Band 2, Heft 3

In this view article, we present potential applications of laboratory-based spectral dual-energy X-ray microtomography imaging for ex vivo animal tissue samples. Technical details on this topic have been reported in previous work, so we focus explicitly on applications here, discussing both dual-energy imaging for the separation of mineralised tissue from one X-ray dense contrast agent, as well as the imaging of samples stained with two X-ray dense contrast agents. Examples are given for a variety of research areas, including preclinical biomedical phenotyping (vasculature, skeletal development), comparative vertebrate morphology, and invertebrate anatomy. Based on the data presented, we conclude that the use of spectral X-ray information can provide new insights into CT datasets. Although using the dual-energy approach initially requires more effort and cost in data acquisition, this additional effort is often worthwhile, as dual-energy datasets allow for more efficient data visualisation, segmentation, and analysis. Until now, software functions for acquisition and processing of dual-energy data have not been implemented in many of the software toolboxes provided by X-ray microtomography vendors with their scanners. We propose that a user-friendly implementation of software tools for acquiring and processing spectral CT data would be a big step towards a wider use of this promising and powerful imaging approach.

A robust, automated workflow for generating high-resolution large field-of-view 3D representations of carbon- and glassfiber reinforced composites with a complex microstructure is presented for three characteristic, very distinct composite specimens with complex fiber architectures: a carbon fiber weave, a unidirectional composite from recycled carbon fiber yarns and an injection molded glass fiber reinforced composite. Overlapping reconstructed images from X-ray computed tomography, taken with a laboratory CT scanner (Zeiss Xradia Versa 520) with a shifted axis of rotation were registered with a rigid transformation, leading to large field of view data sets of approx. 3.1 × 10 10 voxels with a voxel size of 1 µm 3 . Visual assessment of the resulting quality of the images in the overlapping region reveals no artifacts. Exemplarily, the fiber volume content was calculated after segmentation in a selected volume element in the overlapping area. All datasets can be found in separate archives at ZENODO for further use, e.g. for generating digital twins.

Fine sampling of the discharge process revealed details of the anode’s morphology evolution in a commercial zinc-air battery. With special software developed for laboratory XCT scanners, it was possible to observe and quantify the evolution of individual particles. An operando sequence consisting of 30 tomograms within 30 h of discharge at a low C-rate, resulted in shape changes small enough for successful quantification. Two morphological descriptors, i.e. equivalent diameter and complexity factor, were used to assess the morphology of the particles. Details on underlying mechanisms are provided, including the shrinking-core concept, dissolution and the newly observed anisotropic shrinkage.

Sodium-ion batteries (SIBs) are emerging as a promising alternative to lithium-ion technology, with the first commercial cells now available. Understanding their structure and degradation mechanisms is crucial for further development. This study presents a correlative approach combining X-ray and electron microscopy to achieve multi-scale imaging of SIB materials. X-ray microscopy enables non-destructive 3D analysis of electrode architecture, while electron microscopy provides high-resolution insights into particle morphology, interfaces, and failure modes. By integrating these techniques, we establish a comprehensive workflow for analyzing structural and chemical changes. Our results offer one of the first in-depth imaging and analysis of commercial SIB materials and provide valuable feedback for material optimization. This correlative methodology sets a new standard for battery research, advancing the development of next-generation sodium-ion energy storage solutions.

High-resolution X-ray microscopy was used to study the volumetric details of metal-organic framework (MOF) single crystals formed by coordination bonds between copper nitrate and an organic ligand. The three-dimensional information of individual crystals was visualized with submicron resolution, from the virtual slicing of the crystals. Density is one of the basic material properties, but conventional methods cannot provide high resolution mapping. To gain further information on material properties, quantification of the density inside individual crystal were made. The metal salt precursor was used as a standard. By using the same acquisition and reconstruction parameters for the sample and the standard, a correlation between the X-ray attenuation/intensity inside one crystal and its density was established. This correlation allowed the determination of the amount and the spatial distribution of material inside one MOF crystal. The results could provide guidance for future crystal design.

In this study, a comprehensive characterization of the commercially available all-solid-state battery (ASSB) was performed using various analytical techniques. SEM and EDX analyses revealed porosity in the Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) electrolyte and Li 3 V 2 (PO 4 ) 3 (LVP) electrode, which hinders lithium-ion transport and affects electrochemical performance. ToF-SIMS confirmed a higher lithium concentration in the electrode compared to the electrolyte, while EBSD showed that the Cu current collector has randomly oriented grains, ensuring adequate electrical conductivity. AFM provided insights into surface morphology and potential distribution, confirming the effectiveness of ion polishing in sample preparation. Raman spectroscopy detected LATP electrolyte, indicating its potential use for process monitoring. Additionally, X-ray microscopy (XRM) enabled non-destructive imaging of the battery’s internal structure, although it was limited in resolving electrode and electrolyte layers. These findings contribute to a better understanding of solid-state battery design and highlight the strengths and limitations of various characterization techniques for performance optimization.

Detailed understanding of lithium anode morphology is essential for solid-state battery technology development. Non-optimal interfacial contacts and structural changes during cycling present significant challenges, limiting both battery performance and wide adoption of solid-state batteries. Cross-sectional sample preparation combined with advanced electron microscopy techniques provides essential insights into the internal microstructure and composition of materials, particularly at critical interfaces. Visualizing degradation is crucial for identifying failure mechanisms and optimizing material performance. This paper explores the temperature dependence of ion-polished cross-sections, offers detailed guidelines for lithium cross-section preparation using a Ga+ Focused Ion Beam Scanning Electron Microscope (FIB-SEM) system, and compares the results to cross-sections prepared with an Ar+ ion polisher. We demonstrate that artifacts introduced during lithium cross-sectioning at room temperature can be eliminated by conducting the preparation at cryogenic temperatures of −100 °C or lower, regardless of the type of ions used in the sputtering process. This guidance helps ensure researchers generate quality cross-sections when evaluating this important field.

Proton exchange membrane electrolysis cells (PEMECs) are a crucial technology for generating “green hydrogen”, a sustainable energy carrier and versatile platform for synthesizing several chemicals. In the life cycle of a PEMEC, various process stages bare risks of accelerated aging, impacting long-term performance. In the stages of transport and storage of water-filled cell assemblies, a common practice in industry, cation contamination or frost can lead to the degradation of the membrane electrode assembly (MEA) even before its operation. Therefore, as an alternative to transporting and storing the MEA in a hydrated state, this work investigates the possibility of drying the MEA within the cell assembly under controlled conditions to prevent such degradation phenomena. Potential drying induced MEA functionality changes were analyzed using in operando methods, focusing on electrical and gas barrier properties. Butler-Volmer kinetics and electrochemical impedance spectroscopy allowed the allocation of potential performance losses to components. Furthermore, in situ and ex situ X-ray computed tomography (XCT) and optical microscopy investigations gave insights into drying-induced morphological changes within the MEA. In total, three distinct morphological changes were observed and consistently identified: membrane swelling, catalyst layer cracking, and reinforcement detachment, with each posing potential limiting factors for the scalability of the controlled drying process. Ultimately, no significant impact on electrical and gas barrier properties was observed, indicating that the drying process and morphological changes did not adversely affect the short-term operation of the PEMEC.