The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
R D Whaley - One of the best experts on this subject based on the ideXlab platform.
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dependence of lateral Oxidation Rate on thickness of alas layer of interest as a current aperture in vertical cavity surface emitting laser structures
Journal of Applied Physics, 1998Co-Authors: B Koley, M Dagenais, G Simonis, J T Pham, George F Mclane, F G Johnson, R D WhaleyAbstract:The dependence of the wet Oxidation process on the AlAs layer thickness used in selectively oxidized vertical-cavity surface-emitting-laser structures is studied in detail. A theoretical model based on a diffusion-reaction process is proposed. A rapid reduction in the Oxidation Rate is predicted with a reduction in the layer thickness of the ultrathin AlAs layer. The theoretical predictions are verified through experiments.
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dependence of the lateral Oxidation Rate of an alas layer used as a current aperture in vertical cavity surface emitting lasers on different physical parameters
High-power lasers and applications, 1998Co-Authors: B Koley, M Dagenais, J T Pham, George F Mclane, F G Johnson, George J Simonis, R D WhaleyAbstract:The wet Oxidation kinetics of an AlAs layer used as a current aperture in selectively oxidized vertical-cavity- surface-emitting-lasers (VCSELs) is investigated in details. The process is modeled as a diffusion-reaction process. A strong dependence of the Oxidation Rate on the temperature, at which the wet Oxidation is being carried out, is observed. The temperature dependence of the Oxidation process is explained theoretically by considering equivalent reaction activation energies for the Oxidation reaction. Also for Oxidation over a long time interval, variation of the Oxidation Rate with the variation of the radius of the etched mesa of the VCSEL is observed. A theory has been developed considering the 3D diffusion of the oxidant modules is an already oxidized cylindrical AlAs region and the reaction of the diffusion of the oxidant molecules in an already oxidized cylindrical AlAs region and the reaction of the oxidant molecule at the oxidized-unoxidized AlAs interface. Relevant material parameters, that are independent of the size and geometry of the etched VCSELs, are extracted from the experimental results. Using them in the theoretical model, the Rate equation of the lateral Oxidation process is obtained. The theory predicts the dependence of the Oxidation process on the size of the VCSEL, the AlAs layer thickness, as well as on the physical properties of the AlAs layer. The theoretical predictions have been verified by a number of experiments with reproducible results.
Jaakko A. Puhakka - One of the best experts on this subject based on the ideXlab platform.
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high Rate iron Oxidation at below ph 1 and at elevated iron and copper concentrations by a leptospirillum ferriphilum dominated biofilm
Process Biochemistry, 2005Co-Authors: Päivi Kinnunen, Jaakko A. PuhakkaAbstract:Abstract The influences of H+, Fe2+, Fe3+ and Cu2+ ion concentrations and their different combinations on the iron Oxidation by an enrichment culture dominated by Leptospirillum ferriphilum were studied in batch experiments and continuous-flow fluidized-bed reactors. The iron Oxidation Rate did not significantly vary in the pH range of 0.9–1.5 and was only partially inhibited at pH 0.7. Ferric and ferrous iron at 5 and 24 g L−1, respectively, had little or no effect on iron Oxidation by the enrichment culture and the iron Oxidation Rate slightly decreased at higher concentrations. At a loading Rate of 3 g Fe2+ L−1 h−1, 2 g L−1 Cu2+ did not affect the iron Oxidation Rate, whereas at a loading Rate of 10 g Fe2+ L−1 h−1 it reduced the Rate by 69%. The maximum iron Oxidation Rate was 10 g Fe2+ L−1 h−1 at pH 0.9 and in the presence of 21 g L−1 Fe2+ and 2 g L−1 Cu2+.
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The isolation and use of iron-oxidizing, modeRately thermophilic acidophiles from the Collie coal mine for the generation of ferric iron leaching solution.
Applied Microbiology and Biotechnology, 2002Co-Authors: Päivi Kinnunen, W.j. Robertson, J. J. Plumb, J. A. E. Gibson, Peter D. Nichols, P. D. Franzmann, Jaakko A. PuhakkaAbstract:ModeRately thermophilic, iron-oxidizing acidophiles were enriched from coal collected from an open-cut mine in Collie, Western Australia. Iron-oxidizers were enriched in fluidized-bed reactors (FBR) at 60 °C and 70 °C; and iron-Oxidation Rates were determined. Ferrous iron Oxidation by the microbiota in the original coal material was inhibited above 63 ˚C. In addition to four iron-oxidizers, closely related to Sulfobacillus spp that had been earlier isolated from the 60 °C FBR, one heterotroph closely related to Alicyclobacillus spp was isolated. The Alicyclobacillus sp. isolated from the Collie coal mine toleRated a lower pH than known Alicyclobacillus spp and therefore may represent a new species. The optimum temperature for growth of the iron-oxidizing strains was approximately 50 °C and their maximum temperatures were approximately 60 °C. The FBR was adjusted to opeRate at 50 °C and was inoculated with all of the isolated iron-oxidizing strains. At 60 °C, an iron-Oxidation Rate of 0.5 g Fe2+ l–1 h–1 was obtained. At 50 °C, the iron-Oxidation Rate was only 0.3 g Fe2+ l–1 h–1. These Rates compare favourably with the iron-Oxidation Rate of Acidianus brierleyi in shake-flasks, but are considerably lower than mesophilic iron-Oxidation Rates.
