Influence of reduced graphene oxide and carbon black on mechanical and thermal characteristics of TiB2-SiC ceramics

The most crucial goal is the improvement of Ultra High Temperature Ceramic (UHTC) fracture toughness without negatively impacting the ceramic high-temperature properties. Carbon nanostructures in UHTCs appear to be one of the most promising ways forward. The influence of reduced graphene oxide vs. carbon black on microstructure and properties of TiB2-SiC ceramics is studied. The composite ceramic samples with additive contents up to 7.4 wt.% were manufactured via the reactive hot pressing of B4C-TiC-Si-reduced graphene oxide/carbon black precursors at 1850 °С and 30 MPa for 4 min. The sintered materials composition and structure were analysed with Raman spectroscopy, XRD, SEM, and TEM. Reduced graphene oxide (rGO) survives the hot-pressing procedure and, at lower concentrations, distributes inside the TiB2-SiC matrix in the form of separate sheets. However, at 7.4 wt.%, the rGO was shown to agglomerate. The rGO improved the hardness, fracture toughness, and thermal conductivity of the TiB2-SiC by up to 16%, 20%, and 53%, respectively. The composite characteristics reached the values of HV = 26.1 GPa, K1C = 7.4 MPa∙m1/2, and k = 69 W/m∙K. Carbon black additive formed roughly equiaxial two micrometre inclusions and was not observed to impact the investigated properties.