Abstract
Damage mechanism and hydrogen storage ability variation of palladium (Pd) were investigated on hydrogen absorption-desorption multi-cycles. In order to study this problem, palladium plates and round bars with mechanical working or annealing have been used. Specimens were hydrogenated cyclically by the electrochemical method, and hydrogen absorption ratio (H/Pd) as well as deformation of specimens were measured at each hydrogenation cycle. As results, it was shown that damage mechanism of Pd specimens was occurred differently with their geometries and mechanical or heat treatment. In thin plate Pd specimens, the thickness increased in increasing hydrogenation cycles whereas length and width decreased, and grains were greatly deformed however damage of micro and macro structures were scarcely observed, and also hydrogen storage ability scarcely changed. On the other hand, in round Pd specimens, both length and diameter increased with increasing hydrogenation cycles, and significant damage of structures were widely observed which resulted in decrease of the ratio H/Pd to -4.2% at the final hydrogenation stage. The damage of structures and deformation were by far intensive in the specimens with mechanical working than with heat treatment however the hydrogen storage ability were not so different within the two type specimens.
