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

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 degrees C and delays the carbothermal reaction of SiO2/Si3N4 up to 1600 degrees 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 (1.26x10(-6) K-1), remarkable resistance against oxidation to 1400 degrees C and high absorptance (95.8 %).