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Articles 631 - 660 of 914

Full-Text Articles in Chemical Engineering

Interaction Energy Surfaces Of Small Hydrocarbon Molecules, Richard L. Rowley, Jukka-Pekka Jalkanen, Tapani A. Pakkanen, Yan Yang Mar 2003

Interaction Energy Surfaces Of Small Hydrocarbon Molecules, Richard L. Rowley, Jukka-Pekka Jalkanen, Tapani A. Pakkanen, Yan Yang

Faculty Publications

Nonbonding interactions of small alkane molecules were studied with ab initio methods. Previously reported energy data for ethane and propane dimers were supplemented with 1747 new configurations of dimers involving slightly larger hydrocarbons. The completed work provides interaction energy surfaces for all combinations of dimer pairs involving ethane, propane, isobutane, and neopentane and thus contains information of all chemical groups found in acyclic alkanes. The strongest attraction of the studied molecule pairs was encountered in isobutane C2h dimer, where an energy minimum of -1.784 kcal mol^-1 at 4.28 Angstroms separation of centermost carbon atoms was observed. The composite data set …

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Density Of States Simulations Of Proteins, Nitin Rathore, Thomas A. Knotts Iv, Juan J. De Pablo Mar 2003

Density Of States Simulations Of Proteins, Nitin Rathore, Thomas A. Knotts Iv, Juan J. De Pablo

Faculty Publications

A modified version of a recently introduced algorithm that calculates density of states by performing a random walk in energy space has been proposed and implemented to study protein folding in a continuum. A united atom representation and the CHARMM19 [B. R. Brooks, R. E. Bruccoleri, B. D. Olafson, D. J. States, S. Swaminathan, and M. Karplus, J. Comput. Chem. 4, 187 (1983)] force field are employed for these simulations. This method permits estimation of the density of states of a protein via a random walk in the energy space, thereby allowing the system to escape from local free-energy minima …

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Fuel Characteristics Of Processed, High-Fiber Sugarcane, Scott Q. Turn, Charles M. Kinoshita, Lee A. Jakeway, Bryan M. Jenkins, Larry Lin Baxter 8507091, Ben C. Wu, Linda G. Blevins Feb 2003

Fuel Characteristics Of Processed, High-Fiber Sugarcane, Scott Q. Turn, Charles M. Kinoshita, Lee A. Jakeway, Bryan M. Jenkins, Larry Lin Baxter 8507091, Ben C. Wu, Linda G. Blevins

Faculty Publications

A study of treatment methods to improve the fuel characteristics of sugarcane variety B52298 was conducted. Two parent materials, whole cane (WC) and stripped cane (SC), were included in the study. The whole cane material was subjected to three treatments: (1) no treatment, WC-U; (2) a single milling, WC-M; and (3) an initial milling followed by leaching and a secondary milling, WC-MLM. Treatments (1) through (3) are in order of increasing severity. The stripped cane material was subjected to treatment (3) and designated as SC-MLM. Regardless of parent material, milling produced moisture contents of ∼50% wet basis and fiber bulk …

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Comprehensive Model Of Alkali-Salt Deposition In Recovery Boilers, Richard A. Wessel, Larry Lin Baxter 8507091 Feb 2003

Comprehensive Model Of Alkali-Salt Deposition In Recovery Boilers, Richard A. Wessel, Larry Lin Baxter 8507091

Faculty Publications

Algorithms for alkali-salt deposition have been implemented into a comprehensive model for recovery boilers. The model includes (a) mechanisms for particle formation and chemistry, (b) particle deposition and adhesion, and (c) deposit thermal properties. These algorithms are fully coupled with models for turbulent flow, black liquor combustion, and heat transfer in the boiler. Model predictions for particle deposition in the convection pass are presented for a Babcock & Wilcox recovery boiler. This work is part of an ongoing project sponsored by the U.S. Department of Energy to demonstrate an improved ability to anticipate ash behavior with changes in fuel composition, …

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Study Of Ionic Conductivity Profiles Of The Air Cathode Of A Pemfc By Ac Impedance Spectroscopy, Qingzhi Guo, Maria Cayetana, Yu-Min Tsou, Emory S. De Castro, Ralph E. White Jan 2003

