Engineering Commons^™

Decomposition Of Cr(Oh)₃ To Form Active Cr₂C₃, Timothy A. Clancy

Doctoral Dissertations

"This study was concerned with the sinterability of Cr₂C₃ powders produced by the calcination of a Cr(OH)₃ gel. The decomposition of the gel was investigated by thermogravimetric analysis, X-ray analysis and microscopic examination. Comparison was made between the size of crystallites as determined by X-ray line broadening and the size of aggregated particles as determined by independent means. These lineal measurements were compared to surface area measurements on the calcined powders. The degree of sinterability was judged from the density measurements on Cr₂C₃ pellets fired under air, oxygen and nitrogen atmospheres. Energies of activation of 25 and 20 kilocalories per …

A Mechanical Metallurgical Method Of Predicting The Springback Tendencies Of A Bent Metal Strip, Jerrold Myles Alyea

Masters Theses

"Attempted substitution of new solid materials and composite metal strips for those materials presently being used in many applications now being pursued vigorously in industry. A serious problem was created because the newly proposed materials do not exhibit the same springback after bending as did the previously used materials in a particular bend angle and radius situation. Elementary bend theory and mechanical metallurgical techniques have been incorporated into a method which can be used to accurately predict the .2% offset yield strength of any proposed rolled-temper solid metal strip and some composite strips when they must exhibit the same springback …

Kinetics Of The Formation Of Strontium Zirconate, W. H. Parker

Masters Theses

"The decomposition rate of strontium carbonate (SrC0₃) was measured using a TGA apparatus. It was found to deviate slightly from zero order classical reaction. The rate of formation of strontium zirconate (SrZr0₃) from zirconium oxide (ZrO₂) and strontium oxide (SrO) in the form of the decomposition product of SrCO₃ was measured using quantitative x-ray diffraction for mineralogical analysis. It was found to most nearly follow the Zhuravlev-Lesokhin-Tempel' man rate equation. The rate of decomposition of strontium carbonate was found to be more rapid than the rate of formation of strontium zirconate such that for the most part strontium oxide is …

Compressive Creep Of Basic Refractories, Maurice E. Green

Masters Theses

"The microstructure and mineralogical composition of direct bonded, 50 wt.% magnesia - 50 wt.% chrome ore refractory compositions containing controlled additions of silica were correlated with their compressive creep behavior in the temperature range 1450⁰ to 1550⁰C under stresses of 100 to 175 psi. Steady state creep rates were determined from the linear regression of the steady state regions of deformation on time. Apparent activation energies and deformation flow characteristics were determined from the temperature and stress dependence of the steady state creep rates. Silica contents up to 3.5 wt.% increased the amount of direct intergranular bonding which decreased the …

Lattice Parameters, Coefficients Of Thermal Expansion, Densities, And Lattice Perfection Of The Copper-Indium Primary Solid Solutions, Lin Sheng Yu

Masters Theses

"Precise measurements of lattice parameters and densities of the alpha-phase Cu-In solid solutions were made at temperatures of 25°C. The thermal expansion coefficients between 15 and 65°C, the solid solubility of In in Cu at 650°C, and the soundness of crystal structure resulting from alloying were determined. The Cu-In alloys were prepared from high purity (99.999%) Cu and In by melting both metals inside evacuated quartz tubes. The solidified alloys were annealed and then examined by X-ray for homogeneity...The slowly solidified alpha-phase alloys gave densities lower than the theoretical (X-ray) values due to the presence of shrinkage microporosity. This density …

Corrosion Rates And Electrokinetics Of Cobalt And Cobalt-Rich Cobalt-Iron Alloys In Sulfuric And Hydrochloric Acids, Cheng Tzong Horng

Masters Theses

"Corrosion rates for Co and Co-rich Co-Fe alloys were determined in sulfuric and hydrochloric acids under both deaerated and oxygenated conditions. For the purpose of comparison, corrosion rates of Co cut from metal sheet were also determined in the same environments as those of sintered alloys. Sintered alloys were inferior to solid Co as corrosion resistant materials. It was found that the surface was more corrosion resistant than the interior. Thus after long exposure to the corrosive acid, the samples became porous inside while the surfaces remained substantially intact. Oxygen had a pronounced effect in accelerating the corrosion of Co …

Influence Of Nobler Metal Salt Additions Upon The Dissolution Rate Of Aluminum In Hydrofluoric Acid, Barry L. Basden

Masters Theses

"The rate of dissolution of aluminum in 2N HF upon the addition of nobler metallic salts was studied. Aluminum corrodes in HF due to the acid's ability to dissolve the protective oxide present on the surface. Rates were measured by the hydrogen evolution method. Salt additions of AgN0₃, CuSO₄, HAuC₄, and PtCl₄ to aluminum dissolving in 2N HF resulted in the electroless deposition of more or less coherent metals (from the salts mentioned) on the aluminum surface. The dissolution rate initially decreased in all of the cases and was attributed to the "blanketing effect" of the deposits. Ensuing increases of …

Pressure Welding Of Continuously Cast Nodular Iron, Gerald W. Wille

Masters Theses

"The objective of this study was to determine the feasibility of using pressure welding as a joining technique for swaged nodular iron.

