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Die thermische Historie beim additiven Aufbau von komplexen Realkomponenten und geometrisch primitiven Prüfkörpern unterscheidet sich signifikant. Daraus können Eigenschaftsunterschiede resultieren, die zu unterschiedlichem Materialverhalten führen können. In diesem Vortrag wird das Konzept repräsentativer Probekörper eingeführt, das eine Übertragung thermischer Historien von komplexen Geometrien auf einfache Geometrien ermöglicht und hierdurch zu einer besseren Vergleichbarkeit der Werkstoffeigenschaften führen soll.
Compound semiconductors (CS) are promising materials for the development of high-power electrical applications. They have low losses, can withstand high temperatures and can operate at very high voltages and currents. This makes them a key technology for the electrification of many high energy applications, especially electromobility and HVDC power lines.
The challenge with CS technology is that most of the process technology has to be developed anew to the high standards required by electronic applications. Today, compound semiconductors can be produced in thin layers on top of substrates fabricated from classical crystal growth processes that are already well established. A promising method for this is metal organic vapour phase epitaxy (MOVPE). With this method, many different compounds with semiconducting properties can be synthesized. Additionally, this process technology is a direct thin layer deposition method. Therefore, complex multilayer systems can be generated directly by the deposition process and without the need of doping after growing.
There are a number of critical defects that can originate from the deposition process of these thin film devices. Within this project, we intend to develop new correlative imaging and analysis techniques to determine defect types, to quantify defect size and number density, as well as to characterise defects for process optimisation.
We report here on the use of spectroscopic ellipsometry and imaging ellipsometry to investigate defects in several different compound semiconductor materials used in high-power electronic devices. The materials we investigated are β-Ga2O3, SiC, GaN, AlN, and AlGaN materials as well as oxidised SiC surfaces. All of these materials have their typical defects and require optimised measurement and analysis schemes for reliable detection and analysis. Spectroscopic ellipsometry is a highly sensitive method for determining the thicknesses and dielectric function of thin layers, yielding potentially a high number of microscopic properties. The combined method between ellipsometry and optical microscopy is called imaging ellipsometry and is especially powerful for the large amount of data it produces. We have analysed defects in SiC- and AlN-based thin film semiconductors as well as characterised the properties of different types of SiO2 layers created on top of SiC monocrystals. We developed ellipsometric models for the data analysis of the different semiconductor materials.
If the defects have geometric features, it is useful to combine the ellipsometric analysis with topometry method like interference microscopy and scanning probe microscopy. We have successfully characterised function-critical defects in MOVPE SiC layers and correlated the findings with topography from WLIM measurements. We have developed an imaging ellipsometric measurement methodology that allows to estimate the relative defect area on a surface by a statistical raw data analysis.
Compound semiconductors (CS) are promising materials for the development of high-power electrical applications. They have low losses, can withstand high temperatures and can operate at very high voltages and currents. This makes them a key technology for the electrification of many high energy applications, especially electromobility and HVDC power lines.
The challenge is that most of the process technology has to be developed specifically and tailored to the high standards required by electronic applications. Today, many different CS materials can be produced in thin layers on top of substrates fabricated from classical crystal growth processes that are already well established. A promising method for this is metal organic vapour phase epitaxy (MOVPE). This technology is a direct thin layer deposition method capable of producing complex multilayer systems directly from one deposition process without the need of doping after growing.
There are a number of critical defects that can originate from the deposition process when targeting electronic thin film devices. Within this project, we intend to develop new correlative imaging and analysis techniques to determine defect types, to quantify defect size and density, as well as to characterise defects for further process optimisation.
We report here on the use of spectroscopic and multispectral imaging ellipsometry to investigate defects in several different compound semiconductor materials used in high-power electronic devices. The materials we investigated are β-Ga2O3, SiC, GaN, AlN, and AlGaN as well as oxidised SiC. All of these materials have their typical defects and require optimised measurement and analysis schemes for reliable detection and analysis. Spectroscopic ellipsometry is a highly sensitive method for determining the thicknesses and dielectric function of thin layers, yielding potentially a high number of microscopic properties. The combined method between ellipsometry and optical microscopy is known as imaging ellipsometry and is especially powerful for the large amount of data it produces. We have analysed defects in SiC- and AlN-based thin film semiconductors as well as characterised the properties of different types of SiO2 layers created on top of SiC monocrystals. We developed ellipsometric models for the data analysis of the different semiconductor materials.
If the defects have geometric features, it is useful to combine the ellipsometric analysis with topometry methods like interference microscopy and scanning probe microscopy. We have successfully characterised function-critical defects in MOVPE SiC layers and correlated the findings with topography from WLIM measurements. We have developed an imaging ellipsometric measurement methodology that allows to estimate the relative defect area on a surface by a statistical raw data analysis.
Development of representative test specimens by thermal history transfer in laser powder bed fusion
(2024)
The use of components manufactured by laser powder bed fusion (PBF LB/M) and subjected to fatigue loading is still hampered by the uncertainty about the homogeneity of the process results. Numerous influencing factors including the component’s geometry contribute to the risk of process instability and resulting inhomogeneity of properties. This drastically limits the comparability of different built parts and requires expensive full component testing. The thermal history as the spatiotemporal temperature distribution has been identified as a major cause for flaw formation. Therefore, it can be hypothesized that a similar thermal history between components and test specimens enhances their comparability. Following this assumption, a strategy is developed to transfer the intrinsic preheating temperature as a measure of comparability of thermal histories from a region of interest of a complex component to a simple test specimen. This transfer concept has been successfully proved by the use of FEM-based macroscale thermal simulations, validated by calibrated infrared thermography. An adoption of the specimen manufacturing process by the adjustment of the inter layer times was established to manufacture specimens which are representatives of a specific region of a large-scale component in terms of the thermal history similarity criterion. The concept is schematically illustrated in Figure 1 and was demonstrated using a pressure vessel geometry from the chemical industry.
Ellipsometry as optical metrology method for analysis of reference materials for nanoelectronics
(2024)
Electrical properties of materials at the nanoscale can be characterized using scanning microwave microscopes (SMM) and conductive atomic force microscopes (C AFM). However, the measurement results are difficult to compare since different setups and different reference standards are used. The development of new “out-of-lab” reference standards can contribute to the traceability and reliability of these scanning probe microscopy methods (SPM) and facilitate their broader industrial application.
In this study, we discuss the capability of optical methods such as ellipsometry for the characterization of existing and the development of new reference calibration samples for scanning microwave microscopy. Ellipsometry is a fast and non-destructive method, which enables very accurate determination of the layer thickness and the dielectric functions of the materials. Imaging ellipsometry is suitable for spatially resolved measurements when analyzing thin layers in microstructured samples.
