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

Abstract

Dense SiOC-Si3N4 composites have been obtained employing mixtures with 10 % of Si3N4 (SN10) or 5 % Si3N4- 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 SiO2/Si3N4 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 Cfree is studied by conventional/non-conventional Raman parameters. In this sense, SN5N5–16 and SN10–17 show a Cfree 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 %).