来、前者の方法を用いた研究が多くされてきたが、AlON粉末を合成してから焼結するため、プロセスやコストの増加などの問題がある。後者の方法には、高温・長時間の焼結が必要という問題がある。また、セラミックスの透明化には気孔のない高密度な焼結体の作製が重要である。これらの問題を解決するためには、低温・短時間で高密度の焼結体を作製することが求められる。本研究では、スリップキャストで作製したAl2O3とAlNの混合成形体を放電プラズマ焼結によって反応焼結させることで、低温・短時間での透光性AlONの作製を試みた。

  • オキシアパタイト型ランタンシリケートの3段階熱処理プロセスにおける再酸化条件の影響

    山添敦司, 小林 清, 打越 哲郎, 明石 孝也, 鈴木 達

    日本セラミックス協会 第31回秋季シンポジウム  

    発表年月: 2018年09月

     概要を見る

    オキシアパタイト型ランタンシリケート(LSO)は中低温域において高い酸化物イオン伝導性を示す新規固体電解質である。LSOの酸化物イオン伝導度向上には、c軸配向制御が有効である。本研究では強磁場配向法によるc軸配向化と高温熱処理による粒成長を組み合わせたプロセスを検討した。強磁場配向体を作製後、1973Kによるアルゴン雰囲気での熱処理をすると、試料は還元され黒色化したが、c軸配向性は向上することが明らかとなった。そのため、1273K〜1723Kによる大気中での再酸化プロセスを行ったところ、1273Kで再酸化した試料でイオン伝導度の向上が認められ、1523K、1723Kで再酸化させた試料ではさらに高いイオン伝導度を示した。

  • 強磁場配向・コロイドプロセスを用いたB4Cセラミックスの高次構造制御

    東 翔太, 打越 哲郎, 吉田克己, 鈴木 達

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2018年09月

     概要を見る

    高速炉用B4C制御材の信頼性の更なる向上には、中性子照射時の制御材内部に生じる不均一な熱応力の緩和とB4C結晶内部に発生・蓄積していくHeガスの排気による制御材膨張・破損の抑制が重要である。当グループではこの制御材の熱的/機械的特性の向上とHeガス排気機能の付与の二つの課題を同時解決すべく、配向細孔相およびカーボンナノチューブ(CNT)を含むc軸配向B4C緻密母材層のからなる高次構造制御材の創製を目指している。本発表では、B4C母材粒子,CNT,焼結助剤、造孔材からなる四元系分散スラリーの強磁場中での鋳込み成形から得られる四元系配向成形体,およびその成形体を基とした高次構造制御焼結体の基礎的作製手法の検討結果について報告する。

  • イットリウムを置換したオキシアパタイト型ランタンゲルマネートの緻密セラミックス製造と全電気伝導度測定

    寺井 貴哉, 小林 清, 樋口 透, 鈴木 達

    日本セラミックス協会 第31回秋季シンポジウム  

    発表年月: 2018年09月

     概要を見る

    オキシアパタイト型ランタンゲルマネートは中低温領域で高い酸素イオン伝導性をしめす新規固体電解質である.しかし構造相転移により約750℃以下でイオン伝導度が急激に低下することが問題である.また固相法で作製した粉末によるランタン・ゲルマネートは難焼結性であると報告されている.本研究では構造相転移を抑制するためにランタンの一部をイットリウムに置換したランタン・ゲルマネートについて,固相反応法による合成および高焼結性粉末調整のプロセスを検討した.また製造したセラミックスの密度,全電気伝導度と粉体化プロセス条件の関係を検討した.

  • Effect of crystallographic orientation and alumina as sintering additives on densification behavior and mechanical properties of boron carbide by slip casting

    Fajar Muhammad, 吉田克己, 鈴木 達

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2018年09月

     概要を見る

    Crystallographic orientation of boron carbide (B4C) by 5vol% of Al2O3 sintering aid has been performed under rotation in strong magnetic field 12 T using slip casting method, resulting textured B4C ceramics. The green compacts were densified by spark plasma sintering (SPS) under uniaxial 80 MPa at 1700 and 1800oC for 5 min and by hot pressing (HP) under uniaxial 40MPa 1950oC for 1 h. The effect of texturing crystal orientation and Al2O3 addition were investigated in our works. X-ray diffraction (XRD) was performed to evaluate the materials composition and degree of crystal orientation (texturing) by Lotgering factor equation. Scanning electron microscope and energy dispersive X-ray were performed to observe grain size and secondary phase. Mechanical properties had been evaluated.

  • 緻密化と粒成長の組織変化に対する実験および理論的な評価

    金 炳男, 鈴木 達, 森田 孝治, 吉田 英弘, 李 継光, 松原秀彰

    日本セラミックス協会秋季大会  

    発表年月: 2018年09月

     概要を見る

    The densification behavior during the isothermal sintering of 8YSZ was examined in the entire density range. In the intermediate and final sintering stages, the relationship between the grain size and the relative density is obtained experimentally. Then the densification kinetics is predicted as a function of the density and compared with theoretical sintering models. It is found that the densification kinetics in the final stage can be explained more distinctively by the diffusive single-pore model than by the Coble’s corner-pore model.

  • Neutron Irradiation Induced Lattice Parameter Changes of Highly Oriented Aluminum Nitride

    矢野 豊彦, Pornphatdetaudom Thanataon, 吉田克己, 鈴木 達

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2018年09月

     概要を見る

    AlN is one of a ceramic material with excellent mechanical, electrical and chemical properties and expected to be used as corrosion barrier and magneto-hydrodynamic (MHD) barrier. According to previous studies, in terms of effect of neutron fluence, the swelling occurred isotropically in a,b-axes, and c-axis at neutron fluence, while dislocation loop along c-axis was significantly developed at high fluence and brought the swelling anisotropically in c-axis much larger than a,b-axes. In order to develop the properties of materials, in this work, the magnetic field was applied. The prepared sample is expected to have highly oriented particles and induced better properties in each axis.

  • Advanced ceramics processing for controlling crystalline orientation by strong magnetic field

    SUZUKI, Tohru

    CMCEE2018  

    発表年月: 2018年07月

     概要を見る

    Crystallographic orientation is one of the tailored microstructure in ceramics to improve their properties and textured microstructure is expected to be effective way to utilize the anisotropic properties. We have reported that the crystalline orientation can be controlled even in diamagnetic ceramics by a high magnetic field. In addition, the other technique can be used simultaneously to control the elaborate microstructure. We reported that bi-axial orientation could be achieved by slip casting of the platelet particles in a strong magnetic field When the electric field was applied simultaneously, laminar composites with alternate crystalline-oriented layers can be produced by electrophoretic deposition in a strong magnetic field.

  • Transparent polycrystalline ceramics with crystalline orientation prepared by colloidal processing a magnetic field and SPS

    SUZUKI, Tohru, KIM, Byung-Nam

    CMCEE2018  

    発表年月: 2018年07月

     概要を見る

    Transparent polycrystalline ceramics provides flexibility in size and shape design to apply for a wide field. Optical birefringence at grain boundaries have strong effect on the in-line transmittance in anisotropic ceramics. If the crystal direction is aligned, birefringence can be suppressed because of the reduced refractive index difference. In this process, a strong magnetic field is applied to the particles in a stable suspension. The particles become rotated to an angle that minimizes the system energy and one-dimensional orientation can be achieved. The c-axes of alumina and AlN are aligned by a magnetic field. After slip casting, SPS was used for densification. Transparency can be improved by the alignment of the c-axis in alumina and AlN due to the suppression of birefringence.

  • Tailored Microstructure with Aligned Pores in B4C Prepared by slip casting in rotating magnetic field

    AZUMA, Shota, UCHIKOSHI, Tetsuo, Yoshida Katsumi, SUZUKI, Tohru

    ICCCI2018  

    発表年月: 2018年07月

     概要を見る

    Control rods are one of the structural components in nuclear reactor, and are required to have high functionality and reliability to provide the safety of nuclear reactor. Random orientation B4C is normally used as the control rods, but cracks are easily generated during operation of nuclear reaction because of volume swelling due to accommodation of helium gas and inhomogeneous thermal stress distribution during the neutron absorption reaction. Cracks in the control rods suppress reliability and durability. In this study, we attempted to control the crystalline orientation and align the tubal pore for controlling the thermal stress distribution and releasing the helium gas. Controlling of alignment of the tubal pores was achieved as well as the c-axis orientation of B4C matrix.

  • Mechanical Properties Engineering in Boron Carbide by Spark Plasma Sintering

    VASYLKIV, Oleg, DEMIRSKYI, Dmytro, BADICA, Petre, BORODIANS'KA, Hanna, SUZUKI, Tohru, SAKKA, Yoshio

    THERMEC  

    発表年月: 2018年07月

     概要を見る

    Smart grain-boundary (GB) engineering of typically ‘brittle’ boron carbide leads to exceptional toughness. The complex relation between SPS conditions, consolidation mechanisms, features of B4C (B13C2) ceramics and static and dynamic mechanical properties of consolidated ceramics has been analyzed. The possibility of controlling the dynamic toughness as tested by Split Hopkinson Pressure Bar (SHPSB) method by optimization of the reaction-driven spark plasma sintering (RD-SPS) conditions is attempted. A five times improvement of the dynamic toughness of massive B4C ceramics from ~6 MJ / m2 to ~30 MJ / m2 and of the fracture toughness from 2.2-4.0 MPa /m1/2 to 5.0-7.5 MPa / m1/2 was obtained. The composite B4C- (BxOy / BN) with &#61566; 0.4% wt. of turbostatic hBN showed a maximum hardness

  • Microstructure control of ceramics by using strong magnetic field

    SUZUKI, Tohru

    THERMEC2018  

    発表年月: 2018年07月

     概要を見る

    A magnetic field is shown to be very effective in controlling the crystallographic orientation in bulk ceramics. When a strong magnetic field is applied to the particles in a stable suspension, the particles were rotated to an angle minimizing the system energy by a magnetic torque. In this processing, dispersion of powders in a suspension is necessary to effective work of a magnetic field. Colloidal processing was used for particle dispersion because of developing for consolidating fine particles to avoid heterogeneous agglomerates by electrostatic repulsion due to surface charge. In the case of SiC, the c-axis was aligned parallel to the magnetic field. The thermal conductivity perpendicular to the c-axis was superior to that parallel to the c-axis in textured SiC.

  • Fabrication of Highly Controlled Microstructure in B4C Ceramics by Magnetic Field-Assisted Colloidal Processing

    AZUMA, Shota, UCHIKOSHI, Tetsuo, Yoshida Katsumi, SUZUKI, Tohru

    MAP8  

    発表年月: 2018年06月

     概要を見る

    Control rods are one of the structural components in nuclear reactor and are required to have high functionality and reliability to provide the safety of nuclear reactor. Random orientation boron carbide (B4C) is normally used as the control rods, but cracks are easily generated during operation of nuclear reaction because of volume swelling due to accommodation of helium gas and inhomogeneous thermal stress distribution during the neutron absorption reaction. In this study, we attempted to control the crystalline orientation and align the tubal pore for controlling the thermal stress distribution and releasing the helium gas.

  • Fabrication of transparent crystalline oriented alumina by a slip casting in a magnetic field followed by SPS

    SUZUKI, Tohru, Ashikaga Takaharu, KIM, Byung-Nam, Kiyono Hajime

    ISIEM2018  

    発表年月: 2018年06月

     概要を見る

    Transparent polycrystalline ceramics provides flexibility in size and shape design and can be expected to apply for a wide field. When materials possess anisotropic crystal structure, optical birefringence at grain boundaries also affects transmission. If the crystal direction is aligned, effect of birefringence at grain boundary can be reduced. The colloidal processing in a strong magnetic field was able to control the crystallographic orientation even in diamagnetic ceramics. The c-axis of alumina is aligned by a static magnetic field. After slip casting, SPS was used for densification. Transparency can be improved by the alignment of the c-axis in alumina.

  • Analysis of densification kinetics depending on grain growth for zirconia

    KIM, Byung-Nam, SUZUKI, Tohru, MORITA, Koji, YOSHIDA, Hidehiro, LI, Jiguang, Hideaki Matsubara

    14th International Conference on Modern Materials and Technology  

    発表年月: 2018年06月

     概要を見る

    During sintering of powder compacts, several methods have been proposed to determine the activation energy and the grain-size exponent, but no method for the unspecified density function. In this study, an experimental method is proposed to determine the unspecified density function during isothermal sintering of Y2O3-stabilized zirconia. An interesting point is that the relationship between the grain size G and the relative density D is not constant but dependent on the temperature, though a constant relationship has widely been recognized. With increasing temperature, the density-dependence of the grain size decreases in the intermediate stage, whereas it increases in the final stage. The grain-size exponent evaluated is 2.75 and 1-2 in the intermediate and final stage, respectively. The

  • Advanced ceramic processing with external magnetic field

    SUZUKI, Tohru

    CIMTEC2018  

    発表年月: 2018年06月

     概要を見る

    Tailored microstructure in ceramics is important for improving their properties. Especially, crystallographic orientation is expected to be effective way to utilize the anisotropic properties. We have reported that the crystalline orientation can be controlled even in diamagnetic ceramics by a high magnetic field. We also reported that bi-axial orientation could be achieved by slip casting of the platelet particles in a strong magnetic field where the c-axis of the platelet particle was aligned by the force of gravity, and the a- and b-axes were aligned by the magnetic field. We demonstrate that laminar composites with alternate crystalline-oriented layers are produced by electrophoretic deposition in a strong magnetic field.

  • Yb添加透光性アルミナ多結晶セラックスの開発

    古瀬裕章, 中沢俊亮, 森田 孝治, 吉田 英弘, 鈴木 達, 金 炳男, 目 義雄, 平賀 啓二郎

    応用物理学会2018年春期講演会  

    発表年月: 2018年03月

     概要を見る

    YAGよりも約4倍高い熱伝導率を示すAl2O3と希土類(Re3+)イオンの組合せは,高出力光デバイス用の蛍光体として非常に興味深い材料であるが,Al3+とRe3+はイオン半径の差が大きく,高濃度添加は実現困難である.我々は低温・短時間焼結プロセスが可能なパルス通電加圧焼結法を用いて上述の課題に取り組み,Yb添加アルミナ多結晶セラミックスの開発を試みた.市販のYb2O3粉体とAl2O3粉体を,Yb添加濃度が0.2 at.%となるように混合処理した後,得られた粉体をパルス通電加圧焼結装置で焼結した.焼結温度を1000−1400℃,加圧力80 MPa, 昇温速度50−300℃で変化させ,透過特性の評価を行った.波長1000nmにおいて,直線透過率50%を超える試料が得られた.

  • 透光性Yb3+:YAG微結晶セラミックスの開発

    根津優樹, 古瀬裕章, 川村みどり, 藤岡加奈, 宮永憲明, 吉田 英弘, 森田 孝治, 鈴木 達, 金 炳男, 目 義雄, 平賀 啓二郎

    応用物理学会2018年春季講演会  

    発表年月: 2018年03月

     概要を見る

    本研究では,複合酸化物であるYAGに着目し,①液相共沈法によるYb:YAG微粉体の合成,②パルス通電加圧焼結による緻密透明化,③各種評価(透過スペクトル,組織観察,レーザー出力特性)を行ったので報告する.共沈法により粒子径300 nm程度のYb3+:YAG微粉体を合成した後、パルス通電加圧焼結法を用いて焼結した.焼結温度1350℃,昇温速度10℃/minの焼結体において,平均粒径365 nmと透過率73.9%(波長1100 nm)が得られ,微結晶粒組織と透光性を両立することができた.また波長1030nmにおいてレーザー発振することを確認した.

  • 強磁場コロイドプロセスを用いた微細貫通孔を有する配向B4Cの作製

    東 翔太, 打越 哲郎, 吉田克己, 鈴木 達

    日本セラミックス協会 年会  

    発表年月: 2018年03月

     概要を見る

    高速炉用B4C制御材の信頼性の更なる向上には、中性子照射時に発生するHeガスによる制御材膨張での破損の抑制が重要である。B4Cの配向焼結体では熱伝導率異方性と機械特性向上が報告されており[1],貫通型気孔形成によるHeガス排気機能と併せて制御材信頼性向上に寄与することが期待される。当グループでは高次構造制御という観点から制御材の機械特性とHe排気機能を両立すべく、貫通型気孔を有する配向B4C焼結体の創製を目指している。本発表では、B4C母材粒子および造孔材の二元系分散スラリーの強磁場中での鋳込み成形から得られるB4C-造孔材の配向成形体,その成形体を基とした高次構造制御焼結体、それらの基礎的作製手法の検討結果について報告する。

  • CaCO3ナノロッドの集積による配向フィルムの作製

    髙﨑美宏, 鈴木 達, 緒明佑哉, 今井宏明

    日本セラミックス協会 年会  

    発表年月: 2018年03月

     概要を見る

    CaCO3系バイオミネラルは、カルサイトあるいはアラゴナイトのナノ結晶が結晶方位をそろえて集積することで形成された階層構造によって優れた機能を獲得している。特に、ナノロッドが規則的に配列したラメラ構造は高い機械的特性に大きく寄与している。本研究では、分散媒の蒸発を利用したカルサイトナノロッドの配向集積をおこない、基板上にバイオミネラルに類似したナノロッドの配向集積フィルムの作製を試みた。

  • Evaluation of theoretical sintering models from experiments

    KIM, Byung-Nam, SUZUKI, Tohru, MORITA, Koji, YOSHIDA, Hidehiro, LI, Jiguang, Hideaki Matsubara

    The 6th International Symposium on Advanced Ceramics (ISAC-6)  

    発表年月: 2018年03月

     概要を見る

    The densification behavior of powder compacts can be characterized by determining the activation energy, grain-size exponent and unspecified density function. Several methods have been proposed to determine the activation energy and the grain-size exponent, but no method for the density function. In this study, a method is proposed to determine the unspecified density function during isothermal sintering of Y2O3-stabilized zirconia. An interesting point is that the relationship between the grain size G and the relative density D is not constant but dependent on the temperature, though a constant relationship has widely been recognized. With increasing temperature, the density-dependence of the grain size decreases in the intermediate stage, whereas it increases in the final stage. The grai

  • ANALYSIS OF DENSIFICATION BEHAVIOR DEPENDING ON GRAIN GROWTH FOR ZIRCONIA

    KIM, Byung-Nam, SUZUKI, Tohru, MORITA, Koji, YOSHIDA, Hidehiro, LI, Jiguang, Hideaki Matsubara

    42nd International Conference and Expo on Advanced Ceramics and  

    発表年月: 2018年01月

     概要を見る

    The densification behavior of powder compacts can be characterized by determining the activation energy, grain-size exponent and unspecified density function. Several methods have been proposed to determine the activation energy and the grain-size exponent, but no method for the density function. In this study, a method is proposed to determine the unspecified density function during isothermal sintering of Y2O3-stabilized zirconia. An interesting point is that the relationship between the grain size G and the relative density D is not constant but dependent on the temperature, though a constant relationship has widely been recognized. With increasing temperature, the density-dependence of the grain size decreases in the intermediate stage, whereas it increases in the final stage. The grai

  • Transparent polycrystalline ceramics with crystalline orientation controlled by a magnetic field

    SUZUKI, Tohru, Ashikaga Takaharu, KIM, Byung-Nam, MORITA, Koji, Kiyono Hajime

    ICACC2018  

    発表年月: 2018年01月

     概要を見る

    Transparent polycrystalline ceramics provides flexibility in size and shape design and can be expected to apply for a wide field. When materials possess anisotropic crystal structure, optical birefringence at grain boundaries also affects transmission. If the crystal direction is aligned, effect of birefringence at grain boundary can be reduced. The colloidal processing in a strong magnetic field was able to control the crystallographic orientation even in diamagnetic ceramics. The c-axes of alumina and AlN are aligned by a static magnetic field and a rotating magnetic field, respectively. After slip casting, SPS was used for reduction of porosities. Transparency can be improved by the alignment of the c-axis in alumina and AlN.

  • Mechanical properties of alumina with crystalline orientation controlled by a magnetic field

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, KIM, Byung-Nam, MORITA, Koji, SAKKA, Yoshio

    ICACC2018  

    発表年月: 2018年01月

     概要を見る

    Crystallographic orientation in materials is important to improve their mechanical and functional properties. The particles with asymmetric crystal structure were rotated to an angle minimizing the system energy by a magnetic torque. After consolidation of alumina slurry in a magnetic field, the compact bodies are sintered by electric furnace or SPS without a magnetic field. The c-axis of alumina was aligned uniaxially parallel to the magnetic field. The bending strength of textured alumina was higher than that of random alumina at room temperature and high temperature. High temperature deformation of alumina depends on the orientation direction and enhanced to the direction at 45-degree angle to the crystallographic orientation.

  • 層状ペロブスカイト型混合伝導体の配向制御と異方特性評価

    矢野広将, 打越 哲郎, 小林 清, 明石孝也, 鈴木 達

    第56回セラミックス基礎討論会  

    発表年月: 2018年01月

     概要を見る

    層状ペロブスカイト型構造を有するSLFC(Sr3-xLaxFe2-yCoyO7-δ)は、酸化物イオンと電子の混合伝導性を持ち、結晶構造が安定であること、低温域での電気伝導性に優れることなどの特徴を有する。そのため、この材料はSOFCのカソード材料としての利用に期待ができる。また、SLFCは結晶構造に異方性があり、酸素イオンや電子の透過経路にも異方性があると考えられる。そのため、結晶配向をコントロールすることで伝導度の向上が期待でき、さらなる優れた電極材料としての利用が期待できる。本研究ではSOFCカソード材料の基礎研究として、磁場中コロイドプロセスを用いて配向体の作製を行い、SLFCの伝導度に与える配向の影響を調査した。

  • 強磁場・コロイドプロセスによる高速炉用B4C制御材の高次構造制御

    東 翔太, 打越 哲郎, 吉田克己, 鈴木 達

    日本セラミックス協会 基礎科学討論会  

    発表年月: 2018年01月

     概要を見る

    高速炉用B4C制御材の長寿命化を果たすには、中性子照射によって制御材内部に生じる熱応力の不均一性の緩和および同時に生成するヘリウムガスによる制御材膨張の抑制が不可欠である。本研究ではそれらの課題を解決するにあたり、貫通型気孔を有する高次構造制御B4Cセラミックス制御材の創製を目指している。我々は、B4Cマトリックス粒子および気孔形成材の混合分散スラリーを強磁場中でスリップキャスティングすることによって、B4C結晶及び気孔形成材を配向させる試みに取り組んでおり、本発表はその高次構造B4C制御材を得るための強磁場配向プロセスにおける固化成形条件の検討結果について報告する。

  • 強磁場配向法と熱処理最適化によるc軸配向オキシアパタイト型ランタン・シリケートの高イオン伝導体化

    山添 敦司, 小林 清, 打越 哲郎, 明石 孝也, 鈴木 達

    56回セラミックス基礎討論会  

    発表年月: 2018年01月

     概要を見る

    オキシアパタイト型ランタンシリケート(LSO)は新規固体電解質として注目されている。LSOの酸化物イオン伝導度向上には、c軸配向制御や高温焼成が有効と報告されている。本研究では強磁場配向法によるc軸配向化と高温アニールを組み合わせたプロセスを検討し、LSOセラミックスの酸化物イオン伝導性の向上について検討した。強磁場配向体を作製後、1973 Kによるアルゴン雰囲気でのアニールと1273 Kによる大気中での再酸化プロセスによりc軸配向性が向上した。またc軸平行方向における酸化物イオン伝導度はc軸配向度の向上により増加することも明らかになった。

  • 配向制御透光性アルミナの特性評価

    足利昂治, 清野肇, 金 炳男, 鈴木 達

    日本セラミックス協会 基礎科学討論会  

    発表年月: 2018年01月

     概要を見る

    高強度、高耐摩耗性などの機械的特性の優れた透明性の高いアルミナを得るためには、極めて低い気孔率と小さな粒径が不可欠である。磁気異方性を有する物質を強磁場中に置くと磁気トルクが発生し、磁化容易軸が磁場印加方向と平行になる方向へ結晶が回転する。アルミナはc軸が磁化容易軸となり、磁場中成形を用いることによってc軸配向アルミナを作製可能であることを既に報告している。本研究では、コロイドプロセスを用いて微粒子の分散を制御したスラリーを磁場中スリップキャストすることにより、c軸の向きが揃ったアルミナ成形体を作製した。作製した成形体はSPS法を用いた低速昇温焼結によって緻密化し、アルミナ焼結体の配向性と粒径を制御し、透光性の向上を試みた。また、粒界における散乱係数及び粒界での屈折率差を実験的に算出し、磁場配向の有無で比較することにより透光性向上の原因究明を行った。

  • 高機能インピーダンス解析ソフトウェア開発と階層解析法の提案

    小林 清, 鈴木 達

    第56回セラミックス基礎科学討論会  

    発表年月: 2018年01月

     概要を見る

    我々が開発した高機能電気化学インピーダンス解析ソフトを用いた測定で得られたインピーダンス・スペクトルの新たな解析法として階層解析法を提案する.具体的には単純な部分インピーダンスに分解後,隠れた非定常拡散インピーダンスを探索する手法を紹介する.

  • インピーダンス・スペクトルの階層解析法の提案

    小林 清, 鈴木 達

    第26回SOFC研究会  

    発表年月: 2017年12月

     概要を見る

    概要:測定で得られたインピーダンス・スペクトルの新たな解析法として階層解析法を提案する.具体的には単純な部分インピーダンスに分解後,隠れた非定常拡散インピーダンスを探索する手法を紹介する.

  • Densification Kinetics Depending on Grain Growth for Zirconia

    KIM, Byung-Nam, SUZUKI, Tohru, MORITA, Koji, YOSHIDA, Hidehiro, LI, Jiguang, Hideaki Matsubara

    The 34th International Japan-Korea Seminar on Ceramics  

    発表年月: 2017年11月

     概要を見る

    The densification behavior during the isothermal sintering of 8YSZ was examined by using a dilatometer under various environments. Typically, the densification kinetics at constant temperature can be represented as dD=Af(D)G-n, where dD is the densification rate, G is the grain size, n is the grain-size exponent and f(D) is the function dependent mainly on the relative density D. During the isothermal sintering, the relationship between D and G were examined (G「蹈2.4 at 1250 &#730;C in air), and the value of n was evaluated to be 1.8 using a theoretical form of f(D)=1-D. Then the theoretical densification kinetics can be represented as a function of D only, dD=A(1-D)D-4.3. In a wide range of 0.62&lt;D&lt;0.95, the densification behavior can be described well with the theoretical kinetics.

  • Investigation of various properties in lead-free (Bi0.5Na0.5)TiO3-Hexagonal BaTiO3 ceramics fabricated by electrophoretic deposition (EPD) method.

    KIM Minsu, ITO Ryo, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, WADA Satoshi

    ICAE2017  

    発表年月: 2017年11月

     概要を見る

    (Bi0.5Na0.5)TiO3-BaTiO3 (BNT-BT) systems are well known candidate of lead-free piezoelectric materials because of their high Curie temperature and easy to apply mass production. However, it is reported that BNT-BT systems have relatively poor piezoelectric properties and low depolarization temperature. To enhance the piezoelectric properties, we have tried to apply domain engineering mechanism in BNT-BT ceramics. To achieve our goal, we selected electrophoretic deposition (EPD) method because it is reported that [111]-textured BT ceramics can be fabricated using hexagonal BT particles and high magnetic field. We hope that [111] textured BNT-BT ceramics can be fabricated with EPD method with optimum preparation condition and high magnetic field which shows enhanced piezoelectric properties.

  • Fabrication of (111)-oriented BaTiO3 Ceramics by Electropheretic Deposition of Hexagonal and Tetragonal BaTiO3 powders in a High Magnetic Field.

    Nukumizu Kazuki, Ueno Shintaro, Fujii Ichiro, WADA Satoshi, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    ICAE2017  

    発表年月: 2017年11月

     概要を見る

    It is known that the piezoelectric property of BaTiO3 (BT) can be improved by grain-size control or by texture engineering. We previously fabricated (111)-oriented tetragonal BT ceramics consisting of fine grains by electrophoretic deposition (EPD) in a high magnetic field using a hexagonal BT powder [1]. In this study, the degree of the (111) orientation was controlled by changing ratio of hexagonal to tetragonal BT powders, and the effect of the ratio on the dielectric and piezoelectric properties was investigated.

  • ジルコニア(8YSZ)の等温焼結中に起きる緻密化および粒成長挙動の解析

    金 炳男, 鈴木 達, 森田 孝治, 吉田 英弘, 李 継光, 松原 秀彰

    粉体粉末冶金協会 平成29年度秋季大会  

    発表年月: 2017年11月

     概要を見る

    粉体の焼結は緻密化と粒成長を伴う現象であり、焼結挙動を理解・解析するためには、緻密化と粒成長を同時に調べ、緻密化に影響を及ぼす諸因子を厳密に評価する必要がある。一般的に実験的な研究では、緻密化速度に対する活性化エネルギーと粒径指数が評価されるが、焼結応力と体積粘性率に依存する密度関数の評価に関しては全く行われていないのが現状である。本講演では、無加圧焼結時の緻密化挙動に対する従来解析手法の問題点を指摘し、緻密化速度に及ぼす諸因子を厳密に評価する手法を提案する。本手法により、ジルコニア(8YSZ)の中間および最終焼結段階における緻密化速度が精度よく再現・予測できることを示す。

  • Evaluation of theoretical sintering models from experiments

    KIM, Byung-Nam, SUZUKI, Tohru, MORITA, Koji, YOSHIDA, Hidehiro, LI, Jiguang, Hideaki Matsubara

    JSPM International Conference on Powder and Powder Metallurgy  

    発表年月: 2017年11月

     概要を見る

    The densification behavior during the isothermal sintering of 8YSZ was examined by using a dilatometer under various environments. Typically, the densification kinetics at constant temperature can be represented as dD=Af(D)G-n, where dD is the densification rate, G is the grain size, n is the grain-size exponent and f(D) is the function dependent mainly on the relative density D. During the isothermal sintering, the relationship between D and G were examined (G「蹈2.4 at 1250 &#730;C in air), and the value of n was evaluated to be 1.8 using a theoretical form of f(D)=1-D. Then the theoretical densification kinetics can be represented as a function of D only, dD=A(1-D)D-4.3. In a wide range of 0.62&lt;D&lt;0.95, the densification behavior can be described well with the theoretical kinetics.

  • Fabrication of highly structure-controlled ceramics by advanced powder processing

    SAKKA, Yoshio, ESTILI, Mehdi, SUZUKI, Tohru

    CICC-10  

    発表年月: 2017年11月

     概要を見る

    As the developments of the fine powder processing the following advanced ceramics have been demonstrated. (i) Conductive CNT dispersed alumina with excellent mechanical properties by hetero-coagulation of CNT and alumina powders followed by pulsed electric current activated sintering, (ii) Textured ceramics by colloidal processing in a strong magnetic field, (iii) Shell-like structure (nacre) of MAX phase ceramics with excellent mechanical properties by colloidal processing under strong magnetic field.