We show how the electrical resistivity of indium tin oxide (ITO) layers in newly designed resistive calibration samples can be obtained from spectroscopic ellipsometric measurements. The extension of the measurement range into the mid-infrared region was necessary when analyzing ITO layers with low conductivity. This parameter was obtained by fitting a Drude function describing the absorption of the free carriers. The impact of the coating process conditions on the layer properties is discussed.
Imaging ellipsometry was applied for the characterisation of thin ITO and SiO2 layers in microstructured resistive and capacitance calibration kits. The uncertainties of determined layer thicknesses were specified according to standardized practice guides used in ellipsometry. We show how statistical fingerprint analysis of the measured ellipsometric transfer quantities can be used to validate the quality of potential reference materials for nano-electronics and to monitor the processing of structured samples.
As industries move for ever faster development and adoption cycles of emerging new technologies in the field of welding, the meticulous and longer-winded approach of the scientific research process can feel harder to integrate. To help bridge this gap and increase the speed, quality, and adoption rate of publicly funded research, the Bundesanstalt für Materialforschung und -prüfung (BAM) continues to work towards enabling scientists with direct access to necessary software tools and - in the future – highest quality welding research reference data to further foster collaborations.
On the experimental side, the arc welding group at BAM division 9.3 “welding technologies” is continuing to expand and upgrade its capacities of robotic welding systems with integrated state of the art sensor technologies and software solutions. This allows all experiments to be recorded and measured in micro-millimeter accuracy and at sub-millisecond precision, including welding process data, complete spatial geometry and temperature measurements, process video recordings and more. The custom software-based solutions and interfaces allow scaling of the welding systems from large thick plate offshore applications to small additive repair weldments in wind turbine blades to multi-hour continuous weldments in additive manufacturing applications. In addition to the data gathered during the welding process itself, the relevant testing results and materials properties produced at BAM or externally can be integrated seamlessly. This allows detailed traceability of all results back to the actual welding process.
Regardless of the scope and application, complete datasets can be made accessible for research or industry partners in the highest resolution based on the open source WelDX (welding data exchange) file format.
Figure 1. Welding experiment representation including dynamic process data, cross-section imaging and hardness measurements from a single weldx file.
The talk will give an overview of the experimental facilities and workflows as well as current software developments with a focus on research data quality assurance, traceability, and accessibility.
Based on the integration into latest research trends and activities of the “welding technologies” division, the path to publishing reference datasets for arc welding process for various applications and materials is outlined and discussed.
Although intense wildfire research has been done in the US and in Australia, it cannot be transferred directly to the situation in Europe as the local vegetation has a significant influence on the fire spread. The EU-funded project TREEADS and the so-called German pilot within the project are concentrating on wildfire in Europe. Extensive experimental research is done on local vegeta-tion in Germany and the experimental results are used to adjust the Fire Dynam-ics Simulator (FDS) to local vegetation as a fuel in the calculations. The particle model and the boundary fuel model are developed for the simulation of forest fires. Both models require the kinetic input for the dehydration, pyrolysis, and char oxidation process. This three-step simplified model describes the basic fuel combustion kinetic. Most published simulations use the default kinetic input of pine needles from FDS user manual.
To adjust the simulation to local vegetation, the corresponding kinetic parame-ters have been experimental investigated. Samples of pine needles, moss and other falling leaves were collected, air dried and grinded into powder. The TG analysis of all these samples were done under different heating rate of 5, 10 and 20K/min.
The activation energy and the corresponding pre-exponential factor were calcu-lated. The results show that fire spread depends significantly on the vegetation and comparison with small scale experiments show good agreement using the new kinetic parameters. The new model is applied to a larger scenario and will be compared to the results of large-scale experiments for further validation of the model.
Um die Ausbreitungsmechanismen von Vegetationsbränden und besonders bei Bodenbränden besser zu verstehen, wurden die Einflussfaktoren auf die Brandausbreitung näher untersucht. Da die Brandausbreitung auch in starkem Maße von der lokalen Vegetation abhängt, war eine Charakterisierung der lokalen Vegetation und der Bodenverhältnisse wichtig. Die Wetterverhältnisse spielen einerseits im Vorfeld des Brandes durch längere Dürreperioden als auch während des Brandes, z.B. durch den Windeinfluss, zusätzlich eine große Rolle.
Durch die numerische Simulation kann eine größere Variation der Einflussgrößen abgebildet werden als durch die zeitlich und finanziell begrenzten experimentellen Möglichkeiten. Für die Berechnungen wird der Fire Dynamic Simulators (FDS) mit dem Paket WFDS verwendet. Dadurch kann mit einem vereinfachten 3-Phasen-Reaktionskinetikmodell, bestehend aus Dehydrierung, Pyrolyse, Kohleoxidation, die Ausbreitung von Vegetationsbränden verschiedener Waldbodenarten untersucht werden. Es wurden dazu 6 typische Pflanzenarten und Bodenproben aus Kiefern-, Buchen und Eichenbeständen ausgewählt.
Die gesammelten Waldbodenproben wurden alle hinsichtlich des Wassergehalts, des organischen Gehalts, der Packungsdichte, der Dichte und der statistisch ermittelten Pflanzenartenverteilung charakterisiert. Das kinetische Abbrandverhalten wurde durch Thermogravimetrische Analyse (TGA) untersucht. Alle diese Daten wurden als Eingabeparameter für die Simulation verwendet. Die numerischen Simulationen werden mit Experimenten im kleinen, mittleren und Real-Maßstab validiert.
Direct energy deposition additive manufacturing technologies that utilize an electric arc have great potential for generating large volume metal components. However, selecting process parameters that yield the desired near net shape design and requested mechanical component behavior is not a trivial task due to the complex relationship between all process parameters and material characteristics. This presentation exemplifies the application of a newly developed solid welding wire doped with TiB to enhance grain refinement in the deposited metal for additive manufacturing based on DED-Arc of high-strength precipitation hardening AlMgSi-aluminum alloys. It is worth noting that the solid wire is the result of our preliminary metallurgical studies on grain refinement in aluminum weld metal.
Consequently, research focuses on the correlation between process parameters and component quality to understand the underlying mechanisms. This is crucial for evaluating a robust process parameter space that yields component quality in line with corresponding standards which are mainly taken from welding technology.
Specifically, we examine component quality by analyzing pore size and distribution, as well as grain morphology. To enhance the mechanical properties of the deposited metal, a post-weld heat treatment was conducted, comprising of solution treatment, quenching, and artificial aging. The study also evaluates the effects of various heat treatment strategies on the final mechanical properties of the material.
To demonstrate the applicability of 3D metal printing of high-strength aluminium alloys, a more complex demonstrator was created. It has been shown that DED-Arc can produce high-volume aluminium parts with the same quality as the corresponding subtractive processing strategy.
Additionally, the entire additive manufacturing chain has been digitally integrated, enabling traceability of all relevant process steps, which is essential for reliable subsequent quality assessment.
