PAN基碳纤维高温环境下成分结构的温度场效应

Temperature condition effect of composition and structure of PAN-based carbon fibers

采用元素分析、XRD和Raman测试方法从成分含量、聚集态结构和碳化学结构等方面研究了梯度升温方式制备的聚丙烯腈(PAN)基石墨纤维的成分结构演变规律及梯度升温和一步升温方式对纤维成分结构影响。结果发现:在梯度加热处理进程中,纤维中杂元素逐渐脱除,碳原子不断富集重排,1900℃以后纤维中氮元素含量基本不变,碳元素含量保持在很高水平,d002逐渐减小,La、Lc和π逐渐增大,G峰渐强、D峰渐弱。1700℃一步加热法纤维中杂元素含量稍低,碳含量稍高;1500℃加热初级结构的形成,使得梯度升温法纤维的La100和π较大。1900℃两种不同加热方式下纤维中元素含量基本一致,但一步加热方式下样品的Lc较大、样品的石墨化程度较高。

The evolution of element content,aggregation structure and chemical structure of PAN-based carbon fibers treated with step heating was investigated.The effect of heating conditions on composition and structure of the fibers was also studied.Results showed that,during the process of step heating,non-carbon element contents decreased and carbon element content increased,and the element contents were constant after 1900℃.The XRD datum of fibers treated with step heating indicated that,with the high temperature heat treatment,the d002 decreased,and the La,Lc andπincreased.La increased fastest 1500~1700℃and Lc increased fastest 1900~2100℃.The analyses of Raman spectroscopy showed that,the intensities of D band and G band were increased.Compared the fibers treated with step heating and conventional heating at1700℃,the noncarbon elements contents of the fibers which were treated by conventional heating were fewer than the fibers treated by that technic,and the carbon element content was high at the same time.However,because of the primary structure which formed at 1500℃,the graphite crystallite size and orientation degree of the fibers which were treated by step heating at 1700℃.There were only a little differences between the graphitization degrees of the fibers which were treated by the tow technics at 1700℃.Compared the fibers treated with step heating and conventional heating at 1900℃,the elements contents were similar.However,the thicknesses of graphite crystallite of fibers treated with conventional heating conditions were thicker than step heatings＇.The graphitization degree of the sample which was treated with conventional heating at 1900℃ was higher than step heating＇s.