TY - JOUR A1 - Tötzke, Christian A1 - Manke, Ingo A1 - Gaiselmann, Gerd A1 - Bohner, John A1 - Müller, Bernd R. A1 - Kupsch, Andreas A1 - Hentschel, Manfred P. A1 - Schmidt, Volker A1 - Banhart, Jens A1 - Lehnert, Werner T1 - A dedicated compression device for high resolution X-ray tomography of compressed gas diffusion layers JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - We present an experimental approach to study the three-dimensional microstructure of gas diffusion layer (GDL) materials under realistic compression conditions. A dedicated compression device was designed that allows for synchrotron-tomographic investigation of circular samples under well-defined compression conditions. The tomographic data provide the experimental basis for stochastic modeling of nonwoven GDL materials. A plain compression tool is used to study the fiber courses in the material at different compression stages. Transport relevant geometrical parameters, such as porosity, pore size, and tortuosity distributions, are exemplarily evaluated for a GDL sample in the uncompressed state and for a compression of 30 vol.%. To mimic the geometry of the flow-field, we employed a compression punch with an integrated channel-rib-profile. It turned out that the GDL material is homogeneously compressed under the ribs, however, much less compressed underneath the channel. GDL fibers extend far into the channel volume where they might interfere with the convective gas transport and the removal of liquid water from the cell. (C) 2015 AIP Publishing LLC. Y1 - 2015 U6 - https://doi.org/10.1063/1.4918291 SN - 0034-6748 SN - 1089-7623 VL - 86 IS - 4 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Shashev, Yury A1 - Kupsch, Andreas A1 - Lange, Axel A1 - Evsevleev, Sergei A1 - Müller, Bernd R. A1 - Osenberg, Markus A1 - Manke, Ingo A1 - Hentschel, Manfred P. A1 - Bruno, Giovanni T1 - Optimizing the visibility of X-ray phase grating interferometry JF - Materials testing : Materialprüfung ; materials and components, technology and application N2 - The performance of grating interferometers coming up now for imaging interfaces within materials depends on the efficiency (visibility) of their main component, namely the phase grating. Therefore, experiments with monochromatic synchrotron radiation and corresponding simulations are carried out. The visibility of a phase grating is optimized by different photon energies, varying detector to grating distances and continuous rotation of the phase grating about the grid lines. Such kind of rotation changes the projected grating shapes, and thereby the distribution profiles of phase shifts. This yields higher visibilities than derived from ideal rectangular shapes. By continuous grating rotation and variation of the propagation distance, we achieve 2D visibility maps. Such maps provide the visibility for a certain combination of grating orientation and detector position. Optimum visibilities occur at considerably smaller distances than in the standard setup. KW - X-ray imaging KW - grating interferometry KW - Talbot-Lau interferometer KW - X-ray refraction KW - X-ray phase contrast Y1 - 2017 U6 - https://doi.org/10.3139/120.111097 SN - 0025-5300 VL - 59 SP - 974 EP - 980 PB - Hanser CY - München ER - TY - JOUR A1 - Erdmann, Maren A1 - Kupsch, Andreas A1 - Müller, Bernd Randolf A1 - Hentschel, Manfred P. A1 - Niebergall, Ute A1 - Böhning, Martin A1 - Bruno, Giovanni T1 - Diesel-induced transparency of plastically deformed high-density polyethylene JF - Journal of materials science N2 - High-density polyethylene becomes optically transparent during tensile drawing when previously saturated with diesel fuel. This unusual phenomenon is investigated as it might allow conclusions with respect to the material behavior. Microscopy, differential scanning calorimetry, density measurements are applied together with two scanning X-ray scattering techniques: wide angle X-ray scattering (WAXS) and X-ray refraction, able to extract the spatially resolved crystal orientation and internal surface, respectively. The sorbed diesel softens the material and significantly alters the yielding characteristics. Although the crystallinity among stretched regions is similar, a virgin reference sample exhibits strain whitening during stretching, while the diesel-saturated sample becomes transparent. The WAXS results reveal a pronounced fiber texture in the tensile direction in the stretched region and an isotropic orientation in the unstretched region. This texture implies the formation