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

• Published in: Journal of the European Ceramic Society 2025-01, Vol.45 (1), p.116828, Article 116828
• Main Authors: Mazo, M. Alejandra, Caballero, Amador C., Rubio, Juan
• Format: Article
• Language: English
• Subjects: Electrical conductivity; Raman parameters; Silicon oxycarbide-silicon nitride composites; Spark plasma sintering; Thermal properties
• ISSN: 0955-2219
• DOI: 10.1016/j.jeurceramsoc.2024.116828

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 %). •SPS delays the carbothermal reaction of SiO2/Si3N4 to 1600 ºC in SiOC-Si3N4 mixtures.•SiC nano-dots/wires decorated with graphene-like carbon appear all over the matrix.•Conventional/Non-conventional Raman parameters clarify SiOC-Si3N4 properties.•A percolating network of SiC/graphene and Cfree upwards k, σ and downwards CTE.•The SiOC-Si3N4 composites display remarkable oxidation resistance up to 1400 ºC.