Enhanced electrical conductivity of silicon carbide ceramics by addition of graphene nanoplatelets

The paper describes the fabrication by liquid-phase spark plasma sintering (SPS) of composites of dense silicon carbide (SiC) with up to 20 vol.% graphene nanoplatelets (GNPs), and discusses the relationships between composition, microstructure and electrical conductivity. The structural integrity of the GNPs is preserved during the whole process, as observed by Raman spectroscopy. The effects of the applied pressure (50 MPa) during SPS result in the preferential orientation of the GNPs perpendicular to the pressing axis and anisotropic electrical behaviour. The electrical conductivity measured in the direction perpendicular to the SPS pressing axis is 4 to 6 times higher than the parallel counterpart. The conductivity increases up to three orders of magnitude with increasing GNPs fraction, reaching values of 4380 S m−1 at room temperature for materials with 20 vol.% GNPs. The conduction mechanism of the composite is analysed as a function of the GNPs content.