2022/05/26 更新

写真a

ハナダ ノブコ
花田 信子
所属
理工学術院 先進理工学部
職名
講師(専任)

兼担

  • 理工学術院   大学院先進理工学研究科

学内研究所等

  • 2021年
    -
    2022年

    理工学術院総合研究所   兼任研究員

学歴

  • 2003年04月
    -
    2005年03月

    広島大学   大学院先端物質科学研究科   量子物質科学専攻  

  • 2001年04月
    -
    2003年03月

    広島大学   大学院生物圏科学研究科   環境計画科学専攻  

  • 1997年04月
    -
    2001年03月

    広島大学   総合科学部   総合科学科  

経歴

  • 2017年04月
    -
    継続中

    早稲田大学   先進理工学部応用化学科   専任講師

  • 2010年12月
    -
    2017年03月

    筑波大学   システム情報工学研究科構造エネルギー工学専攻   助教

  • 2008年04月
    -
    2010年11月

    上智大学   理工学部 機能創造理工学科   研究プロジェクトポストドクター

  • 2006年04月
    -
    2008年03月

    カールスルーエ研究所   ナノテクノロジー研究所   客員研究員

  • 2005年04月
    -
    2006年03月

    広島大学   自然科学研究支援開発センター   産学連携研究員

 

研究分野

  • 構造材料、機能材料

  • 反応工学、プロセスシステム工学

論文

  • Fast and stable hydrogen storage in the porous composite of MgH2 with Nb2O5 catalyst and carbon nanotube

    Kosuke Kajiwara, Hisashi Sugime, Suguru Noda, Nobuko Hanada

    Journal of Alloys and Compounds   893   162206 - 162206  2022年02月  [査読有り]

    DOI

  • Environmentally friendly chemical synthesis of intermetallic iron aluminide submicrometer particles

    Yasukazu Kobayashi, Heng Yi Teah, Nobuko Hanada

    Journal of Cleaner Production   316   128264 - 128264  2021年09月  [査読有り]

    DOI

  • Low-temperature chemical synthesis of intermetallic TiFe nanoparticles for hydrogen absorption

    Yasukazu Kobayashi, Shohei Yamaoka, Shunta Yamaguchi, Nobuko Hanada, Shohei Tada, Ryuji Kikuchi

    International Journal of Hydrogen Energy   46 ( 43 ) 22611 - 22617  2021年06月  [査読有り]

     概要を見る

    Nanosizing of TiFe hydrogen storage alloy is conducted to facilitate its activation. Here, pure intermetallic TiFe nanoparticles (45 nm) were prepared using chemical reduction of oxide precursors at 600 °C, which is the lowest temperature ever used in chemical synthesis. This was achieved using a strong reducing agent (CaH2) in a molten LiCl. When used for hydrogen absorption, the obtained nanoparticles surprisingly exhibited almost no hydrogen absorption. The results demonstrated that TiFe nanoparticles are more difficult to activate than the bulk powder because the oxidized surface layers of the nanoparticles become stabilized, which prevents the morphological change necessary for their activation.

    DOI

  • Structural Properties of (Ti, Zr)(Mn, Cr)2M0.1 (M = None, Fe, Co, Ni, and Cu) Hydrogen Storage Alloys: Composition Distribution and Occupied Site of Doped Element

    Tessui Nakagawa, Daichi Heshiki, Hiroki Higa, Junko Kawakami, Riki Kobayashi, Nobuko Hanada, Kazutaka Ikeda, Toshiya Otomo, Hironori Ofuchi, Masayoshi Ishida

    MATERIALS TRANSACTIONS   62 ( 6 ) 899 - 904  2021年06月  [査読有り]

    DOI

  • Numerical simulation of heat supply and hydrogen desorptionby hydrogen flow to porous MgH2 sheet

    Keisuke Yoshida, Kosuke Kajiwara, Hisashi Sugime, Suguru Noda, Nobuko Hanada

    Chemical Engineering Journal     129648 - 129648  2021年04月  [査読有り]

    DOI

  • Chemical synthesis of unique intermetallic TiFe nanostructures originating from the morphology of oxide precursors

    Yasukazu Kobayashi, Heng Yi Teah, Nobuko Hanada

    Nanoscale Advances   3 ( 18 ) 5284 - 5291  2021年  [査読有り]

     概要を見る

    TiFe nanostructures where prepared at temperatures as low as 600 °C with a Ti–Fe precursor and a CaH2 reducing agent in molten LiCl. For the first time an intermetallic compound with a unique layered morphology was found which could have originated from the FeTiO3 precursor.

    DOI

  • Electrolysis of ammonia in aqueous solution by platinum nanoparticles supported on carbon nanotube film electrode

    Nobuko Hanada, Yusuke Kohase, Keisuke Hori, Hisashi Sugime, Suguru Noda

    Electrochimica Acta   341   136027 - 136027  2020年05月  [査読有り]

    DOI

  • Effect of CO2 on hydrogen absorption in Ti-Zr-Mn-Cr based AB2 type alloys

    Nobuko Hanada, Hirotaka Asada, Tessui Nakagawa, Hiroki Higa, Masayoshi Ishida, Daichi Heshiki, Tomohiro Toki, Itoko Saita, Kohta Asano, Yumiko Nakamura, Akitoshi Fujisawa, Shinichi Miura

    Journal of Alloys and Compounds   705   507 - 516  2017年05月  [査読有り]

    DOI

  • Material transformation of alumina and influence on leakage current by application of DC high voltage at high temperatures

    Satoshi Kawato, Nobuko Hanada, Masashi Mitsui, Masayoshi Ishida

    IEEJ Transactions on Fundamentals and Materials   137 ( 12 ) 685 - 692  2017年

     概要を見る

    In order to investigate a material transformation of alumina (Al2O3) and an influence on leakage current by application of high DC voltage at high temperatures, the leakage current of two alumina samples were measured for 100 hours and the elemental analyses were carried out. The leakage current tended to decrease, and the electrical conductivity decreased with increasing applied voltage. The activation energies of electrical conduction of two samples were nearly equal. Thus, the reproducibility of these results was confirmed. After the experiments, deposits of impurities contained in alumina were observed in the surrounding area of the positive electrode. Furthermore, Na, which was contained in Pt paste used for preparing the electrodes, can be a charge career of alumina because it was detected from only negative electrodes. Therefore, the reason why the leakage current decreased is the decrease in the amount of charge careers because of the deposits of impurities.

    DOI

  • dc Voltage Insulating Properties of Various Inorganic Materials in Hydrogen Atmosphere at High Temperatures

    Koichi Takahashi, Nobuko Hanada, Masayoshi Ishida

    ELECTRICAL ENGINEERING IN JAPAN   193 ( 4 ) 1 - 8  2015年12月  [査読有り]

     概要を見る

    In this study, the dc voltage insulating properties in a hydrogen atmosphere at high temperatures (600 degrees C to 850 degrees C) were evaluated for alumina (Al2O3), magnesia (MgO), silicon nitride (Si3N4), and mica (KMg3(Si3Al)O-10(OH)(2)) to comprehend the difference in the insulating properties of oxide, nitride, and minerals. The activation energies of the electrical conductivity of alumina and magnesia in hydrogen were larger than those in air. On the other hand, the electrical conduction values for silicon nitride and mica in hydrogen were the same as those in air. Therefore a low oxygen partial pressure would have some influence on the electrical conduction of oxides. Increasing the temperature did not result in a large change in the electrical conduction mechanism in any of the materials in either atmosphere. The maximum partial discharge (PD) in hydrogen tended to increase compared to that in air at high voltage. The applied voltage at which the maximum amount of PD started to increase rapidly became lower with increasing temperature in all materials and in both atmospheres. The total amount of PD tended to decrease with increasing temperature in all materials and in both atmospheres. However, above a certain temperature, the total amount of PD either increased or showed a slight decrease.

