Hydrogenation of MgNi₂ by Atomic Hydrogen at Elevated Temperatures

Abstract

Hydrogenation of MgNi₂ by atomic hydrogen was examined at elevated temperatures. Mg₂Ni powder was compacted into a disk and heated in vacuum at 773 K for outgassing. During this heat treatment, Mg₂Ni was transformed into MgNi₂ by evaporation of Mg. This specimen was hydrogenated at 573, 673 and 773 K by hydrogen gas of 30 Pa and atoms produced by rf-discharge. No significant hydrogenation took place by hydrogen gas. On the other hand, the specimen was hydrogenated by the exposure to atoms at 773 K up to [H]⁄[M]=0.14 within 25 ks. New peaks appeared in the diffraction pattern of Cu Kα X-rays at 2θ=34.0, 42.0, 48.9 and 86.6^°. This observation indicated that the hydride formed was in a cubic structure.