Wang Shuangbao, Dong Zejian, Zhang Lifeng, Tsiakaras Panagiotis, Shen Pei Kang, Luo Langli
Collaborative Innovation Center of Sustainable Energy Materials, School of Physical and Technology & Guangxi Key Laboratory of Electrochemical Energy Materials, Guangxi University, Nanning 530004, China.
Institute of Molecular Plus, Department of Chemistry, Tianjin University, 92 Weijin Road, Tianjin 300072, China.
ACS Appl Mater Interfaces. 2021 Jan 13;13(1):1903-1913. doi: 10.1021/acsami.0c18158. Epub 2020 Dec 22.
The initial growth mode of oxide on alloy plays a decisive role in the development of protective oxide scales on metals and alloys, which is critical for their functionality for high temperature applications. However, the atomistic mechanisms dictating that the oxide growth remain elusive due to the lack of direct observation of the initial oxide nucleation and growth at atomic-scale. Herein, we employed environmental transmission electron microscopy and the first-principles calculations to elucidate the initial atomic process of nickel-chromium (Ni-Cr) alloy oxidation. We directly revealed three different oxide growth modes of initial NiO islands on Ni-Cr alloy upon oxidation by O, which result in distinct crystallography and morphology. The multimode oxide growth leads to irregular-shaped oxides, which is shown to be sensitive to the local mass transport. This localization of oxide growth mode is also demonstrated by the identified vigorous competence in oxide growth and thus shown to be kinetically controlled. The concept exemplified here provides insights into the oxide formation and has significant implications in other material and chemical processes involving oxygen gas, such as corrosion, heterogeneous catalysis, and ionic conduction.
合金上氧化物的初始生长模式对金属和合金上保护性氧化膜的形成起着决定性作用，这对它们在高温应用中的功能至关重要。然而，由于缺乏对原子尺度上初始氧化物成核和生长的直接观察，决定氧化物生长的原子机制仍然难以捉摸。在此，我们采用环境透射电子显微镜和第一性原理计算来阐明镍铬（Ni-Cr）合金氧化的初始原子过程。我们直接揭示了在O氧化下Ni-Cr合金上初始NiO岛的三种不同氧化物生长模式，这导致了不同的晶体学和形态。多模式氧化物生长导致氧化物形状不规则，这表明其对局部质量传输敏感。氧化物生长模式的这种局部化也通过所确定的氧化物生长中的激烈竞争得到证明，因此表明是动力学控制的。这里所举例的概念为氧化物的形成提供了见解，并且在涉及氧气的其他材料和化学过程中具有重要意义，例如腐蚀、多相催化和离子传导。
