8.5 Röntgenbildgebung
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- Additive manufacturing (2)
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- X-ray refraction (2)
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- Advanced Materials (1)
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Organisationseinheit der BAM
Due to their increasing energy density, lithium-ion-batteries (LIBs) play a key role in the traffic energy transition. Regarding their safety behavior, the main challenge of LIB-cells remains the thermal runaway (TR) process. In situ/operando investigations of the TR on commercial cells is possible with radiographic and computer tomographic measurements. Nonetheless, high resolution visualization of the TR persists as a challenge due to the high progression speed of the TR-process itself. Generally, performing abuse tests at cryogenic temperatures allows to slow down or even prevent the TR. Nevertheless, not all abuse methods are suitable for TR investigations at low temperatures. Nail penetration is an appropriate option, however, contains numerous unknown parameters and therefore suffers regarding reproducibility.
Herein, a self-developed high precision nail-penetration-setup is introduced, approaching the necessary mechanically reproducibility with controlled temperatures down to -190°C. The setup allows the preparation of critically abused, however, at cryogenic temperatures stable LIB-cells. These cells were controlled rethermalized to room temperature during synchrotron x-ray computer tomography (SXCT) with a pixel size up to 0.7 μm. During this measurement, the temperature and voltage of the cell is monitored allowing the visualization of the initial internal cell reactions. This study reveals the relation between internal reactions and cell voltage. Finally, the developed set-up enables in-depth analysis of thermal runaway behavior down to material level for various commercial battery cells in the future.
The European Commission has identified Advanced Manufacturing and Advanced Materials as two of six Key Enabling Technologies (KETs). By fully utilizing these KETs, advanced and sustainable economies will be created. It is considered that Metrology is a key enabler for the advancement of these KETs. EURAMET, the association of metrology institutes in Europe, has strengthened the role of Metrology for these KETs by enabling the creation of a European Metrology Network for Advanced Manufacturing. The EMN is made up of National Metrology Institutes (NMIs) and Designated Institutes (DIs) from across Europe and was formally established in October 2021. The EMN aims to provide a high-level coordination of European metrology activities for the Advanced Materials and Advanced Manufacturing community.
The EMN itself is organized in three sections representing the major stages of the manufacturing chain: 1) Advanced Materials, 2) Smart Manufacturing Systems, and 3) Manufactured Components & Products. The EMN for Advanced Manufacturing is engaging with stakeholders in the field of Advanced Manufacturing and Advanced Materials (Large companies & SMEs, industry organisations, existing networks, and academia), as well as the wider metrology community (including TCs) to provide input for the preparation of a Strategic Research Agenda (SRA) for Metrology for Advanced Manufacturing.
This presentation will describe the progress in the development of the SRA by the EMN for Advanced Manufacturing. The metrology challenges identified across the various key industrial sectors, which utilise Advanced Materials and Advanced Manufacturing will be presented.
The EMN for Advanced Manufacturing is supported by the project JNP 19NET01 AdvManuNet.
Ziel der Untersuchung: Evaluation der Eignung der Refraktions-Tomographie zur Analyse von Alterungserscheinungen innerhalb von adhäsiv verankerten Materialien vor und nach künstlicher Probenalterung.
Material und Methode: Vier humane mittlere Oberkieferfrontzähne wurden wurzelkanalbehandelt und ausgedehnte Klasse IV Defekte der Krone mit einer Aufbaufüllung aus dualhärtendem Komposit (Rebilda DC, VOCO) und einem Glasfaserstift (Rebilda Post, VOCO) restauriert. Alle Proben wurden feucht gelagert und in einer Synchrotron-Einrichtung (BAMline, BESSY II, HZB) mit einer Pixelgröße von 4,08 µm gescannt. Für diese Synchrotron-Refraktions-Tomographie (SXRCT) muss zunächst der Analysatorkristall (AK) zu einer Bragg-Reflexion (Beugung) angeregt werden, um eine SXRCT durchzuführen. Die SXRCT wird mit einer Transmissions-Tomographie (ohne AK) verrechnet. Darauf folgte eine künstliche Probenalterung mit 400.000 Kau- und 3.000 Thermozyklen (50N, 5-55°C). Anschließend wurden die Proben ein weiteres Mal gescannt. Die Datensätze beider SXRCT wurden mittels des „filtered back projection“ Algorithmus rekonstruiert, mit einer Bildanalyse-Software aufeinander registriert und ausgewertet. Hierdurch konnten die Veränderungen initialer Schädigungen analysiert werden.
