Effect of Cu or Ti substitution in MgNi on crystal structure and hydrogen absorption-desorption properties

Our previous study showed the noble MgNi intermetallic compound with a CuTi-type crystal structure could be synthesized from amorphous MgNi precursor under more than 5 GPa by high pressure synthesis and could be hydrogenated into novel hydride with a CsCl-type crystal structure at 355 K under 2 MPa of hydrogen. In this study, hydrogen absorption-desorption properties of the MgNi compound with CuTi-type structure were investigated. It was found that the MgNi with CuTi-type structure absorbed and desorbed hydrogen reversibly at 473 K. Effects of substitution of Ni by Cu or Ti in the MgNi compounds were also investigated. Ternary MgNi_1-xCu_x (x = 0.2,0.5) and MgNi_0.9Ti_0.1 compounds were synthesized from amorphous precursors by high pressure synthesis. The MgNi_1-xCu_x (x = 0.2,0.5) and MgNi_0.9Ti_0.1 have CsCl-type crystal structure. The lattice parameter of MgNi_1-xCu_x increased with increasing of Cu content. MgNi_1-xCu_x (x = 0.2,0.5) and MgN_0.9Ti_0.1 could be hydrogenated under hydrogen pressure of 2 MPa and the crystal structure of these hydrides were CsCl-type structure. The hydrogen desorption temperature of these hydrides decreased with increasing of amount of Cu or Ti substitution of Ni. The substitution of Ni by Ti in MgNi improved the hydrogen absorption capacity from 1.65 to 2.06mass%.