沥青基碳纤维的显微结构

各向同性沥青基碳纤维在结构上存在着不均匀性,既存在着有序排列程度较高的晶区,又存在着有序程度较低的非晶区。晶区由无规取向的片状微晶组成,微晶之间相互缠绕,并通过分叉形成网状结构。由发展不充分的微晶或无定形碳组成的非晶区镶嵌在微晶之间的“网眼”中。微晶的尺寸及有序化程度随着热处理温度的升高而增加。微晶大多存在着不同程度的弯曲或畸变,而弯曲或变畸的程度是由微晶中碳片层的大小及错排情况决定的。片层的错排分为两类,一类是若干片层在同一部位发生错排,从而构成亚晶界;另一类是片层错排混乱地分布在微晶中的不同部位,它导致微晶有序化程度的降低。

MICROSTRUCTURE OF PITCH-BASED CARBON FIBERS

Isotropic pitch-based carbon fibers have a structural heterogeneity.Two phasewere distinguished,viz.crystalline graphite phase and amorphous carbon phase.Crystallinegraphite phase is made of sheet-like,randomly preferred crystallites which loosely entangle andform network structure.The amorphous carbon phase which consists of poorly developedcrystallites,single carbon layers and amorphous carbon is inlayed among the crystallites.Thepacking size and order of crystallites are enhanced with the increase of heat treatment tempera-ture.The crystallites are severely distorted.The degree of distortion depends on the size andstacking of carbon layers.There are two types of fault stacking of carbon layers.One is thatfault stackings of carbon layers take place at one place,which forms the sub-grain boundaries.The other is that fault stackings of carbon layers distribute randomly in the different parts of thecrystallite,which leads to a decreasing of order of the crystallite.