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Paper des Monats
- ja (70)
A method to obtain magnetic dipole-dipole coupling information for nuclei exhibiting ultra-wideline NMR spectra in disordered solids is presented. This is achieved via a constant time version of SEDOR (Spin Echo DOuble Resonance) employing WURST (Wideband Uniform Rate Smooth Truncation) pulses and CPMG (Carr Purcell Meiboom Gill) detection. The method – coined CT-WUDOR-CPMG (Constant Time-WURST SEDOR- CPMG) NMR spectroscopy – is tested on Ba2TeO(PO4)2 as a crystalline model compound applying 125Te{31P}- CT-WUDOR-CPMG NMR. Then, 125Te{19F}- and 125Te{31P}-CT-WUDOR-CPMG are performed to obtain structural information on TeO2 – NaPO3 – NaF glasses
Additive manufacturing by DED-Arc enables the production of large and complex high-strength steel components. However, the residual stress state generated during deposition can be significantly altered when the component is separated from the substrate plate as a final manufacturing step. This study investigates the residual stress relaxation and redistribution caused by substrate detachment in DED-Arc manufactured high-strength steel hollow cuboids. The component geometry was varied in terms of height, length, and wall thickness. Longitudinal residual stresses were measured by X-ray diffraction on the side wall surfaces before and after mechanical separation from the substrate plate. In addition, 3D scanning was used to quantify the resulting component distortion. The results show that substrate detachment causes a pronounced redistribution of longitudinal residual stresses, including a reduction of tensile stresses and, in some regions, the formation of compressive residual stresses. The stress differences before and after detachment can be interpreted as a superposition of relaxed longitudinal shrinkage stresses and released bending stresses arising from inhomogeneous restraint over the build height. The sign and magnitude of the bending contribution depend strongly on the component geometry. Low-build and high-build components show opposite bending tendencies after detachment, which is attributed to the interaction between substrate restraint, component stiffness and transformation-affected upper layers. Regression analysis of the geometry variation indicates that height, length, wall thickness, and the height–length interaction significantly affect the released bending stress, while component height is the dominant factor for the normal tensile stress relaxation. The findings demonstrate that substrate detachment is a critical step for residual stress redistribution and distortion in DED-Arc manufactured high-strength steel components and that geometry tailoring is usable to influence the resulting stress state.
Materials Science and Engineering (MSE) increasingly relies on data‐intensive, automated, and distributed workflows that span synthesis, manufacturing, characterization, design, and simulation. These settings require machine‐actionable representations of materials and processes that remain interoperable across laboratories, software stacks, and organizations. Therefore, Platform MaterialDigital Core Ontology (PMDco) 3.0 is introduced as a mid‐level ontology that provides a semantic framework for the processing–structure–properties paradigm in MSE. PMDco 3.0 adopts an architecture aligned with the Basic Formal Ontology that enables a logically consistent classification of fundamental MSE concepts and the explicit representation of intrinsic material properties, contextual roles and functions, and related information artifacts. The work outlines the technical curation approach that supports sustainable ontology evolution through reproducible builds, automated release generation, and systematic validation workflows. Representative semantic patterns are presented as reusable building blocks for consistent modeling and data mapping, including material object duality, intensive versus extensive qualities, role and function assignment, immaterial entities for spatial context, process modeling across production, assay, and computation, and the separation of requirements from observations via set points and measurements. PMDco 3.0 is intended to serve as a community‐driven anchor for interoperable domain and application ontologies and scalable semantic interoperability in MSE.
Introduction to additive manufacturing, including an overview of the most important processes currently used for metals in industry (PBF, DED, and BJT). Discussion of key process characteristics and post-processing steps. Presentation of the most important types of defects, including their causes and corrective measures.
Proper physicochemical characterization of advanced materials and complex industrial composites remains a significant challenge, particularly for nanomaterials, whose nanoscale dimensions and mostly complex chemistry challenge the analysis. In this work, we employed a correlative analytical approach that integrates atomic force microscopy (AFM), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), time-of-flight secondary ion mass spectrometry (ToF- SIMS), Auger electron spectroscopy (AES), and Raman spectroscopy. This combination enables detailed chemical and structural characterization with sub-micrometer spatial resolution. Three commercial graphene-based materials of varying complexity were selected and investigated to test the analytical performance of this approach. Furthermore, one of the commercial graphene oxide samples was chemically functionalized via amination and fluorination. This allowed us to assess how surface modifications influence both the material properties and the limits of the applied analytical techniques.
