Hydrogen absorption characteristics in Zr0.2Ho0.8CoFe
| Autor: | Sundara Ramaprabhu, K.V.S. Rama Rao, T.P. Das, T.R. Kesavan |
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| Rok vydání: | 1998 |
| Předmět: |
Composition effects
Intermetallics Hydrogen Entropy Enthalpy Analytical chemistry chemistry.chemical_element Crystal atomic structure Pressure effects Crystal structure Laves phase Phase composition Isotherms Thermal effects Hydrogen storage Formula unit Gas absorption Materials Chemistry Pressure composition isotherms Zirconium alloys Mechanical Engineering Zirconium alloy Metallurgy Metals and Alloys Amorphization Amorphous solid chemistry Mechanics of Materials |
| Zdroj: | Journal of Alloys and Compounds. 268:10-15 |
| ISSN: | 0925-8388 |
| DOI: | 10.1016/s0925-8388(97)00592-6 |
| Popis: | Hydrogen absorption studies have been carried out on the Zr0.2Ho0.8CoFe alloy which has the C15 cubic Laves phase structure. The data were collected in the temperature and pressure ranges 27�T(�C)�150 and 0.05�P(bar)�45 respectively. A maximum hydrogen concentration of 9 hydrogen atoms per formula unit at 43 bar at RT is observed. The P-C isotherms show two plateau regions which are identified as the (�+?) and (?+?) phases. These are confirmed from the variation of thermodynamic parameters as the function of hydrogen concentration and from the powder X-ray diffractograms of the samples taken at different hydrogen concentrations. The relative partial molar enthalpy (?H?H) and entropy (?S?H) of hydrogen are found to be in the ranges - (1-8) kJ (mol H)-1 and - (13-22) J K-1 (mol H)-1, respectively. The unit cell volume expansion (?V/V) up to 22% is found at the maximum hydrogen concentration at RT without a change in its crystal structure. The powder X-ray diffractogram of Zr0.2Ho0.8CoFeH9 does not indicate the occurrence of hydrogen induced amorphization (HIA) unlike the case of Zr0.2Ho0.8Co2H3 even though the atomic size ratio (RA/RB) of Zr0.2Ho0.8CoFe is more than the critical value estimated for the formation of an amorphous state upon hydrogenation. ? 1998 Elsevier Science S.A. |
| Databáze: | OpenAIRE |
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