Updated on 2022/09/25

写真a

 
SUGAHARA, Yoshiyuki
 
Affiliation
Faculty of Science and Engineering, School of Advanced Science and Engineering
Job title
Professor

Concurrent Post

  • Faculty of Science and Engineering   Graduate School of Advanced Science and Engineering

Research Institute

  • 2020
    -
    2022

    理工学術院総合研究所   兼任研究員

Education

  • 1983.04
    -
    1988.03

    Waseda University   Graduate School, Division of Science and Engineering   Major in Applied Chemistry  

  • 1979.04
    -
    1983.03

    Waseda University   School of Science and Engineering   Department of Applied Chemisty  

Degree

  • 工学修士

  • 早稲田大学   工学博士

Research Experience

  • 2007.09
     
     

    Invited Professor (, University of Montpellier II, France)

  • 2000.04
    -
     

    Professor (, Waseda)

  • 1998.05
    -
    1998.10

    Visiting Scientist (, University of Montpellier II, France)

  • 1992.04
    -
     

    Associate Professor (, Waseda)

  • 1990.04
    -
     

    Assistant Professor (, Waseda)

  • 1989.09
    -
    1990.03

    Post-Doc (, Mass. Inst. Tech., U.S.A.)

  • 1987.04
    -
     

    Waseda University

▼display all

Professional Memberships

  •  
     
     

    The Japanese Sol-Gel Society

  •  
     
     

    Japan Society of Powder and Powder Metallurgy

  •  
     
     

    Research Group on Inorganic Polymers

  •  
     
     

    The Society of Polymer Science

  •  
     
     

    The Japan Society for Analytical Chemistry

  •  
     
     

    American Chemical Society

  •  
     
     

    The Clay Science Society

  •  
     
     

    The Chemical Society of Japan

  •  
     
     

    The Ceramic Society of Japan

▼display all

 

Research Areas

  • Inorganic materials and properties

  • Composite materials and interfaces

  • Inorganic compounds and inorganic materials chemistry

Research Interests

  • Polymer-derived Ceramics

  • Surface Modification

  • Organic-Inorganic Hybrid Materials

  • Metal Oxide Nanosheets

  • Metal Oxide Nanoparticles

  • Ceramic Science

▼display all

Papers

  • N-doped hollow carbon nanoplates with mesoporous thin shells towards high-performance supercapacitors

    Xiangjun Lu, Jie Wang, Tao Li, Bing Ding, Shude Liu, Joel Henzie, Mohammed A. Amin, Brian Yuliarto, Yoshiyuki Sugahara, Yusuke Yamauchi

    Journal of Power Sources   542   231776 - 231776  2022.09  [Refereed]

    DOI

  • Soft Template-Based Synthesis of Mesoporous Phosphorus- and Boron-Codoped NiFe-Based Alloys for Efficient Oxygen Evolution Reaction

    Yunqing Kang, Yanna Guo, Jingjing Zhao, Bo Jiang, Jingru Guo, Yi Tang, Hexing Li, Victor Malgras, Mohammed A. Amin, Hiroki Nara, Yoshiyuki Sugahara, Yusuke Yamauchi, Toru Asahi

    SMALL   18 ( 33 )  2022.08

     View Summary

    Controlling the morphology, composition, and crystalline phase of mesoporous nonnoble metal catalysts is essential for improving their performance. Herein, well-defined P- and B-codoped NiFe alloy mesoporous nanospheres (NiFeB-P MNs) with an adjustable Ni/Fe ratio and large mesopores (11 nm) are synthesized via soft-template-based chemical reduction and a subsequent phosphine-vapor-based phosphidation process. Earth-abundant NiFe-based materials are considered promising electrocatalysts for the oxygen evolution reaction (OER) because of their low cost and high intrinsic catalytic activity. The resulting NiFeB-P MNs exhibit a low OER overpotential of 252 mV at 10 mA cm(-2), which is significantly smaller than that of B-doped NiFe MNs (274 mV) and commercial RuO2 (269 mV) in alkaline electrolytes. Thus, this work highlights the practicality of designing mesoporous nonnoble metal structures and the importance of incorporating P in metallic-B-based alloys to modify their electronic structure for enhancing their intrinsic activity.

    DOI

  • Preparation of double-layered nanosheets containing pH-responsive polymer networks in the interlayers and the conversion into single-layered nanosheets induced by cleavage of cross-linking points

    Takuma Kamibe, Régis Guégan, Masashi Kunitake, Takehiko Tsukahara, Naokazu Idota, Yoshiyuki Sugahara

    Dalton Transactions   51 ( 16 ) 6264 - 6274  2022.03  [Refereed]

    DOI

  • Nanoarchitecturing bimetallic manganese cobaltite spinels for sonocatalytic degradation of oxytetracycline

    Ramin Hassandoost, Ahmed Kotb, Zahra Movafagh, Mohamed Esmat, Régis Guegan, Saki Endo, Wipakorn Jevasuwan, Naoki Fukata, Yoshiyuki Sugahara, Alireza Khataee, Yusuke Yamauchi, Yusuke Ide, Esmail Doustkhah

    Chemical Engineering Journal   431   133851 - 133851  2022.03  [Refereed]

    DOI

  • Microwave one-pot synthesis of CNT-supported amorphous Ni–P alloy nanoparticles with enhanced hydrogenation performance

    Yunqing Kang, Haoran Du, Bo Jiang, Hui Li, Yanna Guo, Mohammed A. Amin, Yoshiyuki Sugahara, Toru Asahi, Hexing Li, Yusuke Yamauchi

    Journal of Materials Chemistry A   10 ( 12 ) 6560 - 6568  2022.02  [Refereed]

     View Summary

    A CNTs supported amorphous Ni–P alloy NPs catalyst is synthesized by a simple one-pot microwave heating method. The resulting outstanding hydrogenation performance is due to the high-dispersion of Ni–P NPs and the enhanced metal–support interaction.

    DOI

  • Preparation of water-dispersible Janus nanosheets from K4Nb6O17·3H2O and their behaviour as a two-dimensional surfactant on air–water and water-toluene interfaces

    Ryoko Suzuki, Tomoki Nagai, Emika Onitsuka, Naokazu Idota, Masashi Kunitake, Taisei Nishimi, Yoshiyuki Sugahara

    Dalton Transactions   51 ( 9 ) 3625 - 3635  2022  [Refereed]

     View Summary

    Water dispersible K4Nb6O17·3H2O-based Janus nanosheets were successfully prepared and exhibited unique behaviour at the water–air interface and at the water–toluene interface.

    DOI

  • Efficient lithium-ion storage using a heterostructured porous carbon framework and its in situ transmission electron microscopy study

    Minjun Kim, Joseph F. S. Fernando, Jie Wang, Ashok Kumar Nanjundan, Jongbeom Na, Md. Shahriar A. Hossain, Hiroki Nara, Darren Martin, Yoshiyuki Sugahara, Dmitri Golberg, Yusuke Yamauchi

    Chemical Communications   58 ( 6 ) 863 - 866  2022.01  [Refereed]

     View Summary

    The unique 3D heterostructure can highly tolerate the volume expansion over repetitive charge/discharge of lithium-ion batteries, which has been demonstrated through in situ transmission electron microscopy.

    DOI

  • Preparation of biocompatible hydrogels reinforced by different nanosheets

    Taiga Ito, Saki Endo, Yoshiyuki Sugahara, Ryota Tamate, Régis Guégan

    RSC Advances   12 ( 2 ) 753 - 761  2022  [Refereed]

     View Summary

    Inclusion of different nanosheets derived from layered materials as a way to control the gelation of a hydrogel based on F127 tri-block copolymers functionalized with dimethacrylate (127-DMA).

    DOI

  • Heterostructuring Mesoporous 2D Iridium Nanosheets with Amorphous Nickel Boron Oxide Layers to Improve Electrolytic Water Splitting

    Yunqing Kang, Bo Jiang, Victor Malgras, Yanna Guo, Ovidiu Cretu, Koji Kimoto, Aditya Ashok, Zhe Wan, Hexing Li, Yoshiyuki Sugahara, Yusuke Yamauchi, Toru Asahi

    Small Methods   5 ( 10 ) 2100679 - 2100679  2021.10  [Refereed]

    DOI

  • Intercalation of a Cationic Cyanine Dye Assisted by Anionic Surfactants within Mg–Al Layered Double Hydroxide

    Rina Sato, Shingo Machida, Minoru Sohmiya, Yoshiyuki Sugahara, Régis Guégan

    ACS Omega   6 ( 37 ) 23837 - 23845  2021.09  [Refereed]

    DOI

  • Nanoarchitecturing Carbon Nanodot Arrays on Zeolitic Imidazolate Framework-Derived Cobalt–Nitrogen-Doped Carbon Nanoflakes toward Oxygen Reduction Electrocatalysts

    Yongqi Yin, Jie Wang, Tao Li, Jonathan P. Hill, Alan Rowan, Yoshiyuki Sugahara, Yusuke Yamauchi

    ACS Nano   15 ( 8 ) 13240 - 13248  2021.08  [Refereed]

    DOI

  • Free-standing membranes from the chemical exfoliation of mesoporous amorphous titania thin film

    Victor Malgras, Yoshitaka Matsushita, Joel Henzie, Yoshiyuki Sugahara, Yusuke Yamauchi

    Chemical Communications   57 ( 61 ) 7513 - 7516  2021.06  [Refereed]

     View Summary

    <p>A method to exfoliate pre-crystallized mesoporous TiO2 thin films in alkaline solutions, preserving the ordered structure.</p>

    DOI

  • Electrochemical energy storage performance of 2D nanoarchitectured hybrid materials

    Jie Wang, Victor Malgras, Yoshiyuki Sugahara, Yusuke Yamauchi

    Nature Communications   12 ( 1 )  2021.06  [Refereed]

    Authorship:Corresponding author

    DOI

  • Single Atom‐Based Nanoarchitectured Electrodes for High‐Performance Lithium–Sulfur Batteries

    Jie Wang, Bing Ding, Xiangjun Lu, Hiroki Nara, Yoshiyuki Sugahara, Yusuke Yamauchi

    Advanced Materials Interfaces   8 ( 8 ) 2002159 - 2002159  2021.04  [Refereed]

     View Summary

    Lithium-sulfur (Li-S) batteries have attracted particular interest as promising next-generation energy storage devices because of their high theoretical energy density and low cost. The real performance of Li-S batteries is, however, far from achieving the expected values, even when using a porous, highly conductive host of sulfurs to improve their electric conductivity and accommodate their volume changes. The performance restrictions are mainly attributable to the slow reaction kinetics of converting lithium polysulfides species to lithium sulfide and elemental sulfur during the charging and discharging processes, respectively. Recent studies show that single-atom catalysts (SACs) with superior catalytic activity offer an effective strategy for solving this tough issue. The recent advances in utilizing SACs for Li-S batteries, which involve catalyst preparation, battery performance, and mechanistic insights, are summarized here. Modification of the cathodes and separators with SACs helps to absorb polysulfide and promote their conversion kinetics, thus suppressing the notorious "shuttle effect." In addition, the introduction of SACs into Li-S batteries promotes the efficiency of Li stripping/plating and prevents the growth of Li dendrites. Overall, the boost effects of SAC on Li-S batteries performance are noticeable and deserving of more research attention to develop better Li-S batteries.

    DOI

  • A kaolinite-tetrabutylphosphonium bromide intercalation compound as an effective intermediate for intercalation of bulky organophosphonium salts

    Shingo Machida, Régis Guégan, Yoshiyuki Sugahara

    Applied Clay Science   206   106038 - 106038  2021.04  [Refereed]

    DOI

  • Loss of a membrane phase under soft confinement conditions imposed by a porous silica colloids network

    Miho Tanimura, Yoshiyuki Sugahara, Régis Guégan

    Colloids and Surfaces A: Physicochemical and Engineering Aspects   608   125554 - 125554  2021.01  [Refereed]

    DOI

  • Ni-Doped Protonated Layered Titanate/TiO2 Composite with Efficient Photocatalytic Activity for NO x Decomposition Reactions

    Kanji Saito, Shota Orikasa, Yusuke Asakura, Yusuke Ide, Yoshiyuki Sugahara, Masataka Ogasawara, Shu Yin, Sumio Kato

    International Journal of Photoenergy   2021   1 - 9  2021.01  [Refereed]

     View Summary

    A unique structural transformation of a lepidocrocite-type layered titanate, K0.8Ti1.73Li0.27O4, into a rutile-type TiO2 has recently been realized via dilute HCl treatment and subsequent drying at room temperature for producing rutile-nanoparticle-decorated protonated layered titanate exhibiting highly efficient photocatalytic activity. Herein, the authors report synthesis of a lepidocrocite-type layered cesium titanate with nominal compositions of <inline-formula>
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    </inline-formula>, 0.05, 0.1, and 0.35) through solid-state reactions of Cs2CO3, TiO2, and Ni(CH3COO)2·4H2O at different temperatures (600 or 800°C), followed by treatment with dilute HCl and subsequent drying to produce a Ni-doped protonated layered titanate/TiO2 composite. <inline-formula>
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    </math>
    </inline-formula> with an optimized Ni content obtained at a lower temperature was converted into a Ni-doped protonated layered titanate/TiO2 composite to exhibit high photocatalytic activity for NO<inline-formula>
    <math xmlns="http://www.w3.org/1998/Math/MathML" id="M5">
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    </inline-formula> decomposition reactions.

    DOI

  • Use of a clay mineral and its nonionic and cationic organoclay derivatives for the removal of pharmaceuticals from rural wastewater effluents

    Tiago De Oliveira, Mohammed Boussafir, Laëtitia Fougère, Emilie Destandau, Yoshiyuki Sugahara, Régis Guégan

    Chemosphere   259   127480 - 127480  2020.11  [Refereed]

    DOI

  • Multiscale structural optimization: Highly efficient hollow iron-doped metal sulfide heterostructures as bifunctional electrocatalysts for water splitting

    Yanna Guo, Xin Zhou, Jing Tang, Shunsuke Tanaka, Yusuf Valentino Kaneti, Jongbeom Na, Bo Jiang, Yusuke Yamauchi, Yoshio Bando, Yoshiyuki Sugahara

    Nano Energy   75   104913 - 104913  2020.09  [Refereed]

    DOI

  • Dual-functional Janus Nanosheets with Cation Exchangeability and Thermo-responsiveness Prepared via Regioselective Modification of K4Nb6O17·3H2O

    Ryoko Suzuki, Naokazu Idota, Taisei Nishimi, Yoshiyuki Sugahara

    Chemistry Letters   49 ( 9 ) 1058 - 1061  2020.09  [Refereed]

    DOI

  • Highly Efficient Surface Modification of Layered Perovskite Nanosheets with a Phosphorus Coupling Reagent Making Use of Microchannels

    Takeshi Sugaya, Régis Guégan, Naokazu Idota, Takehiko Tsukahara, Yoshiyuki Sugahara

    Langmuir   36 ( 26 ) 7252 - 7258  2020.07  [Refereed]

    DOI

  • Phosphorus- and Nitrogen-Doped Carbon Nanosheets Constructed with Monolayered Mesoporous Architectures

    Haibo Tan, Yingji Zhao, Wei Xia, Jiacheng Zhao, Xingtao Xu, Kathleen Wood, Yoshiyuki Sugahara, Yusuke Yamauchi, Jing Tang

    Chemistry of Materials   32 ( 10 ) 4248 - 4256  2020.05  [Refereed]

    DOI

  • Mesoporous Iron-doped MoS2/CoMo2S4 Heterostructures through Organic–Metal Cooperative Interactions on Spherical Micelles for Electrochemical Water Splitting

    Yanna Guo, Jing Tang, Joel Henzie, Bo Jiang, Wei Xia, Tao Chen, Yoshio Bando, Yong-Mook Kang, Md. Shahriar A. Hossain, Yoshiyuki Sugahara, Yusuke Yamauchi

    ACS Nano   14 ( 4 ) 4141 - 4152  2020.04  [Refereed]

    DOI

  • Holey Assembly of Two‐Dimensional Iron‐Doped Nickel‐Cobalt Layered Double Hydroxide Nanosheets for Energy Conversion Application

    Ni Luh Wulan Septiani, Yusuf Valentino Kaneti, Yanna Guo, Brian Yuliarto, Xuchuan Jiang, Yusuke Ide, Nugraha Nugraha, Hermawan Kresno Dipojono, Aibing Yu, Yoshiyuki Sugahara, Dmitri Golberg, Yusuke Yamauchi

    ChemSusChem   13 ( 6 ) 1645 - 1655  2020.03  [Refereed]

    DOI

  • Preparation of Nb-doped TiO2 nanopowder by liquid-feed spray pyrolysis followed by ammonia annealing for tunable visible-light absorption and inhibition of photocatalytic activity

    Kanji Saito, Eongyu Yi, Richard M. Laine, Yoshiyuki Sugahara

    Ceramics International   46 ( 2 ) 1314 - 1322  2020.02  [Refereed]

    DOI

  • Crystalline Porous Organic Polymer Bearing −SO3H Functionality for High Proton Conductivity

    Piyali Bhanja, Arnab Palui, Sauvik Chatterjee, Yusuf Valentino Kaneti, Jongbeom Na, Yoshiyuki Sugahara, Asim Bhaumik, Yusuke Yamauchi

    ACS Sustainable Chemistry & Engineering   8 ( 6 ) 2423 - 2432  2020.02  [Refereed]

    DOI

  • Tuning down the environmental interests of organoclays for emerging pollutants: Pharmaceuticals in presence of electrolytes

    Régis Guégan, Tiago De Oliveira, Julien Le Gleuher, Yoshiyuki Sugahara

    Chemosphere   239   124730 - 124730  2020.01  [Refereed]

    DOI

  • Stabilization of self-assembled lipids in exfoliated organo-nanosheets

    Tomonari Tanaka, Yoshiyuki Sugahara, Régis Guégan

    Chemical Physics Letters   739   136954 - 136954  2020.01  [Refereed]

    DOI

  • Preparation and Comparative Stability of a Kaolinite-Tetrabutylphosphonium Bromide Intercalation Compound for Heat and Solvent Treatments

    Shingo Machida, Régis Guégan, Yoshiyuki Sugahara

    Langmuir   35 ( 42 ) 13553 - 13561  2019.10  [Refereed]

    DOI

  • Preparation of Fe 3 O 4 nanoparticles modified with n-dodecylphosphonic acid via a one-pot nonaqueous process using an oxidation reaction of tetrachloroferrate (III) anions by pyridine-N-oxide

    A. Kamura, M. Ozaki, N. Idota, Y. Sugahara

    Mater. Res. Bull.   118   110475  2019.10  [Refereed]

    DOI

  • Nonaqueous Synthesis of Magnetite Nanoparticles via Oxidation of Tetrachloroferrate Anions by Pyridine-N-Oxide

    A. Kamura, N. Idota, Y. Sugahara

    Solid State Sciences   92   81 - 88  2019.06  [Refereed]

    DOI

  • Interlayer grafting of kaolinite using trimethylphosphate

    S. Machida, N. Idota, Y. Sugahara

    Dalton Trans.   48   11663 - 11673  2019.06  [Refereed]

    DOI

  • Pore shape-reflecting morphosynthesis of lithium niobium oxide via mixed chloride flux growth in the presence of mesoporous silica

    M. Sohmiya, S. Umehara, S. Enomoto, Y. Ide, T. Okada, Y. Sugahara, M. Ogawa

    Nanoscale Adv.   1   1726 - 1730  2019.04  [Refereed]

    DOI

  • Nanoarchitectonics for Transition-Metal-Sulfide-Based Electrocatalysts for Water Splitting

    Y. Guo, T. Park, J. W. Yi, J. Henzie, J. Kim, Z. Wang, B. Jiang, Y. Bando, Y. Sugahara, J. Tang, Y. Yamauchi

    Adv. Mater.   31   1807134  2019.04  [Refereed]

    DOI

  • Surface Modification of Layered Perovskite Nanosheets with a Phosphorus Coupling Reagent in a Biphasic System

    T. Sugaya, M. Ozaki, R. Guegan, N. Idota, Y. Sugahara

    Langmuir   35   6594 - 6601  2019.04  [Refereed]

    DOI

  • Biomolecule-Assisted Synthesis of Hierarchical Multilayered Boehmite and Alumina Nanosheets for Enhanced Molybdenum Adsorption

    I. Saptiama, Y. V. Kaneti, B. Yuliarto, H. Kumada, K. Tsuchiya, Y. Fujita, V. Malgras, N. Fukumitsu, T. Sakae, K. Hatano, K. Ariga, Y. Sugahara, Y. Yamauchi

    Chem. – Eur. J.   25 ( 18 ) 4843 - 4855  2019.03  [Refereed]  [International journal]

     View Summary

    The effective utilization of various biomolecules for creating a series of mesoporous boehmite (γ-AlOOH) and gamma-alumina (γ-Al2 O3 ) nanosheets with unique hierarchical multilayered structures is demonstrated. The nature and concentration of the biomolecules strongly influence the degree of the crystallinity, the morphology, and the textural properties of the resulting γ-AlOOH and γ-Al2 O3 nanosheets, allowing for easy tuning. The hierarchical γ-AlOOH and γ-Al2 O3 multilayered nanosheets synthesized by using biomolecules exhibit enhanced crystallinity, improved particle separation, and well-defined multilayered structures compared to those obtained without biomolecules. More impressively, these γ-AlOOH and γ-Al2 O3 nanosheets possess high surface areas up to 425 and 371 m2  g-1 , respectively, due to their mesoporous nature and hierarchical multilayered structure. When employed for molybdenum adsorption toward medical radioisotope production, the hierarchical γ-Al2 O3 multilayered nanosheets exhibit Mo adsorption capacities of 33.1-40.8 mg g-1 . The Mo adsorption performance of these materials is influenced by the synergistic combination of the crystallinity, the surface area, and the pore volume. It is expected that the proposed biomolecule-assisted strategy may be expanded for the creation of other 3D mesoporous oxides in the future.

    DOI PubMed

  • Continuous mesoporous Pd films with tunable pore sizes through polymeric micelle-assisted assembly

    M. Iqbal, Y. V. Kaneti, K. Kashimura, M. Yoshino, B. Jiang, C. Li, B. Yuliarto, Y. Bando, Y. Sugahara, Y. Yamauchi

    Nanoscale Horiz.   4   960 - 968  2019.02  [Refereed]

    DOI

  • Chemical Design of Palladium-Based Nanoarchitectures for Catalytic Applications

    M. Iqbal, Y. V. Kaneti, J. Kim, B. Yuliarto, Y. M. Kang, Y. Bando, Y. Sugahara, Y. Yamauchi

    Small   15   1804378  2019.02  [Refereed]

    DOI

  • Rational design and construction of nanoporous iron- and nitrogen-doped carbon electrocatalysts for oxygen reduction reaction

    H. Tan, J. Tang, J. Kim, Y. V. Kaneti, Y. M. Kang, Y. Sugahara, Yusuke Yamauchi

    J. Mater. Chem. A   7   1380 - 1393  2019  [Refereed]

    DOI

  • Correction: Competitive Association of Antibiotics with a Clay Mineral and Organoclay Derivatives as a Control of Their Lifetimes in the Environment (ACS Omega (2018) 3:11 (15332-15342) DOI: 10.1021/acsomega.8b02049)

    T. De Oliveira, E. Fernandez, L. Fougère, E. Destandau, M. Boussafir, M. Sohmiya, Y. Sugahara, R. Guegan

    ACS Omega   3   18433  2018.12  [Refereed]

    DOI

  • Hollow Porous Heterometallic Phosphide Nanocubes for Enhanced Electrochemical Water Splitting

    Y. Guo, J. Tang, Z. Wang, Y. Sugahara, Y. Yamauchi

    Small   14   1802442  2018.11  [Refereed]

    DOI

  • Competitive Association of Antibiotics with a Clay Mineral and Organoclay Derivatives as a Control of Their Lifetimes in the Environment

    T. De Oliveira, E. Fernandez, L. Fougère, E. Destandau, M. Boussafir, M. Sohmiya, Y. Sugahara, R. Guegan

    ACS Omega   3   15332 - 15342  2018.11  [Refereed]

    DOI

  • Solid-State 31P Nuclear Magnetic Resonance Study of Interlayer Hydroxide Surfaces of Kaolinite Probed with an Interlayer Triethylphosphine Oxide Monolayer

    S. Machida, M. Sohmiya, Y. Ide, Y. Sugahara

    Langmuir   34   12694 - 12701  2018.10  [Refereed]

    DOI

  • Two-dimensional mesoporous vanadium phosphate nanosheets through liquid crystal templating method toward supercapacitor application

    P. Mei, Y. V. Kaneti, M. Pramanik, T. Takei, O. Dag, Y. Sugahara, Y. Yamauchi

    Nano Energy   52   336 - 344  2018.10  [Refereed]

    DOI

  • Phosphorus-Based Mesoporous Materials for Energy Storage and Conversion

    P. Mei, J. Kim, N. A. Kumar, M. Pramanik, N. Kobayashi, Y. Sugahara, Y. Yamauchi

    Joule   2   2289 - 2306  2018.08  [Refereed]

    DOI

  • Preparation of 3D open ordered mesoporous carbon single-crystals and their structural evolution during ammonia activation

    H. Tan, J. Tang, X. Zhou, D. Golberg, S. K. Bhatia, Y. Sugahara, Y. Yamauchi

    Chem. Commun.   54   9494 - 9497  2018.08  [Refereed]

    DOI

  • Controlled Chemical Vapor Deposition for Synthesis of Nanowire Arrays of Metal-Organic Frameworks and Their Thermal Conversion to Carbon/Metal Oxide Hybrid Materials

    Christine Young, Jie Wang, Jeonghun Kim, Yoshiyuki Sugahara, Joel Henzie, Yusuke Yamauchi

    Chemistry of Materials   30 ( 10 ) 3379 - 3386  2018.05  [Refereed]

     View Summary

    Metal-organic frameworks (MOFs) can serve as high-surface-area templates to generate hierarchically ordered nanoporous carbon electrodes for high-performance supercapacitor devices. Here we describe a simple chemical approach to synthesize dense three-dimensional (3D) arrays of core-shell ZnO@ZIF-8 and Co(CO3)0.5(OH)·0.11H2O@ZIF-67 nanowires on a conductive carbon cloth. Annealing the core-shell structures at high temperatures converted the MOF shell into a composite of nanoporous carbon (NC) mixed with conductive metal oxides. The conformal nature of the MOF-coating process generates a NC film with continuous conductive paths from the outer surfaces of the nanowires down to the flexible carbon electrode. Carbonization of ZIF-67 transforms the material into conductive sp2 type carbon mixed with Co3O4 nanostructures. Because Co3O4 is a faradic metal oxide with a high theoretical capacitance, these Co3O4/NC hybrid heterostructure arrays are a promising candidate material for use in an electrochemical supercapacitor device. The Co3O4/NC hybrid electrodes had good performance and exhibited a high areal capacitance of 1.22 F·cm-2 at 0.5 mA·cm-2. Conformal deposition of MOFs via the chemical vapor method offers a promising new platform to design conductive, ultrahigh surface area electrodes that preserve the 3D morphology for applications in supercapacitors and electrocatalysis.

    DOI

  • Distribution Control-Oriented Intercalation of a Cationic Metal Complex into Layered Silicates Modified with Organosulfonic-Acid Moieties

    Minoru Sohmiya, Takanori Nakamura, Yoshiyuki Sugahara, Makoto Ogawa

    Langmuir   34 ( 16 ) 4762 - 4773  2018.04  [Refereed]

     View Summary

    A layered sodium silicate, octosilicate (Na2Si8O17·nH2O), was modified with an organosulfonic-acid moiety (sulfonated propyl (SPr) group, sulfonated phenethyl (SPhE) group, or sulfonated p-trifluoromethylphenyl (STFPh) group) for use as a host material to accommodate a cationic guest, tris(2,2′-bipyridine)ruthenium(II) cation ([Ru(bpy)3]2+). The organosulfonic-acid moiety was bound to the silicate layer via a reaction of an alkylammonium-exchanged octosilicate with a silane coupling agent, and subsequent treatment (oxidation or sulfonation) of the bound organosilyl groups
    the surface densities of the organosulfonic-acid moiety were varied by controlling the added amount of silane coupling agents. Adsorption of [Ru(bpy)3]2+ onto surface-modified octosilicates was conducted to find that some surface-modified octosilicates successfully adsorbed [Ru(bpy)3]2+ in the interlayer space (intercalation), while other surface-modified octosiliates did not. In addition, the UV-vis absorption and the luminescence indicate that intercalated [Ru(bpy)3]2+ diffused in the interlayer and that the distribution of the time-averaged location varied depending on the kind and amount of the organosulfonic-acid moieties. Thus, the kind and surface density of the organosulfonic-acid moiety, which correlates to the interactions between the group and the guest species, the volume of free nanospace for adsorption and motion of guests, and the swelling properties, are the key factors not only for the intercalation ability but also for the dynamics of the guest in the interlayer space.

    DOI

  • General template-free strategy for fabricating mesoporous two-dimensional mixed oxide nanosheets via self-deconstruction/reconstruction of monodispersed metal glycerate nanospheres

    Yusuf Valentino Kaneti, Rahul R. Salunkhe, Ni Luh Wulan Septiani, Christine Young, Xuchuan Jiang, Yan-Bing He, Yong-Mook Kang, Yoshiyuki Sugahara, Yusuke Yamauchi

    Journal of Materials Chemistry A   6 ( 14 ) 5971 - 5983  2018.04  [Refereed]

     View Summary

    In this work, we propose a general template-free strategy for fabricating two-dimensional mesoporous mixed oxide nanosheets, such as metal cobaltites (MCo2O4, M = Ni, Zn) through the self-deconstruction/reconstruction of highly uniform Co-based metal glycerate nanospheres into 2D Co-based metal glycerate/hydroxide nanosheets, induced by the so-called "water treatment" process at room temperature followed by their calcination in air at 260 °C. The proposed 'self-deconstruction/reconstruction' strategy is highly advantageous as the resulting 2D metal cobaltite nanosheets possess very high surface areas (150-200 m2 g-1) and mesoporous features with narrow pore size distribution. In addition, our proposed method also enables the crystallization temperature to achieve pure metal cobaltite phase from the precursor phase to be lowered by 50 °C. Using the 2D mesoporous NiCo2O4 nanosheets as a representative sample, we found that they exhibit 6-20 times higher specific capacitance and greatly enhanced capacitance retention compared to the NiCo2O4 nanospheres achieved through the direct calcination of the Ni-Co glycerate nanospheres. This highlights another advantage of the proposed strategy for enhancing the electrochemical performance of the mixed oxide products for supercapacitor applications. Furthermore, the asymmetric supercapacitor (ASC) assembled using the 2D NiCo2O4 nanosheets//graphene oxide (GO) exhibits a maximum energy density of 38.53 W h kg-1, while also showing a high capacitance retention of 91% after 2000 cycles at 5 A g-1. It is expected that the proposed general method may be extended to other transition metal elements for creating 2D mixed oxide nanosheets with enhanced surface areas and improved electrochemical performance.

    DOI

  • Inorganic Janus nanosheets bearing two types of covalently bound organophosphonate groups: Via regioselective surface modification of K4Nb6O17·3H2O

    Ryoko Suzuki, Mitsuhito Sudo, Megumi Hirano, Naokazu Idota, Masashi Kunitake, Taisei Nishimi, Yoshiyuki Sugahara

    Chemical Communications   54 ( 45 ) 5756 - 5759  2018  [Refereed]

     View Summary

    Janus nanosheets were prepared from K4Nb6O17·3H2O by modifying surfaces of their two distinct interlayers in a regioselective and sequential manner and subsequent exfoliation. The surface properties of nanosheets were investigated by phase atomic force microscopy imaging and two types of surfaces were discriminated, indicating that Janus nanosheets were successfully prepared.

    DOI

  • Effect of the graft density of cellulose diacetate-modified layered perovskite nanosheets on mechanical properties of the transparent organic-inorganic hybrids bearing covalent bonds at the interface

    Satoru Sato, Kenji Shintani, Naokazu Idota, Takashi Nishino, Yoshiyuki Sugahara

    CELLULOSE   24 ( 12 ) 5463 - 5473  2017.12  [Refereed]

     View Summary

    Transparent organic-inorganic hybrids with a whitish colour were prepared from cellulose diacetate (CDA) nanosheets derived from Dion-Jacobson-type ion-exchangeable layered perovskite HLaNb2O7 center dot xH(2)O (HLaNb) to prepare CDA-based hybrids bearing covalent bonds between HLaNb nanosheets and CDA matrices for improved mechanical properties. An n-decoxy derivative of HLaNb (C10_HLaNb) was exfoliated in acetonitrile by ultrasonication. TEM and AFM images revealed that C10_HLaNb was exfoliated into individual nanosheets. In order to explore the local environment around HLaNb nanosheets, a very small amount of CDA was reacted with a C10_HLaNb nanosheet dispersion [molar ratio COH:(NbOH + NbOC10H21) = 4:1] at 80 A degrees C, and solid-state C-13 NMR with cross polarization and magic angle spinning techniques showed that an alcohol-exchange-type reaction was proceeded to graft the CDA chains to the HLaNb nanosheets via new Nb-O-C covalent linkages. The CDA-based hybrids were prepared by dispersing 5 mass% of HLaNb nanosheets in CDA and subsequent heating at 80 A degrees C for 1-7 days to cause a grafting reaction, and the product prepared by a 1-day grafting reaction exhibited improved mechanical properties compared to neat CDA; the Young's modulus, tensile strength and toughness increased by 18, 34 and 78%, respectively. The mechanical properties deteriorated with further extension of the reaction period, however. In addition, a hybrid film prepared by mixing CDA and a C10_HLaNb nanosheet dispersion exhibited only a slight improvement in mechanical properties. These results clearly indicate that formation of an appropriate number of Nb-O-C bonds at the nanosheet/CDA interfaces is effective for improving mechanical properties.

    DOI

  • Synthesis of mesostructured manganese phosphonate and its promising energy storage application

    Peng Mei, Malay Pramanik, Christine Young, Zhenguo Huang, Md. Shahriar A. Hossain, Yoshiyuki Sugahara, Yusuke Yamauchi

    JOURNAL OF MATERIALS CHEMISTRY A   5 ( 44 ) 23259 - 23266  2017.11  [Refereed]

     View Summary

    Mesostructured manganese phosphonate (MnP) with a uniform nanorod morphology has been prepared through an easy surfactant-mediated procedure, in which cetyltrimethylammonium bromide acts as a structure-directing agent and 1-hydroxyethane 1,1-diphosphonic acid is used as the phosphonic bridging molecule. Suitable interaction between the micelles and precursors is proved to play an essential role in the formation of a mesophase. By optimizing the reaction conditions (e.g., Mn/P ratio, pH, and aging time), a mesostructure can be realized in manganese phosphonate. Furthermore, our MnP sample shows great potential as a high-performance pseudocapacitive material due to the abundant accessible active sites and rapid ion/electron transportation arising from the unique mesostructural architecture.

    DOI

  • Area-selective Surface Modification of Si Substrates with a Fluorescent Organophosphonic Acid Using the Differences in Reactivities of Their Surface Terminal Groups

    Taro Asami, Naokazu Idota, Yoshiyuki Sugahara

    CHEMISTRY LETTERS   46 ( 7 ) 1010 - 1013  2017.07  [Refereed]

     View Summary

    Area-selective surface modification of Si substrates bearing OH-and H-terminated areas by fluorescent 1-pyrenylphosphonic acid (PYPA) was achieved using chlorobenzene at 140 degrees C for 2 h in an autoclave. The OH-terminated area was successfully modified, as shown by X-ray photoemission spectroscopy and contact angle measurement, while no reaction proceeded between PYPA and the H-terminated area. SiO2 nanoparticles were reacted with PYPA under the same conditions to form Si-O-P bonds, suggesting that dehydration coupling proceeded between the OH-terminated area and PYPA.

    DOI CiNii

  • Room-Temperature Rutile TiO2 Nanoparticle Formation on Protonated Layered Titanate for High-Performance Heterojunction Creation

    Kanji Saito, Satoshi Tominaka, Shun Yoshihara, Koji Ohara, Yoshiyuki Sugahara, Yusuke Ide

    ACS APPLIED MATERIALS & INTERFACES   9 ( 29 ) 24538 - 24544  2017.07  [Refereed]

     View Summary

    We report a methodology for creating protonated layered titanate rutile heterojunctions on the outer particle surface of protonated layered titanate by treating layered potassium titanate (K0.8Ti1.73Li0.27O4) with dilute HC1 and then drying it at room temperature under reduced pressure. After Pt co-catalyst loading, this protonated layered titanate/rutile composite with heterojunctions showed higher photocatalytic H-2 evolution activity from water under simulated solar light compared to that of Pt-Poaded P25, the standard photocatalyst for this reaction. The high photo catalytic activity was ascribable to enhanced photocatalytic activity of the protonated layered titanate based on an efficient charge separation at the protonated layered titanate rutile heterojunctions in addition to the sensitization effects of rutile, which absorbs light with longer wavelengths compared to those of protonated layered titanate.

    DOI

  • Enantioselective incorporation of dicarboxylate guests by octacalcium phosphate

    Taishi Yokoi, Shingo Machida, Yoshiyuki Sugahara, Masami Hashimoto, Satoshi Kitaoka

    CHEMICAL COMMUNICATIONS   53 ( 48 ) 6524 - 6527  2017.06  [Refereed]

     View Summary

    Enantioselectivity by octacalcium phosphate (OCP) is revealed through the incorporation of (S)-(-)-methylsuccinic acid (MeSuc) into its crystal lattice, with hardly any (R)-(+)-MeSuc incorporated. This phenomenon clearly indicates that OCP recognizes the steric structures of guest molecules, extending chiral recognition in inorganic materials to three-dimensional crystal growth.

    DOI

  • Synthesis of TiO2-Polythiophene Hybrid Nanotubes and Their Porphyrin Composites

    Noritaka Takeuchi, Shoji Tazawa, Kimihiro Matsukawa, Yoshiyuki Sugahara, Tsukasa Nakahodo, Hisashi Fujihara

    CHEMISTRY LETTERS   46 ( 3 ) 354 - 356  2017.03  [Refereed]

     View Summary

    Template-based electropolymerization of terthienyl-carboxylate-protected TiO2 nanoparticles (1-TiO2 NPs) in a tracketched membrane template produced the corresponding hybrid nanotubes (NTs) of the TiO2 NPs and polythiophene. New multicomponent hybrid NTs consisting of TiO2 NPs, polythiophene, and porphyrin can be synthesized.

    DOI CiNii

  • Borophosphonate Cages as Element-blocks: Ab Initio Calculation of the Electronic Structure of a Simple Borophosphonate, [HPO3BH](4), and Synthesis of Two Novel Borophosphonate Cages with Polymerizable Groups

    Julian Zapico, Marie Shirai, Ryo Sugiura, Naokazu Idota, Hiroyuki Fueno, Kazuyoshi Tanaka, Yoshiyuki Sugahara

    CHEMISTRY LETTERS   46 ( 2 ) 181 - 184  2017.02  [Refereed]

     View Summary

    Ab initio calculations based on the density functional theory (DFT) were performed with respect to the structure and orbital energy values of a simple [HPO3BH](4) cage, and the results were discussed with structural parameters reported for other borophosphonate cages as well as with the calculated orbital energy values of its silsesquioxane analogue, [HSiO1.5](8). In addition, two novel borophosphonate cages capable of use as elementblock monomers were prepared from two boronic acid-t-butylphosphonic acid reactions.

