Effects of mechanical grinding on the hydrogen storage properties of LaNi5:: observation of the intermediate hydride LaNi5H3 stabilised by CO surface treatment

The effects of mechanical grinding on the hydrogen storage properties of LaNi5 were investigated. Ground powders were once hydrogenated. and then the resulting hydride was stabilised with a CO surface treatment to slow down the desorption kinetic of the hydride. It was found that the ball milling provokes the formation of the intermediate phase LaNi5Hx with x approximate to 3, whereas this phase was nor found for activated unground LaNi5 powders. P-C-T measurements performed at room temperature with unactivated ground LaNi5 powder do not reveal the presence of LaNi5H3 at desorption, showing that this phase appears only when the desorption kinetic of the hydride is slow. (C) 1998 Elsevier Science S.A.