of fibrils in the stretched region, while spherulites remain intact in the unstretched parts of the specimens. X-ray refraction reveals a preferred orientation of internal surfaces along the tensile direction in the stretched region of virgin samples, while the sample stretched in the diesel-saturated state shows no internal surfaces at all. Besides from stretching saturated samples, optical transparency is also obtained from sorbing samples in diesel after stretching. Y1 - 2019 U6 - https://doi.org/10.1007/s10853-019-03700-8 SN - 0022-2461 SN - 1573-4803 VL - 54 IS - 17 SP - 11739 EP - 11755 PB - Springer CY - New York ER - TY - JOUR A1 - Kupsch, Andreas A1 - Mueller, Bernd R. A1 - Lange, Axel A1 - Bruno, Giovanni T1 - Microstructure characterisation of ceramics via 2D and 3D X-ray refraction techniques JF - Journal of the European Ceramic Society N2 - 3D imaging techniques are very fashionable nowadays, and allow enormous progress in understanding ceramic microstructure, its evolution, and its link to mechanical, thermal, and transport properties. In this feature article, we report the use of a powerful, yet not so wide-spread, set of X-ray techniques based on refraction effects. X-ray refraction allows determining internal specific surface (surface per unit volume) in a non-destructive fashion, position and orientation sensitive, and with a nanometric detectability. While the techniques are limited by the X-ray absorption of the material under investigation, we demonstrate showcases of ceramics and composite materials, where understanding of process parameter influence or simply of microstructural parameters could be achieved in a way unrivalled even by high-resolution techniques such as electron microscopy or computed tomography. (C) 2016 Elsevier Ltd. All rights reserved. KW - X-ray refraction KW - Porosity KW - Specific surface KW - Crack detection KW - Composites Y1 - 2017 U6 - https://doi.org/10.1016/j.jeurceramsoc.2016.12.031 SN - 0955-2219 SN - 1873-619X VL - 37 SP - 1879 EP - 1889 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Laquai, Rene A1 - Müller, Bernd R. A1 - Schneider, Judith Ann A1 - Kupsch, Andreas A1 - Bruno, Giovanni T1 - Using SXRR to probe the nature of discontinuities in SLM additive manufactured inconel 718 specimens JF - Metallurgical and Materials Transactions A N2 - The utilization of additive manufacturing (AM) to fabricate robust structural components relies on understanding the nature of internal anomalies or discontinuities, which can compromise the structural integrity. While some discontinuities in AM microstructures stem from similar mechanisms as observed in more traditional processes such as casting, others are unique to the AM process. Discontinuities in AM are challenging to detect, due to their submicron size and orientation dependency. Toward the goal of improving structural integrity, minimizing discontinuities in an AM build requires an understanding of the mechanisms of formation to mitigate their occurrence. This study utilizes various techniques to evaluate the shape, size, nature and distribution of discontinuities in AM Inconel 718, in a non-hot isostatic pressed (HIPed) as-built, non-HIPed and direct age, and HIPed with two step age samples. Non-destructive synchrotron radiation refraction and transmission radiography (SXRR) provides additional information beyond that obtained with destructive optical microscopy. SXRR was able to distinguish between voids, cracks and lack of melt in, due to its sensitivity to the orientation of the discontinuity. Y1 - 2020 U6 - https://doi.org/10.1007/s11661-020-05847-5 SN - 1073-5623 SN - 1543-1940 VL - 51 IS - 8 SP - 4146 EP - 4157 PB - Springer CY - New York ER - TY - JOUR A1 - Shashev, Yury A1 - Kupsch, Andreas A1 - Lange, Axel A1 - Müller, Bernd R. A1 - Bruno, Giovanni T1 - Improving the visibility of phase gratings for Talbot-Lau X-ray imaging JF - Materials testing : Materialprüfung ; materials and components, technology and application N2 - Talbot-Lau interferometry provides X-ray imaging techniques with significant enhancement of the radiographic contrast of weakly absorbing objects. The grating based technique allows separation of absorption, refraction and small angle scattering effects. The different efficiency of rectangular and triangular shaped phase gratings at varying detector distances is investigated. The interference patterns (Talbot carpets) are modeled for parallel monochromatic radiation and measured by synchrotron radiation. In comparison to rectangular shapes