Effect of Additive on Phase Composition and Microstructure of Silica Brick Matrix

Abstract

The silica matrix specimens were prepared by adding microsilica and MoSi2 powder. The mixture were pressed to cylinder and then sintered at 1200oC, 1250oC, 1300oC and 1400oC for 8h respectively. The phase compositions of specimens were analyzed by X-ray diffusion and the tridymite crystal morphology and grain sizes were observed by SEM. The results show that with the addition amount of MoSi2 powders increase, the intensity of tridymite diffraction peaks first strengthen slightly and then decrease, becoming more and more amorphous process, while the diffraction peaks of residual quartz phase enhance. When adding 2.5% MoSi2, the precipitation of CaMoO4 phase reduces the O/Si ratio in the liquid phase, and promotes the generation of tridymite, so the number of tridymite increase, but the crystal size decreases. With the sintering temperature increase, the intensity of tridymite diffraction peaks increase, the residual quartzite amount reduces.