EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Almost fully dense silicon carbide composites with 1 vol.% Y2O3–Sc2O3 sintering additives and with different amount of graphene nanoplatelets (GNPs) from 1 to 10 wt. % or 1 wt. % of graphene oxide (GO) were sintered in rapid hot press (RHP) at 2000°C for 30 min with a pressure of 50 MPa under nitrogen atmosphere.
Thermal and electrical conductivity were investigated as a function of amount of graphene, its orientation in SiC matrix and effect of annealing. The electrical conductivity of reference SiC sample (17 S/cm) gradually increased with increasing GO or GNP content, reaching the highest value of 67 S/cm for SiC with 10 wt.% GNPs. Remarkable improvement of electrical conductivity was achieved by annealing the samples in N2 atmosphere and the highest value of 118 S/cm was obtained for the sample with 10 wt.% GNPs. The highest thermal conductivities were obtained at room temperature in parallel direction to GNPs for annealed SiC samples with 1% GO ( = 238 W/m.K) and 5% GNPs ( = 233 W/m.K). To the best of our knowledge, these are the highest values of thermal conductivity for ceramic-graphene composites. The obtained results show that application of freeze granulation, rapid hot-pressing and annealing of samples at 1800°C for 6h in N2 atmosphere allows to obtain SiC ceramics with very high electrical and thermal conductivity.