Pore Structure and Permeation Properties of Kaolin-Silica-Alumina Ceramics

Abstract

The pore structure and permeation properties of kaolin-silica (quartz)-alumina (corundum) ceramics have been investigated using kaolin, SiO₂ and Al₂O₃ powders as staring materials. The Al₂O₃ powders used are of different particle sizes, 0.8 and 4.0μm. Mullite phase appears at approximately 1373K and mullite phase content in the sintered samples increases with the increase in sintering temperature from 1373 to 1573K for 1h. Open porosity decreases from 48.4 and 46.8% to 32.3% for the 0.8- and 4.0-μm Al₂O₃ powders, respectively. The maximum average pore sizes have been noted to be 0.51- and 0.63-μm for the 0.8- and 4.0-μm Al₂O₃ powders as-sintered at 1473K, respectively. The maximum penetrating porosity is 24.1% for the 0.8-μm Al₂O₃ powder as-sintered at 1473K; it decreases with the increase in temperature for the 4.0-μm Al₂O₃ powder. The tortuosity of the 0.8-μm Al₂O₃ powder does not change significantly, but that of the 4.0-μm Al₂O₃ powder decreases from 0.85 to 0.29 with the increase in sintering temperature. Seemingly, the mullite-based filtration material has been shown to be more efficient and durable than conventional polymeric and diatomite materials.