Metallurgy Commons^™

The Effects Of Lead On The Electrochemical And Adhesion Behavior Of Zinc Electrodeposits, Vijay Srinivasan, J. Sami Cuzmar, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

The presence of excessive lead in zinc sulfate electrolytes can lead to problems related to both processing efficiency and the properties of the metal produced. For example, poor adhesion can occur in electrogalvanized steel when it is heated in the temperature range of 215 °C to 280 °C if lead is present in the deposit. The duration of heating necessary to induce the peeling of the zinc was found to be dependent on the temperature, time, and concentration of lead in the electrolyte and the plating parameters. The presence of lead slowed the formation of the intermetallic, and the peeling …

Microstructural Characterization Of Rapidly Solidified And Extruded Ti-Al-Nb Alloys, Danny Joe Edwards

Masters Theses

"Two titanium alloys have been characterized using transmission and scanning electron microscopy, X-ray diffraction, and optical metallography techniques. Both of these alloys were rapidly solidified by melt spinning, the resulting ribbons pulverized, and the powders then extruded into cylindrical billets. The alloys are based on the compositions Ti-21.3Al- 9 Nb-0.6-Mo-2.6V and Ti-13.2Al-2.6Nb-0.5Mo-0.9V-0.5Zr-3.1B in atomic percent. The first alloy was examined in both the as-extruded condition and in the annealed condition (looo0c for 12 hours). The second alloy was examined in the as-extruded condition only.

For the first alloy, the as-extruded microstructure consisted of a B2 matrix with alpha-2 particles at …

Fluid Dynamics Of An Atomizer Nozzle, Bhaskar Sengupta

Masters Theses

"A pilot plant gas atomizer was designed and assembled at the Center of Pyrometallurgy, U.M.R., to produce metal powders. The pilot plant utilizes a confined, annular, supersonic nozzle to yield spherical metal powders (aluminum and zinc alloys have been atomized) of average size of 15μm in diameter.

A cold model of the atomizing nozzle was constructed to simulate the pilot plant. First, the high-speed gas flow was studied and later, modelling of the atomizing process was carried out by using water as the atomized liquid. This work has investigated the complex gas flow in the converging-diverging nozzle and around the …

Comments On The Papers By Kê And Su, Hollis P. Leighly

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Production Of Thin Copper Foils On Microporous Titanium Oxide Substrates, J. L. Delplancke, M. Sun, Thomas J. O'Keefe, R. Winand

Materials Science and Engineering Faculty Research & Creative Works

This study deals with the electrochemical production of thin (35 μm) copper films on anodized titanium substrates. The formation of a microporous oxide layer on the titanium electrodes greatly enhances the surface density of copper nuclei during a potentiostatic experiment so that a complete coverage of the cathode surfaces may be obtained after short term (20 s) polarization. Moreover, the oxide film may act as a parting agent and the copper films may be easily stripped from their substrates. The higher the pore density of the oxide film, the higher the surface density of nuclei and the easier the foil's …

Mass-Transfer Measurements Of Copper Deposition In A Fluosilicate Electrolyte, D. Uceda, Thomas J. O'Keefe, E. Cole

Materials Science and Engineering Faculty Research & Creative Works

The electrodeposition of copper from a fluosilicate electrolyte has been investigated by electrochemical techniques, x-ray diffraction, and scanning electron microscopy. The diffusion coefficient of cupric ion in a fluosilicate solution has been determined with the aid of a rotating disk electrode using the mixed control Levich equation. Gold (Au⁺³) was used as a tracer to evaluate the mass transport properties of the system. The polarization behavior of the electrolyte was measured in the presence and absence of gas sparging on a vertical stationary electrode to study the effect of the mass transport contribution. Sound copper deposits were obtained …

Evaluation Of Mass Transport In Copper And Zinc Electrodeposition Using Tracer Methods, H. M. Wang, S. F. Chen, Thomas J. O'Keefe, M. Degrez, R. Winand

Materials Science and Engineering Faculty Research & Creative Works

Control of the electro crystallization process is essential in the deposition of metals from aqueous electrolytes. A knowledge of the influence of mass transfer on the metal ion reduction is a critical element in any number of electrolytic processes, particularly where relatively high current densities are desired. The use of more positive ion tracer techniques as a means of experimentally determining some of the mass transport properties of interest are described. Examples for copper, zinc and zinc alloys electrolysis are included. © 1989 Chapman and Hall Ltd.