Lecture-like introduction in the topic. Fundamental aspects are discussed: Burning of polymers, fire risks, pyrolysis, combustion in the flame, physical chemistry of ignition, flame spread and steady state burning, flame retardancy mechanisms and groups of flame retardants, fire hazards (smoke, toxic products) and environmental concerns, fire testing.
The manufacture of sintered glasses and glass-ceramics, glass matrix composites, and glass-bounded ceramics or pastes is often affected by un-expected gas bubble formation also named foaming. Against this background, in this presentation the main aspects and possible reasons of foaming are shown for completely different glass powders: a barium silicate glass powders used as SOFC sealants, and bioactive glass powders using different powder milling procedures.
Sintering and foaming were measured by means of heating microscopy backed up by XRD, differential thermal analysis (DTA), vacuum hot extraction (VHE), optical and electron microscopy, and infrared spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS).
Different densification was reached followed by significant foaming starting partly immediately, partly at higher temperature. Foaming increased significantly as milling progressed. For moderately milled glass powders, subsequent storage in air could also promote foaming. Although the milling atmosphere significantly affects the foaming of uniaxially pressed powder compacts sintered in air.
VHE studies show that foaming is driven by carbon gases and carbonates were detected by Infrared spectroscopy to provide the major foaming source. Carbonates could be detected even after heating to 750 °C, which hints on a thermally very stable species or mechanical trapping or encapsulating of CO2. Otherwise, dark gray compact colors for milling in isopropanol indicate the presence of residual carbon as well. Its significant contribution to foaming, however, could not be proved and might be limited by the diffusivity of oxygen needed for carbon oxidation to carbon gas.
Up to now, oriented surface crystallization phenomena are discussed controversially, and related studies are restricted to few glasses. For silicate glasses we found a good correlation between the calculated surface energy of crystal faces and oriented surface nucleation. Surface energies were estimated assuming that crystal surfaces resemble minimum energy crack paths along the given crystal plane. This concept was successfully applied at the Institute of Physics of Rennes in calculating fracture surface energies of glasses. Several oriented nucleation phenomena can be herby explained assuming that high energy crystal surfaces tend to be wetted by the melt. This would minimize the total interfacial energy of the nucleus. Furthermore, we will discuss the evolution of the microstructure and its effect on the preferred crystal orientation.
We investigated the phase transformations during butt-welding of supermartensitic steel plates with help of Neutron-Bragg-Edge Imaging (NBEI). Gas tungsten arc welding (GTAW) was used with a motorized torch allowing for automated weldments. The austenitization in the heat affected zone (HAZ) could be clearly visualized at λ = 0.39 nm, a wavelength smaller than the Bragg edge wavelengths of both austenite and martensite. The re-transformation into the martensitic phase during cooling was clearly detected. However, we observed an unexpected additional change in transmission at λ = 0.44 nm, a wavelength larger than the wavelength of the Bragg edges of both the martensitic and austenitic phases. We attribute this change to the Deybe-Waller-Factor that describes the temperature dependence of coherent scattering at a crystal lattice. The observed two-dimensional attenuation map corresponds well with a temperature distribution modelling by software macros in ANSYS [3]. Here, the absolute temperature values could be achieved by calibrating the modelled attenuation with help of a thermocouple placed at the steel plate. This allows in return for a direct two-dimensional temperature reading based on the Debye-Waller-relation between neutron attenuation and sample temperature.
Bislang wird das Phänomen der orientierten Oberflächenkristallisation kontrovers diskutiert und entsprechende Studien beschränken sich auf nur wenige Gläser. Für Silikatgläser haben wir eine gute Korrelation zwischen der berechneten Oberflächenenergie von Kristallflächen und der orientierten Oberflächenkeimbildung gefunden. Die Oberflächenenergien wurden unter der Annahme abgeschätzt, dass die Kristalloberflächen bei der Keimbildung den Kristallebenen mit minimaler Energie entsprechen, denen ein Riss beim Bruch folgt. Dieses Konzept wurde am Institut für Physik in Rennes erfolgreich bei der Berechnung der Bruchflächenenergien von Gläsern angewandt. Mehrere orientierte Keimbildungsphänomene lassen sich dadurch erklären, dass man annimmt, dass Kristalloberflächen mit hoher Energie dazu neigen, von der Schmelze benetzt zu werden. Dies minimiert die gesamte Grenzflächenenergie des Keims. Darüber hinaus werden wir die Entwicklung der Mikrostruktur beim weiteren Kristallwachstum und ihre Auswirkungen auf die bevorzugte Kristallorientierung diskutieren.
eavy-weight packages for the safe transport of radioactive material are equippedwith impact limiters often built ofwood-filled steel sheet structures to fulfil the requirements of the International Atomic Energy Agency (IAEA) regulations. The requirements definemechanical tests followed by a thermal test, including criteria ensuring the package design’s ability to withstand severe accidents and provide a high level of technical safety. Impact limiters are a package component mainly designed for the packages to withstand severe mechanical accident scenarios. In drop tests the impact limiters absorb the kinetic energy during impact of the package. The package must then - with its pre-damaged impact limiters - endure a thermal test defined precisely in the IAEA regulations as a 30-min fully engulfing 800 °C-fire. After the fire, a wood-filled impact limiter may continue to release thermal energy from an ongoing combustion process, defining relevant package temperatures. The energy flow from a possible burning impact limiter to the package is important for the safety evaluation of transport packages. To investigate the combustion behaviour of densely packed layers of spruce wood, encapsulated in pre-damaged cylindrical metal enclosures, a test set-up has been realised. The set-up consists of a combustion chamber to perform these tests under defined boundary conditions. The temperature development of the test specimens will be observed fromoutside with a thermographic imager, with HD-Cameras, and the mass loss will be measured during the entire test. Airflow conditions in the combustion chamber are analysed using Computational Fluid Dynamics (CFD) calculations in OpenFOAM. The planned combustion test setup is described.
Any surface in the environment acts as hotspot for microbial attachment and activity. These biofilms represent the interface between humans and the environment.
While in the past biofilms were often seen as disturbance, we now start to understand the enormous potential of beneficial biofilms. They can be used in a broad range of applications and are sources for new microorganisms and traits. After all, biofilms represent a great example for a collaborative lifestyle.
Residual stress formation during repeated gouging and repair welding cycles of high-strength steels
(2024)
The construction of foundation and erection structures for wind power plants requires the use of modern, sustainable and resource-efficient high-strength fine-grained structural steels. Weld defects due to the welding process are unacceptable. To overcome this issue, local thermal gouging followed by re-welding is a common and cost-effective method. The high shrinkage restraint of the gouge by the surrounding structure can cause crack initiation when design and re-weld induced residual stresses are superimposed. This risk is intensified by the progressive degradation of the microstructure and mechanical properties of high-strength steels during the weld repair process.
This investigation focuses on high-strength steels S500MLO for offshore applications and S960QL for mobile crane applications. The reduction and development of residual stresses caused by local thermal gouging and re-welding was investigated. Digital Image Correlated (DIC) stress-strain analysis was performed during preheating, welding and cooling. The results of the global DIC analysis and local longitudinal and transverse residual stresses of the weld determined by X-ray diffraction were found to be in good agreement. Furthermore, different stress levels were identified during gouging and welding. Repeated repair cycles led to an increase of longitudinal and transverse residual stresses in the weld metal as well as a hardness increase in the heat affected zone.
Das Ausbreitungsverhalten geführter Ultraschallwellen ermöglicht die großflächige Prüfung von Platten und schalenförmigen Bauteilen wie Rohren und Laminaten auf Fehlstellen von wenigen Prüfpunkten aus. Während die beschränkte Divergenz der geführten Wellen die Ultraschallprüfung begünstigt, erschwert das dispersive und multimodale Verhalten der Lamb-Wellen die Auswertung der Ultraschallsignale. Die dispersive und multimodale Wellenausbreitung verkompliziert die Bestimmung der Fehlerposition bei der Auswertung der Geschwindigkeiten einzelner Wellenpakete. Zudem ist es herausfordernd, einen einfachen Zusammenhang zwischen den Reflexionen der Fehlstelle und deren Größe und Form herzustellen. Eine Möglichkeit zur genauen Bestimmung der Fehlerposition und -geometrie bietet der direkte Vergleich der Messsignale mit den Signalen aus einem Simulationsmodell. Die Nachbildung des Schadens im Simulationsmodell stellt ein inverses Problem dar, das iterativ gelöst werden kann, indem ein Vorwärtsmodell immer weiter optimiert wird. Klassische Ansätze wie die Finite Elemente Methode (FEM) sind für die Simulation von Ultraschallwellen aufgrund der kleinen Wellenlängen im Vergleich zur Bauteilgröße meist ineffizient. Aus diesem Grund basiert das vorgestellte Vorwärtsmodell auf der semi-analytischen Scaled Boundary Finite Element Method (SBFEM), die große Teile der Wellenausbreitung analytisch berechnet. In diesem Beitrag wird die Validierung des zweidimensionalen Modells an Platten mit einer rechteckigen Nut als Ersatzfehler präsentiert und es werden erste Schritte zur Validierung von 3D-Modellen vorgestellt.
This presentation provides an introduction and intermediate results of the Horizon-Europe STAR4BBS project.It focuses on how to maximize the potential of Sustainability Certification Schemes (SCS) and labels to support a successful transition to a sustainable bio-based economy by assessing their effectiveness, robustness, and credibility.
Trace elemental analysis in human serum is integral in both clinical and research settings. Analyzing the level of some specific elements like Se and Zn helps indicate the nutritional and health status. Furthermore, elucidating the roles of trace elements in various physiological and pathological conditions can shed light on disease mechanisms and potential treatments. Inductively coupled plasma mass spectrometry (ICP-MS) stands out as a preeminent method for trace elemental analysis, given its exceptional sensitivity and minimal sample requirements. However, ICP-MS has challenges, such as argon-related interferences that hinder the accurate quantification of elements like Ca, Fe, and Se. The naturally most abundant isotopes of Ca (40Ca), Fe (56Fe), and Se (80Se) are subject to isobaric interference from 40Ar+, 40Ar16O+, and 40Ar2+, thereby complicating their direct measurement and preventing isotope dilution analysis.
In response to these challenges, nitrogen microwave inductively coupled atmospheric pressure mass spectrometry (MICAP-MS) emerges as a viable alternative to ICP-MS, eliminating argon consumption and associated interferences. This study employed MICAP-MS to quantify Ca, Fe, and Se in 11 certified reference human serums using matrix-matched calibration and isotope dilution with the isotopes 40Ca, 56Fe, and 80Se. The results obtained with both methods were validated against certified values, and the suitability of MICAP-MS for isotope dilution was evaluated. Additionally, the performance of MICAP-MS in the Na matrix was investigated and discussed alongside the impact of organic species.
We present our approach and methodology for simulating piping erosion, which occurs during the installation process of suction bucket foundations for offshore wind turbines. We show several simulations and analyze the hydrodynamic and contact forces acting on the granular fabric and the differential pressure of the fluid phase. We demonstrate weak scaling performance on the LUMI supercomputer with a parallel efficiency of up to 90% for 4096 Graphics Compute Dies.
The Microplastic Microbiome
(2024)
Microplastics represent man-made and newly emerging surfaces in our ecosystems, where they interact with microorganisms. The ecosystem in focus of this presentation will be the aquatic environment. It will be portrayed, which microorganisms use microplastics as a habitat, how environmental factors shape this colonization, and why the biodegradation of plastics in the ocean is an overall unlikely process. We will also discuss whether potentially pathogenic microorganisms use microplastics as a raft. Finally, possible adaptation mechanisms of plastic-colonizing microorganisms will be presented, such as the production of photoreactive molecules. The microplastic microbiome has a large potential to harbor so far unknown species with curious traits, representing an exciting research topic for the future.
Die Transformation der Energienutzung von konventionellen zu erneuerbaren Quellen führt dazu, dass zukünftig mehr Energie effizient zwischengespeichert werden muss. Eine Möglichkeit der elektrochemischen Zwischenspeicherung bieten Lithium-Ionen-Batterien. Hierfür können ausgemusterte Automobilantriebsbatterien verwendet werden. Erfüllen sie die hohen Anforderungen des mobilen Bereichs nicht mehr, haben sie oftmals noch eine ausreichende Kapazität und Leistungsfähigkeit für die stationäre Zwischenspeicherung.
Neben der Verwendung der Batterien im größeren Maßstab, z.B. bei Energieversorgern, werden durch den vermehrten Einsatz von Photovoltaik-Anlagen in Ein- und Mehrfamilienhäusern verstärkt Zwischenspeicher für Privathaushalte nachgefragt. Dies birgt auch für Einsatzkräfte neue Herausforderungen in der Gefahrenabwehr.
Im vom Bundesministerium für Bildung und Forschung (BMBF) geförderten Verbundprojekt „SEE-2L – Sicherheit elektrochemischer Energiespeicher in Second Life Anwendungen“ wurden Versuche mit Second Life Modulen durchgeführt. Verbundpartner im Projekt waren neben der vfdb die Otto-von-Guericke-Universität Magdeburg und die Bundesanstalt für Materialforschung und -prüfung. Zudem war das Institut der Feuerwehr Nordrhein-Westfalen eingebunden.
