Dielectric and Microwave Absorbing Properties of Quartz Fiber/Amorphous Carbon/Polyimide Composites at Elevated Temperature

Microwave absorbing composites were designed and fabricated by using the quartz fiber with dc magnetron sputtering amorphous carbon films as reinforcement and phenylethynyl-terminated polyimide as matrix. The dielectric properties of the composites were investigated for microwave absorption at temperatures from 25 degrees C to 300 degrees C in X-band. Results indicate that the complex permittivity of the composites shows strong frequency dispersion characteristics and obvious temperature-dependent behavior. Microwave absorption abilities of the composites with amorphous carbon films sputtered 8 h are significantly enhanced at elevated temperature compared with room temperature. The minimum value of reflection loss of simple 3 can reach -43.9 dB at 300 degrees C, which is -18.5 dB at room temperature, and the -10 dB bandwidth is 3.9 GHz at 300 degrees C. The results suggest that quartz fiber/polyimide composites with sputtering amorphous carbon films can be used as a promising microwave absorbing material from 25 degrees C to 300 degrees C