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Articles 2221 - 2250 of 2359

Full-Text Articles in Engineering

Anodic Oxidation Of Ethylenediaminetetraacetic Acid On Platinum Electrode In Alkaline Medium, S. N. R. Pakalapati, Branko N. Popov, Ralph E. White Jan 1996

Anodic Oxidation Of Ethylenediaminetetraacetic Acid On Platinum Electrode In Alkaline Medium, S. N. R. Pakalapati, Branko N. Popov, Ralph E. White

Faculty Publications

The anodic oxidation of ethylenediaminetetraacetic acid (EDTA) was studied in alkaline medium on a smooth platinum electrode. Bulk electrolysis indicated that stable organic intermediates (formaldehyde and glyoxal) are formed during the oxidation of EDTA and that complete oxidation to CO2 can be achieved. The proposed pathway suggests that the acetate groups in EDTA are initially oxidized, generating formaldehyde and ethylenediamine. The rest potential of EDTA (0.066 to 0.164 V vs. Hg/HgO) was observed to be higher than for other organic species. In alkaline medium, very little EDTA oxidation was found to occur on bare platinum. Limiting-current behavior due to …

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The Effects Of Multiple Electroplated Zinc Layers On The Inhibition Of Hydrogen Permeation Through An Iron Membrane, D. H. Coleman, G. Zheng, Branko N. Popov, Ralph E. White Jan 1996

The Effects Of Multiple Electroplated Zinc Layers On The Inhibition Of Hydrogen Permeation Through An Iron Membrane, D. H. Coleman, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

The Devanathan-Stachurski permeation technique was used to investigate the rate of hydrogen permeation through an iron membrane with consecutively electroplated zinc layers. Hydrogen evolution rates and hydrogen permeation rates were followed as functions of time at different applied potentials. Hydrogen evolution and permeation decreased with each successive zinc layer until finally reaching an average decrease of 93 and 96%, respectively, as compared with bare iron. Hydrogen surface coverage, exchange current density, absorption-adsorption reaction constant, and hydrogen recombination constant were estimated on bare iron and on zinc-plated iron. It was found that the decrease in the permeation rate of hydrogen through …

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Anomalous Codeposition Of Fe-Ni Alloys And Fe-Ni-Sio2 Composites Under Potentiostatic Conditions, M. Ramasubramanian, S. N. Popova, Branko N. Popov, Ralph E. White, K. M. Yin Jan 1996

Anomalous Codeposition Of Fe-Ni Alloys And Fe-Ni-Sio2 Composites Under Potentiostatic Conditions, M. Ramasubramanian, S. N. Popova, Branko N. Popov, Ralph E. White, K. M. Yin

Faculty Publications

A mathematical model has been developed to describe the electrodeposition of Fe-Ni alloys and Fe-Ni-SiO2 composites under potentiostatic conditions. This model can be used to predict the polarization behavior, partial current densities, and alloy composition of each of the components as a function of the applied potential. Fe-Ni-SiO2 samples were deposited on platinum rotating disk electrodes from sulfate electrolytes under potentiostatic conditions, and the results obtained were compared to the model. The model predictions were found to agree well with the experimental observations for the Fe-Ni and Fe-Ni-SiO2 systems.

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Determination Of Transport And Electrochemical Kinetic Parameters Of Bare And Copper-Coated Lani4.27Sn0.24 Electrodes In Alkaline Solution, G. Zheng, Branko N. Popov, Ralph E. White Jan 1996

Determination Of Transport And Electrochemical Kinetic Parameters Of Bare And Copper-Coated Lani4.27Sn0.24 Electrodes In Alkaline Solution, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

Electrochemical properties of bare and copper-coated LaNi4.27Sn0.24 electrodes were investigated in alkaline solution. The exchange current density, polarization resistance, and equilibrium potential were determined as functions of the state of charge in the electrodes. The symmetry factors for bare and copper-coated electrodes were estimated to be 0.53 and 0.52, respectively. By using a constant current discharge technique, the hydrogen diffusion coefficient in bare and coated LaNi4.27Sn0.24 was estimated to be 6.75 × 10–11 cm2/s.