Die durchgeführten Versuche bilden eine Grundlage für die Einordnung der Batteriespeicher, z.B. aus Sicht des baulichen Brandschutzes, zur Methodik der Brandbekämpfung oder zur Risikobewertung hinsichtlich der Prozess- und Anlagensicherheit.
Im Beitrag werden die Versuchsergebnisse vorgestellt und Ansätze für deren Anwendung gezeigt. Um die gewonnenen Erkenntnisse zu vermitteln, wurde im Projekt zudem ein Schulungskonzept für Einsätze mit Lithium-Ionen-Technologien erarbeitet, das im Beitrag präsentiert wird. Es besteht aus theoretischen und praktischen Anteilen, sodass bei den Feuerwehren praxisnah aus- bzw. fortgebildet werden kann.
To address the challenges of the climate crisis, multiple solutions for sustainable energy sources and storage systems are needed. One such solution is lithium-ion batteries (LIBs). Currently, 5 to 30 % of LIBs are discarded immediately after manufacturing. The homogeneous distribution of all materials used in the coating of cathodes and anodes is critical for the quality of LIBs. Furthermore, during formation i.e., the first steps of the charge/discharge cycling, the solid-electrolyte interphase forms on the anode particles, which has a huge impact on the performance. The same happens to some extent on the cathode, forming the cathode-electrolyte interphase. Fluorinated polymers and electrolytes are used in the manufacturing of LIBs. The electrolyte in particular is prone to degradation during formation and aging of the batteries. The interface of the cathode material with the aluminum current collector is also a critical point where degraded fluorine components cause pitting corrosion and at the same time promote passivation of the metal foil. Monitoring the spatial distribution of fluorine on these surfaces and interfaces is essential for sustainable LIB production.
In order to reduce global warming, the use of hydrogen as a renewable energy source is becoming more important. To enable this transition, unprecedently large amounts of hydrogen need to be safely transported and stored. Since hydrogen is usually stored and transported under pressure, one scenario to be considered is the release of hydrogen from a leakage with subsequent ignition. The resulting jet flame must be characterized with respect to the thermal radiation emitted into the environment to define safety distances. Various models that characterize the resulting flame shape and radiation already exist in the literature, but these are mainly based on empirical data from hydrocarbon jet flames. To verify the applicability of these models to hydrogen, real-scale tests are carried out at the BAM Test Site for Technical Safety (BAM-TTS) with the aim to assess the flame geometry and the emitted thermal radiation. Parameters such as leakage diameter (currently up to 30 mm), pressure (currently up to max. 250 bar) and mass flow (up to max. 0.5 kg/s) are varied. In particular, the focus will be laid on the measurement and modelling of the thermal radiation. The challenge here is the characterization of the flame geometry in an open environment and its impact on the thermal radiation. Existing heat radiation data from literature are mostly based on unsteady outflow conditions. The experimental setup used here allows for the generation of a steady-state outflow for several minutes and thus a direct comparability with existing (steady-state) models. Furthermore, stationary outflow tests with hydrocarbons (methane) were also carried out, which are intended to serve as reference tests for checking flame models based on hydrocarbon data. Following from the experimental investigations, modelling parameters such as the Surface Emissive Power (SEP) and the radiant heat fraction for hydrogen and methane will be compared to literature data.
Science Café Adlershof is having its next edition in 2024 on February 20th '24! We will have one speaker next week: Alexander Winckelmann is a PhD student at Bundesanstalt für Materialforschung und -Prüfung and will give a talk about his stay abroad in Switzerland - there will be free chocolates! There will be enough time to ask questions or simply chat with the guests and participants.
Einleitend wird im Vortrag das Aktivitätsfeld Elektrische Energiespeicher und -umwandlung vorgestellt sowie eine kurze Einführung in die Terminologie der elektrischen Energiespeicher gegeben. Im Folgenden wird das BMBF-Vorhaben SEE-2L vorgestellt. Hier wird der Schwerpunkt auf die Entwicklung und den Aufbau eines Großversuchsstand für das thermische Durchgehen von Lithium-Batterien auf Modul- und Batterieebene gelegt. Darüber hinaus werden die Ergebnisse einer ersten Versuchsserie vorgestellt. Zum Abschluss wird ein kurzer Ausblick zu weiteren anstehenden Versuchen gegeben.
Second Life Verwendungen - Untersuchungen und erste Erfahrungen mit einem Ausbildungsdemonstrator
(2024)
Der Vortrag gibt zunächst einen Themeneinstieg in den Bereich der Second-Life-Batterien sowie rechtliche und technische Grundlagen zu Lebenszyklus und Alterung. Im Weiteren werden experimentelle Ergebnisse aus Versuchen zum thermischen Durchgehen mit Batteriemodulen aus dem BMBF-Vorhaben SEE-2L vorgestellt. Darüber hinaus wird ein eigens entwickelter Ausbildungsdemonstrators vorgestellt, welcher einen wesentlichen Baustein des Ergebnistransfers aus dem Vorhaben darstellt.
Die Integration und Wiederverwendung von Wissen und Daten aus der Herstellung, Bearbeitung und Charakterisierung von Materialien wird im Zuge der digitalen Transformation in der Materialwissenschaft und Werkstofftechnologie in verschiedenen Projekten behandelt. Dabei liegt der Fokus auf der Interoperabilität von Daten und Anwendungen, die nach den FAIR-Prinzipien erstellt und veröffentlicht werden. Zur Umsetzung eines komplexen Datenmanagements und der Digitalisierung im Bereich der Materialwissenschaften gewinnen Ontologien zunehmend an Bedeutung. Sie ermöglichen sowohl menschenlesbare als auch maschinenverständliche und -interpretierbare Wissensrepräsentationen durch semantische Konzeptualisierungen.
Im Rahmen des Projektes Plattform MaterialDigital (PMD, materialdigital.de), welches in dieser Präsentation vorgestellt wird, werden Ontologien verschiedener Ebenen entwickelt (verbindende mid-level sowie Domänen-Ontologien). Die PMD-Kernontologie (PMD Core Ontology - PMDco) ist eine Ontologie der mittleren Ebene, die Verbindungen zwischen spezifischeren MSE-Anwendungsontologien und domänenneutralen Konzepten herstellt, die in bereits etablierten Ontologien höherer Ebenen (top-level Ontology) verwendet werden. Sie stellt somit einen umfassenden Satz von durch Konsensbildung in der Gemeinschaft (geteiltes Vokabular) entstanden Bausteinen grundlegender Konzepte aus der Materialwissenschaft und Werkstofftechnik (MSE) dar. In dieser Präsentation wird die PMDco adressiert.
