Dissertations / Theses on the topic 'Oxides'
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1
Gillispie, Meagen Anne. "Metal oxide-based transparent conducting oxides." [Ames, Iowa : Iowa State University], 2006.
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Field, Marianne Alice Louise. "Transition metal oxides and oxide-halides." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401833.
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Romano, Esteban Javier. "A surface science approach to understanding emission control catalyst deactivation due to sulfation of ceria-zirconia mixed-metal oxides." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-03252004-162922.
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McCluskey, Adam. "Carbonyl oxides." Thesis, University of Strathclyde, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303277.
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Lopes, Luis Fernando da Silva. "Síntese e caracterização do WO3-Ag preparado via rota hidrotérmica /." Bauru, 2017. http://hdl.handle.net/11449/152178.
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Orientador: Fenelon Martinho Lima PontesBanca: Adenilson José Chiquito
Banca: Alejandra Hortencia Miranda González
Resumo: As estruturas hierárquicas do WO3-Ag tridimensional (3D) auto-montadas foram sintetizadas através da rota hidrotérmica utilizando como soluções precursoras o ácido túngstico (H2WO4) e peróxido de hidrogênio (H2O2), adicionando diferentes quantidades de Ag. As amostras foram analisadas por difração de raios X (DRX), Microscopia Eletrônica de Varredura de Campo (MEV-FEG), análise termogravimétrica (TGA), espectroscopia micro Raman, espectroscopia no infravermelho por transformada de Fourier (FTIR), espectroscopia no ultravioleta visível UV-VIS e espectroscopia de fotoelétrons excitados por raios X (XPS). Os estudos de DRX e micro Raman mostraram que à medida que a quantidade de Ag variou de 0 a 10% em peso na solução de crescimento hidrotérmico, a fase do cristal mudou gradualmente de WO3•0,33H2O ortorrômbica para WO3 hexagonal. Os estudos de FTIR e TGA revelaram diferentes níveis de hidratação, apoiando os resultados de DRX e micro Raman. Ao controlar a quantidade de Ag na solução precursora, foram obtidos blocos de construção semelhantes a plaquetas e blocos de construção hexagonais, destacando o papel da prata no crescimento hidrotérmico dos microcristais 3D WO3•0.33H2O e WO3. Além disso, as imagens de MEV-FEG de alta magnificação mostraram que as nanopartículas de Ag estão ancoradas na superfície das estruturas hierárquicas WO3-Ag 3D. Medidas no UV-vis demonstraram que as estruturas hierárquicas 3D absorveram gradualmente mais luz quando a quantidade de Ag foi aumentada. Al... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The self-assembled three-dimensional (3D) WO3-Ag hierarchical structures were synthesized through the hydrothermal route using tungstic acid (H2WO4) and hydrogen peroxide (H2O2) as precursor solutions, adding different amounts of Ag. The samples were analyzed by diffraction X-ray diffraction (XRD), field scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), micro Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), visible ultraviolet UVVIS spectroscopy and spectroscopy Photoelectrons (XPS). XRD and micro Raman studies showed that as the amount of Ag ranged from 0 to 10% by weight in the hydrothermal growth solution, the crystal phase gradually changed from orthorhombic WO3•0.33H2O to hexagonal WO3. The FTIR and TGA studies revealed different levels of hydration, supporting the XRD and micro Raman results. By controlling the amount of Ag in the precursor solution, platelet-like building blocks and hexagonal building blocks were obtained, highlighting the role of Ag in the hydrothermal growth of the 3D microcrystals WO3•0.33H2O and WO3. In addition, high magnification FESEM images showed that Ag nanoparticles are anchored on the surface of the WO3-Ag 3D hierarchical structures. UV-vis measurements demonstrated that the 3D hierarchical structures gradually absorbed more light when the amount of Ag was increased. In addition, the energy of the band gap was decreased when the amount of Ag increased from 0% by weight (Eg = 2.65 eV) to 10% by weight... (Complete abstract click electronic access below)
Mestre454
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FLORIO, DANIEL Z. de. "Analise de eletrolitos de ZrO sub(2):Y sub(2) O sub(3) + B sub(2) O sub(3) e de eletrodos de La sub(0,8) Sr sub(0,2) Co sub (0,8) Fe sub (0,2) O sub (3-delta) por espectroscopia de impedancia." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11130.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Taujale, Saru. "INTERACTIONS BETWEEN METAL OXIDES AND/OR NATURAL ORGANIC MATTER AND THEIR INFLUENCE ON THE OXIDATIVE REACTIVITY OF MANGANESE DIOXIDE." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/347169.
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Civil EngineeringPh.D.
Mn oxides have high redox potentials and are known to be very reactive, rendering many contaminants susceptible to degradation via oxidation. Although Mn oxides typically occur as mixtures with other metal oxides (e.g., Fe, Al, and Si oxides) and natural organic matter (NOM) in soils and aquatic environments, most studies to date have studied the reactivity of Mn oxides as a single oxide system. This study, for the first time, examined the effect of representative metal oxides (Al2O3, SiO2, TiO2, and Fe oxides) and NOM or NOM-model compounds (Aldrich humic acid (AHA), Leonardite humic acid (LHA), pyromellitic acid (PA) and alginate) on the oxidative reactivity of MnO2, as quantified by the oxidation kinetics of triclosan (a widely used phenolic antibacterial agent) as a probe compound. The study also examined the effect of soluble metal ions released from the oxide surfaces on MnO2 reactivity. In binary oxide mixtures, Al2O3 decreased the reactivity of MnO2 as a result of both heteroaggregation and complexation of soluble Al ions with MnO2. At pH 5, the surface charge of MnO2 is negative while that of Al2O3 is positive resulting in intensive heteroaggregation between the two oxides. Up to 3.15 mM of soluble Al ions were detected in the supernatant of 10 g/L of Al2O3 at pH 5.0 whereas the soluble Al concentration was 0.76 mM in the mixed Al2O3 + MnO2 system at the same pH. The lower amount of soluble Al in the latter system is the result of Al ion adsorption by MnO2. The experiments with the addition of 0.001 to 0.1 mM Al3+ to MnO2 suspension indicated the triclosan oxidation rate constant decreased from 0.24 to 0.03 h-1 due to surface complexation. Fe oxides which are also negatively charged at pH 5 inhibited the reactivity of MnO2 through heteroaggregation. The concentration of soluble Fe(III) ions ( 4 mg-TOC/L or [alginate/PA] > 10 mg/L, a lower extent of heteroaggregation was also observed due to the negatively charged surfaces for all oxides. Similar effects on aggregation and MnO2 reactivity as discussed above were observed for ternary MnO2‒Al2O3‒NOM systems. HAs, particularly at high concentrations (2.0 to 12.5 mg-C/L), alleviated the effect of soluble Al ions on MnO2 reactivity as a result of the formation of soluble Al-HA complexes. Alginate and PA, however, did not form soluble complexes with Al ions so they did not affect the effect of Al ions on MnO2 reactivity. Despite the above observations, the amount of Al ions dissolved in MnO2+Al2O3+NOM mixtures was too low, as a result of NOMs adsorption on the surface to passivate oxide dissolution, to have a major impact on MnO2 reactivity. In conclusion, this study provided, for the first time, a systematical understanding of the redox activity of MnO2 in complex model systems. With this new knowledge, the gap between single oxide systems and complex environmental systems is much narrower so that it is possible to have a more accurate prediction of the fate of contaminants in the environment.
