Technische Universität Bergakademie Freiberg: Qucosa
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A Review of the Recent Developments and Challenges in Wire Arc Additive Manufacturing (WAAM) Process
No full textWire arc additive manufacturing (WAAM) is an emerging and promising technology for producing medium-to-large-scale metallic components/structures for different industries, i.e., aerospace, automotive, shipbuilding, etc. It is now a feasible alternative to traditional manufacturing processes due to its shorter lead time, low material waste, and cost-effectiveness. WAAM has been widely used to produce components using different materials, including copper-based alloy wires, in the past decades. This review paper highlights the critical aspects of WAAM process in terms of technology, various challenges faced during WAAM process, different in-process and post-process operations, process monitoring methods, various gases, and different types of materials used in WAAM process. Furthermore, it briefly overviews recent developments in depositing different copper-based alloys via WAAM process
Thermodynamics of transamination reactions with aminotrimethylsilanes and diaminodimethylsilanes
No full textTransamination reactions of two different aminosilanes (trimethyl(tert-butylamino)silane and dimethyl(diamino)silane) with amines (diethylamine, pyrrolidine, tert-butylamine, iso-propylamine, and n-propylamine) are studied. For trimethyl(organoamino)silanes, the reaction of trimethyl(iso-propylamino)- or trimethyl(diethylamino)silane as aminosilanes and aniline or pyrrolidine are good starting materials to produce trimethyl(anilino)- and trimethyl(pyrrolidino)silane. The investigated equilibrium constants of the reactions of monoaminosilanes show a good correlation with quantum chemically calculated values. The reaction of two different diaminosilanes Me2Si(NR1R2)2 and Me2Si(NR3R4)2 containing different amino moieties leads to the formation of mixed diaminosilanes Me2Si(NR1R2)(NR3R4) in most cases
AQ-Shuttle - Autonomous robots for last mile delivery
No full textAs part of the AQ-Shuttle project, a feasibility study is being conducted on the use of autonomous neighborhood shuttles (AQ-Shuttle) in public transportation and sustainable neighborhood development in Bielefeld. Together with the municipal partners (City of Bielefeld, Stadtwerke Bielefeld), Bielefeld University of Applied Siences and Arts (HSBI) aims to test innovative mobility solutions and integrate them into the municipal policy Mobilitätsstrategie 2030, which strives to make Bielefeld more dynamic, sustainable, and livable. A particular focus is placed on promoting environmentally-friendly transport, reducing the share of private car use to 25 percent, and introducing new mobility offers. The study, running from January 2024 to September 2025, examines two central areas: (I) the use of autonomous goods shuttles to introduce new transport methods and (II) the establishment of a mobility station as a hub for existing mobility services. The Bielefeld population will be actively involved in the transition to new mobility offers. Citizens will not be obliged to use alternative services and leave their cars behind but should be motivated through participation concepts to make these decisions independently. The results of the study are intended to help sustainably transfer the AQ-Shuttle into practical applications and achieve the ambitious goals of the Mobilitätsstrategie 2030
Particle-based methods to characterise and analyse the microstructure of rocks
No full textNatural rocks normally contain a wide variety of microstructures, which lead to heterogeneous macroscopic behaviour. In this thesis, the Discrete Element Method (DEM) is used to investigate the influence of rock microstructure, where rock is represented by an assembly of bonded particles.
The detailed information obtained in DEM simulations can offer a better insight into the underlying mechanism. The contact force network is quantified and analysed by statistical approaches (e.g., probability density function and orientation distribution) under various confining pressures. Force chain structures are explored and validated in bonded granular materials using the particle deletion method.
Microstructural factors, such as porosity, grain size distribution, spatial distribution and properties of mineral inclusions are involved and studied in this thesis. Especially, with respect to mineral inclusions, µCT-scanned files are used to rebuild the matrix and inclusions in DEM simulations. Then, a series of parametric studies is performed to investigate the effect of inclusion geometry and properties. The evolutions of contact networks, contact forces and force chains during the loading process help to better understand the influence of microstructure on macroscopic mechanical behaviour.
