TY - JOUR A1 - Ziesche, R. F. A1 - Robinson, J. B. A1 - Markötter, Henning A1 - Bradbury, R. A1 - Tengattini, A. A1 - Lenoir, N. A1 - Helfen, L. A1 - Kockelmann, W. A1 - Kardjilov, N. A1 - Manke, I. A1 - Brett, D. J. L. A1 - Shearing, P. R. T1 - Editors’ Choice—4D Neutron and X-ray Tomography Studies of High Energy Density Primary Batteries: Part II. Multi-Modal Microscopy of LiSOCl2 Cells N2 - 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. KW - Lithium-ion battery KW - Room-temperature KW - Thermal runaway KW - Gas evolution KW - Cells PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520890 DO - https://doi.org/10.1149/1945-7111/abbfd9 VL - 167 SP - 140509 PB - IOP Science AN - OPUS4-52089 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bresch, Sophie A1 - Mieller, Björn A1 - Schönauer-Kamin, D. A1 - Moos, R. A1 - Reimann, T. A1 - Giovannelli, F. A1 - Rabe, Torsten T1 - Influence of pressure and dwell time on pressure‐assisted sintering of calcium cobaltite N2 - Calcium cobaltite Ca3Co4O9, abbreviated Co349, is a promising thermoelectric material for high‐temperature applications in air. Its anisotropic properties can be assigned to polycrystalline parts by texturing. Tape casting and pressure‐assisted sintering (PAS) are a possible future way for a cost‐effective mass‐production of thermoelectric generators. This study examines the influence of pressure and dwell time during PAS at 900°C of tape‐cast Co349 on texture and thermoelectric properties. Tape casting aligns lentoid Co349. PAS results in a textured Co349 microstructure with the thermoelectrically favorable ab‐direction perpendicular to the pressing direction. By pressure variation during sintering, the microstructure of Co349 can be tailored either toward a maximum figure of merit as required for energy harvesting or toward a maximum power factor as required for energy harvesting. Moderate pressure of 2.5 MPa results in 25% porosity and a textured microstructure with a figure of merit of 0.13 at 700°C, two times higher than the dry‐pressed, pressureless‐sintered reference. A pressure of 7.5 MPa leads to 94% density and a high power factor of 326 µW/mK2 at 800°C, which is 11 times higher than the dry‐pressed reference (30 MPa) from the same powder. KW - Hot pressing KW - Texture KW - Thermoelectric properties PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-515973 DO - https://doi.org/https://doi.org/10.1111/jace.17541 SN - 0002-7820 VL - 104 IS - 2 SP - 917 EP - 927 PB - Wiley Periodicals LLC AN - OPUS4-51597 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yao, J. A1 - Zhu, G. A1 - Dong, K. A1 - Osenberg, M. A1 - Hilger, A. A1 - Markötter, Henning A1 - Ju, J. A1 - Sun, F. A1 - Manke, I. A1 - Cui, G. T1 - Progress and Perspective of Controlling Li Dendrites Growth in All-Solid-State Li Metal Batteries via External Physical Fields N2 - Li dendrites penetration through solid electrolytes (SEs) challenges the development of solid-state Li batteries (SSLBs). To date, significant efforts are devoted to understand the mechanistic dynamics of Li dendrites nucleation, growth, and propagation in SEs, and various strategies that aim to alleviate and even inhibit Li dendrite formation have been proposed. Nevertheless, most of these conventional strategies require either additional material processing steps or new materials/layers that eventually increase battery cost and complexity. In contrast, using external fields, such as mechanical force, temperature physical field, electric field, pulse current, and even magnetic field to regulate Li dendrites penetration through SEs, seems to be one of the most cost-effective strategies. This review focuses on the current research progress of utilizing external physical fields in regulating Li dendrites growth in SSLBs. For this purpose, the mechanical properties of Li and SEs, as well as the experimental results that visually track Li penetration dynamics, are reviewed. Finally, the review ends with remaining open questions in future studies of Li dendrites growth and penetration in SEs. It is hoped this review can shed some light on understanding the complex Li dendrite issues in SSLBs and potentially guide their rational design for further development. KW - Li dendrites KW - Li dendrites penetration mechanisms KW - Solid electrolytes KW - Solid-state batteries PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-588331 DO - https://doi.org/10.1002/aesr.202300165 SN - 2699-9412 SP - 1 EP - 44 PB - Wiley-VCH CY - Weinheim AN - OPUS4-58833 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Markötter, Henning A1 - Müller, Bernd R. A1 - Kupsch, Andreas A1 - Evsevleev, Sergei A1 - Arlt, T. A1 - Ulbricht, Alexander A1 - Dayani, Shahabeddin A1 - Bruno, Giovanni T1 - A Review of X-Ray Imaging at the BAMline (BESSY II) N2 - The hard X-ray beamline BAMline at BESSY II (Berlin, Germany) has now been in service for 20 years. Several improvements have been implemented in this time, and this review provides an overview of the imaging methods available at the BAMline. Besides classic full-field synchrotron X-ray computed tomography (SXCT), also absorption edge CT, synchrotron X-ray refraction radiography (SXRR), and synchrotron X-ray refraction tomography (SXRCT) are used for imaging. Moreover, virtually any of those techniques are currently coupled in situ or operando with ancillary equipment such as load rigs, furnaces, or potentiostats. Each of the available techniques is explained and both the current and the potential usage are described with corresponding examples. The potential use is manifold, the examples cover organic materials, composite materials, energy-related materials, biological samples, and materials related to additive manufacturing. The article includes published examples as well as some unpublished applications. KW - Material science KW - Radiography KW - Refraction KW - Tomography KW - X-ray imaging PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-572417 DO - https://doi.org/10.1002/adem.202201034 SN - 1438-1656 SP - 1 EP - 22 PB - Wiley VHC-Verlag AN - OPUS4-57241 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tiebe, Carlo A1 - Mieller, Björn A1 - Maiwald, Michael A1 - Kipphardt, Heinrich A1 - Tuma, Dirk A1 - Prager, Jens A1 - Schukar, Marcus A1 - Strohhäcker, J. T1 - Sensoren und Analytik für Sicherheit und Prozesskontrolle in Wasserstofftechnologien N2 - Die Nutzung von Sensortechnologien, insbesondere im Bereich der Gasdetektion mit einem Schwerpunkt auf Wasserstoff, spielt eine entscheidende Rolle in verschiedenen Anwendungsbereichen der Wasserstofftechnologie. Sicherheitsüberwachung, Leckdetektion und Prozesskontrolle gehören zu den prominenten Anwendungsgebieten dieser Sensortechnologien. Ein zentrales Ziel ist die Erkennung von freigesetztem Wasserstoff sowie die genaue Bestimmung des Wasserstoff-Luftverhältnisses mithilfe von Gassensoren. Dies ist von entscheidender Bedeutung, um potenzielle Gefahren frühzeitig zu erkennen und angemessene Maßnahmen zu ergreifen. Ein weiterer Schwerpunkt dieses Beitrags liegt auf der Analytik und der Verwendung zertifizierter Referenzmaterialien in Verbindung mit Metrologie für die Wasserstoffspeicherung. Dies gewährleistet eine präzise und zuverlässige Charakterisierung von Wasserstoff und unterstützt die Entwicklung sicherer Speichertechnologien. Im Rahmen des Euramet-Vorhabens Metrology for Advanced Hydrogen Storage Solutions (MefHySto) wird eine Kurzvorstellung präsentiert. Der Vortrag stellt zwei zerstörungsfreie Prüfverfahren zum strukturellen Zustandsüberwachung (Structural Health Monitoring, SHM) für Wasserstofftechnologien vor. Insbesondere die Fehlstellenerkennung mittels geführter Ultraschallwellen spielt eine bedeutende Rolle bei der Lebensdauerüberwachung von Wasserstoffspeichern. Ein weiterer Aspekt ist die Anwendung faseroptischer Sensorik zur Schadensfrüherkennung von Wasserstoffspeichern. Diese zerstörungsfreien Prüfverfahren ermöglichen eine präzise und frühzeitige Identifizierung von Schäden, was die Sicherheit und Effizienz von Wasserstoffspeichersystemen entscheidend verbessert. T2 - DVGW Kongress H2 Sicherheit CY - Online meeting DA - 15.11.2023 KW - H2Safety@BAM KW - Gassensorik KW - Metrologie KW - zertifizierte Referenzmaterialien KW - Zerstörungsfreie Prüfung KW - Ultraschall KW - Faseroptik PY - 2023 AN - OPUS4-59230 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, Z. A1 - Dong, K. A1 - Mazzio, K. A. A1 - Hilger, A. A1 - Markötter, Henning A1 - Wilde, F. A1 - Heinemann, T. A1 - Manke, I. A1 - Adelhelm, P. T1 - Phase transformation and microstructural evolution of CuS electrodes in solid-state batteries probed by in situ 3D X-ray tomography N2 - Copper sulfide shows some unique physico-chemical properties that make it appealing as a cathode active material (CAM) for solid-state batteries (SSBs). The most peculiar feature of the electrode reaction is the reversible formation of μm-sized Cu crystals during cycling, despite its large theoretical volume change (75%). Here, the dynamic microstructural evolution of CuS cathodes in SSBs is studied using in situ synchrotron X-ray tomography. The formation of μm-sized Cu within the CAM particles can be clearly followed. This process is accompanied by crack formation that can be prevented by increasing the stack pressure from 26 to 40 MPa. Both the Cu inclusions and cracks show a preferential orientation perpendicular to the cell stack pressure, which can be a result of a z-oriented expansion of the CAM particles during lithiation. In addition, cycling leads to a z-oriented reversible displacement of the cathode pellet, which is linked to the plating/stripping of the Li counter electrode. The pronounced structural changes cause pressure changes of up to 6 MPa within the cell, as determined by operando stack pressure measurements. Reasons for the reversibility of the electrode reaction are discussed and are attributed to the favorable combination of soft materials. KW - Copper sulfide KW - Crack evolution KW - Digital volume correlation KW - Phase transformation KW - Solid-state batteries PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-564577 DO - https://doi.org/10.1002/aenm.202203143 IS - 2203143 SP - 1 EP - 12 PB - Wiley VHC-Verlag AN - OPUS4-56457 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bouabadi, Bouchra A1 - Hilger, André A1 - Kamm, Paul H. A1 - Neu, Tillmann R. A1 - Kardjilov, Nikolay A1 - Sintschuk, Michael A1 - Markötter, Henning A1 - Schedel‐Niedrig, Thomas A1 - Abou‐Ras, Daniel A1 - García‐Moreno, Francisco A1 - Risse, Sebastian T1 - Morphological Evolution of Sn‐Metal‐Based Anodes for Lithium‐Ion Batteries Using Operando X‐Ray Imaging N2 - Sn‐based electrodes are promising candidates for next‐generation lithium‐ion batteries. However, it suffers from deleterious micro‐structural deformation as it undergoes drastic volume changes upon lithium insertion and extraction. Progress in designing these materials is limited to complex structures. There is a significant need to develop an alloy‐based anode that can be industrially manufactured and offers high reversible capacity. This necessitates a profound understanding of the interplay between structural changes and electrochemical performance. Here, operando X‐ray imaging is used to correlate the morphological evolution to electrochemical performance in foil and foam systems. The 3D Sn‐foam‐like structure electrode is fabricated in‐house as a practical approach to accommodate the volume expansion and alleviate the mechanical stress experienced upon alloying/dealloying. Results show that generating pores in Sn electrodes can help manage the volume expansion and mitigate the severe mechanical stress in thick electrodes during alloying/dealloying processes. The foam electrode demonstrates superior electrochemical performance compared to non‐porous Sn foil with an equivalent absolute capacity. This work advances the understanding of the real‐time morphological evolution of Sn bulky electrodes. KW - Synchrotron radiation KW - X-ray imaging KW - Lithium-ion battery PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-640112 DO - https://doi.org/10.1002/advs.202414892 SN - 2198-3844 VL - 12 IS - 10 SP - 1 EP - 10 PB - Wiley AN - OPUS4-64011 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pfaff, Jonas A1 - Schopferer, Sebastian A1 - Markötter, Henning A1 - Rack, Alexander A1 - Bruno, Giovanni A1 - Schmidt, Anita A1 - Tichter, Tim A1 - Böttcher, Nils T1 - High-speed