Engineering Commons^™

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 Popov

Faculty Publications

No abstract provided.

Computational Fluid Dynamics Modeling Of A Lithium/Thionyl Chloride Battery With Electrolyte Flow, W. B. Gu, C. Y. Wang, John W. Weidner, Rudolph G. Jungst, Ganesan Nagasubramanian

Faculty Publications

A two-dimensional model is developed to simulate discharge of a lithium/thionyl chloride primary battery. As in earlier one-dimensional models, the model accounts for transport of species and charge, and electrode porosity variations and electrolyte flow induced by the volume reduction caused by electrochemical reactions. Numerical simulations are performed using a finite volume method of computational fluid dynamics. The predicted discharge curves for various temperatures show good agreement with published experimental data, and are essentially identical to results published for one-dimensional models. The detailed two-dimensional flow simulations show that the electrolyte is replenished from the cell head space predominantly through the …

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 …

Modeling Lithium Intercalation Of A Single Spinel Particle Under Potentiodynamic Control, Dong Zhang, Branko N. Popov, Ralph E. White

Faculty Publications

A mathematical model is presented for the lithium intercalation of a single spinel particle as a microelectrode under the stimulus of a cyclic linear potential sweep. The model includes both lithium diffusion within the particle and kinetics at the particle/electrolyte interface. The model is used to predict that peak current densities depend linearly on the scan rate to a certain power with a constant term, which is different from the predicted peak current density for a conventional redox system.

Shrinking Core Model For The Discharge Of A Metal Hydride Electrode, Venkat R. Subramanian, Harry J. Ploehn, Ralph E. White

Faculty Publications

A shrinking core model is presented for the galvanostatic discharge of a metal hydride particle. A quantitative criterion for when the shrinking core can be completely neglected or approximated by a pseudosteady-state solution is presented. The effect of shrinking of the core on the discharge behavior of a metal hydride particle is also studied.

Solid-State 13c Nmr Characterization Of Matched Tars And Chars From Rapid Coal Devolatilization, Steven T. Perry, Eric M. Hambly, Thomas H. Fletcher, Mark S. Solum, Ronald J. Pugmire

Faculty Publications

Matched tar/char sets were prepared by pyrolysis of a lignite and a bituminous coal in two entrained flow reactors at temperatures between 900 K and 1650 K and heating rates of 10⁴–10⁵ K/s. Detailed chemical structural characterization of these tars and chars was performed using elemental analysis and solid-state ¹³C NMR. This is the first set of detailed solid-state ¹³C nuclear magnetic resonance (NMR) data on coal tar samples. The average aromatic cluster sizes of the primary tars from these experiments are quite similar to those of their parent coals, confirming an assumption often made …

Modeling High Pressure Char Oxidation Using Langmuir Kinetics With An Effectiveness Factor, Jianhui Hong, William C. Hecker, Thomas H. Fletcher

Faculty Publications

The global nth order rate equation has been criticized for lack of theoretical basis and has been shown to be inadequate for modeling char oxidation rates as a function of total gas pressure. The simple Langmuir rate equation is believed to have more potential for modeling high pressure char oxidation. The intrinsic Langmuir rate equation is applied to graphite flake oxidation data and agrees well with reaction rates at three temperatures over the entire range of oxygen pressure (1–64 atm). It also explains the change of reaction order with temperature. In this work, the intrinsic Langmuir rate equation is combined …

Improving The Accuracy Of Predicting Effectiveness Factors For Mth Order And Langmuir Rate Equations In Spherical Coordinates, Jianhui Hong, William C. Hecker, Thomas H. Fletcher

Faculty Publications

Char oxidation is often modeled using an mth order intrinsic reaction rate in conjunction with an effectiveness factor to account for intraparticle diffusion of gas species. This approach involves the use of a general modulus (M_T) and using the first-order curve of effectiveness factor vs M_T. This method was originally referred to as the general asymptotic solution. It has been suggested that a simple Langmuir rate equation is more suitable for modeling the effects of pressure on char reactivity. Therefore, several methods of developing general moduli for the Langmuir rate expression are shown. The general asymptotic …

