Enhanced mechanical and thermal properties of anisotropic fibrous porous mullite–zirconia composites produced using sol-gel impregnation

A new lightweight and thermal insulating material was successfully prepared by impregnating Al₂O₃–SiO₂aerogel into a porous mullite–zirconia fiber network with a quasi-layered microstructure. The microstructures, thermal and mechanical properties of the porous mullite–zirconia ceramics were investigated before and after the impregnating of Al₂O₃–SiO₂aerogel. It was observed that the mullite and zirconia fibers combined well with aerogels. Compared with fibrous porous mullite-zirconia ceramics, the Al₂O₃–SiO₂aerogel/porous mullite–zirconia composite exhibited higher compressive strength (i.e. 1.36 MPa in the z direction) and lower thermal conductivity (i.e. 0.052 W/(m·K)). The present work provides an efficient way to fabricate highly porous ceramics with high strength and ultra-low thermal conductivity, which find potential use in high-temperature thermal insulation materials.