Integration of microwave absorption capability into mullite insulation tiles for multifunctionality

Abstract Designing multifunctional integrated composites is a viable approach to meet the diverse requirements in complex environments. By incorporating microwave absorption capability into mullite insulation tiles, it becomes feasible to simultaneously achieve both microwave absorption and thermal insulation effectiveness within a single system, thereby enhancing the materials' adaptability and efficiency. In this study, mullite insulation tiles were utilized as support structures, and polymer‐derived SiCN (PDC‐SiCN) ceramic aerogel with microwave absorption properties was loaded onto the mullite through the high‐pressure impregnation‐pyrolysis technique to fabricate SiCN/mullite insulation tile composite (SM composite). With the inclusion of SiCN aerogel, the SM composite, after one impregnation‐pyrolysis cycle, exhibited exceptional microwave absorption performance, whose minimum reflection loss was −49.24 dB (99.99% microwave absorption) at 15.84 GHz, and effective absorption bandwidth was 9.23 GHz. Additionally, due to the synergistic effect between mullite and SiCN aerogel, the SM composite demonstrated significantly reduced thermal conductivity in 25–1000°C (.064–.086 W·m −1 ·K −1 ), much lower than that of mullite insulation tiles (.076–.156 W·m −1 ·K −1 ). The superior combination of excellent microwave absorption and low thermal conductivity properties makes the SM composite an ideal stealth/thermal insulation integrated material in a thermal protection system operating in a high‐temperature environment.