Preparation and electromagnetic characteristics of the polyaniline-coated short carbon fibers

Combined the nitric acid oxidation treatment and polyaniline (PANI) in-situ polymerization, PANI-coated short carbon fibers (SCF) were prepared for improving their electromagnetic properties. Microstructure and morphology of the modified SCF were observed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). The XPS analysis of the PANI-coated and oxidized SCF reveale that PANI might bond on the surface of oxidized SCF with chemical bonds. SEM images show that PANI films on the surface of SCF are compact and integral. Complex permittivity and complex permeability of SCF, conducting PANI-coated SCF (PASCF) and no-conductive PANI-coated SCF (NPASCF) were measured respectively by Agilent PNA-L N5230A microwave network analyzer in the band ranges of 50 MHz-2 GHz. The absorption loss and reflection loss under the 2 mm coatings were simulated by Matlab 6.5 software. The surface resistance of the paints formed by two kinds of modified SCF was investigated respectively. The results show that, compared with SCF in 50 MHz-2 GHz band, the complex permittivity and complex permeability of PASCF are improved, the magnetic loss tangent is 0, so it is dielectric loss material. But the complex permittivity and complex permeability of NPASCF decrease, the magnetic loss tangent is 0.09, it shows electromagnetic loss characteristic. The simulation absorption losses of PASCF and NPASCF are 4.654 dB and 1.105 dB, respectively. The surface resistances of the paint films containing with PASCF and NPASCF are 1.02·m-2 and 2.32 × 1011Ω·m-2, respectively. The shielding effectiveness (SE) of the paint films containing with PASCF and NPASCF are about 17 dB and 8 dB, respectively.