of phase gratings much higher visibility is obtained for triangular shapes which yield enhanced contrast of a glass capillary test specimen. KW - Talbot-Lau interferometry KW - phase grating KW - synchrotron imaging KW - visibility KW - X-ray refraction Y1 - 2016 U6 - https://doi.org/10.3139/120.110948 SN - 0025-5300 VL - 58 SP - 970 EP - 974 PB - Hanser CY - München ER - TY - GEN A1 - Müller, Bernd Randolf A1 - Kupsch, Andreas A1 - Laquai, Rene A1 - Nellesen, Jens A1 - Tillmann, Wolfgang A1 - Kasperovich, Galina A1 - Bruno, Giovanni T1 - Microstructure Characterisation of Advanced Materials via 2D and 3D X-Ray Refraction Techniques T2 - Materials Science Forum N2 - 3D imaging techniques have an enormous potential to understand the microstructure, its evolution, and its link to mechanical, thermal, and transport properties. In this conference paper we report the use of a powerful, yet not so wide-spread, set of X-ray techniques based on refraction effects. X-ray refraction allows determining internal specific surface (surface per unit volume) in a non-destructive fashion, position and orientation sensitive, and with a nanometric detectability. We demonstrate showcases of ceramics and composite materials, where microstructural parameters could be achieved in a way unrivalled even by high-resolution techniques such as electron microscopy or computed tomography. We present in situ analysis of the damage evolution in an Al/Al2O3 metal matrix composite during tensile load and the identification of void formation (different kinds of defects, particularly unsintered powder hidden in pores, and small inhomogeneity’s like cracks) in Ti64 parts produced by selective laser melting using synchrotron X-ray refraction radiography and tomography. KW - X-ray refraction KW - radiography KW - tomography KW - synchrotron X-ray refraction radiography KW - CT KW - microscopy KW - creep KW - porosity KW - damage evolution KW - additive manufacturing KW - metal matrix composite Y1 - 2018 SN - 978-3-0357-1208-7 U6 - https://doi.org/10.4028/www.scientific.net/MSF.941.2401 SN - 0255-5476 VL - 941 SP - 2401 EP - 2406 PB - Trans Tech Publications Ltd CY - Zurich ER - TY - JOUR A1 - Müller, B. R. A1 - Cooper, R. C. A1 - Lange, A. A1 - Kupsch, Andreas A1 - Wheeler, M. A1 - Hentschel, M. P. A1 - Staude, A. A1 - Pandey, A. A1 - Shyam, A. A1 - Bruno, Giovanni T1 - Stress-induced microcrack density evolution in beta-eucryptite ceramics BT - experimental observations and possible route to strain hardening JF - Acta materialia N2 - In order to investigate their microcracking behaviour, the microstructures of several beta-eucryptite ceramics, obtained from glass precursor and cerammed to yield different grain sizes and microcrack densities, were characterized by laboratory and synchrotron x-ray refraction and tomography. Results were compared with those obtained from scanning electron microscopy (SEM). In SEM images, the characterized materials appeared fully dense but computed tomography showed the presence of pore clusters. Uniaxial tensile testing was performed on specimens while strain maps were recorded and analyzed by Digital Image Correlation (DIC). X-ray refraction techniques were applied on specimens before and after tensile testing to measure the amount of the internal specific surface (i.e., area per unit volume). X-ray refraction revealed that (a) the small grain size (SGS) material contained a large specific surface, originating from the grain boundaries and the interfaces of TiO2 precipitates; (b) the medium (MGS) and large grain size (LGS) materials possessed higher amounts of specific surface compared to SGS material due to microcracks, which decreased after tensile loading; (c) the precursor glass had negligible internal surface. The unexpected decrease in the internal surface of MGS and LGS after tensile testing is explained by the presence of compressive regions in the DIC strain maps and further by theoretical arguments. It is suggested that while some microcracks merge via propagation, more close mechanically, thereby explaining the observed X-ray refraction results. The mechanisms proposed would allow the development of a strain hardening route in ceramics. KW - Beta-eucryptite KW - Microcracked ceramics KW - X-ray refraction KW - Tensile load KW - Strain hardening Y1 - 2017 U6 - https://doi.org/10.1016/j.actamat.2017.10.030 SN - 1359-6454 SN - 1873-2453 VL - 144 SP - 627 EP - 641 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Nellesen, Jens A1 - Laquai, R. A1 - Müller, B. R. A1 - Kupsch, Andreas A1 - Hentschel, M. P. A1 - Anar, N. B. A1 - Soppa, E. A1 - Tillmann, W. A1 - Bruno, Giovanni T1 - In situ analysis of damage evolution in an Al/ Al2O3 MMC under tensile load by synchrotron X-ray refraction imaging JF - Journal of materials science N2 - The in situ analysis of the damage evolution in a metal matrix composite (MMC) using synchrotron X-ray refraction radiography (SXRR) is presented. The investigated material is an Al alloy (6061)/10 vol MMC after T6 heat treatment. In an interrupted tensile test the gauge section of dog bone-shaped specimens is imaged in different states of tensile loading. On the basis of the SXRR images, the relative change of the specific surface (proportional to the amount of damage) in the course of tensile loading was analyzed. It could be shown that the damage can be detected by SXRR already at a stage of tensile loading, in which no observation of damage is possible with radiographic absorption-based imaging methods. Moreover, the quantitative analysis of the SXRR images reveals that the amount of damage increases homogeneously by an average of 25% with respect to the initial state. To corroborate the experimental findings, the damage distribution was imaged in 3D after the final tensile loading by synchrotron X-ray refraction computed tomography (SXRCT) and absorption-based synchrotron X-ray computed tomography (SXCT). It could be evidenced that defects and damages cause pronounced indications in the SXRCT images. Y1 - 2018 U6 - https://doi.org/10.1007/s10853-017-1957-x SN - 0022-2461 SN - 1573-4803 VL - 53 IS - 8 SP - 6021 EP - 6032 PB - Springer CY - New York ER - TY - JOUR A1 - Magkos, Sotirios A1 - Kupsch, Andreas A1 - Bruno, Giovanni T1 - Direct iterative reconstruction of computed tomography trajectories reconstruction from limited number of projections with DIRECTT JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - X-ray computed tomography has many applications in materials science and non-destructive testing. While the standard filtered back-projection reconstruction of the radiographic datasets is fast and simple, it typically fails in returning accurate results from missing or inconsistent projections. Among the alternative techniques that have been proposed to handle such data is the Direct Iterative REconstruction of Computed Tomography Trajectories (DIRECTT) algorithm. We describe a new approach to the algorithm, which significantly decreases the computational time while achieving a better reconstruction quality than that of other established algorithms. Y1 - 2020 U6 - https://doi.org/10.1063/5.0013111 SN - 0034-6748 SN - 1089-7623 SN - 1527-2400 VL - 91 IS - 10 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Magkos, Sotirios A1 - Kupsch, Andreas A1 - Bruno, Giovanni T1 - Suppression of cone-beam artefacts with Direct Iterative Reconstruction Computed Tomography Trajectories (DIRECTT) JF - Journal of imaging : open access journal N2 - The reconstruction of cone-beam computed tomography data using filtered back-projection algorithms unavoidably results in severe artefacts. We describe how the Direct Iterative Reconstruction of Computed Tomography Trajectories (DIRECTT) algorithm can be combined with a model of the artefacts for the reconstruction of such data. The implementation of DIRECTT results in reconstructed volumes of superior quality compared to the conventional algorithms. KW - iteration method KW - signal processing KW - X-ray imaging KW - computed tomography Y1 - 2021 U6 - https://doi.org/10.3390/jimaging7080147 SN - 2313-433X VL - 7 IS - 8 PB - MDPI CY - Basel ER - TY - JOUR A1 - Tötzke, Christian A1 - Gaiselmann, G. A1 - Osenberg, M. A1 - Arlt, T. A1 - Markötter, H. A1 - Hilger, A. A1 - Kupsch, Andreas A1 - Müller, B. R. A1 - Schmidt, V. A1 - Lehnert, W. A1 - Manke, Ingo T1 - Influence of hydrophobic treatment on the structure of compressed gas diffusion layers JF - Journal of power sources : the international journal on the science and technology of electrochemical energy systems N2 - Carbon fiber based felt materials are widely used as gas diffusion layer (GDL) in fuel cells. Their transport properties can be adjusted by adding hydrophobic agents such as polytetrafluoroethylene (PTFE). We present a synchrotron X-ray tomographic study on the felt material Freudenberg H2315 with different PIPE finishing. In this study, we analyze changes in microstructure and shape of GDLs at increasing degree of compression which are related to their specific PTFE load. A dedicated compression device