A High-Temperature Structural And Wave-Absorbing Sic Fiber Reinforced Si3n4 Matrix Composites

The SiCf/Si3N4 composite with low-high-low permittivity sandwich structure was designed for high-temperature electromagnetic (EM) wave absorption and mechanical stability. The SiCf/Si3N4 possessed the remarkable mechanical properties at room temperature (the flexural strength is 357 +/- 16 MPa and the fracture toughness is 10.8 +/- 1.7 MPa m(1/2)) for the strong fiber strength, moderate interface bonding strength and uniform matrix. Furthermore, the retention rate is as high as 80% at 800 degrees C. The A/B/C nanostructure and the sandwich meta structure endowed the SiCf/Si3N4 with an excellent EM absorbing property at room temperature. The SiCf/Si3N4 still absorbed 75% of the incident EM waves energy in X and Ku bands when the temperature increases up to 600 degrees C, which is only 6% lower than that at room temperature, for the partial compensation of the decreased interfacial polarization loss for the increased conductivity loss and dipole polarization loss.