A simple method for introducing ZrB2 using sol-gel processing into a SiBCN matrix is presented in this paper. Zirconium n-propoxide (ZNP), boric acid and furfuryl alcohol (C5H6O2) (FA) were added as the precursors of zirconia, boron oxide and carbon forming ZrB2 dispersed in a SiBCN matrix. SiBCN/ZrB2 composites with different contents of ZrB2 (5, 10, 15, and 20 wt%) were formed at 2000 °C for 5 min by spark plasma sintering (SPS). The microstructures were carefully studied. TEM analysis showed that the as formed ZrB2 grains were typically 100–500 nm in size and had uniform distribution. HRTEM revealed clean grain boundaries between ZrB2 and SiC, however, a separation of C near the SiC boundary was observed. The flexural strength, fracture toughness, Young's modulus and Vicker's hardness of composites all improved with the ZrB2 contents and SiBCN matrix containing 20 wt% of ZrB2 could reach 351±18 MPa, 4.5±0.2 MPa m1/2, 172±8 GPa and 7.2±0.2 GPa, respectively. The improvement in fracture toughness can be attributed to the tortuous crack paths due to the presence of reinforcing particles.
- Mechanical properties