C _0.3N _0.7Ti-SiC Toughed Silicon Nitride Hybrids with Non-Oxide Additives Ti ₃SiC ₂

Abstract

In situ grown C _0.3N _0.7Ti and SiC, which derived from non-oxide additives Ti ₃SiC ₂, are proposed to densify silicon nitride (Si ₃N ₄) ceramics with enhanced mechanical performance via hot-press sintering. Remarkable increase of density from 79.20% to 95.48% could be achieved for Si ₃N ₄ ceramics with 5 vol.% Ti ₃SiC ₂ when sintered at 1600 °C. As expected, higher sintering temperature 1700 °C could further promote densification of Si ₃N ₄ ceramics filled with Ti ₃SiC ₂. The capillarity of decomposed Si from Ti ₃SiC ₂, and in situ reaction between nonstoichiometric TiC _x and Si ₃N ₄ were believed to be responsible for densification of Si ₃N ₄ ceramics. An obvious enhancement of flexural strength and fracture toughness for Si ₃N ₄ with x vol.% Ti ₃SiC ₂ ( x = 1~20) ceramics was observed. The maximum flexural strength of 795 MPa for Si ₃N ₄ composites with 5 vol.% Ti ₃SiC ₂ and maximum fracture toughness of 6.97 MPa·m ^1/2 for Si ₃N ₄ composites with 20 vol.% Ti ₃SiC ₂ are achieved via hot-press sintering at 1700 °C. Pull out of elongated Si ₃N ₄ grains, crack bridging, crack branching and crack deflection were demonstrated to dominate enhance fracture toughness of Si ₃N ₄ composites.