Macro/micro structure dependence of mechanical strength of low temperature sintered silicon carbide ceramic foams

SiC foams with high strength were prepared by polymer replica technique, including coating with SiC slurry (using Al2O3 and Y2O3 as the sintering additives) and polymer replica removal. The results suggest that the macro porous structure, including the pore size and the strut diameter, could be controlled by choosing different polymer sponge templates with the different PPI (pores per inch) values and slurry coating times. Liquid phase sintering plays a significant role in the low temperature densification of the cell struts of SiC foams. The compressive strength increased significantly with the tendency of cell strut densification. SiC ceramic foams with PPI value of 20, porosity of 77%, highly densified strut microstructure and maximum compressive strength of 2.48 MPa were obtained at 1700 °C with SiC as the main phase.