Weiterhin wird eine auf die PMDco bezogene normenkonforme ontologische Repräsentation zur Speicherung und Weiterverarbeitung von Zugversuchsdaten – die Tensile Test Ontology (TTO) – präsentiert, die in enger Zusammenarbeit mit dem zugehörigen DIN-Standardisierungsgremium NA 062-01-42 AA erstellt wurde. Dies umfasst den Weg von der Entwicklung einer Ontologie nach Norm, der Konvertierung von Daten aus Standardtests in das interoperable RDF-Format bis hin zur Verbindung von Ontologie und Daten. Auf Grundlage der dabei entwickelten Struktur und Vorgehensweise können weitere Materialcharakterisierungsmethoden semantisch beschrieben werden, woraus sich in diesem Zusammenhang Kooperationsmöglichkeiten ergeben.
Morphological and chemical analysis of mesoporous mixed IrOx-TiOy thin films as electrode materials
(2024)
Porous films play an important role particularly in energy applications like photovoltaics, electrolysis or batteries. Thin film properties such as thickness, chemical composition, crystallinity of the framework, and porosity define the activity of the porous films. The accurate morpho-chemical characterisation of mesoporous thin films is a challenging analytical task which requires the consideration of new analytical approaches based on the combination of data of different methods able to address the structure and chemical composition at the nanoscale. In this contribution we characterise thin mesoporous iridium-titanium mixed oxide film properties by Electron Probe Microanalysis (EPMA) with Energy-Dispersive X-ray Spectroscopy (EDS) at an SEM applied in a dedicated “thin film analysis” approach (1). Thus, the film mass deposition, film thickness and the film density can be determined. Further, by dividing the measured film density to an assumed (theoretical) metal oxide framework (skeletal) density, the thin film porosity can be extracted, too.
In order to assess the homogeneity of the thin film properties like the chemical composition, Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Auger Electron Spectrometry are applied in the depth profiling mode, so that possible in-depth gradients are detected. Lateral inhomogeneities in the chemical composition and structure of the thin mesoporous films are also identified by applying the same methods in the line-scan or mapping mode, which can be further combined with in-depth sputtering for 3D information. The role of the spatial resolution of the analytical methods considered, which can go down well below 100 nm, will be highlighted.
Traceable morphological and chemical characterization of nanomaterials with respect to the various possible sizes, size distributions, shapes, and concentrations of real-world nanoparticles (NPs) is a challenging task. Particularly for the nonspherical, non-monodisperse nanoparticles – as typically for most of the commercial particles, including their strong tendency to agglomerate, there is a lack of standard operation procedures providing accurate nanoparticle characterisation.
In the framework of the pre-standardisation framework of VAMAS (Versailles Project on Advanced Materials and Standards, www.vamas.org) two interlaboratory comparison (ILC) studies are being carried out under the Technical Working Area (TWA) 34 “Nanoparticle Populations”:i) Project #15 addresses the analysis of the size and shape distribution of TiO2 bipyramidal NPs by traceable imaging methods such as TEM, SEM, STEM-in-SEM, AFM as well as with SAXS as an ensemble method. This ILC is thought as the next level development of the case studies exemplified in the published ISO standards ISO 21363 and ISO 19749. It was agreed to complete the first ILC with the NPs already prepared according to the same procedure on a TEM grid, and, at a later stage, to carry out second ILCs with the same NPs distributed to the participants as liquid suspensions together with protocols for the uniform NP deposition on suited substrates - as developed and optimized within the European project nPSize. Once having good deposition protocols available, the door for automated image analysis gets opened. Corresponding image analysis protocols and reporting templates have been distributed to the ILC participants, too.
ii) Project #16: two spherical SiO2 NP samples with bi-modal size distributions in two nominal relative number concentrations were prepared and distributed also as liquid suspensions accompanied by sample preparation, measurement, and image analysis protocols and reporting templates. Here, the NP concentration is the primary parameter to be measured. For the imaging methods it is targeted to
measure the relative nanoparticle concentrations (relative populations of the two modes).
The results of all the participating laboratories, in both ILCs, compiled in comparative representations will be shown and discussed for the first time. The reduction of the measurement uncertainties associated to the size, shape and number-concentration results induced by the significant improvement of the sample preparation on substrates (as single particles with a high-density coverage), combined with welldefined image analysis procedures will be highlighted.
In infrared thermography, the interaction of the heat flow with the internal geometry or inhomogeneities in a sample and their effect on the transient temperature distribution is used, e.g., to detect defects non-destructively. An equivalent way of describing this is the propagation of thermal waves inside the sample. Although thermography is suitable for a wide range of inhomogeneities and materials, the fundamental limitation is the diffuse nature of thermal waves and the need to measure their effect radiometrically at the sample surface only. The crucial difference between diffuse thermal waves and propagating waves, as they occur, e.g., in ultrasound, is the rapid degradation of spatial resolution with increasing defect depth. This degradation usually limits the applicability of thermography for finding small defects on and below the surface.
A promising approach to improve the spatial resolution and thus the detection sensitivity and reconstruction quality of the thermographic technique lies in the shaping of these diffuse thermal wave fields using structured laser thermography.
Some examples are:
• Narrow crack-like defects below the surface can be detected with high sensitivity by superimposing several interfering thermal wave fields,
• Defects very close to each other can be separated by multiple measurements with varying heating structures,
• Defects at different depths can be distinguished by an optimized temporal shaping of the thermal excitation function,
• Narrow cracks on the surface can be found by robotic scanning with focused laser spots.
We present the latest results of this technology obtained with high-power laser systems and modern numerical methods.
Die zunehmende Bedeutung der luftgekoppelten Ultraschallprüfung (ACUT) in der zerstörungsfreien Prüfung (ZfP) unterstreicht die Notwendigkeit von standardisierten Abläufen und Methoden. Bei der ACUT bestehen grundlegende Unterschiede zur manuell durchgeführten Ultraschallprüfung mit Kontakttechnik oder zur automatisierten Tauchtechnik. Die Unterschiede bei der Bestimmung von Prüfkopfparametern für ACUT wurde von Herstellern, Forschungseinrichtungen und Anwendern bereits als wichtig erkannt, was sie veranlasst hat, im Rahmen des Unterausschusses Luftgekoppelte Ultraschallprüfung der DGZfP die Richtlinie US08 zur standardisierten Charakterisierung von luftgekoppelten Ultraschallwandlern zu erarbeiten. Darüber hinaus bestehen auch bei der Durchführung einer Messung grundlegende Unterschiede, die aktuell in einem Leitfaden zusammengetragen und definiert werden.
