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Laser-induced periodic surface structures (LIPSS) enable a large variety of different surface functionalizations for applications in the fields of optics, fluidics, tribology, or medicine. Moreover, high spatial frequency LIPSS (HSFL) provide an appealing and straightforward way for the generation of surface nanostructures featuring spatial periods even below 100 nm – far beyond the optical diffraction limit. However, the imposed surface functionalities are usually caused by both, topographic and chemical surface alterations. For exploring these effects in detail, multi-method characterization was performed here for HSFL processed on Ti-6Al-4V alloy upon irradiation with near-infrared ps-laser pulses (1030 nm wavelength, ~1 ps pulse duration, 1 – 400 kHz pulse repetition rate) under different scan processing conditions. The subsequent sample characterization involved morphological and topographical investigations by scanning electron microscopy (SEM), atomic force microscopy (AFM), stylus profilometry (SP), as well as near-surface chemical analyses by X-ray photoelectron spectroscopy (XPS), hard X-ray photoelectron spectroscopy (HAXPES) and depth-profiling time-of-flight secondary ion mass spectrometry (TOF-SIMS). The results allow to qualify the laser ablation depth, the geometrical HSFL characteristics and provide detailed insights into the depth extent and the nature of the ps-laser-induced near-surface oxidation arising from the laser-processing in ambient air and into the relevance of heat-accumulation effects at high pulse repetition rates. Moreover, the direct comparison of the HAXPES and XPS data reveals the role of surface-covering organic contaminants adsorbed from the ambient atmosphere without ion-sputter depth profiling. Furthermore, reduction of the oxides by sputtering can be avoided.
Advances in ultrafast laser manufacturing: nanostructures, thin films, and scaling perspectives
(2024)
Advanced ultrafast laser technology is a rapidly growing field that currently enables many new industrial and scientific applications. During the last decades, this has been significantly driven by the availability of high-repetition-rate laser sources and novel beam delivery concepts. At the laser side, Moore’s law equally manifests for ultrafast laser technologies, since the average output power of such lasers doubles approximately every two years. This development is mainly driven by the increase of the pulse repetition rates of energetic laser pulses, currently enforcing the development of smart beam control and novel scanning strategies for preventing heat-accumulation and plasma-shielding effects during laser-based materials processing. This keynote presentation addresses the advantages, recent developments, and perspectives of laser processing with ultrashort laser pulses. A special focus is laid on the tailored structuring of thin films as well as the manufacturing and probing of sub-diffraction surface nanostructures – an ongoing race to extreme scales. Current limitations are identified and an outlook to future scaling perspectives will be provided.
The presentation demonstrates an application of multi-scale optical imaging methods such as spectroscopic imaging ellipsometry and white light interference microscopy for the investigation of wide-bandgap semiconductors for power electronics. The capabilities of these methods for the development of new reference calibration samples for scanning microwave microscopes (SMM) and conductive atomic force microscopes (C AFM) are discussed.
Interactions between a polymer and a substrate interface play a vital role in understanding the improvement in thin film material properties as well as serving as a model for nanocomposites. For any non-repulsive polymer-substrate interactions, polymer segments form an irreversibly adsorbed layer and show a slowdown in the glassy dynamics and thus an increase in the thermal glass transition temperature compared to the bulk-like values. The growth kinetics of the adsorbed layer showed a deviation for both poly (bisphenol-A carbonate) (PBAC) and polysulfone (PSU), two bulky polymers containing a functional group (phenyl ring) in the backbone, compared to conventional polymers previously studied like poly-2-vinyl pyridine (P2VP). This deviation was attributed to the bulkiness of the phenyl rings. . Further investigations into the influence of the adsorbed layer on glassy dynamics were conducted. The molecular mobility and glass transition for thin films of PBAC and PSU were compared to bulk samples of each polymer. Broadband dielectric spectroscopy, atomic force microscopy, and ellipsometry were primarily used and additionally supported by sum frequency generation spectroscopy.
This is a set of use examples for the HDF5Translator framework. This framework lets you translate measurement files into a different (e.g. NeXus-compatible) structure, with some optional checks and conversions on the way. For an in-depth look at what it does, there is a blog post here.
The use examples provided herein are each accompanied by the measurement data necessary to test and replicate the conversion. The README.md files in each example show the steps necessary to do the conversion for each.
We encourage those who have used or adapted one or more of these exampes to create their own conversion, to get in touch with us so we may add your example to the set.
