Hydrogen storage properties of nanocrystalline Mg2Ni prepared from compressed 2MgH2Ni powder. (6th December 2018) - Khan, Darvaish
Abstract: In the present work, nanocrystalline Mg2 Ni with an average size of 20–50 nm was prepared via ball milling of a 2MgH2 Ni powder followed by compression under a pressure of 280 MPa. The phase component, microstructure, and hydrogen sorption properties were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), pressure-composition-temperature (PCT) and synchronous thermal analyses (DSC/TG). Compared to the non-compressed 2MgH2 Ni powder, the compressed 2MgH2 Ni pellet shows lower dehydrogenation temperature (290 °C) and a single-phase Mg2 Ni is obtained after hydrogen desorption. PCT measurements show that the nanocrystalline Mg2 Ni obtained from dehydrogenated 2MgH2 Ni pellet has a single step hydrogen absorption and desorption with fairly low absorption (−57.47 kJ/mol H2 ) and desorption (61.26 kJ/mol H2 ) enthalpies. It has very fast hydrogen absorption kinetics at 375 °C with about 3.44 wt% hydrogen absorbed in less than 5 min. The results gathered in this study show that ball milling followed by compression is an efficient method to produce Mg-based ternary hydrides. Highlights: Single phase Mg2 Ni was prepared from ball milled 2MgH2 Ni compressed pellet. Enthalpies of hydrogenation/dehydrogenation of Mg2 Ni/Mg2 NiH4 were −57.47 kJ/mol H2 and 61.26 kJ/mol H2 respectively. Nanocrystalline Mg2 Ni hydrogen absorption was very fast and absorbed 3.44 wt% hydrogen in less than 5 min.