  • 六方晶-正方晶2相共存BT粒子を用いた&lt;111&gt;配向BaTiO3セラミックスの電気特性

    抜水 一輝, 上野 慎太郎, 藤井 一郎, 和田智志, 鈴木 達, 打越 哲郎

    エレクトロセラミックス研究討論会  

    発表年月: 2017年10月

     概要を見る

    チタン酸バリウム(BT)セラミックスの圧電特性を向上させるため、我々は強磁場電気泳動(HM-EPD)法により、微細な、グレインからなる&lt;111&gt;配向BTセラミックスの作製を試みてきた。六方晶BTを原料としてHM-EPD法にて作製した&lt;111&gt;配向BTセラミックスは100%近い配向度を示すのにもかかわらず、圧電特性の改善は確認できなかった。これはプロセス上BTが六方晶から正方晶に相転移する際、双晶欠陥が生じることが一因だと考えられる。本研究では、原料粒子に六方晶と正方晶相の共存する粒子を採用し、HM-EPD法をもちいてBT配向セラミックスを作製することで相転移の際に生じる双晶欠陥の低減を試みた。

  • Tailored Microstructure of Ceramics by Using Electric and Magnetic Fields

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    6th International Conference on Electrophoretic Deposition  

    発表年月: 2017年10月

     概要を見る

    The mechanical and functional properties of ceramics can be improved by designing their microstructures, such as grain size, grain geometry, crystallographic orientation, second phase and so on. Layered structure with different crystalline orientation layer by layer has been proposed as an alternative for the design of structural ceramics. Grain sliding during the high temperature deformation depends on the grain boundary structure and misorientation angle between grains. Our concept is that the crystalline axis depending on the thermal expansion coefficients aligns for controlling the residual stress in the monolithic ceramics. We controlled the layered structure in the monolithic ceramics, such as alumina and silicon carbide for control the crack deflection.

  • FABRICATION OF POROUS, CRYSTALLINE-ORIENTED TITANIA LAYER ON

    UCHIKOSHI, Tetsuo, SUZUKI, Tohru, MUTO Hiroyuki, MATSUDA Atsunori

    6th International Conference on Electrophoretic Deposition:Funda  

    発表年月: 2017年10月

     概要を見る

    Dye-sensitized solar cells (DSSCs) are the most extensively investigated systems for the conversion of solar energy into electricity. DSSC commercialization is still limited because of its low conversion efficiency and low reliability of the liquid electrolyte. The low conversion efficiency is due to the non-uniformity of the electrode components with respect to the packing density of TiO2 particles and film thickness of the electrode. In this study, crystalline-oriented porous TiO2 thin films were fabricated on indium-tin oxide (ITO) or fluorine-doped tin oxide (FTO) glass substrates by electrophoretic deposition (EPD) in a superconducting magnet.

  • Investigation of Affecting parameters of Electrophoretic deposition (EPD) method in (Bi0.5Na0.5)TiO3-Hexagonal BaTiO3 and their properties

    KIM Minsu, ITO Ryo, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, WADA Satoshi

    6th International Conference on Electrophoretic Deposition  

    発表年月: 2017年10月

     概要を見る

    (Bi0.5Na0.5)TiO3-BaTiO3 (BNT-BT) systems are well known candidate of lead-free piezoelectric materials. However, BNT-BT systems have relatively low piezoelectric constant. Electrophoretic deposition method (EPD) has good advantage in mass production. Our final goal is making [111] oriented BNT-BT ceramics which have enhanced piezoelectric properties and appreciate for mass production. To achieve our goals, we prepared BNT-BT ceramics and investigated important factor of making BNT-BT ceramics using EPD method. In this work BNT-BT ceramics were fabricated with various conditions. We could find optimum preparation condition with avoiding Na+ dissolution. Finally, we characterized piezoelectric and dielectric properties of samples.

  • 配向制御透光性アルミナの特性評価

    足利 昂治, 金 炳男, 清野肇, 鈴木 達

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2017年09月

     概要を見る

    アルミナは、優れた機械的特性や化学的安定性を有している。CobleによってMgOを添加して高温で焼結する透光性アルミナが報告されて以来、様々な研究が報告されている。本研究では、コロイドプロセスを用いて微粒子の分散・凝集を制御したスラリーを磁場中スリップキャストにより成形し、低速昇温SPS法を用いた緻密化を行うことで透光性に優れた配向アルミナを作製した。配向性および粒径と透光性の関係を検討し、機械特性を評価した。

  • 複素非線形最小自乗アルゴリズムとパラメータ誤差の関係

    小林 清, 鈴木 達

    第30回秋季シンポジウム  

    発表年月: 2017年09月

     概要を見る

    インピーダンス・スペクトルの最小自乗に用いられている複素非線形最小自乗法は,複素関数をプログラム内部で仮想的に実数関数化し,パラメータの最適値を求める手法である.一方で複素関数の実数関数化には複数の記述法が存在する.本研究では,この記述法による解析結果の違いについて検討した.その結果,パラメータの標準不確かさが記述法によって大きく変化することが明らかとなっ た.当日はその原因についても議論する.

  • 粒成長に依存するジルコニアの緻密化挙動解析

    金 炳男, 鈴木 達, 森田 孝治, 吉田 英弘, 李 継光, 松原 秀彰

    日本セラミックス協会 第30回秋季シンポジウム  

    発表年月: 2017年09月

     概要を見る

    粉体の焼結は緻密化と粒成長を伴う現象であり、焼結挙動を理解・解析するためには、緻密化と粒成長を同時に調べ、緻密化に影響を及ぼす諸因子を厳密に評価する必要がある。一般的に実験的な研究では、緻密化速度に対する活性化エネルギーと粒径指数が評価されるが、焼結応力と体積粘性率に依存する密度関数の評価に関しては全く行われていないのが現状である。本講演では、無加圧焼結時の緻密化挙動に対する従来解析手法の問題点を指摘し、緻密化速度に及ぼす諸因子を厳密に評価する手法を提案する。本手法により、ジルコニア(8YSZ)の中間および最終焼結段階における緻密化速度が精度よく再現・予測できることを示す。

  • パルス通電加圧焼結法で合成した透光性Yb3+:YAGレーザーセラミックス

    根津優樹, 古瀬裕章, 川村みどり, 藤岡加奈, 宮永憲明, 吉田 英弘, 森田 孝治, 鈴木 達, 金 炳男, 目 義雄, 平賀 啓二郎

    日本セラミックス協会秋季大会  

    発表年月: 2017年09月

     概要を見る

    近年,高出力レーザー用透光性セラミックスの開発が盛んに進められており,医療応用や新エネルギー開発等への展開が期待されている.高出力レーザー材料として利用するためには熱問題とダメージ問題の解決が必須であり、機械的強度の向上等が重要な課題である.我々はパルス通電加圧焼結法に注目し,透光性レーザーセラミックスの開発に取組み、透光性Yb3+:Y2O3セラミックスでレーザー発振の実証について報告を行った.本研究では,液相共沈法によりYb:YAG粉体を合成し,そのパルス通電加圧焼結を行った.その結果,微結晶粒組織を維持しつつ,直線透過率70%以上を得ることができた.さらに波長1030 nmにおいてレーザー発振することを確認した. 講演では焼結条件やアニール条件,粒径評価,レーザー発振実験の詳細について述べる予定である.

  • Al2O3及びSiC添加Ti3SiC2配向体の作製とその力学特性

    打田 雄一, 森田 孝治, 鈴木 達, 目 義雄

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2017年09月

     概要を見る

    Ti3SiC2 is a typical Mn+1AXn (MAX) phase ceramics and shows unique metallic-like and ceramic-like properties. To improve these properties, texturing, Al2O3 and SiC addition have been conducted. Textured Ti3SiC2 was prepared by slip cast in a strong magnetic field followed by spark plasma sintering (SPS) at 1350℃ under 40MPa for 5min. The Lotgering orientation factor of textured Ti3SiC2 was 0.96, and relative density of samples was above 99%. The bending strength and fracture toughness of Ti3SiC2 were improved by texturing. Textured Ti3SiC2 showed excellent value of bending strength of 977.6MPa, but Al2O3 and SiC addition caused deterioration of bending strength and fracture toughness.

  • オキシアパタイト型ランタンシリケートの熱処理による結晶配向と酸化物イオン伝導への影響

    山添 敦司, 小林 清, 打越 哲郎, 明石 孝也, 鈴木 達

    第30回秋季シンポジウム  

    発表年月: 2017年09月

     概要を見る

    オキシアパタイト型ランタンシリケート(LSO)は中低温域においても高い酸素酸化物イオン伝導を示すため新規固体電解質として注目されている.LSOの酸化物イオン伝導度向上には,c軸配向制御または高温焼成が有効と報告されている.本研究では強磁場配向法によるc軸配向化と高温アニールを組み合わせたプロセスを検討し,LSOセラミックスの高酸化物イオン伝導体化について検討した.強磁場配向焼結体を製造後,1973 Kによる高温還元雰囲気でのアニールと1273 Kによる再酸化プロセスによりc軸配向性が向上した.またc軸平行方向における酸化物イオン伝導度はc軸配向度の向上により増加することも明らかになった.

  • 電気泳動堆積法による緻密層/多孔層複合組織セラミックスの作製

    東 翔太, 打越 哲郎, 吉田克己, 鈴木 達

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2017年09月

     概要を見る

    昨今,異なる構成成分や組織構造が共存する高次制御セラミックスは,様々なデバイスの特性向上に有用であると期待されている。電気泳動堆積(EPD)法は簡易的な装置および操作により複雑な構造を有したセラミックスを容易に作製できる手法として近年注目されている。本発表では,セラミックス主成分,造孔材,もしくはその複合粒子のEPDを交互に行うことによって緻密層と多孔層が多層化した組織制御セラミックスの作製を行った。またEPD法における電場印可条件や堆積させる粒子の分散液調製条件を種々に変化させることによってセラミックス体中の各層の膜厚やその比,総積層数,空隙率などの組織構造の制御を行った。

  • 強磁場配向により作製したc軸配向アルミナの機械特性

    鈴木 達, 森田 孝治, 金 炳男, 目 義雄

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2017年09月

     概要を見る

    アルミナは、優れた機械的特性や化学的安定性を有している。強磁場中成形と焼結を用いてc軸配向制御したアルミナの高温強度と高温変形特性に関して検討した。また、アルミナに対して必要な磁場強度の考察も行った。

  • PZT系セラミックスの結晶配向制御と圧電特性の配向方位依存性

    三輪恭也, 川田慎一郎, 木村雅彦, 鈴木 達, 打越 哲郎, 目 義雄, Dragan Damjanovic

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2017年09月

     概要を見る

    Pb(Zr, Ti)O3 (PZT)およびPb(Ni1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PNN-PZT)セラミックスはその優れた圧電特性のため、広く実用化されている。しかしデバイスの小型化や新たな用途への展開のため、更に高い電気機械結合係数や圧電d定数が要求されている。この要求に応える手法の一つとして、結晶配向技術がある。一般的なセラミックスでは構成する粒子の向きはランダムであるが、配向技術によって結晶の方位を揃えることによって、特定の方向での圧電特性を大幅に高められる。本研究では配向手法の一つとして、磁場中での鋳込み成形を採用して配向セラミックスの作製を行った。また本研究では得られた配向セラミックスの構造について詳細な解析を行い、結晶配向方位と分布状態のモデル化、および結晶配向状態と圧電特性の関係についての計算モデルの確立を試みた。

  • GUIを活用するスペクトル重畳モデル型インピーダンス解析ソフト

    小林 清, 鈴木 達

    2017年電気化学秋季大会  

    発表年月: 2017年09月

     概要を見る

    表面コーティングされた金属のインピーダンスは理想的なスペクトル形状を示さないことが多く,解析には仮想素子を用いた等価回路解析を行われる.しかし仮想素子のパラメータは物理的意味が曖昧なため,それ以上の解釈が難しい.本研究ではグラフそのものをユーザーインターフェイスに用いる新しいインピーダンス解析ソフトを開発し,非理想的なインピーダンススペクトルに対しても実素子のみを用いた回路解析を可能にした.

  • 簡易人工知能を用いた自動等価回路推定機能の実装

    小林 清, 鈴木 達

    2017年電気化学秋季大会  

    発表年月: 2017年09月

     概要を見る

    非線形最小自乗モジュールを用いて,測定されたインピーダンススペクトルデータから等価回路を自動で推定する簡易人工知能機能を開発し解析ソフトに実装した.解析者の目による形状認識に頼る従来の等価回路推測を超えた解析が可能になる実証実例を紹介する.

  • FABRICATION AND SOME PROPERTIES OF MAX PHASE CRAMICS

    SAKKA, Yoshio, UCHIDA, Yuichi, MORITA, Koji, SUZUKI, Tohru, Guo-Jun Zhang

    5th International Symposium on SiAlONs and Non-oxides  

    発表年月: 2017年08月

     概要を見る

    Textured MAX phase ceramics have been prepared by slip casting in a strong magnetic field followed by sintering. Textured Nb4AlC3 with plate-like grains are stacked regularly with a clear coherent structure at the grain boundaries without any amorphous phases1. It shows a high flexural strength (about 1200 MPa) and the augmented fracture toughness (about 18 MPa&#8226;m1/2). Additionally, this material has excellent machinability and can be machined by a high-speed steel cutter. Excellent mechanical properties also have been shown for the textured Ti3SiC2, Ti2AlN. In comparison with those of the untextured MAX phase ceramic, the bending strength and fracture toughness have been increased. On the other hand, owing to the existence of oxide particles distributing in the grains and at the grai

  • Tailoring the microstructure in SiC by magnetic field

    SUZUKI, Tohru, KOBAYASHI, Kiyoshi, NISHIMURA, Toshiyuki, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    ISNT2017&ISSNOX5  

    発表年月: 2017年08月

     概要を見る

    The physical and mechanical properties of ceramics can be tailored by controlling their microstructure. The c-axis of alpha-SiC was controlled by a strong magnetic field and the c-axis was aligned parallel to the magnetic field. Aqueous suspensions were prepared and then consolidated in a strong magnetic field by slip casting. The green SiC compacts were densified by spark plasma sintering. The 3-point bending strengths of the samples sintered by hot pressing were 907 and 799 MPa for the crack-growth directions parallel and perpendicular to the c-axis in the oriented SiC, respectively. The thermal conductivity and the electrical conductivity perpendicular to the c-axis was higher than that parallel to the c-axis in the textured SiC.

  • Microstructure control of diamagnetic ceramics by a magnetic field

    SUZUKI, Tohru, KOBAYASHI, Kiyoshi, Suzuki Yoshikazu, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    IUMRS-ICAM 2017  

    発表年月: 2017年08月

     概要を見る

    Tailored microstructure in ceramics is important for improving their properties. Crystallographic orientation is expected to be effective way to utilize the anisotropic properties and to understand their properties as well, such as electric conductivity. In the case of Al2O3, SiC and LiCoO2, the c-axis of hexagonal crystal structure was aligned parallel to the magnetic field. The thermal conductivity perpendicular to the c-axis was superior to that parallel to the c-axis in the textured SiC. If the orientation axis of platelet particles aligned due to a geometrical effect is different from the axis aligned by using a magnetic field, the multi-dimensional orientation can be controlled by simultaneous use of both the effects, and control of the elaborate microstructure will be expected.

  • Orientation control and anisotropy evaluation of layered perovskite-type mixed conductor

    Hiromasa Yano, UCHIKOSHI, Tetsuo, KOBAYASHI, Kiyoshi, Takaya Akashi, SUZUKI, Tohru

    STAC-10  

    発表年月: 2017年08月

     概要を見る

    Layered perovskite-type mixed conductor (Sr3-xLaxFe2-yCoyO7-d) was synthesized by solid state reaction. Further, crystalline oriented ceramics was fabricated by slip casting under strong magnetic field. Anisotropic conductivity by the crystal orientation was investigated using the ceramics.

  • Heat treatment dependence on the degree of crystalline orientation and oxide-ion conductivity of lanthanum silicate oxypatite

    Atsushi Yamazoe, KOBAYASHI, Kiyoshi, UCHIKOSHI, Tetsuo, Takaya Akashi, SUZUKI, Tohru

    STAC-10  

    発表年月: 2017年08月

     概要を見る

    Dependencies of the degree of crystalline orientation on the Heat treatment condition were investigated for lanthanum silicate oxyapatite ceramics fabricated by slip casting under strong magnetic field. Post annealing at 1973 K was found to be effective to improve the degree of crystalline orientation.

  • 強磁場を用いた配向セラミックスの作製とその耐照射性

    鈴木 達

    東工大先導原子力研究所 研究交流・発表会  

    発表年月: 2017年06月

     概要を見る

    セラミックスは熱的安定性、耐食性などに優れ、原子炉・核融合炉用として有力な材料のひとつである。実際に原子炉等に使用するには、耐照射性等の原子力材料に特有の高速中性子照射、高温、腐食性環境などの過酷環境に耐えうる必要があり、この特性を向上させるためには精緻な組織制御が重要となる。物質の諸特性は結晶面や軸方位により異なる場合が多く、多結晶体における個々の結晶方位を揃えたりするなどの配向制御は、近年特に注目されている組織制御手法の一つであり、耐照射性向上の組織制御法としても期待できる。そこで、結晶配向制御した焼結性セラミックスを作製し、結晶方位が耐照射特性に及ぼす影響について検討する。c軸配向AlNでは強度が高く、また耐照射性に関しては、照射フラックスが低い条件では従来と同様である。また、B4C制御材への応用に関しても研究を推進中である。

  • ジルコニア(8YSZ)の等温焼結中に起きる緻密化および粒成長挙動

    金 炳男, 鈴木 達, 森田 孝治, 吉田 英弘, 李 継光, 松原秀彰

    粉体粉末冶金協会春季大会  

    発表年月: 2017年05月

     概要を見る

    粉体の焼結は緻密化と粒成長を伴う現象であり、焼結挙動を理解・解析するためには、緻密化と粒成長を同時に調べ、緻密化に影響を及ぼす諸因子を厳密に評価する必要がある。一般的に実験的な研究では、緻密化速度に対する活性化エネルギーと粒径指数が評価されるが、焼結応力と体積粘性率に依存する密度関数の評価に関しては全く行われていないのが現状である。本講演では、無加圧焼結時の緻密化挙動に対する従来解析手法の問題点を指摘し、緻密化速度に及ぼす諸因子を厳密に評価する手法を提案する。本手法により、ジルコニア(8YSZ)の中間および最終焼結段階における緻密化速度が精度よく再現・予測できることを示す。

  • Ti3SiC2系MAX相セラミックス配向体の作製とその酸化特性

    打田 雄一, 森田 孝治, 鈴木 達, 目 義雄

    粉体粉末冶金 平成29年春季大会  

    発表年月: 2017年05月

     概要を見る

    Ti3SiC2はMAX相セラミックスの1つであり, 結晶内に金属結合と共有結合を持つため, 金属としての特性(電気伝導性, 熱伝導性など)とセラミックスとしての特性(高強度, 耐食性など)を併せ持っているユニークな材料として, 多方面への応用が期待されている。 一方で近年, NIMSでは強磁場スリップキャストを用いて配向体を作製し, 様々なセラミックスの特性の向上に成功している。本研究ではTi3SiC2配向体を作製し, 大気中で熱処理させ、酸化したサンプルの各面を評価することにより、Ti3SiC2の酸化挙動について方位依存性を明らかにすることを目的とした。酸化層についてSEM, XRDを利用して分析し、酸化層の厚さより、活性化エネルギーまで算出した。

  • Fabrication of Highly Textured Hydroxyapatite Ceramics by Colloidal Processing in a High Magnetic Field and Sintering

    SAKKA, Yoshio, Kazuya Takahashi, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    PACRIM2017  

    発表年月: 2017年05月

     概要を見る

    We have demonstrated a new processing of textured ceramics with a feeble magnetic susceptibility by slip casting in a high magnetic field and subsequent heating. In this study, three kinds of hydroxyapatite powders were used for the fabrication of a textured HAP. The effect of the processing parameters on the orientation were examined. Using the de-agglomerated particle by a milling procedure, it can be possible to control the particle orientation, but when using heavily agglomerated particles, it was impossible to control the particle orientation by applying a high magnetic field. Highly-textured HAP can be fabricated by slip casting using a well-dispersed suspension in a high magnetic field (above 4 T) followed by sintering above 1373 K.

  • Mechanical properties of textured alumina prepared by colloidal processing in a magnetic field

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, KIM, Byung-Nam, MORITA, Koji

    12th Pacific Rim Conference on Ceramic and Glass Technology  

    発表年月: 2017年05月

     概要を見る

    Crystallographic orientation is one of the effective microstructure control in ceramics as well as metals. When a strong magnetic field is applied to alumina particles in a stable suspension, the particles were rotated to an angle minimizing the system energy by a magnetic torque. After consolidation of alumina slurry in a magnetic field, the compact bodies are sintered by electric furnace or SPS without a magnetic field. The c-axis of alumina was aligned parallel to the magnetic field. The bending strength of textured alumina was higher than that of random alumina at room temperature and high temperature. High temperature deformation of alumina depends on the orientation direction and enhanced to the direction at 45-degree angle to the crystallographic orientation.

  • Fabrication of textured B4C ceramics by slip casting in a strong magnetic field and their mechanical and thermal properties

    YOSHIDA Katsumi, FAJAR Muhammad, YANO Toyohiko, UCHIKOSHI, Tetsuo, SUZUKI, Tohru

    12th Pacific Rim Conference on Ceramic and Glass Technology  

    発表年月: 2017年05月

     概要を見る

    Boron carbide (B4C) has been used as a neutron absorber material in fast reactor systems due to its high neutron absorption ability, thermal stability and low radioactivity after irradiation. During operation of fast reactors, B4C pellets were fractured into pieces due to thermal stress and swelling, and absorber-cladding mechanical interaction (ACMI) was caused. The authors have been attempting to develop high performance B4C ceramics with excellent mechanical and thermal properties as a neutron absorber material in fast reactor systems to reduce the thermal stress and improve the thermal shock resistance. In this study, textured B4C ceramics were fabricated by slip casting in a strong magnetic field (12 T), and their mechanical and thermal properties were evaluated.

  • Appropriate suspension for the preparation of (Bi0.5Na0.5)TiO3-hexagonal BaTiO3 ceramics by electrophoretic deposition (EPD) method

    KIM Minsu, ITO Ryo, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, WADA Satoshi

    12th Pacific Rim Conference on Ceramic and Glass Technology  

    発表年月: 2017年05月

     概要を見る

    Lead-free piezoelectric materials have been attracting attention as eco-friendly materials, but their properties are still quite poor. To enhance piezoelectric properties, we have studied lead-free ceramics prepared by electrophoretic deposition (EPD) method. In this work, we tried to find optimum preparation condition of (Bi0.5Na0.5)TiO3&#8211;BaTiO3 (BNT-BT) ceramics using EPD method. The preparation condition for EPD was optimized and the electrical properties of the ceramics prepared accordingly was investigated and compared with the ceramics prepared by conventional solid state reaction method. The obtained results are almost similar for both of the cases. However, we could expect superior electrical properties under certain modification in this process, which we will focus now onwar

  • 教師付き回帰法を用いた等価回路自動推定アルゴリズムの開発

    小林 清, 鈴木 達

    (公)日本セラミックス協会 2017年年会  

    発表年月: 2017年03月

     概要を見る

    新規に開発したインピーダンス解析用の等価回路を自動で推定するアルゴリズムについて発表する.

  • パルス通電加圧焼結による透光性Yb:Y2O3レーザーの開発

    古瀬裕章, 中沢俊亮, 吉田 英弘, 森田 孝治, 鈴木 達, 金 炳男, 目 義雄, 平賀 啓二郎

    日本セラミックス協会 2017年年会  

    発表年月: 2017年03月

     概要を見る

    近年,パルス通電加圧焼結法を用いた透光性多結晶セラミックスの合成に関する研究が盛んに行われている.我々はパルス通電加圧焼結法による高品質レーザー材料の合成を試みている.第一ステップとして産業用高出力レーザーの活性元素であるYb系材料のレーザー実証を目的とし,透光性Yb:Y2O3の透明化に取り組んできた.以降,焼結条件や添加濃度が光学品質に与える影響について調査を行い,透過率の向上およびレーザー発振を初めて観測した.焼結の途中から加圧を始めると損失が少なく,高い光学品質が得られた.これは収縮がある程度進んでから加圧力を増大させることで,ネック形成と閉気孔が抑制でき,散乱源の減少につながったと考えられる.添加濃度10 at.%のYb:Y2O3(厚み0.80 mm)において,レーザー発振波長(1075 nm)における直線透過率75%が得られた.次に,焼結体のレーザー発振試験を行った結果、レーザー発振スペクトルを観測した.

  • パルス通電加圧焼結による共沈法YAG粉体の緻密化および透明化

    ヤン ヤウウェ, 根津優樹, 古瀬裕章, 川村みどり, 平賀啓二郎, 藤岡加奈, 宮永憲明, 吉田 英弘, 森田 孝治, 鈴木 達, 金 炳男, 目 義雄

    日本セラミックス協会 2017年年会  

    発表年月: 2017年03月

     概要を見る

    近年,透光性多結晶体を用いたレーザー開発が盛んに行われており,幅広い応用分野への展開が期待されている.特に透光性Y3Al5O12(YAG)多結晶体は単結晶体と同等の光学・熱的性質を有しており,かつ大口径化が可能であることから医療分野や高強度物理分野等の次世代大出力レーザー用の母材として光源開発が進められている.本研究ではこれを避けるために,独自に液相共沈法で合成した平均粒径数百&#61549;mのYAG微粉体を用いて焼結を試みた.液相共沈法は球状で単分散な微粉体の合成が容易であり,YAG微粉体の各種条件が焼結後の光学特性に与える影響について調査を行った.Nd:YAGのレーザーの発振波長である1064 nmにおいて直線透過率77%を得た.また&gt;1150 nmでは直線透過率80%を超えた.

  • 放電プラズマ焼結法を用いた透光性YAG セラミックスの開発

    厳佳月, 根津優樹, 古瀬裕章, 藤岡加奈, 宮永憲明, 川村みどり, 吉田 英弘, 森田 孝治, 鈴木 達, 金 炳男, 目 義雄, 平賀 啓二郎

    第64回応用物理学会春季学術講演会  

    発表年月: 2017年03月

     概要を見る

    透光性多結晶体を用いたレーザー開発が盛んに行われており,特に透光性Y3Al5O12(YAG)多結晶体は単結晶体と同等の光学・熱的性質を有しており,かつ大口径化が可能であることから医療分野や高強度物理分野等の次世代大出力レーザー用の母材として光源開発が進められている.本研究では,従来の無加圧真空焼結やHIPに変わる新しい焼結方法としてパルス通電加圧焼結法に着目し,透光性多結晶YAGの開発に取り組んでいる.本研究では、独自に液相共沈法で合成した平均粒径数百&#61549;mのYAG微粉体を用いて、焼結条件は,昇温速度5℃/min,焼結温度1280℃,保持時間10 min,加圧力80 MPa焼結を試みた.その結果、Nd:YAGのレーザーの発振波長である1064 nmにおいて直線透過率77%、また&gt; 1150 nmでは直線透過率80%を実現した.発表では合成手法や焼結対の特性詳細について報告をする予定である.

  • Fabrication of Textured Iron Oxides by Magnetic Field-Assisted Colloidal Processing

    UCHIKOSHI, Tetsuo, SUZUKI, Tohru, SAKKA, Yoshio

    ISEPD2017  

    発表年月: 2017年02月

     概要を見る

    Textured polycrystalline iron oxides, hematite and magnetite, were synthesized by the magnetic orientation of paramagnetic goethite particles followed by topotactic phase transformation. Commercially-available goethite particles were dispersed in water with a dispersing agent to prepare deflocculated suspension. The a,b axes-oriented goethite green cake was fabricated from the goethite suspension by slip casting technique in a 2 T static magnetic field. Highly c-axis oriented hematite was obtained by sintering the textured goethite cake at 1473 K in air. The c-axis oriented hematite was transformed to &lt;111&gt; oriented magnetite by reducing the textured hematite at 1473 K in Ar. The textured hematite and magnetite showed strong magnetic anisotropy.

  • 放電プラズマ焼結法を用いた透光性Yb:Y2O3セラミックレーザーの開発

    古瀬裕章, 中沢俊亮, 吉田 英弘, 森田 孝治, 鈴木 達, 金 炳男, 目 義雄, 平賀 啓二郎

    第64回応用物理学会春季学術講演会  

    発表年月: 2017年02月

     概要を見る

    パルス通電加圧焼結法は従来の無加圧真空焼結やHIPと比較して低温かつ短時間での焼成が可能である.これにより粒成長が抑えられ,平均粒径sub-&#61549;mの微結晶粒バルク化と機械特性の向上を実現できる点が大きな特長の一つであり,次世代の大出力レーザー材料の焼結技術としての可能性を有している.我々はパルス通電加圧焼結法による高品質レーザー材料の合成を試みている.その第一ステップとして産業用高出力レーザーの活性元素であるYb系材料のレーザー実証を目的とし,透光性Yb:Y2O3の透明化に取り組んできた結果について報告する.温度1250 ℃,昇温速度5 ℃/min,保持時間60 min、最大加圧力は80 MPa、真空中でパルス通電加圧焼結を行い、添加濃度10 at.%のYb:Y2O3において,レーザー発振波長(1075 nm)における直線透過率75%の透明焼結体を作製し、レーザー発振スペクトルを観測した.発表では材料合成,発振実験の詳細について報告する.

  • Anisotropic properties of c-axis oriented sic prepared by using strong magnetic field

    SUZUKI, Tohru, KOBAYASHI, Kiyoshi, UCHIKOSHI, Tetsuo, NISHIMURA, Toshiyuki, SAKKA, Yoshio

    ICACC2017  

    発表年月: 2017年01月

     概要を見る

    The physical and mechanical properties of ceramics can be tailored by controlling their microstructure. We already reported that the crystalline orientation in alpha-SiC could be controlled by a strong magnetic field and the c-axis was aligned parallel to the magnetic field. The preparation of the dense and textured SiC polycrystal was achieved. The 3-point bending strengths of the samples were 907 and 799 MPa for the crack-growth directions parallel and perpendicular to the c-axis in the c-axis oriented SiC, respectively. The thermal conductivity and the electrical conductivity perpendicular to the c-axis was higher than that parallel to the c-axis in the textured SiC. elect

  • Improvement of transparency in textured Alumina by slip casting in a magnetic field and SPS

    Takaharu Ashikaga, Kiyono Hajime, SUZUKI, Tohru

    ICACC2017  

    発表年月: 2017年01月

     概要を見る

    Alumina has excellent optical properties and mechanical properties. In this research, we tried to improve the transparency in alumina by control of the microstructure with the crystalline orientation and densification using a slip casting in a magnetic field and SPS. The preparation of the dense and textured alumina polycrystal was achieved. The in-line transmission of alumina prepared from powder and green compacts without a magnetic field were 17.7% and 38.4%, respectively at a wavelength of 640nm. As a result, the transmittance was improved by colloidal processing. Furthermore, the in-line transmission of the c-axis oriented alumina was 48.5%. Improvement of the transparency of alumina with fine microstructure could be achieved by the c-axis orientation.

