Hydrogenation and dehydrogenation rates of oxide Fe2O3-added magnesium, and effects of Ti addition

Samples with compositions of 80 wt% Mg–14 wt% Ni–6 wt% Fe2O3, 80 wt% Mg–14 wt% Ni–6 wt% Ti, 80 wt% Mg–14 wt% Ni–3 wt% Fe2O3–3 wt% Ti, and 80 wt% Mg–14 wt% Ni–2 wt% Fe2O3–2 wt% Ti–2 wt% Fe were prepared by reactive mechanical grinding. Their hydriding and dehydriding properties were then examined and effects of Ti addition on the hydrogen storage properties of Mg–Ni alloys were investigated. The specific surface area of Mg–14Ni–6Fe2O3 decreased after activation. On the other hand, the specific surface areas of the samples Mg–14Ni–6Ti, Mg–14Ni–2Fe2O3–2Ti–2Fe, and Mg–14Ni–3Fe2O3–3Ti, which contain Ti, increased after activation. This proves that the addition of Ti helps the decrease in particle size with hydriding–dehydriding cycling, and prevents the particles from being sintered. Ti forms Ti hydride during reactive mechanical grinding, and remains undecomposed even after dehydriding reaction.