Electromagnetic Microwave Absorption Performances of Plasma Brominated Carbon Fibers

Polyacrylonitrile-based carbon fibers (PAN CFs) were brominated in a low-temperature gas discharge bromine plasma medium. Depending on the treatment time, 0.11, 0.21, or 0.58 mmol of bromine per gram of PAN CFs can be added. Brominated PAN CFs were imagined with scanning electron microscopy and analyzed with chemical analysis. Their thermal behavior was studied by thermogravimetry and thermoprogrammed desorption mass-spectra. Added bromine desorbs in a wide temperature range of 155–750 °C with maxima at 350±20 °C and 540±20 °C. As compared with the PAN CFs, analysis of the microwave properties of the brominated PAN CFs with 0.11 and 0.21 mmol of bromine per gram of PAN CFs showed that the electromagnetic losses for them increased from 3 to 6 times. But, we registered the opposite effect for the brominated PAN CFs with 0.58 mmol bromine per gram of the PAN CFs. The highest bromine content in the brominated PAN CFs can be a reason for the best masking properties when the respective sample was deposited on a metal surface. This effect can be seen in a wide frequency range of electromagnetic radiation, as confirmed by the value of VSWR of about 4.