高温处理对PAN基碳纤维空隙结构的影响

Effect of heat-treatment on void structure of PAN-based carbon fiber

采用质量法、扫描电子显微镜（SEM）、体密度测试、元素分析（EA）、X射线衍射（XRD）及拉曼光谱（Raman）等手段，探究了高温处理过程PAN基碳纤维空隙结构的变化及其原因。结果表明：热处理过程存在组成元素的逸出及由化学变化和结构转化引起的纤维外形尺寸的变化，在其共同作用下，碳纤维的体密度在800～1500℃范围先增加后减少，在1000℃体密度出现最大值；碳、氢、氧和氮元素的质量减少，碳、氮元素的溢出，造成碳纤维骨架结构的不完整性，形成内部缺陷，且随着温度的升高，碳、氮元素脱除加剧，内部空隙结构增加；由于纤维表面氧含量相对较高，随着温度的升高，纤维表面氧含量脱除量加剧，碳纤维开孔的空隙结构增加，反映在随着温度的升高，碳纤维体密度和表观体密度的差异增大。

The evolution of element mass configuration and microstructure of carbon fiber were studied by means of weight method, element analysis （EA）, density measurement, X-ray diffraction （XRD）, Raman spectroscopy and scanning electron microscopy （SEM） to investigate the void structure of PAN-based carbon fiber during heat treatment. The results show that after heat-treatment at temperatures in the range of 800 ℃ to 1500 ℃ , the volume density of carbon fiber first increases with increasing treatment temperature, reaching a maximum value at 1000 ℃ and then decreases due to the change of chemical composition and morphological dimensions. The masses of carbon, nitrogen, hydrogen and oxygen decrease after heat-treatment at 800 - 1500 ℃ , forming internal defects which increase in quantity with temperature increasing, and lead to defective framework structure of the carbon fiber. The increased difference between volume density and apparent bulk density shows that the aperture defect structure increases with increase of temperature.