Effects of cyclic hydriding–dehydriding reactions of Mg 2Ni alloy on the expansion deformation of a metal hydride storage vessel

Abstract

A high-temperature reaction vessel system was set up to study the wall deformation during cyclic hydriding/dehydriding reactions of Mg 2Ni powders at 255 °C. Effects of packing fraction and initial particle size of Mg 2Ni powders were characterized. Results indicated that a strain accumulation was found on the wall surface with progressive cycles of hydriding/dehydriding reactions. The wall strain varied with position, as a lower position had a larger deformation. Such an accumulation and position-dependence of wall strain in the vertical hydride storage vessel could be attributed to a pulverization-densification mechanism. At a given vessel position, the hoop strain was increased with increasing packing fraction from 50 to 70 vol%. For a 50-vol% packing fraction, the wall deformation was enlarged when the initial powder size was increased from 200 mesh (74 μm) to 100 mesh (149 μm). After 50 cycles of hydriding/dehydriding reactions, the particle size was significantly reduced to about 1 μm.