高强度、高模量聚丙烯腈基碳纤维的微晶取向研究

Microstructure of high tensile strength and high tensile modulus PAN-based carbon fibers determined by X-ray diffraction

用X射线衍射研究了高强度(T系列)与高模量(M系列)聚丙烯腈基碳纤维的微观结构,结果表明两类碳纤维具有不同的结构特征:(1)高模量碳纤维的晶胞尺寸较接近于石墨结构;(2)高模量碳纤维的晶粒尺寸和取向度大于高强度碳纤维;(3)高模量碳纤维的二维层状堆砌比高强度碳纤维排列规整,并存在两种不同晶胞尺寸的六方晶系石墨结构。取向度增大,使晶粒尺寸增大,层状堆砌趋于规整,有利于提高拉伸模量。存在适度的层状紊乱堆砌和不完善微晶以及缺陷,有利于提高拉伸强度。

The microstructures of high tensile strength and high tensile modulus polyacrylonitrile-based carbon fibers were investigated by X-ray diffraction.The results indicated the following different structural characteristics between the two fibers：（1） the microcrystals in high modulus carbon fibers were more graphitic;（2） the crystallite size and orientation degree of high modulus carbon fibers were larger than that of the high strength carbon fibers;（3） the two dimensional layer stack of high modulus carbon fibers were more ordered than that of the high strength carbon fibers;（4） the high modulus carbon fibers developed to the orderly three-dimension structure or possibly had an existence of three-dimension graphite structure and another hexagonal crystallite graphite structure.The high orientation degree,large crystal dimension and orderly layer stack were beneficial to the increase of tensile modulus;at the same time the appropriate disorder stack of the layer,paracrystal and faults were favorable to increase the tensile strength of the carbon fibers.