Hydriding properties of LaNi3 and CaNi3 and their substitutes with PuNi3-type structure

The PuNi3-type intermetallic compounds LaNi3, CaNi3, La0.5Ca0.5Ni3, LaCaMgN i9, La0.5Ca1.5MgNi9, CaTiMgNi9, LaCaMgNi6Al3 and LaCaMgNi6Mn3 have been pre pared using a powder-metallurgy-sintering method. The hydrogenation behavio ur of these materials has been studied through the gas-solid reaction. The as-prepared compounds were easily activated at room temperature under a hyd rogen pressure of 3.3 MPa. The pressure-composition-temperature (P-C-T) cur ves show a single plateau region with the exception of LaNi3-H, which shows no plateau, and La0.5Ca1.5MgNi9-H, which shows two plateaus. All of these alloys can absorb/desorb hydrogen by 1.8 wt.% under the conditions studied. X-ray diffraction (XRD) analysis reveals that LaNi3H4.5 is in the amorphou s state, and the other hydrides are accompanied by different expansions of the unit cell volume of the host alloy. (C) 2000 Elsevier Science S.A. All rights reserved.