Made available in DSpace on 2016-06-02T19:56:52Z (GMT). No. of bitstreams: 1 5331.pdf: 11740082 bytes, checksum: e8f5288e8c937187089b53d5c0ebd1c9 (MD5) Previous issue date: 2013-04-26 / Financiadora de Estudos e Projetos / The combustion of petroleum fuels produces large emissions of NOX, SOX and other strong atmospheric pollutants. The abatement of NOX can be achieved by the nonselective catalytic reduction of NO with CO, for that, supported noble metals have been the most commonly used, with high cost as disadvantage. Transition metal oxides show good activity for this reaction, however, they have poor performance in the presence of SO2, O2 and water steam. Thus, this study aimed to prepare, characterize and evaluate catalysts based on CuO, Fe2O3 and CuO-Fe2O3 supported on TiO2, ZrO2 and their mixtures, in the reduction of NO to N2 with CO in the presence or absence of water steam. XRD data, N2 adsorption and H2-TPR showed that mixed oxides and their catalysts, prepared by sol-gel in-situ, presented specific surface areas between 30 to 60 m2/g, with Cu or Fe species highly distributed, having the last greater interaction with titanium. Rietveld refinement showed preferential formation of zirconium titanate, then showing a close interaction of these species in the mixed supports. All catalysts were highly active in the reduction of NO to N2. At temperatures below 500 °C a CuO catalysts were more active and selective for the formation of N2 than Fe2O3, with the formation of N2O being favored with the increase of zirconium in the support. At 600 °C, the high conversion of NO to N2 on CuO was not influenced by the content of TiO2 in the support. Also at 600 °C, an increasing in the content of titanium in the Fe2O3 catalysts resulted in a significant drop in the conversion of NO to N2. The presence of water steam during the reduction of NO with CO at 600 °C caused a significant decrease in the conversion of NO to N2 and CO to CO2 on the CuO catalyst on the support with higher titanium content. The water steam completely eliminates the activity for the reduction of NO to N2 on Fe2O3 catalysts, but keeping a high conversion of CO to CO2. The CuO and CuO-Fe2O3 catalysts on zirconium-rich supports showed high potential for the abatement of NOX in the presence of water steam at temperatures above 500 ºC. / A combustão de derivados do petróleo gera grandes emissões de NOX, SOX e outros fortes poluentes da atmosfera. O abatimento de NOX pode ser realizado por meio da redução catalítica não seletiva com CO, onde os metais nobres suportados têm sido os mais empregados, com a desvantagem de seu elevado custo. Óxidos de metais de transição apresentam boa atividade nessa reação, no entanto, têm baixo desempenho na presença de SO2, O2 e vapor de água. Assim, este trabalho teve como objetivo preparar, caracterizar e avaliar catalisadores a base de CuO, Fe2O3 e CuO-Fe2O3 suportados em TiO2, ZrO2 ou suas misturas, na redução de NO a N2 com CO na presença ou ausência de vapor de água. Dados de DRX, adsorção de N2 e RTP-H2 mostraram que os suportes mistos e seus catalisadores, que foram preparados via síntese sol-gel in-situ, apresentaram áreas superficiais específicas entre 30 e 60 m2/g, com as espécies de Cu ou Fe altamente distribuídas, tendo essas últimas maior interação com a titânia. Refinamento de Rietveld mostrou formação preferencial de titanato de zircônia, evidenciando a estreita interação dessas espécies nos suportes mistos. Todos os catalisadores foram altamente ativos na redução de NO a N2. Em temperaturas inferiores 500 ºC os catalisadores de CuO foram mais ativos e seletivos à formação de N2 que o Fe2O3, com a formação de N2O sendo favorecida com o aumento de zircônia no suporte. A 600 ºC, a alta conversão de NO a N2 sobre CuO não foi influenciada pelo conteúdo de TiO2 no suporte. Nessa temperatura, o aumento do teor de titânia provocou nos catalisadores de Fe2O3 uma queda significativa na conversão de NO a N2. A presença de vapor de água durante a redução de NO com CO a 600 ºC provocou sobre CuO queda significativa da conversão de NO a N2 e de CO a CO2 sobre o suporte com maior conteúdo de titânia. Nos catalisadores de Fe2O3 puro, o vapor de água anulou completamente a atividade para a redução de NO a N2, mas manteve-se a conversão de CO a CO2. Os catalisadores de CuO e CuO-Fe2O3 sobre suporte contendo alto teor de zircônia apresentaram alto potencial para o abatimento de NOx na presença de vapor de água em temperaturas superiores a 500 ºC.

Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-09-19T19:41:33Z No. of bitstreams: 1 DissBGS.pdf: 2899470 bytes, checksum: a3a468cd5c6b79bbc4f8adf4720788bd (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-20T14:03:37Z (GMT) No. of bitstreams: 1 DissBGS.pdf: 2899470 bytes, checksum: a3a468cd5c6b79bbc4f8adf4720788bd (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-20T14:03:44Z (GMT) No. of bitstreams: 1 DissBGS.pdf: 2899470 bytes, checksum: a3a468cd5c6b79bbc4f8adf4720788bd (MD5) / Made available in DSpace on 2016-09-20T14:03:52Z (GMT). No. of bitstreams: 1 DissBGS.pdf: 2899470 bytes, checksum: a3a468cd5c6b79bbc4f8adf4720788bd (MD5) Previous issue date: 2014-03-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The increasing use of fossil fuels in combustion enginees and power generation plants has caused a large increase in the emission of sulfur oxides, nitrogen oxides (NOx) and carbon monoxide into the atmosphere which creates serious environmental problems. Catalytic processes are used in the abatement of NOx and a promising alternative is the reduction of NOx using CO as reducing agent on catalysts containing supported transition metal oxides. Taking this into account, the aim of this study was to prepare catalysts based on Fe2O3, NiO or Fe2O3-NiO supported on ceria-zirconia (molar ratios Ce:Zr equal to 1:1 and 1:4), incorporating the metal precursor salt in the sun of the support (in situ addition). The results of XRD data, Rietveld refinement and TEM indicated the formation of a solid solution CeO2-ZrO2 with cubic structure fluorite type; furthermore, it was not observed diffraction peaks of intense X-ray of Fe or Ni oxide as a consequence of a proper distribution of these oxides in the supports. The addition of Fe2O3 and/or NiO led to a decrease of the average crystallite size, causing an increase in SBET of the catalysts compared to the pure support. N2 physisorption measurements showed that the catalysts showed significant mesoporosity, which was attributed to the addition of Tween 80 during the sol-gel preparation, moreover, RTPH2 results confirm that the Fe2O3 reduction occurs at lower temperatures in the presence NiO. In addition, the catalysts showed satisfactory performance in the reduction of NO to N2 with CO, suggesting that the sol-gel method is adequate in their preparation. Furthermore, the catalyst 0,90Fe - 1Ce:1Zr reached the highest values of CO conversion to CO2 and NO to N2 at lower temperatures. The Fe2O3 catalysts were more selective to N2 formation compared to those containing NiO. In conclusion, the conversion NO to N2 was significantly affected when in contact with O2 and H2O interferences; however, this conversion did not change significantly in the presence of SO2. The catalysts showed a more significant reduction in conversion of NO to N2 when evaluated in the simultaneous presence of O2, SO2 and H2O. / O crescente uso de combustíveis fósseis em motores de combustão e usinas de geração de energia vem causando um grande aumento na emissão de óxidos de enxofre, óxidos de nitrogênio (NOx) e monóxido de carbono na atmosfera, o que gera sérios problemas ambientais. No abatimento de NOx, em particular, utiliza-se processos catalíticos e uma alternativa promissora é a redução dos NOx utilizando CO como agente redutor sobre catalisadores à base de óxidos de metais de transição suportados. Nessa direção, a pesquisa teve por objetivo preparar catalisadores à base de Fe2O3, NiO ou Fe2O3-NiO suportados em céria-zircônia (proporções molares entre Ce e Zr iguais a 1:1 e 1:4), incorporando o sal precursor do metal no sol do suporte (adição in situ). Dados de DRX e MET indicaram a formação de uma solução sólida CeO2-ZrO2 com estrutura cúbica tipo fluorita, não se observando picos de difração de raios X intensos dos óxidos de Fe ou Ni, o que foi interpretado como uma