Surface thermal treatment of carbon fibers and electromagnetic shielding of carbon fiber/cement composites

Carbon fiber (CF)/cement composites were prepared after CF had been treated at 1200°C through chemical vapor deposition. The fiber surface and the fracture surface of the composites were observed by scanning electron microscopy. The reflectivity of electromagnetic radiation by the composites was measured in the frequency ranges of the C-band, X-band, and Ku-band using the Naval Research Laboratory testing system. The influence of different fiber mass fraction of 0.2%, 0.5%, 0.6% and 1.0% on their reflectivity was investigated. The results show that thermal treatment at high temperatures changes the surface structure of CF. The bonding force between the fiber and the matrix as well as the shielding effectiveness of the composites is improved. At all bands, the minimum reflectivity data appears when the fiber content is 0.2% and there are stronger wave-absorbing properties at this time. The maximum reflectivity data emerges when the fiber content is 0.5% and the wave-reflecting performances is optimal then.