    DOI CiNii

  • Preparation of Element Block by Surface Modification of Magnetite Nanoparticles and Their Application

    KAMURA Atsuo, IDOTA Naokazu, SUGAHARA Yoshiyuki

    Journal of the Japan Society of Powder and Powder Metallurgy   64 ( 3 ) 116 - 120  2017  [Refereed]

     View Summary

    <p>Element blocks, which are composed of various elements, have been widely studied due to their potential application in electric, optical, magnetic and biological fields. Element blocks can be used as functional materials without any further modifications, but it is also possible to polymerize them to prepare element block polymer materials, which are expected to be a series of new functional materials. Magnetite is one of the well-known magnetic oxides, and magnetite nanoparticles are known to exhibit superparamagnetism. In this review, we focus on surface-modified magnetite nanoparticles which can be considered as element blocks. Surface modification of magnetite nanoparticles has been achieved by using silane coupling agents, phosphorus coupling agents, carboxylic acids or alkyl amines based on according to purpose and application to improve their dispersibility and biocompatibility. And magnetite nanoparticles with grafted polymers are potentially useful to the fabrication of magnetite-based medical and biomedical materials. These element blocks prepared from magnetite nanoparticles via surface modification can be applicable to various applications including drug delivery system, hyperthermia and separation of biological matters or heavy metal ions. Examples are demonstrated for typical applications.</p>

    DOI CiNii

  • Modification of TiO2 Nanoparticles with Oleyl Phosphate via Phase Transfer in the Toluene-Water System and Application of Modified Nanoparticles to Cyclo-Olefin-Polymer-Based Organic-Inorganic Hybrid Films Exhibiting High Refractive Indices

    Shiori Takahashi, Shuhei Hotta, Akira Watanabe, Naokazu Idota, Kimihiro Matsukawa, Yoshiyuki Sugahara

    ACS APPLIED MATERIALS & INTERFACES   9 ( 2 ) 1907 - 1912  2017.01  [Refereed]

     View Summary

    Oleyl-phosphate-modified TiO2 nanoparticles (OP_TiO2) were prepared via phase:transfer from an aqueous phase containing dispersed TiO2 nanoparticles to a toluene phase containing oleyl phosphate (OP, a mixture of monoester and diester), and employed for the preparation of OP_TiO2/cyclo-olefin polymer (COP) hybrid films with high-refractive indices. The modification of TiO2 by OP was essentially Completed by reaction at room temperature for 8 h, and essentially all the TiO2 nanoparticles in the aqueous phase were transferred to the toluene phase. The infrared and solid-state C-13 cross-polarization and magic-angle spinning (CP/MAS) NMR spectrum of OP_TiO2 showed the presence of oleyl groups originating from oleyl phosphate. The solid-state P-31 MAS NMR spectrum of OP_TiO2 exhibited new signals at -1.4, 2.1, and 4.8 ppm, indicating the formation of Ti-O-P bonds. CHN and inductively coupled plasma analyses revealed that the major species bound to the TiO2 surface was tridentate CH3(CH2)(7)CH=CH(CH2)(8)P(OTi)(3). These results clearly indicate that the surfaces of the TiO2 nanoparticles were modified by OP moieties via phase transfer. OP_TiO2/COP hybrid films exhibited excellent optical transparency up to 19.1 vol % loading, and the light transmittance of the hybrid films with 19.1 vol % TiO2 loading was 99.8% at 633 nm. The refractive index of these hybrid films rose to 1.83.

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  • Effects of nanostructured biosilica on rice plant mechanics

    Kanako Sato, Noriaki Ozaki, Kazuki Nakanishi, Yoshiyuki Sugahara, Yuya Oaki, Christopher Salinas, Steven Herrera, David Kisailus, Hiroaki Imai

    RSC ADVANCES   7 ( 22 ) 13065 - 13071  2017  [Refereed]

     View Summary

    Nanostructured amorphous silica in rice plants (biosilica or plant opal) plays an important role in plant growth related to food production. However, the same silica has a structural supporting role as well that has not been uncovered. The current study focuses on the structural design of the two main types of biosilicas in rice plants for the improvement of their mechanical properties. One structural motif is platelike silicas, which cover most of the surfaces of leaf blades. Another is fan-shaped silicas, which are aligned inside leaf blades, providing a stiff backbone. These biosilica structures consist of 10-100 nm diameter nanoparticles. The mechanical properties, such as hardness and Young's modulus, of the biosilicas are associated with their relative density. Thus, the rice plant mechanics is inferred to be designed by changing the packing of the nanoparticles. Silica plates consisting of loosely packed particles have relatively low density and high flexibility enabling coverage of leaf blade surfaces, while fan-shaped silicas, which consist of tightly packed nanoparticles, are rigid to support the leaf blades as a backbone.

    DOI

  • Preparation of Transparent Bulk TiO2/PMMA Hybrids with Improved Refractive Indices via an in Situ Polymerization Process Using TiO2 Nanoparticles Bearing PMMA Chains Grown by Surface-Initiated Atom Transfer Radical Polymerization

    Satoshi Maeda, Masato Fujita, Naokazu Idota, Kimihiro Matsukawa, Yoshiyuki Sugahara

    ACS APPLIED MATERIALS & INTERFACES   8 ( 50 ) 34762 - 34769  2016.12  [Refereed]

     View Summary

    Transparent TiO2/PMMA hybrids with a thickness of 5 mm and improved refractive indices were prepared by in situ polymerization of methyl methacrylate (MMA) in the presence of TiO2 nanoparticles bearing poly(methyl methacrylate) (PMMA) chains grown using surface-initiated atom transfer radical polymerization (SI-ATRP), and the effect of the chain length of modified PMMA on the dispersibility of modified TiO2 nanoparticles in the bulk hybrids was investigated. The surfaces of TiO2 nanoparticles were modified with both m-(chloromethyl)phenylmethanoyloxymethylphosphonic acid bearing a terminal ATRP initiator and isodecyl phosphate with a high affinity for common organic solvents, leading to sufficient dispersibility of the surface-modified particles in toluene. Subsequently, SI-ATRP of MMA was achieved from the modified surfaces of the TiO2 nanoparticles without aggregation of the nanoparticles in toluene. The molecular weights of the PMMA chains cleaved from the modified TiO2 nanoparticles increased with increases in the prolonging of the polymerization period, and these exhibited a narrow distribution, indicating chain growth controlled by SI-ATRP. The nanoparticles bearing PMMA chains were well dispersed in MMA regardless of the polymerization period. Bulk PMMA hybrids containing modified TiO2 nanoparticles with a thickness of 5 mm were prepared by in situ polymerization of the MMA dispersion. The transparency of the hybrids depended significantly on the chain length of the modified PMMA on the nanoparticles, because the modified PMMA of low molecular weight induced aggregation of the TiO2 nanoparticles during the in situ polymerization process. The refractive indices of the bulk hybrids could be controlled by adjusting the TiO2 content and could be increased up to 1.566 for 6.3 vol % TiO2 content (1.492 for pristine PMMA).

    DOI

  • Crystallization behavior of cubic boron nitride from an amorphous BN precursor via high-pressure, high-temperature treatment with controlled water addition

    Takahiro Mochizuki, Yusuke Yamamoto, Naokazu Idota, Fumio Kawamura, Takashi Taniguchi, Yoshiyuki Sugahara

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   36 ( 15 ) 3565 - 3569  2016.11  [Refereed]

     View Summary

    Crystallization behavior of cubic boron nitride (c-BN) from amorphous boron nitride (a-BN) by high-pressure, high-temperature (HP-HT) treatment with the intentional addition of a controlled amount of water was studied. The a-BN precursor was prepared by pyrolysis of a boric acid-urea complex with urea/boric acid = 2 at 1000 degrees C for 3 h under an ammonia atmosphere. Hexagonal BN (h-BN) were initially crystallized from a-BN containing 2 mass% of water after HP-HT treatment at 7.7 GPa and 1200 degrees C, and the formation of c-BN was observed after 5 min. The crystallization of c-BN from a-BN containing 8 mass% of water after HP-HT treatment at 7.7 GPa and 1200 degrees C was observed even after 1 min, indicating that the crystallization of c-BN was promoted by increasing the amount of water added. In addition, since neither h-BN nor c-BN was crystallized from a-BN without intentional water addition after the same HP-HT treatment, the addition of water promoted the crystallization of both h-BN and c-BN from a-BN. Since no transformation from h-BN to c-BN was observed during HP-HT treatment at 7.7 GPa and 1200 degrees C, it was concluded that c-BN was directly crystallized from a-BN. After HP-HT treatment at 7.7 GPa and 1650 degrees C for 1 min, both h-BN and c-BN were crystallized from a-BN containing 8 mass% of water. These results clearly indicate that the addition of water has a positive effect on crystallization of c-BN from a-BN. (C) 2016 Elsevier Ltd. All rights reserved.

    DOI

  • Intercalation of n-alkylamines and alkylene diamines into carboxyl functionalized lamellar-type silsesquioxane

    Hironori Ohshita, Machi Ito, Naokazu Idota, Ahmad Mehdi, Bruno Boury, Yoshiyuki Sugahara

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   124 ( 10 ) 1090 - 1093  2016.10  [Refereed]

     View Summary

    A sol-gel-derived carboxyl-functionalized lamellar-type silsesquioxane was prepared to investigate its potential for use as a host material for intercalation reactions with n-alkylamines and alkylene diamines. Upon intercalation of n-alkylamines and alkylene diamines, the interlayer distances increased as shown by X-ray powder diffraction patterns, and IR spectra showed the presence of absorption bands attributable to v(COO-) and delta(NH3+) modes. The amounts of intercalated n-alkylamines were determined from n-CnH2n+1NH2/-COOH molar ratios which, based on CHN analysis, exhibited values from 0.76 to 0.88; whereas the values determined for the alkylene diamines were 0.83 (NH2C4H8NH2), 0.45 (NH2C8H16NH2) and 0.33 (NH2C12H24NH2). These results show that intercalation of n-alkylamines and alkylene diamines into lamellar-type silsesquioxane bearing carboxyl groups proceeded successfully via acid-base mechanisms. (C) 2016 The Ceramic Society of Japan. All rights reserved.

    DOI

  • Remarkable Charge Separation and Photocatalytic Efficiency Enhancement through Interconnection of TiO2 Nanoparticles by Hydrothermal Treatment

    Yusuke Ide, Nozomu Inami, Hideya Hattori, Kanji Saito, Minoru Sohmiya, Nao Tsunoji, Kenji Komaguchi, Tsuneji Sano, Yoshio Bando, Dmitri Golberg, Yoshiyuki Sugahara

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   55 ( 11 ) 3600 - 3605  2016.03  [Refereed]

     View Summary

    Although tremendous effort has been directed to synthesizing advanced TiO2, it remains difficult to obtain TiO2 exhibiting a photocatalytic efficiency higher than that of P25, a benchmark photocatalyst. P25 is composed of anatase, rutile, and amorphous TiO2 particles, and photoexcited electron transfer and subsequent charge separation at the anatase-rutile particle interfaces explain its high photocatalytic efficiency. Herein, we report on a facile and rational hydrothermal treatment of P25 to selectively convert the amorphous component into crystalline TiO2, which is deposited between the original anatase and rutile particles to increase the particle interfaces and thus enhance charge separation. This process produces a new TiO2 exhibiting a considerably enhanced photocatalytic efficiency. This method of synthesizing this TiO2, inspired by a recently burgeoning zeolite design, promises to make TiO2 applications more feasible and effective.

    DOI

  • 無機ナノ構造を利用した表面修飾による元素ブロックの作製とその応用

    Naokazu Idota, Yoshiyuki Sugahara

    セラミックス   51   777 - 780  2016  [Refereed]

  • Fe oxide nanoparticles/Ti-modified mesoporous silica as a photo-catalyst for efficient and selective cyclohexane conversion with O-2 and solar light

    Y. Ide, M. Iwata, Y. Yagenji, N. Tsunoji, M. Sohmiya, K. Komaguchi, T. Sano, Y. Sugahara

    JOURNAL OF MATERIALS CHEMISTRY A   4 ( 41 ) 15829 - 15835  2016  [Refereed]

     View Summary

    We report a new, environmentally and economically friendly photocatalytic process with unprecedentedly high activity for partial cyclohexane oxidation. Mesoporous silicas containing isolated tetra-hedrally coordinated Ti and Fe oxide nanoparticles immobilized on the pore surface were synthesized by reacting SBA-15 with Ti(IV) acetylacetonate and Fe(III) acetylacetonate successively. A variety of characterizations suggested that the grafted tetrahedrally coordinated Ti species were coupled with Fe oxide nanoparticles via Ti-O-Fe bonds. The SBA-15 photocatalysts showed a high yield (up to sub-mmol) and nearly 100% selectivity for the production of cyclohexanol and cyclohexanone with molecular O-2 under solar light. The unprecedentedly high activity could be explained by the lengthened lifetime of the active Ti species by electron delocalization over Ti-O-Fe bonds and the visible light (lambda &gt; 420 nm)-induced activity endowed by Fe oxide nanoparticles coupled to the Ti species.

    DOI

  • h-BN nanosheets as simple and effective additives to largely enhance the activity of Au/TiO2 plasmonic photocatalysts

    Y. Ide, K. Nagao, K. Saito, K. Komaguchi, R. Fuji, A. Kogure, Y. Sugahara, Y. Bando, D. Golberg

    PHYSICAL CHEMISTRY CHEMICAL PHYSICS   18 ( 1 ) 79 - 83  2016.01  [Refereed]

     View Summary

    The activity of Au nanoparticle-loaded P25 TiO2 (Au/P25) plasmonic photocatalysts, evaluated by the oxidative decomposition of formic acid in water under visible light irradiation, was enhanced up to 3 times by simply mixing Au/P25 with photocatalytically inactive h-BN nanosheets as a result of electron transfer from photoexcited Au/TiO2 to the h-BN nanosheets and retardation of the charge recombination.

    DOI

  • Unprecedentedly enhanced solar photocatalytic activity of a layered titanate simply integrated with TiO2 nanoparticles

    Kanji Saito, Misa Kozeni, Minoru Sohmiya, Kenji Komaguchi, Makoto Ogawa, Yoshiyuki Sugahara, Yusuke Ide

    PHYSICAL CHEMISTRY CHEMICAL PHYSICS   18 ( 45 ) 30920 - 30925  2016  [Refereed]

     View Summary

    We report a simple, low-cost methodology for unprecedentedly enhancing the photocatalytic activity of layered inorganic semiconductors. A layered titanate with a lepidocrocite-type structure scarcely showed photocatalytic activity for a test reaction, the oxidative decomposition of formic acid in water into CO2, under simulated solar light, but it showed highly enhanced photocatalytic activity upon mixing with a much smaller amount (approximately 10 wt%) of commercially available TiO2 nanoparticles (P25) in water. The photocatalytic activity of the mixture was approximately 5 times that of P25, a benchmark photocatalyst. From various analyses, the enhancement resulted from the transfer of photoexcited electrons from the layered titanate to P25 at their particle interfaces and retardation of charge recombination. When applied to a photocatalyst for H-2 production from water containing methanol under simulated solar light, the layered titanate/P25 mixture showed considerably enhanced activity and the apparent quantum yield was 23% (at 320 nm). By replacing P25 with Pt co-catalyst-loaded P25, the apparent quantum yield of the mixture increased from 23 to 73%, although an extremely small amount (below 0.06%) of Pt was used in the system.

    DOI

  • Inorganic-organic hybrids by surface modification based on self-assembled monolayers

    Idota, Naokazu, Sugahara, Yoshiyuki

    Kobunshi   64 ( 10 ) 645 - 647  2015.10  [Refereed]

     View Summary

    ? 2015 the Society of Polymer Science, Japan. Design of interfaces is an important factor in control of the structures and properties of inorganic-organic hybrid materials, and surface modification with self-assembly monolayers (SAM) can provide interesting inorganicorganic hybrid materials. Here, we focus on SAM-based surface modification of layered inorganic materials via grafting reactions. Layered perovskites can be modified with alcohols using alcohol-exchange reactions to yield alkoxy-modified products. Methods of surface modification with organophosphonic acids have also been developed for modification of layered perovskites and layered potassium hexaniobate. Modification with organophosphonic acids is more attractive than modification with common silylation reagents, since homocomdensation is unlikely to occur under moderate conditions. Exfoliation of SAM-modified materials provides nanosheets covered with SAM. Since these SAM-modified nanosheets exhibit excellent compatibility with polymers as well as interesting, surface properties, they can be employed for preparation of polymer-based hybrid materials. A similar strategy can be employed for surface modification of titanium oxide nanoparticles.

    CiNii

  • Temperature dependence of Ce:YAG single-crystal phosphors for high-brightness white LEDs/LDs

    Stelian Arjoca, Encarnacinon G. Villora, Daisuke Inomata, Kazuo Aoki, Yoshiyuki Sugahara, Kiyoshi Shimamura

    MATERIALS RESEARCH EXPRESS   2 ( 5 )  2015.05  [Refereed]

     View Summary

    The growth of Ce:Y3Al5O12(Ce:YAG) single-crystal phosphors (SCPs) by the Czochralski technique is analyzed in terms of segregation coefficient, solubility and absorption cross-section. The emission characteristics of these SCPs are investigated in a wide temperature range, from liquid He temperature up to 500 degrees C. The internal quantum efficiency of SCPs achieves its maximum at about 250 degrees C. Thermal quenching of SCPs at high temperature is attributed to the Mott-Seitz mechanism. In the case of ceramic powder phosphors, a continuous droop is observed with the temperature due to defect-related non-radiative recombination paths. It is shown that (Ce:YAG SCPs + blue LEDs/LDs) can cover a wide range of color temperatures 5500-7000 K, with color rendering indices around 70. In conclusion, it is shown that Ce:YAG SCPs are the most efficient and temperature stable converters to fabricate high-brightness white light sources with high-power blue LEDs and LDs.

    DOI

  • Preparation of Thermoresponsive Nanosheets Exhibiting Phase Transitions in Water via Surface Modification of Layered Perovskite Nanosheets with Poly(N-isopropylacrylamide) (PNIPAAm)

    Naokazu Idota, Satoshi Fukuda, Takehiko Tsukahara, Yoshiyuki Sugahara

    CHEMISTRY LETTERS   44 ( 2 ) 203 - 205  2015.02  [Refereed]

     View Summary

    Thermoresponsive inorganic-organic hybrid nanosheets were prepared by surface modification of layered perovskite HLaNb2O7 center dot xH(2)O (HLaNb) with poly(N-isopropylacrylamide) (PNIPAAm) through surface-initiated atom transfer radical polymerization (SI-ATRP). The PNIPAAm-modified HLaNb could be exfoliated into nanosheets, which had a plate-like morphology with a thickness of ca. 25 nm. The aqueous suspension of the PNIPAAm-modified nanosheets in water exhibited phase transitions with increases in temperature to above 34 degrees C. The nanosheets did not form precipitates when dispersed in water, even though the modified polymer chains became hydrophobic at high temperatures.

    DOI CiNii

  • Intercalation of triethylphosphine oxide bearing a phosphoryl group into Dion-Jacobson-type ion-exchangeable layered perovskites

    Nagisa Toihara, Yoriyoshi Yoneyama, Akira Shimada, Seiichi Tahara, Yoshiyuki Sugahara

    DALTON TRANSACTIONS   44 ( 7 ) 3002 - 3008  2015  [Refereed]

     View Summary

    Triethylphosphine oxide [(C2H5)(3)P=O; TEPO] was intercalated into protonated Dion-Jacobson-type ion-exchangeable layered perovskites, HLaNb2O7 center dot xH(2)O (HLaNb) and HCa2Nb3O10 center dot xH(2)O (HCaNb), by hydrolysis of their n-decoxy derivatives (C10O-HLaNb or C10O-HCaNb) in the presence of TEPO. The interlayer distances of the products (TEPO/C10O-HLaNb and TEPO/C10O-HCaNb) were smaller than those of the corresponding n-decoxy derivatives, but still larger than those of anhydrous protonated forms of HLaNb and HCaNb. The solid-state P-31 NMR signals of the products observed at 94 ppm (TEPO/C10O-HLaNb) and 93 ppm (TEPO/C10O-HCaNb) exhibited large downfield shifts from that of the physisorbed TEPO. IR spectroscopy also showed decreases in the nu(P=O) band wavenumbers upon the reactions. These results clearly indicate that TEPO is intercalated and interacted with Bronsted acid sites, the surface hydroxyl groups generated via hydrolysis of n-decoxy groups. The difference in nu(P=O) band wavenumbers as well as that in gallery heights suggests that TEPO exhibited different orientations with respect to the inorganic layers. The chemical shifts of solid-state P-31 NMR signals suggested high Bronsted acidity of HLaNb and HCaNb.

    DOI

  • Preparation of Oleyl Phosphate-Modified TiO2/Poly(methyl methacrylate) Hybrid Thin Films for Investigation of Their Optical Properties

    Masato Fujita, Naokazu Idota, Kimihiro Matsukawa, Yoshiyuki Sugahara

    JOURNAL OF NANOMATERIALS    2015  [Refereed]

     View Summary

    TiO2 nanoparticles (NPs) modified with oleyl phosphate were synthesized through stable Ti-O-P bonds and were utilized to prepare poly(methyl methacrylate)- (PMMA-) based hybrid thin films via the ex situ route for investigation of their optical properties. After surface modification of TiO2 NPs with oleyl phosphate, IR and C-13 CP/MAS NMR spectroscopy showed the presence of oleyl groups. The solid-state P-31 MAS NMR spectrum of the product revealed that the signal due to oleyl phosphate (OP) shifted upon reaction, indicating formation of covalent Ti-O-P bonds. The modified TiO2 NPs could be homogeneously dispersed in toluene, and the median size was 16.1 nm, which is likely to be sufficient to suppress Rayleigh scattering effectively. The TEM images of TiO2/PMMA hybrid thin films also showed a homogeneous dispersion of TiO2 NPs, and they exhibited excellent optical transparency even though the TiO2 content was 20 vol%. The refractive indices of the OP-modified TiO2/PMMA hybrid thin films changed higher with increases in TiO2 volume fraction, and the hybrid thin film with 20 vol% of TiO2 showed the highest refractive index (n = 1.86).

    DOI

  • Chemical processes employing inorganic layered compounds for inorganic and inorganic-organic hybrid materials

    Yoshiyuki Sugahara

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   122 ( 1427 ) 523 - 529  2014.07  [Refereed]

     View Summary

    Recent developments in the preparation of inorganic and inorganic-organic hybrid materials from inorganic layered compounds are reviewed. The focus is placed on three topics: preparation of new ion-exchangeable layered perovskites and a tungstic acid from Aurivillius phases via selective leaching of bismuth oxide sheets; grafting reactions for the preparation of two-dimensional inorganic-organic hybrids; and conversion of two-dimensional inorganic-organic hybrids into inorganic compounds. (C) 2014 The Ceramic Society of Japan. All rights reserved.

    DOI

  • Ce:(Y1-xLux)(3)Al5O12 single-crystal phosphor plates for high-brightness white LEDs/LDs with high-color rendering (Ra &gt; 90) and temperature stability

    Stelian Arjoca, Encarnacion G. Villora, Daisuke Inomata, Kazuo Aoki, Yoshiyuki Sugahara, Kiyoshi Shimamura

    MATERIALS RESEARCH EXPRESS   1 ( 2 ) 25041  2014.06  [Refereed]

     View Summary

    Ce:(Y1-xLux)(3)Al5O12 single-crystals are investigated in detail as phosphors for high-brightness LEDs and LDs. It is demonstrated that single-crystal phosphor plates (SCPPs) present very advantageous characteristics in comparison with standard powder phosphors. On the one side, the very high quantum efficiency of the SCPPs does not decrease with the temperature increase, and on the other side, the SCPPs possess a high thermal conductivity, so that these can be efficiently cooled to avoid device overheating. The optical properties of these SCPPs are investigated from room temperature to 300 degrees C.Ce:Y3Al5O12 SCPPs are adequate for high-brightness cool white light sources. Instead, Ce:(Y1-xLux)(3) Al5O12 SCPPs, whose emission shifts to the green with the Lu concentration, are very promising for neutral and warm white light sources in conjunction with a red-phosphor. It is shown that these white sources exhibit a color rendering over 90 for a wide range of excitation and SCPP emission wavelengths.

    DOI

  • Single- and Double-Layered Organically Modified Nanosheets by Selective Inter layer Grafting and Exfoliation of Layered Potassium Hexaniobate

    Nanako Kimura, Yumi Kato, Ryoko Suzuki, Akira Shimada, Seiichi Tahara, Teruyuki Nakato, Kimihiro Matsukawa, P. Hubert Mutin, Yoshiyuki Sugahara

    LANGMUIR   30 ( 4 ) 1169 - 1175  2014.02  [Refereed]

     View Summary

    Organically modified niobate nanosheets are promising building blocks for the design of advanced hybrid materials. Nanosheets with controlled thickness and surface composition are important for precise structural design of the nanosheet-based materials. In this work, single-layered and Organic double-layered niobate nanosheets functionalized by phenylphosphonate moieties were selectively prepared by interlayer grafting of A-type and B-type intercalation derivatives of potassium hexaniobate (K4Nb6O17 center dot 3H(2)O) with phenylphosphonic acid (PPA), followed by exfoliation by ultrasonication. in acetonitrile. The interlayer grafting of PPA was monitored using X-ray diffraction (XRD), Fourier transform infrared (FTIR), and solid-state NMR spectroscopy, and the thicknesses of the exfoliated nanosheets were measured by atomic force microscopy (AFM). Transparent hybrid films were obtained by incorporating the single- and double-layered nanosheets into an epoxy matrix.

    DOI

  • B1 Liquid-Phase Deposition法を用いたNH_4型γ-リン酸ジルコニウムの合成(口頭発表,一般講演)

    小見山 肇, 小原 岳, 仲田 篤史, 田原 聖一, 井戸田 直和, 菅原 義之

    粘土科学討論会発表論文抄録   58   66 - 67  2014

    DOI CiNii

  • Layered perovskite nanosheets bearing fluoroalkoxy groups: their preparation and application in epoxy-based hybrids

    Yuta Asai, Yusuke Ariake, Hitomi Saito, Naokazu Idota, Kimihiro Matsukawa, Takashi Nishino, Yoshiyuki Sugahara

    RSC ADVANCES   4 ( 51 ) 26932 - 26939  2014  [Refereed]

     View Summary

    Nanosheets bearing CF3(CF2)(7)C2H4O groups on their surface were prepared from a CF3(CF2) 7C2H4O derivative of ion-exchangeable layered perovskite HLaNb2O7 center dot xH(2)O (HLaNb) via exfoliation, and were further utilized to prepare epoxy-based hybrids. The CF3(CF2)(7)C2H4O derivative of HLaNb (C10F_HLaNb) was prepared by reacting the n-decoxy derivative of HLaNb with 1H,1H,2H,2H-perfluorodecanol, CF3(CF2)(7)C2H4OH. TEM and AFM observations revealed that the C10F_HLaNb was exfoliated into individual nanosheets bearing surfaces covered with CF3(CF2)(7)C2H4O groups after ultrasonication in acetonitrile. The nanosheet dispersion in acetonitrile was employed to prepare epoxy-based hybrids, and the FE-TEM image of the epoxy-based hybrid with 5 mass% of the nanosheets (C10F_HLaNb/epoxy_5) showed that the nanosheets were dispersed in the epoxy matrix. Thermogravimetry of C10F_HLaNb/epoxy_5 and neat epoxy resin indicated that the initial mass loss due to water decreased and the thermal decomposition retarded by introducing C10F_HLaNb nanosheets. Dynamic mechanical thermal analysis revealed that the glass transition temperature of C10F_HLaNb/epoxy_5 (161 degrees C) was higher than that of neat epoxy resin (110 degrees C). These results clearly exhibit that thermal properties were improved by incorporating nanosheets bearing hydrophobic CF3(CF2) 7C2H4O groups in the epoxy resin most likely due to a decrease in water content. A water uptake test demonstrated that the water uptake rate of C10F_HLaNb/epoxy_5 was lower than that of the neat epoxy.

    DOI

  • Interlayer Surface Modification of Layered Perovskite HLaNb2O7 center dot xH(2)O with Diol Compounds Possessing Ethylene Oxide Chains

    Shuihei Hotta, Naokazu Idota, Yoshiyuki Sugahara

    ADVANCED CERAMICS AND NOVEL PROCESSING   616   82 - 86  2014  [Refereed]

     View Summary

    Grafting reactions between an n-decoxy derivative of ion-exchangeable layered perovskite HLaNb2O7 center dot xH(2)O and polyethylene glycols (PEGs) with various molecular masses were investigated. X-ray diffraction analysis showed that a reflection corresponding to the interlayer distance of the n-decoxy derivative of HLaNb2O7 center dot xH(2)O (2.73 nm) disappeared and that new diffraction lines ascribable to smaller interlayer distances, which increased with increases in the molecular mass of PEGs, appeared. The solid-state C-13 CP/MAS NMR spectra of the products indicated that ethylene oxide chains were covalently bound to the interlayer surface of HLaNb2O7 center dot xH(2)O. The signal assignable the carbons bound to OH groups suggests that the grafting reactions for the formation of Nb-O-C bonds typically involve one of the terminal OH groups in PEGs.

    DOI

  • Preparation of water-dispersible TiO2 nanoparticles from titanium tetrachloride using urea hydrogen peroxide as an oxygen donor

    Naoko Watanabe, Taichi Kaneko, Yuko Uchimaru, Sayaka Yanagida, Atsuo Yasumori, Yoshiyuki Sugahara

    CrystEngComm   15 ( 48 ) 10533 - 10540  2013.12  [Refereed]

     View Summary

    TiO2 nanoparticles were prepared from titanium tetrachloride (TiCl4) in CH2Cl2 at 80 °C for 30 h, 42 h and 70 h using urea hydrogen peroxide (UHP) as an oxygen donor with a TiCl 4: UHP molar ratio of 1 : 2. The XRD patterns and Raman spectroscopy results showed that the products consisted of anatase TiO2. IR and solid-state 13C NMR with cross polarization and magic angle spinning techniques revealed the presence of urea. TEM observation revealed that the products prepared by the reactions for 30 and 42 h consisted of water-dispersible spheroid nanoparticles with a long axis of ~5 nm, while an aggregation of nanoparticles was evident upon reaction for 70 h. Thermogravimetry, inductively-coupled plasma emission spectrometry and CHN analysis showed that the amount of urea increases in the following order: TiO2-42h, TiO2-70h, TiO2-30h. The photocatalytic activity of the products dispersible in water (TiO 2-30h and TiO2-42h) was estimated based on the degradation behaviour of methylene blue, and TiO2-42h showed higher photocatalytic activity than TiO2-30h. It is proposed that TiCl 4 was directly oxidized by UHP to form anatase TiO2 in the early stage of the process. © 2013 The Royal Society of Chemistry.

    DOI

  • Epoxy-based hybrids using TiO2 nanoparticles prepared via a non-hydrolytic sol-gel route

    Manabu Kobayashi, Hitomi Saito, Bruno Boury, Kimihiro Matsukawa, Yoshiyuki Sugahara

    APPLIED ORGANOMETALLIC CHEMISTRY   27 ( 11 ) 673 - 677  2013.11  [Refereed]

     View Summary

    TiO2 nanoparticles with an average diameter of less than 10 nm were prepared via a non-hydrolytic sol-gel route in a TiCl4-diisopropyl ether-CH2Cl2 system. After modification with n-octylphosphonic acid (OPA) to increase their organophilic character, the TiO2 nanoparticles were used for preparation of TiO2/epoxy hybrid films. Characterization by FT-IR, solid-state C-13 cross-polarization/magic angle spinning (CP/MAS) and P-31 MAS NMR techniques showed the preservation of the n-octyl groups and the presence of TiOP bonds on the surface of TiO2 nanoparticles. Hybrid films with various TiO2 contents were prepared via a wet process and casting using CH2Cl2 as a solvent. The resulting films were highly transparent. The refractive indices of TiO2/epoxy hybrid films at 633 nm increased monotonously from 1.51 for the pure polymer to 1.66 for the hybrid containing 62.4 mass% of TiO2 nanoparticles. Copyright (c) 2013 John Wiley & Sons, Ltd.

    DOI

  • Effects of structural differences in starting materials on the formation behavior of cubic silicon nitride by shock compression

    Yusuke Yamamoto, Hirotaka Yokota, Natsuko Kojima, Shigenobu Hayashi, Takamichi Kobayashi, Toshimori Sekine, Yoshiyuki Sugahara

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   121 ( 1416 ) 741 - 744  2013.08  [Refereed]

     View Summary

    Cubic silicon nitride (c-Si3N4) was prepared at 37-38 GPa and similar to 1773K by shock compression of residues of polysilazane, perhydropolysilazane (PHPS), pyrolyzed at 873, 1073 and 1273 K for 2 h. The residues pyrolyzed at 873 and 1073 K were amorphous materials, while the residue pyrolyzed at 1273 K consisted mainly of crystalline alpha-Si3N4. The relative amount of c-Si3N4 was the smallest in the shock-compressed product of the residue pyrolyzed at 1273 K, indicating that use of amorphous residues is advantageous for formation of c-Si3N4. (C)2013 The Ceramic Society of Japan. All rights reserved.

    DOI

  • Microstructural behavior of gamma-Fe2O3 formation in reactions between layered iron oxychloride and sodium n-pentoxide

    Takeshi Shiono, Fumiaki Tando, Hiromi Nakano, Yoshiyuki Sugahara

    SOLID STATE SCIENCES   19   156 - 161  2013.05  [Refereed]

     View Summary

    Microstructural behavior of gamma-Fe2O3 formation in reactions between FeOCl and n-C5H11ONa was thoroughly investigated. Reactions were conducted at 50-150 degrees C for 3 days in an autoclave using n-C5H11OH as a solvent. X-ray diffraction (XRD) patterns and infrared (IR) spectra of the products suggested the crystallization of gamma-Fe2O3 besides the formation of n-pentoxy derivatives of FeOCl. Scanning electron microscopic observation revealed that the FeOCl particles were divided into thin sheets upon reaction. The selected area electron diffractions (SAED) of the sheets revealed the crystallization of gamma-Fe2O3 at even 80 degrees C, apparently due to the fact that the gamma-Fe2O3 crystallization process involved a collapse from n-pentoxide derivatives with large separations between two adjacent layers. In the reaction at 150 degrees C, a part of the sheets was converted into highly oriented polycrystalline gamma-Fe2O3 in improved crystallinity, and the SAED clearly showed that an oriented transformation with a crystallographic relationship of FeOCl (010)//gamma-Fe2O3 (110) occurred. The reaction at 120 degrees C, on the contrary, led to the formation of randomly oriented gamma-Fe2O3 crystallites within a sheet. (C) 2013 Published by Elsevier Masson SAS.

    DOI

  • Judd-Ofelt analysis and emission quantum efficiency of Tb-fluoride single crystals: LiTbF4 and Tb0.81Ca0.19F2.81

    V. Vasyliev, E. G. Villora, Y. Sugahara, K. Shimamura

    JOURNAL OF APPLIED PHYSICS   113 ( 20 ) 203508  2013.05  [Refereed]

     View Summary

    Terbium is the key element for highly efficient green phosphors and visible-near IR Faraday isolators. We have recently shown the potential of LiTbF4 and Tb0.81Ca0.19F2.81 as visible Faraday rotators. In this work, we present a detail spectroscopic analysis of Tb3+ (4f(8)) in these two compounds with different crystal structures. By means of the Judd-Ofelt theory, the emission branching ratios and lifetimes of the Tb3+ excited states have been estimated. These results are compared with experimental values obtained for the emitting D-5(4) level, as well as with the absolute light yield measurements. Tb3+ in LiTbF4 exhibits a high quantum efficiency, and its radiative lifetime is confirmed to be 7 ms. Instead, the ionic conductor Tb0.81Ca0.19F2.81, which presents a high concentration of vacant sites, shows a lower quantum efficiency and a radiative lifetime about three times larger than estimated. Absorption and emission spectra of Tb0.81Ca0.19F2.81 are broad, so that any fine structure of energy levels can be resolved. In contrast, a detailed study of the splitting of Tb3+ multiplets in Stark energy levels is carried out for LiTbF4. (C) 2013 AIP Publishing LLC.

    DOI

  • Preparation of LiClO4-doped Titanium Organodiphosphonates Possessing Oligomeric Ethylene Oxide Chains and Their Ionic Conductivity

    Hitomi Saito, Masataka Dobashi, Hiroki Naka, Toshiyuki Momma, Tetsuya Osaka, Yoshiyuki Sugahara

    CHEMISTRY LETTERS   42 ( 3 ) 318 - 320  2013.03  [Refereed]

     View Summary

    Hybrids possessing both oligomeric ethylene oxide chains and Ti-O-P networks were prepared from TiCl4 and organodiphosphonic acid [(HO)(2)OP(C2H4O)(3)C2H4PO(OH)(2)] via a nonhydrolytic sol gel process and subsequently treated with a LiClO4 solution. The P/Ti ratio was fixed at 2 and the ethylene oxide unit/Li+ ratio was changed from 5 to 20. Li+ ions are likely to be solvated by ether oxygen atoms. Li+ ion transport in the hybrids with ionic conductivity values in the 10(-5) S cm(-1) range was observed at ambient temperatures.

    DOI

  • Properties of Czochralski grown Ce,Gd:Y3Al5O12 single crystal for white light-emitting diode

    Anastasiya Latynina, Makoto Watanabe, Daisuke Inomata, Kazuo Aoki, Yoshiyuki Sugahara, Encarnacion Garcia Villora, Kiyoshi Shimamura

    JOURNAL OF ALLOYS AND COMPOUNDS   553   89 - 92  2013.03  [Refereed]

     View Summary

    Czochralski grown Ce and Gd-doped Y3Al5O12 (Ce, Gd:YAG) single crystal demonstrated superior performance features in a new concept of white LED where it is used as thin single crystal phosphor plates (SCPPs). New SCPP-based white LED realizes epoxy resin free package, which allows to eliminate the photodegradation issue of the organic material. Optical, thermal and electrical properties of SCPPs and SCPP-based white LEDs are discussed with the powder phosphor and commercial LED reference. SCPPs showed significantly higher values and better stability under the high temperatures, irradiation and current. Quantum efficiency was found to be as high as 93%. (C) 2012 Elsevier B. V. All rights reserved.

