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将聚丙烯腈基炭纤维在石墨化炉中维持定长加热，以模拟炭/炭复合材料制备过程中炭纤维结构的变化，并采用小角X射线散射( SAXS)和高分辨透射电子显微镜( HRTEM)检测石墨化过程中的结构演变。随着温度的提高炭纤维中微孔的平均回转半径、长度、宽度、截面积和体积分数呈现先减小后增大的趋势，并在约2300益出现极小值。炭纤维中孔隙尺寸的变化与炭层片的活动性密切相关。炭层的缩合和有序化导致孔隙率的减小，而炭层在更高温的簇状化导致孔隙尺寸的增大。“,”Polyacrylonitrile-based carbon fiber bundles, with two sides fixed, were heated in a graphitization furnace with temper-ature profiles similar to those used in the preparation of carbon/carbon composites. The microstructure of the microvoids formed was characterized by small-angle X-ray scattering and high resolution transmission electron microscopy ( HR-TEM) . Results showed that the average radius of gyration of the microvoids decreases, and their length, width, cross-sectional area and volume fraction de-crease followed by a slight increase with increasing temperature, with the minima found at around 2300℃. The HR-TEM images showed that the microvoids were formed by stacking defects of the carbon layers. The ordering of the amorphous carbon layers ac-counted for the initial decrease of size and volume fraction of the voids with increasing temperature, while the growth and ordering of the layers at high temperatures gave rise to increases in their size and volume fraction.