    DOI

  • Dependence of constituent elements of AB5 type metal hydrides on hydrogenation degradation by CO2 poisoning

    Nobuko Hanada, Tessui Nakagawa, Hirotaka Asada, Masayoshi Ishida, Keisuke Takahashi, Shigehito Isobe, Itoko Saita, Kohta Asano, Yumiko Nakamura, Akitoshi Fujisawa, Shinichi Miura

    Journal of Alloys and Compounds   647   198 - 203  2015年10月  [査読有り]

    DOI

  • In-Situ XAS for Niobium Oxide Catalyst on Hydrogen Absorption and Desorption of Magnesium

    Toru Kimura, Hiroki Miyaoka, Nobuko Hanada, Takayuki Ichikawa

    JOURNAL OF THE JAPAN INSTITUTE OF METALS   79 ( 3 ) 107 - 111  2015年  [査読有り]

     概要を見る

    The variation of the niobium (Nb) oxide catalyst during hydrogen absorption and desorption reactions was investigated by in-situ X-ray absorption spectroscopy (XAS). Results indicated that H-2 was easily dissociated on the catalyst because the hydrogen absorption kinetics was significantly improved, and then the hydrogen atoms were diffused through inside of the catalyst. Thus, the catalytic mechanism of Nb oxides is different from that of conventional metal catalysts, in which the dissociated H is moved on the surface of catalyst.

    DOI

  • Mgの水素吸蔵/放出におけるNb酸化物触媒のIn-situ X線吸収分光

    木村通, 宮岡裕樹, 花田信子, 市川貴之

    日本金属学会誌   79 ( 3 ) 107 - 111  2015年  [査読有り]

  • PLD法により作製したSOFC用ナノコンポジット空気極の酸素表面交換反応活性評価

    福武秀朗, Jeffrey De Vero, Katherine Develos-Bagarinao, 岸本治夫, 山地克彦, 中山知紀, 花田信子, 石田政義

    燃料電池   15 ( 1 ) 89 - 94  2015年  [査読有り]

  • Study on the capacity fading of pristine and FePO4 coated LiNi1/3Co1/3Mn1/3O2 by Electrochemical and Magnetical techniques

    Xizheng Liu, De Li, Huiqiao Li, Akira Iyo, Nobuko Hanada, Masayoshi Ishida, Haoshen Zhou

    ELECTROCHIMICA ACTA   148   26 - 32  2014年12月  [査読有り]

     概要を見る

    Capacity fading mechanism of pristine and FePO4-coated LiNi1/3Co1/3Mn1/3O2 has been studied by electrochemical and magnetic methods. Along with cycles, significant increase of cell polarization and charger transfer resistance (R-ct), which mainly cause the capacity fading at the initial charge/discharge cycles, have been observed according to the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis. In comparison, the existence of FePO4 coating layer can effectively suppress the deterioration of surface polarization and increase of Rct at the interface of electrode/electrolyte. The coated sample suppress the decrease of Li+ diffusion coefficient with prolonged cycles according to the galvanostatic intermittent titration technique (GITT) tests. It also shows larger Weiss constants (fitting above 130 K) and lower blocking temperatures, which indicate the surface coating can suppress the deterioration of Li/Ni disorder upon repeated cycles. This study may give the researchers some light on understanding the capacity fading mechanism of LiNi1/3Co1/3Mn1/3O2 and the effects of surface coating layer, and thus, give help to the future designing of superior coating layers for layered cathode materials in Li-ion batteries. (C) 2014 Elsevier Ltd. All rights reserved.

    DOI

  • 入出力と貯蔵容量を分担するバッテリーキャパシタハイブリッド蓄電システムの提案と動作検証

    中山知紀, 峯野勝也, 立原亘, 河合祐樹, 長谷川裕樹, 平岡一高, 柿崎信郎, 花田信子, 石田政義

    電気学会論文誌B(電力・エネルギー部門誌)   134 ( 1 ) 76 - 83  2014年  [査読有り]

  • A novel tunnel Na0.61Ti0.48Mn0.52O2 cathode material for sodium-ion batteries

    Shaohua Guo, Haijun Yu, Dequan Liu, Wei Tian, Xizheng Liu, Nobuko Hanada, Masayoshi Ishida, Haoshen Zhou

    CHEMICAL COMMUNICATIONS   50 ( 59 ) 7998 - 8001  2014年  [査読有り]

     概要を見る

    A novel tunnel Na0.61Ti0.48Mn0.52O2 material is explored as a cathode for sodium-ion batteries for the first time. It can deliver a reversible discharge capacity of 86 mA h g(-1) with an average voltage of 2.9 V at 0.2 C rate in a sodium half cell, exhibiting good rate capability and capacity retention at a cut-off voltage of 1.5-4 V. These results indicate that tunnel Na0.61Ti0.48Mn0.52O2 has a great potential application in large scale energy storage.

    DOI

  • 高温水素雰囲気での各種無機材料に関する直流絶縁特性

    高橋晃一, 花田信子, 石田政義

    電気学会論文誌A(基礎・材料・共通部門誌)   134 ( 7 ) 466 - 471  2014年  [査読有り]

  • A hydrogen purification and storage system using CO adsorbent and metal hydride

    Shinichi Miura, Akitoshi Fujisawa, Shuhei Tomekawa, Yukinobu Taniguchi, Nobuko Hanada, Masayoshi Ishida

    Journal of Alloys and Compounds   580 ( 1 ) S414 - S417  2013年

     概要を見る

    The CO Selective Adsorbent and Metal Hydride Intermediate Buffer (COA-MIB) method has been proposed as a hydrogen production/supply system with reformer. First, this method thoroughly eliminates carbon monoxide using an adsorption material that strongly selects carbon monoxide, and second it introduces a mixed gas to a metal hydride that purifies and stores hydrogen. A 100 NL/h laboratory scale apparatus was operated in daily start and stop operations for 1000 cycles for a total of 1500 h with quite good efficiency. The metal hydride used in this apparatus was an AB5-type whose hydrogen equilibrium pressure was adjusted to be 0.1 MPa at 25 C. As a result of the basic performance evaluation, we have experimentally verified that pure hydrogen can be produced from methanol reforming gas for 1000 cycles on a daily start/stop operation basis and a high hydrogen recovery rate of over 89% can be achieved. 3 N m3/h Bench scale apparatus was also operated with same mode for 100 cycles for a total of 150 h and shows almost the same performance. The new method enables us to minimize emissions of carbon dioxide by using compact and highly efficient fuel cells as a part of the smart community technologies. © 2013 Published by Elsevier B.V.

    DOI

  • 高温型燃料電池における主絶縁性能劣化要因

    石田政義, 中川智之, 花田信子, 中山知紀

    燃料電池   12 ( 3 ) 106 - 112  2013年  [査読有り]

  • 高温型燃料内での高電圧誘起に関する考察

    石田政義, 中川智之, 花田信子, 中山知紀

    燃料電池   12 ( 2 ) 106 - 114  2012年  [査読有り]

  • Effect of several metal chlorides on the thermal decomposition behavior of α-Mg(BH4)2

    Elisa Gil Bardají, Nobuko Hanada, Oleg Zabara, Maximilian Fichtner

    International Journal of Hydrogen Energy   36 ( 19 ) 12313 - 12318  2011年09月  [査読有り]

    DOI

  • Existing State of Hydrogen in Electrochemically Charged Commercial-Purity Aluminum and Its Effects on Tensile Properties

    Hiroshi Suzuki, Daisuke Kobayashi, Nobuko Hanada, Kenichi Takai, Yukito Hagihara

    MATERIALS TRANSACTIONS   52 ( 9 ) 1741 - 1747  2011年09月  [査読有り]

