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Highly Efficient CMOS Compatible Ohmic Contacts for WBG Nitride Power Devices
Full text linkThe electrification of transport, the increase in renewable energies, and the power supply for large artificial intelligence data centers represent challenges that require highly efficient power conversion.
To minimize power losses, optimized electronic components are required. Nitride-based compound semiconductors with a large band-gap are very promising and on the way to market entry.
However, the source and drain terminals that connect the semiconductor component to integrated circuits still pose a key challenge.
These ohmic contacts contribute significantly to the power loss of the component, leading to heat generation and energy losses.
In addition, the manufacturing costs for nitride power components must be reduced, which makes integration into the Si-CMOS process chain essential.
However, CMOS requires an Au-free metallization, which represents a major challenge for the ohmic contact development, but also promises further advantages in the long term, such as a significantly improved surface morphology.
In the framework of this thesis, the state-of-the-art Au-based as well as conventional and a newly developed Au-free ohmic contact stack were fabricated on heterostructures with normal and increased Al-content and benchmarked.
For the investigations, various epitaxially grown GaN and AlGaN/GaN wafers from different manufacturers were used.
The origin of the power losses of Au-free contacts was investigated by electrical and microstructural characterizations and discussed.
A CMOS-compatible V/Al/Ti/TiN contact stack with extremely low contact resistance is presented and demonstrated by HEMTs on GaN-on-Si substrates, as it could be used in the CMOS process chain.:1 Introduction
1.1 Power Electronics
1.2 Power Effciency
1.3 Semiconductors for Power Switching
1.4 Devices for Power Switching
1.5 Aims of this Work
2 Fundamentals
2.1 Nitride Semiconductors GaN, AlGaN, AlN
2.2 AlGaN/GaN Heterostructure
2.3 AlGaN/GaN High-Electron-Mobility Transistor
2.4 Ohmic Contacts for AlGaN/GaN High-Electron-Mobility Transistors
3 Test Device Fabrication
3.1 Employed Heterostructure Wafers
3.2 Test Die Fabrication
3.3 Mesa Module
3.4 Ohmic Module
3.5 Gate Module
4 Characterization
4.1 Electrical Characterization
4.2 Structural Characterization
5 Results
5.1 Au-based Contact Formation on High-Al AlGaN
5.2 Au-free Contact Formation on GaN Substrate
5.3 Au-free Contact Formation on AlGaN/GaN Heterostructure
5.4 Au-free V-based Ultra-Low Contact Resistance
5.5 Au-free V-based Contacts on Super-Lattice Buffered Heterostructure
5.6 Au-free V-based Contacts on High-Al AlGaN (Outlook)
6 Summary
List of Publications
Acknowledgements
Bibliography
List of Symbols
List of Abbreviations
List of Tables
List of FiguresDie Elektrifizierung des Verkehrs, der Anstieg regenerativer Energien und die Stromversorgung großer KI-Datencenter stellen Herausforderungen dar, die eine hochgradig effiziente Stromwandlung erfordern.
Um Verlustleistungen zu minimieren, sind optimierte Bauteile notwendig. Dafür vielversprechend sind nitridbasierte Verbindungshalbleiter mit großer Bandlücke, die an der Schwelle zur Marktreife stehen.
Eine zentrale Herausforderung stellen noch immer die Source- und Drain-Terminals dar, die das Halbleiterbauteil in integrierte Schaltungen einbinden.
Diese ohmschen Kontakte tragen signifikant zur Verlustleistung des Bauteils bei, was zu Wärmeentwicklung und Energieverlusten führt.
Zudem müssen die Herstellungskosten für nitridische Leistungsbauteile gesenkt werden, was eine Integration in die Si-CMOS-Prozesskette unabdingbar macht.
CMOS erfordert jedoch eine Au-freie Metallisierung, was eine große Hürde an die Kontaktwicklung stellt, langfristig aber auch weitere Vorteile wie eine deutlich verbesserte Oberflächenmorphologie verspricht.