  • Enhanced Photoluminescent Property of Crystalline-Oriented β-SiAlON:Eu2+ Phosphor Layer Prepared by Magnetic Field-Assisted Electrophoretic Deposition

    UCHIKOSHI, Tetsuo, ZHANG, Chenning, LIU, Lihong, SUZUKI, Tohru, SAKKA, Yoshio, HIROSAKI, Naoto

    ICACC  

    発表年月: 2017年01月

     概要を見る

    β-sialon:Eu2+, one of the important members in the oxy-nitride phosphor family, has been known as a promising green phosphor with very narrow emission band (centered at ~535 nm) and high color purity. Besides, this green phosphor has high thermal and chemical stabilities, due to its stiff framework crystal structure of the host lattice. In this study, electrophoretic deposition (EPD) technique assisted with a 12 T strong magnetic field was utilized to fabricate crystalline-orientedβ-sialon:Eu2+ phosphor deposits on ITO glass substrates. Photoluminescence intensity of the oriented deposits was improved by comparing with that of the randomly oriented samples. This technique, EPD process performed in a strong magnetic field, would be a promising method for the packaging of flat LEDs.

  • Improvement of thermal conductivity and transmittance in AlN by microstructure control

    SUZUKI, Tohru, Imai Kento, NISHIMURA, Toshiyuki, Kiyono Hajime, SAKKA, Yoshio

    ICACC2017  

    発表年月: 2017年01月

     概要を見る

    The thermal conductivity and transmittance of AlN is expected to be improved by controlling crystalline orientation. In previous studies, we reported that the a-axis oriented AlN could be prepared by a static magnetic field. On the other hand, sintering additives are needed to obtain dense AlN because of its low sinterability. In this study, we tried to make the c-axis oriented AlN with high thermal conductivity and possession of translucency by a rotating magnetic field and SPS. The thermal conductivity of the c-axis oriented AlN was improved compared with the random AlN. Translucent AlN can be fabricated with additions of 2 and 3 wt% CaF2. The thermal conductivity and transmittance can be improved by high temperature annealing due to reduction of grain boundary phase caused by CaF2.

  • Microstructure control in bulk ceramics by using a magnetic field

    鈴木 達

    日本MRS年次大会  

    発表年月: 2016年12月

     概要を見る

    強磁場を用いた結晶配向技術はアルミナ、酸化亜鉛、チタニア、炭化ケイ素など様々な非立方晶系セラミックスへの適用が可能である。従来、このプロセスでの配向は結晶軸の一軸のみの制御であった。そこで、さらに形状異方性粒子を用いることで、形状による配向制御と磁場による制御を組み合わせることで、2軸、3軸配向が可能となった。まず、ビスマス系誘電体において板状粒子を用いて、磁場中でのスリップキャストにより、板状によるc軸の配向と磁場によるa軸との配向が同時に可能となり、2軸配向を実証したことを示す。さらに、MgTi2O5の棒状粒子を磁場中でのテープキャストをすることにより3軸配向を達成したことを紹介する。

  • 強磁場を用いたセラミックスの結晶方位制御

    鈴木 達

    レーザー学会「マイクロ固体フォトニクス」専門委員会  

    発表年月: 2016年12月

     概要を見る

    バルクセラミックスの特性制御においては、その微構造をどのようにデザインして造り込んでいくかが重要となる。その一つの組織因子として結晶配向が挙げられる。当グループにおいては強磁場を用いた結晶配向を様々なバルクセラミックスへ適用し、透光性セラミックスへの適用も試みた。透光性セラミックスの作製においては、まず、緻密化においてコロイドプロセスを用いることによる成形体でのパッキングが重要であることを示し、SPSでの焼結に有効であることを実証したことを示し、さらに、結晶配向制御が直線透過性の向上に効果があることを紹介する。また、電気泳動堆積法との組み合わせにより、各層での結晶方位を制御することが可能となり配向積層という微構造制御に成功したことも紹介する。

  • Fabrication of Yb:Y2O3 ceramics by spark plasma sintering

    H. Furuse, S. Nakasawa, YOSHIDA, Hidehiro, MORITA, Koji, SUZUKI, Tohru, KIM, Byung-Nam, M. Kawamura, SAKKA, Yoshio, HIRAGA, Keijiro

    12th Laser Ceramics Symposium (LCS) 2016  

    発表年月: 2016年11月

     概要を見る

    The purpose of this study is to fabricate a new laser material using SPS and to demonstrate its feasibility. As a first step, we fabricated Yb3+-doped Y2O3 ceramics and study its spectroscopic properties for laser oscillation. We obtained over 70% transmittance for 1 at.% Yb:Y2O3 specimen at the laser wavelength of 1030 nm. For 10 at.% specimen, in-line transmittance is slightly lower than 1 at.% specimen, but the amount of absorption at the excited wavelength (976 nm) is large. The fluorescence of 10 at.% Yb:Y2O3 ceramics shows almost the same spectrum with a previously reported data. In the presentation, the possibility of the laser oscillation will be discussed.

  • 強磁場を用いたセラミックスの微構造制御

    鈴木 達

    第17回五セラミックス研究機関(東工大-名工大-JFCC-AIST-NIMS)合同  

    発表年月: 2016年11月

     概要を見る

    バルクセラミックスの特性制御においては、その微構造をどのようにデザインして造り込んでいくかが重要となる。その一つの組織因子として結晶配向が挙げられる。当グループにおいては強磁場を用いた結晶配向を様々なバルクセラミックスへ適用してきた。本発表においては、以下の3つのトピックスについて紹介する。1、静磁場を用いた磁化容易軸の配向制御として炭化ケイ素を挙げ、電気伝導性などの特性異方性が得られること。2、回転磁場を用いた磁化困難軸の配向制御として窒化アルミニウムを挙げ、熱伝導に関する異方性が得られること。3、電気泳動堆積法との組み合わせにより、各層での結晶方位を制御することが可能となり配向積層という微構造制御に成功したこと。

  • 磁場中成形及びSPS法による配向性アルミナの特性向上

    足利昂治, 清野 肇, 金 炳男, 鈴木 達

    日本磁気科学会 年会  

    発表年月: 2016年11月

     概要を見る

    本研究では、コロイドプロセスを用いて微粒子の分散・凝集を制御した磁場中スリップキャストにより、粒子の向きが揃ったアルミナ成形体を作製した。作製した成形体はSpark Plasma Sinteringを用いた二段焼結によって緻密化し、アルミナ焼結体の配向性と粒径を制御し、透光性及び機械的強度等の特性向上を試みた。

  • 磁場中成形SiCの焼結中での配向発達と特性異方

    鈴木 達, 西村 聡之, 小林 清, 目 義雄

    粉体粉末冶金協会 秋季大会  

    発表年月: 2016年11月

     概要を見る

    SiCは優れた耐熱性、高強度をもつ高温構造材料であり、広いバンドギャップを有し、高温化合物半導体材料としても注目される材料であり、この炭化珪素の特性改善のために種々の組織制御が試みられている。組織制御の一つとして結晶配向が有効な手法として種々の材料で行なわれており、SiCにおいてもウィスカーをテンプレートとしてテープキャストにより成形し、粒成長の核として用いることで配向制御を行い、強度、靭性を改善する例も報告されている。我々のグループでは、強磁場を用いることにより非立方晶系構造で結晶磁気異方性を有するアルミナやZnOなどの反磁性セラミックスの配向制御が可能であることを見出し、SiCにも適用することにより配向制御が可能であることを報告してきた。本研究においては、磁場中成形試料の焼結中における液相が配向に及ぼす影響と、またc軸配向したSiCの熱伝導および電気伝導の異方性に関して検討した。

  • Coating of Oriented β-SiAlON:Eu2+ Phosphor Layer on ITO Glass by Magnetic Field-Assisted Electrophoretic Deposition Process

    UCHIKOSHI, Tetsuo, ZHANG, Chenning, LIU, Lihong, SUZUKI, Tohru, HIROSAKI, Naoto, SAKKA, Yoshio

    The 6th NIMS-UR1 Workshop  

    発表年月: 2016年10月

     概要を見る

    Electrophoretic deposition (EPD) technique assisted with a 12 T strong magnetic field was utilized to fabricate crystalline-oriented β-sialon:Eu2+ phosphor deposits on ITO glass substrates. The direction of the applied magnetic field was perpendicular to that of the electric field for EPD. The influence of the horizontally-applied magnetic field assisted the phosphor particles to be oriented in the suspension, simultaneously, the vertically-applied electric field contributed the electrophoretic deposition of the positively-charged β-sialon colloidal particles onto a cathodic ITO glass substrate. Photoluminescence (PL) intensity of the oriented deposits was improved by comparing with that of the randomly oriented samples.

  • Microstructure control in bulk ceramics by colloidal

    SUZUKI, Tohru, KOBAYASHI, Kiyoshi, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    Workshop on Advanced Inorganic Materials (WAIM 2016)  

    発表年月: 2016年10月

     概要を見る

    Tailoring the crystallographic orientation in ceramics is very useful for improving their properties. A magnetic field is shown to be very effective in controlling the crystallographic orientation in bulk ceramics. We reported that the colloidal processing in a strong magnetic field was able to control the crystallographic orientation even in diamagnetic ceramics. The thermal conductivity perpendicular to the c-axis was superior to that parallel to the c-axis in textured SiC. If the orientation axis of platelet particles aligned due to a geometrical effect is different from the axis aligned by using a magnetic field, the multi-dimensional orientation can be controlled by simultaneous use of both the effects, and control of the elaborate microstructure will be expected.

  • The Method of Kramers-Kronig Transform Effective to the Impedance Spectrum of Lithium Battery

    KOBAYASHI, Kiyoshi, SAKKA, Yoshio, SUZUKI, Tohru

    PRiME2016  

    発表年月: 2016年10月

     概要を見る

    The Kramers-Kronig transform algorithm which would applicable to lithium ion battery system is tested for the measured impedance spectrum using coin type lithium ion battery.

  • Fabrication of Dense Ceramics and the Electrical Conductivity Anisotropy of the Textured MgO-doped Lanthanum Silicate Oxyapatite

    Yuki Shimura, KOBAYASHI, Kiyoshi, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio, Takaya Akashi

    PRiME2016  

    発表年月: 2016年10月

     概要を見る

    Crystal oriented MgO-doped lanthanum silicate oxyapatite was fabricated by colloidal process under strong magnetic field. By the conductivity measurements using the crystal oriented ceramicsc, the oxide ion conductivity parallel to c-axis is much higher than the conductivity vertical to c-axis.

  • 放電プラズマ焼結を用いた透光性Yb:Y2O3セラミックスの開発

    中沢俊亮, 古瀬裕章, 吉田 英弘, 森田 孝治, 鈴木 達, 金 炳男, 川村みどり, 目 義雄, 平賀 啓二郎

    第77回応用物理学会秋季学術講演会  

    発表年月: 2016年09月

     概要を見る

    我々は,放電プラズマ焼結法(Spark Plasma Sintering: SPS)による新規レーザー材料の探索に取り組んでいる.SPS法は,高速昇温が可能,低温・短時間で緻密化が可能,大口径焼結体の合成が可能,等の特長を有する通電焼結装置であり,近年多くの機能性材料合成に使用されている.特に短時間焼結によって粒成長を抑制でき,平均粒径sub-&#61549;mの微結晶材料の焼結と,これによる機械強度の向上が期待できる.本研究では、Yb添加Y2O3セラミックスをモデル材料として、SPS法と従来焼結法との比較を行い,上述の有効性を確かめることを目的としている.Yb添加濃度1at.%と5at.%試料において,それぞれ直線透過率71%と58% (波長 1030 nm)を得ており,さらなる透過率の向上を試みている.また波長1030nmの蛍光強度でYb特有の蛍光を観測した.講演では,研究の進展とレーザー発振の展望について報告する予定である.

  • LSCF系層状ペロブスカイト型混合導電体の特性に及ぼすAサイトイオン欠損の影響

    矢野 広将, 小林 清, 鈴木 達, 打越 哲郎, 目 義雄, 明石 孝也

    第29回秋季シンポジウム  

    発表年月: 2016年09月

     概要を見る

    YSZを電解質とするSOFCセルの構築プロセスにおいて、カソード電極材料の選択及びその界面における高抵抗反応相の生成・抑制はSOFC特性に影響を及ぼす重要な課題である。本研究では、固体酸化物型燃料電池の空気極材料の1つであるR-P型層状ペロブスカイト構造を有するLSCF系酸化物((Sr3-xLax)(Fe2-yCoyO6+δ))について、Aサイトイオンにわずかな欠損を与えたSLFC( (Sr2.45La0.55)( FeCo)O6+δ)粉末の合成を行い、合成した試料粉末と8YSZ粉末との反応性を調査した。次にAサイトに欠損を与えた試料粉末と欠損のない試料粉末の焼結体をそれぞれ作製し、伝導度を比較しAサイト欠損が伝導度に与える影響についても検討した。

  • 放電プラズマ焼結を用いた透光性Yb:Y2O3 多結晶体の合成

    中沢俊亮, 古瀬裕章, 川村みどり, 平賀 啓二郎, 吉田 英弘, 森田 孝治, 鈴木 達, 金 炳男, 目 義雄

    日本セラミックス協会 第29回秋季シンポジウム  

    発表年月: 2016年09月

     概要を見る

    透光性多結晶体が固体レーザー分野において大きな役割を果たしており、特に単結晶体と同程度の熱伝導率を有し,10 cm角の大口径化が可能な透光性ヤグ多結晶体は,医療や高強度物理等の次世代レーザー応用のための母材として国内外において盛んにレーザー開発が行われている.我々は放電プラズマ焼結法(SPS)によるレーザー品質の焼結体合成に取り組んでいる.本研究では, SPS 法の有効性をYb:Y2O3 セラミックスの合成において調査した.現在,保持時間60 min の時に添加濃度1 at.%と5 at.%試料において,波長1030 nmにおける直線透過率がそれぞれ71%と58%の最大透過率が得られたを得ている.また波長1030 nm の蛍光強度で規格した蛍光スペクトルはYb 特有の蛍光を確認しており,現在励起LD の高強度化と,蛍光寿命測定の準備を進めている.講演では,研究の進展とレーザー発振の展望について議論する予定である.

  • MgOドープオキシアパタイト型ランタンシリケートの高配向性焼結体のイオン伝導異方性

    志村 裕紀, 小林 清, 鈴木 達, 打越 哲郎, 目 義雄, 明石 孝也

    セラミックス協会 第29回秋季シンポジウム  

    発表年月: 2016年09月

     概要を見る

    オキシアパタイト型ランタンシリケート(LSO)は中低温域でイットリア安定化ジルコニアよりも高い酸化物イオン伝導度を示す。LSOへのMgOドープによる伝導度向上の報告があるが、我々のグループではMgOをドープした系におけるイオン伝導度の異方性を明らかにしている。そこで本研究では、この系での結晶配向制御による、更なる特性向上を目的とした。既往の研究において報告されている伝導度の高い組成の粉末を合成し、粒子が良分散したスラリーを強磁場中においてスリップキャスト成形することで、結晶がc軸に配向した試料を作製した。得られた試料は、無ドープの無配向体LSOと比較して、伝導度の値が著しく向上することを確認した。

  • 微構造制御によるAlNの熱伝導性および透光性の向上

    鈴木 達, 今井 健人, 清野 肇, 西村 聡之, 目 義雄

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2016年09月

     概要を見る

    AlNは難焼結性材料であるが、Y2O3やCaF2などの焼結助剤を用いることで焼結が行われており、透光性の付与も可能である。AlNは六方晶構造であるため、c軸方向を揃えることで粒界での散乱が軽減され、透光性が向上すると期待される。また、c軸方向での熱伝導も他の方位に比べて若干高くなることが報告されている。そこで、焼結時および成形時に外場を印加するプロセスとなる、CaF2助剤とSPSを用いることによる緻密化による透光性付与、さらに12Tでの回転磁場中成形を用いることによる結晶配向制御をおこなうことで熱伝導性と透光性向上の両立を試みた。

  • 磁場中成形及びSPS法による配向性アルミナの特性向上

    足利昂治, 清野 肇, 鈴木 達

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2016年09月

     概要を見る

    本研究では、コロイドプロセスを用いて微粒子の分散・凝集を制御した磁場中スリップキャストにより、粒子の向きが揃ったアルミナ成形体を作製した。作製した成形体はSpark Plasma Sinteringを用いた二段焼結によって緻密化し、アルミナ焼結体の配向性と粒径を制御し、透光性及び機械的強度等の特性向上を試みた。

  • 8YSZの等温焼結中における緻密化挙動

    金 炳男, 鈴木 達, 森田 孝治, 吉田 英弘, 目 義雄, 松原秀彰

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2016年09月

     概要を見る

    The densification behavior during the isothermal sintering of 8YSZ was examined in the initial and intermediate stages of sintering, by using a dilatometer. In the initial stage, a difficulty in evaluating the densification behavior arises from the transition of the stable pore structure and the limitation of the theoretical two-sphere model. In the intermediate stage, as shown in Fig. 1, the densification kinetics is represented as , where is the densification rate, t is the time and C is a constant. This empirical equation of densification kinetics is valid in a wide range of density (0.54~0.9), except when the rapid grain growth takes place. At a relative density of 0.6~0.73, the activation energy is 688 kJ/mol. Rapid grain growth is observed at a relative density of 0.73~0.8 and &gt

  • Control of crystallographic orientation in bulk ceramics by colloidal processing in a high magnetic field

    鈴木 達

    日本磁気学会学術講演会  

    発表年月: 2016年09月

     概要を見る

    各種材料において、特性制御のために微構造組織は重要である。異方性制御もその中で有望な組織因子の1つであり材料の結晶配向制御により、特性発現、改善、また信頼性を向上が期待される。本講演においいては、セラミックスでの配向付与に関して、反磁性、常磁性であっても等軸晶でない結晶構造をもつセラミックスならばコロイドプロセスでの成形時に強磁場を印加することにより結晶配向が可能であることを示す。この場合、焼結は磁場外で行うために通常の電気炉、ホットプレス、SPS等での緻密化が可能となる。さらに他のプロセス因子である電場との重畳により新規な微構造を創製可能であることを紹介する。また、形状異方性粒子を用いることで多軸配向制御が可能となる例も紹介する。

  • Fabrication of c-axis oriented AlN by a rotating magnetic field and SPS

    SUZUKI, Tohru, Imai Kento, NISHIMURA, Toshiyuki, Kiyono Hajime, SAKKA, Yoshio

    HTCMC-9  

    発表年月: 2016年06月

     概要を見る

    The thermal conductivity of AlN is expected to be improved by controlling crystalline orientation, because AlN has hexagonal crystal structure and the thermal conductivity along the c-axis is higher compared with other directions. In previous studies, we reported that the a-axis oriented AlN could be prepared by a static magnetic field. On the other hand, sintering additives are needed to obtain dense AlN because of its low sinterability. Dense AlN was prepared by a slip casting in a rotating 12T magnetic field followed by SPS at 2073K. The thermal conductivity increased with the increasing amount of CaF2. The thermal conductivity of the c-axis oriented AlN was improved about 10 W/(m・K) compared with the random AlN. Translucent AlN can be fabricated with additions of 2 and 3 wt% CaF2.

  • Fabrication of Oriented β-SiAlON:Eu2+ Phosphor Layer by Magnetic Field-Assisted Electrophoretic Deposition

    UCHIKOSHI, Tetsuo, ZHANG, Chenning, LIU, Lihong, SUZUKI, Tohru, SAKKA, Yoshio, HIROSAKI, Naoto

    HTCMC9-GFMAT2016  

    発表年月: 2016年06月

     概要を見る

    β-sialon:Eu2+, one of the important members in the oxy-nitride phosphor family, has been known as a promising green phosphor with very narrow emission band (centered at 〜535 nm) and high color purity. Besides, this green phosphor has high thermal and chemical stabilities, due to its stiff framework crystal structure of the host lattice. In this study, electrophoretic deposition (EPD) technique assisted with a 12 T strong magnetic field was utilized to fabricate crystalline-orientedβ-sialon:Eu2+ phosphor deposits on ITO glass substrates.

  • 配向制御したセラミックスの耐照射性に関する研究

    鈴木 達, 矢野豊彦, 吉田克己

    東工大先導原子力研究所 研究交流・発表会  

    発表年月: 2016年06月

     概要を見る

    セラミックスは熱的安定性、耐食性などに優れ、原子炉・核融合炉用として有力な材料のひとつである。実際に原子炉等に使用するには、耐照射性等の原子力材料に特有の高速中性子照射、高温、腐食性環境などの過酷環境に耐えうる必要があり、この特性を向上させるためには精緻な組織制御が重要となる。物質の諸特性は結晶面や軸方位により異なる場合が多く、多結晶体における個々の結晶方位を揃えたりするなどの配向制御は、近年特に注目されている組織制御手法の一つであり、耐照射性向上の組織制御法としても期待できる。そこで、結晶配向制御した焼結性セラミックスを作製し、結晶方位が耐照射特性に及ぼす影響について検討する。

  • Crystallographic orientation control in ceramics by colloidal processing in a high magnetic field

    SUZUKI, Tohru

    MAP7  

    発表年月: 2016年06月

     概要を見る

    セラミックスなどの材料においては、微構造組織制御は特性向上に重要であり、結晶配向はその効果的手法の一つとしてあげられる。本講演では、強磁場を用いたセラミックスの配向制御プロセスについて概説する。磁場を用いてスラリー中の粒子を回転させる為にはスラリー中での微粒子分散が重要であることを説明し、静磁場による磁化容易軸の一軸配向ではランタンシリケート系への適用による伝導度向上、回転磁場による磁化困難軸の一軸配向ではAlNへの適用における熱伝導性の向上について紹介する。さらに板状粒子と磁場とを重畳作用させることによる多軸配向について解説する。

  • 結晶配向とSPSによるAlNの熱伝導性および透光性の向上

    鈴木 達, 今井 健人, 清野 肇, 西村 聡之, 目 義雄

    粉体粉末冶金協会 春季大会  

    発表年月: 2016年05月

     概要を見る

    AlNは熱伝導性に優れており、高輝度LEDパッケージの放熱基板として期待され、透光性を付与するができれば高温箇所での光学測定用窓への応用も可能となる。AlNは難焼結性材料であり、透光性を示す緻密体の作製には、Y2O3やCaF2などの焼結助剤添加での放電プラズマ焼結(SPS)が有効である。また、AlNはウルツ鉱型の結晶構造であるため特性に異方性を持ち、c軸配向制御により熱伝導性の向上が期待出来る。光学特性においても屈折率に結晶方位依存性を有するため、結晶方向を一方向に揃えることで光の散乱を減らし透光性を向上できると考えられる。AlNは回転磁場を用いることによって磁化困難軸であるc軸が配向したAlNを作製可能である。本研究においてはSPSにより作製したAlNにおいて、c軸配向とCaF2添加量が熱伝導性と透光性に及ぼす影響を検討した。また、熱処理を行うことで熱伝導性と透光性の向上も試みた。

  • 強磁場コロイダルプロセスを用いた一軸および三軸配向オリビン多結晶体の創製

    小泉早苗, 鈴木 達, 目 義雄, 平賀岳彦

    日本地球惑星科学連合2016年大会  

    発表年月: 2016年05月

     概要を見る

    Olivine is the most abundant mineral in the Earth’s upper mantle and it is considered to orient crystallographically in response to the mantle flow. Magnetic field was applied to fine-grained equigranular Fe-free and Fe-bearing olivine particles. To align the magnetic easy and hard axes of olivine, we used a vertical static magnetic field and rotating magnetic field, respectively. For tri-axial alignment, we used a rotating magnetic field with modulated rate. The particles dried in a strong magnetic field were then densified isostatically and sintered under vacuum condition out of magnet. With this technique, we could obtain c-, b-axes uniaxially and triaxially aligned Fe-bearing (Fe:Mg=1:9) olivine aggregates with achievements of high density (≧ 99%) and fine grain size.

  • 磁場成形による微構造設計のエネルギー材料への適用

    鈴木 達, 小林 清, 山田英登, 打越 哲郎, 目 義雄

    粉体工学会 春期研究発表会  

    発表年月: 2016年05月

     概要を見る

    燃料電池での中低温域作動には、ジルコニアよりも低い温度でのイオン伝導性に優れた電解質が求められており、オキシアパタイト型ランタンシリケート(LSO)がその候補としてあげられる。LSOは六方晶アパタイト構造であり、c軸に平行の伝導度が垂直方向より1桁高いことが単結晶により示されており、多結晶セラミックスにおいてもc軸配向を行うことにより、高い伝導度のLSOを期待出来る。また、リチウム2次電池の正極材料であるLiCoO2は層状岩塩型の結晶構造であり、c面内での電子伝導がc軸方向よりも優れており、さらに、Liイオンの伝導性においても層間での挿入脱離を考えれば、c面の方向を揃えることでLiイオンの導電性が向上することが期待出来る。そこで、本報告においては、LSOおよびLiCoO2について、強磁場を用いた結晶配向制御を行い、その微構造制御の特性向上への有効性を検討した。

  • Texture developing and some properties of feeble magnetic ceramics

    SAKKA, Yoshio, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    ICCPS-13  

    発表年月: 2016年05月

     概要を見る

    強磁場中コロイド成形とその後の焼結による配向体作製とその特性に関し、招待講演を行う。特に、本プロセスの原理、酸化物およい非酸化物系セラミックス配向体の特性について発表する。

  • 8YSZの等温焼結における緻密化挙動

    金 炳男, 鈴木 達, 森田 孝治, 吉田 英弘, 目 義雄, 松原秀彰

    日本金属学会春期大会  

    発表年月: 2016年03月

     概要を見る

    The densification behavior during the isothermal sintering of 8YSZ was examined in the initial and intermediate stages of sintering, by using a dilatometer. In the initial stage, a difficulty in evaluating the densification behavior arises from the transition of the stable pore structure and the limitation of the theoretical two-sphere model. In the intermediate stage, as shown in Fig. 1, the densification kinetics is represented as , where is the densification rate, t is the time and C is a constant. This empirical equation of densification kinetics is valid in a wide range of density (0.54~0.9), except when the rapid grain growth takes place. At a relative density of 0.6~0.73, the activation energy is 688 kJ/mol. Rapid grain growth is observed at a relative density of 0.73~0.8 and &gt

  • 強磁場中成形法を用いたMgOドープオキシアパタイト型ランタンシリケートの高配向焼結体作製と電気伝導異方性

    志村 裕紀, 小林 清, 鈴木 達, 打越 哲郎, 目 義雄, 平井 拳也, 明石 孝也

    公益社団法人日本セラミックス協会2016年年会  

    発表年月: 2016年03月

     概要を見る

    固相反応法と遊星ボールミル粉砕により調整された高焼結性のMgOドープ・オキシアパタイト型ランタンシリケート(LSO)を用いて、通常焼結体及び配向焼結体を製造し、電気伝導度の結晶方位依存性を検討した。異なる磁場方向下でのスリップキャスト成形により、a, b軸配向体及びc軸配向体が得られ、これらを1873Kで熱処理することで配向緻密焼結体が製造できた。磁場配向においては、におけるMgOドープLSOの磁化容易軸はa, b軸であり、不純物を含まないLSO(c軸)とは異なっていた。交流インピーダンス法による全電気伝導度測定から、MgOドープLSOにおいても、不純物を含まないLSOと同様に、結晶のc軸方向に高い酸化物イオン伝導が発現することを確認した。

  • Fabrication of b-axis oriented mordenite dense film from b-axis oriented seed layer by the secondary growth method

    UCHIKOSHI, Tetsuo, MATSUNAGA, Chika, SUZUKI, Tohru, SAKKA, Yoshio, Motohide Matsuda

    ICACC2016  

    発表年月: 2016年01月

     概要を見る

    The secondary growth of seed particles pre-deposited on substrates is an effective way to synthesize oriented zeolite films. We have proposed a magneto-scientific seeding process using a strong magnetic field to apply crystalline-oriented seed layer on the substrates. In this study, we attempted to prepare oriented mordenite dense film via the secondary growth from the oriented seed layers in reaction solutions with controlled chemical compositions. The b-axis oriented mordenite seed layers were successfully changed to dense films with retaining the initial orientation structure via hydrothermal treatments using a clear reaction solution having the molar ratio of 6Na2O : Al2O3 : 30SiO2 : 3500H2O.

  • Anisotropic properties of c-axis oriented SiC prepared by slip casting in strong magnetic field and SPS

    SUZUKI, Tohru, KOBAYASHI, Kiyoshi, UCHIKOSHI, Tetsuo, NISHIMURA, Toshiyuki, SAKKA, Yoshio

    ICACC2016  

    発表年月: 2016年01月

     概要を見る

    Tailoring the crystallographic texture in ceramics is one effective way to improve their properties. We already reported that development of texture can be controlled by consolidation in a strong magnetic field followed by heating even for diamagnetic ceramics. In this study, we applied this processing to SiC (6H) for producing the textured SiC and investigate some properties. The c-axis of the SiC was parallel to the direction of the applied magnetic field. The 3-point bending strengths were 907 and 799 MPa for the crack-growth directions parallel and perpendicular to the c-axis in the c-axis oriented SiC, respectively. The thermal conductivity and the electrical conductivity perpendicular to the c-axis was higher than that parallel to the c-axis in the textured SiC.

  • Fabrication of Textured Iron Oxide Bulk Ceramics via Topotactic Phase Transformation

    打越 哲郎, 鈴木 達, 目 義雄

    25th anual meeting of MRS-Japan 2015  

    発表年月: 2015年12月

     概要を見る

    Texture control in polycrystalline materials is promising because it can improve their properties equivalent to those of single crystals from inexpensive, commercially-available raw powder. Magnetic alignment is another good method to texture the microstructure, but the dense packing of iron oxide particles in a magnetic field is difficult due to their ferromagnetic property; they connect to each other and form a chain structure. In this study, textured polycrystalline iron oxides, hematite and magnetite, were synthesized by the magnetic orientation of paramagnetic goethite particles followed by topotactic phase transformation.

  • コロイドプロセスによる粒子固化成形と微構造制御

    打越 哲郎, 鈴木 達

    第46回 Continuing Education シリーズ講習会  

    発表年月: 2015年11月

     概要を見る

    直径が10-7〜10-9 m程度の大きさの粒子が気体や液体に分散している状態をコロイドという。コロイド粒子は、ブラウン運動、チンダル現象、透析、電気泳動などの特有な性質を有し、電解質の存在下で凝析や塩析などの現象を示す。こうしたコロイド粒子の基本的な性質は、物質の種類によらず、粒子のサイズで決まる。コロイド粒子のサスペンションから粒子を適当な方法で凝集させると、緻密な固化成形体を得ることができる。スラリーを経由する粉体成形法はコロイドプロセスと呼ばれ、複雑形状のセラミックス製品を製造する方法として注目されている。本講演では、セラミックスを中心にコロイド粒子の分散、凝集についてまず概説し、次いでコロイドプロセスにおけるサスペンション調製の注意点について、例をあげて紹介する。

  • Control of multi-axial orientation in BLSF by anisometric particles and magnetic field

    SUZUKI, Tohru, Miwa Yasunari, Kimura Masahiko, Kawada Shinichiro, Omiya Suetake, Wada Satoshi, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    US-Japan Seminar on Dielectric and Piezoelectric Ceramics  

    発表年月: 2015年11月

     概要を見る

    Slurry including the mixture of platelet and spherical particles in bismuth layer-structured ferroelectrics (BLSF) was consolidated by slip casting in a strong magnetic field. The c-axis of the platelet particles can be oriented by a gravity and the a, b-axes can be oriented by the applied magnetic field simultaneously.

