成果報告書詳細
管理番号20090000000675
タイトル*平成20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2010/3/2
報告書年度2008 - 2008
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 水素グループ
和文要約以下本編抜粋: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可逆的に水素を吸蔵・放出することを見出し報告した(1) 。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(2)。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 ofhigh storage density raves-phase hydrogen storage alloy (FY2008) Annual Report (Japan Metals & Chemical Co., Ltd)
Summary
In fiscal year 2008, we have been investigating Mg-based Laves phase alloys (Mg1-xPrx)Ni2. The alloys can be synthesized by a conventional induction melting and annealing method. The crystalline structures of major phases of annealed (Mg1-xPrx)Ni2 alloys were C15b-type Laves structures. In the alloys of x=0.3 and 0.5, hydrogenation and dehydrogenation reversibly occurred. On the other hand in the alloys of x=0.7, hydrogen-induced decomposition occurred. The atomic radii ratio RA/RB is a dominant factor for controlling the occurrence of hydrogen-induced amorphization or decomposition and in the case of RA/RB is larger than 1.37, hydrogen-induced amorphization or decomposition occurs. Here, RA and RB are the atomic radii of A and B atoms in C15b-type AB2 Laves phases. In the estimations for the (Mg0.7M0.3)Ni2 alloys, RA is the average of atomic radii of Mg and M. In this study RA/RB of x=0.3 and 0.5 alloys were smaller than 1.37. Therefore we conclude that hydrogen-induced amorphization, disproportionation and decomposition did not occur in the present study. The maximum hydrogen contents of x=0.3 alloy are 1.1mass% (H/M:0.66) under hydrogen pressure of 6MPa at 293K with a single wide flat plateau. On the other hand, as the results of measurements of p-c isotherms of x=0.5 alloy at temperature below 273K, two step plateaus were clearly observed. The maximum hydrogen contents of x=0.5 alloy are 1.7mass% (H/M:1.1) under hydrogen pressure of 8MPa at 273K. After a few hydrogenation/dehydrogenation cycles, the alloys kept C15b-type Laves structures without occurrence of hydrogen-induced amorphization, disproportionation and decomposition. From in-situ X-ray diffraction profiles of x=0.3 alloy, it was found that the metal substructure of hydride are kept C15b-type Laves structure with lattice expansion. On the other hand in the case of x=0.5 alloy, the metal substructure of hydride are orthorhombic crystal.
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