Initial stages of oxidation of near-stoichiometric titanium carbide at low oxygen pressures
Initial stages of oxidation of near-stoichiometric titanium carbide at low oxygen pressures
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DOI：
10.1016/j.jallcom.2008.04.067
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发表时间：
2009-03
影响因子：
6.2
通讯作者：
I. Shabalin;V. Vishnyakov;D. Bull;S. Keens;L. Yamshchikov;L. I. Shabalin
中科院分区：
文献类型：
--
作者：
I. Shabalin;V. Vishnyakov;D. Bull;S. Keens;L. Yamshchikov;L. I. Shabalin
提出了一种研究近化学计量比TiC氧化机理的新方法。通过考虑固体化学动力学模型和电子显微镜观察，证实了这一点。在低氧压和中等温度下，该过程的初始步骤与氧的溶解和随后氧过饱和的碳氧化合物的分解有关，最终导致氧化物相的形核，特别是锐钛矿相，被残余碳稳定。锐钛矿到金红石的转变伴随着氧化皮中更深层次的碳燃烧，氧化皮在更高的温度下烧结。由于温度的进一步升高伴随着氧化速率的降低，这一机制将过程转变为气体扩散区域，由尺度渗透率控制，但由反映在动力学中的固态扩散决定，因此通常该过程的特征是表观活化能为负值。
A novel approach to the oxidation mechanism of near-stoichiometric TiC is presented. It is confirmed by consideration of solid-state chemical kinetics model and electron microscopy observations in parallel. At low oxygen pressures and moderate temperatures the initial step of the process is connected with the dissolution of oxygen and subsequent decomposition of oxygen-oversaturated oxycarbide, which ultimately results in the nucleation of oxide phase, in particular anatase, belike stabilised by residual carbon. An anatase–rutile transformation is concurrent with deeper carbon burn-off in the oxide scale, which sinters at higher temperatures. This mechanism shifts the process to a gas diffusion regime, governed by the scale permeability, but determined by solid-state diffusion that is reflected in the kinetics, as further temperature increase is accompanied by a decrease of the oxidation rate, so in general the process is characterised by the negative value of apparent activation energy.