synchrotron radiography of nail penetration-induced thermal runaway: Understanding the explosive behavior of commercial sodium-ion batteries with NFM cathode N2 - The dynamics of mechanically initiated thermal runaway (TR) events in cylindrical 18650 cells with NFM (Na(Ni1/3Fe1/3Mn1/3)O2), LFP (LiFePO4), and NMC532 (LiNi1/2Mn1/3Co1/5O2) cathode chemistries were investigated using high-speed synchrotron X-ray imaging. Structural similarity index measures (SSIM) were employed to identify and track rapid structural changes. In this manner, thermal decompositions and internal propagation dynamics, influencing the safety mechanisms of the cells, were studied. This lead to two major findings: (I) Among NFM, LFP, and NMC532 cells, the TR-characteristics differ significantly in temperature and internal propagation speed. Internal safety mechanisms appear, however, visually similar. Among all samples, LFP cells exhibit higher safety performance concerning the initiation of TR by nail penetration and the progression of TR. (II) The NFM cells used in this study displayed an almost explosive TR. This finding appears counterintuitive on a first glance, since sodium-ion batteries are usually considered safe. High-speed imaging revealed that the explosive TR is not necessarily caused by the thermochemical decomposition reactions, but rather by a failure of the venting mechanism. This results in a significant pressure buildup within the cell upon TR initiation and eventually a severely violent TR. These results underline that battery safety depends on many factors and not solely on optimized cell chemistries or materials. KW - High-speed X-ray radiography KW - Synchrotron X-rays KW - 18650 KW - SIB KW - Na-NFM KW - Structure similarity index measure PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-642649 DO - https://doi.org/10.1016/j.powera.2025.100188 SN - 2666-2485 VL - 36 SP - 1 EP - 7 PB - Elsevier Ltd. AN - OPUS4-64264 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Erdmann, Maren A1 - Kupsch, Andreas A1 - Müller, Bernd R. A1 - Hentschel, Manfred P. A1 - Niebergall, Ute A1 - Böhning, Martin A1 - Bruno, Giovanni ED - Erdmann, Maren T1 - Diesel-induced transparency of plastically deformed high-density polyethylene 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. KW - PE-HD Sorption KW - Cavitation KW - Diesel Fuel KW - X-ray refraction KW - WAXS KW - Internal Surfaces KW - Crystal Texture PY - 2019 DO - https://doi.org/10.1007/s10853-019-03700-8 SN - 1573-4803 SN - 0022-2461 VL - 54 IS - 17 SP - 11739 EP - 11755 PB - Springer US CY - US AN - OPUS4-48226 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Markötter, Henning A1 - Dayani, Shahabeddin T1 - Tomographic Imaging of Battery Materials at BAMline (Bessy II) N2 - Different scientific questions in battery research can be addressed by synchrotron X-Ray imaging. The BAMline at the 3rd generation synchrotron X-ray source BESSY II has been supporting researchers in a wide range of research areas for over 20 years. Being a non-destructive characterization method, synchrotron X-ray imaging, in particular tomography (SXCT), plays a particularly important role in structural characterization. This poster gives few examples from battery research conducted at BAMline. As a non-destructive characterization method, synchrotron X-ray imaging, especially tomography with hard X-Rays, plays an important role in structural 3D characterization. The upgraded dual multilayer monochromator offers flexibility by providing different energy spectra to optimize flux and energy resolution as desired. The upgraded detector (in white beam configuration, equipped with an sCMOS camera) allows the higher flux to be exploited with reduced readout times. Shorter tomographic acquisition times in the range of seconds are now possible. Hence, in-situ and operando examinations are routinely available. An integrated slip ring allows continuous rotation of the sample stage for ease of wiring. The pink beam option allows tomographic observation of processes occurring in the time domain of a few seconds with a resolution down to ~ 1 µm. The in-situ capabilities include electrochemical cycling, mechanical load (tension and compression) and heating up to 1100°C. Ergebnisse The method, equipment, data handling pipeline as well as various examples from battery research conducted at BAMline are presented and discussed. In particular, the 3D morphology and distribution of deposited Li within the widely used Celgard® 2325 polyolefin separator are visualized in situ, thus promoting the understanding of the short-circuiting process of Li metal batteries. In addition, we also visualized and quantified the spatial distribution of Li depositions inside a porous carbon host to unravel the deposition behavior that can hardly be probed by surface imaging techniques. The Li electrodeposition behavior found here could help to promote the understanding and development of surface modifications related to Li anodes, separators as well as novel 3D geometry electrode designs for accommodation of Li depositions and alleviation of volumetric changes. T2 - Batterieforum Deutschland CY - Berlin, Germany DA - 18.01.2023 KW - BAMline KW - X-ray tomography KW - Li-ion battery PY - 2023 AN - OPUS4-56909 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bresch, Sophie T1 - Texturing of calcium cobaltite for thermoelectric applications by pressure assisted sintering N2 - Thermoelectric materials can convert waste heat directly into electrical power by using the Seebeck effect. Calcium cobaltite (CCO) is considered as a promising thermoelectric p-type oxide for energy harvesting applications at temperatures above 500 °C. The properties and morphology of single-crystal CCO are strongly anisotropic because of its crystal structure of alternating layers of CoO2 and Ca2CoO3. By aligning the plate-like grains, the anisotropic properties of the grains can be assigned to the poly-crystalline parts. In this study, the combination of tape casting and pressure-assisted sintering is used to texture and densify large scale components (50 cm²). Thereby, the influence of powder preparation and applied pressure during sintering on texturing and thermoelectric properties is investigated. The analysis of XRD pole figures revealed that tape casting already leads to highly textured CCO. By pressure variation during sintering, the microstructure of CCO can be tailored either toward maximum power factor as required for energy harvesting or toward maximum figure of merit as required for energy recovery. Low pressure lead to a porous microstructure and maximum figure of merit and higher pressure to full densification and maximum power factor. The electrical and thermal conductivity of CCO seem depending on both texture and sinter density. T2 - KERAMIK 2021 / CERAMICS 2021 CY - Online meeting DA - 19.04.2021 KW - Thermoelectrics KW - Hot pressing KW - Pole figures PY - 2021 AN - OPUS4-52490 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bresch, Sophie T1 - Thermoelectric multilayer generators: development from oxide powder to demonstrator N2 - Thermoelectric generators can be used for energy harvesting by directly transforming a temperature gradient into a voltage. Multilayer generators based on ceramic multilayer technology are an interesting alternative to conventional π-type generators. They exhibit several advantages like high filling factor, possibility of texturing, co-firing of all materials in one single-step, and reduction of production costs due to the high possible degree of automation. But, co-firing of promising oxide thermoelectric materials, Ca3Co4O9 (p-type) and CaMnO3 (n-type), is very challenging due to the large difference in sintering temperature (300 K). In this work we show the material development of Ca3Co4O9, CaMnO3, and insulation for multilayer generators co-fired under uniaxial pressure at 900 °C. The materials are tailored regarding their sintering behavior, electrical performance and coefficients of thermal expansion. Tape-casting and pressure assisted sintering are applied to fabricate textured Ca3Co4O9. Compared to conventional sintering, pressure assisted sintering increases the strength by the factor 10 and the power factor by the factor of 20. The combination of sintering additives and uniaxial pressure is used to decrease the sintering temperature of CaMnO3 to 900 °C while maintaining acceptable thermoelectric properties. Different generator designs (unileg and pn-type) were fabricated and analyzed regarding microstructure and thermoelectric performance. A lower level of complexity is beneficial for co-firing and performance. The unileg demonstrators reach 80% of the simulated output power and the power output is highly reproducible between the different demonstrators (99%). T2 - Ceramics in Europe 2022 CY - Krakow, Poland DA - 10.07.2022 KW - Thermoelectrics KW - Multilayer technology KW - Co-firing KW - Texture PY - 2022 AN - OPUS4-55357 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Eddah, Mustapha A1 - Markötter, Henning A1 - Mieller, Björn A1 - Sintschuk, Michael A1 - Beckmann, Jörg A1 - Bruno, Giovanni T1 - Mitigation of DMM-induced stripe patterns in synchrotron X-ray radiography through dynamic tilting N2 - In synchrotron X-ray radiography, achieving high image resolution and an optimal signal-to-noise ratio (SNR) is crucial for the subsequent accurate image analysis. Traditional methods often struggle to balance these two parameters, especially in situ applications where rapid data acquisition is essential to capture specific dynamic processes. For quantitative image data analysis, using monochromatic X-rays is essential. A double multilayer monochromator (DMM) is successfully used for this aim at the BAMline, BESSY II (Helmholtz Zentrum Berlin, Germany). However, such DMMs are prone to producing an unstable horizontal stripe pattern. Such an unstable pattern renders proper signal normalization difficult and thereby causes a reduction of the SNR. We introduce a novel approach to enhance SNR while preserving resolution: dynamic tilting of the DMM. By adjusting the orientation of the DMM during the acquisition of radiographic projections, we optimize the X-ray imaging quality, thereby enhancing the SNR. The corresponding shift of the projection during this movement is corrected in post-processing. The latter correction allows a good resolution to be preserved. This dynamic tilting technique enables the homogenization of the beam profile and thereby effectively reduces noise while maintaining high resolution. We demonstrate that data captured using this proposed technique can be seamlessly integrated into the existing radiographic data workflow, as it does not need hardware modifications to classical X-ray imaging beamline setups. This facilitates further image analysis and processing using established methods. KW - Double multilayer monochromators KW - Synchrotron X-ray imaging KW - Signal normalization KW - BAMline KW - Dynamic tilting PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-615049 DO - https://doi.org/10.1107/S1600577524008646 SN - 1600-5775 VL - 31 SP - 1551 EP - 1560 PB - International Union of Crystallography (IUCr) AN - OPUS4-61504 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, Y. A1 - Lu, X. A1 - Cho, J.I.S. A1 - Rasha, L. A1 - Whiteley, M. A1 - Neville, T. P. A1 - Ziesche, R. A1 - Kardjilov, N. A1 - Markötter, Henning A1 - Manke, I. A1 - Zhang, X. A1 - Shearing, P. R. A1 - Brett, D. J. L. T1 - Multi-length scale characterization of compression on metal foam flow-field based fuel cells using X-ray computed tomography and neutron radiography N2 - The mechanical compression of metal foam flow-field based polymer electrolyte fuel cells (PEFCs) is critical in determining the interfacial contact resistance with gas diffusion layers (GDLs), reactant flow and water management. The distinct scale between the pore structure of metal foams and the entire flow-field warrant a multilength scale characterization that combines ex-situ tests of compressed metal foam samples and in-operando analysis of operating PEFCs using X-ray computed tomography (CT) and neutron radiography. An optimal ‘medium’ compression was found to deliver a peak power density of 853 mW/cm². The X-ray CT data indicates that the compression process significantly decreases the mean pore size and narrows the pore size distribution of metal foams. Simulation results suggest compressing