Improved mechanical and high-temperature electromagnetic wave absorption properties of SiC_f/BN/AlPO₄ composites with absorber multiwalled carbon nanotubes

Abstract

An electromagnetic wave absorbing material acting from 8.2 to 12.4 GHz (X-band) is fabricated by mixing BN-coated SiC fiber with AlPO4 matrix, and using multiwalled carbon nanotubes (MWNCTs) as the absorber. The effect of temperature on the microstructure of BN interface is disclosed by XRD and FT-IR characterizations. The crystallinity of BN increased with elevated temperature. The fracture strength of SiCf/BN/AlPO4 composites rise from 175 to 350 MPa and the fracture displacement was elevated from 0.25 to 0.7 mm. The increasing complex permittivity of SiCf/BN/AlPO4/MWCNTs composites in the temperature range of 25–600 °C is ascribed to the shortened electron polarization-relaxation time and improved electrical conductivity. Attenuation constant and input impedance are chosen to discuss the reflection loss of the composites. Finally, a 4.2 GHz absorbing bandwidth below −8 dB is achieved with 3.1 mm thickness in the range of 25–600 °C.