consequência de uma adequada distribuição desses óxidos nos suportes. Os resultados do refinamento de Rietveld confirmaram os dados de DRX, indicando uma composição mássica baixa para os óxidos de Fe e/ou Ni. A adição de Fe2O3 e/ou NiO levou à uma diminuição do tamanho médio de cristalitos, causando um aumento na SBET dos catalisadores em relação ao suporte puro. Medidas de fisissorção de N2 mostraram que os catalisadores apresentaram mesoporosidade considerável, que foi atribuída à adição de Tween 80 durante a preparação sol-gel, além do mais, resultados de RTP-H2 corroboraram que a redução de Fe2O3 ocorre em temperaturas menores quando na presença de NiO. Os catalisadores apresentaram comportamento satisfatório na redução de NO a N2 com CO, indicando que o método sol-gel se mostrou adequado na sua preparação, sendo o sólido 0,90Fe - 1Ce:1Zr o que atingiu maiores valores de conversão de CO a CO2 e de NO a N2 em menores temperaturas. Em comparação aos catalisadores de NiO, os de Fe2O3 foram mais seletivos à formação de N2. Quando em contato com os interferentes O2 e H2O, a conversão NO a N2 foi consideravelmente afetada e na presença de SO2, essa conversão não se alterou significativamente. Quando avaliados na presença simultânea de O2, SO2 e H2O, os catalisadores apresentaram quedas de conversão de NO a N2 mais consideráveis.

Submitted by Marta Toyoda (1144061@mackenzie.br) on 2018-09-04T17:03:54Z No. of bitstreams: 2 Dênison Angelotti Moraes.pdf: 4087093 bytes, checksum: 92e8923c2697fbf1a44b31c6c7fb05d1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Paola Damato (repositorio@mackenzie.br) on 2018-09-19T18:27:52Z (GMT) No. of bitstreams: 2 Dênison Angelotti Moraes.pdf: 4087093 bytes, checksum: 92e8923c2697fbf1a44b31c6c7fb05d1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-09-19T18:27:52Z (GMT). No. of bitstreams: 2 Dênison Angelotti Moraes.pdf: 4087093 bytes, checksum: 92e8923c2697fbf1a44b31c6c7fb05d1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-06-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Automotive components are always in development, aiming to improve performance and quality, either by reducing costs, market need, increased sales and productivity or some new environmental or safety legislation. In the last years the environmental theme has gained interest and has become central to vehicles that use fossil fuels, especially Diesel oil, and must comply with new emission laws. For this, new engines and exhaust systems and gas filtration have been developed, such as catalytic converters. The upcoming legislation, called PROCONVE P8, restricts the values of nitrous oxides (NOx) and particulate matter to very low values. In order to achieve these values, the post-treatment system called the ATS (After Treatment System) was developed. In order for the process to reduce pollutants to be made within the ATS, the exhaust gases burned in the combustion process inside the engine must be between 450 and 550 ºC. The burned gases, or exhaust gases, are piped to the catalyst by metal tubing. In this work was proposed the use of 8% by weight (ZrO2-Y2O3) stabilized Zirconia oxide ceramic, known as YSZ (Ytria Stabilized Zirconia), or 8YSZ, known as TBC (Thermal Barrier Coating). The TBC was studied as a coating of exhaust pipe, through analytical calculation and CFD (Computer Fluid Dynamics). The results showed that the YSZ is a potential material for the studied application, as well as for applications where the thermal barrier theme is relevant. / Componentes automotivos estão sempre em desenvolvimento, seja objetivando a melhoria de performance e qualidade, seja pela redução de custos, necessidade de mercado, aumento de vendas e produtividade ou alguma nova legislação ambiental ou de segurança. Nos últimos anos o tema ambiental ganhou corpo e passou a ser central para os veículos que utilizam