In-situ atomic-scale phase transformation of Mg under hydrogen conditions.

Abstract

Magnesium hydrogenation issue poses a serious obstacle to designing strong and reliable structural materials, as well as offering a safe alternative for hydrogen applications. Understanding phase transformation of magnesium under hydrogen gas plays an essential role in developing high performance structural materials and hydrogen storage materials. Herein, we report in-situ atomic-scale observations of phase transformation of Mg and Mg-1wt.%Pd alloy under hydrogen conditions in an aberration-corrected environmental transmission electron microscopy. Compare with magnesium hydrogenation reaction, magnesium oxidation reaction predominately occurs at room temperature even under pure hydrogen gas (99.9%). In comparison, magnesium hydrogenation is readily detected in the interface between Mg and Mg6Pd, due to catalytic role of Mg6Pd. Note that the nanoscale MgH2 compound transfers into MgO spontaneously, and the interface strain remarkably varies during phase transformation. These atomic-level observations and calculations provide fundamental knowledge to elucidate the issue of magnesium hydrogenation