C_0.3N_0.7Ti-SiC Toughed Silicon Nitride Hybrids with Non-Oxide Additives Ti₃SiC₂

In situ grown C_0.3N_0.7Ti and SiC, which derived from non-oxide additives Ti₃SiC₂, are proposed to densify silicon nitride (Si₃N₄) ceramics with enhanced mechanical performance via hot-press sintering. Remarkable increase of density from 79.20% to 95.48% could be achieved for Si₃N₄ ceramics with 5 vol.% Ti₃SiC₂ when sintered at 1600 °C. As expected, higher sintering temperature 1700 °C could further promote densification of Si₃N₄ ceramics filled with Ti₃SiC₂. The capillarity of decomposed Si from Ti₃SiC₂, and in situ reaction between nonstoichiometric TiC and Si₃N₄ were believed to be responsible for densification of Si₃N₄ ceramics. An obvious enhancement of flexural strength and fracture toughness for Si₃N₄ with x vol.% Ti₃SiC₂ (x = 1~20) ceramics was observed. The maximum flexural strength of 795 MPa for Si₃N₄ composites with 5 vol.% Ti₃SiC₂ and maximum fracture toughness of 6.97 MPa·m^1/2 for Si₃N₄ composites with 20 vol.% Ti₃SiC₂ are achieved via hot-press sintering at 1700 °C. Pull out of elongated Si₃N₄ grains, crack bridging, crack branching and crack deflection were demonstrated to dominate enhance fracture toughness of Si₃N₄ composites.