Bifunctional SiC/Si3N4 aerogel for highly efficient electromagnetic wave absorption and thermal insulation

SiC ceramics are attractive electromagnetic (EM) absorption materials for the application in harsh environment because of their low density, good dielectric tunable performance, and chemical stability. However, the performance of current SiC-based materials to absorb EM wave is generally unsatisfactory due to poor impedance matching. Herein, we report ultralight SiC/Si3N4 composite aerogels (~15 mg·cm−3) consisting of numerous interweaving SiC nanowires and Si3N4 nanoribbons. Aerogels were prepared via siloxane pyrolysis and chemical vapor reaction through the template method. The optimal aerogel exhibits excellent EM wave absorption properties with a strong reflection loss (RL, −48.6 dB) and a wide effective absorption band (EAB, 7.4 GHz) at a thickness of 2 mm, attributed to good impedance matching and multi attenuation mechanisms of waves within the unique network structure. In addition, the aerogel exhibits high thermal stability in air until 1000 ℃ and excellent thermal insulation performance (0.030 W·m−1·K−1). These superior performances make the SiC/Si3N4 composite aerogel promising to become a new generation of absorption material served under extreme conditions.