Hydriding Properties of (Mg<SUB>1−<I>x</I></SUB>M<I><SUB>x</SUB></I>)Ni<SUB>2</SUB> C15-Type Laves Phase Alloys

Abstract

Mg-based Laves phase alloys (Mg0:7M0:3)Ni2, where M elements were Ca, La, Ce, Pr, Nd and Gd were successfully developed. The alloys can be synthesized by a conventional induction melting and annealing method from intermetallic compounds MgNi2 and MNi2 as a source of Mg, Ni and M elements. The crystal structures of the major phases of annealed (Mg0:7M0:3)Ni2 alloys were C15-type for M ¼ Ca and C15b-type for M ¼ La, Ce, Pr, Nd and Gd Laves structures, respectively. In the alloys except M ¼ Ce, hydrogenation and dehydrogenation reversibly occurred. The maximum hydrogen contents of the alloys are 1.2–1.6 mass% (H/M:0.6–0.8) under hydrogen pressure of 5 MPa at 243–273 K. As the results of measurements of p-c isotherms, in the case of the M ¼ Pr and Nd, two step plateaus were clearly observed. After a few hydrogenation/dehydrogenation cycles, the alloys kept C15-type or C15b-type Laves structures without hydrogen-induced amorphization, disproportionation and decomposition. [doi:10.2320/matertrans.47.1890]