Natural nanominerals are abundant in Earth's critical zone and important in innumerable environmental processes that affect water quality. The chemical behavior of many natural nanominerals is related to their extreme small size (<10 nm) and high surface area. Atomic structural and chemical heterogeneity are also important factors affecting nanoparticle reactivity, and are a consequence of the mechanisms and complex (natural) conditions by which they form. The relationships between these factors remain poorly understood and limit our ability to predict the formation, transformation, and chemical behavior of natural nanominerals in the environment. We are using a poorly crystalline ferric hydroxysulfate nanomineral, schwertmannite, as a model system to understand the effect of formation conditions, specifically solution chemistry, on its physico-chemical characteristics. Previous studies indicate schwertmannite has highly variable bulk sulfate (Fe/S molar from 3-15) and water contents (Caraballo et al., 2013). In addition, both natural and synthetic schwertmannites have recently been described as "polyphasic" (i.e., consisting of sulfate-poor, goethite-like ordered domains embedded in a sulfate-rich, amorphous material) from observations using transmission electron microscopy (French et al., 2012). We hypothesize that solution chemistry at the time of schwertmannite formation directly affect its composition and structure. Using a factorial experiment design, we investigated the effects of increasing solution sulfate concentration ([SO4]/[Fe] at 1, 2, 3 and 5) and pH (2.4-5.6) on the crystallinity and composition of the products. Ferric hydroxide and hydroxysulfate solids were precipitated in batches by the rapid oxidation of Fe(II) by hydrogen peroxide, similar to what is seen in natural environmental systems. Sulfate and hydroxide concentrations were varied by addition of NaSO4 and NaOH, respectively. Solids were characterized using synchrotron X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), inductively coupled plasma-mass spectrometry (ICP-MS), scanning electron microscopy (SEM), and high resolution- transmission electron microscopy (HR-TEM). Our results show that schwertmannite is the only precipitate formed at low pH and that goethite rapidly becomes dominant at pH > 3.5. High-resolution TEM showed our synthetic schwertmannite samples consist of poorly crystalline goethite-like nanodomains within an amorphous solid, similarly seen in previous results. ICP-MS results reveal a narrow Fe/S molar ratio of 4.5 ±0.1 for our synthetic schwertmannite, which suggests that schwertmannite chemical composition does not depend strongly on pH or initial solution sulfate concentration. Increasing pH from 2.4 to 3.2 also has little effect on the crystallinity, bulk Fe/S ratio and water contents of schwertmannite. Increasing solution [SO4]/[Fe] also has little to no impact on crystallinity, water content or the amount of sulfate incorporated in schwertmannite. Thus, schwertmannite crystallinity and composition is not affected by initial solution sulfate and concentration under our experimental conditions. Thermal analysis allows us to independently measure OH and SO4 content in synthetic schwertmannite. In doing so, we propose a more accurate chemical formula (Fe8Oz(OH)24-2z-2x(SO4)x). The average stoichiometry based on thermal analysis of schwertmannite precipitated at [SO4]/[Fe] = 1 and pH ranging from ~2.4 2.9 is Fe8O6.51(OH)8.4(SO4)1.28. Interestingly, the calculated number of moles of oxygen is less than 8, which suggests that the standard formula Fe8O8(OH)8-2x(SO4)x is incorrect. These results for synthetic samples provide important constraints for future studies aimed at better understanding the formation, compositional variability and chemical behavior of natural schwertmannite. / Master of Science

Yes / Aluminium alloys are widely used structural materials in automotive, aerospace, and transportation, among several other notable industries. However, aluminium alloys' low hardness and poor tribological performance prevent potential use in applications requiring high contact pressures and wear resistance. This paper presents a novel two-step technique for enhancing the mechanical properties of the aluminium alloy by impregnating the surface with Ni-coating containing hard TiO2 nanoparticles using a high-intensity electric arc generated during tungsten inert gas welding. The results show that the process significantly changes the Microstructure and mechanical properties. The surface hardness increased from 0.48 GPa to 0.65 GPa with a corresponding change of Young's modulus from 15 GPa to 24 GPa of the treated surface.