Im Rahmen dieser Arbeit wurde der state-of-the-art Au-basierte sowie herkömmliche als auch ein neu entwickelter Au-freier ohmscher Kontakstapel auf Heterostrukturen mit üblichem und erhöhtem Al-Gehalt hergestellt und hinsichtlich ihrer elektrischen Kenngrößen miteinander verglichen.
Für die Untersuchungen wurden verschiedene epitaktisch gewachsene GaN- und AlGaN/GaN-Wafer von unterschiedlichen Herstellern verwendet.
Die Ursachen der Verlustleistung Au-freier Kontakte wurden durch elektrische und mikrostrukturelle Charakterisierungen untersucht und diskutiert.
Ein CMOS-kompatibler V/Al/Ti/TiN Kontaktstapel mit extrem niedrigem Kontaktwiderstand wird vorgestellt und an einem HEMT auf GaN-on-Si Substrat demonstriert, wie er in der CMOS-Prozesskette eingesetzt werden könnte.:1 Introduction
1.1 Power Electronics
1.2 Power Effciency
1.3 Semiconductors for Power Switching
1.4 Devices for Power Switching
1.5 Aims of this Work
2 Fundamentals
2.1 Nitride Semiconductors GaN, AlGaN, AlN
2.2 AlGaN/GaN Heterostructure
2.3 AlGaN/GaN High-Electron-Mobility Transistor
2.4 Ohmic Contacts for AlGaN/GaN High-Electron-Mobility Transistors
3 Test Device Fabrication
3.1 Employed Heterostructure Wafers
3.2 Test Die Fabrication
3.3 Mesa Module
3.4 Ohmic Module
3.5 Gate Module
4 Characterization
4.1 Electrical Characterization
4.2 Structural Characterization
5 Results
5.1 Au-based Contact Formation on High-Al AlGaN
5.2 Au-free Contact Formation on GaN Substrate
5.3 Au-free Contact Formation on AlGaN/GaN Heterostructure
5.4 Au-free V-based Ultra-Low Contact Resistance
5.5 Au-free V-based Contacts on Super-Lattice Buffered Heterostructure
5.6 Au-free V-based Contacts on High-Al AlGaN (Outlook)
6 Summary
List of Publications
Acknowledgements
Bibliography
List of Symbols
List of Abbreviations
List of Tables
List of Figure
Ready for robots? Assessment of autonomous delivery robot operative accessibility in German cities
No full textUnlike autonomous car applications, the operational area of urban service autonomous robots like autonomous delivery robots (ADRs) is not clearly defined at the moment. Due to large variations in the different robot designs, specific local infrastructure and regulation, assessing the feasibility of different operational scenarios is difficult. This paper presents a prototype evaluation methodology based on Open Street Map data for the assessment of ADR deployments considering one-to-many delivery schemes. Four different robot configurations and potential operational specifications are modeled and evaluated in a sample of German cities. The bandwidth of considered robot types ranges from large ADRs operating on roadways down to small size systems operating on sidewalks. The performance of the first category is limited by the reduced accessibility in areas with higher traffic. On the contrary, small ADRs present a higher detour time but increased accessibility. The evaluated operational scenarios show very diverse performance depending on the considered metrics and cities. For all the metrics considered in the paper, sidewalk ADRs show poor performance when compared to other potential ADR deployments
Homogenization Approaches for the Inelastic Behavior of Porous Structures
No full textDie Beschreibung des effektiven mechanischen Verhaltens hoch-poröser, zellularer Medien, wie beispielsweise schaumartiger Strukturen, stellt aufgrund ihrer komplexen strukturellen Abhängigkeiten und ausgeprägten Größeneffekte eine erhebliche Herausforderung dar. Traditionelle makroskopische Modellierungsansätze haben oft Schwierigkeiten, diese Phänomene, insbesondere bei inelastischen Deformationen, genau abzubilden. Mikromorphe Kontinuumstheorien bieten eine geeignete Herangehensweise, indem sie nicht-klassische Deformationsgrößen integrieren, die Größeneffekte und mikrostrukturelle Einflüsse abbilden. Diese Theorien komplizieren jedoch die Formulierung geeigneter konstitutiver Beziehungen und Bestimmung der erforderlichen Materialparameter, die experimentell schwer zu erfassen sind.
