Enhancement of Reaction Kinetics with Hydrogen in Mg by Addition of Ni and TaF5 via Reactive Mechanical Grinding

A sample with a composition of 80 wt% Mg-14 wt% Ni-6 wt% TaF5 was prepared by reactive mechanical grinding. Its hydriding and dehydriding properties were then examined. The hydriding rate in the beginning was very high from the first cycle, even at a relatively low temperature of 553 K. At n = 1, the sample absorbed 4.53 wt% H for 5 min, 4.78 wt% H for 10 min, 5.15 wt% H for 30 min, and 5.26 wt% H for 60 min at 553 K under 12 bar H2. At n = 1, the sample desorbed 1.32 wt% H for 5 min, 2.32 wt% H for 10 min, 4.53 wt% H for 30 min, and 5.00 wt% H for 60 min at 593 K under 1.0 bar H2. Activations of the samples were completed after two hydriding (under 12 bar H2)-dehydriding (in vacuum) cycles at 573 K. The activated 80 wt% Mg-14 wt% Ni-6 wt% TaF5 had an effective hydrogen-storage capacity near 6 wt%, absorbing 5.78 wt% H under 12 bar H2 and desorbing 5.16 wt% H under 1.0 bar H2 at 593 K for 60 min.