Modification of carbon surfaces in cold plasmas

Abstract

Various forms of carbon, including carbon black, carbon fibre and pyrolytic graphite, have been surface-modified in a cold-plasma reactor. Plasma fluorination of the carbon surfaces was performed using variable flow rates, treatment times, and types of gas. The plasma-modified carbon surfaces were characterized using electron spectroscopy (ESCA), contact angle measurements, and scanning electron microscopy (SEM). The surface chemical structure of the plasma-fluorinated carbon blacks appeared to be similar to that of commercial Fluorographite. Nitrogen-containing groups were introduced into the surfaces of carbon blacks and carbon fibres by exposure to glow discharges in mixtures of ammonia and N2-H2. The surface concentration of functional groups containing nitrogen decreased with time. Several mechanisms for this degradation have been proposed. Plasma-modified carbon blacks and carbon fibres have potential for improving the properties of composites by achieving appropriate levels of adhesion between filler and matrix through physical compatibility and/or chemical bonding.