Investigation on the effect of Nb doping on the oxidation mechanism of Ti3SiC2

Nb doping substantially changes the oxidation mechanism and significantly enhances its oxidation resistance of Ti3SiC2 at 800 °C. After Nb doping, the oxidation of Ti3SiC2 is only controlled by the inward diffusion of O, while the outward diffusion of Ti is restrained totally. The oxide layer structure changes from a duplex-layer of TiO2 outer layer and TiO2+SiO2 mixture inner layer to a single TiO2+SiO2 mixture layer. It is proposed that Nb doping decreases the concentrations of oxygen vacancies and Ti interstitials in the formed TiO2, leading to the completely restrained outward diffusion of Ti and the decreased oxidation rate.