Simultaneous microwave absorption and thermal insulation properties of porous rigid mullite by loading SiCN aerogel

Abstract

Abstract Porous rigid mullite is desirable for lightweight and highly efficient thermal insulation in the aerospace field. However, the limited functionality constrains its application. To fulfill the requirements of anti-radar detection and defense stealth, possessing thermal insulation while simultaneously having the ability of electromagnetic wave (EMW) absorption in materials is essential. Herein, porous rigid mullite-based composites with stealth capability and high-temperature resistance were successfully fabricated by assembling SiCN ceramic aerogels (SiCNa) as microwave absorber through high-pressure impregnation-pyrolysis. Benefiting from the inclusion of SiCNa, S1 reached the minimum reflection loss (RLmin) of -49.24 dB at 15.84 GHz, and the effective absorption bandwidth achieved 9.23 GHz. The thermal conductivity of SiCN ceramic aerogels/mullite composites (SMC) decreased initially and then increased. The composites demonstrated quite low high-temperature thermal conductivity (0.086 W·m-1·K-1 at 1000°C of sample S1) with the cooperation of mullite fibers and SiCNa. Furthermore, there was a slight increase in density. The SMC with superior EMW absorption and low thermal conductivity properties making them an ideal material for stealth in weapon systems enduring high temperatures. What’s more, the multifunctional integration of EMW absorption and thermal insulation offers a feasible method for the preparation of defense materials in the future.