High-temperature electromagnetic wave absorption, mechanical and thermal insulation properties of in-situ grown SiC on porous SiC skeleton

Multi-functional integrated materials used in extreme environments are gaining increased interest. In this study, a binary porous SiC was fabricated by in-situ synthesis in a SiC skeleton. The binary porous SiC exhibited unique features of synergistic effects of high-temperature electromagnetic (EM) wave absorption, mechanical and thermal-insulation properties. The chemical-composition evolution was characterized by transmission electron microscopy and Raman spectroscopy. Electronic structures were investigated by X-ray absorption near-edge structure at the C K-edge. Based on a vapor–solid–liquid growth mechanism, a decrease in the vacancy defects and unoccupied C density of states (DOS) was manifested in the binary porous SiC. Introducing the second SiC phase resulted in sharply enhanced EM wave absorption performance. The minimum reflection loss was as low as −51 dB, and the effective absorption bandwidth at 600 °C was 3.2 GHz (from 9.2 GHz to 12.4 GHz) with a thickness of 2.4 mm. Meanwhile, the in-situ grown second SiC phase substantially increased the compressive strength to 34.25 MPa, which was nearly 15-fold that of the porous SiC. Moreover, the binary SiC showed a low thermal conductivity of 0.1572 W/m·K. All these results indicated that the binary porous SiC system was ideal for EM wave absorption applications at extremely high temperatures.