中文摘要：

x射线小角散射（SmallAngleX．rayScattering，SAXS）是研究纳米尺度微观结构的重要手段。本文利用同步辐射SAXS技术测量了25℃、100℃、200℃、300℃和400℃时，IG-110和NBG-18核石墨在纳米尺度范围内孔隙的数量分布及其分形特征的变化。实验结果表明，IG-110和NBG-18核石墨的微观结构中存在微小尺寸上的不均匀区域，且核石墨孔隙的固气结构具有明锐的界面。但随着温度的升高，固气界面的变化并没有呈现出明显的规律性。此外，在纳米尺度上，IG-110和NBG-18核石墨的孔隙数量随温度呈现增加的趋势，且IG-110核石墨孔隙数量的增加幅度大于NBG-18核石墨，其平均孔隙尺寸的减小幅度大于NBG-18核石墨。在核石墨的微孔结构内，其固气界面的分形维数随温度升高逐渐减小，且NBG-18核石墨分形维数的变化幅度小于IG-110核石墨。这表明核石墨的分形结构随温度的升高逐渐光滑。

英文摘要：

Background： The distribution ofnanoscale pore is of great significance to irradiation damage behavior of nuclear graphite under intense radiation. Small angle X-ray scattering （SAXS） is an important method used to study the number distribution and its fractal characteristics of pore in nanoscale. Purpose： This study aims at the changes in number distribution and its fractal characteristics of nanoscale pore in nuclear graphite. Methods： Two typical nuclear graphite, i.e., IG-110 and NBG-18 were sampled and tested at synchrotron radiation SAXS beamline station at temperatures of 25 ℃, 100 ℃, 200 ℃, 300 ℃ and 400 ℃, respectively. Results： The results showed that there was a non-uniform area in the microstructure of nuclear graphite, and the solid-gas structure of the nuclear graphite pore had a sharp interface, but the change of solid-gas interface does not show obvious regularity with the increase of temperature. In addition, the number of nanoscale pore in IG-110 nuclear graphite increases with the temperature, and is more obvious than that of NBG-18. The fractal dimension of the solid-gas interface decreases with the tempera~tre increasing, indicating that the fractal structure of the graphite become smoother with the increasing of temperature. And the change of IG-110 is more obvious than that of NBG-18. Conclusion： The temperature has a significant impact on the pore number distribution and its fractal characteristics.