Role of Annealing for Improving Hydrogen Storage Properties of Ti-Cr-V Alloy

摘要

The Cyclic degradation of Ti-Cr-V, a solid solution type hydrogen storage alloy with Body-Centered Cubic, has been investigated by SEM and TEM. The cyclic test resulted in fine powders with cracking, and then the size was resulted over 100 cycles. Microstructural observation revealed the dislocation density increased more than one order of magnitude during this test, meaning that the decrease in effective storage capacity could depend on the stored lattice defects and strain. To prevent the cyclic degradation, the sub-micron sized particles were annealed for reducing dislocation density. This treatment enables to expand the plateau in hydrogenation process, but it has no effect at de-hydrogenation, that is the plateau returned to the un-improved level. This means that the stability of beta-hydride is strongly depended on the lattice defect and strain level created by the hydrogenation. If the particle size is reduced to less than several hundred nm, the degradation could be improved.