Abstract: The changes of preferred orientation of PAN-based carbon fibers during continuous high temperature graphitization and hot stretching graphitization were investigated by X-ray diffraction (XRD). The results showed that the degree of preferred orientation within PAN-based carbon fibers increased with the increasing heat treatment temperature (HTT) and the ratio of hot stretching，respectively. Both in high temperature graphitization and in hot stretching graphitization the fiber’s tensile modulus increased with increasing preferred orientation，but the values of preferred orientation (Z) determined by XRD were different for the same value of modulus. The relationship between microstructure and modulus showed that tensile modulus did not only depend on the preferred orientation，but also related to the crystallite size. In addition，even after heat treated to 3 000 ℃，the fiber’s preferred orientation (Z) was only 14.71°，indicating the fiber’s turbostratic layers were still not highly aligned.

摘要： 利用XRD研究了PAN基碳纤维在连续高温石墨化和热牵伸石墨化过程中纤维内石墨微晶沿纤维轴择优取向性的变化。结果表明：碳纤维中石墨微晶的择优取向性随石墨化温度的提高和热牵伸的增大而增加。两种工艺中纤维的拉伸模量均随微晶取向性的增加而增大，但在获得相同的模量下其取向参数却不同；碳纤维的拉伸模量不仅仅取决于石墨微晶的择优取向，而且与晶体的大小有关。另外，经过3000℃的高温处理后，纤维的择优取向参数Z仅为14.71°，说明纤维中乱层石墨的层面仍没有高度取向。