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In-Situ Atomic-Scale Phase Transformation of Mg under Hydrogen Conditions C

Peng, Qiuming, Sun, Yong, Ge, Bingcheng, Feng, Jiawen, Guo, Jianxin, Fernandez, Carlos, Huang, Jianyu
Journal of physical chemistry 2018 v.122 no.34 pp. 19532-19539
alloys, ambient temperature, hydrogen, hydrogenation, magnesium, magnesium oxide, oxidation, phase transition, transmission electron microscopes
The 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-1 wt % Pd alloy under hydrogen conditions in an aberration-corrected environmental transmission electron microscope. Compared with the magnesium hydrogenation reaction, the 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 the 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.