Since force chains act as the main skeleton to bear external loads and present different characteristics with various microstructures, the prediction of force chains provides the potential for forecasting macroscopic properties of rock. Graph Neural Network (GNN) is used in this study to predict force chains in numerical models with various degrees of polydispersity, porosities, spatial distributions and properties of inclusions. The results indicate that the GNN model is able to provide a high-accuracy prediction for force chains. The prediction of force chains may help to predict the macroscopic properties of rock or rock-like materials based on geometrical features
Transport and Fate of Microplastics in Terrestrial Environments: The Role of Surface Runoff, Root-Mediated Infiltration, and Fragmentation-Driven Mobility
No full textMicroplastics are widely distributed in terrestrial environments due to processes such as plastic fragmentation, tire wear, and the reuse of plastic-rich materials in agriculture. Their transport is influenced by hydrological, biological, and physicochemical factors. This dissertation applies principles from classical sediment transport to microplastic movement, focusing on three key processes: surface runoff, root-mediated infiltration, and fragmentation-driven mobility. The role of particle characteristics—density, size, and shape—is examined through field studies and laboratory experiments. Tire wear particles (TWP) and their chemical markers (6PPD-Q, DPG, and 2-OHBT) are investigated across different road and soil conditions. While 6PPD-Q tends to accumulate in soils, 2-OHBT demonstrates higher mobility, highlighting runoff as a key dispersal pathway. Rhizotron experiments with wheat plants demonstrate that roots influence the transport of microplastics, with fibres adhering to the roots and fragments infiltrating deeper soil layers. Fragmentation increases the mobility of microplastics, potentially accelerating groundwater contamination. Column experiments confirm that smaller, irregular fragments move more readily through porous media than spherical particles. The results contribute to understanding microplastic transport, informing environmental risk assessment and pollution mitigation. They also support the need for sustainable soil and water management, as well as stricter regulation of plastic additives and their degradation products
Preliminary experimental study on simultaneous polishing and shape setting of Nitinol wire
No full textSeparate processes for shape setting and polishing of Nitinol workpieces are well investigated in scientific literature and adopted industrially. However, a simultaneous process for shape setting and polishing of Nitinol has not yet been reported. In this study, preliminary results of such process are presented, providing insights and directions for further research on post-processing shape memory materials. For this purpose, Nitinol wire samples with phase transformation temperatures Af = 4.5 °C, Af = 31 °C and Af = 61 °C were plasma electrolytic polished (PEP) while fitted in a specially designed sample holder at three electrolyte temperatures te = 50 °C, te = 65 °C and te = 80 °C. The PEP process duration was τPEP = 60 s, τPEP = 180 s and τPEP = 300 s. After the PEP processes, the samples were investigated for the shape memory effect (SME). The training effect, known to be present in shape memory alloys (SMA), was taken into account. The surface roughness of the investigated wires was measured before and after the PEP process. The obtained results demonstrate that both a phase transformation temperature and an electrolyte temperature have a strong effect on polishing and shape setting results
Synthesis and crystal structures of two solvates of 1-{[2,6-bis(hydroxymethyl)-4-methylphenoxy]methyl}-3,5-bis{[(4,6-dimethylpyridin-2-yl)amino]methyl}-2,4,6-triethylbenzene
No full textIn the crystal structures of the formamide monosolvate (1a) and the n-propanol/ H O solvate/hydrate (1b) of the title compound, C 38 H 50 N 4 O 3 (1), the tripodal host molecule adopts a conformation in which the substituents attached to the central benzene ring are arranged in an alternating order above and below the ring plane. As a result of the different nature of the involved guest species, the crystal components in 1a create a three-dimensional supramolecular architecture, while the crystal structure of 1b consists of two-dimensional supramolecular aggregates extending parallel to the crystallographic ab plane
