Positron lifetime study on degradation of TiCrV hydrogen storage alloy

Kawasuso, Atsuo; Arashima, Hironobu*; Maekawa, Masaki; Ito, Hideaki*; Kabutomori, Toshiki*

Using positron lifetime spectroscopy, we examined the evolution of defects in the TiCrV alloy prepared by the arc-melting method during hydriding cycles. After one hydriding cycle dislocations were responsible for positron trapping. The dislocation-related lifetime showed no significant change with increasing the hydriding cycle suggesting that the dislocation density is well above the dynamic range of positron trapping rate. After 20 hydriding cycles, prolonged lifetime components (0.4-0.5 ns and 1.9-2 ns) were obtained. These lifetimes were nearly constant during the further hydriding cycles while their intensities increased. Vacancy defects were generated and slowly developed to microvoids during the hydriding cycles. After 200 hydriding cycles the rechargeable hydrogen capacity decreased to 90% relative to the initial amount. It is thus inferred that the reduction of rechargeable hydrogen capacity is partly caused by the formation of microvoids and dislocations.