Morphological and microstructural evolution of mesophase-pitch-based carbon-fiber-reinforced carbon matrix composite under Ar ions irradiation

[Display omitted] •Ar-ion irradiation induced amorphization and surface morphology changes in both the carbon fiber and matrix, with the matrix exhibiting more pronounced volumetric shrinkage compared to the fiber.•Ar-ion irradiation resulted in the degradation of the ordered graphite layers and closure of the initial cracks within the fiber and matrix.•The matrix contained a greater number of initial cracks and crack closure was more pronounced during irradiation compared to the fiber.•The differential shrinkage observed between the fiber and matrix is primarily attributed to the differences in the irradiation-induced closure behavior of the initial cracks in each component. Carbon/carbon (C/C) composites are critical structural materials for advanced reactors, including molten salt reactors. However, the irradiation mechanisms, particularly the differences in irradiation-induced damage between fibers and matrices, remain inadequately understood. In this study, the irradiation behavior of mesophase-pitch-based carbon-fiber-reinforced carbon matrix composites was investigated under 1.8-MeV Ar-ion irradiation at a dose of 3 × 1016 ions/cm2 at room temperature. Following irradiation, both the carbon fiber and matrix underwent amorphization and exhibited significant changes in surface morphology, the matrix exhibiting pronounced volumetric shrinkage compared to the fiber. Additionally, irradiation resulted in the degradation of the ordered graphite layers and closure of the initial cracks within the fiber and matrix. Notably, the matrix contained a greater number of initial cracks and crack closure was more pronounced during irradiation compared to the fiber. The differential shrinkage observed between the fiber and matrix is primarily attributed to the differences in the irradiation-induced closure behavior of the initial cracks in each component. These findings provide insights into enhancing the irradiation performance of C/C composites by adjusting the microstructural composition of the fiber and matrix.