电化学表面处理对碳纤维结构及性能的影响

Effect of the process of electrochemical modification on the surface structure and properties of PAN-based carbon fibers

采用新型电化学表面处理设备,以10%(质量分数)NH4HCO3溶液为电解质,对12KPAN基碳纤维进行连续化的表面处理,探索了在提高碳纤维/树脂复合材料层间剪切强度的同时降低碳纤维本征拉伸强度损失的结构变化特征及规律。利用SEM、XRD、XPS、Raman等方法研究了改性前后碳纤维表面的物理和化学状态、晶体尺寸和表面有序度。结果显示,在适当的条件下,碳纤维/树脂复合材料的层间剪切强度提高了23.3%,同时碳纤维的拉伸强度仅损失了4.4%。碳纤维/树脂复合材料层间剪切强度的提高是碳纤维表面粗糙度和表面含氧、含氮官能团共同作用的结果。表面处理后碳纤维石墨网片层尺寸减小了6.3%～27.6%,微晶尺寸相应减小;适度的氧化刻蚀使碳纤维表面有序度略有提高,并且产生新的活性点;以上两种作用减小了碳纤维的本征拉伸强度的损失量。

The PAN-based carbon fiber（CF）bundles with 12K were treated continuously by a new equipment of electrochemical modification in 10%（mass fraction） NH4HCO3 electrolyte solution to improve its interfacial bounding strength without compromising the tensile strength simultaneously.SEM,XRD,XPS and Raman spectra were employed to characterize the morphology,chemical states,crystallites size and ordered degree of the CF surface.The results indicate that the interlaminar shear strength（ILSS）of CF/resin composites increases by 23.3% while its tensile strength only decreases by 4.4% under the optimal modified condition.The improvement of interlaminar shear strength causes not only by the increase of surface roughness,but also by the interaction effects of oxygen-containing and nitrogen-containing functional groups on CFs.After electrochemical oxidation the crystallites size decreases by 6.3%~27.6%,and the ordered degree on CF surface increases with the suitable etching which does not peel off the ordered region on the CF surface and creates new cracks;both above reduce the loss of tensile strength.