TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Dufrenoy, Philippe A1 - Magnier, Vincent T1 - Rationalizing the microstructure interplay in the thermal conductivity of a metal matrix composite via 3D imaged-based finite element modeling N2 - The thermal performance of metallic brake lining materials plays a decisive role in the safety and efficiency of high-speed railway braking systems. In this study, a combined experimental–numerical methodology is developed to rationalize the influence of microstructural constituents on the effective thermal conductivity of a sintered metal matrix composite (MMC) brake lining. Laser Flash Analysis (LFA) is first employed to determine the thermal conductivity of some individual constituents as well as that of reference composites. X-ray CT (XCT) provides three-dimensional reconstructions of the microstructure that are subsequently used to generate realistic image-based finite element meshes. The unknown thermal conductivities of the graphite particles are identified through a Finite Element Model Updating (FEMU) scheme, where numerical predictions of the effective conductivity are iteratively matched to LFA measurements. These findings highlight the strong anisotropy of graphite particles and their favored orientation after compaction, which governs heat transport pathways. Moreover, the presence of intra-, inter-, and inter-connectivity porosity within and around the graphite is shown to significantly reduce the transverse conductivity, rationalizing the discrepancy between the FEM predictions and experimental values. Overall, the proposed approach demonstrates how combining LFA, XCT and FEMU enables the identification of constituent-level conductivities and provides new insights into the microstructure/thermal-property relationships of MMC brake linings. KW - Brake lining material KW - Thermal conductivity KW - Graphite particles KW - Laser flash analysis (LFA) KW - X-ray computed tomography (XCT) KW - 3D finite element model updating (FEMU) PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-657756 UR - https://www.sciencedirect.com/science/article/pii/S0017931026004114?via%3Dihub DO - https://doi.org/10.1016/j.ijheatmasstransfer.2026.128735 SN - 0017-9310 VL - 264 SP - 1 EP - 14 PB - Elsevier Ltd. AN - OPUS4-65775 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Bayat, Mehmet Emin A1 - Nandayapa, Edgar R. A1 - Tiebe, Carlo A1 - Unger, Eva L. A1 - List-Kratochvil, Emil J. W. T1 - Raw data from: "An operando spectroscopic examination of the influence of trace humidity on interdigital back contact metal halide perovskite solar cells" N2 - Controlling trace humidity is vital for both the fabrication and long-term stability of metal halide perovskite (MHP) solar cells. Relevant humidity levels are typically below 10 ppmV, especially in glovebox-based processing and in well-encapsulated devices. Even minute amounts during fabrication can influence crystallization, introducing defects and lowering efficiency. Over time, humidity accelerates degradation of the perovskite layer and internal interfaces, ultimately reducing operational lifetime. Probing these effects at low concentrations under operando conditions is therefore essential for advancing device performance and durability. In this work, we employed a high-precision transfer standard dew point hygrometer to investigate humidity levels between 5 and 35 ppmV in non-encapsulated MHP solar cells. To permit unobstructed water migration during operation, we fabricated interdigital back contact devices. Operando measurements revealed water transport through the perovskite layer and enabled quantification of outgassing. Under trace-humidified conditions, devices exhibited initial charge-carrier quenching, followed by gradual recovery. Notably, the photocurrent response to humidified nitrogen demonstrated that the MHP layer behaves fully reversibly within the explored timescale and across the investigated humidity levels and conditions. These findings establish a systematic operando framework for examining extrinsic stressors in perovskites and highlight opportunities for assessing passivation strategies. KW - Metal halide perovskite PY - 2026 DO - https://doi.org/10.5281/zenodo.18600851 PB - Zenodo CY - Geneva AN - OPUS4-65757 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bayat, Mehmet Emin A1 - Nandayapa, Edgar R. A1 - Tiebe, Carlo A1 - Unger, Eva L. A1 - List-Kratochvil, Emil J. W. T1 - An operando spectroscopic examination of the influence of trace humidity on interdigital back contact metal halide perovskite solar cells N2 - Controlling trace humidity is vital for both the fabrication and long-term stability of metal halide perovskite (MHP) solar cells. Relevant humidity levels are typically below 10 ppmV, especially in glovebox-based processing and in well-encapsulated devices. Even minute amounts during