Microwave dielectric properties of Nextel-440 fiber fabrics with pyrolytic carbon coatings in the temperature range from room temperature to 700 ℃

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 ℃ 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 ℃ compared with that at lower temperatures.