Zahlreiche Geräte, die in den Naturwissenschaen, in der Industrie und im Gesundheitswesen unverzichtbar sind, basieren auf Strahlen schneller geladener Teilchen. Dazu zählen unter anderem Elektronen- und Ionenmikroskope, entsprechende Lithographiestrahlanlagen und Röntgenstrahlungsquellen. Magnetische Optiken, die Strahlen geladener Teilchen ablenken, formen und fokussieren, sind das Rückgrat aller Geräte die mit hochenergetischen Teilchen arbeiten, da sie im Vergleich zu Optiken, die auf elektrischen Feldern basieren, bei hohen Teilchengeschwindigkeiten eine überlegene optische Leistung aufweisen. Konventionelle makroskopische magnetische Optiken sind jedoch groß, teuer und platzraubend, nicht hochfrequenzfähig und erfordern aktive (Wasser-)Kühlung zur Wärmeabfuhr. Sie sind daher für Mehrstrahlinstrumente, miniaturisierte Anwendungen und schnelle Strahlmanipulation ungeeignet, die für zukünftige Fortschritte in der Nanofabrikation und -analyse gebraucht werden. Im Rahmen dieser Arbeit wurden die ersten magnetischen selbst-assemblierenden Mikro-Origami-Elektronenoptiken entwickelt, hergestellt und charakterisiert. Mit dem verwendeten Miniaturisierungsansatz können, bei ähnlicher optischer Leistung, alle oben genannten Nachteile von konventionellen magnetischen Optiken überwunden werden. Die außergewöhnlichen Eigenschaften dieser optischen Elemente werden durch die einzigartigen Merkmale der Mikrospulen ermöglicht: geringe Größe, geringe Induktivität und geringer Widerstand. Im Rahmen dieser Arbeit wurden unter anderem adaptive Phasenplaen hergestellt, die Elektronenvortexstrahlen mit einem bislang unerreichten Bahndrehimpuls von bis zu mehreren 1000 ̄h erzeugen. Des Weiteren wurden schnelle Elektronenstrahldeflektoren zur Strahlablenkung, zum zweidimensionalen Rastern und für stroboskopische Experimente gefertigt. Sie besitzen eine Ablenkleistung im mrad-Bereich für 300 kV Elektronen und einen Frequenzdurchgang bis zu 100 MHz. Darüber hinaus wurden miniaturisierte adrupollinsen mit Brennweiten kleiner als 46 mm für 300 kV Elektronen entwickelt. Diese drei Arten elektronenoptischer Elemente sind von großem Interesse für verschiedenste Anwendungen in der Nanofabrikation und -analyse, da sie unter anderem als integrale Bestandteile von zu entwickelnden Mehrstrahlinstrumenten, miniaturisierten Geräten und stroboskopischen Messaufbauten dienen können.:1 Introduction 1.1 Charged Particle Optics 1.2 Miniaturized Charged Particle Optics 1.3 Phase Plates for Transmission Electron Microscopy 2 Charged Particle Optics 2.1 Hamiltonian Formalism 2.2 Gaussian Matrix Optics 2.3 Transfer Matrices of Magnetic Elements 2.3.1 Single Quadrupole 2.3.2 Quadrupole Multiplets 2.3.2.1 Quadrupole Doublet 2.3.2.2 Quadrupole Triplet 2.3.2.3 Higher Order Quadrupole Multiplets 2.4 Scaling Laws for Charged Particle Optics 2.4.1 Thin Film 2.4.2 Electrostatic Scaling Laws 2.4.3 Magnetic Scaling Laws 3 Design and Fabrication of Miniaturized Electron Optics 3.1 Basics of Polymer-Based Self-Assembly Technology 3.2 Basic Coil Design and Magnetic Field Simulations 3.3 CoFeSiB-Pyrex Core-Shell Micro Wires 3.4 Fabrication of Self-Assembled Micro Coil Devices 4 Optical Properties of Self-Assembled Miniaturized Electron Optics 4.1 Electron Vortex Phase Plate 4.1.1 Projected Magnetic Fields 4.1.2 Vortex Beam Characteristics 4.2 Miniaturized Deflector 4.3 Quadrupole Focusing Optic 4.4 High Frequency Characteristics of Self-Assembled Electron Optics 5 Summary and Outlook 5.1 Applications of Electron Vortex Beams with Large OAM 5.2 Optics of Large Optical Power for Pulsed Instruments 5.3 Stroboscopic TEM Measurements 5.4 Miniaturized