fabrication can influence crystallization, introducing defects and lowering efficiency. Over time, humidity accelerates degradation of the perovskite layer and internal interfaces, ultimately reducing operational lifetime. Probing these effects at low concentrations under operando conditions is therefore essential for advancing device performance and durability. In this work, we employed a high-precision transfer standard dew point hygrometer to investigate humidity levels between 5 and 35 ppmV in non-encapsulated MHP solar cells. To permit unobstructed water migration during operation, we fabricated interdigital back contact devices. Operando measurements revealed water transport through the perovskite layer and enabled quantification of outgassing. Under trace-humidified conditions, devices exhibited initial charge-carrier quenching, followed by gradual recovery. Notably, the photocurrent response to humidified nitrogen demonstrated that the MHP layer behaves fully reversibly within the explored timescale and across the investigated humidity levels and conditions. These findings establish a systematic operando framework for examining extrinsic stressors in perovskites and highlight opportunities for assessing passivation strategies. KW - Metal halide perovskite KW - IBC solar cells KW - In operando KW - Extrinsic stressors KW - Fabrication and encapsulation KW - Trace humidity KW - Two-site Stern-Volmer KW - Charge-carrier quenching PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-657560 DO - https://doi.org/10.1039/D6TA01295G SN - 2050-7496 SP - 1 EP - 16 PB - The Royal Society of Chemistry CY - London AN - OPUS4-65756 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Avila Calderon, Luis Alexander T1 - On the role of the manufacturing-induced cell structure in laser-powder-bed-fused stainless steel 316L during cyclic plastic deformation N2 - The room temperature cyclic plastic deformation behavior of stainless steel 316L produced by laser powder bed fusion and heat treated to two microstructural conditions was investigated in strain-controlled incremental-step-test low-cycle fatigue experiments. The heat treatments were performed at 450 °C for 4 h and at 900 °C for 1 h. The lower temperature heat treatment retains the cell structure present in the as-built material. The higher temperature heat treatment leads to disappearance of the cell structure and a decreased proof strength. Both investigated heat treatment conditions exhibited cyclic softening. In the condition heat treated at 900 °C for 1 h, the ability of the cell structure to act as barrier against plastic deformation when cyclically strained is degraded, which is reflected in the reduction of the cyclic yield strength. In that same condition, the cyclic softening was less pronounced. The presence or absence of the manufacturing-induced cell structure seems to determine the slip mode. When present, the microstructural evidence points to a planar slip behavior. After heat treatment at 900 °C for 1 h, which led to its dissolution, microstructural investigations revealed a wavy slip behavior, which has been also reported for the conventionally manufactured 316L counterpart [1]. In this case, the formation of low-energy dislocation structures acts as softening agent. T2 - Additive Manufacturing 2026 CY - Kassel, Germany DA - 25.03.2026 KW - AGIL KW - Additive Fertigung KW - Low-Cycle-Fatigue KW - 316L KW - Mikrostruktur PY - 2026 AN - OPUS4-65746 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Risserkennung an Spannbetonschwellen mittels Ultraschall und luftgekoppeltem Impakt-Echo N2 - Jährlich werden ca. 2,5 Millionen Betonschwellen auf den Bahnstrecken Deutschlands ausgetauscht. Ob ein Austausch notwendig ist, wird durch Sichtprüfung, also anhand äußerer Schäden, entschieden. Derzeit werden keine Verfahren eingesetzt, die Bahnschwellen auch auf nicht sichtbare Schäden überprüfen. Hier setzt das luftgekoppelte Impakt-Echo-Verfahren an, das innenliegende Schäden diagnostiziert. Mit Hilfe eines Überschall-Freistrahls wird die Eigenfrequenz der Schwelle angeregt. Ist diese durch Risse geschädigt, sinkt die Frequenz deutlich. Die Anregung erfolgt berührungslos und kontinuierlich, so dass auch Messungen in Bewegung und bei Überfahrten möglich werden. T2 - 14. Fachtagung ZfP im Eisenbahnwesen CY - Erfurt, Germany DA - 17.03.2026 KW - Spannbetonschwelle KW - Rissdetektion KW - Ultraschallprüfung KW - Impakt-Echo Verfahren KW - Luftgekoppelte Impakt-Echo Anregung PY - 2026 AN - OPUS4-65730 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suarez Ocano, Patricia T1 - Effect of the powder composition on the microstructure and mechanical properties of 316L stainless steel fabricated by laser powder bed fusion N2 - Additive manufacturing (AM) has seen rapid growth in recent decades, with Laser Powder Bed Fusion (PBF-LB/M) emerging as the leading technique