Nucleation Of Electrodeposited Copper On Anodized Titanium, J. L. Delplancke, M. Sun, Thomas J. O'Keefe, R. Winand

Materials Science and Engineering Faculty Research & Creative Works

A study has been made to determine the effect of an electrochemically produced titanium-oxide film on the nucleation of copper. The oxide films were made galvanostatically at 25°C in 1 M sulphuric acid on pure titanium metal. Potentiodynamic, potential step and current step experiments were performed in an additive-free copper sulphate-sulphuric acid electrolyte at 25°C. It was found that the oxide film played an important role during nucleation. By increasing the thickness of the anodic film, it was possible to decrease the diameter and to increase the surface density of copper nuclei. The kinetics of nucleation and growth of the …

Premartensitic Anelasticity In Indium-Thallium Alloys., Manfred Wuttig, C. Y. Lei, Tetsuro Suzuki

Materials Science and Engineering Faculty Research & Creative Works

The linear and nonlinear low frequency internal friction of In-24 at. pct Tl displays a Curie-Weiss type behavior in the temperature range above the transformation temperature. The critical temperature equals the martensite start temperature. It is proposed that the origin of the observed internal friction is the diffusion-controlled interaction of substitutional atoms with the premartensitic strain modulation, tweed.

Effects Of 0.5 Weight Percent Boron On Cobalt Aluminide, Kevin Thomas Slattery

Masters Theses

"A study was made on the effects of adding 0.5 weight percent boron to the ordered intermetallic Cobalt Aluninide. Thirty gram (30g) specimens were induction melted in an pure argon atmosphere and cast into a copper alloy bar mold. The addition of boron raised the modulus of rupture from 30.1 to 44.3 ksi; increased the Knoop microhardness from 543 to 693; reduced the average grain size from 190 to 70 microns; and gave a more equiaxed grain structure. X-ray diffraction detected the presence of a second phase, AlB , 12 in the material containing boron. Scanning electron micro-scopy revealed that …

Influence Of Prior Deformation On Structure And Properties Of Heat Treated Aluminum Casting Alloy, Chungwei Hsia

Masters Theses

"A1 356 alloy is extensively used for a wide variety of casting applications. The structure is composed of primary dendrites and eutectic silicon formed during the eutectic reaction. It has long been recognized that the shape of the eutectic silicon significantly affects the ductility of the alloy. Traditionally, the morphology of the silicon is changed by certain chemical and/or thermal processes to improve the ductility. Mechanically deforming the castings to "modify" the shape of silicon has been shown by this research to be an effective alternative method to improve the spheroidization rate of eutectic silicon during heat treatment. The best …

Reductive Stripping Of Iron(Iii) From Di(2-Ethylhexyl) Phosphoric Acid, Byron G. Belew

Masters Theses

"Unwanted impurities, present in raw materials, are often coextracted along with desired constituents during leaching. If left unchecked, impurity levels may increase in hydrometallurgical process streams until their presence has deleterious effects upon subsequent unit processes. Due to its abundance and ease of extraction, the presence of ferric iron in solvent extraction circuits has always been a problem. The technique proposed herein constitutes a novel approach to remove iron from zinc hydrometallurgical circuits; but the principles employed may find a variety of applications.

This research investigated the reduction and stripping of ferric iron from di(2-ethylhexyl) phosphoric acid into a …

Comments On A Paper By No, Esnouf, San Juan, And Fontozzi, Hollis P. Leighly

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

South East Missouri Lead Belt - A Review 1987, Johh L. Watson

Materials Science and Engineering Faculty Research & Creative Works

The south-east Missouri Lead Belt is, and has been for many years, a major world producer of lead concentrate. This paper reviews the current mill operations in the area and presents detailed information on equipment, operating parameters and metallurgical performance. © 1988.

Nucleation And Growth Of Zinc Electrodeposited From Acidic Zinc Solutions, A. C. Beshore, B. J. Flori, G. Schade, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

The nucleation and initial crystal growth kinetics by electrodeposition from acidic zinc solutions was studied in the absence and presence of antimony and glue on a glassy carbon electrode. Zinc exhibits instantaneous nucleation under the experimental conditions employed in the potential region from -1600 to -2000 mV (mercurous sulphate reference). At low overpotentials antimony and glue increase the number of nuclei. © 1987 Chapman and Hall Ltd.

