並列タイトル等NH3BH3-MHn複合物質の水素放出特性 : 副生成ガス放出の抑制方法
一般注記Hydrogen storage is a big challenge for a future hydrogen energy society. Currently, the compressed hydrogen gas tanks are utilized for fuel cell vehicles. For future applications, more compact and lightweight storage of hydrogen is demanded. Therefore, novel hydrogen storage materials should be explored. Chapter 1 shows the introduction part of this thesis. Ammonia borane (NH3BH3, AB) is a promising hydrogen storage material because of its high hydrogen capacities. Nevertheless, its poor recyclability, sluggish kinetics and by-product gas emissions (ammonia (NH3), diborane (B2H6) and borazine (B3H6N3)) are disadvantages for its applications. To overcome these disadvantages, ammonia borane ‐ metal hydride (AB-MHn) mixtures, such as AB-LiH and AB-MgH2, have been extensively studied. However, systematic investigation on these mixtures has not been explored. In this study, various kinds of AB-MHn (M = K, Na, Li, Ca, Mg, Al) mixtures were synthesized. The objectives of the thesis are following three parts; (1) Exploring important factors to reduce H2 desorption temperature and amounts of by-product gas emissions from the systematic investigation on H2 desorption properties, (2) Synthesizing advanced AB-MHn mixtures based on the factors and investigating their H2 desorption properties, (3) Investigating H2 desorption processes of the advanced mixtures. In the following chapters, those issues were targeted on the basis of a series of experiments. In chapter 2, the crystalline phases and H2 desorption properties of AB-MHn (M = K, Na, Li, Ca, Mg, Al) mixtures were investigated. The results revealed that the Pauling electronegativity of metal, χp, is an important factor to predict the crystalline phases, H2 desorption temperatures and amounts of by-product gas emissions. The correlation between H2 desorption temperatures and χp was observed. Coulombic attraction between Hδ− of MHn and Hδ+ of AB would result in the temperature decrease. The amount of NH3 has a tendency to be low when χp becomes high value. On the other hand, the amount of B2H6 has a tendency to be low when χp becomes low value. The key issues for NH3 and B2H6 suppressions are NH3 absorption properties of MHn and v the formation of stable M(BH4)n phase, respectively. In chapter 3, AB-MAlH4 (M = Na, Li) mixtures were synthesized based on the factor proposed in chapter 2. The mixtures were synthesized by hand-mixing and ball-milling methods. Hand-mixing was performed in an Ar purified glovebox. In case of hand-mixing, the violent exothermic H2 desorption reaction occurred. By-product gases were not suppressed. Ball-milling under Ar atmosphere also showed a similar reaction as hand-mixing. On the other hand, ball-milling under H2 atmosphere can generate a novel hydrogen storage material of NaAl(NH2BH3)4 in AB-NaAlH4 system. The synthesized NaAl(NH2BH3)4 desorbed about 8.3 mass% H2 with a small amount of by-product gas emissions. AB-MAlH4 mixture with a molar ratio of 1 : 1 showed no by-product gas emissions. Thus, MAlH4 is effective to decrease the by-product gas emissions from AB. Chapter 4 shows general discussions and conclusions. The strategy for synthesizing advanced AB-MHn mixtures was proposed. AB-AlH3 mixture should be considered as base material because it showed the highest hydrogen amount among the investigated mixtures. By combining alkali metal hydride and FeCl2 (CuCl2) with the mixture, it would be possible to synthesize the material with high hydrogen amounts, low desorption temperature and no by-product gas emissions.
(主査) 特任教授 大貫 惣明, 教授 鵜飼 重治, 教授 秋山 友宏, 准教授 橋本 直幸, 教授 亀川 厚則 (室蘭工業大学)
工学院（材料科学専攻）
コレクション（個別）国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文
受理日（W3CDTF）2019-05-06T10:27:56+09:00
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