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 expansio n have been studied using pressure vessel controlled to be no pressure difference between the inner and outer wall of the reactor tube occur red. Strain gauges were set on the various locations in the reactor. T he change of strain was continuously monitored using the strain analyz er. The metal hydride in the reactor after hydriding-dehydriding cycle s was subjected to optical and scanning electron micrograph study, par ticle size analysis and the measurement of the angle of repose to inve stigate the flowability of metal hydride. The results indicate that on ce the elastic deformation of the reactor occurred during hydriding-de hydriding cycles, its deformation did not become larger anymore becaus e the grain size of the alloy in the reactor changed to a lesser exten t after subsequent cycles. The formation of metal hydride aggregates d uring cycling exerts a great influence on the advent of strain imposed to the reactor because the strain caused by the expansion of the aggr egate becomes larger than that of the fine grain itself. The aggregate formation tends to occur easily due to the increase of cohesion and f riction within the metal hydride powder during hydriding-dehydriding c ycles.