C/C复合材料石墨化度与导电性能的关系

研究了五种具有二维及准二维结构的炭/炭复合材料在不同石墨化度下各自的电阻率的变化，分析了引起这些变化的原因。结果表明，在所研究的石墨化度范围内，随着石墨化度的升高，材料的电阻率都呈下降的趋势，且电阻率ρ随石墨化度g的变化符合线性关系ρ=a*g+b，线性相关系数的绝对值大于99?%。但对于不同的材料，公式中参数a、b的取值不同。影响a、b值大小的因素主要有复合材料的结构和表观密度：具有类似结构的两种复合材料，两者的a值相等；复合材料的表观密度越高，则其a的绝对值、b值越小，亦即：在石墨化度相同时，表观密度较高的材料导电性能较好；由于石墨化度的升高对其导电性能的提高较少，故导电性能对石墨化度的敏感程度较低。同时认为，由于电阻率测量的较高准确度和易操作性，电阻率可以作为一种间接测量和表征炭/炭复合材料石墨化程度的方法。

Five kinds of C/C composites were selected as object materials to investigate the electrical resistivity dependence on graphitization degree. The effecting factors were analyzed and summarized. Experimental results showed a tendency that the electrical resistivity of all C/C composites decreased linearly with the increase of graphitization degree, and their relation can be written into the following equation of ρ=ag+b. Such relation is valid at least in the whole range of graphitization degree investigated. It should be ponited out that the parameters of a and b have different values for various materials and they are controlled by microstructure and apparent density. For composites with similar microstructures, parameter a is equal. The composites with higher apparent density always have lower values for parameters a and b. It implies that their electrical conductivity can be improved. The electrical conductivity of the composites is less sensitive to the graphitization degree, as compared with the apparent density. Because of the relatively high accuracy and easier operation for detecting, electrical resistivity can be used as an indirect index to reflect the graphitization degree of C/C composites.