Investigation of surface properties of pristine and γ-irradiated PAN-based carbon fibers: Effects of fiber instinct structure and radiation medium

Highlights: • T300, T400, T700, T800 and T1000 were irradiated in argon atmosphere and epoxy chloropropane. • The graphitization changes after irradiation were determined by the instinct structure of CFs. • Specific surface areas of T300, T400 and T800 were changed clearly, while those of T700 and T1000 remained almost unchanged after irradiation. • The surface chemistry change after irradiation was determined by the type of the irradiation medium. • CFs irradiated in ECP had higher surface free energy compared with CFs irradiated in Ar. - Abstract: The different rules for γ-ray modifications of carbon fiber (CF) surface were found in previous literature, and the contributing factors were not clear. To investigate the effects of fiber instinct structure and radiation medium on surface modification of CFs in γ-ray irradiation, argon atmosphere (Ar) and epoxy chloropropane (ECP) were chosen as the irradiation media for T300, T400, T700, T800 and T1000, respectively. Based on the Raman spectroscopy and specific surface area results, changes of surface graphitization and roughness depended on the fiber instinct structure after irradiation. The graphitization of T300, T400 and T800 with low graphitization and rough surface was increased after irradiation, while that of T700 and T1000 with high graphite degree and smooth surface was decreased. Specific surface areas of low-graphitization CFs (T300, T400 and T800) were changed clearly, while those of high-graphitization CFs (T700 and T1000) remained almost unchanged after irradiation. X-ray photoelectron spectroscopy provided the evidence that the surface chemistry change after irradiation was determined by the type of the irradiation medium. The oxygen ratio of CFs irradiated in Ar was decreased while that of CFs irradiated in ECP was increased with Cl element detected. Surface free energy of all CFs was improved obviously after irradiation, and CFs irradiated in ECP had higher surface free energy compared with CFs irradiated in Ar