Filtern
Dokumenttyp
- Zeitschriftenartikel (30)
Schlagworte
- Neutron imaging (7)
- Tomography (4)
- Phase distribution (3)
- X-ray imaging (3)
- Fuel cell (2)
- Geometrical effect (2)
- Neutron radiography (2)
- Neutron scattering (2)
- Neutron tomography (2)
- Rectangular cross-section (2)
- Solid electrolytes (2)
- Solid-state batteries (2)
- Torsion (2)
- 3D imaging (1)
- 4D tomographic data (1)
- Alkali metal anodes (1)
- Alkali metal batteries (1)
- All-solid-state batteries (1)
- Attenuation coefficient (1)
- BAMline (1)
- Backlighting (1)
- Batteries (1)
- Battery failure mechanisms (1)
- Bragg-edge (1)
- Catalyst Layer (1)
- Cathode deactivation (1)
- Cells (1)
- Codependent failure mechanism (1)
- Compression effect (1)
- Computertomographie (1)
- Copper sulfide (1)
- Crack evolution (1)
- Current density distribution (1)
- Darkfield imaging (1)
- Debye-Waller-Faktor (1)
- Debye–Waller factor (1)
- Diffraction contrast neutron imaging (1)
- Digital detector array (1)
- Digital volume correlation (1)
- Distribution of relaxation times analysis (1)
- Electrochemical impedance spectra (1)
- Fiber composites (1)
- Full-field phase tomography (1)
- Gas diffusion electrodes (1)
- Gas diffusion layers (1)
- Gas evolution (1)
- HT-PEFC (1)
- High-temperature polymer electrolyte membrane fuel cell (1)
- In-situ characterization of GDLs (1)
- In-situ synchrotron X-ray computed tomography (1)
- In-situ synchrotron X-ray radiography (1)
- Laser powder-bed fusion (1)
- Lattice Boltzmann simulation (1)
- Li composite electrode (1)
- Li dendrites (1)
- Li dendrites penetration mechanisms (1)
- Li metal batteries (1)
- Li-B-Mg (1)
- LiS battery (1)
- Lithium ion flux (1)
- Lithium metal batteries (1)
- Lithium-ion battery (1)
- Lithium/sodium−carbon dioxide batteries (1)
- Mass transport (1)
- Metal foam microstructure (1)
- Microporous Layer (1)
- Multi-energy CT (1)
- NaO-battery (1)
- Neutron Bragg edge imaging (1)
- Neutron instrument (1)
- Neutronenlaminographie (1)
- Nneutron imaging (1)
- Non-destructive testing (1)
- Operando cell (1)
- Oxygen reduction reaction (1)
- Phase transformation (1)
- Phosphoric acid (1)
- Platinum-free catalyst (1)
- Polycromatic neutrons (1)
- Polymer Electrolyte Membrane Fuel Cell (1)
- Polymer electrolyte membrane fuel cell (1)
- Preferential orientation (1)
- Primary Battery (1)
- Radiography (1)
- Radiology (1)
- Room-temperature (1)
- Scintillator (1)
- Solid-state lithium metal batteries (1)
- Spectral CT (1)
- Sulfide solid electrolytes (1)
- Super martensitic stainless steel (1)
- Synchrotron Imaging (1)
- Synchrotron X-Ray (1)
- Synchrotron X-ray computed tomography (1)
- Synchrotron X-ray tomography (1)
- Synchrotron radiation (1)
- Talbot-Lau interferometer (1)
- Temperature-dependent neutron transmission (1)
- Texture (1)
- Thermal runaway (1)
- Water Distribution (1)
- X-Ray imaging (1)
- X-ray CT (1)
- X-ray computed tomography (1)
- X-ray tomography (1)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (30) (entfernen)
Paper des Monats
- ja (1)
Die Computer-gestützte Laminografie (CL) wurde als komplementäre Methode zur Computertomografie für die dreidimensionale Bildgebung von lateral ausgedehnten Objekten entwickelt. Ursprünglich für medizinische Zwecke verwendet, wurde diese Methode kürzlich als zerstörungsfreie nicht-invasive Methode nicht nur in der Materialforschung, sondern auch mit steigendem Interesse für kunsthandwerkliche und historische Objekte eingesetzt. Hier wird die Computer-gestützten Laminografie mit polychromatischer Neutronenstrahlung an einer historischen Tsuba eingesetzt, einem Stichblatt eines japanischen Schwerts. Eine Analyse der Lötstellen gibt Rückschlüsse auf das Herstellungsverfahren. Zudem wurden unterschiedliche Materialsysteme gefunden, vermutlich um dem Tsuba lokal eine höhere Stabilität zu verleihen. Die Messungen wurden an der Imaging-Beamline CONRAD-2 an der Neutronenquelle BER 2 des Helmholtz-Zentrums Berlins (HZB) durchgeführt.
