Effects of ball-milling on the hydrogen sorption properties of LaNi_5

摘要

Pressure-composition isotherms of LaNi_5 alloys were studied as function of ball-milling time. Results indicate that ball-milling convert a part of the LaNi_5 to a non-absorbing state--a state which does not absorb hydrogen under conditions where un-milled LaNi_5 powders absorb and transform to LaNi_5H_6, 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 LaNi_5 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.