Fabrication and properties of Si3N4f/RBSN porous ceramic composite

Porous Si3N4 has excellent properties such as high temperature resistance, corrosion resistance, high porosity, and high specific surface area, but the inherent brittleness limits the application of Si3N4 in some special environments. Si3N4f/RBSN porous ceramic composites were prepared by reaction bonding method using reaction-bonded silicon nitride(RBSN) as the matrix and continuous Si3N4 fibers (fiber mats) as the reinforcement. The results show that the composite with Si/Si3N4 = 70:30 in the raw material has a superior nitridation rate and flexural strength of 96.5% and 23.5 MPa, respectively. The nitridation process of the Si3N4f/RBSN matrix is dominated by the vapour-phase reaction between SiO and N2, and the products are mainly α-Si3N4 whiskers. The residual flexural strength of the composites is essentially unchanged after 10 thermal cycles in air at 800 °C. The composites have excellent thermal shock resistance and can be used as the reusable crucible.