Enhanced graphitization and reduced radial heterogeneity of carbon fibers inheriting from irradiated/thermo-chemically stabilized PAN-fibers

The cross-section of carbon fibers (CFs) possessed radial heterostructure, which restricted its mechanical properties. In this paper, heating and γ-irradiation were integrated during PAN fibers stabilization process to improve the radial structure of CFs. The synergy between irradiation and heating during stabilization caused the decrease of ID/IG, increase of crystal size, and reduction of pore fractal dimension in whole CFs. Through Raman spectra along fibers cross-section, a radial heterogeneity was found during the whole carbonization process. The combination of γ-irradiation and heating reduced the ID/IG of core part more significantly compared to the skin part of CFs, which weakened radial heterogeneity of CFs. At the same time, it significantly enhanced the tensile strength of CFs. Subsequently, a hierarchy model with three zones containing outer-surface, sub-surface and core parts was presented to explain the evolution of tensile strength for CFs. The γ-irradiation during stabilization enhanced the structure of each part in CFs by generating more cross-linked structures. [Display omitted] •γ-irradiation in stabilization enhance tensile strength of carbon fibers (CFs).•Three-zone radial heterogeneity model for CFs.•γ-irradiation in stabilization reduce ID/IG and radial heterogeneity of CFs.•Study on micromechanics of CFs by nanoindentation.