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  • Characterization of gas barrier silica coatings prepared from perhydropolysilazane films by vacuum ultraviolet irradiation

    Yuta Kobayashi, Hirotaka Yokota, Yasushi Fuchita, Atsushi Takahashi, Yoshiyuki Sugahara

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   121 ( 1410 ) 215 - 218  2013.02  [Refereed]

     View Summary

    Gas barrier silica coatings were prepared from perhydropolysilazane (PHPS) by vacuum ultraviolet (VUV) irradiation under several irradiation conditions to investigate the relationship between their water vapor transmission rate (WVTR) and the irradiation conditions. PET substrates were coated with PHPS using its xylene solution, and the coatings were irradiated with VUV light (172nm). The oxygen concentrations and irradiation distances were varied. The sample irradiated under conditions of lower oxygen concentration (less than 5%) and shorter irradiation distance (2.6 mm) showed the lowest WVTR (0.721 g m(2) d(-1)). The sample irradiated under conditions of higher oxygen concentration (19%) and longer irradiation distance (13.4 mm), on the other hand, showed the highest WVTR (2.738 g m(2) d(-1)). These results suggest that VUV irradiation improves the gas barrier properties by Si-N bond cleavage rather than by oxidative reactions caused by O(D-1) and O-3. (C)2013 The Ceramic Society of Japan. All rights reserved.

    DOI

  • P21 層状ニオブ酸塩K_4Nb_6O_<17>のn-アルコールによる層表面修飾(ポスター発表,一般講演)

    岩崎 莉沙, 木村 奈々子, 井戸田 直和, 菅原 義之

    粘土科学討論会発表論文抄録   57   184 - 185  2013

    DOI CiNii

  • Analysis of disordered nonstoichiometric single crystals

    Vasyliev, Valentyn, Michiue, Yuichi, Villora, Encarnacion G, Matsushita, Yoshitaka, Sato, Akira, Nagao, Masahiro, Sugahara, Yoshiyuki, Shimamura, Kiyoshi

    ZEITSCHRIFT FUR KRISTALLOGRAPHIE   228 ( 11 ) 576 - 582  2013  [Refereed]

    DOI

  • Preparation, characterization, and surface modification of periodic mesoporous silicon-aluminum-carbon-nitrogen frameworks

    O. Majoulet, C. Salameh, M. E. Schuster, U. B. Demirci, Y. Sugahara, S. Bernard, P. Miele

    Chemistry of Materials   25 ( 20 ) 3957 - 3970  2013  [Refereed]

     View Summary

    Periodic mesoporous silicon-aluminum-carbon-nitrogen (Si/Al/C/N) frameworks with P6mm hexagonal symmetry were synthesized by a solvent nanocasting route using mesoporous carbon (CMK-3) as hard template and preceramic polymers containing both -[R1R2Si-N(R3)]n- and -[R4Al-N(R5)]n- backbones (with R 1 = R2 = R3 = R4 = H and R 5 = CH2CH3) as ceramic precursors. The preceramic polymers are prepared through a simple and cost-effective procedure by blending poly(perhydropolysilazane) and poly(ethyliminoalane) as precursors of silicon nitride/silicon (Si3N4/Si) and carbon-containing aluminum nitride (Al/C/N), respectively. The blended polymers with various and controlled Al:Si ratios were infiltrated into the porous structure of CMK-3, followed by a pyrolysis-template removal cycle performed under nitrogen at 1000 C (2 h, ceramic conversion), then in an ammonia atmosphere at 1000 C (5 h, template removal). This procedure resulted in the formation of periodic mesoporous Si/Al/C/N frameworks with surface areas of 182-326 m2 g-1, a pore size distribution of 4.1-5.9 nm, and pore volumes in the range of 0.51-0.65 cm3 g-1. The uniformity of the mesopores and periodicity of the obtained amorphous micrometer-size powders, studied by transmission electron microscopy (TEM), small-angle X-ray diffraction (SA-XRD), and N2 sorption, are affected by the Al:Si ratio. Amorphous materials did not exhibit weight change up to 1400-1470 C in flowing nitrogen, and their behavior in air, up to 1000 C (with dwelling time of 5 h), is dependent on the proportion of AlN and Si 3N4 phases. The as-obtained powders then were decorated with Pt (nano)particles by impregnation to form supported catalysts. The as-formed catalysts showed attractive reactivity and robustness in our probe reaction, namely, the hydrolysis of an alkaline solution of sodium borohydride at 80 C. Our main results are reported therein. © 2013 American Chemical Society.

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  • Preparation of epoxy-based hybrid films from an aqueous TiO2 dispersion via solvent exchange and surface modification with n-octylphosphonic acid

    Taichi Kaneko, Yoshitaka Kamochi, Hiroyuki Yamamoto, Kimihiro Matsukawa, Yoshiyuki Sugahara

    COMPOSITE INTERFACES   19 ( 9 ) 593 - 601  2012.12  [Refereed]

     View Summary

    Transparent TiO2/epoxy hybrid films with high refractive indices have been prepared from a 9-mass% aqueous TiO2 (rutile form) dispersion by a combination of dispersion medium exchange and surface modification with n-octylphosphonic acid (OPA). The dispersion medium was exchanged from H2O to N-methylformamide (NMF) by distilling off H2O after the addition of NMF. The TiO2 surface was then modified with OPA by heating at 80 degrees C for 24h. IR and NMR spectra of the OPA-modified TiO2 nanoparticles (NPs) revealed that the OPA moiety was grafted onto the surface of the TiO2 NPs through TiOP bonds. The resulting OPA-modified TiO2 NPs were employed to prepare epoxy-based hybrid films possessing excellent transparency. The transmittance in the entire visible range (400800nm) of the hybrid film containing 66.3mass% TiO2 was above 94%. This hybrid film also exhibited the highest refractive index (n=1.74), which represented a remarkable increase from that of the pure epoxy resin film (n=1.51).

    DOI

  • Sol-Gel-derived Bridged Polysilsesquioxane as a Hydrogen Peroxide Decomposition Catalyst: Immobilization of a Dimanganese Complex and Its Improved Thermal Stability

    Hitomi Saito, Akira Ishisone, Yuhei Horikawa, Takeshi Ishiyama, Hideyuki Higashimura, Yoshiyuki Sugahara

    CHEMISTRY LETTERS   41 ( 6 ) 591 - 592  2012.06  [Refereed]

     View Summary

    Bridged polysilsesquioxane possessing dimanganese complex moiety, a model complex for catalase, exhibited catalytic activity for the hydrogen peroxide decomposition reaction without any deactivation. The catalytic activity was mostly retained, even after 24-h acid treatment at 80 degrees C, improving thermal stability after immobilization.

    DOI

  • UV-visible Faraday rotators based on rare-earth fluoride single crystals: LiREF4 (RE = Tb, Dy, Ho, Er and Yb), PrF3 and CeF3

    Valentyn Vasyliev, Encarnacion G. Villora, Masaru Nakamura, Yoshiyuki Sugahara, Kiyoshi Shimamura

    OPTICS EXPRESS   20 ( 13 ) 14460 - 14470  2012.06  [Refereed]

     View Summary

    High optical quality LiREF4 (RE = Tb3+, Dy3+, Ho3+, Er3+ and Yb3+), PrF3 and CeF3 single crystals have been grown by the Czochralski technique. Their magneto-optical properties have been measured and analyzed in detail in the ultraviolet-visible wavelength region, and their figures of merit as Faraday rotators have been determined. CeF3 presents superior properties above 300 nm, showing a figure of merit higher than that of the reference material, terbium-gallium-garnet, which is nowadays used in the visible-near infrared. PrF3 is the best rotator for the 220-300 nm range. Towards shorter wavelength and in the vacuum ultraviolet, it is shown that the LiREF4 crystals are unique rotators. Overall, the rare-earth fluoride single crystals studied here exhibit better properties than other materials considered so far, and therefore they have potential to cover the increasing demand for new and improved Faraday rotators in the ultraviolet-visible wavelength region. (C)2012 Optical Society of America

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  • Preparation of alpha-Zirconium Phosphate from Fluorozirconate and Phosphoric Acid by Liquid-phase Deposition

    Seiichi Tahara, Yoshie Takakura, Yoshiyuki Sugahara

    CHEMISTRY LETTERS   41 ( 5 ) 555 - 557  2012.05  [Refereed]

     View Summary

    alpha-Zirconium phosphate (alpha-ZrP) was prepared by liquid-phase deposition. Boric acid was added to a solution containing [ZrF6](2-) anions, and phosphoric acid dropwise to cause slow decomposition of [ZrF6](2-) and the subsequent reaction with H3PO4 to form alpha-ZrP. X-ray diffraction, scanning electron microscopy, solid-state P-31 nuclear magnetic resonance spectroscopy, infrared spectroscopy, thermogravimetry, and elemental analyses indicate the formation of single-phase alpha-ZrP.

    DOI

  • Synthesis of spherical aggregates of leaf-like YPO4 particles via hydrolysis of tri-n-butylphosphate

    Atsushi Nakata, Kazuhiro Sugiyama, Yoshiyuki Sugahara

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   120 ( 1401 ) 204 - 206  2012.05  [Refereed]

     View Summary

    Spherical aggregates of leaf-like YPO4 particles have been prepared by the reactions of tri-n-butylphosphate [PO(OC4H9)(3), TBP] with the acidic Y(NO3)(3) aqueous solution in an autoclave at 180 degrees C. The products of the reactions for 1,3 and 6 h consisted of an intermediate exhibiting an intense X-ray diffraction line at d approximate to 1.28 nm, while those of reactions for 12-48 h were pure YPO4. The products of the reactions for 8 and 8.5 h were mixtures of the intermediate and YPO4. YPO4 formation thus seems to proceed via the formation of the intermediate. Since the intermediate seems to be Y[PO2(OC4H9)(2)](3), it is likely that TBP was hydrolyzed to form PO2(OC4H9)(2)(-) ions, which then reacted with Y3+ ions to form the solid intermediate, Y[PO(OC4H9)(2)](3). Scanning electron microscopy (SEM) revealed the corresponding morphological change from the belt-like products to spherical aggregates of leaflike particles, indicating that the solid intermediate Y[PO2(OC4H9)(2)](3) was hydrolyzed to form leaf-like YPO4 particles. (C) 2012 The Ceramic Society of Japan. All rights reserved.

    DOI

  • Smoothing of surface of silica glass by heat treatment in wet atmosphere

    Kenta Osawa, Hiroyuki Inoue, Atsunobu Masuno, Keiichi Katayama, Yingjiu Zhang, Futoshi Utsuno, Yoshiyuki Sugahara, Kazuo Koya, Akira Fujinoki, Hiromasa Tawarayama, Hiroshi Kawazoe

    JOURNAL OF APPLIED PHYSICS   109 ( 10 )  2011.05  [Refereed]

     View Summary

    The effect of heat treatment on the surface morphology of fused silica glass substrates was investigated. It was found that the water vapor pressure during heat treatment had a strong influence on the flattening of the silica glass surface. The surface of the frosted glass changed into a transparent and lustrous surface after heat treatment with water vapor at 1200 degrees C for 48 h, whereas surface irregularities remained for heat treatment under a dry atmosphere. It was suggested that the difference in surface flattening was caused by changes in surface viscosity that depended on the concentration of OH groups on the surface. In order to quantitatively understand the effect of the heat treatment atmosphere, power spectral density (PSD) analysis and a novel peak and valley method were applied to the experimental results. From the PSD analysis, it was found that the Mullins&apos; model could not explain the smoothing behavior by heat treatment. The peak and valley method, which could separate the surface morphology into the surface irregularities and the background undulation, revealed that the Mullins&apos; model limitation was mainly for the surface and the background undulation could be understood within the model. These results indicate that there are different mechanisms between for the surface smoothing and for the relaxation of the background undulation. (C) 2011 American Institute of Physics. [doi:10.1063/1.3587229]

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  • Hydrolysis behavior of a precursor for bridged polysilsesquioxane 1,4-bis(triethoxysilyl)benzene: a Si-29 NMR study

    Hitomi Saito, Yuki Nishio, Manabu Kobayashi, Yoshiyuki Sugahara

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   57 ( 1 ) 51 - 56  2011.01  [Refereed]

     View Summary

    The hydrolysis behavior of 1,4-bis(triethoxysilyl)benzene (BTB), a precursor of bridged polysilsesquioxane, was investigated with high-resolution Si-29 nuclear magnetic resonance (Si-29 NMR) spectroscopy at ambient temperature in a system with BTB:ethanol:water:HCl = 1:10:x:0.8 x 10(-4) (x = 3, 6 or 9). Signals due to hydrolyzed triethoxysilyl groups as well as unhydrolyzed triethoxysilyl groups [-Si(OEt)(3), -Si(OEt)(2)(OH), -Si(OEt)(OH)(2) and -Si(OH)(3) (OEt = OCH2CH3)] formed four sub-regions based on the number of hydroxyl groups bound to a silicon atom. In addition, one silicon environment influenced the other silicon environment by an intra-molecular interaction between two silicon atoms, and each sub-region for monomeric species thus contained four signals. Based on the development of signal intensity, it is revealed that one of the two triethoxysilyl groups in BTB is hydrolyzed preferentially. Thus, when a triethoxysilyl group is hydrolyzed, the -Si(OH) (x) (OEt)(3-x) (x = 1, 2) groups formed undergo further hydrolysis, which is opposite to the tendency expected from the hydrolysis behavior of organotrialkoxysilanes under acidic conditions.

    DOI

  • Preparation of Precursors for Si-B-O-C-N Ceramics via Hydrosilylation of Building Blocks with Cyclic Structures

    K. Fuchigami, Y. Uchimaru, Y. Sugahara

    Design, Processing and Properties of Ceramic Materials from Preceramic Precursors     1 - 11  2011  [Refereed]

  • Formation of Si-O-N networks from silsesquiazanes

    Hirotaka Yokota, Noriko Imanari, Yoshiyuki Sugahara

    APPLIED ORGANOMETALLIC CHEMISTRY   24 ( 8 ) 608 - 611  2010.08  [Refereed]

     View Summary

    Silsesquiazanes bearing different groups [RSi(NH)(1.5)](n) (R = C(12)H(25), Ph, H) were hydrolyzed and the resulting products were characterized. (C(12)H(25)Si(NH)(1.5))(n) was hydrolyzed by heating in an autoclave with water at 120 degrees C for 16 h. [PhSi(NH)(1.5)](n) was hydrolyzed by heating with water at 50 degrees C for 16 h. [HSi(NH)(1.5)](n) was dispersed in water at room temperature to induce hydrolysis. In the cases of [C(12)H(25)Si(NH)(1.5)](n) and [PhSi(NH)(1.5)](n), IR analysis showed that Si-NH-Si bonds remained and that terminal Si-NH(2) bonds in silsesquiazane were preferentially hydrolyzed to form Si-OH bonds or Si-O-Si bonds. Solid-state (29)Si CP/MAS NMR analysis revealed the formation of a Si-O-N network containing various Si environments. All the Si-H and Si-N bonds in [HSi(NH)(1.5)](n), on the other hand, were converted into Si-O bonds. These results reveal that Si-O-N networks can be formed from silsesquiazanes bearing dodecyl and phenyl groups under relatively moderate conditions. Copyright (C) 2010 John Wiley & Sons, Ltd.

    DOI

  • Preparation of Phenylsilsesquioxane Films from Phenylsilsesquiazane Possessing Si-N Backbones

    Noriko Imanari, Yoshiyuki Sugahara

    SCIENCE OF ADVANCED MATERIALS   2 ( 2 ) 195 - 199  2010.06  [Refereed]

     View Summary

    Phenylsilsesquiazane (PhSSz) prepared by ammonolysis of phenyltrichlorosilane was spin-coated on Si(100) substrates. The resulting PhSSz films were subsequently converted into phenylsilsesquioxane films via hydrolysis in an autoclave under various hydrothermal conditions. IR spectroscopy revealed that the relative intensities of Si-N-Si and N-H stretching bands decreased, while a Si-O-Si stretching band appeared. Upon heating at 160 degrees C for 72 h with 0.5 mL of water, PhSSz was completely converted into phenylsilsesquioxane. Another poysiloxane film was obtained from a polysilazane prepared by ammonolysis of a mixture of phenyltrichlorosilane and trichlorosilane (PhHSSz). FE-SEM and AFM observations revealed that the phenylsilsesquioxane film and the poysiloxane film had dense structures and smooth surfaces.

    DOI

  • Interlayer surface modification of the protonated ion-exchangeable layered perovskite HLaNb2O7 center dot xH(2)O with organophosphonic acids

    Akira Shimada, Yoriyoshi Yoneyama, Seiichi Tahara, R. Hubert Mutin, Yoshiyuki Sugahara

    CHEMISTRY OF MATERIALS   21 ( 18 ) 4155 - 4162  2009.09  [Refereed]

     View Summary

    The interlayer surface of a protonated form of the Dion-Jacobson-type ion-exchangeable layered perovskite, HLaNb2O7 center dot xH(2)O (HLaNb), has been successfully modified with various organophosphonic acids [phenylphosphonic acid (PhPO(OH)(2), PPA) and n-alkylphosphonic acids (n-CnH2n+1PO(OH)(2) with n = 4-18, APAs)] to produce graft-type organic derivatives using all n-decoxy derivative of HLaNb (C10O-HLaNb) as an intermediate. The interlayer distances of the products are changed from that of the intermediate, 2.73 nm, to 2.31 (PPA/C10O-HLaNb) and 2.31-5.26 (APAs/C10O-HLaNb) nm. IR and solid-state C-13 CP/MAS NMR spectra of the products reveal that n-decoxy groups are removed and phenyl (PPA/C10O-HLaNb) or n-alkyl groups (APA/C10O-HLaNb) are introduced. Elemental analysis reveals that the amounts of PPA- and APA-moieties are 0.88-0.99 per [LaNb2O7], corresponding approximately to the amount of the n-decoxy groups in C10O-HLaNb. The environment of interlayer species in PPA/C10O-HLaNb is assumed to be monodentate PhPO(OH)(ONb) based on the IR results (the P-O stretching and P-OH stretching bands at similar to 1030 and similar to 950 cm(-1)) and the reaction between PPA/C10O-HLaNb and n-butylamine (-NH2/POH = 1.0). Scanning electron micrographs of the products reveal that the morphology is clearly preserved during the reactions with PPA or APAs, indicating that they are graft-type rather than dissolution-recrystallization-type reactions. Because water is required for the reaction between PPA and C10O-HLaNb, this reaction is assumed to proceed via the formation of an (HO)NbO5 site and its subsequent reaction with PPA. A linear relationship is clearly observed between the number of carbon atoms in the n-alkyl chains and the interlayer distances of APAs/C10O-HLaNb, and a structural model of APAs/C10O-HLaNb with a n-alkyl chain tilt angle of 57 degrees is proposed.

    DOI

  • An Inorganic-Organic Hybrid Possessing a Two-dimensional Ti-O Network and Surface Ethoxy Groups Prepared via a Reaction of Titanium Oxychloride with Lithium Ethoxide

    Natsuki Watanabe, Yoshitaka Kamochi, Seiichi Tahara, Nobuhiro Kumada, Yoshiyuki Sugahara

    CHEMISTRY LETTERS   38 ( 3 ) 244 - 245  2009.03  [Refereed]

     View Summary

    A new layered inorganic-organic hybrid possessing a Ti-O network has been prepared by a reaction between titanium oxychloride (TiOCl) and lithium ethoxide (LiOEt) at 120 degrees C for 7 days. The XRD analysis indicates that the interlayer distance of TiOCl increases from 0.80 to 1.19 nm, and the solid-state C-13 NMR spectroscopy and elemental analysis show partial substitution of ethoxy groups for chlorine atoms.

    DOI

  • Single-crystalline Tungsten Oxide Nanoplates

    D. Chen, H. Wang, R. Zhang, L. Gao, Y. Sugahara, A. Yasumori

    J. Ceram. Process. Res.   9   596 - 600  2009

  • Preparation of Precursors for Aluminum Nitride-Based Ceramic Composites from Cage-type and Cyclic Building Blocks

    Yoshiyuki Sugahara, Hiroaki Nakashima, Seiichi Koyama, Yusuke Mori

    SIAIONS AND NON-OXIDES   403   249 - 250  2009  [Refereed]

     View Summary

    Precursors for nitride-based ceramic composites have been prepared from two types of building blocks, cage-type poly(iminoalane) with Al-N backbones and cyclic poly(silazane) with Si-N backbones. Two combinations of poly(iminoalane) and cyclic poly(silazane) were utilized to prepare precursors. For the combination of poly(isopropyliminoalane) and [MeSi(H)NH](n), two building blocks were connected via dehydrocoupling, while Pt-catalyzed hydrosilylation was utilized for the combination of poly(allyliminoalane-co-ethyliminoalane) and [Me(H)SiNH](n). The ceramic yields of poly(iminoalane)s increased upon reactions with [MeSi(H)NH](n).

    DOI

  • Size- and Shape-Controlled Conversion of Tungstate-Based Inorganic-Organic Hybrid Belts to WO3 Nanoplates with High Specific Surface Areas

    Deliang Chen, Lian Gao, Atsuo Yasumori, Kazuyuki Kuroda, Yoshiyuki Sugahara

    SMALL   4 ( 10 ) 1813 - 1822  2008.10

     View Summary

    Two-dimensional monoclinic WO3 nanoplates with high specific surface areas are synthesized through a novel conversion process using tungstate-based inorganic-organic hybrid micro/nanobelts as precursors. The process developed involves a topochemical transformation of tungstate-based inorganic-organic hybrid belts into WO,3 nanoplates via an intermediate product of H2WO4 nanoplates, utilizing the similarity of the W-O octahedral layers in both H2WO4 and WO3. The as-obtained WO3 nanoplates show a single-crystalline nanostructure with the smallest side along the [001] direction. The WO3 nanoplates are 200-500 nm x 200-500 nm x 10-30 nm in size, and their specific surface areas are up to 180 m(2) g(-1). Photocatalytic measurements of visible-light-driven oxidation of water for O-2 generation in the presence of Ag+ ions indicate that the activity of the as-obtained WO3 nanoplates is one order of magnitude higher than that Of commercially available WO3 powders.

    DOI

  • Characterization of Bi5Nb3O15 by refinement of neutron diffraction pattern, acid treatment and reaction of the acid-treated product with n-alkylamines (vol 180, pg 2517, 2007)

    Seiichi Tahara, Akira Shimada, Nobuhiro Kumada, Yoshiyuki Sugahara

    JOURNAL OF SOLID STATE CHEMISTRY   181 ( 8 ) 2121 - 2121  2008.08  [Refereed]

    DOI

  • Synthesis, characterization and formation mechanism of single-crystal WO3 nanosheets via an intercalation-chemistry-based route

    Chen De-Liang, Wang Hai-Long, Zhang Rui, Guan Shao-Kang, Lu Hong-Xia, Xu Hong-Liang, Yang Dao-Yuan, Yoshiyuki Sugahara, Gao Lian

    CHEMICAL JOURNAL OF CHINESE UNIVERSITIES-CHINESE   29 ( 7 ) 1325 - 1330  2008.07  [Refereed]

     View Summary

    In this work an intercalation-chemistry-based method to synthesize tungstate and tungsten oxide nanosheets was described. A layered bismuth tungstate (Bi2W2O9) was used as the W-containing starting material. After the bismuth oxide layers were leached by a chloride acid, a protonated form, H2W2O7 center dot xH(2)O with sizes of 5-15 mu m, was achieved. The intercalation reaction of n-octylamine with H2W2O7 center dot xH(2)O in heptane and the subsequent dissolution-recrystallization process led to the formation of tungstate-based inorganic organic hybrid nanobelts. Orthorhombic WO3 center dot H2O nanosheets were obtained by removing the organic species of the as WO3 center dot H2O nanosheets at 250-450 degrees C, monoclinic WO3 nanosheets were achieved. The results of XRD, TEM and SEM indicate that the obtained WO3 center dot H2O and WO, were single-crystalline nanosheets with areas of (200-500) nm x (200-500) nor and thicknesses of 10-30 nm. The SAED patterns suggest that the WO3 center dot H2O and WO3 nanosheets possessed a reduced directions of [010] and [001], respectively. N-2 adsorption measurement results indicate that the specific surface areas of the as-obtained WO3 center dot H2O and WO3 nanosheets were up to 250 and 180 m(2)/g, respectively. The formation mechanisms for hybrid nanobelts, WO3 center dot H2O and WO3 nanosheets were discussed. The proposed novel route was efficient in producing two-dimensional WO3 nanosheets on a large scale.

  • Single-crystalline tungsten oxide nanoplates

    D. Chen, H. Wang, R. Zhang, L. Gao, Y. Sugahara, A. Yasumori

    J. Ceram. Process. Res.   4   1813 - 1822  2008

    DOI

  • Organic derivatives of the layered perovskite HLaNb(2)O(7)center dot xH(2)O with polyether chains on the interlayer surface: characterization, intercalation of LiClO(4), and ionic conductivity

    Yosuke Takeda, Toshiyuki Momma, Tetsuya Osaka, Kazuyuki Kuroda, Yoshiyuki Sugahara

    JOURNAL OF MATERIALS CHEMISTRY   18 ( 30 ) 3581 - 3587  2008  [Refereed]

     View Summary

    Polyether chains have been successfully grafted onto the interlayer surface of a Dion - Jacobson- type layered perovskite, HLaNb(2)O(7)center dot xH(2)O, by a reaction between an n- decoxy- derivative of HLaNb(2)O(7)center dot xH(2)O and CH(3)(OCH(2)CH(2))(m)OH (1 &lt;= m &lt;= 4). After the reaction, the interlayer distance decreases from 2.73 nm to 1.58 (m = 1), 2.07 (m = 2), 2.28 (m = 3), and 2.69 (m = 4) nm. Solid- state (13)C CP/MAS NMR spectroscopy indicates that the CH(3)(OCH(2)CH(2))(m)O-groups are bound to the interlayer surface of HLaNb(2)O(7)center dot xH(2)O. The n- decoxy groups are completely removed by the reaction with CH(3)(OCH(2)CH(2)) mOH (m = 2 and 3), while a part of the n- decoxy groups remain after the reaction with CH(3)(OCH(2)CH(2))(m)OH (m = 1 and 4). Upon treatment of the CH(3)(OCH(2)CH(2))(m)O-grafted HLaNb(2)O(7)center dot xH(2)O (m = 2 or 3) with a CH(3)(OCH(2)CH(2)) mOH solution of LiClO(4), the interlayer distance decreases further to 1.78 (m = 2) and 2.01 (m = 3) nm. Inductively coupled plasma emission spectrometry reveals the presence of lithium (0.22 (m = 2) and 0.24 (m = 3) per [LaNb(2)O(7)]). The presence of ClO(4)(-) ions is demonstrated by Raman spectroscopy, and the position of the nu(1)(A(1)) band indicates the presence of isolated ClO(4)(-) ions in the interlayer space. After treatment with a LiClO(4) solution, CH(3)(OCH(2)CH(2))(m)O-grafted HLaNb(2)O(7)center dot xH(2)O (m = 2 and 3) exhibits ionic conductivity, and no clear temperature dependence is observed.

    DOI

  • Preparation of a Reduced Layered Tungstic Acid HxW2O9 via Acid Treatment of Bi2W2O9 in the Presence of Sn2+ Ions

    S. Tahara, T. Minato, N. Kumada, S. Hayashi, Y. Sugahara

    Mater. Res. Soc. Symp. Proc.   1056   246 - 251  2008

    DOI

  • Modification of perhydropolysilazane with aluminum hydride: Preparation of poly(aluminasilazane)s and their conversion into Si-Al-N-C ceramics

    Ryoji Toyoda, Satoshi Kitaoka, Yoshiyuki Sugahara

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   28 ( 1 ) 271 - 277  2008  [Refereed]

     View Summary

    Perhydropolysilazane (PHPS) was modified with trimethylamine-alane adduct, AIH(3)center dot NMe(3), with two nominal Si/Al molar ratios (I and 5), and the resulting poly (aluminasilazane)s were pyrolyzed under an N(2) atmosphere. Poly(aluminasilazane) with a nominal Si/Al molar ratio of 5 (PAS5) was insoluble because of the formation of cross-link points via dehydrocoupling. In the system with a nominal Si/Al molar ratio of I (PAS 1), on the contrary, AIH(3-)N center dot Me(3) cleaved the Si-N bonds in addition to forming Al-N bonds, drastically modifying the Si-N backbone of PHPS. In addition, a large portion of aluminium was lost in the PAS1 preparation. Thermogravimetric analysis revealed that PAS5 exhibited a ceramic yield of 78% up to 900 degrees C, while the ceramic yield for PAS1 was 61%. The XRD patterns of the pyrolyzed residues from PAS1 and PAS5 suggest the formation of a 2H wurtzite-type compound and silicon nitride. (c) 2007 Elsevier Ltd. All rights reserved.

    DOI

  • Luminescence of Tris(2,2'-bipyridine)ruthenium(II) cations ([Ru(bpy)(3)](2+)) adsorbed in mesoporous silicas modified with sulfonated phenethyl group

    Minoru Sohmiya, Yoshiyuki Sugahara, Makoto Ogawa

    JOURNAL OF PHYSICAL CHEMISTRY B   111 ( 30 ) 8836 - 8841  2007.08  [Refereed]

     View Summary

    The adsorption of tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)(3)](2+)) complex cation into modified mesoporous silicas was investigated. In order to immobilize [Ru(bpy)(3)](2+), the mesopore surface was modified with sulfonic acid groups by the reactions between MCM-41 and phenethyl(dichloro)methylsilane and the subsequent sulfonation of the attached phenethyl groups with chlorosulfonic acid. The modified mesoporous silicas effectively adsorbed [Ru(bpy)(3)](2+) from ethanol solution. It was thought that the effective adsorption was the cause of the cooperative effects of the electrostatic interactions between [Ru(bpy)(3)](2+) cation and sulfonic acid group and the interactions between the phenyl rings on the mesopore surface and the bipyridine rings of the complex. The variation of the position and the intensity of the luminescence of [Ru(bpy)(3)](2+) suggested that the average distance between the adjacent [Ru(bpy)(3)](2+) changed with the loading amounts.

    DOI

  • Surface modification of titania particles with urushiol (Japanese lacquer) and its application to the preparation of polymer-titania hybrids

    Takeyuki Suzuki, Yusuke Ito, Bruno Boury, Yoshiyuki Sugahara

    CHEMISTRY LETTERS   36 ( 7 ) 856 - 857  2007.07  [Refereed]

     View Summary

    To prepare stable polymer-titania hybrids, titania particles were modified using urushiol (extracted from Japanese lacquer) via surface complexation. The urushiol moieties underwent hydrosilylation and radical graft-polymerization to yield polymer-titania hybrids in which the titania particles were dispersed in polymer matrices.

    DOI

  • Reactivity of the Ruddlesden-Popper phase H2La2Ti3O10 with organic compounds: Intercalation and grafting reactions

    Seiichi Tahara, Tomomichi Ichikawa, Go Kajiwara, Yoshiyuki Sugahara

    CHEMISTRY OF MATERIALS   19 ( 9 ) 2352 - 2358  2007.05  [Refereed]

     View Summary

    A protonated form of the Ruddlesden-Popper-type ion-exchangeable layered perovskite H2La2Ti3O10 (H2LaTi) has been modified with n-alkylamine and n-alcohols to yield intercalation compounds and alkoxy derivatives, respectively. As concerns the intercalation of n-alkylamines into H2LaTi, no reaction of H2LaTi with n-butylamine occurred in anhydrous solvent, and the addition of water was required for the successful intercalation of n-butylamine into H2LaTi. The successful uptake of n-butylammonium ions from an n-butylammonium hydroxide aqueous solution suggests that the intercalation mechanism is of the ion-exchange type rather than the acid-base type. For interlayer surface modification with n-alcohol, no direct reaction of H2LaTi with n-alcohol occurred, but the n-propoxy derivative of H2LaTi formed by using the intercalation compound of H2LaTi with n-butylamine as an intermediate. In addition, reactions between the n-propoxy derivative of H2LaTi and n-alcohols (n-butanol, n-octanol, n-decanol, and n-dodecanol) led to the formation of various n-alkoxy derivatives via an alcohol-exchange-type reaction. As the model for n-alkoxy derivatives of H2LaTi, a bilayer arrangement of the n-alkyl chain possessing an all-trans ordered state with a 75 degrees tilting angle is proposed. The reaction mechanisms of these reactions are also discussed.

    DOI

  • Tungstate-based inorganic-organic hybrid nanobelts/nanotubes with lamellar mesostructures: Synthesis, characterization, and formation mechanism

    Deliang Chen, Yoshiyuki Sugahara

    CHEMISTRY OF MATERIALS   19 ( 7 ) 1808 - 1815  2007.04  [Refereed]

     View Summary

    The formation process of novel tungstate-based inorganic-organic hybrid nanobelts/nanotubes with lamellar mesostructures has been investigated, with an emphasis on monitoring the morphological and microstructural changes of the products during the reactions of H(2)W(2)O(7)center dot xH(2)O (x = 3.49) with n-alkylamines (C(m)H(2m+1)NH(2), 4 &lt;= m &lt;= 14) in a system of heptane/n-alkylamine/H(2)W(2)O(7)center dot xH(2)O (n-alkylamine:H(2)W(2)O(7)center dot xH(2)O molar ratio of about 30) under ambient conditions. The results indicate that normal intercalation occurrs in the early stage to form intercalation compounds with double-octahedral W-O layers, which are then dissolved in the highly alkaline aqueous solutions confined in the reverse-micelle-like media, where the dissolved species recrystallize to form hybrid nanobelts/nanotubes with single-octahedral W-O layers. Both the intercalation compounds obtained after a short reaction time (e.g., 30 min) and the hybrid nanobelts/nanotubers formed after a long reaction time (e.g., 5 days) possess a bilayered arrangement of n-alkyl chains, but their tilt angle in the intercalation compounds (42 degrees) is much smaller than that in the hybrid nanobelts/nanotubes (71 degrees). The interlayer water released from H(2)W(2)O(7)center dot xH(2)O upon intercalation of n-alkylamine reacts with excess n-alkylamine molecules to form highly alkaline aqueous solutions, which have vital effects on the subsequent dissolution of the double-octahedral W-O layers to be single-octahedral layers. In addition, the high molar n-alkylamine:H(2)W(2)O(7)center dot xH(2)O ratios (e.g., 30) are necessary to form tungstate-based inorganic-organic nanobelts/nanotubes, and the nonpolar solvents not only facilitate the reactions between n-alkylamines and H(2)W(2)O(7)center dot xH(2)O but also favor the formation of belt/tubelike morphology.

    DOI

  • Local environments and dynamics of hydrogen atoms in protonated forms of ion-exchangeable layered perovskites estimated by solid-state H-1 NMR

    Shinsuke Tani, Yoshihiko Komori, Shigenobu Hayashi, Yoshiyuki Sugahara

    JOURNAL OF SOLID STATE CHEMISTRY   179 ( 11 ) 3357 - 3364  2006.11  [Refereed]

     View Summary

    The local environments and dynamics of hydrogen atoms in five samples of protonated forms of ion-exchangeable layered perovskites, Dion-Jacobson-type H[LaNb2O7] and H[LaTa2O7], Ruddlesden-Popper-type H-2[SrTa2O7] and H-2[La2Ti3O10], and H-1.8[(Sr0.8Bi0.2)Ta2O7] derived from an Aurivillius phase, Bi2Sr2Ta2O9, have been investigated by solid-state H-1 nuclear magnetic resonance spectroscopy (NMR). Solid-state H-1 NMR with a magic-angle spinning technique conducted at room temperature reveals that the mean electron densities around the H-1 nuclei in these protonated forms are relatively low, and that they decrease in the following order: H-1.8[(Sr0.8Bi0.2)Ta2O7]&gt; H-2[LaNb2O7]&gt; H-2[SrTa2O7]&gt; H[LaTa2O7]&gt; H-2[La2Ti3O10]. The temperature-dependent solid-state H-1 broad-line NMR spectra measured at 140-400 K reveal a decrease in the signal width for all of these five samples upon heating due to motional narrowing. The NMR spectra of H[LaNb2O7] and H[LaTa2O7] are different from the other three protonated forms due to the weaker dipole-dipole interactions at low temperatures and lower mobility of the hydrogen atoms at high temperatures. (c) 2006 Elsevier Inc. All rights reserved.

    DOI

  • Intercalation of alpha,omega-diaminoalkanes in the interlayer space of the protonated form of the layered perovskite H1.8Bi0.2Sr0.8Ta2O7

    Seiichi Tahara, Takashi Yamashita, Go Kajiwara, Yoshiyuki Sugahara

    CHEMISTRY LETTERS   35 ( 11 ) 1292 - 1293  2006.11  [Refereed]

     View Summary

    alpha,omega-Diaminoalkanes (NH2(CH2) NH2; n = 2, 4, 8, and 12) are intercalated in the interlayer space of the protonated form of a layered perovskite, H1.8Bi0.2Sr0.8Ta2O7 (HSrTa). The amounts of a,co-diaminoalkanes, which possess a monolayer arrangement in the interlayer space, are calculated as ca. 0.5 per [Bi0.2Sr0.8Ta2O7]. A model for alpha,omega-diaminoalkane-HSrTa intercalation compounds is proposed, and the model is consistent with that proposed for n-alkylamine-HSrTa intercalation compounds.

    DOI

  • One-pot synthesis of soluble precursors possessing both Al-N and B-N backbones and their pyrolysis

    Yusuke Mori, Yoshiyuki Sugahara

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   79 ( 11 ) 1681 - 1687  2006.11  [Refereed]

     View Summary

    Soluble precursors possessing both Al-N and B-N backbones have been prepared from LiAlH4, LiBH4, and RNH2 center dot HCl (R = Me and Et) in one pot. The infrared (IR) and nuclear magnetic resonance (NMR) spectra of the precursors indicate that the precursors possess Al-H and B-H groups as well as Al-N, B-N, Al-(mu-H)(2)-Al, and Al(mu-H)(2)-B bonds. TG analysis reveals that the ceramic yield of the precursor [AB11_Me (LiAlH4/LiBH4/MeNH2 center dot HCl = 1/1/2)] up to 1000 degrees C under an argon atmosphere is 74.4 mass %. The transmission electron microscopic (TEM) images and the X-ray diffraction (XRD) pattern of AB11_Me that was pyrolyzed at 1600 degrees C indicate that the average size of crystalline aluminum nitride (AlN) is about 14nm and that crystalline AlN particles are distributed homogeneously in an amorphous matrix.

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  • Preparation and pyrolysis of poly(allyl iminoalane-co-ethyl iminoalane)s [HAlN(allyl)]m[HAlNEt](n)

    Yusuke Mori, Yasuhiro Kumakura, Yoshiyuki Sugahara

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   691 ( 20 ) 4289 - 4296  2006.10  [Refereed]

     View Summary

    Poly(allyl iminoalane-co-ethyl iminoalane)s {[HAlN(allyl)](m)[HAlNEt](n); Allyl/Et-alanes}, have been prepared by reactions of lithium hydridoaluminate (LiAlH4) with a mixture of allylamine hydrochloride (CH2=CHCH2NH2 center dot HCl; allylNH(2) center dot HCl) and ethylamine hydrochloride (CH3CH2NH2 center dot HCl; EtNH2 center dot HCl) with various allyl/Et ratios. Spectroscopic analyses indicate that Allyl/Et-alane(1/3) (allyl/Et = 1/3) contains octamers possessing Al-H and C-H groups as well as C=C, Al-N, and C-N bonds. The loss of aluminum during pyrolysis of Allyl/Et-alane(1/3) at 1600 degrees C under an Ar atmosphere is 15%, which is less than the value reported for the pyrolysis of poly(ethyliminoalane) (36%). The suppression can be ascribed to cross-linking reactions involving allyl groups (hydroalumination and polymerization of the allyl groups), judging from infrared (IR) and solid-state nuclear magnetic resonance (NMR) spectroscopy. (c) 2006 Elsevier B.V. All rights reserved.