Measurement Of Soot And Char In Pulverized Coal Fly Ash, John M. Veranth, Thomas H. Fletcher, David W. Pershing, Adel F. Sarofim

Faculty Publications

The unburned carbon in the fly ash produced by low-NOx pulverized coal combustion has been shown by electron microscopy to be a mixture of porous coal char particles and aggregates of submicron particles, which are thought to be soot. The carbon is bimodally distributed with large soot aggregates mixed with the char in the particles larger than 10 microns and dispersed soot found with the submicron particles. A method for determining the mass of soot and char by liquid-suspension gravity separation was used with both laboratory-scale and power plant fly ash samples. For low-NOx, staged, pilot-scale combustion of bituminous coal …

The Use Of Two Mixture Fractions To Treat Coal Combustion Products In Turbulent Pulverized-Coal Flames, Daniel V. Flores, Thomas H. Fletcher

Faculty Publications

Previous coal combustion models using assumed-shape PDF's to treat turbulence-chemistry interactions have used only one progress variable to treat products from coal reactions. This assumes that the products of all coal reactions have the same composition. However. the composition of the combustion products of coal particles is known to vary with burnout, especially between devclatilization and char oxidation. In this work, two progress variables were implemented which distinguish between the products of devolatilization and those of char oxidation. This new approach requires as input the specified volatile content and elemental release during devolatilization. The values for these parameters were estimated …

Modeling And Simulation Of The Dynamic Behavior Of Monoliths: Effects Of Pore Structure From Pore Network Model Analysis And Comparison With Columns Packed With Porous Spherical Particles, Athanasios I. Liapis, J. J. Meyers, Orrin K. Crosser

Chemical and Biochemical Engineering Faculty Research & Creative Works

A mathematical model is presented that could be used to describe the dynamic behavior, scale-up, and design of monoliths involving the adsorption of a solute of interest. The value of the pore diffusivity of the solute in the pores of the skeletons of the monolith is determined in an a priori manner by employing the pore network modeling theory of Meyers and Liapis [J. Chromatogr. A, 827 (1998) 197 and 852 (1999) 3]. The results clearly show that the pore diffusion coefficient, D(mp), of the solute depends on both the pore size distribution and the pore connectivity, n(T), of the …

The Effect Of System And Oxygen Partial Pressure On Single Coal Particle Heterogeneous Ignition Temperature Under Conditions Of Negligible Convection; Experimental Observation, H. Katalambula

Tanzania Journal of Engineering and Technology (TJET)

Abstract Under conditions of high volatile concentrations, the influence of oxygen concentration on single coal particle ignition becomes more significant. The high volatile concentration conditions have been simulated by employing a microgravity environment. Results show that under these conditions, the heterogeneous ignition temperature decreases faster with increasing oxygen concentration than under normal conditions. The ignition temperature also decreases with increasing system and oxygen partial pressure under both conditions. Generally, the system and oxygen partial pressure show similar and complimenting effects on ignition temperature.

Application Of Vibrational Techniques In Determination Of Dynamic Properties Of Agricultural Products-State Of The Arton Of Vibrational Techniques In Determination Of Dynamic Properties Of Agricultural Products-State Of The Art, Silas Kajuna

Tanzania Journal of Engineering and Technology (TJET)

Vibration is one of the techniques employed in the determination of dynamic properties of fruits and vegetables. It entails generation of a mechanical or acoustic vibrational signal which is propagated through the flesh of the agricultural material. A transducer is either attached or held close to the specimen to monitor the propagation of the signal through the specimen. The manner in which the signal is transmitted through the material is analyzed, and the dynamic properties of the specimen which relate to its firmness or its internal being are derived. The technique has been around for the past 30 years or …

Production Of Fermentable Sugars From Waterhyacinth By High-Temperature Dilute-Acid Hydrolysis Method, J. H. Y. Katima

