Improvement of the Reaction Rates of Mg with Ha by the Addition of TaF_5 via Reactive Mechanical Grinding

摘要

A sample with a composition of 90 wt% Mg-10 wt% TaF_5 (named Mg-10TaF_5) was prepared by reactive mechanical grinding, and its hydriding and dehydriding properties were examined. The activation of Mg-10TaF_5 was not required. At n=l, the sample absorbed 3.63 wt% H for 5 min, 4.03 wt% H for 10 min, and 4.53 wt% H for 30 min at 593 K under 12 bar H_2. At n=l, the sample desorbed 0.59 wt% H for 5 min, 1.46 wt% H for 10 min, 3.42 wt% H for 30 min, and 4.24 wt% H for 60 min at 593 K under 1.0 bar H_2. Mg-l0TaF_5 after reactive mechanical grinding contained MgH_2, Mg, and very small amounts of MgF_2 and Ta_2H. The XRD pattern of Mg-10TaF_5 dehydrided at n=3 revealed Mg, MgH_2, a small amount of MgO, and very small amounts of MgF_2 and Ta_2H phases. Mg-10Fe_2O_3 and Mg-10MnO were reported to have quite high hydriding rate and dehydriding rates, respectively. Mg-10TaF_5 had a larger initial hydriding rate but a lower quantity of hydrogen absorbed for 60 min than Mg-10Fe_2O_3. However, Mg-10TaF_5 had a higher initial dehydriding rate (after the incubation period) and a larger quantity of hydrogen desorbed for 60 min than Mg-l0MnO.