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  • Pyrolytic conversion of an Al-Si-N-C precursor prepared via hydrosilylation between [Me(H)SiNH](4) and [HAIN(allyl)]m[HAIN(ethyl)](n)

    Yusuke Mori, Yoshiyuki Sugahara

    APPLIED ORGANOMETALLIC CHEMISTRY   20 ( 8 ) 527 - 534  2006.08  [Refereed]

     View Summary

    An iminoalane-silazane polymer (ISP), an Al-Si-N-C precursor, has been synthesized via Pt-catalyzed hydrosilylation between poly(allyl iminoalane-co-ethyl iminoalane) ([HAlN(allyl)](m)[HAlN (ethyl](n) AE-alane) and 1,3,5,7-tetrahydro-1,3,5,7-tetramethylcyclotetrasilazane {[Me(H)SiNH](4), TCS}. The IR and H-1 NMR spectra of ISP indicate that the relative amounts of the allyl groups decrease slightly in comparison with those of AE-alane, suggesting that hydrosilylation occurs partially. TG analysis up to 900 degrees C reveals that the ceramic yield of ISP is 83.1 mass%. It is suggested that the high ceramic yield can be ascribed to cross-linking reactions occurring during pyrolysis. Possible reactions during pyrolysis are hydrosilylation, polymerization of the C=C bonds in the allyl groups and dehydrocoupling among the SiH groups, NH groups and AlH groups in ISP. The pyrolyzed residue at 1700 degrees C contains crystalline AlN, 2H-SiC, beta-SiC and beta-Si3N4 and amorphous carbon, as revealed by solid-state nuclear magnetic resonance (NMR) spectroscopy, Raman spectroscopy and X-ray diffraction (XRD) analysis. Copyright (c) 2006 John Wiley & Sons, Ltd.

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  • Preparation of a nanocomposite consisting of a siloxane network and perovskite-related nanosheets via a sol-gel process

    Seiichi Tahara, Takafumi Okamoto, Yoshiyuki Sugahara

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   7 ( 5 ) 446 - 450  2006.07  [Refereed]

     View Summary

    A nanocomposite possessing perovskite-related nanosheets dispersed in a siloxane network was prepared by cohydrolysis of the n-decoxy derivative of an ion-exchangeable layered perovskite, HCa2Nb3O10.xH(2)O (HCaNb), and tetramethoxysilane (TMOS) via a sol-gel process involving exfoliation. In the X-ray diffraction (XRD) pattern of the product after drying for 1d, the (00l) reflections disappeared. The transmission electron microscopy (TEM) image of the product after drying for 1d showed dark lines with a thickness of 1.5 nm, which was consistent with the thickness of an individual nanosheet, indicating exfoliation of HCaNb. In the XRD patterns of the reaction products of the n-decoxy derivative of HCaNb and TMOS before drying and after drying for 60 min, (00l) reflections were detected. After drying for 80 min, the intensity of the (00l) reflections decreased. The intensity decreased with an increase in the drying time, indicating that the exfoliation of HCaNb occurred during the drying process. (c) 2006 NIMS and Elsevier Ltd. All rights reserved.

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  • Organic-to-inorganic conversion process of a cage-type AIN precursor poly (ethyliminoalane)

    Seiichi Koyama, Hikaru Takeda, Takahisa Tsugoshi, Koji Watari, Yoshiyuki Sugahara

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   114 ( 1330 ) 563 - 566  2006.06  [Refereed]

     View Summary

    The organic-to-inorganic conversion process of cage-type poly (ethyliminoalane), (HAINEt)(n) (n is mainly 8), was investigated by analyzing the gases evolved during pyrolysis. The conversion process can be divided into three temperature ranges: up to 300 degrees C, 300-600 degrees C, and above 600 degrees C. Below 300 degrees C, ethylene and ethylamine were formed probably via Al-N bond cleavage to form nitrogen terminal ( N:), and polymerization of cages could occur via two possible reactions involving nitrogen terminals. The conversion process between 300 and 600 degrees C involved the evolution of ethylene, ethane and methane, whose formation can be attributed to radical reactions. Ethylamine was also formed in this temperature range. Methane formation was also observed in the temperature range above 600 degrees C, and appears to be ascribable to the rearrangement of the mineralized network.

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  • Preparation of Si-Al-N-C ceramic composites by pyrolysis of blended precursors

    Yusuke Mori, Takeshi Ueda, Satoshi Kitaoka, Yoshiyuki Sugahara

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   114 ( 1330 ) 497 - 501  2006.06  [Refereed]

     View Summary

    Si-Al-N-C precursors have been prepared from perhydropolysilazane (PHPS) and cage-type poly (ethyliminoalane) [(HAINEt)(n); PEIA, n is mainly 8] with different Si/Al molar ratios (Si/Al = 3, 1, 1/3). Spectroscopic analysis indicates that essentially no Si-N-Al linkages form, indicating that the precursors are blended polymers. TG analysis reveals that the ceramic yields of the blended precursors up to 900 degrees C are higher than those of PHPS and (HAINEt)n, suggesting that cross-linking reactions occur during pyrolysis. Possible reactions are dehydrocoupling and radical reactions, as suggested by the results of solid-state nuclear magnetic resonance (NMR) spectroscopy. The results of solid-state NMR spectroscopy and X-ray diffraction (XRD) analysis indicate that the residue pyrolyzed at 1600 degrees C contains mainly crystalline AIN, 2H-SiC and beta-SiC.

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  • Preparation of a novel organic derivative of the layered perovskite bearing HLaNb2O7 center dot nH(2)O interlayer surface trifluoroacetate groups

    Y Takeda, H Suzuki, K Notsu, W Sugimoto, Y Sugahara

    MATERIALS RESEARCH BULLETIN   41 ( 4 ) 834 - 841  2006.04  [Refereed]

     View Summary

    Trifluoroacetate (TFA, CF3COO) groups have been successfully bound to the interlayer surface of a protonated form of Dion-Jacobson-type layered perovskite, HLaNb(2)O(7)(.)nH(2)O (HLaNb), via a reaction between its n-propoxy derivative and trifluoroacetic acid (TFAH, CF3COOH). The interlayer distance increases approximately to 1.8 nm upon treatment with TFAH, and varies in the range from similar to 1.7 to similar to 2.0 nm depending on the amount of water adsorbed in the interlayer space. The high stability of the guest species upon dispersal in organic solvents and the change in the infrared (IR) spectrum profile with respect to that of TFAH indicate that the guest species are TFA groups bound to the surface of perovskite-like slabs of HLaNb. The interlayer distance indicates that the TFA groups possess a bilayer arrangement, and a unidentate type of coordination is proposed based on consideration on the coordination geometry. (c) 2005 Elsevier Ltd. All rights reserved.

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  • Novel Materials Derived from Layered Perovskites Using a Chimie Douce Approach

    Seiichi Tahara, Yoshiyuki Sugahara

    ChemInform   37 ( 3 )  2006.01  [Refereed]

    DOI

  • Pyrolytic Organic-to-Inorganic Conversion of Precursors into AlN-A Review

    Yusuke Mori, Yoshiyuki Sugahara

    Journal of the Ceramic Society of Japan   114 ( 1330 ) 461 - 472  2006  [Refereed]

    DOI

  • Organic-to-inorganic conversion process of a cage-type AlN precursor poly (ethyliminoalane)

    Seiichi Koyama, Hikaru Takeda, Takahisa Tsugoshi, Koji Watari, Yoshiyuki Sugahara

    Journal of the Ceramic Society of Japan   114 ( 1330 ) 563 - 566  2006  [Refereed]

     View Summary

    The organic-to-inorganic conversion process of cage-type poly(ethyliminoalane), (HAlNEt)n (n is mainly 8), was investigated by analyzing the gases evolved during pyrolysis. The conversion process can be divided into three temperature ranges: up to 300°C, 300-600°C, and above 600°C. Below 300°C, ethylene and ethylamine were formed probably via Al-N bond cleavage to form nitrogen terminal (≡ N:), and polymerization of cages could occur via two possible reactions involving nitrogen terminals. The conversion process between 300 and 600°C involved the evolution of ethylene, ethane and methane, whose formation can be attributed to radical reactions. Ethylamine was also formed in this temperature range. Methane formation was also observed in the temperature range above 600°C, and appears to be ascribable to the rearrangement of the mineralized network.

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  • Preparation of Si-Al-N-C ceramic composites by pyrolysis of blended precursors

    Yusuke Mori, Takeshi Ueda, Satoshi Kitaoka, Yoshiyuki Sugahara

    Journal of the Ceramic Society of Japan   114 ( 1330 ) 497 - 501  2006  [Refereed]

     View Summary

    Si-Al-N-C precursors have been prepared from perhydropolysilazane (PHPS) and cage-type poly (ethyliminoalane) [(HAlNEt)n
    PEIA, n is mainly 8] with different Si/Al molar ratios (Si/Al-3, 1, 1/3). Spectroscopic analysis indicates that essentially no Si-N-Al linkages form, indicating that the precursors are blended polymers. TG analysis reveals that the ceramic yields of the blended precursors up to 900°C are higher than those of PHPS and (HAlNEt)n, suggesting that cross-linking reactions occur during pyrolysis. Possible reactions are dehydro-coupling and radical reactions, as suggested by the results of solid-state nuclear magnetic resonance (NMR) spectroscopy. The results of solid-state NMR spectroscopy and X-ray diffraction (XRD) analysis indicate that the residue pyrolyzed at 1600°C contains mainly crystalline AlN, 2H-SiC and β-SiC.

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  • Silicon-29 cross-polarization/magic-angle- spinning NMR study of inorganic-organic hybrids: homogeneity of sol-gel derived hybrid gels

    Y Komori, H Nakashima, S Hayashi, Y Sugahara

    JOURNAL OF NON-CRYSTALLINE SOLIDS   351 ( 2 ) 97 - 103  2005.01  [Refereed]

     View Summary

    The structures of sol-gel derived hybrid gels prepared by co-hydrolysis of tetraethoxysilane (TEOS)-organotrialkoxysilane (RTES, RSi(OC2H5)(3), R = CH3, C5H11, C8H17 and C6H5) mixtures (TEOS: RTES: CH3CH2OH: HO: HNO3 = 0.5:0.5:10:x:0.3; x = 2, 5, 10 and 20) were characterized based on signal intensities of Si-29 CP/MAS NMR as a function of the contact time. The contact time dependencies of the signals for Q(4) (Si(OSi)(4)) units were successfully simulated by assuming distributed cross relaxation times (T-SiH) and an intrinsic H-1 spin-lattice relaxation time in the rotating frame (T-1p(H)); the latter was different from the apparent T-1p(H) value estimated by assuming single T-SiH. The distribution ranges of T-SiH for the TEOS-RTES gels broadened as the water content increased, suggesting that the Q(4) units tended to be separated from the T units and that the local concentration of H-1 spins around the Q(4) unit tended to decrease. (C) 2004 Published by Elsevier B.V.

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  • Effects of selective leaching of bismuth oxide sheets in triple-layered Aurivillius phases on their photocatalytic activities

    M Kudo, S Tsuzuki, K Katsumata, A Yasumori, Y Sugahara

    CHEMICAL PHYSICS LETTERS   393 ( 1-3 ) 12 - 16  2004.07  [Refereed]

     View Summary

    The photocatalytic activities of triple-layered Aurivillius phases, Bi(2)A'NaNb3O12 (A'= Sr, Ca) and Bi2CaNaTa3O12, and of protonated forms prepared from these Aurivillius phases through selective leaching of bismuth oxide sheets were investigated. UV-Vis diffuse reflectance spectra showed blue shifts of the adsorption edges upon selective leaching. Although none of the triple-layered Aurivillius phases were active for photocatalytic H-2 evolution from a 20 vol% ethanol solution, all the corresponding protonated forms showed photocatalytic activities for H-2 evolution. The effects of the changes in electronic structures and interlayer surface creation on photocatalytic activities are discussed. (C) 2004 Elsevier B.V. All rights reserved.

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  • Hydrolysis and condensation processes of titanium iso-propoxide modified with catechol: An NMR study

    K Egawa, K Suzaki, Y Sugahara

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   30 ( 2 ) 83 - 88  2004.05  [Refereed]

     View Summary

    The hydrolysis and condensation processes of titanium iso-propoxide modified with catechol (C6H4(OH)(2); H(2)cat) have been investigated by H-1, C-13 and O-17 nuclear magnetic resonance spectroscopy. The hydrolysis reactions of the modified titanium iso-propoxide in the system with Ti:tetrahydrofuran (THF): H2O = 1:20: x (x = 1, 2 and 5 in a molar ratio) are essentially completed in the initial stage (&lt;1 h), and the condensation reactions also proceed significantly during this stage. Upon hydrolysis with H2O/Ti = 1, the iso-propoxy groups are selectively hydrolyzed and the catecholate groups remain bound to titanium. With H2O/Ti = 2 and 5, both the iso-propoxy and catecholate groups are hydrolyzed, and the hydrolysis of the iso-propoxy groups is relatively preferential. Approximately half the catecholate groups are stably bound to titanium, even after hydrolysis with H2O/Ti = 5.

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  • Hydrosilylation in the 2D interlayer space between inorganic layers: reaction between immobilized C=C groups on the interlayer surface of layered perovskite HLaNb2O7 center dot xH(2)O and chlorohydrosilanes

    S Yoshioka, Y Takeda, Y Uchimaru, Y Sugahara

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   686 ( 1-2 ) 145 - 150  2003.11  [Refereed]

     View Summary

    The C-C bonds immobilized in the interlayer space of layered perovskite, HLaNb2O7.xH(2)O, have undergone hydrosilylation reactions with chlorohydrosilanes. The C=C bonds are immobilized by the reaction between an n-propoxyl derivative of HLaNb2O7-xH(2)O and 4-penten-l-ol to form a CH2=CH(CH2)(3)O- derivative of HLaNb2O7.xH(2)O, and a corresponding increase in the interlayer distance from 1.54 to 1.85 nm is observed. The CH2=CH(CH2)(3)O- derivative is further treated with dichloromethylsilane or trichlorosilane, and the interlayer distance increases to 2.41 (dichloromethylsilane) or 2.07 (trichlorosilane) nm. Solid-state C-13-CP/MAS-NMR spectroscopy and infra-red (IR) spectroscopy reveal that the C=C groups disappear after the treatment with dichloromethylsilane or trichlorosilane, and C-13-NMR signals assignable to the hydrosilylated products are clearly observed. Besides hydrosilylation reactions, siloxane formation involving hydrolysis of the Si-Cl groups also proceeds. The structure of the perovskite-like slabs in HLaNb(2)O(7)(.)xH(2)O is preserved throughout the process, indicating the successful modification of immobilized C-C groups via hydrosilylation with no structural change in the inorganic host layers. (C) 2003 Elsevier B.V. All rights reserved.

    DOI

  • Interlayer surface modification of the protonated triple-layered perovskite HCa2Nb3O10 center dot xH(2)O with n-alcohols

    S Tahara, Y Sugahara

    LANGMUIR   19 ( 22 ) 9473 - 9478  2003.10  [Refereed]

     View Summary

    Organic derivatives of the protonated triple-layered perovskite HCa2Nb3O10.xH(2)O with n-alkoxyl groups on the interlayer surface have been prepared by grafting n-alcohols. Interlayer surface modification of HCa2Nb3O10.xH(2)O is achieved by a direct reaction of HCa2Nb3O10.xH(2)O with methanol or ethanol, and single-phase n-alkoxyl derivatives of HCa2Nb3O10.xH(2)O (n greater than or equal to 3 in n-CnH2n+1O-\groups) can be formed by reacting n-alkoxyl derivatives (methoxyl and n-propoxyl derivatives) with n-alcohols in an autoclave at 150 C. X-ray diffraction analysis shows the changes in interlayer distances upon treatment of HCa2Nb3O10.xH(2)O or intermediate n-alkoxyl derivatives with n-alcohols. Solid-state C-13 CP/MAS (cross polarization and magic-angle spinning) NMR spectroscopy demonstrates the presence of signals due to n-alkoxyl groups originating from the reactant n-alcohol molecules. Differential thermal analysis curves of the products exhibit exothermic peaks at temperatures higher than 200 C. These results indicate successful preparation of HCa2Nb3O10.xH(2)O derivatives possessing various n-alkoxyl groups (n-CnH2n+1O-, n = 1-4, 6, 8, 10, 12, 14, 16, and 18) on the interlayer surface. Although a reaction between an n-propoxyl derivative and n-decanol does not proceed at 80 degreesC, a single-phase n-decoxyl derivative can be obtained at 80 C by adding a small amount of water (1 mass %), which strongly suggests a hydrolysis-esterification mechanism. IR and solid-state C-13 CP/MAS NMR spectroscopies indicate that the n-alkyl chains in n-alkoxyl derivatives (n greater than or equal to 10 in n-CnH2n+1O-groups) possess an all-trans conformation. A linear relationship with a slope of 0.166 nm/carbon atom is observed between the interlayer distance and the number of carbon atoms in the n-alkyl chains, suggesting that the n-alkyl chains of n-alkoxyl groups are present as bilayers with a tilt angle of 41 in the interlayer space.

    DOI

  • A layered tungstic acid H2W2O7 center dot nH(2)O with a double-octahedral sheet structure: Conversion process from an aurivillius phase Bi2W2O9 and structural characterization

    M Kudo, H Ohkawa, W Sugimoto, N Kumada, Z Liu, O Terasaki, Y Sugahara

    INORGANIC CHEMISTRY   42 ( 14 ) 4479 - 4484  2003.07  [Refereed]

     View Summary

    The conversion process of an Aurivillius phase, Bi2W2O9, into a layered tungstic acid by hydrochloric acid treatment has been investigated, and resultant H2W2O7.nH(2)O has been fully characterized. The c parameter of Bi2W2O9 (2.37063(5) nm] decreases to 2.21(1) nm in an acid-treated product dried at ambient temperature. The a and b parameters of Bi2W2O9 [a = 0.54377(1) nm and b = 0.54166(1) nm] also decrease slightly to a = 0.524(1) nm and b = 0.513(1) nm in the acid-treated product dried at ambient temperature, indicating structural changes in the ReO3-like slabs in Bi2W2O9 upon acid treatment. Drying at 120 degreesC leads to a further decrease in the c parameter (1.86(1) nm] with no notable change in the a and b parameters [a = 0.5249(2) nm and b = 0.513(2) nm]. The formation of an expandable layered structure is demonstrated by the successful intercalation of n-octylamine [interlayer distance 2.597(9) nm] and n-dodecylamine (interlayer distance 3.56(2) nm]. The compositions of the acid-treated products are determined to be H2W2O7-nH(2)O typically with n = 0.58 for the air-dried product and n = 0 for the product dried at 120 degreesC. As a consequence, the composition of the layer is H2W2O7, and the decrease in the c parameter upon drying is ascribable to the loss of interlayer water. Scanning electron microscopy reveals no morphological change during acid treatment, which strongly suggests a selective leaching of the bismuth oxide sheets as a reaction mechanism. High-resolution transmission electron microscopy (HREM) observation of the acid-treated product shows consistency with a structural model for H2W2O7, derived from Bi2W2O9 through removal of the bismuth oxide sheets and contraction along the c axis. HREM observation also reveals that the WO6 octahedra arrangement changes slightly with acid treatment. A one-dimensional electron density map projected on the c axis for the product dried at 120 degreesC, H2W2O7, shows good consistency with that calculated for the structural model.

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  • Reactions of alkoxyl derivatives of a layered perovskite with alcohols: Substitution reactions on the interlayer surface of a layered perovskite

    H Suzuki, K Notsu, Y Takeda, W Sugimoto, Y Sugahara

    CHEMISTRY OF MATERIALS   15 ( 3 ) 636 - 641  2003.02  [Refereed]

     View Summary

    Organic derivatives of a layered perovskite compound, HLaNb2O7.xH(2)O (HLN), with interlayer surfaces possessing n-alkoxyl groups (n-decoxyl and n-propoxyl) have been allowed to react with various alcohols and a diol (ethylene glycol) to form new organic derivatives via substitution reactions. The reaction of an n-propoxyl derivative of HLN with n-decanol leads to the formation of n-decoxyl groups bound to the interlayer surface of the perovskite-like [LaNb2O7] slab. In a similar fashion, the reaction of an n-decoxyl derivative of HLN with 2-propanol results in the formation of an isopropoxyl derivative. The reaction of the n-decoxyl derivative of HLN with tert-butyl alcohol also proceeds, though the reaction is not completed even after 14 days. After the reaction of the n-decoxyl derivative of HLN with ethylene glycol, only one of the two hydroxyl groups in ethylene glycol is reacted, and -OCH2-CH2OH groups are present on the interlayer surface. Water is required for proceeding the substitution reaction between the n-propoxyl derivative of HLN and n-decanol, and the reaction mechanism involving hydrolysis of the alkoxyl groups on the interlayer surface and subsequent esterification is proposed.

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  • Intercalation behavior of n-alkylamines into a protonated form of a layered perovskite derived from Aurivillius phase Bi2SrTa2O9

    Y Tsunoda, W Sugimoto, Y Sugahara

    CHEMISTRY OF MATERIALS   15 ( 3 ) 632 - 635  2003.02  [Refereed]

     View Summary

    Intercalation behavior of n-alkylamines into a protonated form of a layered perovskite, H-1.8[Sr0.8Bi0.2Ta2O7] derived from an Aurivillius phase, Bi2SrTa2O9, has been investigated. H-1.8[Sr0.8Bi0.2Ta2O7] can accommodate n-alkylamines (CmHm+1NH2; m = 4, 8, 12, 18) to form intercalation compounds via an acid-base mechanism. The interlayer distance increases to 2.071(2) (m = 4) 2.840(9) (m = 8), 3.83(1) (m = 12), and 5.17(2) (m = 18) nm. In contrast, H-1.8[Sr0.8Bi0.2Ta2O7] does not form any intercalation compound with pyridine, which is a weaker base, indicating that the protons in H-1.8[Sr0.8Bi0.2Ta2O7] are weakly acidic. The IR spectra of the intercalation compounds with n-alkylamines (m = 12 and 18) clearly show that n-alkyl chains possess an all-trans conformation. A linear relationship is observed between the interlayer distance and the number of carbon atoms in n-alkyl chains, and this corresponds to a bilayer arrangement of the n-alkyl chains with a tilt angle of 60degrees. Despite the relatively high proton content (1.8 H+ per [Sr0.8Bi0.2Ta2O7]), only 0.9-1.0 mol of n-alkylamines per [Sr0.8Bi0.2Ta2O7] is intercalated. This observation can be reasonably interpreted based on the surface geometry of the perovskite-like slab and the size of n-alkylamines.

    DOI

  • Preparation and Pyrolysis of Polyphosphosilazane

    Y. Mori, R. Toyoda, S. Kitaoka, Y. Sugahara

    Trans. Mater. Res. Soc. Jpn.   28 ( 2 ) 305 - 308  2003  [Refereed]

  • Chemical modification of niobium pentaethoxide with catechol

    K Egawa, K Minami, Y Sugahara

    ADVANCED CERAMICS AND COMPOSITES   247 ( 401 ) 401 - 404  2003  [Refereed]

     View Summary

    Chemical modification of niobium pentaethoxide (Nb(OCH2CH3)(5); Nb(OEt)(5)) with catechol (C6H4(OH)(2); H(2)cat) was investigated using infrared spectroscopy, H-1 and C-13 nuclear magnetic resonance spectroscopy, compositional analysis and mass spectrometry. Niobium pentaethoxide was chemically modified with catechol by the formation of catecholate groups (cat(2-)) bound to niobium, and a corresponding release of ethanol Was observed. The obtained product was [(cat)Nb(OEt)(3)](n), which included the dimmer [(cat)Nb(OEt)(3)](2).

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  • Conversion process of strontium-titanium bimetallic methoxyethoxide precursor into SrTiO3 via hydrolysis/calcination

    J Okayama, Takaya, I, K Nashimoto, Y Sugahara

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   85 ( 9 ) 2195 - 2199  2002.09  [Refereed]

     View Summary

    The conversion of a Sr-Ti bimetallic methoxyethoxide precursor into SrTiO3 via hydrolysis and/or calcination was investigated. Hydrolysis with various water/metal molar ratios (r(H); r(H) = 0.5, 2, 4, 6, 8, 10) in tetrahydrofuran at reflux resulted in a decrease in the amount of the methoxyethoxyl groups, and the hydrolyzed products were soluble with r(H) less than or equal to 2. At r(H) greater than or equal to 8, SrTiO3 was crystallized without calcination. Both the hydrolyzed and unhydrolyzed precursors (r(H) = 0, 0.5, 2) were calcined in dry air at 550degrees-800degreesC. SrTiO3 was crystallized on calcination at greater than or equal to550degreesC from amorphous materials with a considerable loss of carbon, which was present as both chars and carbonate ions.

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  • Conversion of Aurivillius phases Bi(2)ANaNb(3)O(12) (A = Sr or Ca) into the protonated forms of layered perovskite via acid treatment

    W Sugimoto, M Shirata, K Kuroda, Y Sugahara

    CHEMISTRY OF MATERIALS   14 ( 7 ) 2946 - 2952  2002.07  [Refereed]

     View Summary

    Protonated forms of layered perovskites were derived from Aurivillius phases, Bi(2)ANaNb(3)O(12) (A = Sr or Ca), by the substitution of bismuth oxide sheets with protons via acid treatment. The conversion into the protonated forms was achieved easily using 6 M HCl at room temperature. Preservation of the structure of the perovskite-like slabs and contraction in the e axis were confirmed by X-ray and electron diffraction analysis as well as by transmission electron microscopy. The compositions of the resulting products were determined to be H-1.8[A(0.8)Bi(0.2)NaNb(3)O(10)] (A = Sr or Ca) by inductively coupled plasma emission spectroscopy and thermogravimetry. The acid-treated product H-1.8[Sr0.8Bi0.2NaNb3O10] was capable of accommodating n-alkylamines in the interlayer space, which is in good agreement with the proposed layered structure.

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  • Conversion of a precursor derived from cage-type and cyclic molecular building blocks into Al-Si-N-C ceramic composites

    H Nakashima, S Koyama, K Kuroda, Y Sugahara

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   85 ( 1 ) 59 - 64  2002.01  [Refereed]

     View Summary

    A precursor derived from (HAIN(i)Pr)(m) and [MeSi(H)NH](n), which mainly consisted of cage-type compounds and cyclic compounds, respectively, was converted into Al-Si-N-C ceramic composites via pyrolysis. A dehydrocoupling reaction between AlH groups and NH groups occurred at low temperatures (less than or equal tosimilar to250degreesC), which mainly accounts for its high ceramic yield (69% up to 900degreesC). At high temperatures (greater than or equal tosimilar to250degreesC), the organic groups were decomposed. The product pyrolyzed at 1350degrees and 1500degreesC under Ar contained a 2H wurtzite-type compound and a beta-Si3N4-type compound, while beta-SiC was clearly detected in addition to these compounds in the product pyrolyzed at 1600degreesC under Ar. On the other hand, the product pyrolyzed at 800degreesC under NH3 and subsequently at 1350degreesC under N-2 consisted of AIN and beta-Sialon.

    DOI

  • Preparation and HREM characterization of a protonated form of a layered perovskite tantalate from an Aurivillius phase Bi2SrTa2O9 via acid treatment

    Y Tsunoda, M Shirata, W Sugimoto, Z Liu, O Terasaki, K Kuroda, Y Sugahara

    INORGANIC CHEMISTRY   40 ( 23 ) 5768 - 5771  2001.11  [Refereed]

     View Summary

    An Aurivillius phase, Bi2SrTa2O9, which consists of perovskite-like stabs and bismuth oxide sheets, was treated with 3 M hydrochloric acid for 72 h, and the resultant product was characterized. Scanning electron microscopy investigation indicated that no morphological change occurred during the acid treatment. X-ray diffraction (XRD) analysis revealed that the product exhibited tetragonal symmetry with a = 0.391 +/- 0.004 run and c = 0.98 +/- 0.01 run, and the a parameter is consistent with a typical value for cubic perovskite oxides. High-resolution electron microscopy (HREM) observations along both [001] and [010] showed that the structure of the perovskite-like slabs in Bi2SrTa2O9 was retained after the acid treatment. The compositional analyses revealed the loss of a large portion of bismuth and a part of strontium (present in the bismuth oxide sheets due to B &lt;----&gt; Sr disorder) and the introduction of protons. These observations indicate that the bismuth oxide sheets in Bi2SrTa2O9 were selectively leached and that protons were introduced into the interlayer space to form a protonated layered perovskite, H-1.8[Sr0.8Bi0.2Ta2O7]. Though diffraction techniques (XRD and electron diffraction) demonstrated that an average structure of H-1.8[Sr0.8Bi0.2Ta2O7] consisted of perovskite-like slabs stacked without displacement, HREM observation along [010] demonstrated that both a simple stacking sequence without displacement (P-type) and a stacking sequence with a relative displacement by (a + b)/2 (I-type) were present in H-1.8[Sr0.8Bi0.2Ta2O7].

    DOI

  • Interlamellar esterification of H-magadiite with aliphatic alcohols

    Y Mitamura, Y Komori, S Hayashi, Y Sugahara, K Kuroda

    CHEMISTRY OF MATERIALS   13 ( 10 ) 3747 - 3753  2001.10  [Refereed]

     View Summary

    Magadiite, a layered sodium polysilicate, was organically modified by esterification of interlayer silanol groups with various aliphatic alcohols. Methanol was directly reacted with H-magadiite (acid-treated magadiite) by refluxing. The methanol-treated product showed an increase in the basal spacing and the C-13 NMR signals due to methyl groups. The H-2 NMR spectrum of CD3OD-treated H-magadiite showed Pake doublet patterns of quadrupole coupling constants of 43 and 48 kHz and asymmetry factors of 0, indicating the fixation of the C-O axis. When aliphatic alcohols with the carbon chain length longer than 4 were used, an H-magadiite/N-methylformamide (NMF) intercalation compound was used as an intermediate for esterification. The basal spacing of butanol-treated H-magadiite was 1.40 nm, the value of which was smaller than that of H-magadiite/NMF (1.63 nm) and larger than that of H-magadiite (1.15 nm). C-13 spin-lattice relaxation times (T-1) of butyl groups showed a low mobility of the alpha carbon. Other alcohols (CnH2n+1OH (n = 2-16) and (CH3)(3)COH) were also reacted with the silanol groups. The differential thermal analysis (DTA) curves of the products showed exothermic peaks. The alkyl chains are apparently lying parallel to the inner surface because almost constant basal spacings were observed despite the variation in the alkyl chain length. The butanol-treated H-magadiite was dispersed in toluene and cast, resulting in the formation of a transparent nanocomposite film.

    DOI

  • Control of hydrolysis and condensation reactions of titanium tert-butoxide by chemical modification with catechol

    H Honda, K Suzaki, Y Sugahara

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   22 ( 1-2 ) 133 - 138  2001.09  [Refereed]

     View Summary

    Titanium tert-butoxide (Ti(OC(CH3)(3))(4); Ti((OBu)-Bu-t)(4)) was chemically modified with catechol (C6H4(OH)(2)) and hydrolysis and condensation behavior of a resultant modified alkoxide was studied. Spectroscopic results revealed that the reaction between titanium tert-butoxide and catechol resulted in the formation of catecholate groups (C6H4O22-) bound to titanium and corresponding release of tert-butanol. The mass spectrometry and cryoscopy indicated that main species was a dimer [(C6H4O2)(2)Ti-2((OBu)-Bu-t)(4)]. The hydrolysis of the modified alkoxide in the system with Ti:tetrahydrofuran (THF):H2O = 1:10:x (x = 0.5-10) resulted in the partial hydrolysis, and all the hydrolyzed products after the drying under reduced pressure were soluble in THF and chloroform.

    DOI

  • Preparation and pyrolysis of a blended precursor possessing Ti-N and Al-N bonds

    F Cheng, Y Sugahara, K Kuroda

    APPLIED ORGANOMETALLIC CHEMISTRY   15 ( 8 ) 710 - 716  2001.08  [Refereed]

     View Summary

    The preparation and pyrolysis of a blended precursor possessing Ti-N and Al-N bonds were investigated. The precursor was prepared by mixing (HAIN(i)Pr)(n), whose main component was a cage-type compound, and an aminolysis product of Ti(NMe2)(4) with MeHNCH2CH2NHMe with a molar ratio of Ti:Al = 2:1. IR analysis of the products pyrolyzed under NH3-N-2 indicated that a large proportion of the organic groups in the precursor were removed by an amine-exchange reaction during the pyrolysis under NH3; thus, the products contained only a small amount of carbon. On the contrary, a considerable amount of carbon was present in the product pyrolyzed under Ar. Composites consisting of AIN and an NaCl-type compound were obtained after pyrolysis of the precursor under both NH3-N-2 and Ar. The composition of the NaCl-type compound depended significantly on the pyrolysis atmosphere. Copyright (C) 2001 John Wiley & Sons, Ltd.

    DOI

  • Preparation of a kaolinite-nylon 6 intercalation compound

    A Matsumura, Y Komori, T Itagaki, Y Sugahara, K Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   74 ( 6 ) 1153 - 1158  2001.06  [Refereed]

     View Summary

    A kaolinite-nylon 6 intercalation compound was prepared by the polymerization of 6-aminohexanoic acid (AHA) in the interlayer space of kaolinite. The intercalation of AHA was achieved by a guest displacement reaction using a kaolinite-methanol intercalation compound as an intermediate. After AHA dissolved in a mixed solvent of methanol and water (1:3) was added to a kaolinite-methanol intercalation compound, the mixture was stirred for 3 h. The basal spacing of the product increased to 1.23 nm, indicating the intercalation of AHA molecules with a monolayer arrangement between the layers of kaolinite. AHA was polymerized by a heat treatment at 250 degreesC for 1 h under a nitrogen flow. Although the basal spacing of the heat-treated product slightly decreased to 1.16 nm, the spacing was larger than those of kaolinite and the kaolinite-methanol intermediate. The formation of a kaolinite-nylon 6 intercalation compound was confirmed by the appearance of IR bands due to amide I (1637 cm(-)1) and amide II (1550 cm(-1)).

    DOI

  • Synthesis of a kaolinite-poly(beta-alanine) intercalation compound

    T Itagaki, Y Komori, Y Sugahara, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   11 ( 12 ) 3291 - 3295  2001  [Refereed]

     View Summary

    A kaolinite-poly(beta -alanine) intercalation compound (kaolinite/poly(beta -alanine)) was synthesized by in-situ polycondensation of preintercalated beta -alanine, which is an initial step toward the extension of the variety of host materials for polymer-clay nanocomposites. beta -Alanine was intercalated into kaolinite by a displacement method using kaolinite/ammonium acetate as the intermediate. Zwitterionic beta -alanine was ordered in a monolayer arrangement between the layers, which was confirmed by powder XRD, IR and NMR. Although beta -alanine was mostly polymerized by thermal treatment of kaolinite/beta -alanine at 250 degreesC for 10 h under an N-2 atmosphere, a part of the guest species was decomposed. Kaolinite/poly(beta -alanine) had a higher thermal stability than bulk poly( beta -alanine), as evidenced by TG-DTA.

    DOI

  • Characterization of silanol groups in protonated magadiite by H-1 and H-2 solid-state nuclear magnetic resonance

    Y Komori, M Miyoshi, S Hayashi, Y Sugahara, K Kuroda

    CLAYS AND CLAY MINERALS   48 ( 6 ) 632 - 637  2000.12  [Refereed]

     View Summary

    Silanol groups in protonated magadiite (H-magadiite) were characterized by H-1 and H-2 solid-state nuclear magnetic resonance (NMR). H-magadiite and deuterated (D) magadiite were synthesized by the treatment of Na-rich magadiite with 0.2 N HCl and 0.2 N DCl, respectively. In the H-1 NMR spectrum measured at room temperature, silanol groups of H-magadiite showed two signals at 3.75 and 5.70 ppm, indicating that two types of silanol groups were present. The ratio of silanol groups associated with strong hydrogen bonding (5.70 ppm) to those with weaker hydrogen bending (3.75 ppm) was 2 to 1. The H-2 NMR spectra of deuterated magadiite were measured in the temperature range from 150 to 440 K. In the spectra measured at temperatures below 294 K, silanol groups showed Pake doublet patterns. These patterns were composed of two components corresponding to the two types of silanol groups shown in the H-1 NMR analysis. Both silanol groups produced wobbling motions with increasing temperature. Above 294 K, the profile of the Pake doublet pattern was transformed gradually to a near triangular pattern, indicating that the silanol groups underwent other motions also, such as a two-site jump.

  • Immobilization of photosynthetic pigments into silica-surfactant nanocomposite films

    H Hata, T Kimura, M Ogawa, Y Sugahara, K Kuroda

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   19 ( 1-3 ) 543 - 547  2000.12  [Refereed]

     View Summary

    Highly transparent silica-surfactant nanocomposite films containing photosynthetic pigments have been successfully formed through the solubilization of chlorophyll a (Chl a) into surfactant micelles. The UV-vis absorption spectra indicated that a large amount of Chl a were transformed into pheophytin a in the films. These photosynthetic pigments were well dispersed in the surfactant assemblies and their chlorin rings were exposed to the surface of silica layers. Even under an air atmosphere, the photostability of immobilized pigments was largely improved in comparison with that in a homogeneous Chl a solution. Because both Chl a and pheophytin a molecules are effective for the photosensitive charge separation, the present film system is very suitable for heterogeneous immobilizing media for photosynthetic pigments from the viewpoint of in vitro biomimetic devices for solar energy conversion.

  • Preparation of titania from tetrakis(diethylamino)titanium via hydrolysis

    Y Ishikawa, H Honda, Y Sugahara

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   19 ( 1-3 ) 365 - 369  2000.12  [Refereed]

     View Summary

    The conversion of tetrakis(diethylamino)titanium (Ti(NEt2)(4)) into titania via either a combination of hydrolysis (Ti(NEt2)(4) : THF : H2O = 1 : 10 : x, x = 2, 4, 10) at ambient conditions and calcination (method A) or hydrolysis in a water-tetrahydrofuran (THF) mixture (Ti(NEt2)(4) : THF : H2O = 1 : 10 : 100) at reflux (method B) was investigated. Titanium tertiary butoxide (Ti((OBu)-Bu-t)(4)) was also used as a substitute for Ti(NEt2)(4). The hydrolysis via method A resulted in the formation of amorphous solids containing organics. Thermal analyses showed that the hydrolysis products showed mass losses up to 500 degreesC probably due to the presence of diethylamine (Et2NH) formed via the hydrolysis of Ti(NEt2)(4) in the hydrolysis products, while a mass loss of the hydrolysis product from Ti((OBu)-Bu-t)(4) was completed up to about 200 degreesC. After calcination at greater than or equal to 600 degreesC, anatase or a mixture of anatase and rutile was obtained. The crystallization behavior of the hydrolysis products from Ti(NEt2)(4) was different from that of the hydrolysis product from Ti((OBu)-Bu-t)(4). The hydrolysis via method B gave only an amorphous material from Ti(NEt2)(4), while a crystalline titania (anatase and brookite) formed from Ti((OBu)-Bu-t)(4).

