Exploring the hydrogen sorption capacity of Mg–Ni powders produced by the vapour deposition technique

Nanocrystalline Mg–Ni alloy powder was produced via the magnetron co-sputtering technique. The samples obtained showed crystallisation of Mg and Mg2Ni and an overall morphological heterogeneity with different enriched zones, as evidenced by microstructural analysis. A number of pressure-composition-isotherms (PCI) were carried out on these samples at a range of temperatures.Following hydrogenation, different hydrogen sorption behaviours were observed depending on the samples’ relative composition in terms of Mg and Mg2Ni. Hydrogenation/dehydrogenation cycling is believed to have caused modification of the nanocrystalline materials investigated. The derived dissociation enthalpies of the corresponding hydrides, MgH2 and Mg2NiH4, were found to be coherent with values reported in literature, with the exception of two samples. In addition, one of these samples showed a third plateau pressure pointing to the presence of a hydrogenated metastable phase.