Short-carbon-fiber reinforced alumina ceramic with improved mechanical property and dielectric property in the Ku-band

Short carbon fibers (C_sf) reinforced alumina composites were prepared by a hot-pressing sintering process. The influences of C_sf content and fiber length on mechanical and dielectric properties of the composites in the Ku-band (12.4-18 GHz) were evaluated. The flexure strength of the ceramic increased with the C_sf incorporation and the maximum value of 475 MPa was obtained by the addition of 0.3 wt% C_sf with the length being 2 mm. The electronic polarization relaxation is contributed to the variation of the real part of the permittivity (Ïμ′) with increasing C_sf content and fiber length. The associated polarization relaxation and conductivity of the composites are responsible for the variation of the imaginary part (Ïμ″). When 0.1 wt% C_sf with length of 4 mm was incorporated, the reflection loss below -6 dB can be obtained in the Ku-band with the coating thickness being 1.2 mm. The results indicate that C_sf/Al₂O₃ composite could be a potential microwave absorbing material used in the Ku-band.