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Data selection strategies for minimizing measurement time in materials characterization
No full textEvery new material needs to be assessed and qualified for an envisaged application. A steadily increasing number of new alloys, designed to address challenges in terms of reliability and sustainability, poses significant demands on well-known analysis methods in terms of their efficiency, e.g., in X-ray diffraction analysis. Particularly in laboratory measurements, where the intensities in diffraction experiments tend to be low, a possibility to adapt the exposure time to the prevailing boundary conditions, i.e., the investigated microstructure, is seen to be a very effective approach. The counting time is decisive for, e.g., complex texture, phase, and residual stress measurements. Traditionally, more measurement points and, thus, longer data collection times lead to more accurate information. Here, too short counting times result in poor signal-to-background ratios and dominant signal noise, respectively, rendering subsequent evaluation more difficult or even impossible. Then, it is necessary to repeat experiments with adjusted, usually significantly longer counting time. To prevent redundant measurements, it is state-of-the-art to always consider the entire measurement range, regardless of whether the investigated points are relevant and contribute to the subsequent materials characterization, respectively. Obviously, this kind of approach is extremely time-consuming and, eventually, not efficient. The present study highlights that specific selection strategies, taking into account the prevailing microstructure of the alloy in focus, can decrease counting times in X-ray energy dispersive diffraction experiments without any detrimental effect on data quality for the subsequent analysis. All relevant data, including the code, are carefully assessed and will be the basis for a widely adapted strategy enabling efficient measurements not only in lab environments but also in large-scale facilities
On the preference of liquid-metal embrittlement along high-angle grain-boundaries in galvanized steels
No full textFocusing on the early stages of liquid-metal embrittlement (LME) of Zinc (Zn) coated advanced high-strength steels, we show that the Zn infiltration path prior to grain-boundary decohesion and therefore cracking distinctly follows high-angle grain boundaries (HAGBs). This selective transport prior to LME-induced microcracking rationalizes the experimentally observed post-mortem cracking along martensitic HAGBs. We discuss the selective Zn transport and GB-weakening in terms of an misorientation-angle dependent atomic density and diffusivity, and its effect on GB-segregation
Extrinsic and Intrinsic Factors Governing the Electrochemical Oxidation of Propylene in Aqueous Solutions
No full textThe electrochemical synthesis of commoditychemicals such as epoxides and glycols offers a sustainablealternative to conventional methods that involve hazardouschemicals. Efforts to improve the yield and selectivity of propyleneoxidation using Pd-based catalysts have been shown to be highlysensitive to applied potential, pH, and electrochemical cell design.Record efficiencies and yields were obtained by substitution ofPdO by 4d or 5d transition metals, including Pt, with thus far littlerationale regarding the origin for the improvement. Throughelectrochemical analysis, scanning transmission electron micros-copy, X-ray absorption spectroscopy, and surface-enhanced infraredabsorption spectroscopy, we investigated the mechanism ofpropylene oxidation on Pd-based catalysts. We demonstrate thatadsorbates forming on PdO, where Pd adopts a square-planar coordination [PdO4], differ from that forming on the surface ofoxidized metallic Pd catalysts with an oxo intermediate mediating propylene oxidation on PdO. We further show that Pt substitutionin PdO does not modify this oxo intermediate. Varying pH, we found that the onset for propylene oxidation is pH independent,indicating a potential-determining step where the proton is not involved in and similar reaction pathway in acidic and near-neutralconditions. Finally, our work undoubtedly demonstrates that high Faradaic efficiency toward propylene glycol and propylene oxideformation, such as those previously reported in the literature, can be achieved by means of electrode engineering and mastery ofmass transport and local pH. Notably, we achieved ≈100% faradaic efficiency for propylene glycol at 1.7 V vs RHE in acidic mediausing a Pt-substituted PdO catalyst loaded onto a gas diffusion electrode
Vermeidung von Kaltrissen in UP-Dickblechschweißungen aus hochfesten Stählen
No full textDer Einsatz hochfester Stähle wie S690 erlaubt durch geringeren Materialeinsatz nicht nur eine immer wichtiger werdende Verringerung von CO₂-Emissionen, sondern auch eine effektive Kosten- und Gewichtsreduktion dickwandiger Bauteile. Insbesondere bei Wandstärken von bis zu 200 mm ist das Unterpulver- (UP-)Mehrdrahtschweißen aufgrund seiner hohen Effizienz eine gängige Praxis. Allerdings steigt bei hochfesten Stählen, hier vorliegend S690, die Gefahr wasserstoffunterstützter Kaltrisse (HAC), aufgrund ihrer Mikrolegierungskonzepte im Zusammenspiel mit hohen Eigenspannungen aus dem Schweißprozess und resultierend aus hohen Bauteilsteifigkeiten. Zusätzlich kann die erhebliche Aufmischung von Grund- und Zusatzwerkstoff beim UP-Schweißen zu risskritischen Gefügen führen, in denen der diffusible Wasserstoff besonders schädlich wirkt. Für Gefüge UP-geschweißter Bauteile liegen keine gesicherten Daten bezüglich Wasserstoffdiffusionskoeffizienten bzw. HAC-Rissanfälligkeit vor. Insbesondere die mikrostrukturabhängige Diffusion von durch den