Although the metallurgical industry has made great strides in the reduction of unwanted emissions to the atmosphere as a result of production processes, significant challenges still exist. From a global perspective, even large reductions in emissions per produced ton become immaterial when considering that the total world production of metals continues to increase. Two such particularly hazardous emissions are sulfur dioxide, primarily from copper ore roasting, and mercury, which has had increasing emissions from the steel industry in recent years. Both pollutants have severe consequences for the environment and also for human health. The primary motivations of this work have hence been: (1). to study sulfate formation on soot from sulfur dioxide emissions reacting with ozone and H2O in the vapor phase and (2). to study factors involving the behavior of mercury adsorption on metal surfaces involved in steelmaking, in order to further the understanding of select emissions from scrap-based steelmaking. Gas phase experiments were conducted to examine the heterogeneous oxidation of sulfur dioxide on soot in the presence of ozone and water vapor. The sulfur dioxide oxidation into sulfate was quantified using a particle-into-liquid sampler coupled with ion chromatography to measure the sulfate formation at atmospheric pressure. Water vapor, ozone and sulfur dioxide concentrations were controlled. Due to the ozone oxidation, multilayer adsorption of sulfur dioxide on soot, as well as sulfate formation and physisorption on secondary surface layer sites were observed. The exposure also caused the soot to become hydrophilic, due to the sulfur dioxide adsorption and also likely the formation of carboxyl groups on the surface. No significant increase in sulfate formation was observed at ozone concentrations above 1000 ppm. The effects of common surface contaminants such as oxygen and chlorine were examined on the metal surfaces, as well as the impact of changes in temperature, with controlled conditions using thermal desorption auger electron spectroscopy. It was established that low temperatures (82 K through 111 K) were conducive to mercury adsorption, wherein physisorption and subsequent lateral mercury interactions in mercury adlayers occurred. Chlorine appeared to favor mercury uptake, as determined by the increased mercury coverage at low temperatures on polycrystalline iron, copper and zinc. Oxygen, however, was found to be an inhibitor of mercury, most notably at room temperature. It was surprising to establish that no mercury adsorbed on zinc surfaces at room temperature and only on polycrystalline samples at low temperature. The mercury signal intensity increased up to the limit of the melting temperature for iron systems, on the oxidized copper surface and the polycrystalline zinc surfaces, prior to desorption from the surfaces. It is suggested that this is due to a rearrangement of mercury atoms on the surface at increasing temperatures, whereas at 85 K, mercury adhered to its initial adsorption position. In other words, mercury wet these surfaces on annealing, transitioning from an islanded surface at low temperature to a smooth layer before desorption. Based on these results, it was concluded that the mercury bond to the oxidized surface was weakened compared to clean copper. Furthermore, it is proposed that a surface phase transition occurred on polycrystalline zinc prior to desorption. No such transition was observed on iron. Activation energies of desorption were calculated for the relevant metal surfaces. It was established that clean iron had the highest activation energy of desorption. The large bond strength between mercury and iron may account for the highest desorption temperature of the iron systems. Zinc and copper had similar activation energies and desorption temperatures, which were respectively lower than that of iron. X-Ray Photoelectron and Auger Electron Spectroscopy were used to ascertain common surface contamination, i.e. chlorine, oxygen and sulfur, which affected mercury adsorption. Laser Ablation Inductively Coupled Plasma Time of Flight Mass Spectrometry was used to determine the depth of mercury adsorption on the samples. The technique also showed that the samples contained mercury in the surface layers. Accompanied by the rising demand for metals is the increase in emissions from metals manufacturing. Moreover, it is critical to minimize sulfur dioxide emissions as particulates from soot continue to be released in the atmosphere. For scrap-based steelmaking, monolayer mercury adsorption on clean iron and copper at room temperature are significant results. With the rising use of electronic devices in vehicles, the sorting of scrap becomes increasingly important. Mercury not adsorbing on zinc at room temperature is also of relevance as it disproves the theory of increased mercury adsorption with the increased use of galvanized scrap in summer conditions. However, the low temperature studies showed multilayer adsorption of mercury on iron, zinc and copper, which has relevance for the reported temporal variations of mercury deposition in arctic regions. Keywords: mercury, iron, zinc, sulfur dioxide, adsorption, pollution, thermal desorption, polycrystalline, surfaces, spectroscopy / QC 20120326

