The hydrogen or deuterium absorption capacities of the Fe2P-type hexagonal compounds ZrNiAl, YNiAl and UNiAl were measured at pressures of approximately 70 atm and room temperature. The maximum capacities of these compounds were found to be 0.7 H atoms (formula unit)-1, 1.5 H atoms (formula unit)-1 and 2.5 H atoms (formula unit)-1 respectively. Desorption isotherms obtained at several temperatures for the UNiAl-H2 system revealed the existence of at least two hydride phases. Their heats of formation were estimated to be -63.6 kJ (mol H2)-1 and -46.5 kJ (mol H2)-1. The phase limits of the hydride phases in UNiAlHx seem to coincide approximately with the hydrogen capacities of ZrNiAl and YNiAl. The hydrogen absorption of the intermetallic compounds investigated is examined with respect to their crystal structures and the available interstitial sites.
ASJC Scopus subject areas
- Engineering (all)