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Application Of Porous Electrode Theory On Metal Hydride Electrodes In Alkaline Solution, G. Zheng, Branko N. Popov, Ralph E. White Jan 1996

Application Of Porous Electrode Theory On Metal Hydride Electrodes In Alkaline Solution, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

Porous electrode theory was applied to estimate the exchange current density, the polarization resistance, and symmetry factor for LaNi4.27Sn0.24 hydride electrode in alkaline solution. The exchange current density, polarization resistance, and symmetry factor were determined from polarization curves which were obtained at low overpotentials.

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Linear Algebra Used To Determine Independent Half‐Cell Equations, D. H. Coleman, Ralph E. White Jan 1996

Linear Algebra Used To Determine Independent Half‐Cell Equations, D. H. Coleman, Ralph E. White

Faculty Publications

No abstract provided.

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Use Of A Hydrogen Anode For Nitrate Waste Destruction, E. E. Kalu, Ralph E. White, D. T. Hobbs Jan 1996

Use Of A Hydrogen Anode For Nitrate Waste Destruction, E. E. Kalu, Ralph E. White, D. T. Hobbs

Faculty Publications

No abstract provided.

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A Multiphase Mathematical Model Of A Nickel/Hydrogen Cell, Pauline De Vidts Jan 1996

A Multiphase Mathematical Model Of A Nickel/Hydrogen Cell, Pauline De Vidts

Faculty Publications

No abstract provided.

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Galvanostatic Pulse And Pulse Reverse Plating Of Zinc-Nickel Alloys From Sulfate Electrolytes On A Rotating Disc Electrode, Branko N Popov, M. Ramasubramanian, S. N. Popova, Ralph E. White, K-M. Yin Jan 1996

Galvanostatic Pulse And Pulse Reverse Plating Of Zinc-Nickel Alloys From Sulfate Electrolytes On A Rotating Disc Electrode, Branko N Popov, M. Ramasubramanian, S. N. Popova, Ralph E. White, K-M. Yin

Faculty Publications

Galvanostatic pulse and pulse reverse techniques have been used to study the plating of zinc–nickel alloys in the presence of nonyl phenyl polyethylene oxide. The effects of average current density, rotation speed of disc electrode and the presence of nonyl phenyl polyethylene oxide in the electrolyte on deposition of zinc–nickel alloys were evaluated. Zinc–nickel plating bath solution chemistry was studied by determining the equilibrium concentrations at various pH levels. It was found that the alloy composition was determined by solution equilibria, mass transfer of the electroactive species within the diffusion layer and by the surface coverage of nonyl phenyl polyethylene …

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A Model For The Galvanostatic Deposition Of Nickel Hydroxide, Mahesh Murthy, Gowri S. Nagarajan, John W. Weidner, John W. Van Zee Jan 1996

A Model For The Galvanostatic Deposition Of Nickel Hydroxide, Mahesh Murthy, Gowri S. Nagarajan, John W. Weidner, John W. Van Zee

Faculty Publications

A mathematical model is presented for the galvanostatic deposition of Ni(OH)2 films in stagnant Ni(NO3)2 solutions. The objective is to quantify the anomalous deposition behavior reported previously in which the utilization of the electrochemically generated OH– species decreased drastically as the concentration of Ni(NO3)2 increased beyond 0.1 M. For example as the Ni(NO3)2 concentration increased from 0.1 to 2.0 M, the deposition rate decreased by a factor of ten at 2.5 mA/cm2. At this high ratio of concentration to current density, a comparison with Faraday's …

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Analysis Of Transient Hydrogen Uptake By Metal Alloy Particles, Wenlin Zhang, Supramaniam Srinivasan, Harry J. Ploehn Jan 1996