Wigglers, Undulators and Free Electron Lasers 5.5 Towards Integrated Electron Optical Systems / Beams of highly accelerated charged particles are essential for numerous indispensable devices used throughout natural sciences, industry and the healthcare sector, e.g., electron and ion microscopes, charged particle lithography machines and X-ray radiation sources. Magnetic charged particle optics that deflect, shape and focus high-energy charged particles are the backbone of all such devices, because of their superior optical power compared to electric field optics at large particle velocities. Conventional macroscopic magnetic optics, however, are large, costly and bulky, not high frequency capable and require active cooling for heat dissipation. They are therefore unsuitable for fast beam manipulation, multibeam instrumentation, and miniaturized applications, much desired for future advances in nanofabrication and analysis. The first on-chip micro-sized magnetic charged particle optics realized via a self-assembling micro-origami process were designed, fabricated and characterized within the frame of this work. The utilized micro-miniaturization approach overcomes all the aforementioned obstacles for conventional magnetic optics, while maintaining similar optical power. The exceptional properties of these optical elements are rendered possible by the unique features of strain-engineered micro-coils: small size, small inductance and small resistivity. Within the frame of this work, adaptive phase plates were fabricated, which generate electron vortex beams with an unprecedented orbital angular momentum of up to several 1000 ̄h. Furthermore, fast electron beam deflectors for beam blanking, two-dimensional scanning and stroboscopic experiments were manufactured. They possess a deflection power in the mrad regime for 300 kV electrons and a high frequency passband up to 100 MHz. Additionally, miniaturized strong quadrupole lenses with focal lengths down to 46 mm for 300 kV electrons have been developed. These three types of electron optical elements are of great interest for a wide range of applications in nanofabrication and analysis, as they serve as integral components of future multibeam instruments, miniaturized devices, and stroboscopic measurement setups to be developed.:1 Introduction 1.1 Charged Particle Optics 1.2 Miniaturized Charged Particle Optics 1.3 Phase Plates for Transmission Electron Microscopy 2 Charged Particle Optics 2.1 Hamiltonian Formalism 2.2 Gaussian Matrix Optics 2.3 Transfer Matrices of Magnetic Elements 2.3.1 Single Quadrupole 2.3.2 Quadrupole Multiplets 2.3.2.1 Quadrupole Doublet 2.3.2.2 Quadrupole Triplet 2.3.2.3 Higher Order Quadrupole Multiplets 2.4 Scaling Laws for Charged Particle Optics 2.4.1 Thin Film 2.4.2 Electrostatic Scaling Laws 2.4.3 Magnetic Scaling Laws 3 Design and Fabrication of Miniaturized Electron Optics 3.1 Basics of Polymer-Based Self-Assembly Technology 3.2 Basic Coil Design and Magnetic Field Simulations 3.3 CoFeSiB-Pyrex Core-Shell Micro Wires 3.4 Fabrication of Self-Assembled Micro Coil Devices 4 Optical Properties of Self-Assembled Miniaturized Electron Optics 4.1 Electron Vortex Phase Plate 4.1.1 Projected Magnetic Fields 4.1.2 Vortex Beam Characteristics 4.2 Miniaturized Deflector 4.3 Quadrupole Focusing Optic 4.4 High Frequency Characteristics of Self-Assembled Electron Optics 5 Summary and Outlook 5.1 Applications of Electron Vortex Beams with Large OAM 5.2 Optics of Large Optical Power for Pulsed Instruments 5.3 Stroboscopic TEM Measurements 5.4 Miniaturized Wigglers, Undulators and Free Electron Lasers 5.5 Towards Integrated Electron Optical Systems

