Investigation of ball-milling process on microstructure, thermodynamics and kinetics of Ce–Mg–Ni-based hydrogen storage alloy

Abstract

Aiming at improving hydrogen storage performance of Mg-base alloy, the Mg90Ce3Ni7 alloy is prepared by medium-frequency induction melting and following mechanical ball-milling process. X-ray diffraction analysis reveals that the ball-milling Mg90Ce3Ni7 alloy is composed of Mg, Mg2Ni and CeMg12 phases, whereas subsequent milling induces grain refinement and the formation of amorphous phase. In addition, the extension of ball-milling time also not further improve the thermodynamic properties, whereas has a very significant effect on the kinetic properties, which is mainly attributed to the change of microstructure of the alloy by ball milling process. The ball-milling not only creates the nanocrystalline and amorphous structures, but also refines the particle size of the alloy. This is beneficial to the nucleation and diffusion of the alloy during reversible hydrogenation reaction. Concretely, the ball-milling time enhances the kinetics of hydrogen absorption at low temperature, especially for the alloy milled for 20 h, in which can absorb more than 3.5 wt % H2 over 30 min at 100 °C. Meanwhile, the ball-milling time enhances the kinetics of hydrogen desorption. It leads to effectively reducing the dehydrogenation activation energy to 72.2 kJ/mol H2, which allows the alloy can release more than 5 wt % H2 in 10 min at 280 °C. The work provides a scientific way to promote the practical application of Mg-based hydrogen storage alloy.