Self-propagating high temperature synthesis (SHS) of porous Si3N4-based ceramics with considerable dimensions and study on mechanical properties and oxidation behavior

The aim of present work is to fabricate porous Si3N4 ceramics with considerable dimensions and homogeneous microstructure by self-propagating high temperature synthesis (SHS) using Si, Si3N4 diluent and Y2O3 as raw materials. The results indicate that Si3N4 diluent with coarse particle sizes and appropriate β-phase content is beneficial to obtain porous Si3N4 ceramics with homogeneous microstructure and excellent mechanical property by controlling the shrinkage inside the sample. The produced Si3N4 ceramics possessed excellent flexural strength of 168 MPa∼259 MPa, and high Weibull modulus of 11.0∼17.2. Additionally, BN and SiC are added as second phase to modify the properties of Si3N4-based ceramics. Optimum flexural strength of 170 MPa and 137 MPa were obtained with 10 wt.% addition of BN and SiC respectively. After oxidation at 1100 °C∼1300 °C, second phase-doped Si3N4 ceramics also presented higher residual strength than pure Si3N4 ceramics.