Hydriding and Dehydriding Rates of Mg, Mg-10TaFa5, and Mg-10NbF5 Prepared via Reactive Mechanical Grinding

In this work, TaF5 and NbF5 were chosen as additives to enhance the hydriding and dehydriding rates of Mg. Mg, Mg-10TaF(5), and Mg-10NbF(5) samples were prepared by reactive mechanical grinding. The hydriding and dehydriding properties of the samples were then examined. Mg-10TaF(5) had the largest amount of hydrogen absorbed for 30 min and the highest initial dehydriding rate after incubation period, followed in order by Mg-10NbF(5), and Mg. At 593 K under 12 bar H-2 at the first cycle, Mg-10TaF(5) absorbed 3.63 wt% H for 5 min and 4.53 wt% H for 30 min At 593 K under 1.0 bar H-2 at the first cycle, Mg-10TaF(5) desorbed 0 wt% H for 2.5 min, 0.59 wt% H for 5 min, 3.42 wt% H for 30 min, and 4.24 wt% H for 60 min. The reactive mechanical grinding of Mg with TaF5 or NbF5 is believed to have facilitated the nucleation and to have decreased the diffusion distances of hydrogen atoms. These two effects are believed to have increased the hydriding and dehydriding rates of Mg. The MgF2 and Ta2H formed in Mg-10TaF(5), and the MgF2, NbH2, and NbF3 formed in Mg-10NbF(5) are considered to have enhanced both of these effects.