for producing high-density, geometrically complex metal parts. Austenitic stainless steel 316L is one of the most studied alloys for PBF-LB/M due to its excellent strength, ductility, and corrosion resistance [1]. The microstructure formed during PBF-LB/M processing can improve certain mechanical properties compared to conventionally manufactured 316L [2]. However, the current 316L standards allow broad ranges for key alloying elements, particularly Cr and Ni. While such variations have little effect on conventionally produced alloys, emerging evidence shows that they can markedly alter the microstructure and mechanical properties in PBF-LB/316L—even within specification limits [3]. This study investigates through microstructural and thermodynamical assessment, how two powders of nominally standard 316L composition (Alloys A and B) respond to identical PBF-LB/M processing parameters. Despite identical printing conditions, Alloy A exhibited twice the grain size and five times higher low-angle grain boundary (LAGB) density compared to Alloy B . Conversely, Alloy B showed a significantly higher density of Σ3 twin boundaries, nearly absent in Alloy A. These microstructural differences are attributed primarily to variations in Cr and Ni content in the liquid, which may influence icosahedral short-range ordering (ISRO) mechanism [4]. ISRO potentially facilitates twin boundary formation, ultimately refining grain structure [5]. This work highlights the critical impact of compositional control on final part microstructures and consequent mechanical properties and emphasizes the need to reassess compositional tolerances for AM-specific applications. T2 - 5th Symposium on Materials and Additive Manufacturing (Additive 2026) CY - Kassel, Germany DA - 24.03.2026 KW - Additive manufacturing KW - 316L stainless steel KW - Chemical composition KW - Lcosahedral short-range ordering mechanism KW - Grain size PY - 2026 AN - OPUS4-65738 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bijeljic, Jelena A1 - Niederleithinger, Ernst T1 - Concrete performance assessment based on gas permeability testing N2 - Designing of structures with medium to high performance requirements is a demanding and challenging engineering task. Depending on the location and type of the planned structure, various pre-testing methods should be applied. In recent decades, there has been a focus on the durability of concrete. Concrete is a porous material with a relatively thin protective cover layer, making it vulnerable to the penetration of external agents such as carbon dioxide. Gas permeability testing (kT), a relatively new non-destructive method (NDT), should therefore be considered. This paper presents results of gas permeability testing on a set of larger concrete samples made under controlled conditions with some paroperty variations order to find initial kT parameters important for quality assurance. KW - Concrete KW - Permeability KW - Durability KW - Torrent Tester PY - 2025 DO - https://doi.org/10.62683/ZRGAF41.2 SN - 3009-4674 VL - 41 IS - 1 SP - 15 EP - 23 PB - Faculty of Civil Engineering and Architecture, University of Nis AN - OPUS4-65715 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wosniok, Aleksander A1 - Ettaouaje, Omar T1 - Fiber optic sensors for SHM of solid bridges - BAM activities in work packages 2–5 N2 - We report on wire break detection and traffic load monitoring using embedded, distributed fiber optic sensors as part of a concept for structural health monitoring of solid bridges. Fiber optic measurements provide real-time data for identifying loads, structural responses, and damages. The development includes methods for data evaluation and information extraction from large DFOS datasets, contributing to the digital transformation of bridge infrastructure. T2 - FOSsure Jahrestreffen CY - Dresden, Germany DA - 18.03.2026 KW - Distributed fibre optic sensor (DFOS) KW - SHM KW - Bridge monitoring KW - Distributed acoustic sensing PY - 2026 AN - OPUS4-65704 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Battistella, Beatrice T1 - Plasma-Based Analytical Approaches for the Investigation of Li-ion Battery Degradation N2 - The research conducted at the Federal Institute for Material Research and Testing (BAM) focuses on key challenges of the energy transition, spanning hydrogen technologies, electrical energy storage, and renewable energy systems. In the field of energy storage, our primary areas of interest include the safety of electrical energy storage systems, sustainable energy materials, and advanced battery diagnostics. One of our central objectives is to deepen our understanding of the processes contributing to lithium-ion cell degradation, an essential step toward improving next-generation systems and meeting the rapidly growing demand for lithium-ion battery technology. The complexity of these systems, which