<p>In this thesis we report on the metal-mediated-thermally induced changes of the structural and optical properties of hydrogenated amorphous silicon deposited by hot-wire CVD, where aluminium and nickel were used to induce crystallization. The metal-coated amorphous silicon was subjected to a thermal annealing regime of between 150 and 520&deg / C. The structural measurements, obtained by Raman spectroscopy, show partial crystallization occurring at 350 &deg / C. At the higher annealing temperatures of 450&deg / C and 520&deg / C complete crystallization occurs. Reflection and transmission measurements in the UV-visible range were then used to extract the optical properties. By adopting the effective medium approximation a single optical model could be constructed that could successfully model material that was in different structural phases, irrespective of metal contamination. Changes in the absorption of the material in various stages of transition were confirmed with a directly measured absorption technique, and the modelled absorption closely followed the same trends This study forms part of the larger overall solar cell research project, of which the primary aim is to eventually develop a silicon solar panel that optimises the characteristics for best performance.</p>

<p>Hydrogenated amorphous silicon (a-Si:H) is second only to crystalline silicon in volume manufacturing of solar cells due to its attractive characteristics for solar panel manufacturing. These are lower manufacturing costs, and the fact that it can be deposited on any surface, and in any shape even on flexible substrates. The metal induced crystallization of hydrogenated amorphous silicon has been the subject of intense scrutiny in recent years. By combining the technology of hydrogenated amorphous silicon thin films with the superior characteristics of c-Si material, it is hoped that more efficient solar cells can be produced. In this thesis we report on the metal-mediated-thermally induced changes of the structural and optical properties of hydrogenated amorphous silicon deposited by hot-wire CVD, where aluminium and nickel were used to induce crystallization. The metal-coated amorphous silicon was subjected to a thermal annealing regime of between 150 and 520&deg / C. The structural measurements, obtained by Raman spectroscopy, show partial crystallization occurring at 350 &deg / C. At the higher annealing temperatures of 450&deg / C and 520&deg / C complete crystallization occurs. Reflection and transmission measurements in the UV-visible range were then used to extract the optical properties. By adopting the effective medium approximation a single optical model could be constructed that couldsuccessfully model material that was in different structural phases, irrespective of metal contamination. Changes in the absorption of the material in various stages of transition were confirmed with a directly measured absorption technique, and the modelled absorption closely followed the same trends This study forms part of the larger overall solar cell research project, of which the primary aim is to eventually develop a silicon solar panel that optimises the characteristics for best performance.</p>

Germanium is a brittle semi-metal, used for lenses and windows in Thermal Imaging Systems since it transmits infrared energy in the 2 &micro / m - 12 &micro / m wavelength range at peak. In this thesis study, polycrystalline diamond is used as cutting tool material to machine germanium. Diamond is the hardest, most abrasion-resistant material and polycrystalline diamond is produced by compacting small diamond particles under high pressure and temperature conditions, which results more homogeneous, improved strength and a durable material. However, slightly reduced hardness is obtained when compared with natural diamond. Different from finish cutting, rough cutting, performed before finishing, is used to remove most of the work-piece material. During rough cutting, surface roughness is still an important concern, since it affects the finishing operations. Roughness of the surface of product is affected by a number of factors such as cutting speed, depth of cut, feed rate as cutting parameters, and also rake angle as tool geometry parameter. In the thesis, the optimum cutting and tool geometry parameters are investigated by experimental studies for rough cutting of germanium with polycrystalline diamond tools. Single Point Diamond Turning Machine is used for rough cutting, and the roughness values of the optical surfaces are measured by White Light Interferometer. Experiments are designed by making use of &ldquo / Full Factorial&rdquo / and &ldquo / Box-Behnken&rdquo / design methods at different levels considering cutting parameters as cutting speed, depth of cut, feed rate and tool geometry parameter as rake angle.