The filiform-like corrosion of Magnesium (Mg) alloys AZ31B and AM30 was investigated with electrochemical and microanalytical techniques. Potentiodynamic polarization testing and scanning vibrating electrode technique (SVET) measurements confirmed the “differential electrocatalytic” mechanism previously reported for filiform and filiform-like corrosion on pure Mg and AZ31B. Transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) revealed that the MgO corrosion filaments on both alloys were likely a product of the direct reaction of Mg and water (H2O), responsible for the rapid hydrogen (H2) evolution observed at the propagating corrosion fronts. TEM analysis also revealed through-thickness cracks and noble intermetallic particles within the corrosion filaments and noble metal enrichment at the corrosion filament/metal interfaces, which were proposed to play significant roles in the cathodic activation of the corrosion filaments. The higher susceptibility of the AZ31B alloy to cathodic activation versus AM30 suggested that Zinc (Zn) has a detrimental effect on the resistance of Magnesium-Aluminum-Zinc (Mg-Al-Zn) alloys to filiform and filiform-like corrosion. / Thesis / Master of Applied Science (MASc)

First devised over half a century ago, metal-on-polyethylene (MoP) hip prostheses have become the gold standard for total hip arthroplasty (THA), a surgical intervention for degenerative hip joint conditions. The accumulation of polyethylene wear debris after long-term, in vivo articulations, can induce adverse cellular reactions, osteolysis and aseptic loosening of the implant – ultimately resulting in the failure of the THA. Despite the distinct differences between the biotribology of MoP and MoM prostheses, there is a lack of congruent high resolution research investigating the biotribological interactions and surface structures of MoP hip prosthesis components. This study characterized the surface and subsurface microstructural changes in failed MoP hip prosthesis retrievals using advanced electron microscopy techniques. The samples were comprised of retrieved metallic cobalt-chromium-molybdenum (CoCrMo) alloy femoral head components, one ultra-high molecular weight polyethylene (UHMWPE) acetabular cup component, and unused CoCrMo reference samples. The surface of the reference samples contained linear, parallel, uniform scratches as a result of the manufacturing process; whereas the surface of the retrieval samples were covered in an abundance of scratches and a layer of residual deposits, attributable to in vivo articulation of the implant. Characteristic hard phases were observed and examined on the surface and from the cross-sectional preparation of the cast CoCrMo samples. The multiphasic hard phases on the cast samples can strengthen the material but also be sites of crack propagation and material detachment, contributing to the generation of wear particles. Lastly, a nanocrystalline layer, 20 to 400 nm in thickness was observed in the subsurface microstructure of all samples (including references). Previous MoM studies suggest that the nanocrystalline layer is a result of dynamic crystallization in response to multidirectional, chronic loading in vivo, however, the presence of the layer in the unimplanted references suggest that the nanocrystalline layer can be formed during the production of the prosthesis component and therefore, pre-exists implantation. The imperfections on new, unused implants can have protective effects (e.g. troughs from scratches can be a reservoir for wear debris) but may influence in vivo wear processes after implantation (e.g. scratches may be a source of wear debris). Higher resolution analyses on more retrieval and reference samples are required to pinpoint the exact mechanism of failure in MoP hip prostheses and extend the longevity and efficacy of THA. / Thesis / Master of Applied Science (MASc)

The localised corrosion behaviour of various grades of Austenitic Stainless Steels has been demonstrated by optical and electron microscopy. The effect of sensitisation upon subsequent corrosive attack has been investigated. A theoretical model based upon thermodynamic and kinetic considerations has been proposed to account for the observed experimental results. / Thesis / Master of Engineering (ME)

Scanning Electron Microscopy combined with Energy Dispersive X-ray Spectroscopy (SEM-EDS) is a widely applied elemental microanalysis method. The integration of silicon drift detectors (SDDs) has notably enhanced EDS performance, enabling precise elemental identification due to its large sensitive area and low output capacitance.  Accurate simulations of SDDs can provide insights that enable the design and optimization of future models without the need for costly and time-consuming experimental iterations. Moreover, the current model-based quantification methods for EDS applications have reached their maximum predictive accuracy. As such, creating a more accurate simulation model could help achieve a higher level of precision in these quantification models, which would be immensely valuable for all EDS applications.  With this objective in mind, a simulation framework for modeling SDDs in EDS was developed based on Geant4, Allpix Squared, and COMSOL Multiphysics. The simulation encompasses the entire physics pipeline, including characteristic X-ray emission from the target sample and its absorption in the detector. The generated charge carriers within the detector are propagated through the internal electric field of the SDD, and their individual charge contribution is measured to simulate EDS spectra. The simulated model was compared to existing literature and in-house experimental measurements, showing strong agreement in the case of a well-tuned SDD. Limitations of the simulation framework are discussed, and further research to enhance accuracy and speed is explored.

Ion channels are fundamental to the functioning of life, regulating processes as diverse as neural signaling, homeostasis, and environmental sensing, across the complexities of life from bacteria to the most advanced organisms. Among this vast diversity of ion channels, cyclic-nucleotide gated (CNG) channels hold particular significance and play a pivotal role in the sensory transduction across a variety of species. They transduce chemical signals into electrical signals, linking the external environment and our sensory perceptions. CNG channels were discovered almost 40 years ago and much knowledge has been gained on their physiological roles, biophysical properties, molecular characteristics, and channelopathies. However, the structural details of these channels remained elusive for a long time, mainly due to the lack of a full-length channel structure. It was only recently that atomic-resolution structures of full-length CNG channels became available, and structures of native mammalian CNG channels were only determined within the last two years. In my thesis, I use single particle cryogenic electron microscopy (cryo-EM) to determine the structures of native human cone CNGA3/CNGB3 channel in different biochemical environments and in different states, spanning the full spectrum of channel activation by its natural ligand cGMP. In addition, I use cryo-EM, electrophysiology, calcium imaging, and other biochemical techniques to characterize both wild-type and disease-associated mutant (DAM) CNG channels. Collectively, my thesis work contributes to a deeper understanding of the structural determinants of CNG channel properties, provides a detailed dissection of the CNG channel gating mechanism, demonstrates a potential CNG channel pathogenic mechanism, and calls for an interdisciplinary reevaluation of CNG channel DAMs.