Tanzania Journal of Engineering and Technology (TJET)

A study on acid-catalyzed hydrolysis of Waterhyacinth (WH) biomass for production of monomeric sugars has been done. Waterhyacinth (Eichhornia Crassipes) plants were obtained from Lake Victoria. A yield of 18.5% w/w fermentable sugars was achieved during hydrolysis of oven-dried Waterhyacinth (ODWH) biomass at 220°C and 1.5% w/w H₂SO₄ acid. The waterhyacinth (WH) hydrolysates obtained from a high-temperature dilute-acid hydrolysis were rich in six-carbon (C₆) sugars (glucose) which could be fermented to ethanol. The production of fermentable sugars from waterhyacinth biomass is a promising new opportunity for its economic value which can in turn accelerate its rate of harvest and utilization.

Estimation Of Volatile Cloud Density For Single Coal Particles Using Microgravity Condition, H. Katalambula

Tanzania Journal of Engineering and Technology (TJET)

Single coal particle’s volatile cloud density has been estimated by employing a microgravity condition. The volatile yield was found to decrease with pressure while the density was found to increase, indicating that volatiles occupies less space when under pressure and hence causing some volatiles to be retained within the particle. The volatile cloud density was also found to increase with volatile yield suggesting volatile composition changes with yield. The effect of heating rate on volatile yield was found to be the same as reported by other investigators where the yield increased with heating rate.

Measurement Of Markstein Lengths In Laminar Spherical Explosion Flames, E .M.J Mushi

Tanzania Journal of Engineering and Technology (TJET)

Schlieren photography was used to record the development of spherical flames in a combustion bomb. Flame speed and flame stretch were evaluated from the data and used to evaluate Markstein lengths and numbers. The results indicate a strong influence of both the spark discharge energy and equivalence ratio. Low spark discharge energy is observed to give rise to more unstable flames compared to high energy sparks. It is observed that for the range of energy tested, 80 and 400 mJ gave the best stability for the flames. For equivalence ratio less or equal to 1.225 an 80 mJ discharge results …

Lead-Free Interconnection For Electronic Devices, Ravi F. Saraf

Department of Chemical and Biomolecular Engineering: Patents

An electronic device that is equipped with a plurality of bonding pads positioned on the device for making electrical interconnections and electrically conductive composite bumps adhered to the bonding pads wherein the bumps are formed of a composite material consisting of a thermoplastic polymer and at least about 30 volume percent of conductive metal particles based on the total volume of the metal particles and the thermoplastic polymer. The present invention is also directed to a method of making electrical interconnections to an electronic device by pressing a plurality of composite bumps of a polymeric based material against a substrate …

Method For Providing Discharge Protection Or Shielding, Ravi F. Saraf

Department of Chemical and Biomolecular Engineering: Patents

Electrostatic discharge protection or electromagnetic interference shielding is provided by applying a composition comprising a thermoset or thermoplastic polymeric matrix, and a conductive filler component, where said filler component comprises electrically conductive particles and at least one conducting polymer to a dielectric substrate.

Double Twist In Helical Polymer "Soft" Crystals, Christopher Y. Li, Stephen Z. D. Cheng, Jason J. Ge, Feng Bai, John Z. Zhang, Ian K. Mann, Frank W. Harris, Lang-Chy Chien, Donghang Yan, Tianbai He, Bernard Lotz

College of Polymer Science and Polymer Engineering

In natural and synthetic materials having non-racemic chiral centers, chirality and structural ordering each play a distinct role in the formation of ordered states. Configurational chirality can be extended to morphological chirality when the phase, structures possess low liquid crystalline order. In the crystalline states the crystallization process suppresses the chiral helical morphology due to strong ordering interactions, In this Letter, we report the first observation of helical single lamellar crystals of synthetic non-racemic chiral polymers. Experimental evidence shows that the molecular chains twist along both the long and short axes of the helical lamellar crystals, which is the first …

The Electrochemical Behaviors Of Superoxide Dismutase At Promoter Modified Gold Electrode, Xia-Qin Wu, Xiao-Yun Meng, Zhe-Su Wang, Zong-Rang Zhang

Journal of Electrochemistry

The electron-transfer process of superoxide dismutase was investigated by cyclic voltammetry at the 4,4'-dithiodipyridine, L-cysteine, histidine and arginine modified gold wire electrodes repectively. The quasi-reversible behavior was observed at L-cysteine modified gold electrode. An irreversible electrochemical behavior has been observed at hisdinine modified gold wire electrode.

