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

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.