Preparation of porous Si3N4 ceramics via tailoring solid loading of Si3N4 slurry and Si3N4 poly-hollow microsphere content

Porous Si 3 N 4 ceramics were prepared by aqueous gelcasting using Si 3 N 4 poly-hollow microspheres (PHMs) as pore-forming agent. The effects of solid loading of Si 3 N 4 slurry and Si 3 N 4 PHM content on the properties of porous Si 3 N 4 ceramics were investigated. Only β-Si 3 N 4 phase is observed in porous Si 3 N 4 ceramics, and Si 3 N 4 PHMs distribute uniformly both in Si 3 N 4 green samples and porous Si 3 N 4 ceramics. Results show that solid loading of Si 3 N 4 slurry and Si 3 N 4 PHM content could considerably influence the properties of porous Si 3 N 4 ceramics. With the increase of solid loading of Si 3 N 4 slurry (decrease of Si 3 N 4 PHM content), the distributing state of Si 3 N 4 PHMs changes from contacting with each other to just embedding in the matrix, thus their porosity decreases, while their shrinkage, flexural strength, and fracture toughness increase.