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Full-Text Articles in Engineering
Novel Pemfc Cathodes Prepared By Pulse Deposition, Subasri M. Ayyadurai, Yoon-Seok Choi, Prabhu Ganesan, Swaminatha P. Kumaraguru, Branko N. Popov
Novel Pemfc Cathodes Prepared By Pulse Deposition, Subasri M. Ayyadurai, Yoon-Seok Choi, Prabhu Ganesan, Swaminatha P. Kumaraguru, Branko N. Popov
Faculty Publications
A pulse electrodeposition method of preparing thin platinum catalyst layers for polymer electrolyte membrane fuel cell (PEMFC) cathodes has been developed through surface activation of the gas diffusion layer (GDL) by a wetting agent. The performance of the catalyst layer was optimized by wetting agent type, immersion time in the wetting agent, and pulse deposition parameters such as total charge density, peak current density, and duty cycle ratio. The Toff time played a more important role than the Ton time in determining the electrode characteristics such as high concentration of Pt, smaller particle size, and loading. Pt cathodes …
High-Pressure Torsion-Induced Grain Growth In Electrodeposited Nanocrystalline Ni, X. Z. Liao, A. R. Kilmametov, R. Z. Valiev, Hongsheng Gao, Xiaodong Li, A. K. Mukherjee, J. F. Blingert, Y. T. Zhu
High-Pressure Torsion-Induced Grain Growth In Electrodeposited Nanocrystalline Ni, X. Z. Liao, A. R. Kilmametov, R. Z. Valiev, Hongsheng Gao, Xiaodong Li, A. K. Mukherjee, J. F. Blingert, Y. T. Zhu
Faculty Publications
Deformation-induced grain growth has been reported in nanocrystalline (nc) materials under indentation and severe cyclic loading, but not under any other deformation mode. This raises an issue on critical conditions for grain growth in nc materials. This study investigates deformation-induced grain growth in electrodeposited nc Ni during high-pressure torsion (HPT). Our results indicate that high stress and severe plastic deformation are required for inducing grain growth, and the upper limit of grain size is determined by the deformation mode and parameters. Also, texture evolution suggests that grain-boundary-mediated mechanisms played a significant role in accommodating HPT strain.
Development Of An Electroless Method To Deposit Corrosion-Resistant Silicate Layers On Metallic Substrates, Swaminatha P. Kumaraguru, Basker Veeraraghavan, Branko N. Popov
Development Of An Electroless Method To Deposit Corrosion-Resistant Silicate Layers On Metallic Substrates, Swaminatha P. Kumaraguru, Basker Veeraraghavan, Branko N. Popov
Faculty Publications
A novel electroless method for depositing corrosion-resistant silicate layers on metallic substrates from aqueous solutions has been developed. The silicate layer was deposited from an aqueous solution of sodium silicate (3.22 weight ratio sodium silicate, 37.5% solution in water from PQ Corporation) and sodium borohydride. The technique is demonstrated by forming a passive film on galvanized steel. Deposition parameters such as concentration of the bath, temperature, and pH have been optimized based on the corrosion characteristics of the final coating. Studies on the coating reveal the formation of a very thin (5 nm) zinc disilicate layer followed by a much …
Mechanics Of Hydrogenated Amorphous Carbon Deposits From Electron-Beam-Induced Deposition Of Paraffin Precursor, W. Ding, D. A. Dikin, X. Chen, R. D. Piner, R. S. Ruoff, E. Zussman, X. Wang, Xiaodong Li
Mechanics Of Hydrogenated Amorphous Carbon Deposits From Electron-Beam-Induced Deposition Of Paraffin Precursor, W. Ding, D. A. Dikin, X. Chen, R. D. Piner, R. S. Ruoff, E. Zussman, X. Wang, Xiaodong Li
Faculty Publications
Many experiments on the mechanics of nanostructures require the creation of rigid clamps at specific locations. In this work, electron-beam-induced deposition(EBID) has been used to depositcarbonfilms that are similar to those that have recently been used for clamping nanostructures. The film deposition rate was accelerated by placing a paraffin source of hydrocarbon near the area where the EBIDdeposits were made. High-resolution transmission electron microscopy, electron-energy-loss spectroscopy, Raman spectroscopy, secondary-ion-mass spectrometry, and nanoindentation were used to characterize the chemical composition and the mechanics of the carbonaceous deposits. The typical EBIDdeposit was found to be hydrogenated amorphous carbon (a-C:H) having …
Development Of Novel Method For Preparation Of Pemfc Electrodes, Hansung Kim, Branko N. Popov
Development Of Novel Method For Preparation Of Pemfc Electrodes, Hansung Kim, Branko N. Popov
Faculty Publications
A method based on pulse electrodeposition technique was developed for preparation of membrane electrode assemblies (MEAs). In this approach, platinum is deposited directly on the surface of the carbon electrode. The method ensures most of the platinum to be in close contact with the membrane. Using this method it is possible to increase the Pt/C ratio up to 75 wt % near the surface of the electrode resulting in a 5 µm thick catalyst layer. The MEA prepared by pulse electrodeposition exhibits a current density of 0.33 A/cm2 at 0.8 V with platinum loading of 0.25 mg of Pt/cm …
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
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 …
A Novel Electrodeposition Process For Plating Zn-Ni-Cd Alloys, Hansung Kim, Branko N. Popov, Ken S. Chen
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 …
Simulating Shape Changes During Electrodeposition: Primary And Secondary Current Distribution, Venkat R. Subramanian, Ralph E. White
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.
