Microstructural optimization of high-temperature SiC/SiC composites by NITE process

Two kinds of SiC fiber-reinforced SiC (SiC/SiC) composites (high strength type and high ductility type) were prepared by NITE process and their thermo-mechanical properties were investigated from room to high temperature. Furthermore, thermal stress figure of merit of advanced SiC/SiC composites including prepared NITE-SiC/SiC composites were discussed. Matrix densification, especially inter-fiber-tows, was effective way to restrict the oxygen diffusion through pores and hence fiber and matrix interface was protective against the oxidation. In NITE process, excess additional additives for matrix densification, like high ductility type, caused weight loss with pore formation derived from the oxide segregations over 1300 °C. There was no degradation in strength by 1500 °C and simultaneously high thermal conductivity was kept up to 1500 °C for high strength type, resulting in the excellent thermal figure of merit.