Preparation and performance characterization of SiC/ZrB2 multiphase ceramics by reactive hot press sintering

SiC/ZrB2 ceramic matrix composites were prepared by reactive hot pressing at 1850°C under 20 MPa with zirconium diboride, silicon, activated carbon as raw materials. The effects of sintering additives (silicon and activated carbon) content on sintering behavior and mechanical properties of ZrB2 were studied. Phase composition and microstructure of the composites were analyzed by XRD and SEM, respectively. The results indicate that the sintering additives could significantly improve the densities and mechanical properties of the composites. Only the diffraction peaks of ZrB2 and SiC were found in the X-ray diffraction patterns of the hot-pressed ceramics. For the specimen with sintering additives content of 12wt%, flexural strength of 584 MPa and fracture toughness of 7.25 MPa·m1/2 were obtained. It seems that the improvement in mechanical properties was attributed to the improvement of density, the decrease of grain size and the change of fracture mode.