In the production of polyacrylonitrile-based carbon fibers (PAN-CFs), preoxidation is a key step to improving the thermal stability of the fibers and forming their structural prototype. However, structural evaluation of PAN fibers during preoxidation remains ambiguous, partly due to a lack of in situ studies. This contribution reports an in situ study of the preoxidation of PAN fibers using wide-angle X-ray scattering and small-angle X-ray scattering techniques on a synchrotron radiation beamline. The structural changes of the skeleton and pores in the fibers are revealed and correspond to five kinds of diffraction spots (peaks) and two kinds of scattering streaks, respectively. The preoxidation shows obvious stages, and the corresponding possible mechanism is analyzed.

中文翻译：

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聚丙烯腈纤维预氧化的原位研究

在聚丙烯腈基碳纤维（PAN-CFs）的生产中，预氧化是提高纤维热稳定性和形成其结构原型的关键步骤。然而，预氧化过程中 PAN 纤维的结构评估仍然模棱两可，部分原因是缺乏原位研究。该贡献报告了在同步辐射束线上使用广角 X 射线散射和小角 X 射线散射技术对 PAN 纤维进行预氧化的原位研究。揭示了纤维中骨架和孔隙的结构变化，分别对应于五种衍射点（峰）和两种散射条纹。预氧化表现出明显的阶段，并分析了相应的可能机理。