Degradation of carbon nanotubes in oxygen glow discharges

Abstract

A study has been undertaken of the degradation of carbon nanotube (CNT)-covered stainless steel mesh cathodes during exposure to low-pressure oxygen glow discharges. Emission spectroscopy and molecular absorption spectroscopy in DC glow discharge and in RF afterglow experiments, as well as morphological evidence, mass spectrometry spectra of condensed oxidation products, and molecular structure models have shown that plasma oxidation favors the production of 2,3 naphthalic anhydride. Absorption spectra taken during plasma oxidation match both literature sources for 2,3 naphthalic anhydride, as well as spectra of a chemical standard. MS data indicate that the only heavy compounds produced during plasma oxidation are poly-cyclic aromatics that can be attributed either directly to 2,3 naphthalic anhydride or to toluene, its major plasma decomposition product. Morphological observations using the scanning electron microscope support the conclusion that the reaction is facilitated by the field enhancement effect that accelerates oxygen ions to the tips of CNTs, where the oxidation takes place. Tests using water vapor show that oxidation is anhydrous, even in the presence of hydrogen.