Rapid oxidative activation of carbon nanotube yarn and sheet by a radio frequency, atmospheric pressure, helium and oxygen plasma

Carbon nanotube yarn and sheet were activated using radio frequency, atmospheric pressure, helium and oxygen plasmas. The nanotubes were exposed to the plasma afterglow, which contained 8.0 × 1016 cm−3 ground state O atoms, 8.0 × 1016 cm−3 metastable O2 (1Δg), and 1.0 × 1016 cm−3 ozone. X-ray photoelectron spectroscopy and infrared spectroscopy revealed that 30 s of plasma treatment converted 25.2% of the carbon atoms on the CNT surface to oxidized species, producing 17.0% alcohols, 5.9% carbonyls, and 2.3% carboxylic acids. The electrical resistivity increased linearly with the extent of oxidation of the CNT from 4 to 9 × 10−6 Ω m. On the other hand, the tensile strength of the yarn was decreased by only 27% following plasma oxidation.