Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 56 for “"x-ray absorption spectroscopy (XAS)"”.
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Scanning transmission electron microscopy (STEM) and X-ray absorption spectroscopy (XAS) investigations of catalytic systems
… metal nanoparticles using, predominantly, X-ray absorption spectroscopy (XAS) and scanning transmission electron microscopy (STEM) or spherical aberration-corrected STEM (Cs-STEM). Although the majority of the work focuses on γ-Al2O3 supported nanoparticles because of their industrial …
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Ozone Decomposition and Acetone Oxidation on Manganese Oxide Catalysts
… through various techniques, including x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS), Brunauer-Emmett-Teller (BET) surface area analysis, temperature-programmed reduction (TPR), and oxygen chemisorption. The use of these techniques allowed better understanding of the nature …
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OPERANDO X-RAY ABSORPTION SPECTROSCOPY STUDIES OF (PHOTO)ELECTRODE MATERIALS FOR H2 PRODUCTION/CONVERSION
… (SEM), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) analysis. (2) The electrochemical performance, reaction mechanism, charge transfer kinetics, and overpotential of the synthesized electrodes were rigorously …
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Organocobalt Mediated Cyclizations and Biochemically Inspired Isomerizations - Method Development and Mechanistic Studies.
This dissertation describes research on a wide array of topics. Chapter one follows closelya review publication from our group which details the synthetic and mechanistic progress in the literature from the early to mid-2010s of the Pauson-Khand Reaction(PKR). Chapter two focuses on our work …
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A Theoretical and Experimental Investigation of the Physical and Chemical Properties of Solid Nanoscale Interfaces
… surfaces. Secondly, the detailed analysis of x-ray absorption spectroscopy (XAS), scanning transmission electron microscopy (STEM), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements will be presented. These investigations will be dedicated to the study of (i) …
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Phosphate and thermal stabilization of heavy metals in dredged sediments
… addition and thermal treatment at 700 C. X- ray absorption spectroscopy (XAS) in combination with principal component analysis, target transformation, and linear combination revealed that in the untreated sediments Zn precipitated as the relatively soluble smithsonite (ZnCO_3) (67%) and …
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X-ray absorption spectroscopy of actinide speciation in solid solutions
… to a wide range of conditions is required. X-ray absorption spectroscopy (XAS), a nondestructive technique that is ideal for determining the molecular composition of materials in dilute quantities in solution and solid forms, was used to determine the speciation of actinides in various solid …
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A comparative study of PtCo/C Alloys and Pt/C as cathode catalysts for fuel cell applications
… Transmission Electron Microscopy (TEM) and X-ray absorption spectroscopy (XAS).<br/><br/>XAS has also been used to explore the relationship between catalyst activity and structure. This has been achieved by building and validating a specially adapted fuel cell, enabling study of fuel cell …
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Structural and chemical characterization of complex nanomaterials at atomic resolution
… Pt catalysts supported on γ-Al2O3 using X-ray absorption spectroscopy (XAS) and scanning transmission electron microscopy (STEM) revealed non-bulk-like behavior. Anomalous, temperature-dependent structural dynamics were characterized in the form of negative thermal expansion (NTE) and …
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Defect Engineering in Cuprous Oxide (Cu₂O) Solar Cells
… junction. Then, I apply synchrotron-based X-ray absorption spectroscopy (XAS) to characterize two front contact buffer materials: amorphous Zn-Sn-O (a-ZTO) and Sndoped Ga₂O₃. I elucidate a fundamental loss mechanism in the amorphous Zn-Sn-O (a-ZTO) electron-blocking layer that has origin in …
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Sintesi e caratterizzazione di nanocompositi aerogel altamente porosi per applicazioni catalitiche
… involving conventional techniques, such as X-ray diffraction (XRD), nitrogen physisorption at 77 K and transmission electron microscopy (TEM), associated with more advanced techniques such as X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy and SQUID magnetometry. These …
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Structure and Dynamics in Ligand-Protected and Supported Metal Nanoparticles
This dissertation describes the use of x-ray absorption spectroscopy (XAS) and advanced electron microscopy methods to develop fundamental understandings of nanoparticle structure. Analysis of the x-ray absorption spectra provides structural information with 0.001 A precision. Quantitative …
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Development of new pyrochlore-type electrocatalysts for oxygen evolution reaction in acid
… and stability. To explain this behavior, X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations were used to study the electronic and structural properties of these materials. Additionally, a range of iridium-based pyrochlores with lanthanide (La) series metals …
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URANYL DEPOSITION IN UNCONFORMITY-RELATED DEPOSITS IN THE ATHABASCA BASIN: EVIDENCE FROM URANIUM SPECIATION IN HEMATITE AND GOETHITE
… (up to 2.16 wt.% UO3). Synchrotron U L3-edge X-ray absorption spectroscopy (XAS) and U 4f X-ray photoelectron spectroscopy (XPS) analyses show that uranium in hematite occurs dominantly as the uranyl species, providing unambiguous evidence for direct uranyl deposition in the Athabasca basin. …
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Comparative Analysis and Speciation of Sulfur K, L-edge X-ray Absorption Spectroscopy
… state ranging from -2 to +6, using K-edge X-ray absorption spectroscopy is particularly useful for determining oxidized species. There are, however, limitations on the ability to visually resolve spectra for reduced and mixed sulfur compounds using the K-edge that may be better resolved using …
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Heavy metal adsorption on iron oxide and iron oxide-coated silica : macroscopic, spectroscopic, and modeling studies
… affected metal affinity to the coated media. X-ray absorption spectroscopy (XAS) analysis revealed that both Ni(II) and Pb(II) ions form mononuclear bidentate edge-sharing surface complexes on FeO_6 octahedra. This mechanism appeared to be invariant of pH, ionic strength, metal loading, and …
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Study of the Valence Tautomer Complex [Co(sq)(cat)(3-tpp)2] for Applications in Molecular Spintronics
… used to characterize the VT thin films include X-ray Absorption Spectroscopy (XAS), UV-visible Spectrometry (UV-Vis) and Differential Scanning Calorimetry. Experimental results obtained from these techniques are discussed and analyzed in the third section. PVDF-HFP polarization dependent …
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The stress and strain behavior of materials for energy storage and production
… bond distance changes are iii examined via X-ray Absorption Spectroscopy (XAS), in particular Extended X-ray Absorption Fine Structure (EXAFS), and also with same tabletop surface stress measurement mentioned previously. The tabletop method shows loose quantitative agreement with the EXAFS …
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Studying the kinetics and mechanism of the formation and degradation of electrocatalysts using in situ characterization techniques
… transmission electron microscopy (LTEM) and x-ray absorption spectroscopy (XAS) are presented. More specifically, this chapter aims to explain the fundamentals that enable the material characterizations by in situ LTEM and XAS and showcase the capability and usefulness of those two techniques …
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Understanding Structure-Property Relationships for Palladium-Gold Nanoparticles as Colloidal Catalysts
… better catalysts than monometallic Pd ones. X-ray absorption spectroscopy (XAS) of carbon-supported Pdf Au NPs with different surface Pd coverages verified their core-shell structure (Au-rich core and Pdrich shell). Structure evolution was observed upon heat treatment, in which Pd was in the …
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