In Situ Multiscale Study of Iron Oxidation at High Temperatures.

Although high-temperature oxidation of metals results in significant failure of structure materials, in situ understanding of these processes and developing improved strategies are still very limited. Herein, using environmental scanning electron microscopy (ESEM), environmental transmission electron microscopy (ETEM), and X-ray photoelectron spectroscopy (XPS), we report the in situ dynamic high-temperature oxidation behaviors of iron in O, HO, and O + HO atmospheres, respectively. The results demonstrate that an oxygen-rich environment (1.6 mbar) leads to transient formation of polycrystalline FeO without passivation effects on further oxidation, while sparse oxygen environments (10 mbar) promote formation of a uniform thin passivation layer of FeO, protecting itself from further oxidation in ambient air. In contrast to O, the HO vapor accelerates oxidation, and the products consist of FeO and FeOOH. These in situ results give insights into designing technically universal antioxidation strategies.