Study Of Ionic Conductivity Profiles Of The Air Cathode Of A Pemfc By Ac Impedance Spectroscopy, Qingzhi Guo, Maria Cayetana, Yu-Min Tsou, Emory S. De Castro, Ralph E. White

Faculty Publications

A characterization of the ionic conduction of the active layer of a polymer electrolyte membrane fuel cell (PEMFC) cathode by ac impedance measurement at open-circuit potential conditions was conducted. Porous electrode theory was used to derive a compact equation, ∂2Φ̑2/∂y2+∂lnf(y)/∂y×∂Φ̑2/∂y−R/f(y)(1+jΩ)Φ̑2=0, to solve for the impedance response of a cathode at open-circuit potential conditions. This equation includes a parameter R, the ratio of an ionic resistance (evaluated at the active layer/membrane interface), to the total charge-transfer resistance of the active layer. The influence of an assumed ionic conductivity distribution profile f(y) on the error in the estimation of total double-layer …

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Synthesis And Characterization Of Mno2-Based Mixed Oxides As Supercapacitors, Hansung Kim, Branko N. Popov Jan 2003

Synthesis And Characterization Of Mno2-Based Mixed Oxides As Supercapacitors, Hansung Kim, Branko N. Popov

Faculty Publications

Mn/Pb and Mn/Ni mixed oxide were prepared at ambient temperature by reduction of KMnO4 with Mn, Pb, and Ni salts. This low-temperature approach provides amorphous structure of the active material. The specific capacitance of pure MnO2 was estimated to be 166 F/g and increased to 210 and 185 F/g for Mn/Ni and Mn/Pb oxides, respectively. The carbon loading was optimized at 20 wt %. Based on a single electrode, the Mn/Ni mixed oxide showed a high rate capability of 3.12 Wh/kg at constant power discharge of 1 kW/kg.

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Corrosion Protection Of Steel Using Nonanomalous Ni-Zn-P Coatings, Basker Veeraraghavan, Bala Haran, Swaminatha P. Kumaraguru, Branko N. Popov Jan 2003

Corrosion Protection Of Steel Using Nonanomalous Ni-Zn-P Coatings, Basker Veeraraghavan, Bala Haran, Swaminatha P. Kumaraguru, Branko N. Popov

Faculty Publications

A novel technique for obtaining nonanomalous Ni-Zn-P coatings with high Ni content (74 wt % as compared to 15-20 wt % in the conventional plating method) has been developed. These coatings show promise as a replacement for Cd in sacrificially protecting steel. Ni-Zn-P coatings were deposited using an electroless method from a solution containing NiSO4, complexing agent and ammonium chloride. Varying the concentration of ZnSO4 in the bath controls the final amount of Zn in the deposit. The Zn content in the coating was optimized based on the corrosion resistance of the final deposit. Coatings with 16.2 …

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Full Cell Mathematical Model Of A Mcfc, N. Subramanian, B. S. Haran, Ralph E. White, Branko N. Popov Jan 2003

Full Cell Mathematical Model Of A Mcfc, N. Subramanian, B. S. Haran, Ralph E. White, Branko N. Popov

Faculty Publications

A theoretical model for the molten carbonate fuel cell was developed based on the three-phase homogeneous approach. Using this model, the contribution of different cell components to losses in cell performance has been studied. In general, at low current densities, the electrolyte matrix contributed to the major fraction of potential losses. Mass transfer effects became important at high current densities and were more prominent at the cathode. Electrolyte conductivity and cathode exchange current density seemed to play a limiting role in determining cell performance. Using the model, the maximum power density from a single cell for different cell thicknesses was …

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Thermally Stable Gel Polymer Electrolytes, Min-Kyu Song, Young-Taek Kim, Yong Tae Kim, Byung Won Cho, Branko N. Popov, Hee-Woo Rhee Jan 2003

Thermally Stable Gel Polymer Electrolytes, Min-Kyu Song, Young-Taek Kim, Yong Tae Kim, Byung Won Cho, Branko N. Popov, Hee-Woo Rhee