metal foam increases the pressure drop and gas velocity, improving the convective liquid water removal. This is in agreement with the neutron imaging results that demonstrates an increase in the mass of accumulated liquid water with minimum compression compared to the medium and maximum compression cases. The results show that a balance between Ohmic resistance, water removal capacity and parasitic power is imperative for the optimal performance of metal foam based PEFCs. KW - Fuel cell KW - Compression effect KW - Metal foam microstructure KW - Neutron radiography KW - X-ray CT PY - 2021 DO - https://doi.org/10.1016/j.enconman.2020.113785 VL - 239 SP - 10 EP - 113785 PB - Elsevier Ltd. AN - OPUS4-53842 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ulbricht, Alexander T1 - Skalenübergreifende Materialcharakterisierung basierend auf Computertomographiedaten N2 - Die BAM präsentiert anhand ausgewählter Beispiele wie mithilfe von Computertomographiedaten dringende technische Fragestellungen zum Verständnis von Schädigungsmechanismen in verschiedensten Materialien und Komponenten, zum Beispiel in additiv gefertigten Metallen oder Batterien, beantwortet werden können. T2 - VisiConsult Röntgen-Technologietag 2024 -- Transformation in der ZfP CY - Stockelsdorf, Germany DA - 10.10.2024 KW - Computertomographie KW - Batterie KW - Additive Fertigung KW - Synchrotron KW - BAMline PY - 2024 AN - OPUS4-61431 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bresch, Sophie T1 - Thin-film capability of commercial LTCC N2 - Low-temperature co-fired ceramics (LTCC) are used to fabricate multilayer circuits which are robust in harsh environments. Thick-film technology is well established for the metallization of circuit boards and microsystems. For specific sensor applications, the combination of LTCC and thin-film technology is advantageous to reach higher structure resolutions. Due to the high roughness of as-fired LTCC surfaces compared with silicon-wafers, the deposition of low-defect- films with narrowly specified properties is challenging. The deposited thin-films are structured either by lift-off or by etching. The latter is less error-prone and thus preferred in industry provided the selected materials allow it. There is spare literature about thin films on commercial LTCC comparing different material systems or sintering techniques. For developing thin-film sensors on multilayer circuits it is crucial to identify thin-film-compatible commercial LTCC material as well as the crucial surface properties. In this work we evaluate the thin-film capability of different LTCC compositions and surface qualities. To evaluate the influence of the material composition on the thin film capability, 200 nm Ni-thin films were deposited on three different constrained-sintered LTCC (CT708, CT800 and DP951) by electron beam physical vapour deposition. The effect of surface quality was assessed by thin-film deposition on free-sintered, pressure-assisted sintered, and polished DP951. The thin-films were structured by covering corresponding sections with a UV-curable photo resin and subsequent etching of the uncovered surface, leaving behind the desired structure. The etched Ni-thin films showed high difference in failure rate and sheet resistance regarding the used LTCC-material. DP951 had the lowest sheet resistance and no failure, whereas CT800 had a high sheet resistance and a failure rate of 40 %. These results are correlated with surface roughness of the LTCC, scanning electron micrographs of the deposited thin-films, and the chemical resistance of the LTCC against commonly used etching media. Contrary to the expectations, no correlation between roughness and thin-film capability was found. The LTCC with high failure rate showed a strong chemical attack by the used etching medium. Additionally, the adhesion of thin-films on DP951 is better than on CT708 and CT800. T2 - XVIII EcerS Conference & Exhibition CY - Lyon, France DA - 02.07.2023 KW - Glass-ceramics KW - Etching KW - Resistance PY - 2023 AN - OPUS4-58019 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Widjaja, Martinus Putra T1 - Effect of the time dependent loading of type IV cylinders using a multiscale model N2 - Based on the burst test results conducted at BAM, loading rates will affect the strength of composite pressure vessels (CPV). The multiscale fibre-break model developed at Mines ParisTech is able to described this behaviour explained by the stress relaxation in the viscoelastic matrix. The experiment showed an increase of burst pressure when an extreme slow loading rate is used compare to the slow loading rate. Is is then discovered that the model could predict well for the slow loading rate but not for the extreme slow loading rate. It may have something to do with the fibre re-orientation of the hoop layer during the extreme slow loading rate test. Further investigation is required to discover this hypothesis. T2 - International Conference on Hydrogen Safety CY - Adelaide, Australia DA - 24.09.2019 KW - Composite pressure vessels KW - Fibre break KW - Multiscale model KW - Time dependent effect PY - 2019 AN - OPUS4-50262 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Widjaja, Martinus Putra A1 - Joannes, S. A1 - Bunsell, A. A1 - Mair, Georg W. A1 - Thionnet, A. T1 - Defining a Reduced Volume Zone for the Simulation of Burst Test on a Composite Pressure Vessels N2 - The random nature of fibre break in composite materials has to be modelled in all part of the structure as it may contain millions of fibres. The reduced volume method was introduced to determine a smaller zone where we could characterise the strength based on the accumulation of fibre break, hence increasing the computation time T2 - The 8th International Conference on Structural Analysis of Advanced Materials CY - Tarbes, France DA - 28.08.2018 KW - Reduced volume method KW - Composite structures KW - Pressure vessels KW - Finite element method KW - Multiscale model PY - 2018 SP - 217508 AN - OPUS4-48928 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Widjaja, Martinus Putra T1 - Effect of input properties on the predicted failure of a composite pressure vessel using a multiscale model N2 - The effect of different Weibull parameter from different carbon fibres to predict the failure of a type IV pressure vessel has been analysed. In addition, the effect of the shape and scale parameter has also been done. T700S fibres gave higher burst pressure prediction as it has higher scale parameter and higher stiffness of the fibres. When smaller scale parameter is introduced, lower burst pressure prediction was found and vice versa. Whereas, higher burst pressure prediction was observed when smaller shape parameter was used and vice versa. The latter must have something to do with the higher probability of stronger and weaker fibres in the smaller percentile. T2 - FiBreMoD Conference CY - Leuven, Belgium DA - 11.12.2019 KW - Composite pressure vessel KW - Fibre break KW - Multiscale model KW - Weibull parameters PY - 2019 AN - OPUS4-50115 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bresch, Sophie T1 - Development of textured multilayer thermoelectric generators based on calcium cobaltite N2 - Thermoelectric generators can be used as energy harvesters for sensor applications. Multilayer thermoelectric generators (ML-TEGs) are a promising alternative to conventional π-type generators due to their high filling factor, high capability of automated production and the texturing potential during the production process. Calcium cobaltite is a promising thermoelectric oxide (p-type) with highly anisotropic properties. The following study shows the development of a textured unileg ML-TEG using ceramic multilayer technology. Tape-casting and pressure assisted sintering are applied to fabricate textured calcium cobaltite. Compared to conventional sintering, pressure assisted sintering increases the strength by the factor 10. Thermoelectric properties can be tuned either towards maximum power factor or towards maximum figure of merit depending on the pressure level. As electrical insulation material, a screen-printable glass-ceramic with high resistivity and adapted coefficient of thermal expansion is developed. From various commercial pastes a metallization with low contact resistance is chosen. The unileg ML-TEG is co-fired in one single step. The demonstrators reach 80% of the simulated output power and the power output is highly reproducible between the different demonstrators (99%). These results provide the first proof-of-concept for fabricating co-fired multilayer generators based on textured calcium cobaltite with high power factor, high density, and high strength. T2 - Virtual Conference on Thermoelectrics 2021 (VCT) CY - Online meeting DA - 20.07.2021 KW - Thermoelectrics KW - Multilayertechnik KW - Screen printing PY - 2021 AN - OPUS4-52993 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stargardt, Patrick T1 - Analysis of reaction layers and cooling simulations of co-fired thermoelectric multilayers N2 - Ceramic multilayer technology is an attractive approach for the cost-effective fabrication of thermoelectric generators. Therefore, efforts are being made to co-sinter two promising thermoelectric oxides, namely calcium cobaltite and calcium manganate. In this study, calcium cobaltite, calcium manganate and release tapes were pressure assisted sintered. A major challenge here is the cracking of calcium manganate during cooling. A relationship between the properties of the release tape used in pressure-assisted sintering and the cracking behavior was observed experimentally. To understand the origin of failure, formed reaction layers in the multilayer were analyzed by EDX and grazing incident XRD. Based on this analysis, bulk samples were prepared, and thermal expansion and Young's modulus and were determined thereon, if they were not known from the literature. The biaxial strength of the thermoelectric oxides was determined by the ball on three ball method. The thermal stresses during cooling of different multilayer designs were estimated by finite element simulations. The stresses caused by the reaction layers turned out to be negligible. The FEM study indicated further, and a validation experiment proved, that the thickness of the release tape has the main effect on thermal stresses during cooling in single material. For best performance, the design of a thermoelectric multilayer generator needs to consider thermoelectric performance and thermal stresses during cooling. T2 - Virtual Conference on Thermoelectrics CY - Online meeting DA - 20.07.2021 KW - Ceramic multilayer KW - Cooling simulations KW - Thermal stress KW - Thermoelectric PY - 2021 AN - OPUS4-52994 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stargardt, Patrick T1 - Comparison of design concepts for ceramic oxide thermoelectric multilayer generators N2 - Multilayer thermoelectric generators are a promising perspective to the conventional π-type generators. Ceramic multilayer technology is well established for production of microelectronics and piezo-stacks. Key features of ceramic multilayer technology are full-automation, cost-effectiveness, and the co-firing of all materials in one single step. This requires similar sintering temperatures of all used materials. The development of multilayer thermoelectric generators is a subject of current research due to the advantages of this technology. One of the challenges is the compatibility of the different materials with respect to the specific design. The presented study compares three different designs of multilayer generators based on a given set of material properties. Dualleg, unileg and transverse multilayer generators are compared to conventional π-type generators., the designs are evaluated regarding the expected maximum output power and power density using analytical calculations and FEM simulations. Additionally, the complexity of the production process and material requirements are assessed and design optimizations to simplify production are discussed. Besides the theoretical aspects, unileg multilayer generator prototypes were produced by tape-casting and pressure-assisted sintering. These prototypes are compared to other multilayer generators from literature regarding the power factors of the used material system and the power density. Improvements of the power output by design optimizations are discussed T2 - 18th European