Synthesis and characterization of onion-like carbon/TiN0.3 enhanced Si₃N₄ composites

Research on how to obtain Si3N4 composites with high hardness and toughness at lower temperatures is important. Si3N4 composites with onion-like carbon (OLC)-TiN0.3 were prepared using high pressure and high temperature techniques. The effects of TiN0.3 and OLC additives on the mechanical properties and microstructure of the silicon nitride ceramics were analyzed. During the sintering process, the vacancies in TiN0.3 promoted the formation of the TiC03N0.7 interface between the three compositions, whose particles were homogeneously dispersed in the silicon nitride matrix with strong bonding to the substrate. OLC (10 vol%)-TiN0.3 (10 vol%)-Si3N4 composites were prepared at 5 GPa, 1500 degrees C and held for 15 min. The Vickers hardness and fracture toughness were determined to be 18.6 GPa and 6.6 MPa m(1/2), flexural strength of 531 MPa, and showed higher high-temperature hardness. This was higher than the typical values reported for Si3N4 ceramics (15-17 GPa). This work provides a new strategy for low-temperature of Si3N4 composites with both high hardness and high toughness.