C(0.3)N(0.7)Ti-SiC Toughed Silicon Nitride Hybrids with Non-Oxide Additives Ti(3)SiC(2)

In situ grown C(0.3)N(0.7)Ti and SiC, which derived from non-oxide additives Ti(3)SiC(2), are proposed to densify silicon nitride (Si(3)N(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(3)N(4) ceramics with 5 vol.% Ti(3)SiC(2) when sintered at 1600 °C. As expected, higher sintering temperature 1700 °C could further promote densification of Si(3)N(4) ceramics filled with Ti(3)SiC(2). The capillarity of decomposed Si from Ti(3)SiC(2), and in situ reaction between nonstoichiometric TiC(x) and Si(3)N(4) were believed to be responsible for densification of Si(3)N(4) ceramics. An obvious enhancement of flexural strength and fracture toughness for Si(3)N(4) with x vol.% Ti(3)SiC(2) (x = 1~20) ceramics was observed. The maximum flexural strength of 795 MPa for Si(3)N(4) composites with 5 vol.% Ti(3)SiC(2) and maximum fracture toughness of 6.97 MPa·m(1/2) for Si(3)N(4) composites with 20 vol.% Ti(3)SiC(2) are achieved via hot-press sintering at 1700 °C. Pull out of elongated Si(3)N(4) grains, crack bridging, crack branching and crack deflection were demonstrated to dominate enhance fracture toughness of Si(3)N(4) composites.