Characterization of the uppermost layer of plasma-treated carbon nanotubes

The overall adhesion of carbon nanotubes to the surrounding matrix in polymer based composite materials was improved by forming polar groups on their surfaces and by modifying the surface morphology. For this, two kinds of low-pressure plasma reactors with different gases, flow rates, pressures and powers were used. Especially the uppermost surface layers of the nanotubes was the subject of our investigation. X-Ray photoelectron spectroscopy was used to characterize the efficiency of plasma treatment. The results obtained by this method represent only an average value of a more or less large assemblage of nanotubes. It turns out that the thicknesses of these layers were approximately 1-2 nm after some minutes of oxygen plasma treatment and could not be enlarged by further treatment. The layers mainly consist of hydroxide, carbonyl and carboxyl groups. (C) 2002 Elsevier Science B.V. All rights reserved.