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Materials Science and Engineering Faculty Research & Creative Works

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Articles 931 - 960 of 1011

Full-Text Articles in Materials Science and Engineering

Evaluation Of Organic Additives For Use In Zinc Electrowinning, R. C. Kerby, H. E. Jackson, Thomas J. O'Keefe, Yar Ming Wang Dec 1977

Evaluation Of Organic Additives For Use In Zinc Electrowinning, R. C. Kerby, H. E. Jackson, Thomas J. O'Keefe, Yar Ming Wang

Materials Science and Engineering Faculty Research & Creative Works

Organic additives are used extensively in zinc electrowinning to assist in controlling the process. A cyclic voltammetry technique has been developed to provide a rapid, quantitative evaluation of the effectiveness of selected organic additives in minimizing the deleterious effects that impurities, such as antimony, have on zinc deposition. Results have indicated that animal glues are more effective than the other organic additives tested, which included several gums, enzymes, and amino acids, in relation to the current efficiency of zinc production. Of the various animal glues compared in this research, the most effective appeared to have average molecular weights in the …

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Dense Chromium Sesquioxide, P. D. Ownby Oct 1977

Dense Chromium Sesquioxide, P. D. Ownby

Materials Science and Engineering Faculty Research & Creative Works

A sintered, fine grained, polycrystalline, essentially fully dense, essentially single phase Cr2O3 body is prepared by sintering Chromium Sesquioxide (Cr2O3) at essentially the equilibrium oxygen partial pressure (PO2) for the formation of CrO 3 from its elements at the sintering temperature. To achieve optimum theoretical density a second metal oxide dopant such as MgO, capable of controlling the grain size, is added. In addition, Cr2O3 bodies are rendered more stable, and thus have a longer life, by maintaining over the body an atmosphere which is essentially equilibrium Po, …

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Evaluation Of Organic Additives For Use In Zinc Electrowinning, R. C. Kerby, H. E. Jackson, Thomas J. O'Keefe, Yar Ming Wang Sep 1977

Evaluation Of Organic Additives For Use In Zinc Electrowinning, R. C. Kerby, H. E. Jackson, Thomas J. O'Keefe, Yar Ming Wang

Materials Science and Engineering Faculty Research & Creative Works

Organic additives are used extensively in zinc electrowinning to assist in controlling the process. A cyclic voltammetry technique has been developed to provide a rapid, quantitative evaluation of the effectiveness of selected organic additives in minimizing the deleterious effects that impurities, such as antimony, have on zinc deposition. Results have indicated that animal glues are more effective than the other organic additives tested, which included several gums, enzymes, and amino acids, in relation to the current efficiency of zinc production. Of the various animal glues compared in this research, the most effective appeared to have average molecular weights in the …

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Positron Lifetime As A Function Of Grain Size, Hollis P. Leighly Feb 1977

Positron Lifetime As A Function Of Grain Size, Hollis P. Leighly

Materials Science and Engineering Faculty Research & Creative Works

Published data on positron annihilation lifetime in copper as a function of grain size have been analyzed to show that there is a linear relationship between the internal grain boundary surface area, per unit volume, S v, and the positron lifetime, τ. The analysis indicates that grain boundaries are important in the trapping of positrons. It is suggested that the slope of the resulting straight line, dS v/dτ, can be used to determine the annihilation rate of the grain boundaries. © 1977 Springer-Verlag.

