ELECTROCHEMICAL OXIDATION OF CARBON-FIBERS IN AQUEOUS-SOLUTIONS AND ANALYSIS OF THE SURFACE OXIDES

Carbon fibres with notably different surface oxides can be prepared by varying the electrochemical oxidation conditions. Through correlation of voltammetric analysis and mass spectroscopy, interpretation of the reduction peaks of the surface oxides on the basis of their potential and width is possible. Narrow voltammetric reduction peaks at strongly negative potential are indicative of the predominance of -COOH type groups, while wide peaks at more positive potential are indicative of the presence of an excess of[Figure not available: see fulltext.] type groups. A quantitative determination of the surface acidic groups (-COOH and[Figure not available: see fulltext.]) is achieved by combination of Ag+ ion exchange and esterification of[Figure not available: see fulltext.] groups with 3,5-dinitrobenzoyl chloride. All results are confirmed by the independent method of -COOH group determination via their electrocatalytic behaviour in the reduction of azobenzene in methanol. The amounts of the -COOH and[Figure not available: see fulltext.] groups formed depend notably on the conditions of the electrochemical oxidation of the carbon fibres. The ratio between -COOH and[Figure not available: see fulltext.] groups coincides in all cases with that obtained by the mass spectrosopic data. © 1990 Chapman and Hall Ltd.