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 17 of 17 for “"oxygen activity"”.
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Effect of base metal oxygen content and oxygen activity on mechanical properties of EN-GJL- GG - 26 Cu-Cr grey cast-iron heavy-duty crank cases
… emissions. This research investigates how the oxygen content and oxygen activity of the liquid EN-GJL-GG - 26 Cu-Cr Grey Cast Iron metal are affected by holding the metal for a duration of 0 to 24 hours in a closed furnace/inert atmosphere, and how the addition of reactive iron oxide from 0 to …
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Electrical and structural properties of compositions in the systems Y₁₋ₓCaₓMnO₃ and La₁₋ₓCaₓMnO₃
… studied as functions of temperature and ambient oxygen activity in order to determine the mechanism of electrical transport and defect structure. Thermal expansion was also measured. Electrical conduction appeared to occur via a small polaron hopping mechanism for compositions with 0.30 ≤ x ≤ …
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Point Defects And Defect-Related Transport Of Matter In Transition Metal-Containing Orthosilicates
… studied as a function of crystal orientation, oxygen activity and temperature using high purity, synthetic cobalt and manganese orthosilicate single crystals grown by the floating zone method. Modeling of the observed oxygen activity dependancies of the cation tracer diffusion coefficients and …
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Oxidation kinetics of polycrystalline SrTiO₃ and LaCrO₃
… on Nb-doped LaCrO<sub>3</sub> show that at low oxygen activity the material is a n-type conductor and as oxygen activity increases changes to a p-type conductor. This is consistent with a defect structure whose majority defects at low oxygen activity are electrons due to the donor; at high …
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Sintering and electrical properties of the perovskite system (La,Ca) (Cr,Co) O₃
… were made as a function of temperature and oxygen activity. At 1000° C and 1 atm. oxygen the electrical conductivity ranged from 17 to 51 S/cm for La<sub>0.9</sub>Ca<sub>0.1</sub>Cr<sub>0.9</sub>Co<sub>0.1</sub>O<sub>3</sub> and …
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Oxygen Diffusion in Vanadium-Based Alloys
… study of transport and equilibrium properties of oxygen in vanadium-based alloys was made by EMF measurements on solid electrolytic cells over the temperature range of 873-1423(DEGREES)K. The oxygen diffusion in vanadium was not significantly modified by small additions of Ti, Cr, Ni, Nb and Ta. …
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Phase equilibria and thermodynamic studies in the system Ca0-Fe0-Fe₂0₃₋Si0₂
… by analyses of quenched samples equilibrated at oxygen pressures from about 10⁻¹¹ to 1 atm. Isothermal phase diagrams were constructed from data for 0, 5, 10, 20, and 30 weight percent silica sections of the CaO-FeO-Fe₂O₃-SiO₂ system, and the effect of temperature and increased silica additions …
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Thermogravimetric, thermopower, and electrical conductivity studies of the Ba₂YCu₃O₇₋ₓ system
… a p-type semiconductor over the temperature and oxygen activity ranges studied.</p> <p>The conductivity, carrier concentration, and mobility behaviors of the oxide are primarily functions of its oxygen content. All three properties exhibited only a slight temperature dependence. The carrier …
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Characterization and control of non-stoichiometry in Pr₀.₁Ce₀.₉O₂-[d̳e̳l̳t̳a̳] thin films : correlation with SOFC electrode performance
… oxide thin films often depend strongly on oxygen nonstoichiometry (6), there have been few means available for its measurement and control in a reliable and in-situ fashion. In this work, we investigate means for extracting the oxygen nonstoichiometry of dense oxide thin films as a function …
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Ore mineralogy and paragenesis of a portion of the Great Gossan Lead district, Virginia
… the ore assemblage would have developed a sulfur activity of approximately 10-9 to 10-7 atm. and would have been subject to an oxygen activity of about 10 -25 to 10 -27 atm. The Great Gossan Lead is interpreted to have formed either as synsedimentary deposits or massive pyritic volcanism. Later …
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Investigating chlorite dismutase biocatalyst reuse using columns
… dismutase treats chlorite to chloride and oxygen. Activity tests were conducted in batch for the purified and attached biocatalysts and in column to determine impact of attachment on the biocatalyst’s activity and inactivation. Activity results showed no impact of tag addition, with a …
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Trends in C-H bond dehydrogenation energetics for small molecule conversion
… formaldehyde oxidation and show that catalytic activity can further be improved by the addition of water. We then show that room temperature selective methanol oxidation towards methyl formate and methane oxidation to CO2 can be realized by increasing the surface oxygen activity of iridium …
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Ab initio thermodynamics of phase-separating and cation-disordered cathodes for Li-ion batteries
… value at which it is likely to be preceded by oxygen activity. We further investigate the effect of cation-disorder on the voltage slope of lithium transition metal oxides, which controls the total capacity accessible below the stability limit of the electrolyte. We demonstrate that …
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Characterization and catalytic application of an engineered cupredoxin possessing a potential in excess of 1 volt
… polymerization catalyst, including: activity in the presence of oxygen, activity in water, and activity at room temperature, as well as potentially tactic polymerization capability. These advantages may make a protein-based catalyst of interest when aqueous functionality is …
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Functional dna: Biochemical/biophysical characterization & sensing applications
… with divalent metal ions, showing the highest activity with Pb2+. The 8-17 DNAzyme has been isolated multiple times by different groups and has been the subject of many studies – both fundamental and practical. Mutational studies by the Peracchi and Lu groups have shown that certain bases in …
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The interactions of cytochrome bo3 from Escherichia coli with its substrates - ubiquinone and oxygen
Heme-copper respiratory oxygen reductases reduce O2 to water and use the redox free energy to generate the proton motive force. Among the heme-copper oxygen reductases are the quinol oxidases, which catalyze the 2-electron oxidation of ubiquinol or menaquinol instead of cytochrome c. Escherichia …