The on-going interest in thermoelectric (TE) materials, in the form of bulk and films, motivates investigation of materials that exhibit low thermal conductivity and good electrical conductivity. Such materials are phonon-glass electron-crystals (PGEC), and the multi-component type-I clathrate Ba8Ga16Ge30 is in this category. This work reports the first investigation of Ba8Ga16Ge30 films grown by pulsed laser deposition (PLD). This dissertation details the in-situ growth of polycrystalline type-I clathrate Ba8Ga16Ge30 thin-films by pulsed laser ablation. Films deposited using conventional laser ablation produced films that contained a high density of particulates and exhibited weak crystallinity. In order to produce high quality, polycrystalline, particulate-free films, a dual-laser ablation process was used that combines the pulses of (UV) KrF excimer and (IR) CO2 lasers that are temporally synchronized and spatially overlapped on the target surface. The effect of the laser energy on stoichiometric removal of material and morphology of the target has been investigated. In addition, in-situ time-gated emission spectroscopy and imaging techniques were used to monitor expansion of components in the ablated plumes. Through these investigations, the growth parameters were optimized not only to significantly reduce the particulate density but also to produce large area stoichiometric films. Structure and electrical transport properties of the resultant films were also evaluated. This work provides new insight toward the in-situ growth of complex multi-component structures in thin-film form for potential TE applications.

<p>Hydrogenated amorphous silicon (a-Si:H) is second only to crystalline silicon in volume manufacturing of solar cells due to its attractive characteristics for solar panel manufacturing. These are lower manufacturing costs, and the fact that it can be deposited on any surface, and in any shape even on flexible substrates. The metal induced crystallization of hydrogenated amorphous silicon has been the subject of intense scrutiny in recent years. By combining the technology of hydrogenated amorphous silicon thin films with the superior characteristics of c-Si material, it is hoped that more efficient solar cells can be produced. In this thesis we report on the metal-mediated-thermally induced changes of the structural and optical properties of hydrogenated amorphous silicon deposited by hot-wire CVD, where aluminium and nickel were used to induce crystallization. The metal-coated amorphous silicon was subjected to a thermal annealing regime of between 150 and 520&deg / C. The structural measurements, obtained by Raman spectroscopy, show partial crystallization occurring at 350 &deg / C. At the higher annealing temperatures of 450&deg / C and 520&deg / C complete crystallization occurs. Reflection and transmission measurements in the UV-visible range were then used to extract the optical properties. By adopting the effective medium approximation a single optical model could be constructed that couldsuccessfully model material that was in different structural phases, irrespective of metal contamination. Changes in the absorption of the material in various stages of transition were confirmed with a directly measured absorption technique, and the modelled absorption closely followed the same trends This study forms part of the larger overall solar cell research project, of which the primary aim is to eventually develop a silicon solar panel that optimises the characteristics for best performance.</p>

<p>In this thesis we report on the metal-mediated-thermally induced changes of the structural and optical properties of hydrogenated amorphous silicon deposited by hot-wire CVD, where aluminium and nickel were used to induce crystallization. The metal-coated amorphous silicon was subjected to a thermal annealing regime of between 150 and 520&deg / C. The structural measurements, obtained by Raman spectroscopy, show partial crystallization occurring at 350 &deg / C. At the higher annealing temperatures of 450&deg / C and 520&deg / C complete crystallization occurs. Reflection and transmission measurements in the UV-visible range were then used to extract the optical properties. By adopting the effective medium approximation a single optical model could be constructed that could successfully model material that was in different structural phases, irrespective of metal contamination. Changes in the absorption of the material in various stages of transition were confirmed with a directly measured absorption technique, and the modelled absorption closely followed the same trends This study forms part of the larger overall solar cell research project, of which the primary aim is to eventually develop a silicon solar panel that optimises the characteristics for best performance.</p>

