Hydrogen absorption in Ce xGd 1-x alloys

M. Bereznitsky, J. Bloch, M. Yonovich, D. Schweke, M. H. Mintz, I. Jacob

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

The effect of alloying on the thermodynamics of hydrogen absorption was studied for Ce xGd 1-x alloys (0 ≤ x ≤ 1) at temperatures between 850 K and 1050 K in the 1-10 -4 Torr pressure range. The temperature-dependent hydrogen solubilities and plateau pressures for hydride formation were obtained from hydrogen absorption isotherms. The terminal hydrogen solubility (THS) at a given temperature changes in a monotonic way as a function of x. It is approximately three times higher in Gd, than in Ce, throughout the investigated temperature range. This monotonic behavior is opposed to that of many other substitutional alloys, for which the hydrogen terminal solubility increases with increasing solute concentrations. The enthalpies, ΔH f, and the entropies, ΔS f, of the dihydride formation exhibit a pronounced and broad negative minimum starting at x ≈ 0.15, yielding the most negative ΔH f values ever found for metal hydrides. On the other hand, the enthalpies and entropies of ideal solution display a positive trend at x = 0.15 and x = 0.3. Both behaviors are considered in view of a reported distinct variation of the Ce xGd 1-x hardness as a function of x. The particular compositional variations of the entropies of solution and formation as a function of x reflect most likely the vibrational properties of the hydrogen atoms in the metal matrices.

Original languageEnglish
Pages (from-to)102-108
Number of pages7
JournalJournal of Alloys and Compounds
Volume532
DOIs
StatePublished - 15 Aug 2012

Keywords

  • Ce-Gd alloys
  • Correlation with plastic and elastic properties
  • Hydride formation
  • Hydrogen absorption
  • Hydrogen solution
  • Terminal hydrogen solubility

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