Diese Arbeit untersucht einen alternativen Ansatz, indem ein hierarchisches mikromorphes Multiskalen-Framework, die direkt FE²-Methode, verwendet wird, um das komplexe irreversible Verhalten heterogener Feststoffe zu simulieren. Die Studie vergleicht die Vorhersagen der Cosserat- (mikropolaren) und voll mikromorphen Theorien mit konventionellen Cauchy FE²-Ergebnissen und direkten numerischen Simulationen unter verschiedenen Lastbedingungen, einschließlich elastischer, elastisch-plastischer und Kriechdeformationen. Die Analyse hebt nicht-klassische Deformationsmoden und deren Beiträge zu makroskopischen Hyperspannungen und Gesamtverformungen hervor und bietet Einblicke in das Materialverhalten bei unterschiedlichen Skalenseparationen.
Um die Herausforderungen bei der Erfassung des inelastischen makroskopischen Verhaltens zellularer Medien innerhalb eines nicht-assoziativen Plastizitätsrahmens zu bewältigen, wurde ein neuartiger dreidimensionaler Hybrid-Ansatz zur Skalenüberbrückung entwickelt. Dieser Ansatz integriert Invarianten effektiver Größen aus räumlich aufgelösten Finite-Elemente-Analysen repräsentativer Volumenelemente in ein neuronales Netzwerk. Das Volumenelement approximiert relevante Schaum-Morphologien und ist austauschbar. Ein zentrales Merkmal dieses hybriden Modells ist die Einbindung neuronaler Netze, um ausschließlich jene Teile der komplexen Fließfläche und plastischen Fließrichtung darzustellen, für die analytische Beschreibungen unzureichend sind. Zu diesem Zweck werden die neuronalen Netze aus einem Datensatz trainiert, der durch numerische Homogenisierung gewonnen wurde.
Die vorgeschlagene Methodik wird anhand einer dreidimensionalen Weaire-Phelan-Struktur mit elastoplastischem Verhalten auf der Mikroebene validiert. Die Anforderungen an Trainingsdatensätze und Konfigurationen neuronaler Netze werden untersucht, um ein Gleichgewicht zwischen Vorhersagengenauigkeit und Recheneffizienz zu erreichen. Die Ergebnisse dieser Arbeit tragen zur Entwicklung prädiktiver Berechnungswerkzeuge für die Untersuchung von Struktur-Eigenschafts-Leistungsfähigkeits-Beziehungen in heterogenen Materialien bei und bieten vielversprechende Perspektiven für zukünftige Forschungsarbeiten in diesem Bereich.:List of Symbols
Operators
Variables
Abbreviations
1. Introduction
1.1. Motivation
1.2. State of the Art
1.3. Aim and Scope
1.4. Structure of the Thesis
2. Fundamentals
2.1. Continuum Mechanics
2.1.1. Nomenclature
2.1.2. Cauchy Continuum
2.1.3. Micromorphic Continuum
2.1.4. Cosserat Continuum
2.2. Constitutive Theory
2.2.1. Coleman-Noll-Procedure
2.2.2. Elasto-Plasticity
2.2.3. Creep
2.3. Multi-Scale Modeling
2.3.1. Representative Volume Element
2.3.2. Micro-Macro-Transition
2.3.3. Specifics for Generalized Continua
2.4. Finite Element Method
2.5. Direct FE²
2.6. Neural Networks
2.6.1. Type of Neural Networks
2.6.2. Training Procedure
2.6.3. Data Set
2.7. Overview and Implications
3. Quantification of Size Effects by Means of Micromorphic Investigation
3.1. Implementation of Generalized Continua in the Direct FE² Framework
3.2. Non-classical Microscopic Deformations
3.2.1. Deformation Modes
3.2.2. Deformation Moduli
3.2.3. Internal Length
3.3. Pure Bending of a Beam
3.3.1. Modeling Approaches and Mesh Convergence
3.3.2. Elastic and Plastic Bending
3.4. Plate with a Hole
3.4.1. Modeling and Mesh Convergence
3.4.2. Ligament and Hoop Stresses
3.5. Flow-Through Filter
3.6. Spherical Indenter
3.7. Overview and Implications
