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

Abstract Nb doping substantially changes the oxidation mechanism and significantly enhances its oxidation resistance of Ti 3 SiC 2 at 800 °C. After Nb doping, the oxidation of Ti 3 SiC 2 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 TiO 2 outer layer and TiO 2 +SiO 2 mixture inner layer to a single TiO 2 +SiO 2 mixture layer. It is proposed that Nb doping decreases the concentrations of oxygen vacancies and Ti interstitials in the formed TiO 2 , leading to the completely restrained outward diffusion of Ti and the decreased oxidation rate.