Freeze-cast porous silica ceramics with alumina nanofibers addition

Porous ceramics have a broad application prospect in thermal insulation field. In this work, porous silica ceramics added with alumina nanofibers were prepared by freeze-casting method. Commercial silica sol and electrospun alumina nanofibers were used as the raw materials. The effect of sol content on the microstructure and properties of the porous silica were studied. The results show that the water in the precursor slurry turned to be ice during the freezing process, and pores generated after the sublimation of the ice. With the increased dosage of silica sol, the pores increased in amount but decreased in size, and the pore wall increased in thickness. Such variations for the porous silica resulted in the increased compressive strength and the worse thermal insulation performance. This study provides experimental guidance for the development of porous ceramics with nanofiber addition. Porous silica ceramics were synthesized by freeze-casting method at increased sol content.Continuous electrospun alumina nanofibers were added to enhance the pore walls.The pores increased in amount but decreased in size, and the pore wall increased in thickness.Porous silica possessed increased compressive strength and thermal conductivity.