Glycolide was polymerized in bulk by means of four different ROPPOC catalysts: tin(II) 2-ethylhexanoate (SnOct2), dibutyltin bis(pentafluoro-phenoxide) (BuSnOPF),zinc biscaproate (ZnCap), and zinc bis(pentafluoro-phenyl sulfide) (ZnSPF). The temperature was varied between 110 and 180°C and the time between 3 h and 7 days. For the few polyglycolides (PGAs) that were soluble extremely high molecular masses were obtained. The MALDI TOF mass spectra had all a low signal-to-noise ration and displayed the peaks of cyclic PGAs with a“saw-tooth pattern ”indicating formation of extended-ring crystallites in the mass range below m/z 2500. The shape of DSC curves varied considerably with catalyst and reaction conditions, whereas the long-distance values measured by SAXS were small and varied little with the polymeriza-tion conditions.
A corrosion study is performed on six variations of titanium grade 5 (Ti6Al4V) samples. Samples are prepared in different conditions by variation of preanodization, postanodization, and picosecond-laser (ps-laser) surface treatment, while polished and anodized samples serve as reference. Microcones and nanosized periodic surface features are successfully produced on Ti6Al4V samples. The morphology and topography of the structures are visualized by scanning electron microscopy and white light interference microscopy. Furthermore, the relative electrochemically active surface area (ECSA) is determined for the ps-laser-treated samples. It is determined that the preanodized and laser-treated sample has 3.5 times larger ECSA than a polished sample, and that the laser-treated sample has 4.1 times larger area. Moreover, Tafel analysis is performed to determine the corrosion properties of the samples. It is shown that the corrosion resistance improves for both laser-structured samples after the anodization. To further study the surface of the samples, electrochemical impedance spectroscopy measurements are conducted. The study indicates that the ps-laser-treated and anodized Ti6Al4V is suitable to be used for the fabrication of bone screws and plates due to its improved corrosion resistance as compared to nonanodized samples.
The use of a dedicated approach: DoE for synthesis + characterization + Chemometric Analysis, is a valuable method for the safe-by-design synthesis of several types of materials for large-scale application in catalysis, energy harvesting, biomedical and environmental applications, etc. This approach is not only related to the material synthesis, but can be expanded to any type of molecules/material, with relevant saving of solvents, energy and times.
Optical constants of In2O3-SnO2 (Indium tin oxide, ITO)
Minenkov et al. 2024: on glass; n,k 0.191–1.69 µm
Optical constants of In2O3-SnO2 (Indium tin oxide, ITO)
Minenkov et al. 2024: on Si wafer, top; n,k 0.191–1.69 µm
Optical constants of In2O3-SnO2 (Indium tin oxide, ITO)
Minenkov et al. 2024: on Si wafer, bottom; n,k 0.191–1.69 µm
New analytic ways to characterise mesoporous thin layers used in electrocatalytic water splitting
(2024)
Mesoporous materials are needed in many applications where a high specific surface area and adsorptive behaviour is needed. Important examples are separation techniques and barrier layers and catalysts. Electrochemical water splitting is the key technology for producing green hydrogen and there is no foreseeable alternative to this process for producing elementary hydrogen from green electrical power. Water electrolysis can be divided into the anodic Oxygen Evolution Reaction (OER) and the cathodic Hydrogen Evolution Reaction (HER). Both processes have to be heavily optimised to a large extent to avoid energy losses caused by overvoltage. The development of electrodes for these processes is especially difficult due to the many boundary conditions. Water splitting is a catalytic as well as electrochemical process. The contact area between the electrolyte and the electrode must be maximised maintaining the stability of the surface. Side reactions must be suppressed, and effective gas transport must be ensured. The whole process has to be tolerant with respect to temperature, harsh chemical conditions from the electrolyte as well as high current densities.
We present a hybrid analytical method combining several analytical techniques for determining the properties of thin layers of mixed oxides of the general composition Ir:TiOx. These materials are promising candidates for electrocatalytical top coatings of OER electrodes. To lower the costs of the electrolysers, the main goal is to lower the Ir content retaining the system efficiency. The main properties which are hard to determine are the porous volume fraction and the Ir:Ti element ratio. By a combination of electron microscopy, spectroscopic operando ellipsometry, ellipsometric porosimetry, and other techniques, we can determine key features of mesoporous thin layer materials. We aim to develop operando capable techniques used in process monitoring as well as measurement techniques optimised for accuracy. By developing reference materials, we support long term uptake of our methodology. This work can directly be used for optimising electrocatalytic layers and is a good example for the power of hybrid metrology for improving materials design.
Polydopamine (PDA) is a biological / biomimetic polymer which has spiked considerable interest in recent years. Its monomer is an important neurotransmitter and it is one of the strongest glues produced by biological organisms. Polydopamine is a candidate for several applications, mainly in the field of biology and medicine, but also - recently - for layer coatings with optical, electrical, and mechanical function.
