Evolution of Ti2O3 and mullite in Si-Al2O3-fused mullite containing Ti2O3 composite at 1600 °C

Abstract

Si-Al2O3-fused mullite containing Ti2O3 composite was sintered at 1600 °C in N2. Changes in the structure and activity of fused mullite containing Ti2O3 raw material during the coupled reaction of metallic silicon and Ti2O3 are explored. The mechanism of regulating the phase composition and microstructure of the composite with the changes of Ti2O3 and fused mullite is also revealed. At high temperatures and low oxygen partial pressures, the stability of fused mullite decreases and decomposes to form SiO(g) and alumina-rich mullite. SiO(g) reacts with N2 to form Si3N4, which solidifies with mullite to form X-Sialon, further optimizing the phase composition. With the transformation of Ti2O3 to Ti(C,N)ss, the inhibitory effect of Ti3+ on the growth and development of fused mullite disappears, and the morphology of the fused mullite is gradually transformed from a dense structure to a classical elongated columnar morphology. A model for the mechanism of non-oxide formation and the regulation of micro-morphology is developed.