4. Homogenization of the Inelastic Deformation of Foam Structures
4.1 Hybrid Material Model
4.1.1. Constitutive Model of the Bulk Material
4.1.2. Computational Homogenization
4.1.3. Macroscopic Constitutive Model Incorporating Neural Networks
4.1.4. Extension of the Material Model
4.1.5. General Return Algorithm
4.2. Preliminaries of the Weaire-Phelan Foam
4.2.1. Relevance of Size Effects
4.2.2. Data Sampling on the Unit Cell
4.2.3. Neural Network Accuracy Depending on Network Topology
4.3. Prediciton Accuracy for Different Load Cases
4.4. Plate with Prohibited Transverse Strain
4.5. Plate with a Hole
4.6. Overview and Implications
5. Summary and Conclusion
A. Finite Deformation Stresses for the Micromorphic Continuum
B. Extension of the FFNET Library with Activation Functions
C. Non-classical Coupling Moduli
C.1. Microdeformation Moduli
C.2. Derivation of Hyperstress Moduli
C.3. Harmonic Hyperstress Moduli Depending on Implemented Components
D. Verification of Macroscopic Curvature Components
E. Comparison of Micromorphic FE² and DNS Computational Costs
E.1. Flow-Through Filter
E.2. Spherical Indenter
F. Evaluation of Sampling Strategies for Neural Network Applications
F.1. Data Sampling
F.2. Network Topology
F.3. Results
G. Derivatives for the Hybrid Material Model
BibliographyDescribing the effective mechanical behavior of highly porous cellular media, such as foam-like structures, remains a significant challenge due to their complex structural interdependencies and pronounced size effects. Traditional macroscopic modeling approaches often struggle to accurately capture these phenomena, particularly under inelastic deformations. Micromorphic continuum theories offer an appropriate approach by incorporating non-classical deformation measures that account for size effects and microstructural influences. However, these theories introduce complexities in formulating appropriate constitutive relations and determining the required material parameters, which are difficult to obtain experimentally.
This thesis explores an alternative approach by employing a hierarchical micromorphic multi-scale framework, the direct FE² method, to simulate the complex irreversible behavior of heterogeneous solids. The study compares the predictions of micropolar (Cosserat) and fully micromorphic theories with conventional Cauchy FE² results and direct numerical simulations under various loading conditions, including elastic, elastic-plastic, and creep deformations. The analysis highlights non-classical deformation modes and their contributions to macroscopic hyperstresses and overall deformations, providing insights into the materials response at different scale separations.
To address the challenges in capturing the inelastic macroscopic behavior of cellular media within a non-associative plasticity framework, a novel three-dimensional hybrid scale-bridging approach is developed. This approach integrates invariant representations of effective quantities from spatially resolved finite element analysis of representative volume elements within a neural network. The volume element approximates relevant foam morphologies and is interchangeable. A key feature of this hybrid model is the incorporation of neural networks to represent exclusively parts of the complex yield surface and plastic flow direction where analytical descriptions are inadequate. For this purpose, the neural networks are trained from a data set obtained through numerical homogenization.
