Structural characterization and hydrogen sorption properties of nanocrystalline Mg2Ni

The structure, chemical distribution, microstructure and thermal stability of a 2Mg-Ni mixture milled at different times in a low energy ball mill were investigated. After short time processing, a mixture of amorphous Mg-rich phase, nanocrystalline Mg and crystalline Ni was obtained. The crystallite size reduction and strain increment along with the formation of an amorphous phase was associated to the refinement of Mg at this stage. After long time milling, nanocrystalline Mg2Ni was produced and both amorphous Mg-rich phase and Ni remained in the mixture as residual phases. Stable nanocrystalline Mg2Ni was successfully synthesized by a combination of low energy mechanical alloying and further non-isothermal heating up to 300 °C. The reactivity and equilibrium features of Mg2Ni were characterized by both hydrogen absorption/desorption and pressure-composition isotherm measurements. The nanostructured intermetallic showed a 3.0 wt% hydrogen storage capacity without activation and excellent hydrogen absorption/desorption kinetics.