UP-Schweißprozess eingebrachtem Wasserstoff war nicht hinreichend gesichert. Ziel des Forschungsvorhabens war es daher, einen Beitrag zur kaltrisssicheren UP-Schweißverarbeitung hochfester Dickbleche zu leisten. Hierzu wurden systematisch unterschiedliche GW (S690 TM/QL) untersucht, die sich insbesondere in ihren Mikrostrukturen unterscheiden. Diese zeigten in Voruntersuchungen stark divergente Härteverteilungen im Besonderen in der letzten Lage der Schweißung, sodass ein ebenfalls stark divergentes Diffusionsverhalten postuliert wurde. Zunächst wurde der Wasserstoffeintrag über die Draht-Pulver-Kombination gemäß ISO 3690 ermittelt. Anschließend erfolgten mehrlagige Schweißungen sowohl unter freiem Schrumpfen als auch unter äußerer Zwängung. Eine detaillierte Gefügecharakterisierung und mechanisch-technologische Prüfungen, sowie Eigenspannungsmessungen ermöglichten die Bewertung der Rissanfälligkeit bei variierter Wärmeführung (schweißgeschwindigkeitsgesteuert). Zur quantitativen Beschreibung der Wasserstoffdiffusion wurden das Schweißgut (SG), die Wärmeeinflusszone (WEZ) und die Grundwerkstoffe (GW) mittels elektrochemischer Beladung und Trägergasheißextraktion (TGHE), sowie Permeationsversuchen untersucht. Basierend auf den ermittelten Diffusionskoeffizienten wurden numerische Modelle erstellt, um den Einfluss verschiedener Diffusionskoeffizienten auf die Wasserstoffverteilung in der Schweißnaht zu evaluieren. Entgegen dem Postulat wurden keine signifikanten Unterschiede in der Wasserstoff-Diffusionsgeschwindigkeit gemessen. Beide GW-Klassen (QL vs. TM) als auch das SG und die WEZ wiesen für diesen Werkstofftyp charakteristische Diffusionskoeffizienten mit nur geringen Unterschieden auf. Dies zusammen mit den nur sehr geringen Unterschieden in der Ausprägung der Eigenspannungen und mechanisch-technologischen Eigenschaften der Nähte, weisen auf eine hohe Kaltrisssicherheit hin. Die in allen Untersuchungen geringen Unterschiede zwischen QL und TM sprechen, hinsichtlich des HAC-Risikos aufgrund einer differenten Wasserstoffdiffusion, für die Austauschbarkeit der beiden Werkstoffe in der Produktion
Reinventing Piping for Hydrogen Applications – A Composite Approach
No full textA key step towards achieving climate neutrality in the European Union (EU) by 2050 is the transition to renewable energy sources. Green hydrogen plays a central role in this shift but remains costly, particularly through the utilization of PEM electrolysis. Currently, around 50% of the costs associated with electrolyser systems are attributed to system peripherals, underscoring the potential for cost savings through standardization and the use of cost-effective materials [Tja17, IRE20].
In the collaborative project "PolyH2Pipe", the Institute of Plastics Processing in Industry and Craft (IKV), the Welding and Joining Institute (ISF) and BAM Division 5.3 are developing media-carrying pipe systems made of continuous fiber-reinforced thermoplastics (TP-FR) for hydrogen applications. The project aims to design these pipes, develop suitable joining techniques and validate the requirements for these piping systems. This research initiative serves as a foundational basis for the subsequent market introduction of large-scale TP-FR pipe systems for electrolysers and fuel cell systems. Initial test results will be presented as a part of the talk during the colloquium
Modelling of hydrogen-induced ductility loss in titanium-based hydrogen storage
No full textOne promising solution for decarbonisation is the use of hydrogen as energy carrier. Besides its exceptional advantages like high calorific value, better safety and non-existent harmful emissions, one major challenge is still hydrogen embrittlement of Ttitanium alloys used as a hydrogen storage. In this work, a method is presented that can numerically model and determine a threshold concentration of hydrogen in solid solution responsible for a sudden ductile-to-brittle transition. The origin of this sudden loss of ductility lies in the segregation kinetics thermodynamics that is modelled together with an elastoplastic fracture mechanics model. Starting from experimental fracture mechanics test data, a meaningful coupling mechanism was found for the fracture mechanics cohesive zone model in the form of a segregation-modified cohesive energy that triggers an acceleration of crack extension above defined concentration values. It can be demonstrated that above a threshold of only few atomic percent hydrogen in the solid solution, the segregated hydrogen concentration exceeds 20 at.%. The current results present a mechanism that enables the modelling of the sudden ductility loss triggered by a segregation-affected crack energy expression in titanium alloys exposed to hydrogen. This method is not only applicable to other various materials but can also be a substantial benefit for the safety assessment of hydrogen storage devices
Update on the revision of test method for oxidizing solids
No full textThe results of the round robin test on the solid oxidiser test have already been presented at IGUS EOS. In this presentation, we will show how the findings from the round robin test can be transferred into the regulations as easily as possible. This proposal serves as a basis for a proposal that can be discussed in the ECOSOC Sub-Committee of Experts on TDG (30 June - 04 July 2025)
Influence of heat input on properties and residual stresses in hybrid addi-tive manufacturing of high strength steels using MSG processes