The proposed methodology is validated using a three-dimensional Weaire-Phelan structure with elasto-plastic microscale behavior. The research examines the requirements for the training data sets and neural network configurations to balance approximation accuracy and computational efficiency. The findings of this thesis contribute to the development of predictive computational tools for studying structure-property-performance relations in heterogeneous materials, offering a promising avenue for future research in this area.:List of Symbols
Operators
Variables
Abbreviations
1. Introduction
1.1. Motivation
1.2. State of the Art
1.3. Aim and Scope
1.4. Structure of the Thesis
2. Fundamentals
2.1. Continuum Mechanics
2.1.1. Nomenclature
2.1.2. Cauchy Continuum
2.1.3. Micromorphic Continuum
2.1.4. Cosserat Continuum
2.2. Constitutive Theory
2.2.1. Coleman-Noll-Procedure
2.2.2. Elasto-Plasticity
2.2.3. Creep
2.3. Multi-Scale Modeling
2.3.1. Representative Volume Element
2.3.2. Micro-Macro-Transition
2.3.3. Specifics for Generalized Continua
2.4. Finite Element Method
2.5. Direct FE²
2.6. Neural Networks
2.6.1. Type of Neural Networks
2.6.2. Training Procedure
2.6.3. Data Set
2.7. Overview and Implications
3. Quantification of Size Effects by Means of Micromorphic Investigation
3.1. Implementation of Generalized Continua in the Direct FE² Framework
3.2. Non-classical Microscopic Deformations
3.2.1. Deformation Modes
3.2.2. Deformation Moduli
3.2.3. Internal Length
3.3. Pure Bending of a Beam
3.3.1. Modeling Approaches and Mesh Convergence
3.3.2. Elastic and Plastic Bending
3.4. Plate with a Hole
3.4.1. Modeling and Mesh Convergence
3.4.2. Ligament and Hoop Stresses
3.5. Flow-Through Filter
3.6. Spherical Indenter
3.7. Overview and Implications
4. Homogenization of the Inelastic Deformation of Foam Structures
4.1 Hybrid Material Model
4.1.1. Constitutive Model of the Bulk Material
4.1.2. Computational Homogenization
4.1.3. Macroscopic Constitutive Model Incorporating Neural Networks
4.1.4. Extension of the Material Model
4.1.5. General Return Algorithm
4.2. Preliminaries of the Weaire-Phelan Foam
4.2.1. Relevance of Size Effects
4.2.2. Data Sampling on the Unit Cell
4.2.3. Neural Network Accuracy Depending on Network Topology
4.3. Prediciton Accuracy for Different Load Cases
4.4. Plate with Prohibited Transverse Strain
4.5. Plate with a Hole
4.6. Overview and Implications
5. Summary and Conclusion
A. Finite Deformation Stresses for the Micromorphic Continuum
B. Extension of the FFNET Library with Activation Functions
C. Non-classical Coupling Moduli
C.1. Microdeformation Moduli
C.2. Derivation of Hyperstress Moduli
C.3. Harmonic Hyperstress Moduli Depending on Implemented Components
D. Verification of Macroscopic Curvature Components
E. Comparison of Micromorphic FE² and DNS Computational Costs
E.1. Flow-Through Filter
E.2. Spherical Indenter
F. Evaluation of Sampling Strategies for Neural Network Applications
F.1. Data Sampling
F.2. Network Topology
F.3. Results
G. Derivatives for the Hybrid Material Model
Bibliograph
Collected Volume of the Workshop on Autonomous Delivery and Service Robots on Pedestrian and Cycle Paths
No full textThe increasing proliferation of autonomous systems is steadily transforming the structure and dynamics of urban environments. While autonomous vehicles continue to dominate public discourse, their potential extends far beyond traditional road traffic. Smaller autonomous robots operating on pedestrian and cycling infrastructure offer novel opportunities for urban logistics and public services. These developments raise not only technical but also societal questions, including those concerning public acceptance, social integration, and human-robot interaction in shared spaces.
Against this backdrop, the 'WonDeSeRo 2025 – Workshop on Delivery and Service Robots' provided a dedicated platform for interdisciplinary exchange among researchers, developers, and practitioners. The workshop focused on the challenges and potentials of service robots in the context of smart cities - particularly with regard to their integration into existing infrastructures, their social compatibility, and their operational robustness in real-world scenarios. Held in conjunction with the final meeting of the research project Ready for Smart City Robots, which featured practical deployments in the city of Schkeuditz, the workshop contributed valuable empirical insights to ongoing academic and technological discussions.