Conference on Thermoelectrics CY - Barcelona, Spain DA - 13.09.2022 KW - Thermoelectric oxides KW - Thermoelectric generator design PY - 2022 AN - OPUS4-55820 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bresch, Sophie T1 - Chemical resistance of commercial LTCC against thin film etching media N2 - Low-temperature co-fired ceramics (LTCC) are used to fabricate robust multilayer circuits. Typically, thick-film technology is applied for metallization. For specific sensor applications, thin films are deposited directly on the as-fired LTCC-surface. These deposited thin films are structured either by lift-off or by etching. The latter is less error-prone and thus preferred in industry provided the selected materials allow it. 200 nm Ni-thin films were deposited on three different commercial constrained-sintered LTCC (CT708, CT800 and DP951) by electron beam physical vapour deposition. The thin-films were structured by covering corresponding sections with a UV-curable photo resisn and subsequent etching of the uncovered surface, leaving behind the desired structure. The etched Ni-thin film showed high difference in failure rate and sheet resistance regarding the used LTCC-material. DP951 had the lowest sheet resistance and no failure, whereas the CT800 had a failure rate of 40 %. The LTCC with high failure rate showed a strong chemical attack by the used etching medium. To address this phenomenon, the chemical resistance of the three different commercial LTCC (CT708, CT800 and DP951) against four different commonly used etching media (sulphuric acid, phosphoric acid, aqua regia, and hydrofluoric acid) is investigated. The dissolved ions are analyzed by ICP-OES to correlate the LTCC-composition and its chemical resistance. T2 - KERAMIK 2023 / 98. DKG-Jahrestagung CY - Jena, Germany DA - 27.03.2023 KW - Glass-ceramics KW - Hydrogen sensors KW - Acids PY - 2023 AN - OPUS4-57273 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grelle, Tobias A1 - Wolff, Dietmar A1 - Jaunich, Matthias T1 - Leakage behaviour of elastomer seals under dynamic unloading conditions at low temperatures N2 - In technical applications, static seals are sometimes also subjected to dynamic loadings. Therefore, the leakage behaviour under dynamic conditions has to be evaluated as well. For this purpose, FKM elastomer seals have been tested by using newly designed equipment that allows for rapid partial release of the seal and simultaneous leakage rate measurement at a wide range of test temperatures. Furthermore, material characterisation was done by using Dynamic Mechanical Analysis, Differential Scanning Calorimetry and Compression Set. It was shown that, under static conditions, the leakage rate increased significantly during cooling at temperatures around 18 K lower than the glass transition range. On reheating, the seal’s functionality was restored in the high temperature region of the glass rubber transition. In the subsequent dynamic release tests, that comprised a reduction of the seal compression within 1 s from 25 % to 23 %, increased leakage rates were observed in the high temperature region of the glass transition range. It was shown that the temperature that is critical for increased leakage is significantly lower under static conditions compared to dynamic conditions. The obtained leakage rates for static tests and dynamic release tests at different temperatures were analysed with reference to results of the material characterisation. KW - Sealing material KW - Rubber KW - Partial release KW - Low temperature behaviour KW - Leakage rate PY - 2017 DO - https://doi.org/10.1016/j.polymertesting.2016.12.018 SN - 0142-9418 SN - 1873-2348 VL - 58 SP - 219 EP - 226 PB - Elsevier Ltd. CY - Oxford, UK AN - OPUS4-38911 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sachse, René T1 - Operando electrochemical spectroscopic ellipsometry: Material properties of highly active mesoporous IrOx films revealed under realistic OER conditions N2 - Hydrogen production via water electrolysis will be an essential cornerstone in development of sustainable, fossil-free fuel and chemical production on a global scale. The activity and stability of each catalyst is highly dependent on the properties of the coating, i.e., phase composition, crystallinity, accessible surface area, and many other factors. The key to developing improved catalysts is a better understanding of the relationships between their performance, stability, and physicochemical properties. However, these relationships can be complex and are also strongly influenced by the reaction environment. Therefore, operando analysis of the catalyst material during catalysis at realistic potentials and current densities is highly desirable. However, many analytical techniques cannot be applied in liquid environments at realistic potentials and current densities. We propose environmental ellipsometric analysis in a dedicated electrochemical flow cell as a method to evaluate gas evolution reactions operando under realistic working conditions. Figure 1 illustrates schematically the developed technique. Key factors to success are highly active model-type catalysts, a suitable sample environment, and a deep understanding of the appropriate model development, as well as concise cross validation with numerous other analytical techniques. The method was developed and validated by analyzing a calcination series (300 – 600 °C) of mesoporous templated IrOx films ex-situ and operando under oxygen evolution reaction (OER) conditions. The employed environmental electrochemical spectroscopic ellipsometric (ECSE) analysis revealed during OER the change of optical and electronic properties, i.e. the dielectric functions, resistivity and band-to-band transitions (p-d band transitions). Film thickness and porosity were validated by means of scanning electron microscopy (SEM), X-ray reflectometry (XRR) or ellipsometric porosimetry (EP), electrical and electronic properties by means of conductivity measurements, X-ray photoelectron spectroscopy (XPS) or UV-Vis-NIR absorption spectroscopy. The electronic structures of the catalysts from valence electron energy loss spectra (VEELS) derived from ε1 and ε2 from SE measurements reveal a direct correlation with electrochemical activities in OER. In the presentation reversible and irreversible potential-dependent changes of the catalyst properties during operation will be discussed along with the dynamics of gas formation, transport and dissolution at different potentials. T2 - 11th Workshop Ellipsometry (WSE 11) CY - Steyr, Austria DA - 06.09.2021 KW - Ectrocatalysis KW - Mesoporous iridium oxide films KW - Non-destructive operando analysis KW - Oxygen evolution reaction KW - Spectroscopic ellipsometry PY - 2021 AN - OPUS4-53915 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, M. A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Oxidative ageing of elastomers: experiment and modelling N2 - During an extensive test programme at the Bundesanstalt für Materialforschung und prüfung, material property changes of EPDM O-rings were investigated at different ageing times and two ageing temperatures of 125 ◦ C and 150 ◦ C. To exclude possible diffusion-limited oxidation (DLO) effects that can distort the data, IRHD microhardness measurements were taken over the cross section of compressed O-rings. Continuous stress relaxation measurements were taken on samples free of DLO effects. The additional effect of physical processes to irreversible chemical ones during a long-term thermal exposure is quantified by the analysis of compression set measurements under various test conditions. By combining the different experimental methods, characteristic times relative to the degradation processes were determined. On the basis of experimental data, a microphysically motivated model that takes into account reversible and irreversible processes was developed. The parameter identification strategy of the material model is based on our experimental investigations on homogeneously aged elastomer O-rings. The simulated results are in good agreement with the experiments. KW - Compression Set KW - Compression stress relaxation KW - Modelling KW - Ageing KW - Microhardness PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-609332 DO - https://doi.org/10.1007/s00161-022-01093-9 VL - 36 SP - 289 EP - 297 PB - Springer Nature AN - OPUS4-60933 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - Overview of metal seal tests performed at BAM and implications for extended interim storage N2 - The investigation of the long-term performance of sealing systems employed in containers for radioactive waste and spent nuclear fuel is one research focus area for division 3.4 “Safety of Storage Containers” at the Bundesanstalt für Materialforschung und -prüfung. The behaviour of metallic seals, which are employed in interim storage casks for used fuel and high active waste, over time is of high importance for ensuring safe enclosure. Therefore, investigations on these systems were started at BAM to get a general understanding of the relevant processes. Our investigations comprise investigations on different parameters which influence the seal performance and the main part is focussed on the time and temperature dependent behaviour. In this contribution an overview of the performed tests and their respective results will be given. A focus will lie on a comparison between seals with large torus diameter in comparison to small diameters. Our aim is to understand the long-term behaviour of the sealing systems for evaluation of their performance during possible extended interim storage and subsequent transportation. T2 - 4th Workshop on Safety of Extended Dry Storage of Spent Nuclear Fuel CY - Online meeting DA - 03.06.2020 KW - Seal performance KW - Metal seal KW - Leakage rate PY - 2020 AN - OPUS4-50843 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Influence of Ageing on Sealability of HNBR, EPDM and FKM O-rings N2 - At BAM, which is the federal institute for materials research and testing in Germany, it is one of our tasks to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes assessment of elastomeric seals applied in the containers. Besides examining the low-temperature behaviour and irradiation effects of elastomeric seals, it is our goal to evaluate the service lifetime of the seals with regard to the requirements for long-term safety (40 years and more) of the containers. Therefore, we started an accelerated ageing programme with selected rubbers often used for seals (HNBR, EPDM and FKM) which are aged at four different temperatures (75 °C, 100 °C, 125 °C and 150 °C) up to 1 year. In order to assess sealability, O-rings are aged in compression by 25 % (corresponding to the compression during service) between plates as well as in flanges that allow leakage rate measurements. For comparison, uncompressed O-rings are aged as well. Further methods characterising seal performance are compression stress relaxation (CSR) reflecting the loss of sealing force of a compressed seal over time, and compression set (CS) which represents the recovery behaviour of a seal after release from compression. Additionally, hardness is measured for information about the change of mechanical properties. The experimental results indicate that while hardness, CSR and CS show considerable degradation effects, the leakage rate stays constant or even decreases until shrinkage and the loss of resilience of the aged seal leads to the formation of a leakage path. This indicates that static leakage rate, which is the only available direct seal performance criterion, has only limited sensitivity for the degradation of the seal material. T2 - International Sealing Conference CY - Stuttgart, Germany DA - 12.10.2016 KW - Rubber KW - Seal KW - Degradation PY - 2016 SN - 978-3-8163-0674-9 VL - 2016 SP - 551 EP - 563 PB - VDMA AN - OPUS4-38014 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Mike A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - A numerical approach to correlate compression stress relaxation and compression set of elastomer O-rings with tightness N2 - The excellent mechanical properties of elastomer seals at a wide range of temperatures as well as their high versatility and recovery potential under several load conditions make these materials well suitable for the application in containers designed for transport and disposal of negligible heat generating radioactive waste. While