Αντικείμενο της παρούσας διπλωματικής είναι η μελέτη του παράγοντα ποιότητας για τρία διαφορετικά πλαίσια για διαφορετικές καιρικές συνθήκες. Τα πλαίσια που μελετήθηκαν ήταν ένα πλαίσιο μονοκρυσταλλικού πυριτίου CONERGY Q 80 MI , ένα πλαίσιο πολυκρυσταλλικού πυριτίου sharp NE-80E2EA και ένα πλαίσιο δισεληνοϊνδιούχου χαλκού (CIS) τεχνολογίας thin –film SHELL ECLIPSE 75 –C . Στο θεωρητικό μέρος παραθέτονται οι βασικές αρχές της φυσικής των ημιαγωγών και περιγράφονται οι τεχνολογίες των τριών πλαισίων που μελετάμε. Επίσης, αναλύονται τα ηλεκτρικά χαρακτηριστικά του ηλιακού στοιχείου και τέλος παρουσιάζονται οι πρόσφατες μελέτες σχετικά με τον παράγοντα ποιότητας οι οποίες χρησιμοποιήθηκαν ως αναφορά για τη διεξαγωγή της πειραματικής διαδικασίας. Για την διεξαγωγή του πειραματικού μέρους πραγματοποιήθηκαν πειραματικές μετρήσεις διάρκειας πέντε μηνών (Οκτώβριος 2009 – Φεβρουάριος 2010 ) . Οι μετρήσεις αφορούσαν όλα τα ηλεκτρικά χαρακτηριστικά των τριών πλαισίων και έγιναν σε πραγματικές συνθήκες στην ταράτσα του κτιρίου του τμήματος Ηλεκτρολόγων Μηχανικών του πολυτεχνείου Πάτρας για την κλίση των 38° . Τα πειραματικά δεδομένα οδήγησαν σε συμπεράσματα σχετικά με την συμπεριφορά του παράγοντα ποιότητας των τριών πλαισίων σε διαφορετικές καιρικές συνθήκες. Επιπλέον, μελετήθηκε η επίδραση της θερμοκρασίας υπό σταθερή ακτινοβολία και της ακτινοβολίας υπό σταθερή θερμοκρασία στον παράγοντα ποιότητας και στις παραμέτρους που τον επηρεάζουν. Η μελέτη ολοκληρώθηκε με τον υπολογισμό της αποδιδόμενης ενέργειας των τριών πλαισίων στο ίδιο διάστημα. Τέλος υπολογίστηκε η ετήσια αποδιδόμενη ισχύς για την ίδια κλίση για τα τρία πλαίσια με την βοήθεια του προγράμματος PV SOL και έγινε σύγκριση αυτών των τιμών με τις πειραματικές. / The purpose of this thesis is to study the fill factor for three different photovoltaic modules under different weather conditions. The modules under investigation were a mono-crystalline CONERGY Q 80 MI, a polycrystalline silicon sharp NE-80E2EA and a CIS technology thin-film SHELL ECLIPSE 75–C. In the literature review the basic physical principles of semiconductor technology are presented and the technical characteristics of the three modules under study are described. Also, the electrical characteristics of a solar cell are analyzed. Finally, recent studies on the fill factor of solar cells are presented. In order to conduct the experimental part of this thesis, extensive outdoor measurements have been realized during five months (October 2009 - February 2010). We have realized measurements of the electrical characteristics of the three modules under environmental conditions, on the roof of the building of the Department of Electrical and Computer Engineering of the University of Patras, at tilt angle of 38°. Conclusions were extracted, from experimental data, about the behavior of the fill factor of each of the three modules under varying weather conditions. Moreover, the effect of temperature and solar radiation on the fill factor of a solar cell was presented. The study was completed by calculating the energy yield from these modules during five months (October to February). Finally, the annual energy output was calculated using PV SOL software.

