High-Temperature Oxidation Behavior of Ti-Doped SiOC Ceramics

Silicon oxycarbide (SiOC) ceramics are prone to failure prematurely in high-temperature applications for thermal stress-induced cracks. Doping Ti into SiOC can improve the oxidation resistance by forming a SiO₂-TiO₂ composite oxide layer. In this study, the oxidation behavior of Ti-doped SiOC ceramics in air at 1500 °C for 32 h was examined comprehensively. SiTiOC ceramics with a titanium-to-silicon molar ratio of 0.05 demonstrated the best oxidation resistance. The oxide layer was enhanced by the distribution of TiO₂ and TiSiO₄ at the grain boundaries of SiO₂, which reduced the interfacial energy and inhibited crack propagation. Furthermore, the oxide layer composed primarily of SiO₂ and minor TiO₂ exhibited low oxygen diffusion coefficients and strong self-healing capability. However, increasing the titanium-to-silicon molar ratio to 0.2 generated many pores and cracks in the oxide layer, and the outward diffusion of Ti and active oxidation of TiC were been exacerbated during oxidation.