预炭化过程中升温速率对碳纤维结构与性能的影响

借助13C核磁共振波谱（13C-NMR），X射线衍射（XRD），拉曼光谱（Raman）等表征手段，研究了预炭化过程中聚丙烯腈基热氧稳定化纤维的热化学反应以及微观结构的变化，且重点研究了预炭化过程（400~800 ℃）升温速率对纤维热应力、结构、力学性能的影响。结果表明：随着预炭化升温速率的提高，纤维类石墨层间距 d₀₀₂ 呈现出先减小后增大，晶区堆叠厚度 L_c 呈现出先增大后减小的的趋势；与之相对应的纤维拉伸强度和拉伸模量则呈现出先增大后减小的变化；当升温速率达到132 ℃/min时， d₀₀₂ 和 L_c 分别出现最小值和最大值，此时所得碳纤维的力学性能最高。

Effect of heating rate-induced microstructure changes during pre-carbonization on the mechanical properties of carbon fibers

The chemical reactions and microstructure evolution occurring during pre-carbonization(400-800 ℃) of thermally stabilized polyacrylonitrile(PAN) fibers have been investigated by Raman spectroscopy,XRD and 13C-NMR,with a focus on the effects of varying the heating rate during the pre-carbonization process on the morphological structures,thermal stress and mechanical properties of the pre-carbonized fibers and carbon fibers.With increasing heating rate during pre-carbonization,the crystallite size(Lc) in both pre-carbonized fibers and carbon fibers initially increased and then decreased,whilst the interlayer spacing(d002) showed the opposite trend.The mechanical properties of the carbon fibers showed a strong dependence on the differences in structural evolution caused by variation in heating rate during pre-carbonization.When the heating rate was 132 ℃/min,the value of Lc was a maximum and d002 was a minimum,which resulted in carbon fibers having the optimum mechanical properties.