CLVD快速致密C/C复合材料的高温热物理性能

High temperature thermophysical properties of carbon/carbon composites prepared by chemical liquid-vapor deposition

以聚丙烯腈预氧丝整体毡为增强体,采用快速液气相沉积联合沥青浸渍-炭化增密制备高速列车用C/C复合制动材料。研究了所制材料在30℃～800℃时的热扩散率、比热容、导热系数等热物理性能。研究发现:随温度升高,C/C复合材料平行于纤维叠层方向和垂直于纤维叠层方向的热扩散率均呈非线性降低,而比热容呈非线性增大。材料的导热性能表现出明显的各向异性,平行纤维叠层方向的导热系数先升后降,在200℃时出现极大值186.7W.m-.1K-1,是垂直于纤维方向导热系数的5.8倍。而垂直于纤维叠层方向的导热系数表现平稳。通过Wiedmann-Franz比值的分析,认为所制C/C复合材料在低温区以声子导热为主,高温区以电子导热为主。采用本制备工艺可获得导热性能优良的C/C复合材料。

To reduce the cost and shorten the production time of carbon/carbon（C/C）composites for high speed train brakes,C/C composites were prepared from preforms made of polyacrylonitrile-based preoxidized fibers.They were densified by rapid chemical liquid-vapor infiltration followed by cycles of impregnation-carbonization and graphitization at 2300℃.Thermophysical properties of the composites at temperatures from 30 to 800℃ were investigated.Results showed that the thermal diffusivities of the C/C composites decreased nonlinearly with temperature both in parallel（X-Y）and perpendicular（Z）directions to the side of the preforms,while the specific heat increased nonlinearly with temperature.The thermal conductivity was anisotropic.In the X-Y direction it exhibited a maximum value of 186.7W·m^-1·K^-1 at 200℃,but in the Z direction it remained almost unchanged with temperature.The maximum thermal conductivity in the X-Y direction was 5.8 times higher than in the Z direction.It was found by analyzing the Wiedemann-Franz ratio that thermal conduction in the C/C composites might be dominated by phonons at low temperature and by electrons at high temperature.