comprise organic and inorganic compounds in multiple aggregation states, presents significant analytical challenges. To address these challenges, we are developing novel analytical methods to further expand our insight into battery degradation mechanisms. Using GD-MS for depth-resolved lithium isotope analysis, we have recently established a correlation between lithium isotope fractionation and the growth of electrode–electrolyte interphases at electrode surfaces. In addition, we are developing GD-OES and LIBS methods for depth-resolved and lateral fluorine analysis, respectively, of lithium-ion battery electrodes to monitor electrolyte and additive degradation. These approaches might also provide valuable analytical tools for assessing the homogeneity of fluorinated active materials. T2 - Applied Spectra Inc. CY - Sacramento, CA, USA DA - 05.03.2026 KW - Lithium-Ion Battery PY - 2026 AN - OPUS4-65696 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Battistella, Beatrice T1 - Plasma-Based Analytical Approaches for the Investigation of Li-ion Battery Degradation N2 - The research conducted at the Federal Institute for Material Research and Testing (BAM) focuses on key challenges of the energy transition, spanning hydrogen technologies, electrical energy storage, and renewable energy systems. In the field of energy storage, our primary areas of interest include the safety of electrical energy storage systems, sustainable energy materials, and advanced battery diagnostics. One of our central objectives is to deepen our understanding of the processes contributing to lithium-ion cell degradation, an essential step toward improving next-generation systems and meeting the rapidly growing demand for lithium-ion battery technology. The complexity of these systems, which comprise organic and inorganic compounds in multiple aggregation states, presents significant analytical challenges. To address these challenges, we are developing novel analytical methods to further expand our insight into battery degradation mechanisms. Using GD-MS for depth-resolved lithium isotope analysis, we have recently established a correlation between lithium isotope fractionation and the growth of electrode–electrolyte interphases at electrode surfaces. In addition, we are developing GD-OES and LIBS methods for depth-resolved and lateral fluorine analysis, respectively, of lithium-ion battery electrodes to monitor electrolyte and additive degradation. These approaches might also provide valuable analytical tools for assessing the homogeneity of fluorinated active materials. T2 - Berkeley Lab - Prof. Dr. Zorba group seminar (Energy Technologies Area) CY - Berkeley, CA, USA DA - 27.02.2026 KW - Li-ion Batteries KW - Li Isotopes KW - Diagnostic on batteries PY - 2026 AN - OPUS4-65695 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Trambitski, Yahor A1 - Kizinievič, Olga A1 - Kizinievič, Viktor A1 - Pavasaryte, Lina T1 - Revealing the Structural Transformation of Biopolymer-Modified Clay Materials Through Microtomography and Hygroscopic Analysis N2 - This study focuses on the structural assessment of unfired clay materials (UCM) treated with different biopolymers using microtomography (microCT) and hygroscopic analysis. It addresses a significant research gap, as the analysis of hygroscopic properties in biopolymer-modified clays remains limited in the literature, while microCT investigations of such materials have been scarcely explored. The clay materials were modified using aqueous gelled biopolymer solutions of starch, alginate, and chitosan, each prepared under processing conditions adapted to their chemical characteristics and solubility: starch was dissolved in hot water, alginate in cold water, and chitosan in a slight acid solution. Moisture adsorption of the clay-biopolymer materials (CBM) increased up to 32.2%, as observed in the CBM, modified with a 7.5% alginate-based solution. Sorption hysteresis analysis revealed an increase in the hysteresis rate from 0.30% to 0.76–1.01% in CBMs, indicating that biopolymer modification enhanced the structural complexity of the clay matrix and promoted additional molecular interactions with water molecules within the CBM. MicroCT results demonstrated that within the CBM, biopolymers can function either as surface-coating agents (starch and alginate) or as organic clusters within the clay structure (chitosan). The obtained results highlight that biopolymer incorporation significantly enhances the hygroscopic buffering capacity of clay materials, offering a pathway toward sustainable building composites that can be applied in humidity-regulating finishes, eco-friendly construction blocks, and heritage conservation, where both moisture control and structural cohesion are essential. KW - Unfired clay material KW - Micro computed tomography KW - Clay-biopolymer material PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-656872 DO - https://doi.org/10.1007/s40684-026-00865-x SN - 2288-6206 SP - 1 EP - 14 PB - Springer Science and Business Media LLC AN - OPUS4-65687 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Averin, Anton A1 - Hirsch, Philipp Daniel A1 - Lecompagnon, Julien T1 - Thermographic Reference Dataset: Defect Detection in Nuclear Waste Barrel Cutouts Using Long Pulse Thermography N2 - We introduce a thermographic dataset for subsurface defect detection in radioactive waste storage drums, comprising thermal sequences from 7 barrel specimens with artificially manufactured internal defects. The dataset was acquired using cost-effective halogen-lamp excitation (2kW per lamp) as an alternative to laser-based systems, with dual-camera thermal imaging (CMOS and bolometric) to enable performance comparison across imaging modalities. The specimens include both new and aged barrel types with controlled defects — FBHs, lines, crosses, triangles, and rectangles — simulating internal corrosion at varying scales (4mm to 60mm). Three heating regimes (both lamps, left only, right only) were systematically applied across multiple measurement regions per sample, yielding normalized thermal sequences. To lower the barrier for machine learning practitioners without thermography expertise, the dataset provides pre-computed features derived from principal component analysis, pulse phase thermography, and independent component analysis extracted using experimentally optimized time windows. Ground-truth binary masks mapping defect locations are included to enable supervised learning. This resource is designed to support the development and benchmarking of automated defect detection algorithms for non-destructive testing of curved, thin-walled metallic structures under realistic surface conditions (paint inhomogeneity, dirt, geometric artifacts), while validating low-cost thermographic inspection alternatives for industrial deployment. KW - Nondestructive Testing KW - Corrosion detection KW - Waste storage KW - Thermography KW - Safety PY - 2026 DO - https://doi.org/10.5281/zenodo.18916290 PB - Zenodo CY - Geneva AN - OPUS4-65666 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hilberg, Alec T1 - Multispektrale Thermografie zur quantitativen Temperaturbestimmung im DED-LB/M Prozess N2 - Additive Fertigungsverfahren bieten konstruktive Freiheiten, die mit konventionellen Herstellungsverfahren nur schwer zu realisieren sind. Durch die Möglichkeit hochkomplexe Bauteile aus Metall fertigen zu können, stellt die additive Fertigung in vielen Industriezweigen eine vielversprechende Fertigungsalternative da. Allerdings treten prozessbedingt hohe Temperaturgradienten und schnelle Phasenumwandlungen auf, die maßgeblich entscheidend für die Mikrostruktur und die Bildung von internen Spannungen, Rissen und weiteren Defekten sind. Diese Effekte wirken sich direkt auf die mechanischen Eigenschaften der gefertigten Bauteile aus und verdeutlichen die Notwendigkeit einer zuverlässigen Bauteilprüfung. Dabei sind nachgelagerte Verfahren in der Regel zeit- und kostenaufwändig, weshalb die Anwendung von in-situ Verfahren zur Qualitätssicherung im Fokus diverser Forschungsprojekte steht. Die Thermografie erlaubt die orts- und zeitaufgelöste Messung der im Prozess auftretenden Temperaturfelder. Allerdings müssen die tatsächlich gemessenen digitalen Sensorwerte mittels geeigneter radiometrischer Modelle in Temperaturen umgewandelt werden. Da diese Modelle in der Regel auf Basis von Messungen an Schwarzkörperstrahlern kalibriert werden, kann dieses Vorgehen nur zufriedenstellende Werte liefern, sofern der Emissionsgrad des zu messenden Objektes bekannt ist. Während in statischen Anwendungen häufig ein konstanter Materialreferenzwert hinreichend befriedigende Ergebnisse liefert, ist man in der additiven Fertigung mit dem Problem konfrontiert, dass der Emissionsgrad lokal in kürzester Zeit starke Änderungen durchläuft. Beeinflusst wird dieser Effekt unter anderem durch Temperatur, Phasenzustand und Oberflächenzustand. Das hier vorgestellte Verfahren nutzt Referenzmessungen des Emissionsgrades in Abhängigkeit von Temperatur, Winkel und Phasenzustand, um in einem DED-LB/M-Prozess (auch Laser-Pulver-Auftragschweißen, LPA) sowohl den Emissionsgrad als auch die tatsächliche Temperatur orts- und zeitaufgelöst zu bestimmen. Grundlage hierfür sind multispektrale thermografische Messungen, bei denen (quasi-) synchron in acht unterschiedlichen Wellenlängenbereichen gemessen wird. In diesem Beitrag werden Ergebnisse der im Rahmen des DFG-Projektes QT-LPA (Nr. 516965606) durchgeführten Arbeiten präsentiert. T2 - Thermo25 CY - Garching bei München, Germany DA - 11.11.2025 KW - Thermografie KW - TES KW - Multispektral KW - DED-LB/M KW - Laserpulverauftragschweißen PY - 2025 AN - OPUS4-65652 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -