Effect Of Electrochemical Oxidation On The Surface Structure And Mechanical Performance Of High Strength And High Modulus Carbon Fibers

The effect on mechanical performance of high strength and high modulusCF with anodic oxidation surface treatment in different electrolytes、currentdensity and oxidation time were discussed.The reason why the tensile strengthof carbon fiber changed after anodic oxidation surface treatment was studyedby using Laser Raman spectroscopy.And the conclusions were as follows:①Comparing to NH₄H2PO₄solution,the loss of tensile strength of CFafter surface treatment can be effectively reduced in the mixed electrolytes ofNH₄H2PO₄and CH₃COONH₄.And as CH₃COONH₄content increases,the lossof fiber strength decreases.When treated in the mixed electrolytes ofNH₄H2PO₄and CH₃COONH₄with ratio of2:1、with a current density of2mA/cm²and the processing time is30seconds, the ILSS ofCFRP increasedby168%compared to untreated fibers,and the tensile strength and modulus islittle decreased compared to the untreated fibers.②The fiber strength decrease was primarily because of the change of thecrystal structure on the fiber surface from the microscopic structure.Therelative content of SP²C hybrid atomic on the fiber surface is higher,the structure of the graphite crystallites is more perfect,and microcrystallinedefects is less.It’s good for the improvement of the fiber strength.And the fibersurface crystal structure has more influence on the fiber strength compared tothe crystallites size.③In the surface treatment,CH₃COONH₄electrolyte has a significant impactto improve the oxygen functional groups on fiber surface.When treatedin themixed electrolytes with CH₃COONH₄, the oxygen functional groups on fibersurface have significantly increased, especially the content of carbonyl andhydroxyl.