The contributions presented in this volume reflect the thematic diversity and practical relevance of the field. Topics range from technical implementations for socially aware navigation to energy-efficient environmental data collection using rental bikes, and the integration of delivery robots into public transportation systems. What becomes clear is a broader shift from controlled laboratory experimentation toward real-world application - accompanied by the associated regulatory, infrastructural, and social challenges. The workshop demonstrated that the successful deployment of autonomous service robots depends not only on technological innovation but also on a nuanced understanding of the urban contexts into which these systems are embedded.
The collected papers in this volume offer important insights in this regard. They document the current state of research, illustrate practical applications, and identify unresolved issues that will shape future work. Thus, this compilation serves not only as a snapshot of an evolving field but also as an impetus for its continued development at the intersection of technology, urban planning, and society
European Summer Synoptic Circulations and Their Observed 2022 and Projected Influence on Hot Extremes and Dry Spells
No full textIn 2022, western Europe experienced its hottest summer on record and widespread dry conditions, with substantial impacts on health, water and vegetation. We use a reanalysis to classify daily mean sea level pressure fields and to investigate the influence of synoptic circulations on the occurrence of temperature extremes and dry days. Summer 2022 featured an above-normal occurrence of anticyclones extending from the British Isles to the Baltic countries, as well as enhanced easterly, southerly and low-flow conditions which contributed to the observed extremes over southern and western Europe. While the hot summer of 2022 is only partially explained by circulation anomalies, such anomalies played a key role in the exceptional occurrence of dry days. The comparison with summer circulation anomalies projected by twenty global climate models moreover suggests that future circulation changes will further exacerbate hot and dry extremes over Europe
Crystal structure of the complex of 2,4,6-triethyl- 1,3,5-tris[(4-methyl-1H-indazol-1-yl)methyl]- benzene with NH4PF6
No full textThe complex of 2,4,6-triethyl-1,3,5-tris[(4-methyl-1H-indazol-1-yl)methyl]benzene with ammonium hexafluorophosphate, C39H42N6·NH4+·PF6−, crystallizes in the monoclinic space group P21 with two molecules of the receptor, two NH4+ and two PF6− ions in the asymmetric unit. In each of the complexes the ammonium ion resides in the cavity of the receptor molecule and is fixed in its position by three N—H⋯N bonds, while the remaining hydrogen atom of the cation acts as a bifurcated binding site for N—H⋯F bonding to the counter-anion. The crystal is composed of one-dimensional supramolecular aggregates extending along the a-axis direction
Functional stability of syntrophic consortia involved in anaerobic contaminant degradation: Elucidating key and accessory microbes in a benzene-degrading community
No full textBenzene is the main contaminant of an aquifer in the area of a former hydrogenation plan near Zeitz, Saxony-Anhalt. In its anoxic zone, investigations revealed an indigenous microbial consortium degrading benzene under sulfate-reducing conditions. A member of this consortium belongs to the Epsilonproteobacteria but its specific role remained unclear so far. One aim of this thesis was to clarify its function. The population genome of this species was reconstructed from a metagenome dataset and allowed an insight into its genetic capabilities. It revealed a microbe with a versatile metabolism potentially adaptable to various environments. Another part of this thesis dealt with the impact on the community by changing the terminal electron acceptor from sulfate to nitrate. For a microbe, nitrate is a thermodynamically more favorable electron acceptor compared to sulfate and thus, has the potential to accelerate the remediation of the contaminant plume. Indeed, the capability of benzene degradation was preserved under nitrate-reducing conditions and resulted in an altered community composition more adapted to the new redox conditions. Analysis on single-cell level allowed the identification of the new key microbes responsible for the degradation of benzene
Forschungssoftware im Kontext von Open Science
Full text linkForschungssoftware ist ein zentraler Bestandteil wissenschaftlicher Arbeit, der gut dokumentiert, öffentlich zugänglich und reproduzierbar sein sollte. Initiativen wie die FAIR4RS-Principles, Software Heritage oder die neuen DFG-Förderprogramme und NFDI-Dienste in Deutschland fördern die nachhaltige Nutzung, Entwicklung und Anerkennung von Forschungssoftware. Neben dem Überblick zum Thema stellen wir in dieser Ausgabe auch die international genutzte Forschungssoftware OpenGeoSys (OGS) vor, zu deren Hauptentwicklern Mitarbeiter des Instituts für Geotechnik der TU Bergakademie Freiberg gehören
Application of thermal methods to enhanced oil recovery: Numerical and experimental investigations
Full text linkReservoir simulation is a powerful tool to model fluid flow within oil and gas reservoirs and predict their behaviour. This dissertation is devoted primarily to model some thermal enhanced oil recovery (TEOR) methods. Two software were used for this purpose and namely; Comsol Multiphysics® and CMG® (Computer Modelling Group). The dissertation can be classified into three parts and all of them are standalone that discuss different topics within TEOR.