Faculty Publications

To prepare miscible polyethylene glycol diacrylate/polyvinylidene fluoride (PEGDA/PVdF) blend gel polymer electrolytes, low molecular weight (M = 742) liquid PEGDA oligomer was mixed with PVdF-HFP dissolved in ethylene carbonate/dimethyl carbonate/LiPF6 liquid electrolytes, and then cured under ultraviolet irradiation. Room temperature conductivity of PEGDA/PVdF blend films was found to be comparable to that of PVdF-HFP gel polymer electrolytes, and they were electrochemically stable up to 4.6 V vs. Li/Li+. Scanning electron micrographs revealed that PEGDA/PVdF blend electrolytes have pore size intermediate between dense PEGDA and highly porous PVdF-HFP. It was confirmed by weight change measurement that liquid electrolyte …

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Development Of A Novel Electrochemical Method To Deposit High Corrosion Resistant Silicate Layers On Metal Substrates, Basker Veeraraghavan, Bala Haran, Dragan Slavkov, Swaminatha Prabhu, Branko N. Popov, Bob Heimann Jan 2003

Development Of A Novel Electrochemical Method To Deposit High Corrosion Resistant Silicate Layers On Metal Substrates, Basker Veeraraghavan, Bala Haran, Dragan Slavkov, Swaminatha Prabhu, Branko N. Popov, Bob Heimann

Faculty Publications

A novel method for electrodepositing silicates on metallic substrates from aqueous solutions has been developed. The technique is demonstrated by forming a passive film on galvanized steel. The silicate layer was deposited cathodically from a bath containing PQ Corporation N sodium silicate solution (3.22 weight ratio sodium silicate, 37.5% solution in water). A post-treatment drying process increased the Si content in the coating and improved the corrosion characteristics of the silicate layer. Deposition parameters like bath concentration and temperature have been optimized using corrosion characteristics and surface morphology of the final coating. Finally, stability studies show that the silicate coatings …

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Polyetheretherketone Membranes For Elevated Temperature Pemfcs, Balasubramanian Lakshmanan, Wayne Huang, David Olmeijer, John W. Weidner Jan 2003

Polyetheretherketone Membranes For Elevated Temperature Pemfcs, Balasubramanian Lakshmanan, Wayne Huang, David Olmeijer, John W. Weidner

Faculty Publications

Membrane electrode assemblies ~MEAs! made from polyetheretherketone ~PEEK! showed excellent fuel cell performance and thermal stability in the presence of substantial CO at elevated temperatures ~i.e., 120°C! in proton exchange membrane fuel cells ~PEMFCs!. For example, the current from a MEA made from PEEK membrane at 0.6 V and 120°C was 0.50 A/cm2 when run on pure hydrogen and 0.45 A/cm2 when run on reformate ~50% H2 , 1300 ppm CO, and balance N2). The current density from a MEA made from Nafion at 0.6 V and 120°C was 0.61 A/cm2 when run on pure hydrogen. The main difference between …

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Theoretical Analysis For Obtaining Physical Properties Of Composite Electrodes, Parthasarathy M. Gomadam, John W. Weidner, Thomas A. Zawodzinski, Andrew P. Saab Jan 2003

Theoretical Analysis For Obtaining Physical Properties Of Composite Electrodes, Parthasarathy M. Gomadam, John W. Weidner, Thomas A. Zawodzinski, Andrew P. Saab

Faculty Publications

A theoretical analysis is presented that allows in situ measurements of the physical properties of a composite electrode, namely, the electronic conductivity, the ionic conductivity, the exchange-current density, and the double-layer capacitance. Use is made of the current-voltage responses of the composite electrode to dc and ac polarizations under three different experimental configurations. This analysis allows the physical properties to be obtained even when the various resistances in the composite (e.g., ionic, electronic, and charge-transfer) are of comparable values.