Temple University--Theses
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Heap, Richard John. "Synthesis and characterisation of K2NiF4-related oxides and oxide fluorides." Thesis, University of Surrey, 2006. http://epubs.surrey.ac.uk/843525/.
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In the work presented here, a synthetic and structural study of K2NiF4-related oxides and oxide fluorides is reported. Several ranges of oxides and oxide fluorides have been synthesised and structurally characterised by Rietveld refinement of X-ray and Neutron diffraction data. Many of these materials are novel, and show some interesting structural, chemical and physical properties. These materials were all prepared via the standard solid state technique. Because most of the oxide fluorides presented here are not stable at high temperatures, their synthesis involved a two stage process; production of an oxide precursor, followed by low temperature fluorination of this precursor. Throughout this study, the polymer-based fluorinating agent, PVDF, was shown to be effective for the production of a number of novel oxide fluorides. In addition, during the course of the work presented here, the new fluorinating agent, (PTFE) was discovered, and also shown to be effective for this purpose.
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ARAKAKI, ALEXANDER R. "Obtencao de ceramicas de ceria - samaria - gadolinia para aplicacao como eletrolito em celulas a combustivel de oxido solido (SOFC)." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9506.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Romano, Esteban Javier. "In-situ surface science studies of the interaction between sulfur dioxide and two-dimensional palladium loaded-cerium/zirconium mixed metal oxide model catalysts." Diss., Mississippi State : Mississippi State University, 2005. http://library.msstate.edu/etd/show.asp?etd=etd-04062005-093500.
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Womiloju, Olusola Olumuyiwa. "(Pentamethylcyclopentadienyl)molybdenum oxides." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0017/NQ54601.pdf.
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Southerington, I. Gary. "Organoantimony (V) oxides." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334820.
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Wyatt, Paul Jeffery. "Homochiral phosphepin oxides." Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/272998.
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Bernuy-Lopez, Carlos. "Novel mixed conducting oxides for sold oxide fuel cells (SOFC's) applications." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501713.
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This thesis describes the search for new mixed conductors as potential anodes and cathodes for applications in Solid Oxide Fuel Cells. Several compounds have been synthesised and characterised by means of different diffraction techniques (X-Rays, neutrons and electrons), high resolution electron microscopy and electrical measurements (AC Impedance Spectroscopy and DC resistivity measurements).
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Liu, Dameng. "High-K gate oxides for future complementary metal-oxide-semiconductor transistors." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611517.
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OLIVEIRA, OLAVO R. de. "Desenvolvimento de condutores protonicos ceramicos para operacao de celulas a combustivel de oxido solido com combustiveis metano e hidrogenio." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9439.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
FAPESP:07/51631-0
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GARCIA, RAFAEL H. L. "Síntese e processamento de compósitos de zircônia-alumina para aplicação como eletrólito em células a combustível de óxido sólido." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11554.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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SANTANA, LEONARDO de P. "Estudo de conformacao de ceramicas a base de zirconia para aplicacao em celulas a combustivel do tipo oxido solido." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11727.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Togo, Atsushi. "Point defects and lattice dynamics of tin oxides and lead oxides." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/136157.
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Ren, Xiaolin. "Synthesis and characterisation of metal oxides and fluorinated perovskite-related oxides." Thesis, Open University, 2005. http://oro.open.ac.uk/54200/.
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Perovskite-related materials of composition LaFe1-xCoxO3 prepared by conventional calcination methods and mechanical milling are shown by temperature programmed reduction to be more susceptible to reduction in a flowing mixture of hydrogen and nitrogen by the incorporation of cobalt. X-ray powder diffraction and Mossbauer spectroscopy show that in iron-rich systems the limited reduction of iron and cobalt leads to the segregation of discrete metallic phases without destruction of the perovskite structure. In cobalt-rich systems, the reduction of Co3+ to Coo precedes complete reduction of Fe3+ and the segregation of alloy and metal phases is accompanied by destruction of the perovskite structure. Phases made by milling techniques were of smaller particle size and are more susceptible to hydrogen reduction than their counterparts made by conventional techniques. Materials of the type La0.5Sr0.5MO3 (M= Fe, Co) made by calcination methods are more susceptible to reduction when the transition metal M is cobalt as compared to iron. Perovskite-related oxides of composition La1-xSrxFe1-yCoyO3 have been fluorinated by reaction with poly(vinylidene fluoride). The materials have been characterised by X-ray powder diffraction and Mossbauer spectroscopy. Fluorination induces a reduction in the oxidation state of iron from Fe4+ to Fe3+. The fluorinated materials were magnetically ordered at 298 K. Compounds of the type SrFe1-xSnxO3 were found to contain Fe5+ and Fe3+. Fluorination resulted in reduction of the transition metal to Fe3+ and, in iron-rich systems, magnetic order. The compound Ba2SnO4 which adopts the K2NiF4-type structure has also been fluorinated by reaction with zinc fluoride. X-ray powder diffraction shows an enlargement of the unit cell of the fluorinated phase along the c-axis. Small particle iron- and vanadium- antimonate have been prepared by mechanical milling methods. The phases have been examined by M6ssbauer spectroscopy and can be formulated M3+Sb5+O4 (M = Fe, V). Thermal analysis suggests that the vanadium animonate formed by milling V2O5 and Sb2O3 in an inert atmosphere may be oxygen deficient. X-ray powder diffraction shows that milling also induces the phase transformation of the cubic senarmontite Sb2O3 form to the orthorhombic valentinite Sb2O3 form and of a-Sb2O4 to B-Sb2O4.
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Rowley, Adrian. "Computer simulation of oxides." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298405.
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Boltz, Janika [Verfasser]. "Sputtered tin oxide and titanium oxide thin films as alternative transparent conductive oxides / Janika Boltz." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1019850485/34.
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Messi, C. "Nanostructured catalytic metal oxides supported over oxide supports of various nature : the iron oxide system." Doctoral thesis, Università degli Studi di Milano, 2008. http://hdl.handle.net/2434/57081.