  • Study of Textured Piezoelectric Ceramics Fabricated by a Magnetic Alignment

    Kimura Masahiko, Miwa Yasunari, Kawada Shinichiro, Omiya Suetake, Kubodera Noriyuki, Ando Akira, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    US-Japan Seminar on Dielectric and Piezoelectric Ceramics  

    発表年月: 2015年11月

     概要を見る

    Textured ceramics has gotten a lot of attention as a method to improve properties of electronic ceramics. We fabricated textured ceramics of perovskite type lead-containing piezoelectric materials by magnetic alignment. Then, highly textured ceramics were successfully obtained, and the piezoelectric constants were drastically improved.

  • 強磁場を用いたセラミックス粒子の配向制御

    鈴木 達

    デンカ NIMS講演会  

    発表年月: 2015年11月

     概要を見る

    各種材料において、特性制御のために微構造組織は重要である。異方性制御もその中で有望な組織因子の1つであり材料の結晶配向制御により、特性発現、改善、また信頼性を向上が期待される。本講演においいては、セラミックスでの配向付与に関して、反磁性、常磁性であっても等軸晶でない結晶構造をもつセラミックスならばコロイドプロセスでの成形時に強磁場を印加することにより結晶配向が可能であることを示す。この場合、焼結は磁場外で行うために通常の電気炉、ホットプレス、SPS等での緻密化が可能となる。さらに他のプロセス因子である電場との重畳により新規な微構造を創製可能であることを紹介する。また、形状異方性粒子を用いることで多軸配向制御が可能となる例も紹介する。

  • Fabrication and some properties of Textured MAX phase Ceramics

    SAKKA, Yoshio, MUSHA, Shotaro, SUZUKI, Tohru

    APMA2015  

    発表年月: 2015年11月

     概要を見る

    Textured MAX phase ceramics have been prepared by slip casting in a strong magnetic field followed by sintering. Textured Nb4AlC3 with plate-like grains are stacked regularly with a clear coherent structure at the grain boundaries without any amorphous phases. It shows a high flexural strength (about 1200 MPa) and the augmented fracture toughness (about 18 MPa&#8226;m1/2). Additionally, this material has excellent machinability and can be machined by a high-speed steel cutter. Excellent mechanical properties also have been shown for the textured Ti3Si(Al)C2, Ti2AlN.

  • 12T超伝導マグネット中におけるモルデナイト膜の水熱合成

    打越 哲郎, 松永知佳, 廣田 憲之, 鈴木 達, 田中優実, 松田元秀

    無機マテリアル学会第131回講演会  

    発表年月: 2015年11月

     概要を見る

    ゼオライトの配向膜は優れた分子選択性を示す高度な分離材として注目され,これまでに様々な膜作製方法が提案されてきた.Secondary growth法として知られる膜作製法は,種粒子を基板上に予め塗布し,その後水熱処理を行うことによって膜を得る方法である.我々は,これまでの研究で,磁場を利用したプロセスでゼオライトを配向させ,配向ゼオライト種結晶前駆体膜を作製し,それを強磁場の外で緻密固化する水熱処理により,種結晶前駆体膜の優先配向方位を保持した緻密配向膜を作製することに成功している.しかし,水熱合成過程においても強磁場を印加した場合,どのような微構造のゼオライト膜が得られるかは大変興味深い.そこで本研究では,強磁場中での水熱処理を行う反応システムの設計,試作を行い,それを用いてモルデナイト膜の作製を試みた.

  • 形状異方性粒子の強磁場中テープキャストによる3軸配向制御

    鈴木 達, 鈴木義和, 打越 哲郎, 目 義雄

    無機マテリアル学会 学術講演会  

    発表年月: 2015年11月

     概要を見る

    従来では、形状異方性粒子と強磁場中スリップキャストを用いてビスマス層状化合物において2軸配向制御を達成してきた。さらに、擬ブルッカイト系の斜方晶系結晶構造であるMgTi 2O5(MT2)を用いて、3軸配向制御を試みた。まずMT2の棒状粒子を粒状粒子を混合したスラリーを磁場中でテープキャストを用いることにより成形した。焼結後の試料において、b軸が磁場と平行に配向し、a軸を粒子の形状効果により配向させることができ、明確な3軸配向制御を達成した。このとき、配向度はb軸>c軸>a軸となった。通常、磁気トルクの算出はa軸とb軸を等価とするために、磁気トルクは一方向だけに発生する結果となるが、a、b、c軸の磁化率が全て異なる場合には、他の方向の磁気トルクも発生することを示し、配向性に与える影響を考察した。

  • 形状異方性粒子の強磁場による3軸配向制御

    鈴木 達, 鈴木義和, 打越 哲郎, 目 義雄

    日本磁気科学会 年会  

    発表年月: 2015年10月

     概要を見る

    結晶配向を用いた構造制御は材料の特性を支配する重要な因子の一つとして挙げられる。近年では多機能性の付与やさらなる特性向上などのため、より精緻な組織制御が求められており、多軸配向制御はその1つの組織制御手法として期待される。そこで、板状粒子を強磁場中でスリップキャストするプロセスにより2軸配向することを試みて成功してきた。しかしながら、これらのビスマス層状化合物では、a軸とb軸の差が小さく、解析が困難であることと、磁気異方性が極めて小さいと考えられるために3軸配向制御を明確にはすることが出来なかった。そこで、本研究においては、擬ブルッカイト系で斜方晶結晶構造を持つMgTi2O5(MT2)に注目し、その形状異方性粒子と磁場を用いた3軸配向制御を試みた。

  • Control of multi-axis orientation in ceramics by geometric effect and magnetic field

    SUZUKI, Tohru, SUZUKI Yoshikazu, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    International Conference on Magneto-Science 2015  

    発表年月: 2015年10月

     概要を見る

    Tri- or bi-axially orientation is expected to obtain the single crystal-like ceramics with superior properties compared with the random orientation ceramics. In the TGG process, anisometric particles are aligned with share stress in a matrix of fine particles during consolidation, such as tape casting and one directional extrusion. On the other hand, the colloidal processing in a strong magnetic field was able to control the crystallographic orientation even in diamagnetic ceramics. However, basically control of the orientation was restricted to the uni-axis orientation by means of these methods. In this study, control of the multi-axis orientation was achieved by the geometric effect of anisometric particles and a magnetic field.

  • Neutron irradiation effects on textured ceramics prepared by slip casting in strong magnetic field

    SUZUKI, Tohru, Yoshida Katsumi, SAKKA, Yoshio, Yano Toyohiko

    BR2共同利用照射成果報告会・大洗研究会  

    発表年月: 2015年10月

     概要を見る

    セラミックスは熱的安定性、耐食性などに優れ、原子炉・核融合炉用として有力な材料のひとつである。実際に原子炉等に使用するには、耐照射性等の原子力材料に特有の高速中性子照射、高温、腐食性環境などの過酷環境に耐えうる必要があり、この特性を向上させるためには精緻な組織制御が重要となる。物質の諸特性は結晶面や軸方位により異なる場合が多く、多結晶体における個々の結晶方位を揃えたりするなどの配向制御は、近年特に注目されている組織制御手法の一つであり、耐照射性向上の組織制御法としても期待できる。そこで、結晶配向制御した焼結性セラミックスを作製し、結晶方位が耐照射特性に及ぼす影響について検討する。

  • Fabrication of Crystalline-Oriented Porous Tinania Films on Transparent Electrode by Electrophoretic Deposition

    UCHIKOSHI, Tetsuo, SUZUKI, Tohru, MUTO Hiroyuki, MATSUDA Atsunori, SAKKA, Yoshio

    STAC-9&TOEO-9  

    発表年月: 2015年10月

     概要を見る

    Dye-sensitized solar cells (DSSCs) are the most extensively investigated systems for the conversion of solar energy into electricity, since it can convert light at longer wavelengths into electricity and can be manufactured using less energy compared to the bulk semiconductor-type cells with a p-n junction. In order to significantly enhance the cell performance, it is important to optimize the photo-anode structure of the DSSC on the basis of its fundamental properties. In this study, crystalline-oriented porous TiO2 thin films were fabricated on indium-tin oxide (ITO) or fluorine-doped tin oxide (FTO) glass substrates by electrophoretic deposition (EPD) in a superconducting magnet.

  • Densification Kinetics during Isothermal Sintering of 8YSZ

    KIM, Byung-Nam, SUZUKI, Tohru, MORITA, Koji, YOSHIDA, Hidehiro, SAKKA, Yoshio, Hideaki Matsubara

    STAC-9  

    発表年月: 2015年10月

     概要を見る

    The densification behavior during the isothermal sintering of 8YSZ was examined in the initial and intermediate stages of sintering. In the initial stage, a difficulty in evaluating the densification behavior arises from the transition of the stable pore structure and the limitation of the theoretical two-sphere model. In the intermediate stage, a linear relationship with a slope of -1/2 is observed between the densification rate and the time. An empirical equation of the densification kinetics is proposed and found to be valid in a wide density range. At a relative density of 0.6~0.73, the activation energy is 688 kJ/mol.

  • Fabrication of c-axis oriented ceramic of lanthanum silicate oxyapatite by slip casting in a strong magnetic field using the highly sinterable powder

    Kenya Hirai, KOBAYASHI, Kiyoshi, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, Takaya Akashi, SAKKA, Yoshio

    STAC-9  

    発表年月: 2015年10月

     概要を見る

    The c-axis oriented ceramic bulk of lanthanum silicate oxyapatite is successfully prepared by slip casting in a strong magnetic field using above sinterable powder. Lanthanum silicate oxyapatite was synthesized by heating at 1673 K for 10 h from lanthanum hydroxide and quartz silica. The resultant powder was milled with dispersant in water as solvent using planetary ball-milling for preparing slurry.

  • Preparation of c-axis oriented AlN by CaF2 sintering additive and a rotating magnetic field

    Imai Kento, Kiyono Hagime, SAKKA, Yoshio, SUZUKI, Tohru

    STAC-9  

    発表年月: 2015年10月

     概要を見る

    Because AlN has high thermal conductivity. of this property, AlN is used as heat release substrate. AlN has hexagonal crystal structure. The thermal conductivity is expected to be improved by controlling crystallographic orientation. Crystallographic orientation can be controlled by using a strong magnetic field. In previous studies, we reported that we can obtain the c-axis oriented AlN by a rotating magnetic field. In this study, we tried to make the textured AlN with high thermal conductivity using CaF2 as sintering aid and a rotating magnetic field. The thermal conductivity of the sample prepared in a strong magnetic field was improved about 10 W/(m・K) compared with the sample prepared without a magnetic field. Translucent AlN can be fabricated with additions of 2 and 3 wt% CaF2.

  • Ln2NiO4(Ln=La,Nd)系配向カソードの作製

    村田充史, 橋本実和, 松田元秀, 打越 哲郎, 鈴木 達, 目 義雄

    日本セラミックス協会第28回秋季シンポジウム  

    発表年月: 2015年09月

     概要を見る

    K2NiF4 型化合物として知られる Ln2NiO4(Ln = La, Pr and Nd, 以後 LNO)は低温でも優れた混合導電性を示し、現在低温作動固体酸化物形燃料電池用カソードとして注目されている。既報によれば、LNO における酸 化物イオンの拡散性は一般に広く検討されている(La, Sr)(Co, Fe)O3 よりも高いことが指摘されている。しかし、K2NiF4 型化合物はペロブスカイト層と岩塩層が c 軸方向に沿って積層した構造を持つため、観測される物性には大きな異方性が生じ、高い混合導電性はab面に沿って観測されることが報告されている。そのため、LNOをカソード材として用いるには、配向性制御が極めて重要となる。本研究では、Ln 元素としてLaを導入した La-LNO の配向カソードの作製を検討した結果を報告する。

  • 複酸化物表面へのポリマー修飾が電気泳動堆積プロセスに及ぼす効果

    打越 哲郎, 鈴木晴絵, 松永知佳, 小林 清, 鈴木 達, 武藤浩行, 松田厚範

    日本セラミックス協会第28回秋季シンポジウム  

    発表年月: 2015年09月

     概要を見る

    ポリカチオンおよびポリアニオンの静電交互吸着(LbL)は、液中における粒子表面のチャージを高電位かつ均一に制御するために有効な手法として知られている。本発表では、複数の電位決定点を有するLSGMやGDCなどの複酸化物粒子を例に、LbL法による表面電荷制御がEPD 特性の改善に有効であることを紹介する。また、EPD後の堆積体の乾燥割れは、本プロセスの実用化において解決すべき重要な問題の一つである。しかし、スラリーへのバインダー添加は、しばしばスラリーの安定性を損ねEPD特性をむしろ劣化させる要因となる。その改善策として、EPD後にポリマーをディップコートすることで、乾燥割れを効果的に防止するテクニックについても紹介する。

  • 回転磁場を用いた透光性c軸配向AlNの作製

    今井健人, 清野肇, 目 義雄, 鈴木 達

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2015年09月

     概要を見る

    AlNは熱伝導にすぐれ、また透光性を付与することで蛍光体のホスト材としてや光学材料として期待出来る。また、ウルツ鉱型の結晶構造を有するため、一軸配向制御することで透光性が向上することも期待出来る。イットリアやフッ化カルシュウムを焼結助剤とすることで透光性AlNが作製可能であることが報告させている。さらに我々は、回転磁場を用いることにより、c軸配向AlNを作製可能であることを報告してきている。そこで、本研究においてはフッ化カルシュウムと回転磁場を用いてc軸が一方向に揃った透光性AlNの作製を試みた。

  • 高配向性オキシアパタイト型ランタンシリケートの作製とその異方的特性評価

    平井 拳也, 小林 清, 鈴木 達, 打越 哲郎, 明石 孝也, 目 義雄

    日本セラミックス協会第28回秋季シンポジウム  

    発表年月: 2015年09月

     概要を見る

    オキシアパタイト型ランタンシリケートは高い酸化物イオン伝導性や化学的安定性から酸素センサーや中低温域作動の固体酸化物形燃料電池としての応用が期待されている。この材料はc軸方向に高い酸化物イオン伝導性が確認されている一方、焼結温度の高さや単相合成が困難であることが問題である。本研究では、固相法により大量合成しやすいプロセスで単相のオキシアパタイト型ランタンシリケート高焼結性粉末を作製した。さらに緻密体作製時にコロイドプロセス中で強磁場を印加することで高い酸化物イオン伝導度を有するc軸配向焼結体を作製し、イオン伝導度を測定した。

  • 強磁場を用いて作製したc軸配向SiCの特性異方性

    鈴木 達, 小林 清, 西村 聡之, 打越 哲郎, 目 義雄

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2015年09月

     概要を見る

    当グループでは強磁場中でのスリップキャストにより作製した成形体をホットプレス焼結やSPSを用いることによりc軸配向炭化ケイ素を作製することに成功してきており、アルミナやイットリアを助剤として用いた場合でも配向制御が可能であることを示してきた。また、曲げ強度においてはc軸平行方向で900MPa以上となり他の方位やランダム体よりも高い強度が得られていた。本発表においては、c軸配向した炭化ケイ素の熱伝導および電気伝導異方性に関して、助剤の影響も含めて報告する。焼結助剤無添加配向試料においては、熱伝導度はc面内での伝導度が高いことが明らかとなり、助剤を用いた場合には異方性がほとんど無くなった。

  • 能性セラミックスの磁場中コロイド成形における配向制御と応力緩和

    打越 哲郎, 鈴木 達, 目 義雄, 松田元秀

    日本セラミックス協会第28回秋季シンポジウム  

    発表年月: 2015年09月

     概要を見る

    配向セラミックスの作製法として、強磁場コロイドプロセスは極めて有効な手法である。しかし、結晶方位の揃ったセラミックスでは、高機能性が期待できる一方で、乾燥または焼結時における収縮異方性が原因で成形体の一方向に細かいひび割れが顕著に生じ、材料の高密度化を妨げる場合がしばしば生じる。本研究では、水平磁場を印加した状態で、試料を載置したステージを鉛直方向を回転軸としてゆっくり回転させて、ab軸を鉛直方向に高配向させつつc軸をランダム配向させて割れを緩和させた試みについて、c軸を磁化容易軸とする機能性セラミックス材料を例にとり紹介する。

  • 8YSZの等温焼結中における緻密化挙動

    金 炳男, 鈴木 達, 森田 孝治, 吉田 英弘, 目 義雄, 松原秀彰

    日本セラミックス協会 第28回秋季シンポジウム  

    発表年月: 2015年09月

     概要を見る

    The densification behavior during the isothermal sintering of 8YSZ was examined in the initial and intermediate stages of sintering. In the initial stage, a difficulty in evaluating the densification behavior arises from the transition of the stable pore structure and the limitation of the theoretical two-sphere model. In the intermediate stage, a linear relationship with a slope of -1/2 is observed between the densification rate and the time. An empirical equation of the densification kinetics is proposed and found to be valid in a wide density range. At a relative density of 0.6~0.73, the activation energy is 688 kJ/mol.

  • Control of multiaxis orientation in ceramics by geometric effect and magnetic field

    SUZUKI, Tohru, SUZUKI Yoshikazu, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    GMAC2015  

    発表年月: 2015年08月

     概要を見る

    The physical properties of a crystal depend on the direction of the crystal axis. Tri- or bi-axially orientation is expected to obtain the single crystal-like ceramics with superior properties compared with the random orientation ceramics. In this study, we attempt to control multi-dimensional orientation of ceramics by using the geometric effect and a strong magnetic field. The tape casting and slip casting was performed for making effective use of geometric anisotropy of particles. After the consolidation in a horizontal magnetic field, a certain axis was aligned by the magnetic field and the other axis was aligned by the geometric anisotropy. Therefore, we achieved to control multi-dimensional orientation of ceramics by a magnetic field and a geometric effect.

  • Fabrication and characterization of textured bulk ceramics of lanthanum silicate oxyapatite

    UCHIKOSHI, Tetsuo, TAKAHASHI, Satoshi, KOBAYASHI, Kiyoshi, SUZUKI, Tohru, SAKKA, Yoshio, Taskamasa ISHIGAKI

    PacRim-11  

    発表年月: 2015年08月

     概要を見る

    Lanthanum silicate oxyapatite (LSO) is lately-found oxide ion conductor. The oxide ion conduction mainly occurs along the c-axis; therefore, the c-axis orientation in dense polycrystals is preferable for its potential applications. LSO has anisotropic magnetic susceptibility due to its anisotropic crystalline structure. This anisotropy is quite small but the energy in a strong magnetic field can be higher than the energy of thermal motion at room temperature, therefore, when the LSO particles suspended in a liquid medium are placed in a strong magnetic field, they will rotate to an angle minimizing the system energy. We demonstrate in this paper that c-axis oriented ceramics are successfully fabricated using magnetic field-assisted colloidal processing technique.

  • Texture developing and some properties of feeble magnetic ceramics

    SAKKA, Yoshio, HU, Chunfeng, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    PACRIM 11  

    発表年月: 2015年08月

     概要を見る

    Some trials also have been presented to fabricate highly textured ceramics using template particles, changing magnetic susceptibility of different cationic doping, rotation magnetic field, etc. This processing can be applied to fabricate many kinds of textured ceramics with non-cubic structure, such as &#61524;i&#61519;&#61490;, AlN, SiC, Si3N4, MAX phase ceramics, ZrB2, B4C, etc. Some another anisotropic properties, such as high thermal conductivity of Si3N4, high mechanical properties of MAX phase ceramics, will be demonstrated.

  • Control of crystallographic orientation in ceramics by a strong magnetic field

    SUZUKI, Tohru

    NIMS/MANA-Waseda University International Symposium  

    発表年月: 2015年07月

     概要を見る

    セラミックス材料における各種特性改善と信頼性向上のために、その微細組織が特性を支配する重要な因子の一つであるため、結晶粒微細化、粒子分散、粒界制御等において巧緻な組織制御技術が試みられてきた。Al2O3、AlN、TiO2などの反磁性体、常磁性体では、その磁化率が極めて小さいことから磁場による配向などの組織制御は出来ないとするのが常識的な考えであったが、我々は、コロイドプロセスを用いることでこれらの弱磁性セラミックスにおいて強磁場配向が可能であることを見出している。さらに、電気泳動堆積法との組み合わせによる配向積層構造の造り込みや、形状異方性粒子を磁場中で配向させることによる多軸配向制御も可能にしている。本発表では、セラミックスにおける磁場配向プロセスを概説し、筆者らの結果も含めた適用例を紹介する。

  • Fabrication and some properties of Textured MAX phase Ceramics

    SAKKA, Yoshio, MUSHA, Shotaro, SATO, Kimitoshi, HU, Chunfeng, SUZUKI, Tohru

    ICCI 2015  

    発表年月: 2015年07月

     概要を見る

    we have fabricated textured MAX phase ceramics, which possessed a shell-like microstructure configuration from the nano- scale to the milli- scale. MAX phases are the layered ternary ceramics with the general formula Mn+1AXn (where M is an early transition metal, A is an A group element in the periodic table, X is a C or N, and n = 1, 2, 3). They show unique combination of metallic and ceramic properties, which were derived from their layered hexagonal structure and the anisotropy of the bonding strength. There are strong M-X bonds and weak M-A bonds in the nano-laminate.

  • Control of tri-axis orientation in MgTi2O5 by geometric effect and strong magnetic field

    SUZUKI, Tohru, SUZUKI Yoshikazu, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    14th International Conference of the European Ceramic Soceity  

    発表年月: 2015年06月

     概要を見る

    The physical properties of a crystal depend on the direction of the crystal axis. Tri- or bi-axially orientation is expected to obtain the single crystal-like ceramics with superior properties compared with the random orientation ceramics. In this study, we attempt to control three dimensional orientation of MgTi2O5 (MT2) by using the rod-like particles and a strong magnetic field. The tape casting was performed for making effective use of geometric anisotropy of particles. After the tape casting in a horizontal magnetic field, the b-axis was aligned by the magnetic field and the a-axis is aligned by the geometric anisotropy. Therefore, we achieved to control three dimensional orientation of MT2 by a magnetic field and a geometric effect.

  • Preparation and some properties of textured Ti2AlN ceramics

    MUSHA, Shotaro, SATO, Kimitoshi, SUZUKI, Tohru, SAKKA, Yoshio

    European Ceramic Society 2015  

    発表年月: 2015年06月

     概要を見る

    We attempt to fabricate textured Ti2AlN by using the strong magnetic field and measure some properties of textured one.

  • Anisotropic properties of textured SiC prepared by slip casting in a strong magnetic field

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    CMCEE 2015  

    発表年月: 2015年06月

     概要を見る

    In general, the physical properties of a crystal depend on the direction of the crystal axis. Tailoring the crystallographic texture in ceramics is one way of effectively improving their properties, such as electrical property, thermal conductivity and mechanical properties. In this study, we applied this processing to silicon carbide for producing the textured SiC and investigate the thermal and mechanical properties. The c-axis of the SiC was parallel to the direction of the applied magnetic field. The bending strength of the textured SiC depends on the crack-growth direction. The 3-point bending strengths were 907 and 799 MPa for the crack-growth directions parallel and perpendicular to the c-axis in the textured SiC, respectively, and for the random SiC, the strength was 724 MPa.

  • Surface modification of GDC and LSGM powders with polyelectrolyte layers to improve their EPD characteristics

    UCHIKOSHI, Tetsuo, Eiji ETO, Harue T. SUZUKI, MATSUNAGA, Chika, KOBAYASHI, Kiyoshi, SUZUKI, Tohru, Hiroyuki MUTO, Atsunori MATSUDA

    11th CMCEE  

    発表年月: 2015年06月

     概要を見る

    The surface modification of Gd doped ceria (GDC) and Sr- and Mg-codoped lanthanum gallate (LSGM) powders with cationic and anionic polyelectrolytes, PDDA and PAMPS, respevtively, was performed in ethanol by the layer by layer adsorption technique to improve the surface-charging uniformity. The laminar composites of GDC/LSGM/GDC tri-layers were fabricated on a polypyrrole-coated porous NiO-YSZ substrates by the sequential electrophoretic deposition (EPD) process using the ethanol-based suspensions of the surface-modified GDC and LSGM powders aiming SOFC applications. The topcoating of hydroxyl-propyl cellulose on the tri-layers was conducted to control the drying rate with suppressing cracking and peeling-off. The advantage of the use of those polymers for EPD process was demonstrated.

  • 磁場中スリップキャストによるTi2AlN配向体と特性評価

    武舍 翔太郎, 鈴木 達, 藤本憲次郎, 目 義雄

    材料科学会年会  

    発表年月: 2015年06月

     概要を見る

    本研究では, Ti3SiC2などの炭化物と比較すると研究例の少ない窒化物のMAX相に着目し, Ti2AlN配向体を作製した2). また、配向の及ぼす影響について, 力学特性の評価を行った.

  • 配向制御したセラミックスの耐照射性に関する研究

    鈴木 達, 目 義雄, 矢野豊彦, 吉田克己

    東工大原子炉工学研究所 研究交流・発表会  

    発表年月: 2015年06月

     概要を見る

    セラミックスは熱的安定性、耐食性などに優れ、原子炉・核融合炉用として有力な材料のひとつである。実際に原子炉等に使用するには、耐照射性等の原子力材料に特有の高速中性子照射、高温、腐食性環境などの過酷環境に耐えうる必要があり、この特性を向上させるためには精緻な組織制御が重要となる。物質の諸特性は結晶面や軸方位により異なる場合が多く、多結晶体における個々の結晶方位を揃えたりするなどの配向制御は、近年特に注目されている組織制御手法の一つであり、耐照射性向上の組織制御法としても期待できる。そこで、結晶配向制御した焼結性セラミックスを作製し、結晶方位が耐照射特性に及ぼす影響について検討する。

  • SPSによるZrB2基超高温セラミックスの作製と力学特性

    目 義雄, ウ ウェンウェン, エスティリ メーディ, 西村 聡之, 鈴木 達

    粉体粉末冶金協会春季大会  

    発表年月: 2015年05月

     概要を見る

    The Electric Current Activated/Assisted Sintering (ECAS) is an ever growing class of versatile techniques for sintering particulate materials. Among ECAS, the unique potentials of spark plasma sintering (SPS) are highlighted by our recent research works.

  • 強磁場鋳込み成形法によるオキシアパタイト型ランタンシリケート配向バルク体の組織制御と電気伝導異方性の評価

    打越 哲郎, 高橋聡志, 小林 清, 鈴木 達, 目 義雄, 石垣隆正

    粉体粉末冶金協会平成27年度春季大会  

    発表年月: 2015年05月

     概要を見る

    オキシアパタイト型ランタンシリケート(LSO)は、c軸方向に酸化物イオンが配列した結晶構造を有し、c軸方向に高い伝導性を示す新しい酸化物イオン伝導体である。一方、従来からよく知られているYSZ、ScSZ、GDC、LSGM等の酸化物イオン伝導体は、いずれも立方晶系の螢石型もしくはペロブスカイト型構造を持ち、伝導度の結晶方位依存性は報告されていない。我々はこれまでに、LSOの結晶磁気異方性に着目し、強磁場を用いた粒子配向技術とコロイドプロセスによる固化成形技術を融合させた強磁場鋳込み成形法で、c軸方向に高配向したLSOの緻密多結晶バルク体の作製と、電気伝導特性の向上について検討してきた。本講演では、強磁場鋳込み成形法で作製した配向バルクLSOについて、結晶配向度や電気伝導度の異方性を評価するとともに、配向LSOを電解質とする固体酸化物形燃料電池(SOFC)の単セルを作製して、発電特性に及ぼす配向効果について検討した結果を報告する。

  • 強磁場印加コロイドプロセスを 用いた細粒緻密配向性オリビン多結晶体の創製

    小泉 早苗, 鈴木 達, 目 義雄, 平賀 岳彦

    日本地球惑星科学連合2015年大会  

    発表年月: 2015年05月

     概要を見る

    Crystallographic preferred orientation (CPO) of minerals is considered to be widely produced in the Earth’s interior. Due to the presence of anisotropic physical properties of single crystal minerals. Magnetic field was applied to fine-grained (&#8764;120nm) equigranular Fe-free and Fe-bearing olivine particles. The aligned particles were gradually deposited on a solid-liquid separation filter during ethanol drainage. The dried particles were sintered using the alumina tube furnace. Highly dense (density of ≧99%) and fine grained (&#8764;1um) samples with a-axis alignment for Fe-free and c-axis alignment for Fe-bearing olivine to the magnetic direction were obtained. Such synthesized aggregates will allow us to measure CPO effect on the physical properties of olivine aggregate.

