Temperature-dependent electromagnetic wave absorption and multi-relaxation behavior in SiCf/Y3Si2C2/Mullite composites

The development of high-temperature stable electromagnetic wave absorption (EMA) materials is crucial for extreme aerospace service environments. In this study, SiC f /Y 3 Si 2 C 2 /Mullite composites with a quasi-vertically oriented Y 3 Si 2 C 2 interfacial layer were fabricated by integrating in-situ molten salt reaction, gel-casting, and pressureless sintering techniques. The composites demonstrated outstanding temperature-dependent EMA performance, featuring multiple relaxation behaviors from 25 to 800 °C. Specifically, at 800 °C and a thickness of 2.34 mm, the composite achieved a minimum reflection loss (RL min ) of −57.32 dB, and an effective absorption bandwidth (EAB) of 2.14 GHz in the X-band. Following oxidation at 1300 °C for 10 h, the composite still maintained an RL min of −23.39 dB at a thickness of 2.85 mm with an EAB of 1.93 GHz, showcasing impressive thermal stability. The superior EMA performance mainly originated from synergistic effects of multiple reflection/scattering induced by the quasi-vertical structure of Y 3 Si 2 C 2 nanosheets, enhanced conductive loss, and interfacial polarization relaxation at elevated temperatures. Cole–Cole plots and relaxation factor analysis verified the temperature-dependent emergence and enhancement of multiple relaxation processes. Radar cross-section (RCS) simulations demonstrated maximum RCS reduction of 19.9 dB at 25 °C and 23.4 dB at 800 °C compared to metal plates. The SiC f /Y 3 Si 2 C 2 /Mullite composite represents a promising candidate for high-temperature EMA applications in the aerospace industry.