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

• Nanostructured carbon coating can be obtained by low temperature plasma assisted chemical vapor deposition method on carbon fiber fabrics using methane and argon gases.
• The structure and thickness of coating are controlled by direct current and time.
• By raising the pulsed direct current from 2.5 A to 3.5 A, the fraction of sp3 bonds varied from 0.381 to 0.499 under a constant deposition time.
• The analysis results revealed that the specimen experiencing the lowest pulsed direct current with smallest amount of thickness showed higher tensile strength.

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 sp3 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.

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