In diesem Beitrag wird ein Überblick über die geplanten Inhalte dieses Leitfadens gegeben. Insbesondere wird die Auswahl von Prüfparametern in Form von Frequenzen, Abständen und Positionierung sowie die Auswertung behandelt. Darüber hinaus werden die Ergebnisse eines Ringversuchs vorgestellt, welcher an einem eigens hierfür entwickelten und mit Defekten versehenem Prüfkörper, der sog. ACUT-Prüfplatte, durchgeführt wurde. In diesem Ringversuch werden unterschiedliche Messanordnungen, die mittels luftgekoppeltem Ultraschall möglich sind, anhand des erreichbaren Signal-Rausch-Verhältnisses sowie der messbaren Defektgröße quantifiziert. Zudem findet eine Abgrenzung zu weiteren gängigen Verfahren der ZfP statt. Anhand der hier vorgestellten Ergebnisse ist es möglich, die Anwendbarkeit des luftgekoppelten Ultraschalls unter Berücksichtigung unterschiedlicher Messanordnungen besser einzuschätzen.
Die größten Vorteile der luftgekoppelten Ultraschallprüfung sind: die berührungslose Prüfung und der Verzicht auf ein flüssiges Koppelmittel. Allerdings weisen die meisten luftgekoppelten Prüfszenarien ein sehr geringes Signal-zu-Rausch-Verhältnis (SNR) auf und die Pegel, die von luftgekoppelten Ultraschallwandlern realisiert werden, sind um mehrere Größenordnungen kleiner.
Da diese Herausforderung auch in anderen Disziplinen wie bspw. der Radartechnik existiert und dort ebenfalls eine entscheidende Rolle spielt, wurde die dort eingesetzte Pulskompression auf die physikalischen Gegebenheiten der luftgekoppelten Ultraschallprüfung angepasst und angewandt.
Dieser Beitrag präsentiert die Ergebnisse von zwei Versuchsaufbauten: 1) ein thermoakustischer Sender und ein optisches Mikrofon und 2) ein Paar Ferroelektret-Wandler als Sender und Empfänger. Aufgrund der physikalischen Randbedingungen wurden unipolare Kodierungen verwendet. Die Verwendung von unipolaren Kodes zur Modulation der Anregungssignale stellt dabei eine neue Methode dar, die so die Pulskompression für Ferroelektret- und thermoakustische Wandler ermöglichen soll. Die Anwendung der Pulskompression auf die Kombination aus thermoakustischem Sender und optischem Mikrofon konnte das Signal-zu-Rausch-Verhältnis um bis zu 15 dB und für die Ferroelektret-Wandler um bis zu 23 dB erhöhen.
In this paper, we investigate the influence of different heat source pulse shapes by Infrared impulse thermography (IRT) on the results of the thermal shock response spectrum (TSRS) methodology. TSRS is a new alternative approach for evaluating impulse thermography (IRT) data based on an analogy to Shock Response Spectrum (SRS) analysis (ISO 18431) for mechanical systems. It allows processing the entire recorded signal without truncating the saturated thermogram, as in pulse-phase thermography (PPT) or thermal signal reconstruction (TSR). For this purpose, we use a widespread halogen lamp as heat source as well as laser spot. The laser source enables not only to generate a precise shape of the pulse, but also to heat a specific area of the sample uniformly. This makes it possible to suppress influences of lateral fluxes due to uneven distribution of the excitation source on the surface of the specimen and leads to improved results. In order to quantitatively compare the results and to investigate the possible influence of the source shape on the TSRS, the Tanimoto criterion and the signal-to-noise ratio (SNR) were applied to the region of interest (ROI) of the carbon fiber reinforced polymer (CFRP) laminate with artificial defects as defect detectability criterion.
Mikroplastik Detektion mit Thermoanalytischen Methoden: Analytik, Referenzmaterial, Ringversuche
(2024)
Ich dem Vortrag geht es um die Vorstellung von thermoanalytischen Methoden für die Mikroplastik-Detektion. Verschiedene Kopplungsmöglichkeiten werden gezeigt und die Funktionsweise der TED-GC/MS wird erklärt. Im zweiten Teil werden Referenzmaterialien für die Mikroplastik-Analytik diskutiert. PET -Tabletten des PlasticTrace Projektes werden vorgestellt. Am Ende wird der VAMAS Ringversuch zur Mikroplastik-Detektion gezeigt.
Die additive Fertigung von Metallen hat inzwischen einen Reifegrad erreicht, der einen Einsatz in vielen Industriezweigen ermöglicht oder in greifbare Nähe rückt. Die Vorteile liegen vor allem in der Möglichkeit der Fertigung komplexer Bauteile, die sich konventionell nicht oder nur sehr aufwändig produzieren lassen, sowie in der Fertigung von hochindividualisierten Bauteilen in kleinen Stückzahlen. Allerdings ist der additive Fertigungsprozess hoch komplex und fehleranfällig. Um eine insbesondere für sicherheitsrelevante Bauteile notwendige Qualitätskontrolle zu gewährleisten, ist aktuell aufwändige nachgelagerte ZfP der einzelnen Bauteile notwendig. Alternativen könnten die In-situ-Prozessüberwachung und -prüfung bieten, die aktuell aber noch keinen ausreichenden Entwicklungsstand erreicht haben. Industrielle Fertigungsanlagen bieten keine oder nur geringe Flexibilität und Zugänglichkeit, um umfangreiche Untersuchungen auf diesem Gebiet zu ermöglichen. Daher haben wir an der BAM ein System für den Prozess des selektiven Laserschmelzens (PBF-LB/M) entwickelt, genannt SAMMIE. Es bietet eine komplett offene Systemarchitektur mit voller Kontrolle über den Prozess und flexiblem Zugang zur Baukammer, z.B. optisch sowohl direkt als auch koaxial zum Fertigungslaser. In diesem Beitrag stellen wir das System vor und zeigen erste experimentelle Ergebnisse der In-situ-Überwachung und -prüfung: Thermografische Schmelzbadüberwachung, optische Tomografie und In-situ-Laserthermografie. SAMMIE ermöglicht uns grundlegende Untersuchungen, die helfen werden, die In-situ-Prozessüberwachung und -prüfung weiterzuentwickeln, neue Erkenntnisse über die additive Fertigung zu gewinnen und die Sicherheit und Zuverlässigkeit des Prozesses zu verbessern.
Several investigation groups have studied the flame-retardancy modes of action and properties of epoxy resins in the past; nevertheless, the selection of suitable flame retardants for epoxy resins remains challenging, and the transfer to fiber composites is difficult. The addition of flame retardants and glass fibers (GFs) to a polymeric system in a fire scenario changes the polymer's pyrolytic path and burning characteristics, reduces the heat released in the combustion, and suppresses the modes of action in the condensed and gas phase. In this study, the thermal analysis, flammability, fire behavior, residue analysis, fire stability, and quantification of modes of action of three different systems with three halogen-free flame retardants (melamine polyphosphate (MPP), ammonium polyphosphate (APP), and silane ammonium polyphosphate (SiAPP)) and three different types of GFs (unidirectional (UD), bidirectional (BD), and woven roving (WR)) will be compared with pure epoxy resin as a reference.
