中间相沥青碳纤维径向辐射结构形成机理研究

The study on formation mechanism of radial structure of mesophase pitch-based carbon fibers

中间相沥青碳纤维(MPCF)由于沥青分子沿轴向高度取向,其径向结构容易呈现辐射状态。为研究辐射形成机理,研究了相同的不熔化沥青纤维在不同炭化温度下得到的中间相沥青碳纤维的径向结构。通过SEM,DSC,XRD,FT-IR以及强度测试表征发现,在不熔化纤维和较低炭化温度得到的碳纤维内部沥青分子通过含氧官能团交联,结构致密,辐射状结构不明显。随着炭化温度的升高,碳纤维内部含氧官能团分解,在600℃时纤维内部沥青分子发生芳构化、环化等反应,芳香平面分子连接构成碳网面。温度继续升高,碳网面逐渐堆积,微晶结构优化,形成条带状的辐射结构,当炭化温度达到900℃时碳纤维内部形成完全的层状条带结构。受到碳网面的收缩应力作用,这一过程中始终伴随纤维直径的收缩和辐射结构的强化。

Mesophase pitch-based carbon fibers（MPCF）always show radial texture because of their high orientation degree. To study the formation of the radial structure, oxidative fibers of the same passel were carbonized at different temperature. SEM, DSC, XRD, FF-IR, and tensile strength test were used to find out the mechanism of the process. The results indicated that the radial structure inside the oxygenized fiber and carbon fiber carbonized at lower temperature was not obvious under low carbonization temperature because the pitch molecules were cross-linked through oxygen functional groups. The oxygen functional groups decomposed accompanied with the increment of temperature. The aromatization and cyclization reactions of pitch molecular happened and the aromatic planes formed carbon meshes at 600℃, which resulted in the formation of the radial structure. A complete coiled sheet structure inside the fiber forms at 900℃. The constriction of the fibers was accompanied with the carbonization process because of the contraction stress of carbon meshes.