石墨化过程中元素铁对PAN基碳纤维成分及结构的影响

Effect of iron on the evolution of the structure and composition of polyacrylonitrile based carbon fibers during graphitization

运用EA、Raman和XRD等方法分别研究了PAN基碳纤维石墨化过程中非结构型成分铁对碳纤维中C、N、H等结构型成分、化学结构和聚集态结构的影响,探讨了碳纤维成分变化与结构演变的关联关系。研究表明,元素铁对碳纤维中N元素的逸出具有较强的催化作用,碳纤维中C元素含量由于N元素被催化脱除而提高的更快;元素铁催化脱氮减少了碳纤维结构重排中的能耗,从而有利于碳纤维中的乱层结构碳向石墨结构碳的转变;同时,元素铁促进石墨片层基面宽度(La)增长;由于N元素沿纤维径向地逸出,元素铁催化脱氮产生的气胀作用力阻碍石墨片层的堆叠,因此铁对石墨片层层间距(d002)几无影响,层间距的发展主要体现温度效应。

The effect of elemental iron on the composition of carbon, nitrogen and hydrogen of polyacrylonitrile（PAN） based carbon fibers during graphitization was investigated by means of elemental analysis, Raman spectroscopy, and X-ray diffraction （XRD）. The relationship between the constituent element nitrogen and dopant iron and the structural evolution of the PAN based carbon fibers is discussed. The results suggest that iron shows a high catalytic activity for the removal of nitrogen during graphitization, resulting in a higher content of carbon and higher degree of early structural order in the fibers. The effect of catalytic denitrification may reduce the activation energy for the growth of graphite layers, and thus catalyze the transformation of thermodynamically unstable carbon into graphite. The presence of iron promotes evolution of gaseous nitrogen by catalytic denitrification which enhances the growth of crystallite size （La ） but has a negligible effect on the interlayer spacing （d002 ） .