Irradiation induced interface modification of carbon fiber/carbon composite revealed by in-situ transmission electron microscopy

Carbon/Carbon (C/C) composites are considered as one of the most candidate materials for next generation nuclear power plant, aerospace, car and so on. Herein, the irradiation effect on the fiber and matrix interfaces of C/C composites induced by electron beam are in situ monitored by a higher of 200 kV electron microscope at room temperature, demonstrating that their finer microstructures showed two different evolutions with a strong bonding interface and a weak bonding interface, respectively. In the strong bonding interface, there is no obvious boundary between the fiber and the matrix; while in the weak bonding interface, there is a transition layer composed of amorphous materials between the fiber and the matrix. During the process of electron irradiation, the banded microcrystals at the longitudinal interface of the fibers are amorphous, the substrate surface expands and microcracks are gradually closed. It is notable that the weak bonding interface becomes contract under electron irradiation, which is similar to the phenomenon of lenticular microcracks under electron irradiation. Nano indenter experimental further illustrates the significantly enhanced mechanical properties of fiber and matrix induced by the electron irradiation. Therefore, the microporosity and its evolution induced by electron irradiation at these two interfaces of C/C composites can play a key role in developing a novel network of interpenetrating fibrils which effectively bond fiber to matrix.