a seal exchange at defined intervals is typical in many conventional applications, it is impossible or at least hard to perform when principles of minimization of radiation exposure have to be considered which prohibit an avoidable cask handling. An extensive knowledge of the change of the elastomer properties during aging and the availability of reliable end-of-lifetime criteria to guarantee the safe enclosure of the radioactive material for the required time are mandatory. As BAM is involved in most of the national cask licensing procedures and in the evaluation of cask-related long-term safety issues, great efforts have already been made and are still ongoing to scientifically support this task. Among other representative types of elastomers, specimen made from ethylene propylene diene rubber (EPDM) were tested before, during and after aging to capture the with respect to application most important of their complex mechanical properties. Exemplary results of these investigations were used to calibrate material models implemented in the commercial finite element software ABAQUS/Standard®. The finite element model already presented in previous works uses a sequential temperature displacement coupling. The calculated compression stress relaxation (CSR) and compression set (CS) values do satisfactorily match the experimental results. In many investigations performed at BAM both values (CSR and CS) were identified as key indicators of elastomer’s long-term performance. However, the possibility to correlate these equivalent indicators with performance values such as tightness and leakage rate, measurable in the mounted state, is an important goal of our future work. In the presented study the ABAQUS® feature of “pressure penetration” is introduced in the suggested finite element model for this purpose. It provides the possibility to simulate the penetration of a gas into a possible gap between flange and O-ring causing an opening of a leakage path. Three dimensional and axis-symmetric finite element models were generated to represent flat and grooved flanges of different dimensions. The sensitivity of the feature to several input parameters is investigated and the observed behavior of the O-ring is correlated with the results of performed leakage tests. T2 - ASME 2021 Pressure Vessels & Piping Conference (PVP2021) CY - Online meeting DA - 13.07.2021 KW - Elastomer KW - Tightness KW - Leakage KW - Compression set KW - Compression stress relaxation PY - 2021 SN - 978-0-7918-8535-2 DO - https://doi.org/10.1115/PVP2021-61976 SP - 1 EP - 8 PB - American Society of Mechanical Engineers (ASME) CY - New York, NY, USA AN - OPUS4-54422 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Mike T1 - A numerical approach to correlate compression stress relaxation and compression set of elastomer O-rings with tightness N2 - The excellent mechanical properties of elastomer seals at a wide range of temperatures as well as their high versatility and recovery potential under several load conditions make these materials well suitable for the application in containers designed for transport and disposal of negligible heat generating radioactive waste. While a seal exchange at defined intervals is typical in many conventional applications, it is impossible or at least hard to perform when principles of minimization of radiation exposure have to be considered which prohibit an avoidable cask handling. An extensive knowledge of the change of the elastomer properties during aging and the availability of reliable end-of-lifetime criteria to guarantee the safe enclosure of the radioactive material for the required time are mandatory. As BAM is involved in most of the national cask licensing procedures and in the evaluation of cask-related long-term safety issues, great efforts have already been made and are still ongoing to scientifically support this task. Among other representative types of elastomers, specimen made from ethylene propylene diene rubber (EPDM) were tested before, during and after aging to capture the with respect to application most important of their complex mechanical properties. Exemplary results of these investigations were used to calibrate material models implemented in the commercial finite element software ABAQUS/Standard®. The finite element model already presented in previous works uses a sequential temperature displacement coupling. The calculated compression stress relaxation (CSR) and compression set (CS) values do satisfactorily match the experimental results. In many investigations performed at BAM both values (CSR and CS) were identified as key indicators of elastomer’s long-term performance. However, the possibility to correlate these equivalent indicators with performance values such as tightness and leakage rate, measurable in the mounted state, is an important goal of our future work. In the presented study the ABAQUS® feature of “pressure penetration” is introduced in the suggested finite element model for this purpose. It provides the possibility to simulate the penetration of a gas into a possible gap between flange and O-ring causing an opening of a leakage path. Three dimensional and axis-symmetric finite element models were generated to represent flat and grooved flanges of different dimensions. The sensitivity of the feature to several input parameters is investigated and the observed behavior of the O-ring is correlated with the results of performed leakage tests. T2 - ASME 2021 Pressure Vessels & Piping Conference (PVP2021) CY - Online meeting DA - 13.07.2021 KW - Elastomer KW - Tightness KW - Leakage KW - Compression set KW - Compression stress relaxation PY - 2021 AN - OPUS4-54423 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - Grelle, Tobias A1 - Wolff, Dietmar T1 - Low temperature properties of elastomer seals - Comparison between purely static and partially released seals - N2 - Rubber is widely used as sealing material in various applications. In many fields the function of seal materials at low temperatures is necessary. Therefore the understanding of failure mechanisms that lead to leakage at low temperatures is of high importance. It is known that the material properties of rubbers are strongly temperature dependent. At low temperatures this is caused by the rubber-glass transition (abbr. glass transition). During continuous cooling the material changes from rubber-like entropy-elastic behaviour to stiff energy-elastic behaviour, that allows nearly no strain or retraction, due to the glass transition. Hence rubbers are normally used above their glass transition but the minimum working temperature limit is not defined precisely, what can cause problems during application. Therefore the lower operation temperature limit of rubber seals should be determined in dependence of the material properties. In the past we investigated the material properties and sealing behaviour of elastomeric seals at low temperatures. Additionally we started to study the effect of a small partial release of elastomer seals at low temperatures. To study the influence of dynamic events on seal performance and to enhance the understanding of occurring seal failure, a setup for a fast partial seal release was designed. In this contribution we focus on the correlation of material properties and component behaviour under different application conditions. It is desired to widen the understanding of the process of seal failure at low temperature. T2 - 12. Kautschuk-Herbst-Kolloquium CY - Hannover, Germany DA - 22.11.2016 KW - Seal properties KW - Low temperature KW - Partial release KW - Leakage rate PY - 2016 SN - 9783981407648 SP - 34 AN - OPUS4-38501 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Scission, cross-linking, and physical relaxation during thermal degradation of elastomers N2 - Elastomers are susceptible to chemical ageing, i.e., scission and cross-linking, at high temperatures. This thermally driven ageing process affects their mechanical properties and leads to limited operating time. Continuous and intermittent stress Relaxation measurements were conducted on ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) samples for different ageing times and an ageing temperature of 125 °C. The contributions of chain scission and cross-linking were analysed for both materials at different ageing states, elucidating the respective ageing mechanisms. Furthermore, compression set experiments were performed under various test conditions. Adopting the two-network model, compression set values were calculated and compared to the measured data. The additional effect of physical processes to scission and cross-linking during a long-term thermal exposure is quantified through the compression set analysis. The characteristic times relative to the degradation processes are also determined. KW - Ageing KW - Scission KW - Cross-linking KW - Compression set KW - Physical relaxation PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-486091 DO - https://doi.org/10.3390/polym11081280 SN - 2073-4360 VL - 11 IS - 8 SP - 1280, 1 EP - 12 PB - MDPI AN - OPUS4-48609 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Grelle, Tobias A1 - Jaunich, Matthias A1 - Goral, Milan A1 - Wolff, Dietmar T1 - Three-dimensional thermal expansion of neat and irradiated (U)HMWPE materials at elevated temperatures N2 - The thermal expansion of polymeric parts can be an issue in many applications where the available space is limited, or exact dimensions of the part are required. For this study, a device was designed and built that allowed measuring the thermal expansion simultaneously in all three spatial directions on cubic samples with real-scale dimensions (78 mm edge length). The results are shown between 25 °C and 125 °C for two PE materials, one HMWPE and one tempered UHMWPE, for non-irradiated samples as well as cubes that have been irradiated with 100 and 400 kGy. The results measured with the new device were very similar to those measured with conventional thermo-mechanical analysis equipment and to literature data of UHMWPE. The HMWPE material shows a much larger thermal expansion coefficient in one direction compared to the other two directions during the first heating due to frozen stresses from the pressing step during material manufacturing. These stresses are mostly released by the expansion during the first heating, so that the expansion during the second heating is more uniform. The overall volumetric expansion is the same for both heating runs. By contrast, the tempered UHMWPE material shows no significant difference between first and second heating run, as the stresses from processing could already relax in the tempering step. The irradiation treatment does not affect the values significantly for the given test set-up. KW - Lupolen KW - Ultra high molecular weight polyethylene KW - GUR KW - Coefficient of thermal expansion KW - High temperature PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563987 DO - https://doi.org/10.1016/j.polymertesting.2022.107841 SN - 0142-9418 VL - 117 SP - 1 EP - 8 PB - Elsevier Ltd. AN - OPUS4-56398 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja T1 - Research at BAM for evaluating long term safety of container systems and components N2 - Safety of long term containment and storage of radioactive waste is an essential issue, which is increasingly gaining international attention. Extending interim storage beyond initial license periods is one of the major challenges worldwide. BAM has been involved in all kinds of radioactive waste container safety evaluation for storage and transportation including their long term performance from the very beginning. Today, all work related to the safe management of radioactive waste is linked by the activity field “Nuclear Waste Management” within the Focus Area “Energy” at BAM and in conjunction with a research strategy and agenda. Most recently, the working group “Long Term Safety of Container Systems and Components” was established to launch and perform research projects related to safety issues concerning the extended interim storage of radioactive waste. For example, within our project LaMEP, we investigate ageing effects of metal and elastomer seals as well as polymeric neutron shielding materials, which are container components that fulfil major safety functions. The results of the experiments help to understand the long term behaviour of these components. Likewise, our project BRUZL started at BAM in 