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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 33 for “"Oxide Phases"”.
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Reactive radio frequency sputtering of iron oxide thin films for electrical resistivity characterization
… useful semiconductors could be made in the iron oxide thin film system by controlling the ratio of Fe<sup>2+</sup> to Fe<sup>3+</sup> ions. For the added versatility of producing all of the oxide phases from one source (target), reactive (in an oxygen/argon atmosphere) sputtering was chosen. In …
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Oxyanion Adsorption by Iron and Ruthenium Oxides: A Macroscopic, Spectroscopic, and Kinetic Investigation
… was evaluated solids—goethite and ruthenium oxide. The importance of anion displacement as a mechanism responsible for arsenic release from iron oxides was investigated on goethite. The adsorption and polymerization of silicate on goethite was examined as a function of surface concentration …
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Composite cathodes for lithium rechargeable batteries
… of incorporating continuous, nanoscale vanadium oxide phases within preferred domains of self-organizing copolymers was investigated towards the fabrication of composite, nanoarchitectured electrode materials for solid-state rechargeable batteries. In situ growth of cathodic phases within …
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Mechanisms of metal release from contaminated coastal sediments
… The trace metals are scavenged by iron oxyhydroxides and released to the porewaters when these oxides are reduced. At the strongly reducing site in Boston Harbor, there is seasonal transfer of trace metals from oxide phases in winter, to sulfides phase in summer. At the Massachusetts Bay site, …
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Tracing past and present Arctic geochemical cycling and its link to climate change using neodymium isotopes
… A large compilation of εNd in authigenic phases of deep-sea sediments is used to investigate past changes in deep water sourcing and formation in the Nordic Seas from the last glacial to modern. During the Last Glacial Maximum, εNd in the Nordic Seas is found to have a similar homogeneity …
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Controls on arsenic mobility in contaminated wetland and riverbed streams
… strongly influenced by associations with solid phases. This dissertation investigates the mechanisms affecting arsenic retention in contaminated wetland and riverbed sediments. A sequential extraction procedure was designed and tested to differentiate solid phase arsenic speciation, including …
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Arsenic mobilization through bioreduction of iron oxide nanoparticles
… sorbs strongly to the surfaces of Fe(III) (hydr)oxides. Under aerobic conditions, oxygen acts as the terminal electron acceptor in microbial respiration and Fe(III) (hydr)oxides are highly insoluble, thus arsenic remains associated with Fe(III) (hydr)oxide phases. However, under anaerobic …
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First-principles simulations of the oxidation of methane and CO on platinum oxide surfaces and thin films
… from the presence of highly reactive superficial oxide phases which form under oxygen-rich reaction conditions. The thermodynamic stability of platinum oxide surfaces and thin films was studied, as well as their reactivities towards oxidation of carbon compounds by means of first-principles …
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Synthesis, properties, and morphology of lignin based epoxy resins
Star-like lignin-poly(propylene oxide) copolymers were prepared by chain-extending steam exploded lignins (tulipifera liriodendron) with propylene oxide and by subsequent endcapping with ethylene oxide. Epoxidation of these copolymers was carried out with epichlorohydrin at room temperature, using …
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Impact modification of Mercury's mantle composition
… consider the effects of multiple silicate and oxide phases. In this study, we extend the present theory by investigating the consequences of a more realistic chemical model on the evolution of the ejected material. We suggest that the majority of condensation within the expanding vapor plume …
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A study of internal oxidation in carburising steels
… in the free energy of formation of the various oxides types. The observed morphology of the internal oxidation zone at different carburised exposure time, in range of 0.25-16.6h, related to the penetration depth and density of the internal oxides in the internal oxidation zone, with particular …
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Mechanisms of metal release from contaminated coastal sediments
… The trace metals are scavenged by iron oxyhydroxides and released to the porewaters when these oxides are reduced. At the strongly reducing site in Boston Harbor, there is seasonal transfer of trace metals from oxide phases in winter, to sulfides phase in summer. At the Massachusetts Bay site, …
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Lead Sorption Efficiencies of Natural and Sunthetic Mn and Fe-oxides
… for a number of natural and synthetic Mn and Fe-oxides using a flow through reactor. The Mn-oxide phases examined included synthetic birnessite, natural and synthetic cryptomelane, and natural and synthetic pyrolusite; the Fe-oxides studied were synthetic akaganeite, synthetic ferrihydrite, …
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Influence of protozoan grazing on the marine geochemistry of particle reactive trace metals
… to determine the effect of grazers on mineral phases, specifically colloidal iron oxide (ferrihydrite). Several independent techniques were employed, including size fractionation ors9Fe-labeled colloids, competitive ligand exchange, and iron-limited diatoms as "probes" for bioavailable Fe. …
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Effect of polymorphic phase transformations within an alumina layer on the ignition of aluminum particles
… from selected intermediate temperatures and the oxide phases present were analyzed by x-ray diffraction. Both micron- and nanosized aluminum powders were observed to exhibit characteristic stagewise oxidation in the temperature range from 300 to 1500 C. Kinetic parameters for both direct …
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Structural and electronic properties of noble metals on metal oxide surfaces
Noble metals on metal oxide surfaces play crucial roles in many catalysis applications. Due to extreme complexity of the interfaces and catalytic reaction processes, basic science studies of model systems are needed to guide the construction and optimization of new industrial catalysts. We have …
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Structure, magnetism and multiferroicity in self-assembled oxide nanocomposites
… and the use of new materials structures. Oxides, in particular, exhibit a wide range of highly tunable properties due to the interplay of lattice, orbital, charge and spin degrees of freedom. Recently, a new paradigm for epitaxy has been studied, where two oxide phases self-assembled into …
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Nickel laterites, origin and climate
… low topography, resulting in the formation of an oxide deposit. In addition silica precipitation is common in the upper horizons of the deposit, where it creates an indurated layer, protecting the deposit from erosion. The Bitincke Nickel laterite, Albania is composed of two distinct zones …
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Oxygen permeation and thermo-chemical stability of oxygen separation membrane materials for the oxyfuel process
… from the fact that secondary non-ion conducting oxide phases are formed in the bulk of every material, forming obstacles for oxygen ion migration, and also that a reaction with chromia occurs, preventing their use without protection.
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Synthesis, characterization, and properties of carbide dispersion-strengthened tungsten alloys for use as a plasma-facing material in nuclear fusion reactors
… of tungsten carbide and transition-metal-oxide phases after sintering. As the amount of added second phase powder increased, the hardness increased and grain size decreased. Finally, samples alloyed with 1.0 wt.% zirconium carbide may be able to resist recrystallization. Exposures to low …
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