Martin Andrew, Kiarie Winnie, Chang Boyce, Thuo Martin
Department of Materials Science and Engineering, Iowa State University, 2220 Hoover Hall, Ames, IA, 50011, USA.
Angew Chem Int Ed Engl. 2020 Jan 2;59(1):352-357. doi: 10.1002/anie.201912639. Epub 2019 Dec 2.
Studies on passivating oxides on liquid metals are challenging, in part, due to plasticity, entropic, and technological limitations. In alloys, compositional complexity in the passivating oxide(s) and underlying metal interface exacerbates these challenges. This nanoscale complexity, however, offers an opportunity to engineer the surface of the liquid metal under felicitous choice of processing conditions. We inferred that difference in reactivity, coupled with inherent interface ordering, presages exploitable order and selectivity to autonomously present compositionally biased oxides on the surface of these metals. Besides compositional differences, sequential release of biased (enriched) components, via fractal-like paths, allows for patterned layered surface structures. We, therefore, present a simple thermal-oxidative compositional inversion (TOCI) method to introduce fractal-like structures on the surface of these metals in a controlled (tier, composition, and structure) manner by exploiting underlying stochastic fracturing process. Using a ternary alloy, a three-tiered (in structure and composition) surface structure is demonstrated.
对液态金属上的钝化氧化物进行研究颇具挑战性，部分原因在于可塑性、熵以及技术限制。在合金中，钝化氧化物与底层金属界面处的成分复杂性加剧了这些挑战。然而，这种纳米级别的复杂性为在恰当选择加工条件的情况下对液态金属表面进行工程设计提供了契机。我们推断，反应性差异与固有的界面有序性相结合，预示着在这些金属表面可自主呈现成分偏向性氧化物的可利用的有序性和选择性。除了成分差异外，通过类似分形的路径依次释放偏向性（富集）成分，可形成图案化的分层表面结构。因此，我们提出一种简单的热氧化成分反转（TOCI）方法，通过利用潜在的随机断裂过程，以可控（层数、成分和结构）的方式在这些金属表面引入类似分形的结构。使用一种三元合金，展示了一种三层（结构和成分上）的表面结构。