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Modeling Heat Conduction In Spiral Geometries, Parthasarathy M. Gomadam, Ralph E. White, John W. Weidner Jan 2003

Modeling Heat Conduction In Spiral Geometries, Parthasarathy M. Gomadam, Ralph E. White, John W. Weidner

Faculty Publications

A two-dimensional (2-D) energy balance (the 2D model) is reduced to a one-dimensioanl (1-D) energy balance (the 1D-radial-spiral model) by a coordinate transformation approach. The 1D-radial-spiral model, even though 1-D, captures both radial and spiral heat conductions over a wide range of design parameters. By comparing the temperature predictions of the 1D-radial-spiral model and the 2D model, parameter ranges were identified where spiral conduction was important and where the 1D-radial-spiral model held. The 1D-radial-spiral model provided a sixtyfold savings in computation time over the 2D model. When coupled to electrochemistry, the 2D model took approximately 20 h to simulate a …

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Analysis Of Molten Carbonate Fuel Cell Performance Using A Three-Phase Homogeneous Model, N. Subramanian, B. S. Haran, P. Ganesan, Ralph E. White, Branko N. Popov Jan 2003

Analysis Of Molten Carbonate Fuel Cell Performance Using A Three-Phase Homogeneous Model, N. Subramanian, B. S. Haran, P. Ganesan, Ralph E. White, Branko N. Popov

Faculty Publications

In this study a three-phase homogeneous model was developed to simulate the performance of the molten carbonate fuel cell (MCFC) cathode. The homogeneous model is based on volume averaging of different variables in the three phases over a small volume element. This approach can be used to model porous electrodes as it represents the real system much better than the conventional agglomerate model. Using the homogeneous model the polarization characteristics of the MCFC cathode was studied under different operating conditions.

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A Mathematical Model Of Oxide/Carbon Composite Electrode For Supercapacitors, Hansung Kim, Branko N. Popov Jan 2003

A Mathematical Model Of Oxide/Carbon Composite Electrode For Supercapacitors, Hansung Kim, Branko N. Popov

Faculty Publications

A pseudo two-dimensional model is developed for the general application of supercapacitors consisting of an oxide/carbon composite electrode. The model takes into account the diffusion of protons in the oxide particle by employing the method of superposition. RuO2/carbon system is modeled as a specific example. From the simulation data, it is found that the oxide particle size and proton diffusion coefficient have an enormous effect on the performance at high discharge rate due to the limitation of proton transport into RuO2 particles. With increasing carbon ratio, the porosity of electrode increases, which causes the potential drop in …

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A Novel Electrodeposition Process For Plating Zn-Ni-Cd Alloys, Hansung Kim, Branko N. Popov, Ken S. Chen Jan 2003

A Novel Electrodeposition Process For Plating Zn-Ni-Cd Alloys, Hansung Kim, Branko N. Popov, Ken S. Chen

Faculty Publications

Zn-Ni-Cd alloy was electrodeposited from an alkaline electrolytic bath under potentiostatic conditions. Bath analyses using a pH concentration diagram reveal that addition of a complexing agent is essential to maintain the bath stability. Introduction of a low concentration of CdSO4 reduces the anomalous nature of the Zn-Ni deposit. Deposits obtained from the electrolytic bath which contains 60 g/L of ZnSO4·7H2O, 40 g/L of NiSO4·6H2O, 1 g/L of CdSO4, and 80 g/L of (NH4)2SO4 in the presence of additives and ammonium hydroxide at pH 9.3 …

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High-Pressure Coal Pyrolysis In A Drop Tube Furnace, Koichi Matsuoka, Zhi-Xin Ma, Hiroyuki Akiho, Zhan-Guo Zhang, Akira Tomita, Thomas H. Fletcher, Marek A. Wojtowicz, Stephen Niksa Jan 2003

High-Pressure Coal Pyrolysis In A Drop Tube Furnace, Koichi Matsuoka, Zhi-Xin Ma, Hiroyuki Akiho, Zhan-Guo Zhang, Akira Tomita, Thomas H. Fletcher, Marek A. Wojtowicz, Stephen Niksa

Faculty Publications

To obtain useful and reliable pyrolysis data under high pressures, continuous pyrolysis experiments were carried out using a drop tube furnace. To ascertain the reliability of data, a mass balance during pyrolysis was carefully checked. The pyrolysis data obtained in this equipment was compared with previous results, and it was found that the weight loss observed in the drop tube furnace was somewhat larger than those obtained with other apparatuses. The experimental results were compared with those predicted by three pyrolysis models. Although discrepancies between predictions and experimental results were observed under a certain condition, the agreement between the experimental …

