Preparation and complex permittivity of 3D textile C/SiC composites

The carbon fiber is conductive material, and SiC exhibits semiconducting properties. Three dimensional textile carbon fiber reinforced silicon carbide composites exhibit good mechanical properties. So the C/SiC composites appear to be a good system for the study of problems associated with the preparation of ceramic matrix composites with tailored complex permittivity. Three dimensional textile carbon fiber reinforced silicon carbide composites with pyrolytic carbon interfacial layer were fabricated by chemical vapor infiltration (CVI), and the microstructure and complex permittivity at the frequency range of 8.2-12.4GHz were investigated. A thin pyrolysis carbon layer (0.2±μm) was firstly deposited on the surface of carbon fiber as the interfacial layer with C₃H₆ at 850°C and 0.1 MPa. Methyltrichlorosilane (CH₃SiCl₃ or MTS) was used for the deposition of the silicon carbide matrix. The conditions used for SiC deposition were 1100°C, a hydrogen to MTS ratio of 10 and a pressure of 0.1MPa. The real part (ε') and imaginary part (ε") of the complex permittivity of the 3D-C/SiC composites are 51.53-52.44 and 41.18-42.08 respectively at the frequency range of 8.2-12.4GHz. The 3D-C/SiC composites would be a good candidate for microwave absorbent.