Structure and hydrogenation properties of nanocrystalline Mg2Ni prepared by hydriding combustion synthesis and mechanical milling

In the present work, a nanocrystalline Mg2Ni alloy was prepared by hydriding combustion synthesis followed by mechanical milling (HCS + MM), and its structure as well as hydrogenation properties, especially the thermodynamic properties were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and pressure–concentration isotherms (PCIs). It was found that the product milled for the optimized duration of 40 h absorbed 2.76 wt.% of hydrogen within 100 s at 313 K. However, this excellent hydriding property degenerated fast with cycling. The enthalpy derived from the Van’t Hoff equation of this product was −53.13 kJ/mol for hydrogenation, which was slightly higher than that reported for the HCS product. From the results of SEM and XRD the dimensions of particle and grains of Mg2Ni hydride were drastically reduced after MM, and the nanostructured alloy Mg2Ni experienced noticeable grain growth during dehydring/rehydriding reactions.