In this work, we investigate PDA layers intended as reflectivity enhancers for mirror surfaces in X-ray astronomical observatories. It has previously been shown, that such X-ray telescopes can be improved by a coating of PDA in the thickness range of several nm. Accurate thickness determination is required to monitor and optimise the coating process. We use spectroscopic ellipsometry to determine first the dielectric function of the polydopamine layers using model coatings of sufficient thickness. This data is then used to accurately determine the layer thickness of much thinner PDA layers. This study resulted in data on the thickness and dielectric function of PDA layers that could lead to a better understanding of the correlation of layer thickness and layer properties depending on the process parameters.
There is only sparse empirical data on the settling velocity of small, non-buoyant microplastics thus far, although it is an important parameter governing their vertical transport within aquatic environments. This study reports the settling velocities of 4031 exemplary microplastic particles. Focusing on the environmentally most prevalent particle shapes, irregular microplastic fragments of four different polymer types (9–289 µm) as well as five discrete length fractions (50–600 µm) of common nylon and polyester fibers were investigated, respectively. All settling experiments were carried out in quiescent water using a specialized optical imaging setup. The method has been previously validated in order to minimize disruptive factors, e.g. thermal convection or particle interactions, and thus enable the precise measurements of the velocities of individual microplastic particles (0.003–9.094 mm/s). Based on the obtained data, ten existing models for predicting a particle’s terminal settling velocity were assessed. It is concluded that models, which were specifically deduced from empirical data on larger microplastics, fail to provide accurate predictions for small microplastics. Instead, a different approach is highlighted as a viable option for computing settling velocities across the microplastics continuum in terms of size, density and shape.
AbstractMicroplastics (MP) can be detected in all environmental systems. Marine and terrestrial aquatic systems, especially the transported suspended solids, have often been the focus of scientific investigations in the past. Sediments of aquatic river systems, on the other hand, were often ignored due to the time‐consuming sample preparation and analysis procedures. Spectroscopic measurement methods counting particle numbers are hardly suitable as detection methods, because there are plenty of natural particles next to a small number of MP particles. Integral methods, such as thermoanalytical methods are determining the particle mass independently of the inorganic components.In this study, a workflow for sample preparation via density separation and subsequent analysis by thermal extraction desorption‐gas chromatography/mass spectrometry is presented, which leads to representative and homogeneous samples and allows fast and robust MP mass content measurements suitable for routine analysis. Polymers were identified and quantified in all samples. Polyethylene and styrene‐butadiene rubber are the dominant polymers, besides polypropylene and polystyrene. Overall, total polymer masses between 1.18 and 337.0 µg/g could be determined. Highest MP concentrations in riverbed sediment are found in sites characterized by low flow velocities in harbors and reservoirs, while MP concentrations in sandy/gravelly bed sediments with higher flow velocities are small.
The plastic value chain, central part of modern living, caused environmental pollution and bioaccumulation of plastic nanoparticles (PNPs). Their ubiquitous presence in different environmental and biological compartments has become a serious threat to human health and ecosystems. Frequently used plastic materials such as polypropylene (PP), polystyrene (PS) and polyethylene (PE) have been detected in the form of PNPs in the food chain, soil, water and air, as well as in human feces and blood. In this study, we aimed to provide novel insights in endocrine disrupting properties of PNPs using in vitro estrogen receptor (ER) transactivation assay. The effects of PP-NPs, PE-NPs and PS-NPs and their mixture on T47D-KBluc cell line stably transfected with luciferase as reporter enzyme was evaluated by means of cytotoxicity, cellular uptake and ER activation. Tested dose range for PNPs was 0.001 – 10 mg/L. Both cellular uptake and cytotoxicity for all PNPs was found to be dose-dependent. Only the highest dose of PP-NPs and PE-NPs induced apoptosis and cell death, while PS-NPs were not cytotoxic in tested dose range. For tested concentrations, PP-NPs and PE-NPs showed significant agonistic activity on ER, while PS-NPs cannot be considered ER active. When, applied as mixture, PNP demonstrated additive toxicity effects compared to the effect of each individual PNPs. Additivity was also observed for ER agonistic effect of PNPs mixture according to the benchmark dose-addition modelling approach. This study provides missing science-based evidence on endocrine disrupting effects of PE-NPs, PP-NPs, PS-NPs and their mixtures and highlights the importance of considering unintentional, aggregate and combined exposure to different PNPs in risk management.
Bonds and local atomic environments are crucial descriptors of material properties. They have been used to create design rules and heuristics and as features in machine learning of materials properties. Implementations and algorithms (e.g., ChemEnv and LobsterEnv) for identifying local atomic environments based on geometrical characteristics and quantum-chemical bonding analysis are nowadays available. Fully automatic workflows and analysis tools have been developed to use quantum-chemical bonding analysis on a large scale. The lecture will demonstrate how our tools, that assess local atomic environments and perform automatic bonding analysis, help to develop new machine learning models and a new intuitive understanding of materials. Furthermore, the general trend toward automation in density functional-based materials science and some of our recent contributions will be discussed.