B Koley - One of the best experts on this subject based on the ideXlab platform.
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dependence of lateral Oxidation Rate on thickness of alas layer of interest as a current aperture in vertical cavity surface emitting laser structures
Journal of Applied Physics, 1998Co-Authors: B Koley, M Dagenais, G Simonis, J T Pham, George F Mclane, F G Johnson, R D WhaleyAbstract:The dependence of the wet Oxidation process on the AlAs layer thickness used in selectively oxidized vertical-cavity surface-emitting-laser structures is studied in detail. A theoretical model based on a diffusion-reaction process is proposed. A rapid reduction in the Oxidation Rate is predicted with a reduction in the layer thickness of the ultrathin AlAs layer. The theoretical predictions are verified through experiments.
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dependence of the lateral Oxidation Rate of an alas layer used as a current aperture in vertical cavity surface emitting lasers on different physical parameters
High-power lasers and applications, 1998Co-Authors: B Koley, M Dagenais, J T Pham, George F Mclane, F G Johnson, George J Simonis, R D WhaleyAbstract:The wet Oxidation kinetics of an AlAs layer used as a current aperture in selectively oxidized vertical-cavity- surface-emitting-lasers (VCSELs) is investigated in details. The process is modeled as a diffusion-reaction process. A strong dependence of the Oxidation Rate on the temperature, at which the wet Oxidation is being carried out, is observed. The temperature dependence of the Oxidation process is explained theoretically by considering equivalent reaction activation energies for the Oxidation reaction. Also for Oxidation over a long time interval, variation of the Oxidation Rate with the variation of the radius of the etched mesa of the VCSEL is observed. A theory has been developed considering the 3D diffusion of the oxidant modules is an already oxidized cylindrical AlAs region and the reaction of the diffusion of the oxidant molecules in an already oxidized cylindrical AlAs region and the reaction of the oxidant molecule at the oxidized-unoxidized AlAs interface. Relevant material parameters, that are independent of the size and geometry of the etched VCSELs, are extracted from the experimental results. Using them in the theoretical model, the Rate equation of the lateral Oxidation process is obtained. The theory predicts the dependence of the Oxidation process on the size of the VCSEL, the AlAs layer thickness, as well as on the physical properties of the AlAs layer. The theoretical predictions have been verified by a number of experiments with reproducible results.
Elizabeth J. Opila - One of the best experts on this subject based on the ideXlab platform.
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variation of the Oxidation Rate of silicon carbide with water vapor pressure
Journal of the American Ceramic Society, 2004Co-Authors: Elizabeth J. OpilaAbstract:Chemically vapor deposited silicon carbide (CVD SiC) was oxidized at temperatures of 1000°-1400°C in H2O/O2 gas mixtures with compositions of 10-90 vol% water vapor at a total pressure of 1 atm. Additional experiments were conducted in H2O/argon mixtures at a temperature of 1100°C. Experiments were designed to minimize impurity and volatility effects, so that only intrinsic water-vapor effects were observed. The Oxidation kinetics increased as the water-vapor content increased. The parabolic Oxidation Rates in the range of 10-90 vol% water vapor (the balance being oxygen) were approximately one order of magnitude higher than the Rates that were observed in dry oxygen for temperatures of 1200°-1400°C. The power-law dependence of the parabolic Oxidation Rate on the partial pressure of water vapor at all temperatures of the study indicated that the molecular species was not the sole Rate-limiting oxidant. The determination of an activation energy for diffusion was complicated by variations in the Oxidation mechanism and oxide-scale morphology with the partial pressure of water vapor and the temperature.
Y Gavin P Chua - One of the best experts on this subject based on the ideXlab platform.
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controlling the co Oxidation Rate over pt tio2 catalysts by defect engineering of the tio2 support
Journal of Catalysis, 2014Co-Authors: Y Gavin P Chua, G Kasun Kalhara T Gunasooriya, Mark Saeys, Edmund G SeebauerAbstract:Abstract The activity and selectivity of supported metal clusters can in principle be manipulated by controlling the electronic properties of the support, as initially proposed by Schwab. To quantitatively demonstRate this effect, a series of anatase TiO2 thin films with an order of magnitude variation in the carrier concentration were grown by atomic layer deposition. The change in the TiO2 carrier concentration influences the electronic properties of supported Pt clusters, as shown by photoelectron spectroscopy. The gradual increase in the carrier concentration increases the CO Oxidation Rate over the Pt/TiO2 catalysts by 70% for excess CO conditions and decreases the Rate by 30% for excess O2 conditions, providing a quantitative connection between the support properties and the measured reaction Rate. Density functional theory calculations and natural bond analysis show that charge injection into Pt clusters reduces the CO adsorption energy due to increased Pauli repulsion, which is consistent with the observed changes in the reaction Rate.