combustíveis fósseis, em especial o óleo Diesel, devendo atender a novas legislações de emissão. Para isso, novos motores e sistemas de exaustão e filtragem dos gases foram desenvolvidos, como os conversores catalíticos. A próxima legislação que entrará em vigor, chamada de PROCONVE P8 restringe os valores de óxidos nitrosos (NOx) e material particulado a valores muito baixos. Para que esses valores sejam atingidos foi desenvolvido o sistema de pós-tratamento de gases chamado de ATS (After Treatment System). Para que o processo de redução dos agentes poluidores seja feito dentro do ATS, os gases de escapamento queimados no processo de combustão dentro do motor devem estar a temperatura entre 450 e 550ºC. Os gases queimados, ou gases de exaustão, são conduzidos por tubulação metálica até o catalisador. Neste trabalho foi proposta a utilização de revestimento cerâmico de óxido de Zircônia estabilizado com Ítria a 8% em peso (ZrO2-Y2O3), conhecido como YSZ (Ytria Stabilized Zirconia), ou ainda 8YSZ, conhecido como TBC (Thermal Barrier Coating). Foi estudado o TBC como revestimento de tubulação de escapamento, por meio de cálculo analítico e por CFD (Computer Fluid Dynamics). Os resultados mostraram que o YSZ é um material de potencial para a aplicação estudada, bem como para aplicações onde o tema barreira térmica seja relevante.

No description available.

Currently available solid lubricants only perform well under a limited range of environmental conditions. Unlike them, oxides are thermodynamically stable and relatively inert over a broad range of temperatures and environments. However, conventional oxides are brittle at normal temperatures; exhibiting significant plasticity only at high temperatures (>0.5Tmelting). This prevents oxides' use in tribological applications at low temperatures. If oxides can be made lubricious at low temperatures, they would be excellent solid lubricants for a wide range of conditions. Atomic layer deposition (ALD) is a growth technique capable of depositing highly uniform and conformal films in challenging applications that have buried surfaces and high-aspect-ratio features such as microelectromechanical (MEMS) devices where the need for robust solid lubricants is sometimes necessary. This dissertation investigates the surface and subsurface characteristics of ALD-grown ZnO/Al2O3 nanolaminates and ZrO2 monofilms before and after sliding at room temperature. Significant enhancement in friction and wear performance was observed for some films. HRSEM/FIB, HRTEM and ancillary techniques (i.e. SAED, EELS) were used to determine the mechanisms responsible for this enhancement. Contributory characteristics and energy dissipation modes were identified that promote low-temperature lubricity in both material systems.

This thesis deals with a CAD programmed construction design of dental prosthetics and its subsequent production by means of a five axis machine tool. In the theoretical part of the thesis one can find characteristics and analysis of materials designed for a production of dental prosthetics constructions. Among other things, the practical part of the thesis follows up digitization of a patient´s oral cavity part with the use of Trios intraoral scanner representing the latest scanning technology. The obtained data created a basis for a design of the respective dental prosthetics construction using the shape dental system programme called DentalDesigner 2015. Furthermore, the paper deals with a production of a dental prosthetics construction by means of a five axis machine tool and pursues completion works which resulted in the prosthetics final shape. The paper is concluded with discussion comprising a summary of results acquired in the practical part beginning from dental implant introduction to insertion of the made prosthetics construction into the patient´s oral cavity.

