Effect of the electrolytes on the electrochemical treatment of the PAN-based carbon fibers

PAN-based carbon fibers were modified by electrochemical treatment using phosphoric acid, sodium hydroxide and ammonium acid carbonate as electrolyte. Effects of electrolytes on the electrochemical treatment of carbon fibers were studied. Titration analysis, atom force microscopy (AFM) and composites IFSS measurement were used to characterize the acidic functional groups contents on the fibers surface, the surface topography and its composites interfacial shear strength. The results indicated that in phosphoric acid and sodium hydroxide electrolyte, the acidic functional groups contents on the fiber surface were increased quickly with the enlarging of the current density at first and then decreased, the maximum content was obtained at 0.4 A/g; in ammonium acid carbonate electrolyte, the acidic functional groups content was increased slowly with the current density enlarging at first and then decreased quickly, the maximum content was got at 1.4 A/g. Combining with the surface topography analysis by AFM, the IFSS of the composites was mainly controlled by the etching action in phosphoric acid and sodium hydroxide electrolyte. In ammonium acid, the carbonate electrolyte of the composites was mainly determined by the acidic functional groups contents on the fiber surface.