中文摘要：

采用密度分析、红外吸收光谱（Fr-IR）分析仪、广角X射线衍射（WXRD）仪、差示扫描量热（DSC）分析仪和扫描电子显微镜（SEM）等手段，系统地研究了聚丙烯腈（PAN）原丝预氧化过程中的结构变化。结果表明，在预氧化过程中，PAN原丝的密度和相对环化率均增加，结晶尺寸先变大后变小，结晶度降低，说明环化反应先主要在非晶区引发环化反应，然后扩展至晶区，最终形成耐热的梯形环化结构。PAN原丝在240—280％：反应最剧烈，当预氧化时间为90min时，其预氧化效果较好。

英文摘要：

The structure evolution of polyacrylonitrile（PAN） precursor fibers during stabilization process was studied systemical- ly by density, fourier transform infrared spectroscopy （FT-IR）, wide-angle X-ray diffraction（ WXRD）, differential scanning calorimeter（DSC） and scanning electron microscope（SEM）. The results showed that the density and relative cyclization index of PAN fibers was increased,the crystallite size was increased at first and decreased later and the crystallinity was decreased, which manifested that the eyelization reaction firstly occurred in amorphous region, and then in ordered region and as a result, the ladder cyclized structure was formed. The reaction became violent at 240 -280℃ according to DSC test. It was found that with the stabilization for 90 min the stabilization extent was better.