Effect of anodic oxidation on the properties of Ni-coated carbon fibers produced by electrodeposition

PAN-based carbon fibers were continuously treated by anodic oxidation followed by electrodeposition of Ni on their surface. The influence of anodic oxidation on mechanical properties, surface morphology, amount of surface acidic groups and growth mode of the Ni coating were studied by SEM, XRD, TG and conductometric titration. Results showed that the total amount of surface acidic groups on the oxidized carbon fibers is about 10 times as large as that of the untreated ones and the tensile strength of carbon fibers decreased slowly at first and then quickly with increasing depth of oxidation. The growth mode of the Ni coating changed from a Volmer-Weber mode to a Frank-van der Merwe mode and the grain size of the Ni coating decreased from 14.5 to 11.2 nm for the untreated and treated carbon fibers respectively. The oxidation resistance of the carbon fibers was improved by the Ni coating. The initial oxidation temperature of the Ni-coated treated-carbon fibers with anodic oxidation is about 50 degrees C higher than that of the Ni-coated carbon fibers without the oxidation. Appropriate oxidation could improve the adhesion between the Ni coating and the carbon fibers.