The work starts with reviewing enhanced oil recovery (EOR) methods with concentration on thermal methods (TEOR) for heavy oil and bitumen. Basics of mathematical modelling of single, two-phase, and three-phase flow in porous media that is the base of all commercial and scientific reservoir simulation software are reviewed. Formulations of the set of representative PDEs are reviewed and other formulations are suggested and applied directly in subsequent sections in Comsol Multiphysics®.
Part-1:
The application of finite element method (FEM) in reservoir simulation has been discussed and evaluated using Comsol Multiphysics package which is based on Galerkin approach. In the demonstrated problems, the mathematical model is solved using mathematics module in Comsol Multiphysics. Energy equation in 1D, Buckley-Leverett benchmark, two-phase flow model on ¼ inverted 5-spot scheme in 3D, and SAGD process PDE model are all solved and discussed. FEM using Comsol Multiphysics looks promising at moderate mobility ratios.
Part-2:
A comparison of water flooding with steam injection in heavy oil reservoirs as secondary stage is demonstrated and discussed. The whole modelling was achieved by CMG-STARS. A comparison of five different scenarios is shown. SPE4 comparative project data were used for this purpose. The results showed that steam can achieve more recovery in a short period of time with an ultimate recovery factor higher than cold recovery followed by steam flooding process.
Part-3:
A series of flooding and in-situ combustion experimental work that has been achieved in Kazan Federal University in cooperation with Institute of Drilling Engineering and Fluid Mining (IBF) is elaborated briefly and discussed. Four experiments with different core samples (consolidated and unconsolidated) were run between 05-2020 and 05-2021. The samples were taken from a Russian extra-heavy oilfield with initial viscosity around 600,000 cP. The results were evaluated and a numerical model was built using CMG-STARS. The numerical results were correlating the experimental results. Relative permeability data were history matched for flooding processes and this data was used for in-situ combustion model. Modelling of the reactions in in-situ combustion was a challenge to match the experimental results. The final results showed that steam injection was not the best recovery method for this oilfield and in-situ combustion was the best available technique with the highest recovery factor
Influences of different pre-treatments, settings and cell types on the first process stage of a mechanical recycling process for automotive lithium-ion batteries
Full text linkThis thesis addresses the mechanical recycling of lithium-ion batteries, more precisely the influences on the first process stage of the process developed at TU Bergakademie Freiberg. The recycling of lithium-ion batteries becomes more important with the increasing number of electric vehicles due to the transition in the transport sector. To achieve the new recycling targets introduced by the European Union in 2023, mechanical recycling in combination with hydrometallurgical treatment is the one option that gains more and more importance. The investigated process employs a two-stage comminution, classification and separation process. This thesis focuses only on the first stage and investigates possible variations of input materials and machine settings as well as an additional subprocess and their impact on the products. The varied parameters are the depth of discharge of the battery cells, an additional thermal pre-treatment at different temperatures, a variation of the crusher discharge grid size and the drying temperature after crushing. Furthermore, the robustness of the process was tested with various cell types to ensure its effectiveness with different inputs. Generally speaking, the process consists of a comminution followed by drying and separation of the liberated coatings by sieving as so-called black mass. The coarse fraction is further treated by air classification to produce three products: separator, electrodes and casing fraction. The influence of the different parameters is analysed regarding the crushing in terms of required specific stress energy and particle size distribution of the crushing product. The products of the air classifier and the black mass are analysed regarding their composition to evaluate the product quality and to calculate the recovery rates. Finally, recommendations are given for an optimisation of this part of the mechanical recycling process.:1. Introduction
2. Lithium-ion batteries
3. Mechanical recycling of lithium-ion batteries
3.1. Legal conditions
3.2. Market situation
3.3. Health and safety
3.4. Processing
3.4.1. Discharge
3.4.2. Comminution
3.4.3. Thermal treatment
3.4.4. Separation
3.4.5. Hydrometallurgy
4. Materials, methodology and preliminary tests
4.1. Materials
4.1.1. Investigated cell types
4.1.2. Materials for preliminary tests
4.1.3. Materials used in the publications
4.2. Methodology and preliminary tests
4.2.1. Recycling process and machines
4.2.2. Analysis Methods
4.2.3. Calculations
5. Data
6. Conclusion and outlook
References
Publications
AppendixDie vorliegende Arbeit befasst sich mit dem mechanischen Recycling von Lithium-Ionen-Batterien, genauer gesagt mit den Einflüssen auf die erste Prozessstufe des an der TU Bergakademie Freiberg entwickelten Verfahrens.
