6 Materialchemie
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- Anlagensicherheit (2)
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- Anodization (1)
- Bonding Analysis (1)
- Bone screws (1)
Organisationseinheit der BAM
- 6 Materialchemie (11)
- 6.2 Material- und Oberflächentechnologien (3)
- 5 Werkstofftechnik (2)
- 6.0 Abteilungsleitung und andere (2)
- 6.3 Strukturanalytik (2)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (2)
- 6.6 Physik und chemische Analytik der Polymere (2)
- 7 Bauwerkssicherheit (2)
- 7.6 Korrosion und Korrosionsschutz (2)
- 5.1 Mikrostruktur Design und Degradation (1)
We present Jobflow, a domain-agnostic Python package for writing computational workflows tailored for high-throughput computing applications. With its simple decorator-based approach, functions and class methods can be transformed into compute jobs that can be stitched together into complex workflows. Jobflow fully supports dynamic workflows where the full acyclic graph of compute jobs is not known until runtime, such as compute jobs that launch
other jobs based on the results of previous steps in the workflow. The results of all Jobflow compute jobs can be easily stored in a variety of filesystem- and cloud-based databases without the data storage process being part of the underlying workflow logic itself. Jobflow has been intentionally designed to be fully independent of the choice of workflow manager used to dispatch the calculations on remote computing resources. At the time of writing, Jobflow
workflows can be executed either locally or across distributed compute environments via an adapter to the FireWorks package, and Jobflow fully supports the integration of additional workflow execution adapters in the future.
The production of plastics is rising since they have been invented. Micro, submicro- and nanoplastics are produced intentionally or generated by environmental processes, and constitute ubiquitous contaminants which are ingested orally by consumers. Reported health concerns include intestinal translocation, inflammatory response, oxidative stress and cytotoxicity. Every digestive milieu in the gastrointestinal tract does have an influence on the properties of particles and can cause changes in their effect on biological systems. In this study, we subjected plastic particles of different materials (polylactic acid, polymethylmethacrylate, melamine formaldehyde) and sizes (micro- to nano-range) to a complex artificial digestion model consisting of three intestinal fluid simulants (saliva, gastric and intestinal juice). We monitored the impact of the digestion process on the particles by performing Dynamic Light Scattering, Scanning Electron Microscopy and Asymmetric Flow Field-Flow Fractionation. An in vitro model of the intestinal epithelial barrier was used to monitor cellular effects and translocation behavior of (un)digested particles. In conclusion, artificial digestion decreased cellular interaction and slightly increased transport of all particles across the intestinal barrier. The interaction with organic matter resulted in clear differences in the agglomeration behavior. Moreover, we provide evidence for polymer-, size- and surface-dependent cellular effects of the test particles.
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.
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.
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.
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.
A giant Zn segregation transition is revealed using CALPHAD-integrated density-based modeling of segregation into Fe grain boundaries (GBs). The results show that above a threshold of only a few atomic percent Zn in the alloy, a substantial amount of up to 60 at.% Zn can segregate to the GB. We found that the amount of segregation abruptly increases with decreasing temperature, while the Zn content in the alloy required for triggering the segregation transition decreases. Direct evidence of the Zn segregation transition is obtained using high-resolution scanning transmission electron microscopy. Base on the model, we trace the origin of the segregation transition back to the low cohesive energy of Zn and a miscibility gap in Fe-Zn GB, arising from the magnetic ordering effect, which is confirmed by ab-initio calculations. We also show that the massive Zn segregation resulting from the segregation transition greatly assists with liquid wetting and reduces the work of separation along the GB. The current predictions suggest that control over Zn segregation, by both alloy design and optimizing the galvanization and welding processes, may offer preventive strategies against liquid metal embrittlement.
Durch Auslagerungs- und elektrochemische Tests im Labor kann das Korrosionsverhalten verschiedener metallener Werkstoffe beurteilt werden. Aus den Versuchsergebnissen, die in verschiedenen synthetischen Geothermalwässern im Labor erzielt wurden, lassen sich die folgenden Schlussfolgerungen ziehen:
• Die Anfälligkeit für Spaltkorrosion wurde als wichtigster Aspekt für die Werkstoffqualifizierung ermittelt.
