炭基体的结构对C/C复合材料导电性能的影响

采用CVI+PIC工艺制备以2D碳纤维预制体为增强体、由不同炭基体结构组成的C/C复合材料，随后在不同温度对其进行热处理得到不同石墨化度的炭基体结构，研究了PyC/ReC比值和石墨化度对材料电阻率的影响。结果表明，随着PyC/ReC比的提高低密度C/C复合材料的电阻率在27.3×10^-6~28.0×10^-6 Ω·m间基本不变，因为石墨微晶的尺寸和结构完整性的增大与材料孔隙率的提高对电阻的影响相反。随着PyC/ReC比的提高，高密度C/C复合材料的电阻率从24.9×10^-6 Ω·m降低到20.5 ×10^-6 Ω·m。其可能的原因是，材料内部的孔隙较少，孔隙率的轻微提高使阻碍载流子在导电网络中的有效传递的作用显著下降。随着热处理温度从1800℃提高到2500℃，C/C复合材料的石墨化度明显提高，电阻率明显降低，其主要原因是载流子浓度的提高和晶界散射的减弱。

Effect of Carbon Matrix Structure on Electrical Properties of C/C Composites

C/C composites with different carbon matrix structures were prepared by CVI(chemical vapor infiltration) +PIC(resin precursor impregnation cracking) process using 2D carbon fiber needle-punched preforms as reinforcement and then were heat-treated at different temperatures. The effect of PyC (pyrolysis carbon)/ReC (resin carbon) ratio and degree of graphitization on the electrical resistivity of the composites was investigated. The results show that the electrical resistivity of the C/C composites of low density remains basically unchanged in a range of 27.3×10^-6~28.0×10^-6 Ω·m with the increase of PyC/ReC, which can be mainly attributed to the opposite effect of the increase of lattice size and structural integrity of graphite microcrystals and the increase of porosity of the composites. However, the electrical resistivity of C/C composites of high density decreases from 24.9×10^-6 Ω·m to 20.5×10^-6 Ω·m with the increase of PyC/ReC ratio. Because the slight increase of the porosity has a small contribution on the difference of electrical resistivity by hindering the effective carrier transfer in the conductive network for the C/C composites of low porosity. The graphitization degree of C/C composites increases and the electrical resistivity decreases with the heat treatment temperature increased from 1800℃ to 2500℃, which can be mainly attributed to the increase of carrier concentration and the weakening of grain boundary scattering.