     概要を見る

    Hydrogen was introduced in commercial-purity (99%) aluminum by electrochemical charging to study the existing state of hydrogen and its effects on the mechanical properties of aluminum. Electrochemical charging was conducted in an aqueous H2SO4 solution with 0.1% NH4SCN as a hydrogen recombination poison. The potential and during the charging were determined from the immune. passive, and corrosive regions in the Pourbaix diagram to determine the optimum conditions or the charging. The maximum amount of hydrogen absorbed was obtained in the immune region. The amount of hydrogen and its existing state were examined using hydrogen desorption curves, which were obtained by thermal desorption spectroscopy. The curves showed distinctive peaks corresponding to trapping sites of hydrogen in the material. One of the peaks was observed at approximately 100 degrees C, and it corresponds to vacancies and dislocations in the material; another peak was observed at approximately 400 degrees C and it corresponds to molecular hydrogen in blisters. It was presumed that charged hydrogen diffuses into the bulk of the material to form hydrogen-vacancy pairs, and then these pairs cluster to form blisters. The fracture strain of charged aluminum in the immune region decreased with decreasing strain rate, showing an inverse dependence on the fracture strain of the uncharged material. This phenomenon was considered to be caused by hydrogen transport by dislocations through the interaction between hydrogen and dislocations. The phenomenon was further confirmed by the observation of hydrogen release during tensile deformation, where the amount of hydrogen was high in the strain rate range where the interaction between dislocations and hydrogen was prominent. [doi: 10.2320/matertrans.M2011035]

    DOI

  • Effects of deformation on hydrogen absorption and desorption properties of titanium

    Hiroshi Suzuki, Hisashi Taniguchi, Nobuko Hanada, Kenichi Takai, Yukito Hagihara

    JOURNAL OF ALLOYS AND COMPOUNDS   509   S759 - S762  2011年09月  [査読有り]

     概要を見る

    In this study, we analyzed the effects of deformation on hydrogen absorption and desorption properties of titanium to improve such properties. Hydrogen was introduced into commercially pure (99.5%) titanium by the electrochemical method. The amount and existing state of hydrogen were examined using hydrogen desorption curves obtained by thermal desorption spectroscopy. Hydrogen absorption was promoted by applying tensile deformation prior to charging, which leads to hydride formation within a short charging time. The amount of hydrogen absorbed decreased when the volume fraction of deformation twins exceeded about 0.2. It was considered that hydrogen was mainly trapped by dislocations forming hydride while a large fraction of deformation twins hindered dislocation motion, thus reducing dislocation density leading to a decrease in the amount of absorbed hydrogen. Almost half the charged hydrogen was released when in-plane compressive stress was applied to a charged plate specimen at room temperature due to hydride decomposition under compressive stress. (C) 2010 Elsevier B.V. All rights reserved.

    DOI

  • Liquid ammonia electrolysis by platinum electrodes

    B. -X. Dong, T. Ichikawa, N. Hanada, S. Hino, Y. Kojima

    JOURNAL OF ALLOYS AND COMPOUNDS   509   S891 - S894  2011年09月  [査読有り]

     概要を見る

    Liquid ammonia was electrolyzed based on a new concept by using metal amide as the supporting electrolyte for generation of hydrogen. Different metal amides including LiNH(2), NaNH(2) and KNH(2) were tested, and the influences of the solubility and the concentration of different electrolytes upon the electrolysis current were investigated. Electrolysis efficiency was evaluated on the basis of chronopotentiometry tests at different current densities. Platinized platinum electrodes with fine structure were introduced in order to improve the electrolysis current and reduce the electrolysis potential. (C) 2010 Elsevier B.V. All rights reserved.

    DOI

  • Electrochemical charge and discharge properties for the formation of magnesium and aluminum hydrides

    Nobuko Hanada, Akito Kamura, Hiroshi Suzuki, Kenichi Takai, Takayuki Ichikawa, Yoshitsugu Kojima

    JOURNAL OF ALLOYS AND COMPOUNDS   509   S584 - S587  2011年09月  [査読有り]

     概要を見る

    The electrochemical properties of Mg + 2LiH and Al + 3LiH are investigated by applying a Li-ion insertion and extraction system to form magnesium and aluminum hydrides. For MgH(2) formation, the voltage-composition (VC) curve for Mg + 2LiH during charging exhibits a plateau voltage at 0.58 V, then the final composition is obtained with 1.05 mol Li extraction at 3.0 V. After the charging, the MgH(2) phase is observed by XRD measurement. Therefore, MgH(2) is produced from Mg and LiH by electrochemical charging. With respect to AlH(3) formation, Al + 3LiH is charged at a plateau voltage of 0.81 V, which corresponds to the reaction of Al with hydrogen in LiH to form AlH(3). And the final composition at 3.0 V is 0.6 mol Li. In the XRD profile after charging, the AlH(3) phase is not detected. (C) 2010 Elsevier B.V. All rights reserved.

    DOI

  • The Existing State of Hydrogen in Electrochemically Charged Commercial Purity Aluminum and Its Effect on the Tensile Properties

    Hiroshi Suzuki, Daisuke Kobayashi, Nobuko Hanada, Kenichi Takai, Yukito Hagihara

    JOURNAL OF THE JAPAN INSTITUTE OF METALS   74 ( 2 ) 65 - 71  2010年02月  [査読有り]

     概要を見る

    Hydrogen is introduced in commercial (99% pure) aluminum by electrochemical charging to study the existing state of hydrogen and its effect on the mechanical properties of aluminum. Electrochemical charging is conducted in an aqueous solution of H2SO4 with 0.1 mass% NIH4SCN as a hydrogen recombination poison. The potential and pH during the charging are chosen from the immune, passive, and corrosive regions on Pourbaix diagram to determine the optimum conditions for the charging. The maximum amount of hydrogen absorbed is obtained in the immune region. The amount of hydrogen and its existing state are examined using hydrogen desorption curves, which are obtained by thermal desorption spectroscopy. The curves show distinctive peaks that correspond to trapping sites of hydrogen in the material. One of the peaks is observed at approximately 100 degrees C and it corresponds to vacancies and dislocations in the material; another peak is observed at approximately 400 degrees C and it corresponds to molecular hydrogen in blisters. It is presumed that charged hydrogen diffuses into the bulk of the material to form hydrogen vacancy pairs, and then these pairs cluster to form blisters. The fracture strain of charged aluminum in the immune region decreased with a slower strain rate, showing an inverse dependence on the fracture strain of the uncharged material. This phenomenon is considered to be caused by the transport of hydrogen by dislocations through the interaction between hydrogen and the dislocations. The phenomenon is further confirmed by the observation of hydrogen release during tensile deformation, where the amount of hydrogen is higher in the strain rate region where the interaction between the dislocations and hydrogen is more prominent.

