Filtern
Erscheinungsjahr
Dokumenttyp
Sprache
- Englisch (26) (entfernen)
Referierte Publikation
- ja (26) (entfernen)
Schlagworte
- Neutron tomography (6)
- Neutron imaging (5)
- Neutron radiography (5)
- Tomography (4)
- Computed tomography (3)
- Bragg-edge imaging (2)
- Darkfield imaging (2)
- Fuel cell (2)
- Hydrogen diffusion (2)
- Hydrogen embrittlement (2)
- Magnetic domains (2)
- Phase distribution (2)
- Water management (2)
- X-ray compton scattering (2)
- X-ray imaging (2)
- 4D tomographic data (1)
- Anosteocytic bone (1)
- Austenite-to-martensite transformation (1)
- Backlighting (1)
- Biodegradable implant (1)
- Blister (1)
- Bone porosity (1)
- Bragg-edge (1)
- Bragg-edge neutron 2D imaging (BENI) (1)
- Catalyst (1)
- Compression effect (1)
- Crystallographic texture control (1)
- Debye–Waller factor (1)
- Diffraction contrast neutron imaging (1)
- Diffusion (1)
- Digital detector array (1)
- Electron backscatter diffraction (EBSD) (1)
- Electron tomography (1)
- Energy-dispersive x-ray spectroscopy (1)
- Fiber composites (1)
- Full-field phase tomography (1)
- Gas diffusion layer (1)
- Gas tungsten arc welding (GTAW) (1)
- Geometrical effect (1)
- Grating interferometry (1)
- Hydrogen (1)
- IN718 PBF-LB/M (1)
- Imaging (1)
- In situ (1)
- Instrumentation for neutron sources (1)
- Iron (1)
- Laser powder-bed fusion (1)
- Low transformation temperature (LTT) steel (1)
- Magnesium-gadolinium alloy (1)
- Manifold stack (1)
- Metal additive manufacturing (MAM) (1)
- Metal foam microstructure (1)
- Micro-computed tomography (1)
- Multi-energy CT (1)
- Multimodal analysis (1)
- Neutron computed tomography (1)
- Neutron detectors (cold, thermal, fast neutrons) (1)
- Nneutron imaging (1)
- Non-destructive testing (1)
- PEM fuel cell (1)
- Phase transformation (1)
- Polymer electrolyte membrane fuel cell (1)
- Polymer electrolyte membrane fuel cell (PEMFC) (1)
- Preferential orientation (1)
- Primary Battery (1)
- Proteoglycans (1)
- Radiography (1)
- Radiology (1)
- Reconstruction algorithm (1)
- Reconstruction algrorithm (1)
- Rectangular cross-section (1)
- Shearing gratings (1)
- Spectral CT (1)
- Steel (1)
- Synchrotron (1)
- Talbot-Lau (1)
- Talbot-Lau interferometer (1)
- Talbot-Lau neutron tomography (1)
- Texture (1)
- Three-dimensional data quantification (1)
- Tomographic reconstruction (1)
- Torsion (1)
- Two-phase flow (1)
- Water permeability (1)
- Water transport (1)
- X-ray CT (1)
- X-ray radiography (1)
- cold neutrons (1)
- iron embrittlement (1)
- neutron imaging (1)
- neutron instrumentation (1)
Organisationseinheit der BAM
Neutron Bragg-edge imaging was applied for the visualization of a γ-Austenite to α'-martensite phase transformation. In the present study, a super martensitic
stainless steel sample was heated until complete austenitization and was subsequently cooled down to room temperature. The martensitic phase Transformation started at Ms = 190 °C. Using a monochromatic neutron beam with λ = 0.390 nm, the transmitted intensity was significantly reduced during cooling below Ms, since the emerging martensitic phase has a higher attenuation coefficient than the austenitic phase at this wavelength. The phase Transformation process was visualized by filming the transmission images from a scintillator screen with a CCD camera with a temporal resolution of 30 s and a spatial
resolution of 100 µm.
The potentials of incoherent X-ray scattering (Compton) computed tomography (CT) are investigated. The imaging of materials of very different atomic number or density at once is generally a perpetual challenge for X-ray tomography or radiography. In a basic laboratory set-up for simultaneous perpendicular Compton scattering and direct beam attenuation tomography are conducted by single channel photon counting line scans. This results in asymmetric distortions of the projection profiles of the scattering CT data set. In a first approach, corrections of Compton scattering data by taking advantage of rotational symmetry yield tomograms without major geometric artefacts. A cylindrical sample composed of PE, PA, PVC, glass and wood demonstrates similar Compton contrast for all the substances, while the conventional absorption tomogram only reveals the two high order materials. Comparison to neutron tomography
reveals astonishing similarities except for the glass component (without hydrogen). Therefore, Compton CT offers the potential to replace neutron tomography, which requires much more efforts.
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 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.
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.
One of the main advantages of metal additive manufacturing (MAM) techniques is their ability to produce components with site-specific microstructural features. Nevertheless, microstructural defects and lack of repeatability are still major concerns in MAM. In this study, a laser powder bed fusion (PBF-LB/M) IN718 material, produced using two different scan length vectors, is investigated using Bragg-edge neutron 2D imaging (BENI) combined with electron backscatter diffraction (EBSD) analysis. BENI is able to detect, on a macroscopic scale, process-induced changes in texture in a large field of view covering the entire sample (20×80 mm2). In addition, high-resolution BENI (HR-BENI), with a pixel size of 12.8 µm, provides a micro-scale examination of the local variations of texture and grain morphology, otherwise undistinguishable using the standard resolution. As such, HR-BENI offers a straightforward and detailed way of screening the integrity of MAM parts at cm-length scales.