循环伏安法对PAN基高模碳纤维阳极氧化表面处理的研究

Study of anodic oxidation surface treatment of PAN-based high-modulus carbon fibers by cyclic voltammetry

以未表面处理的PAN基高模碳纤维(HMCF)为工作电极,分别用NH4H2PO4、NH4HCO3和KOH为电解质,进行循环伏安多重扫描,以研究HMCF在不同电解质中的电化学反应行为以及电解质的氧化能力。同时采用连续恒流阳极氧化的方法对HMCF进行表面处理,验证循环伏安法得到的结论。通过联碱滴定、SEM等方法表征处理前后纤维表面官能团、表面形貌的变化;处理前后纤维与环氧树脂界面粘接性能的变化通过层间剪切强度(ILSS)表征。循环伏安结果显示:在NH4H2PO4溶液中扫描时氧化反应峰值电流最高,表明纤维表面生成的官能团最多;在KOH溶液中扫描时平台电流最高,表明纤维表面粗糙度提高幅度最大。联碱滴定结果表明NH4H2PO4溶液处理后纤维表面官能团含量提高最多;SEM结果显示KOH溶液处理后纤维表面粗糙度增加最明显;这两点验证了循环伏安多重扫描的结果。用NH4H2PO4、KOH处理后的纤维与环氧树脂ILSS达到75MPa、60MPa,分别提高240%和170%。

Untreated PAN-based high-modulus carbon fibers（HMCF） were used as an anode and electrochemically oxidized by multi-scan cyclic voltammetry in NH4H2PO4,NH4HCO3 and KOH.The electrochemical reactivity in different electrolytes and the ability of each electrolyte to oxidize HMCF were investigated.The carbon fibers were then treated by the method of continuous constant current anodic oxidation which confirmed the conclusions of cyclic voltammetry.The chemical titration method and SEM were used to study the changes in number of functional groups and surface morphology of the carbon fibers.The adhesive properties of the carbon fiber/epoxy resin composites were characterized in terms of their interlaminar shear strength（ILSS）.Cyclic voltammetry indicated that the oxidation peak current in NH4H2PO4 solution is the highest,showing that the number of functional groups on the fiber surface is the highest in this electrolyte.The background current in KOH is higher than those in other electrolytes,revealing that the roughness of the fiber surface has undergone the greatest change.The titration results indicate that the content of surface functional groups in the fiber treated in NH4H2PO4 is larger than in those treated in the other electrolytes.SEM results demonstrate that the surface roughness of the fiber treated in KOH is the largest,which is consistent with the cyclic voltammetry data.The ILSS of fiber/epoxy resin composites,in which the fibers were treated in NH4H2PO4 and KOH,were 75 MPa and 60 MPa,respectively,corresponding to increases of 240% and 170% relative to the untreated fiber.