No full textThe application of steels with a higher yield strength allows reductions in wall thickness, component weight and production costs. Hybrid additive manufacturing based on Gas Metal Arc Welding (GMAW) processes (DED-Arc) can be used to realise highly effi-cient component modifications and repairs on semi-finished products and additively manufactured structures. There are still a number of key issues preventing widespread implementation, particularly for SMEs. In addition to the manufacturing design, detailed information about assembly strategy and geometric adaptation of the component for modifications or repairs are missing. These include the welding-related stresses associ-ated with the microstructural influences caused by the additive manufacturing steps, particularly in the transition area of the substrate and filler material interface. The pre-sent research focuses the effect of welding heat control during DED-Arc process on the residual stresses, especially in the transition area. Defined specimens were welded fully automatically with a high-strength solid wire (yield strength > 790 MPa) especially adapted for DED-Arc on S690QL substrate. The working temperature and heat input were systematically varied for a statistical effect analysis on the residual stress state of the hybrid manufactured components. Regarding heat control, t8/5 cooling times within the recommended processing range (approx. 5 s to 20 s) were complied. The investiga-tion revealed a significant influence of the working temperature Ti on the compressive residual stresses in the transition area and the tensile residual stresses at the base of the substrate. High working temperatures result in lower compressive residual stresses, heat input E does not significantly affect the tensile stresses
Elemental distribution as a key indicator of manufacturing quality and state of health in lithium and sodium ion batteries
No full textLithium-Ion Batteries (LIBs) dominate the energy storage market due to their high energy density, lightweight, and substantial power output.[1] Since their manufacture involves the usage of critical materials such as lithium, cobalt and copper, Sodium-Ion Batteries (SIBs) are currently emerging as a more sustainable alternative due to the high availability of sodium and other required raw materials on Earth.[2] These two technologies share similar electrochemical principles and currently find different applications in the global market.[3] While LIBs dominate the portable electric devices and electromotive field, SIBs are becoming relevant for stationary energy storage applications, for which energy density plays a less decisive role.
The increasing global demand for LIBs, expected to grow by about 27% annually,[4] raises questions about the fate of the millions of tons of exhausted batteries generated. Considering that battery production gigafactories have a scrap rate of about 30% across the entire production chain,[5] it appears evident that improved manufacturing processes and increased battery lifetime are demanded. To meet these requirements, a deeper understanding of the processes that concur with battery degradation is essential.
With the aim of gaining further insight into these aspects, this work focuses on the formation, composition, and degradation of the Solid Electrolyte Interphase (SEI). This complex, heterogeneous passivation layer that forms on the negative electrode is essential for the reversible charging of batteries and the understanding of its formation and degradation is essential for producing batteries with superior performances.[6] To gain insight into these intricate phenomena, the distribution of the main elemental components of SEI in LIBs and SIBs electrodes is investigated. Positive electrodes are self made using lithium- and sodium-layered transition metal oxides as active material, while graphite and hard carbon are used to produce the negative electrodes. After their assembly, the cells are formed and artificially aged under different conditions. Post mortem analysis is performed on freshly formed, early failed, and differently aged cells by lateral profile (Laser-Induced Breakdown Spectroscopy LIBS) and in-depth profile (Glow-Discharge Optical Emission Spectroscopy GD-OES and Mass Spectrometry GD-MS) techniques.[7] We present a new GD-OES analytical method where electrodes are sputtered with a neon/argon mixture. This allows for in-depth profiling of fluorine (IE 17.4 eV) due to the higher ionization energy of neon (IE 21.6 eV) compared to argon (IE 15.8 eV). Qualitative analysis of solvents and electrolytes degradation products is performed by GC-MS. Furthermore, Electrochemical Impedance Spectroscopy analysis (EIS), performed on each cell at different stages of life, facilitates the correlation between internal resistance and degradation process.
The pool of experimental data is used as feedstock for Machine Learning (ML) methods. By merging data obtained from multiple sources, ML algorithms can unveil correlations between the data sets and, thus, provide insight into the cell’s chemical/physical deterioration. Furthermore, ML tools are employed to correlate chemical degradation of the cells with their electrochemical features, investigated by non-destructive analysis (EIS). Using the acquired experimental data as training set, this work targets the development of a data-driven approach for battery State of Health (SOH) and Remaining Useful Lifetime (RUL) evaluation based on non-destructive analysis results. The method aims to offer a simple way to establish battery RUL, avoiding time consuming and expensive end of life chemical analysis, which offers remarkable implications to the large-scale battery production.[8
The Metabuilding Labs approach to Quality Assurance – Results of Task 8.4 & Task 8.5
No full textThe finalization of the Standard Operating Procedures and Work Instructions for the O3BETs is described. The setuo of the internal system for quality checks is outlined. Major achievements are shown and future work is adressed