  • 強磁場電気泳動法により作製した(111)配向チタン酸バリウムセラミックスの微構造及び圧電特性評価

    小林 英悟, 上野 慎太郎, 中島 光一, 熊田 伸弘, 鈴木 達, 打越 哲郎, 目 義雄, 和田 聡志

    日本セラミックス協会 年会  

    発表年月: 2015年03月

     概要を見る

    チタン酸バリウム(BaTiO3, BT)セラミックスの圧電特性は、グレインの微細化や、配向付与により向上することが知られている。水素雰囲気下にて高温熱処理を行うことで得られる反磁性異方性を持つ六方晶 BT 微粒子を用いて磁場配向により作製した配向集積体は、焼結することで配向を維持したまま強誘電体相である正方晶BTに相転移させることが可能である。しかしこれまでの研究で、磁場中電気泳動堆積による圧電特性の向上は確認できなかった。これは焼結後のセラミックスに、六方晶BTに由来する双晶欠陥が含まれているためだと考えられる。そこで本研究では、テンプレート粒子成長(TGG)法にならい、六方晶BT 粒子にフィラーとして擬立方晶BTナノ粒子を混ぜることで双晶欠陥を含まない(111)配向 BT セラミックスの作製、及びそのグレインサイズ微細化を検討し、圧電特性の向上を試みた。

  • 高校生を対象とした磁場体験学習

    鈴木 達, 打越 哲郎, 松永 知佳

    日本セラミックス協会 年会  

    発表年月: 2015年03月

     概要を見る

    ネオジム磁石や超伝導マグネットの発生する強磁場を用いると、いわゆる非磁性体と呼ばれる磁石につかない材料が磁場の作用を受ける興味深い変化を観察することができる。本講演では、物質・材料研究機構(NIMS)において一般の高校生の見学者を対象に行っている様々なデモンストレーション実験を紹介して、物質(強磁性物質、反磁性物質)と磁場の相互作用を体験する学習とその効果について討論する。

  • オキシアパタイト型ランタンシリケート配向多結晶バルク体の作製とその特性評価

    打越 哲郎, 高橋 聡志, 小林 清, 鈴木 達, 目 義雄, 石垣隆正

    日本セラミックス協会 2015年年会  

    発表年月: 2015年03月

     概要を見る

    オキシアパタイト型ランタンシリケート(LSO)は、c軸方向に酸化物イオンが配列した結晶構造を有し、c軸方向に高いイオン伝導性を発現する。一方、酸化物イオン伝導体としてSOFCの電解質に利用されるYSZ、ScSZ、GDC、LSGM等は、いずれも立方晶系の螢石型もしくはペロブスカイト型構造を持ち、酸化物イオン伝導度の結晶方位依存性は報告されていない。我々はこれまでに、La9.33Si6Oxの結晶磁気異方性に基づく強磁場を用いた粒子配向技術とコロイドプロセスによる固化成形技術を融合させた強磁場鋳込み成形法により、多結晶ながら結晶粒がc軸方向に高配向したLSOの緻密バルク体の作製について報告してきた。この方法は、サイズの大きなバルク体の作製が容易であり、中低温域で高い発電効率を持つセル作製への応用も期待できる。本研究では、上記の方法により作製した配向LSOについて、結晶配向度や電気伝導度の異方性を評価した。

  • 強磁場を用いたセラミックス微構造組織制御の高度化

    鈴木 達

    日本セラミックス協会 年会  

    発表年月: 2015年03月

     概要を見る

    セラミックスにおいて、その微構造は特性を支配する重要な因子の一つであり、結晶粒微細化、粒子分散、粒界制御などが行われてきている。結晶配向を用いた微構造制御もその一つとして挙げられ、テンプレート粒子成長法、ホットフォージ、一軸押し出し成形など種々の配向プロセスにより特定の結晶軸を一方向に揃えることが行われている。一方、近年の超伝導技術の発達と冷凍技術の著しい進歩により、10Tを超える強磁場が比較的容易に得られるようになっている。常磁性体や反磁性体などの弱磁性セラミックスは、その極めて僅少な磁化率から磁場の作用を受けない物質(いわゆる非磁性体)として扱うことが通常であったが、強磁場を用いればその効果が期待できるようになった。そこで、強磁場利用した配向制御の実証とその汎用性の高さ、また、他のプロセスとの重畳作用による新規な微構造創製の可能性を示す。

  • 強磁場を用いたバルクセラミックスの配向組織制御

    鈴木 達

    物質化学セミナー  

    発表年月: 2015年02月

     概要を見る

    各種材料において、特性制御のために微構造組織は重要である。異方性もその中で有望な因子の1つであり、材料の配向を制御することは、特性発現、改善、また信頼性を向上さるために有望である。本講演においいては、バルクセラミックスにおける配向付与に関して、反磁性セラミックスであっても強磁場を用いたコロイドプロセスにより結晶配向が可能であることを示し、さらに他のプロセス因子との重畳により新規な微構造を創製可能であることを紹介する。

  • Development of 3-dimensional orientation in MgTi2O5 by tape casting in a strong magnetic field

    SUZUKI, Tohru, SUZUKI Yoshikazu, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    ICACC2015  

    発表年月: 2015年01月

     概要を見る

    The colloidal processing in a strong magnetic field was able to control the crystallographic orientation even in diamagnetic ceramics. In this study, we attempt to control three dimensional orientation of MgTi2O5 (MT2) by using the rod-like particles and a strong magnetic field. MT2 has orthorhombic psuedobrookite-type structure and shows anisotropic thermal expansion. Aqueous slurries were prepared from the MT2 granular powder and 50 wt% rod-like MT2 particles. The tape casting was performed in a strong 12T magnetic field. We achieved to control three dimensional orientation by a magnetic field. The b-axis of MT2 was aligned parallel to the magnetic field and the a-axis is aligned by the geometric effect during tape casting.

  • Study of Textured Piezoelectric Ceramics Fabricated by a Magnetic Alignment

    Kimura Masahiko, Miwa Yasunari, Kawada Shinichiro, Omiya Suetake, Kubodera Noriyuki, Ando Akira, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    Electronic Materials and Applications  

    発表年月: 2015年01月

     概要を見る

    Recently, improvement of the piezoelectric constants is strongly required as never before according with rapid downsizing of the electric components. One of the solutions is textured ceramics. Some of the texturing methods need high crystal anisotropy of the materials, and their applicability is limited. On the other hand, magnetic alignment does not require high crystal anisotropy for the materials. Therefore, we studied fabrication of textured ceramics of perovskite type lead- containing piezoelectric ceramics. Then, we successfully obtained the highly textured ceramics, and the improvements of piezoelectric constants were observed. Thus, we see magnetic alignment is an effective texturing method also for perovskite type piezoelectric ceramics.

  • プロセス制御による高次微構造材料の構築

    鈴木 達

    材料科学談話会  

    発表年月: 2014年12月

     概要を見る

    材料における機械的特性や電気的特性などの各種特性改善、また信頼性向上が求められる中で、その微構造組織は特性を支配する因子の一つであることから、結晶粒微細化、粒子分散、粒界制御、配向制御等を行う組織制御プロセスが重要となる。金属材料では加工・再結晶などの手法を用いて精緻な組織制御が可能であるが、脆性材料であるセラミックスへ適用することは難しい。そのため、粉末冶金同様にセラミックスの創製プロセスでも、原料、成形、焼結での制御が重要となる。ここでは、組織制御プロセスの1つであるコロイドプロセスを取り上げ、外場と組み合わせた微構造制御プロセスについても紹介する。

  • Milliwave Sintering of Silicon Carbide with Carbon Additives

    UCHIKOSHI, Tetsuo, SUZUKI, Tohru, TANAKA, Hidehiko, NISHIMURA, Toshiyuki, SAKKA, Yoshio

    The 31st Korea-Japan International Seminar on Ceramics  

    発表年月: 2014年11月

     概要を見る

    Microwave heating is one of the new sintering processes in which the materials absorb the electromagnetic energy of microwave and transform it into heat. Microwave sintering has a lot of advantages, e.g. selective heating, self-heating, rapid and volumetric heating. Microwave sintering is an effective method for the sintering of dielectric materials because their loss tangent (tanδ) is quite large. Selective heating is a distinct characteristic that has not been seen in any other heating process: The material with the highest loss tangent is selectively heated if two or more materials with different dielectric losses exist in a compact. In this study, we utilized the milliwave of 28 GHz for densifying hard-to-sinter SiC by coating the SiC particles with high loss tangent carbon additives.

  • Texture developing and some properties of feeble magnetic ceramics by colloidal processing in a strong magnetic field

    SAKKA, Yoshio, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    Materiaux2014  

    発表年月: 2014年11月

     概要を見る

    Some trials have been presented to fabricate highly textured ceramics using template particles, changing magnetic susceptibility of different cationic doping, rotation magnetic field, etc. This processing can be applied to fabricate many kinds of textured ceramics with non-cubic structure, such as &#61537;-Al2O3, TiO2, ZnO, AlN, SiC, Si3N4, MAX phase materials, ZrB2, B4C, etc. Some anisotropic properties, such as mechanical properties, thermal conductivity, oxidation resistance, etc. will be demonstrated. Typical examples of excellent properties of textured ceramics are high thermal conductive Si3N4, shell-like structure of MAX phase ceramics such as Nb3AlC2, Ti3Al(Si)C2 with excellent bending strength and fracture toughness.

  • 強磁場と異方性粒子を用いた2チタン酸マグネシウムの3軸配向制御

    鈴木 達, 鈴木義和, 打越 哲郎, 目 義雄

    無機マテリアル学会 学術講演会  

    発表年月: 2014年11月

     概要を見る

    従来では、形状異方性粒子と強磁場中スリップキャストを用いてビスマス層状化合物において多軸配向制御を達成してきた。しかしながら、これらの系では、a軸とb軸の区別をすることが困難であり、2軸配向として表すことが限界であった。そこで、擬ブルッカイト系の斜方晶系結晶構造であるMgTi 2O5(MT2)を用いて、3軸配向制御を試みた。まずMT2の棒状粒子を固相反応により作製し、その形状異方性粒子と粒状粒子を混合したスラリーを磁場中での成形にスリップキャストではなくテープキャストを用いることにより成形した。焼結後の試料において、b軸が磁場と平行に配向し、a軸を粒子の形状効果により配向させることができ、明確な3軸配向制御を達成した。

  • オキシアパタイト型ランタンシリケート配向バルク体の作製とその特性評価

    打越 哲郎, 高橋聡志, 小林 清, 鈴木 達, 目 義雄, 石垣隆正

    無機マテリアル学会 第129回講演会  

    発表年月: 2014年11月

     概要を見る

    ランタンシリケートは、c軸方向に酸素イオンが配列したアパタイト型の結晶構造を有し、この方向に高い酸素イオン伝導性を示す。本研究では、La9.33(SiO4)6O2の粉体を強磁場中で鋳込み成形した後に焼成することで、ランタンシリケートのc軸配向バルク配向体の作製を試みた。また、この配向体の電気伝導度異方性およびSOFCセルの発電特性を測定して、配向性が機能特性に与える影響を評価した。

  • 配向制御した炭化ケイ素における特性の方位依存性

    鈴木 達, 西村 聡之, 打越 哲郎, 目 義雄

    セラミックスエンジニアリングワークショップ  

    発表年月: 2014年11月

     概要を見る

    炭化ケイ素は優れた熱伝性および耐熱性を有し、また強度、硬度および耐磨耗性を兼ね備えた材料であり、これらの特性を生かして様々な分野での応用が期待される。結晶方位の配向制御は重要な微構造制御の一つとして挙げられ、6Hのような非対称の結晶構造をとるα-SiCでは、結晶方位を揃えることで結晶方向に依存する特性の向上が期待出来る。強磁場中成形後にホットプレスまたはSPSを用いて、緻密なc軸配向炭化ケイ素を作製した。配向度はEBSDの測定からc軸の傾き分布を計算した。配向方向に対して20度以内に80%の結晶粒が存在する高い配向性を得られた。配向方位に依存した、曲げ強度、熱拡散率などを測定し、その方位依存性について調べたので報告する。

  • 形状異方性粒子と強磁場を用いたMgTi2O5の3軸配向制御

    鈴木 達, 鈴木義和, 目 義雄

    セラミックス総合研究会  

    発表年月: 2014年11月

     概要を見る

    従来では、形状異方性粒子と強磁場中スリップキャストを用いてビスマス層状化合物において多軸配向制御を達成してきた。しかしながら、これらの系では、a軸とb軸の区別をすることが困難であり、2軸配向とすることが限界であった。そこで、擬ブルッカイト系であるMgTi2O5を用いて、まず棒状粒子を作製し、その形状異方性粒子と粒状粒子を混合して磁場中での成形にスリップキャストではなくテープキャストを用いることにより明確な3軸配向制御を達成したので、報告する。

  • Texture developing and some properties of feeble magnetic ceramics by colloidal processing in a strong magnetic field

    SAKKA, Yoshio, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    Japan-Korea International Symposium on Materials Science & Tech  

    発表年月: 2014年11月

     概要を見る

    New Processing for textured ceramics is demonstrated. Strong magnetic application to the colloidal processing can be applied to fabricate manykinds of textured ceramics with non-cubic structure, such as Al2O3, AlN, SiC, Si3N4, MAX phase ceramics, ZrB2, B4C, etc. Several typical examples of excellent properties of textured ceramics are shown such as excellent mechanical properties of textured MAX phase (Nb4AlC3, Ti3Al(Si)C2, Ti2SiN) ceramics, excellent thermal conductivity of c-axis in beta-Si3N4, etc.

  • A Study of Oriented PbTiO3 Ceramics Formed in Magnetic Field

    Hideki Ishii, Yasunari Miwa, Shinichiro Kawada, Suetake Omiya, Noriyuki Kubodera, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    第6回日中強誘電体応用会議  

    発表年月: 2014年11月

     概要を見る

    粒子配向技術は圧電体の圧電d定数の向上に効果があると言われており、近年、様々な粒子配向技術が研究されている。今回、我々は磁場印加による粒子配向技術に注目し、PbTiO3セラミックスの粒子配向を試みた。その結果、配向度90%(Lotgering法)の高配向試料を得ることに成功した。

  • Fabrication and Piezoelectric Properties of (111)-oriented BaTiO3 Ceramics by an Electrophoretic Deposition in a High Magnetic Field

    Eigo Kobayashi, Koichi Nakashima, Shintaro Ueno, Nobuhiro Kumada, Satoshi Wada, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    第6回日中強誘電体応用会議  

    発表年月: 2014年11月

     概要を見る

    チタン酸バリウム(BaTiO3, BT)は代表的な非鉛系圧電材料である。その圧電特性は、グレインの微細化や、粒子を(110)配向させることにより向上することが知られている。我々は、微細な六方晶BT粒子を強磁場電気泳動(HM-EPD)法により堆積させることで、微細なグレインからなる配向BTセラミックスの作製を検討してきた。水素雰囲気下にて還元処理を行うことで作製した六方晶BT配向体は、焼結時にその配向を維持したまま正方晶BTに相転移する。しかし、六方晶BTを完全に正方晶に相転移させるには高温での熱処理が必要であり、得られるセラミックスのグレインを微細化することは難しい。BTセラミックスは適量のMnを添加することで、粒成長を抑制することができると考えられる。そこで本研究ではMnを添加し、焼成条件を最適化させることで微細なグレインからなる(111)配向BTセラミックスの作製を試みた。

  • 電気泳動堆積法により形成した粒子堆積膜の乾燥割れを防ぐ2,3のアイデア

    打越 哲郎, 鈴木 達

    第5回 セラミックスエンジニアリングワークショップ  

    発表年月: 2014年11月

     概要を見る

    電気泳動堆積プロセスにおける液中粒子表面のチャージコントロールや、堆積体の乾燥割れの防止をポリマー修飾により効果的に行うためのテクニックについて、LSGMやGDCなどの複酸化物を例に紹介する。

  • 配向性SiCのSPSによる緻密化と熱伝導異方性

    鈴木 達, 西村 聡之, 目 義雄

    粉体粉末冶金協会 秋季大会  

    発表年月: 2014年10月

     概要を見る

    炭化ケイ素は優れた熱伝性および耐熱性を有し、また強度、硬度および耐磨耗性を兼ね備えた材料であり、これらの特性を生かして様々な分野での応用が期待される。材料において機能の新規発現や特性の向上には、微構造組織制御は極めて重要であり、組織粒の微細化、第2相や粒子の分散、粒界制御などの様々な組織因子の制御が行われてきている。結晶方位の配向制御も重要な微構造制御の一つとして挙げられ、6Hのような非対称の結晶構造をとる&#61537;-SiCでは、結晶方位を揃えることで結晶方向に依存する特性の向上が期待出来る。そこで、本研究においては、強磁場を用いた結晶配向制御を行い、さらにSPSを用いることで、緻密な配向炭化ケイ素を作製し、熱伝導などの特性に及ぼす配向性の影響について検討することを目的とした。

  • Nd2NiO4配向カソードの作製と低温での燃料電池電極特性

    村田充史, 小塚敏之, 松田元秀, 打越 哲郎, 鈴木 達, 目 義雄

    日本セラミックス協会 第27回秋季シンポジウム  

    発表年月: 2014年09月

     概要を見る

    現在、低温作動可能な固体酸化物形燃料電池(SOFC)のカソード材として、高いイオン・電子混合導電性を有するK2NiF4型酸化物が注目されている。K2NiF4型酸化物は層状構造であるため、導電率に異方性を有しており、c軸方向の導電率よりもab面上の導電率の方が高いことで知られる。そのため、カソードとしてK2NiF4型酸化物を用いる際には、カソード層の微細構造制御が重要となる。一方、近年、結晶磁気異方性に基づく強磁場印加の下でのセラミックス粒子の配向制御が注目されている。そこで現在我々の研究グループでは、磁場を用いたプロセスにより、K2NiF4型カソードの配向制御を検討している。本研究では、カソード材としてNd2NiO4(NNO)を用い、その磁場配向性および配向カソードの作製について検討した。

  • モルデナイト膜の水熱合成に及ぼす強磁場印加の影響

    松永 知佳, 打越 哲郎, 廣田 憲之, 鈴木 達, 松田元秀, 武藤浩行, 松田厚範

    日本セラミックス協会 第27回秋季シンポジウム  

    発表年月: 2014年09月

     概要を見る

    ゼオライトの配向膜は優れた分子選択性を示す高度な分離材として注目され、これまでに様々な膜作製方法が提案されてきた。Secondary growth法として知られる膜作製法は、種粒子を基板上に予め塗布し、その後水熱処理を行うことによって膜を得る方法である。現在我々の研究グループは、磁場を利用したプロセスでゼオライトを配向させ、配向ゼオライト種結晶前駆体膜を作製し、それを緻密固化する水熱処理条件を用いることにより、種結晶前駆体膜の配向を有する緻密配向膜の作製に成功した。しかし、水熱合成過程においても強磁場を印加した場合、どのような膜が得られるかは大変興味深い。そこで本研究では、強磁場中での水熱処理を行うシステム設計、機構を行い、それを用いてモルデナイト膜作製を試みた。

  • 強磁場プロセスを用いたMgTi2O5の3軸配向制御

    鈴木 達, 鈴木義和, 打越 哲郎, 目 義雄

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2014年09月

     概要を見る

    従来では、形状異方性粒子と強磁場中スリップキャストを用いてビスマス層状化合物において多軸配向制御を達成してきた。しかしながら、これらの系では、a軸とb軸の区別をすることが困難であり、2軸配向とすることが限界であった。そこで、擬ブルッカイト系であるMgTi2O5を用いて、まず棒状粒子を作製し、その形状異方性粒子と粒状粒子を混合して磁場中での成形にスリップキャストではなくテープキャストを用いることにより明確な3軸配向制御を達成したので、報告する。

  • 強磁場電気泳動法により作製した(111)配向チタン酸バリウムセラミックスの圧電特性のグレインサイズ依存性

    小林 英悟, 上野 慎太郎, 中島 光一, 熊田 伸弘, 和田 聡志, 鈴木 達, 打越 哲郎, 目 義雄

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2014年09月

     概要を見る

    チタン酸バリウム(BT)の圧電特性は、グレインの微細化や配向付与により向上することが知られている。我々は強磁場電気泳動(HM-EPD)法により、配向BT セラミックスの作製を検討してきた。磁気異方性を持つ六方晶 BT 微粒子を用いて、配向した集積体を作製し、焼成すると、配向性を維持したまま強誘電体相である正方晶 BT に相転移させることが可能で、最終的に(111)配向 BT セラミックスが得られる。しかし、六方晶 BT を完全に正方晶 BT に相転移させるには高温で熱処理する必要があるため、グレインを微細化することが難しい。そこで本研究では、焼結温度や昇温速度などの焼結条件を制御することで、BT 配向セラミックスのグレインサイズを変化させ、得られた BT セラミックスの配向度や圧電特性のグレインサイズ依存性を明らかにすることによって、グレインの微細化による特性向上を検討した。

  • 配向性セラミックスにおける内部応力制御

    鈴木 達

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2014年09月

     概要を見る

    結晶方位がランダムである通常のセラミックスにおいては、結晶方位に依存した焼結収縮異方性、熱膨張異方性などにより結晶粒界において、焼結後に不均一な応力が残留する。しかし、結晶配向させることによりその残留応力が緩和されることが予想される。また、各層での結晶方位を制御した構造とすることにより、単相材でも積層体のように振る舞う構造を作り込むことが可能となった。この場合にも、焼結収縮と熱膨張の異方性により各層に引張り応力と圧縮応力が残留する。これらミクロとマクロの視点で、配向セラミックスの残留応力制御の可能性を検討する。

  • Fabrication of textured MAX phase ceramics through colloidal processing in strong magnetic field and subsequent sintering

    SAKKA, Yoshio, SATO, Kimitoshi, HU, Chunfeng, SUZUKI, Tohru

    Sintering 2014  

    発表年月: 2014年08月

     概要を見る

    The design of bionic shell-like (nacre) structures has led to the strengthening and toughening of ceramics. Hybrid organic and inorganic materials have been extensively used for configuring layered composites. However, the high-temperature application is the forbidden zone for these ceramics. In the present investigation, we applied a strong magnetic field to align nanolayered MAX phase (Nb4AlC3 and Ti3SiC2) particles in an aqueous suspension and then densified the dried green body by sintering (spark plasma sintering or pressureless sintering). Here we will demonstrate processing of textured MAX phase ceramics (Nb4AlC3 and Ti3SiC2).

  • Anisotropic shrinkage during sintering in textured ceramics

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    International Conference on Sintering 2014  

    発表年月: 2014年08月

     概要を見る

    Anisotropic shrinkage can be controlled by anisometric particle morphology, anisotropic surface or grain boundary energy. Furthermore, processing parameters determine particle-packing characteristics which can play an important role in determining the nature of the sintering shrinkage. We focus on the effect of the crystallographic orientation on anisotropic shrinkage during sintering. In this study, we fabricated the c-axis oriented alumina by slip casting in a strong magnetic field without using the anisometric particles and analyzed the anisotropic shrinkage during sintering. Sintering shrinkage in the c-axis direction was larger than that of the direction perpendicular to the c-axis. Shrinkage in the c-axis direction depended on the heating rate.

  • Fabrication of textured MAX phase ceramics through colloidal processing in strong magnetic field and subsequent sintering

    SAKKA, Yoshio, SATO, Kimitoshi, MUSHA, Shotaro, HU, Chunfeng, SUZUKI, Tohru

    The 5th International Congress on Ceramics (ICC5)  

    発表年月: 2014年08月

     概要を見る

    we will demonstrate processing of textured MAX phase ceramics (Nb4AlC3, Ti3Si(Al)C2 and Ti2AlN). Synthesis of high purity MAX phase powder, well-dispersion of powder adding appropriate amount of dispersion, and sintering methods of SPS for Nb4AlC3, Ti3Si(Al)C2 and Ti2AlN, and pressure-less sintering for Ti3SiC2) will be demonstrated. The as-prepared bulk ceramic possessed a shell-like microstructure configuration from the nano- scale to the milli- scale, which endowed it with a high flexural strength (about 1200 MPa) and the augmented fracture toughness (about 18 MPa&#8226;m1/2) for Nb4AlC3. Additionally, this material has excellent machinability and can be machined by a high-speed steel cutter.

  • Tailored Microstructure of Laminar Ceramics by Using Electric and Magnetic Fields

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    International Conference on Composites or Nano Engineering  

    発表年月: 2014年07月

     概要を見る

    結晶配向は組織制御に有効であり、セラミックスではTGGなどで付与される。超電導マグネットが発達してきた近年、弱磁性セラミックスの配向付与を強磁場を用いることで可能となることを報告してきている。また、EPD法はコロイド成形の1つであり、泳動と堆積という2つのステップがある。EPDは積層体や傾斜機能材料などの様々な材料創製に展開されている。セラミックスの機械特性は、その微構造に敏感に影響される。残留応力の導入による亀裂偏向などで靭性などの特性の向上が見込める。我々のコンセプトは単相材料において残留応力の導入を行うために、結晶軸に依存した熱膨張と焼結収縮を使うことであり、ここでは、磁場中EPDを用いて、異なる結晶配向を持つ層を積層させることで、単相材において残留応力の導入を試みた。

  • Fabrication and some properties of textured Ti2AlN ceramic by slip casting in a strong magnetic field and spark plasma sintering

    MUSHA, Shotaro, SATO, Kimitoshi, HU, Chunfeng, SUZUKI, Tohru, SAKKA, Yoshio

    MAP6  

    発表年月: 2014年07月

     概要を見る

    MAX phases are the layered ternary ceramics with the general formula Mn+1AXn, (n = 1, 2,3). They show unique combination of metallic and ceramic properties. The properties were derived from their layered hexagonal structure and the anisotropy of the bonding strength. There are strong M-X bonds and weak M-A bonds in the nano-laminate. Recently, we fabricated textured a kind of MAX phases, Nb4AlC3 ceramic by slip casting in a magnetic field, and indicated that the textured MAX phases show excellent mechanical properties. In this study, we attempt to fabricate textured Ti2AlN by using the strong magnetic field and show excellent mechanical properties.

  • Texture developing and some properties of feeble magnetic ceramics

    SAKKA, Yoshio, SATO, Kimitoshi, HU, Chunfeng, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    MAP6  

    発表年月: 2014年07月

     概要を見る

    Strong magnetic application to the colloidal processing can be applied to fabricate manykinds of textured ceramics with non-cubic structure, such as Al2O3, AlN, SiC, Si3N4, MAX phase ceramics, ZrB2, B4C, etc. Several typical examples of excelent properties of textured ceramics are shown such as excellent mechanical properties of textured MAX phase (Nb4AlC3, Ti3Al(Si)C2, Ti2SiN) ceramics, excellent thermal conductivity of c-axis in beta-Si3N4, etc.References

  • Selective Orientation Control of Mordenite Seed Particles for the Fabrication of Mordenite Membrane with Oriented Channels

    MATSUNAGA, Chika, UCHIKOSHI, Tetsuo, SUZUKI, Tohru, HIROTA, Noriyuki, SAKKA, Yoshio, MotohideMATSUDA

    6th International Workshop on Materials Analysis and Processing  

    発表年月: 2014年07月

     概要を見る

    Secondary growth is one of fabrication methods for zeolite films: Fine seed crystals are applied on a substrate, and then the seeded substrate is hydrothermally treated in a reaction sol. The microstructures of the resultant zeolite films are generally dominated by the seeding process. In this study, fabrication of orientation controlled mordenite compacts were performed by slip casting in a 12 T strong magnetic field.

  • Design of multi-axial orientation in piezoelectric ceramics by anisometric particles and magnetic field

    SUZUKI, Tohru, Yasunari Miwa, Shinichiro Kawada, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    ELECTROCERAMICS XIV  

    発表年月: 2014年06月

     概要を見る

    Tailoring the crystallographic orientation in piezoelectric ceramics is very useful for improving their properties. We reported that the colloidal processing in a strong magnetic field was able to control the crystallographic orientation even in diamagnetic ceramics. In this presentation, our concept is that control of multi-axial crystalline orientation in ceramics by using both anisometric particles and a magnetic field. When the crystal axis controlled by the magnetic field is different from the direction aligned by their geometrical shape, the multi-dimensional orientation can be simultaneously tailored using the anisometric particles and the magnetic field. We applied this method to some ceramics, such as bismuth titanate, and achieved the multi-axial orientation.

  • 磁場中スリップキャストとパルス通電焼結によるTi2AlN配向体の作製とその特製評価

    武舍 翔太郎, 藤本憲次郎, 佐藤 仁俊, 鈴木 達, 目 義雄

    粉体粉末冶金協会春季大会  

    発表年月: 2014年06月

     概要を見る

    MAX相セラミックスは、一般式はMn+1AXnで表され、MはSc、Ti、Cr、Zr、Nb、Mo、Hf、Taなどの遷移金属元素、AはAl、Si、P、Ga、Ge、As、In、Sn、PbなどのAグループ元素、XはCかNである。MAX相セラミックスは、電気伝導性、熱伝導性などに代表される金属の特徴と、耐食性、高強度などのセラミックスの特徴を併せ持った材料であり、多くの関心が寄せられている。本研究では、炭化物系と比較すると研究例の少ない窒化物のMAX相に着目し、Ti2AlNを合成した。また、強磁場を用いて配向体を作製し、その特性についても評価を行った。

  • 六方晶チタン酸バリウム粒子を用いた強磁場電気泳動法による配向セラミックスの作製とその誘電・圧電特性

    小林 英悟, 上野 慎太郎, 中島 光一, 和田 聡志, 武井 貴弘, 熊田 伸弘, 鈴木 達, 打越 哲郎, 目 義雄, 馬込 栄輔, 森吉 千佳子, 黒岩 芳弘, 三輪 恭也, 川田慎太郎, 大宮 季武, 久保寺 紀之

    強誘電体応用会議  

    発表年月: 2014年05月

     概要を見る

    近年環境にやさしく誘電・圧電特性の大きなBaTiO3(BT)配向セラミックスが注目されている。これまでの研究より、正方晶構造において&lt;110&gt;または&lt;111&gt;方位に配向させ、かつ組織粒の小さな BTを作製できれば、更なる圧電特性の向上が期待でき、作製には強磁場スリップキャスト法や強磁場電気泳動法が有効と考えられている。六方晶構造の BT 粒子の使用では、いくつかの報告において配向可能であることが明らかとなった。しかし、六方晶 BT を強誘電体である正方晶 BT に変換することができず、立方晶 BT が形成され、圧電特性が正しく評価できないという問題点があった。そこで、本研究では六方晶 BT 粒子を用いたプロセスを再検討し、セラミックス作製条件を最適化した結果、ほぼ 100%&lt;111&gt;方位に配向した正方晶構造 BT セラミックスを作製できたので、その誘電、圧電特性とともに報告する。

  • Fabrication of highly textured &#61538;-Si3N4 and &#61538;-Sialon by slip casting in a strong magnetic field and reaction-sintering

    SAKKA, Yoshio, ZHU, Xinwen, SUZUKI, Tohru

    ISSNOX4  

    発表年月: 2014年05月

     概要を見る

    It reveals that the &#61538;-Si3N4 nuclei play a key role in the texture development in &#61538;-Si3N4/&#61538;-sialon. This technique developed provides highly conductive &#61538;-Si3N4 with conductivity to the thickness direction, which is a major advantage in practical use. The technique is also simple, inexpensive and effective for producing textured Si3N4 with high thermal conductivity of over 170 Wm-1K-1.

  • Effect of pulverized particles on crystallographic orientation in AlN prepared by slip casting in a strong magnetic field

    Kento Imai, SUZUKI, Tohru, SAKKA, Yoshio

    International Symposium on SiAlONs and Non-oxides  

    発表年月: 2014年05月

     概要を見る

    AlN has hexagonal crystal structure, and the control of asymmetric crystal structure is expected to improve their properties. It is possible to use a strong magnetic field to control the crystallographic orientation. However, many agglomerated particles were observed in as-received AlN powder, and the strong agglomeration prevents each particle from rotating in a magnetic field. Colloidal processing is very effective in rotating AlN particles and consolidating fine particles by breaking heterogeneous agglomerates. The number of small particles with average size of 0.4 &#61549;m increased and the size distribution became narrow by the planetary-type ball mill. When the pulverized powder are used for preparing the textured AlN, the degree of orientation are expected to be high.

  • Control of Orientation in Aluminum Nitride Prepared by Slip Casting in a Strong Magnetic Field

    SUZUKI, Tohru, Kento Imai, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    International Symposium on SiAlONs and Non-oxides  

    発表年月: 2014年05月

     概要を見る

    AlN exhibits anisotropy in its properties because of its hexagonal crystal structure, consequently the textured microstructure is expected to make an improvement of the properties. In this study, the starting materials were commercially available AlN powders. The suspension with this powder was consolidated by a slip casting in a static and a rotating strong magnetic field of 12 T. The a, b-axis and the c-axis of AlN were aligned using the static and the rotating magnetic field, respectively. The c-axis of the 61% of grains were aligned with less than 20 degree of tilting angle between the c-axis and rotating plane of a magnetic field in the c-axis oriented AlN. The some properties depend on the orientation direction in the textured AlN.