  • Hydrogen generation by electrolysis of liquid ammonia

    Nobuko Hanada, Satoshi Hino, Takayuki Ichikawa, Hiroshi Suzuki, Kenichi Takai, Yoshitsugu Kojima

    Chemical Communications   46 ( 41 ) 7775 - 7777  2010年  [査読有り]

  • 電解チャージにより水素吸蔵した純アルミニウムにおける水素存在状態と引張特性に与える水素の影響

    鈴木啓史, 小林大輔, 花田信子, 高井健一, 萩原行人

    本金属学会誌   74   65 - 71  2010年  [査読有り]

  • Hydrogen generation by electrolysis of liquid ammonia”, Chemical Communication

    Nobuko Hanada, Satoshi Hino, Takayuki Ichikawa, Hiroshi Suzuki, Kenichi Takai, Yoshitsugu Kojima

    Chemical Communication   46   3982 - 3984  2010年  [査読有り]

  • X-ray Absorption Spectroscopic Study on Valence State and Local Atomic Structure of Transition Metal Oxides Doped in MgH2

    Nobuko Hanada, Takayuki Ichikawa, Shigehito Isobe, Tessui Nakagawa, Kazuhiko Tokoyoda, Tetsuo Honma, Hironobu Fujii, Yosbitsugu Kojima

    JOURNAL OF PHYSICAL CHEMISTRY C   113 ( 30 ) 13450 - 13455  2009年07月  [査読有り]

     概要を見る

    A valence state and a local structure of transition metals (Nb, V, and Ti) in MgH2 doped with metal oxides (Nb2O5, V2O5, and TiO2nano) by ball milling were examined by X-ray absorption spectroscopy (XAS). The main edge regions of the Nb, V, and Ti K-edges in the X-ray absorption near edge structure (XANES) profiles are located between 0 and +5 in the oxidation states. Since these spectra coincide with those of NbO, VO, and Ti2O3, respectively, the additives are reduced by MgH2 to the metal oxides, which have lower oxidation states than those of the starting materials. Furthermore, in order to examine the local structures around the transition metal atoms, the extended X-ray absorption fine structure (EXAFS) spectra were analyzed. In the Fourier transformation curves of the EXAFS spectra, all samples doped with the metal oxides show two peaks corresponding to metal-oxygen and metal-metal bonds, being the same as the references of NbO, VO, and Ti2O3. The local structure formed after ball milling or dehydrogenation is close to that of each of the reduced metal oxides (NbO, VO, and Ti2O3) but in a more disarrangement state.

    DOI

  • Evaluation of enthalpy change due to hydrogen desorption for lithium amide/imide system by differential scanning calorimetry

    Shigehito Isobe, Takayuki Ichikawa, Kazuhiko Tokoyoda, Nobuko Hanada, Haiyan Leng, Hironobu Fujii, Yoshitsup Kojima

    THERMOCHIMICA ACTA   468 ( 1-2 ) 35 - 38  2008年02月  [査読有り]

     概要を見る

    Enthalpy change (Delta H) due to hydrogen desorption (H-desorption) for the lithium amide/imide system was evaluated by differential scanning calorimetry (DSC) measurement. In order to obtain the accurate and precise value of Delta H, we have paid special attention to following two points for correcting raw experimental data. One is to determine a cell constant of DSC equipment, which was evaluated by using the TiO2-doped MgH2 compound as a reference because of its quite similar hydrogen desorption properties to that of the lithium amide/imide system. The other is to estimate the sample amount corresponding to the H-desorption reaction from weight loss in the thermogravimetric (TG) analysis. By performing both the corrections, the Delta H value due to the H-desorption reaction from LiNH2 + LiH to Li2NH + H-2 was evaluated to be 67 kJ/mol H-2. (c) 2007 Elsevier B.V. All rights reserved.

    DOI

  • SEM and TEM characterization of magnesium hydride catalyzed with Ni nano-particle or Nb2O5

    Nobuko Hanada, Enoki Hirotoshi, Takayuki Ichikawa, Etsuo Akiba, Hironobu Fujii

    JOURNAL OF ALLOYS AND COMPOUNDS   450 ( 1-2 ) 395 - 399  2008年02月  [査読有り]

     概要を見る

    The microstructures of MgH2 catalyzed with Ni nano-particle or Nb2O5 mesoporous powders are examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. For MgH2 catalyzed with Ni, the Ni particles with the diameter smaller than 1 mu m were detected on the MgH2 particles with the diameter smaller than 5 mu m by the back scattering electron (BSE) microscopy. In details, the TEM micrograph indicates that the Ni particles distribute similar to 20 nm in diameter on MgH2 uniformly, which was the same size as the additive doped in MgH2 before milling. On the other hand, for MgH2 catalyzed with Nb2O5, the additive particles could not be found anywhere in the BSE image. Even in the TEM micrograph by much larger magnification than the SEM micrograph, the particles corresponding to the additive cannot be observed at all. Furthermore, an energy dispersive X-ray (EDX) analysis in spots with a diameter of 20 nm indicated that the existing ratio of Mg to Nb was evaluated to 98:2, being the same as the starting ratio before milling. Therefore, the metal oxide Nb2O5 becomes extremely small particle that could not be observed by the present work after milling compared to metal Ni-nano. (C) 2006 Elsevier B.V. All rights reserved.

    DOI

  • Thermal decomposition of Mg(BH(4))(2) under He flow and H(2) pressure

    Nobuko Hanada, Krzysztof Chopek, Christoph Frommen, Wiebke Lohstroh, Maximilian Fichtner

    JOURNAL OF MATERIALS CHEMISTRY   18 ( 22 ) 2611 - 2614  2008年  [査読有り]

     概要を見る

    The thermal decomposition steps of Mg(BH(4))(2) were investigated under He flow and various hydrogen pressures up to 50 bar. In a He flow, the main decomposition of Mg(BH(4))(2) occurs between 250 and 410 degrees C until 12.2 mass% is lost, with three main peaks of hydrogen desorption. In the first decomposition step the crystalline phase of Mg(BH(4))(2) disappears while a small amount of Mg is detected in the XRD profile. However, the major part of the sample is in an amorphous state. After the second step, crystalline MgH(2) is observed together with the Mg phase. The third step of hydrogen desorption corresponds to the decomposition of MgH(2) and Mg remains the only crystalline phase observed by XRD measurement after heating to 410 degrees C. Further hydrogen evolution of 1.4 mass% is observed from 410 degrees C to 580 degrees C. Only after this hydrogen desorption, MgB(2) appears in the XRD spectra of the sample. These results indicate that amorphous, hydrogen containing boron compounds take part as intermediates in the reaction. Under hydrogen pressure, the decomposition events of Mg(BH(4))(2) shift to higher temperatures in the DSC (differential scanning calorimetry) profiles: while there is only a small shift for steps 1 and 2 there is a clear separation of the succeeding reactions under a background pressure of hydrogen. These data show that the decomposition proceeds via several well defined steps. The final stable decomposition compound of Mg(BH(4))(2) is MgB(2) under both inert and hydrogen gas atmosphere.

    DOI

  • Comparison of the calculated and experimental scenarios for solid-state reactions involving Ca(AIH(4))(2)

    Nobuko Hanada, Wiebke Lohstroh, Maximilian Fichtner

    JOURNAL OF PHYSICAL CHEMISTRY C   112 ( 1 ) 131 - 138  2008年01月  [査読有り]

     概要を見る

    Solid-state reactions of Ca(AIH(4))(2) and various additives were investigated experimentally for hydrogen desorption. The Ca(AIH(4))(2) + Si, Ca(AIH(4))(2) + 2MgH(2), Ca(AIH(4))(2) + 2LiH, and Ca(AIH(4))(2) + 2LiNH(2) systems were chosen among reactions proposed theoretically(1) to study their hydrogen storage capacity and an appropriate reaction enthalpy. For all systems investigated, the reversible reactions proposed should have more than 6.5 mass % hydrogen capacity and reaction enthalpies in the range of 30-55 kJ/mol H-2. However, most of the experimentally observed reactions do not conform to theoretical propositions because different final products were obtained in all cases but one. Two tendencies were observed in the experiments. One is that the reaction comprises several distinct steps at different temperatures as observed in the Ca(AIH(4))(2) + Si and Ca(AIH(4))(2) + 2 MgH2 systems. In this case, Ca(AIH(4))(2) decomposes first and is followed by a reaction of the remaining compounds. The same kinetic reaction barriers are encountered here as in pure Ca(AIH(4))(2). Second, LiH and LiNH2 additions yield exothermic reactions of Ca(AIH(4))(2) and the other reactant as early as in the ball milling or annealing steps, leading to final products not considered in the reactions calculated.