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Low Order Correction For Subsurface Contributions In Diffusion Experiments, D. Powers, Manfred Wuttig Jan 1977

Low Order Correction For Subsurface Contributions In Diffusion Experiments, D. Powers, Manfred Wuttig

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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The Al2o3‐Sio2‐Zro2 Liquidus Surface: A Discussion, Charles A. Sorrell Jan 1977

The Al2o3‐Sio2‐Zro2 Liquidus Surface: A Discussion, Charles A. Sorrell

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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Glass In The Year 2000, Norbert J. Kreidl Jan 1977

Glass In The Year 2000, Norbert J. Kreidl

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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Subsolidus Equilibria And Stabilization Of Tetragonal Zro2 In The System Zro2‐Al2o3‐Sio2, Charles A. Sorrell Jan 1977

Subsolidus Equilibria And Stabilization Of Tetragonal Zro2 In The System Zro2‐Al2o3‐Sio2, Charles A. Sorrell

Materials Science and Engineering Faculty Research & Creative Works

The irreversible reaction between zircon and alumina to form mullite and zirconia was observed to proceed very slowly at 1480°C, confirming the existence of a stable join between mullite and zirconia in addition to the join between mullite and zircon. Attempts to determine equilibrium assemblages in powder samples of several combinations of the constituents at 1300° and 1400°C were unsuccessful. Metastable tetragonal ZrO2 was observed in fired powder samples containing kaolinite, in fired zircon‐alumina samples, and in calcined gels prepared from zirconyl nitrate, aluminum nitrate, and colloidal silica in water. Tetragonal ZrO2 was the dominant crystalline phase in …

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Suggested Chemistry Of Zinc Oxychloride Cements, Charles A. Sorrell Jan 1977

Suggested Chemistry Of Zinc Oxychloride Cements, Charles A. Sorrell

Materials Science and Engineering Faculty Research & Creative Works

Solutions of ZnCl2 were prepared from ZnCl2·nH2O and by reaction of zinc metal with HCl. Specific gravities and pH values were determined as a function of composition. A ternary phase, 4ZnO·ZnCl2·5H2O, was precipitated when the ZnCl2 solutions were diluted to a pH of 5.48 ± 0.05. Mixtures of ZnO with ZnCl, and HCI solutions were equilibrated in sealed containers and analyzed by X‐ray diffraction. The resulting phase diagram shows 2 ternary phases, 4ZnO·ZnCl2·5H2O (4·1·5) and ZnO·ZnCl2·2H2O (1.1.2), both of which are soluble …

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Evaluation Of Zinc Sulfate Electrolytes By Cyclic Voltammetry And Electron Microscopy, Bruce A. Lamping, Thomas J. O'Keefe Dec 1976

Evaluation Of Zinc Sulfate Electrolytes By Cyclic Voltammetry And Electron Microscopy, Bruce A. Lamping, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

A cyclic voltammetric technique has been developed for approximating the quantities of active chemical species present in zinc sulfate electrolytes. The experimental apparatus consisted of a Pyrex "H" cell, an aluminum cathode encased in a Teflon holder, a carbon anode and a mercurous sulfate reference electrode. Voltammograms were obtained using industrial, purified neutral leach solution (Cominco Ltd., Trail, BC) acidified to give a final concentration of 0.77 M Zn++ and 1 M H2SO4. The polarization curves were then evaluated and used as reference standards to compare with results obtained when various organic and inorganic additions were made. The deposit morphologies …

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Intermetallic Reactions In Vacuum-Deposited Nickel And Gold Films On (111) Silicon Single Crystals, K. H. Yoon, Gordon Lewis, L. L. Levenson Apr 1976

Intermetallic Reactions In Vacuum-Deposited Nickel And Gold Films On (111) Silicon Single Crystals, K. H. Yoon, Gordon Lewis, L. L. Levenson

Materials Science and Engineering Faculty Research & Creative Works

Pure nickel and gold thin films were vacuum-deposited on (111) silicon single crystals. When Ni/Au/Si or Au/Ni/Si samples were heated to about 550° in situ, hexagonal or deformed hexagonal shaped crystallites were formed on the silicon substrates. The composition of these crystallites was determined by using x-ray diffraction, scanning electron microscopy and scanning Auger microprobe methods. The crystallites were identified as NiSi2. The crystal-lites on the (111) silicon plane parallel to the surface appeared as regular hexagons while the inclined crystal-lites resembled trapezia. The results of Auger spectra and in-depth composition profiles for Ni, Au, and Si showed that the …

