A study on hydrogen-induced amorphization in C15 Laves phase DyNi 2 under different hydrogen pressures

H. W. Li, K. Ishikawa, K. Aoki

Research output: Contribution to journalArticle

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Abstract

Four exothermic reactions of (1) hydrogen absorption forming crystalline (c-) and amorphous (a-) DyNi2Hx, (2) the transformation of c-DyNi2Hx to a-DyNi2Hx, i.e., hydrogen-induced amorphization (HIA), (3) the precipitation of DyNi5 in a-DyNi2Hx and (4) the decomposition of the remaining amorphous hydride into DyNi5 and BiF3-type DyH3 were observed sequentially when the C15 Laves phase DyNi2 was heated using a pressure differential scanning calorimeter (PDSC) at 2.0 MPa H 2 or higher hydrogen pressures. On the other hand, (1) the formation of c- and a-DyNi2Hx, (2) partial HIA and (3) the decomposition of the mixture of a- and c-DyNi2Hx into DyNi5 and DyH3 (or DyH2) were observed below 2.0 MPa H2. Simultaneous formations of c- and a-DyNi 2Hx at the first exothermic peak were explained by the local temperature increment resulting from the low activation energy for hydrogen absorption forming c-DyNi2Hx. On the other hand, the formation of DyNi5 during the decomposition was explainable in consideration of the large formation enthalpy of DyNi2. Furthermore, the mechanism of the phase transformations of DyNi2 heated in a hydrogen atmosphere was discussed on the basis of the experimental results such as the pressure dependence of Tp and Tp/Tm (the peak temperature/the melting point of DyNi2), the activation energy EA, and the enthalpy change ΔH.

Original languageEnglish
Pages (from-to)69-77
Number of pages9
JournalJournal of Alloys and Compounds
Volume399
Issue number1-2
DOIs
Publication statusPublished - Aug 16 2005
Externally publishedYes

Fingerprint

Amorphization
Hydrogen
Decomposition
Enthalpy
Activation energy
Exothermic reactions
Calorimeters
Hydrides
Melting point
Phase transitions
Crystalline materials
Scanning
Temperature

All Science Journal Classification (ASJC) codes

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

Cite this

A study on hydrogen-induced amorphization in C15 Laves phase DyNi 2 under different hydrogen pressures. / Li, H. W.; Ishikawa, K.; Aoki, K.

In: Journal of Alloys and Compounds, Vol. 399, No. 1-2, 16.08.2005, p. 69-77.

Research output: Contribution to journalArticle

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