Electro-Oxidation Of Phenol On Sno2/Ti Electrodes Prepared By Thermal Oxidation, Qing-Song Zhang, Hui-Huang Wu

Journal of Electrochemistry

A SnO₂/Ti electrode prepared by thermal oxidation was used as the anode for galvanostatic electrolysis in acidic solution containing phenol, the time-dependances of phenol concentration, chemical oxygen demand in solution(COD) and instantaneous current efficiency were determined during electrolysis. The results show that with the SnO₂/Ti anode instead of Pt, the COD significantly decreases at the same charge passage, and average current efficiency of oxidation increases by three times. The mechanism for phenol oxidation at two electrodes was discussed.

Studies On Methods Of Fuel Cells Electrodes Preparation, Jun Gu, Sheng Sui, Guang-Qiang Li, Zhitong Sui

Journal of Electrochemistry

In fuel cells, the structure of electrodes is an important factor which effect the cell performance. To improve the structure and the performance of electrodes, a new method of providing fuel cell electrodes is proposed in this paper. PTFE (polytetrafluoroethylene) and ethyne black was ground for about half an hour in a high-speed grinder, then the catalyst was added into the grinder and milled for an hour. This milled catalyst was transferred into a mixer followed by the addition of surface-active agent. After a suspension was formed, it was filtered under vacuum condition.Then a thin uniform filter-cake of the catalyst …

Study On Electrochemical Reduction Properties Of Nitrobenzene, Chu-Na Ma, Wen-Kui Zhang, Hui Huang, Yong-Ping Gan

Journal of Electrochemistry

The electrochemical reduction characteristics of nitrobenzene was extensively investigated by using the techniques such as quasi-steady-state polarization, cyclic voltammetry, fast linear potential sweep method and chronoamperometry in this paper. The electroanalytic properties of Cu, Cu-Hg and Cu-Ni electrodes were evaluated. Based on the study of the transient steping behaviour of nitrobenzene to PAP, the reduction mechanism was discussed. The results showed that the transition steps existed on the electrochemical reduction of nitrobenzene in acidic solution, the reactant is also absorbed on electrodes surface. The control step in the reduction of nitrobenzene was ascribed to the diffusion of nitrobenzene and its …

High Performance Proton Exchange Membrane Fuel Cells, Jing-Rong Yu, Bao-Lian Yi, Ming Han, Xiao-Liang Cheng, Zhi-Gang Shao, Jing-Xin Zhang

Journal of Electrochemistry

Proton-exchange membrane fuel cells(PEMFC) using a perfluorosulfonic acid proton exchange membrane as an electrolyte can simplify water and electrolyte management. In this paper, the effects of thickness of PEM on the performance of PEMFC were studied. The Nafion-112 PEM and low platinum loading E-TEK electrode yielded very high power density, of the order of 0.95 W/cm². The energy-conversion efficiency, the degree of platinum utilization and stability for PEMFC using Nafion 112 and E-TEK electrode were also investigated.

Investigation Of Sodium Hypophosphite Anodic Oxidizing Behavior In The Process Of Acid Electroless Nickel Deposition, Mei-Yuan Wang, Ya-Fei Kuang, Yan Xu

Journal of Electrochemistry

The anodic oxidizing behavior of sodium hypophosphite in the process of electroless nickle deposition (pH=5.5) was investigated with the linear potential sweep method and alternating current impedance. The results indicated that, the oxidation of NaH₂PO₂ was a complicated electrochemical process and affected by the concentration of NaH₂PO₂, the temperature of the bath, the sweep rate and the existence of nickel ion. The NaH₂PO₂ electrooxidation reaction was very likely preceded by heterogeneous interface transformation process, which might be the control step of the whole anodic process.