In recent years, low-temperature polymer electrolyte fuel cells have become an increasingly important pillar in a zero-carbon strategy for curbing climate change, with their potential to power multiscale stationary and mobile applications. The performance improvement is a particular focus of research and engineering roadmaps, with water management being one of the major areas of interest for development. Appropriate characterisation tools for mapping the evolution, motion and removal of water are of high importance to tackle shortcomings.
This article demonstrates the development of a 4D high-speed neutron imaging technique, which enables a quantitative analysis of the local water evolution. 4D visualisation allows the time-resolved studies of droplet formation in the flow fields and water quantification in various cell parts. Performance parameters for water management are identified that offer a method of cell classification, which will, in turn, support computer modelling and the engineering of next-generation flow field designs.
Herein, we present a detailed investigation of the electrochemically triggered formation and dissolution processes of α- and β-sulfur crystals on a monolithic carbon cathode using operando high-resolution synchrotron radiography (438 nm/pixel).
The combination of visual monitoring with the electrical current response during cyclic voltammetry provides valuable insights into the sulfur formation and dissolution mechanism. Our observations show that the crystal growth process is mainly dictated by a rapid equilibrium between long-chain polysulfides on one side and solid sulfur/short-chain polysulfides on the other side, which is consistent with previous studies in this field. The high temporal and spatial resolution of synchrotron imaging enables the observation of different regimes during the sulfur formation and dissolution process. The appearance of short-chain polysulfides after the first anodic CV peak initiates a rapid dissolution process of α-sulfur crystals on the cathode. The increase in the long-chain lithium polysulfide concentration at the cathode surface during charge results in an increased crystal growth rate, which in turn produces imperfections in α- and β-sulfur crystals. There are strong indications that these defects are fluid inclusions, which may trap dissolved polysulfides and therefore reduce the electrochemical cell capacity.
Clarifying the Electro-Chemo-Mechanical Coupling in Li10SnP2S12 based All-Solid-State Batteries
(2022)
A fundamental clarification of the electro-chemo-mechanical coupling at the solid–solid electrode|electrolyte interface in all-solid-state batteries (ASSBs) is of crucial significance but has proven challenging. Herein, (synchrotron) X-ray tomography, electrochemical impedance spectroscopy (EIS), time-of-flight secondary-ion mass spectrometry (TOF-SIMS), and finite element analysis (FEA) modeling are jointly used to decouple the electro-chemo-mechanical coupling in Li10SnP2S12-based ASSBs. Non-destructive (synchrotron) X-ray tomography results visually disclose unexpected mechanical deformation of the solid electrolyte and electrode as well as an unanticipated evolving behavior of the (electro)chemically generated interphase. The EIS and TOFSIMS probing results provide additional information that links the interphase/electrode properties to the overall battery performance. The modeling results complete the picture by providing the detailed distribution of the mechanical stress/strain and the potential/ionic flux within the electrolyte.
Collectively, these results suggest that 1) the interfacial volume changes induced by the (electro)chemical reactions can trigger the mechanical deformation of the solid electrode and electrolyte; 2) the overall electrochemical process can accelerate the interfacial chemical reactions; 3) the reconfigured interfaces in turn influence the electric potential distribution as well as charge transportation within the SE. These fundamental discoveries that remain unreported until now significantly improve the understanding of the complicated
electro-chemo-mechanical couplings in ASSBs.
In various kinds of radiography, deficient transmission imaging may occur due to backlighting inside the detector itself arising from light or radiation scattering. The related intensity mismatches barely disturb the high resolution contrast, but its long range nature results in reduced attenuation levels which are often disregarded. Based on X-ray observations and an empirical formalism, a procedure is developed for a first order correction of detector backlighting. A backlighting factor is modeled as a function of the relative detector coverage by the sample projection. Different cases of sample transmission are regarded at different backlight factors and detector coverage. The additional intensity of backlighting may strongly affect the values of materials’ attenuation up to a few 10%. The presented scenario provides a comfortable procedure for corrections of X-ray or neutron transmission imaging data.