  • Pyrolysis of poly(isopropyliminoalane) to aluminum nitride

    Y Saito, Y Sugahara, K Kuroda

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   83 ( 10 ) 2436 - 2440  2000.10  [Refereed]

     View Summary

    The pyrolysis processes of poly(isopropyliminoalane) ((HAIN(i)Pr)(n)) were investigated, using mass spectrometry to analyze the gases and infrared spectroscopy to analyze the residual solids. The major mass loss (in the temperature range of 240 degrees-540 degrees C) consisted of two different pyrolysis stages. At the first stage (240 degrees-320 degrees C), (HAIN(i)Pr)(6) was detected continuously as a gas, and the precursor was converted to a cross-linked structure. A polymerization mechanism without a release of organic compounds has been proposed, and the formation of (HAIN(i)Pr)(6) during polymerization (besides its evaporation) has been suggested. The second stage (320 degrees-560 degrees C) involved the formation of various organic compounds, and radical processes for their formation were proposed.

  • Lamellar hexadecyltrimethylammonium silicates derived from kanemite

    T Kimura, D Itoh, N Okazaki, M Kaneda, Y Sakamoto, O Terasaki, Y Sugahara, K Kuroda

    LANGMUIR   16 ( 20 ) 7624 - 7628  2000.10  [Refereed]

     View Summary

    Lamellar organoammonium silicates with variable silicon environments have been synthesized by the reaction of a layered polysilicate kanemite with aqueous solutions of hexadecyltrimethylammonium (C(16)TMA) chloride. While the structure of kanemite is composed of only Q(3) silicate species ((SiO)(3)SiO), SiO4 units with both Q(3) and Q(4) ((SiO)(4)Si) environments were present in the silicate frameworks of the lamellar C(16)TMA silicates. The Q(4) species mainly formed by intralayer condensation of the Q(3) species in the individual silicate sheets in kanemite rather than by interlayer condensation between the adjacent sheets. The intralayer condensation can be suppressed by lowering the reaction temperature and/or shortening the reaction time, which results in the relative retention of the silicate framework of kanemite in the lamellar C(16)TMA silicates.

  • Effective adsorption of chlorophyll a by FSM-type mesoporous silica modified with 1,4-butanediol

    S Murata, H Hata, T Kimura, Y Sugahara, K Kuroda

    LANGMUIR   16 ( 18 ) 7106 - 7108  2000.09  [Refereed]

     View Summary

    Surface silanol groups of FSM-type mesoporous silica were modified with 1,4-butanediol, and the esterified material was successfully used as the adsorbent to accommodate chlorophyll alpha molecules. Pheophytinization was effectively suppressed by the presence of the surface organic groups grafted onto the mesoporous silica, whereas pheophytinization occurred in unmodified mesoporous silica.

  • Modification of the interlayer surface of kaolinite with methoxy groups

    Y Komori, H Enoto, R Takenawa, S Hayashi, Y Sugahara, K Kuroda

    LANGMUIR   16 ( 12 ) 5506 - 5508  2000.06  [Refereed]

  • Synthesis of a soluble precursor possessing an Nb-N backbone structure and its pyrolytic conversion into niobium-based ceramics

    F Cheng, Y Sugahara, K Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   73 ( 5 ) 1299 - 1305  2000.05  [Refereed]

     View Summary

    Synthesis and pyrolysis of a soluble precursor possessing an Nb-N backbone structure were investigated. The precursor was prepared by aminolysis reaction of tetrakis(diethylamido)niobium with isopropylamine. The precursor was soluble in benzene, and had a polymeric structure possessing Nb-N-Nb imido-bridges. The precursor was pyrolyzed under NH3-N-2 (at 600 degrees C for 2 h under NH3 and subsequently at 1350 degrees C for 8 h under N-2) and Ar (at 1500 degrees C for 2 h) atmospheres. delta-NbN was obtained as a main crystalline phase after the pyrolysis of the precursor under NH3-N-2 whereas pyrolysis of the precursor under Ar led to the formation of NbC as the only crystalline phase. More than 90% of niobium which was present in the precursor remained in both of the pyrolyzed products.

  • Preparation of a soluble precursor by an aminolysis reaction of Zr(NEt2)(4) and its pyrolytic conversion into ZrN

    F Cheng, Y Sugahara, K Kuroda

    CHEMISTRY LETTERS   2000 ( 2 ) 138 - 139  2000.02  [Refereed]

     View Summary

    A novel soluble precursor with a Zr-N-Zr backbone structure was prepared by an aminolysis reaction of Zr(NEt2)(4) with Pr(i)N(H)2. Pyrolysis of the precursor under NH3-N-2 atmospheres led to the formation of ZrN as a main crystalline phase with a ceramic yield of 45.2%. Aggregated particles consisting of very minute particles with diameters of 50-300 nrl were obtained.

  • Pyrolytic Conversion of Blended Precursors into Ti-Al-N Ceramic Composites

    Korean J. Ceram./Korean Ceram. Soc.   6 ( 1 ) 32 - 36  2000.01  [Refereed]

  • Formation of novel ordered mesoporous silicas with square channels and their direct observation by transmission electron microscopy

    T Kimura, T Kamata, M Fuziwara, Y Takano, M Kaneda, Y Sakamoto, O Terasaki, Y Sugahara, K Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   39 ( 21 ) 3855 - +  2000  [Refereed]

  • Synthesis and structures of reduced niobates with four perovskite-like layers and their semiconducting properties

    W Sugimoto, H Ohkawa, M Naito, Y Sugahara, K Kuroda

    JOURNAL OF SOLID STATE CHEMISTRY   148 ( 2 ) 508 - 512  1999.12  [Refereed]

     View Summary

    Carriers were successfully doped into RbCa2NaNb4O13 by the substitution of Sr2+ for Na+, yielding electroconducting niobates with a layered structure consisting of four perovskite-like layers. Single-phase products of polycrystalline RbCa2Na1-xSrxNb4O13 (x = 0.2 and 0.4) were synthesized by the solid-state reaction of RbCa2Nb3O10, Sr5Nb4O15, Nb2O5 and Nb metal. The solid solutions were indexed based on a tetragonal structure, corresponding to the end-member RbCa2NaNb4O13. With the increase in the amount of strontium substitution, an expansion of the c-axis was observed while the a-axis was essentially constant. The products showed semiconducting properties. (C) 1999 Academic Press.

  • New conversion reaction of an Aurivillius phase into the protonated form of the layered perovskite by the selective leaching of the bismuth oxide sheet

    W Sugimoto, M Shirata, Y Sugahara, K Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   121 ( 49 ) 11601 - 11602  1999.12  [Refereed]

  • New Conversion Reaction of an Aurivillius Phase into the Protonated Form of the Layered Perovskite by the Selective Leaching of the Bismuth Oxide Sheet

    J.Am.Chem.Soc./Am.Chem.Soc.   121 ( 49 ) 11602 - 11603  1999.12  [Refereed]

  • Structure and Semiconducting Properties of Carrier-Doped Niobates with a Four-Layered Perovskite Structure

    J.Solid State Chem./Academic Press   148 ( 2 ) 508 - 513  1999.12  [Refereed]

  • Intercalation of alkylamines and water into kaolinite with methanol kaolinite as an intermediate

    Y Komori, Y Sugahara, K Kuroda

    APPLIED CLAY SCIENCE   15 ( 1-2 ) 241 - 252  1999.09  [Refereed]

     View Summary

    Alkykamines and water were intercalated between the layers of kaolinite by utilizing a kaolinite/methanol intercalation compound as an intermediate. A kaolinite/methanol intercalation compound was synthesized by guest displacement reaction of a kaolinite/N-methylformamide intercalation compound with methanol. The basal spacing increased up to 5.75 nm when octadecylamine was used. It increased linearly with the length of alkyl chains by 0.255 nm per carbon atom, suggesting that the alkylamine molecules in the interlayer space of kaolinite take a bilayer arrangement with their alkyl chains almost perpendicular to the layers of kaolinite. Water molecules were also intercalated into kaolinite by displacement of methanol. The basal spacing of the product was 1.00 nm under wet conditions and 0.85 nm after drying. By using hydrated kaolinite as an intermediate, pyridine molecules were intercalated into kaolinite, thus, the hydrated kaolinite also shows the ability as an intermediate for displacement reactions. These results demonstrate that kaolinite has higher intercalation ability for a wider variety of guest species than previously accepted if appropriate intermediates are used. (C) 1999 Elsevier Science B.V. All rights reserved.

  • Organic Modification of FSM-type Mesoporous Silicas Derived from Kanemite by Silylation?

    Langmuir/Am.Chem.Soc.   15 ( 8 ) 2794 - 2798  1999.08  [Refereed]

  • ゾル-ゲル法による新しい機能性無機-有機複合材料:有機修飾セラミ

    色材協会誌/色材協会   72 ( 6 ) 373 - 381  1999.06  [Refereed]

  • Synthesis and Structural Study of the KNb_4O_6-Type Compound

    SUGIMOTO Wataru, MIMURO Ken, SUGAHARA Yoshiyuki, KURODA Kazuyuki

    Journal of the Ceramic Society of Japan   107 ( 1244 ) 318 - 321  1999.04

     View Summary

    Polycrystalline samples with nominal compositions K_<1+x>Nb_4O_6(0&le;x&le;1.0)were prepared by the solid-state reaction of KNbO_3, Nb_2O_5 and Nb. Powder X-ray diffraction analysis revealed that the KNb_4O_6-type compound was obtained as the major phase when x&ge;0.4. Transmission electron microscopy observations showed that when x=0.4, the KNb_4O_6-type compound contained intergrowth defects. In contrast, when x=1.0, practically no intergrowth defects were observed, although this sample contained KNbO_3 as an impurity phase. The relation between the nominal composition and the formation of the intergrowth defects is discussed.

    DOI CiNii

  • Adsorption of taxol into ordered mesoporous silicas with various pore diameters

    H Hata, S Saeki, T Kimura, Y Sugahara, K Kuroda

    CHEMISTRY OF MATERIALS   11 ( 4 ) 1110 - 1119  1999.04  [Refereed]

     View Summary

    Taxol, an anticancer substance, was adsorbed into FSM-type mesoporous silicas with the pore sizes larger than 1.8 nm, while it was not adsorbed into the channels with the pore size less than 1.6 nm, indicating that mesoporous silicas have a molecular sieving property for relatively large molecules. The adsorption behavior of Taxol depended on the solvents; Taxol was not adsorbed into mesoporous silicas when methanol or acetone was used but was adsorbed when dichloromethane or toluene was used. The adsorption behavior of Taxol is discussed on the basis of the solubility parameters of the solvents. The proton-acceptor solubility parameter (delta a) is a predominant factor in this liquid-solid partition system. The adsorption-desorption of an extract from yew needles was performed using the mesoporous silica and several elution solvents. In the adsorption, many components including Taxol were adsorbed into mesoporous silica. When the desorption of the extract components adsorbed into the mesoporous silica was performed with a mixture of methanol and water with varied ratios, the targeted molecule, Taxol, with a few addition of components was separated from the adsorbed components. This adsorption-desorption behavior was elucidated by the solubility parameter (delta) as well as delta a.

  • Synthesis and structural study of the KNb4O6-type compound

    W Sugimoto, K Mimuro, Y Sugahara, K Kuroda

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   107 ( 4 ) 318 - 321  1999.04  [Refereed]

     View Summary

    Polycrystalline samples with nominal compositions K1+xNb4O6 (0 less than or equal to x less than or equal to 1.0) were prepared by the solid-state reaction of KNbO3, Nb2O5 and Nb. Powder X-ray diffraction analysis revealed that the KNb4O6-type compound was obtained as the major phase when x greater than or equal to 0.4. Transmission electron microscopy observations showed that when x=0.4, the KNb4O6-type compound contained intergrowth defects. In contrast, when x=1.0, practically no intergrowth defects were observed, although this sample contained KNbO3 as an impurity phase. The relation between the nominal composition and the formation of the intergrowth defects is discussed.

    DOI

  • Pyrolytic Convertion of the Cage-type Precursors into AIN

    Key Engineering Mater/Trans Tech Publications   159-160   77 - 82  1999.02  [Refereed]

  • Synthesis and characterization of lamellar and hexagonal mesostructured aluminophosphates using alkyltrimethylammonium cations as structure-directing agents

    T Kimura, Y Sugahara, K Kuroda

    CHEMISTRY OF MATERIALS   11 ( 2 ) 508 - 518  1999.02  [Refereed]

     View Summary

    Lamellar and hexagonal mesostructured aluminophosphates (AlPOs) were prepared and characterized. The lamellar mesostructured AlPO (APW-1) formed hydrothermally and the condensed framework was composed of alternating AlO4 and PO4 units. The hexagonal mesostructured. AlPO (APW-2) is formed by transformation of a layered precipitate composed of both aluminophosphate oligomers and alkyltrimethylammonium (ATMA) cations. Calcined APW-2 had a mesoporosity with the BET surface area of 980 m(2) gl and a pore diameter of 1.8 nm after substantial shrinkage of the framework. Lamellar APW-1 formed under most of the conditions surveyed, while hexagonal APW-2 was obtained under very restricted conditions. In this system, the charge matching in the products is the most important factor, although the assemblies of ATMA cations are essential as the structure-directing agents.

  • Direct intercalation of poly(vinylpyrrolidone) into kaolinite by a refined guest displacement method

    Y Komori, Y Sugahara, K Kuroda

    CHEMISTRY OF MATERIALS   11 ( 1 ) 3 - +  1999.01  [Refereed]

     View Summary

    Direct intercalation of poly(vinylpyrroridone) (PVP) into the interlayer space of kaolinite at room temperature is achieved by a refined guest displacement method by utilizing both a kaolinite-methanol intercalation compound and PVP dissolved in methanol.

  • Synthesis of Na(1-x)Ln(x)NbO(3) (Ln=La, Nd, Sm, Gd) and their structures and electrical properties

    W Sugimoto, M Naito, Y Sugahara, K Kuroda

    SOLID-STATE CHEMISTRY OF INORGANIC MATERIALS II   547   267 - 272  1999  [Refereed]

     View Summary

    Polycrystalline samples of Na(1-x)Ln(x)NbO(3) (Ln=La, Nd, Sm, Gd) were synthesized by solid-state reactions. Reduced niobates were obtained as single-phase perovskites for x=0.05 and 0.1 when Ln=La and Nd and x=0.05 when Ln=Sm. The Gd-substituted samples could not be prepared under the synthetic conditions studied. Compositional analysis of the products revealed a slight amount of sodium loss during synthesis. The structural parameters obtained from Rietveld analysis revealed an increase in unit-cell volume. All of the obtained samples showed semiconducting behavior. Similar semiconducting behavior was observed for the same x value, suggesting the weak influence of the different Ln species to the electrical properties.

  • Synthesis of reduced layered titanoniobates KTi1-xNb1+xO5

    Wataru Sugimoto, Naritoshi Hirota, Ken Mimuro, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Materials Letters   39 ( 3 ) 184 - 187  1999  [Refereed]

     View Summary

    Polycrystalline samples of KTi1-xNb1+xO5 (x = 0.1, 0.2, 0.3) were synthesized by solid-state reactions. The synthesized compounds were blue-colored, suggesting reduced oxidation states. Single phase KTi1-xNb1+xO5 was obtained for 0 ≤ x &lt
    0.2, suggesting that the solubility limit is between x = 0.2 and 0.3. The reduced oxides exhibited semiconducting behavior.

    DOI

  • An acentric arrangement of p-nitroaniline molecules between the layers of kaolinite

    K Kuroda, K Hiraguri, Y Komori, Y Sugahara, H Mouri, Y Uesu

    CHEMICAL COMMUNICATIONS   1999 ( 22 ) 2253 - 2254  1999  [Refereed]

     View Summary

    p-Nitroaniline molecules were intercalated between the layers of kaolinite, and an acentric arrangement of p-nitroaniline induced by the asymmteric environment of the interlayer region was accomplished.

  • An acentric arrangement of p-nitroaniline molecules between the layers of kaolinite

    K Kuroda, K Hiraguri, Y Komori, Y Sugahara, H Mouri, Y Uesu

    CHEMICAL COMMUNICATIONS   1999 ( 22 ) 2253 - 2254  1999  [Refereed]

     View Summary

    p-Nitroaniline molecules were intercalated between the layers of kaolinite, and an acentric arrangement of p-nitroaniline induced by the asymmteric environment of the interlayer region was accomplished.

  • Thermal transformation of a kaolinite-poly(acrylamide) intercalation compound

    Y Komori, Y Sugahara, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   9 ( 12 ) 3081 - 3085  1999  [Refereed]

     View Summary

    The thermal transformation of a kaolinite-poly(acrylamide) (PAAm) intercalation compound has been investigated. Acrylamide molecules were intercalated between the layers of kaolinite and were subsequently polymerized by heat treatment at 300 degrees C for 1 h. The kaolinite-PAAm intercalation compound was heated in the range 460-620 degrees C under a nitrogen atmosphere. XRD analysis revealed that carbonaceous materials remained between the layers in this temperature range. The Si-29 and Al-27 NMR spectra of the kaolinite-PAAm compounds heated above 500 degrees C showed that the structural change of aluminosilicate layers was relatively suppressed compared with that of kaolinite itself, indicating that the carbonaceous materials hindered the transformation of aluminosilicate layers. This new finding provides a method for controlling the skeletal transformation of inorganic layered materials upon thermal treatment.

  • Pyrolytic conversion of precursors prepared in Ti(NMe2)(4)-diamine systems

    S Koyama, D Iizuka, Y Sugahara, K Kuroda

    APPLIED ORGANOMETALLIC CHEMISTRY   12 ( 10-11 ) 787 - 792  1998.10  [Refereed]

     View Summary

    Precursors possessing Ti-N bonds were prepared by the reactions between Ti(NMe2)(4) and each of three diamines H2NCH2CH2NH2, Me(H)NCH2CH2N(H)Me, HN(CH2CH2)(2)NH (Ti(NMe2)(4):diamine = 1:2), and were converted into ceramics by pyrolysis, The reactions with H2NCH2CH2NH2 and HN(CH2CH2)(2)NH led to the formation of insoluble solids, whereas a soluble oil was obtained by the reaction with Me(H)NCH2CH2N(H)Me. The pyrolyses under argon gave carbon-rich Ti(N,C,O) phases, but those under NH3- N-2 resulted in the formation of Ti(N,C,O) phases with higher nitrogen contents. Despite the difference in precursor structures the pyrolysis behavior of three precursors under argon was rather similar, suggesting that the precursor obtained from Me(H)NCH2CH2N(H)Me was effectively crosslinked during pyrolysis. (C) 1998 John Wiley & Sons, Ltd.

  • スーパーボールを作ろう

    現代化学   1998 ( 8 )  1998.08  [Refereed]

  • Synthesis of mesoporous aluminophosphates and their adsorption properties

    T Kimura, Y Sugahara, K Kuroda

    MICROPOROUS AND MESOPOROUS MATERIALS   22 ( 1-3 ) 115 - 126  1998.06  [Refereed]

     View Summary

    Hexagonal mesostructured alkyltrimethylammonium-aluminophosphate materials were prepared by using hexadecyltrimethylammonium and dococyltrimethylammonium chlorides as surfactants and by utilizing 1,3,5-triisopropylbenzene as an auxiliary organic additive. Calcination of these materials at 600 degrees C yielded thermally stable mesoporous aluminophosphate materials with large surface areas above 700 m(2) g(-1) and with pore diameters in the range from 1.8 to 3.9 nm. The hexagonal mesostructured materials before calcination had less condensed frameworks as determined by P-31 MAS NMR, which caused certain shrinkages during calcination for the formation of the porous structures. Water and benzene adsorption data indicated that the mesoporous aluminophosphate materials had comparatively hydrophilic mesopores. (C) 1998 Elsevier Science B.V. All rights reserved.

  • Synthesis of oriented inorganic-organic nanocomposite films from alkyltrialkoxysilane-tetraalkoxysilane mixtures

    A Shimojima, Y Sugahara, K Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   120 ( 18 ) 4528 - 4529  1998.05  [Refereed]

  • Synthesis and structures of carrier doped titanates with the Ruddlesden-Popper structure (Sr0.95La0.05)(n+1)TinO3n+1 (n = 1, 2)

    W Sugimoto, M Shirata, M Takemoto, S Hayami, Y Sugahara, K Kuroda

    SOLID STATE IONICS   108 ( 1-4 ) 315 - 319  1998.05  [Refereed]

     View Summary

    Carrier doping in Srn+1TinO3n+1 (n = 1, 2) was conducted by the substitution of La for Sr and the simultaneous introduction of oxygen vacancies. Single-phase products of (Sr0.95La0.05)(n+1)TinO3n+1-delta(n = 1, delta = 0.05; n = 2, delta = 0.125) were synthesized by the solid-state reaction of Sr2TiO4 (or Sr3Ti2O7), La2O3 and Ti. When TiO2 was used as one of the starting compounds to maintain oxygen stoichiometry, compounds with higher n were observed besides the object phases. Structural refinement by Rietveld analysis revealed that the a-axis expands while the c-axis contracts with La doping. The contraction of the c-axis is attributed to a shortened (Sr,La)-O distance, since the TiO6 octahedra elongated in both a and c directions with doping. The change in the structure is discussed on the basis of the size of the substituting ion. The resistivity of the single-phase products was semiconducting with a very weak temperature dependence down to 80 K. (C) 1998 Elsevier Science B.V. All rights reserved.

  • セラミックス実験技術講座 ゾル-ゲル法(2)

    セラミックス   33 ( 4 ) 386 - 389  1998.05  [Refereed]

  • Synthesis of Mesoporous Aluminophosphates by using Surfactants with Long Alkyl Chain Length and Triisopropylbenzene as a Solubilizing Agent

    Chem. Commun./Royal Soc. Chem.   1998 ( 5 ) 559 - 560  1998.04  [Refereed]

  • A kaolinite-NMF-methanol intercalation compound as a versatile intermediate for further intercalation reaction of kaolinite

    Y Komori, Y Sugahara, K Kuroda

    JOURNAL OF MATERIALS RESEARCH   13 ( 4 ) 930 - 934  1998.04  [Refereed]

     View Summary

    A kaolinite-organic intercalation compound containing methanol was proved to be a versatile host for further displacement reaction with aIkylamines, Kaolinite-organic intercalation compounds with polar molecules, such as N-methylformamide (NMF) and formamide, were used as the starting materials. After stirring the kaolinite-NMF intercalation compound with methanol, the basal spacing increased to 1.11 nm. The C-13 MBS NMR result of the product indicated that methanol was intercalated into kaolinite by partial displacement with NMF. By use of the methanol-treated kaolinite intercalation compound as the intermediate, alkylamines were intercalated into the interlayer space of kaolinite by displacing with methanol.

  • Esterification of the Silanol Groups in the Mesoporous Silica Derived form Kanemite

    J. Porous Mater./Kluwer Academic Publishers   5   127 - 132  1998.04  [Refereed]

  • セラミックス実験技術講座 ゾル-ゲル法(1)

    セラミックス   33 ( 4 ) 308 - 312  1998.04  [Refereed]

    CiNii

  • The relationship between structural variation and electrical properties in the spinel MgV2-xTixO4 (0 &lt;= x &lt;= 1.8) system

    W Sugimoto, H Yamamoto, Y Sugahara, K Kuroda

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   59 ( 1 ) 83 - 89  1998.01  [Refereed]

     View Summary

    Polycrystalline samples of MgV2-xTixO4 (0 less than or equal to x less than or equal to 1.8) were prepared by solid-state reactions under an argon atmosphere and their electrical properties were studied. X-ray powder diffraction analysis indicated the formation of the spinel phase as the major compound. Solid solutions were formed throughout the system, as indicated by the monotonic variation of the unit-cell parameter. All the samples were semiconducting below room temperature. A minimum in the activation energy required for semiconduction was observed at x = 1.0. A change in resistivity behavior was observed when the titanium content was increased. For 0 less than or equal to x less than or equal to 1.2, the conduction behavior was interpreted as the hopping conduction of thermally activated electrons, whereas the resistivity behavior for 1.4 less than or equal to x less than or equal to 1.8 was characterized by a weak temperature dependence at low temperatures. (C) 1997 Elsevier Science Ltd. All rights reserved.

  • Preparation of a hybrid preceramic precursor for Al-Si-C-N nanocomposites via a molecular building block approach

    S Koyama, H Nakashima, Y Sugahara, K Kuroda

    CHEMISTRY LETTERS   1998 ( 2 ) 191 - 192  1998  [Refereed]

     View Summary

    The reaction between (HAINPr(i))(m) (Pr-i=CH(CH3)(2)) and [MeSi(H)NH](n) (Me=CH3) led to hydrogen elimination to form a hybrid precursor. Thermogravimetry revealed that the ceramic yield of the hybrid precursor was much higher than those of (HAINPr(i))(m) and [MeSi(H)NH](n), which was ascribed to the hydrogen elimination condensation between the AIH groups in (HAINPr(i))(m) and the NH groups in [MeSi(H)NH](n) during precursor synthesis and pyrolysis. The pyrolyzed product under Ar was a mixture of beta-SiC, beta-Si3N4 and 2H wurtzite-type compound, and the particle sizes were in the range of 20-30 nm.

  • Preparation of Aluminum Nitride from Precursors with Cage-type Structures (HAlNR)n (R=Et, iPr)

    Proc. 14th Internat. Japan-Korea Seminar on Ceram.     405 - 410  1997.11  [Refereed]

  • Formation of layered Inorganic-Organic Nanocomposites by the Hydrolysis and Polycondensation of Alkyltriethoxysilane

    Proc. 14th Internat. Japan-Korea Seminar on Ceram.     284 - 288  1997.11  [Refereed]

  • Inorganic-organic layered materials derived via the hydrolysis and polycondensation of trialkoxy(alkyl)silanes

    A Shimojima, Y Sugahara, K Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   70 ( 11 ) 2847 - 2853  1997.11  [Refereed]

     View Summary

    Triethoxy(alkyl)silanes containing 12-18 carbon atoms in the alkyl groups were hydrolyzed and polycondensed to form ordered structured materials. The XRD pattern of each condensed product showed sharp diffraction peaks with higher orders. The basal spacings approximately corresponded to twice the extended molecular length of the alkyl groups, and increased linearly as a function of the alkyl chain length. The SEM images of the products exhibited a platy morphology, and the (SiCP)-Si-29/MAS NMR spectra revealed the formation of siloxane bonds with various silicon sites from T-1 to T-3 environments. All of these results indicated the formation of highly-organized inorganic-organic layered materials.

  • Synthesis of a Hexagonal Mesostructured Aluminophosphate

    Chem. Lett./Chem. Soc. Jpn.   1997 ( 10 ) 1227 - 1228  1997.10  [Refereed]

  • セラミック前駆体からのAlN合成

    Fine Ceramics Report/日本ファインセラミックス協会     200 - 203  1997.09  [Refereed]

  • 可溶性セラミック前駆体からの窒化アルミニウムの合成

    無機マテリアル/無機マテリアル学会   4 ( 5 ) 280 - 286  1997.05  [Refereed]

  • The Rare-Earth Dependence on the Solid Solution Formation and Electrical Properties of KCa_<2-x>R_xNb_3O_<10>(R=Nd, Sm, Gd, and Ce)

    HAMADA Daisuke, SUGIMOTO Wataru, SUGAHARA Yoshiyuki, KURODA Kazuyuki

    Journal of the Ceramic Society of Japan   105 ( 1220 ) 284 - 287  1997.04

     View Summary

    The solid solution KCa_<2-x>R_xNb_3O_<10>(R=Nd, Sm, Gd, and Ce) was prepared by solid-state reaction using KCa_2Nb_3O_<10> KNbO_3, Nb_2O_5, Nb and rare-earth oxides. The solubility limit of the solid solutions was extended with an increase in the ionic radii of the rare earths. All the solid solutions exhibited similar semiconductive behavior with a linear log ρ-T relationship over a wide temperature range. These results suggest that the conduction mechanism is independent of the type of rare earths and also the unit-cell parameters, which agrees well with the tunneling conduction model with a vibrating barrier.

    DOI CiNii

  • The rare-earth dependence on the solid solution formation and electrical properties of KCa2-xRXNb3O10 (R=Nd, Sm, Gd and Ce)

    D Hamada, W Sugimoto, Y Sugahara, K Kuroda

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   105 ( 4 ) 284 - 287  1997.04  [Refereed]

     View Summary

    The solid solution KCa2-xRxNb3O10 (R = Nd, Sm, Gd and Ce) was prepared by solid-state reaction using KCa2Nb3O10, KNbO3, Nb2O5, Nb and rare-earth oxides, The solubility limit of the solid solutions was extended with an increase in the ionic radii of the rare earths. All the solid solutions exhibited similar semiconductive behavior with a linear log p-T relationship over a wide temperature range. These results suggest that the conduction mechanism is independent of the type of rare earths and also the unit-cell parameters, which. agrees well with the tunneling conduction model with a vibrating barrier.

    DOI

  • Preparation of stoichiometric and nonstoichiometric magnesium titanate spinels

    W Sugimoto, N Kaneko, Y Sugahara, K Kuroda

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   105 ( 2 ) 101 - 105  1997.02  [Refereed]

     View Summary

    Polycrystalline samples of stoichiometric spinels, Mg1+xTi2-xO4 (0 less than or equal to x less than or equal to 1.0), and spinels with cation diversity, Mg((1+x)y)Ti2-xO4 and Mg(1+x)Ti((2-x)y)O-4 (x=0.4215, y=0.95-1.05), and oxygen deficiency Mg1+xTi2-xO4-delta (x=0.4215, delta=0.05-0.30) were prepared by solid-state reaction of MgO, TiO2 and Ti to examine the effects of the composition and holding time on the structure of the spinel phase, the impurity phase formation behavior and the electrical properties, In addition to Mg2TiO4 (x=1) prepared at 1300 degrees C under an ambient atmosphere, samples were prepared at 1250 degrees C under an argon atmosphere, Compositional analyses revealed that volatilization of compounds and oxidation during firing were negligible, The variation in the unit cell parameter a of the spinel phase indicated solid-solution formation for all stoichiometric samples in spite of the presence of impurities, The impurity-phase formation behavior was strongly dependent upon synthetic conditions, x-value, and induced nonstoichiometry, Other than the insulating Mg2TiO4, resistivity measurements indicated that all samples were semiconducting below room temperature. No distinct variation in resistivity behavior was observed for samples with different holding time or with induced nonstoichiometry.

    DOI

  • Synthesis of a hexagonal mesostructured aluminophosphate

    T Kimura, Y Sugahara, K Kuroda

    CHEMISTRY LETTERS   ( 10 ) 983 - 984  1997  [Refereed]

     View Summary

    A hexagonal mesostructured aluminophosphate was successfully synthesized from the mixture of Al((OPr)-Pr-1)3, 85% H3PO4, tetramethylammonium hydroxide, hexadccyltrimethylammonium chloride, and water.

  • Si-29 NMR study on co-hydrolysis processes in Si(OEt)(4)-RSi(OEt)(3)-EtOH-water-HCl systems (R=Me,Ph): Effect of R groups

    Y Sugahara, T Inoue, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   7 ( 1 ) 53 - 59  1997.01  [Refereed]

     View Summary

    Hydrolysis and initial polycondensation processes in the Si(OEt)(4)(TEOS)-RSi(OEt)(3)-EtOH-water-HC; systems (R=Me, Ph) [TEOS: RSi(OEt)(3):EtOH:water:HCl=1:1:24:x:y (x=12,2/3; y=2x10(-3), 4x10(-3), 8x10(-2))] have been investigated by using Si-29 NMR spectroscopy. For comparison, the alkoxysilanes [TEOS, MeSi(OEt)(3)(MTES), PhSi(OEt)(3)(PTES)] were hydrolysed separately in a similar manner. In a water-rich TEOS-MTES system (water:Si=12:1), a silanol-terminated codimer [Me(HO)(2)SiOSi(OH)(3)] was detected as well as (HO)(3)SiOSi(OH)(3) and Me(HO)(2)SiOSi(OH)(2)Me, suggesting that the hydrolysed monomers were condensed rather randomly. In contrast, ina water-rich TEOS-PTES system, hydrolysed monomers derived from TEOS and those from PTES were condensed independently; a silanol-terminated codimer [Ph(HO)(2)SiOSi(OH)(3)] did not form, and only (HO)(3)SiOSi(OH)(3) and Ph(HO)(2)SiOSi(OH)(2)Ph were detected. These observations in the TEOS-PTES system suggest the presence of the association of the phenyl groups. In water-restricted systems (water:Si=1:3), monomers were only partially hydrolysed, and ethoxy-terminated codimers [R(EtO)(2)SiOSi(OEt)(3) (R=Me, Ph)] formed in both the TEOS-MTES and the TEOS-PTES systems.

  • Polymerization reactions in an Al(OBu(s))(3)-(COOH)(2) system

    Y Sugahara, Takaya, I, J Chiba, K Kuroda

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   8 ( 1-3 ) 95 - 99  1997  [Refereed]

     View Summary

    Reactions in an Al(OBu(s))(3)-(COOH)(2) (OA)-tetrahydrofuran (THF)/(CD3)(2)SO (DMSO-d(6)) system (Al(OBu(s))(3):THF:DMSO-d(6):OA = 1:5:5:x, x = 0.01-3) were studied, without the addition of water and the process was monitored by NMR. When x less than or equal to 10.3, homogeneous solutions were obtained, whereas white precipitates formed with x greater than or equal to 0.7. The formation of sec-butyl alcohol was evident with x greater than or equal to 0.6, indicating that oxalate groups coordinate to aluminum to release sec-butyl alcohol. C-13 NMR spectra of the solutions after 1 day suggest the presence of polymeric species if 0.03 less than or equal to x less than or equal to 0.6. The addition of a small amount of water resulted in the formation of a white precipitate (Al(OBu(s))(3):THF:DMSO-d(6):OA:H2O = 1:5:5:0.3:y, y = 0.03-0.3), indicating that water, possibly formed by esterification in the Al(OBu(s))(3)-OA-THF/DMSO-d(6) system, does not take a major role in the present system.

  • Pyrolytic preparation of gallium nitride from [Ga(NEt2)(3)](2) and its ammonolysis compound

    S Koyama, Y Sugahara, K Kuroda

    GALLIUM NITRIDE AND RELATED MATERIALS II   468   93 - 98  1997  [Refereed]

     View Summary

    Gallium nitride (GaN) was prepared by the pyrolytic conversion of both [Ga(NEt2)(3)](2) and its ammonolysis product at 600 degrees C for 4 h under Ar. The pyrolyzed residues were analyzed by Xray powder diffraction and scanning electron microscopy, and the pyrolysis processes of the precursors under He were investigated by thermogravimetry-mass spectrometry. The XRD pattern of the pyrolyzed residue of [Ga(NEt2)(3)](2) showed well-resolved peaks due to a mixture of cubic and hexagonal close-packed layers of GaN. The broad XRD pattern of the pyrolyzed residue of the ammonolysis product was also attributed to the mixture of cubic and hexagonal close-packed layers of GaN. For the pyrolysis of [Ga(NEt2)(3)](2), the evolution of hydrocarbons was extensively observed at relatively high temperature, but a large amount of carbon (11 mass%) was still detected in the pyrolyzed residue. On the other hand, the amount of carbon was only 1.1 mass% in the pyrolyzed residue of the ammonolysis product. The pyrolysis results of the ammonolysis product under Ar were very similar to those of [Ga(NEt2)(3)](2) under NH3.

  • SYNTHESIS of A(1-x)A'xNbO3 (A=Na+, K+; A'=La3+, Sr2+) and its electrical properties

    W Sugimoto, T Tahara, Y Sugahara, K Kuroda

    SOLID-STATE CHEMISTRY OF INORGANIC MATERIALS   453   361 - 366  1997  [Refereed]

     View Summary

    Polycrystalline samples of A(1-x)A'xNbO3 (A=Na+, K+; A'=La3+, Sr2+) were prepared by solid-state reactions and the relationship between the structure and electrical properties was examined. Single-phase products were obtained for Na1-xLaxNbO3 (x less than or equal to 0.1), K1-xLaxNbO3 (x less than or equal to 0.15), Na1-xSrxNbO3 (x less than or equal to 0.3), and K1-xSrxNbO3 (x less than or equal to 0.5). The structures of the sodium-containing compounds and potassium-containing compounds were indexed according to a pseudocubic and cubic symmetry, respectively. The resistivity measurements showed semiconductive behavior for the lanthanum-containing samples. The strontium-containing samples showed semiconducting properties for x less than or equal to 0.2, while a transition to metallic conduction at low temperature was observed for x &gt;0.2.

  • Preparation of soluble AlN precursors in a LiAlH4-CH3NH2 center dot HCl-(CH3)(2)NH center dot HCl system

    S Koyama, Y Saito, Y Sugahara, K Kuroda

    CHEMISTRY LETTERS   1997 ( 12 ) 1227 - 1228  1997  [Refereed]

     View Summary

    Novel AlN precursors have been prepared by reactions in a LiAlH4-CH3NH2 . HCl-(CH3)(2)NH . HCl system with several nominal CH3NH2 . HCl:(CH3)(2)NH . HCl (M:D) ratios (M:D=4:1, 6:1 and 8:1). Considerable amounts of precursors were soluble in both tetrahydrofuran and benzene. Soluble precursors consist of polymeric/oligomeric species possessing both [H2AlNMe2] and [HAlNMe] units, and ring-type (H2AlNMe2)(3) was also present only if M:D=4:1. The precursors were converted into single-phase AIN with relatively high ceramic yields (up to 58 %) by pyrolysis at 1600 degrees C under Ar.

  • Syntesis of A Lamellar Mesostructured Aluminophosphate

    Phosphorous Res. Bull/日本無機リン化学会   6   205 - 208  1996.12  [Refereed]

  • Preparation of AlN from poly(ethyliminoalane) via pyrolysis

    S Koyama, H Takeda, Y Saito, Y Sugahara, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   6 ( 6 ) 1055 - 1058  1996.06  [Refereed]

     View Summary

    Aluminium nitride (AIN) powder has been prepared by pyrolysing poly(ethyliminoalane) under Ar (at 1600 degrees C for 2 h) and NH3-N-2 (at 600 degrees C for 2 h under NH3 and at 1350 degrees C for 8 h under N-2) atmospheres, and the products have been characterized by X-ray powder diffraction, solid-state (27)A1 NMR spectroscopy, elemental analysis, scanning electron microscopy, and nitrogen adsorption measurement. The only crystalline product was AIN, in which carbon and oxygen were hardly present by solid-solution formation. A considerable amount (17.1 mass%) of carbon remained in the product pyrolysed under Ar, whereas most of carbon was removed during the pyrolysis under NH3-N-2(0.1 mass%). The AIN particles obtained by pyrolysis under NH3-N-2 were finer than those obtained by pyrolysis under Ar. The ceramic yields were 50% (Ar) and 57% (NH3-N-2); the latter value is close to the theoretical yield (58%).

