VPW: Role of Impurities in Compositional Changes in Copper Sulfides During Anodic Dissolution (Manufacturing Processes)

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Synthetic samples of copper sulfides will be prepared containing controlled amounts of impurity elements in order to investigate the effects impurities have on the anodic dissolution of these materials. Specimen composition will be determined before and after reaction by electron microprobe and x-ray diffraction. Reacted sulfide disk electrodes will be sectioned normal to the exposed surface so that composition changes can be measured as a function of depth, applied potential, and reaction time. The composition of a partially reacted copper sulfide is know to be a function of applied potential, reaction time, and sample origin, and it is hypothesized that there is a composition gradient with distance from the exposed surface and that the composition is also related to the impurities present. Electrochemical techniques, including differential capacitance, resistivity, and cyclic voltammetry, will be used to characterize the electrical properties of the sulfides and to identify electroactive surface species involved in the dissolution reactions. Peak height data from the cyclic voltammograms will be collected at intervals over an extended period and integrated in order to determine whether the number of electrons transferred in the dissolution reactions is constant over time; this quantity is already know to be potentially dependent. Rotating ring disk electrodes with demountable sulfide disks will be used to measure the concentrations of soluble conducts, Cu(I) and Cu (II), so that the rate of formation of these species can be correlated with composition changes in the solid and with the impurities present. This research effort to examine the electrochemistry of semiconducting copper sulfides which contain controlled amounts of various impurities is of technological interest because of similar reactions occurring in hydrometallurgical processing, and is of scientific interest because little work has been published on the kinetics of the electrochemistry of semiconductors that undergo chemical-composition changes. The project furthers VPW program objectives to provide opportunities for women to advance their careers in science or engineering through research, and to encourage other women to pursue careers in these areas through the investigators' enhanced visibility as role models on the host campuses. In this project, the proposed activities which contribute to the second objective include: conducting a seminar course, and informal mentoring of undergraduate and graduate women students enrolled in engineering or interested in careers in the field.