Engineering Commons^™

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.

Subsolidus Equilibria And Metastable Phase Development In The System Zro₂-Al₂O₃-Sio₂, Charles Christopher Sorrell

Bachelors Theses

"Subsolidus equilibria in the low silica portion of the system ZrO₂-Al₂O₃-SiO₂ were studied by X-ray diffraction of quenched samples fired at 1300°, 1400°, and 1480°C. Samples prepared as powders from combinations of a-Al₂O₃, Al(OH)₃, silicic acid, ZrO₂, and kaolinite reacted very slowly at 1300° and 1400°C and the trends toward equilibria are not apparent. A mixture of zircon and Al(OH)₃ reacted slowly at 1480°C to form mullite and ZrO₂, indicating that the latter phases are the stable assemblage rather than zircon and alumina. A gel prepared from aluminum nitrate, zirconyl nitrate, and colloidal silica reacted at 1480°C to form alumina, …

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.

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

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Analogy Between Spinodal Decomposition And Martensitic Transformation, Tetsuro Suzuki, Manfred Wuttig

Physics Faculty Research & Creative Works

The translation of the theory developed for the spinodal decomposition of a supercooled alloy to the language appropriate for the martensitic transformation is carried out. In the spinodal theory, the stability of the alloy with respect to the composition fluctuation is examined, while in the present theory the stability of the crystal with respect to the shear displacement fluctuation, the transverse phonon, is studied. The analogy to the spinodal theory requires the revival of the strain gradient energy term or the couple stress term, the presence of which has been a subject of controversies for a long time since Laval. …

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 …

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 …

Application Of Voltammetry To Copper Electrodeposition, Louis Francis Toth Jr.

Doctoral Dissertations

"A study was undertaken to determine the feasibility of using voltammetry and scanning electron microscopy techniques to characterize copper deposition from an acid-sulfate electrolyte. The main process variables investigated were temperature and addition agents (chloride ion, glue, separan or thiourea) at different concentrations, over a range of current densities. Cathodes employed were either polycrystalline titanium or copper. Some long-time copper deposits were also made using Ti cathodes and the orientations of these deposits were determined by x-ray diffraction.

Observations of copper crystals produced during voltammetry scans, on a Ti cathode, indicated that a characteristic morphology was associated with each type …

Corrosion And Electrochemical Behavior Of Indium And Indium-Bismuth Alloys In Hydrochloric Acid, Yar Ming Wang

Doctoral Dissertations

"The corrosion of In-Bi alloys was studied using X-ray, scanning electron microscopy, atomic absorption spectroscopy, and cyclic voltammetry techniques.

Calculated activation energy values indicated that the corrosion of In-Bi alloys was activation controlled. The effect of amine mixtures on the corrosion of In and In₂Bi (ß₁ phase) was studied. Morphological studies revealed that the porosity of the resulting physical surface structure was influential in determining the corrosion rate. In deaerated 3N HCl solutions, the selective dissolution of indium was the predominant mechanism in the corrosion of In-Bi alloys. The corrosion was always accompanied by a phase change …

Variables Affecting The Rate Of Solution Of Mold Inoculants In Cast Iron, Jose Osorno Fonnegra

Masters Theses

"The purpose of this investigation was to measure the effectiveness of an inoculant alloy reacting with molten cast iron in a reaction chamber properly located in the gating system.

The chemical composition of the gray iron was held constant while several metallurgical factors were varied to produce test samples with different cementite thicknesses. These chill depths were measured as an indication of the inoculation effectiveness.

Appreciable differences in chilling tendency were observed within the different variables studied. The results indicate that pouring temperature, as well as the other variables studied, are of considerable importance when dealing with inoculation of gray …

Characterization Of Two Mexican Raw Dolomites For Refractory Brick Production, Rodolfo Trevino Cantu

Masters Theses

"Two Mexican dolomites were characterized in order to discover their suitability for production of refractory brick.

The results were compared with other dolomites from American Companies. Some samples were burned in a gas fired Laboratory Furnace and others were obtained in the burned state after processing in Industrial Rotary Kilns.

The characterization procedures included X-Ray Diffraction, Scanning Auger Microprobe, DTA and TGA techniques, Chemical Analysis and Bulk Density measurements.

The procedure to control the quality of the dead-burned dolomite at the industrial level was established taking as the main criteria, bulk density, hydration susceptibility, and impurity levels"--Abstract, page ii.