Calculation Of Mass Transfer Coefficients In Metal Deposition Using Electrochemical Tracer Techniques, Thomas J. O'Keefe, J. S. Cuzmar, S. F. Chen

Materials Science and Engineering Faculty Research & Creative Works

A modification of the tracer technique of Ettel has been developed for determining mass-transfer coefficients in electrolytes for both electrowinning and electrorefining systems. The method involves the direct measurement of the limiting current density of a more noble tracer ion at low concentration by cyclic voltammetry techniques in an electrolyte of choice. A Ag+tracer in acid copper sulfate is used as the example. Additional tests were made by code positing the tracer with copper to compare the results of the two methods. The effect of copper ion concentration and temperature on the electrochemical and transport properties of the solution were …

Characterization Of The Fluid-Dynamic Mixing Of A Bottom Gas-Injected Channel Reactor Using Low-Temperature Modelling, Jay Bernett Gassel

Masters Theses

"Variables influencing the mixing in a single-phase (30.5 x 60 x 606 cm) and a two-phase (20 x 40 x 200 cm) channel reactor model were studied. Tracer and/or neutral density particle techniques were used to determine an eddy diffusivity, De, for the system(s). Three bubbler arrangements were investigated in the one-phase work. A separate apparatus was developed to withstand the corrosiveness of the tetrachloroethylene used in the two-phase work.

Both the electrical conductivity tracer technique and the neutral density particle technique were shown to be feasible experimental techniques for determining an eddy diffusivity in the systems studied. Decreasing liquid …

Formability Of 356 Aluminum, Karol Krumrey Schrems

Masters Theses

"Although aluminum casting alloys are not often thought of as being formable, this thesis examines this possibility. Aluminum alloy 356 was cast in permanent molds and subsequently deformed by rolling (providing compressive loading) and bending (providing tensile loading). Cold forming was found to be very limited, while forming at elevated temperatures was comparatively easy and permitted reductions of up to 90%. Tensile properties and microstructures were examined in detail. Forming breaks up the eutectic silicon and intermetallic compounds. The yield strength and tensile strength increased almost linearly with increasing total percent reduction. The elongation at first increases with total percent …

The Use Of Computerized Data Acquisition Techniques To Measure The Kinetics Of A Batch Flotation Process, Jose Antonio Barrera-Godinez

Masters Theses

"The flotation response of a lead ore was measured by utilization of a computer driven data acquisition system. A symmetric, fast and automatic froth removal and weighing system was attached to a conventional laboratory flotation cell. The rate controlling mechanisms were identified by manipulation of the froth removal rate, (FRR), froth layer thickness, (FT), and air flow rate, (AFR). The production of froth, water, solids and value in addition to value recovery and concentrate grade were determined as a function of time of flotation.

The flotation response was controlled by events dependent of AFR when using shallow froths of less …

Fundamental Study Of The Role Of Cathode Structure On Zinc Electrowinning, Horacio M. Aros

Doctoral Dissertations

"The influence of cathode macromorphology on the current efficiency of zinc electrowinning was determined.

The studies have shown that surface roughness affects current efficiency during zinc electrowinning, particularly when the electrolyte contains impurities such as nickel and antimony. Current efficiency does not change with surface roughness as long as the electrolyte is sufficiently pure.

Zinc deposited on smooth zinc cathodes tends to retain a more favorable structure and macromorphology, which is less sensitive to the effects caused by antimony and nickel. Glue helps to counteract the effect of the impurities; however, its presence in the electrolyte at certain combinations with …

The Mg-Sb System, A. A. Nayeb-Hashemi, J. Beverley Clark

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Electrochemical Monitoring Of Electrogalvanizing Solutions, Thomas J. O'Keefe, S. F. Chen, E. R. Cole, M. Dattilo

Materials Science and Engineering Faculty Research & Creative Works

The corrosion resistance of steel is vastly improved when a zinc cathodic protective layer is applied. In recent years there has been renewed interest in producing this galvanized coating electrolytically. As with many deposition processes, the control of the operating parameters is very important in order to produce good quality zinc coatings. The homogeneity, ductility and smoothness of the zinc layer are critical. These factors are usually influenced by the electrochemical nature of the solution and organic additives are often used to assist in control. Studies on the polarization behavior of solutions for electro galvanizing electrolytes were made. Cyclic voltammetry …

Elasto-Composition Waves In Inhomogeneous Solids, R. C. Batra, Manfred Wuttig

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

A Study Of Problem Lead-Zinc Ores Of Southeast Missouri In Terms Of Mineralogy And Galena Oxidation, Michael G. Schroer

Masters Theses

"Recovery problems encountered at some of the St. Joe Lead Company's milling facilities prompted the study of 6 different ores. High and low grade ores had characteristics that varied from poor lead - zinc selectivity to excessive lead losses to the flotation tailings. Three ores from both the Fletcher and Viburnum mills were studied through flotation tests, mill water analysis, and ore analysis using an ore microscope.