Der Vortrag gibt einen Überblick zu ultrakurzen Laserpulsen, der Ultrakurzpulslaser-Materialbearbeitung und der dabei ggf. auftretenden unerwünschten Röntgenstrahlung. Es wird die Laserbearbeitung von technischen und biologischen Materialien diskutiert. Schutzmöglichkeiten gegenüber der Röntgenstrahlung werden erörtert.
Der Vortrag gibt einen Überblick über die vielfältigen Möglichkeiten der Oberflächenfunktionalisierung mittels Mikro- und Nanostrukturierung durch Ultrakurzpuls-Lasermaterialbeabeitung. Dies schließt eine Diskussion des Phänomens der Laser-induzierten periodischen Oberflächenstrukturen (LIPSS, engl.: Laser-induced Periodic Surface Structures, Ripples), sowie deren Klassifikation und Bildungsmechanismen mit ein. Ein Schwerpunkt der Präsentation liegt auf der Diskussion verschiedener Anwendungsmöglichkeiten der LIPSS in Bereichen der Optik, Fluidik, Tribologie und Medizin, sowie auf einem Ausblick auf die industrielle Skalierbarkeit der LIPSS-Technologie.
Zirconium chloro fluoride as catalyst for C-F bond activation and HF transfer of fluoroalkanes
(2024)
In this work1, we have successfully synthesised amorphous zirconium chloro fluoride (ZCF), which exhibits medium lewis acidity. In addition to investigating the local coordination sphere around the Zr atoms and the material properties, we were able to establish a catalytic behavior of ZCF in C-F bond activation reactions. We present the first heterogeneous catalyst that performs dehydrofluorination of a fluoroalkane and consecutive hydrofluorination of an alkyne at room temperature.
Trinamic TMCL IOC is a Python package designed for controlling stepper motors connected to a Trinamic board using the TMCL language (all boards supported by PyTrinamic should now work, has been tested on the TMCM 6110 and the TMCM 6214). Since it is implementing the TMCL protocol, it should be easy to adapt to other Trinamic motor controller boards. This package assumes the motor controller is connected over a machine network via a network-to-serial converter, but the underlying PyTrinamic package allows for other connections too.
This allows the control of attached motors via the EPICS Channel-Access virtual communications bus. If EPICS is not desired, plain Pythonic control via motion_control should also be possible. An example for this will be provided in the example.ipynb Jupyter notebook.
This package leverages Caproto for EPICS IOCs and a modified PyTrinamic library for the motor board control, and interfaces between the two via an internal set of dataclasses. Configuration for the motors and boards are loaded from YAML files (see tests/testdata/example_config.yaml).
The modifications to PyTrinamic involved extending their library with a socket interface. This was a minor modification that should eventually find its way into the official package (a pull request has been submitted).
Biofuels, particularly biodiesel, have gained significant attention as an alternative to traditional fossil fuels in recent years. Unlike diesel, which contains hundreds of compounds, biodiesel only contains a few compounds in the C16-C18 carbon chain. However, the use of biodiesel in automobile and transportation applications can result in problems of degradation or even damage in materials. Among the commonly used polymer materials, fluorocarbon (FKM) shows excellent performance and high stability and compatibility towards oil, diesel, ethanol, and other chemicals. FKM is a family of fluorocarbon-based fluoroelastomer materials, which provide excellent high-temperature and chemical stability compared to other elastomers. As a result, FKM is widely used in chemical processes such as petroleum refining, where it is used for sealings, pumps, and other components.
Interactions between a polymer and a substrate interface play a vital role in understanding the improvement in thin film material properties as well as serving as a model for nanocomposites. For any non-repulsive polymer-substrate interactions, polymer segments form an irreversibly adsorbed layer and show a slowdown in the glassy dynamics and thus an increase in the thermal glass transition temperature compared to the bulk-like values. The growth kinetics of the adsorbed layer showed a deviation for both poly (bisphenol-A carbonate) (PBAC) and polysulfone (PSU), two bulky polymers containing a functional group (phenyl ring) in the backbone.
This presentation highlights ongoing scientific misconduct as found in academic literature. This includes data- and image manipulation, and paper mills. Starting with an expose of examples, it delves deeper into the causes and metrics driving this phenomenon. Finally a range of possible tools is presented, that the young researcher can use to prevent themselves from sliding into the dark scientific methods.
By automatically recording as much information as possible in automated laboratory setups, reproducibility and traceability of experiments are vastly improved. This presentation shows what such an approach means for the quality of experiments in an X-ray scattering laboratory and an automated synthesis set-up.
