Periodic Reporting for period 4 - AtoFun (Atomic Scale Defects: Structure and Function)
Reporting period: 2021-09-01 to 2023-04-30
Atomic scale defects play a key role in determining the behaviour of all crystalline materials, profoundly modifying mechanical, thermal and electrical properties. Many current technological applications make do with phenomenological descriptions of these effects; yet myriad intriguing questions about the fundamental link between defect structure and material function remain.
Transmission electron microscopy revolutionised the study of atomic scale defects by enabling their direct imaging. The novel coherent X-ray diffraction techniques developed in this project promise a similar advancement, making it possible to probe the strain fields that govern defect interactions in 3D with high spatial resolution (<10 nm). They will allow us to clarify the effect of impurities and retained gas on dislocation strain fields, shedding light on opportunities to engineer dislocation properties. The exceptional strain sensitivity of coherent diffraction will enable us to explore the fundamental mechanisms governing the behaviour of ion-implantation-induced point defects that are invisible to TEM. While we concentrate on dislocations and point defects, the new techniques will apply to all crystalline materials where defects are important. Our characterisation of defect structure will be combined with laser transient grating measurements of thermal transport changes due to specific defect populations. This unique multifaceted perspective of defect behaviour will transform our ability to devise modelling approaches linking defect structure to material function.
A deep, fundamental understanding of atomic scale defects and their effect on material function is an essential prerequisite for exploiting and engineering defects to enhance material properties for next generation power generation, energy storage and transport applications.
At the conclusion of this project, we were able to fully realise the goals formulated at the outset. The new X-ray techniques developed in this project enable unique insight into the nanoscale insitu structure of crystal defects. They have become universally accepted in the field and are now a cornerstone for upgrades under way at major synchrotron facilities worldwide. In irradiation-damaged materials we established the presence of a large, previously overlooked population of point defects too small to be observed by TEM. By combining experiments with atomistic simulations, we could establish the clear link between these defects and dramatic changes in material properties. These insights are of pivotal importance of the design of materials for intense irradiation environments in next generation fission and fusion power reactors.
Transmission electron microscopy revolutionised the study of atomic scale defects by enabling their direct imaging. The novel coherent X-ray diffraction techniques developed in this project promise a similar advancement, making it possible to probe the strain fields that govern defect interactions in 3D with high spatial resolution (<10 nm). They will allow us to clarify the effect of impurities and retained gas on dislocation strain fields, shedding light on opportunities to engineer dislocation properties. The exceptional strain sensitivity of coherent diffraction will enable us to explore the fundamental mechanisms governing the behaviour of ion-implantation-induced point defects that are invisible to TEM. While we concentrate on dislocations and point defects, the new techniques will apply to all crystalline materials where defects are important. Our characterisation of defect structure will be combined with laser transient grating measurements of thermal transport changes due to specific defect populations. This unique multifaceted perspective of defect behaviour will transform our ability to devise modelling approaches linking defect structure to material function.
A deep, fundamental understanding of atomic scale defects and their effect on material function is an essential prerequisite for exploiting and engineering defects to enhance material properties for next generation power generation, energy storage and transport applications.
At the conclusion of this project, we were able to fully realise the goals formulated at the outset. The new X-ray techniques developed in this project enable unique insight into the nanoscale insitu structure of crystal defects. They have become universally accepted in the field and are now a cornerstone for upgrades under way at major synchrotron facilities worldwide. In irradiation-damaged materials we established the presence of a large, previously overlooked population of point defects too small to be observed by TEM. By combining experiments with atomistic simulations, we could establish the clear link between these defects and dramatic changes in material properties. These insights are of pivotal importance of the design of materials for intense irradiation environments in next generation fission and fusion power reactors.
In this project, we developed the new coherent X-ray diffraction techniques that allow us to characterise the full lattice strain field within micro-crystals with ~10 nm 3D resolution. Our new experimental protocols make these experiments routinely feasible even on complex materials and allow their application to the study of crystal defect evolution insitu. Laser Transient grating spectroscopy (TGS) techniques developed in this project allow the characterisation of elastic properties and thermal diffusivity within few-micron-thick surface layers.
We have applied these new tools to the study or irradiation damage in tungsten, as well as iron-chromium alloys. By combining experiments with atomistic and continuum calculations we could establish how irradiation-induced defects alter key material properties that are of direct importance for the design of next generation fission and fusion power plants. Furthermore, using coherent X-ray diffraction approaches, we could shed light on the structural evolution of defects during annealing, corrosion and hydrogen charging of metallic alloys. These results have been published in a series of papers in the open literature. All data and developed code have also been made available in publicly accessible repositories. New results were presented at numerous international conference, features on the university website as well as on the university outreach platform.
We have applied these new tools to the study or irradiation damage in tungsten, as well as iron-chromium alloys. By combining experiments with atomistic and continuum calculations we could establish how irradiation-induced defects alter key material properties that are of direct importance for the design of next generation fission and fusion power plants. Furthermore, using coherent X-ray diffraction approaches, we could shed light on the structural evolution of defects during annealing, corrosion and hydrogen charging of metallic alloys. These results have been published in a series of papers in the open literature. All data and developed code have also been made available in publicly accessible repositories. New results were presented at numerous international conference, features on the university website as well as on the university outreach platform.
In this project, we observed that irradiation of Tungsten and FeCr alloys produces a large population of atomic-scale point defects that TEM is not sufficiently sensitive to detect. Indeed, most of the changes in physical and mechanical material properties can be traced back to this “invisible” defect population. By combining X-ray diffraction measurements of strain, as well as thermal transport and elastic property measurements, we have been able to unambiguously establish the presence of these defects. Using atomistic and continuum simulations, we could link their presence to the experimentally observed changes in material behaviour. This has been a significant breakthrough with substantial impact for the design of new material for intense irradiation environments in future fission and fusion reactors.
Using coherent X-ray diffraction, we were able to probe the evolution of dislocations and their strain fields insitu during annealing, corrosion or insitu hydrogen loading. From these experiments we were able to gain fundamental new insight into dislocation behaviour that highlighted potential mechanism that could be explored in the development of new materials with enhanced properties.
The applicability of the techniques and tools developed in this project to a wide variety of other materials has been demonstrated by several exploratory studies tangential to the mains goals of the project.
Using coherent X-ray diffraction, we were able to probe the evolution of dislocations and their strain fields insitu during annealing, corrosion or insitu hydrogen loading. From these experiments we were able to gain fundamental new insight into dislocation behaviour that highlighted potential mechanism that could be explored in the development of new materials with enhanced properties.
The applicability of the techniques and tools developed in this project to a wide variety of other materials has been demonstrated by several exploratory studies tangential to the mains goals of the project.