Effects of Milling and Hydriding-Dehydriding Cycling on the Hydrogen-Storage Behaviors of a Magnesium-Nickel-Tantalum Fluoride Alloy

In this study, Ni and TaF5 were picked as additives to enhance the hydriding and dehydriding rates of Mg. A sample with a composition of 80 wt% Mg+14 wt% Ni+6 wt% TaF5 (named Mg-14Ni-6TaF5) was prepared by reactive mechanical grinding. Its hydriding and dehydriding properties were then examined and the effects of milling and hydriding-dehydriding cycling were investigated. To activate the prepared sample, two hydriding-dehydriding cycles were required at 573 K and 593 K. At the second cycle, the sample absorbed 5.74 wt% H for 60 min under 12 bar H2 at 573 K. At 623 K, the activated Mg-14Ni-6TaF5 absorbed 2.53 wt% H for 2.5 min, 4.20 wt% H for 10 min, and 5.31wt% H for 60 min under 12 bar H2, and desorbed 2.01 wt% H for 2.5 min, 4.76 wt% H for 15 min, and 4.83 wt% H for 60 min under 1.0 bar H2. The initial hydriding rate increased as the temperature increased from 423 K to 573 K (due to the predominance of the acceleration of the thermally activated process) and then decreased from 573 K to 623 K due to the predominance of the decrease in the driving force for the hydriding reactionunder 12 bar H2.