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On The Effects Of Antimony And Glue On Zinc Electrocrystallization Behaviour, D. J. Robinson, Thomas J. O'Keefe Jan 1976

On The Effects Of Antimony And Glue On Zinc Electrocrystallization Behaviour, D. J. Robinson, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

An investigation has been made to determine the effects that additions of glue and antimony have on the electrowinning of zinc from acid sulphate solutions. In particular, the zinc crystal growth and cathode current efficiencies were studied in an attempt to establish a correlation between morphology and the nature of the additives. Operating conditions of 55 A ft-2* and 35°C were used for most of the experiments with electrolyte concentrations of approximately 55 gl-1 zinc and 150 gl-1 H2SO4. Additional runs were made at 40,75 and 100 Aft-2 at 30,40 and 50°C in order to verify certain trends. Primarily by …

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Interpretation Of Some Of The Basic Features Of Field-Ion Image Projections From A Hemispherical To A Planar Surface Using Moire Patterns, P. D. Ownby, Robert M. Doerr, Walter Bollmann Jan 1976

Interpretation Of Some Of The Basic Features Of Field-Ion Image Projections From A Hemispherical To A Planar Surface Using Moire Patterns, P. D. Ownby, Robert M. Doerr, Walter Bollmann

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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The Effect Of Receiver Pressure On The Observed Flow Pattern In The Hydrostatic Extrusion Of Bimetal Rods, Ronald A. Kohser Jan 1976

The Effect Of Receiver Pressure On The Observed Flow Pattern In The Hydrostatic Extrusion Of Bimetal Rods, Ronald A. Kohser

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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The Martensite Transformation, Manfred Wuttig, Tetsuro Suzuki Jan 1976

The Martensite Transformation, Manfred Wuttig, Tetsuro Suzuki

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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Void-Strengthening In Aluminum And Its Nature, P. G. Manusmare, Hollis P. Leighly Jan 1976

Void-Strengthening In Aluminum And Its Nature, P. G. Manusmare, Hollis P. Leighly

Materials Science and Engineering Faculty Research & Creative Works

Temperature and strain rate dependence of yield strength were used to analyze the nature of aluminum strengthened by the formation of voids. Aluminum rods 99.999% pure were quenched and heat treated to form voids with an approximate density of 1013-1014 voids/cm3. Voids in selected samples were observed by electron microscopy. The yield strength of the void strengthened samples was measured at various temperatures from 77 to 593 K and at two strain rates, 3.33 x 10-2/s and 1.67 x 10-3/s. Tests at room temperature and at 77 K were made at various strain rates. The similarity of Coulomb's approach to …

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A Suboptimal Control Law To Improve The Transient Stability Of Power Systems, Aditya Kumar, Earl F. Richards Jan 1976

A Suboptimal Control Law To Improve The Transient Stability Of Power Systems, Aditya Kumar, Earl F. Richards

Materials Science and Engineering Faculty Research & Creative Works

The application of optimal control theory to damp the electromechanical oscillations associated with the transient conditions in power systems has been given little attention. A suboptimal control law which minimizes the sum of the performance indices of the two linear systems given by a piecewise linear model of a power system improves the transient stability better than the usual "optimal" control law obtained from a linearized model. Further, the suboptimal control law presented in this paper assures stability of the system for all disturbances resulting in rotor oscillations of magnitudes less than a preselected limit. Copyright © 1976 by The …

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Anion Grain-Boundary Diffusion In Soidum Chloride, K. S. Sabharwal, J. Mimkes, Manfred Wuttig Dec 1975

Anion Grain-Boundary Diffusion In Soidum Chloride, K. S. Sabharwal, J. Mimkes, Manfred Wuttig

Materials Science and Engineering Faculty Research & Creative Works

The grain-boundary diffusion of 131I in Harshaw pure and Ca-doped NaCl was investigated in the temperature range between 430 and 560°C. The Arrhenius plot of the grain-boundary diffusivity parameter Dδ displays a marked dip at around 510°C. It is proposed that this dip is due to a phase transformation occurring at the grain boundary, possibly calcium segregation.