• Der niedriglegierte Stahl 25CrMo4 zeigte bei niedrigem Salzgehalt in MB-Geothermalwasser eine gleichmäßige Korrosion unterhalb der akzeptierten Schwelle von 0,3 mm/Jahr. Daher kann er als geeignet für geothermische Bedingungen mit niedrigem Salzgehalt angesehen werden, wie sie für MB getestet wurden. Es besteht keine Notwendigkeit, auf höherlegierte (teurere) Werkstoffe auszuweichen. Ein niedrigerer pH-Wert (wie bei LHD) führt zu Korrosionsraten oberhalb der akzeptablen Grenzwerte, so dass die niedriglegierten Werkstoffe nicht für Flüssigkeiten mit niedrigem pH-Wert geeignet sind.
• Stark salzhaltige Geothermalwässer erfordern höherlegierte Werkstoffe, da die Korrosionsrate von niedriglegiertem Stahl zu hoch ist.
• Der Duplexstahl X2CrNiMo22-5-3 und der Superduplexstahl X2CrNiMoCuWN25-7-4 wurden aufgrund ihrer kritischen Anfälligkeit für örtliche Korrosion in Form von Loch- und Spaltkorrosion unter Betriebsbedingungen nicht als geeignet für geothermische Anwendungen in Geothermalwässern mit einer mit NDB und ORG vergleichbaren Zusammensetzung angesehen.
• Der superaustenitische Stahl X1CrNiMoCu32-28-7 eignet sich für ORG und salzarme Wässer. In NDB-Geothermalwasser wurde er bei 100 °C als geeignet angesehen. Jedoch schränkt seine Anfälligkeit für Spaltkorrosion seine Anwendbarkeit ein. Neben seiner guten Korrosionsbeständigkeit ist sein Repassivierungsverhalten für seine begrenzte Anwendbarkeit in Geothermalwässern mit niedrigem pH-Wert verantwortlich.
• Die Nickelbasislegierung NiCr23Mo16Al wurde als geeignet erachtet und stellt eine sichere Option für den Einsatz in geothermischen Anlagen dar, selbst wenn mit stark salzhaltigem Geothermalwasser gearbeitet wird.
Durch Auslagerungs- und elektrochemische Tests im Labor kann das Korrosionsverhalten verschiedener metallener Werkstoffe beurteilt werden. Aus den Versuchsergebnissen, die in verschiedenen synthetischen Geothermalwässern im Labor erzielt wurden, lassen sich die folgenden Schlussfolgerungen ziehen:
• Die Anfälligkeit für Spaltkorrosion wurde als wichtigster Aspekt für die Werkstoffqualifizierung ermittelt.
• Der niedriglegierte Stahl 25CrMo4 zeigte bei niedrigem Salzgehalt in MB-Geothermalwasser eine gleichmäßige Korrosion unterhalb der akzeptierten Schwelle von 0,3 mm/Jahr. Daher kann er als geeignet für geothermische Bedingungen mit niedrigem Salzgehalt angesehen werden, wie sie für MB getestet wurden. Es besteht keine Notwendigkeit, auf höherlegierte (teurere) Werkstoffe auszuweichen. Ein niedrigerer pH-Wert (wie bei LHD) führt zu Korrosionsraten oberhalb der akzeptablen Grenzwerte, so dass die niedriglegierten Werkstoffe nicht für Flüssigkeiten mit niedrigem pH-Wert geeignet sind.
• Stark salzhaltige Geothermalwässer erfordern höherlegierte Werkstoffe, da die Korrosionsrate von niedriglegiertem Stahl zu hoch ist.
• Der Duplexstahl X2CrNiMo22-5-3 und der Superduplexstahl X2CrNiMoCuWN25-7-4 wurden aufgrund ihrer kritischen Anfälligkeit für örtliche Korrosion in Form von Loch- und Spaltkorrosion unter Betriebsbedingungen nicht als geeignet für geothermische Anwendungen in Geothermalwässern mit einer mit NDB und ORG vergleichbaren Zusammensetzung angesehen.
• Der superaustenitische Stahl X1CrNiMoCu32-28-7 eignet sich für ORG und salzarme Wässer. In NDB-Geothermalwasser wurde er bei 100 °C als geeignet angesehen. Jedoch schränkt seine Anfälligkeit für Spaltkorrosion seine Anwendbarkeit ein. Neben seiner guten Korrosionsbeständigkeit ist sein Repassivierungsverhalten für seine begrenzte Anwendbarkeit in Geothermalwässern mit niedrigem pH-Wert verantwortlich.
• Die Nickelbasislegierung NiCr23Mo16Al wurde als geeignet erachtet und stellt eine sichere Option für den Einsatz in geothermischen Anlagen dar, selbst wenn mit stark salzhaltigem Geothermalwasser gearbeitet wird.