The major cause for poor recovery was found to be due to ore oxidation. Not only was lead, in the form of oxides, reporting to the tails, but high levels of copper ions …

Characteristics Of A Stirred Bed Reactor Used For Gas-Solid Reactions, Christine Joy Beyke

Masters Theses

“A fluidized bed gas-solid reactor was designed and tested in which most of the fluidization energy is provided by a helical stirrer, with gas being used primarily as a reactant. The bulk gas in which the particles are suspended is practically constant in composition except for the area immediately adjacent to the gas inlet. The reactor is capable of withstanding temperatures up to at least 800°C and can be used with a wide range of flow rates. It is intended primarily as a laboratory tool, with the potential to be scaled up to multikilogram size.

The reactoor is a useful …

Screening Design Test For Cyclic Voltammetric Evaluation Of Zinc Sulfate Electrolyte, R. K. Singh, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

A statistical screening design program was conducted to determine the effects of certain operating parameters in the cyclic voltametric evaluation of zinc sulfate electrolyte. The variables studied included solution temperature, sulfuric acid and zinc concentrations, and scan rate. Solution temperature was found to be the most significant factor affecting the initial potential, followed by scan rate and zinc concentration. Based on screening design data, mathematical equations were developed to predict polarization behavior of addition-free zinc sulfate electrolytes. A few preliminary tests on the effect of impurities and organic additives, such as Sb(III) and glue, on potential, deposit morphology, and crystal …

An Analysis Of Mill Sound Levels To Aid In The Control And Understanding Of The Grinding Process, Scott Douglas Morrison

Doctoral Dissertations

“An experimental study has been made to evaluate the relationships between grinding parameters and the directional sound levels emitted from the collision of the grinding media with the mill wall for a laboratory batch ball mill.

Discrete frequency and single frequency band sound pressure level measurements were performed to investigate the changes in sound levels with grind time. It was demonstrated that the reduction in sound levels with grind time observed for a narrow sized feed can be used to indicate optimum breakage rates, overall time-based particle size distribution, and ore character.

The relationships established with the discrete frequency and …

Electrochemical Evaluation Of Zinc Electrolyte, Rajesh Kumar Singh

Doctoral Dissertations

"The polarization characteristics of acidified zinc sulfate electrolyte with varying solution chemistries were examined by cyclic voltammetry. An attempt was made to correlate the polarization results with the morphological and current efficiency data in order to develop a better understanding of the more fundamental aspects of impurity and additive behavior during the zinc electrodeposition process.

A statistical screening design program was conducted to determine the effects of certain operating parameters on the nucleation potential of zinc from sulfate electrolyte. The variables studied included: solution temperature, H₂SO₄ and Zn concentration, and scan rate. The solution temperature was found to be the …

Mass Transport Considerations In Electrometallurgical Reactions, Jose Rolando Sami Cuzmar

Doctoral Dissertations

"The research program described is divided into three segments. In the first part, the morphology and kinetic studies of Cd²⁺ removal from ZnSO₄ solutions using Zn dust as a reducing agent are presented. In the absence of impurities, the morphology of the Cd deposit shows the formation of two-dimensional or leaf-like dendrites capable of interlocking and forming agglomerates or balls. The size and strength of the agglomerates depend on the initial Cd²⁺ concentration to Zn metal surface area ratio, the rate of Cd ²⁺ removal, and the reactor geometry. The presence of additives, like Cu²⁺ and …

The Oxidation Of Dilute Alloys Of Magnesium In Aluminium, Hollis P. Leighly, A. Alam

Materials Science and Engineering Faculty Research & Creative Works

The oxide layers developed during the oxidation of aluminum alloys containing 500 and 1000 PPM of magnesium at 850K were examined with the aid of electron spectroscopy for chemical analysis. The magnesium content of the oxide layers was relatively high because of the preferential depletion of the magnesium atoms from the base alloys. Near the outer surfaces of the oxide layers, spinel (MgAl2O4) was the predominant magnesium-bearing compound. At depth, MgO was more dominant. The preferential depletion of magnesium from the alloys injected vacancies into the material. This led to the formation of defect clusters. The presence of these defect …