Impact of Soil Inoculation with Bacillus amyloliquefaciens FZB42 on the Phytoaccumulation of Germanium, Rare Earth Elements, and Potentially Toxic Elements
Full text linkBioaugmentation promises benefits for agricultural production as well as for remediation and phytomining approaches. Thus, this study investigated the effect of soil inoculation with the commercially available product RhizoVital®42, which contains Bacillus amyloliquefaciens FZB42, on nutrient uptake and plant biomass production as well as on the phytoaccumulation of potentially toxic elements, germanium, and rare earth elements (REEs). Zea mays and Fagopyrum esculentum were selected as model plants, and after harvest, the element uptake was compared between plants grown on inoculated versus reference soil. The results indicate an enrichment of B. amyloliquefaciens in inoculated soils as well as no significant impact on the inherent bacterial community composition. For F. esculentum, inoculation increased the accumulation of most nutrients and As, Cu, Pb, Co, and REEs (significant for Ca, Cu, and Co with 40%, 2042%, and 383%, respectively), while it slightly decreased the uptake of Ge, Cr, and Fe. For Z. mays, soil inoculation decreased the accumulation of Cr, Pb, Co, Ge, and REEs (significant for Co with 57%) but showed an insignificant increased uptake of Cu, As, and nutrient elements. Summarily, the results suggest that bioaugmentation with B. amyloliquefaciens is safe and has the potential to enhance/reduce the phytoaccumulation of some elements and the effects of inoculation are plant specific
Innovations in Mechanical Recycling of automotive Lithium-Ion Batteries: A Focus on Discharge Depths and Material Classification
No full textIn dieser Arbeit wird das mechanische Recycling von Lithium-Ionen-Batterien unter Anwendung des an der TU Bergakademie Freiberg entwickelten Verfahrens untersucht. Ziel ist es, das Recyclingverhalten zu verbessern, da das Recycling von Lithium-Ionen-Batterien im Zusammenhang mit der zunehmenden Elektrifizierung des Verkehrssektors immer wichtiger wird. Um die von der EU geforderten Verwertungsquoten, zu erreichen, ist es notwendig, Recyclingprozesse robust zu gestalten. Das mechanische Recycling stellt in Kombination mit der Hydrometallurgie eine vielversprechende Option zur Erreichung dieser Ziele dar, insbesondere angesichts der Rolle, die es bei dem Aufschluss der Lithium-Ionen-Batterie, einer komplexen Materialverbindung, spielt. Der Schwerpunkt liegt dabei auf der Interaktion zwischen Maschine und Material, wobei der Sortierung und Analyse der Produkte sowie den Auswirkungen unterschiedlicher Batterietypen oder Entladestufen auf den Prozess besondere Aufmerksamkeit gewidmet wird. Im Rahmen der Modellierung und Simulation wird der Zick-Zack-Sichter im Hinblick auf seine Trennleistung und die verwendeten Materialien, nämlich die Stromsammlerfolien der Batterie, untersucht. Darüber hinaus werden Fallstudien vorgestellt, die die zunehmende Komplexität des zu recycelnden Materials im mechanischen Recycling verdeutlichen. Die Robustheit des Prozesses wird unter Berücksichtigung verschiedener Batterietypen und Entladestufen untersucht. Besonderes Augenmerk wird dabei auf die Qualität der Schwarzmasse, die erzielten Rückgewinnungsraten, die Herkunft der Verunreinigungen sowie das Sortier- und Freisetzungsverhalten gelegt. Folglich werden die Partikelgröße, die Produktzusammensetzung, die spezifische Energie, die Sinkgeschwindigkeitsverteilungen und die Analyse der Schwarzmasse (chemisch und optisch) untersucht, um die Ergebnisse mit den von der EU geforderten Rückgewinnungsraten zu vergleichen. Ausblickend wird angeführt, dass die Absiebung der Separatorfolie anstelle der Windsichtung die Robustheit des mechanischen Recyclings erhöht. Abschließend werden neue Forschungsansätze für das mechanische Recycling vorgestellt.:1. Motivation
2. Outline
3. State of the art: Lithium-Ion batteries
