Preparation of the hydrides Mg2FeH6 and Mg2CoH5 by mechanical alloying followed by sintering

Mg2CoK5 and Mg2FeH6 were prepared by mechanical alloying (MA) and followed by sintering under mild conditions. The effect of milling atmosphere on the end products was also studied. The mixtures 2Mg+Fe and 2Mg+Co were milled in a planetary ball mill under hydrogen and argon atmospheres. After milling, the mixtures were sintered at 623 K for 1 day under 50 bars of hydrogen. X-ray powder diffraction analysis was used not only for identification of phases formed but also for crystal structural refinement and mass fraction calculation using the Rietveld method. We found that, under the above sintering conditions, the hydrides Mg2FeH6 and Mg2CoH5 were produced only in samples that were milled prior to sintering. For 2Mg+Fe mixture, milling under hydrogen prior to sintering produced 84% Mg2FeH6 in the product excluding oxide. The mixture 2Mg+Co was milled and sintered producing MgH2 and Mg2CoH5, but the mass fraction of Mg2CoH5 was independent of the milling atmosphere.