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Graves-Brook, Melissa Kaye. "Synthesis and characterization methods of palladium-doped ceria-zirconia compounds." Master's thesis, Mississippi State : Mississippi State University, 2005. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
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Isherwood, Patrick J. M. "Development of transparent conducting oxides for photovoltaic applications." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18886.
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Metal oxides are a very important class of materials with a wide range of photovoltaic applications. Transparent conducting oxides (TCOs) are the primary front contact materials used in thin film solar cells. Identification of methods for reducing the resistivity of these materials would have significant benefits. Development of p-type TCOs would provide alternative back contact materials and could enable further development of technologies such as bifacial, window and multijunction cells. A series of studies into these areas is presented in this work. Aluminium doped zinc oxide (AZO) is a well-known n-type TCO consisting entirely of Earth-abundant materials. Targets were manufactured from AZO powder, which was synthesised using a patented emulsion detonation process developed by Innovnano S.A. All films showed good optical transmission. Resistivity was found to decrease with both increasing time and temperature up to 300 degree C. Temperatures above 300 degree C were found to be detrimental to film formation, with increasing amounts of damage to the crystal structure and consequent increases in the resistivity. The effect of alloying molybdenum oxide with molybdenum nitride through reactive sputtering in a mixed oxygen-nitrogen atmosphere was investigated. All alloys were found to show p-type behaviour. Resistivity was found to improve with increased nitrogen content, in contrast to optical transmission, which reduced. A selection of compositions were deposited onto CdTe cells as back contacts. These cells showed an increase in efficiency with increasing nitrogen content. Work function was found to increase with increasing oxygen content, but all work functions were low. Resistivity was shown to correlate strongly with efficiency, caused by a corresponding increase in cell voltage. This implies that to form an ohmic contact on CdTe with p-type materials, work function may be less important than resistivity. The copper oxides are p-type, but uses are limited by the narrow band gaps. Cupric oxide was chosen for investigation and for alloying with other oxides with the aim of increasing the band gap. It was found that temperature and deposition environment have significant impacts on sputtered cupric oxide (CuO) films, with low temperatures and high oxygen environments producing the lowest resistivities. Extrinsic sodium doping was found to reduce the resistivity by up to four orders of magnitude. High oxygen content sodium-doped films were found to have carrier concentrations two orders of magnitude higher than that of indium tin oxide.
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Hosokawa, Saburo. "Solvothermal Synthesis of Rare Earth Oxides and Rare-Earth-Based Mixed-Oxides." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/77797.
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Almar, Liante Laura. "Ordered mesoporous metal oxides for solid oxide fuel cells and gas sensors." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/283997.
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Nanomaterials have received increasing attention during the last decades in the solid state field since they play a major role as catalyst and catalyst supports for many applications including fuel cells or gas sensors. The interest is mainly due to their high specific surface area, which leads to an increase of performance and a cost-effective solution for expensive or rare materials. However, many studies have reported the collapse of nanostructures at high temperature as one of the main drawbacks for their implementation in real devices and therefore, routes to thermally stabilize these materials must be explored.
In this thesis, the unique features of ordered mesoporous materials fabricated by nanocasting are exploited to create quasi-universal thermal stabilization methodologies, allowing implementing and evaluating them in high temperature energy applications e.g. solid oxide fuel cells.
The work developed is divided into seven parts. The first chapter introduces the basics of mesoporous materials, solid oxide fuel cells, catalysis and gas sensors. The second chapter focuses on the experimental procedures and the characterization tools employed. In the third chapter, a novel route to thermally stabilize 3-D open mesoporous structures is presented. The next three chapters, show the fabrication and evaluation of thermal stable mesoporous materials as electrodes for solid oxide fuel cells. Finally, chapter seven presents the suitability of mesoporous ceramic oxides as functional materials in humidity sensors.Los nano-materiales han recibido especial atención durante estas últimas décadas en el campo del estado sólido dado el importante papel que desempeñan como catalizadores y/o soportes catalíticos en diversas aplicaciones, tales como las pilas de combustible o los sensores de gas. Este interés se debe principalmente a su elevada área específica, que da lugar a una mejora del rendimiento y es una solución efectiva para aquellas aplicaciones que requieran materiales de elevado coste. Sin embargo tal y como señalan muchos estudios, el colapso de estas nano-estructuras a elevadas temperaturas es uno de los mayores inconvenientes para su implementación en dispositivos reales, siendo por tanto necesario explorar nuevas rutas que consigan estabilizar estos materiales térmicamente. El objetivo de la presente tesis es desarrollar metodologías cuasi-universales de estabilización térmica, mediante la explotación de las características exclusivas que poseen los materiales mesoporosos ordenados fabricados a partir de un template. Lo cual nos permite implementarlos y evaluarlos en aplicaciones energéticas que operan a elevada temperatura p.ej. pilas de combustible de óxido sólido. El trabajo desarrollado se divide en siete partes. El primer capítulo introduce los fundamentos de los materiales mesoporosos, las pilas de combustible de óxido sólido, la catálisis y los sensores de gas. En el segundo capítulo se detallan los procedimientos experimentales y las técnicas de caracterización empleados. El tercer capítulo presenta una nueva metodología para estabilizar térmicamente los materiales mesoporosos de estructura 3-D abierta. Los siguientes tres capítulos, muestran la fabricación y el comportamiento electroquímico de materiales mesoporosos térmicamente estables trabajando como electrodos de pilas de combustible de óxido sólido. Por último, en el capítulo siete se demuestra la viabilidad de los óxidos cerámicos mesoporosos como materiales funcionales en sensores de humedad.
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Jewmaidang, Jirasak. "Homogeneous sulfur tri-oxide formation in gas reburning for nitrogen oxides control." Ohio : Ohio University, 1999. http://www.ohiolink.edu/etd/view.cgi?ohiou1175801641.
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Yue, Wenbo. "Mesoporous crystalline metal oxides." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/830.
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Langley, Tracey Annette. "Studies of mixed oxides." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365837.
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Su, Zixue. "Porous anodic metal oxides." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1019.
