Novel analytical methods for assessing local environments in multicomponent systems for nuclear applications

高熵合金是一类相对较新的材料，代表了一种基于近等原子比例组合多种元素的新型合金设计策略。该领域基于四个核心原则，其中许多与系统内的原子尺度结构效应直接相关，例如局部原子位移和构型环境。目前正在研究这些材料的一些可能的应用。一些高、中熵合金显示出的一个潜在的有益特性是核应用的辐射损伤容忍，有人认为这与当地环境有关。如果要对这些材料进行调优，就必须回答有关这些材料中的局部原子环境的问题。全散射是一种基于检查样品中x射线/中子散射产生的图案的衍射方法，它提供了对材料系统中局部原子环境的探测。大盒子建模方法的发展，反向蒙特卡罗，已经从总散射数据中提供了许多复杂化学系统，功能氧化物和金属有机框架[1]的有用见解。最近，该技术已被用于探索简单二元金属体系中的局部效应，如短程有序[2,3]。然而，使用这种方法可以探测的系统的复杂性目前是未知的。这个博士项目将着眼于使用总散射分析多组分系统的方法的发展。我们将从简单的案例材料开始，在复杂的情况下建立更多涉及工业利益的系统。这将涉及冶金样品制备，包括粉末制造方法，以及通过扫描和透射电子显微镜对样品进行表征。总散射数据将在ISIS中子源和钻石光源获取，涉及与英国国家研究机构的科学家密切合作。这些数据的分析将使用RMCProfile和PDFGui进行，并开发定制的分析代码。在进行这些研究的同时，计算模拟将用于评估该技术的理论分析极限。

High entropy alloys, a relatively new class of materials, represent a novel alloy design strategy based on combining multiple elements in near-equiatomic proportions. The field is based on four core principles, many of which directly relate to atomic scale structural effects within the system, such as local atomic displacements and configurational environments. These materials are being investigated for a number of possible applications. One potential beneficial property demonstrated by some high- and medium-entropy alloys is radiation damage tolerance for nuclear applications, which it has been suggested relates to the local environment. Answering questions about the local atomic environment in these materials is essential if they are to be tuned for purpose.Total scattering, a type of diffraction method based on examining the pattern produced by X-rays/Neutrons scattered from a sample, provides a probe of the local atomic environment in material systems. The development of large box modelling methods, Reverse Monte Carlo, has already provided useful insights in a host of complex chemical systems, functional oxides and metal organic frameworks [1] from total scattering data. Recently, the application of the technique has been demonstrated for exploring local effects, such as short-range order, in simple binary metallic systems [2,3]. However, the complexity of the system that can be probed using this method is currently unknown.This PhD project will look at development of methodologies for the analysis of multi-component systems using total scattering. We will begin with simple case example materials, building in complexity to more involved systems of industrial interest. This will involve, metallurgical sample preparation including powder manufacturing methods, and characterisation of the samples by scanning and transmission electron microscopy. Total scattering data will be acquired at the ISIS Neutron Source and Diamond Light Source, involving close collaboration with scientists at UK national research facilities. Analysis of these data will be carried out using RMCProfile and PDFGui, as well as developing bespoke analysis code. Concurrent with these studies, computational simulation will be used to assess theoretical analytical limits of the technique.