  • 種結配向体を用いたモルデナイト緻密配向膜の作製

    松永 知佳, 打越 哲郎, 鈴木 達, 目 義雄, 松田元秀

    第3回JACI/GSCシンポジウム  

    発表年月: 2014年05月

     概要を見る

    斜方晶系に属する反磁性体材料のモルデナイトの配向挙動を磁場によって制御し、得られた前駆体を適当な反応溶液組成からなる溶液中で水熱処理することによって、前駆体の配向に由来する配向性を持つモルデナイト緻密膜が作製できることがわかった。

  • Application of magnetic field for crystalline orientation in diamagnetic diamagnetic ceramics

    SUZUKI, Tohru

    The 9th International Symposium on Advanced Materials and Techno  

    発表年月: 2014年05月

     概要を見る

    セラミックスや金属において,その微構造は特性を支配する重要な因子であり高度に制御することが求められる.結晶配向は微構造制御の一つとして特性を改善するものと期待される。セラミックスにおいては、金属材料のように加工熱処理することが難しいために、成形段階でのプロセスの工夫が試みられてきており、強磁場を印加するプロセスも当グループをはじめとして提案されてきている。反磁性、常磁性セラミックスでは、その磁化率が極めて小さく通常では10T級の強磁場を用いても配向制御は難しい。しかし、微粒子の分散制御に有効なコロイドプロセスを用いることでスラリー中の粒子を回転させやすい状態とし、磁場配向に成功した。本発表においては、磁場中成形を用いた配向制御とこのプロセスをアルミナ、チタニア、酸化亜鉛、炭化ケイ素、窒化アルミニウムなど多様なセラミックスへ適応した結果について紹介する。

  • New Developments in Electrophoretic Deposition Process

    UCHIKOSHI, Tetsuo, SUZUKI, Tohru, SAKKA, Yoshio

    2nd Workshop of YU, Korea and NIMS, Japan  

    発表年月: 2014年05月

     概要を見る

    Electrophoretic deposition (EPD) is a colloidal process wherein ceramic bodies are directly shaped from a stable colloid suspension by a DC electric field. EPD is gaining increasing interest as a processing technique for production of novel inorganic nanostructured materials. In this presentation, we will introduce our recent studies on EPD for variety of applications in structural and functional ceramics, and discuss its versatility and potentiality.

  • Fabrication of textual polycrysgalline forsterite using colloidal processing in a magnetic field

    小泉 早苗, 平賀 岳彦, 鈴木 達, 目 義雄

    日本地球惑星科学連合2014年大会  

    発表年月: 2014年04月

     概要を見る

    It is well known that the crystallographic preferred orientation (CPO) of minerals is commonly produced in the Earth’s interior. Thus, it is important to understand the physical properties of the mineral aggregates that exhibit CPO. We used a technique of slip casting in a high magnetic field to align certain crystallographic axis of mineral particles. Vacuum sintering of the powders that were composed of the aligned particles was expected to produce a polycrystalline material aggregate that exhibits CPO, which allows us to examine the effect of CPO on the physical properties of the earth

  • モルデナイト モルデナイト 細孔配向 膜の作製− 強磁場利用と水熱反応固化の作製− 強磁場利用と水熱反応固化−

    松永 知佳, 打越 哲郎, 鈴木 達, 目 義雄, 松田元秀

    第1回資源・環境関連セラミックス材料・技術研究講演会  

    発表年月: 2014年03月

     概要を見る

    現在我々の研究グループは、近年注目されている磁場を利用したプロセスで、ゼオライトの配向化を検討している。磁場配向プロセスでは、結晶の磁気異方性という物理パラメータを利用して物質の配向挙動を制御できる。本研究では斜方晶系に属する反磁性体材料のモルデナイト(Na8Al8Si40O96&#8226;nH2O)を検討対象材とし、磁場を用いることにより配向前駆体膜を作製し、次いで得られた配向前駆体膜を水熱処理することによって緻密な配向膜へ水熱固化するプロセスの有効性と可能性を検討した。

  • バルクセラミックスの配向組織制御

    鈴木 達

    日本セラミックス協会 年会サテライトプログラム  

    発表年月: 2014年03月

     概要を見る

    セラミックス材料における機械的特性や電気的特性などの各種特性改善、また信頼性向上が求められる中で、その微細組織は特性を支配する重要な因子の一つであることから、金属材料と同様に結晶粒微細化、粒子分散、粒界制御等において巧緻な組織制御技術が期待されている。気体や液体を除いた物質や材料においては、その特性が完全に等方的であることは稀であり、性質が異方的であることを利用して有用な材料とする場合が多くある。よって、材料の配向を制御することは、その特性を改善させたり、信頼性を向上させたりするのに非常に有効である。金属材料では加工・再結晶などの手法を用いて精緻な集合組織制御が可能であり、その技術も既に高度に発達しているが、これら集合組織制御手法を脆性材料であるセラミックスへ適用することは難しい。本発表においいては、セラミックスでの結晶配向付与方法および、結晶配向による特性制御に関して概観する。

  • 高配向LNTセラミックス作製のための粉砕条件の検討

    末廣 志穂, 中野 裕美, 武田 忠彦, 木村 善衛, 鈴木 達, 目 義雄

    日本セラミックス協会 年会  

    発表年月: 2014年03月

     概要を見る

    Li-Nb-Ti-O系固溶体(以後LNTと省略)は,特定の組成域でユニークな周期構造(超構造)を有するM相が存在する。これまでLNT固溶体は,誘電特性や,最近では,蛍光体の母体材料としての研究が報告されてきた.著者らは,このユニークな構造を最大限に活かし,異方性工学により電気特性の異方性を発現させ,構造との関連性を明確にする研究に着手した.今回は,初期段階として強磁場(12 T)中でスリップキャストによる配向セラミックスの作製を試み,配向度向上のための紛体条件を検討した.その結果,粒子の粒度分布を精緻に制御することにより,配向度を向上させた。

  • 強磁場電気泳動法による微細なグレインからなる(111)配向チタン酸バリウムセラミックスの作製と圧電特性評価

    小林 英悟, 上野 慎太郎, 中島 光一, 熊田 伸弘, 和田 聡志, 鈴木 達, 打越 哲郎, 目 義雄, 三輪 恭也, 川田慎太郎, 大宮 季武, 久保寺 紀之

    日本セラミックス協会 年会  

    発表年月: 2014年03月

     概要を見る

    チタン酸バリウム(BaTiO3, BT)は代表的な非鉛系圧電材料である。その圧電特性は、結晶粒の微細化や、粒子を(110)配向させることにより向上することが知られている。我々は、微細な六方晶BT粒子を強磁場電気泳動法により堆積させることで、微細な結晶粒からなる配向BTセラミックスの作製を検討してきた。水素還元処理で作製した六方晶BTは、磁場中での配向を焼結時に維持したまま強誘電体相である正方晶BTに相転移する。しかしながら、六方晶BTを完全に正方晶に相転移させるには高温で熱処理しなければならないため、得られるセラミックスの結晶粒を微細化することは難しい。BTは適量のMnを添加することで、その粒界にMnが分布し粒成長が抑制されると考えられる。そこで本研究ではMnを添加し、焼成条件を最適化させることで微細な結晶粒からなる(111)配向BTセラミックスの作製を試みた。

  • Neutron irradiation effects on textured AlN prepared by slip casting in strong magnetic field

    SUZUKI, Tohru, Katsumi Yoshida, Areerak Rueanngoen, Toyohiko Yano, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    ICACC2014  

    発表年月: 2014年01月

     概要を見る

    The development of crystallographic orientation is an interesting topic in ceramics and one of the effective ways to improve their properties. Recently, we reported that the successful control of the development of a textured microstructure even in diamagnetic ceramics was achieved by a colloidal processing in a strong magnetic field. The c-axis of AlN was aligned perpendicular to the rotating magnetic field. The random and textured AlN were neutron irradiated. Neutron irradiation increased lattice parameters both in the textured and random AlN. Effect of irradiation on the a-axis was more sensitive in random sample than textured sample. The increments in lattice parameter of the c-axis in random AlN were similar to the textured sample.

  • 強磁場コロイドプロセス法を用いたオキシアパタイト型ランタンシリケート配向バルク体の作製

    高橋聡志, 小林 清, 鈴木 達, 目 義雄, 石垣隆正, 打越 哲郎

    法政大学マイクロ・ナノテクノロジー研究センター公開シンポジウム  

    発表年月: 2014年01月

     概要を見る

    強磁場鋳込み成形法によるオキシアパタイト型ランタンシリケート配向バルク体の作製を行い、得られた配向バルク多結晶体について配向度や電気伝導度の特性評価を行った。作製したバルク体のXRD測定から、(00l)面でのロットゲーリングファクターの値は0.84であり、非常に配向度の高いc軸配向体が得られたことが示された。SEM画像から、結晶粒は異方性を持ちa, b軸方向に扁平になっている様子が観察され、この材料はa軸およびb軸方向に粒成長しやすい傾向があることが明らかとなった。さらに、電気伝導度の測定から顕著な異方性が確認され、配向体c軸平行方向>無配向体>配向体c軸垂直方向の順に伝導度が高いことが示された。

  • Fabrication and Characterization of c-Axis Oriented Lanthanum Silicate Oxyapatite Polycrystalline Ceramics

    TAKAHASHI Satoshi, KOBAYASHI, Kiyoshi, SUZUKI, Tohru, SAKKA, Yoshio, ISHIGAKI Takamasa, UCHIKOSHI, Tetsuo

    5th International Symposium on Advanced Ceramics (ISAC-5)  

    発表年月: 2013年12月

     概要を見る

    Lanthanum silicate oxyapatite La9.33+2x(SiO4)6O2+3x is a lately-found oxide ion conductor. The oxide ion conduction mainly occurs along the c-axis; therefore, the c-axis orientation in dense polycrystals is preferable for its potential applications such as gas-sensing devices and solid oxide fuel cells at moderate temperatures. We demonstrate in this presentation that the c-axis oriented ceramics can be fabricated using a magnetic field-assisted colloidal processing technique. The crystalline orientation was investigated by X-ray diffraction (XRD). The electric conductivity of the bulk compacts was evaluated by the complex impedance method.

  • Design of multi-axial orientation in ceramics by anisometric particles and magnetic field

    SUZUKI, Tohru, Yasunari Miwa, Shinichiro Kawada, Masahiko Kimura, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    THERMEC 2013  

    発表年月: 2013年12月

     概要を見る

    Design of the crystallographic orientation in ceramics is expected to improve their functional and mechanical properties. Recently we have achieved the control of orientation in ceramics by a strong magnetic field. The driving force for the magnetic alignment is a magnetic torque, thus the orientation of the crystal depends on the axis having easy magnetization and one-dimensional orientation can be achieved. In this presentation, our concept is that control of multi-axial crystalline orientation in ceramics by using both anisometric particles and a magnetic field. The multi-dimensional orientation can be simultaneously tailored using the anisometric particles and the magnetic field. We applied this process to some ceramics and achieved the multi-axial orientation.

  • Tailored microstructure of ceramics by EPD in strong magnetic field

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    Japan-Korea International Seminar on Ceramics  

    発表年月: 2013年11月

     概要を見る

    単相アルミナにおいて、強磁場中電気泳動堆積法を用いて結晶配向を導入することで単相でありながら層状構造を制御することが可能であることを実証し、残留応力を発生させることも可能であることを報告してきている。残留応力は配向角度と層厚で制御可能であり、この配向制御による劈開面の並びと導入された残留応力が亀裂偏向や破面形態に及ぼす影響を検討する。

  • Fabrication and some properties of Textured MAX phase Ceramics

    SAKKA, Yoshio, HU, Chunfeng, SATO, Kimitoshi, SUZUKI, Tohru

    Korea-Japan International Ceramic Seminar  

    発表年月: 2013年11月

     概要を見る

    In the present investigation, we applied a strong magnetic field to align nanolayered Nb4AlC3 particles in an aqueous suspension and then densified the dried green body by spark plasma sintering (SPS). The as-prepared bulk ceramic possessed a shell-like microstructure configuration from the nano- scale to the milli- scale, which endowed it with a high flexural strength (about 1200 MPa) and the augmented fracture toughness (about 18 MPa&#8226;m1/2). Additionally, this material has excellent machinability and can be machined by a high-speed steel cutter.

  • 強磁場プロセスを用いたc軸配向L型ゼオライト膜の作製

    松永 知佳, 打越 哲郎, 鈴木 達, 目 義雄, 松田元秀

    無機マテリアル学会第127回講演会  

    発表年月: 2013年11月

     概要を見る

    ゼオライトの緻密配向膜は,高いガス選択性を示す高度な分離材やメンブレンリアクターなど様々な分野への応用が期待できる材料として,その開発が求められている.これまで,水熱反応条件の調整や,種結晶に用いる粒子の形状制御といった点などから検討されているが,得られた知見は検討対象としたゼオライトに適用できるものの,その適用範囲は限定される.ゼオライト種の多様性を考えると,より広範囲に応用可能なゼオライト配向化技術の開発が望まれる.本研究では,成膜が短時間で作製可能であり膜厚制御性も良い電気泳動堆積(EPD)法を強磁場中で用いることにより,c軸方向に細孔を有するL型ゼオライトの配向種結晶膜を多孔質基板上に作製し,水熱処理することにより緻密な配向膜を作製することを検討した.

  • 強磁場コロイドプロセスと熱処理による酸化鉄配向バルク体の作製と磁気特性評価

    打越 哲郎, 鈴木 達, 白幡 直人, 目 義雄

    無機マテリアル学会第127回講演会  

    発表年月: 2013年11月

     概要を見る

    材料の結晶磁気異方性を利用した磁場配向プロセスは,市販の安価な粉体を出発原料とした配向多結晶材料の作製に非常に有効であり,すでに多くの常磁性または反磁性セラミックスの配向による特性改善に成功してきた.しかし,本方法を強磁性材料に適用し磁場中で固化成形を行った場合では,粒子間の磁気的相互作用が邪魔をして粒子がネットワークを形成してしまい,最終的に緻密なバルク体が得られない難点があった.しかし,強磁性材料であっても,結晶磁気異方性を有する常磁性または反磁性体である前駆体が存在し,後処理で強磁性体に転換できるケースでは,前述の磁場配向プロセスの適用が可能である.これらの前駆体として,斜方晶系に属しかつ常磁性体であるα-FeOOH (goethite)に注目し, α-FeOOHに対して強磁場プロセスを適用して固化成形体を作製し,次いでこれを熱処理することで酸化鉄配向体の作製を試みた.

  • 磁場中成形を用いた窒化アルミニウムの配向制御

    鈴木 達, 打越 哲郎, 目 義雄

    セラミックス総合研究会  

    発表年月: 2013年11月

     概要を見る

    AlNは優れた熱伝導特性と電気絶縁性を持ち、基板材料や半導体製造装置用部材として注目されている。これらの特性は結晶方位により優劣があることが予想され、結晶方向を揃える配向制御は特性を改善するための一手法として期待できる。当グループにおいては、強磁場を用いた結晶配向制御プロセスを実証してきており、Al2O3、TiO2、ZnO、SiCなどの非立方晶系物質への適用が可能であることを報告してきている。本研究では、ウルツ鉱型結晶構造であるAlNに対して強磁場を用いて結晶配向をさせることにより、諸特性の改善の可能性を探る。

  • FABRICATION OF TEXTURED LANTHANUM SILICATE BULK CERAMICS BY MAGNETIC FIELD-ASSISTED COLLOIDAL PROCESSING

    UCHIKOSHI, Tetsuo, SatoshiTAKAHASHI, KOBAYASHI, Kiyoshi, SUZUKI, Tohru, SAKKA, Yoshio, TakamasaISHIGAKI

    The 2013 Composites at Lake Louise Conference  

    発表年月: 2013年11月

     概要を見る

    Lanthanum silicate oxyapatite La9.33+2x(SiO4)6O2+3x is lately-found oxide ion conductor. The oxide ion conduction mainly occurs along the c-axis; therefore, the c-axis orientation in dense polycrystals is preferable for its potential applications such as gas-sensing devices and solid oxide fuel cells (SOFCs) at moderate temperatures. We demonstrate in this paper that c-axis oriented ceramics are successfully fabricated using magnetic field-assisted colloidal processing technique.

  • Controlling orientation in each layer of ceramics by using electric and magnetic fields

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    Composites at Lake Louise 2013  

    発表年月: 2013年11月

     概要を見る

    Tailoring the crystallographic orientation in ceramics is one of effective ways for improving their properties. Layered structure has been proposed as an alternative for the design of structural ceramics. The suspension was consolidated by EPD in a strong magnetic field of 12T to control the lamellar structure with different orientated-layers in monolithic ceramics. The direction of the electric field relative to the magnetic field was altered to control the dominant crystal faces. The grains in alternate layers are aligned differently in the multilayer composite. This processing was applied to alumina and SiC, and the lamellar microstructure was examined by EBSD analysis.

  • Texture developing and some properties of feeble magnetic ceramics by colloidal processing in a strong magnetic field

    SAKKA, Yoshio, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    ISIEM2013  

    発表年月: 2013年10月

     概要を見る

    This processing can be applied to fabricate many kinds of textured ceramics with non-cubic structure, such as alpha-alumina, aluminium nitride, silicon carbide, silicon nitride, MAX phase materials, ZrB2, B4C, etc. Crystalline-textured controlled laminated composites can be fabricated by two methods: one is textured layered structure materials, such as textured MAX phase ceramics, and the other is using electrophoretic deposition by varying the angle between the vectors of electric field and magnetic field. Some anisotropic properties, such as mechanical properties, thermal conductivity, oxidation resistance, etc. will be demonstrated.

  • Synthesis of Oriented Mordenite Dense Film Using Magnetically-Oriented Seed layer by Secondary Growth Method

    MATSUNAGA, Chika, UCHIKOSHI, Tetsuo, SUZUKI, Tohru, SAKKA, Yoshio, MATSUDAMotohide

    3rd Workshop NIMS-UR1  

    発表年月: 2013年10月

     概要を見る

    Randomly-oriented and b-axis oriented mordenite seed layers, which were pre-fabricated out of and in a strong 12T magnetic field, were hydrothermally treated in clear reaction solutions with molar ratios of 6Na2O:Al2O3:30SiO2:xH2O (x = 1500, 3500 and 10000). Crystal growth of the seed particles slightly occurred in the solution of x = 10000, but occurred in the solutions of x = 1500 and 3500, giving rise to densified films. However, the films treated with x = 1500 were composed of two layers with different morphologies.-the precipitation of crystals from the solution was considered to induce the upper layer in the bilayered films. Homogenized films were formed in the solutions of x = 3500. The initial orientation of the seed layer was retained in the continuous films treated at x = 3500.

  • Fabrication and Characterization of Li-ion Secondary Batteries using Sintered Oriented LiCoO2

    YAMADA, Hideto, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, Hozumi Masato, SAITO Toshiya, SAKKA, Yoshio

    ISIEM 2013  

    発表年月: 2013年10月

     概要を見る

    Li-ion batteries have widely been utilized in consumer’s electronic devices such as cellular phones, laptop PCs, etc. The improvement of the energy density is highly desired to the Li-ion batteries for reducing on board space. One of the popular cathode materials for the Li-ion battery is LiCoO2. We have reported that LiCoO2 has a crystalline-induced magnetic anisotropy and can be textured using a strong magnetic field: The c- and a-axes of LiCoO2 align parallel and perpendicular to the magnetic field, respectively. In this study, we attempted to fabricate dense LiCoO2 electrodes with various crystalline orientations by slip casting in a strong magnetic field followed by sintering. We also characterized the relationship between the crystal orientation and the battery performance.

  • Development of Microstructure in Textured Ceramics during Sintering

    SUZUKI, Tohru, YAMADA, Hideto, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    MS&T  

    発表年月: 2013年10月

     概要を見る

    Tailoring the crystallographic orientation in ceramics is effective way for improving their properties. In this decade, we have reported that the successful control of the crystallographic orientation in diamagnetic ceramics was achieved by a colloidal processing in a strong magnetic field and the textured microstructure was developed during sintering outside of the magnet. Effect of the crystalline orientation on the grain growth and the sintering behavior was studied. Abnormal grain growth was suppressed and anisotropic grain growth was observed in the textured ceramics. The suppression of the abnormal grain growth enhanced with the increasing degree of orientation. Shrinkage during densification depended on the orientation axis in the textured ceramics.

  • 酸化物イオン伝導性オキシアパタイトの合成プロセス開発から電解質特性解明まで

    小林 清, 北嶋 将太, 三原 俊哉, 高橋 聡志, 鈴木 達, 打越 哲郎, 樋口 透, 明石 拓也, 石垣 隆正, 目 義雄

    第33回エレクトロセラミックス討論会  

    発表年月: 2013年10月

     概要を見る

    1995年,中山らによって発見された酸化物イオン伝導性オキシアパタイトは優れた酸化物イオン伝導性と高い化学的安定性から次世代固体電解質として期待されている.一方で発見当初から非常に高い焼結温度や固体電気化学特性の特異性が問題となっていた.本公演ではNIMSで独自に開発したオキシアパタイト低温合成プロセスとその反応過程解析,固体電気化学特性の解明について概論する.さらに本材料固有の性質を利用した高イオン伝導性を発現させる特殊プロセスを利用した配向性バルク体製造の結果とSOFC応用を見据えた電極特性の結果も紹介する.

  • 板状粒子と強磁場を用いた圧電セラミックスの多軸配向制御

    鈴木 達, 三輪 恭也, 川田 慎一郎, 打越 哲郎, 目 義雄

    第33回エレクトロセラミックス研究討論会  

    発表年月: 2013年10月

     概要を見る

    圧電セラミックスにおいては、その電気特性を向上させるために配向制御などの組織制御が用いられている。しかしながら、TGG法のように、形状異方性がある板状セラミック粒子をスリップキャストあるいはシート成形しただけでは、セラミック粒子の結晶軸のうち、形状異方性のある1軸しか配向させることができなかった。同様に、磁場中での成形でも、セラミック粒子の結晶軸のうち、静磁場で磁化容易軸、回転磁場を用いて磁化困難軸しか配向させることができなかった。すなわち、従来の配向技術では、セラミック粒子の結晶軸のうち、1軸しか配向させることができなかった。しかしながら、より精緻な組織制御が求められており、多軸配向制御はその1つの組織制御手法として期待される。そこで、形状異方性粒子を用いた配向制御と磁場を用いた配向制御技術を組み合わせることにより、非鉛系で圧電性を有するセラミックスについて多軸配向制御を試みた。

  • 強磁場コロイドプロセス法を用いたオキシアパタイト型ランタンシリケート配向バルク体の作製

    高橋 聡志, 小林 清, 鈴木 達, 目 義雄, 石垣 隆正, 打越 哲郎

    第33回エレクトロセラミックス討論会  

    発表年月: 2013年10月

     概要を見る

    1995年,中山らによって発見されたオキシアパタイト型ランタンシリケートは優れた酸化物イオン伝導性と高い化学的安定性から次世代固体電解質として期待されている.オキシアパタイト型ランタンシリケートは六方晶系の結晶構造を有し,c軸にそって高いイオン伝導度が発現することが知られている.したがってc軸配向したセラミックスバルク体の製造が重要である.本研究では強磁場コロイドプロセスを用いたc軸高配向オキシアパタイトセラミックスの製造に成功した.またイオン伝導度の結晶方位依存性についても検討した.

  • 強磁場中電気泳動堆積法で作製した配向積層アルミナ中での亀裂偏向

    鈴木 達, 打越 哲郎, 目 義雄

    日本金属学会 秋期大会  

    発表年月: 2013年09月

     概要を見る

    セラミックスの材料特性の向上や新規発現のための組織制御として、結晶配向が有効である。これまでに、常磁性体や反磁性体粒子も磁場配向できる強磁場コロイドプロセスの一つである強磁場中電気泳動堆積法(Electorophoretic Deposition: EPD)において、磁場印加方向に対し、電極基板の傾き(&#61546;B-E)を変化させることで、粒子の配向方向を任意に設定し、一定時間ごとに電極基板の傾きを変化させることで、層ごとに配向方向が異なる配向積層体を単一組成で作製できることを報告してきた。そこで、本研究では、強磁場中EPD法を用いて、Al2O3単一組成の配向積層体を作製し、その破壊形態と亀裂進展挙動を調べた。

  • 結晶配向したセラミックスの照射特性

    鈴木 達, 吉田 克己, Areerak Rueanngoen, 矢野 豊彦, 打越 哲郎, 目 義雄

    東北大学金属材料研究所大洗研究会  

    発表年月: 2013年09月

     概要を見る

    強磁場を用いた結晶配向プロセスによりAlNおよびSiCでのc軸一軸配向制御し、その中性子照射特性についてAlNの照射後の格子定数変化を検討した。

  • 配向積層セラミックスの組織制御と機械特性

    鈴木 達, 打越 哲郎, 目 義雄

    日本セラミックス協会 シンポジウム  

    発表年月: 2013年09月

     概要を見る

    組織と結晶の配向は材料特性に大きく影響し、特性改善のための効果的な組織制御手法の一つである。セラミックス積層コンポジットでは、機械特性を改善する手法の一つとして熱膨張率の異なる材料を積層させ残留応力を発生させることにより亀裂進展を制御する方法が試みられている。我々のグループでは電気泳動堆積法の積層体成形方法と強磁場を組み合わせることで、各々の層の結晶方位を制御した配向制御積層構造を作製することに成功している。本研究では、層厚と結晶方位を制御したアルミナや炭化ケイ素を作製し、その微構造発達と機械特性について検討する。

  • コロイドプロセスを用いたランタンシリケートの作製

    高橋聡志, 小林 清, 鈴木 達, 鱒渕友治, 目 義雄, 石垣隆正, 打越 哲郎

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2013年09月

     概要を見る

    一般に、ランタンシリケートの合成にはLa2O3粉とSiO2粉を原料とし、1575-1700 ℃の高温で長時間焼成する固相反応が用いられる。しかし、ランタンシリケート相のLa2O3過剰側およびSiO2過剰側には、それぞれ高抵抗物質であるLa2SiO5およびLa2Si2O7組成の安定相が存在するため、十分な混合が必要である。粉末を均一に混合する方法として静電吸着を利用した液中ヘテロ凝集法が知られており、粒径の大きなコア粒子表面に、粒径の小さなシェル粒子を均一に修飾させるために、原料粒子の一方または両方の表面にポリカチオンおよびポリアニオンの静電交互吸着(Layer-by-Layer(LbL))を行って、粒子表面の電荷を均質にする方法が近年注目されている。本研究では、LbL法を適用したLa(OH)3粉とSiO2粉を用いてヘテロ凝集を行い、凝集粉を鋳込み成形した後に焼成することで、ランタンシリケートの単相の作製を試みた。

  • EPD積層法による構造用セラミックスの残留応力制御

    打越 哲郎, 鈴木 達

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2013年09月

     概要を見る

    例えば、真珠やアワビの貝殻の炭酸カルシウム−タンパク質の積層構造に見られるように、層状化したセラミックスの界面に低強度な第三相を挿入して積層化し、割れによりもたらされたクラックを界面相で偏向させる方法は、セラミックス材料の高靱化に有効な方法として知られている。他方で、こうした弱い相を界面に挿入するのではなく、熱膨張係数の異なるセラミックスを積層、緻密焼結し、残留応力を導入する方法も高靱化方法の一つである。本研究では、アルミナやジルコニアなどの構造セラミックスの積層化を取り上げ、電気泳動堆積(EPD)法による異種材料の交互積層コンポジットおよび強磁場EPD法を用いた同種材料の配向積層コンポジットをそれぞれ作製して、残留応力制御による高靱化機構の有効性について検討した。

  • 陽極酸化アルミナをテンプレートに用いた酸化物1次元ナノ材料の合成と評価

    愛須 一史, 鈴木 達, 中村 衣利, 阿部 浩也, 鈴木 義和

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2013年09月

     概要を見る

    チタニアの様々な機能性を向上させるため、1次元ナノ構造を有するチタニアが研究されている。1次元ナノ構造のチタニアの作製方法としては、水熱合成、テンプレート法、陽極酸化法などがある。本研究は、陽極酸化アルミナをプレートに用いる作製方法を選択し、従来の方法よりシンプルなプロセスで様々な長さの1次元ナノ構造を有するチタニアの作製を試みた。

  • 強磁場電気泳動法によるチタン酸バリウム-チタン酸ビスマスカリウム配向セラミックスの作製

    稲葉 勝也, 上野 慎太郎, 中島 光一, 熊田 伸弘, 和田 聡志, 鈴木 達, 打越 哲郎, 目 義雄

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2013年09月

     概要を見る

    環境問題の観点から、新規非鉛系圧電材料の開発が急務となっている。代表的な非鉛系圧電材料として知られるチタン酸バリウムは、&lt;110&gt;方位へ配向させることで圧電定数が向上することが報告されている。またBTの低いキュリー温度は、室温でBTと同じ正方晶系のペロブスカイト小僧を持つチタン酸ビスマスカリウムと固溶体を作製することで、130℃から380℃の間で任意に変化させることが出来る。本研究では、出発原料に六方晶BTを用い、強磁場中で電気泳動堆積を行うことで配向制御を試みた。

  • 六方晶チタン酸バリウム粒子を用いた強磁場電気泳動法による配向セラミックスの作製と圧電特性評価

    小林 英悟, 上野 慎太郎, 中島 光一, 熊田 伸弘, 和田 聡志, 鈴木 達, 打越 哲郎, 目 義雄, 三輪 恭也, 川田慎太郎, 大宮 季武, 久保寺 紀之

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2013年09月

     概要を見る

    チタン酸バリウム(BaTiO3)セラミックスは代表的な非鉛系圧電材料である。その圧電特性は、組織の微細化や、(110)配向させることで向上することが知られている。BaTiO3は反磁性粒子であり、これまでに六方晶BaTiO3を用いた強磁場スリップキャスト成形法による配向セラミックスの作製などが報告されている。また特定の作製条件下で得られた六方晶BaTiO3は、適切な熱処理によって強誘電体相である正方晶に相転移させることができる。従って本研究では、強磁場EPD法によって得られた配向性の六方晶BaTiO3集積体を熱処理により相転移させることで、配向性の正方晶BaTiO3セラミックスの作製を試みた。また、これらの集積体及びセラミックスの配向度、圧電特性の評価を行った。

  • 強磁場電気泳動堆積法による多孔質基板上へのL型ゼオライト配向種結晶層の作製

    松永 知佳, 打越 哲郎, 鈴木 達, 目 義雄, 松田元秀

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2013年09月

     概要を見る

    我々は、モルデナイトを静磁場中で鋳込み成形することよりb軸が配向した種結晶膜を作製し、それを水熱処理することにより種結晶の配向を保持した緻密な配向膜の作製に成功している1)。しかしながら、種結晶の塗布プロセスとして鋳込み成形法は、時間がかかる上、膜厚の制御性に劣る欠点があった。本研究では、成膜が短時間で作製可能であり膜厚制御性も良い電気泳動堆積(EPD)法を強磁場中で用いることにより、c軸方向に細孔を有するL型ゼオライトの配向種結晶膜を多孔質基板上に作製することを検討した。

  • Fabrication of b-axis oriented mordenite dense film from b-axis oriented seed layer by the secondary growth method

    UCHIKOSHI, Tetsuo, MATSUNAGA, Chika, SUZUKI, Tohru, SAKKA, Yoshio, Motohide MATSUDA

    EEMR-2013  

    発表年月: 2013年08月

     概要を見る

    The secondary growth of seed particles pre-deposited on substrates is an effective way to synthesize oriented zeolite films. We have proposed a magneto-scientific seeding process using a strong magnetic field to apply crystalline-oriented seed layer on the substrates. We have already succeeded in the selective preparation of b- or c-axis oriented mordenite compacts using a strong magnetic field of 12 T. In this study, we attempted to prepare oriented mordenite dense film via the secondary growth from the oriented seed layers in reaction solutions with controlled chemical compositions.

