Changes of Hydrogen Storage Properties upon Hydrogen Absorption-Desorption Cycling in AB5-type Alloys

AB5계 합금에 있어서 수소 흡수-방출 cycling에 따른 수소 저장 특성 변화

  • Noh, Hak ;
  • Choi, Jeon (Dept. of Iron & Metallurgical Eng., Hanlyo Sanup University) ;
  • Jung, So-Ri (Dept. of Metallurgical Eng., Chonnam National University) ;
  • Choi, Seung-Jun (Dept. of Metallurgical Eng., Chonnam National University) ;
  • Park, Choong-Nyeon (Dept. of Metallurgical Eng., Chonnam National University)
  • 노학 (알파텐트기술연구소) ;
  • 최전 (한려산업대학교 제철금속학과) ;
  • 정소이 (전남대학교 금속공학과) ;
  • 최승준 (전남대학교 금속공학과) ;
  • 박충년 (전남대학교 금속공학과)
  • Published : 2001.09.15


T hydrogen absorption-desorption behavior induced by thermal or hydrogen pressure cycling in a closed system was observed in hydrogen storage alloys, $(La-R-Mm)Ni_{4.5}Fe_{0.5}$, $MmNi_4Fe_{0.85}Cu_{0.15}$ and $(Ce-F-Mm)Ni_{4.7}Al_{0.2}Fe_{0.1}$. Thereby (La-R-Mm), Mm and (Ce-F-Mm) refer to La-rich mischmetal, mischmetal and Ce-free mischmetal respectively. As the results, it is found that the alloy stabilities during thermal cycling varies with alloy composition change. The highest stability occurs in $MmNi_4Fe_{0.85}Cu_{0.15}$ and the lowest stability in $(La-R-Mm)Ni_{4.5}Fe_{0.5}$. Comparing hydrogen pressure cycling with thermal cycling, pressure cycling causes severer degradation of the alloy $(Ce-F-Mm)Ni_{4.7}Al_{0.2}Fe_{0.1}$ than thermal cycling. When the 1500 times-cycled alloy is annealed at $400^{\circ}C$ for 3hrs under 1 atm of hydrogen pressure the hydrogen storage capacity is recovered only partially but not completely to the initial capacity. The amount of capacity loss after annealing is larger in the hydrogen pressure cycled samples than in the thermal cycled, suggesting an incoming of impure gas during hydrogen pressure cycling.