Complex permittivity control of SiCf/SiC composite through thermal oxidation

In this letter, we propose a process for fabricating a Silicon Carbide fiber (SiCf)/Silicon Carbide (SiC) composite radar-absorbing structure (RAS); the process can precisely control the complex permittivity of the composite in high-temperature environments. During the manufacturing of the SiCf/SiC composite, sufficient carbon is supplied to the SiC fibre to ensure conductive properties. Thereafter, thermal oxidation is performed to remove carbon, which transformed the conductive property of the composite material into the dielectric property. The duration of thermal oxidation was controlled because of which the complex permittivity of the composite material approached the optimal complex permittivity for impedance matching. A specimen of the SiCf/SiC composite radar-absorbing structure was produced, and the reflection loss of the specimen was measured. The results indicated that the specimen could absorb more than 99% of the incident electromagnetic waves in the frequency range from 9.02 to 9.84 GHz.