液相汽化TG-CVI法制备C/C复合材料的组织和性能

Liquid Phase Vaporization TG-CVI Method Prepared C/C Composites:Microstructure and Properties

为了提高C/C复合材料的致密化速率,本研究以环己烷为碳源前驱体、普通碳毡为预制体,设计了前驱体蒸发与热解碳沉积一体的沉积装置。采用液相汽化TG-CVI法快速制备C/C复合材料,并对复合材料进行2000℃下保温2 h的高温热处理。采用偏光显微镜(PLM)、扫描电子显微镜(SEM)、X射线衍射(XRD)仪表征了复合材料的显微组织、断口形貌、物相结构及晶化程度,并采用万能试验机测试复合材料的抗弯强度。结果表明,初始密度为0.14 g/cm^3的环形预制体在温度为1000℃及压力为20 kPa下沉积20 h后,其平均密度可达1.65 g/cm^3;液相汽化TG-CVI的致密化速率为0.0755 g·cm^-3·h^-1,较传统ICVI提高了近一个数量级;复合材料的组织均为粗糙层热解碳,弯曲强度约为63.24 MPa,断裂形式为假塑性断裂。复合材料经2000℃下2 h热处理后,C(002)层间距显著减小,微晶由乱层结构向理想石墨转化,具有较高的石墨化度。

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 2000℃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/cm^3 can attain the average density of 1.65 g/cm^3 after 20 h long experience under 1000℃and 20 kPa.A 0.0755 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 2000℃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.