Analysis Of Transient Hydrogen Uptake By Metal Alloy Particles, Wenlin Zhang, Supramaniam Srinivasan, Harry J. Ploehn

Faculty Publications

This paper describes a new approach to solving the equations comprising the shrinking core model for diffusion and reaction of a chemical species in a solid spherical particle. The reactant adsorbs on the particle surface, diffuses into the particle's interior, and reacts with the particle to form a solid product. The shrinking core model assumes a fast reaction rate compared to reactant diffusion so that the reaction is localized in the interfacial zone between the unreacted solid core and the surrounding shell of reacted product. Analytical solutions of the governing conservation equations usually invoke the pseudo-steady state (PSS) approximation which …

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Structural Characterization Of Aluminum Films Deposited On Sputtered-Titanium Nitride/ Silicon Substrate By Metalorganic Chemical Vapor Deposition From Dimethylethylamine Alane, Xiaodong Li, Byoung-Youp Kim, Shi-Woo Rhee Dec 1995

Structural Characterization Of Aluminum Films Deposited On Sputtered-Titanium Nitride/ Silicon Substrate By Metalorganic Chemical Vapor Deposition From Dimethylethylamine Alane, Xiaodong Li, Byoung-Youp Kim, Shi-Woo Rhee

Faculty Publications

Alfilmsdeposited on sputtered‐TiN/Si substrate by metalorganic chemical vapor deposition(MOCVD) from dimethylethylamine alane (DMEAA) were characterized using x‐ray diffraction(XRD),Auger electron spectroscopy(AES),atomic force microscopy(AFM), and transmission electron microscopy (TEM). The TiN filmsputtered on the Si has a preferred orientation along the growth direction with the 〈111〉 of the film parallel to the Si〈111〉. Sputtering of the TiN film on the Si induced strains at the interface. The TiN/Si interface is flat while the Al/TiN interface is rough. There exist many dislocations at the Al/TiN interface. The Al2O3 phase was formed at the Al/TiN interface during the early stages of …

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Hydrogen-Atom Direct-Entry Mechanism Into Metal Membranes, G. Zheng, Branko N. Popov, Ralph E. White Jan 1995

Hydrogen-Atom Direct-Entry Mechanism Into Metal Membranes, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

The hydrogen-atom direct-entry mechanism is used to explain why the steady-state hydrogen permeation current density through a metal membrane is directly proportional to the cathodic current density, ic, and is independent of the membrane thickness when ic is small.

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Electrowinning Of Non-Noble Metals With Simultaneous Hydrogen Evolution At Flow-Through Porous Electrodes Ii. Experimental, Mahmoud M. Saleh, John W. Weidner, Bahgat E. Ei-Anadouli, Badr G. Ateya Jan 1995

Electrowinning Of Non-Noble Metals With Simultaneous Hydrogen Evolution At Flow-Through Porous Electrodes Ii. Experimental, Mahmoud M. Saleh, John W. Weidner, Bahgat E. Ei-Anadouli, Badr G. Ateya

Faculty Publications

This paper presents an interpretation of the experimental results obtained on the electrowinning of zinc at a flow-through porous electrode in light of a mathematical model which was presented in Part I. The process is accompanied by simultaneous hydrogen evolution within the electrode, which increases the pore electrolyte resistivity and decreases the coulombic efficiency. We measured polarization curves, coulombic efficiencies, and current distributions under various conditions of zincate concentrations, flow rates, cell current, and electrode thickness. Reasonable agreement between the measured and predicted current distributions was obtained only under conditions of high electrolyte flow rates, low cell currents, and thinner …

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Mathematical Modeling Of A Nickel-Cadmium Cell: Proton Diffusion In The Nickel Electrode, Pauline De Vidts, Ralph E. White Jan 1995

Mathematical Modeling Of A Nickel-Cadmium Cell: Proton Diffusion In The Nickel Electrode, Pauline De Vidts, Ralph E. White