2018 with the aim of developing a fracture mechanics approach to understand and describe a potential brittle failure mechanism of fuel cladding during long-term interim storage. BAM also contributes to the GRS project “Development of methods and models and international exchange for safety evaluation in the frame of interim storage of radioactive waste”. Additionally, BAM is involved in several international research programmes dealing with extended interim storage, such as the European Joint Programme on Radioactive Waste Management (EURAD), the Extended Storage Collaboration Program (ESCP) and IAEA Coordinated Research Projects. The present contribution provides a comprehensive overview of BAM research activities contributing to national and international gap analyses and to filling knowledge gaps regarding the safe long term management of radioactive waste. T2 - Annual Meeting on Nuclear Technology 2019 CY - Berlin, Germany DA - 07.05.2019 KW - Radioactive Waste KW - Container Safety KW - Metal Seals KW - Elastomer Seals KW - Fuel cladding PY - 2019 AN - OPUS4-48437 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agroui, K. A1 - Jaunich, Matthias A1 - Hadj Arab, A. T1 - Analysis techniques of polymeric encapsulant materials for photovoltaic modules: Situation and perspectives N2 - The properties of the encapsulant are critical to the long-term performance of photovoltaic (PV) modules under the influence of sunlight including UV, elevated temperature, humidity and diffusion of oxygen. Encapsulation process represents about 40% of the whole PV module cost. The introduction of new non-EVA encapsulant material type “Low-Cost, High-Performance” should provide a solution to outdoor yellowing degradation problems. The emerging encapsulant materials exhibit a good compatibility with emerging PV solar cells for long term durability. This new generation of encapsulant materials has the advantage to improve the PV module performances and long term durability for specific climate like desert regions. This scientific contribution presents an overview of the different encapsulant materials currently on the market, the general requirements of the emerging encapsulant materials and characterizations techniques for degradation, diagnostic and reliability lifetime estimation in the framework of Algerian renewable energy strategy. T2 - Africa-EU Symposium on Renewable Energy Research and Innovation CY - Tlemcen, Algeria DA - 08.03.2016 KW - solar cells KW - PV modules KW - polymer encapsulant KW - encapsulation KW - analysis techniques PY - 2016 SP - 27 EP - 27 PB - European Union Energy Initiative – Partnership Dialogue Facility (EUEI PDF) CY - Eschborn, Germany AN - OPUS4-35917 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo A1 - Roohbakhshan, Farshad T1 - Cyclic Operation Performance of 9-12% Cr Ferritic-Martensitic Steels. Part 2: Microstructural Evolution during Cyclic Loading and its Representation in a Physically-based Micromechanical Model N2 - The current trend towards cyclic, “flexible” operation of fossil-fueled power plants constitutes a major issue regarding lifetime and operational safety of the respective installations and their components, as was outlined in our complementary contribution (Part 1). The present contribution reports on the investigation of the microstructure evolution in cyclically loaded ferritic-martensitic steels and its representation in a physically-based micromechanical model. For this purpose, specimens of P92 steel grade from the mechanical test programme outlined in our companion contribution (Part 1) were analyzed by scanning electron microscopy (SEM), including backscattered diffraction (EBSD) mapping, and transmission electron microscopy (TEM). A novel method was implemented to improve angular resolution of EBSD scans. Additionally, a correlative microscopy approach was developed and used to correlate EBSD and TEM measurements on the same locations of thick regions of electron transparent specimens. By applying these techniques, a detailed quantitative microstructure description of the as-received material condition, namely in terms of subgrain morphology and dislocation density/distributions, was established. Comparisons of as-received and cyclically loaded conditions from tests interrupted at different stages of lifetime indicate a rapid redistribution of in-grain dislocations with a strong interaction between mobile dislocations and low angle grain boundaries (LABs). The proposed micromechanical model is formulated in a viscoplastic self-consistent (VPSC) scheme, which is a mean-field approach that allows us to include the crystal details at the level of slip systems while avoiding the considerable computational costs of full-field approaches (such as the classical crystal plasticity finite element analysis). Being physically-based, the model uses dislocation densities and includes the interaction between dislocations, e.g. annihilation of mobile dislocations, and evolution of microstructure, e.g. the grain coarsening. Particularly, the constitutive laws for dislocation evolution and interaction between dislocations and low angle boundaries are calibrated based on two-dimensional discrete dislocation dynamic (2D DDD) simulations, which are performed at a micro-/meso-scale. The results of the beforementioned EBSD experiments are considered as a direct input, involving e.g. the amount of geometrically necessary dislocations, average misorientations and grain characteristics. T2 - 45th MPA-Seminar 2019 CY - Leinfelden-Echterdingen, Germany DA - 01.10.2019 KW - Tempered martensite ferritic steel KW - Dislocation KW - Electron backscattered diffraction (EBSD) KW - Transmission electron microscopy (TEM) KW - Microstructure KW - Physically based material model PY - 2019 AN - OPUS4-49346 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bresch, Sophie A1 - Mieller, Björn A1 - Moos, R. A1 - Rabe, Torsten T1 - Lowering the sintering temperature of calcium manganate for thermoelectric applications N2 - This study combines three different approaches to lower the sintering temperature of Sm-doped CaMnO3 to save energy in production and facilitate co-firing with other low-firing oxides or metallization. The surface energy of the powder was increased by fine milling, sintering kinetics were enhanced by additives, and uniaxial pressure during sintering was applied. The shrinkage, density, microstructure, and thermoelectric properties were evaluated. Compared to micro-sized powder, the use of finely ground powder allows us to lower the sintering temperature by 150 K without reduction of the power factor. By screening the effect of various common additives on linear shrinkage of CaMnO3 after sintering at 1100 ○C for 2 h, CuO is identified as the most effective additive. Densification at sintering temperatures below 1000 ○C can be significantly increased by pressure-assisted sintering. The power factor at room temperature of CaMnO3 nano-powder sintered at 1250 ○C was 445 μW/(m K2). Sintering at 1100 ○C reduced the power factor to 130 μW/(m K2) for CaMnO3 nano-powder, while addition of 4 wt.% CuO to the same powder led to ∼290 μW/(m K2). The combination of fine milling, CuO addition, and pressureassisted sintering at 950 ○C resulted in a power factor of ∼130 μW/(m K2). These results show that nano-sized powder and CuO addition are successful and recommendable strategies to produce CaMnO3 with competitive properties at significantly reduced temperatures and dwell times. KW - Sintering additive KW - Liquid phase sintering KW - Pressure assisted sintering PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-555467 DO - https://doi.org/10.1063/5.0098015 SN - 2158-3226 VL - 12 IS - 8 SP - 1 EP - 9 PB - American Institute of Physics (AIP) CY - New York, NY AN - OPUS4-55546 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bresch, Sophie A1 - Stargardt, Patrick A1 - Moos, Ralf A1 - Mieller, Björn T1 - Co‐Fired Multilayer Thermoelectric Generators Based on Textured Calcium Cobaltite N2 - Thermoelectric generators are very attractive devices for waste heat energy harvesting as they transform a temperature difference into electrical power. However, commercially available generators show poor power density and limited operation temperatures. Research focuses on high‐temperature materials and innovative generator designs. Finding the optimal design for a given material system is challenging. Here, a theoretical framework is provided that allows appropriate generator design selection based on the particular material properties. For high‐temperature thermoelectric oxides, it can be clearly deduced that unileg multilayer generators have the highest potential for effective energy harvesting. Based on these considerations, prototype unileg multilayer generators from the currently best thermoelectric oxide Ca3Co4O9 are manufactured for the first time by industrially established ceramic multilayer technology. These generators exhibit a power density of 2.2 mW/cm² at a temperature difference of 260 K, matching simulated values and confirming the suitability of the technology. Further design improvements increase the power density by a factor of 22 to facilitate practicable power output at temperature differences as low as 7 K. This work demonstrates that reasonable energy harvesting at elevated temperatures is possible with oxide materials and appropriate multilayer design. KW - Optical and Magnetic Materials KW - Electronic PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-596306 DO - https://doi.org/10.1002/aelm.202300636 SN - 2199-160X VL - 10 IS - 3 SP - 1 EP - 12 PB - Wiley VHC-Verlag AN - OPUS4-59630 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Trogadas, P. A1 - Cho, J. I. S. A1 - Rasha, L. A1 - Lu, X. A1 - Kardjilov, N. A1 - Markötter, Henning A1 - Manke, I. A1 - Shearing, P. R. A1 - Brett, D. J. L. A1 - Coppens, M. O. T1 - A nature-inspired solution for water management in flow fields for electrochemical devices N2 - A systematic, nature-inspired chemical engineering approach is employed to solve the issue of flooding in electrochemical devices. The mechanism of passive water transport utilized by lizards living in arid environments is leveraged to design flow-fields with a microchannel structure on their surface, through which capillary pressure rapidly removes the water generated in the electrochemical device. This water management strategy is implemented in proton exchange membrane fuel cells (PEMFCs) with a lunginspired flow-field, which ensures uniform distribution of reactants across the catalyst layer. Jointly, this nature-inspired approach results in flood-free, stable operation at 100% RH and a B60% increase in current (B1.9 A cm-2) and peak power density (B650 mW cm−2) compared to current PEMFCs with a flood-prone, serpentine flow-field (B0.8 A cm-2 and 280 mW cm-2, respectively). This significant advance allows for PEMFC operation at fully humidified conditions. KW - Neutron imaging KW - X-ray tomography KW - Fuel cell PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-596662 DO - https://doi.org/10.1039/d3ee03666a VL - 17 SP - 2007 EP - 2017 PB - Royal Society of Chemistry (RSC) AN - OPUS4-59666 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Duan, K. A1 - Zhu, L. A1 - Li, M. A1 - Xiao, L. A1 - Bevilacqua, N. A1 - Eifert, L. A1 - Manke, I. A1 - Markötter, Henning A1 - Zhang, R. A1 - Zeis, R. A1 - Sui, P. -C. T1 - Multiphase and Pore Scale Modeling on Catalyst Layer of High-Temperature Polymer Electrolyte Membrane Fuel Cell N2 - Phosphoric acid as the electrolyte in high-temperature polymer electrolyte membrane fuel cell plays an essential role in ist performance and lifetime. Maldistribution of phosphoric acid in the catalyst layer (CL) may result in performance degradation. In the present study, pore-scale simulations were carried out to investigate phosphoric acid’s multiphase flow in a cathode CL. A reconstructed CL model was built using focused ion beam-SEM images, where distributions of pore, carbon support, binder, and catalyst particles can be identified. The multi-relaxation time lattice Boltzmann method was employed to simulate phosphoric Acid invading and leaching from the membrane into the CL during the membrane electrode assembly fabrication process. The predicted redistribution of phosphoric acid indicates that phosphoric acid of low viscosity or low wettability is prone to leaching into the CL. The effective transport properties