In this thesis, two objectives related to Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy have been studied. The first objective was to develop surface sensitivity in Scanning Transmission X-ray Microscopy (STXM) at the Canadian Light Source (CLS) and the Advanced Light Source (ALS). The second objective was to study sulphur 1s NEXAFS spectra of organosulphur compounds relevant to petroleum by experimental and computational methods. Towards the first objective, Total Electron Yield (TEY) detection has been implemented in a STXM microscope, by conventional sample current and single electron counting detection modes. This provides improved surface-sensitive detection, simultaneous with existing bulk-sensitive transmission detection in the STXM microscopes. Both approaches provide improved surface sensitive imaging and spectroscopy, although channeltron-based detection is superior. TEY-STXM provides surface sensitive imaging of ultrathin films such as phase-separated Langmuir-Blodgett monolayer films, phase separated polymer thin films, as well as differentiation of surface and bulk oxides of patterned metal thin films. The challenge for TEY-STXM measurements is the poor vacuum environment in the STXM chamber at the CLS, which greatly impacts the function of the channeltron as well as the rate of the photodeposition. Although the effect of photodeposition can be minimal in bulk spectroscopy of organic samples, it is a challenge in spectroscopy of organic thin films, where the photodeposits can dominate the weak signal originating from the surface. Chapter 4 of this thesis discusses the details of this study along with the challenges encountered in the development of this new TEY-STXM technique. The second goal of my research was the detailed study of sulphur 1s NEXAFS spectra of organosulphur compounds by experimental and computational methods to obtain a complete database of sulphur 1s NEXAFS spectra. The speciation and quantification of sulphur compounds is of great interest in different areas such as fossil fuel studies, biology, geology, and archaeology. Sulphur 1s NEXAFS spectroscopy can be used for speciation and quantification of these compounds. For this purpose a firm understanding of NEXAFS spectra of sulphur compounds is required. Therefore, the sulphur 1s NEXAFS spectra of different sulphur functionalities have been studied including thiols, thioethers, disulphides, sulfoxides, sulfones, and thiophenic compounds in gas and condensed phases. These highly resolved spectra have been further analyzed with the aid of ab initio calculations. The highly resolved experimental spectra showed fine features predicted by calculations. The combination of experiment and calculation has been used to improve assignment of spectroscopic features relevant for the speciation and quantification of sulphur compounds.

Energy storage systems such as batteries and supercapacitors store electrical energy in the form of chemical energy and release it when required. Among the various electrode materials, manganese oxides (MnOx) are promising electrode materials for these devices. Despite its outstanding theoretical capacitance, Mn-based oxide electrodes have several limitations that impede their electrochemical performance. Understanding how the charges are efficiently stored in the electrodes or across the electrode/electrolyte interface is crucial for developing advanced electrode material in the field of energy storage applications. The goal of my thesis is to develop and apply synchrotron-based scanning transmission X-ray microscopy (STXM) to investigate changes in the oxidation state of Mn and their spatial distributions in MnOx electrodes in the context of energy storage and release. To achieve high- precision qualitative and quantitative STXM identification and mapping of different MnOx species, calibrated and high-quality reference Mn 2p and O 1s NEXAFS (near edge X-ray absorption fine structure) spectra were measured. In collaboration with Wenjuan Yang and her PhD supervisor, Prof. Igor Zhitomirsky, I performed ex-situ STXM studies on Mn3O4-based supercapacitor electrode materials to investigate the influence of different synthesis methods and activation protocols on the charging behavior and capacitance performance. In collaboration with Pablo Ingino and his supervisor, Prof. Martin Obst (Bayreuth University), and my colleague, Dr. Chunyang Zhang, I helped develop a three-electrode, microfluidic-based flow electrochemical device for in-situ STXM. This device was used to electrodeposit MnO2 on the working electrode (WE) and track the oxidation state and morphological changes by STXM while scanning the potential of the cell in different electrolyte pH. The in-situ STXM studies showed a spontaneous reduction of the initially deposited MnO2 resulting from the local pH change at the WE. Additionally, a significant change from a quasi-uniform MnO2 film to a dendritic MnO2 structure was observed at oxidative potential. This dendritic growth resulted from dissolution/redeposition of MnO2 during charging/discharging processes, indicating a partial reversibility of dissoluble Mn species. The ex-situ and in-situ STXM studies I performed provide mechanistic insights that will help further improve Mn oxides-based electrodes and their applications as energy storage devices. / Thesis / Doctor of Philosophy (PhD)

