Study on the mechanisms of electrochemical surface treatment of carbon fibers in H₃PO₄ solution

The carbon fibers were electrochemical treated in H₃PO₄ solution. The treatment mechanisms are investigated using cyclic voltammetry, XPS, SEM and XRD measurements. The results indicate that the electro active substances on the fibers are reacted to produce new active carbon atom under the polarization current in initial stage, then the fibers are oxidized and etched more and more greatly under the couple action of polarization current and the electrolyzation of water. The content of oxygen element on the fiber surface was increased. The concentration of different functional groups which contained oxygen element was changed continuously during the surface treatment period. The carboxyl group and acid anhydride were increased with the treatment time extending. The surface morphology of carbon fibers was rougher and the grooves on the fiber surface were wider and deeper after treatment. Whereas the bulk structure of the fiber was not changed during treatment, the structure of micro crystallite on the fiber surface was changed slightly.