Hydrogen desorption of Mg-Mg2Ni hypo-eutectic alloys in Air, Ar, C02, N2 and H2

The hypo-eutectic Mg-MgNi system can be modified by trace elemental additions of Na which change the microstructure and the functional properties of the alloy. The modified microstructure results in improvements to the hydrogen storage properties. In alloys of optimal composition, it has been shown that the reversible storage of 6.5-7 wt% H is possible at a rate of reaction that is realistic for industrial applications. This research investigates the release of H in air under atmospheric pressure as well as under 0.2 MPa atmospheres of Ar, CO, N, and H. The release kinetics were characterised using in situ crystallographic phase transformation analysis obtained by synchrotron Powder X-ray diffraction (PXRD) at the Australian Synchrotron. The mole fraction of MgH, Mg, MgNi, and MgNiH was determined by Rietveld refinement using RIETAN-FP. It was found that the hydrogen release temperature largely depends on the atmosphere