Fe2O3, Ti, Fe, and TiCl3 were chosen as additives to increase the hydrogen absorption and release rates of Mg. Samples with compositions of 80 wt% Mg + 14 wt% Ni + 6 wt% Fe2O3 (named Mg-14Ni-6Fe2O3), 80 wt% Mg + 14 wt% Ni + 3 wt% Fe2O3 + 3 wt% Ti (named Mg-14Ni-3Fe2O3-3Ti), 80 wt% Mg + 14 wt% Ni + 2 wt% Fe2O3 + 2 wt% Ti + 2 wt% Fe (named Mg-14Ni- 2Fe2O3-2Ti-2Fe), and 80 wt% Mg + 14 wt% Ni + 6 wt% TiCl3 (named Mg-14Ni-6TiCl3) were prepared by high-energy ball milling in hydrogen. The hydrogen absorption and release properties of the prepared samples were investigated and compared. The halide and nickel-added Mg, Mg-14Ni-6TiCl3, had larger quantities of hydrogen absorbed and released for 60 min and a larger initial dehydriding rate than the oxide and nickel-added Mg samples. In particular, the hydrogen absorption and release properties of Mg-14Ni-6TiCl3 were examined in more detail. The activation of Mg-14Ni-6TiCl3 was completed after two hydriding-dehydriding cycles (cycling between hydriding under 12 bar H2 at 593 K and dehydriding in vacuum at 623 K). Mg- 14Ni-6TiCl3 had an effective hydrogen-storage capacity of about 5.2 wt%. At the third cycle, the sample released 1.05 wt% H for 2.5 min, 2.82 wt% H for 10 min, and 4.88 wt% H for 60 min.

Keywords: Hydrogen absorbing materials, Phase transition-accompanying milling, Phase transition of Fe2O3, Microstructure, Fe2O3, TiCl3, and Ni addition to Mg