Study of Mg-M (M = Co, Ni and Fe) mixture elaborated by reactive mechanical alloying - hydrogen sorption properties

Reactive mechanical alloying (MA in H₂) of magnesium powder allowed us to obtain a partial conversion of Mg to MgH₂. The ratio MgH₂/Mg can be improved by increasing the milling time or by adding a 3 d-element (with the same initial particle size). X-ray diffraction was applied successfully to determine the quantity of MgH₂ formed. The RMA allows us to eliminate the activation procedure generally requested for magnesium. The hydriding results from the combination of two steps: nucleation at first and then diffusion. A direct relationship exists between the nucleation duration and the specific surface area. It is demonstrated that RMA for a short time (2 h) is an effective way to strongly improve the hydrogen storage properties of both magnesium and (Mg+10 wt.% Co, Ni or Fe) mixtures.