Nanostructured Mg based hydrogen storage bulk materials prepared by high pressure torsion consolidation of arc plasma evaporated ultrafine powders

•New processing route by HPT consolidation of arc plasma evaporated nano-Mg particles.•Formation of ultrafine Mg–MgO based composites by HPT of passivated Mg particles.•Improved hydrogen storage due to the fine Mg structure and dispersion of nano-MgO.•Hydrogen uptake at 100 °C obtained in the Mg–MgO-2 wt%Ni composite.•Comparatively, addition of 2 wt% Fe catalyst did not bring additional advantage.

Nanostructured Mg based bulk materials were prepared using a new processing route: consolidation by high pressure torsion (HPT) of ultrafine powders obtained by arc plasma method. The bulk material was mainly composed of ultrafine Mg grains and dispersed nanosized MgO. In comparison to pure Mg ultrafine powders prepared using only arc plasma method, the hydrogenation enthalpy was slightly increased and the absorption activation energy was reduced through the HPT treatment. The structure refinement and the fragmentation of the MgO layer induced by the HPT account for the improved hydrogen sorption thermodynamic and kinetic properties. The additions of Ni catalyst nano-powders reduced the storage capacity but improve the reaction kinetics and lowered the temperature for storage. Comparatively, the alloying by Fe had little beneficial effect because the Fe nano-powder did not deform plastically and remained unaltered under HPT.