Distributed fiber optic sensing (DFOS) technique is a promising and robust non-destructive testing tool that can seamlessly acquire environmental conditions over large scales. Therefore, it has found extensive applications in structural health monitoring. Its appeal for monitoring underground facilities lies in the intrinsic properties of the optical fiber, such as immunity to magnetic interference, small size, chemical inertia, etc. This paper provides a concise overview of DFOS applications in underground facility monitoring. Following a brief introduction to the working principle of the DFOS technique, various examples are provided to demonstrate how distributed fiber sensors contribute to monitoring underground facilities. The paper presents unpublished field test results with an emphasis in the energy sector, including monitoring gas storage facilities, geothermal reservoir exploration, and ground movement detection. Furthermore, the paper identifies several directions for enhancing the DFOS system.
Im Rahmen des BMBF-Vorhabens SEE-2L wurde auf dem Testgelände Technische Sicherheit (BAM TTS) ein Großversuchsstand für das thermische Durchgehen von Lithium-Batterien auf Modul- und Batterieebene entwickelt und aufgebaut. Im Zuge des Projektes konnte eine erste Versuchsserie zu den Auswirkungen des thermischen Durchgehens von Batteriemodulen durchgeführt werden. Im Vortrag werden die wesentlichen Ergebnisse der Versuche vorgestellt.
Im Rahmen des Forschungsprojekts "Artificial Intelligence for Rail Inspection" (AIFRI) wird ein KI-Algorithmus entwickelt, um die Fehlererkennung und Bewertung bei der Auswertung von Schienenprüfungen mittels Ultraschall- und Wirbelstromprüfverfahren zu verbessern. Die Bandbreite möglicher Defekte und die Menge an Einflussgrößen auf die Schienenprüfung ist sehr groß, aber die Prüfdaten aus dem Feld bilden diese Bandbreite nicht balanciert ab und sind unzureichend gelabelt. Durch Simulationen werden große Mengen detailliert gelabelter Daten für relevante Schienenschädigungen und Artefakte bereitgestellt. Aus diesen Daten werden wiederum virtuellen Prüffahrten erstellt, die für das Training und die Validierung der KI genutzt werden können.
In unserem Vortrag stellen wir den Erstellungsprozess der Datensätze vor. Jeder Schritt von der Geometriedarstellung bis zur Datenverarbeitung wird erfasst. Der Fokus wird auf Simulationsergebnisse und deren Verarbeitung gelegt. Die Signalverarbeitung spielt in den Datensätzen eine große Rolle, dabei werden die Datensätze an die realen Daten angepasst. Für Wirbelstrom und Ultraschall werden diese Prozesse im Hinblick auf die Fehlertypen Head Checks und Bohrungsanrisse veranschaulicht. Ferner diskutieren wir die Simulation von Schweißnähten, die von beiden Prüfsystem detektiert werden können; und somit besondere Abstimmung bedürfen aber auch Synergieeffekte zwischen den Prüfsystem ermöglichen.
Für die Ablage der Datensätze verweisen wir auf das ebenfalls eingereichte Poster „Verwendung von DICONDE bei der Eisenbahn-Schienenprüfung“.
Das Projekt AIFRI wird im Rahmen der Innovationsinitiative mFUND unter dem Förderkennzeichen 19FS2014 durch das Bundesministerium für Digitales und Verkehr gefördert.
Revolutionizing our polymer industry for adaption to a sustainable carbon circular economy has become one of today’s most demanding challenges. Exploiting renewable resources to replace fossil-fuel—based plastics with biopolymers such as poly(lactic acid) (PLA) is inevitable while using waste streams as a raw material resource at least is promising. When it comes to using PLA as technical polymer, its high flammability must be addressed by flame retardants compatible with the thermoplastic processing of PLA and its compostability. This study proposes microalgae enriched with phosphorus from wastewater (P-Algae) as an elegant way towards a kind of sustainable organophosphorus flame retardant. The concept is demonstrated by investigating the processing, pyrolysis, flammability, and fire behavior of PLA/P-Algae, while varying the P-Algae content and comparing P-Algae with four alternative bio-fillers (phosphorylated lignin, biochar, thermally treated sewage sludge, and metal phytate) with different P-contents as meaningful benchmarks.
This presentation gives an overview of the recent achievements in simulating piping erosion during the installation process of suction bucket foundations for offshore wind turbines. The physical correctness of the code is validated, and the simulation code's performance on the LUMI supercomputer is presented. The simulation results are compared to experimental data.
Low Transformation Temperature (LTT)-Schweißzusätze stellen einen innovativen Ansatz zur Erhöhung der Ermüdungsfestigkeit geschweißter Konstruktionen dar. LTT-Schweißzusätze zeichnen sich durch eine martensitische Phasenumwandlung nahe der Raumtemperatur aus, welche Druckeigenspannungen in der Schweißnaht und der Wärmeeinflusszone (WEZ) generieren.
Dieser Vortrag fokussiert sich auf die gezielte Einbringung zusätzlicher LTT-Lagen an ermüdungskritischen Stellen von konventionell geschweißten Verbindungen. Dies ermöglicht eine ökonomische Anwendung, ohne dass die Schweißnahtintegrität zu stark beeinflusst wird. Die Auswirkungen zusätzlicher LTT-Lagen wurden anhand geschweißter Längssteifen aus hochfestem Stahl hinsichtlich der chemischen Zusammensetzung und der Eigenspannungen untersucht. Unter Variation der Schweißgeschwindigkeit und Abstand zur konventionellen Naht konnten 3 unterschiedliche Nahtausführungen des Chrom-Nickellegierten LTT-Zusatzes bewertet werden.
Die chemische Zusammensetzung wurde mittels OES-Analysen untersucht. Dabei stellte heraus, dass die Aufmischung in allen Varianten sehr ähnlich war trotz teils unterschiedlicher LTT-Volumina. Härtebestimmungen ergaben in allen 3 Varianten eine ähnliche Härte. Daraus lässt sich annehmen, dass die Martensitstarttemperatur bei allen Nahtvarianten ähnlich ist.
Röntgenografische Eigenspannungsmessungen belegen, dass die Eigenspannungen am versa-genskritischen Nahtübergang bei Einsatz von LTT-Schweißzusätzen deutlich abgesenkt werden. Während die konventionelle Schweißnaht Zugeigenspannungen von ca. 350 MPa aufweist, können an den LTT-Nähten teilweise Druckeigenspannungen von bis zu -150 MPa nachgewiesen werden. Je höher der Abstand zur konventionellen Naht und je größer das eingebrachte LTT-Volumen ist, umso stärker sind die Eigenspannungsreduzierungen am Nahtübergang. Da in allen 3 Varianten eine ähnliche Martensitstarttemperatur angenommen werden kann, ist somit die Geometrische Komponente der LTT-Zusatzlage ein entscheidender Faktor für die Eigenspannungsreduzierung.