邓海金 孙立 李明
北京清华大学 材料科学与工程系

摘要：
对不同温度石墨化处理得到的碳/碳复合材料的磁电阻特性进行了研究。结果表明1) 实验材料出现最大磁电阻的位向均为45°/135°，碳/碳复合材料磁电阻-位向关系不受石墨化处理温度、外磁场强度、测量温度等因素的影响。2）在同一磁场强度情况下，样品磁电阻与测量温度（5－300K）呈线性关系变化，温度越高磁电阻越低。并且较低石墨化温度处理样品在一定温度以上磁电阻降低为0，不再变化；2880℃石墨化处理样品在一定温度以下出?quot;磁阻饱和值"。3）磁电阻-测量温度曲线回归方程的斜率项随热处理温度的增加而降低，而截距项随热处理温度的增加而增加。4）测量温度相同时，磁电阻随外加磁场强度的增大而增大，在低场（小于1.2Tesla）下，呈现二次函数关系，场强高于1.2Tesla后，磁电阻-磁场强度关系为线性。不同磁场强度下，随石墨化处理温度的提高，磁电阻也增大。

关键词： 碳/碳复合材料，磁电阻，石墨化

Abstract:
The characteristic of magnetoresistance of C/C composites graphitized in different HTT was investigated in this paper. The magnetoresistance of C/C composites varies with the orientation (0-90°) angles, and the maximal magneto -resistance presents at 45°for all samples. HTT, the intensity of magnetic field (H) and measured temperature (MT) don't change the shape of magnetoresistance - orientation curves. Magnetoresistance - temperature curves are linear in the same magnetic field. Higher MT, less magnetoresistance. The magnetoresistance of samples in lower HTT is ziro in case of enough high MT; but the magnetoresistance of sample in the maximal HTT is saturated when MT is enough low. Regressing magnetoresistance - temperature curves, the slope falls and the intercept increases with HTT increasing. The magnetoresistance of C/C composites increases with increasing the intensity of magnetic field in the same MT. The curves are parabola when H is less than 1.2T and the curves are straight when H is higher than 1.2T. Magnetoresistance increases with increasing HTT in any intensity of magnetic field.

Keywords: C/C composite, magnetoresistance, graphitization,