PAN基碳纤维制备过程中微孔结构的形成与转变

Micropore Structure Formation and Transformation of PAN-based Carbon Fiber During Preparation

利用扫描电镜(SEM)、小角X射线散射(SAXS)对PAN基碳纤维制备过程中不同阶段纤维的表面形貌、微孔结构进行了测试,计算了PAN基碳纤维制备过程中不同阶段微孔的大小、各微孔占总微孔的体积分数、微孔的平均尺寸及表面的分形维数,分析了碳纤维的微孔结构在制备过程中的形成与转变。结果表明,原丝内部微孔的平均尺寸较大,预氧化过程中、后期,纤维内部微孔的平均尺寸及各相微孔的体积分数都发生了较大变化。低温碳化后,纤维中微孔的平均尺寸减小,且大孔洞的体积分数增大。高温碳化后,微孔的平均尺寸进一步减小,大孔的体积分数增大。原丝的微孔表面比较粗糙,在预氧化过程中微孔表面的分形维数减小。低温碳化后,微孔表面的分形维数增加。高温碳化后,微孔的形状由曲面转变为曲线。

The surface morphology,micropore structure of PAN-based carbon fibers of various stages during its preparation process were investigated by means of scanning electron microscopy （SEM）,small-angle X-ray scattering （SAXS）.The size of micropore,volume percentage of each phase micropore,average size of micropore and surface fractal dimension of micropore in various stages of PAN-based Cf preparation were calculated respectively.The formation and transformation of micropore structure during preparation process were analyzed.Results showed that the average micropore size of precursor is bigger,average micropore size and volume percentage of each phase micropore change greatly in late preoxidation process.The average micropore size decreases continually after low-temperature carbonization and high-temperature carbonization,while the relative percentage of big micropore keeps increasing.The surface of precursor is comparatively rough.The surface fractal dimension of micropore reduces in the preoxidation then increases after low-temperature carbonization.Micropore shape converts from curved surface to curve after low-temperature carbonization.