Mortazavi N, Geers C, Esmaily M, Babic V, Sattari M, Lindgren K, Malmberg P, Jönsson B, Halvarsson M, Svensson J E, Panas I, Johansson L G
Department of Physics, Chalmers University of Technology, Gothenburg, Sweden.
Department of Chemistry and Chemical Engineering, Division of Energy and Materials, Chalmers University of Technology, Gothenburg, Sweden.
Nat Mater. 2018 Jul;17(7):610-617. doi: 10.1038/s41563-018-0105-6. Epub 2018 Jun 11.
High-temperature alloys are crucial to many important technologies that underpin our civilization. All these materials rely on forming an external oxide layer (scale) for corrosion protection. Despite decades of research on oxide scale growth, many open questions remain, including the crucial role of the so-called reactive elements and water. Here, we reveal the hitherto unknown interplay between reactive elements and water during alumina scale growth, causing a metastable 'messy' nano-structured alumina layer to form. We propose that reactive-element-decorated, hydroxylated interfaces between alumina nanograins enable water to access an inner cathode in the bottom of the scale, at odds with the established scale growth scenario. As evidence, hydride-nanodomains and reactive element/hydrogen (deuterium) co-variation are observed in the alumina scale. The defect-rich alumina subsequently recrystallizes to form a protective scale. First-principles modelling is also performed to validate the RE effect. Our findings open up promising avenues in oxidation research and suggest ways to improve alloy properties.
高温合金对于支撑我们文明的许多重要技术至关重要。所有这些材料都依赖于形成外部氧化层（氧化皮）来进行腐蚀防护。尽管对氧化皮生长进行了数十年的研究，但仍存在许多未解决的问题，包括所谓的活性元素和水的关键作用。在此，我们揭示了在氧化铝氧化皮生长过程中活性元素与水之间迄今未知的相互作用，导致形成了一种亚稳态的“杂乱”纳米结构氧化铝层。我们提出，氧化铝纳米晶粒之间由活性元素修饰的羟基化界面使水能够进入氧化皮底部的内部阴极，这与既定的氧化皮生长情况不同。作为证据，在氧化铝氧化皮中观察到了氢化物纳米域以及活性元素/氢（氘）的共变现象。富含缺陷的氧化铝随后再结晶形成保护性氧化皮。还进行了第一性原理建模以验证活性元素的作用。我们的发现为氧化研究开辟了有前景的途径，并提出了改善合金性能的方法。
