LAUSR

ABSTRACT In this work, ZrB2–SiC and novel C3N4-doped ZrB2–SiC composites were manufactured at 1850°C under an external load of 40 MPa for 6 min via spark plasma sintering. The effects of C3N4 on the mechanical characteristics (flexural strength, Vickers hardness, and fracture toughness) and microstructure of the ZrB2–SiC-based composites were investigated. By adding 5 wt% g-C3N4, a fully dense ceramic composite was fabricated, compared to the C3N4-free ZrB2–SiC composite with a relative density of 95%. Removal of ZrO2 and B2O3 from the surface of ZrB2 particles via chemical reactions with C3N4, and the in-situ synthesis of ZrC and BN as new phases were studied by XRD and SEM analyses. Indentation fracture toughness, flexural strength, and Vickers hardness improved from 4.5 MPa.m1/2, 460.2 MPa and 17.4 GPa to 6.1 MPa.m1/2, 580.2 MPa and 21.2 GPa, respectively, by adding g-C3N4 to the ZrB2–SiC ceramic.