Preparation and properties of C/C–SiC nano-composites

Recently, there seems to be a great emphasis on the development of advanced thermostructural composites such as C/C–SiC. In these composites the core is made of C/C composite and the surface is protected by a layer of SiC. Due to the different thermal expansions of the two materials, cracking occurs in the top SiC layer. The solution to this problem would be the preparation of gradient composite with SiC present in the matrix phase. In this work various options for the production of the C/C composite with SiC nano-particles dispersed in the matrix were investigated. Such material will enable the production of C/C–SiC composites with gradient structure form the carbon in the core to silicon carbide on the surface and consequently with improved mechanical and thermal properties. Two approaches were used to enable the in situ formation of the SiC nano-particles in the carbon matrix: one was the synthesis of SiC precursors by sol–gel and the other was the use of ceramic forming polymers, which after the pyrolysis form silicon carbide. The preparation of the composites and its influence on the microstructure and the mechanical properties of composites were investigated.