mimicking the channel-land pattern of the flowfield is used to reproduce the inhomogeneous compression found in a fuel cell. Transport relevant geometrical parameters such as porosity, pore size distribution and geometric tortuosity are calculated and consequences for media transport discussed. PTFE finishing results in a marked change of shape of compressed GDLs: surface is smoothed and the invasion of GDL fibers into the flow field channel strongly mitigated. Furthermore, the PTFE impacts the microstructure of the compressed GDL. The number of available wide transport paths is significantly increased as compared to the untreated material. These changes improve the transport capacity liquid water through the GDL and promote the discharge of liquid water droplets from the cell. (C) 2016 Elsevier B.V. All rights reserved. KW - Gas diffusion layer KW - Synchrotron tomography KW - Compression KW - Hydrophobic treatment KW - Water transport Y1 - 2016 U6 - https://doi.org/10.1016/j.jpowsour.2016.05.118 SN - 0378-7753 SN - 1873-2755 VL - 324 SP - 625 EP - 636 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Laquai, René A1 - Schaupp, Thomas A1 - Griesche, Axel A1 - Müller, Bernd R. A1 - Kupsch, Andreas A1 - Hannemann, Andreas A1 - Kannengiesser, Thomas A1 - Bruno, Giovanni T1 - Quantitative analysis of hydrogen-assisted microcracking in duplex stainless steel through X-ray refraction 3D imaging JF - Advanced engineering materials N2 - While the problem of the identification of mechanisms of hydrogen-assisted damage has and is being thoroughly studied, the quantitative analysis of such damage still lacks suitable tools. In fact, while, for instance, electron microscopy yields excellent characterization, the quantitative analysis of damage requires at the same time large field-of-views and high spatial resolution. Synchrotron X-ray refraction techniques do possess both features. Herein, it is shown how synchrotron X-ray refraction computed tomography (SXRCT) can quantify damage induced by hydrogen embrittlement in a lean duplex steel, yielding results that overperform even those achievable by synchrotron X-ray absorption computed tomography. As already reported in the literature, but this time using a nondestructive technique, it is shown that the hydrogen charge does not penetrate to the center of tensile specimens. By the comparison between virgin and hydrogen-charged specimens, it is deduced that cracks in the specimen bulk are due to the rolling process rather than hydrogen-assisted. It is shown that (micro)cracks propagate from the surface of tensile specimens to the interior with increasing applied strain, and it is deduced that a significant crack propagation can only be observed short before rupture. KW - 2101 duplex stainless steel KW - computed tomography KW - fractography KW - hydrogen KW - embrittlement KW - microcracking KW - synchrotron radiation KW - X-ray refraction Y1 - 2022 U6 - https://doi.org/10.1002/adem.202101287 SN - 1527-2648 VL - 24 IS - 6 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Mani, Deepak A1 - Kupsch, Andreas A1 - Müller, Bernd R. A1 - Bruno, Giovanni T1 - Diffraction Enhanced Imaging Analysis with Pseudo-Voigt Fit Function JF - Journal of imaging : open access journal N2 - Diffraction enhanced imaging (DEI) is an advanced digital radiographic imaging technique employing the refraction of X-rays to contrast internal interfaces. This study aims to qualitatively and quantitatively evaluate images acquired using this technique and to assess how different fitting functions to the typical rocking curves (RCs) influence the quality of the images. RCs are obtained for every image pixel. This allows the separate determination of the absorption and the refraction properties of the material in a position-sensitive manner. Comparison of various types of fitting functions reveals that the Pseudo-Voigt (PsdV) function is best suited to fit typical RCs. A robust algorithm was developed in the Python programming language, which reliably extracts the physically meaningful information from each pixel of the image. We demonstrate the potential of the algorithm with two specimens: a silicone gel specimen that has well-defined interfaces, and an additively manufactured polycarbonate specimen. KW - diffraction enhanced imaging KW - analyzer-based imaging KW - X-ray refraction; KW - non-destructive evaluation KW - Pseudo-Voigt fit function KW - Python Y1 - 2022 U6 - https://doi.org/10.3390/jimaging8080206 SN - 2313-433X VL - 8 IS - 8 PB - MDPI CY - Basel ER -