The presence of residual stresses in engineering components may significantly affect damage evolution and progression towards failure. Correct evaluation of residual stress is of crucial importance for assessing mechanical components, predicting response and ensuring reliability. For example, when failure occurs due to cyclic loading, the underlying damage begins at the nano-, and then micro-scale. It is clear that improving engineering reliability at the micro-scale requires the ability to evaluate residual stress and mechanical properties at the appropriate scale. The key objective of the thesis is to advance the understanding and practice of residual stress evaluation at the micro-scale, and to examine the implications and applications that follow. Significant effort was devoted to the evaluation of two aspects of the relatively novel FIB-DIC micro-ring-core experimental technique: assessing the effects of Ga-ion damage and the quantification of uncertainty in stress evaluation due to unknown crystal orientation. FIB-DIC micro-ring-core milling was then used alongside with synchrotron XRD to study residual stress effects on fatigue crack growth propagation rate following the occurrence of overload or underload. The effects of the two principal mechanisms of crack retardation following an overload, residual stress and crack closure, were separated by testing samples at different loading ratios. Whilst, the acceleration after an underload was studied using validated non-linear FEM analyses. Conceptual focus was placed on the macro-micro-nano residual stress decomposition into Type I, II &amp; III according to scale and, detailed examination was conducted experimentally and numerically. In the context of shot-peening surface treatment, residual stresses were modelled using a novel eigenstrain-based modelling procedure for arbitrarily shaped components. Furthermore, a fine scale characterisation was performed of the recast layer produced by EDM, with particular attention paid to the residual stress. The investigations presented in this thesis open new perspectives for the assessment of material reliability. Improved failure prediction models will be elaborated based on the insights obtained in the present study.

xvi, 117 p. ; ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / High efficiency thin film solar cells have the potential for being a world energy solution because of their cost-effectiveness. Looking to the future of solar energy, there is the opportunity and challenge for thin film solar cells. The main theme of this research is to develop a detailed understanding of electronically active defect states and their role in limiting device performance in copper indium gallium diselenide (CIGS) solar cells. Metastability in the CIGS is a good tool to manipulate electronic defect density and thus identify its effect on the device performance. Especially, this approach keeps many device parameters constant, including the chemical composition, grain size, and interface layers. Understanding metastability is likely to lead to the improvement of CIGS solar cells. We observed systematic changes in CIGS device properties as a result of the metastable changes, such as increases in sub-bandgap defect densities and decreases in hole carrier mobilities. Metastable changes were characterized using high frequency admittance spectroscopy, drive-level capacitance profiling (DLCP), and current-voltage measurements. We found two distinctive capacitance steps in the high frequency admittance spectra that correspond to (1) the thermal activation of hole carriers into/out of acceptor defect and (2) a temperature-independent dielectric relaxation freeze-out process and an equivalent circuit analysis was employed to deduce the dielectric relaxation time. Finally, hole carrier mobility was deduced once hole carrier density was determined by DLCP method. We found that metastable defect creation in CIGS films can be made either by light-soaking or with forward bias current injection. The deep acceptor density and the hole carrier density were observed to increase in a 1:1 ratio, which seems to be consistent with the theoretical model of V Cu -V Se defect complex suggested by Lany and Zunger. Metastable defect creation kinetics follows a sub-linear power law in time and intensity. Numerical simulation using SCAPS-1D strongly supports a compensated donor- acceptor conversion model for the experimentally observed metastable changes in CIGS. This detailed numerical modeling yielded qualitative and quantitative agreement even for a specially fabricated bifacial CIGS solar cell. Finally, the influence of reduced hole carrier mobility and its role in limiting device performance was investigated. / Adviser: J. David Cohen