Novel Three-Dimensional SiC/Melamine-Derived Carbon Foam-Reinforced SiO2 Aerogel Composite with Low Dielectric Loss and High Impedance Matching Ratio

Novel three-dimensional SiC/melamine-derived carbon foam composite filled by silica aerogel (SiC/MDCF–Aerogel) was first fabricated by the pyrolysis process of commercial melamine foam, chemical vapor deposition of ultrathin SiC films, and the sol–gel method of silica aerogel. The results indicated that the SiC/MDCF–Aerogel composite consisted of the SiC three-dimensional open-celled network structure and the pregnant silica aerogel in the pores. Tiny cracks on the interface of skeletons and clumps were induced during the aging process, which was drastically beneficial to the microwave-absorbing properties. A minimum reflection loss could be obtained as low as −18.41 dB at the measured frequency of 16.92 GHz when the thickness of the absorber was 3.65 mm, and the reflection loss could drop below −10 dB when the selected frequencies ranged from 15.80 to 17.52 GHz, along with the thickness ranging from 2.75 to 5.0 mm, which possessed a relatively better microwave absorption performance especially at a higher frequency. Furthermore, the absorption mechanism was also investigated in detail to discuss the influence of the dielectric loss and the impedance matching ratio on the microwave-absorbing performance of SiC/MDCF–Aerogel, which provided certain scientific directions for evaluating the absorbing materials.