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High-Pressure Intrinsic Oxidation Kinetics Of Two Coal Chars, William C. Hecker, Peter M. Madsen, Michael R. Sherman, Jared W. Allen, Rebecca J. Sawaya, Thomas H. Fletcher Jan 2003

High-Pressure Intrinsic Oxidation Kinetics Of Two Coal Chars, William C. Hecker, Peter M. Madsen, Michael R. Sherman, Jared W. Allen, Rebecca J. Sawaya, Thomas H. Fletcher

Faculty Publications

Chars were produced from two coals (North Dakota lignite and Pittsburgh No. 8 hva bituminous coal) in a flat flame burner at atmospheric pressure. Intrinsic char reactivities to oxygen were then measured in a high-pressure thermogravimetric analyzer as a function of temperature, total pressure, and partial pressure of oxygen. Care was taken to avoid mass transfer effects. Reactivities were normalized by the available mass of char at any given time (g/(gavailâs)). Reactivity data were obtained over a wide range of char burnout and were found to be independent of burnout level between char burnouts of 20 and 60%. Data were …

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Effect Of Catalyst Structure On Oxidative Dehydrogenation Of Ethane And Propane On Alumina-Supported Vanadia, Morris D. Argyle, Kaidong Chen, Alexis T. Bell, Enrique Iglesia Feb 2002

Effect Of Catalyst Structure On Oxidative Dehydrogenation Of Ethane And Propane On Alumina-Supported Vanadia, Morris D. Argyle, Kaidong Chen, Alexis T. Bell, Enrique Iglesia

Faculty Publications

The catalytic properties of Al2O3-supported vanadia with a wide range of VOx surface density (1.4-34.2 V/nm2) and structure were examined for the oxidative dehydrogenation of ethane and propane. UV-visible and Raman spectra showed that vanadia is dispersed predominately as isolated monovanadate species below ~2.3 V/nm2. As surface densities increase, two-dimensional polyvanadates appear (2.3-7.0 V/nm2) along with increasing amounts of V2O5 crystallites at surface densities above 7.0 V/nm2. The rate constant for oxidative dehydrogenation (k1) and its ratio with alkane and alkene combustion (k2/k1 and k3/k1, respectively) were compared for both alkane reactants as a function of vanadia surface density. Propene …

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Global Expression Profiling Of Acetate-Grown Escherichia Coli, Min-Kyu Oh, Lars Rohlin, Katy Kao, James Liao Jan 2002

Global Expression Profiling Of Acetate-Grown Escherichia Coli, Min-Kyu Oh, Lars Rohlin, Katy Kao, James Liao

Faculty Publications

This study characterized the transcript profile of Escherichia coli in acetate cultures using DNA microarray on glass slides. Glucose-grown cultures were used as a reference. At the 95% confidence level, 354 genes were up-regulated in acetate, while 370 genes were down-regulated compared with the glucose-grown culture. Generally, more metabolic genes were up-regulated in acetate than other gene groups, while genes involved in cell replication, transcription, and translation machinery tended to be down-regulated. It appears that E. coli commits more resources to metabolism at the expense of growth when cultured in the poor carbon source. The expression profile confirms many known …

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Effects Of Welding Electropolished 316l Stainless Steel As Used In Ultra-Pure Fluid Delivery Systems For The Semiconductor And Pharmaceutical Industries, Guna S. Selvaduray, S. Trigwell Jan 2002

Effects Of Welding Electropolished 316l Stainless Steel As Used In Ultra-Pure Fluid Delivery Systems For The Semiconductor And Pharmaceutical Industries, Guna S. Selvaduray, S. Trigwell

Faculty Publications

In the semiconductor and pharmaceutical industries, care is taken to prevent any contribution to product contamination or corrosion from the fluid delivery systems. Electropolished 316L stainless steel has become the industry standard due to its superior corrosion resistance. However, welding of the tubing often leads to discoloration in the heat affected zone (HAZ) which can lead to corrosion. Electropolished specimens from various lots of 316L stainless steel tubing were welded under identical parameters, but with varying concentrations of oxygen leaked into the argon purge gas during the welding, simulating on-site welding conditions. Various levels of discoloration were observed in the …

