Effect of microsilica content on microstructure and properties of foamed ceramics with needle-like mullite

In this study, five foamed ceramics with struts containing needle-like mullite were prepared by direct-foaming method using white clay, industrial alumina and microsilica powder as raw materials. The effects of microsilica content on the phase compositions, microstructures and properties of foamed ceramics were investigated. The results showed that the adding of microsilica decreased the average pore size and apparent porosity and increased the compressive strength and thermal conductivity of the foamed ceramics by affecting the properties of foamed slurry and reaction sintering process. The foamed ceramics with 10 wt. % microsilica content showed the best properties with high porosity of 75.8%, positive reheating linear change, compressive strength of 1.44 MPa and low thermal conductivity of 0.219 W/(m.K) (at 350 degrees C).