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

• The SiCf/PyC/SiC composites were prepared by chemical vapor infiltration.
• ɛ′ of the SiCf/PyC/SiC composites increased with increasing temperature.
• ɛ″ of the SiCf/PyC/SiC composites decreased with increasing temperature.
• Microwave absorption of SiCf/PyC/SiC composites at higher temperature was stronger.

In this paper, the SiC fiber-reinforced SiC matrix composites with pyrolytic carbon (PyC) interphase (SiCf/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 SiCf/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 ɛ′ of complex permittivity of the SiCf/PyC/SiC composites increased with increasing temperature, which was ascribed to the shortened relaxation time of polarization. Whereas, the imaginary part ɛ″ decreased with increasing temperature, which was attributed to the decrease of the electrical conductivity of the PyC interphase. The reflection loss of the SiCf/PyC/SiC composites was calculated. Results indicated that the microwave absorption of the composites at higher temperature was stronger than that at lower temperature.