In this thesis, we present three novel algorithms. The first algorithm is a method of identifying numerical landmarks (a definition coined in this thesis). The second algorithm uses the projection of image regions onto x- and y- axes and the matching of the resulting 1D projections to determine an overall 2D translation for use in registration. The third algorithm aligns SEM images of successive layers of a semiconductor device by first extracting the positions of vias in the lower layer, and then searching for the best translation for subsets of vias such that they all or mostly connect to metalization in the upper layer. / To acquire high-resolution Scanning Electron Microscopy (SEM) images over wide areas, we must acquire several images ``tiling'' the surface and assemble them into a single composite image, using a process called image stitching. While for some applications, stitching is now routine, SEM mosaics of semiconductors pose several challenges: (1) by design, the image features (wire, via and dielectric) are highly repetitive, (2) the overlap between image tiles is small, (3) sample charging causes intensity variation between captures of the same region, and (4) machine instability causes non-linear deformation within tiles and between tiles. In this study, we compare the accuracy and computational cost of three well-known pixel-based techniques: Fast Fourier Transform (FFT), Sum of Squared Differences (SSD), and Normalized Cross Correlation (NCC). We compare well-known 2D algorithms, as well as novel projection-onto-1D versions. The latter reduces the computational complexity from O(n^2) to O(n), where n is the number of pixels, without loss of accuracy, and in some cases, with greater accuracy. Another approach to reducing the computational complexity of image alignment is to compare isolated landmarks, rather than pixels. In semiconductor images, there are no natural fiducials and adding them would destroy the information required to reconstruct their circuits, so we introduce a new class of landmarks which we call numerical landmarks. Related to Harris corners, the novel numerical landmarks are insensitive to brightness variations and noise. Finally, we consider the alignment problem between layers of image mosaics. Unlike in the ``horizontal'' directions, the vertical dimension is only sparsely sampled. Consequently, image features and landmarks cannot be used for alignment. Instead, we must rely on the relationship between vias (through-plane metalization) and wires (in-plane metalization), and we have developed a novel algorithm for matching vias in the lower layer with wires above, and use this to align subimages. / Thesis / Doctor of Philosophy (PhD) / Applications in materials science often require the acquisition of images of semiconductor computer chips at very high resolution. Using cameras with even tens of millions of pixels might not give us enough resolution over a wide field of view. One approach is to acquire several images of parts of the sample at high magnification and assemble them into a single composite image. This way, we can preserve the high resolution over a wide area. Algorithms developed for assembling the composite image are known as tiling or mosaicing. This whole process is known as image stitching (and includes image registration). In this thesis, we develop specialized algorithms suited for the 2D stitching of semiconductor images, including the generalization to 3D. This case is challenging because slight alignment errors may completely change the reconstructed circuit, and the images contain both repeated patterns (such as many parallel wires) and changes in brightness and distortions caused by the scanning device.

The application of the entropy concept to stabilize oxide systems opens the possibility of discovering new materials with unique structural and functional properties. High-entropy alloys and oxides, which are based on the entropy stabilization concept and composed of multi-principal elements, have the potential to tailor structural and functional properties to meet specific needs. The study of lanthanum-based perovskite materials that benefit from the entropy stabilization approach is a promising area of research.However, the inherent randomness of multi-principal elements presents new challenges, making it difficult to predict their behavior. To understand these difficulties, we have initiated a methodical investigation of La-based medium- and high-entropy perovskite oxides. This study focuses on the synthesis, characterization, sintering mechanism, and electrical conductivity properties of nine La1-xCax(A1/3, B1/3, C1/3)O3 medium-entropy perovskite oxide systems (A, B, and C = three combination of Cr or Co or Fe or Ni or Mn) and one La1-xCax(Cr0.2Co0.2Fe0.2Ni0.2Mn0.2)O3 high-entropy perovskite oxide system (for x = 0.1 to 0.3). This research aims to provide better understanding of: (1) synthesis process, (2) temperature of single-phase formation, (3) the impact of various combinations of multiple B-site transitional elements and Ca doping on crystal structure, and microstructure (4) sintering mechanism and (5) electrical conductivity properties.