Synthesis, properties and Mossbauer study of ZrFe(2-x)Ni(x) hydrides (x = 0.2-0.8)

Interaction of ZrFe(2-x)Ni(x) (x = 0.2,0.4.0.6, and 0.8) pseudobinary intermetallic compounds with hydrogen was studied. It was found that these compounds can accumulate up to 1.7-1.8 wt.% H(2) at room temperature. Forall investigated ZrFe(2-x)Ni(x)-H(2) systems, thermodynamic functions of the beta-hydride (right arrow) alpha-solution phase transition and changes of metal matrix volume during formation of hydrides were calculated. It was shown that increase in Ni content leads to reduction of both desorption pressures and starting pressures of reaction with hydrogen in the first hydrogenation cycle compared to ZrFe(2). Mossbauer investigations, which have been carried out for all alloys as well as hydrides, revealed that Curie temperatures (T(c)) and average hyperfine fields (HF(av)) of initial alloys decrease with Ni content increase, while isomer shifts (IS) remain constant. Absorption of H(2) results in significant increase in IS together with some increase in T(c) and HF(av) for all samples. The decomposition of the hydride phases to intermetallic phases while heating from 78 K to room temperature was found to be a two-step process involving formation of the hydride phases with intermediate hydrogen content.