Zijiao Zhang1, Xiaoqian Fu1, Minmin Mao1, Qian Yu1(*), Scott X. Mao1,2 (*), Jixue Li1, and Ze Zhang1
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1 Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science & Engineering, Zhejiang University, Hangzhou 310027, China 2 Department of Mechanical Engineering & Materials Science, University of Pittsburgh, Pittsburgh, PA 15261, USA
Oxidation plays a tremendous role in the long-term performance of metals. As an important lightweight metal for industrial applications, magnesium suffers from its high reactivity with oxygen and increased evaporation at high temperatures. To understand the oxidation mechanism of magnesium at elevated temperatures, in situ environmental transmission electron microscopy (E-TEM) was performed on magnesium nanoparticles. At a relatively low temperature, the growth of a MgO lamellae via the outward diffusion of bulk magnesium atoms dominated the oxidation process. In contrast, a sublimation-enhanced oxidation via gas phase reaction occurred at 200 °C, leading to the growth of MgO dendrites over the particle that finally leads to the degradation of the magnesium structure. This study provides a direct observation and model of the oxidation mechanism of a direct gas–gas reaction that improves our understanding of the oxidation mechanism at elevated temperatures.