Hydrogen storage properties of Pr-Mg-Ni- based alloys prepared by vacuum induction melting

Pr5Mg95-xNix(x = 5,10,15) alloys were melted in a vacuum induction furnace. The phase composition, microstructure and storage properties of gaseous hydrogen were investigated using X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The hydrogen storage properties of the alloy were systematically studied, including activation property, hydrogen absorption capacity, comminution property and plateau pressure. The results show that PrMg12 and Mg2Ni are the main and secondary phases of the alloys, respectively. As the Ni content increases, the activation ability is improved, and the hydrogen uptake ability reaches the best level at the first activation. The hydrogenation process leads to many cracks and fractures in the alloy, which reduces the grain size. PCT test results show that the alloy has two plateaus caused by the reversible processes of Mg reversible arrow MgH2 and Mg2NiH4 reversible arrow Mg2NiH4 during the hydrogenation cycle. The change of Ni content has a significant effect on the hysteresis effect during hydrogen cycling. PrH2.93 has poor thermal stability and can be easily decomposed into PrH2.