Das Recycling von Lithium-Ionen-Batterien wird mit der zunehmenden Anzahl von Elektrofahrzeugen aufgrund des Wandels im Verkehrssektor immer wichtiger. Um die neuen Recyclingziele der Europäischen Union zu erreichen, gewinnt das mechanische Recycling in Kombination mit einer hydrometallurgischen Behandlung immer mehr an Bedeutung. Der untersuchte Prozess basiert auf einem zweistufigen Zerkleinerungs- und Trennungsverfahren. Diese Arbeit konzentriert sich nur auf die Primärstufe und untersucht mögliche Variationen des Inputs und der Einstellungen sowie die Erweiterung um einen zusätzlichen Teilprozess und die sich daraus ergebenen Auswirkungen auf die Produkte. Die veränderten Parameter sind die Entladetiefe, eine zusätzliche thermische Vorbehandlung bei unterschiedlichen Temperaturen, eine Variation der Rostweite im Austrag des Zerkleinerers und die Trocknungstemperatur nach dem Zerkleinern. Zusätzlich wird der Prozess mit verschiedenen Zelltypen auf seine Robustheit bei unterschiedlichen Aufgabematerialien getestet. Der Prozess besteht aus einer Zerkleinerung mit anschließender Trocknung und einer Abtrennung der aufgeschlossenen Beschichtungen durch Absiebung als so genannte Schwarzmasse. Die Grobfraktion wird mit einer Aerostromsortierung weiterverarbeitet, um drei Produkte zu erzeugen: Separator-, Elektroden- und Gehäusefraktion. Der Einfluss der verschiedenen Parameter auf die Zerkleinerung wird im Hinblick auf die erforderliche spezifische Beanspruchungsenergie und die Partikelgrößenverteilung des Zerkleinerungsprodukts analysiert. Die Produkte des Windsichters und die Schwarzmasse werden hinsichtlich ihrer Zusammensetzung analysiert um die Produktqualität zu bewerten und das Wertstoffausbringen zu berechnen. Abschließend werden Empfehlungen für eine Optimierung des mechanischen Recyclingprozesses gegeben.:1. Introduction
2. Lithium-ion batteries
3. Mechanical recycling of lithium-ion batteries
3.1. Legal conditions
3.2. Market situation
3.3. Health and safety
3.4. Processing
3.4.1. Discharge
3.4.2. Comminution
3.4.3. Thermal treatment
3.4.4. Separation
3.4.5. Hydrometallurgy
4. Materials, methodology and preliminary tests
4.1. Materials
4.1.1. Investigated cell types
4.1.2. Materials for preliminary tests
4.1.3. Materials used in the publications
4.2. Methodology and preliminary tests
4.2.1. Recycling process and machines
4.2.2. Analysis Methods
4.2.3. Calculations
5. Data
6. Conclusion and outlook
References
Publications
Appendi