and the active electrochemical active surface area (ECSA) were computed using a pore-scale model. They were subsequently used in a macroscopic model to evaluate the cell performance. A parametric study shows that cell performance first increases with increasing phosphoric acid content due to the increase of ECSA. However, further increasing phosphoric acid content results in performance degradation due to mass transfer limitation caused by acid flooding. KW - Gas diffusion layers KW - Lattice Boltzmann simulation KW - Electrochemical impedance spectra KW - Phosphoric acid KW - HT-PEFC PY - 2021 DO - https://doi.org/10.1149/1945-7111/abff03 VL - 168 IS - 5 SP - 054521 PB - IOP Science AN - OPUS4-53836 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tang, F. A1 - Li, D. A1 - Liu, X. A1 - Huang, H. A1 - Wu, C. A1 - Hilger, A. A1 - Markötter, Henning A1 - Wilde, F. A1 - Manke, I. A1 - Sun, F. A1 - Chen, L. T1 - Exploring optimal Li composite electrode anodes for lithium metal batteries through in situ X-ray computed tomography N2 - The uncontrolled Li dissolution/deposition dynamics and rapid Li pulverizations hinder the widespread deployment of Li metal batteries (LMB). Designing a Li composite electrode possessing a mechanically robust and lithiophilic three-dimensional (3D) framework represents a promising strategy to address these challenges. This study involves the preparation of three uniquely tailored Li-B-Mg composites using a combined metallurgical process of melting, casting, and rolling, along with the synergistic application of in situ X-ray computed tomography (CT) and post-mortem failure analysis to explore the most promising composite electrode candidate for LMBs. During the in-depth investigation, the optimal 70Li-B-Mg composite electrode stands out due to its robust skeleton fiber structure, uniform Li dissolution/deposition characteristics and high capacity of free-Li. Its promising prospects for enabling high-performance LMBs are showcased by the superior performance of the built Li||O2, Li||LiFePO4, Li||NCM622 and Li||NCM811 battery systems. This work offers a novel approach for exploring universally applicable and robust Li composite electrodes to realize high-performance LMBs using in situ CT analysis. KW - Li metal batteries KW - Li composite electrode KW - X-ray computed tomography KW - Li-B-Mg PY - 2024 DO - https://doi.org/10.1016/j.ensm.2024.103746 VL - 72 SP - 12 PB - Elsevier B.V. AN - OPUS4-61039 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bresch, Sophie T1 - Pressure-assisted sintering of tape cast calcium cobaltite for thermoelectric applications N2 - Thermoelectric materials can convert waste heat directly into electrical power by using the Seebeck effect. Calcium cobaltite Ca3Co4O9 is a promising p-type oxide thermoelectric material for applications between 600 °C and 900 °C in air. The properties and morphology of Ca3Co4O9 are strongly anisotropic because of its crystal structure of alternating layers of CoO2 and Ca2CoO3. By aligning the plate-like grains, the anisotropic properties can be assigned to the component. Pressure-assisted sintering (PAS), as known from large-scale production of low temperature co-fired ceramics, was used to sinter multilayers of Ca3Co4O9 green tape at 900 °C with different pressures and dwell times. In-situ shrinkage measurements, microstructural investigations and electric measurements were performed. Pressure-less sintered multilayers have a 2.5 times higher electrical conductivity at room temperature than dry pressed test bars with randomly oriented particles. The combination of tape casting and PAS induces a pronounced alignment of the anisotropic grains. Relative density increases from 57 % after free sintering for 24 h to 94 % after 2 h of PAS with 10 MPa axial load. By applying a uniaxial pressure of 10 MPa during sintering, the electrical conductivity (at 25°C) improves by a factor of 15 compared to test bars with randomly oriented particles. The high temperature thermoelectric properties show the same dependencies. The smaller the applied axial load, the lower the relative densities, and the lower the electrical conductivity. Longer dwell times may increase the density and the electrical conductivity significantly if the microstructure is less densified as in the case of a small axial load like 2 MPa. At higher applied pressures the dwell time has no significant influence on the thermoelectric properties. This study shows that PAS is a proper technique to produce dense Ca3Co4O9 panels with good thermoelectric properties similar to hot-pressed tablets, even in large-scale production. T2 - Electroceramics XVI CY - Hasselt, Belgium DA - 09.07.2018 KW - Texturation KW - Hot Press KW - Calcination KW - Multilayer PY - 2018 AN - OPUS4-45491 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bresch, Sophie A1 - Mieller, Björn A1 - Selleng, Christian A1 - Stöcker, T. A1 - Moos, R. A1 - Rabe, Torsten T1 - Influence of the calcination procedure on the thermoelectric properties of calcium cobaltite Ca3Co4O9 N2 - Calcium cobaltite is one of the most promising oxide p-type thermoelectric materials. The solid-state reaction (or calcination, respectively), which is well known for large-scale powder synthesis of functional materials, can also be used for the synthesis of thermoelectric oxides. There are various calcination routines in literature for Ca3Co4O9 powder synthesis, but no systematic study has been done on the influence of calcination procedure on thermoelectric properties. Therefore, the influence of calcination conditions on the Seebeck coefficient and the electrical conductivity was studied by modifying calcination temperature, dwell time, particle size of raw materials and number of calcination cycles. This study shows that elevated temperatures, longer dwell times, or repeated calcinations during powder synthesis do not improve but deteriorate the thermoelectric properties of calcium cobaltite. Diffusion during calcination leads to idiomorphic grain growth, which lowers the driving force for sintering of the calcined powder. A lower driving force for sintering reduces the densification. The electrical conductivity increases linearly with densification. The calcination procedure barely influences the Seebeck coefficient. The calcination procedure has no influence on the phase formation of the sintered specimens. KW - Thermoelectrics KW - Calcination KW - Calcium Cobaltite KW - Solid-State-Synthesis KW - Reaction-sintering PY - 2018 DO - https://doi.org/10.1007/s10832-018-0124-3 SN - 1385-3449 SN - 1573-8663 VL - 40 IS - 3 SP - 225 EP - 234 PB - Springer AN - OPUS4-44336 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kardjilov, N. T1 - Quantification of hydrogen in metals applying neutron imaging techniques N2 - Hydrogen interaction with metals is well known to have severe detrimental effects on their mechanical properties. The use of modern high-strength steels, which are attractive to improve fuel economy by reducing weight as well as candidates for H storage cylinders and other components, is currently being severely limited by the fact that the presence of H can cause embrittlement of the material. In addition to steel, several other metals and alloys used in the nuclear industry, like Ti and Zr, are susceptible to H degradation through hydride formation and subsequent cracking. Microstructure-specific H mapping has been recognized as the most important challenge on the pathway towards a better understanding of the nature of H embrittlement in metallic alloys as well as the development of H storage solutions based on metal hydrides. Unfortunately, the characterization of H interactions with metals is an extremely challenging task and neutron-based techniques are of exceptional importance in this matter because – contrary to X-rays and electrons – thermal and cold neutrons interact strongly with the H nuclei, while the neutron beam is only weakly attenuated by the relevant metallic materials. Therefore, hydrogen distributions can be measured and quantified even in 3D by tomographic methods. Here we present several neutron imaging investigations of embrittlement and cracking in Fe and Zr based metal alloys and optimization studies of hydrogen storage systems containing metal hydrides as an active substance. The advantages and the limitations of the experimental methods as well as the attempts for hydrogen quantification will be discussed in detail. T2 - M&M 2022 Annual Meeting (Microscopy & Microanalysis) CY - Portland, Oregon, USA DA - 31.07.2022 KW - Neutron imaging techniques KW - Hydrogen in metals PY - 2022 DO - https://doi.org/10.1017/S1431927622006638 AN - OPUS4-55716 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mieller, Björn T1 - Synthesis and testing of beta aluminate sodium electrolyte (BASE) for sodium ion battery development N2 - Sodium beta aluminate, or beta aluminate solid electrolyte (BASE), is an established material for tubular electrolytes in NaNiCl2 and NaS batteries, and a promising candidate for planar electrolytes in safe all solid-state batteries. The synthesis of BASE with high ionic conductivity is still challenging due to process dependent formation of different phases in the sintered material. However, to drive forward the development of active materials for all solid-state sodium ion batteries, the fabrication of solid electrolyte specimens with reproducible performance is required. With respect to the various testing scenarios in the field, for example cell assembly for cycling, electrolyte parts are needed in various shapes, sizes, and thicknesses in the lab. Different ceramic shaping technologies can be applied to produce such geometries, including pressing combined with green or hard machining, or tape casting combined with punching. Typically, different shaping technologies require adapted pre-treatment of the powder which might affect the resulting properties and thus need to be investigated. In this contribution, starting from the raw materials mixture, aspects of milling, drying, aqueous slurry preparation for tape casting, and firing are discussed with respect to particle size distribution, stability, energy consumption and resulting material properties. Finally, the fabrication and cyclic testing of Na/electrolyte/Na coin cells is presented. T2 - XIXth Conference of the European Ceramic Society / SBS6 International Sodium Battery Symposium CY - Dresden, Germany DA - 01.09.2025 KW - Ceramics KW - Beta aluminate solid electrolyte KW - Sodium ion battery PY - 2025 AN - OPUS4-64054 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zheng, Y. A1 - Zhang, S. A1 - Ma, J. A1 - Sun, F. A1 - Osenberg, M. A1 - Hilger, A. A1 - Markötter, Henning A1 - Wilde, F. A1 - Manke, I. A1 - Hu, Z. A1 - Cui, G. T1 - Codependent failure mechanisms between cathode and anode in solid state lithium metal batteries: mediated by uneven ion flux N2 - An in-depth understanding of the degradation mechanisms is a prerequisite for developing the nextgeneration all solid-state lithium metal battery (ASSLMB) technology. Herein, synchrotron X-ray computed tomography (SXCT) together with other probing tools and simulation method were employed to rediscover the decaying mechanisms of LiNi0.8Co0.1Mn0.1O2 (NCM)|Li6PS5Cl (LPSCl)|Li ASSLMB. It reveals that the detachment and isolation of NCM particles cause the current focusing on the remaining active regions of cathode. The extent of Li stripping and the likelihood of Li+ plating into LPSCl facing the active NCM particles becomes higher. Besides, the homogeneity of Li stripping/plating is improved by homogenizing the electrochemical reactions at the cathode side by LiZr2(PO4)3 (LZP) coating. These results suggest a codependent failure mechanism between cathode and anode that is mediated by uneven Li ion flux. This work contributes to establish a holistic understanding of the degradation mechanisms in ASSLMBs and opens new opportunities for their further optimization and evelopment. KW - Current density distribution KW - Lithium ion flux KW - Solid-state lithium metal batteries KW - Codependent failure mechanism KW - Cathode deactivation PY - 2023 DO - https://doi.org/10.1016/j.scib.2023.03.021 SN - 2095-9273 VL - 68 IS - 8 SP - 813 EP - 825 PB - Elsevier B.V. AN - OPUS4-57309 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tötzke, C. A1 - Gaiselmann, G. A1 - Osenberg, M. A1 - Arlt, Tobias A1 - Markötter, Henning A1 - Hilger, A. A1 - Kupsch, Andreas A1 - Müller, Bernd R. A1 - Schmidt, V. A1 - Lehnert, W. A1 - Manke, I. T1 - Influence of hydrophobic treatment on the structure of compressed gas diffusion layers 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 PTFE 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. KW - Gas diffusion layer KW - Synchrotron Tomography KW - Compression KW - Hydrophobic treatment KW - Water transport PY - 2016 DO - https://doi.org/10.1016/j.jpowsour.2016.05.118 SN - 0378-7753 VL - 324 SP - 625 EP - 636 PB - Elsevier CY - Amsterdam AN - OPUS4-36918 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schulz, T. A1 - Reimann, T. A1 - Bochmann, A. A1 - Vogel, A. A1 - Capraro, B. A1 - Mieller, Björn A1 - Teichert, S. A1 - Töpfer, J. T1 - Sintering behavior, microstructure and thermoelectric properties of calcium cobaltite thickfilms for transversal thermoelectric multilayer generators N2 - The sintering behavior and the thermoelectric performance of Ca3Co4O9 multilayer laminates were studied, and a multilayer thermoelectric generator was fabricated. Compacts and multilayer samples with anisotropic microstructure and residual porosity were obtained after conventional sintering at 920 °C, whereas dense and isotropic multilayer samples were prepared by firing at 1200 °C and reoxidation at 900 °C. A hot-pressed sample has a dense and anisotropic microstructure. Samples sintered at 920 °C exhibit low electrical conductivity due to the low density, whereas the Seebeck coefficient is not sensitive to preparation conditions. However, thermal conductivity of multilayers is very low, and, hence acceptable ZT values are obtained. A ransversal multilayer thermoelectric generator (TMLTEG) was fabricated by stacking layers of Ca3Co4O9 green tapes, AgPd conductor printing, and co-firing at 920 °C. The TMLTEG has a power output of 3 mW at ΔT =200 K in the temperature interval of 25 °C to 300 °C. KW - Thermoelectric oxide KW - Calcium cobaltite KW - Pressure-assisted sintering KW - Multilayer PY - 2018 DO - https://doi.org/10.1016/j.jeurceramsoc.2017.11.017 SN - 0955-2219 SN - 1873-619X VL - 38 IS - 4 SP - 1600 EP - 1607 PB - Elsevier Ltd. AN - OPUS4-43983 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Widjaja, Martinus Putra A1 - Alves, M. A1 - Mavrogordato, M. A1 - Joannes, S. A1 - Bunsell, A. A1 - Mair, Georg W. A1 - Thionnet, A. T1 - Effect of the Time Dependent Loading of Type IV Cylinders Using a Multiscale Model N2 - The Reduced Volume Method (RVM) has been used to evaluate the multiscale fibre break model developed at Mines ParisTech. It allows the model to be assigned only at certain part of the structures without necessarily compromising the final prediction. An attempt to model a simple unidirectional composite structure has also been carried out and gave a satisfying result. This paper deals with the application of the RVM to real scale type IV composite cylinders, where its stacking sequence was evaluated through micro-CT scans conducted with the collaboration of the University of Southampton. Two modelling geometries were evaluated and compared with the corresponding experimental results. T2 - 8th International Conference on Hydrogen Safety (ICHS) CY - Adelaide, Australia DA - 24.09.2019 KW - Fibre break KW - Multiscale modelling KW - Type IV pressure vessel KW - Time dependent loading PY - 2019 SP - ID131 AN - OPUS4-49273 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Widjaja, Martinus Putra T1 - General update of the PhD work for mid_term consortium meeting N2 - Before the multiscale model is used to calculate real scale composite structures, a study to improve the effectiveness is required, especially the computation time. The reduced volume method has been studied and proved to be useful for the multiscale model of Mines ParisTech. T2 - Mid_Term Consortium Meeting of FiBreMoD CY - Imperial College London, United Kingdom DA - 11.09.2018 KW - Reduced volume method KW - Integral range KW - Composite pressure vessels KW - Multiscale model KW - Fibre breaks PY - 2018 AN - OPUS4-48570 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bresch, Sophie T1 - Material development for oxide multilayer generators N2 - Thermoelectric generators can be used for energy harvesting by directly transforming a temperature gradient into a voltage. Multilayer generators based on low-temperature co-fired ceramics technology (LTCC) are an interesting alternative to conventional π-type generators. They exhibit several advantages like high filling factor, possibility of texturing, co-firing of all materials in one single-step, and reduction of production costs due to the high possible degree of automation. Pressure-assisted sintering enables the theoretical possibility of co-firing two promising oxide thermoelectric materials: Ca3Co4O9 (p-type) and CaMnO3 (n-type). Due to the large difference in sintering temperature (300 K) the process is very challenging. In this work we show the material development of Ca3Co4O9, CaMnO3, insulation and metallization for multilayer generators co-fired under pressure at 900 °C. The materials are tailored regarding their sintering behavior, electrical performance and coefficients of thermal expansion. Different generator designs (unileg and pn-type) were fabricated and analyzed regarding crack formation, interaction layers and thermoelectric performance. Simulated stresses during cooling in the multilayers are compared with actual crack formation for different sintering conditions. This study shows that a lower pressure level and a lower level of complexity are beneficial for co-firing and performance. T2 - 45th International Conference and Expo on Advanced Ceramics and Composites (ICACC 2021 Virtual) CY - Online meeting DA - 08.02.2021 KW - Thermoelectrics KW - Multilayer PY - 2021 AN - OPUS4-52462 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Spitzer, Stefan A1 - Adamus, Wojciech A1 - Askar, Enis A1 - Benke, Alexander A1 - D’Hyon, Sebastian A1 - Dyduch, Zdzislaw A1 - Dufaud, Olivier A1 - Flemming, Friederike A1 - Gehle, Nicole A1 - Hohenberger, Michael A1 - Jankuj, Vojtech A1 - Jian, Wang A1 - Krietsch, Arne A1 - Kuracina, Richard A1 - Mynarz, Miroslav A1 - Norman, Frederik A1 - Osborne, David A1 - Prodan, Maria A1 - Sandsta, Nelly A1 - Toman, Adrian A1 - Skjold, Trygve A1 - Skrinsky, Jan A1 - Szabova, Zuzana A1 - Vignes, Alexis A1 - Wingerden, Mattheus van A1 - Zhong, Shenjung T1 - Validation of a new standard for safety characteristics of hybrid mixtures: HYBRID II N2 - Safety characteristics are used for the safe operation of processes. Designing protection measures requires explosion characteristics to be determined, namely the maximum explosion pressure and the maximum rate of pressure rise. Safety characteristics of single-phase components (solid, liquid or gas) can be determined according to standards that were developed 40 years ago and are continuously improved. For hybrid mixtures containing a flammable gas and a combustible dust there has been an approach in the 80s but it has never been improved nor applied ever since (ISO 6184-3). A new approach by four German research facilities and the German Institute for standardization (DIN) with the aim of developing a new standard was launched in 2019. In 2022 the key findings led to a first international round robin test with eleven participating facilities from seven countries. The dust component was corn starch and methane was chosen as gas component. In order to strengthen the data foundation before finalizing and publishing the new standard, a second round robin test was initiated with hydrogen as gas component and lycopodium as dust. The paper will summarize the findings and their influence on the new standard. KW - Explosionsschutz KW - Anlagensicherheit KW - Konstruktiver Explosionsschutz KW - Hybride Gemische KW - Round robin tests KW - Hybrid mixtures KW - Industrial explosions KW - Safety characteristics PY - 2025 DO - https://doi.org/10.1016/j.jlp.2025.105560 SN - 1873-3352 VL - 94 SP - 1 EP - 6 PB - Elsevier Ltd. AN - OPUS4-62486 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Martínez, E. A1 - Lejeune, N. A1 - Frechilla, J. A1 - Porta-Velilla, L. A1 - Forneau, E. A1 - Angurel, L. A. A1 - de la Fuente, G. F. A1 - Bonse, Jörn A1 - Silhanek, A. V. A1 - Badía-Majós, A. T1 - Laser engineered architectures for magnetic flux manipulation on superconducting Nb thin films N2 - Custom shaped magnetic flux guiding channels have been fabricated on superconducting Nb thin films by laser nanopatterning of their surface. Preferential pathways are defined by suitable combination of imprinted anisotropic pinning domains through laser-induced periodic surface structures (LIPSS). Generated by the selective energy deposition of femtosecond UV laser pulses, quasi-parallel ripple structures are formed under optimized irradiation conditions. On average, each domain is formed by grooves with a lateral period of 260–270 nm and a depth about 80 nm. By combination of scanning and transmission electron microscopy, magneto-optical imaging, and conductive atomic force microscopy techniques, we conclude that the boundaries of the LIPSS-covered domains play a prominent role in the magnetic flux diversion process within the film. This is confirmed by dedicated modeling of the flux dynamics, combined with the inversion of the magneto-optical signal. The created metasurfaces enable control of the flux penetration process at the microscale. KW - Laser-induced periodic surface structures (LIPSS) KW - Magnetic flux KW - Magneto-optical imaging (MOI) KW - Critical current density PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-611243 UR - https://www.sciencedirect.com/science/article/pii/S0169433224019287 DO - https://doi.org/10.1016/j.apsusc.2024.161214 SN - 1873-5584 (Online) SN - 0169-4332 (Print) VL - 679 SP - 1 EP - 12 PB - Elsevier AN - OPUS4-61124 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Averin, Anton T1 - Automated thermographic inspection of radioactive waste drums N2 - In Germany, more than 130,000 cubic meters of low- and medium-level radioactive waste, comprising approximately 90% of the nation’s total radioactive waste, are stored in 200-liter drums. These waste drums, housed in interim storage facilities, are subject to human visual inspections for outer corrosion, while the final disposal site, the Konrad mine, is scheduled for completion in 2030. Manual inspections introduce the risk of human error, making the process less reliable and less safe. The proposed study aims to automate these inspections by implementing remote and non-destructive testing (NDT) methods. The part of project specifically focuses on the application of infrared thermography to detect inner defects in the metallic drums, which could not have been detected so far using visual inspection alone. However, several challenges affect the accuracy of thermographic inspections, such as the presence of surface contaminants (scratches, dirt, stickers), multiple paint layers with low thermal conductivity, and barrel curvature, which disrupt heat distribution and obscure defect signals. This study explores the effectiveness of various thermographic heat sources—flash lamps and laser—as well as techniques including conventional pulse thermography (PT), lock-in thermography. It explores various thermal data processing methods as principal component thermography (PCT), pulse-phase thermography (PPT) and thermal signal reconstruction (TSR). Additionally, machine learning models were estimated to process thermographic images, effectively filtering artifacts (e.g. surface contaminants). The findings suggest that combining advanced thermography techniques with machine learning improves defect detection, ensuring more reliable and automated inspection processes for radioactive waste storage. T2 - SPIE Defense + Commercial Sensing - Thermosense: Thermal Infrared Applications XLVII CY - Orlando, FL, USA DA - 13.04.2025 KW - Automated inspection KW - Defect detection KW - Infrared thermography KW - Laser thermography KW - Machine Learning KW - Principal component thermography KW - Pulse-phase thermography KW - Thermal Data Processing PY - 2025 UR - https://www.spiedigitallibrary.org/conference-proceedings-of-spie/13470/3052732/Automated-thermographic-inspection-of-radioactive-waste-drums/10.1117/12.3052732.short DO - https://doi.org/10.1117/12.3052732 SP - 1 EP - 19 PB - SPIE AN - OPUS4-63285 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -