Abstract:

M50J and M55J grade high modulus carbon fibers were prepared by using carbon fiber of self-made T800 grade polyacrylonitrile(PAN)-based high strength carbon fibers as raw material. In the conversion of high strength carbon fiber to high modulus carbon fiber, the evolution of graphite characteristic features such as microcrystallites, orientation, the relative content of micropore and graphitization degree were investigated by X-ray diffractometer (XRD) and Raman. The relationship between the graphite characteristic features and the mechanical properties of carbon fiber was also studied in detail. Results showed that with decreases in the value of interlayer spacing d ₀₀₂ and increases in the value of graphite thickness L _c, the tensile modulus of carbon fibers were significantly increased. It was also found that the interlayer spacing and crystallite orientation were two important parameters which could affect the tensile strength of high modulus carbon fiber. The tensile strength increased with increasing d ₀₀₂ value and improving crystallite orientation. In the conversion of high strength carbon fiber to high modulus carbon fiber, increased graphitization degree took place which led to decreases in voids or cavities. After high temperature graphitization, decreases in the tensile strength of carbon fiber were accompanied with decrease in the intensity ratio of disordered induced D-band to the graphite structure G-band.

Key words: polyacrylonitrile, high modulus carbon fiber, graphite structure, interlayer spacing

摘要：

以实验室自制T800级聚丙烯腈（PAN）基高强中模碳纤维为原料，经连续石墨化处理得到M50J级、M55J级高模量碳纤维，以X射线衍射（XRD）、Raman光谱为表征手段研究了高强碳纤维向高模量碳纤维转变过程中石墨微晶、取向、微孔含量、石墨化度等石墨特征结构的演变规律，并开展了PAN基碳纤维石墨特征结构与力学性能的关联性研究。研究结果表明：在高强碳纤维向高模量碳纤维转变过程中，随着石墨微晶层间距d ₀₀₂的下降以及石墨微晶堆砌厚度L _c的增加，碳纤维的拉伸模量逐渐提升；石墨微晶层间距和微晶取向是影响碳纤维拉伸强度的两个主要因素，石墨微晶层间距d ₀₀₂值增加、石墨微晶取向越高，纤维拉伸强度也越高；在高模量碳纤维的成型过程中，纤维内部微孔含量随着石墨化程度的提高而降低；经过高温石墨化处理后，碳纤维的拉伸强度会随着Raman光谱中无序结构D峰和石墨特征结构G峰积分强度比值I _D /I _G的下降而下降。

关键词: 聚丙烯腈, 高模碳纤维, 石墨结构, 层间距