Abstract Electric contacts are the essential components of electric equipment. In the past, the silver-cadmium oxide is used as the materials contacts. However, because it generates the poison cadmium gas during the service, which causes the cancer, the silver-cadmium oxide will be prohibited in the near future. Now the silver-tin oxide is often used as the materials of the electrical contacts. To oxidize pure tin more easily,¡AIn2O3 is usually added as the auxiliary oxide agent. However, In2O3 is expensive. Hence, in this study, the other metal oxide agents are added to the silver-tin oxide to investigate the agent effect on the erosion characteristics (such as the erosion amount, the contact resistance, the arc energy, etc). This study uses the powder metallurgy to produce the electrical contacts, where the sizes of pure silver powder and tin oxide powder are 2~3£gm and 4~5£gm, respectively. The doping agents are made of 3~4£gm tungsten oxide and 3~5£gm molybdenum oxide, respectively. The powder are mixed in a suitable proportion to produce electrical contacts. The effect of metal oxide on the erosion of electrical contacts is investigated under different electric conditions. Results show that when the tin oxide powder is added to the pure sil-ver, the splashing of material can be prevented efficiently, and the erosion of electrical contacts can be reduced. Among the materials of silver-tin oxide, the contacts have the minimum erosion at the concen-tration of 5wt%. In order to reduce the cost of electrical con-tacts, the concentration of tin oxide is increased to 10wt% to investigate the influence of the doping agent. Results show that the addition of 0.3wt%WO3 has the minimum erosion. This electrical contact has lower erosion than the commercial ones. Furthermore, the regions, where the electrical contact has lower erosion than the commercial pure silver contacts and the silver-cadmium oxide, respectively, are established. These re-gions will be the best usable regions of silver tin oxide, and it will be the basis for the choice and the application of silver-tin oxide electrical contacts.

Thesis (M.S.)--Youngstown State University, 2009. / Includes bibliographical references (leaves 65-67). Also available via the World Wide Web in PDF format.

published_or_final_version / Physics / Master / Master of Philosophy

Dissertation (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Thesis(M.S.)--Auburn University, 2006. / Abstract. Includes bibliographic references (p.55-59).

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: Robert L. Opila, Dept. of Materials Science & Engineering. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 151-152).

Thesis (M.S.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (July 14, 2006) Includes bibliographical references.

This thesis addresses two important aspects of automatic assembly viz., assembly sequence planning and assembly path planning. These issues are addressed separately starting with sequence planning followed by assembly path planning. For efficient assembly without feedback systems (or, passive assembly), an assembler should know the ideal orientation of each component and the order in which to put the parts together (or, assembly sequence). A heuristic is presented to find the optimal assembly sequence and prescribe the orientation of the components for a minimum set of grippers = ideally one. The heuristic utilizes an index of difficulty (ID) that quantifies assembly. The ID for each task in the assembly process is computed on the basis of a number of geometrical and operational properties. The objective of the optimization problem here is to minimize the assembly ID and categorize parts/subassemblies based on their preferred direction of assembly while allowing re-orientation of the base part. It is assumed that the preferred direction of assembly is vertically downward, consistent with manual as well as most automatic assembly protocols. Our attempt is to minimize the number of degrees of freedom required in a re-orienting fixture and derive the requirements for such a fixture. The assembly of a small engine is used as an example in this study due to the variety of ideally rigid parts involved. In high precision assembly tasks, contact motion is common and often desirable. This entails a careful study of contact states of the parts being assembled. Recognition of contact states is crucial in planning and executing contact motion plans due to inevitable uncertainties. Dr. Jing Xiao of UNCC introduced the concept of principal contacts (PC) and contact formation (CF) for contact state recognition. The concept of using CFs (as sets of PCs) has the inherent advantage that a change of CF is often coincident with a discontinuity of the general contact force (force and torque). Previous work in contact motion planning has shown that contact information at the level of PCs along with the sensed location and force information is often sufficient for planning high precision assembly operations. In this thesis, we present results from experiments involving planned contact motions to validate the notion of PCs and CFs -- an abrupt change in general contact force often accompanies a change between CFs. We are only concerned with solving the 2D peg-in-corner problem. / Master of Science

Passivating-contact technologies fabricated from polycrystalline-silicon (poly-Si) are increasingly considered by the crystalline silicon (c-S) PV industry to be key enablers towards record performance. This is largely thanks to their ability to provide excellent carrier collection and surface passivation, while being compatible with industrial scale production. Poly-Si based passivating contacts consist of a stack of an ultrathin silicon oxide (SiOx) film on the surface of crystalline silicon (c-Si), covered by a doped silicon film. Thin films of SiOx can be grown by several different methods: chemically, thermally, or via UV-ozone exposure. However, each of these methods presents challenges towards industrial implementation. Here, we report an alternative method to grow SiOx films using an in-situ plasma process, where we subsequently deposit the doped poly-Si layer in the same process chamber by plasma enhanced chemical vapor deposition (PECVD). This process presents several advantages, such as ease of fabrication, inherently single-side oxide growth and poly-Si deposition, and the combined deposition in one chamber, lowering capital expenditure. Subsequently, we studied the structure of the SiOx films and the doped poly-Si(p+) capping layers using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) in order to determine the films’ elemental composition, and the band alignment at the semiconductor/oxide interfaces. A less p-type polysilicon was observed grown on top of a wet SiOx/c-Si with the origin tentatively attributed to depletion of the boron dopant via pin holes evidenced by AFM. A surface photo-voltage (SPV) was observed by XPS under in-situ light bias (AM 1.5) and a representation of the band alignment of the c-Si/SiOx/p-polysilicon under illumination is derived. The SPV was attributed to the photo accumulation of holes at the p-polysilicon and a splitting of quasi-fermi levels with its magnitude correlated to the device measured iVoc . Finally, a valuable application for this contact technology is the integration of silicon with perovskite solar cells, in the so-called monolithic tandem configuration. This approach is very promising to develop a new generation of PV with unmatched performances. Here, poly-Si contacts offer a variety of advantages, thanks to their broader material selection and to the stability at high processing temperature.