High frequency capacitively coupled RF plasma discharge effects on the order/disorder structure of PAN-based carbon fiber

High-resolution confocal Raman microscopy was used to investigate the effects of nitrogen plasma on unsized high strength (HS) PAN-based carbon fiber surfaces. The fibers were treated by a high frequency (40.68 MHz) capacitively coupled single RF-PECVD reactor under different processing conditions (exposure times, RF powers and gas pressures). It was found that the order/ disorder structure of the treated carbon fiber changed with different processing conditions. At low pressures, the degree of disordered structure increased with HF–RF power and process time. However, at high pressures, highorder structure (IG=IT ¼ 84:51%) was observed and almost no observable structural effects appeared at long treatment time. Also, the first-order Raman-band peaks (D and G) of the treated carbon fibers shifted. And, FWHM (wD=wG), intensity (ID=IG) and D-band relative integrated intensity (ID=IT) ratios increased with ordering whereas they decreased with disordering