JI Genshun1,2, CHEN Xiaolong1,2, JIA Jiangang1,2, LI Xiaolong1, GONG Jingbo1, HAO Xiangzhong3
1 State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals,Lanzhou University of Technology,Lanzhou 730050,China 2 Baiyin Research Institute of Novel Materials,Lanzhou University of Technology,Baiyin 730900,China 3 Technology Center of Gansu Haoshi Carbon Fiber Co.Ltd,Lanzhou 730010,China
Abstract: For the sake of improving the densification rate of C/C composites, a reaction device combining precursor evaporation and pyrolytic carbon deposition was designed, taking cyclohexane as the carbon source precursor and carbon felt as the preform. Rapid preparation of the C/C composites was implemented by liquid phase vaporization TG-CVI and followed by heat treatment on the C/C composites at 2 000 ℃ for 2 h. Polarized light microscopy (PLM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to characterize the microstructure, fracture morphology, phase structure and crystallization degree of the C/C composites. Further, the bending strength of the C/C composites was measured by universal testing machine. According to the results, the annular preform with initial density of 0.14 g/cm3 can attain the average density of 1.65 g/cm3 after 20 h long experience under 1 000 ℃ and 20 kPa. A 0.075 5 g·cm-3·h-1 densification rate of liquid phase vaporization TG-CVI was achieved, which was nearly an order of magnitude higher than that of conventional ICVI. Rough layer carbon pyrolytic constituted the structure of the C/C composites, and the C/C composites presented a bending strength of about 63.24 MPa, and pseudo-plastic fracture. Undergoing heat treatment at 2 000 ℃ for 2 h, there were a phenomenal narrowing in the C(002) plane space, a converting of crystallites structure from chaotic graphite to ideal graphite crystal, and a considerable degree of graphitization in the C/C composites.
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