Test pressure welds were produced with swaged continuous cast nodular iron at temperatures between 1750⁰F and 2050⁰F with welding pressures between 15,900 psi and 51,400 psi using an induction coil to heat the weld zone.

Pressure welds of greater strength than the as-received nodular iron were produced by swaging the material before welding. The optimum welding parameters were a temperature of 2050⁰F with a welding pressure of 46,700 psi.

On the basis of these tests it is concluded …

Effect Of Micelles On Flotation Of Metal Ions, Uriel Michael Oko

Doctoral Dissertations

"A study of the anionic surfactant, sodium dodecyl sulfate (SDS), and the dependency of the adsorption of divalent metal counterions such as copper and zinc at the air-water interface on its concentration in the solution, was undertaken in order to better understand the process of ion flotation. The study is divided into two broad categories, the first of which consists of the evaluation of the extent of aggregation of the surfactant molecules into micelles, and the effect of the divalent metal counterion concentration on this aggregation and on the critical concentration at which micelles start forming (cmc). This was accomplished …

Isotope Effect Of Interstitial Diffusion Of Carbon In A Dilute Fe-Si Alloy, Edward T. Yen

Masters Theses

"The isotope effect of carbon interstitial diffusion in a Fe-2.75at%Si alloy has been measured at -3.10°C using the disaccommodation technique. The disaccommodation has been analyzed in terms of two relaxation processes which are discussed on the basis of the reorientation mechanism of carbon interstitials at Fe-Fe sites and Fe-Si sites respectively. The ratios of the relaxation times [tau]₁₃/[tau]₁₂ are 1.0382 for the former and 1.0072 for the latter relaxation process. This result is discussed on the basis of many-body reaction rate theory"--Abstract, page ii.

The Effect Of Prior Cold Work On The Pressure Welding Of Ferritic Nodular Iron, Ronald Morris Ledbetter

Masters Theses

"The purpose of this investigation was to determine the effect of prior cold work by swaging on the pressure welding of ferritic nodular iron. Test pressure welds were produced from continuously cast ferritic nodular iron in the as cast condition and with prior cold work of 20, 30, 40, and 50 per cent reductions in area. Welding pressures of 23,500 psi, 35,300 psi, and 47,100 psi were employed. All welds were made at interface temperatures of 2000°F. Welds made with the as cast material at high welding pressures possessed relatively low tensile strengths due to the creation of planes of …

The Inert Gas Effect On The Rate Of Evaporation Of Zinc And Cadmium, Chu Sheng Wu

Masters Theses

"An experimental study has been made to investigate the effect of argon and helium on the rate of evaporation of zinc and cadmium under one atmosphere pressure at temperatures ranging from 500⁰C to 850⁰C. The experimental results were compared with the maximum rates calculated using the effusion formula as well as with values obtained using three different types of equations based on kinetic theory, diffusion theory, and empirical data. The rate of evaporation in this study appeared to be diffusion controlled. Equations have been derived for expressing the rate of evaporation of zinc and cadmium in both argon and helium …

Surface Self-Diffusion On Nickel (111) By Radioactive Tracers, James Ronald Wolfe

Doctoral Dissertations

"Surface self-diffusion coefficients have been measured by a radioactive tracer method over the temperature range 614⁰ to 840⁰C on nickel (111) surfaces characterized by LEED. Previously unrecognized tracer evaporation during surface diffusion resulted in restricted spreading of the tracer at higher temperatures. A theoretical treatment of the tracer evaporation phenomenon is presented and subsequently used in the analysis of the data. The temperature dependence of the surface self-diffusion coefficient (D_s) for nickel (111) can be represented, over the experimental temperature range, by a single Arrhenius type relationship...Arguments are presented to justify an adatom surface diffusion mechanism which is …

The Damage Assessment Of Thermally Shocked High Density, High Purity Aluminum Oxide, John H. Ainsworth

Doctoral Dissertations

"The traditional approach to thermal shock testing in brittle materials has been to determine the temperature difference required to nucleate cracks in these materials. Recent work has indicated that the degree of damage after crack nucleation should be an additional consideration. The degree of damage resulting from cooling thermal shocks has been the primary consideration of the present work. Test specimens of two geometries: long, solid rods and short, solid cylinders were quenched from selected temperatures into ice water. The degree of damage was determined through strength measurements and sonic damping analysis. Initial damage occurred at a temperature difference above …

Optical Reflectance Spectra Of Chromium (Iii) In Mgo-Ss, Thomas Spencer Montgomery

Doctoral Dissertations

"The valence state and coordination site of the transition-metal ion, chromium, was investigated in a MgO host lattice. The chromium ion incorporated into poly-crystalline MgO by quenching from elevated temperatures allowed investigation of a single crystalline phase, MgO-solid solution (ss). The chromium ion was confirmed to occur in the trivalent state and to occupy octahedral cation sites in the MgO lattice by the use of optical reflectance spectroscopy. The effect of the concentration of the chromium ion on the crystal field splitting energy, 10 Dq, permitted analysis over a range of Dq/B values. In conjunction, MgO-ss lattice parameters examined as …