    DOI

  • Hydrogen absorption kinetics of the catalyzed MgH2 by niobium oxide

    Nobuko Hanada, Takayuki Ichikawa, Hironobu Fujii

    JOURNAL OF ALLOYS AND COMPOUNDS   446   67 - 71  2007年10月  [査読有り]

     概要を見る

    The hydrogen absorption kinetics of magnesium hydride (MgH2) composite doped with 1 mol% Nb2O5 prepared by ball milling was examined under various temperatures and pressures. The composite after dehydrogenation at 200 degrees C absorbs gaseous hydrogen of similar to 4.5 mass% within 15 s even at room temperature under 1.0 MPa hydrogen pressure or at 0 degrees C under 3.0 MPa, and finally their capacities reach up to 5 mass%. At 150 and 250 degrees C, a large amount of hydrogen gas of more than 5.0 mass% is absorbed within 30 s and their capacity reach up to 5.7 mass% under 1.0 MPa. Interestingly, the absorption kinetics of the catalyzed Mg shows two unusual behaviors in the initial reaction stage of the time scale within 30 s. One is that the kinetics decreases with increase in the temperature from 150 to 250 degrees C under any pressures (0.2, 1.0 and 3.0 MPa). The other is that the amount of hydrogen absorption drastically increases with increase in the initial pressure from 1.0 to 3.0 MPa at 0 degrees C or from 0.2 to 1.0 MPa at room temperature (similar to 20 degrees C). These behaviors may be explained by taking into account heat generation of Mg due to fast hydrogen uptake in such a short time. (C) 2006 Elsevier B.V. All rights reserved.

    DOI

  • Thermal analysis on the Li-Mg-B-H systems

    Tessui Nakagawa, Takayuki Ichikawa, Nobuko Hanada, Yoshitsugu Kojima, Hironobu Fujii

    JOURNAL OF ALLOYS AND COMPOUNDS   446   306 - 309  2007年10月  [査読有り]

     概要を見る

    Thermal analyses of the mixture of MgH(2) and LiBH(4) doped with TiCl(3), and each element MgH(2) or LiBH(4) doped with TiCl(3) were performed under an inert gas flow and 0.5 MPa H(2)-gas conditions. It was indicated that the hydrogen desorption reaction of MgH(2) + 2LiBH(4) to MgB(2) + 2LiH + 4H(2) phases proceeded at temperature above 400 degrees C under 0.5 MPa hydrogen, whereas, under an inert gas atmosphere, the reaction of the same mixture was transformed into Mg + 2B + 2LiH + 4H(2) phases in a temperature range from 350 to 430 degrees C. Before these reactions, the dehydrogenation of MgH(2) and the melting of LiBH(4) took place under both hydrogen and the inert gas atmospheres with increasing temperature. In addition, the molten LiBH(4) did not decompose into LiH, B and H(2) below 450 degrees C under 1 MPa H(2), while the LiBH(4) decomposed even below 450 degrees C under an inert gas atmosphere. From these results, it is deduced that the reaction producing MgB(2) is a solid-liquid reaction between solid Mg and liquid LiBH(4) above 400 C without decomposition of molten LiBH(4) Under a hydrogen atmosphere, while MgH(2) dehydrogenate. A characteristic solid-liquid reaction is realized under a hydrogen atmosphere for proceeding of the MgB(2) producing reaction in this system. (C) 2007 Elsevier B.V. All rights reserved.

    DOI

  • Recent development on hydrogen storage properties in metal-N-H systems

    T. Ichikawa, H. Y. Leng, S. Isobe, N. Hanada, H. Fujii

    JOURNAL OF POWER SOURCES   159 ( 1 ) 126 - 131  2006年09月  [査読有り]

     概要を見る

    In this paper, we review our recent results on hydrogen storage properties in light metals(M)-nitrogen(N)-hydrogen(H) systems prepared by mechanochemical method. At first, the composite mixture of LiH and LiNH2 doped with TiCl3 as a catalyst was prepared by ball milling for 2 h under a H-2 gas pressure of 1 MPa. The TDS profile indicated that similar to 6 mass% H-2 was desorbed by the reaction LiH + LiNH2 <-> Li2NH + H-2 in the temperature range from 150 to 250 degrees C under a He gas flow at a heating rate of 5 degrees C min(-1), but the H-desorption equilibrium pressure P-H2 was similar to 0.1 MPa at 250 degrees C. This temperature is too high for onboard use, indicating that further improvement is necessary to destabilize the above Hstorage reaction. For that, we clarified the H-desorption mechanism by the isotopic exchange experiments, on the basis of which we designed a new Li-Mg-N-H composite system with the reaction 8LiH + 3Mg(NH2)(2)<-> 4Li(2)NH + Mg3N2 + 8H(2). This composite materials desorbed similar to 7 mass% H-2 in the range from 120 to 200 degrees C and the H-desorption equilibrium pressure P-H2 was higher than 5 MPa at 200 degrees C, indicating that this system has an excellent potential for onboard applications. (c) 2006 Elsevier B.V. All rights reserved.

    DOI

  • Remarkable improvement of hydrogen sorption kinetics in magnesium catalyzed with Nb2O5

    Nobuko Hanada, Takayuki Ichikawa, Satoshi Hino, Hironobu Fujii

    JOURNAL OF ALLOYS AND COMPOUNDS   420 ( 1-2 ) 46 - 49  2006年08月  [査読有り]

     概要を見る

    Kinetics of hydrogen absorption and desorption reactions was investigated on the MgH2 composite doped with 1 mol% Nb2O5 as a catalyst by ballmilling. The composite after dehydrogenation at 200 degrees C absorbed gaseous hydrogen of similar to 4.5 mass% even at room temperature under lower pressure than I MPa within 15 s and finally its capacity reached more than 5 mass%. On the other hand, the catalyzed MgH2 after rehydrogenation desorbed similar to 6 mass% hydrogen at 160 degrees C under purified He flow, which followed the first order reaction. From the Kissinger plot, the activation energy for hydrogen desorption was estimated to be similar to 71 kJ/mol H-2, indicating the product was significantly activated due to the catalytic effect of Nb2O5. (c) 2005 Elsevier B.V. All rights reserved.

    DOI

  • Catalytic effect of niobium oxide on hydrogen storage properties of mechanically ball milled MgH2

    Nobuko Hanada, Takayuki Ichikawa, Hironobu Fujii

    PHYSICA B-CONDENSED MATTER   383 ( 1 ) 49 - 50  2006年08月  [査読有り]

     概要を見る

    We examined a catalytic effect of niobium oxide (Nb2O5) on the hydrogen storage properties of MgH2 prepared by mechanical ball milling method. The MgH2 composite doped with I mol% Nb2O5 by ball milling for 20 h desorbed hydrogen up to similar to 6 mass% in the temperature range from 200 to 250 degrees C at the heating rate of 5 degrees C/min under a purified helium flow. After dehydrogenation at 200 degrees C, the product showed remarkable hydrogen absorption kinetics. A large amount of gaseous hydrogen up to similar to 4.5 mass% was absorbed even at room temperature under 1 MPa hydrogen pressure within 15 s and finally its capacity reached up to 5 mass%. Furthermore, the valence state of Nb2O5 doped in MgH2 was examined by X-ray absorption near edge structure (XANES) measurement. The results indicated that additive Nb2O5 was reduced by MgH2 during mechanical milling. This suggests that the Nb compound, in which the valence state of Nb atom is less than 5 +, acts as a catalyst for the hydrogen absorbing/desorbing kinetics. (c) 2006 Elsevier B.V. All rights reserved.

