Abstract

Si3N4 has high thermal and mechanical resistance, as well as high resistance to thermal shock and high thermal conductivity (320 Wm-1K-1). On the other hand, silicon oxycarbide glasses (SiOC) have a SiO2 matrix where part of the oxygen has been replaced by carbon and also contain a carbon phase homogeneously embedded within the mixed Si-O-C matrix. The properties of these materials can be designed depending on the precursors, synthesis-processing conditions, pyrolysis temperature and, above all, the addition of reinforcement materials, being able to obtain materials with certain characteristics depending on the application. In this work, dense SiOC/Si3N4 composite materials have been developed using the non-conventional sintering technique spark plasma sintering (SPS), which reduces the temperature and sintering times since it simultaneously uses a uniaxial pressing and an electric current to produce sintering by means of the Joule effect. Sintering improves as the temperature increases from 1500 to 1700 ºC. A large increase in thermal conductivity from 1.4 to 1.7 wm-1K-1 is observed in the composite materials obtained. These materials show good mechanical strength with microhardness and elastic modulus values of 10.2 GPa and 82.1 GPa, respectively, and an extraordinary resistance to oxidation. All these results indicate that these materials are excellent candidates for high temperature structural and functional applications such as solar receiver collectors and propulsion systems.