Faculty Publications

In this paper we present a mathematical model of a sealed nickel-cadmium cell that includes proton diffusion and ohmic drop through the active material in the nickel electrode. The model is used to calculate sensitivity coefficients for various parameters in the model. These calculations show that the discharge voltage of the cell is affected mostly by the kinetics of the nickel reaction. Toward the end of discharge, proton diffusion also becomes important, because the proton diffusion process affects the active material utilization significantly. During charge, the cell voltage is mainly affected by the kinetics of the nickel reaction until the …

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Ac Impedance Studies On Metal Hydride Electrodes, Wenlin Zhang, M. P. Sridhar Kumar, Supramaniam Srinivasan, Harry J. Ploehn Jan 1995

Ac Impedance Studies On Metal Hydride Electrodes, Wenlin Zhang, M. P. Sridhar Kumar, Supramaniam Srinivasan, Harry J. Ploehn

Faculty Publications

The metal hydride (MHx) electrode is the negative electrode in one of the most advanced secondary batteries (i.e.,nickel/metal hydride). The objective of this study is to obtain insight on the mechanism of the hydriding/dehydridingreaction in the battery by using the electrochemical impedance spectroscopy (EIS) technique. An equivalent circuit for the MHx electrode reaction is proposed. The rate capability of charge and discharge of the MHx electrode is determined by thekinetics of the charge-transfer reaction at the alloy surface, which is mainly represented by the EIS responses in the lowfrequency region. Transient and pseudo-steady-state analyses …

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Mathematical Modeling For The Discharge Of A Metal Hydride Electrode, Pauline De Vidts, Javier Delgado, Ralph E. White Jan 1995

Mathematical Modeling For The Discharge Of A Metal Hydride Electrode, Pauline De Vidts, Javier Delgado, Ralph E. White

Faculty Publications

No abstract provided.

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Electrochemical Determination Of The Diffusion Coefficient Of Hydrogen Through An Lani4.25Al0.75 Electrode In Alkaline Aqueous Solution, G. Zheng, Branko N. Popov, Ralph E. White Jan 1995

Electrochemical Determination Of The Diffusion Coefficient Of Hydrogen Through An Lani4.25Al0.75 Electrode In Alkaline Aqueous Solution, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

Theconstant potential and constant current discharge techniques were used todetermine the hydrogen diffusion coefficients in an LaNi4.25Al0.75 electrode. The valuesobtained were 2.97 × 10–11 and 3.30 × 10–11 cm2/s, respectively. The advantages and disadvantages of these two techniques are discussed.

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The Effect Of Current And Nickel Nitrate Concentration On The Deposition Of Nickel Hydroxide Films, Christopher C. Streinz, Andrew P. Hartman, Sathya Motupally, John W. Weidner Jan 1995

The Effect Of Current And Nickel Nitrate Concentration On The Deposition Of Nickel Hydroxide Films, Christopher C. Streinz, Andrew P. Hartman, Sathya Motupally, John W. Weidner

Faculty Publications

An electrochemical quartz crystal nanobalance (EQCN) has been utilized to measure the mass of Ni(OH)2 films electrochemically deposited from Ni(NO3)2 solutions. The objective of this work was to quantify electrochemical deposition as a function of deposition conditions. The changing mass recorded on the EQCN was demonstrated to be the result of Ni(OH)2 deposition. Deposited mass was observed to increase proportionally with applied charge as suggested by previous investigators. Most significantly, the rate of deposition was found to decrease more than an order of magnitude as the Ni(NO3)2 concentration increased from 0.2 to …

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Proton Diffusion In Nickel Hydroxide Films: Measurement Of The Diffusion Coefficient As A Function Of State Of Charge, Sathya Motupally, Christopher C. Streinz, John W. Weidner Jan 1995