Ergebnisse: Alle 4 Proben zeigten in den Scans Veränderungen des inneren Gefüges und an Grenzflächen nach Belastung. Es zeigten sich Ansammlungen von Wasser innerhalb eingeschlossener Hohlräume, subkritisches Risswachstum, Ausdehnung des Komposit und Quellung des Glasfaserstiftes um 0,4%. In den SXRCT Aufnahmen waren außerdem Dentintubuli, die bei Auflösungen von 4,08 µm sonst nicht deutlich sichtbar sind darstellbar. Dadurch konnte Eindringen von Wasser in die Tubuli im Anschluss an die Alterung belegt werden.
Zusammenfassung: SXRCT bietet die Möglichkeit, trotz einer vergleichbar geringen Auflösung, kleinste Strukturen und Veränderungen abzubilden. Dies ermöglicht unter anderem die detaillierte Analyse relativ großer Proben, wie eines vollständigen Zahnes in einem Scanvorgang.
Virtual CT with aRTist
(2023)
The software aRTist is a simulation tool for the generation of realistic radiographs of virtual radiographic superstructures.
With radiographic simulations, virtual component models can be scanned as in a computer tomograph.
Industrial X-ray computed tomography (CT) enables the non-destructive detection of internal and external surfaces as well as inhomogeneities of technical objects. Virtual CT offers new possibilities for the investigation of parameter influences of this complex testing and measuring technique. In addition to the option of switching physical effects on and off, scanning movements can also be tested before their technical realization.
The virtual CT generates projection images from different directions for the subsequent reconstruction of a volume model of the examined object. The reconstruction of the simulated scans is carried out with the algorithms and programs for real scans. Tomographic scans consist of a large number of projections, which practically cannot be generated individually by the user of a simulation. The software offers various options for the automated simulation of tomographic scans. These range from standard CT to scans on free trajectories or with individual projection matrices.
In dentistry it is of great interest to achieve good sealing interzones between tooth tissue and restoration materials to avoid, e. g. secondary caries. μXRF and CμXRF are suitable to investigate the elemental composition at these interzones in respect to diffusion of elements. Synchrotron X-ray refraction radiography (SXRR) and μCT measurements deliver highly resolved structural information and make structural changes such as micro cracks within the filling and the tooth tissue visible. The presented measurements are part of the DFG funded project IXdent (Integrative X-ray techniques for chemical and structural characterizations of dental interzones.)
The depth-resolved CμXRF measurements are affected by absorption effects, making a quantitative investigation of the interzone in depth difficult. Full 3D quantification of heterogenous samples requires a complete model including dark matrix and density for each voxel. The combination of different techniques paves the way for a quantitative analysis of dental interzones.
Synchrotron X-ray computed tomography (SXCT) at BAMline has been paired with in-situ tensile loading to monitor damage evolution in LPBF Metal Matrix Composite (MMC) 7017 Aluminium alloy + 3 wt% Zr + 0.5 wt% TiC. The processing of the material leads formation to different categories of Zr-rich inclusions, precipitates and defects. In-situ SXCT test disclosed the critical role of the pre-cracks in the reinforcement phases in the failure mechanisms of LPBF MMC. The damage was initiated from lack-of-fusion defects and cracks propagated through coalescence with other defects.
