Preparation and electromagnetic microwave absorption performances of sulfurated and oxidized polyacrylonitrile carbon fibers

Polyacrylonitrile carbon fibers (PAN CFs) were sulfurated at high temperatures and then oxidized with an H2O2 solution. Thermal and chemical analysis showed high thermal stability and the sulfur content up to 4 mmol g(-1). From the microwave absorption studies, the voltage standing wave ratio and the attenuation through one adsorbent layer decrease almost linearly with increasing frequency. The reflection coefficient equals 0.79 +/- 0.017 and 0.473 +/- 0.02 at 10 and 30 GHz. "Transparency windows" with a bandwidth of about 300 MHz are observed at 30 and 36 GHz. The 1000 times attenuation of the signal power is found at 30 GHz.