Proton Diffusion In Nickel Hydroxide Films: Measurement Of The Diffusion Coefficient As A Function Of State Of Charge, Sathya Motupally, Christopher C. Streinz, John W. Weidner

Faculty Publications

Electrochemical impedance spectroscopy (EIS) was used to measure the solid-state diffusion coefficient of protons in nickel hydroxide films at room temperature as a function of state of charge (SOC). A model for the complex faradaic impedance of the nickel hydroxide active material is presented and used to extract the diffusion coefficient of protons from the EIS data. Impedance data over a range of frequencies can be used to extract a constant diffusion coefficient without the knowledge of the initial mobile proton concentration or the form of the charge-transfer kinetic expression. The proton diffusion coefficient is a strong function of SOC …

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A Boundary-Layer Model Of A Parallel-Plate Electrochemical Reactor For The Destruction Of Nitrates And Nitrites In Alkaline Waste Solutions, Shailesh Prasad, John W. Weidner, Andrew E. Farell Jan 1995

A Boundary-Layer Model Of A Parallel-Plate Electrochemical Reactor For The Destruction Of Nitrates And Nitrites In Alkaline Waste Solutions, Shailesh Prasad, John W. Weidner, Andrew E. Farell

Faculty Publications

Electrochemical processes appear to be attractive for treating low level nuclear wastes. The development of a simple divided electrochemical-cell model operating in a batch mode, used for the reduction of nitrates and nitrites from nuclear wastes, is presented. This model, based on a boundary-layer approach, is simple and yet encompasses the key features of a previously developed distributed-parameter model that includes diffusion, migration, and convection as the flux components. Because it dramatically reduces computation time, this boundary-layer model is well suited for use in a complex interactive flowsheet model and for optimization studies. The boundary-layer model is used to predict …

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The Effect Of Temperature And Ethanol On The Deposition Of Nickel Hydroxide Films, Christopher C. Streinz, Sathya Motupally, John W. Weidner Jan 1995

The Effect Of Temperature And Ethanol On The Deposition Of Nickel Hydroxide Films, Christopher C. Streinz, Sathya Motupally, John W. Weidner

Faculty Publications

The objective of this work was to determine the effect of the temperature and the ethanol content of the Ni(NO3)2 solution on: (i) the efficiency of electrochemical deposition of nickel hydroxide; and (ii) the molecular weight of the deposited film. An electrochemical quartz crystal nanobalance (EQCN) was used to measure the mass of films electrochemically deposited from Ni(NO3)2 solutions and constant current discharges were used to determine the electrochemical capacity of the films. The data indicates that increasing the temperature increases both the efficiency of the deposition reaction and the …

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Electrowinning Of Non-Noble Metals With Simultaneous Hydrogen Evolution At Flow-Through Porous Electrodes I. Theoretical, Mahmoud M. Saleh, John W. Weidner, Badr G. Ateya Jan 1995

Electrowinning Of Non-Noble Metals With Simultaneous Hydrogen Evolution At Flow-Through Porous Electrodes I. Theoretical, Mahmoud M. Saleh, John W. Weidner, Badr G. Ateya

Faculty Publications

A mathematical model is developed to simulate the electrowinning of non-noble metals (e.g., Zn, Cr) within flow-through porous electrodes under the conditions of simultaneous evolution of hydrogen gas bubbles. The results of the model are presented as a function of several dimensionless groups representing kinetics, mass transfer, ohmic resistance, and gas bubbles. These coupled, nonlinear effects are investigated by examining the distributions of the metal reduction and hydrogen evolution currents, coulombic efficiency of the metal electrowinning reaction, and gas void fractions under a series of limiting conditions. The gas bubbles accentuate the nonuniform distribution of the potential and …

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A Parallel-Plate Electrochemical Reactor Model For The Destruction Of Nitrate And Nitrite In Alkaline Waste Solutions, D. H. Coleman, Ralph E. White, D. T. Hobbs Jan 1995