3.1 Composition and design
3.2 Hazards potential of Lithium-ion batteries
3.3 Recycling of Lithium-Ion Batteries
3.3.1 Process combinations of Lithium-Ion Battery recycling and their application in industry
3.3.2 Discharge
3.3.3 Mechanical processing
3.3.3.1 Comminution
3.3.3.2 Material separation
4. Materials and Methods
4.1 Material
4.2 Methodology
4.2.1 Recycling procedure
4.2.2 Analysis Methods
4.2.3 Definition of core parameters
5. Conclusion and Outlook
References
Publications
AppendixThis thesis investigates the mechanical recycling of Lithium-Ion Batteries (LIB), applying the process developed by TU Bergakademie Freiberg. The objective is to enhance the recycling behaviour, given the growing importance of lithium-ion battery recycling in the context of the increasing electrification of the transport sector. It is necessary to design recycling processes in a robust way in order to achieve the recovery rates required by the EU, as published in July 2023. The mechanical recycling process, when used in combination with hydrometallurgical treatment represents a promising option for achieving these goals, particularly given its role in liberating the components of LIB, a complex material compound. The focus is on the interaction between the machine and the material, with particular attention paid to the sorting and analysis of products, as well as the impact of varying battery types or discharge levels on the process. In the context of modelling and simulation, the Zig Zag air classifier is investigated with regard to its separation efficiency and the feed material, namely the current collector foils of the battery. Furthermore, case studies are presented, which illustrate the increasing complexity of the material to be recycled in the mechanical recycling process. The robustness of the process is investigated by considering different battery types and discharge levels. In this context, particular attention is paid to the quality of the black mass, the recovery rates achieved, the origin of the impurities, and the sorting and liberation behaviour. Consequently, the particle size, product composition, specific energy consumption, settling velocity distributions and black mass analysis (chemical and optical) are investigated in order to compare the results to the recovery rates requested by the EU. Looking ahead, it is stated that screening off the separator foil instead of air classification enhances the robustness of the mechanical recycling process. Finally, new research approaches for mechanical recycling are presented.:1. Motivation
2. Outline
3. State of the art: Lithium-Ion batteries
3.1 Composition and design
3.2 Hazards potential of Lithium-ion batteries
3.3 Recycling of Lithium-Ion Batteries
3.3.1 Process combinations of Lithium-Ion Battery recycling and their application in industry
3.3.2 Discharge
3.3.3 Mechanical processing
3.3.3.1 Comminution
3.3.3.2 Material separation
4. Materials and Methods
4.1 Material
4.2 Methodology
4.2.1 Recycling procedure
4.2.2 Analysis Methods
4.2.3 Definition of core parameters
5. Conclusion and Outlook
References
Publications
Appendi
Innovative Optimierung von Single-Layer-Einzelzahnwicklungen
No full textDiese Arbeit stellt ein analytisches Rechenmodell zur systematischen Optimierung von Permanentmagneterregten Synchronmaschinen mit Single-Layer-Einzelzahnwicklungen vor. Im Fokus steht die gezielte Anpassung der Zahnbreite, um die Drehmomentqualität zu verbessern. Es wird gezeigt, dass sich durch geeignete Breiten der bewickelten Zähne das Nutzmoment erhöhen und gleichzeitig die Drehmomentrippel deutlich reduzieren lassen. Zur Verifikation wird das analytische Modell mit einer FEM-Simulation verglichen. Dabei zeigt sich für das Nutzmoment, unter Vernachlässigung der Sättigung, eine hohe Übereinstimmung. Darüber hinaus bestätigt sich der positive Einfluss der Anpassung der Zahnbreite. Durch das analytische Modell lassen sich die Drehmomentanteile einzelner Ordnungen veranschaulichen und damit den Wirkmechanismus der Drehmomentanpassung nachvollziehen.
Weiterhin wird mit FEM und dem analytischen Modell nachgewiesen, dass die Anpassung der Zahnbreite neue Motorkonfigurationen mit weiteren Polpaarzahlen erlaubt