Kemnitz et al. developed a fluorolytic route to access metal fluorides 2 such as AlF3 3 and MgF2 4 which possess a high surface area. In aluminium-based systems, the synthetic approach led to amorphous xerogels that can be further converted into Lewis superacids.3 Still, despite zirconium oxide being described as a stronger Lewis acid than other metal oxides 4 zirconium fluoride-based materials have only recently been reported or investigated. 6 In this work we extend the class of amorphous Lewis acidic heterogeneous catalysts to an amorphous ZrF4 that is active in C-F bond activation.
Mechanical stress often accelerates the failure of polymer materials. The aim of this research is to study the interaction between the sealing material FKM and biofuels B10 (heating oil with 10% biodiesel). The mechanical stress test was carried out in a special apparatus. Both mechanical and non-mechanical stress tests were conducted on specimens at 20, 40, and 70 °C for 28 days to document changes in mass, volume, and tensile properties. Both increasing temperature and mechanical stress have a significant effect on the tensile strength of the FKM polymer when exposed to B10. The combination of increasing temperature and mechanical stress induced rupture within 2 h. It was also established that FKM polymer with pre-exposure in B10 survived longer during mechanical stress compared to specimens exposed only to air. With the support of infrared (IR) spectroscopy, we were able to confirm the penetration of B10 into the FKM polymer.
Nanoparticles (NPs) are tiny – around 1 to 100 billionths of a meter – and can have different chemistries and behaviours than the same material of larger size. This property has led to advances in a wide range of industries, but it can also confer toxicity. Size measurements are the main way NPs are identified but a lack of standardised methods for identifying ones with complex shapes has hindered evaluation of their potential harm.
Amorphous materials play an important role in C-F bond activation but face the difficulty of limited available structural information by methods such as powder XRD and solid-state MAS NMR spectroscopy especially if the nucleus is not abundant enough. Here, we present heterogeneous catalysts, active in C-F bond activation, where EXAFS allowed specifically elucidating the local structure, which would have not been possible elsewise.
Bakterielle Biofilme stellen in medizinischen und industriellen Bereichen ein ernsthaftes Problem dar. Eine der größten gesellschaftlichen Herausforderungen liegt in der zunehmenden Resistenz von Bakterien gegen Biozide, die bei antimikrobiellen Behandlungen eingesetzt werden, z.B. durch übermäßigen Einsatz in Medizin, Industrie und Landwirtschaft oder durch Reinigung und Desinfektion in Privathaushalten. Daher sind neue effiziente bakterienabweisende Strategien, die den Einsatz von Bioziden vermeiden, dringend erforderlich.
Ein vielversprechender Weg zur Erzielung bakterienabweisender Oberflächen liegt in der berührungslosen und aseptischen großflächigen Laserbearbeitung von technischen Oberflächen. Maßgeschneiderte Oberflächentexturen, ermöglicht durch verschiedene Laserbearbeitungsstrategien, die zu topographischen Skalen im Bereich von Nanometern bis Mikrometern führen, können eine Lösung für diese Herausforderung darstellen.
In dem Vortrag wird ein Überblick über den aktuellen Stand der Technik bei der subtraktiven Texturierung von Laseroberflächen zur Kontrolle der Biofilmbildung bei verschiedenen Bakterienstämmen und in unterschiedlichen Umgebungen gegeben. Auf der Grundlage spezifischer Eigenschaften von Bakterien und laserbearbeiteten Oberflächen werden die Herausforderungen antimikrobieller Oberflächendesigns erörtert und zukünftige Richtungen aufgezeigt.
The LOBSTER (Deringer et al., 2011;Maintz et al., 2013 ,2016 ;Nelson et al., 2020 ) software aids in extracting quantum-chemical bonding information from materials by projecting the plane-wave based wave functions from density functional theory (DFT) onto an atomic orbital basis. LobsterEnv, a module implemented in pymatgen (Ong et al., 2013) by some of the authors of this package, facilitates the use of quantum-chemical bonding information obtained from LOBSTER calculations to identify neighbors and coordination environments. LobsterPy is a Python package that offers a set of convenient tools to further analyze and summarize the LobsterEnv outputs in the form of JSONs that are easy to interpret and process. These tools enable the estimation of (anti) bonding contributions, generation of textual descriptions, and visualization of LOBSTER computation results. Since its first release, both LobsterPy and LobsterEnv capabilities have been extended significantly. Unlike earlier versions, which could only automatically analyze Crystal Orbital Hamilton Populations (COHPs) (Dronskowski & Blöchl, 1993), both can now also analyze Crystal Orbital Overlap Populations (COOP) (Hughbanks & Hoffmann, 1983) and Crystal Orbital Bond Index (COBI) (Müller et al., 2021). Extracting the information about the most important orbitals contributing to the bonds is optional, and users can enable it as needed. Additionally, bonding-based features for machinelearning (ML) studies can be engineered via the sub-packages “featurize” and “structuregraphs”. Alongside its Python interface, it also provides an easy-to-use command line interface (CLI) that runs automatic analysis of the computations and generates a summary of results and publication-ready figures. LobsterPy has been used to produce the results in Ngo et al. (2023), Chen et al. (2024), Naik et al. (2023), and it is also part of Atomate2 (2023) bonding analysis workflow for generating bonding analysis data in a format compatible with the Materials Project (Jain et al., 2013) API.
