Cheap, abundant and easily-obtained carbon fillers such as graphite (GR), carbon black (CB), lamp black and active carbon were successfully incorporated into a silicon oxycarbide (SiOC) matrix using attrition milling followed by spark plasma sintering to obtain dense crack-free bulk composites. Carbon-enriched SiOC composites (C-SiOC) showed enhanced electrical (σ) and thermal (k) conductivities. Values as high as 667 Sm-1 for σ and an increase of 63% for k compared with SiOCs were obtained when GR flakes were incorporated into the SiOC. Very interesting values were also achieved (250 Sm-1 and a 46% increase) when CB was used, due to the formation of a percolating network of highly-interconnected tortuous graphene-like carbon domains which promoted phonon/electron transport.
Raman parameters such as the tortuosity index, 3D ordering of graphene layers and the I2D/IG ratio, in conjunction with AB stacking, were crucial for understanding the electronic and/or phonon transport.