Preparation of silicon nitride-barium aluminum silicate composites by freeze gelation

An effective approach to prepare silicon nitride-barium aluminum silicate (Si3N4/BAS) composites by freeze gelation was described. Utilizing the gelation of particulate silica sol by freezing to solidify ceramic slurry, in the forming and drying process, the cracking and warpage of green body were avoided, and the shrinkage rate was 0.6%. The added barium oxide and alumina absorbed silica in sol to prepare Si3N4/BAS glass ceramic matrix composites, and the flexural strength, work of fracture and density of Si3N4/BAS composites were 342 MPa, 181 J/m2 and 3.0 g/cm3, respectively.