Der Vortrag gibt einen Überblick über die Erzeugung und Charakterisierung anisotroper Nanostrukturen mittels ultrakurzgepulster Laserstrahlung. Besonderes Augenmerk liegt dabei auf dem Phänomen der sogenannten Laser-induzierten periodischen Oberflächen-Nanostrukturen auf dielektrischen Werkstoffen und ihrer zeitlichen Dynamik. Weitere Beispiele von Volumen-Nanostrukturen aus der Literatur werden diskutiert.
Bonds and local atomic environments are crucial descriptors of material properties. They have been used to create design rules and heuristics and as features in machine learning of materials properties. Implementations and algorithms (e.g., ChemEnv and LobsterEnv) for identifying local atomic environments based on geometrical characteristics and quantum-chemical bonding analysis are nowadays available. Fully automatic workflows and analysis tools have been developed to use quantum-chemical bonding analysis on a large scale. The lecture will demonstrate how our tools, that assess local atomic environments and perform automatic bonding analysis, help to develop new machine learning models and a new intuitive understanding of materials.[5,6] Furthermore, the general trend toward automation in density functional-based materials science and some of our recent contributions will be discussed.
The main objective was to assess homogeneity of two bimodal gold materials, namely nPsize1 and nPSize2, containing approximately 1:1 and 10:1 particle number-based ratio of ~30nm and ~60nm particles. Particle number-based concentration within the two size fractions was determined with spICP-MS using the particle frequency method of calibration.
The principles of (Hard) X-ray photoelectron spectroscopy and some application in the field of (core-shell) nanoparticles will be presented. The presentation should answer hoe to get reliable results. Furthermore, examples of the correlation between physical-chemical measurments and toxicological results are given which are crucial for the risk assessment of nanoparticles.
Climate change and increasing demand for electricity require the use of power electronics based on new wide bandgap (WBG) compound semiconductors. Power electronics devices are used in numerous application areas to control and convert electric energy. These may include generation and distribution of renewable energy for green hydrogen, electrification of transport or 5G communication. WBG electronics have much higher efficiency than the silicon-based ones and can operate at higher power densities, voltages, temperatures and switching frequencies with low energy losses. However, defects in the semiconductors can considerably affect the performance of power electronic devices or make their operation even impossible. The presentation will show the application of spectroscopic and imaging ellipsometry as well as white light interference microscopy for defect characterisation in SiC, GaN and Ga2O3 over a wide wavelength range.
We used parameterized modelling of ellipsometric transfer parameters to determine the dielectric properties of bulk materials and thin layers. Imaging ellipsometry offers more information and is an advanced variant of optical microscopy, combining the lateral resolution of optical microscopy with the extreme sensitivity to surface and interface effects of ellipsometry. Surface topography and morphology of different types of defects were additionally investigated with imaging white light interference microscopy. Modern electronic thin film components require complex surface analysis methodologies and hybrid metrology. Hybrid measurement techniques enable fast and non-destructive traceable characterisation of thin film compound semiconductors as well as accurate detection and identification of defects. This methodical approach leads to a better understanding of the materials themselves and of the defect formation mechanisms during manufacturing.
This work aims to enable highly reproducible manufacturing of compound semiconductor power electronics as well as operation monitoring to ensure failure-safety of electronic systems in power electronic devices.
Die Material Acceleration Platform der BAM (MAPz@BAM) bündelt unsere Automatisierungs-Expertise auf dem Gebiet der Materialwissenschaft und -prüfung. Wir entwickeln modulare Experimentmodule, automatische Prüf- und Auswerteverfahren und setzen künstliche Intelligenz für eine effiziente und autonome Versuchsplanung, - vorhersage und Datenanalyse ein.
Die Material Acceleration Platform der BAM (MAPz@BAM) bündelt unsere Automatisierungs-Expertise auf dem Gebiet der Materialwissenschaft und -prüfung. Wir entwickeln modulare Experimentmodule, automatische Prüf- und Auswerteverfahren und setzen künstliche Intelligenz für eine effiziente und autonome Versuchsplanung, - vorhersage und Datenanalyse ein.
