Study On Electrochemical Surface Modification Of Domestic PAN-Based High Strength And High Modulus Carbon Fiber

Electrochemical anodic oxidation is one of the most commonly used methods for surface modification of carbon fiber(CF).In this thesis,the surface oxidation and nitridation of PAN-based high-strength and high-modulus carbon fibers were firstly carried out in different organic composite electrolyte solutions by cyclic voltammetry(CV).The electrolyte was screened by combination of CV curve and X-ray photoelectron spectroscopy(XPS).The surface composition and surface morphology of CF were characterized by Fourier transform infrared spectroscopy(FT-IR)and Scanning electron microscopy(SEM).The nitridation mechanism of CF surface was studied by comparative analysis of XPS peak fitting data.Then CF was subjected to constant current oxidation treatment under the different conditions of the above electrolyte,and the mechanical properties and surface order of CF before and after oxidation treatment were characterized by bundle tension test and Raman spectroscopy.The interfacial properties of CF/epoxy 6101 composites were characterized by the interfacial shear strength(ILSS),and the feasibility of the selected electrolyte for cyclic voltammetry was verified.The results show that the optimal electrolyte system obtained by CV method is an organic composite electrolyte composed of ethylene glycol,urea,NH4HSO4.This electrolyte system can effectively improve the surface activity of the fiber.The CV surface treatment of M55J grade CF was performed at a scanning speed of 200 mv·s-1,and the oxygen content of the CF surface increases from 4.97 at.%to 18.36 at.%,and the nitrogen content increases from 0.22 at.%to 6.2 at.%.The presence of water helps to increase the oxygen-containing functional group of CF surface,and the oxygen-containing functional group can react with the amino group of urea and the ammonium ion in the solution to form a C-N bond on the CF surface.The mechanism of CF surface nitridation:from the anidation of functional groups to nitrogen oxides,then to the conversion of pyridine,pyrrole,and finally to the nitrogen bond structure of graphitized nitrogen.The M50J grade and M55J grade CF are subjected to constant current oxidation treatment at a reaction temperature of 50?,a solution water content of 50%,and a current density of 2 mA·cm-2,respectively.The ILSS of M50J grade CF/epoxy 6101 is increased by 51%compared with untreated,and the ILSS of M55J grade CF/epoxy 6101 is increased by 132%compared whit untreated.At the same time,the strength and the modulus of CF do not decrease.