High-temperature electromagnetic wave absorption of Si₃N₄ composite ceramics reinforced with continuous SiC fibers and SiC particles

High-temperature electromagnetic wave (EMW) absorbing materials are essential for advanced aerospace and stealth applications due to their functional stability and mechanical reliability. In this study, SiC fiber/powder-reinforced Si₃N₄ ceramic matrix composites were fabricated through spark plasma sintering, with carefully controlled compositions and microstructures. We systematically evaluated the electromagnetic and mechanical properties of the optimized composite, SCNF20, in the X band. The SCNF20 composite exhibits exceptional EMW absorption performance, achieving an ultra-low minimum reflection loss of −56.2 dB and an effective absorption bandwidth that spans the entire X band. Moreover, the composite retains effective absorption at elevated temperatures up to 600 °C, demonstrating excellent high-temperature stability. CST electromagnetic simulations further indicate a substantial reduction in radar cross-section at various incident angles, confirming the composite's strong potential for electromagnetic stealth applications. The enhanced absorption performance is primarily attributed to optimal impedance matching and multiple dielectric loss mechanisms, facilitated by the SiC reinforcements. Additionally, SCNF20 shows reliable mechanical properties, including a flexural strength of 442.6 ± 5.4 MPa and a fracture toughness of 11.47 ± 0.55 MPa m^1/2, attributed to fiber-related toughening mechanisms such as crack deflection, fiber pull-out, and fiber bridging. These results suggest that SCNF20 is a promising candidate for high-temperature, load-bearing EMW-absorbing ceramic applications.