Hydrogen storage properties of 2Mg–Fe mixtures processed by hot extrusion: Influence of the extrusion ratio

Hot extrusion processing was employed to produce 2Mg–Fe bulk mixtures for hydrogen storage. 2Mg–Fe powder mixtures were prepared by high-energy ball milling. These mixtures were cold pressed into cylindrical pre-forms, which were then processed by hot extrusion (at 300 °C) to produce bulks. In this work, we analyzed the influence of the extrusion ratio (3/1, 5/1 and 7/1) on the sorption properties of the bulks. The nanometric grain size remained unaltered after all hot extrusion conditions. More porous bulks were produced at an extrusion ratio of 3/1. In the first cycle of hydrogenation, the sample processed at 3/1 absorbed more hydrogen (4 wt% of H) than the precursor powders (3 wt% of H). The results showed that the desorption temperature of bulks were very similar to that of 2Mg–Fe powders, which is good considering the lower surface area of bulks, and that samples with Fe in excess presented lower desorption temperatures.

► 2Mg–Fe powder mixtures were produced by high-energy ball milling.
► Extrusion at different extrusion ratios produced samples with different porosities.
► In the activation, the most porous bulk sample presented the highest capacity.
► The H desorption properties of bulk hydrides were very similar to those of powders.
► Fe acts as grain boundary pinning, and in excess improves H desorption properties.