Nanostructured MgH 2 prepared by cold rolling and cold forging

Abstract

Magnesium is a promising material for solid state hydrogen storage, since it has low cost and its hydride can store reversibly up to 7.6 wt.% of hydrogen. Fast H-sorption kinetics at around 300 °C can be achieved after processing Mg-based mixtures by high energy ball milling (HEBM), which produces nanostructured composite powders. Severe plastic deformation (SPD) processing techniques are being explored as an alternative to HEBM in order to obtain more air-resistant materials and to reduce the time and energy required for processing. In this paper, MgH 2 and MgH 2–Fe mixtures were severely mechanically processed by extensive cold forging (CF) and cold rolling (CR). A very significant grain refinement (up to 10 nm) was achieved, which is comparable to the values typically obtained after processing by HEBM. Enhanced H-sorption properties were observed for these mechanically processed MgH 2-based nanocomposites in comparison with commercial magnesium hydride. The obtained compacts after CR and CF presents a much lower specific surface area than the ball-milled powders and therefore show higher air-resistance. These results are promising from the point of view of applications since it reveals the potential of the use of low cost mechanical processing routes to produce Mg-based nanomaterials for hydrogen storage.