  • Characterization of aluminum nitride from a precursor poly(isopropyliminoalane)

    Y Saito, S Koyama, Y Sugahara, K Kuroda

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   104 ( 2 ) 143 - 145  1996.02  [Refereed]

     View Summary

    Aluminum nitride (AlN) was prepared by pyrolysis of poly(isopropyliminoalane) under Ar and NH3/N-2 atmospheres. X-ray powder diffraction analysis revealed that the only crystalline phase was AlN, whose lattice constants showed that possible amounts of carbon and oxygen in the lattice should be very small. Chemical analyses showed the presence of carbon only in the product pyrolyzed in Ar; almost all carbon was removed by pyrolysis in NH3/N-2. The ceramic yield for two-step pyrolysis in Ar (1000 degrees C for 2h, 1600 degrees C for 2h) was 32%, while that for pyrolysis in NH3/N-2 (600 degrees C for 2h in NH3, 1350 degrees C for 8h in N-2) was 47%.

    DOI

  • Preparation and electrical properties of KCa2-xLaxNb3O10

    D Hamada, M Machida, Y Sugahara, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   6 ( 1 ) 69 - 72  1996.01  [Refereed]

     View Summary

    Electron-doped layered perovskite KCa2-xLaxNb3O10 was prepared from KNbO3, Nb2O5, Nb, La2O3 and KCa2Nb3O10 at 1200 degrees C for 10 h under Ar. Essentially single-phase KCa2-xLaxNb3O10 with plate-like morphology was obtained with 0 less than or equal to x less than or equal to 0.3, and lattice parameters increased with increasing x. All the La-doped products showed semiconducting behaviour. Linear (log rho)-T relationships were clearly observed, but the resistivity behaviour deviates from the linear relationship at lower temperatures. A possible conduction mechanism is discussed.

  • Characterization of aluminum nitride from a precursor poly (isopropyliminoalane)

    Yasuo Saito, Seiichi Koyama, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Journal of the Ceramic Society of Japan   104   143 - 145  1996.01  [Refereed]

     View Summary

    Aluminum nitride (AlN) was prepared by pyrolysis of poly(isopropyliminoalane) under Ar and NH3/N2atmospheres. X-ray powder diffraction analysis revealed that the only crystalline phase was AlN, whose lattice constants showed that possible amounts of carbon and oxygen in the lattice should be very small. Chemical analyses showed the presence of carbon only in the product pyrolyzed in Ar; almost all carbon was removed by pyrolysis in NH3/N2. The ceramic yield for two-step pyrolysis in Ar (1000°C for 2h, 1600°C for 2h) was 32%, while that for pyrolysis in NH3/N2(600°C for 2h in NH3, 1350°C for 8h in N2) was 47%.

    DOI

  • AFM Observation of Kaolinite using "Pressed" Powder

    Clay Sci./Clay Sci. .Soc.Jpn.   9 ( 5 ) 311 - 316  1995.12  [Refereed]

  • Formation of Methoxy-Modified Interlayer Surface via the Reaction between Methanol and Layered Perovskite HLaNb2O7・xH2O

    Inorg. Chem./Am. Chem. Soc.   34 ( 20 ) 5065 - 5069  1995.10  [Refereed]

  • Synthesis and Electrical Properties of MgTi2-xVxO4

    Advances in Superconductivity VII/Springer-Verlag     401 - 404  1995.10  [Refereed]

  • リアルタイムX線回折分析によるインターカレーション反応の追跡

    化学と工業   48 ( 8 ) 947 - 947  1995.08  [Refereed]

    CiNii

  • Novel Polysiloxane Formation Process from Dimethyldiethoxysilane in the Presence of Oxalic Acid

    J. Chiba, Y. Sugahara, K. Kuroda

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   2 ( 1-3 ) 153 - 156  1994.01  [Refereed]

     View Summary

    Polysiloxane formation in dimethyldiethoxysilane (DMDES)-ethyl alcohol (EtOH(D))-oxalic acid (OA) (DMDES: EtOH(D): OA = 1:2:0.5) and DMDES-dimethylsulfoxide (DMSO)-OA (DMDES: DMSO: OA = 1: 2: 0.5) systems was investigated by gas chromatography-mass spectrometry and Si-29-nuclear magnetic resonance. While the DMDES-EtOH(D)-OA system was homogeneous, the DMDES-DMSO-OA system consisted of two immiscible phases. In both systems, ethoxy-terminated linear oligomers ((EtO)Me2SiO(Me2SiO)(n)SiMe2(OEt); n = 0-4, Et = C2H5, Me = CH3) and cyclic tetramer ((Me2SiO)(4)) were identified. The reaction mechanism for polysiloxane formation is discussed.

  • SI-29-NMR STUDY OF HYDROLYSIS AND INITIAL POLYCONDENSATION PROCESSES OF ORGANOALKOXYSILANES .2. METHYLTRIETHOXYSILANE

    Y SUGAHARA, S OKADA, S SATO, K KURODA, C KATO

    JOURNAL OF NON-CRYSTALLINE SOLIDS   167 ( 1-2 ) 21 - 28  1994.01  [Refereed]

     View Summary

    The hydrolysis and initial polycondensation processes of methyltriethoxysilane (MTES) have been investigated by high-resolution Si-29-nuclear magnetic resonance spectroscopy (Si-29-NMR). MTES was hydrolyzed in the system with MTES:ethyl alcohol:water:HCl = 1:4:x:y; x = 1, 2, 3, 6; y = 1 X 10(-4), 1 X 10(-2). Signals due to end and middle groups of polysiloxanes formed sub-regions on the basis of the number of hydroxyl groups attached to silicon, and the sub-region for silicon possessing more hydroxyl groups was observed at a lower field. Based on signal intensities, the signals due to the dimers (Me(HO)2SiOSi(OH)2Me and Me(HO)2SiOSi(OH)(OEt)Me) and the trimer (Me(HO)2SiOSiMe(HO)OSi(OH)2Me) (Me = CH3, Et = C2H5) were identified.

  • SI-29-NMR STUDY OF HYDROLYSIS AND INITIAL POLYCONDENSATION PROCESSES OF ORGANOALKOXYSILANES .2. METHYLTRIETHOXYSILANE

    Y SUGAHARA, S OKADA, S SATO, K KURODA, C KATO

    JOURNAL OF NON-CRYSTALLINE SOLIDS   167 ( 1-2 ) 21 - 28  1994.01  [Refereed]

     View Summary

    The hydrolysis and initial polycondensation processes of methyltriethoxysilane (MTES) have been investigated by high-resolution Si-29-nuclear magnetic resonance spectroscopy (Si-29-NMR). MTES was hydrolyzed in the system with MTES:ethyl alcohol:water:HCl = 1:4:x:y; x = 1, 2, 3, 6; y = 1 X 10(-4), 1 X 10(-2). Signals due to end and middle groups of polysiloxanes formed sub-regions on the basis of the number of hydroxyl groups attached to silicon, and the sub-region for silicon possessing more hydroxyl groups was observed at a lower field. Based on signal intensities, the signals due to the dimers (Me(HO)2SiOSi(OH)2Me and Me(HO)2SiOSi(OH)(OEt)Me) and the trimer (Me(HO)2SiOSiMe(HO)OSi(OH)2Me) (Me = CH3, Et = C2H5) were identified.

  • EVIDENCE FOR THE FORMATION OF BI-2(SR2-XCAX)CUOY WITH THE 2201 STRUCTURE

    S SERA, Y SUGAHARA, K KURODA, C KATO

    PHASE TRANSITIONS   41 ( 1-4 ) 205 - 208  1993  [Refereed]

     View Summary

    The formation of the solid solution Bi-2(Sr2-xCax)CuOy with the 2201 structure has been demonstrated by comparing its lattice parameters with those in Bi2+xSr2-xCuOy and Bi-2(Sr2-xMgx)CuOy systems. The solid-solution range of Bi-2(Sr2-xCax)CuOy has been found to be 0 less than or equal to x less than or equal to 0.15 under the present experimental conditions.

  • SYNTHESIS OF LA(1-X)M(X)TIO(3) (M=NA,K 0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.4) AND THE ELECTRICAL-PROPERTIES

    H YAMAMOTO, T TAHARA, Y SUGAHARA, K KURODA, C KATO

    PHASE TRANSITIONS   41 ( 1-4 ) 137 - 141  1993  [Refereed]

     View Summary

    Polycrystalline materials of La(1-x)M(x)TiO(3) (M = Na, K; 0 less than or equal to x less than or equal to 0.4) were prepared by solid-state reactions under an Ar atmosphere and their electrical properties were investigated as possible candidates for superconducting oxides. XRD analysis showed that the formation of orthorhombic perovskite-type compounds were obtained when x = 0 (LaTiO3) and that pseudo-cubic or cubic phases were obtained when x greater than or equal to 0.1. The lattice constants of the products decreased when x increased, suggesting the formation of solid solutions. There were small deficiencies of the alkali metals. The products in both systems showed semiconductor to metal transitions as temperature decreased when x greater than or equal to 0.1, and striking decreases of resistivity around 25 K were observed in both systems.

    DOI

  • SI-29 NMR-STUDY ON THE INITIAL-STAGE OF THE COHYDROLYSIS OF TETRAETHOXYSILANE AND METHYLTRIETHOXYSILANE

    Y SUGAHARA, Y TANAKA, S SATO, K KURODA, C KATO

    BETTER CERAMICS THROUGH CHEMISTRY V   271   231 - 236  1992  [Refereed]

  • Clay-organic nano-composite; preparation of a kaolinite-poly (vinylpyrrolidone) intercalation compound

    Yoshiyuki Sugahara, Tomohide Sugiyama, Tetsuji Nagayama, Kazuyuki Kuroda, Chuzo Kato

    Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan   100 ( 1160 ) 413 - 416  1992  [Refereed]

     View Summary

    A kaolinite-poly(vinylpyrrolidone) intercalation compound has been prepared by the intercalation of an N-vinyl-2-pyrrolidone monomer (VP) and subsequent heat treatment. The intercalation of VP was achieved by treating a kaolinite-ammonium acetate intercalation compound with a VP aqueous solution. The basal spacing decreased from 14.2 to 12.6 , and infra-red spectroscopy (IR) and solid-state 13C nuclear magnetic resonance with cross polarization and magic angle spinning techniques (13C CP/MAS NMR) showed the displacement of ammonium acetate by VP. When the kaolinite-VP intercalation compound was heated at 200°C for 1 h, the basal spacing did not vary. The IR and 13C CP/MAS NMR spectra showed the disappearance of vinyl groups and became similar to those of poly(vinylpyrrolidone) (PVP). These results clearly indicate the polymerization of VP between the layers of kaolinite.

    DOI

  • Polysiloxane formation from a tetraethoxysilane-ethyl alcohol-oxalic acid system

    Yoshiyuki Sugahara, Shuji Sato, Kazuyuki Kuroda, Chuzo Kato

    Journal of Non-Crystalline Solids   147-148 ( C ) 24 - 29  1992  [Refereed]

     View Summary

    Polysiloxane formation in a tetraethoxysilane (TEOS)-ethyl alcohol (EtOD(H))-oxalic acid (OA) system without the addition of water was investigated by 29Si nuclear magnetic resonance spectroscopy (29Si-NMR). In the system with TEOS:EtOD(H):OA = 1:6:1, considerable amounts of linear oligosiloxanes possessing only ethoxy groups formed, and (EtO)3SiOSi(OEt)3, (EtO)3SiOSi(OEt)2OSi(OEt)3, and (EtO)3Si(OSi(OEt)2)2OSi(OEt)3 were identified. When the amount of OA increased to TEOS:EtOD(H):OA = 1:6:2, the polymerization rate increased considerably. The observed Si-species scarcely possessed hydroxyls, suggesting unique siloxane formation in this system. © 1992 Elsevier Science Publishers B.V. All rights reserved.

    DOI

  • SI-29-NMR STUDY OF HYDROLYSIS AND INITIAL POLYCONDENSATION PROCESSES OF ORGANOALKOXYSILANES .1. DIMETHYLDIETHOXYSILANE

    Y SUGAHARA, S OKADA, K KURODA, C KATO

    JOURNAL OF NON-CRYSTALLINE SOLIDS   139 ( 1 ) 25 - 34  1992.01  [Refereed]

     View Summary

    The hydrolysis and initial polycondensation processes of dimethyldiethoxysilane (DMDES) have been investigated by high-resolution Si-29 nuclear magnetic resonance spectroscopy (NMR) in a variety of acidic systems (DMDES:ethyl alcohol:water:HCl = 1:4:x:y; x = 2 or 4, 1 x 10(-5) less-than-or-equal-to y less-than-or-equal-to 1 x 10(-2)). On the basis of the behavior of signal intensities, those due to the following monomers and oligomers have been identified: Me2Si(OEt)(OH), Me2Si(OH)2, Me2(HO)SiOSi(OH)Me2, Me2(EtO)SiOSi(OH)Me2, Me2(EtO)SiOSiMe2OSi(OH)Me2, Me2(HO)SiOSiMe2OSi(OH)Me2, (Me2SiO)3, Me2(HO)SiO(SiMe2O)2Si(OH)Me2, and (Me2SiO)4 (where Me = CH3, Et = C2H5). It was shown that the substitution of the hydroxyl group for the ethoxy group resulted in an upfield shift of a signal, which was not consistent with the previous observations in tetra-functional alkoxysilane systems. In the course of the polycondensation process, cyclization reactions became predominant to form a considerable amount of the cyclic tetramer directly from the completely hydrolyzed dimer (Me2(HO)SiOSi(OH)Me2).

  • PREPARATION OF ALUMINUM NITRIDE FROM POLY(ISOPROPYLIMINOALANE)

    Y SUGAHARA, T ONUMA, O TANEGASHIMA, K KURODA, C KATO

    NIPPON SERAMIKKUSU KYOKAI GAKUJUTSU RONBUNSHI-JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   100 ( 1 ) 101 - 103  1992.01  [Refereed]

     View Summary

    Aluminum nitride (AIN) was formed by two-step pyrolysis of poly (isopropyliminoalane) in Ar. The product pyrolyzed at 1000-degrees-C was an amorphous material. Solid-state Al-27-nuclear magnetic resonance spectroscopy (NMR) showed that an AlN-like structure was present in the product. Heat treatment of the pyrolyzed product at 1600-degrees-C yielded crystalline AlN from the amorphous material.

  • PHOTOREDUCTION OF METHYLVIOLOGEN IN THE INTERLAYERS OF SOME LAYERED TITANATES AND NIOBATES

    T NAKATO, Y SUGAHARA, K KURODA, C KATO

    SYNTHESIS/CHARACTERIZATION AND NOVAL APPLICATIONS OF MOLECULAR SIEVE MATERIALS   233   169 - 173  1991  [Refereed]

  • Preparation of intercalation compounds between V2O5 gel and bipyridyl metal complexes

    Teruyuki Nakato, Tsuyoshi Ise, Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Materials Research Bulletin   26 ( 4 ) 309 - 315  1991  [Refereed]

     View Summary

    The intercalation of tris-bipyridyl metal complexes (M(bpy)3 2+, M=Ru, Ni, and Co) into the interlayer region of vanadium pentoxide gel (V2O5·nH2O) was confirmed for the first time. The intercalation of the guest species was conducted by the reaction of the complexes with undried V2O5 gel. The saturated amount of adsorbed M(bpy)3 2+ was less than the ion exchange capacity of the V2O5 gel because of bulkiness of M(bpy)3 2+. The transition temperature to orthorhombic V2O5 was higher than that of original V2O5 gel, indicating the stabilization of the layered structure by the intercalation. © 1991.

    DOI

  • Polymerization of Hydrolysis Products of Methyltriethoxysilane in Aqueous Solutions

    HASEGAWA Isao, SAKKA SumiO, SUGAHARA Yoshiyuki, KURODA Kazuyuki, KATO Chuzo

    Journal of the Ceramic Society of Japan   98 ( 1139 ) 647 - 652  1990.07

     View Summary

    The structure and distribution of chemical species of hydrolysis and polycondensation products of methyltriethoxysilane in aqueous solutions containing sodium ions have been studied with the trimethylsilylation technique and by <29>^Si n. m. r. spectroscopy. 11 trimethylsilylated derivatives of the products were obtained from the solutions. The recovery of methyltrisilanol (CH_3Si(OH)_3) was much higher than that of the monosilicic acid in an aqueous sodium silicate solution; at the same Si concentration and the same sodium ion-to-silicon molar ratio, suggesting that the polymerization of silicate anions is easier than that of hydrolysis products of methyltriethoxysilane in aqueous solutions. On the basis of the distribution, assignment of <29>^Si n. m. r. peaks corresponding to low-molecular weight species formed from methyltriethoxysilane has been discussed.

    DOI CiNii

  • PREPARATION OF A KAOLINITE-POLYACRYLAMIDE INTERCALATION COMPOUND

    Y SUGAHARA, S SATOKAWA, K KURODA, C KATO

    CLAYS AND CLAY MINERALS   38 ( 2 ) 137 - 143  1990.04  [Refereed]

  • POLYMERIZATION OF HYDROLYSIS PRODUCTS OF METHYLTRIETHOXYSILANE IN AQUEOUS-SOLUTIONS

    HASEGAWA, I, S SAKKA, Y SUGAHARA, K KURODA, C KATO

    NIPPON SERAMIKKUSU KYOKAI GAKUJUTSU RONBUNSHI-JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   98 ( 7 ) 647 - 652  1990  [Refereed]

  • CARBOTHERMAL REDUCTION PROCESS OF PRECURSORS DERIVED FROM ALKOXIDES FOR SYNTHESIS OF BORON-DOPED SIC POWDER

    Y SUGAHARA, Y TAKEDA, K KURODA, C KATO

    JOURNAL OF MATERIALS SCIENCE LETTERS   8 ( 8 ) 944 - 946  1989.08  [Refereed]

  • KAOLINITE-PYRIDINE INTERCALATION COMPOUND DERIVED FROM HYDRATED KAOLINITE

    Y SUGAHARA, S SATOKAWA, KI YOSHIOKA, K KURODA, C KATO

    CLAYS AND CLAY MINERALS   37 ( 2 ) 143 - 150  1989.04  [Refereed]

  • Preparation of nitrides from 1:1 type clay minerals by carbothermal reduction

    Yoshiyuki Sugahara, Jyunji Miyamoto, Kazuyuki Kuroda, Chuzo Kato

    Applied Clay Science   4 ( 1 ) 11 - 26  1989  [Refereed]

     View Summary

    In order to investigate the possibility of the use of 1:1 type clay minerals as raw materials for nitride production, kaolinite and antigorite were converted into nitrides by carbothermal reduction. Kaolinite or antigorite was mixed with carbon in two separate experiments. The resulting mixture was heated in N2. Kaolinite was converted into β'-sialon and AIN. Kaolinite was initially transformed into cristobalite and mullite, which were then reduced. In addition to the nitrides, SiC and α-Al2O3 also formed as the reactions proceeded. Essentially, both the SiO2 and Al2O3 components were converted into nitrides and oxynitrides by carbothermal reduction. From the antigorite-carbon mixture, α- and β-Si3N4 were obtained. Forsterite initially crystallized and was reduced. Additionally, MgSiN2 and MgO formed during the conversion. α-Fe and FexSi were also detected. MgSiN2 seemed to act as an intermediate for Si3N4 formation. Therefore, all the Mg-containing phases can not be present as nitrides finally
    magnesium was lost as the reactions proceeded. © 1989.

    DOI

  • Silicate anions formed in tetramethylammonium silicate methanolic solutions as studied by &lt;sup&gt;29&lt;/sup&gt;Si nuclear magnetic resonance

    Isao Hasegawa, Sumio Sakka, Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Journal of the Chemical Society, Chemical Communications   ( 4 ) 208 - 210  1989  [Refereed]

     View Summary

    The Si&lt
    inf&gt
    8&lt
    /inf&gt
    O&lt
    inf&gt
    20&lt
    /inf&gt
    &lt
    sup&gt
    8-&lt
    /sup&gt
    silicate anion is selectively formed in tetramethylammonium silicate methanolic solution from the SiO &lt
    inf&gt
    4&lt
    /inf&gt
    &lt
    sup&gt
    4-&lt
    /sup&gt
    silicate anion or at the expense of Si &lt
    inf&gt
    6&lt
    /inf&gt
    O&lt
    inf&gt
    15&lt
    /inf&gt
    &lt
    sup&gt
    6-&lt
    /sup&gt
    and highly cross-linked polymeric silicate anions which are once formed.

    DOI

  • The carbothermal reduction process of a montmorillonite-polyacrylonitrile intercalation compound

    Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Journal of Materials Science   23 ( 10 ) 3572 - 3577  1988.10  [Refereed]

     View Summary

    To develop a carbothermal reduction process for the conversion of oxides to nitrides, a montmorillonite-polyacrylonitrile (PAN) intercalation compound was applied as a precursor. Montmorillonite-carbon mixtures were heated as well as the intercalation compound in N2 at 1100 to 1500° C for comparison. From the intercalation compound, β-sialon, AIN and SiC were mainly formed. Oxides were reduced without their crystallization. On the other hand, in the reactions of the mixtures, some oxides and other kinds of nitride were obtained as principal products in addition to these phases. Furthermore, the intercalation compound was more favourable than the mixtures having a larger amount of carbon in terms of the reduction of oxides and the formation of nitrides. These observations suggest that the layered structure of the intercalation compound led to an effective and specific carbothermal reduction process. © 1988 Chapman and Hall Ltd.

    DOI

  • Nitride formation by the carbothermal reduction of a zeolite-polyacrylonitrile inclusion compound

    Yoshiyuki Sugahara, Hiromitsu Hiraiwa, Kazuyuki Kuroda, Chuzo Kato

    Journal of Materials Science   23 ( 9 ) 3181 - 3186  1988.09  [Refereed]

     View Summary

    An inclusion compound between zeolite and polyacrylonitrile has been applied as a precursor for the carbothermal reduction process. By heat treatment at 1400 to 1600° C in N2, β-sialon was mainly obtained. The X phase, α-Si3N4, the 15R-AlN phase, AIN, and mullite also formed under certain firing conditions. On the other hand, α-Si2N4 was detected as the principal crystalline phases as well as β-sialon in the products from zeolite-carbon mixtures. Hence, the use of the inclusion compound was advantageous for β-sialon production in the conversion of zeolite to nitrides. © 1988 Chapman and Hall Ltd.

    DOI

  • EVIDENCE FOR THE FORMATION OF INTERLAYER POLYACRYLONITRILE IN KAOLINITE

    Y SUGAHARA, S SATOKAWA, K KURODA, C KATO

    CLAYS AND CLAY MINERALS   36 ( 4 ) 343 - 348  1988.08  [Refereed]

  • THE FORMATION OF SIC-AIN SOLID-SOLUTION BY THE CARBOTHERMAL REDUCTION PROCESS OF MONTMORILLONITE

    Y SUGAHARA, K SUGIMOTO, H TAKAGI, K KURODA, C KATO

    JOURNAL OF MATERIALS SCIENCE LETTERS   7 ( 7 ) 795 - 797  1988.07  [Refereed]

  • PREPARATION OF SILICON-CARBIDE AND ALUMINUM SILICON-CARBIDE FROM A MONTMORILLONITE POLYACRYLONITRILE INTERALATION COMPOUND BY CARBOTHERMAL REDUCTION

    Y SUGAHARA, K SUGIMOTO, K KURODA, C KATO

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   71 ( 7 ) C325 - C327  1988.07  [Refereed]

  • Synthesis of a viologen-tetratitanate intercalation compound and its photochemical behaviour

    Hirokatsu Miyata, Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases   84 ( 8 ) 2677 - 2682  1988  [Refereed]

     View Summary

    Methyl viologen has been intercalated into the interlayer space of layered tetratitanic acid by a method involving the displacement of guest molecules using an n-propylammonium tetratitanate intercalation compound. The viologen tetratitanate intercalation compound changed colour to blue when irradiated by a mercury lamp under vacuum conditions or a nitrogen atmosphere. The formation of radical cations was confirmed by visible and e.s.r. spectroscopy. The electron donor for the photoreduction is thought to originate from the tetratitanate layers. The colour was stable as long as the vacuum conditions were maintained, and fading did not occur rapidly even after the introduction of air, requiring &gt
    1 h for the colour to fade completely. These results indicate remarkable stability of the viologen radical cations in this intercalation compound.

    DOI

  • The preparation of boron-doped silicon carbide powder by the carbothermal reduction of oxides derived from the hydrolyzed methyltriethoxysilane

    Yoshiyuki Sugahara, Yasuharu Takeda, Kazuyuki Kuroda, Chuzo Kato

    Journal of Non-Crystalline Solids   100 ( 1-3 ) 542 - 546  1988  [Refereed]

     View Summary

    A precursor prepared from a methyltriethoxysilane ((CH3)Si(OC2H5)3, MTES)-B(OC2H5)3-polyacrylonitrile (PAN) composition was used for the synthesis of boron-doped SiC by carbothermal reduction. Initially, MTES was hydrolyzed with HCl (MTES: H2O: HCl = 1 : 1 : 0.01) for 1 h in a sealed vessel. The number-average molecular weight measurement and a NMR spectrum revealed that the species in the solution were mainly oligometric. With the addition of B(OC2H5)3, no significant changes in the distribution of the Si containing species were detected. The mixing of the hydrolyzed solution with a PAN-dimethylsulfoxide solution led to a homogeneous solution. After the evaporation of the solvents and the subsequent heat treatment at 220° C, brown precursor powder was obtained. By the heat treatment at 1600° C in Ar, it was converted to boron-doped SiC powder. © 1988.

    DOI

  • AlN formation from a hydrotalcite-polyacrylonitrile intercalation compound by carbothermal reduction

    Yoshiyuki Sugahara, Norimasa Yokoyama, Kazuyuki Kuroda, Chuzo Kato

    Ceramics International   14 ( 3 ) 163 - 167  1988  [Refereed]

     View Summary

    As a precursor for AlN production by carbothermal reduction, a hydrotalcite (layered magnesium-aluminum double hydroxide)-polyacrylonitrile (PAN) intercalation compound has been prepared for the first time. After the layers were expanded by the replacement of the interlayer anions with the CH3(CH2)11OSO3- ions, the acrylonitrile monomer was intercalated and subsequently polymerized. By the heat treatments at 1100°C-1600°C in N2, AlN, MgO and MgS formed. MgO was detected in the products heated up to 1300°C. MgS formation was observed in the reactions below 1500°C. On heating at 1600°C, single phase submicron AlN grains were obtained. © 1988.

    DOI

  • The formation of β-sialon in the carbothermal reduction process of montmorillonite-polyacrylonitrile intercalation compounds at 1100°C

    Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Ceramics International   14 ( 1 ) 1 - 5  1988  [Refereed]

     View Summary

    Only β-sialon was obtained from n-alkylammonium-montmorillonite-polyacrylonitrile (PAN) intercalation compounds in the carbothermal reduction process at 1100°C in N2. Very little oxide crystallized during the conversion. However, an amorphous phase was still present after treatment for 6 h. The main constituent metals in montmorillonite (Si, Al, Mg, and Fe) were mostly retained during the treatment. Since similar XRD patterns were obrained from two kinds of intercalation compounds, having different carbon contents, the suppression of the formation of other phases was not subject to the amount of carbon. When a montmorillonite-carbon mixture having a larger amount of carbon was heated at 1150°C for 6 h, oxides were mainly formed. Therefore, the intimate mixing in the 2D structure of the intercalation compounds resulted in a lower threshold temperature for β-sialon formation, at which other phases did not form. © 1988.

    DOI

  • The Preparation of a Magadiite-Polyacrylonitrile Intercalation Compound and Its Conversion to Silicon Carbide(2. Vapor Phase Reactions)(<Special Issue>Syntheses of Ceramics by New Techniques (I))

    SUGAHARA Yoshiyuki, SUGIMOTO Ken-ichi, YANAGISAWA Tsuneo, NOMIZU Yasuyuki, KURODA Kazuyuki, KATO Chuzo

    Journal of the Ceramic Association, Japan   95 ( 1097 ) 117 - 123  1987.01

     View Summary

    A magadiite (layered polysilicate)-polyacrylonitrile (PAN) intercalation compound was first prepared to investigate its potential as a precursor for the synthesis of non-oxide ceramics by carbothermal reduction. Acrylonitrile monomer was intercalated and polymerized in the interlayer space of a C12H25N(CH3)3-magadiite complex. After the cyclization of PAN by the heat treatment in air, the compound was heated in Ar flow for 2h. Above 1300°C, β-SiC was formed without the formation of any crystalline SiO2 phases. Since the reactions of a magadiite-carbon mixture involved the formation of cristobalite, it was shown that SiO2 from magadiite was reduced to form β-SiC without crystallization, which was caused by the presence of PAN in the interlayer space.

    DOI CiNii

  • Si_3N_4 Formation in the Carbothermal Reduction Process of a Magadiite-Polyacrylonitrile Intercalation Compound(2. Vapor Phase Reactions)(<Special Issue>Syntheses of Ceramics by New Techniques (I))

    SUGAHARA Yoshiyuki, NOMIZU Yasuyuki, KURODA Kazuyuki, KATO Chuzo

    Journal of the Ceramic Association, Japan   95 ( 1097 ) 124 - 129  1987.01

     View Summary

    Silicon nitride was formed from a magadiite (layered polysilicate)-polyacrylonitrile (PAN) intercalation compound through a novel process of carbothermal reduction. SiO2 from magadiite was reduced above 1400°C without the formation of any crystalline oxides. On heating above 1400°C, both α-and β-Si3N4 were detected, and the additional formation of α-and β-SiC was observed by heating at 1600°C. On the other hand, the reactions for the synthesis from a magadiite-carbon mixture involved the formation of cristobalite as well as α-and β-Si3N4, and β-SiC. In addition, it was also indicated that the mixture was less reactive for the formation of Si3N4. These observations suggest that the reaction process of the magadiite-PAN complex was different from that of the magadiite-carbon mixture, and that the use of the intercalation compound was favorable for Si3N4 production.

    DOI CiNii

  • SYNTHESIS OF MONTMORILLONITE VIOLOGEN INTERCALATION COMPOUNDS AND THEIR PHOTOCHROMIC BEHAVIOR

    H MIYATA, Y SUGAHARA, K KURODA, C KATO

    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I   83   1851 - 1858  1987  [Refereed]

  • THE PREPARATION OF A MAGADIITE POLYACRYLONITRILE INTERCALATION COMPOUND AND ITS CONVERSION TO SILICON-CARBIDE

    Y SUGAHARA, K SUGIMOTO, T YANAGISAWA, Y NOMIZU, K KURODA, C KATO

    YOGYO-KYOKAI-SHI   95 ( 1 ) 117 - 123  1987  [Refereed]

  • SI3N4 FORMATION IN THE CARBOTHERMAL REDUCTION PROCESS OF A MAGADIITE-POLYACRYLONITRILE INTERCALATION COMPOUND

    Y SUGAHARA, Y NOMIZU, K KURODA, C KATO

    YOGYO-KYOKAI-SHI   95 ( 1 ) 124 - 129  1987  [Refereed]

  • SYNTHESES OF NITRIDE AND CARBIDE CERAMICS FROM INTERCALATION COMPOUNDS BY CARBOTHERMAL REDUCTION.

    Kazuyuki Kuroda, Yoshiyuki Sugahara, Chuzo Kato

    British Ceramic Proceedings     15 - 20  1986.10  [Refereed]

     View Summary

    To establish a new method for the carbothermal reduction process, the conversion of the montmorillonite-polyacrylonitrile (PAN) intercalation compound to nitride and carbide ceramics was studied. In the case of Ar atmosphere, the formation of SiC was observed above 1200 degree C. alpha -SiC was detected above 1300 degree C, while beta -SiC was formed above 1200 degree C. As oxides, Mg-Al-O compound was detected above 1300 degree C. On the other hand, the formation of beta -sialon and SiC was observed by the treatment in N//2 atmosphere above 1200 degree C. AlN was also detected above 1300 degree C. In these processes, the reaction route became unique because of preventing the crystallization of oxides. This fact was ascribed to the presence of PAN in the interlayer space.

  • SYNTHESIS OF KAOLINITE-LACTAM INTERCALATION COMPOUNDS

    Y SUGAHARA, S KITANO, S SATOKAWA, K KURODA, C KATO

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   59 ( 8 ) 2607 - 2610  1986.08  [Refereed]

  • Nitridation of sepiolite by carbothermal reduction

    Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Journal of Materials Science Letters   4 ( 7 ) 928 - 931  1985.07  [Refereed]

    DOI

  • SYNTHESIS OF BETA-SIALON FROM A MONTMORILLONITE-POLYACRYLONITRILE INTERCALATION COMPOUND BY CARBOTHERMAL REDUCTION

    Y SUGAHARA, K KURODA, C KATO

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   67 ( 11 ) C247 - C248  1984  [Refereed]

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    情報機構  2015

  • 元素ブロック高分子―有機-無機ハイブリッド材料の新概念―

    中條 善樹監修

    シーエムシー出版  2015

  • 無機高分子の開発最前線

    シーエムシー出版  2009

  • 有機-無機ナノハイブリッド材料の新展開

    シーエムシー出版  2009

  • ナノシートの化学と応用

    黒田一幸, 佐々木高義編

    シーエムシー出版,  2005

  • ナノコンポジットマテリアル

    井上明久編

    フロンティア出版  2005

  • 実力養成化学スクール セラミックス材料化学

    日本化学会編

    丸善  2005

  • 季刊化学総説 無機有機ナノ複合物質

    日本化学会編

    学会出版センター  1999.04

▼display all

Misc

  • 非水ゾル-ゲル法を用いたホウ素原子含有リチウムイオン伝導性Ti-O-P系ハイブリッドの作製

    宮代広輝, 井戸田直和, 奈良洋希, 門間聰之, 門間聰之, 逢坂哲彌, 菅原義之, 菅原義之

    セラミックス基礎科学討論会講演要旨集   57th  2019

    J-GLOBAL

  • 直鎖ポリエチレンオキシドを用いたチタニアナノ粒子架橋型固体電解質の作製

    村瀬裕太, 井戸田直和, 奈良洋希, 門間聰之, 門間聰之, 門間聰之, 逢坂哲彌, 逢坂哲彌, 逢坂哲彌, 菅原義之, 菅原義之

    セラミックス基礎科学討論会講演要旨集   56th  2018

    J-GLOBAL

  • 非水ゾル‐ゲル法を用いたリチウムイオン伝導性Ti‐O‐P系ハイブリッドの作製

    鈴木建吾, 井戸田直和, ZAPICO Julian, 奈良洋希, 門間聰之, 門間聰之, 逢坂哲彌, 菅原義之, 菅原義之

    セラミックス基礎科学討論会講演要旨集   55th   149  2017.01

    J-GLOBAL

  • 層状六ニオブ酸塩の層表面修飾によるヤヌス型ナノシートの作製

    須藤充人, 鈴木涼子, 井戸田直和, 國武雅司, 西見大成, 菅原義之, 菅原義之

    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)   29th   ROMBUNNO.3M20  2016.08

    J-GLOBAL

  • エチレンオキシド鎖を組み込んだリチウムイオン伝導性Ti‐O‐P系ハイブリッドの作製

    土橋正卓, 井戸田直和, 斉藤ひとみ, 奈良洋希, 門間聰之, 逢坂哲彌, 菅原義之

    粉体粉末冶金協会講演概要集   2014   157  2014.06

    J-GLOBAL

  • ゾル‐ゲル法により合成したラメラ状ポリシルセスキオキサン層間へのエチレンオキシド鎖のグラフト反応

    大下浩範, 奈良洋希, 門間聰之, BRUNO Boury, MEHDI Ahmed, 逢坂哲彌, 菅原義之

    粉体粉末冶金協会講演概要集   2013   29  2013.11

    J-GLOBAL

  • オキシエチレン鎖を有するリチウムイオン伝導性Ti‐O‐P系ハイブリッドの作製

    土橋正卓, 斉藤ひとみ, 奈良洋希, 井戸田直和, 門間聰之, 逢坂哲彌, 菅原義之

    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)   26th   ROMBUNNO.1C01  2013.08

    J-GLOBAL

  • エチレンオキシド鎖架橋ジホスホン酸と四塩化チタンを用いたリチウムイオン伝導性Ti‐O‐P系ハイブリッドの作製

    土橋正卓, 斉藤ひとみ, 奈良洋希, 門間聰之, 逢坂哲彌, 菅原義之

    粉体粉末冶金協会講演概要集   2013   201  2013.05

    J-GLOBAL

  • エチレンオキシド鎖架橋ジホスホン酸を用いたリチウムイオン伝導性Ti‐O‐P系ハイブリッドの作製

    土橋正卓, 斉藤ひとみ, 奈良洋希, 門間聰之, 逢坂哲彌, 菅原義之

    セラミックス基礎科学討論会講演要旨集   51st   86  2013.01

    J-GLOBAL

  • Global innovation in advanced ceramics

    Junichi Hojo, Takashi Goto, Kimihiro Yamashita, Koji Watari, Takaaki Tsurumi, Kunihito Kournoto, Yoshiyuki Sugahara

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   116 ( 1351 )  2008.03

    Other  

  • Organic-to-inorganic conversion process for polymer-derived ceramics - Preface

    Yoshiyuki Sugahara, Yuji Iwamoto, Masaki Narisawa

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   114 ( 1330 )  2006.06

    Other  

  • Thermomechanical Properties of Silicon Carbide Fiber-Reinforced SiAlON-Based Composites Fabricated by Reactive Melt Infiltration

    S. Kitaoka, N. Kawashima, Y. Sugahara, Y. Sugita, Y. Kagiya, T. Banno

    Ceram. Trans.   144   253 - 261  2002  [Refereed]

  • B16 カオリナイト-ナイロン6層間化合物の合成 (第44回粘土科学討論会発表論文抄録)

    松村 麻子, 板垣 哲朗, 小森 佳彦, 菅原 義之, 黒田 一幸

    粘土科学   40 ( 2 ) 125 - 125  2000.11

    CiNii

  • A7. 有機修飾マガディアイトと有機高分子の複合化 (第43回粘土科学討論会発表論文抄録)

    礒田 圭, 小川 誠, 菅原 義之, 黒田 一幸

    粘土科学   39 ( 2 ) 90 - 90  1999.12

    CiNii

  • A3. カオリナイト-ε-カプロラクタム層間化合物の合成 (第43回粘土科学討論会発表論文抄録)

    松村 麻子, 板垣 哲朗, 小森 佳彦, 菅原 義之, 黒田 一幸

    粘土科学   39 ( 2 ) 89 - 89  1999.12

    CiNii

  • PREPARATION OF A KAOLINITE-ε-CAPROLACTAM INTERCALATION COMPOUND

    KOMORI Yoshihiko, MATSUMURA Asako, ITAGAKI TETSURO, SUGAHARA Yoshiyuki, KURODA Kazuyuki

    Clay Science   11 ( 1 ) 47 - 55  1999.12

     View Summary

    Intercalation of ε-caprolactam into kaolinite was achieved by the guest displacement method using a kaolinite-methanol intercalation compound as the intermediate. The basal spacing of the kaolinite-ε-caprolactam intercalation compound was 1.31 nm, which was larger than those of both kaolinite (0.72 nm) and the kaolinite-methanol intercalatlon compound (1.11 nm). IR analysis revealed the formation of hydrogen bondings between the carbonyl groups of ε-caprolactam and the hydroxyl groups of kaolinite. The thermal behavior of the product implied that in-situ polymerization of ε-caprolactam to nylon 6 by heat treatment was unsuccessful because of deintercalation reaction of ε-caprolactam molecules.

