Effect of Electrochemical Treatment of the Pan-based Carbon Fiber Using Different Electrolytes

The PAN-based carbon fibers were modified using anodic oxidation method with different electrolyte such as sulfuric acid, sodium sulfate and sodium hydroxide for improving its surface properties and its composites interphase properties. It is well know that different electrolyte have different oxidizability and electrochemical characterization. The influence of different electrolytes on the effect of carbon fibers’ treatment is investigated in this paper. The mechanism of the electrochemical treatment in different electrolyte is predicted to understand. The electrochemical characteristics of the carbon fibers as anode during the treatment are analyzed by linear sweep voltammetry. The surface properties of the fiber before and after treatment, such as chemical component, surface morphology and crystal fine structure, are estimated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Raman spectroscopy, respectively. The consistency profile is employed to determine the infiltrating angle of the fiber. The interlaminer shear strength (ILSS) of its composites is also tested to evaluate the interphase strength. The results indicate that different electrolyte with the same ion concentration made different modification effects on the carbon fiber and its composites. For the acid electrolyte, there exist most oxidation and gentle etching. The increasing oxygen functional groups and fine roughness are found. For the alkali electrolyte, less oxidation and intense etching happen. For the saline electrolyte, the oxidation degree and etching degree are between in acid electrolyte and in alkali electrolyte. The increasing oxygen functional groups are similar to that of the acid electrolyte, while the etching degree is more deeply than the acid one and less than the alkali. The ILSS of the composites treated in alkali electrolyte is improved better than the anther of two. This predicts that the roughness of the carbon fiber surface is the important fact on the interphase strength. ACKNOWLEDGEMENT The authors would like to thank the National Nature Science Foundation of China (Grant No. 50503007) for financial support.