LTCCs (Low-temperature co-fired ceramics) consist of three-dimensionally distributed, hermetically bonded ceramic and metallic components with structure sizes within [10; 100] µm. A non-destructive imaging technique is needed that provides 3D, sharp, high-contrast resolution of these structures, as well as porosity and defect analysis, which is made difficult by the very different X-ray absorption coefficients of the individual components of the microstructure. A HDR method is being developed that allows a combination of different tomograms, each with X-ray energies adapted to individual materials.
Quantification of Deep Discharge Mechanism in a Li-Ion Battery by operando X-ray Computed Tomography
(2023)
Lithium-ion batteries connected in series are prone to an electrical abuse called over discharge. We present a comprehensive investigation of the over discharge abuse mechanism in lithium-ion batteries using operando non-destructive imaging. The study focuses on understanding the behavior of copper dissolution and deposition during over discharge, which can lead to irreversible capacity loss and internal short circuits. By utilizing synchrotron X-ray computed tomography (SXCT), the concentration of dissolved and deposited copper per surface area is quantified as a function of depth of discharge (DoD).
Die Brechung von Röntgenstrahlen (Röntgenrefraktion) an Grenzflächen zwischen Materialien unterschiedlicher Dichte ist analog zur Ablenkung von sichtbarem Licht an z.B. Glasoberflächen. Es gibt jedoch zwei wesentliche Unterschiede:
a) konvexe Grenzflächen verursachen Divergenz (d.h. der Brechungsindex n ist kleiner als 1), und
b) die Ablenkungswinkel sind sehr klein, und reichen von einigen Bogensekunden bis zu einigen Bogenminuten (d.h. n ist nahe bei 1);
Wie auch bei sichtbarem Licht ist die Ablenkungsrichtung der Röntgenstrahlen abhängig von der Orientierung der durchstrahlten Grenzfläche. Aufgrund dieser Eigenschaften eignen sich Röntgenrefraktionsmethoden hervorragend für:
a) die Erkennung und Quantifizierung von Defekten wie Poren und Mikrorissen und
b) die Bewertung von Porosität und Partikeleigenschaften wie Orientierung, Größe und räumliche Verteilung.
Wir zeigen die Anwendung der Röntgenrefraktionsradiographie (2,5D Technik) und der -tomographie (3D Technik) für die Untersuchung verschiedener Probleme in der Werkstoffwissenschaft und -technologie:
a) Sintern von SiC-Grünkörpern
b) Porositätsanalyse in Dieselpartikelfiltersilikaten
c) Faser-Matrix-Haftung in Metall- und Polymermatrixverbundwerkstoffen
d) Mikrorissbildung in Glaskeramik.
Wir zeigen, dass der Einsatz von Röntgenrefraktionsmethoden quantitative Ergebnisse liefert, die direkt als Parameter in Werkstoffmodellen verwendet werden können.
X-ray refraction is analogous to visible light deflection by matter; it occurs at boundaries between different media. The main difference between visible light and X-rays is that in the latter case deflection angles are very small, from a few seconds to a few minutes of arc (i.e., the refraction index n is near to 1). Trivially but importantly, deflection of X-rays is also sensitive to the orientation of the object boundaries. These features make X-ray refraction techniques extremely suitable to a) detect defects such as pores and microcracks and quantify their densities in bulk (not too heavy) materials, and b) evaluate porosity and particle properties such as orientation, size, and spatial distribution (by mapping). While X-ray refraction techniques cannot in general image single defects, their detectability is simply limited by the wavelength of the radiation.
We thereby show the application of X-ray refraction 2D mapping (topography) and tomography to different sorts of problems in materials science and technology: 1) Sintering of SiC green bodies; 2) Porosity analysis in additively manufactured alloys; 3) Fiber de-bonding in metal and polymer matrix composites.
Such techniques, especially at the Synchrotron BESSY II, Berlin, Germany, can be used in-situ, i.e. when the specimen is subjected to temperatures or external loads. Applications of in-situ X-ray refraction radiography on aluminum alloys and composites are also shown.
The use of X-ray refraction analysis yields quantitative information, which can be directly input in kinetics, mechanical and damage models.