Die Material Acceleration Platform der BAM (MAPz@BAM) bündelt unsere Automatisierungs-Expertise auf dem Gebiet der Materialwissenschaft und -prüfung. Wir entwickeln modulare Experimentmodule, automatische Prüf- und Auswerteverfahren und setzen künstliche Intelligenz für eine effiziente und autonome Versuchsplanung, - vorhersage und Datenanalyse ein.
AbstractThe high-temperature corrosion behaviors of the equimolar CrCoNi medium-entropy alloy and CrMnFeCoNi high-entropy alloy were studied in a gas atmosphere consisting of a volumetric mixture of 10% H2O, 2% O2, 0.5% SO2, and 87.5% Ar at 800 °C for up to 96 h. Both alloys were initially single-phase fcc with a mean grain size of ~ 50 μm and a homogeneous chemical composition. The oxide layer thickness of CrMnFeCoNi increased linearly with exposure time while it remained constant at ~ 1 μm for CrCoNi. A Cr2O3 layer and minor amounts of (Co,Ni)Cr2O4 developed on the latter while three oxide layers were detected on the former, i.e., a thin and continuous chromium rich oxide layer at the oxide/alloy interface, a dense (Mn,Cr)3O4 layer in the center and a thick and porous layer of Mn3O4 and MnSO4 at the gas/oxide interface. Additionally, a few metal sulfides were observed in the CrMnFeCoNi matrix. These results were found to be in reasonable agreement with thermodynamic calculations.
Die Laserbearbeitung von Materialien mit ultrakurzen Laserpulsen kann zu einer sekundären Emission gefährlicher Röntgenstrahlen führen. Dieser Effekt wurde bisher bei der Bearbeitung von technischen Materialien wie Metallen beobachtet. Die Röntgenemission bei der abtragenden Bearbeitung von biologischen Geweben ist noch weitgehend unerforscht. Der Vortrag präsentiert erste Untersuchungen und Ergebnisse des radiologischen Gefährdungspotentials bei der medizinischen Anwendung von Ultrakurzpulslasern am Menschen.
The efficient exploration of novel alloy compositions is crucial for advancing the development of new materials. One widely utilized approach for creating phase diagrams is the use of diffusion-controlled synthesis for gradient alloys. This method is also an effective means for rapidly identifying potential material combinations.
The present study focusses on the exploration of quaternary multi-principle-element alloys (MPEAs) using diffusion multiples. We established a diffusion system by combining an equimolar ternary alloy (FeNiCr) with single diffusing elements Mn and Mo. Using ThermoCalc simulations, we determined suitable temperature ranges where we can expect the formation of single-phase alloys. Depending on the diffusion constants of the selected metals, diffusion times were adjusted to obtain diffusion zones with a depth of greater than 50 μm. Microstructural and compositional information was gathered via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) and correlated to local mechanical properties evaluated by means of nanoindentation. Local corrosion properties were examined using Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM).
Our results indicate that the ThermoCalc simulations have a good predictive power for crystallographic phases. However, especially with the Mn-FeNiCr system, formation of Cr-rich secondary phases were observed, which led to Cr-depletion and thus to localized corrosion processes in the matrix at the vicinity of the secondary phases. Based on the results of the local electrochemical tests, we have selected single-phase compositions along the diffusion zone and synthesized these alloys in bulk for corrosion studies by means of potentiodynamic polarization and SECM.
The presentation will summarize our methodology using diffusion couples as an
efficient tool for exploring compositional spaces of MPEAs in the search for novel single-phase alloys and the results of our correlative study on the mechanical and corrosion properties of these materials.
The efficient exploration of novel alloy chemistries is crucial for advancing the development of new materials. Diffusion-controlled synthesis of gradient alloys is an intelligent approach for creating phase diagrams and to effectively identify potential material combinations with tailored properties.
This project focusses on the design of quaternary multi-principle-element alloys (MPEAs) using diffusion couples. Our diffusion system contains an equimolar ternary alloy (FeNiCr) and additional single diffusing elements e.g. Mn and Mo. We determined the optimal temperature ranges for the diffusion thermal treatment by means of ThermoCalc simulations with the aim to form single-phase MPEAs. Microstructure and chemical characterization of the diffusion couples were performed by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). For most alloy couples, the diffusion zone contained a single-phase alloy matrix with diffusion-induced compositional gradient as well as precipitation phases. This heterogeneity makes the diffusion couples interesting materials to investigate local mechanical and corrosion properties. Thus, local corrosion properties were examined using Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM). Nanoindentation was used for the analysis of local mechanical properties.
Based on the results of the local corrosion analysis, we have selected single-phase alloy chemistries along the diffusion zone and reproducibly synthesized these alloys in bulk for detailed corrosion studies by means of potentiodynamic polarization and SECM.
The presentation will briefly summarize our methodology and motivation for using diffusion couples as an efficient tool for exploring phase diagrams of MPEAs in the search for new alloy chemistries and the results of our correlative study on the mechanical and corrosion properties of these materials.
