OBSERVATION OF THE DEFECTS INDUCED BY HYDROGEN ABSORPTION AND DESORPTION IN LANI5

Abstract

The types and densities of defects generated in LaNi5 lattice have been observed using transmission electron microscopy after hydrogen absorption and desorption with increasing hydrogen concentration. Basically two types of dislocations, ripple-like facile dislocations and misfit super dislocations having Burgers vectors of [hk1] and [hk0], respectively, were observed. After full absorption and desorption of hydrogen, the generation and dynamic recovery of these dislocations resulted in well-developed dislocation walls and slip band structure. Structural disorders and micro-twins were also occasionally observed. The macroscopic effects such as, the solubility enhancement in alpha-phase, anisotropic X-ray peak broadening and large stored energy in the activated LaNi5 could be related to the dislocations and anti-structural defects observed in this study.