Microwave dielectric properties of Nextel-440 fiber fabrics with pyrolytic carbon coatings in the temperature range from room temperature to 700 °C**Project supported by the National Natural Science Foundation of China (Grant No. 51072165) and the Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University, China (Grant Nos. KP201307 and SKLSP201313).

Abstract

Pyrolytic carbon (PyC) coatings are deposited on the Nextel-440 fiber fabrics by chemical vapor deposition (CVD). The dielectric properties of the Nextel-440 fiber fabrics with PyC coatings (Nextel-440/PyC) are investigated in a temperature range from room temperature to 700 °C in X-band. Compared with the permittivity of the original Nextel-440 received, the complex permittivity of the Nextel-440/PyC (the real part ε′ and the imaginary part ε″), is significantly improved: ε′ of the Nextel-440/PyC has a positive temperature coefficient, in contrast, ε″ of the Nextel-440/PyC exhibits a negative temperature coefficient. Moreover, the reflection loss in units of dB is calculated. The results indicate that the microwave absorbing properties of the Nextel-440/PyC coatings is enhanced at 700 °C compared with that at lower temperatures.