Quantitative Defect Analysis of PAN-based Carbon Fibers Treated by Single and Dual HF RF-CCP

This work states the effects of single (40.68 MHz) and dual (40.68/2.1 MHz) RF-CCPs on defect structure of the PAN-based carbon fibers. The fibers were treated between two identical aluminum electrodes with R$\sim $200 mm in a 78.5 L stainless steel cylindrical reactor (R$\sim $500 mm, H$\sim $400 mm). The gap distance was 4 cm. In SRF mode, P$_{\mathrm{HF}}=$50-200 W, p$=$0.3, 0.5, 0.75 and 1 Torr, t$=$30, 60 and 90 min. In DRF mode, P$_{\mathrm{LF}}=$50-200 W, p$=$ 0.1-0.9 Torr and t$=$15, 30, 45 and 60 min at fixed P$_{\mathrm{HF}}=$50 W. The structural analyses of the treated fibers were done by using high sensitive confocal Raman spectroscopy and the surfaces were excited by 532 nm-100 mW He-Ne (2.33 eV) laser. The average defect size and density of the treated fibers were calculated according to the following formulas; L$_{\mathrm{D\thinspace }}$(size) $=$ (1.8\texttimes 10$^{\mathrm{-9}}\lambda _{\mathrm{L}}^{\mathrm{4}}$I$_{\mathrm{G}}$/I$_{\mathrm{D}})^{\mathrm{\thinspace 1/2}}$ and n$_{\mathrm{D}}$ (density) $=$ (1.8\texttimes 10$^{\mathrm{22}}$/$\lambda_{\mathrm{L}}^{\mathrm{4}})$ \texttimes I$_{\mathrm{D}}$/I$_{\mathrm{G\thinspace }}$where $\lambda_{\mathrm{L}}$ is the laser wavelength, I$_{\mathrm{D}}$ is the intensity of D-band (\textasciitilde 1350 cm$^{\mathrm{-1}})$ and I$_{\mathrm{G\thinspace }}$is the intensity of G-band (\textasciitilde 1580 cm$^{\mathrm{-1}})$.