Development Of A New Electrodeposition Process For Plating Of Zn-Ni-X (X = Cd, P) Alloys: I. Corrosion Characteristics Of Zn-Ni-Cd Ternary Alloys, Anand Durairajan, Bala S. Haran, Ralph E. White, Branko N. Popov
Development Of A New Electrodeposition Process For Plating Of Zn-Ni-X (X = Cd, P) Alloys: I. Corrosion Characteristics Of Zn-Ni-Cd Ternary Alloys, Anand Durairajan, Bala S. Haran, Ralph E. White, Branko N. Popov
Faculty Publications
A new Zn-Ni-Cd plating process was developed which offers a unique way of controlling and optimizing the Ni and Cd contents in the final deposit. Zinc-nickel-cadmium alloy was deposited from a 0.5 M NiSO4 + 0.2 M ZnSO4 bath in the presence of 0.015 M CdSO4 and 1 g/L nonyl phenyl polyethylene oxide. Using this process a Zn-Ni-Cd ternary alloy, with a higher nickel content as compared to that obtained from conventional Zn-Ni baths, was synthesized. The Zn-Ni-Cd alloy coatings deposited from an electrolyte containing 0.015 M (0.3%) CdSO4 has a Zn to Ni ratio of …
Development Of A New Electrodeposition Process For Plating Of Zn-Ni-X (X = Cd, P) Alloys: Permeation Characteristics Of Zn-Ni-Cd Ternary Alloys, A. Durairajan, B. S. Haran, Ralph E. White, Branko N. Popov
Development Of A New Electrodeposition Process For Plating Of Zn-Ni-X (X = Cd, P) Alloys: Permeation Characteristics Of Zn-Ni-Cd Ternary Alloys, A. Durairajan, B. S. Haran, Ralph E. White, Branko N. Popov
Faculty Publications
It is shown that an electrodeposited Zn-Ni-Cd alloy coating produced from sulfate electrolyte inhibits the discharge of hydrogen on carbon steel. The newly developed ternary alloys have approximately ten times higher corrosion resistance when compared to a Zn-Ni alloy. Hydrogen permeation characteristics of Zn-Ni-Cd alloy coatings were studied and compared with those of a bare and a Zn-Ni alloy coated steel. The transfer coefficient, a, exchange current density, io, thickness dependent adsorption-absorption rate constant, k0, recombination rate constant, k3, surface hydrogen coverage, θH, were obtained by applying a mathematical model to experimental results. Alloys obtained from baths containing higher concentration …
A Model For The Galvanostatic Deposition Of Nickel Hydroxide, Mahesh Murthy, Gowri S. Nagarajan, John W. Weidner, John W. Van Zee
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 …
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
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.
Linear Algebra Used To Determine Independent Half‐Cell Equations, D. H. Coleman, Ralph E. White
Linear Algebra Used To Determine Independent Half‐Cell Equations, D. H. Coleman, Ralph E. White
Faculty Publications
No abstract provided.
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
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 …
Use Of Underpotential Deposition Of Zinc To Mitigate Hydrogen Absorption Into Monel K500, G. Zheng, Branko N. Popov, Ralph E. White
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%.