  • Texture developing and some properties of feeble magnetic ceramics by colloidal processing in a strong magnetic field

    SAKKA, Yoshio, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    ICCP-12  

    発表年月: 2013年08月

     概要を見る

    This processing can be applied to fabricate many kinds of textured ceramics with non-cubic structure, such as alpha-alumina, aluminium nitride, silicon carbide, silicon nitride, MAX phase materials, ZrB2, B4C, etc. Crystalline-textured controlled laminated composites can be fabricated by two methods: one is textured layered structure materials, such as textured MAX phase ceramics, and the other is using electrophoretic deposition by varying the angle between the vectors of electric field and magnetic field. Some anisotropic properties, such as mechanical properties, thermal conductivity, oxidation resistance, etc. will be demonstrated.

  • Control of lamellar structure with different orientated layers by using electric and magnetic fields

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    ICCPS-12  

    発表年月: 2013年08月

     概要を見る

    Layered structure has been proposed as an alternative for the design of structural ceramics. On the other hand, in this decade, we have reported that the successful control of the crystallographic orientation in diamagnetic ceramics, such as alumina, titania, alpha-SiC, was achieved by a colloidal processing in a strong magnetic field. The suspension was consolidated by EPD in a strong magnetic field of 12T to control the lamellar structure with different orientated-layers. The direction of the electric field relative to the magnetic field was altered to control the dominant crystal faces. This processing was applied to alumina and SiC, and the lamellar microstructure was examined by EBSD analysis.

  • 配向LiCoO2焼結体の作製とLiCoO2焼結体を電極として用いたLiイオン二次電池の特性評価

    山田 英登, 鈴木 達, 打越 哲郎, 穂積正人, 齋藤俊哉, 目 義雄

    第49回夏期シンポジウム:「粉体による材料微細構造創製とその新展  

    発表年月: 2013年07月

     概要を見る

    Liイオン二次電池は携帯機器をはじめ様々な分野に適用されており、LiCoO2は層状酸化物の正極材料として広く知られている。物質の諸特性は結晶方位により異なることが多く、その特性向上のひとつの手法として、特定の結晶方位を優先的に成長させたり並べたりするなどの配向制御が注目されている。我々は、反磁性セラミックス粒子のコロイド分散系に強磁場を印加、成形することにより結晶方位の制御されたセラミックス材料を創製し、種々の特性向上を図る試みを行っている。そこで、我々はLiCoO2の磁気異方性に着目し、強磁場印加コロイドプロセスによるLiCoO2配向体の作製を試みた。また、得られた配向焼結体を正極とする電池を作製し、配向と電池特性の関係について検討した。

  • Preparation of oriented Li1+x-yNb1-x-3yTix+4yO3 solid solution with superstructure by slip casting in a high magnetic field

    Hiromi Nakano, Shiho Suehiro, SUZUKI, Tohru, SAKKA, Yoshio

    13th International Conference of the European Ceramic Society  

    発表年月: 2013年06月

     概要を見る

    In the Li2O-Nb2O5-TiO2 system, Li1+x-yNb1-x-3yTix+4yO3 (0.11 &lt; x &lt; 0.33, 0 &lt; y &lt; 0.09) (LNT) forms with a superstructure, and this is known as the M-phase. The superstructure of the M-phase is formed by periodical insertion of an intergrowth layer in a matrix having a trigonal structure. In this work, as an application of the unique qualities of an electro-ceramic with an anisotropy structure, we prepared an oriented LNT ceramic by slip casting in a high magnetic field. TEM images showed that the superstructure was maintained even after ball milling for 32 h. The c-axis of the LNT was aligned parallel to the magnetic field. A high orientation degree was achieved with slurries having small grains and a higher aspect ratio of the grain.

  • Tailored microstructure of ceramics by using electric and magnetic fields

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    13th International Conference of the European Ceramic Society  

    発表年月: 2013年06月

     概要を見る

    Tailoring the crystallographic orientation in ceramics is one of effective ways for improving their properties. We have reported that crystallographic oriented ceramics films and layers were fabricated by EPD in a strong magnetic field in order to control their microstructures. The direction of the electric field relative to the magnetic field was altered to control the dominant crystal faces. The composite was fabricated by alternately changing the angle between the directions of the magnetic and electric fields layer by layer during EPD in 12T. The grains in alternate layers are aligned differently in the multilayer composite. The crack deflection was observed at the boundary between the layers with different orientation. This processing can be applied to alpha-SiC.

  • Fabrication of textured MAX phase ceramics and their some properties through colloidal processing in strong magnetic field

    SAKKA, Yoshio, SATO, Kimitoshi, MISHRA, Mrinalini, SUZUKI, Tohru

    13th Conference of the European Ceramic Society  

    発表年月: 2013年06月

     概要を見る

    we will demonstrate processing of textured MAX phase ceramics (Nb4AlC3 and Ti3SiC2). Synthesis of high purity MAX phase powder, well-dispersion of powder adding appropriate amount of dispersion, and sintering methods of SPS for Nb4AlC3 and pressure-less sintering for Ti3SiC2) will be demonstrated. Highly textured MAX phase ceramics have been fabricated by the colloidal processing and sintering. Some anisotropic properties of electric conductivity, mechanical properties will be also demonstrated.

  • Fabrication of Oriented Mordenite Dense Film from Oriented Seed Layer by the Secondary Growth Method

    MATSUNAGA, Chika, UCHIKOSHI, Tetsuo, SUZUKI, Tohru, SAKKA, Yoshio, MotohideMATSUDA

    第7回先進セラミックス国際会議(STAC-7)  

    発表年月: 2013年06月

     概要を見る

    The secondary growth of seed particles pre-deposited on substrates is an effective way to synthesize oriented zeolite films. We have proposed a magneto-scientific seeding process using a strong magnetic field to apply crystalline-oriented seed layer on the substrates. We have already succeeded in the selective preparation of b- or c-axis oriented mordenite compacts using a strong magnetic field of 12 T . In this study, we attempted to prepare oriented mordenite dense film via the secondary growth from the oriented seed layers in reaction solutions with controlled chemical compositions.

  • Effect of Initial Orientation on Abnormal Grain Growth of LiCoO2

    YAMADA, Hideto, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, Hozumi Masato, SAITO Toshiya, SAKKA, Yoshio

    STAC-7  

    発表年月: 2013年06月

     概要を見る

    The development of crystallographic orientation is an interesting topic in ceramics science and technology since it is one of the effective ways to improve their properties. One of the popular cathode materials for Li-ion secondary battery is LiCoO2, which has a layered rock-salt structure. We have reported that LiCoO2 has a magnetic anisotropy and the particles can be aligned in a strong magnetic field.[1,2] In this study, we prepared a crystalline-oriented bulk LiCoO2 by slip casting in a strong magnetic field. The relationship between the development of the crystallographic orientation and the grain growth behavior will be discussed.

  • Fabrication of c-axis Oriented Lanthanum-Silicate Bulk Ceramics by Magnetic Field-Assisted Colloidal Processing

    Satoshi TAKAHASHI, KOBAYASHI, Kiyoshi, SUZUKI, Tohru, SAKKA, Yoshio, Takamasa ISHIGAKI, UCHIKOSHI, Tetsuo

    第7回先進セラミックス国際会議(STAC-7)  

    発表年月: 2013年06月

     概要を見る

    Lanthanum silicate oxyapatite La9.33+2x(SiO4)6O2+3x is lately-found oxide ion conductor. The oxide ion conduction mainly occurs along the c-axis; therefore, the c-axis orientation in dense polycrystals is preferable for its potential applications such as gas-sensing devices and solid oxide fuel cells (SOFCs) at moderate temperatures. We demonstrate in this paper that dense, c-axis oriented bulk lanthanum silicate ceramics can be fabricated using magnetic field-assisted colloidal processing technique.

  • Two-dimensional orientation in piezoelectric ceramics prepared using platelet particles and a strong magnetic field

    SUZUKI, Tohru, Yasunari Miwa, Shinichiro Kawada, Masahiko Kimura, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    Pacific Rim Conference on Ceramic and Glass Technology  

    発表年月: 2013年06月

     概要を見る

    Tailoring the crystallographic orientation in piezoelectric ceramics is very useful for improving their properties. We reported that the colloidal processing in a strong magnetic field was able to control the crystallographic orientation even in diamagnetic ceramics. In many cases of piezoelectric ceramics, a crystal texture with the &lt;100&gt; axis parallel to a magnetic field had been developed. In this study, development of the orientation of not only the &lt;100&gt; axes, but also the c-axis, was achieved by using platelet particles and a magnetic field. A magnetic field enhanced not only the&lt;100&gt; axes orientation but also the c-axis orientation. Furthermore, orientation of matrix particles by a magnetic field effectively enhanced the 2-dimensional orientation after densificatio

  • Electrophoretic Deposition of Orientation-Controlled Zeolite L Layer on Porous Ceramic Substrate

    UCHIKOSHI, Tetsuo, MATSUNAGA, Chika, SUZUKI, Tohru, SAKKA, Yoshio, MATSUDA Motohide

    10th Pacific Rim Conference on Ceramic and Glass Technology  

    発表年月: 2013年06月

     概要を見る

    Oriented zeolite films have recently attracted much attention for various applications. The secondary growth is an effective way to make the oriented zeolite films. During the hydrothermal process, the orientation of seed particles can be retained in the final films; therefore, forming seed layers is an important step in the process. In this study, magneto-scientific technique combined with colloidal processing was applied to obtain crystalline-oriented zeolite L seed layers.

  • FABRICATION OF C-AXIS ORIENTED LANTHANIUM-SILICATE BULK CERAMICS BY MAGNETIC FIELD-ASSISTED COLLOIDAL PROCESSING

    Satoshi TAKAHASHI, KOBAYASHI, Kiyoshi, SUZUKI, Tohru, SAKKA, Yoshio, Takamasa ISHIGAKI, UCHIKOSHI, Tetsuo

    The 19th International Conference on Solid State Ionics  

    発表年月: 2013年06月

     概要を見る

    We demonstrate in this paper that c-axis oriented ceramics are fabricated using magnetic field-assisted colloidal processing technique. The lanthanum silicate oxyapatite bulk ceramics pre-pared in the 12 T magnetic field have very good c-axis orientation. The degree of texturing evaluated by the Lotgering method was 0.84. The XRD result also re-vealed that the c-axis of lanthanum silicate oxyapatite is the easy-magnetization axis. Higher electric conductivity along the c-axis direction was also confirmed from the electric conductivity measurements.

  • Texture developing and some properties of feeble magnetic ceramics by colloidal processing in a strong magnetic field

    SAKKA, Yoshio, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    10th Pacific Rim Conference on Ceramic and Glass Technology  

    発表年月: 2013年06月

     概要を見る

    We have demonstrated a new processing of textured ceramics with a feeble magnetic susceptibility by colloidal processing in a high magnetic field and subsequent heating. This processing can be applied to fabricate many kinds of textured ceramics with non-cubic structure, such as alpha-alumina, aluminium nitride, silicon carbide, silicon nitride, MAX phase materials, ZrB2, B4C, etc. Crystalline-textured controlled laminated composites can be fabricated using electrophoretic deposition by varying the angle between the vectors of electric field and magnetic field. Some anisotropic properties will be demonstrated.

  • DISTRIBUTION OF MAGNESIUM IONS IN LANTHANUM SILICATE OXYAPATITE

    KOBAYASHI, Kiyoshi, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    SSI-19  

    発表年月: 2013年06月

     概要を見る

    Mechanism of magnesium ion substitution in lanthanum silicate oxyapatite is investigated by combinations of the density and X &#8211; ray diffraction analysis. The magnesium ions are substituted to the silicon site as well as the lanthanum ion sites. Neutral lanthanum ion vacancy also exists as similar to the non &#8211; doped lanthanum silicate oxyapatite. Number of oxide ions on the c &#8211; axis is almost independent of magnesium concentration in the composition line on 58.4 mol% LaO1.5 &#8211; (41.6 &#8211; x) mol% SiO2 &#8211; x mol% MgO (3.2 x 6) due to the complex substitution of magnesium ion on several sites.

  • 結晶系の異なるチタン酸バリウム粒子を用いた強磁場電気泳動法による配向セラミックスの作製とその誘電・圧電特性

    和田 智志, 小林 英悟, 上野 慎太郎, 中島 光一, 武井 貴弘, 熊田 伸弘, 鈴木 達, 打越 哲郎, 目 義雄, 馬込 栄輔, 森吉 千佳子, 黒岩 芳弘, 三輪 恭也, 川田 慎一郎, 大宮 季武, 久保寺 紀之

    強誘電体応用会議  

    発表年月: 2013年05月

     概要を見る

    近年環境にやさしく誘電・圧電特性の大きなチタン酸バリウム(BT)配向セラミックスが注目されている。これまでの研究より、正方晶構造において&lt;110&gt;または&lt;111&gt;方位に配向させ、かつグレインサイズの小さなBTセラミックスを作製できれば、更なる圧電特性の向上が期待できることが予測されており、この理想のBT配向セラミックスの作製において、強磁場スリップキャスト法や強磁場電気泳動法が有効と考えられている。そこで本研究では、正方晶構造でかつシングルドメイン構造の強誘電体BT粒子と、六方晶構造の常誘電体BT粒子という2種類のBT粒子を用い強磁場電気泳動法によりBT配向セラミックスの作製を検討し、更にそれらの誘電・圧電特性について評価を行ったので、その結果について報告する。

  • Texture developing and some properties of feeble magnetic ceramics

    SAKKA, Yoshio, HU, Chunfeng, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    The 8th International Symposium on Advanced Materials and Techno  

    発表年月: 2013年05月

     概要を見る

    We have demonstrated a new processing of textured ceramics with a feeble magnetic susceptibility by colloidal processing in a high magnetic field and subsequent heating. This process is applied to fabricate many kinds of textured ceramics with non-cubic structure, such as alpha-alumina, aluminium nitride, silicon carbide, silicon nitride, MAX phase materials, ZrB2, B4C, etc. Crystalline-textured controlled laminated composites can be fabricated using electrophoretic deposition by varying the angle between the vectors of electric field and magnetic field. Some anisotropic properties will be demonstrated.

  • 均質水溶液を用いたオキシアパタイト型ランタンゲルマネートの新規低温合成法

    北嶋将太, 小林 清, 鈴木 達, 樋口 透, 目 義雄

    電気化学会第80回大会  

    発表年月: 2013年03月

     概要を見る

    オキシアパタイト型ランタンゲルマネートは新規酸素イオン伝導体として注目されている.我々はランタンとゲルマニウムが共存する均質水溶液の調整に成功した.発表では共沈法によるランタンゲルマネートの低温合成過程について報告する.

  • 強磁場コロイドプロセス法によるランタンシリケート配向体の作製

    高橋聡志, 小林 清, 鈴木 達, 鱒渕友治, 目 義雄, 石垣隆正, 打越 哲郎

    電気化学会第80回大会  

    発表年月: 2013年03月

     概要を見る

    ランタンシリケートは、c軸方向に酸化物イオンが配列したアパタイト型の結晶構造を有し、この方向に高い酸化物イオン伝導性を示すことが報告されている。本研究では、La9.33(SiO4)6O2の粉体を強磁場中で鋳込み成形した後に焼成することで、大きなサイズで高配向なランタンシリケートの緻密配向体の作製を試みた。その結果、極めて高配向なc軸配向体の作製に成功した。電気伝導度の測定結果から、電気伝導度に顕著な異方性が認められ、c軸//>ランダム体>c軸⊥の順に伝導度が高いことが示された。微細組織にも明らかな異方性が認められた。

  • 種々のチタン酸バリウム粒子を用いた強磁場堆積法による配向セラミックスの作製

    小林 英悟, 武井 貴弘, 熊田 伸弘, 上野 慎太郎, 藤井 一郎, 中島 光一, 和田 智志, 鈴木 達, 打越 哲郎, 目 義雄, 三輪 恭也, 川田 慎一郎, 大宮 季武, 久保寺 紀之, 黒岩 芳弘

    日本セラミックス協会 年会  

    発表年月: 2013年03月

     概要を見る

    近年環境にやさしく誘電・圧電特性の大きなチタン酸バリウム(BaTiO3)配向セラミックスが注目されている。我々はこれまで12Tという強磁場下での、電気泳動(EPD)法やスリップキャスト法といった堆積法による配向セラミックスの作製を検討してきた。そのために本研究では、二段階熱分解法を導入したシュウ酸塩法により合成された高結晶性を持つBaTiO3ナノ粒子を合成した。その粒子を強磁場下で堆積させ集積体を得た後、その集積体を焼結することで配向セラミックスの作製を行う。また、MnをドープしたBaTiO3粒子等による作製も同様に行った。このようにして得られた集積体及びセラミックスの配向度、電気特性の評価を行ったので報告する。

  • 強磁場印加によるモルデナイトゼオライトの配向制御 −静磁場及び回転磁場印加効果−

    松永知佳, 松田元秀, 打越 哲郎, 鈴木 達, 目 義雄

    日本セラミックス協会2013年年会  

    発表年月: 2013年03月

     概要を見る

    我々のは、近年注目されている磁場を利用したプロセスで、ゼオライトの配向化を検討している。磁場配向プロセスでは、物質の化学合成プロセス条件に依存しない結晶の磁気異方性という物理パラメータを利用して物質の配向挙動を制御できる。すなわち、立方晶以外の結晶では、磁場印加によって、その配向挙動の制御が可能である。本研究では、斜方晶系のモルデナイトを検討対象材として取り上げ、モルデナイトの磁場配向制御について検討した。

  • Effects of Strong Magnetic Field and Sintering Methods on the Microstructure of Al2O3/SiC Nanowires Composites

    Noppasint Jiraborvornpongsa, 今井 雅三, 吉田 克己, 矢野 豊彦, 鈴木 達, 目 義雄

    日本セラミックス協会 年会  

    発表年月: 2013年03月

     概要を見る

    Recently, the texture-controll of ceramics has gained much interest because it has led to the improvement of their mechanical, electrical and thermal properties. Alumina matrix composites were developed to enhance the properties of alumina by adding secondary phases. We produced silicon carbide nanowires (SiCNWs) by thermal evaporation method and the SiCNWs were used as the reinforcement of alumina composites. To synthesize composites, we employed spark plasma sintering (SPS) and milliwave sintering. Milliwave sintering is a pressureless sintering technique that involves internal heating and selfheating. This experiment was conducted to investigate the effects of strong magnetic field and sintering methods on the microstructure of alumina composites.

  • ネッキング構造を持つチタン酸バリウム粒子/ポリマー複合体の微構造制御とその誘電特性

    塚本 修平, 小林 英悟, 中島 光一, 武井 貴弘, 熊田 伸弘, 和田 聡志, 鈴木 達, 打越 哲郎, 目 義雄

    日本セラミックス協会 年会  

    発表年月: 2013年03月

     概要を見る

    将来の大容量通信に対応する電子デバイス基盤技術としてフィルム状で、且つ比誘電率が高いフィルムキャパシタを作製することが必要である。高誘電率なフィルムキャパシタを作製するためには、(Ⅰ)高誘電率のBaTiO3ナノ粒子を使用する、(Ⅱ)電気泳動法による高密度集積体の作製、(Ⅲ) 集積体にネッキング構造の導入を行う必要がある。我々はこの条件を満たしたフィルムキャパシタを作製し、その誘電特性を評価したので報告する。

  • モルデナイト配向前駆体膜を出発材とする緻密配向膜への水熱固化

    松永知佳, 松田元秀, 打越 哲郎, 鈴木 達, 目 義雄

    日本セラミックス協会2013年年会  

    発表年月: 2013年03月

     概要を見る

    これまでの検討で、モルデナイトの磁場配向挙動を明らかにし、モルデナイトのb 軸およびc 軸が優先的に配向した成形体を得ることに成功している。もし、その配向組織を崩壊させることなく、試料を緻密化できれば、モルデナイトのb 軸およびc 軸配向緻密膜を得ることができる。本研究では、モルデナイト無配向膜およびb 軸優先配向膜を前駆体膜とし、緻密固化の実現を目指して、水熱反応条件を検討した。

  • 強磁場コロイドプロセス法によるランタンシリケート配向体の作製

    高橋聡志, 小林 清, 鈴木 達, 鱒渕友治, 目 義雄, 石垣隆正, 打越 哲郎

    日本セラミックス協会2013年年会  

    発表年月: 2013年03月

     概要を見る

    固体酸化物燃料電池(SOFC)は、貴金属触媒を用いることなく多様な燃料を利用可能という特徴がある一方で、作動温度の高さによる周辺部材の劣化の問題が指摘されており、中低温域でYSZを凌ぐ酸素イオン導電性を示す材料の研究が盛んにおこなわれている。ランタンシリケートは、c軸方向に酸素イオンが配列したアパタイト型の結晶構造を有し、この方向に高い酸素イオン伝導性を示す。それ故、結晶c軸が配向した焼成体の作製が近年特に注目されている。これまでにLa2SiO5とLa2Si2O7の焼成体からなる拡散対を1600℃、〜100h熱処理することで、2層の中間にランタンシリケートの薄い配向多結晶層を作製した例が福田らにより報告されているが、大きなサイズで高配向な緻密配向体を作製した報告はない。本研究では、La9.33(SiO4)6O2の粉体を強磁場中で鋳込み成形した後に焼成することで、ランタンシリケートのバルク配向体の作製を試みた。

  • 陽極酸化アルミナをテンプレートとする酸化チタンナノ材料の合成と評価

    愛須 一史, 鈴木 達, 鈴木 義和

    日本セラミックス協会 年会  

    発表年月: 2013年03月

     概要を見る

    チタニアは顔料、化粧品、ガスセンサー、電子デバイス、光触媒、触媒担体、色素増感型太陽電池などの幅広い用途で利用されている。チタニアの様々な機能性を向上させるため、1次元ナノ構造を有するチタニアが研究されている。1次元ナノ構造のTiO2の作製方法としては、水熱合成法、テンプレート法、陽極酸化法などがある。我々は、陽極酸化アルミナをテンプレートとして用いることで、形状を制御し、高比表面積のチタニアナノ材料の作製を試みた。

  • Anisotropic Science and Technology for Ceramics

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    IWNMD2012  

    発表年月: 2012年12月

     概要を見る

    セラミックス材料における各種特性改善と信頼性向上のために、その微細組織が特性を支配する重要な因子の一つであるため、結晶粒微細化、粒子分散、粒界制御等において巧緻な組織制御技術が試みられてきた。気体や液体を除いた物質や材料においては、その特性が完全に等方的であることは稀であり、性質が異方的であることを利用して有用な材料とする場合が多くある。Al2O3、AlN、TiO2などの反磁性体、常磁性体では、その磁化率が極めて小さいことから磁場の作用を受けない物質(いわゆる非磁性物質)として扱われることが通常であり、磁場による配向などの組織制御は出来ないとするのが常識的な考えであったが、我々は、コロイドプロセスを用いることでこれらの弱磁性セラミックスにおいて強磁場配向が可能であることを見出している。本発表では、セラミックスにおける磁場配向プロセスを概説し、筆者らの結果も含めた適用例を紹介する。

  • Fabrication of Orientation Controlled Mordenite Seed Layer on Porous Ceramic Substrate in Strong Magnetic Field

    UCHIKOSHI, Tetsuo, MATSUNAGA, Chika, SUZUKI, Tohru, Motohide MATSUDA

    2012 Collaborative Conference on Crystal Growth  

    発表年月: 2012年12月

     概要を見る

    Fabrication of orientation controlled mordenite seed layer on porous ceramics substrates were performed by slip casting in a 12 T strong magnetic field. The magnetic field was applied in the following ways: (a) vertically-applied static magnetic field, (b) horizontally-applied static magnetic field, (c) horizontally-applied, rotating magnetic field. It became apparent that the b- or c-axis orientated mordenite layer can be selectively obtained by applying a static or a rotating magnetic field.

  • Fabrication of dense textured Ti3SiC2 films by electrophoretic deposition in a strong magnetic field

    MISHRA, Mrinalini, SATO, Kimitoshi, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    29th International Korea-Japan Seminar on Ceramics  

    発表年月: 2012年11月

     概要を見る

    Texture development was achieved by performing EPD in a strong magnetic field (12T). The c-planes could be aligned on the substrates when the applied electric field was perpendicular to magnetic field and a,b-planes could be aligned when the applied electric field was parallel the magnetic field direction. Application of strong magnetic field (~12T) followed by pressure-less sintering by adding sintering aids resulted in dense, textured films of Ti3SiC2 on Al2O3

  • Fabrication of Textured Ti3AlC2 Ceramic by Slip Casting in Strong Magnetic Field and Spark Plasma Sintering

    MIZUNO, Yutaka, SAKKA, Yoshio, MISHRA, Mrinalini, SATO, Kimitoshi, SUZUKI, Tohru

    29th International Korea-Japan Seminar on Ceramics  

    発表年月: 2012年11月

     概要を見る

    The Plate-like Ti3AlC2 powder was fabricated by ball-milling of the heated powder mixture. A dense, textured Ti3AlC2 was fabricated by SPS of green body. The relative density was found to exceed 99%.The degree of orientation calculated from the above equation was 0.99.

  • 水系電気泳動堆積プロセスに関する研究

    打越 哲郎, Laximidhar BESRA, 鈴木 達, 目 義雄

    粉体粉末冶金協会 平成24年度秋季大会  

    発表年月: 2012年11月

     概要を見る

    EPD用サスペンションの分散媒には、現在有機溶媒が多く用いられている。コストや環境問題、粒子分散性の高さや多岐にわたる分散剤が利用できる利点から水系サスペンションの利用が求められているが、水の電気分解で発生する気泡が粒子堆積層内に巻き込まれ膜質や膜密度を低下させる問題を抱えており、水系溶媒の使用は実用化に至っていない。我々は、電極基材や添加剤の選択などから気泡の発生を抑止するための様々な工夫を行い、EPDプロセスを非水系プロセスから環境負荷の少ない水系プロセスへ転化させるための基礎研究を行ってきた。本講演では、Pdカソード基板を用いたりDCパルス電場を用いた気泡の抑止方法の他に、水系EPDプロセスにおける粒子堆積のメカニズムや、EPDプロセスに適したサスペンションの設計指針などについても紹介する。

  • 強磁場コロイドプロセス法によるランタンシリケート配向体の作製

    高橋聡志, 打越 哲郎, 小林 清, 鈴木 達, 目 義雄, 鱒渕友治, 石垣隆正

    無機マテリアル学会 第125回学術講演会  

    発表年月: 2012年11月

     概要を見る

    ランタンシリケートは、六方晶系アパタイト型構造をとり、c軸方向に酸素イオンが配列した結晶構造に由来して、c軸方向に高い酸素イオン伝導性が発現することが知られている。このバルク焼結体の結晶粒配向を制御することができれば、中低温域で高い発電効率を持つSOFCの作製が期待できる。本研究では、La9.33Si6Oxの粉体を強磁場中で鋳込み成形したのちに焼成することで、ランタンシリケートのc軸配向バルク多結晶体を作製し、その電気伝導度異方性について評価した。

  • New developments in electrophoretic deposition process

    UCHIKOSHI, Tetsuo, SUZUKI, Tohru, SAKKA, Yoshio

    3rd NIMS-Saint Gobain Center Workshop  

    発表年月: 2012年10月

     概要を見る

    Electrophoretic deposition (EPD) is a colloidal process wherein ceramic bodies are directly shaped from a stable colloid suspension by a dc electric field. Compared to other advanced shaping techniques, the EPD process is very versatile since it can be modified easily for a specific application. EPD is also gaining increasing interest as a processing technique for production of novel inorganic nanostructured and nanoscale materials. In this presentation, we will introduce our recent studies on EPD for variety of applications in structural and functional ceramics, and discuss its versatility and potentiality.

  • 磁場と電場を用いた配向積層セラミックスの創製と亀裂偏向

    鈴木 達, 打越 哲郎, 目 義雄

    セラミックス総合研究会  

    発表年月: 2012年10月

     概要を見る

    単相アルミナにおいて、電場と強磁場を用いたコロイドプロセスを行うことで結晶配向と層状構造を制御することにより残留応力を発生させることが可能であることを報告してきている。この残留応力は配向角度と層厚で制御可能であり、この配向制御による劈開面の並びと導入された残留応力が亀裂偏向や破面形態に及ぼす影響を検討した結果について報告する。また、炭化ケイ素への展開も可能であることを述べる。

  • Texturing and anisotropic properties of Borides Ceramics via Strong Magnetic Field Alignment

    Wen-Wen Wu, SAKKA, Yoshio, SUZUKI, Tohru, Wen-Wen Wu

    Materials Science & Technology 2012 Conference & Exhibition  

    発表年月: 2012年10月

     概要を見る

    Highly textured ZrB2-ceramics with an oriented microstructure of elongated ZrB2 grains were fabricated by colloidal processing in a high magnetic field and subsequent sintering. Anisotropic properties of textured ZrB2-based ceramics as well as elongated grain growth behavior of ZrB2 were investigated.

  • Taylored Microstructure of Ceramics by using Magnetic and Electric Field

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    ICAT 64th International Smart Actuator Symposium  

    発表年月: 2012年10月

     概要を見る

    The residual stress generated in each layer during cooling down from the sintering temperature has an influence on the crack deflection, hence the control of the residual stress is important for the crack growth resistance in order to improve the mechanical properties. Our concept is that the crystalline axis depending on the CTE aligns for controlling the residual stress in the monolithic ceramics. The composite was fabricated by alternately changing the angle between the directions of the magnetic and electric fields layer by layer during EPD in 12T. The grains in alternate layers are aligned differently in the multilayer composite. The crack deflection was observed at the boundary between the layers with different orientation. The fracture behavior depended on each layer.

  • 電気泳動堆積法によるSOFC 多孔質電極上への固体電解質積層膜の形成

    鈴木晴絵, 打越 哲郎, 小林 清, 古谷健司, 鈴木 達, 目 義雄, 宗像文男

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2012年09月

     概要を見る

    高温型と呼ばれている固体酸化物形燃料電池(Solid Oxide Fuel Cell:SOFC)の燃料極では、ガスの流通と界面反応をスムーズに行わせるために、高い多孔性が必要となる。燃料極支持型セルでは、電解質膜形成後の焼成過程でも燃料極が高い多孔性を保持し、かつ適度な強度を有するような微細構造設計が重要である。そこで、本研究では気孔を均一に分散することで通気性と強度に優れた多孔性燃料極の形成する条件について検討した。また、その多孔質燃料極上へ電気泳動堆積(EPD)法により電解質及び緩衝層の固体電解質積層膜の形成を行った。

  • 強磁場中EPDによる配向制御した緻密なTi3SiC2薄膜形成

    ミシュラ ムリナリニ, 目 義雄, 佐藤 仁俊, 鈴木 達, 打越 哲郎

    日本セラミックス協会秋季シンポジウム  

    発表年月: 2012年09月

     概要を見る

    Electrophoretic deposition (EPD) was performed from 1 vol% ethanol suspension of Ti3SiC2 to which 30-70 wt% of Ti-Si-TiC (1:1.2:2) molar mixture had been added. 1 wt% PEI and 1 wt% PVB have been used as dispersant and binder respectively. High quality green films of thickness ~1mm on porous Al2O3 substrates, which were devoid of cracks and peel-off could be fabricated. Application of strong magnetic field (~12T) followed by pressure-less sintering resulted in dense, textured thin films of Ti3SiC2 on Al2O3.

