高导热炭纤维改性C/C复合材料的微观结构、力学与导热性能研究

Micro-structure, mechanical and thermal conductivity properties ofC/C composites modified with high thermal conductivity carbon fibers

以中间相沥青基炭纤维为增强相,热解炭与树脂炭为基体,采用化学气相沉积与液相浸渍-炭化补充增密工艺制备了高导热炭纤维改性C/C复合材料,研究了不同热处理温度(2 000和3 000℃)材料的微观结构、力学与导热性能。结果表明,经2 000℃处理后,高导热炭纤维与热解炭结构变化不明显,且热解炭与炭纤维界面结合紧密,结合处未形成裂纹等缺陷;当热处理温度提升至3 000℃时,高导热炭纤维与热解炭石墨化度明显升高,且炭纤维与热解炭的界面结合处均产生了较明显的微裂纹缺陷。高导热炭纤维改性C/C复合材料经2 000℃处理后,其弯曲强度与室温热导率分别为101.81 MPa和14.739 W/m·K;当热处理温度升高至3 000℃时,材料的弯曲强度降低为49.35 MPa,热导率提升为63.568 W/m·K。材料弯曲强度的降低与热导率的增加主要与3 000℃处理后,材料内各炭相的石墨化度提升有关。

Using mesophase pitch based carbon fibers(CF MP)as reinforcement and pyrolytic carbon(PyC)and resin carbon as matrix,high thermal conductivity carbon fiber modified carbon/carbon(C/C)composites were prepared by chemical vapor deposition and liquid phase impregnation process.The micro-structure,mechanical and thermal conductivity properties of the modified C/C composites that heat treated at different temperature(2000 and 3000℃)were investigated.The results show that the structure of CF MP and PyC is not changed obviously after 2000℃heat treatment,and the interface between PyC and carbon fiber is tightly bonded,with fewer micro-cracks observed at the interface.However,after 3000℃heat treatment,the graphitization degree of CF MP and PyC increases significantly,meanwhile,obvious micro-cracks are formed at the interface between CF MP and PyC.With 2000℃heat treatment,the average flexural strength and thermal conductivity of the modified C/C composites are 101.81 MPa and14.739 W/m·K,respectively.However,after 3000℃heat treatment,the average flexural strength is declined to 49.35 MPa,whereas the thermal conductivity is enhanced to 63.568 W/m·K.The declined flexural strength and enhanced thermal conductivity are mainly associated with the increased graphitization degree of different carbon phases after 3000℃heat treatment.