Hydrogenation and degradation of Mg–10 wt% Ni alloy after cyclic hydriding–dehydriding

Hydrogenation and degradation properties of Mg–10 wt% Ni hydrogen storage alloys were investigated by cyclic hydriding–dehydriding tests. Mg–10 wt% Ni alloy was synthesized by rotation-cylinder method (RCM) under 0.3% HFC-134a/air atmosphere and their hydrogenation and degradation properties were evaluated by pressure-composition-isotherm (PCI) measurement. Hydrogen storage capacities gradually increased following 160 hydriding–dehydriding cycles and thereafter started to decrease. Measured maximum hydrogen capacity of Mg–10 wt% Ni alloy is 6.97 wt% at 623 K. Hydriding and dehydriding plateau pressure were kept constant for whole cycles. Reversible hydrogen capacity started to descend after 280 hydriding–dehydriding cycles. The lamellar eutectic structure of Mg–Ni alloy consists of Mg-rich αα-phase and ββ-Mg2NiMg2Ni. It is assumed that the lamellar eutectic structure enhances hydrogenation properties.