Influence of expansion of metal hydride during hydriding-dehydriding cycles

The mechanical behavior of metal hydride reactor and the mechanism of the advent of strain caused by Ti0.71Zr0.29Mn0.8CrCu0.2 alloy expansion have been studied using pressure vessel controlled to be no pressure difference between the inner and outer wall of the reactor tube occurred. Strain gauges were set on the various locations in the reactor. The change of strain was continuously monitored using the strain analyzer. The metal hydride in the reactor after hydriding-dehydriding cycles was subjected to optical and scanning electron micrograph study, particle size analysis and the measurement of the angle of repose to investigate the flowability of metal hydride. The results indicate that once the elastic deformation of the reactor occurred during hydriding-dehydriding cycles, its deformation did not become larger anymore because the grain size of the alloy in the reactor changed to a lesser extent after subsequent cycles. The formation of metal hydride aggregates during cycling exerts a great influence on the advent of strain imposed to the reactor because the strain caused by the expansion of the aggregate becomes larger than that of the fine grain itself. The aggregate formation tends to occur easily due to the increase of cohesion and friction within the metal hydride powder during hydriding-dehydriding cycles.