Temperature dependence of dielectric properties of SiC_f/PyC/SiC composites

Highlights: • The SiC_f/PyC/SiC composites were prepared by chemical vapor infiltration. • ε′ of the SiC_f/PyC/SiC composites increased with increasing temperature. • ε″ of the SiC_f/PyC/SiC composites decreased with increasing temperature. • Microwave absorption of SiC_f/PyC/SiC composites at higher temperature was stronger. - Abstract: In this paper, the SiC fiber-reinforced SiC matrix composites with pyrolytic carbon (PyC) interphase (SiC_f/PyC/SiC) were prepared by chemical vapor infiltration (CVI). The SEM micrographs indicated that there was a uniform PyC interphase between the fiber and the matrix. The dielectric properties of the SiC_f/PyC/SiC composites were investigated in the temperature range of room temperature to 700 °C in X-band to analysis the effect of the temperature on the dielectric properties. Results showed that the real part ε′ of complex permittivity of the SiC_f/PyC/SiC composites increased with increasing temperature, which was ascribed to the shortened relaxation time of polarization. Whereas, the imaginary part ε″ decreased with increasing temperature, which was attributed to the decrease of the electrical conductivity of the PyC interphase. The reflection loss of the SiC_f/PyC/SiC composites was calculated. Results indicated that the microwave absorption of the composites at higher temperature was stronger than that at lower temperature