    CiNii

  • 28p-XG-2 Structure and Formation Mechanism of a Novel Mesoporous Silica kSW-2

    Kaneda M, Sakamoto Y, Takano Y, Kimura T, Sugahara Y, Kuroda K, Terasaki O

    Meeting abstracts of the Physical Society of Japan   54 ( 1 ) 721 - 721  1999.03

    CiNii

  • P24. ポリビニルピロリドンのカオリナイトへの直接インターカレーション (第42回粘土科学討論会発表論文抄録)

    小森 佳彦, 菅原 義之, 黒田 一幸

    粘土科学   38 ( 2 ) 126 - 126  1998.12

    CiNii

  • スメクタイトへの陽イオン性シアニン色素の吸着

    川合 亮, 宮元 展義, 小川 誠, 菅原 義之, 黒田一幸

    粘土科学   37 ( 3 ) 128 - 128  1997.12

    CiNii

  • スメクタイトへのアルキルジメチルアミン-N-オキシドのインターカレーションにより得られる分子集合構造

    金岡 長之, 小川 誠, 菅原 義之, 黒田 一幸

    粘土科学   37 ( 3 ) 128 - 128  1997.12

    CiNii

  • カオリナイト配向膜の作製・評価

    小森 佳彦, 菅原 義之, 黒田 一幸

    粘土科学   36 ( 3 ) 163 - 163  1996.12

    CiNii

  • スメクタイト-アルキルジメチルアミン-N-オキシド配向薄膜の合成

    金岡 長之, 和田 哲哉, 小川 誠, 菅原 義之, 黒田 一幸

    粘土科学   36 ( 3 ) 167 - 167  1996.12

    CiNii

  • 長鎖アルキルアンモニウム型フッ素四ケイ素雲母層間でのアゾベンゼンの異性化挙動

    浜 雅之, 植村 裕司, 小川 誠, 菅原 義之, 黒田 一幸

    粘土科学   36 ( 3 ) 166 - 167  1996.12

    CiNii

  • カオリナイト-ポリアクリルアミド層間化合物の加熱変化

    小森 佳彦, 植村 裕司, 菅原 義之, 黒田 一幸

    粘土科学   35 ( 3 ) 134 - 134  1995.12

    CiNii

  • PREPARATION OF ALUMINUM NITRIDE FROM POLY(ALKYLIMINOALANE)

    Y SUGAHARA, S KOYAMA, Y SAITO, H TAKEDA, K KURODA

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   209   222 - INOR  1995.04

    Research paper, summary (international conference)  

  • サポナイト-2, 4-Hexadiyne-1, 6-diol 層間化合物の合成

    植村 裕司, 高橋 克, 小川 誠, 菅原 義之, 黒田 一幸

    粘土科学   34 ( 3 ) 195 - 195  1994.12

    CiNii

  • FORMATION OF INTERCALATION COMPOUNDS OF A LAYERED SODIUM OCTOSILICATE WITH N-ALKYLTRIMETHYLAMMONIUM IONS AND THE APPLICATION TO ORGANIC DERIVATIZATION

    K ENDO, Y SUGAHARA, K KURODA

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   67 ( 12 ) 3352 - 3355  1994.12

    Article, review, commentary, editorial, etc. (scientific journal)  

     View Summary

    In this study, n-alkyltrimethylammonium ions ([CnH2n+N-1(CH3)(3)](+); n=12, 14, 16, 18) were intercalated in the interlayer space of layered sodium octosilicate (Na2Si8O17.nH(2)O) via an ion-exchange reaction. The interlayer space was further modified by grafting of the trimethylsilyl groups via a reaction between a dodecyltrimethylammonium-octosilicate intercalation compound and chlorotrimethylsilane.

  • 層状Na_2Si_8O_<17>・nH_2Oの陽イオン交換反応

    遠藤 公晴, 菅原 義之, 黒田 一幸

    粘土科学   33 ( 3 ) 164 - 164  1993.12

    CiNii

  • 31.機能性有機分子の組織化媒体としての長鎖アルキルアンモニウム型モンモリロナイト(第36回粘土科学 32.討論会発表論文抄録)

    小川 誠, 青野 友寿, 菅原 義之, 黒田 一幸, 加藤 忠蔵

    粘土科学   32 ( 4 ) 285 - 285  1992.03

    CiNii

  • 29.カオリナイト-アミノ酸層間化合物の合成(第35回粘土科学討論会発表論文抄録)

    杉山 智英, 小川 誠, 菅原 義之, 黒田 一幸, 加藤 忠蔵

    粘土科学   31 ( 4 ) 250 - 250  1991.02

    CiNii

  • 28.モンモリロナイト-尿素層間化合物の合成とその非線形光学効果(第35回粘土科学討論会発表論文抄録)

    長房 靖之, 小川 誠, 菅原 義之, 黒田 一幸, 加藤 忠蔵

    粘土科学   31 ( 4 ) 250 - 250  1991.02

    CiNii

  • ORGANIC MODIFICATION OF INTERLAYER SILANOL GROUPS OF LAYERED POLYSILICIC ACIDS

    K KURODA, T YANAGISAWA, M OGAWA, Y SUGAHARA, C KATO

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   200   135 - COLL  1990.08

    Research paper, summary (international conference)  

  • "カオリナイト-ポリアクリルアミド層間化合物の不活性雰囲気での加熱変化"(第34回粘土科学討論会講演発表論文抄録)

    水野 誠一, 小川 誠, 菅原 義之, 黒田 一幸, 加藤 忠蔵

    粘土科学   30 ( 4 ) 251 - 252  1990.02

    CiNii

  • セラミックス前駆体の合成と窒化・炭化反応に関する研究

    黒田 一幸, 菅原 義之, 加藤 忠蔵

    旭硝子財団研究報告   ( 57 ) p347 - 354  1990

    CiNii

  • カオリナイト-ジメチルスルホキシド層間化合物を用いたアクリル酸のインターカレーション(第33回粘土科学討論会講演発表論文抄録)

    長山 哲治, 菅原 義之, 黒田 一幸, 加藤 忠蔵

    粘土科学   29 ( 3 ) 137 - 137  1989.11

    CiNii

  • 固相反応を利用した粘土有機層間化合物の合成 : その1 有機アンモニウムイオンのインターカレーション(第33回粘土科学討論会講演発表論文抄録

    繁田 徳彦, 小川 誠, 菅原 義之, 黒田 一幸, 加藤 忠蔵

    粘土科学   29 ( 3 ) 137 - 137  1989.11

    CiNii

  • 固相反応を利用した粘土有機層間化合物の合成 : その2 アクリルアミド等のインターカレーション(第33回粘土科学討論会講演発表論文抄録)

    小川 誠, 菅原 義之, 黒田 一幸, 加藤 忠蔵

    粘土科学   29 ( 3 ) 137 - 137  1989.11

    CiNii

  • モンモリロナイト・ポリアクリルアミド層間化合物の合成(第32回粘土科学討論会講演発表論文抄録)

    小川 誠, 菅原 義之, 黒田 一幸, 加藤 忠蔵

    粘土科学   28 ( 4 ) 212 - 212  1988.12

    CiNii

  • カオリナイト-ポリアクリル酸層間化合物の合成(第32回粘土科学討論会講演発表論文抄録)

    長山 哲治, 黒川 重夫, 菅原 義之, 黒田 一幸, 加藤 忠蔵

    粘土科学   28 ( 4 ) 212 - 212  1988.12

    CiNii

  • SYNTHESIS OF SILICON CARBIDE FROM MONTMORILLONITE-POLYACRYLONITRILE INTERCALATION COMPOUNDS BY CARBOTHERMAL REDUCTION.

    Yoshiyuki Sugahara, Ken ichi Sugimoto, Kazuyuki Kuroda, Chuzo Kato

    Memoirs of the School of Science and Engineering, Waseda University     61 - 75  1987.12

     View Summary

    To apply intercalation compounds as precursors for carbide production by carbothermal reduction, n-CH//3(CH//2)//nNH//3** plus -montmorillonite polyacrylonitrile (PAN) intercalation compounds (n equals 5, 11) were converted into SiC. For the comparison, montmorillonite-carbon mixtures were also applied to the conversion. They were heated at 1100-1600 degree C for 1 h in Ar. From the intercalation compound with n equals 5, both alpha - and beta -SiC were detected. beta -SiC formed by the treatments above 1200 degree C, while alpha -SiC was obtained on heating above 1300 degree C. As oxides, only the Mg-Al-O compound crystallized, and no Si-containing oxides formed. The same products were obtained from the intercalation compound with n equals 11. However, it showed the lower reactivity in spite of its larger carbon content. On the other hand, only beta -SiC formed as carbide by heating the montmorillonite-carbon mixtures above 1200 degree C. Silicates of mullite and cordierite were obtained in addition to spinel, the Mg-Al-O compound, and alpha -Al//2O//3. These observations suggest that the presence of PAN in the interlayer space strongly affected the carbothermal reduction process.

  • THE CARBOTHERMAL REDUCTION PROCESS OF 2 : 1 TYPE CLAY MINERALS

    SUGAHARA YOSHIYUKI, FUKAISHI AKIHIRO, KURODA KAZUYUKI, KATO CHUZO

    Clay science   7 ( 1 ) 29 - 40  1987

     View Summary

    The 2 : 1 type clay minerals of pyrophyllite and talc were converted into nitrides by carbothermal reduction. The mixtures of the minerals and carbon black were heated at 1200-1600℃ in an N_2 flow. Pyrophyllite was converted into β-sialon and α-Si_3N_4. As oxides, mullite, α-quartz, and cristobalite were detected. On the other hand, α- and β-Si_3N_4 were obtained from talc. MgSiN_2 and Si_2N_2O were also formed as intermediates. Forsterite and enstatite were dectected as oxides. The variation in the compositions of the products suggests that both the minerals were converted into the nitrides via the decomposition to the oxides and their subsequent reduction.

    CiNii

  • PREPARATION OF A MAGADIITE-POLYACRYLONITRILE INTERCALATION COMPOUND AND ITS CONVERSION TO SILICON CARBIDE.

    Yoshiyuki Sugahara, Ken ichi Sugimoto, Tsuneo Yanagisawa, Yasuyuki Nomizu, Kazuyuki Kuroda, Chuzo Kato

    Yogyo Kyokai Shi/Journal of the Ceramic Society of Japan   95   117 - 123  1987.01

     View Summary

    A magadiite (layered polysilicate)-polyacrylonitrile (PAN) intercalation compound was first prepared to investigate its potential as a precursor for the synthesis of non-oxide ceramics by carbothermal reduction. Acrylonitrile monomer was intercalated and polymerized in the interlayer space of a C//1//2H//2//5N(CH//3)//3** plus -magadiite complex. After the cyclization of PAN by the heat treatment in air, the compound was heated in Ar flow for 2 h. Above 1300 degree C, beta -SiC was formed without the formation of any crystalline SiO//2 phases.

    DOI

  • Si//3N//4 FORMATION IN THE CARBOTHERMAL REDUCTION PROCESS OF A MAGADIITE-POLYACRYLONITRILE INTERCALATION COMPOUND.

    Yoshiyuki Sugahara, Yasuyuki Nomizu, Kazuyuki Kuroda, Chuzo Kato

    Yogyo Kyokai Shi/Journal of the Ceramic Society of Japan   95   124 - 129  1987.01

     View Summary

    Silicon nitride was formed from a magadiite (layered polysilicate)-polyacrylonitrile (PAN) intercalation compound through a novel process of carbothermal reduction. SiO//2 from magadiite was reduced above 1400 degree C without the formation of any crystalline oxides. On heating above 1400 degree C, both alpha - and beta -Si//3N//4 were detected, and the additional formation of alpha - and beta -SiC was observed by heating at 1600 degree C. On the other hand, the reactions for the synthesis from a magadiite-carbon mixture involved the formation of cristobalite as well as alpha - and beta -Si//3N//4, and beta -SiC. In addition, it was also indicated that the mixture was less reactive for the formation of Si//3N//4.

    DOI

  • CARBIDE FORMATION FROM A MONTMORILLONITE-POLYACRYLONITRILE INTERCALATION COMPOUND BY CARBOTHERMAL REDUCTION.

    Yoshiyuki Sugahara, Kenichi Sugimoto, Kazuyuki Kuroda, Chuzo Kato

    Yogyo Kyokai Shi/Journal of the Ceramic Society of Japan   94 ( 1085 ) 38 - 43  1986.01

     View Summary

    The montmorillonite-polyacrylonitrile (PAN) intercalation compound was heated in Ar flow for the application of clay-organic complexes to the preparation of carbide through the carbothermal reduction. beta -SiC was formed at 1200 degree C and both alpha -SiC and beta -SiC were detected above 1300 degree C. SiO//2 component was reduced without forming any crystalline compounds, while Al//2O//3 component formed Mg-Al-O compound. Compared with the reactions of a montmorillonite-carbon mixture, it was clarified that the presence of PAN in the interlayer space led to the formation of alpha -SiC and suppressed the crystallization of oxides.

    DOI CiNii

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Industrial Property Rights

  • 樹脂組成物、樹脂成形体、及び光学部品

    菅原 義之

    Patent

  • 結晶性シリコチタネートの製造方法

    菅原 義之

    Patent

  • 樹脂組成物、樹脂成形体、及び光学部品

    6311143

    菅原 義之

    Patent

  • 微細パターニング用表面化学処理装置

    5956053

    菅原 義之

    Patent

  • 光増幅器及びその製造方法

    菅原 義之

    Patent

  • 光増幅器及びその製造方法

    菅原 義之

    Patent

  • 多核錯体、及びその縮合体

    菅原 義之

    Patent

  • アルミナ膜とその製造方法並びに光学装置

    5062507

    菅原 義之

    Patent

  • H型層状ペロブスカイト系光触媒の製造方法およびH型層状ペロブスカイト系光触媒

    菅原 義之, 安盛 敦雄

    Patent

  • 炭化ケイ素の製造方法

    4191939

    菅原 義之

    Patent

  • 可溶性窒化アルミニウム前駆体

    菅原 義之, 黒田 一幸, 廣瀨 純子

    Patent

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Awards

  • CerSJ Fellow

    2019   The Ceramic Society of Japan  

  • JSPM Award for Distinguished Achievements in Research (2018)

    2018   Japan Society of Powder and Powder Metallurgy  

  • The Chemical Society of Japan Award for Chemical Education for 2014

    2014   The Chemical Society of Japan  

  • CerSJ Awards for Academic Achievements in Ceramic Science and Technology

    2013   The Ceramic Society of Japan  

  • 日本セラミックス協会JCerSJ優秀総説賞

    2006  

  • 日本化学会BCSJ賞

    2006  

  • 日本セラミックス協会賞進歩賞

    1992  

  • 日本粘土学会奨励賞

    1989  

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Research Projects

  • Hierarchical assemblies based on mixtures of graphene oxides and nonionic surfactants liquid crystalline phases

    Project Year :

    2019.04
    -
    2022.03
     

  • マイクロリアクターを利用した金属酸化物ナノ粒子・ナノシートの高効率表面修飾

    Project Year :

    2018.04
    -
    2021.03
     

     View Summary

    金属酸化物ナノ粒子や金属酸化物ナノシートなどの金属酸化物ナノ材料は,その大きさが十分小さい場合は,金属酸化物が有する特性に加えて透光性を示すことから,有機高分子を用いた有機-無機ハイブリッド材料のナノフィラーとして広く検討されている.しかし,金属酸化物ナノ材料は凝集してしまうと透光性が失われるため,表面修飾により有機官能基を金属酸化物ナノ材料の表面に固定化し,有機高分子マトリクス中での高分散を達成することが必要となる.そこで本研究では,効率的な金属酸化物ナノ粒子・ナノシートの表面修飾法として,マイクロリアクターを用いた二相流による表面修飾法の開発を目的としている.本年度は,これまで報告されていない液-液二相系による無機ナノシートの表面修飾の条件探索を目的として,mLスケールでの液-液二相系を用いて,無機ナノシートの表面修飾を行った.本年度は,イオン交換性層状ペロブスカイト(HLaNb2O7・xH2O,HLaNb)ナノシートの水分散液とリン酸オレイルを溶解したシクロヘキサンを用い,ガラス容器に液-液二相系を形成させ,界面でのリン酸オレイルによる表面修飾を行った.HLaNbナノシートの水分散液は,テトラブチルアンモニウムイオンを層間に導入した後,超音波を用いた剥離により調製した.二相状態を形成させた後,界面に泡立ちが起きないように水相とシクロヘキサン相をゆっくり撹拌した.最初は水相は白濁し,シクロヘキサン相は透明であったが,徐々に水相は透明となり,シクロヘキサン相は白濁した.シクロヘキサン相の生成物は,ナノシートの表面にリン酸オレイル基が固定化されたものであった.水相のpHが高いと反応が進行しないことから,ナノシート表面のテトラブチルアンモニウムイオンがプロトンと交換されることにより,反応が進行していることが推定された.2018年度の成果は,マイクロリアクターにおける二相流による表面修飾をナノシートに適用するための基礎的検討に相当し,この結果からHLaNbナノシートの水分散液ととリン酸オレイルを溶解したシクロヘキサンを用いたマイクロリアクターにおける二相流による表面修飾へ展開する.mLスケールでの液-液二相系は,金属あるいは金属酸化物のナノ粒子の表面修飾には広く応用されてきた.その際,水相にあるナノ粒子が修飾後に有機相に移動する”相間移動“現象が知られている.2018年度の結果は,”相間移動“がナノシートでも起こることを見出しており,同様の現象がマイクロリアクターの二相流でも期待できる.加えて,2018年度の成果は,新しいナノシートの表面修飾法と考えており,表面修飾技術の発展の観点からも重要な進展であると考える.金属酸化物ナノ粒子については,予備的検討の結果を踏まえ,2019年度はマイクロリアクターを用いた表面修飾の最適条件の探索を予定している.金属酸化物ナノシートについては,2018年度のmLスケールでの液-液二相系の結果と予備的検討結果を踏まえ,マイクロリアクターを用いた表面修飾の条件探索を予定している.金属酸化物ナノ粒子・ナノシートの表面修飾後,生成物の分析を固体高分解能核磁気共鳴分光分析,赤外分光分析,走査型電子顕微鏡,元素分析等により行い,その結果を作製条件にフィードバックすることにより研究を推進する

  • Preparation of thermoresponsive layered perovskites and protein separation based on dynamic control of their structures

    Project Year :

    2015.04
    -
    2017.03
     

     View Summary

    Thermoresponsive copolymer-modified inorganic nanosheets bearing N-isopropylacrylamide (NIPAAm) and (N,N-dicarbonylmethyl)aminomethylstyrene (DCAS) were prepared using layered perovskite HLaNb2O7・xH2O (HLN) through surface-initiated atom transfer radical polymerization (SI-ATRP) at the interlayer followed by their exfoliation. Their thermoresponsibility, metal-coordination ability and protein accessibility were evaluated for development of functional protein separation system. Thermoresponsive phase transition and effective coordination to Cu ions were successfully investigated using the modified nanosheets, although no reproducible results of temperature-dependent protein adsorption on the surfaces were obtained

  • New Polymeric Materials Based on Element-Blocks

    Project Year :

    2012.06
    -
    2017.03
     

     View Summary

    A structural unit consisting of various groups of heteroatoms is defined an "element-block." By employing new element-blocks and achieving hierarchical interface control in order to yield the desired functions, the creation of new materials that share, at a high level, various properties not achievable with conventional organic polymeric materials as well as forming properties of molding processability and flexible designability that inorganic materials lack can be expected. Based on this idea, we have developed various kinds of element-blocks. Furthermore, highly-functional materials can be constructed by combination of element-blocks. From these results, we can say that new diagnoses for material designs were able to be established by our research group based on element-blocks

  • Preparation of Element-blocks by Utilizing Transition Metal Oxide Nanoparticles

    Project Year :

    2012.06
    -
    2017.03
     

     View Summary

    As a new strategy for the preparation of element-blocks, which are monomers of new materials, element-block polymers, and composed of groups of a variety of elements, synthetic methods for transition-metal-oxide-based element-blocks have been developed. The preparation of titania nanoparticles and the conversion of titania nanoparticles into element-blocks by surface modification have been achieved. The conversion of oxide nanosheets into element-blocks via graft reactions has also been studied

  • 元素ブロック高分子材料の創出

    科学研究費助成事業(京都大学)  科学研究費助成事業(新学術領域研究(研究領域提案型))

    Project Year :

    2012
    -
    2016
     

     View Summary

    総括班においては、領域代表者と各班長および事務局からなる組織を形成し、研究計画から必要不可欠な高額測定機器を選定し、適切な年度と機器の管理を行うにふさわしい機関に設置できるように予算配分を行った。これらの機器を本領域研究に関係する全ての研究者が円滑かつ有効に利用できるとともに、有機的な連携を伴いながら共同利用を行える体制をつくり、特に班間における共同研究を積極的に支援するようマネジメントした。また、班間での共同研究の促進を目的として第四班を設置しているが、この第四班を主軸として、計画班が新たに開発した元素ブロックの物性や、元素ブロック高分子の材料物性に関して理論的サポートを提供する体制が整い、また、A01班からA03班の間でも共同研究が行われるようになった。各班内でも班長を中心に班会議が定期的に開かれていることに加え、キックオフミーティングの開催後、総括会議や合同班会議を行い、計画班同士の研究進捗や共同研究状況を確認した。以上、各計画班との研究体制が構築され、予定している研究体制を整えることができた。また、公開シンポや日本化学会春季年会や高分子討論会で特定セッションを開催し、元素ブロックの概念の説明や研究成果の普及に努めた。また、ホームページの立ち上げや学会などでの広報活動に関しても国内の様々な規模の学会で「元素ブロック」の概念を紹介することができた。公募班が本領域に参画し、領域内のシンポや班会議を通して連携を深めた。さらに、年度末には領域主催での合同修士論文発表会を開催した。学生間での活発な議論が行われ、若手育成の新しい方法を提示できたといえる。事務局においては領域の公開シンポジウム等の企画と運営を行うとともに、三か月に一回、ニュースレターを発行し、受賞や論文掲載など本領域に所属する研究者の対外的な成果を紹介している。

  • New Polymeric Materials Based on Element-Blocks

    Project Year :

    2012
    -
    2016
     

     View Summary

    A structural unit consisting of various groups of heteroatoms is defined an "element-block." By employing new element-blocks and achieving hierarchical interface control in order to yield the desired functions, the creation of new materials that share, at a high level, various properties not achievable with conventional organic polymeric materials as well as forming properties of molding processability and flexible designability that inorganic materials lack can be expected. Based on this idea, we have developed various kinds of element-blocks. Furthermore, highly-functional materials can be constructed by combination of element-blocks. From these results, we can say that new diagnoses for material designs were able to be established by our research group based on element-blocks

  • Preparation of "Janus"-type Nanosheets

    Project Year :

    2011.04
    -
    2013.03
     

     View Summary

    K_4Nb_6O_<17>・3H_2O ion-exchanged with (C_<18>H_<37>)_2N(CH_3)_2+ ions were reacted with phenylphosphonic acid to prepare a A-type derivative possessing modified an interlayer I. Then, C_<12>H_<25>NH_3+ ions were introduced into an unmodified interlayer II and a resulting intermediate was further treated with carboxyalkylphosphonic acids (COOHCnP;n=1-3). The nanosheets in the products were likely to possess two interlayer surfaces modified with different organophosphonate moieties

  • Synthesis of Silica-Based Nanostructured Hybrid via Supramolecular Chemical Approaches

    Project Year :

    2004
    -
    2005
     

     View Summary

    A variety of ordered hybrid materials have been obtained by self-assembly of designed amphiphilic silicon-based precursors. Alkoxysilanes and chlorosilanes with covalently attached hydrophobic organic tails are hydrolyzed to form amphiphilic molecules containing silanol groups, leading to the formation of layered (lamellar) structures. The design of molecules having alkyl chains and large oligosiloxane heads led to the formation of mesophases consisting of cylindrical assemblies, providing a direct pathway to ordered porous silica. We also reported the synthesis of silica-based hybrids with lamellar and wormhole-like mesostructures using of 1-alkynyltrimethoxysilanes. The hybrids with wormhole-like mesostructures, prepared in the presence of TMOS, were converted into mesoporous silica either by chemical treatment or by calcination. Furthermore, we have demonstrated the formation of novel layered materials from alkoxy-derivatives of bis(trichlorosilanes) having methylene, ethylene, and phenylene bridges. On the other hand, we discovered a new class of cage-like oligomers which were selectively formed by hydrolysis and polycondensation of a methylene-bridged bistrialkoxysilane precursor in the presence of tetramethyl-ammonium hydroxide.

  • 層状オクトシリケートの有機修飾による新規ケイ酸塩骨格の構築

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(萌芽研究)

    Project Year :

    2003
    -
    2004
     

     View Summary

    1)アルコキシシリル化オクトシリケートの加水分解による2次元および三次元ケイ酸骨格の分子操作
    層状ポリケイ酸塩の一種であるオクトシリケートにアルコキシトリクロロシラン類でシリル化することにより、アルコキシクロロシリル基が層表面に規則的に配列して固定化した。さらにアルコキシ基およびクロロ基を加水分解し、Si-OH基へ転換することでケイ酸ナノ構造を構築した。得られた構造について詳細に検討したところ、加水分解の際に用いる溶媒を変化させることにより、得られるケイ酸ナノ構造を2次元構造と3次元構造とに作り分けることが可能であることが分かった。本手法は、各段階(層状ポリケイ酸塩・シリル化剤・加水分解条件)で様々なシリカナノ構造を調整が可能であるという特長を有し、より設計性の高いシリカ構造の構築が可能である。今後、結晶構造が明確な様々な層状ポリケイ酸に本手法を適用し、新たなナノ構造の構築を試みるとともに、得られた構造と機能(吸着能・触媒能)との相関について検討する。
    2)フェニレン架橋化オクトシリケートの合成
    上記の系で、層間の三次元化はSi-O-Si結合で架橋していたが、層間を有機基で架橋する系への展開を試みた。架橋する有機種を剛直なフェニル基とすることによって、ケイ酸層と架橋有機分子との間にナノ空間を作り出すことに成功した。本手法により得られたナノ空間は、規則的なケイ酸表面と有機分子に規則的に囲まれており、吸着能などに特異的な影響を与えると予想される。今後、有機基やケイ酸構造を精密に設計することで、より精緻に構造を設計することを計画している。

  • Formation and Functionalization of Inorganic-Organic Nanostructured Materials Prepared by Self-Organization of Organoalkoxysilanes.

    Project Year :

    2002
    -
    2003
     

     View Summary

    Structural control of silica-based hybrids derived from organoalkoxysilanes is a subject of great importance. We developed a new approach to create mesostructured silica-based hybrids by using newly designed siloxane oligomers (C_nH_<2n+1>Si(OSi(OMe)_3)_3, n=8-18) as single precursors. Either well-ordered lamellar phase or slightly distorted 2D hexagonal phase was obtained depending on the alkyl chain lengths in the precursor. The hybrids with a hexagonal structure can be converted to meso-or micro-porous silica upon calcination to remove organic groups, which is the first example of the synthesis of hexagonally ordered porous silica without the use of surfactants as template.
    We also reported the synthesis of novel layered silica-organic nanostructured materials, consisting of bimolecular layers of long-chain alcohols and thin silica layers, from alkoxytrichlorosilanes (n-C_nH_<2n+1>OSiCl_3, n=12-20). The formation relies on the self-assembly of alkoxysilanetriols (n-C_nH_<2n+1>OSi(OH)_3) generated by the preferential hydrolysis of Si-Cl groups in the precursors. Polycondensation of alkoxysilanetriols was found to proceed in the solid state to form silica networks, being accompanied by the cleavage of the alkoxy groups.

  • 微生物機能を利用した資源循環型水環境プロセスの構築

    文部科学省 

    Project Year :

    1999
    -
    2003
     

  • 高機能性新半導体デバイス開発

    文部科学省 

    Project Year :

    1998
    -
    2002
     

  • Chemical design of inorganic-organic mesostructured materials and mesoporous materials using molecular assemblies

    Project Year :

    1999
    -
    2000
     

     View Summary

    The formation of novel mesoporous silicas KSW-2 with rectangular arrangements of square or lozenge one-dimensional channels by mild acid treatment of a layered alkyltrimethylammonium (C16TMA)-kanemite complex was performed.
    A continuous mesoporous silica film with uniaxially aligned hexagonal mesochannels was formed on a silica glass substrate using a rubbing-treated thin polyimide coating on the substrate.
    Taxol and chlorophyll a were adsorbed into FSM-type mesoporous silicas. The adsorption behavior of Taxol depended on the pore size and the solvents. The desorption of Taxol could be performed with a mixture of methanol and water. Chlorophyll a was adsorbed into the mesoporous silica without pheophytinization when the surface silanol groups were modified with 1, 4-butanediol, whereas pheophytinization occurred in unmodified mesoporous silica. In order to understand the nature of mesoporous silicas as immobilizing media for organic guest species, the adsorption of a cationic luminescence probe, tris (2, 2'-bipyridine) ruthenium (II), into a mesoporous silica was investigated. The adsorption of a cationic azobenzene derivative into aluminium containing mesoporous silica films was also investigated. Photoisomerization was found to occur and the mesoporous aluminium containing silica films were proved to be useful reaction media to immobilize organic photochromic species.

  • Preparation of Layered Perovskite-Organic Composites and their Application to Photo-induced Electroconduction

    Project Year :

    1998
    -
    2000
     

     View Summary

    Preparation of new protonated layered perivskite
    Since the number of layered perovskits is very limited, we found a novel route to prtonated layered perovskites. Aurivillius phases (Bi_2O_2[A_<n-1>B_nO_<3n+1>] ; n=3, A=(Sr, Na), B=Nb ; n=2, A=Sr, B=Ta ; n=2, without A-ions, B=W) were acid-treated at room temperature. Bismuth oxide sheets were selectively leached, and the structures of perovskite-like slabs were retained. For charge compensation, protons were introduced to form protonated layered perovskites with new compositions.
    Preparation of inorganic-organic hybrids
    Layered perovskite H[LaNb_2O_7] with interlayer surface modifled with alkoxyl groups was prepared. Using n-alkoxyl derivatives as intermediates, H[LaNb_2O_7] can be modified with various alcohols. In a similar fashion, H[LaNb_2O_7] can be modified with silanol-terminated poly(dimetylsiloxane) (HO(SiMe_2O)_mH).
    Preparation of intercalation compounds
    H_<1.8>[Bi_<0.2>Sr_<0.8>Nb_2O_7] prepared via selective leaching from an Aurivillius phase Bi_2SrTa_2O_9 was allowed to react with n-alkylamines. All the n-alkylamines can form intercalation compounds via an acid-base reaction.
    Ptotochromism upon UV irradiation
    A methoxyl derivative of H[LaNb_2O_7] turned brue when it was irradiated with UV light. The blue color vanished gradually in air, but it can develop again upon UV irradiation. The electrical resistivity of the colored sample was significantly larger than that of the uncolored sample.

  • Preparation of Aluminum Nitride-Titanium Nitride Solid-Solutions using Preceramic Materials

    Project Year :

    1998
    -
    1999
     

     View Summary

    Pyrolytic preparations of Ti-Al-N ceramics from three blended precursors were investigated. The precusors were perpared by stirring (HAINィイD1iィエD1Pr)ィイD2mィエD2 and an aminolysis product of Ti (NMeィイD22ィエD2)ィイD24ィエD2 with MeHNCHィイD22ィエD2CHィイD22ィエD2NHMe in CィイD26ィエD2HィイD26ィエD2. IR and ィイD11ィエD1H NMR analyses suggested that essentially no Ti-N-Al bonds were present in the precursors. Pyrolysis of the precursors under NHィイD23ィエD2-NィイD22ィエD2 led to the formation of brown solids with ceramic yields of about 30%, and the Ti : Al ratios in the pyrolyzed products were close to those of the precursors. XRD analysis of the pyrolyzed product from the precursor with Ti : Al=5 : 1 indicated the formation of a NaCl-type compound as the only crystalline phase. Pyrolysis of the precursor with Ti : Al=2 : 1 led to the formation of AIN besides the major NaCl-type compound. A ceramic composite containing AIN and the NaCl-type compound was formed by pyrolysis of the precursor with Ti : Al=1 : 2. The lattice parameters of the NaCl-type compounds indicate that it is Ti (N, C, O) rather than (Ti, Al) N. The SEM observation revealed that the products consisted of particles with diameters of 20-40 nm.

  • Development of Synthetic Methods for New Porous Materials by the Conversion of Inorganic Layred Compounds into Three-dimensional Networks

    Project Year :

    1993
    -
    1995
     

     View Summary

    1) Reactions between a surfactant hexadecyltrimethylammonium ion (C_<16>TMA^+)and kanemite (NaHSi_2O_5・3H_2O) was studied with various C_<16> TMA^+/Si rations. If C_<16>TMA^+/Si was larger than 0.2, lamellar phase was obtained. Solid-state NMR showed that this phase contained Q^4 silicate species, indicating that this reaction was not topotactic intercalation one. When the reaction proceeded at ambient temperature, the lamellar phase at the intial stage contained no Q^4 silicate species, suggesting that the initial product was intercalation compound. Thus, it is assumed that the initially-formed intercalation compound was converted into a cross-linked structure during the reaction.
    2) The surface of a porous material derived from kanemite via folded-sheet mechanism was modified by using various silylating reagents. The surface was modified by the reactions with RMe_2SiCl in toluene under protective nitrogen atmosphere. IR,solid-state NMR and DTA showed the successful immobilization of RMe_2Si-groups via siloxane bonding. XRD analysis showed that the structure of the silicate was maintained during the surface modifications. The pore-size distributions indicate that the mean pore size decreased as the length of the alkyl chain increased, suggesting successful control of pore size by surface modification.

  • 無機高分子を前駆体としたAlN生成過程に対する前駆体の分子量の影響

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(奨励研究(A))

    Project Year :

    1993
     
     
     

     View Summary

    本研究では2種の窒素源を共存させたLiAlH_4-CH_3NH_2・HCl-(CH_3)_2NH・HCl系を用い、溶媒に可溶な前駆体ポリマーの合成を試み、さらにその分子量の影響について検討を行った。LiAlH_4、CH_3NH_2・HCl及び(CH_3)_2NH・HClをTHF溶媒中、N_2雰囲気下で環流し、AlN前駆体を合成した。続いて、合成された前駆体をAr雰囲気下において1600℃で2h焼成した。分析は前駆体に関してはIR、^1H-NMRを、焼成物に関してはXRDを用いた。
    CH_3NH_2・HCl:(CH_3)_2NH・HCl(モル比)=4:1で共存させた時、沈殿は生成したものの、沈殿に対し約1/2の重量の可溶性前駆体が得られた。この可溶性前駆体の^1H-NMRでは2.5〜3.1ppmにブロードな共鳴線が観測された。一方、窒素源として(CH_3)_2NH・HClのみを用いた時には[H_<>AIN(CH_3)_2]_3のCH_3基に夜と推定される2.55ppmの共鳴線が主に観測された。なお、2.55ppm以外の共鳴線は弱いものであった。また、窒素源としてCH_3NH_2・HClのみを用いたときは可溶性生成物が得られなかった。以上のことから2種の窒素源を共存させたLiAlH_4-CH_3NH_2・HCl-(CH_3)_2NH・HCl系においては、可溶性前駆体の窒素源として、CH_3NH_2・HCl及び(CH_3)_2NH・HClの両者が寄与していることが示唆された。続いてこの前駆体を1600℃で焼成したところ約60%の収率で灰色の個体が得られ、XRD分析の結果、焼成物はAlNであることが明らかとなった。
    次にCH_3NH_2・HCl:(CH_3)_2NH・HClのモル比を変化させて合成を行ったところ、CH_3NH_2・HClの量を増大させると溶解物が得られず、重合反応がさらに進行して分子量が増大したものと推定された。一方、(CH_3)_2NH・HClの量を減少させると[H_2AIN(CH_3)_2]_3が明らかに生成しており、分子量が大きく減少したものと推定され、また熱分解時の収率も大きく低下した。

  • The Study on the Intercalation Chemistry of Layered Oxides for the Potential Use of the Resultant Intercalation Compounds as Functional Materials

    Project Year :

    1989
    -
    1990
     

     View Summary

    In order to establish the synthetic ways of intercalation compounds having possible application as functional materials, various intercalation compounds were prepared by using appropriate guests and hosts. The following results were obtained.
    1. A viologen was intercalated into the interlayer space of vanadium pentoxide hydrate chemically (by ionーexchange) and electrochemically.
    2. When tris (2,2'-bipyridine) metal complexes were allowed to react with K_4Nb_6O_<17>, potassium ions were replaced with the complexes ; however, the tris-form complexes transformed into bisーform ones during the reaction. On the contrary, when potassium ions were exchanged for alkylammonium ions in advance, the complexes were incorporated in the interlayer space as trisーform ones. K_4Nb_6O_<17> has two kinds of interlayers, so that the intercalation compound containing the complexes in one kind of interlayers and that containing in both kinds of interlayes can be prepared.
    3. When sodium ions in synthetic sodium polysilicate of kanemite were exchanged for trimethylalkylammonium ions, the layers deformed to form three dimensional network. Further heat treatment resulted in the formation of microporous materials having narrow pore size distribution.
    4. Anionic porphyrin and dyes were successfully intercalated into the interlayer space of hydrotalcite, which has anionーexchange property.
    5. Some kinds of guests (acrylamide, alkylammonium salts, and alkylamines) were intercalated into montmorillonite by solidーsolid reactions easily. Similarly, 2,2'-bipyridine was intercalated into transition metalーform montmorillonites to form tris (2,2'-bipyridine) metal complexes in the interlayer space.

