Electrically functional 3D-architectured graphene/SiC composites

Lightweight, three-dimensional (3D) cellular structures of graphene/silicon carbide (SiC) showing very low densities (<1.6 g cm^-3) as compared to the dense skeleton (<3.2 g cm^-3) have been fabricated by a filament-based printing technique known as Robocasting. These scaffolds have been assembled from pseudoplastic inks containing homogeneous mixtures of SiC ceramic powders and up to 20 vol.% of graphene nanoplatelets (GNPs), and densified by pressureless spark plasma sintering. The electrical conductivity (σ) of the scaffolds shows certain anisotropy with the structure orientation and increases with the GNPs volume fraction. In this way, σ values of up to 611 S m^-1 for the longitudinal and 273 S m^-1 for the transverse orientations of the structures relative to the extruded rods are achieved. First attempts to model the electrical behavior of robocast scaffolds using both analytical and finite-element methods are described. The models provide a correct description of general trends in the conductivity and anisotropy, and are expected to be useful as a first approach to anticipate the trends of other properties, as the thermal conductivity, of such complex multifunctional cellular materials, thus narrowing the experimental workload. Scaffolds tested under compression show crushing strengths in the range of 10-50 MPa, which increase with the relative density of the skeletons.