Sintering and microstructural characterization of calcium alumino-titanate-bauxite-SiC composite refractories

摘要

Calcium alumino-titanate (CAT) is a composite refractory material that exhibits a low thermal conductivity, high melting point, high refractoriness, low thermal expansion coefficient, and good thermal shock resistance. CAT-bauxite-SiC composites were prepared by using bauxite, CAT, SiC, alpha-Al2O3, metallic Si, and Guangxi white clay as starting materials and an Al(H2PO4)(3) solution as a binder. Their densification behavior, phase changes, and microstructures were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermodynamic analysis. The results show that the bulk density initially increases and then decreases with temperature because of SiC oxidation and the formation of a liquid phase. In addition, the aggregation of corundum particles is enhanced at higher temperatures for bauxite grains, and excessively high temperatures cause abnormal growth of the corundum particles. Furthermore, the mullite whiskers present in the CAT grains begin to break through the surface of the liquid phase at firing temperatures above 1450 degrees C; these whiskers show perfect crystallization at 1600 degrees C. Finally, the quantity of Ca-rich (anorthite) regions around the SiC grains increase with temperature due to an increase in SiC oxidation and calcium ion diffusion.