A Parallel-Plate Electrochemical Reactor Model For The Destruction Of Nitrate And Nitrite In Alkaline Waste Solutions, D. H. Coleman, Ralph E. White, D. T. Hobbs

Faculty Publications

A parallel-plate electrochemical reactor model with multiple reactions at both electrodes and anolyte and catholyte recirculation tanks was modeled for the electrochemical destruction of nitrate and nitrite species in an alkaline solution. The model can be used to predict electrochemical reaction current efficiencies and outlet concentrations of species from the reactor, given inlet feed conditions and cell operating conditions. Also, predictions are made for off-gas composition and liquid-phase composition in the recirculation tanks. The results of case studies at different applied potentials are shown here. At lower applied potentials, the model predictions show that the destruction process is more energy …

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Electrochemical Determination Of The Diffusion Coefficient Of Hydrogen Through An Lani4.25Al0.75 Electrode In Alkaline Aqueous Solution, G. Zheng, Branko N. Popov, Ralph E. White Jan 1995

Electrochemical Determination Of The Diffusion Coefficient Of Hydrogen Through An Lani4.25Al0.75 Electrode In Alkaline Aqueous Solution, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

The constant potential and constant current discharge techniques were used to determine the hydrogen diffusion coefficients in an LaNi4.25Al0.75 electrode. The values obtained were 2.97 × 10–11 and 3.30 × 10–11 cm2/s, respectively. The advantages and disadvantages of these two techniques are discussed.

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Low Cost Schottky Barrier Solar Cells Fabricated On Cdse And Sb2S3 Films Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal Oct 1994

Low Cost Schottky Barrier Solar Cells Fabricated On Cdse And Sb2S3 Films Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.

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Automating Workflows For Service Provisioning: Integrating Ai And Database Technologies, Munindar P. Singh, Michael N. Huhns Oct 1994

Automating Workflows For Service Provisioning: Integrating Ai And Database Technologies, Munindar P. Singh, Michael N. Huhns

Faculty Publications

Workflows are the structured activities that take place in information systems in typical business environments. These activities frequently involve several database systems, user interfaces, and application programs. Traditional database systems do not support workflows to any reasonable extent: usually human beings must intervene to ensure their proper execution. We have developed an architecture based on AI technology that automatically manages workflows. This architecture, which executes on top of a distributed computing environment, has been applied to automating service provisioning workflows; an implementation that operates on one such workflow has been developed. This work advances the Carnot Project’s goal of developing …

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The Asymptotic Structure Of Transient Elastodynamic Fields At The Tip Of A Stationary Crack, Xiaomin Deng Jul 1994

The Asymptotic Structure Of Transient Elastodynamic Fields At The Tip Of A Stationary Crack, Xiaomin Deng

Faculty Publications

The asymptotic structure of the transient elastodynamic near-tip fields around a stationary crack is investigated for all three fracture modes. The transient fields are obtained as the sum of their quasi-static counterparts and corresponding transient correction terms, in terms of variable-separable expansions. By allowing the coefficients of terms in the quasi-static expansion to deviate from their quasi-static restrictions, the correction terms are shown to be the particular solutions of a set of first order (for mixed mode I and II) or second order (for mode III) ordinary differential equations with constant coefficients and non-homogeneous terms involving only sine and cosine …

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Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu Jan 1994

Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu

Faculty Publications

No abstract provided.

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Use Of Underpotential Deposition Of Zinc To Mitigate Hydrogen Absorption Into Monel K500, G. Zheng, Branko N. Popov, Ralph E. White Jan 1994

Use Of Underpotential Deposition Of Zinc To Mitigate Hydrogen Absorption Into Monel K500, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

Polarization experiments and a potentiostatic pulse technique have been used to show that a monolayer coverage of zinc effectively inhibits the absorption of hydrogen into Monel K500. By depositing a monolayer of zinc on Monel K500, the hydrogen evolution reaction and hydrogen ingress flux rate were reduced by 60%.

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