Influence of boron on the graphitization of carbon fibers prepared by boron-modified polyacrylonitrile gel fibers
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摘要: 对聚丙烯腈凝胶纤维进行渗硼处理所制炭纤维在1 600~2 400℃进行石墨化热处理，利用电感耦合等离子体光谱仪、扫描电子显微镜、能谱仪、X射线光电子能谱仪、X射线衍射仪和万能力学测试机对石墨纤维进行表征，研究了硼对其结构及性能的影响。结果表明，在石墨化温度范围内，随着温度的升高，炭纤维中的硼含量逐渐降低。硼在石墨化过程中以取代的方式进入到碳网内并在其中进行扩散，但因炭纤维中硼含量较低，其并未对微晶尺寸的生长产生影响，而明显提高了取向度，导致炭纤维的杨氏模量提高的同时，其拉升强度的降幅也显著降低。在达到相同模量的情况下，含硼炭纤维的石墨化温度可降低200℃。Abstract: Carbon fibers prepared from boron-doped polyacrylonitrile gel fibers were graphitized at 1600~2400℃, and the graphitized fibers were characterized by inductively coupled plasma atomic emission spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and mechanical tests to investigate the influence of boron on their microstructures and properties. The results showed that the boron content in the carbon fibers decreased with increasing heat treatment temperature. Boron occupied substitutional sites in carbon network and moved by diffusion during graphitization. The development of crystallite size was not affected but the orientation of the fibers was significantly improved by the low boron content in the fibers, which made the Young's modulus increase substantially and the loss of tensile strength was reduced. The graphitizing temperature of the boron-doped carbon fibers was lowered by 200℃ in order to prepare samples with the same Young's modulus.
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