ZrB₂[sbnd]SiC_w composites with different carbonaceous additives

Various carbonaceous phases have different impacts on the qualifications of ZrB₂-SiC_w based ceramics. In this research, 5 wt% of different forms of carbon, namely carbon nanoparticles, carbon fibers, graphite, and graphene, were added to ZrB₂-25 vol% SiC_w composites sintered by spark plasma under 40 MPa at 1900 °C external pressure for 7 min. All samples approached their theoretical density regardless of the addition of carbon and its morphology. The microstructural and XRD evaluations revealed the in-situ synthesis of ZrC and B₄C phases in carbon-doped specimens. The addition of carbonaceous reinforcements resulted in refined microstructure, as the finest texture was related to the sample doped with graphene. The highest Vickers hardness (21.9 GPa) was measured for the ceramic having no carbonaceous additive, while the lowest hardness (17.3 GPa) belonged to the composite doped with carbon nanoparticles. In contrary, adding carbon nanoparticles increased the fracture toughness, yielding an outstanding value of 7.1 MPa.m^1/2.