Development of hydrogen-storage alloys by mechanical alloying of Mg with Fe and Co

Abstract

The hydriding and dehydriding kinetics of Mg are reviewed. In order to improve the reaction kinetics of Mg with hydrogen, mechanically-alloyed Mg-10 wt.%Fe and Mg-10 wt.%Co mixtures are prepared and their hydrogen-storage properties are investigated. The activation of Mg-10 wt.%Fe is easier than that of Mg-10 wt.%Co. However, The hydriding rates (at 569–589 K, 7–11 bar H₂) and dehydriding rates (at 589 K, 1.0 bar H₂) of the mechanically-alloyed Mg-10wt.%Co are higher than those of the mechanically-alloyed Mg-10 wt.%Fe after activation. The H_a value of Mg-10 wt.%Co after 60 min is 3.08 wt.% at 589 K under 11 bar H₂ and its H_d value after 60 min is 1.48 wt.% at 589 K under 1.0 bar H₂. Mg-10 wt.%Co has a smaller particle size than has Mg-10 wt.%Fe after hydriding and dehydriding cycling. The mechanical alloying of Mg with Fe and Co and the hydriding-dehydriding cycling increased the hydriding and dehydriding rates by facilitating nucleation (by creating defects on the surface of the Mg particle and by the additive) and by shortening the diffusion distances (by reducing the Mg particle sizes).