Structure and hydrogen storage properties of La1-Pr MgNi3.6Co0.4 (x = 0–0.4) alloys prepared by melt spinning

Melt spinning technology was applied to prepared La1-xPrxMgNi3.6Co0.4 (x = 0–0.4) alloys, and phase composition, micro-structure, morphology and hydrogen storage properties were systematically investigated. The results show that the alloys contain two phases, LaMgNi4 and LaNi5 which have been detected by XRD and SEM. The grain of the alloys is refined by increasing Pr content and the phase abundance changed obviously. The hydrogen absorption capacity (wt%) of the alloys is 1.663, 1.659, 1.60, 1.593 and 1.566, corresponding the Pr substation of x from 0 to 0.4. The hydrogenation cycle stability indicates that the hydrogen capacity declined severely with the hydrogenation cycles. It is attributed to the hydrogen-induced amorphization which is confirmed by the XRD results after hydrogenation cycles. In order to recover the hydrogen storage capacity after cycles, the annealing treatment at 673 K for 3 h was carried out. And the XRD and HRTEM results show that the amorphization structure after hydrogen absorption/desorption cycles is re-crystallized by annealing treatment.