# High-Temperature Oxidation Behavior of Ti-Doped SiOC Ceramics

## TL;DR

This study explores how adding titanium improves the high-temperature oxidation resistance of SiOC ceramics.

## Contribution

The novel contribution is identifying the optimal titanium-to-silicon ratio (0.05) that enhances oxidation resistance in SiOC ceramics.

## Key findings

- Ti-doped SiOC with a Ti/Si ratio of 0.05 showed the best oxidation resistance due to a composite oxide layer.
- Higher Ti/Si ratios (0.2) led to more cracks and pores, reducing oxidation resistance.
- The SiO2-TiO2 layer exhibited low oxygen diffusion and self-healing properties.

## Abstract

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.