Microstructure and fabrication of C/C composites at super-short gas residence time

The infiltration of 2D-needle bundle fiber preforms was studied by the novel isothermal chemical vapor infiltration technique (ICVI), natural gas as the carbon source gas, no diluent gas, at 1100°C and absolute pressure 10kPa with gas residence time of 0.01, 0.02, 0.03s, respectively. The densification rules were analyzed by densification rate and radial-direction density distribution with different residence time. The textures of samples were observed by polarized light microscopy (PLM) and scanning electron microscopy (SEM). The results show that 2D preform can be densified from inside to outside at 1100°C for 150h, with gas residence time 0.01s, the C/C composites have a higher bulk density of 1.75g/cm³. Simultaneously, the micrographs show that the double-layer textures of the pyrocarbon change from medium-textured (MT) to high-textured (HT), only lower 2μm thickness MT on the fiber surface.