Thesis (Ph. D.)--Yale University, 1982. / Includes bibliographical references (leaves 169-174).

Thesis (Ph. D.)--University of Wisconsin, 1965. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 56-57). Also available on the World Wide Web.

An investigation was conducted on the dissolution of copper metal in aqueous solutions of ethylenediamine, glycine, α-alanine and β-alanine, under oxygen pressure. The kinetics of these reactions were investigated over a wide concentration range of the corresponding ionized species. The rate of dissolution of copper, in all solutions, has been found to be independent of the initial copper concentration, the volume of the solution and the area of the copper sample. No intermediate products, i.e., cuprous ions, were observed. Two regions were observed, having different dependence on oxygen pressure. In one, the rate depends on the first power of the oxygen pressure, and is independent of the concentration of the chelating agent. In the other region, the reaction is first order in chelating agent and independent of oxygen pressure. The rate of the reaction in this second region appears to be chemically controlled at the copper surface. The neutral and charged species of the chelating agent were found to have independent rates. These two dissolution reactions were found to be first order with respect to the concentration of the respective complexing species. The mechanism proposed by Halpern previously for the ammonia system was found to be applicable to the systems studied in the present work. The rate constants for each chelating agent have been computed and appear to be related to the stability constants. No steric effect was observed. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

In order to test the apparently conflicting predictions of some current theories of strain hardening, slip line length measurements were made on a series of oriented copper single crystals, identically prestrained at 673°K, polished and incrementally strained at temperatures between 573°K and 4.2°K; slip lines formed during low temperature increments were found to be longer than those formed during strain increments at higher temperature (Garner and Alden, 1974). The result is shown to be in conflict with any theory of strain hardening in which slip lines are blocked by specific obstacle configurations, such as Lomer-Cottrell barriers, ribbons of converted pile-ups or dislocation cell walls. In contrast, the result is shown to be consistent with theories of strain hardening in which slip lines are blocked by statistical interaction between expanding glide loops and forest dislocations, on the condition that, within the framework of such a theory, the glide loops are able to expand athermally over a newly available free area of slip plane, after a thermally activated process. Two possible thermally activated processes are discussed. A unified view of slip lines properties is presented which is shown to provide a self-consistent explanation of the temperature variation of slip line length, slip band formation, the existence of multipole carpets and the variation of flow stress with temperature. The statistical aspects of this interpretation were investigated further by obtaining 77°K microstrain curves from a series of oriented copper single crystals, prestrained at temperatures between 1000°K and 77°K, to produce dislocation microstructures with differing degrees of regularity, yet with approximately the same overall density. The forest dislocation microstructures of an identically prepared series of crystals were examined using a dislocation etch on the primary slip plane. A statistical sampling technique was devised, which was used to measure local dislocation densities. In addition, new parameter is introduced, namely the ratio of the sampled standard deviation, to mean local dislocation density, which quantifies the degree of regularity of a dislocation micro-structure. All microstructures were found to have a smaller degree of regularity than a random distribution. For crystals prestrained at temperatures above 293°K, at any given fraction of the 77°K yield stress, the amount of microstrain was found to increase as the microstructures became less regular. Crystals prestrained at and below 293°K exhibited the Haasen-Kelly effect, which was attributed to restricted source operation. However, once sources begin to operate, the amount of microstrain anticipated from the degree of regularity was indeed detected. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

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Thesis (Ph. D.)--University of Arizona, 1991. / Includes bibliographical references (leaves 199-204).

Typescript, etc. / Digitized by Kansas State University Libraries

Owing to the environmental problems associated with copper extraction alternative processes are sought. The carbothermic reduction of natural chalcopyrite concentrates, from Ghatsila mines in Bihar, India, in the presence of lime, was studied across the temperature range 850-1250°C. Studies have been completed previously in synthetic chalcopyrite. This study stresses the need to investigate the reduction of natural chalcopyrite. The reduction of chalcopyrite proceeds in two steps, initially with the direct reduction by carbon. This is followed by indirect reduction by the carbon monoxide evolved from the first stage of reduction. Both stages of the reduction were investigated to determine the reaction mechanism. Metallic copper and iron are produced from the reduction of chalcopyrite. The oxysulphide phase, Cm, also produced from the reduction of chalcopyrite, was not previously categorised. X-ray diffraction analysis and scanning electron microscopy were utilised to evaluate the structure of Cm. Silver is an important by-product of copper extraction therefore it was necessary to study its path during the reduction of chalcopyrite. This was achieved by additions of Ag and Ag2S prior to reduction. Silver will preferentially segregate out with the copper phase hence providing a valuable metallic product from the reduction reaction. The addition of Ag to the reduction mixtures facilitates metallic phase separation of copper and iron. Arsenic and antimony are deleterious elements present in naturally occurring chalcopyrite. The addition of calcium sulphate and silica to chalcopyrite, heat treated under partially reducing conditions, will produce a calcium silicate slag phase that will entrain impurities such as arsenic and antimony, thus providing a method of control of those elements. An initial investigation into the possible control and elimination of impurities during extraction of copper has been conducted with favourable results.

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