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通过全谱拟合法对碳纤维制备过程中不同阶段纤维的XRD谱图进行处理,得到不同阶段纤维的微观结构参数,研究了聚丙烯腈(PAN)基碳纤维制备过程中晶态结构的演变.全谱拟合法基于晶体衍射的严格物理理论,拟合目标为整个衍射谱,并不是个别衍射峰,所得结果具有更高的可信度.研究结果表明:PAN原丝中的高分子链沿纤维轴高度取向,表观晶粒尺寸为6.5nm左右;经过预氧化处理,纤维中的有序结构遭到破坏,表观晶粒尺寸锐减.纤维中逐渐形成梯形结构并沿纤维轴取向,从而形成新的有序结构;经过碳化处理后,环状梯形结构转变为碳的层状结构,层状结构沿纤维轴取向形成X射线衍射中的衍射域,表现为表观晶粒尺寸.随着碳化温度的提高,层状结构在垂直纤维轴方向的尺寸明显增加,沿纤维轴方向的取向提高,层状结构排列规整度提高.
The full-spectrum fitting method was used to process the XRD spectra of the fibers during different stages of carbon fiber preparation, and the microstructure parameters of the fibers at different stages were obtained. The evolution of the crystalline structure during the preparation of polyacrylonitrile (PAN) -based carbon fibers was investigated. Fitting method based on the strict physics of crystal diffraction theory, the fitting target for the entire diffraction spectrum, not individual diffraction peak, the results obtained with higher confidence. The results show that: PAN raw fiber in the polymer along the fiber axis height Orientation, the apparent grain size of about 6.5nm; after pre-oxidation treatment, the ordered structure in the fiber is destroyed, the apparent grain size sharply reduced.Fibers gradually form a trapezoidal structure and orientation along the fiber axis, thus forming a new Of the ordered structure; after carbonization, the annular trapezoidal structure into a carbon layer structure, the layered structure along the fiber axis to form X-ray diffraction diffraction domain, showing the apparent grain size with the carbonization temperature The size of the layered structure in the direction of the vertical fiber axis is significantly increased, the orientation along the fiber axis is increased, and the arrangement regularity of the layered structure is improved.