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Water Transport In Polymer Electrolyte Membrane Electrolyzers Used To Recycle Anhydrous Hcl: I. Characterization Of Diffusion And Electro-Osmotic Drag, Sathya Motupally, Aaron J. Becker, John W. Weidner Jan 2002

Water Transport In Polymer Electrolyte Membrane Electrolyzers Used To Recycle Anhydrous Hcl: I. Characterization Of Diffusion And Electro-Osmotic Drag, Sathya Motupally, Aaron J. Becker, John W. Weidner

Faculty Publications

In this paper, diffusion and electro-osmotic drag of water across Nafion® membranes in the presence of HCl are characterized. For all the measurements, one side of the Nafion membrane was in contact with liquid water and the other side with gaseous anhydrous HCl. To characterize diffusion of water, the open-circuit flux of water across a catalyst-coated Nafion 115 membrane was measured as a function of HCl flow rate and temperature at a constant cell pressure of 1 atm. Due to the nature of varying driving force for diffusion as a function of HCl flow rate, the experimental data was analyzed …

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Development Of A Novel Co Tolerant Proton Exchange Membrane Fuel Cell Anode, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang Jan 2002

Development Of A Novel Co Tolerant Proton Exchange Membrane Fuel Cell Anode, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang

Faculty Publications

Typically Pt is alloyed with metals such as Ru, Sn, or Mo to provide a more CO-tolerant, high-performance proton exchange membrane fuel cell (PEMFC) anode. In this work, a layer of carbon-supported Ru is placed between the Pt catalyst and the anode flow field to form a filter. When oxygen is added to the fuel stream, it was predicted that the slow H2 kinetics of Ru in this filter would become an advantage compared to Pt and Pt:Ru alloy anodes, allowing a greater percentage of O2 to oxidize adsorbed CO to CO2. With an anode feed …

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Studies On Capacity Fade Of Spinel-Based Li-Ion Batteries, Ramadass Premanand, Anand Durairajan, Bala Haran, Ralph E. White, Branko N. Popov Jan 2002

Studies On Capacity Fade Of Spinel-Based Li-Ion Batteries, Ramadass Premanand, Anand Durairajan, Bala Haran, Ralph E. White, Branko N. Popov

Faculty Publications

The performance of Cell-Batt® Li-ion cells using nonstoichiometric spinel as the positive electrode material has been studied at different charging rates. The capacity of the cell was optimized based on varying the charging current and the end potential. Subsequent to this, the capacity fade of these batteries was studied at different charge currents. During cycling, cells were opened at intermittent cycles and extensive material and electrochemical characterization was done on the active material at both electrodes. For all charge currents, the resistance of both the electrodes does not vary significantly with cycling. This result is in contrast with cells …

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Modeling The Effects Of Ion Association On Alternating Current Impedance Of Solid Polymer Electrolytes, Changqing Lin, Ralph E. White, Harry J. Ploehn Jan 2002

Modeling The Effects Of Ion Association On Alternating Current Impedance Of Solid Polymer Electrolytes, Changqing Lin, Ralph E. White, Harry J. Ploehn

Faculty Publications

This work presents a rigorous continuum model describing the transport of ions and associated ion pairs in solid polymer electrolytes subjected to small amplitude alternating current (ac) excitation. The model treats ion association as a reversible reaction among ions and ion pairs. Dimensionless governing equations are developed from component mass balances, flux equations based on dilute solution theory, and the Poisson equation. Assuming reversible electrode reactions and electroneutrality, the model equations have an analytical solution. Further simplifications are possible in limiting cases (weak and strong association, zero and infinite frequency excitation), giving expressions consistent with previously published models. We use …

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Estimation Of Diffusion Coefficient Of Lithium In Carbon Using Ac Impedance Technique, Qingzhi Guo, Venkat R. Subramanian, John W. Weidner, Ralph E. White Jan 2002

Estimation Of Diffusion Coefficient Of Lithium In Carbon Using Ac Impedance Technique, Qingzhi Guo, Venkat R. Subramanian, John W. Weidner, Ralph E. White

