Effects of Mineral Composition on Phase Formation Process of Anorthite-mullite Composite Materials

The anorthite-mullite composite materials were in-situ synthesized by using different mineral materials at different sintering temperatures (1 100-1 400 ℃). The effects of mineral composition on the phase formation process of the composite materials were studied by the phase composition and microstructure analysis. The results show that with the quartz (fused quartz or quartz sand), Ca(OH)2 and α-Al2O3 as the raw materials, the wollastonite and gehlenites were firstly formed, and then the anorthites were produced by the reaction of wollastonite, corundum and quartz. The mullites were obtained by the reaction of corundum and cristobalite at 1 350 ℃. With the wollastonites or grossites, natural Al-Si minerals like kyanites and clays as raw materials, the anorthites were directly produced by the raw materials and mullites were obtained by the secondary mullitization. After sintered at 1 400 ℃, the anorthite-mullite samples prepared with different raw materials all consisted of mullite, anorthite and few corundum phases. The columnar mullite crystals with large sizes existed in the fine anorthite grains.