Parametric Studies Of The Formation Of Calcareous Deposits On Cathodically Protected Steel In Seawater, J. F. Yan, Ralph E. White, R. B. Griffin
Parametric Studies Of The Formation Of Calcareous Deposits On Cathodically Protected Steel In Seawater, J. F. Yan, Ralph E. White, R. B. Griffin
Faculty Publications
A first principle mathematical model has been used to study the effects of ocean environment and cathodic protection on the formation of calcareous deposits and their ability to reduce the cathodic current density. These parameters include applied potential, rotation speed, temperature, salinity, and depth. The results showed the applied potential strongly influences the formation of calcareous deposits and their ability to reduce the cathodic current density. Among the environmental factors, rotation speed has the most influence on the cathodic current density. Salinity slightly influences the cathodic current density over the range of interest. Temperature is much more influential than salinity …
A Mathematical Model For The Electrodeposition Of Alloys On A Rotating Disk Electrode, Shiuan Chen, Ken-Ming Yin, Ralph E. White
A Mathematical Model For The Electrodeposition Of Alloys On A Rotating Disk Electrode, Shiuan Chen, Ken-Ming Yin, Ralph E. White
Faculty Publications
A general multiple electrode reaction model for electrodeposition of alloys on a rotating disk electrode is presented. Included in the model are mass transport equations with the effect of ionic migration, Butler-Volmer kinetic rate expressions, and the mole fractions of the individual components in the solid state. The model shows that the effect of ionic migration is important and that plating variables such as applied potential, pH, and bulk concentration can be included. Two examples (Ni-P and Ru-Ni-P) are used to illustrate the predictions of the model.
Electrochemical Production And Corrosion Testing Of Amorphous Ni-P, Jose L. Carbajal, Ralph E. White
Electrochemical Production And Corrosion Testing Of Amorphous Ni-P, Jose L. Carbajal, Ralph E. White
Faculty Publications
Ni-P alloys were prepared by electrodeposition under different conditions on a rotating disk electrode. A variety of alloys were prepared ranging from Ni-15P to Ni-25P. An indirect reduction of species in solution involving several steps appears to be favored over the direct reduction at the electrode based on the low P content in the alloy. Energy dispersion x-ray microanalysis was used to determine composition of the alloy. Transmission electron microscopy and x-ray diffraction corroborated the amorphous nature of the structure. The physical and chemical homogeneity of the metallic glasses produced electrochemically is substantiated by the absence of electrochemical localized attack. …
Electrodeposition Of Copper-Nickel Alloys From Citrate Solutions On A Rotating Disk Electrode, Ramona Y. Ying, Patrick K. Ng, Z. Mao, Ralph E. White
Electrodeposition Of Copper-Nickel Alloys From Citrate Solutions On A Rotating Disk Electrode, Ramona Y. Ying, Patrick K. Ng, Z. Mao, Ralph E. White
Faculty Publications
A mathematical model is developed to simulate the electrodeposition of Cu-Ni alloy from citrate solutions onto a rotating disk electrode under potentiostatic control. The model includes the influence of diffusion, ionic migration, forced convection, and homogeneous equilibria. The three major electrochemical reactions treated in the model are copper deposition, nickel deposition, and hydrogen evolution. Using experimental parameters when available, the model was fitted and tested against experimentally-obtained results for different bath compositions and operating conditions. The model agreed reasonably well with the experimental results particularly in the codeposition region, –1.0 to –1.2V vs. SCE, where hydrogen evolution is not the …
Potential-Selective Deposition Of Copper From Chloride Solutions Containing Iron, Ralph E. White, James A. Trainham, John Newman, Thomas W. Chapman
Potential-Selective Deposition Of Copper From Chloride Solutions Containing Iron, Ralph E. White, James A. Trainham, John Newman, Thomas W. Chapman
Faculty Publications
The hydrometallurgy of copper may involve leaching of the metal from its ore with an aqueous solution containing cupric and ferric chloride. The subsequent deposition of copper from such a process stream is modeled here in an idealized electrochemical cell with a rotating-disk electrode. The potential distribution and concentration profiles within the diffusion layer are predicted for given potential differences between the electrode and the solution. The cuprous ion, which is formed by the reduction of the complexed cupric ion at the electrode, is stabilized in the chloride solution and can react either at the electrode or with ferric species …