Thermodynamic Model And The Controlling Variables Of Phosphate Lattice Loss, Mohammad Abutayeh

USF Tampa Graduate Theses and Dissertations

A thermodynamic model was developed based upon five equilibrium reactions to predict the limits of distribution of phosphates between the liquid and the solid phases in a reactor used to extract phosphoric acid from phosphate rock. A computer code was generated to carry out different simulations of the model using several inputs of temperatures and liquid phase sulfuric acid contents. Ideal Solution, Debye-Hückel, and Robinson-Guggenheim-Bates electrolyte activity coefficient models were employed alternately in each simulation to complete the thermodynamic model and the outputs were compared to one another.

Experimental data of equilibrium constants were regressed to adjust the values of …

Simulation And Density Functional Study Of A Simple Membrane Separating Two Restricted Primitive Model Electrolytes, Richard L. Rowley, Dezso Boda, Douglas Henderson, Stefan Sokolowski

Faculty Publications

A simple membrane, supporting charge densities on its inner and outer surfaces, is considered. In addition to the electrostatic potential, the membrane interacts with the surrounding fluid by a short range van der Waals-like potential. The fluid beyond the outer surface is a three-component restricted primitive electrolyte consisting of two cations and one anion. The membrane is impermeable to one of the cations so that the fluid in the membrane and beyond the inner surface is a two-component restricted primitive electrolyte. We use Monte Carlo simulations and density functional theory to study the density profiles of the electrolyte and the …

Method Of Destroying Hazardous Organic Compounds, Dibakar Bhattacharyya, Susan Mawhinney

Chemical and Materials Engineering Faculty Patents

The present invention relates to a method of destroying hazardous vapor phase or aqueous phase organic compound(s) by providing a polymeric siloxane based solvent in a vessel and adding the hazardous organic compound(s) and ozone to the solvent. The solvent may also comprise a mixture of polymeric siloxane based solvent and fluorinated hydrocarbon solvent.

Inside-Out Crosslinked And Commercial-Scale Hydrogels, And Sub-Macromolecular Selective Purification Using The Hyrdogels, William H. Velander, Kevin E. Van Cott

Department of Chemical and Biomolecular Engineering: Patents

Relating to chromatographic processes and ion-exchange and affinity matrices, a spatial installation method for a bifunctional reagent that crosslinks and/or activates a polymer matrix is disclosed, with inside-outside installation of a bifunctional reagent on and within a polymer matrix. The polymer matrix is cellulose, agarose, or chitosan particles. The installation may be followed by inside-outside ligand attachment, by further reacting the matrix with a ligand or ionic group so that a higher concentration of ligand or ionic moiety occurs on the intra-particle volume than the outer matrix surface.

Helical Single-Lamellar Crystals Thermotropically Formed In A Synthetic Nonracemic Chiral Main-Chain Polyester, Christopher Y. Li, Donghang Yan, Stephen Z. D. Cheng, Feng Bai, Jason J. Ge, Bret H. Calhoun, Tianbai He, Liang-Chy Chien, Frank W. Harris, Bernard Lotz

College of Polymer Science and Polymer Engineering

Phase structures and transformation mechanisms of nonracemic chiral biological and synthetic polymers are fundamentally important topics in understanding their macroscopic responses in different environments. It has been known for many years that helical structures and morphologies can exist in low-ordered chiral liquid crystalline (LC) phases. However, when the chiral liquid crystals form highly ordered smectic liquid crystal phases, the helical morphology is suppressed due to the crystallization process. A double-twisted morphology has been observed in many liquid crystalline biopolymers such as dinoflaggellate chromosomes (in Prorocentrum micans) in an in vivo arrangement. Helical crystals grown from solution have been reported in …