Microstructure characterization is of great value to understanding nuclear graphite's properties and irradiation behavior. However, graphite is soft and could be easily damaged during sample preparation. A three-step polishing method involving mechanical polishing, ion milling, and rapid oxidation is proposed for graphite. Ion milling is adopted to remove the broken graphite pieces produced by mechanical polishing. Rapid oxidation is then adopted to remove irradiation-induced damage layer during ion milling. The Raman spectra show very small G peak width and very low I_D/I_G ratio after rapid oxidation. The microcracks that were conventionally observed via a transmission electron microscope can be observed on rapid-oxidized surface in a scanning electron microscope. By digital image processing, the microcracks along with the gas-escape pores in nuclear graphite IG-110 are statistically analyzed. Porosity's distributions on crack (pore) size (spanning from 10 nm to 100 μm) are given, which could help to understand and simulate graphite's performances in reactors.

中文翻译：

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核石墨孔隙和微裂纹的统计分析

微观结构表征对于理解核石墨的特性和辐照行为具有重要价值。然而，石墨很软，在样品制备过程中很容易损坏。针对石墨提出了一种包括机械抛光、离子研磨和快速氧化的三步抛光方法。采用离子研磨去除机械抛光产生的石墨碎块。然后在离子铣削过程中采用快速氧化去除辐射诱导的损伤层。拉曼光谱显示非常小的 G 峰宽和非常低的I _D / I _G快速氧化后的比例。传统上通过透射电子显微镜观察到的微裂纹可以在扫描电子显微镜下观察到快速氧化的表面。通过数字图像处理，对核石墨IG-110中的微裂纹和排气孔进行了统计分析。给出了裂缝（孔）尺寸（从 10 nm 到 100 μm）的孔隙率分布，这有助于理解和模拟石墨在反应器中的性能。