    DOI

  • Synthesis and decomposition reactions of metal amides in metal-N-H hydrogen storage system

    HY Leng, T Ichikawa, S Hino, N Hanada, S Isobe, H Fujii

    JOURNAL OF POWER SOURCES   156 ( 2 ) 166 - 170  2006年06月  [査読有り]

     概要を見る

    The synthesis and decomposition properties of some metal amides M(NH2)(x) such as LiNH2, NaNH2, Mg(NH2)(2) and Ca(NH2)(2) were investigated, which play important roles for designing a new family of metal-N-H hydrogen storage systems. Both the gas chromatographic examination and X-ray diffraction measurement indicated that the reaction between alkali or alkaline earth metal hydride MHx (such as LiH, NaH, MgH2 and CaH2) and gaseous NH3 could quickly proceed at room temperature by ball milling and the corresponding metal amides were easily synthesized in high quality. The kinetics of these kind of reactions is faster in the order of NaH > LiH > CaH2 > MgH2, which is consistent with the inverse order of electronegativity of those metals, i.e. Na < Li = Ca < Mg. The thermal decomposition properties indicated that both Mg(NH2)(2) and Ca(NH2)(2) decomposed and emitted NH3 at lower temperature than LiNH2. (c) 2005 Elsevier B.V. All rights reserved.

    DOI

  • Catalytic effect of Ni nano-particle and Nb oxide on H-desorption properties in MgH2 prepared by ball milling

    N Hanada, T Ichikawa, H Fujii

    JOURNAL OF ALLOYS AND COMPOUNDS   404   716 - 719  2005年12月  [査読有り]

     概要を見る

    We examined the catalytic effect of Ni nano-particle and Nb oxide on hydrogen desorption (HD) properties in MgH2 prepared by mechanical ball milling under a hydrogen gas atmosphere of 1 MPa. The MgH2 composite with 2 mol% Ni nano-particle prepared by milling for a short time of 15 min at 200 rpm desorbed a large amount of hydrogen (similar to 6.5 wt.%) in the temperature range from 150 to 250 degrees C at heating rate of 5 degrees C/min. On the other hand, the MgH2 Composite with I mol% Nb-2 O-5 prepared by milling for a long time of 20 h at 400 rpm desorbed similar to 6.0 wt.% H-2 in the temperature range from 200 to 250 degrees C at heating rate of 5 degrees C/min. After second hydrogen absorption/desorption cycles at 200 degrees C, the HD properties of the Ni-catalyzed MgH2 composite became worse than those before cycling, while the Nb2O5-catalyzed composite showed better HD properties than those before cycling. (c) 2005 Elsevier B.V. All rights reserved.

    DOI

  • Effect of Ti catalyst with different chemical form on Li-N-H hydrogen storage properties

    S Isobe, T Ichikawa, N Hanada, HY Leng, M Fichtner, O Fuhr, H Fujii

    JOURNAL OF ALLOYS AND COMPOUNDS   404   439 - 442  2005年12月  [査読有り]

     概要を見る

    The effect of some different type Ti additives on kinetics of the reaction, LiH + LiNH2 <-> Li2NH + H-2, was intensively investigated in this work. The mixture of LiH and LiNH2 powders with the 1: 1 molar ratio and Ti additives with different chemical form were mechanically ball milled under a hydrogen gas atmosphere of I MPa at 400 rpm for 2 It and the measurements of thermal hydrogen desorption spectrum (TDS), thermogravimetry (TG) and X-ray diffraction (XRD) were performed. Here, we used Ti (nano particle), Ti (micro particle), TiCl3, TiO2 (nano particle) and TiO2 (micro particle) as the additives. The results indicated that the Ti-nano, TiCl3 and TiO2nano doped composites revealed a superior catalytic effect on the TDS properties, while the Ti-micro and TiO2micro did not show so good catalytic effect being similar to the sample without any additives. In the XRD profiles, there are traces of Ti and TiO2 phases in the Ti-micro and TiO2micro doped composites, respectively, whereas no trace of Ti, TiCl3 and TiO2 was found in the Ti-nano TiCl3 and TiO2nano doped composites. These results indicate that the uniform distribution of nano particle Ti metal between LiH and LiNH2 plays an important role for catalytic effect. (c) 2005 Elsevier B.V. All rights reserved.

    DOI

  • Desorption behaviours from metal-N-H systems synthesized by ball milling

    HY Leng, T Ichikawa, S Isobe, S Hino, N Hanada, H Fujii

    JOURNAL OF ALLOYS AND COMPOUNDS   404   443 - 447  2005年12月  [査読有り]

     概要を見る

    Three metal amides LiNH2, NaNH2 and Mg(NH2)(2) were synthesized by ball milling the metal hydrides under gaseous ammonia NH3 at room temperature. The decomposition behaviours from these metal amides were investigated by thermal desorption mass spectroscopy and thermogravimetry analysis methods. The results showed that LiNH2 decomposed at T > 230 degrees C and was transformed into the imide Li2NH with emitting NH3, while Mg(NH2)(2), decomposed at T > 180 degrees C and was transformed into MgNH and finally into Mg3N2 with emitting NH3 within 500 degrees C. Then, a new metal-N-H system composed of Mg(NH2)(2) and LiH with a molar ratio of 3:8 was designed by ball milling treatment and examined the hydrogen storage properties. The results showed that this system could reversibly absorb/desorb a large amount of hydrogen (similar to 7 wt.%) at a moderate temperature and pressure, which was better than the system of LiNH2 and LiH for hydrigen storage. (c) 2005 Elsevier B.V. All rights reserved.

    DOI

  • Catalytic effect of nanoparticle 3d-transition metals on hydrogen storage properties in magnesium hydride MgH2 prepared by mechanical milling

    N Hanada, T Ichikawa, H Fujii

    JOURNAL OF PHYSICAL CHEMISTRY B   109 ( 15 ) 7188 - 7194  2005年04月  [査読有り]

     概要を見る

    We examined the catalytic effect of nanoparticle 3d-transition metals on hydrogen desorption (HD) properties of MgH2 prepared by mechanical ball milling method. All the MgH2 composites prepared by adding a small amount of nanoparticle Fe-nano, Co-nano, Ni-nano, and Cu-nano metals and by ball milling for 2 h showed much better HD properties than the pure ball-milled MgH2 itself. In particular, the 2 mol % Ni-nano-doped MgH2 composite prepared by soft milling for a short milling time of 15 min under a slow milling revolution speed of 200 rpm shows the most superior hydrogen storage properties: A large amount of hydrogen (similar to 6.5 wt %) is desorbed in the temperature range from 150 to 250 degrees C at a heating rate of 5 degrees C/min under He gas flow with no partial pressure of hydrogen. The EDX micrographs corresponding to Mg and Ni elemental profiles indicated that nanoparticle Ni metals as catalyst homogeneously dispersed on the surface of MgH2. In addition, it was confirmed that the product revealed good reversible hydriding/dehydri ding cycles even at 150 degrees C. The hydrogen desorption kinetics of catalyzed and noncatalyzed MgH2 could be understood by a modified first-order reaction model, in which the surface condition was taken into account.

    DOI

  • Composite Materials Based on Light Elements for Hydrogen Storage”, Materials

    Takayuki Ichikawa, Nobuko Hanada, Shigehito Isobe, Haiyan Leng, Hironobu Fujii

    Materials Transactions   46 ( 1 ) 1 - 14  2005年01月  [査読有り]

  • Hydrogen Storage Properties in Ti Catalyzed Li-N-H Ststem”, Journal of Alloys and Compounds

    Takayuki Ichikawa, Nobuko Hanada, Shigehito Isobe, Haiyan Leng, Hironobu Fujii

    Journal of Alloys and Compounds   404-406   716 - 719  2005年

  • New metal-N-H system composed of Mg(NH2)(2) and LiH for hydrogen storage

    HY Leng, T Ichikawa, S Hino, N Hanada, S Isobe, H Fujii

    JOURNAL OF PHYSICAL CHEMISTRY B   108 ( 26 ) 8763 - 8765  2004年07月  [査読有り]

     概要を見る

    We have investigated the hydrogen storage properties of a ball-milled mixture of 3Mg(NH2)(2) and 8LiH after first synthesizing Mg(NH2)(2) by ball milling MgH2 under an atmosphere of NH3 gas at room temperature. The thermal desorption mass spectra of the mixture without any catalysts indicated that a large amount of hydrogen (similar to7 wt %) was desorbed from 140 degreesC, and the desorption peaked at similar to190 degreesC under a heating rate of 5 degreesC/min with almost no ammonia emission. Moreover, the reversibility of the hydrogen absorption/desorption reactions was confirmed to be complete. The above results indicate that this system is one of the promising metal-N-H systems for hydrogen storage.