One of the critical challenges in the Canadian oil sand industry is improving processes used to separate bitumen from oil sands and to remove clay particulates from produced oil. The fine clay particles are believed to play a significant role in the oil sands industry, from stabilizing process emulsions to fouling problems in water treatment. Addressing the problems caused by these fine clay particulates is limited by the ability to characterize the hydrocarbon-clay interactions. Scanning Transmission X-ray Microscopy (STXM) is used to study hydrocarbon-clay interactions in controlled model systems, where all components are known, and in process samples extracted from oil sands. To use STXM to study our desired systems, many experimental developments were required. Well developed sample preparation was needed to provide samples free from contaminants and experiments free of artifacts. Clean clays, free of extraneous carbon were required for model studies. A device to reduce photodeposition in the STXM chamber was also required to examine interactions of hydrocarbons on clay surfaces. <p>Using these developments, Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of model clays and model hydrocarbon mixtures were recorded using the STXM microscope on beamline 5.3.2 at the Advanced Light Source, in Berkeley CA. Using NEXAFS spectroscopy in conjunction with the STXM microscope, allowed us to explore preferential interactions between specific hydrocarbon and fine clay particles (smaller than 1 µm) in our model studies. We were also able to assess the chemistry of the hydrocarbons before association with the clay particles. <p>Process samples, consisting of a set of four bitumen froths extracted from the oil sands were investigated. The carbon chemistry of the froths was assessed and quantitatively analyzed. The findings were correlated with previous confocal microscopy results from our collaborators at CANMET Energy Technology Centre in Devon, Alberta.

One of the critical challenges in the Canadian oil sand industry is improving processes used to separate bitumen from oil sands and to remove clay particulates from produced oil. The fine clay particles are believed to play a significant role in the oil sands industry, from stabilizing process emulsions to fouling problems in water treatment. Addressing the problems caused by these fine clay particulates is limited by the ability to characterize the hydrocarbon-clay interactions. Scanning Transmission X-ray Microscopy (STXM) is used to study hydrocarbon-clay interactions in controlled model systems, where all components are known, and in process samples extracted from oil sands. To use STXM to study our desired systems, many experimental developments were required. Well developed sample preparation was needed to provide samples free from contaminants and experiments free of artifacts. Clean clays, free of extraneous carbon were required for model studies. A device to reduce photodeposition in the STXM chamber was also required to examine interactions of hydrocarbons on clay surfaces. <p>Using these developments, Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of model clays and model hydrocarbon mixtures were recorded using the STXM microscope on beamline 5.3.2 at the Advanced Light Source, in Berkeley CA. Using NEXAFS spectroscopy in conjunction with the STXM microscope, allowed us to explore preferential interactions between specific hydrocarbon and fine clay particles (smaller than 1 µm) in our model studies. We were also able to assess the chemistry of the hydrocarbons before association with the clay particles. <p>Process samples, consisting of a set of four bitumen froths extracted from the oil sands were investigated. The carbon chemistry of the froths was assessed and quantitatively analyzed. The findings were correlated with previous confocal microscopy results from our collaborators at CANMET Energy Technology Centre in Devon, Alberta.

In dieser Arbeit werden magnetische Vortex-Dreifachlagen-Systeme untersucht. Mittels Magnetfeld, Strom und Röntgenzirkulardichroismus kann erstmals die magnetische Konfiguration der Vortexlagen mit dem simultan gemessenen Magnetowiderstand verglichen werden. Die senkrecht mit Strom durchflossenen Kobalt-Kupfer-Permalloy Scheiben werden in einem Mehrschrittprozess mittels Elektronenstrahllithographie auf einer Membran hergestellt, um mit Rastertransmissions-Röntgenmikroskopie untersuchbar zu sein. Die Auswertung der STXM-Bilder zeigt das gleiche Verhalten wie die Widerstandsmessungen und erlaubt eine eindeutige Zuordnung. Um auch die kleinsten scheibenförmigen Dreifachlagensysteme mittels ferromagnetischer Resonanz zu messen, wurde die Mikroresonator FMR optimiert. Damit können bereits etwa 2.3*10^7 Kobaltatome gemessen werden, wobei die Empfindlichkeit bis zu 4*10^6 Atomen ausreichend sein sollte. Durch 6-fache Mittelung lässt sich ein Kobaltwürfel mit einer Kantenlänge von 12,5nm detektieren. Dabei sind nicht nur die uniforme Mode, sondern auch lokal angeregte Moden sichtbar. Mittels mikromagnetischer Simulationen lassen sich den Resonanzen Modenbilder zuordnen. Die scheibenförmige Dreifachlage wird mit den FMR-Messungen sowohl mit verringertem Durchmesser, als auch mit reduzierter Zwischenschicht untersucht.