  • Study of Human Oriented Manufacturing System in EC

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    Three European researchers were invited to the international symposium at Waseda Univ., and human-oriented manufacturing systems (HOMS) in EC were studied through them.(1) Prof.Dr.B.Knave, Dept.of Neuromedicine National Inst.of Occupational Health introduced the health effects at the computer works in EC.Some of the health effects are eye discomforts, skin symptoms and hypersensitivity to electricity. To solve these problems HOMS concept is very important.(2) Dr.D.Brandt, University of Technolohy, Aachen introduced human-oriented machine tools. In order to design the human interface he insisted the cognitively compatible design methodology using mental models. An actual human-machine interface has been developed for CNC lathes. And users generally appreciated the straightforward way of working with this system.(3) Dr.E.A.Hartmann, John Deere Werke Mannheim introduced the methodical steps of the human-oriented tractor final assembly system. Nine scenarios were proposed and evaluated according to the newly developed criteria. And one scenario was selected and it is now under construction.Through these presentations the most advanced technologies of HOMS and related problems were effectively studies. This symposium was very useful for not only our research members but also many other persons concerned

  • Preparation of Photofunctional Materials using Porous Organoamonium-Mdified Clay Minerals as Porous Media

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    Various photofunctional materials have been prepared by intercalating organic molecules in the interlayr space of clay minerals modified organically by ion-exchange with various organoammonium ions. Two kinds of host materials were used ; one was smectite with various small organoammonium ions such as tetaramethylammonium (Me_4N^<+・>, TMA) ion to give porous media, and the other was ammonium ions possessing long-chain alkyl groups (R_<4-x>NH_x) to offer extremely hydrophobic environmetns. As guest species C1,4-dihyroxyantraquinone (DAQ), 2,4-hexadiyne-1,6-diol (DA), pyrene, and azobenzene were used. When DAQ was intercalated into pillared saponites, the adsorption and fluorescent spectra were dependent on the type of the pillars, suggesting that the type of the pillars changed the environments of DAQ.DA was also successfully intercalated into the interlayr space of pillared saponites, but DA cannot be polymerized in the interlayr space by UV irradiation, suggesting that the polymerization was sterically inhibited in the interlayr space. Pyrene was intercalated into the interlayr space of smectite ion-exheanged by long-chain alkylammonium ions. Excimer formation behavior of pyrene was not subjected to the type of ammonium ions, but depended on the orientation of alkyl chains. Azobenzene in the interlayr space of tetra-fluor-silicic mica ion-exchanged by long-chain alkylammonium ions exhibited reversible cis-trans photo-isomerization. The photo-isomerization behavior depended on the length of alkyl chain and temperature

  • 無機高分子を前駆体とする窒化アルミニウム/窒化ケイ素ナノコンポジットの合成

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    有機金属化合物(前駆体)の熱分解を利用してセラミックスを合成することが可能である、本手法はセラミック複合材料合成法として有用である。そこで、本研究ではAlN前駆体である(HAlNPr^i)_mとSi_3N_4前駆体である(MeSiHNH)_nが均質に分散した前駆体を合成し、これを熱分解してセラミックス複合材料を得ることを試みた。生成物中のAl:Si比が1:1となるように(HAlNPr^i)_m〔固体〕と(MeSiHNH)_n〔液体〕を仕込んで室温で攪拌したところ、次第に粘性が高まり最終的には白色の固体となった。これを前駆体とした際のセラミック収率は、室温〜900℃のTG測定において約70%であり、(HAlNPr^i)_mの35%、(MeSiHNH)_nの30%に比べ非常に高い値を示した。また、(HAlNPr^i)_mと(MeSiHNH)_nを単独で熱分解した際に観測される(HAlNPr^i)_m、(MeSiHNH)_nなどの分子イオンやフラグメントイオンが、この前駆体を用いた場合は観測されなかった。従って、前駆体合成時または熱分解時に(HAlNPr^i)及び(MeSiHNH)間で架橋構造が形成されていることが示唆された。前駆体のAr雰囲気下での焼成物は、800℃処理ではアモルファスであったが、1350℃処理によりブロードな回折線を生じた。さらに1600℃処理を行うと結晶化の進行が確認され、主にAlNとSiCが生成していると考えられた。この試料のSEM観察では20〜30nmの粒子が見られた。一方、NH_3雰囲気下の焼成物では、主にAlN及びSi_3N_4が生成していると考えられた。またSEM観察の結果、60〜200nmの粒子から構成されていることがわかった

  • 構造を制御した窒化チタン前駆体の合成とその熱分解過程の検討

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    金属(Ti)-窒素結合を持つ前駆体の熱分解によるTiN合成の手法を確立するため、テトラキスジメチルアミドチタン(Ti(NMe_2)_4)とジアミン類のアミン交換反応により得られた前駆体の熱分解について検討した。ジアミン類にはRHNCH_2CH_2NHR(R=H,Me)及びMeHNCH_2CH_2NHMeと炭素数(C/N=2)の等しいHN(CH_2CH_2)_2NHを用いた。MeHNCH_2CH_2NHMeとのアミン交換により得られた前駆体は有機溶媒に可溶であり、オリゴマーであると考えられたのに対し、H_2NCH_2CH_2NH_2やHN(CH_2CH_2)_2NHから得られた前駆体は有機溶媒に不溶なポリマーであった。これらの前駆体の熱分解はAr雰囲気下1500°CあるいはNH_3雰囲気下600°Cとそれに続くN_2雰囲気下1350°Cで行った。Ar雰囲気下における熱分解では全ての系において多量のTiが損失していることが明らかになった。特にMeHNCH_2CH_2NHMeから得られたオリゴマーを用いた場合には約43%のTiが熱分解中に失われていた。焼成物のXRD分析により、Ar雰囲気下で得られた焼成物は全てTi(N,C,O)固溶体であることが示された。また焼成物は多くの炭素を含有しており、その量は官能基の種類に大きく依存していた(18.2%:H_2NCH_2CH_2NH_2、25.7%:MeHNCH_2CH_2NHMe、36.3%:HN(CH_2CH_2)NH)。一方、NH_3/N_2雰囲気下では熱分解過程におけるTiの損失が抑制された。特にH_2NCH_2CH_2NH_2から得られた前駆体の熱分解では、ほとんど全てのTiが熱分解過程において損失することなく、焼成物中に残存した。またNH_3/N_2雰囲気下で得られた焼成物の格子定数は全て報告されているTiNの値とよく一致し、焼成物中にはほとんど炭素が含まれていなかった

  • Preparation of novel protonated forms of the ion-exchangeable layered perovskite via selective reaching of bismuth oxide sheets and their application to photocatalytic activities

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    Photocatalytic activities of the protonated forms of ion-exchangeable layered perovskites.We investigated the photocatalytic activities of the Aurivillius phases Bi_2ANaNb_3O_<12> (A=Ca or Sr,Bi_2CaNaTa_3O_<12> and the protonated forms of ion-exchangeable layered perovskite prepared from these Aurivillius phases via selective leaching of bismuth oxide sheets by acid treatment. Photocatalytic activities were estimated based on H_2 evolution behavior from aqueous ethanol solutions (containing 20% ethanol) under UV irradiation. Aurivillius phases showed no activities for H_2 evolution, while the protonated forms exhibited the photocatalytic activities. UV-Vis diffuse reflectancee spectra indicated that selective leaching of bismuth oxide sheets led to the change in electric structure. XRD patterns of the protonated forms after H_2 evolution showed the increase in the interlayer distance, indicating the effective use of the interlayer space during H_2 evolution. Therefore, the difference in the photocatalytic activity behavior between the Aurivillius phases and the protonated forms is attributable to the change in the position of the bottom of the conduction bands and/or the increases in surface area caused by the selective leaching of bismuth oxide sheets.Preparation of novel double-layered tungstic acid.We conducted acid treatment of an Aurivillius phase, Bi_2W_2O_9, whose structure was similar to that of ion-exchangeable layered perovskite. XRD,ICP and TG analyses as well as TEM observation showed the selective leaching of the bismuth oxide sheets, indicating the formation of the novel tungstic acid, H_2W_2O_7・nH_2O, which could potentially exhibit the photocatalytic activities.Reaction of the protonated forms of layered perovskite and alcohols.Since the n-alcohol is generally used as a sacrificial reagent for photocatalytic H_2 evolution from water, we investigated the interaction between the protonated forms of ion-exchangeable layered perovskite HCa_2Nb_2O_<10>・xH_2O and n-alcohol. The reaction of HCa_2Nb_2O_<10>・xH_2O with n-alcohols led to the formation of alkoxy-derivatives of HCa_2Nb_2O_<10>・xH_2O.To achieve high photocatalytic activities, we explored the new pillaring method using organic derivatives of layered perovskite. When we conducted the reaction of CH_2=CH(CH_2)_nO- derivatives (n=3,8) of HLaNb_2O_7・xH_2O with hydrochlorosilanes and oligosiloxanes, XRD,IR and NMR analyses showed the occurrence of hydrosilylation in the interlayer space, indicating that hydrosily lation is utilizable for pillaring

  • カテコール誘導体修飾遷移金属アルコキシドからの有機-無機ハイブリッドの合成

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    昨年度カテコール誘導体がチタンアルコキシドと反応する事が明らかとなったので、環状シロキサン(1,3,5,7-テトラメチルシロキサン;TMCTS)のヒドロシリル化反応を利用して複数のカテコレート基を持つ分子を合成し、チタンイソプロポキシドとの反応を試みた。まずTMCTSと4-アリルベラトロールとのヒドロシリル化反応を行ったところ^1H、^<13>C NMR、IRからSi-H基、C=C基の消失が明らかとなった。さらに^<29>Si NMRではTMCTSで見られた-30ppm付近のシグナルが試料において-20ppm付近にシフトしており、Si環境が変化していた。以上からヒドロシリル化反応の進行が示された。次に生成物とBBr_3との反応によりエーテル結合の開裂を行った。^1H、^<13>C NMR、IRからOMe基の消失とOH基の生成が示されたことからOMe基からOH基への変換が示唆された。^<29>Si NMRではシクロテトラシロキサン骨格が反応後も維持されていた。エーテル結合の開裂後の化合物とTi(O^iPr)_2(acac)_2(acac=アセチルアセトナト配位子)との反応を行ったところ、^1H NMR、IRからOH基の消失が、^1H、^<13>C NMRからO^iPr基の消失が示された。また^<13>C NMRからカテコールのC-Oを示すシグナルが大きく高周波数側にシフトしており、反応によりC-O環境が変化していたことがわかった。これらの結果はカテコール誘導体が、^iPrOHの脱離を伴いカテコレート基としてTiに配位したことに起因すると考えられる。さらに^<29>Si NMRからシクロテトラシロキサン骨格は維持されていることが明らかになった

  • 有機修飾ナノシートのゾル-ゲル反応による多孔質材料の合成とその光触媒能の調査

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    層状金属カルコゲンハロゲン化物の一種であるTiOCIは、層表面に反応活性なTi-Cl結合が規則正しく配列していることから、アルカリ金属アルコキシドと反応させることにより、アルカリハライドの脱離と同時にアルコキシ基が層表面に固定されることを昨年度は明らかにし た。本年度は、これらの結果を受け、まずアルコキシ基修飾ナノシートのゾル-ゲル反応を試みたが、溶媒中で剥離挙動が認められず、多孔体を合成する事はできなかった。そこで高分子中にナノシートをランダムに分散させ、得られたハイブリッドを熱処理する事により多孔体化するルートを探索した。2重結合を持つアルコールを用いてナノシートを修飾し、その後SiH基を持つケイ素系高分子のグラフトをヒドロシリル化反応を行った。ヒドロシリル化反応により層間距離は増加したものの、積層方向の規則性は反応後も保たれており、多孔体化の前駆体とはならないと考えられた。そこで、ポリエチレングリコール(PEG)をりチオ化し、TiOClと直接反応させてオキシエチレン鎖の固定化を試みた。平均分子量約200のPEGを用いた反応では、層間距離は増加したものの、積層方向の規則性は保たれていた。一方、平均分子量約600のPEGを用いた反応では、積層方向の規則性が認められないハイブリッドを得る事ができた。しかしながら、微構造を観察したところ、積層が乱れただけで剥難には至っておらず、ハイブリッドを多孔体の前駆体として用いる事はできなかった

  • Development of High Performance Hybrid Ceramics by Atomic Scale Modification

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    As a part of development of high performance hybrid ceramics by atomic scale modification, functions of dopants segregated at grain-boundaries of oxide protective layers that were formed on the heat resisting alloys was elucidated. The oxide layers with excellent grain-boundary diffusion barrier were designed to further improve the high-temperature durability of the alloys. Furthermore, a three-dimensional orientation of zeolite crystals that contain dopants acting as catalysts and adsorbents could be performed, and unique nano-structures in the crystals were produced by ion irradiation

  • 層状リン酸ジルコニウムと及びその有機誘導体の新規な化学的合成ルートの開発

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    ZrOCl2・8H2Oとリン酸モノエステルROP(O)(OH)2から,層表面にP-OR基を有する層状リン酸ジルコニウム(ZrP)有機誘導体を合成できることが知られている.そこで本研究では,金属イオンや金属錯体への親和性の高さから抽出剤として広く用いられているリン酸トリブチル(TBP)を用い,ZrPの有機誘導体の直接合成を試みた.ZrOCl2・8H2OとTBPをオートクレーブ中で150℃,2日間反応させた.その後遠心分離,アセトンによる洗浄,風乾を経て生成物を得た.生成物のXRDパターンでは,1.62nmに回折線が観測され,これは報告されているα-ZrPの有機誘導体Zr(O3POC4H9)2の層間距離(1.59nm)に類似した値であった.生成物のIRスペクトルにおいては,TBPで観測されるP=O岡の伸縮振動が反応後ほぼ消失した.また,P-O伸縮振動付近のプロファイルはP-OH基による吸収帯が観測されなかった事以外はα-ZrPのスペクトルに類似していた.一方,31P MAS NMRスペクトルにおいては,0ppm[(C4H9O)3P=0],-6ppm[ZrOP(OC4H9)3],-14ppm[(ZrO)2P(OC4H9)2],-21ppm[(ZrO)3POC4H9]にシグナルが観測された.シグナル強度から主なP環境は(ZrO)3POC4H9であり,これはα-ZrPのP環境に対応する.以上の結果から,反応過程中にTBPの有する3つのn-ブトキシ基のうち2つがZrOCl2・8H2O中に含まれる水により加水分解され,n-ブトキシ基を有するα-型構造の誘導体が生成したと推定される

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Specific Research

  • Hf-N系前駆体を用いた立方晶窒化ハフニウムとその固溶体の高圧合成とその特性評価

    2019   谷口尚, 川村史朗, ゲガンレジス

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    切削工具等へ応用されている超硬材料として期待される立方晶窒化ハフニウム(Hf3N4)の合成には高温・高圧が必要である。立方晶窒化ハフニウムは、これまで10 GPaを超える圧力で合成されてきたが、提案されている相図からはより低い圧力で合成できる可能性が考えられる。そこで本研究では、立方晶窒化ハフニウムの新たな合成法を探索するため、ベルト型高圧装置を用い、ハフニウム-窒素結合を有する非晶質固体からの5.5-7.7 GPaでの立方晶窒化ハフニウムの合成を試みた。種々の温度で合成を試みたが、今回の実験条件では、立方晶窒化ハフニウムの生成は認められなかった。

  • 二層構造ナノシートをナノ容器とした色素の固定化と色素/ポリマーハイブリッドの作製

    2017  

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     本研究は、二層構造ナノシート層間に色素を凝集させることなく固定化するとともに外部表面からポリマー鎖を生長させ、さらに二層構造ナノシートをポリマーマトリクス中に分散させて、色素/ポリマーハイブリッドを作製することを目的とした。二層構造ナノシートの合成は、反応性の異なる2種類の層間が交互に存在している構造を有する層状六ニオブ酸三水和物を用いて行い、色素にはトリスビピリジルルテニウム錯体を用いた。ドデシルアンモニウムイオンイオンを層間Iと層間IIの両方にイオン交換反応で導入して中間体とし、トリス(2,2'-ビピリジル)ルテニウム(II)錯体とのイオン交換を試みたが、適切な条件を見出すことはできなかった。

  • チタニアナノ粒子と有機高分子との複合化による高屈折率ハイブリッド材料の作製

    2012   斉藤 ひとみ, Bruno Boury, 松川 公洋

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     二酸化チタンは高い屈折率を示すため、二酸化チタンナノ粒子は高屈折率有機―無機ハイブリッド材料の作製に応用されている酸化物である。そこで、二酸化チタンナノ粒子を用い、表面修飾による表面への有機基の導入と、得られた有機修飾ナノ粒子のエポキシ樹脂への添加を試みた。二酸化チタンナノ粒子は、一般には水分散液として入手できる。しかしながら、水分散液を用いると、有機基の導入反応が難しいことに加え、表面にある程度有機基が導入された時点で沈殿するため、有機基の導入には水分散液は適さないと考えられる。また、二酸化チタン表面はそれほど反応性が高くないので、有機基の導入には還流操作が必要になる。 そこで本研究では、反応活性基を二酸化チタン表面に導入し、これを用いて有機基の導入を行うことを試みた。様々な合成法の中で、非水ゾル-ゲル法を利用すると、表面に反応活性なCl 基やO-i-Pr 基を有する二酸化チタンナノ粒子の合成が可能となる。そこで出発物質に四塩化チタンを用い、ジイソプロピルエーテルを酸素ドナーとしてソルボサーマル条件で二酸化チタンナノ粒子の合成を行った。得られた二酸化チタンナノ粒子は粒径10 nm以下の球形粒子であった。またX線回折分析から、生成物は非晶質であることがわかった。 二酸化チタンナノ粒子のジクロロメタン分散液とn-オクチルホスホン酸の反応を、室温で24時間処理することにより行った。生成物の赤外吸収スペクトルでは、n-オクチル基による吸収帯が現れており、生成物中にn-オクチル基が存在することが示された。生成物の固体31P NMR測定では、21 ppmと27 ppmにシグナルが現れており、2種類の環境が存在することが示唆された。熱重量分析では、2段階の重量減少が観測され、2段目の200℃以上の約22%の重量減少はオクチル基の分解によると思われた。 n-オクチルホスホン酸で修飾した二酸化チタンナノ粒子をエポキシ樹脂に導入したところ、いずれの組成でも透明な有機―無機ハイブリッドフィルムを得ることができた。633 nmでの屈折率はポリマー単独の値(1.51)から増加し、62.4 mass%の二酸化チタン添加では、1.66となった。

  • トリアルキルホスフィンオキシドのインターカレーションによる層状酸化物の酸性点評価

    2010  

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     積層しているナノシートからなる層状遷移金属酸化物は、層間のイオンをプロトンで交換する事により固体酸となる。プロトン交換された層状遷移金属酸化物は、ナノシートを剥離させて高表面積を持つ構造に変換することにより、固体酸触媒として応用できる。一方、これらの層状遷移金属酸化物は、層間にイオンや分子をインターカレートする事が可能である。従って、層間にプローブ分子を導入する事ができれば、剥離させる事なく、固体酸としての評価を簡単に行う事ができる。そこで本研究では、層状固体酸であるH型層状ペロブスカイト[HLaNb2O7・xH2O (HLaNb)、HCa2Nb3O10・xH2O (HCaNb)]の固体酸性を、トリアルキルホスフィンオキシド(TEPO)を層間に導入する事により評価した。H型層状ペロブスカイトへのインターカレーション反応はn-デコキシ基修飾体を中間体に用いて少量の水とともにTEPOと150&#730;Cで5日間反応させることにより進行させた。反応は層構造を保持したまま進行した。層間内におけるTEPOの存在状態は固体31P MAS NMR、IRから評価した。31P MAS NMRでは物理吸着したTEPO (50 ppm)からそれぞれ低磁場シフトした単一のシグナルを観測した(TEPO-HLaNb:94 ppm、TEPO-HCaNb: 93 ppm)。したがって、TEPOは酸点に配位しており、その配位環境はそれぞれ単一であると考えられる。IRスペクトルにおいても、ν(P=O)の吸収帯がTEPOの1157 cm-1からTEPO-HLaNbでは81 cm-1、TEPO-HCaNbでは71 cm-1低波数側へシフトしており、31P MAS NMR結果を支持していた。以上の結果から、TEPOはn-デコキシ基の加水分解と同時に生じた層表面のBr&#248;nsted酸点であるOH基に配位して存在していると考えられる。

  • 層状遷移金属酸化物へのオルガノホスホン酸のグラフト反応を利用した層表面修飾

    2009  

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    イオン交換性層状ペロブスカイトは, Ruddlesden-Popper相と交換性陽イオンの密度がRuddlesden-Popper相の半分となっているDion-Jacobson相がある.これらの化合物を酸処理すると,層間のアルカリ金属イオンがプロトンに置き換わったH型層状ペロブスカイトが得られる.そこで本研究では,Dion-Jacobson型層状ペロブスカイトであるHLaNb2O7・xH2O(HLaNb)を用い,有機ホスホン酸による層表面修飾を検討した.HLaNbのデコキシ基誘導体(C10-HLaNb)とフェニルホスホン酸(PPA)またはアルキルホスホン酸[CnP (nは炭素数)]をモル比1 : 4で加え,溶媒として2-ブタノン20 mL(含水量1 mass %)とともにアンプル封入し80℃,48 h反応させ,生成物を得た(PPA/C10-HLaNb,CnP/C10-HLaNb).これを遠心分離し,アセトンで洗浄した後,風乾したものを試料とした.反応後,XRDパターンにおいて,C10-HLaNbのペロブスカイト層と垂直方向の規則性を示す(001)面による回折線が消失し,新規回折線が出現した.それらの回折線のd値はPPA/C10-HLaNbでは2.31 nm, CnP/C10-HLaNb では2.09~5.26 nmであった.反応生成物の31P MAS NMR測定では,PPA/C10-HLaNbでは13 ppm, CnP/C10-HLaNbでは28~30 ppmにそれぞれ1本のブロードなシグナルを観測した.これらの値はそれぞれのホスホン酸のケミカルシフトから2~11 ppm高磁場へシフトしたものであり,P-O-Nb結合の生成が示唆される.これらの結果から,有機ホスホン酸が層表面にグラフトしたことが明らかとなった.

  • 層状オキシハロゲン化物ナノシートを利用した共有結合界面型有機-無機ハイブリッド

    2008  

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    層状遷移金属オキシハライド(MOX;Mは遷移金属,Xはハロゲン)は,インターカレーションのホストとしても用いられているが,ハロゲンが反応活性であることを利用すると,ハロゲンの置換反応により官能基をグラフトさせる事ができる.代表的なホストであるFeOClと同一構造を持つTiOClに関しては,これまでほとんど検討は行われていない.そこで本研究では,TiOClとリチウムエトキシド(LiOEt)との反応について検討を行った.エタノール中で両者を混合してアンプルに封入し(TiOCl:LiOEt = 1:1.3),120℃ で7 日間反応させた.TiOClは層間距離に対応する回折線が d = 0.80 nm に現れるが,反応後この回折線は消失し,新たにd = 1.19 nmに対応する回折線が認められた.また対応する2次回折も現れた.走査型電子顕微鏡で形態を観察したところ,TiOClと反応生成物はともに板状結晶であり,形態は極めて類似していた.電子線を板状結晶に対して垂直方向から入射して回折パターンを計測したところ,TiOClと反応生成物は極めて類似したパターンを示した.また,反応生成物では新しいスポットが認められており,対称性が低下したことが明らかとなった.固体高分解能NMRで有機基について調査したところ,反応後アルファ炭素によるシグナルだけが大きくシフトし (71 ppm),この値はTi(III)を含むTi(OEt)3のアルファ炭素のシグナルのケミカルシフト(68.5と66.7 ppm)に近い値であった.以上の結果から, Cl基をエトキシ基で置換した生成物が得られたものと推定された.

  • 層状タングステン酸・層状モリブデン酸のインターカレーション化学

    2006  

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    H2WO4は、ReO3型の層状化合物であり、八面体頂点酸素の一つが水分子として存在していることが報告されている。この物質にピリジン、あるいはビピリジンを150°Cで反応させると、WO6八面体中の水分子とピリジンあるいはビピリジン中の窒素分子が置換し、WO6-ピリジン(ビピリジン)層間化合物が得られることが報告されている[1]。一方、H2W2O9は、Aurivillius 相Bi2W2O9の酸処理により得られる2層のH型層状ペロブスカイトとして知られており、H2WO4同様八面体頂点酸素の一つが水分子として存在すると考えられる。そこで本研究ではタングステン酸化物、H2WO4、H2W2O7&#183;xH2Oとピリジン水溶液(ピリジンと水の体積比1:1)を反応させ、その反応条件や生成機構について調査した。 XRDより、反応後いずれの出発物質から始めた試料も、既報[1]のXRDと同様の回折線が得られたことから3)、層状構造を有していること示された。IR分析より、ピリジニウムイオンの吸収帯が見られなかったことから、ハイブリッド中のピリジンはイオンとして存在していないことがわかった。また15N-CP/MAS NMR分析より、ピリジン分子中の窒素原子の化学シフトはニトロメタン基準で -113 ppmとなった。この値はルイス酸点に結合したピリジンの窒素原子のケミカルシフトに非常に近いことから、窒素原子がタングステン原子に直接配位し、W-N結合を形成していることが示唆された。また、TG分析より、26%の質量減少が見られたことから、組成は、WO3C5H5Nであると考えられる。また、SEM観察より、反応後の試料はいずれも反応前に比べ粒径が大きく、正方形の粒子になっていることから、溶解-再析出により反応が進行したと考えられる。1) J. W. Johnson et al, J. Am. Chem. Soc,. 103, 5246 (1981).

  • アルコキシ基修飾ナノシートをビルディングブロックとして用いた多孔質材料の合成

    2005  

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     FeOCl型の層状金属オキシクロライドであるTiOClは、チタンイオンに4つの酸化物イオンと2つの塩化物イオンが配位した歪んだ八面体が酸化物イオンを介して稜共有することにより、チタンイオンと酸化物イオンからなる層の表面が塩化物イオンの層により覆われた形のシートを形成し、このシート同士が弱いファンデルワールス力によりc軸方向に積層している。FeOClの層表面修飾については、アンモニアまたはアミンとの反応、中間体を用いたアルコールとの反応、アルカリ金属アルコキシドとの反応の3つが報告されているが、TiOClについてはほとんど報告がない。そこで本研究ではリチウムエトキシド(LiOEt)との反応を試みた。反応はエタノールを溶媒として120℃で密閉容器中で行った(TiOCl : LiOEt = 1 : 1.3)。 X線解説分析の結果、反応後層間距離がTiOClの値(0.80 nm)から1.19 nmに増加した。チタンイオンと酸化物イオンのネットワーク構造が変化しないことは、両者の電子線回折の結果から明らかとなった。炭素-13固体高分解能NMRスペクトルでは、エチル基に帰属されるシグナルが19 ppmと71 ppmに出現した。特に、アルファ炭素のシグナル位置がリチウムエトキシドの値(58 ppm)から71 ppmに大きくシフトしていたことから、チタンにエトキシ基が結合していることがわかる。層間距離の増加分から考えて、生成物はバイレイヤー構造を持つと推定される。また、生成物の組成分析を行ったところ、塩化物イオンの約半数がエトキシ基と一部水酸基に置換されたことが明らかとなった。これは、隣接する塩化物イオンの位置を2つのエトキシ基で置き換えることが、空間的に不可能であるためと推定される。

  • タングステン酸-モリブデン酸系ナノシート:組成・構造の制御と材料への展開

    2005   Chen De-Liang

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     三酸化タングステンは、その興味深い電気的・光学的性質や触媒活性から広く注目を集めているが、関連する構造として二次元的な構造を持つ結晶性層状タングステン酸が知られている。これらの構造は三酸化タングステンをスライスし、電荷補償のために層間に水素イオンが導入された構造であり、酸化物ナノシートとみなすことができる。本研究では、2層構造を持つ層状タングステン酸を取り上げ、その層間に有機塩基を取り込むインターカレーション反応について検討を行い、得られる無機層と有機層が交互に積層した構造を解析した。 2層構造を持つタングステン酸は、対応する2層構造のAurivillius相を6規定の塩酸で処理することにより合成した。これを様々な溶媒を用い、過剰量のn-アルキルアミンと反応させた。溶媒を適切に選択すると、反応初期には酸-塩基反応によるインターカレーション反応が進行し、より大きな層間距離を持つ層間化合物が得られた。走査型電子顕微鏡で生成物を観察すると、ほぼ反応前の粒子の形状を保っていることが明らかとなった。一方、長時間の反応では、ほぼ類似した層間距離を示す生成物が得られたが、走査型電子顕微鏡の観察結果からは形状の大きな変化が認められ、生成物はナノベルトあるいはナノチューブへと変化していた。無機層の構造を解析した結果、2層構造は崩壊し、1層構造となっていることが明らかとなった。従って、反応はインターカレーション反応ではなく、溶解-再析出を経て進行していると考えられる。長時間反応させた生成物を硝酸で処理することにより、有機層を除去して一層構造のタングステン酸を得ることができた。一方、長時間反応させた生成物を熱分解することにより、ハニカム構造を持つ結晶性酸化タングステンが生成した。

  • カテコール誘導体修飾遷移金属アルコキシドからの無機-有機ナノコンポジットの合成~無機成分と有機成分間に化学結合をもつナノコンポジットの合成手法の開発~

    2002  

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    無機-有機ハイブリッドにおいて無機成分と有機成分をナノレベルでハイブリッド化することにより、無機化合物あるいは有機化合物単独では得られない物性が発現することが期待されている。その代表的合成法であるゾル-ゲル法による無機-有機ハイブリッドは、一般にSi-C結合を有するSiアルコキシドを加水分解・重縮合反応することで合成されている。一方、遷移金属酸化物の前駆体である遷移金属アルコキシドは金属炭素結合が不安定であることから、キレート結合を利用する必要がある。そこで本研究では1,3,5,7-テトラメチルシロキサン(TMCTS)を出発物質として、テトラシクロシロキサン骨格を有するカテコール誘導体を合成し、さらにこの誘導体とTi(OiPr)2(acac)2を反応させることにより、4つのカテコレート基がそれぞれTiに配位したSiO2-TiO2系有機無機ハイブリッドの前駆体を合成した。まずTMCTSと4-アリルベラトロールとのヒドロシリル化反応を行ったところ、Si-H基、C=C基の消失が明らかとなり、また新たにプロピル基の生成が示された。さらに29SiNMRではTMCTSで見られた-30 ppm付近のシグナルが-20ppm付近にシフトしていた。以上の結果からヒドロシリル化反応が進行したことが示された。BBr3との反応によりアリールメチルエーテルの開裂を行った後、Ti(OiPr)2(acac)2との反応を行ったところ、OH基とOiPr基の消失が示された。また13CNMRからカテコールのC-O基のシグナルが大きく高周波数側にシフトしており、反応によりC-O環境が変化したことがわかった。これらの結果はカテコール誘導体が、iPrOHの脱離を伴いカテコレート基としてTiに配位したことに起因すると考えられる。さらに29Si NMRからシクロテトラシロキサン骨格は維持されていることが明らかになった。以上の結果から、カテコール誘導体が4つのTi(acac)2基に配位した化合物が合成されたものと結論した。

  • ビルディングブロック複合型前駆体からのAlN/BNセラミックコンポジットの合成

    2000  

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     セラミックコンポジットは、単一のセラミックスでは得られない多彩な性質を示すことから、新しい材料として期待されている。本研究では、カゴ型構造や環状構造を持つ化合物をビルディングブロックとして利用し、AlN/BNセラミックコンポジットの前駆体を合成した。出発物質としては、カゴ型構造を持つ(HAlNiPr)mと環状構造を持つボラジン〔(HBNH)3〕を用いた。両者を異なるB/Al比で仕込み(B/Al=0.5、1、2、3)、トルエン溶媒中、40℃で40時間反応させると、水素の発生が認められた。前駆体の27Al NMRからはAlN4環境が出現したことが明らかとなっており、NH基とAlH基の間で脱水素反応が起こったことが明らかとなった。また、前駆体の11B NMRからはBN3環境が確認されており、(HBNH)3間の脱水素反応も進行したことが推定された。しかしながら、前駆体中のB/Alの値は仕込みの値から大きく減少しており、仕込みのB/Alが最大の場合(B/Al=3)でも、生成物中ではB/Alは0.72まで減少した。これは反応が進行し難いことと、(HBNH)3が揮発性であることによると考えられた。 前駆体をAr雰囲気下1600℃で熱分解したところ,黒色の粉末が得られた。収率はB/Al比の増加に伴って向上した。(B/Al=0.5、40%;B/Al=3、50%)。組成分析から、いずれの試料においても、生成物中のB/Al比は前駆体中の値から増加しており、これはAl成分が熱分解中により多く失われたことに対応すると考えられた。X線回折分析の結果、AlNだけが結晶相として検出された。しかしながら、IR分析によりν(B-N)に帰属される吸収帯が検出されたことから、非晶質のBNが生成しているものと考えられた。また、生成物中に炭素が存在することから、非晶質炭素の存在も推定された。透過型電子顕微鏡観察では、非晶質のマトリクス中にAlN微粒子が存在する構造であることが明らかとなった。

  • カテコールにより化学修飾したチタンアルコキシドの合成とそのセラミックスへの変換

    1999  

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     チタンアルコキシド(Ti(OR)4)は一般に加水分解が早く、ゾルゲル反応の前駆体として用いるためには、反応の制御が必要である。そこでβ-ジケトン類等の脱離しにくい官能基による化学修飾が従来行なわれてきた。本研究では、新しい化学修飾剤としてカテコール(C6H4(OH)2)に着目し、カテコールにより化学修飾したチタンアルコキシド(R=Et 、tBu;カテコール/Ti=1)からのチタニア(TiO2)の合成について検討した。チタンアルコキシドのベンゼン溶液に、カテコールのベンゼン溶液をゆっくり滴下したところ、カテコールの2つのOH基が消失したことが赤外吸光分光分析により明らかとなった。さらにNMR測定においては、カテコレート(C6H4O22‐)に帰属可能なシグナルが、アルコキシル基のものに加えて観察された。また、反応によりアルコキシル基がアルコール(ROH)として脱離したことが明らかとなった。以上の結果から、アルコキシル基とのアルコール交換反応によりカテコールがカテコレート基の形で構造中に導入され、キレート環を形成したものと推定された。R=Etの場合はNMRシグナルがブロードとなっており、高分子化が進行していたものと考えられたのに対し、R=tBuの場合ではシグナルのブロード化は認められなかった。そこで、R=tBuの場合について生成物の分子量測定を凝固点降下法により行ったところ、生成物は主に2量体として存在したことがわかった。耐加水分解性を調査するためにTiに対して100倍の水を加え、THFを溶媒として反応を試みた。通常のチタンアルコキシドでは沈殿を生じるのに対し、カテコール修飾した化合物では均質溶液のままであった。加水分解された溶液の1H NMR測定から、アルコキシル基/カテコール基比はほぼ1であり、修飾時の理想的な値2から大きく減少していた。加水分解していない溶液を空気中600℃で熱処理したところ、チタニアがアナターゼとして結晶化した。

  • 重合可能な有機基を持つケイ素アルコキシドからの無機ガラス・有機ポリマーハイブリッドの合成と構造

    1997  

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    重合可能な有機基を有するオルガノアルコキシシランと有機モノマーを共重合させることにより無機・有機複合材料を合成し、得られた生成物の構造を固体高分解能CP/MAS NMRを用いて検討した。オルガノアルコキシシランとしては3-メタクリロキシプロピルトリメトキシシラン(CH2=C(CH3)COOCH2CH2 Si(OCH3)3)、共重合させる有機モノマーとしてはメチルメタクリレート(CH2=C(CH3)COOCH3)を用いた。得られた複合材料を固体13C CP/MAS NMRで分析し、その運動性を回転系スピン-格子緩和時間(T1ρH)を測定して評価した。 まず3-メタクリロキシプロピルトリメトキシシランとメチルメタクリレートの二重結合を、開始剤(αα'-アゾビスイソブチロニトリル)を加えたUV照射により開裂させることで共重合させ、ついで塩酸を触媒に用いて加水分解・重縮合反応を行いシロキサン結合を生成させた。また、3-メタクリロキシプロピルトリメトキシシラン、メチルメタクリレートのみを重合させたホモポリマーも作製した。 3-メタクリロキシプロピルトリメトキシシランのみを用いた場合は、有機基を重合した時点では高い運動性を有した。また、その後のアルコキシル基の加水分解・重縮合反応により運動がかなり制限された。一方3-メタクリロキシプロピルトリメトキシシランとメチルメタクリレートの共重合の系では、有機基を重合した時点で3-メタクリロキシプロピルトリメトキシシランのみの系より運動は制限されていたが、ポリメチルメタクリレートのみの系よりは運動性が高かった。また、共重合の系では、シロキサン結合の生成によってT1ρHはほとんど変化しなかった。これらの結果から、T1ρHを測定することにより、アモルファスな複合材料の構造に関する知見が得られることが明らかとなった。

  • プレセラミックポリマーの熱分解による(Ti,Al)Nセラミックスの合成

    1996  

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     金属-窒素結合を持つ無機高分子(前駆体)を熱分解する事で窒化物セラミックスを合成する方法は、液相において前駆体を分子レベルで分散させることが可能であり、固溶体合成において理想的な手法と考える。しかしながら、これまでこうした観点からの研究はほとんど行われていないのが現状である。 本研究では2種のセラミックスの前駆体を用い、窒化物セラミックス固溶体を得る手法を提案するため、高強度、高耐食性を示し、拡散障壁セラミックス等への応用が期待されている(Ti,Al)Nセラミックスの合成を試みた。TiN前駆体にはTi(NMe2)4とMeHNCH2CH2NHMeの反応により得られた有機溶媒に可溶なオリゴマーを、AlN前駆体には有機溶媒に可溶なカゴ型6量体(HAlNiPr)6を用いた。(Ti,Al)N前駆体はTiとAlのモル比が5:1となるようにTiN前駆体及びAlN前駆体を仕込み、2種の前駆体が均一に分散するようにC6H6溶媒中、室温で6時間撹拌する事により調製した。(Ti,Al)N前駆体の熱分解はNH3雰囲気下600℃、2hと続くN2雰囲気下1350℃、8hで行った。得られた焼成物の粉末XRD回折分析パターンでは、岩塩型化合物(TiNは岩塩型化合物)による回折パターンが観測され、格子定数を算出したところ報告されているTiNの格子定数よりも小さな値を示した。また窒化アルミニウムによる回折線が観測されなかったことから、アモルファスなAlNの生成も考えられたが、(HAlNiPr)6を単独で同条件下で熱処理したときには結晶性のAlNが生成しており、その可能性は低いと考えられた。以上の結果から岩塩型化合物は(Ti,Al)N固溶体であると考えられ、2種の前駆体を熱分解する手法がセラミックス固溶体の合成方法として有効であることが示唆された。

  • 光プローブを用いた有機修飾セラミックスのミクロ環境の検討

    1995  

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    ゾルゲル法において,4官能性のアルコキシシランと共に,Si-C結合を持つオルガノアルコキシシランを出発物質として用いることにより,有機・無機複合材料を合成することができる。本研究では,テトラエトキシシランSi(OEt)4(TEOS) とSi-C結合を持つメチルトリエトキシシランMeSi(OEt)3(MTES) が共存する系について,MTES/(TEOS+MTES) の比を様々に変え,得られるゲルの構造に関する検討を行った。分子レベルでの構造に関する情報を得る方法として,1)励起二量体を生成する,2)分子周囲の極性に依存してその蛍光挙動が敏感に変化する,などの蛍光特性を有するピレンを光プローブとして用い,MTES含量の増加に伴う構造の変化を追った。 反応は,TEOSのみの系で亀裂のないキセロゲルを合成した報告例に基づき,TEOS-MTES-EtOH-HCONH2-H2O-HNO3系で行った。TEOS,MTES,EtOH,HCONH2を混合して,HNO3とH2Oを滴下し10分間攪拌した後,密閉して60℃に保ち,ゲル化熟成後,溶媒を取り除いて引き続き60℃で乾燥させた。ピレンはあらかじめエタノールに溶解させて加え,キセロゲルについて蛍光スペクトルを測定した。 MTES/(TEOS+MTES) が0から0.5までの試料については透明でひび割れのないキセロゲルを得ることができたが,MTES/(TEOS+MTES) が0.5以上になるとゲルは白濁した。キセロゲルの発光スペクトルを測定したところ,励起二量体による蛍光はほとんどみられず,ピレンモノマーに起因する5本の鋭いピークのみがみられた。このことから,ゲル中でピレン分子は十分に分散しているものと思われる。MTES含量の増加に伴ってI1/I3が減少しており,I1/I3の減少はピレン分子周囲の極性の減少を示すことから,ゲル骨格中にメチル基が増加することにより,分子レベルでの極性が減少していることが分かった。

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