Hydrophobic Coating of Carbon Nanotube by CH4 Glow Plasma at Low-Pressure and its Wettability

Summary form only given. This study demonstrates the hydrophobic coating by methane (CH₄) glow discharge plasma at low-pressure and investigates the superhydrophobic behavior of the treated carbon nanotubes (CNTs). Carbonaceous species produced from the CH₄ glow plasma were identified by an optical emission spectroscopy. The treated CNTs have floated on water for several months, exhibiting hydrophobic properties. Contact angles (CAs) with test liquids were measured from the capillary rise method based on the Washburn equation, to identify the total surface free energies of CNTs with and without CH₄ plasma treatment. The total surface free energy of the CNTs can be determined by making use of the measured CA and the van Oss-Chaudhury-Good equation. It was shown that the surface free energy of the plasma-treated CNTs decreased drastically from 27.04 mN/m to 1.32times10⁷ mN/m, revealing super-hydrophobic modification of CNTs by the CH₄ plasma.