The effect of Al on thermal stability and kinetics of decomposition of MgH2 prepared by mechanochemical reaction at different conditions

This work is directed at decreasing decomposition temperature of MgH2. In accordance with the theoretical predictions, hydride of solid solution of Al in Mg should decompose at lower temperature compared to that of MgH2, and numerous experiments indicate that thermodynamic stability of the hydride depends on methods and conditions of its synthesis. Therefore, the goal of this article is to study the possibility of obtaining the hydride of solid solution of aluminum in magnesium by different technological approaches. Three mechanical composite alloys derived by the different approaches are studied employing the X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermodesorption spectroscopy (TDS) methods. XRD Rietveld analysis reveals that the hydrogenation of a Mg + 10 wt% Al powder by means of reactive milling in the hydrogen atmosphere as well as hydrogenation of the powder from the gaseous phase after milling the powder for 20 h in the argon atmosphere leads to formation of aluminum-free MgH2 hydride and the Mg17Al12 phase. Our TDS studies (at PH2 = 0.1 MPa) indicate that additives of 10 wt% Al to magnesium do not lead to decreasing the decomposition temperature of MgH2 prepared by mechanochemical reaction at the different conditions.