Crack-healing behavior and bending strength of Si3N4/SiC composite ceramics by SiO2 colloidal

Si3N4/SiC composite ceramics were sintered in order to investigate their bending strength behavior after crack-healing. Y2O3 and TiO2 powder was added as sintering additives to enhance itʹs sintering property. A three-point bending specimen was cut out from sintered plates. About 100 μm semi-circular surface cracks were made on the center of the tension surface of the three-point bending specimen using Vickers indenter. After the cracked specimen with SiO2 colloidal coating healed from 500 to 1300 °C for 1 h in air, the bending strength behavior was carried out systematically at room temperature. Si3N4/SiC ceramics using additive powder (Y2O3 + TiO2) were superior to that of additive powder Y2O3. The additive powder TiO2 exerted influence at growth of Si3N4. The optimum crack-healing conditions coated SiO2 colloidal were 1000 and 1300 °C at Si3N4/SiC using additive powder (Y2O3 + TiO2) and Y2O3, respectively.