Improvement of film boiling chemical vapor infiltration process for fabrication of large size C/C composite

An improved film boiling chemical vapor infiltration process was developed to fabricate a large size C/C composite with homogeneous density and microstructure. The C/C composite was prepared by processing a disc-shaped carbon felt preform, whose upper and lower sides were fixed and heated simultaneously by two flat surfaces of two heat sources, with kerosene as a precursor at 1050 °C for 3 h at an atmospheric pressure. The in-situ temperature distribution along the radial direction of the preform upper surface was analyzed to get better information and control of the process. Experimental results show that the average density of the composite of Φ 110 × 10 mm³ size is about 1.72 g/cm³ and its maximal difference along radial direction is 0.05 g/cm³. Polarized light microscopy (PLM) and scanning electron microscopy (SEM) reveal that the carbon fibers of the composite are surrounded by ring-shaped pyrocarbons with a thickness of ∼ 20 μm, and that pyrocarbons are delaminated to 4-6 layers. A schematic model is proposed to analyze the process by dividing the reactor into different regions associated with specific functions.