  • アルミナ単相での残留応力を利用した亀裂進展制御

    鈴木 達, 打越 哲郎, 目 義雄

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2012年09月

     概要を見る

    単相アルミナにおいて、電場と強磁場を用いたコロイドプロセスを行うことで結晶配向と層状構造を制御することにより残留応力を発生させることが可能であることを報告してきている。この残留応力は配向角度と層厚で制御可能であり、この配向制御による劈開面の並びと導入された残留応力が亀裂偏向や破面形態に及ぼす影響を検討する。

  • Na-cancriniteの単結晶育成と結晶構造精密化

    越後 拓也, 山田 裕久, 田村 堅志, 鈴木 達

    日本鉱物科学会2012年年会  

    発表年月: 2012年09月

     概要を見る

    Cancrinite [(Na, Ca)6-8(SiAlO4)6(CO3)1.0-1.7・2H2O] は準長石族の一種であり、3次元フレームワーク構造を持つアルミノ珪酸塩鉱物である。Cancrinite族鉱物の結晶化学的研究は数多く行われているが、陽イオンとしてNaイオンのみを含む結晶 (Na-cancrinite) の構造解析結果は報告されていない。そこで本研究では、Na-cancriniteの良質な単結晶を育成し、単結晶X線回折法による結晶構造の精密化を行った。結晶構造解析の結果、炭酸イオンは動的無秩序分布を示し、水分子は静的無秩序分布を示すことが明らかになった。この結果は、cancrinite構造において、陽イオンの種類と量が陰イオンおよび水分子の挙動にも影響を与えることを示唆する。

  • 陽極酸化アルミナをテンプレートとする酸化チタンナノチューブの合成と評価

    愛須 一史, 小澤 隆弘, 鈴木 達, 鈴木 義和

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2012年09月

     概要を見る

    TiO2 は色素、化粧品、ガスセンサー、電子デバイス、光触媒、触媒担体、色素増感型太陽電池などの幅広い用途で利用されている。その中でTiO2 の様々な機能性を向上させるため、1 次元ナノ構造のTiO2 が研究されている。1 次元ナノ構造のTiO2 の作製方法としては、水熱合成法、テンプレート法、陽極酸化法などがある。我々は、陽極酸化アルミナをテンプレートとして用いることで、形状を制御し、また熱安定性に優れたTiO2 ナノチューブの作製を試みた。

  • ネッキング構造を持つチタン酸バリウム粒子/ポリマー複合キャパシターの微構造制御とその誘電特性

    塚本 修平, 藤井 一郎, 中島 光一, 武井 貴弘, 熊田 伸弘, 和田 聡志, 鈴木 達, 打越 哲郎, 目 義雄

    日本セラミックス協会 秋季シンポジウム  

    発表年月: 2012年09月

     概要を見る

    将来の大容量通信に対応する電子デバイス基盤技術としてフィルム状で、比誘電率が100以上のフィルムキャパシタを作製することが求められる。高誘電率なフィルムキャパシタを作製するためには、(I)高誘電率のBaTiO3ナノ粒子を使用する、(II)電気泳動法による高密度集積体の作製、(III)集積体にネッキング構造の導入を行うことが重要となる。我々は、この条件を満たしたフィルムキャパシタを開発してきている。今回は、このフィルムキャパシタについて様々な微構造制御をおこなったので報告する。

  • EPD 法を用いたセラミックスコーティングによる固体酸化物燃料電池カソードの作製

    橋本実和, 松永知佳, 松田元秀, 打越 哲郎, 鈴木 達, 目 義雄

    2012年日本金属学会秋期講演大会  

    発表年月: 2012年09月

     概要を見る

    現在我々は、高効率な発電デバイスとして注目されている固体酸化物燃料電池(Solid Oxide Fuel Cell : SOFC)へのEPD 法の応用を検討している。本研究では、低温作動SOFC の電解質として注目されているGd0.1Ce0.9O1.95(GDC)を導電性ポリマーであるPolypyrrole(Ppy)によって表面コーティングし、EPD によるカソード層の作製を検討した。焼成後に、電解質とカソード層間で、焼付け処理中での電解質とカソード層の熱挙動が異なるためと考えられる剥離が観測された。多孔材として用いたてんぷんの添加量を変化させ焼付けを検討した結果、適当量のでんぷんを添加することによって焼付け状態の改善に成功した。

  • Na-cancriniteの結晶構造とイオン吸着特性

    ECHIGO, Takuya, YAMADA, Hirohisa, TAMURA, Kenji, SUZUKI, Tohru

    The 2nd Asian Clay Conference  

    発表年月: 2012年09月

     概要を見る

    Single crystals of cancrinite were grown under hydrothermal condintion (500&#730;C under 1 kbar for 14 days) using synthetic hydroxyl-sodalite and sodium oxalate. SC-XRD data were collected by Bruker SMART APEX II CCD diffractometer. The successive stacking of the layers forms large channels running along [001] in which extra-framework cation (Na+), anion (CO32-) and H2O molecules are hosted. These extra-framework ions/molecules show disordered distribution which were not observed in other cancrinite group minerals.

  • Control of orientation in ceramic films and layers using EPD in a strong magnetic field

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, KAWAKITA, Mamiko, KAWAKITA, Jin, SAKKA, Yoshio

    ICFPE  

    発表年月: 2012年09月

     概要を見る

    Tailoring the crystallographic orientation in ceramics is one way of effectively improving their properties, such as electrical, piezoelectric and mechanical properties. In this decade, we have reported that the successful control of the crystallographic orientation in diamagnetic ceramics was achieved by a colloidal processing in a strong magnetic field. Electrophoretic deposition (EPD) is a colloidal processing technique wherein ceramics bodies are directly shaped from a stable colloid suspension by a dc electric field. Complex shaped ceramics, ceramic films and coating of the metallic substrate can be easily attained. In this study, crystallographic oriented ceramics films and layers were fabricated by EPD in a strong magnetic field in order to improve their properties.

  • EFFECT OF TEHRMAL TREATMENT ON DEVELOPMENT OF TEXTURED MICROSTRUCTURE OF HEMATITE PREPARED BY MAGNETIC FIELD-ASSISTED COLLOIDAL PROCESSING

    UCHIKOSHI, Tetsuo, SUZUKI, Tohru, SAKKA, Yoshio

    ICCCI2012  

    発表年月: 2012年09月

     概要を見る

    Textured hematite was fabricated via thermal treatment of textured goethite using magneto scientific technique. The consolidated cake of the goethite, which was prepared by slip casting in a 2 T magnetic field, was dried and then thermally treated in air out of the magnetic field in order to transform it into hematite. It was observed that the orientation of hematite was improved by heating, and a completely-textured microstructure with the Lotgering factor, which is an index of the degree of c-axis grain alignment, F=1.0 was accomplished at 1473 K.

  • Control of Laminar Structure in Alumina Using EPD in a Strong Magnetic Field

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    ICCCI 2012  

    発表年月: 2012年09月

     概要を見る

    Layered structure has been proposed as an alternative for the design of structural ceramics. The residual stress generated in each layer during cooling down from the sintering temperature has an influence on the crack deflection and crack bifurcation, hence the control of the residual stress is important for the crack growth resistance in order to improve the mechanical properties. We have reported that the layered structure in alumina could be produced by EPD in a strong magnetic field. Hence, in this study we attempt to control the residual stress in alumina/alumina laminar composites with different crystalline-oriented layers by EPD in a strong magnetic field to study the crack deflection and the fracture behavior in the laminar alumina composites.

  • The impact of crystalline orientation control on Li ion battery

    穂積正人, 小谷 幸成, 山田 英登, 鈴木 達, 打越 哲郎, 目 義雄

    ICCCI2012  

    発表年月: 2012年09月

     概要を見る

    Rechargeable Li ion batteries are expected as a key device for environmentally friendly technology, and further increase of energy density is required for EV, Plug-in HV and other large scale applications. The simple and direct way for increasing energy density is to enlarge ratio of active material in electrodes ideally up to 100 %. The LiCoO2 is the most commonly used cathode active material in Li ion batteries and has reasonably high ionic and electronic conductivity. However, we need to control grain boundary and crystalline orientation of LiCoO2 to realize 100 % active material electrode with this material due to anisotropic ionic/electronic conductivity. In this study, we evaluated the oriented cathode material as an electrode of Li ion batteries.

  • Relationship between grain growth and orientation of the oriented LiCoO2 prepared by colloidal processing in a strong magnetic field

    YAMADA, Hideto, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, Hozumi Masato, KOTANI Yukinari, SAKKA, Yoshio

    ICCCI2012  

    発表年月: 2012年09月

     概要を見る

    An all-solid-state Li-ion battery is expected to have a high durability and safety. Despite this advantage, the problems are lower ionic conductivity of the solid electrolyte and lower power as compared with the general liquid type Li-ion batteries. One of the solutions is to optimize the interface of the active material. LiCoO2 is one of the popular cathode materials for Li-ion secondary battery, which has a layered rock-salt structure. The property of layered materials depends on the anisotropic crystallographic structure. We prepared a crystalline-oriented bulk LiCoO2 by slip casting in a strong magnetic field. In this study, we will discuss the relationship between the grain growth and the crystal orientation.

  • Fabrication of textured ceramics and their some properties through colloidal processing in strong magnetic field

    SAKKA, Yoshio, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    CMEET-2012  

    発表年月: 2012年08月

     概要を見る

    The colloidal processing in a strong magnetic field can be applied to fabrication of textured ceramics, such as &#61537;-alumina, titania, zinc oxide, hydroxyapatite (HAP), aluminium nitride, silicon carbide, silicon nitride, MAX phase materials, LiCoO2, etc. Also textured ceramics with complicated structure can be fabricated by reaction sintering, such as &#61538;&#61485;alumina, &#61538;-Si3N4, etc.

  • Control of Textured Microstructure in SiC by Colloidal Processing in a Strong Magnetic Field

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    CMEET  

    発表年月: 2012年08月

     概要を見る

    High efficiency of energy production is required and expected to be achieved by increasing the operating temperature of engines and turbines combined with a reduction of the weight of their components. Engineering ceramics for high temperature is excellent candidate to fulfill them. The crystallographic orientation is one possible way to enhance their properties for high temperature. The orientation processing, which was slip casting in a strong magnetic field, could be applied to the SiC and the c-axis of the SiC became aligned parallel to the magnetic field. The 3-point bending strength in the direction parallel to the c-axis is higher than that in the direction perpendicular to the c-axis in the textured SiC. Development of orientation was examined.

  • Characterization of the Magnetic Anisotropy of α-Fe2O3 by Using Highly-Textured Polycrystalline α-Fe2O3 Sintered Bodies

    UCHIKOSHI, Tetsuo, SUZUKI, Tohru, SAKKA, Yoshio

    ICTA2012  

    発表年月: 2012年08月

     概要を見る

    α-Fe2O3 is a well-known iron oxide. It is magnetically classified in a weak ferromagnetic group at room temperature and it possesses magnetic anisotropy which is originated in asymmetric crystalline structure. The magnetic properties of α-Fe2O3 have been characterized using natural hematite single crystals; however natural hematite usually includes impurity elements and the doping effect of the impurities cannot be excluded. In this study, the anisotropic magnetic property of α-Fe2O3 was investigated using highly-textured polycrystalline α-Fe2O3 bulks.

  • Powder Processing Researches in NIMS

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    2012年度第2回関東談話会 「ジャカルタ研修会」  

    発表年月: 2012年07月

     概要を見る

    粉体の合成、および粉体を用いたプロセスは材料創製において重要な技術の一つである。粉体の合成では、水熱合成、ゾルゲルなどの化学的作製法や噴霧法やプラズマを用いた物理的方法などがある。本発表では、NIMSにおける粉体に関する研究について紹介を行う。特に、ハイブリッド噴霧法、強制プラズマ蒸発法による粉末作製、さらに粉末成形にコロイドプロセスを用いた組織制御に関して概説する。

  • lectrophoretic deposition of cathode layer on dense electrolyte coated with conducting polypyrrole for solid oxide fuel cell

    Miwa HASHIMOTO, MATSUNAGA, Chika, UCHIKOSHI, Tetsuo, SUZUKI, Tohru, SAKKA, Yoshio, Motohide MATSUDA

    STAC6  

    発表年月: 2012年06月

     概要を見る

    Electrophoretic deposition (EPD) is a colloidal process, having some technological advantages. One of the advantages is easy fabrication of thickness-controlled multi-layers on planar or cylindrical substrates. On the application of the EPD process for SOFC assembly, the substrate materials should be electrically conductive; therefore, some type of conducting coating which should be easily removed during sintering is prerequisite. In this study, conducting polypyrrole (Ppy) was applied on dense Gd0.1Ce0.9O1.95 (GDC) electrolytes for the fabrication of La2NiO4 (LNO) cathode layer by the EPD process.

  • Shrinkage Behavior of Oriented LiCoO2 Prepared by Slip Casting in Strong Magnetic Field

    YAMADA, Hideto, SUZUKI, Tohru, UCHIKOSHI, Tetsuo, Hozumi Masato, SAKKA, Yoshio

    STAC-6  

    発表年月: 2012年06月

     概要を見る

    The development of crystallographic orientation is an interesting topic in ceramics science and technology since it is one of the effective ways to improve their properties. One of the popular cathode materials for Li-ion secondary battery is LiCoO2, which has a layered rock-salt structure. The property of layered materials depends on the anisotropic crystallographic structure. We have previously reported that LiCoO2 has a magnetic anisotropy and the particles can be aligned using a strong magnetic field. We prepared a crystalline-oriented bulk LiCoO2 by slip casting in a strong magnetic field. In this study, we will discuss the relationship between the development of the crystallographic orientation and the sintering behavior.

  • Fabrication of Textured Polycrystalline Hematite via Topotactic Phase Transformation of Goethite using Magneto-Scientific Technique

    UCHIKOSHI, Tetsuo, SUZUKI, Tohru, SAKKA, Yoshio

    STAC6  

    発表年月: 2012年06月

     概要を見る

    Textured hematite was fabricated from paramagnetic goethite by electrophoretic deposition in a strong magnetic field followed by thermal treatment via topotactic phase transformation. The completely-textured hematite was obtained by sintering the goethite compact at 1200 &#61616;C in air. Fig.1 shows the XRD patterns of the compact before and after the sintering. The a,b-axes of the goethite was taken over the c-axis of the hematite through the topotactic phase transformation The textured hematite showed magnetic anisotropy depending on the direction of the crystallographic axes.

  • Fabrication of GDC/LSGM/GDC Layered Composite on Porous NiO-YSZ by Sequential Electrophoretic Deposition Process

    Harue SUZUKI, UCHIKOSHI, Tetsuo, KOBAYASHI, Kiyoshi, SUZUKI, Tohru, Tatsuo SUGIYAMA, Kenji FURUYA, SAKKA, Yoshio, Fumio MUNAKATA

    STAC6  

    発表年月: 2012年06月

     概要を見る

    The formation of the layered structures of GDC/LSGM/GDC on the polypyrrole-coated NiO-YSZ substrate was performed by a sequential electrophoretic deposition process. After the lamination process, the deposited layers were dried in air and then sintered together with the porous NiO-YSZ substrate at 1400 &ordm;C for 2h. The GDC/LSGM/GDC layered composite with good interfacial bonding was successfully fabricated on the porous NiO-YSZ.

  • The Orientation of L-type Zeolite Particle through Colloidal Processing in Strong Magnetic Field

    MATSUNAGA, Chika, UCHIKOSHI, Tetsuo, SUZUKI, Tohru, SAKKA, Yoshio, Motohide MATSUDA

    STAC6  

    発表年月: 2012年06月

     概要を見る

    Fabrication of orientation controlled L-type zeolite seed layer on porous ceramics substrates were attempted in a strong magnetic field to extend the applicability of the magneto-scientific process to another zeolite. A commercial L-type zeolite powder was dispersed in distilled water and agglomerated secondary particles were removed by sedimentation prior to the use. The supernatant suspension was consolidated by slip casting or electrophoretic deposition under a static magnetic field of 12 T. It was revealed that the c-axis of L-type zeolite can be aligned by applying a static magnetic field.

  • Densification of SiC by colloidal processing and SPS without sintering additives

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    STAC6  

    発表年月: 2012年06月

     概要を見る

    It is difficult to densify SiC at temperatures below 2000&#61616;C without sintering additives even if SPS is used. Colloidal processing is a very effective technique for controlling the pore size distribution in green compacts before sintering. The green compacts having small residual pores with a narrow size distribution is expected to enhance the densification at low sintering temperature. When the green compact prepared by slip casting was sintered by hot pressing, the density was 78%. However, the density of SiC sintered by SPS increased with the increasing sintering temperature. The relative density of SiC prepared by SPS was more than 97% at the sintering temperature of 1950C.

  • Uniformly Porous MgTi2O5 with Narrow Pore-Size Distribution: XAFS Study, Improved In-Situ Synthesis, and New In-Situ Surface Coating

    Yoshikazu Suzuki, SUZUKI, Tohru, Yutaka Shinoda, Katsumi Yoshida

    STAC6  

    発表年月: 2012年06月

     概要を見る

    Recently, we have focused another pseudobrookite-type oxide, MgTi2O5, as a low thermal expansion material. Thinking about its low thermal expansion, low-cost, non-toxicity, and refractory composition, MgTi2O5 is a potential thermal-shock resistant material. In our previous report, substantially single-phase porous MgTi2O5 ceramics with very narrow pore-size distribution were successfully prepared by one-step reactive sintering. In this presentation, further studies on the porous MgTi2O5 will be reported, viz., (1) XAFS study of porous MgTi2O5 based on our previous paper, (2) improved in-situ synthesis, and (3) new &quot;in-situ surface coating,&quot; which enables in-situ MgTi2O5 synthesis, in-situ uniform pore formation, and in-situ surface coating in only one-step heating.

  • Textured ZrB2-based ultra high temperature ceramics from rod-like ZrB2 starting powders

    Hai-Tao Liu, WU, Wenwen, SUZUKI, Tohru, Guo-Jun Zhang, SAKKA, Yoshio

    STAC6  

    発表年月: 2012年06月

     概要を見る

    Using rod-like ZrB2 powder as starting materials, textured ZrB2-based UHTCs can be obtained via tape casting together with hot pressing and slip casting in strong magnetic field alignment followed by SPS.

  • Tailored microstructure of ceramics by using electric and magnetic fields

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    NIMS Conference 2012  

    発表年月: 2012年06月

     概要を見る

    組織と結晶の配向は材料特性に大きく影響し、特性改善のための効果的な組織制御手法の一つである。セラミックス積層コンポジットでは、機械特性を改善する手法の一つとして熱膨張率の異なる材料を積層させ残留応力を発生させることにより亀裂進展を制御する方法が試みられている。圧縮応力層と引張り応力層との界面では、亀裂進展が偏向・阻害されることで強靭化が期待される。我々のグループで検討してきた組織制御手であるEPD法の積層体成形と強磁場を組み合わせる方法での各々の層の結晶方位を制御した配向制御積層構造の作製とその亀裂偏向について紹介する。

  • EPD法による多孔質NiO‐YSZ基板上へのセリア系およびランタンガレート系固体電解質積層膜の形成

    鈴木晴絵, 打越 哲郎, 小林 清, 古谷健司, 鈴木 達, 目 義雄, 宗像文男

    粉体粉末冶金協会春季大会  

    発表年月: 2012年05月

     概要を見る

    SOFCの特性向上には電極と電解質の微細構造設計が重要である。このとき、前者では機械的強度に加え高い多孔性と十分な三相界面の形成が、後者では緻密化と膜厚制御に加え電極材との反応抑制が大きな要因となる。特にランタンガレート系電解質では、電極との反応を防ぐセリア系緩衝層の挿入が、セル構築において検討されている。そこで、本研究では、まずNiO-YSZ複合粒子とライススターチのヘテロ凝集を利用した多孔質燃料極の作製方法について検討した。次に、この多孔質電極上に電気泳動堆積(EPD)法でGDC/LSGM/GDCの交互積層膜を形成させ、さらにこれを一体焼成することにより、高い多孔性を保持した燃料極上に緻密な電解質積層膜を形成させるプロセス条件について検討した。

  • 配向と積層成形を用いたセラミックスの微構造制御

    鈴木 達, 川名 孝弥, 打越 哲郎, 阿部 修実, 目 義雄

    粉体粉末冶金協会 春季大会  

    発表年月: 2012年05月

     概要を見る

    これまでに、常磁性体や反磁性体粒子も磁場配向できる強磁場コロイドプロセスの一つである強磁場中電気泳動堆積法(Electorophoretic Deposition: EPD)において、磁場印加方向に対し、電極基板の傾き(&#61546;B-E)を変化させることで、粒子の配向方向を任意に設定でき、一定時間ごとに電極基板の傾きを変化させることで、層ごとに配向方向が異なる配向積層体を単一組成で作製できることを報告してきた。本手法により作製した配向積層アルミナは、単一組成で構成されているが残留応力の導入が可能であり、さらに、層を構成する粒子が結晶配向しているため、結晶異方性による亀裂偏向も期待できる。そこで、本研究では、強磁場中EPD法を用いて、Al2O3単一組成の配向積層体を作製し、その破壊形態と亀裂進展挙動を調べた。

  • Fabrication and some properties of textured ceramics by colloidal processing in a strong magnetic field

    SAKKA, Yoshio, SUZUKI, Tohru, UCHIKOSHI, Tetsuo

    10th CMCEE  

    発表年月: 2012年05月

     概要を見る

    Crystalline-textured controlled laminated composites can be fabricated using electrophoretic deposition by varying the angle between the vectors of electric field and magnetic field. Some anisotropic properties will be demonstrated.

  • シュウ酸を含む溶液中における sodalite から cancrinite への相転移機構

    越後 拓也, 山田 裕久, 田村 堅志, 鈴木 達

    日本地球惑星科学連合2012年大会  

    発表年月: 2012年05月

     概要を見る

    Cancrinite [Na6Ca2(AlSiO4)6(CO3)2&#8226;2H2O] は3次元フレームワーク構造を持つ準長石族の一種で、ケージ内に陽イオンとしてNa+、K+、Ca2+、陰イオンとしてCO32-、Cl-、OH-、SO42-、NO3-, C2O42- を含むものが天然環境に産出する(Gaines et al. 1996, Chukanov et al. 2010)。最近、ロシアのコラ半島において、シュウ酸イオンを含有した cancrinite族鉱物 kyanoxalite [Na7(AlSiO4)6(C2O4)0.5-1.0&#8226;5H2O] がアルカリ深成岩体中から報告された (Chukanov et al. 2010)。同地域に産出するkyanoxalite は、sodalite [Na4(AlSiO4)3Cl] を交代した産状を持つことから、シュウ酸を含む熱水の作用があったと考えられるが、その生成機構については不明な点が多い。そこで本研究では、kyanoxaliteの生成場を模した環境でシュウ酸を含有したcancriniteを合成し、kyanoxaliteの生成機構を考察することを目的とする。

  • Preparation of Laminar Ceramics with Different Oriented Layers by Electrophoretic Deposition in a Strong Magnetic Field

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    MAP 5  

    発表年月: 2012年05月

     概要を見る

    We demonstrate that laminar composites with different crystalline-oriented layer are produced by electrophoretic deposition (EPD) in a strong magnetic field. This composite was fabricated by alternately changing the angle between the directions of the magnetic and electric fields layer by layer during EPD in 12T. The grains in alternate layers are aligned differently. The crack deflection was observed at the boundary between layers with different orientations due to the residual stress.

  • Highly controlled orientation of Piezoelectric Ceramics using a strong magnetic field

    SUZUKI, Tohru, Yashinari Miwa, Shinichiro Kawada, Masahiko Kimura, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    Ceramic Interconnec and Ceramic Microsystems Technologies  

    発表年月: 2012年04月

     概要を見る

    Bi層状化合物などの無鉛圧電セラミックスにおいて、その特性を向上させるために結晶軸を揃える配向制御が行われている。配向を付与するために、TGG法やホットホージ、強磁場を用いた成形が用いられ、TGG法ではc軸配向が可能であり、強磁場を用いた場合にはa,b軸配向が可能となる。しかし、これらの手法を用いた場合には、一軸のみの配向制御であった。そこで、本研究においては、板状粒子による配向付与と強磁場成形を組み合わせることにより、a, b軸とc軸という異なる軸の配向を同時に制御することを考え、CaBi4Ti4O15への適用を試みた。さらに他の圧電体への展開も試みた。

  • Control of crystallographic orientation in SiC by EPD in a strong magnetic field

    SUZUKI, Tohru, UCHIKOSHI, Tetsuo, SAKKA, Yoshio

    ISASC2012  

    発表年月: 2012年03月

     概要を見る

    The successful control of the development of a textured microstructure in feeble magnetic ceramics was achieved by EPD in a strong magnetic field and the combination of the orientation and lamination was one of the possible ways of tailoring the microstructure to improve the mechanical properties and other properties due to the superposition effect. We have already reported that production of alumina/alumina laminar composites with different crystalline-oriented layers by EPD in a strong magnetic field was achieved.In this study, we demonstrate that control of the crystallographic orientation in SiC was achieved by EPD in a strong magnetic field.

  • Fabrication of textured &#61538;-Si3N4 and &#61538;-Sialon by slip casting

    SAKKA, Yoshio, ZHU, Xinwen, SUZUKI, Tohru

    ISASC2012  

    発表年月: 2012年03月

     概要を見る

    This paper reviews the important results by the authors on the processing of textured &#61538;-Si3N4 and beta-sialon by slip casting in a strong magnetic filed of 12 T and reaction-sintering with additives of alumina and yttria. The a, b-axis textured beta-Si3N4 and beta-sialon have been obtained using the static magnetic field because of the magnetic susceptibility of &#61539;a, b &gt; &#61539; c for beta-Si3N4. Moreover, the c-axis textured &#61538;-Si3N4 has also been successfully obtained using a rotating magnetic field.

  • 固体酸化物燃料電池のプロセッシング−電気泳動堆積法の適用−

    橋本実和, 松永 知佳, 松田元秀, 打越 哲郎, 鈴木 達, 目 義雄

    第4回資源・環境対応セラミックス材料/技術研究講演会  

    発表年月: 2012年03月

     概要を見る

    現在我々の研究グループは、廉価的なプロセスで、薄膜から厚膜まで膜の厚さを広範囲に制御可能な電気泳動堆積(EPD)法を用いてSOFCのプロセッシングに取り組み、逐次EPDによる薄膜電解質型セルの簡便製造や電極構造の高次制御などを検討している。ここでは、カソード層形成に対するEPDの適用について報告する。

  • LiCoO2配向焼結体を用いたLi-ion電池の作製と電池特性評価

    山田 英登, 鈴木 達, 打越 哲郎, 穂積正人, 小谷 幸成, 目 義雄

    益社団法人日本セラミックス協会 2012年 年会  

    発表年月: 2012年03月

     概要を見る

    Liイオン2次電池は携帯機器をはじめ様々な分野に適用されており、LiCoO2は層状酸化物の正極材料として広く知られている。物質の諸特性は結晶方位により異なることが多く、その特性向上のひとつの手法として、特定の結晶方位を優先的に成長させたり並べたりするなどの配向制御が注目されている。我々は、反磁性セラミックス粒子のコロイド分散系に強磁場を印加、成形することにより結晶方位の制御されたセラミックス材料を創製し、種々の特性向上を図る試みを行っている。そこで、我々はLiCoO2の磁気異方性に着目し、強磁場印加コロイドプロセスによるLiCoO2配向体の作製を試みた。また、得られた配向焼結体を正極とする電池を作製し、配向と電池特性の関係について検討した。

  • 強磁場中EPD用いた積層アルミナの配向制御と亀裂進展特性

    鈴木 達, 川名 孝弥, 打越 哲郎, 阿部 修実, 目 義雄

    日本セラミックス協会 年会  

    発表年月: 2012年03月

     概要を見る

    組織と結晶の配向は材料特性に大きく影響し、特性改善のための効果的な組織制御手法の一つである。セラミックス積層コンポジットでは、機械特性を改善する手法の一つとして熱膨張率の異なる材料を積層させ残留応力を発生させることにより亀裂進展を制御する方法が試みられている。圧縮応力層と引張り応力層との界面では、亀裂進展が偏向・阻害されることで強靭化が期待される。我々のグループではEPD法の積層体成形方法と強磁場を組み合わせることで、各々の層の結晶方位を制御した配向制御積層構造の作製を行い、結晶方位に依存した熱膨張係数の差異による残留応力を導入することに成功している。本研究では、層厚と結晶方位を制御したアルミナを作製し、その積層体での亀裂進展過程を検討した。

  • Tailoring ZrB2-based Ultra High Temperature Ceramics via Strong Magnetic Field Alignment

    Wen-Wen Wu, 目 義雄, 鈴木 達, Guo-Jun Zhang

    日本セラミックス協会年会  

    発表年月: 2012年03月

     概要を見る

    With a combination of excellent properties, including extremely high melting temperatures, high hardness, low volatilities, good thermal and electrical conductivities, ZrB2-based ultra high temperature ceramics (UHTCs) become viable candidates for high-temperature structural applications. ZrB2 owns AlB2-type hexagonal structure (P6/mmm) and shows high anisotropy in single-crystal form, platelet ZrB2 grains could be formed in reactive hot pressed ZrB2-MoSi2 at temperature of 1650 &#61472;&#61616;C. In present work, textured ZrB2 and ZrB2-MoSi2 ceramics were fabricated via strong magnetic field alignment during slip casting, followed by spark plasma sintering. The results on sintering, microstructure and the anisotropic properties of the received textured ceramics will be reported

  • 電気泳動堆積法を用いた固体酸化物燃料電池の電極形成

    橋本実和, 松永 知佳, 松田元秀, 打越 哲郎, 鈴木 達, 目 義雄

    日本セラミックス協会2012年年会  

    発表年月: 2012年03月

     概要を見る

    現在、SOFCの電極層形成はtape-casting、screen-printingおよびdip-coatingなどによって行われているが、更なる高性能化に向け、より高度な微細構造制御を可能とする電極形成プロセスの開発が求められている。我々は、堆積膜の微細構造を原理上粒子サイズオーダーで制御でき複雑形状の基板上にも均質な膜形成が可能な電気泳動堆積(EPD)法の適用について検討を進めている。しかし、EPDプロセスにおいては、堆積用基板に導電性が必要となるが、電解質基板は導電性が低いためEPD電極として通常用いることができない。そこで本研究では、GDC電解質表面に導電性を付与させる目的で、導電性ポリマーによる表面コーティングを行い、EPDによるLNO電極の作製を検討した。

  • 強磁場中電気泳動堆積法で作製したAl2O3配向積層材料の亀裂進展挙動

    川名 孝弥, 鈴木 達, 打越 哲郎, 目 義雄, 阿部 修実

    セラミックス基礎科学討論会  

    発表年月: 2012年01月

     概要を見る

    積層構造をもつセラミックス材料は、組成の異なる材料を重ね合わせて、焼成することで作製することが多いが、粒子の結晶方位を任意に制御することが出来る強磁場中電気泳動堆積法を用いると、単一組成で層毎に結晶方位がことなる配向積層材料を作製することが出来る。本研究では、層毎の結晶方位の組み合わせと層厚を変化させ、作製したアルミナ配向積層材料の強度や亀裂進展挙動の検討を行った。

  • L型およびモルデナイトゼオライトの磁場配向

    松永 知佳, 打越 哲郎, 鈴木 達, 目 義雄, 松田元秀

    セラミックス基礎科学討論