Mathematical modelling of diffusion-driven oxidation in metals

这个工业赞助的项目旨在提供金属表面保护性氧化层形成的预测性定量描述。在纯氧气、纯湿气和两者的混合物（例如湿空气）中的氧化是令人感兴趣的。这些氧化反应的动力学性质在过去已经被广泛研究，并且已经提出了大量描述反应速率的模型。然而，除了少数明显的例外，这些模型本质上是经验性的，而不是对合理的潜在物理机制的数学描述。在不存在水分的情况下，氧化主要是氧阴离子通过氧化物基质向金属迁移，而在存在水分的情况下，羟基阴离子的离子扩散可能是速率限制步骤。因此，整个过程是一个组合的温度和时间依赖性的化学和离子扩散内不断增长的基板的可变组成。至关重要的是，主要的物理机制是很好的建模，提供定性的理解和定量预测能力的长期材料老化。

This industrially-sponsored project is aimed at providing a predictive quantitative description of the formation of a protective oxide layer on a metal surface. Oxidation in pure oxygen, pure moisture, and mixtures of the two (e.g. humid air) are of interest. The kinetic properties of these oxidation reactions have been studied extensively in the past, and a large number of models describing the rates of reaction have been proposed. However, with just a few notable exceptions, these models have been empirical by their nature rather than mathematical descriptions of plausible underlying physical mechanisms. Oxidation in the absence of moisture is dominated by migration of oxygen anions through the oxide substrate towards the metal, while in the presence of moisture it is likely that ionic diffusion of hydroxyl anions is the rate limiting step. The overall process is thus one of combined temperature- and time-dependent chemical and ionic diffusion within a growing substrate of variable composition. It is vital that the dominant physical mechanisms are well modelled to provide both qualitative understanding and a quantitative predictive capability for long-term material ageing.