Role of graphene nano-platelets on thermal conductivity and microstructure of TiB2-SiC ceramics

The current research investigates the influence of adding 2 wt% graphene nano-platelets (GNP) on microstructure and thermal conductivity of the TiB2-25 vol% SiC composite. The disk-shape pellets were fabricated using spark plasma sintering method at a temperature of 1800 degrees C for 7 min under a pressure of 40 MPa. Measured relative densities were about 95.5% and 96% for TiB2-SiC and graphene containing TiB2-SiC ceramics, respectively. According to the microstructure analysis of the polished area and fractured surfaces, captured via scanning electron microscopy (SEM), the addition of graphene nano-platelets to the TiB2-25 vol% SiC resulted in finer, denser, and more uniform microstructure. The laser flash method was employed to measure the thermal diffusivity of the specimens followed by evaluating the thermal conductivity of the sintered specimens. Despite a remarkable thermal conductivity of graphene (about 5 x 10(3) W/m.K), the TiB2-SiC-GNP composite showed lower thermal conductivity than the graphene-free sample. Based on SEM images, the finer grains with increased boundaries are the reason for decreased thermal conductivity of the TiB2-SiC sample doped with graphene nano-platelets.