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An equifield strength model has been established to elucidate the formation mechanism for the highly ordered alumina pore arrays and titanium oxide nanotubular arrays prepared via a common electrochemical methodology, anodisation. The fundamentals of the equifield strength model was the equilibrium between the electric field driven oxidation rate of the metal and electric field enhanced dissolution rate of oxide. During the anodic oxidation of metal, pore initiation was believed to generate based on dissolution rate difference caused by inhomogeneity near the metal/oxide interface. The ionic nanoconvection driven by the electric force exerted on the space charge layer in the vicinity of electrolyte/oxide interface is established to be the main driving force of the pore ordering at the early stage of the anodisation. While the equifield strength requirement governs the following formation of the single pore and the self-ordering of random distributed pore arrays during the anodisation process. Hexagonal patterned Al2O3 nanopore arrays and TiO2 nanotubular arrays have been achieved by anodisation of corresponding metal substrates in proper electrolytes. The two characteristic microstructural features of anodic aluminium oxide (AAO) and anodic titanium oxide (ATO) were investigated using scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The observations of the hemispherical electrolyte/oxide and oxide/metal interfaces, uniform thickness of the oxide layer, as well as self-adjustment of the pore size and pore ordering can be well explained by the equifield strength model. Field enhanced dissociation of water is extremely important in determination of the porosity of anodic metal oxide. The porosity of AAO and ATO films was found to be governed by the relative dissociation rate of water which is dependent on anodisation conditions, such as electrolyte, applied voltage, current density and electric field strength. Using an empirical method, the relations between the porosity of the AAO (ATO) films and the anodisation parameters, such as electric field strength, current density and applied voltage, have been established. Besides, the extent that an external electric field can facilitate the heterolytic dissociation of water molecule has been estimated using quantum-chemical model computations combined with the experimental aspect. With these achievements, the fabrication of anodic metal oxide films can be understood and controlled more precisely. Additionally, the impacts of other factors such as the electrolyte type and the temperature effect on the morphology of the anodic products were also investigated. Some important experimental evidences on the pore diameters variation with applied voltage in the anodisation of aluminium and the titanium were obtained for future investigation of the anodic metal oxide formation processes.
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Baxter, J. E. "Acylphosphine oxides as photoinitiators." Thesis, City University London, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380699.
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Droessler, Laura Melanie. "Lead oxides for photovoltaics." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:8a0216a2-3efe-4de4-a853-d5b6ec53eeee.
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This thesis investigates lead oxides as photovoltaic materials. Vacuum deposition methods and ex-situ annealing are used to produce different stoichiometries of lead oxide. The relationship between structure and the optoelectronic properties is then investigated. Following this, a number of photovoltaic devices are prototyped and a Kelvin probe used to determine and understand the band structure of devices. Thin films of PbO produced via air annealing of thermally evaporated lead consist of a mixture of two phases, orthorhombic and tetragonal, that determine the materials properties and effectiveness as absorber layer in a Schottky device. Films of higher tetragonal content are more photoactive, showing lower series resistance. Kelvin probe reveals that with an increasing work function of the PbO with increasing duration of the annealing, the Schottky barrier between PbO and Al increases, which results in a higher VOC. This trend is inverted when the Fermi level of PbO drops below that of ITO, creating an opposing junction. Reactively sputtered PbO2 films are highly conductive degenerate semiconductors. Increasing oxygen flow rate during deposition leads to increased resistivity and decreased mobility, resulting from a decrease in grain size. Alongside this an increase in carrier concentration is observed as the material gets less ordered at higher oxygen flow rates, which results in an increase in Fermi level. Due to its high conductivity the material is not photoactive, and the high work function between -5.6 and -5.8 eV does not allow the formation of a Schottky junction or a p-n junction with the evaporated p- type PbO. Post deposition annealing of the sputtered films leads to the formation of the more resistive Pb3O4 phase. This material shows lower carrier concentration and mobility, however, work functions are similarly high. The changes induced by the heat treatment are not substantial enough to be able to create a junction between the as-deposited and the annealed material, as is revealed by Kelvin probe and Hall Effect measurements. Heterojunctions between P3HT and Pb3O4 were made to test predictions made by KP measurements. A heat treatment on P3HT improved its electronic properties and raised the Fermi level, resulting in the transformation of a diode in to a photovoltaic device and a decrease in dark current.
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Weerakkody, D. A. "Engineered high-k oxides." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3003448/.
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The evolution of integrated circuit technology over the five decades resulted in scaling down the minimum feature size of a transistor from 10 μm to ~14 nm. The high-k dielectrics were identified as potential candidates to replace SiO2 from 2007 due to the large leakage current observed when scaling down SiO2. These materials captured the attention of many researchers and led them to focus on many emerging applications in addition to metal oxide semiconductor field effect transistors (MOSFET). In this thesis, two emerging applications of high-k dielectrics were investigated: (i) germanium based MOSFETs and (ii) high frequency high speed rectifiers for optical rectennas.
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Hutton, Gordon Eric. "Stereocontrol with phosphine oxides." Thesis, University of Cambridge, 1994. https://www.repository.cam.ac.uk/handle/1810/273009.
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Todorov, Neno. "Phonons in complex oxides." Nantes, 2014. http://archive.bu.univ-nantes.fr/pollux/show.action?id=501ad770-9596-41d0-9e83-227ef7a790d9.
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Dans cette thèse, une étude vibrationnelle de plusieurs oxydes complexes a été effectuée sur différentes structures de type perovskites : les matériaux orthorhombiques YCrO3 et YMnO3 rhomboédrique Sc3CrO6 et de type C Sc2O3 . La principale méthode utilisée pour la caractérisation des échantillons est la spectroscopie de diffusion Raman. La composition chimique et la structure cristalline des oxydes a été déterminée par diffraction des rayons X sur poudres et cristaux et par microscopie électronique à balayage. Des calculs de dynamique de réseau ont été menés à bien pour déterminer l'origine des bandes spectrales Raman observées, en utilisant des modèles à coquilles ou des méthodes ab initio. Une analyse systématique des données structurales et de diffusion Raman a porté sur les cristaux du type R3+B3+O3 (R- terre rare, B=Al,Sc,Ti, V,Cr,Mn,Fe,Co,Ni, et Ga) pour établir la relation entre la fréquence de modes Raman mous et le ou les angle (s) d'inclinaison des octaèdres BO6. Une dépendance générale entre les fréquences Raman et le paramètre cristallin a été établie pour les sesquioxydes cubiques de terres rares R2O3The thesis presents the results of the studies on different oxides with perovskite or perovskite-like structures like orthorhombic YCrO3 and YMnO3 rhombohedral Sc3CrO6, and C-type Sc2O3 . The main experimental method used for the characterization of the samples is Raman spectroscopy. In addition to that, to find their chemical content and crystal structure, other methods like scanning electron microscopy, single-crystal diffractometry, and x-ray powder diffraction were used. Lattice dynamical calculations (empirical shell model and ab initio methods) were used to determine the origin of the observed in the Raman spectra lines. A systematic analysis of the structural and Raman data for R3+B3+03 (R-rare earth,B = Al, Sc, Ti, V, Cr, Mn,Fe,Co,Ni, and Ga) was made to establish dependency between the frequency of the quasi-soft Raman-active modes and the tilt angle(s) of the BO6 octahedra. A general dependency of the frequencies of the Raman lines on the cubic crystal lattice parameter was shown as a result of a comparative study of the rare earth sesquioxides R2O 3
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Thorpe, Heidi Ruth. "Chemistry of allene oxides." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/13751.
