Passive Oxide Film Growth Observed On the Atomic Scale
Passive Oxide Film Growth Observed On the Atomic Scale
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DOI：
10.1002/admi.202102487
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发表时间：
2022-02-26
影响因子：
5.4
通讯作者：
Zhou, Guangwen
中科院分区：
文献类型：
--
作者：
Chen, Xiaobo;Liu, Zhenyu;Zhou, Guangwen
尽管钝化在大多数金属表面上普遍存在，但表面钝化如何发生的微观层面的图片迄今为止还不清楚。使用典型的例子，铝的表面钝化，在这里原位原子透射电子显微镜观察和计算建模解开纠缠微观过程，并确定原子过程导致表面钝化。基于原子尺度的金属晶格的逐层膨胀及其随后的转变成非晶氧化物的观察，它表明，表面钝化发生通过两个阶段的氧化过程，其中第一阶段是由层内原子洗牌为主，而第二阶段是由层间原子无序后，逐步吸氧。第一阶段可以通过增加表面缺陷来绕过，以促进层间原子迁移，这导致金属晶格的多个原子层的直接非晶化。所确定的两阶段反应机制和表面缺陷在促进层间原子重排中的作用可以在利用表面缺陷来调节质量传输和钝化动力学以及钝化膜的组成、结构和传输性质方面找到更广泛的适用性。
Despite the ubiquitous presence of passivation on most metal surfaces, the microscopic-level picture of how surface passivation occurs has been hitherto unclear. Using the canonical example of the surface passivation of aluminum, here in situ atomistic transmission electron microscopy observations and computational modeling are employed to disentangle entangled microscopic processes and identify the atomic processes leading to the surface passivation. Based on atomic-scale observations of the layer-by-layer expansion of the metal lattice and its subsequent transformation into the amorphous oxide, it is shown that the surface passivation occurs via a two-stage oxidation process, in which the first stage is dominated by intralayer atomic shuffling whereas the second stage is governed by interlayer atomic disordering upon the progressive oxygen uptake. The first stage can be bypassed by increasing surface defects to promote the interlayer atomic migration that results in direct amorphization of multiple atomic layers of the metal lattice. The identified two-stage reaction mechanism and the effect of surface defects in promoting interlayer atomic shuffling can find broader applicability in utilizing surface defects to tune the mass transport and passivation kinetics, as well as the composition, structure, and transport properties of the passivation films.