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Moiré Simulation Of Field-Ion Micrographs, P. D. Ownby, Robert M. Doerr Jan 1975

Moiré Simulation Of Field-Ion Micrographs, P. D. Ownby, Robert M. Doerr

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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Crystallization Of A Tetrasilicic Fluormica Glass, W. H. Daniels, Robert E. Moore Jan 1975

Crystallization Of A Tetrasilicic Fluormica Glass, W. H. Daniels, Robert E. Moore

Materials Science and Engineering Faculty Research & Creative Works

The crystallization of a tetrasilicic synthetic mica glass of nominal composition K2Mg5Si8O20F4 was investigated at selected temperatures from 560° to 1150°C using DTA, density measurements, electron microscopy, and X‐ray diffraction techniques. Crystallization is shown to occur in 2 stages. (1) Initial structural ordering occurs at ∼600°C, as indicated by a strongly exothermic reaction, an increase in density, and the appearance of X‐ray diffraction lines. (This transformation temperature is related to fluorine content.) (2) The crystal morphology of the glass‐ceramic changes at 900° to 1150°C. A mechanism is proposed for the transformation from amorphous to crystalline structure in this synthetic mica …

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Determination Of Oxygen Chemical Diffusion Coefficients In Single Crystal Srtio By Capacitance Manometry, D. B. Schwarz, Harlan U. Anderson Jan 1975

Determination Of Oxygen Chemical Diffusion Coefficients In Single Crystal Srtio By Capacitance Manometry, D. B. Schwarz, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

The oxidation kinetics of a single crystal of SrTiOs were measured with a tensivolumetric system over the temperature range 700 -975 at 0.03 atm oxygen pressure. The oxidation was found to be oxygen diffusion limited with an activation energy of 14.9 - 1.3 kcal/mole. Combining the kinetic data with relative defect concentration data yielded an activation energy for oxygen self-diffusion of 57 - 16 kcal/mole. The enthalpy of formation of doubly ionized oxygen vacancies was calculated to be 126 - 13 kcal/mol. © 1975, The Electrochemical Society, Inc. All rights reserved.

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Mechanism Of Uai3 To Uai4 Transformation, Ling Ping Lee, Hollis P. Leighly Jan 1975

Mechanism Of Uai3 To Uai4 Transformation, Ling Ping Lee, Hollis P. Leighly

Materials Science and Engineering Faculty Research & Creative Works

The compound, UA14, which forms during the peritectic reaction (Liquid + UA13 → UAI4), has a long needlelike shape and reveals the characteristic morphology of a fishtail when cut along the long axis. When cut perpendicular to the long axis, it shows an internal core of another phase, which has been identified as a primary aluminum solid solution. Because of the interesting relationship between the crystallographic structures of UA13 and UA14, the peculiar UA14 morphology can be explained on the basis of a proposed mechanism. The mechanism of UA13 to UA14 transformation has been identified as shear and diffusion controlled …

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X-Ray Powder Data And Unit Cell Parameters Of Mgbr2.6h2o, Charles A. Sorrell, Roy R. Ramey Oct 1974

X-Ray Powder Data And Unit Cell Parameters Of Mgbr2.6h2o, Charles A. Sorrell, Roy R. Ramey

Materials Science and Engineering Faculty Research & Creative Works

Detailed X-ray powder data for MgBr2·6H2O were obtained by diffractometry by use of CuKα radiation at 22°C. The data were indexed on a bimolecular monoclinic unit cell, space group C2/m, with a = 10.290 ± 0.001 Å; b = 7.334 ± 0.001 Å; C = 6.211 ± 0.001 Å; β = 93° 25′ ± 10′. Calculated density was 2.074 g/cm3, compared with a measured density of 2.07 ± 0.01 g/cm3. © 1974, American Chemical Society. All rights reserved.