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Chapter One reviews aspects of the chemistry of allene oxides reported in the chemical literature. The review is organised into three sections describing the available methods for the preparation of allene oxides, the reactions of allene oxides and allene oxides in biological systems. Chapter Two discusses attempts to develop new methods for the generation and trapping of allene oxides. Firstly, an unsuccessful attempt to employ a selenoxide elimination to generate an allene oxide is described. This is followed by a section detailing an improved method for the generation and in situ capmre of allene oxides with alcohols. Sodium alkoxides were found to trigger elimination in β,γ-epoxy-β-trimethylsilyl mesylates to afford allene oxides and also act as the nucleophilic trapping component. This methodology was used to synthesise a range of α alkoxyketones. Attempts to employ other nucleophiles in this process are also discussed. Chapter Three describes how the successful chemistry described in Chapter Two was modified in order to generate and trap chiral, non-racemic allene oxides. The preparation of homochiral β,γ-epoxy-β-trimethylsilyl mesylates and their subsequent reaction with potassium alkoxides at low temperature under aprotic conditions is described. The α alkoxyketone products were found to be of high enantiomeric excess and the absolute configuration of the product was determined in one case. Finally, attempts to effect a threecomponent coupling of an aIlene oxide, by reaction of an allene oxide with a nucleophile and subsequently an electrophile, are discussed. Chapter Four describes pioneering work towards a general method for the preparation of methylene cyclic sulfites as potential allene oxide equivalents is presented. A series of such compounds were prepared by reaction of α-hydroxyketones with thionyl chloride and via selenoxide elimination chemistry. Chapter Five describes the detailed experimental work undertaken in this thesis.
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YOSHITO, WALTER K. "Estudo de rotas de síntese e processamento cerâmico do compósito NiO-YSZ para aplicação como anodo em células a combustível do tipo óxido sólido (SOFC)." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9966.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Gu, Jingjing. "Ternary Oxide Structures for High Temperature Lubrication." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc804963/.
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In this research, a temperature dependent tribological investigation of selected ternary oxides was undertaken. Based on the promising results of previous studies on silver based ternary oxides, copper based ternary oxides were selected to conduct a comparative study since both copper and silver are located in the same group in the periodic table of the elements. Two methods were used to create ternary oxides: (i) solid chemical synthesis to create powders and (ii) sputtering to produce thin films. X-ray diffraction was used to explore the evolution of phases, chemical properties, and structural properties of the coatings before and after tribotesting. Scanning electron microscopy, Auger scanning nanoprobe spectroscopy, and X-ray photoelectron spectroscopy were used to investigate the chemical and morphological properties of these materials after sliding tests. These techniques revealed that chameleon coatings of copper ternary oxides produce a friction coefficient of 0.23 when wear tested at 430 °C. The low friction is due to the formation of copper tantalate phase and copper in the coatings. All sputtering coatings showed similar tribological properties up to 430 °C.
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Drisko, Glenna L. "Template synthesis and surface modification of metal oxides /." Connect to thesis, 2010. http://repository.unimelb.edu.au/10187/7090.
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CAMPOS, MAGALI de. "Obtencao da zirconia (ZrO2) estabilizada com itria (Y2O3) via precipitacao simultanea." reponame:Repositório Institucional do IPEN, 1993. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10326.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Smith, Andrew William John. "An experimental and computer modelling study of ternary rutile oxides and molybdenum oxides." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318583.
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Penner, S., and H. Lorenz. "From Pure Oxides to Mixed Oxides: Model Systems for Structural and Catalytic Studies." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35049.
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As pure oxides and mixed oxide systems play an ever-increasing role in a variety of research fields ranging from catalysis over electrochemical applications to microelectronics, the present contribution aims at introducing a straightforward concept for the easy and reproducible preparation of well-defined and well-structured thin film model systems both for pure and mixed oxide systems. Exploiting the special structural and surface properties of vacuum-cleaved NaCl (001) growth templates, the concept is exempli-fied for the formation of nano-spheres (Ga2O3), nano-pyramids (In2O3), plates and needles (V2O5) and den-dritic structures (Ga2O3-WO3). Careful tuning of the preparation conditions (substrate temperature, depo-sition rate, oxygen partial pressure or post-annealing temperature) allows the formation of special particle morphologies at much lower substrate temperatures (less than 400°C) than previously and usually applied.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35049
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SILVA, MAVIAEL J. da. "Desenvolvimento de selantes vitrocerâmicos para uso em SOFC pertencentes ao sistema BAS (BaO-Alsub(2)0sub(3)-SiOsub(2)) modificados com Bsub(2)Osub(3)." reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23655.
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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Wei, Daming. "Study of high dielectric constant oxides on GaN for metal oxide semiconductor devices." Diss., Kansas State University, 2014. http://hdl.handle.net/2097/17393.
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Doctor of PhilosophyDepartment of Chemical Engineering
James H. Edgar
Gallium nitride is a promising semiconductor for fabricating field effect transistors for power electronics because of its unique physical properties of wide energy band gap, high electron saturation velocity, high breakdown field and high thermal conductivity. However, these devices are extremely sensitive to the gate leakage current which reduces the breakdown voltage and the power-added efficiency and increases the noise figures. To solve this problem, employing a gate dielectric is crucial to the fabrication of metal insulator semiconductor high electron mobility transistors (MISHEMTs), to reduce the leakage current and increase the magnitude of voltage swings possible. For this device to be successful, imperfections at the oxide-semiconductor interface must be suppressed to maintain the high electron mobility of the device. This research explored multiple high dielectric constant gate oxides (Al[subscript]2O[subscript]3, TiO[subscript]2, and Ga[subscript]2O[subscript]3), deposited on different crystalline orientations and polarities of GaN by atomic layer deposition (ALD) to form metal oxide semiconductor capacitors, including effects of pretreatment on N-polar GaN, ALD TiO[subscript]2/Al[subscript]2O[subscript]3 nano-laminate on thermal oxidized Ga-polar GaN and ALD Al[subscript]2O[subscript]3 on [Italic]c- and [Italic]m-plane GaN Surface pretreatments were shown to greatly alter the morphology of reactive N-polar GaN which is detrimental to the electrical properties. 14 nm thick ALD Al[subscript]2O[subscript]3 films were directly deposited on N-polar GaN without thermal or chemical pretreatments which yield a smooth surface (RMS=0.23 nm), low leakage current (2.09 x 10[superscript]-[superscript]8 A/cm[superscript]2) and good Al[subscript]2O[subscript]3/GaN interface quality, as indicated by the low electron trap density (2.47 x 10[superscript]10 cm[superscript]-[superscript]2eV[superscript]-[superscript]1). In the nano-laminate study, a high dielectric constant of 12.5 was achieved by integrating a TiO[subscript]2/Al[subscript]2O[subscript]3/Ga[subscript]2O[subscript]3 oxide stack layer, while maintaining a low interface trap density and low leakage current. There was a strong correlation between the surface morphology and electrical properties of the device discovered from comparing the ALD Al[subscript]2O[subscript]3 on [Italic]c- and [Italic]m-plane GaN, namely smooth surface lead to small hysteresis. These results indicate the promising potential of incorporation gate dielectric for future GaN devices.