Faculty Publications

The validity of estimating the solid phase diffusion coefficient, Ds, of a lithium intercalation electrode from impedance measurement by a modified electrochemical impedance spectroscopy (EIS) method is studied. A macroscopic porous electrode model and concentrated electrolyte theory are used to simulate the synthetic impedance data. The modified EIS method is applied for estimating Ds. The influence of parameters such as the exchange current density, radius of active material particle, solid phase conductivity, porosity, volume fraction of inert material, and thickness of the porous carbon intercalation electrode, the solution phase diffusion coefficient, and transference number, on the …

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Using Sputter Deposition To Increase Co Tolerance In A Proton-Exchange Membrane Fuel Cell, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang, Steven Shi, Narender Rana, Stephan Grunow, Timothy C. Stoner, Alain E. Kaloyeros Jan 2002

Using Sputter Deposition To Increase Co Tolerance In A Proton-Exchange Membrane Fuel Cell, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang, Steven Shi, Narender Rana, Stephan Grunow, Timothy C. Stoner, Alain E. Kaloyeros

Faculty Publications

Placing a layer of Ru atop a Pt anode increases the carbon monoxide tolerance of proton-exchange membrane fuel cells when oxygen is added to the fuel stream. Sputter-deposited Ru filter anodes composed of a single Ru layer and three Ru layers separated by Nafion-carbon ink, respectively, were compared to Pt, Pt:Ru alloy, and an ink-based Ru filter anodes. The amount of Pt in each anode was 0.15 mg/cm2 and the amount of Ru in each Ru-containing anode was 0.080 mg/cm2. For an anode feed consisting of hydrogen, 200 ppm CO, and 2% O2 (in the form …

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Increasing Proton Exchange Membrane Fuel Cell Catalyst Effectiveness Through Sputter Deposition, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang, Steven Shi, Timothy Stoner, Narender Rana Jan 2002

Increasing Proton Exchange Membrane Fuel Cell Catalyst Effectiveness Through Sputter Deposition, Andrew T. Haug, Ralph E. White, John W. Weidner, Wayne Huang, Steven Shi, Timothy Stoner, Narender Rana

Faculty Publications

Sputter deposition has been investigated as a tool for manufacturing proton-exchange membrane fuel cell (PEMFC) electrodes with improved performance and catalyst utilization vs. ink-based electrodes. Sputter-depositing a single layer of Pt on the gas diffusion layer provided better performance (0.28 A/cm2 at 0.6 V) than sputtering the Pt directly onto a Nafion membrane (0.065 A/cm2 at 0.6 V) and equaled the performance of the baseline for an equivalent Pt loading. Sputter-depositing alternating layers of Pt and Nafion-carbon ink (NCI) onto the membrane did not increase the performance over the baseline as measured in amperes per centimeter squared due …

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Simulating Shape Changes During Electrodeposition: Primary And Secondary Current Distribution, Venkat R. Subramanian, Ralph E. White Jan 2002

Simulating Shape Changes During Electrodeposition: Primary And Secondary Current Distribution, Venkat R. Subramanian, Ralph E. White

Faculty Publications

A technique based on the analytical method of lines is presented for predicting shape changes during electrodeposition. The technique is presented for both primary and secondary current distributions. The method presented does not require iterations for nonlinear Butler-Volmer boundary conditions or changing electrode shapes. The technique is based on a semianalytical method developed earlier for predicting current distributions in electrochemical cells. This technique is attractive because it provides a symbolic solution for the Laplace equation, and hence requires less computation time to perform case studies.

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Electrochemical Filtering Of Co From Fuel-Cell Reformate, Balasubramanian Lakshmanan, Wayne Huang, John W. Weidner Jan 2002

Electrochemical Filtering Of Co From Fuel-Cell Reformate, Balasubramanian Lakshmanan, Wayne Huang, John W. Weidner

Faculty Publications

A proton exchange membrane fuel cell was used as a flow reactor for continuous preferential oxidation of CO over H2 from 1.0% CO in H2 under pulse-potential control. By varying the pulse profile ~e.g., on-time, off-time, pulse potential! the CO and H2 oxidation currents were varied independently. The improvement in faradaic selectivity between CO and H2 oxidation results from the promotion of CO adsorption during the off ~i.e., open-circuit! portion of the pulse. Therefore, during the on portion CO oxidation was preferred while the surface was covered with CO.

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