Effects of PACVD parameters including pulsed direct current and deposition time on nanostructured carbon coating deposited on carbon fiber fabrics

A nanostructured carbon film was deposited on carbon fiber fabrics by plasma assisted chemical vapor deposition (PACVD) to overcome the limitations of carbon fibers and improve the interface with the composites in the carbon fiber fabrics. The main process parameters investigated were the intensity of the pulsed direct current and deposition time on the chemical and structural features of the coating. Methane gas was used as the reactant gas in PACVD. FESEM images revealed good uniformity of the deposited coating. The thickness of the coating varied from 40 to 320 nm for different specimens and the thickness increased as the intensity of the pulsed direct current and deposition time increased. Raman spectroscopy results showed that increasing the magnitude of the pulsed direct current increased the fraction of sp(3) bonds and the residual stress. Diamond nanoparticles 10-20 nm in size were revealed after etching. Increasing the pulsed direct current created a smoother surface with 45.59 nm of average roughness. Depositing a thin coating (40 nm) increased fracture strength 27.6%; however, the fracture strength decreased significantly with further increases in the thickness of the coating. (C) 2016 Elsevier Ltd. All rights reserved.