Silicon oxycarbide composites reinforced with silicon nitride and in situ formed silicon carbide

Dense SiOC-Si 3 N 4 composites have been obtained employing mixtures with 10 % of Si 3 N 4 (SN10) or 5 % Si 3 N 4 - and an extra amount of carbon-5 % carbon nanofibers- (SN5N5) using spark plasma sintering (SPS). SPS produces densification at 1300/1400 °C and delays the carbothermal reaction of SiO 2 /Si 3 N 4 up to 1600 °C. It is observed the formation of a percolating network of SiC nanodots/nanowires widespread all over the matrix decorated with graphene-like carbon generated by Joule heating during SPS. The evolution of the C free is studied by conventional/non-conventional Raman parameters. In this sense, SN5N5–16 and SN10–17 show a C free phase composed by large highly tortuous and ordered graphene layers with the highest degree of interconnection and crystallinity determinant for understanding the highest thermal and electrical conductivities (1.91 WmK −1 and 33.6 Sm −1 ). Finally, this material displays a low coefficient of thermal expansion (1.26×10 −6 K −1 ), remarkable resistance against oxidation to 1400 °C and high absorptance (95.8 %). • SPS delays the carbothermal reaction of SiO 2 /Si 3 N 4 to 1600 ºC in SiOC-Si 3 N 4 mixtures. • SiC nano-dots/wires decorated with graphene-like carbon appear all over the matrix. • Conventional/Non-conventional Raman parameters clarify SiOC-Si 3 N 4 properties. • A percolating network of SiC/graphene and C free upwards k, σ and downwards CTE. • The SiOC-Si 3 N 4 composites display remarkable oxidation resistance up to 1400 ºC.