Characterization of hydrogen storage properties of Mg-Fe-CNT composites prepared by ball milling, hot-extrusion and severe plastic deformation

A systematic investigation was performed on the hydrogen storage properties of mechanically prepared 2MgFe/carbon nanotube (CNT) composites. The powders were transformed into bulk form by three processing routes (hot-extrusion, cold-rolling and extrusion followed by cold-rolling). The samples were kept in air to test their resistance to oxidation. Hydrogen absorption capacity and hydriding kinetics of the composites were dependent on the quantity of added CNTs. A 5 wt% addition of CNTs is optimum to facilitate the hydrogen absorption and desorption. Single cold-rolling (CR) was found to be the best route. Compared with powder composites, samples prepared by CR presented improved kinetics, the same hydrogen capacity and a decrease in the incubation time for activation. The cold-rolled composite 2MgFe/5 wt% CNTs achieved 73% of the theoretical capacity of Mg2FeH6, and desorbs almost the same quantity. Moreover, these absorption and desorption processes occur faster than in the powders. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.