Quantitative Characterisation of Structure in Nuclear Graphite

这项博士研究的目的是建立可靠的/新颖的方法来量化核石墨内部的关键结构特征。这种定量表征对于支持在不同载荷和温度条件下中子辐照诱导和/或辅助核石墨损伤和变形的真正机制至关重要。这种基于证据的机制理解将指导从原子、纳米、微米到宏观尺度上的性质和结构变化的建模。为实现这一目标，提出以下研究课题为博士研究重点：(a)利用聚焦离子束显微技术进行孔隙和微裂纹结构分析。研究重点是对二维图像进行定量分析，重建三维孔隙/微裂纹层析成像结构。将开发先进的图像分析技术和算法，用于不同等级的石墨之间的定量比较研究，以及相同等级的不同反应器/MTR历史的石墨。研究结果将通过其他研究小组使用的其他技术获得的断层扫描数据进一步分析。(b)晶体结构的拉曼和透射电镜分析。本研究的目的是建立一种非破坏性的方法，可以定量绘制细胞核石墨内无序石墨晶体或石墨烯的变化。这种无序信息预计与辐照历史有很强的关系，即中子剂量、温度、负荷水平和类型以及氧化。(c)石墨的真实纹理特征。石墨的织构对石墨的物理性能有很强的影响，并在不同方向上带来物理性能的非均质性。纹理可以在辐照过程中进一步演变，特别是在压缩/拉伸加载的帮助下。博士研究将使用各种方法定量表征核石墨的真实纹理。

The aim of this PhD research is to establish reliable/novel approaches to quantify the key structural features inside nuclear graphite. Such quantitative characterisation is essential for underpinning true mechanisms governing neutron irradiation-induced and/or -assisted damage and deformation of nuclear graphite under different loading and temperature conditions. Such evidence-based mechanistic understanding will instruct the modelling of property and structure changes at a scale from atomic, nanometer, micron, up to macro. To achieve the aim, the following research topics are proposed as the main focus of the PhD researcher: (a) Pore and micro-crack structure analysis with focused ion beam microscopy. The research will focus on the quantitative analysis of 2D images and reconstructed 3D pore/micro-crack tomography structure. Advanced image analysis techniques and algorithms will be developed for quantification-based comparative studies among different graphite grades, and those with different reactor/MTR histories for the same grade. The research outcomes will be further analysed with tomography data acquired via other techniques used in other research groups. (b) Crystal structure disordering analysis by Raman and TEM. The objective of this research is to establish a non-destructive method that can quantitatively map the variation of disordered graphite crystallites, or graphene, inside nuclear graphite. Such disordering information is expected to have a strong relationship with irradiation history, i.e. neutron dosage, temperature, loading level and type, and oxidation. (c) True texture characterisation of graphite. Texture of graphite can have strong influence on the physical properties of graphite, and brings the heterogeneity in physical properties along different directions. Texture can be further evolved during irradiation, particularly with help of compression/tension loading. The PhD research will use various methods to quantitatively characterise the true texture of a nuclear graphite.