GE Shengtao, BI Yubao, SI Yaochen, ZHANG Haijun
(The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China)
Abstract: Porous mullite ceramics were fabricated at 1400 ℃ for 2 h by foam-gelcasting method using industrial grade mullite powder as the main raw materials, CaCO3 (0-4wt.%) as an additive, Isobam-104 as the dispersing and gelling agent, sodium carboxymethyl cellulose as the foam stabilizing agent, and triethanolamine lauryl sulfate as the foaming agent. The effects of the addition of CaCO3 on linear shrinkages, porosity, bulk density, flexural strength and thermal properties of porous mullite samples were examined, and the phase composition, microstructures and pore size distribution of the resultant porous ceramic were characterized by XRD and SEM. The results indicated: Addition of CaCO3 had no clearly effect on the stability of the mullite slurries; such addition of CaCO3 andin-situ formed anorthite might play a positive role in decreasing the overall thermal conductivity of the final product. Most importantly, they also exhibited a very low thermal conductivity, e.g., 0.178 W·m-1·K-1 at 200 °C with the addition of 2wt.% CaCO3.
Key words: porous mullite ceramics; foam-gelcasting; thermal conductivity