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Boratto, Miguel Henrique. "Semiconducting and insulating oxides applied to electronic devices." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153215.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho compreende o estudo de óxidos semicondutores (Sb:SnO2 e TiO2) e isolantes (ZrO2) obtidos via sol-gel, e a investigação de suas propriedades, de modo a avaliar estes materiais como alternativa para aplicação em dispositivos eletrônicos, tais como Capacitor Metal-Isolante-Metal (MIM), transistores de filmes finos (TFT) e memristores. Os filmes finos de SnO2 foram obtidos através de duas soluções com diferentes tempos de envelhecimento. Os filmes finos de ZrO2 também foram obtidos a partir de duas soluções, produzidas por dois métodos distintos, não-alcoóxido e polimérico. A deposição dos filmes finos foi realizada por dip- e spin-coating, e as caracterizações foram realizadas através das técnicas de DRX, AFM, MEV, Microscopia Confocal, EDX, RBS, TG/DSC, Espectroscopia no espectro UV-Vis, Voltametria Cíclica e Espectroscopia de Impedância, afim de melhor compreender as relações entre propriedades morfológicas e estruturais dos filmes e suas propriedades elétricas. As características de filmes finos de Sb:SnO2 e ZrO2 foram analisadas em dispositivos TFT e MIM, respectivamente. Alternativamente, TiO2 foi acoplado ao Sb:SnO2 e juntos foram aplicados em memristores devido às propriedades elétricas da junção destes semicondutores. Os resultados das análises dos diferentes tipos de dispositivos eletrônicos investigados neste trabalho são discutidos considerando suas diversas características, e são também propostas opções de possíveis melhorias para tais dispositivos tornarem-se comparáveis aos estados-da-arte já existentes.
This work comprises the study of oxide semiconductors (Sb-doped SnO2 and TiO2) and insulating materials (ZrO2) obtained by sol-gel, and the investigation of their properties, aiming to evaluate these materials as alternative for application in electronic devices, such as Metal-Insulator-Metal (MIM) capacitors, Thin Film Transistors (TFT), and Memristors. The SnO2 thin films were obtained by two solutions with different aging times. The ZrO2 thin films were also obtained by two solutions, synthesized from two distinct methods, non-alkoxide and polymeric. The thin film deposition occurred mainly by dip- and spin-coating techniques, and the characterizations were performed through the techniques of XRD, AFM, SEM, Confocal Microscopy, EDX, RBS, TG/DSC, UV-Vis Spectroscopy, cyclic voltammetry and Impedance spectroscopy, in order to better understand the relations between the morphological and structural properties of these films and their electrical properties. The properties of Sb:SnO2 and ZrO2 thin films were analyzed in TFT and MIM devices, respectively. Alternatively TiO2 was coupled with Sb:SnO2 and applied to Memristors due to the electrical properties of this semiconductor junction. The analysis and results of the different devices investigated in this work are discussed considering their several characteristics, and it is also suggested options for possible enhancements for these devices become comparable to existent state-of-the-art devices.
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Reeder, Askia Enrico. "STUDY OF THE STRUCTURE AND THE ELECTRONIC PROPERTIES OF THE OXIDE/OXIDE INTERFACES IN MIXED METAL OXIDES." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423844.
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A very important role is played by metal oxides in many areas of chemistry, physics, and materials science. Transition metal and rare-earth metal elements are able to form a large diversity of oxide compounds which can adopt an ample array of atomic structures and electronic properties that can exhibit metallic, semiconductor, or insulator characteristics. In technological applications, metal oxides are used in the fabrication of microelectronic components, sensors, fuel cells, coatings to protect surfaces against corrosion, and as catalysts. In this thesis we have decided to study two known catalytic materials Zirconia-Titania and Ceria-Titania mixed oxides. For both materials bibliography principally concerns powders thus in order to better study their interfaces, of which a deeper study is still lacking, we decided to deposit zirconia and ceria as thin films onto rutile TiO2(110).
We first studied the zirconia-titania system by depositing an ultra-thin film of zirconium oxide via a metal-organic precursor: Zirconium Tetra tert-Butoxide. The deposition was carried at three different substrate temperatures 677 K, 738 K, 773 K in five stages of a minute each and the results were traced by using XPS. The chemical characterization via XPS showed an interesting chemistry undergoing on the substrate’s surface and we have observed the formation of carbonaceous species at the interface. Zirconium appeared to be at its highest oxidation state while titanium was seen to undergo reduction with each successive deposited layer. The ratio of the Zr/Ti signals showed that zirconia didn’t completely wet the surface. Furthermore, no long range order was observed via LEED. XPD measurements showed that zirconia does not form a substitutional oxide with titania. However with the aid of computer simulation we deduced that very likely zirconia forms nanochains on the surface of TiO2(110). This surface was exposed to 100 L of pyridine to test its acidity.
