成果報告書詳細
管理番号20100000001969
タイトル*平成21年度中間年報 水素製造・輸送・貯蔵システム等技術開発 水素貯蔵材料 貯蔵・輸送機器要素技術に関する研究開発 ラーベス構造を有した高容量水素吸蔵合金の開発
公開日2011/5/10
報告書年度2009 - 2009
委託先名日本重化学工業株式会社
プロジェクト番号P08003
部署名燃料電池・水素技術開発部
和文要約和文要約等以下本編抜粋:1. 研究開発の内容及び成果等 緒言 本事業では新規な高容量の水素吸蔵合金を開発する目的で、マグネシウム、カルシウムおよびリチウムを含んだラーベス構造を有した合金に着目し研究・開発を行っている。これまでの我々の研究で(Mg1-xCax)Ni2組成のC15型ラーベス相合金が常温・常圧でも可逆的に水素を吸蔵・放出することを見出し報告した。その後(Mg1-xREx)Ni2(RE=希土類、x=0.3)組成のC15b型ラーベス相合金の水素化特性についても報告した。これらの合金はいずれも室温で安定して可逆的に大気圧力程度で水素を吸蔵・放出するものの、水素貯蔵量がH/M=0.7程度((Mg1-xCax)Ni2組成では1.5mass%)である。
英文要約Title: Development of high storage density raves-phase hydrogen storage alloy (FY2008-FY2010) FY2009 Annual Report (Japan Metals & Chemical Co., Ltd)
Summary
In fiscal year 2009, we have been investigating Mg-based Laves phase alloys Mg2-xPrxNi4 (0.6 < x < 1.4) and MgRENi4 (RE: La, Ce, Pr, Nd, Sm, and Gd). Mg-based alloys have been studied for developing hydrogen storage materials with a larger capacity. Hydrogenation of the ternary compounds MgRENi4 (RE=La, Nd and Gd) have been reported so far. Some of the results are in disagreement with others even for similar composition. This is probably because of variation in the quality of the samples, considering that preparation of Mg-based alloys with accurate target compositions needs good technique due to a high vapor pressure of Mg. In this study, we have investigated hydrogenation properties of Mg2-xPrxNi4 (0.6 < x < 1.4) and MgRENi4 (RE: La, Ce, Pr, Nd, Sm, Gd) systematically using a good quality homogeneous samples to understand composition dependence on hydrogenation properties. The compounds were prepared using induction melting technique under helium atmosphere. The weights of each ingot were approximately 9-10 kilograms. This process has already been successfully industrialized. The Pressure-Composition (p-c) isotherms were measured by automatically operated Sieverts’ apparatus. XRD patterns of samples before and after p-c measurements and hydrides were measured in air. Mg2-xPrxNi4 has a cubic ordered C15b-type Laves phase. Mg1.4Pr0.6Ni4, Mg1.2Pr0.8Ni4 and MgPrNi4 absorbed hydrogen reversibly, and kept the C15b-type structure after desorption. On the other hand, the hydrogenation of both Mg0.8Pr1.2Ni4 and Mg0.6Pr1.4Ni4 led to amorphization. The p-c isotherm of stoichiometric MgPrNi4 at ~30 MPa and 273 K showed distinct two plateaus, while Mg1.4Pr0.6Ni4 and Mg1.2Pr0.8Ni4 have only one plateau. The enthalpies of hydride formation of Mg1.4Pr0.6Ni4, Mg1.2Pr0.8Ni4 and MgPrNi4 were evaluated to be -39.2, -40.3 and -42.4* kJ/mol H2, respectively [*: for the hydride with the smaller hydrogen content]. MgRENi4 (RE: Nd, Sm, Gd) showed similar p-c isotherms with one plateau. Relations among the atomic size of rare-earth elements, lattice constants, and the formation enthalpies were obtained.
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