A new approach for the net-shape fabrication of porous Si₃N₄ bonded SiC ceramics with high strength

In this study, Si₃N₄ bonded porous SiC ceramics with high strength had been net-shapely fabricated by a new approach. In this approach, we proposed a two-step processing route composed of freeze casting and carbothermal reduction reactions in which carbon aerogels, derived from sol infiltration and pyrolysis, involved. The phase components, microstructures and properties of the prepared ceramics were investigated. The results showed that carbon aerogels with high apparent surface area had been completely reacted and new SiC and Si₃N₄ grains had been produced. The porous ceramics with flexural strength of 164.3MPa at 33% porosity and 80.5MPa at 46% porosity were obtained, whose linear shrinkages were only 1.06% and 1.94% during the whole processing respectively.