Degradation by water vapor of MmNi5-based hydrogen-absorbing alloys with different compositions

Yutaka Sangu, Toshiyuki Hirosawa, Satoshi Kikuchi, Yohsuke Matsushita, Yoshio Morozumi, Hideyuki Aoki, Takatoshi Miura, Yoshiaki Kawakami

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


The effects of water concentration in hydrogen and the composition of MmNi5-based hydrogen-absorbing alloys on their absorbing-desorbing properties were investigated. Absorption-desorption cycling tests of hydrogen containing 660 ppm and 1600 ppm H2O were carried out for two kinds of MmNi5-based hydrogen-absorbing alloys. The hydrogen absorbing-desorbing fraction of MmNi4.04Co0.60Mn 0.31Al0.05 with a high content of Ce, where the fraction is defined as the amount of hydrogen undergoing absorption-desorption relative to the maximum amount, decreased significantly, because of a decrease in the rate of hydrogen absorption-desorption. On the other hand, that Of MmNi 4.23Co0.51Mn0.12 with a low content of Ce did not greatly decrease. Although the rate of hydrogen absorption Of MmNi 4.23Co0.51Mn0.12 decreased in the early cycles, it reactivated with an increase of the number of cycles. Degradation by water vapor leads to differences in the hydrogen absorbing-desorbing fraction because of the different contents of Ce. With a low content of Ce, MmNi 5-based hydrogen-absorbing alloys have a high resistance to degradation by water vapor. Therefore, when MmNi5-based hydrogen-absorbing alloys are applied to electric-load leveling systems, they should be chosen according to their Mm composition.

Original languageEnglish
Pages (from-to)606-614
Number of pages9
Journalkagaku kogaku ronbunshu
Issue number6
Publication statusPublished - 2007


  • Degradation
  • Misch metals
  • MmNi-based hydrogen-absorbing Alloys
  • Water vapor

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)


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