Phase evolution of a novel silicon-alumina-fused mullite-containing Ti2O3 refractory at 1300 °C in N2

Abstract

A novel silicon-alumina-fused mullite-containing Ti2O3 composite refractory is prepared and sintered in the presence of solid carbon at 1300 °C in N2. The sintered samples exhibit a functional gradient characteristic. The phase evolution can be described as follows: Passive and active oxidation of Si to form SiO2 and SiO to reduce the partial pressure of oxygen. SiO(g) and Si react with N2 to form Si3N4 respectively. As the temperature increases and the partial pressure of oxygen decreases, Ti2O3 reacts with CO and N2 to form Ti(C,N)ss, which is accompanied by the release of O2. Si3N4 fixes the O2 and reacts to form Si2N2O, and Si2N2O reacts with Al2O3 to form O′-Sialon, thereby realizing the transformation from Si3N4 to Sialon. CO and residual carbon from the pyrolysis of phenolic resin react with SiO(s) and Si to form SiC. The dense layer formed by SiC and SiO2 blocks the diffusion of external gas to the central parts of the samples, there is still free Si which can continue to react and transform into a non-oxide reinforcing phase. In this paper, the reaction models are presented.