Hydrogen sorption enhancement in cold rolled LaNi5

In this paper, we report the effects of cold rolling on hydrogen sorption properties of LaNi5. We found that cold rolling LaNi5 greatly reduces particle sizes as well as crystallite sizes. After cold rolling, the activation kinetic is highly enhanced with shorter time to reach full hydrogen capacity. Cold rolling five times offers the best compromise between high capacity and fast kinetic. For completeness, we compared cold rolling with high energy ball milling for 15 and 60 min under argon atmosphere. Results showed that 15 min of ball milling had a positive effect on the time of the first absorption, but a loss in capacity was also observed. Further milling to 60 min resulted in an important degradation of hydrogen sorption properties. We also found that sample's morphology could drastically change the first absorption kinetic. In conclusion, cold rolling is a good and simple method to enhance hydrogen sorption properties of LaNi5. (C) 2014 Elsevier B.V. All rights reserved.