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A Microscopy Study Of Lead Sinter, Thomas J. O'Keefe, C. Bennett, E. R. Cole Feb 1974

A Microscopy Study Of Lead Sinter, Thomas J. O'Keefe, C. Bennett, E. R. Cole

Materials Science and Engineering Faculty Research & Creative Works

Samples of up-draft sinters produced at three different Missouri lead smelters were studied, to determine the chemical phases present, as a first step toward a more complete understanding of the lead blast furnace operation. The sinters seemed to be basically similar, and all the results reported are from samples from one smelter (Herculaneum smelter, St. Joe Minerals). Analytical tools used included the electron microprobe and scanning electron microscope with a non-dispersive X-ray spectrometer attachment Major phase that were positively identified are metallic lead, lead sulfide and zinc ferrite. The predominant lead phase was tentatively identified as a lead oxide-silicate compound. …

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Film Formation On Anodically Polarized Lead, H. Vaidyanathan, Ram A. Narasagoudar, Thomas J. O'Keefe, William Joseph James, James W. Johnson Jan 1974

Film Formation On Anodically Polarized Lead, H. Vaidyanathan, Ram A. Narasagoudar, Thomas J. O'Keefe, William Joseph James, James W. Johnson

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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A Mass Spectrometric Study Of Positive Ions Produced In An Experimental Diode, L. A. Addington, Gordon Lewis Jan 1974

A Mass Spectrometric Study Of Positive Ions Produced In An Experimental Diode, L. A. Addington, Gordon Lewis

Materials Science and Engineering Faculty Research & Creative Works

A simple diode ion source has been developed for direct observation in a mass spectrometer of the positive ions created in an operating diode. The ionic species accelerated toward the cathode were identified. The shape of the peak displayed in the spectrum is related to the region of the diode in which the ions were formed. Variation of experimental parameters, including the composition of the background gases, indicated that the characteristic shapes of the peaks can be related to space charge in the diode. This is complicated by the tendency of some of the species to fragment and further work …

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Field Emission Of Boron On Tungsten, P. D. Ownby, Thomas A. Flaim Jan 1974

Field Emission Of Boron On Tungsten, P. D. Ownby, Thomas A. Flaim

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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Magnetic Properties Of Cadmium Manganese Ferrite, B. W. Jong, P. D. Ownby Jan 1974

Magnetic Properties Of Cadmium Manganese Ferrite, B. W. Jong, P. D. Ownby

Materials Science and Engineering Faculty Research & Creative Works

The room-temperature saturation magnetization of CdxMn1-xFe2O4 decreased with increasing cadmium concentration. When 0 < x < 0.5, the decrease in saturation magnetization was due to the increase in the amount of non-mgnetic distorted cubic Cd(Mn, Fe) 2O4.

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Thermal Decomposition Of Boron Triiodide On Molybdenum Field Emitter Surfaces, Richard E. Moore, P. Darrell Ownby Jan 1974

Thermal Decomposition Of Boron Triiodide On Molybdenum Field Emitter Surfaces, Richard E. Moore, P. Darrell Ownby

Materials Science and Engineering Faculty Research & Creative Works

Boron has been adsorbed onto molybdenum field emitter surfaces by the thermal decomposition of boron triiodide at corrected partial pressures of 1.4 x 10-9 Torr to 4.5 x 10-9 Torr. Based on field emission work function data and an analytical work function versus adsorbate-coverage relationship, a quantitative measure of the monolayer coverage of boron on molybdenum has been determined; this value is 6.3 x 1014 atoms/cm2/monolayer. A parameter, β, is defined which is a measure of the effective yield of adsorbed boron on molyb-denum from BI3. β is formulated in terms of the free energy of dissociation of the BI3 …

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Electronic Contribution To The Entropy Of Solution, Manfred Wuttig Jan 1974

Electronic Contribution To The Entropy Of Solution, Manfred Wuttig

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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