Old materials, new life: Using diffusion-controlled synthesis for discovery of novel alloy systems
(2023)
Multi principal element alloy (MPEAs) concept allows us to rethink how we develop application-tailored, sustainable materials. The vast composition space leads to nearly indefinite material combinations and will facilitate finding Pareto optimal materials with lower CO2 footprint and avoidance of critical minerals as design criteria. To probe this large compositional space efficiently, the use high-throughput screening methods is inevitable. Diffusion-controlled synthesis of gradient materials is the optimal technique for screening complex compositional materials that would otherwise require comprehensive modelling or experimental efforts.
In this study, we have used a series of diffusion couples of pure metals and alloys with the aim to create a materials library with correlated data on composition and microstructure. With future recycling prospects in mind, and possible applications of Cu containing alloys in electrocatalytic carbon dioxide reduction and antimicrobial alloys we have generated diffusion couples of brass (Cu63Zn37) and bronze (Cu89Sn11) with either pure metals (Fe, Ni, etc.) or with binary or ternary alloys (FeNi, FeNiCr etc.). For different diffusion times and temperatures, we calculated diffusion constants for the material combinations. Following a detailed characterisation of the gradient materials, we have investigated general and local corrosion properties, electrocatalytic activity for oxygen evolution reaction (OER) and carbon dioxide reduction reaction (CRR) as well as mechanical properties (hardness, elastic modulus) on single-phase alloys synthesized in bulk by means of vacuum arc-melting based on the selected local compositions.
In most cases, due to the short diffusion times, the contact between the diffusion couples lead to two separate diffusion zones and thus, different alloy families on both sides. Especially with ternary alloys, interesting selective diffusion processes and unexpected repulsion effects were observed. The presentation will provide an overview of the gradient materials with a focus on the functional properties of single-phase alloy families derived from them.
Due to their favorable mechanical and anti-corrosion properties, medium entropy alloys (MEA) are of high academic and industrial interest as novel materials for engineering and catalytic applications. Previous studies on general corrosion behavior indicate high current densities at high anodic potentials for MEAs. Further investigations of the underlying transpassive dissolution and local corrosion behavior remain scarce.
To understand the passivation behavior of MEAs CrCoNi and FeCrNi at high anodic potentials, the mechanisms of transpassive dissolution and the oxygen evolution reaction were investigated in this project. Scanning electrochemical microscopy (SECM) was applied in the interrogative mode for the detection of evolving metal species and oxygen. By means of ICP-MS analysis, dissolved metal species were quantified to provide a fundamental understanding on the transpassive dissolution. As the oxygen evolution reaction (OER) may contribute a large percentile to the observed current at high anodic potentials, SECM measurements were employed to analyze the onset of the OER. Potentiodynamic, potentiostatic and chronoamperometric techniques as well as different electrolytes were used to induce precisely controlled corrosion loads during the SECM experiments and for the ICP-MS analysis. Macroscopic corrosion properties of the alloys, electrical and chemical properties of the passive films were studied by means of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and X-Ray Photoelectron Spectroscopy (XPS), respectively.
Finally, the analysis of the corrosion morphology and the potential of the surface before, during and after passivity breakdown was carried out by means of in-situ atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM). The presentation will summarize our results on the interplay of anodic passivation and oxygen evolution of MEAs in aqueous NaCl electrolytes.
The high-throughput synthesis and characterization of potential material combinations plays an important role in accelerating the development of new materials. Diffusion controlled synthesis of gradient alloys is widely used to create phase diagrams, and it is also one of the most effective combinatorial approaches for rapid realization of potential material combinations.
This study focuses on the synthesis and investigation of the quaternary multi-principle-element alloy (MPEA) FeNiCrMn by means of diffusion multiples, the correlation of their microstructural and chemical characterization data with their application relevant properties like local mechanical and corrosion properties. A diffusion system was set up by combining an equimolar ternary alloy (FeNiCr) with a single diffusing metallic component (Mn) with the highest interdiffusion coefficient. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to collect microstructural and compositional information which were correlated to local mechanical properties studied with nanoindentation. Local corrosion properties were investigated by means of Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM). We have observed that a >50 μm deep homogeneous diffusion zone was formed the thickness of which scales with the duration of the thermal treatment. Beyond the Mn-concentration gradient in the FeNiCr matrix, a distinct Cr-rich secondary phase, characterized by high hardness and elastic modulus values appeared. We synthesized MPEAs with selected compositions from the diffusion zone as well as the Cr-rich phase as bulk alloys for electrochemical corrosion studies under different environmental conditions. The presentation will summarize the results of our correlative study on the mechanical properties and corrosion resistance of the quaternary multi-principle-element alloy (MPEA) FeNiCrMn family.