In the case of ceria, we have deposited the oxide on a heated TiO2(110) substrate via metal evaporation from a Mo crucible since the process is rather easy and garners clean deposits. During deposition the substrate was kept at 677 K and in an O2 environment of 5.2•10-6mbar, and, in order to obtain an ordered homogeneous surface the sample was further annealed in the same environment at 900 K. Through LEED imaging different phases were observed and were dependent on sample history and film thickness. Via computer simulation these phases were then referred to the parent oxide in order to better comprehend the difference in respect to the bulk phase. All films showed cerium present at Ce(III). Ultra-violet Photoelectron Spectroscopy showed the electronic properties of the film showing a binding energy shift and the population of Ce4f states due to stabilization of Ce(III) by TiO2(110). The reactivity of the ceria-titania system was the probed by using methanol and ethanol. Results showed that the addition of ceria opened the dehydrogenation path from alcohol to aldehyde. We have observed that oxygen pre-oxidation of the CeOx-TiO2(110) system had an impact on its selectivity by opening also a dehydration path from methanol and ethanol to respectively, methane and ethylene. This alternative path was viable only for low cerium oxide coverages as interaction with the substrate was needed for dehydration to occur. Aldehyde formation was seen to occur at mild temperatures (330 K) and was independent of film thickness. Subsequently, ceria-titania mixed oxide powders were characterized via XPS and we have observed that for increasing amount of cerium the element gradually became present at its highest oxidation state Ce(IV). By XPS we have also determined the formation of a very intimate composite between the two oxides by observing the increasing the full width at half maximum of the Ti2p peak for increasing amounts of cerium. Furthermore, compositional calculation showed that cerium had the tendency to disperse within the titania particles. These data helped to uncover a possibly good recipe for the formation of cerium titanate a composite with good oxygen storage capacity.Un ruolo molto importante è svolto dagli ossidi metallici in molti settori della chimica, fisica e scienza dei materiali. I metalli di transizione e le terre rare sono in grado di formare una grande diversità di composti ossidici che possono adottare un'ampia gamma di strutture atomiche ed proprieta’ elettroniche che possono esibire caratteristiche metalliche, semiconduttrici o isolanti. In applicazioni tecnologiche, gli ossidi metallici sono impiegati nella fabbricazione di componenti microelettronici, sensori, celle a combustibile, rivestimenti per proteggere le superfici dalla corrosione, e come catalizzatori. In questa tesi abbiamo deciso di studiare due noti materiali catalitici: gli ossidi misti di Zirconia-Titania Ceria-Titania. Per entrambi i materiali la bibliografia riguarda principalmente le polveri quindi, al fine di studiare meglio le loro interfacce, di cui uno studio più approfondito e’ tuttora neccessario, abbiamo deciso di depositare film sottili di ossido di zirconio e ossido di cerio su rutilo TiO2(110). Abbiamo prima studiato il sistema zirconia-titania depositando un film ultra-sottile di ossido di zirconio mediante un precursore metallo-organico: Zirconio Tetra tert-butossido. La deposizione è stata effettuata a tre diverse temperature del substrato 677. K, 738 K, 773 K in cinque fasi di un minuto ciascuno. La caratterizzazione mediante XPS ha mostrato una chimica interessante sulla superficie del substrato e abbiamo osservato la formazione di specie carboniose all'interfaccia. Lo zirconio sembrava essere nel suo piu’ alto stato di ossidazione mentre il titanio è stato visto gradualmente ridursi con ogni successive strato di deposito. Il rapporto dei segnali Zr/Ti ha mostrato che la zirconia non ha completamente coperto la superficie. Inoltre,tramite LEED non si e’ osservato nessun ordine a lungo raggio. Misure XPD ha mostrato che la zirconia non forma un ossido di sostituzione con la titania. Tuttavia, con l'ausilio di simulazione al computer abbiamo dedotto che la zirconia forma, molto probabilmente nanocatene sulla superficie di TiO2(110). Questa superficie è stato esposta a 100 L di pyridinina per testarne la acidita’. Nel caso di ceria, abbiamo depositato l'ossido su un substrato riscaldato di TiO2 (110) tramite evaporazione del metallo da un crogiolo Mo poiché il processo è piuttosto facile e fornisce depositi puliti. Durante la deposizione il substrato è stata mantenuto a 677 K in un ambiente di 5,2 • 10 -6 mbar di O2, e, al fine di ottenere una superficie omogenea e ordinata il campione è stato ulteriormente sottoposto a trattamento termico nello stesso ambiente a 900 K. Tramite la tecnica LEED sono state osservate differenti fasi dipendenti dalla storia del campione e dallo spessore del film. Tramite simulazione al computer queste fasi sono stati poi riferite rispetto al biossido di cerio per meglio comprendere le differenze rispetto alla fase massiva. Tutti i film hanno mostrato cerio presenti come Ce(III). La Spettroscopia Fotoelettronica a Ultravioletti ha mostrato le proprietà elettroniche del film che mostra uno spostamento in energia di legame e un popolamento degli stati Ce4f. Questo e’ dovuto alla stabilizzazione di Ce (III) da parte di TiO2 (110). Si e’ volute osservare la reattività del sistema ceria-titania nei confronti di metanolo ed etanolo. I risultati hanno mostrato che l'aggiunta di ceria ha aperto il percorso della deidrogenazione degli alcoli ad aldeidi. Abbiamo osservato che la pre-ossidazione con ossigeno del sistema CeOx-TiO2(110) ha avuto un impatto sulla sua selettività aprendo anche un percorso di disidratazione di metanolo ed etanolo rispettivamente a metano ed etilene. Questa via alternativa era valida solo per basse coperture di ossido di cerio avendo osservato che l’interazione con il substrato è stato necessario perche’ avvenga la disidratazione. La formazione di aldeidi fu osservata avvenire a temperature piuttosto (330 K) ed essere indipendente dallo spessore del film. Successivamente sono state caratterizzate tramite XPS delle polveri di ossidi misti di ceria e titania. Abbiamo osservato che per quantità crescenti di cerio l'elemento diventa gradualmente sempre piu’ presente al suo stato di ossidazione più alto Ce (IV). Con XPS abbiamo anche determinato la formazione di un composito molto intimo tra i due ossidi osservando l'aumento della larghezza a metà altezza del picco Ti2p per quantità crescenti di cerio. Inoltre, la determinazione della composizione ha mostrato che il cerio ha la tendenza di disperdersi all'interno delle particelle di titania. Questi dati hanno contribuito a scoprire una possibile buona ricetta per la formazione di cerio titanato; un composito con buona capacità di stoccaggio di ossigeno.
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NOBREGA, SHAYENNE D. da. "Fabricação e testes de células a combustível de óxido sólido a etanol direto usando camada catalítica." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10184.
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IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Azevedo, Neto Nilton Francelosi [UNESP]. "Deposição e caracterização de filmes de óxido de cobalto por sputtering reativo." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/115988.
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Filmes de óxido de cobalto apresentam interesses para aplicações em catálise, sensores de gás e para estudos do efeito de exchange bias em multicamadas de CoO/Co/CoO. Neste trabalho, filmes de óxido de cobalto foram depositados usando a técnica de DC sputtering, nas potências 80,120 e 240W. A superfície dos filmes preparados a potências menores não apresentaram trincas. Medidas de difração de raios X indicaram a presença da fase Co3O4 nas deposições de 80 e 120 W. Para deposição com 240 W, observa-se apenas a presença da fase CoO. Os espectros de espalhamento Raman dos filmes apresentaram bandas referentes aos modos do Co3O4 para todas as amostras crescidas, já a análise de transmitância no infravermelho apresentou bandas de absorção relacionadas à fase CO3O4 nos filmes depositados com baixa potência, e uma mistura de bandas do CoO e Co3O4 na deposição a 240 W. O espectro de transmitância no UV/VIS/NIR apresentou absorções relacionadas a transições eletrônicas do óxido de cobalto em em 0,8,0,9,1,7 e 3eV na amostra crescida em 80 W. Com o objetivo de criar camadas nanométricas de cobalto puro, intercaladas com filmes de óxido de cobalto, foram depositados filmes nos quais o fluxo de oxigênio foi interrompido. A potência utilizada foi 120 W e os tempos de interrupção foram 120 e 12s. Imagens de microscopia eletrônica de varredura indicaram que não houve rachaduras na superfície dos filmes e medidas na seção transversal das amostras indicaram formaram das camadas metálicas no interior do filme depositado com interrupção de oxigênio por 120s. Análise de difração de raios X das multicamadas mostrou um favorecimento da fase CoO em relaçãoao tetraóxido, porém o espectro Raman dos filmes apresentaram picos claros da fase Co3O4. Utilizando uma simulação computacional baseada no método de Monte Carlo (Stopping and Range of lons in Matter-SRIM) estimou-se a energia com que os átomos e íons...