Doctor of Philosophy / Department of Agronomy / Ganga M. Hettiarachchi / Soil carbon (C) sequestration has been recognized as one of the most effective potential mitigation options for climate change. Underlying mechanisms of soil C sequestration/preservation is poorly understood, even after decades of soil C research. The main research objectives of this dissertation were three-fold: (1) enhancing our understanding in mineralogical and physicochemical mechanisms of soil C sequestration in microaggregates, (2) understanding the chemistry of organic C sequestered in soil aggregates, and (3) to determine the resilience of C to different temperature-moisture regimes and physical disturbance in a six-month incubation. An integrated approach was used in obtaining a better picture on mechanisms of C preservation. Two long-term agroecosystems located at the North Agronomy Farm, Manhattan, KS (Mollisols) and the Center of Experimentation and Research Fundacep in Cruz Alta-RS, Brazil (Oxisols) were used. Main plots of both systems were till and no-till. Mollisols consisted of three fertilizer treatments; control, manure/compost and urea. Oxisols had three different crop rotations; simple, intermediate, and complex. Submicron level information gathered by spectromicroscopy approaches, identified the direct preservation of OC structures with the original morphology; suggesting that the preservation of OC is a primary mechanism of C sequestration in these soils. Physical protection and organo-mineral associations seemed to also be involved in OC preservation. Manure/compost addition and no-till favored labile C preservation in aggregates of Mollisols. Significant associations observed between reactive minerals and C pools in Mollisols indicated the significance of organo-mineral associations in OC preservation. Large microaggregates exerted strong C preservation through physical protection and organo-mineral associations. Unlike in Mollisols, Oxisols showed a poor correlation between reactive mineral fraction and organic C which indicated the significance of physical protection over organo-mineral associations. Resilience of sequestred C was significantly affected by temperature across both temperate and tropical soil ecosystems, directly and indirectly. High temperature influenced soil acidity and reactive minerals, ultimately affecting organo-mineral associations. Macromolecular propeties of humic acid fraction showed changes after six months. Overall, direct and indirect evidence from this study suggested that the preservation of SOC is an ecosystem property supporting the newly proposed theories in soil C dynamics.

<p> Micro- and nanoplastic (MNP ) particles are an increasing environmental concern related to the widespread uncontrolled degradation of various commercial products made of plastic materials and their associated waste disposal. Most frequently MNP particles are documented as pollutants in terrestrial, aquatic, and marine environments. Reports of MNP detected in snow samples from mountain glaciers in remote locations suggest their atmospheric transport. Recently, common technology used to repair sewer pipes was reported as one of the direct emission sources of airborne MNP in urban areas. This research reports on the multi-modal detailed chemical characterization of the MNP particles related to waste discharged in the repair process and compares MNP composition with the components of uncured resin and cured plastic material used in the process. Comprehensive analysis of these materials employed complementary use of surface-enhanced Raman spectroscopy, scanning transmission x-ray spectro-microscopy, single particle laser ablation time-of-flight mass spectrometry, and direct analysis in real-time high-resolution mass spectrometry. It is shown that the composition of the relatively large MP particles resembles components of plastic material used in the process. In contrast, composition of the NP particles is significantly different, suggesting their formation from unintended polymerization of water-soluble components occurring in drying droplets of the air-discharged waste. Results are further discussed to guide the detection and advanced characterization of NP particles in future field studies. </p>

Understanding electrically activated processes at electrode-electrolyte interfaces is needed to improve many technologies, including energy conversion, semiconductor devices, bio-sensors, corrosion protection, etc. In-situ spectro-electrochemical studies based on a wide range of spectroscopies are particularly useful. Scanning Transmission X-ray microscopy (STXM) is a synchrotron-based technique which measures near-edge X-ray absorption fine structure (NEXAFS) with high spatial resolution. In addition to information on morphology, STXM also provides chemical state analysis using the X-ray absorption data, which makes in-situ STXM studies of electrochemical process of special interest. This thesis reports ex-situ and in-situ STXM based qualitative and quantitative studies on copper (Cu) electrodeposition and electrostripping. The influence of electrolyte pH on the distribution of Cu(I) and Cu(0) species electrodeposited from aqueous CuSO4 solutions was studied. An instrument capable of performing in-situ flow electrochemical STXM studies was designed and fabricated. The performance of this device was evaluated for in-situ Cu electrodeposition studies. Findings based on ex-situ and in-situ STXM studies are discussed. Suggestions are made for further instrumentation improvements. / Thesis / Master of Science (MSc)

In dieser Arbeit werden magnetische Vortex-Dreifachlagen-Systeme untersucht. Mittels Magnetfeld, Strom und Röntgenzirkulardichroismus kann erstmals die magnetische Konfiguration der Vortexlagen mit dem simultan gemessenen Magnetowiderstand verglichen werden. Die senkrecht mit Strom durchflossenen Kobalt-Kupfer-Permalloy Scheiben werden in einem Mehrschrittprozess mittels Elektronenstrahllithographie auf einer Membran hergestellt, um mit Rastertransmissions-Röntgenmikroskopie untersuchbar zu sein. Die Auswertung der STXM-Bilder zeigt das gleiche Verhalten wie die Widerstandsmessungen und erlaubt eine eindeutige Zuordnung. Um auch die kleinsten scheibenförmigen Dreifachlagensysteme mittels ferromagnetischer Resonanz zu messen, wurde die Mikroresonator FMR optimiert. Damit können bereits etwa 2.3*10^7 Kobaltatome gemessen werden, wobei die Empfindlichkeit bis zu 4*10^6 Atomen ausreichend sein sollte. Durch 6-fache Mittelung lässt sich ein Kobaltwürfel mit einer Kantenlänge von 12,5nm detektieren. Dabei sind nicht nur die uniforme Mode, sondern auch lokal angeregte Moden sichtbar. Mittels mikromagnetischer Simulationen lassen sich den Resonanzen Modenbilder zuordnen. Die scheibenförmige Dreifachlage wird mit den FMR-Messungen sowohl mit verringertem Durchmesser, als auch mit reduzierter Zwischenschicht untersucht.

Dans le contexte de stockage des déchets radioactifs en profondeur, des interactions entre le fer métal d’une part et la roche du Callovo-Oxfordien (COx), sa fraction argileuse purifiée (SCOx) ou des phases argileuses pures (kaolinite, illite, smectites) d’autre part, sont réalisées à 90°C sous atmosphère anoxique en solution chlorurée-salée. Le rôle des minéraux non argileux du COx est également étudié. L'oxydation rapide du fer métal entraine une libération d’ions fer en solution, une augmentation du pH et une diminution du Eh (réducteur). Une dissolution partielle des phases argileuses ainsi que la précipitation de serpentines ferrifères (odinite ou berthiérine, principalement) et de magnétite en faible quantité sont alors observées. En cas d’apport d'O2 au système, les serpentines ferrifères sont déstabilisées. L'exsolution du fer permet la formation d'oxydes et d’hydroxydes de fer et des particules argileuses proches des phases initiales précipitent. Lorsque du quartz est ajouté à SCOx, la dissolution partielle de ce minéral est responsable de la modification des chemins réactionnels. La formation de magnétite est alors limitée et les serpentines ferrifères sont enrichies en silice. Dans le cas de la kaolinite, DRX, MET, XPS et analyses texturales mettent en évidence la croissance des serpentines ferrifères (berthierines majoritairement) sur la surface basale des kaolinites, formant des particules kaolinite-serpentines-Fe démixées. Les techniques spectroscopiques (Mössbauer, XAS et STXM) permettent de déterminer les rapports Fe2+/Fe3+ et AlIV/AlVI jusqu'au niveau des particules élémentaires et de proposer des formules structurales pour ces serpentines ferrifères / In the context of underground disposal of high-level radioactive waste, interactions between metallic iron and Callovo-Oxfordian rock (COx), its purified clay fraction (SCOx) or pure clay phases (kaolinite, illite, smectites) were investigated at 90°C under anoxic atmosphere in chlorine solution. Role of COx non clay minerals in these reactions was also studied. Rapid metallic iron oxidation conducts to iron cations release in solution, pH increase (8-10) and Eh decrease (reducive conditions). The partial dissolution of initial clay phases and the crystallization of Fe-serpentines (odinite or berthierine mainly) and of low amount of magnetite were observed. The introduction of O2 into the system leads to Fe-serpentines destabilisation. Iron exsolution conducts to iron oxides and hydroxides formation and clay particles with composition close to the initial ones precipitate. Addition of quartz into the system leads to the partial dissolution of this mineral and to the modification of reaction pathways. Precipitation of magnetite is reduiced and Fe-serpentines are silica enriched. In the case of kaolinite-metallic iron interaction, combinated used of XRD, MET, XPS and textural analyses evidences the growth of berthierine on the basal face of kaolinites, resulting in Fe-serpentine-kaolinite demixed particles. Through the used of spectroscopic analyses (Mössbauer, XAS and STXM), we were able to determine Fe2+/Fe3+ and AlIV/AlVI ratio in elementary particles, which allows proposing structural formulae for the Fe-serpentines