Hydriding and dehydriding properties of Mg$_{2}$Ni/Ni and Mg$_{2}$ Ni/Ni + 5 wt.% Cu prepared by mechanical alloying

Abstract

Elemental powders of Mg, Ni and Cu are subjected to high-energy ball milling in order to produce alloys of nominal compositions Mg$_{2}$Ni and Mg$_{2}$Ni$_{0.95}$Cu$_{0.05}$. Nanocrystalline phases based on the Mg$_{2}$Ni structure are produced after 21 hours of milling. As-milled powders were hydrided for 5 min at temperatures of 373, 423 and 473 K, under hydrogen pressures of between 0.69 and 2.07 MPa. The mass loss of the hydrided powders during thermogravimetric analysis was associated with hydrogen release. Maximum amounts of H$_{2 }$ release of 2.9 and 3.1 wt.% were obtained, respectively, for the Mg$_{2}$Ni and Mg$_{2}$Ni$_{0.95}$Cu$_{0.05}$ samples hydrided at 473 K without prior activation. These are some of the most advantageous results ever reported concerning the behavior of the Mg$_{2}$Ni phase as a hydrogen storage material.