The ability to track electrode degradation, both spatially and temporally, is fundamental to understand performance loss during operation of lithium batteries. X-ray computed tomography can be used to follow structural and morphological changes in electrodes; however, the direct detection of electrochemical processes related to metallic lithium is difficult due to the low sensitivity to the element. In this work, 4-dimensional neutron computed tomography, which shows high contrast for lithium, is used to directly quantify the lithium diffusion process in spirally wound Li/SOCl2 primary cells. The neutron dataset enables the quantification of the lithium transport from the anode and the accumulation inside the SOCl2 cathode to be locally resolved. Complementarity between the collected neutron and X-ray computed tomographies is shown and by applying both methods in concert we have observed lithium diffusion blocking by the LiCl protection layer and identified all cell components which are difficult to distinguish using one of the methods alone.
Electrochemical impedance spectroscopy (EIS) is a well-established method to analyze a polymer electrolyte membrane fuel cell (PEMFC). However, without further data processing, the impedance spectrum yields only qualitative insight into the mechanism and individual contribution of transport, kinetics, and ohmic losses to the overall fuel cell limitations. The distribution of relaxation times (DRT) method allows quantifying each of these polarization losses and evaluates their contribution to a given electrocatalyst's depreciated performances. We coupled this method with a detailed morphology study to investigate the impact of the 3D-structure on the processes occurring inside a high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC). We tested a platinum catalyst (Pt/C), a platinum-cobalt alloy catalyst (Pt3Co/C), and a platinum group metal-free iron-nitrogen-carbon (Fe–N–C) catalyst. We found that the hampered mass transport in the latter is mainly responsible for its low performance in the MEA (along with its decreased intrinsic performances for the ORR reaction). The better performance of the alloy catalyst can be explained by both improved mass transport and a lower ORR resistance. Furthermore, single-cell tests show that the catalyst layer morphology influences the distribution of phosphoric acid during conditioning.
The understanding of dynamic processes in Li-metal batteries is an important consideration to enable the full capacity of cells to be utilised. These processes, however, are generally not directly observable using X-ray techniques due to the low attenuation of Li; and are challenging to visualise using neutron imaging due to the low temporal resolution of the technique. In this work, complementary X-ray and neutron imaging are combined to track the dynamics of Li within a primary Li/SOCl2 cell. The temporal challenges posed by neutron imaging are overcome using the golden ratio imaging method which enables the identification of Li diffusion in operando. This combination of techniques has enabled an improved understanding of the processes which limit rate performance in Li/SOCl2 cells and may be applied beyond this chemistry to other Li-metal cells.
This work describes the effects of catalyst layers (CLs) consisting of hydrophobic PTFE on the performance and water management of PEM fuel cells. Catalyst inks with various PTFE contents were coated on Nafion membranes and characterized using contact angle measurements, SEX-EDX, and mercury porosimetry. Fuel cell tests and electrochemical impedance spectroscopy (EIS) were conducted under varying operating conditions for the prepared materials. At dry conditions, CLs with 5 wt.% PTFE were advantageous for cell performance due to improved membrane hydration, whereas under humid conditions and high air flow rates CLs with 10 wt.% PTFE improved the performance in high current density region. Higher PTFE contents (⩾20 wt.%) increased the mass transport resistance due to reduced porosity of the CLs structure. Operando neutron radiography was utilized to study the effects of hydrophobicity gradients within CLs and cathode microporous layer (MPLC) on liquid water distribution. More hydrophobic CLs increased the water content in adjacent layers and improved performance, especially at dry conditions. MPLC with higher PTFE contents increased the overall liquid water within the CLs and GDLs and escalated the water transfer to the anode side. Furthermore, the role of back-diffusion transport mechanism on water distribution was identified for the investigated cells.
Spectral neutron tomography
(2021)
Combined three-dimensional (3D) mapping of (micro-)structures with elemental and crystalline phase variations is of significant importance for the characterization of materials. Neutron wavelength selective imaging is a spectral imaging technique that exploits unique contrast differences e.g. for mapping dissimilar elemental, isotope, or phase compositions, and has the particular advantage of being applicable to sample volumes on the meso- and macroscale. While being mostly applied as radiography (2D) so far, we herein report that the extension to tomography allows for the display of the full spectral information for every voxel and in 3D. The development is supported by example data from a continuous as well as a pulsed neutron source. As a practical example, we collected 4D data sets (3D + spectral) of plastically deformed metastable stainless steel and herein demonstrate an improved quantification strategy for crystalline phase fractions. These exemplary results illustrate that localized phase transformations can be quantified even in complex geometries within centimeter-sized samples, and we will discuss the limits and future prospects of the technique that is not limited to crystalline materials.