Multiscale and Multimodal X-ray Imaging of Heterogeneous Materials

Doktorsavhandling, 2025

The increasing complexity and heterogeneity of advanced materials present a need for imaging methodologies and workflows that can provide comprehensive characterisation of material properties. The development of third- and fourth-generation synchrotron sources has opened new possibilities for both multiscale and multimodal imaging approaches which can greatly enhance resolution, sensitivity and measurement time. This thesis focuses on leveraging state-of-the art X-ray imaging techniques to develop and apply methodologies that optimise resolution and contrast in low attenuating samples and allows for dynamic imaging at conditions close to those for a materials intended application. The developed methodologies are showcased in studies of phase behaviour of pharmaceutical formulations, the charge and discharge processes in anode materials for next generation batteries and for providing insight into the chemical composition distribution in lignocellulose fibres.
 
The key results of the thesis can be divided into a methodological aspect and the direct scientific questions answered within the different projects. Using the highly sensitive phase retrieval technique ptychographic X-ray computed tomography (PXCT) combined with scanning small- and wide angle X-ray scattering (S/WAXS) and soft X-ray spectro-microscopy, I provide multiscale and multimodal characterisation approaches that utilises both structural and chemical contrast to provide better understanding of how the morphology and drug distribution within pharmaceutical formulations relate to drug release behaviour. With S/WAXS contrast I perform dynamic imaging of sodiation of hard carbon electrodes, providing insight into the sodiation mechanism under different conditions. I also introduce time-resolved S/WAXS tomography, relying on sparse data acquisition and reconstruction protocols, for monitoring dissolution of pharmaceutical formulations, providing mechanistic insight into the dissolution mechanism of amorphous solid dispersions. In this way, the thesis presents a toolbox of advanced characterisation techniques for heterogeneous materials, with demonstrated applications ranging from pharmaceutical formulations to next-generation battery materials. These methodologies have potential for further studies of dynamic processes and hierarchical structures in a wide range of heterogeneous materials, enabling deeper insight into structure–property relationships under realistic conditions.