Characterization of heterogeneity in NBG-18 nuclear graphite microstructure by correlative analysis of optical texture and focused ion beam transmission electron microscopy observations
Characterization of heterogeneity in NBG-18 nuclear graphite microstructure by correlative analysis of optical texture and focused ion beam transmission electron microscopy observations
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通过光学织构和聚焦离子束透射电子显微镜观察的相关分析表征 NBG-18 核石墨微观结构的不均匀性
DOI：
10.1016/j.carbon.2021.12.035
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发表时间：
2022
期刊：
影响因子：
10.9
通讯作者：
Kang Feiyu
中科院分区：
文献类型：
--
作者：
Shen Ke;Zhang Xue;Yu Suyuan;Kang Feiyu
NBG-18是一种核石墨，已被考虑用于南非和中国计划的高温气冷反应堆。虽然已经对NBG-18核石墨进行了许多表征实验，但导致微观不均匀性的一些结构特征尚未被注意到。在这项研究中，光学织构和聚焦离子束透射电子显微镜（FIB-TEM），拉曼映射，和原子力显微镜（AFM）的结果进行了详细的相关性分析。首先，确定了各种光学纹理元素，包括NBG-18填料的精细光学结构（颗粒域和各向同性基质）的方面。在粘合剂中也观察到类似的双重结构（各向同性基质中的各向异性组分），并且偶尔观察到流动型粘合剂结构。然后，在大面积光学显微镜图的指导下，使用先进的显微镜（FIB TEM，AFM）和光谱学（拉曼）技术详细探索了各种元素。因此，揭示了意想不到的结构性质（局部各向同性和各向异性、取向、晶格尺寸、取向、局部原子有序和无序）、起源（例如，碳化过程中的变化）和将来的演变（例如，电子辐照引起的变化）进行了讨论。因此，本研究探索了NBG-18核石墨微观结构复杂性和异质性的新水平。
NBG-18 is a nuclear graphite that has been considered for use in high-temperature gas-cooled reactors planned by South Africa and China. Although many characterization experiments have been performed on NBG-18 nuclear graphite, some structural features leading to microscopic heterogeneity have not yet been noticed. In this study, a detailed correlative analysis of optical texture and results from focused ion beam transmission electron microscopy (FIB-TEM), Raman mapping, and atomic force microscopy (AFM) was performed. First, various optical texture elements were identified, including aspects of the fine optical structure (granular domains and isotropic matrix) of the NBG-18 filler. A similar dual structure was also observed in the binder (anisotropic components in an isotropic matrix), and occasionally flow-type binder structures were seen. Then, guided by the large-area optical microscopy maps, various elements were explored in detail using advanced microscopy (FIB-TEM, AFM) and spectroscopy (Raman) techniques. Thus, unexpected structural properties were revealed (local isotropy and anisotropy, orientations, lattice sizes, rosettes, local atomic order and disorder), the origins (e.g., changes during carbonization process) and future evolution (e.g., changes induced by electron irradiation) of which were discussed. Thus, this study explores a new level of microstructure complexity and heterogeneity of NBG-18 nuclear graphite.