A relation between the vacancy concentration and hydrogen concentration in the Ni-H, Co-H and Pd-H systems

S. Harada, S. Yokota, Y. Ishii, Y. Shizuku, M. Kanazawa, Y. Fukai

研究成果: Article

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The formation of superabundant vacancies (Vac-H clusters) has been observed in many M-H alloys, but the factors that determine the equilibrium concentration of vacancies have not been identified yet. To identify these factors, the equilibrium concentration of vacancies was estimated from lattice contraction measurements on Ni, Co and Pd having a fcc structure, at high temperatures (930-1350 K) and high hydrogen pressures (2.4-7.4 GPa). The results show that the vacancy concentration is not so much dependent on temperature and hydrogen pressure as the hydrogen concentration. In Ni and Co, the vacancy concentration (xcl) increases linearly with the hydrogen concentration (xH) for the whole concentration range, reaching xcl∼0.3 at xH∼1.0. In Pd, the vacancy concentration is very small up to xH∼0.6 and increases linearly thereafter with nearly the same slope as in Ni and Co. The maximum vacancy concentration reached in Pd is xcl∼0.12. It is noted that the observed difference in the xH -xcl relation correlates with the magnitude of the formation energy of Vac-H clusters, which is very small in Ni and Co and relatively large in Pd.

元の言語English
ページ(範囲)247-251
ページ数5
ジャーナルJournal of Alloys and Compounds
404-406
発行部数SPEC. ISS.
DOI
出版物ステータスPublished - 2005 12 8
外部発表Yes

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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