Improvement of hydriding and dehydriding rates of Mg via addition of transition elements Ni, Fe, and Ti

An Mg–10wt%Ni–5wt%Fe–5wt%Ti sample was prepared by mechanical grinding under H2 (reactive mechanical grinding) using a planetary ball mill. The phases and their weight percentages were analyzed with the Full Proof program from the XRD patterns of the Mg–10Ni–5Fe–5Ti samples after reactive mechanical grinding and after dehydriding at the seventh cycle. The Mg–10Ni–5Fe–5Ti sample after reactive mechanical grinding contained Mg, TiH2, MgH2, and Ni phases, and the sample dehydrided at the seventh cycle contained Mg, TiH2, MgO, Mg2Ni, and Fe phases. The prepared Mg–10Ni–5Fe–5Ti sample had an effective hydrogen-storage capacity larger than 5 wt%H. The activated Mg–10Ni–5Fe–5Ti sample absorbed 5.31 and 5.51 wt%H for 5 and 60 min, respectively, at 573 K under 12 bar H2 and desorbed 1.58, 3.64, and 5.18 wt%H for 10, 30, and 60 min, respectively, at 573 K under 1.0 bar H2. The effects of reactive mechanical grinding, hydriding–dehydriding cycling, and addition of transition elements Ni, Fe, and Ti were discussed.

► Preparation of Mg–10wt%Ni–5wt%Fe–5wt%Ti by reactive mechanical grinding. ► Analysis by Full Proof program of XRD patterns after RMG and after cycling. ► Formation of Mg, TiH2, MgO, Mg2Ni, and Fe phases in the dehydrided sample. ► Samples after RMG as well as samples dehydrided after cycling contain TiH2. ► Effective hydrogen-storage capacity larger than 5 wt%H.