    DOI

  • Mechanism of novel reaction from LiNH2 and LiH to Li2NH and H-2 as a promising hydrogen storage system

    T Ichikawa, N Hanada, S Isobe, HY Leng, H Fujii

    JOURNAL OF PHYSICAL CHEMISTRY B   108 ( 23 ) 7887 - 7892  2004年06月  [査読有り]

     概要を見る

    The mechanism of the hydrogen desorption (HD) reaction from the 1:1 mixture of lithium amide (LiNH2) and lithium hydride (LiH) to lithium imide (Li2NH) and hydrogen (H-2) has been proposed on the basis of our experimental results in this paper. The proposed model is constituted by 2 kinds of elementary reactions: the one is that 2LiNH(2) decomposes to Li2NH and ammonia (NH3) the other is that the emitted NH3 reacts with LiH and transforms into LiNH2 and H-2. Since the former and the latter reactions are, respectively, endothermic and exothermic, the HD reaction corresponding to the latter reaction occurs as soon as LiNH2 has decomposed into Li2NH and NH3. Therefore, the HD reaction can be understood by the following processes: at the first step, LiNH2 decomposes into Li2NH/(2) + NH3/2, and then the emitted NH3/2 quickly reacts with LiH/2, transforming into LiNH2/2 + H-2/2; at the second one, the produced LiNH2/2 decomposes to Li2NH/4 + NH3/4, and then NH3/4 + LiH/4 transform to LiNH2/4 + H-2/4, and such successive steps continue until LiNH2 and LiH completely transform into Li2NH and H-2, even at low temperatures, by the catalytic effect of TiCl3.(.)

  • Correlation between hydrogen storage properties and structural characteristics in mechanically milled magnesium hydride MgH2

    N Hanada, T Ichikawa, SI Orimo, H Fujii

    JOURNAL OF ALLOYS AND COMPOUNDS   366 ( 1-2 ) 269 - 273  2004年03月  [査読有り]

     概要を見る

    In this work, we clarified the correlation between hydrogen storage and crystallographic properties in nanostructural magnesium hydride MgH2 prepared by mechanical milling under hydrogen gaseous atmosphere. At the early stage within 2h milling, the amount of desorbed hydrogen decreases similar to16% from 7.3 to 6.1 wt.% and the onset temperature of dehydrogenation decreases by 70 K from 670 K, while both the powder size and the crystallite size in powder decrease with increasing the milling time down to 1 mum and 15 nm, respectively, and the lattice strain of 0.3% is rapidly introduced. At the middle stage with longer milling time than 2 h, however, the crystallite size hardly change, but the lattice strain is once released at 2-5 h milling and again increases for longer milling time than 5 h. On the other hand, the amount of desorbed hydrogen suddenly increases from 2 to 5 h, and again decreases with a little increase of lattice strain during 5-80 h milling. At the final stage, the hydrogen capacity and desorption temperature reach to saturation of, respectively, 6.5 wt.% and 600 K, whereas the crystallite size and lattice strain reach to saturation of similar to7 nm and 0.2%, respectively. The results obtained indicate that the reduction of crystallite size as well as the introduction of lattice strain in MgH2 during milling gives rise to the decrease in hydrogen storage capacity. (C) 2003 Elsevier B.V. All rights reserved.

    DOI

  • Lithium nitride for reversible hydrogen storage

    T Ichikawa, S Isobe, N Hanada, H Fujii

    JOURNAL OF ALLOYS AND COMPOUNDS   365 ( 1-2 ) 271 - 276  2004年02月  [査読有り]

     概要を見る

    In this paper, we examined the basic properties in the 1:1 mixture of lithium amide LiNH2 and lithium hydride LiH as a candidate of reversible hydrogen storage materials. The thermal desorption mass spectra of the ball milled mixture without any catalysts indicated that hydrogen H-2 is released in the temperature range from 180 to 400degreesC while emitting a considerable amount of ammonia NH3. On the other hand, the ball milled mixture containing a small amount of TiCl3 as a catalyst showed the most superior hydrogen storage properties among the 1: 1 mixtures with a small amount of catalysts, Ni, Fe, Co metals and TiCl3 (I mol.%). That is, the product desorbs a large amount of hydrogen (similar to5.5 wt.%) in the temperature from 150 to 250degreesC under the condition of a heating rate of 5 degreesC/min, but it does not desorb ammonia at all within our experimental accuracy. In addition, we confirmed that the product shows an excellent cycle retention with an effective hydrogen capacity of more than 5 wt.% and a high reaction rate until at least 3 cycles. (C) 2003 Elsevier B.V. All rights reserved.

    DOI

  • Hydriding properties of ordered-/disordered-Mg-based ternary Laves phase structures

    N Hanada, S Orimo, H Fujii

    JOURNAL OF ALLOYS AND COMPOUNDS   356   429 - 432  2003年08月  [査読有り]

     概要を見る

    Ternary Laves phase structures with compositions MgYNi4, MgCaNi4 and CaYNi4 were prepared, and the relationship between the structures and hydriding properties was studied in detail. Only in MgYNi4 are Mg and Y found to be ordered and a plateau pressure is clearly observed in the P-C isotherm during the dehydriding process. In MgCaNi4, however, Mg and Ca are disordered, and hydrogen content of MgCaNi4 is similar to30% larger than that of MgYNi4. Control of their order/disorder in Laves phase structures may provide the hydriding properties with higher hydrogen concentrations and flatter plateau regions. (C) 2003 Elsevier B.V. All rights reserved.

    DOI

  • マグネシウムを含む3元系Laves相構造の規則化・不規則化と水素化特性

    花田信子, 折茂慎一, 藤井博信

    日本金属学会誌   66   466 - 469  2002年  [査読有り]

▼全件表示

共同研究・競争的資金等の研究課題

  • 触媒を付与した窒素吸蔵材料電極適用による液体アンモニア電気分解反応の過電圧低減

    研究期間:

    2016年04月
    -
    2018年03月
     

     概要を見る

    液体アンモニアから電気分解により水素を取り出す際の課題として、窒素放出を伴うアノード反応の過電圧が大きいことが挙げられる。1元系および2元系触媒電極を適用して、アノード反応の評価を行った。一元系触媒の効果を調べるために、窒素との結合のしやすさが異なる触媒金属を用いた。低電位での各触媒金属における電流密度を金属窒化物生成エンタルピーに対してプロットすることにより火山型の相関関係が得られることが明らかになった。二元系触媒はPt-Fe系を検討し、粒子レベルおよび原子レベルでの複合化どちらにおいても、一元系触媒よりもアノード反応活性が下がることが分かった。水素キャリアとしての液体アンモニアから電気分解により水素を取り出す方法の研究を行った。窒素放出を伴うアノード反応の過電圧を下げるために、一元系もしくは二元系触媒電極を適用した。窒素との結合のしやすさが異なる一元系触媒金属を用いた場合は、低電位での各触媒金属における電流密度と金属窒化物生成エンタルピーの間に相関関係が得られることが明らかになった。二元系触媒は粒子レベルおよび原子レベルでの複合化の影響を調べ、今回検討したPt-Fe系触媒では、一元系触媒よりもアノード反応活性が下がることが分かった

  • 固体酸化物形燃料電池の大容量化に資する電気絶縁信頼性向上

    研究期間:

    2015年04月
    -
    2018年03月
     

     概要を見る

    高温領域(600-900℃)および酸化還元雰囲気中での無機材料であるアルミナの電気絶縁特性と材料性状の関係を調査した。ガスの違いが絶縁特性と材料性状それぞれの変化に大きな影響を与えることを示した。絶縁特性の距離依存性の調査では沿面距離に単純比例しないことを明らかにした。無機材料への空間電荷分布測定法の適用を図ったところ,大半の材料では分布が反転する傾向が得られた。電気特性の異なる一部の無機材料ではそのような傾向は見られないことから,その要因として材料の電気特性が大きく影響していることが示唆された

  • 水素貯蔵媒体としての液体アンモニア利用のための高効率電気分解セルの構築

    研究期間:

    2012年04月
    -
    2014年03月
     

     概要を見る

    液体アンモニアから水素を取り出す高効率な電気分解セルの構築のために、電極形態及び電極材料の検討を行い液体アンモニア電気分解に対する過電圧低減効果を明らかにした。電気めっきにより作製した白金黒電極の電極形態の影響を調べた結果、電極反応表面積ではなく、Pt担持量とPt粒子径が過電圧低減に寄与することが示された。またPt電極を用いた電極反応において、アノード過電圧はカソード過電圧の5倍大きいことが分かった。アノード過電圧を低減するPt-Ru電極を適用することで、理論分解電圧付近である0.1Vでの液体アンモニア電気分解反応が示された

  • 固体酸化物形燃料電池における高温電気絶縁の特性解明に基づく設計指針の確立

    研究期間:

    2011年04月
    -
    2014年03月
     

     概要を見る

    高温領域(600-850℃)およびSOFCのアノードガス雰囲気中での無機材料の電気絶縁現象の把握および解明を行い、絶縁設計の指針を示した。各種無機材料に対する直流絶縁特性評価より、マグネシアが最も絶縁抵抗が高く絶縁材料として最適であることが示された。マグネシアを主成分とするSOFCの主絶縁部に対するアノードガス成分の影響調査より、水素ガス自体およびそのリークにより発生し得る水素燃焼反応の熱や火炎が絶縁性能を劣化させることが明らかになった

特定課題研究

  • アンモニア電気分解におけるアノード反応の高電流密度・高効率化

    2021年   野田優, Patil Neel, 沓抜佳奈, 宮越すみれ

     概要を見る

    高容量水素貯蔵のキャリアとしてアンモニアに着目し、液体アンモニアから電気分解により水素を生成するシステム開発を目指している。理論分解電圧は0.077 Vであるが、窒素発生反応であるアノード側で高い反応過電圧を持つことが課題である。本研究では、活性なアノード触媒電極の低電位での電流効率評価を行った。高い触媒活性を持つNi電極を用いた場合のアノード反応(窒素発生反応)の電流効率を調べた。ガスの定量評価によりH2/N2の比がおおよそ3となり、アンモニアの分解を確認した。窒素発生反応の電流効率は90%と高いが、100%ではないため副反応が一部起こっていることが分かった。副反応としてNiの腐食が確認されたが、電流効率に対してNiの腐食が占める割合は0.74%であり、影響は小さいことが分かった。

  • Ruナノ粒子担持カーボンナノチューブ膜電極による液体アンモニアの電気分解

    2021年   宮越すみれ

     概要を見る

    液体アンモニアは17.3 mass%の質量水素密度を持ち、エネルギーキャリアとして優れている。室温で電解反応が進行し、水素生成が可能である。理論分解電圧は0.077 Vであるが、窒素発生反応であるアノード側で高い反応過電圧を持つことが課題である。これまでにRu電極がアノード反応に対して高い活性を持つことが分かっている。Ruナノ粒子を担持した3次元電極により電極触媒表面積を増加させ低電位での電流密度の向上を目的とした。Ruナノ粒子をCNT上に担持したRu-CNT電極を作製し、液体アンモニア電解のアノード反応への活性評価を行った。CNT上に1-2 nmのRu粒子の担持が確認され、ポリオール法によりCNT上へのRuナノ粒子の担持に成功した。触媒表面積増加の効果によりRu-CNT電極ではRu板電極に対し電流密度が6.1倍向上した。

  • 液体アンモニア電気分解のカソード反応機構解明および高電流効率化

    2020年   佐々木隆一

     概要を見る

    高容量水素貯蔵のキャリアとしてアンモニアに着目し、液体アンモニアから室温で電気分解により水素生成を行った。電気分解が起きていることは確認されているが、電流効率は85%程度であり100%に達していない。この原因がカソード反応における溶媒和電子発生の副反応にあるという仮説のもと、電流効率と溶媒和電子発生の関係を調べた。液体アンモニア電気分解の定電位測定において電位を-0.3、-0.5、-0.7 V vs H2/NH3 と変化させた結果、低電位であるほど溶媒和電子が多く発生することが観察された。しかし、-0.3 Vと-0.5 Vでの定電位測定の電流効率は82.9 %、82.5%とほとんど同じであったことから、低電流効率の要因は他にも存在することが示唆された。

  • オンボード水素供給に向けたアンモニア電気分解の高電流密度・高効率化

    2020年   野田優, 赤木夏帆, Patil Neel, 佐々木隆一, 沓抜佳奈

     概要を見る

    高容量水素貯蔵のキャリアとしてアンモニアに着目し、液体アンモニアもしくはアンモニア水溶液から電気分解により水素を生成する。本研究では、高電流密度を低電圧で出力するために、2元系アノード電極触媒の検討を行った。液体アンモニア電気分解反応に対して、比較的窒素との結合強さが近い金属の組み合わせであるNi-Pt触媒を適用した。Ni板にPtをスパッタしてアニール処理した電極を用い、表面積変化の影響を除去して評価を行った。Pt単体触媒比べてNi-Pt の二元系触媒はアノード反応に対して効果が見られなかった。Ni とPt の組み合わせでは、N との結合が強いNi に律速が支配されてしまい二元系の効果が見られない可能性が高い。

  • 水素生成のための液体アンモニアおよび水溶液中アンモニア電気分解特性の向上

    2019年   野田優, 小長谷優佑, 赤木夏帆, Patil Neel

     概要を見る

    高容量水素貯蔵のキャリアとしてアンモニアに着目し、液体アンモニアもしくはアンモニア水溶液から電気分解により水素を生成した。本研究では、高電流密度を低電圧で出力する高効率な電気分解セル構築のための基礎検討を行った。液体アンモニア電気分解反応に対して、過電圧の高いアノード反応特性の向上のために、触媒金属の窒素との結合のしやすさに着目した。窒素との結合が中間の強さである触媒金属が高電流密度を示すことが明らかになった。また、アンモニア水溶液電気分解反応に対しては、電極の反応場を3次元的に拡張するために白金ナノ粒子を担持したカーボンナノチューブ膜電極を適用し、アノード電流密度の増大を実現した。

  • 液体アンモニア電気分解への電極触媒を内包したカーボンナノチューブ膜電極の適用

    2017年  

     概要を見る

    Ammonia (NH3), which has high volumetric hydrogen density and high gravimetric hydrogen density, is one of the promising media to store and transport hydrogen. We have performed the direct electrolysis of liquid ammonia for hydrogen generation. This method would be able to decompose ammonia itself by keeping high hydrogen density at room temperature. In this study 3D structured electrode with platinum nanoparticles supported on carbon nanotube (CNT) film was fabricated to increase the current density and decrease anode over potential for liquid ammonia electrolysis. The platinum nanoparticles were loaded on CNT by reducing Pt ion in Ethylene Glycol at 100 to 180 ºC. The smaller Pt nanoparticles were synthesized by increasing loading temperature. The average particle size of Pt nanoparticles on CNT was 3.6 nm and surface area of Pt was several hundred times of the electrode area. The electrode of Pt nanoparticles on CNT decreased anode overpotential and increased the current density at lower potential in ammonia electrolysis.

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