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Abstract: Spent AGR (Advanced gas-cooled reactor) fuel cladding 20/25/Nb stainless steel may suffer from stress corrosion cracking (SCC) in cooling ponds and compromise storage safety. Therefore, a better understanding of the 3D SCC development is required, as subsurface SCC propagation may be different from surface SCC propagation. In this research, in-situ corrosion tensile experiments were performed on heat-treated 20/25/Nb and 304 stainless steels to capture the real-time development of SCC by X-ray tomography at a synchrotron beamline, and the relationship between SCC and surface roughness was studied. Post-exposure materials were further characterised to analyse the corrosion behaviours of different materials and surface finishes by milling and profiling some corroded grain boundaries with focused ion beam (FIB) and energy dispersive spectroscopy (EDS). SCC evolution was not found in 20/25/Nb stainless, but it was only observed in the tomography of 304 stainless steel. The rough surface finish of 304 stainless steel also induced a deeper crack penetration depth and a higher crack growth rate. The post-test characterization further confirmed that the materials suffered from different corrosion modes, where 304 stainless steel specimen showed more features of SCC, and 20/25/Nb stainless steel was more susceptible to intergranular corrosion (IGC) and pitting corrosion.

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Abstract: Thick electrodes are a promising route to increase battery energy density by increasing the fraction of active material relative to inactive components. However, at high cycling rates, greater mass transport limitations in thick electrodes can lead to poor capacity utilisation and reduced power density. Although advanced electrode structuring strategies have been explored, many require expensive manufacturing changes or complex post-processing. An alternative approach uses standard battery manufacturing methods to sequentially coat active materials with different particle sizes or compositions. In this work, polycrystalline LiNi1/3Mn1/3Co1/3O2 (NMC111) particles of two sizes were used to fabricate particle size-graded bilayer electrodes. An impedance-based finite element model was developed to evaluate transport properties in the graded structures and was validated using electrochemical impedance spectroscopy (EIS) and rate tests. Operando synchrotron diffraction revealed a more homogeneous state of charge when smaller particles were positioned near the separator and larger particles near the current collector. Together, the modelling and experimental results show that simple particle size grading improves ion transport and reaction uniformity, enhancing capacity utilisation. This approach offers a practical pathway to improve the power performance of next-generation battery electrodes.

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Abstract: The biomechanical function of the musculoskeletal system depends on hierarchical structures spanning the molecular to whole-organ scales. In the spine, intervertebral discs (IVDs) must balance flexibility with efficient transfer of load between soft and hard tissues. This relies on a complex mechanical interplay across scales, from mineral nanostructure and pre-strain, through collagen–fibril and fibre-level mechanics, up to tissue microarchitecture and regional variations at the organ level. This thesis explores these interactions using advanced multimodal synchrotron X-ray imaging techniques, capable of probing mechanics across multiple length scales. The first section employs in situ imaging of vertebral endplates to examine how structure relates to mechanical strain across spatial scales. Digital volume correlation (DVC) combined with microarchitectural analysis reveals that high tensile and shear strains play a role in the cartilage to bone transition. Correlative imaging and diffraction show that bone contains narrower mineral nano-crystallites under greater compressive pre-strain compared with calcified cartilage. The second section introduces TomoSAXS, a full-field 3D small-angle X-ray scattering tomography that maps fibril-to-fibre mechanics across the annulus fibrosus in the IVD. This method, combined with in situ mechanical loading and DVC, enables correlative measurements of structure and strain at the organ, tissue, fibre and fibrillar scales. This reveals that collagen fibrillar pre-strain is lamellar-textured and tightly correlated with microscale fibre strain. Fibre strain increases with fibre curvature, and radial strain bridges emerge as critical regulators of local mechanics. Scaling the technique from small animal to human IVDs is demonstrated by utilising high-energy X-rays at a 4th generation synchrotron source. Together, these studies provide an integrated, multiscale view of IVD biomechanics, linking mineral and fibrillar nanostructure to tissue and organ-level function. The methods and insights developed here not only advance our understanding of spinal biomechanics but also offer inspiration for the design of biomimetic materials and orthopaedic implants.

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Abstract: Utilizing green and renewable materials derived from biological sources is crucial for reducing environmental pollution. Natural wood is a clean and sustainable material. Densification methods have been shown to greatly enhance the mechanical properties of wood. However, the inherent hydrophilic and hygroexpansion characteristics of wood significantly limit the application of densified wood in various engineering fields. This study aimed to investigate the water absorption behavior and dimensional stability of natural and densified pine through water absorption experiments. The results showed that densified pine exhibited a similar three-stage water absorption behavior to that of natural pine. The water absorption behavior of densified pine caused by diffusion of water molecules as bound water in the cell wall (stage I), conforming to the Fickian model. In the subsequent stage II, excess water in the cell wall diffused into the cell lumen as free water. The water absorption behavior then deviated from the Fickian model and followed the Langmuir model. The significant reduction in the equilibrium moisture content of densified pine, compared to natural pine, can be attributed to a decrease in hemicellulose as well as smaller cell interstices and lumens. Moreover, unlike natural pine, where hygroexpansion was only in stage Ⅰ, densified pine expanded further in stage Ⅱ due to partial recovery of the cell lumen. Nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR), Scanning electron microscopy (SEM) and X-ray computed tomography and diffraction techniques were employed to elucidate the effect of densification on dimensional stability and water absorption behavior of pine.

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Abstract: Anode-free solid-state batteries (AF-SSBs) hold great promise for next-generation transportation electrification, offering improved safety, recyclability, and high performance (energy density >1500 Wh/L, specific energy >500 Wh/kg) at reduced cost (<$100/kWh) compared to conventional Li-ion batteries. However, their practical deployment is hindered by poor chemo-mechanical stability at the evolving anode|solid electrolyte (SE) interface, where localized ionic flux during cycling drives dendrite formation, internal short-circuiting, and premature failure. The buried and dynamic nature of this interface makes direct characterization especially challenging, and existing methods lack the ability to capture non-invasive, 3D operando insights into interfacial morphology, spatial dynamics, and strain evolution in full-cell AF-SSBs. In this work, we conducted operando correlative synchrotron X-ray micro-computed tomography (XCT) and X-ray diffraction (XRD) at the DIAD beamline, Diamond Light Source (UK), to map interface evolution in real time. Custom PEEK-housed tube cells were cycled at 35 µA (2 mm Li | 19 mg LPSC | 3 mm stainless steel), with 13 tomographic scans collected across three charge–discharge cycles prior to short-circuiting. XCT resolved void formation, crack initiation, and fracture propagation, while XRD provided spatially resolved strain mapping and crystallographic fingerprints of interfacial contact evolution. Our imaging data revealed pre-existing cracks within the SE pellet, as well as the nucleation of new spallation-like cracks originating at the current collector–SE interface that widened progressively during cycling. XRD mapping confirmed that these cracks coincided with regions of strain accumulation and interfacial delamination, offering a crystallographic fingerprint of contact evolution. Importantly, these structural changes could be directly correlated with electrochemical signatures: the onset of fracture formation aligned with abrupt cell polarization and preceded catastrophic short-circuiting. Together, this correlative XCT–XRD methodology provides the integrated view of how morphology, strain, and electrochemistry couple to govern failure in AF-SSBs.