Microstructure and Microwave Absorption Performance Variation of SiC/C Foam at Different Elevated-Temperature Heat Treatment

The porous structure has been proved to be beneficial to improve the microwave absorption performance. In this article, the SiC coating reinforced carbon foam (SiC/C) was synthesized via the direct pyrolysis of melamine foam and chemical vapor deposition process of SiC coating. Then the wrapping architecture consisting of three-dimensional carbon foam and ultrathin SiC coating was annealed at elevated temperature. The result shows that the anneal temperature does have a big impact on the dielectric property as the real and imaginary permittivities remain at a certain level with the increasing heat treatment temperature and finally drop to a low level until 900 °C. After being heated at 900 °C, the SiC/C foam attains a minimum reflection loss value of −51.58 dB with a matching thickness of 3.60 mm at 8.96 GHz, which is enhanced by 30.88% compared with the raw SiC/C foam. It also possesses an effective bandwidth frequency of 10.84 GHz ranging from 7.16 to 18.00 GHz, which is ascribed to the three-dimensional hollow structure to improve the polarization relaxation and interfacial polarization. The superior microwave absorption performance guarantees the potential application of a promising efficient microwave absorber in the harsh realities.