The accuracy of teh standardless quantification of the light elements with SEM/EDS will be also demonstrated.
Current and future directions in probing structural dynamics and transport of metallic glasses
(2026)
In this article, we discuss the challenges in assessing dynamics and structural changes of metallic glasses as amorphous out-of-equilibrium materials by means of coherent x-ray scattering. We focus on the fundamental understanding of the x-ray photon correlation spectroscopy (XPCS) technique and on how such an experimental probe may facilitate a deeper quantitative understanding of the underlying structural fluctuations occurring within the amorphous solid. Furthermore, we present how atomistic simulations and simulated x-ray photon correlation spectroscopy experiments can guide the interpretation of experimentally measured data. We conclude with a broader perspective on how contemporary advances in modeling, detector technology, and high flux x‑ray sources are transforming the study of glassy dynamics, enabling access to wider time and length scales and thus offering new avenues to probe the broad relaxation spectrum and complex nonequilibrium relaxation processes characteristic of amorphous solids.
Liquid-metal embrittlement (LME) in Zn-coated steels is traditionally understood as a consequence of liquid Zn penetration along grain boundaries (GBs) during thermo-mechanical processing. However, recent thermodynamic predictions brought to light a massive Zn segregation transition at Fe GBs that suggest a strong driving force for intermetallic phase formation at substantially lower temperatures than the melting point of Zn. Leveraging bulk mechanical testing, high-energy synchrotron diffraction, and transmission electron microscopy, we demonstrate here that embrittling Fe-rich intermetallic grain-boundary phases emerge in an advanced high-strength steel prior to any melting of Zn. Their formation and increasing presence with temperature correlates with severe mechanical degradation. These findings provide consistent evidence that the solid-state formation of Fe-rich Fe-Zn intermetallic phases constitutes an early contributing step to LME in galvanized high-strength steels.
Phase separation is a well‐known approach to increase the damage tolerance of oxide glasses. Here, we report the separation of a silicon‐ and boron‐rich phase in a Si‐poor sodium‐borosilicate glass. This phase separation follows initially a strongly suppressed growth‐law, shows a droplet to needle morphology phase evolution, and exhibits a phase inversion. We discuss the phase separation and inversion in terms of structural mobility constraints and internal stresses. Once a needle‐dominated phase morphology is established, a marked increase of of the indentation fracture toughness and an enhanced crack resistance by more than a factor of 5 is observed.
Accurate determination of particle number concentration is essential in the industry as well the healthcare sector. Widely applied methods for the measurement of particle number concentration, such as MADLS, SAXS, spICP-MS, rely on material specific input parameters, modelling assumptions, or calibration strategies, which contribute to measurement uncertainty, making absolute quantification challenging and limiting direct metrological traceability. In the framework of the European project ConcenSus (https://concensusproject.org/home), a dedicated approach is being studied to determine (nano)particle number concentration using imaging methods. SEM, TEM and other imaging methods are well established for characterising the sizes and shapes of advanced materials with ISO standards in place (ISO 19749:2021, ISO 21363:2020). However, no corresponding standard operation procedures exist for (nano)particle number concentration determination using imaging methods. This work presents a proof-of-principle study for determining the particle number concentration using SEM by employing a dedicated sample preparation method. First, relatively simpler materials such as Ag and Pd nanoparticles have been tested, with future project work increasing particle complexity to include other material types, for example, liposomes, QDs, mesoporous SiO2, etc. The performance of our approach has been assessed by comparison with concentrations measured with MADLS. The results obtained with both methods are in the same order of magnitude (10E11 particles/mL), which demonstrate the strong potential of SEM combined with dedicated sample preparation as a powerful method for the number metrology of (nano)particles independent of material-type and theoretical assumptions, focusing mainly on direct particle counting. Further optimisation of the sample preparation will enable an automated workflow for the measurement of particle number concentration by imaging.
Der 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.
