Effects of ball-milling on the hydrogen sorption properties of LaNi5

Pressure-composition isotherms of LaNi5 alloys were studied as function of ball-milling time. Results indicate that ball-milling convert a part of the LaNi5 to a non-absorbing state-a state which does not absorb hydrogen under conditions where un-milled LaNi5 powders absorb and transform to LaNi5H6, in addition to particle size reduction and creation of defects. The non-absorbing fraction in the milled sample is found to grow with increase in the ball-milling time. The resistance to the hydride formation of the long-time ball-milled LaNi5 samples is found to continue even after a 1-h high vacuum annealing at around 1000 K. This indicates that the hydrogen-absorption-resist-anomalous state formed during the long-time ball-milling is rather stable.