Surface modification of carbon nanofibres in low temperature plasmas

Carbon nanofibres (vapour grown carbon fibres, VGCF) were treated in RF plasma to enhance the wettability and thus to improve the bonding to the matrix in polymer composites. The surface of these fibres was modified using nitrogen and oxygen containing plasma gases. The water contact angles of VGCF nanofibres decrease at plasma treatments in NH3, O-2, CO2, H2O and formic acid. The wettability strongly depends on applied process pressure. In the range of 0.01 to 1 mbar the water contact angle at treatments in NH3 increases with increasing pressure. However, using O-2, CO2, H2O and HCOOH the water contact angle decreases with increasing process pressure. The investigations of the surface composition by XPS measurements show that the oxygen containing gases differ in oxidation strength. O-2 and CO2 lead to the higher concentrations of COOH and C=O functional groups on the surface in comparison to H2O and HCOOH. (C) 2003 Elsevier B.V. All rights reserved.