Effects of Mullite Content on the Properties and Microstructure of Porous Anorthite/Mullite Composite Ceramics

Porous anorthite/mullite composite ceramics with different mullite contents were fabricated by foam-gelcasting method, using CaCO3, SiO2, alpha-Al2O3 as raw materials. Effects of mullite content on bulk density, porosity, compressive strength, thermal conductivity and microstructure of the porous composite ceramics were researched. Mullite content has great effect on the apparent porosity of the porous anorthite/mullite composite ceramics. As a result of the appearance of liquid phase in the sintering, the sample shrunk, which is the main reason for the porosity decrease. Compressive strength and thermal conductivity increase with the mullite content under the condition of the similar porosity. Dense pore wall and rod-like mullite grain are benefit for compressive strength of porous anorthite/mullite composite ceramics. The apparent porosity of the prepared porous anorthite/mullite composite ceramics is in the range of 60.8%-75.2%, the compressive strength is between 12.94 MPa and 36.95 MPa, and the thermal conductivity is in the range of 0.30-1.33 W/(m.K).