Cobalt oxide films have interest for application in catalysis, gas sensors, and for studies of the exchange bias effect in CoO/Co/CoO multilayers. In this work, cobalt oxide films were deposited using DC sputtering technique. The deposition powers tested were 80,120 and 240 W. The surfaces of the films prepared at 240 W have cracked, while films prepared at lower powers showed no cracks. X-ray diffraction measurements indicated that films prepared at lower powers are deminated by the Co3O4 with spinel strucuture while at higher powers the CoO rocksalt phase is favored. Raman scattering measurements of the films showed bands related to Co3O4 spinel modes for all samples, while the infrared transmittance analysis showed absorption bands related to the Co3O4 phase on films deposited at low power and a mixture of CoO and Co3O4 bands deposition to 240 W. In the UV/VIS/NIR spectrum, absorption bands related to electronic transitions of cobalt oxide at 0.8, 0.9, 1.7 and 3 eV were observed in the sample grown at 80 W. Aiming to create nanometric layers of pure cobalt interspersed cobalt oxide films, depositions in which the oxygen flow was periodically stopped were made. In these experiments, the power was kept at 120W and interrupetion periods of 120 and 12 s were used. Scanning electron microscopy image indicated that there were no cracks on the surfaces of the films and cross section measurements idicated the formation of metal layers inside the film deposited with interruption of oxygen for 120 s. Analysis of X-ray diffraction of multilayers showed a favoring of the CoO phase, but the Raman spectra of the films showed clear peaks of Co3O4 phase. Using a computer simulation based on the Monte Carlo method (Stopping and Range of Ions in Matter, SRIM) the energies of the atoms and ions that reach the substrate were estimated. The estimations were performed when deposition is taken with outputs of 120 and 240 W. An increase of the average...
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Azevedo, Neto Nilton Francelosi. "Deposição e caracterização de filmes de óxido de cobalto por sputtering reativo /." Bauru, 2014. http://hdl.handle.net/11449/115988.
Full textAbstract:
Orientador: José Humberto Dias da SilvaBanca: Paulo Noronha Lisboa Filho
Banca: Fernando Rogerio de Paula
Resumo: Filmes de óxido de cobalto apresentam interesses para aplicações em catálise, sensores de gás e para estudos do efeito de exchange bias em multicamadas de CoO/Co/CoO. Neste trabalho, filmes de óxido de cobalto foram depositados usando a técnica de DC sputtering, nas potências 80,120 e 240W. A superfície dos filmes preparados a potências menores não apresentaram trincas. Medidas de difração de raios X indicaram a presença da fase Co3O4 nas deposições de 80 e 120 W. Para deposição com 240 W, observa-se apenas a presença da fase CoO. Os espectros de espalhamento Raman dos filmes apresentaram bandas referentes aos modos do Co3O4 para todas as amostras crescidas, já a análise de transmitância no infravermelho apresentou bandas de absorção relacionadas à fase CO3O4 nos filmes depositados com baixa potência, e uma mistura de bandas do CoO e Co3O4 na deposição a 240 W. O espectro de transmitância no UV/VIS/NIR apresentou absorções relacionadas a transições eletrônicas do óxido de cobalto em em 0,8,0,9,1,7 e 3eV na amostra crescida em 80 W. Com o objetivo de criar camadas nanométricas de cobalto puro, intercaladas com filmes de óxido de cobalto, foram depositados filmes nos quais o fluxo de oxigênio foi interrompido. A potência utilizada foi 120 W e os tempos de interrupção foram 120 e 12s. Imagens de microscopia eletrônica de varredura indicaram que não houve rachaduras na superfície dos filmes e medidas na seção transversal das amostras indicaram formaram das camadas metálicas no interior do filme depositado com interrupção de oxigênio por 120s. Análise de difração de raios X das multicamadas mostrou um favorecimento da fase CoO em relaçãoao tetraóxido, porém o espectro Raman dos filmes apresentaram picos claros da fase Co3O4. Utilizando uma simulação computacional baseada no método de Monte Carlo (Stopping and Range of lons in Matter-SRIM) estimou-se a energia com que os átomos e íons...
Abstract: Cobalt oxide films have interest for application in catalysis, gas sensors, and for studies of the exchange bias effect in CoO/Co/CoO multilayers. In this work, cobalt oxide films were deposited using DC sputtering technique. The deposition powers tested were 80,120 and 240 W. The surfaces of the films prepared at 240 W have cracked, while films prepared at lower powers showed no cracks. X-ray diffraction measurements indicated that films prepared at lower powers are deminated by the Co3O4 with spinel strucuture while at higher powers the CoO rocksalt phase is favored. Raman scattering measurements of the films showed bands related to Co3O4 spinel modes for all samples, while the infrared transmittance analysis showed absorption bands related to the Co3O4 phase on films deposited at low power and a mixture of CoO and Co3O4 bands deposition to 240 W. In the UV/VIS/NIR spectrum, absorption bands related to electronic transitions of cobalt oxide at 0.8, 0.9, 1.7 and 3 eV were observed in the sample grown at 80 W. Aiming to create nanometric layers of pure cobalt interspersed cobalt oxide films, depositions in which the oxygen flow was periodically stopped were made. In these experiments, the power was kept at 120W and interrupetion periods of 120 and 12 s were used. Scanning electron microscopy image indicated that there were no cracks on the surfaces of the films and cross section measurements idicated the formation of metal layers inside the film deposited with interruption of oxygen for 120 s. Analysis of X-ray diffraction of multilayers showed a favoring of the CoO phase, but the Raman spectra of the films showed clear peaks of Co3O4 phase. Using a computer simulation based on the Monte Carlo method (Stopping and Range of Ions in Matter, SRIM) the energies of the atoms and ions that reach the substrate were estimated. The estimations were performed when deposition is taken with outputs of 120 and 240 W. An increase of the average...
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