The submerged entry nozzle (SEN) has been used to transport the molten steel from tundish to the mould. The main purpose of the SEN usage is both to prevent oxygen and nitrogen pick-up by molten steel and to achieve the desired flow condition in the mould. Therefore, the SEN can be considered as a vital factor for a stable casting process and the steel quality. Furthermore, the steelmaking processes occur at high temperatures around 1873 K so the interaction between the refractory materials of the SEN and molten steel is unavoidable. Therefore, the knowledge of the SEN behaviors during pre-heating and casting is necessary for the design of the steelmaking processes. The internal surfaces of modern SENs are coated with a glass/silicon powder layer to prevent the SEN graphite oxidation during pre-heating. The effects of the interaction between the coating layer and the SEN base refractory materials on clogging were studied in supplement 1. The results of the study indicated the penetration of the formed alkaline-rich glaze into the Alumina/graphite base refractory during pre-heating. More specifically, the alkaline-rich glaze reacts with graphite to form carbon monoxide gas. Thereafter, dissociation of CO at the SEN/molten metal interface takes place. This leads to reoxidation of dissolved REM (Rare Earth Metal), which form the “In Situ” REM oxides at the interface between the SEN and the REM alloyed molten steel. Also, the interaction of the penetrated glaze with alumina in the SEN base refractory materials leads to a formation of a high-viscous alumina-rich glaze during the SEN pre-heating process. This in turn, creates a very uneven surface at the SEN internal surface. The “In Situ” formation of the REM oxides together with the uneven internal surface of the SEN may facilitate the accumulation of the primary inclusions. Supplement 1 revealed the disadvantages of the glass/silicon powder layer. On the other hand the carbon oxidation is a main industrial problem for un-coated Alumina/Graphite Submerged Entry Nozzles (SEN) during pre-heating. This led to the proposal of a new refractory material for the SEN. In supplement 2, the effect of ZrSi2 antioxidant and the coexistence of antioxidant additive and (4B2O3 ·BaO) glass powder on carbon oxidation were investigated at simulated non-isothermal heating conditions in a  controlled atmosphere. Also, the effect of ZrSi2 antioxidant on carbon oxidation was investigated at isothermal temperatures at 1473 K and 1773 K. The specimens’ weight losses and temperatures were plotted versus time and compared to each others. The thickness of the oxide areas were measured and also examined using XRD, FEG-SEM and EDS. The coexistence of 8 wt% ZrSi2 and 15 wt% (4B2O3 ·BaO) glass powder of the total alumina/Graphite base refractory materials, presented the most effective resistance to carbon oxidation. The 121% volume expansion due to the Zircon formation during heating and filling up the open pores by (4B2O3 ·BaO) glaze during green body sintering led to an excellent carbon oxidation resistance. In supplement 3, decarburization behaviors of Al2O3-C, ZrO2-C and MgO-C refractory materials constituting a commercial Submerged Entry Nozzle (SEN), have been investigated in different gas atmosphere consisting of CO2, O2 and Ar. The (CO2/O2) ratio values were kept the same as it is in propane combustion flue gas at Air Fuel Ratio (AFR) values equal to 1.5 and 1 for both Air-fuel and Oxygen-fuel combustions. Laboratory experiments were carried out non-isothermally in the temperature range 873 K to 1473 K at 15 K/min followed by isothermal heating at 1473 K for 60 min. The decarburization ratio (α) values of the three refractory types were determined by measuring the weight losses of the samples. The results showed that the decarburization ratio (α) values of the MgO-C refractory became 3.1 times higher for oxygen-fuel combustion compared to air-fuel combustion both at AFR equal to 1.5 in the temperature range 873 K to 1473 K. The decarburization ratio (α) values for Al2O3-C samples were the same as for the isothermal heating at 1473 K and non-isothermal heating in the temperature range 473  to 1773 K with a 15 K/min heating rate. It substantiates the SEN preheating advantage at higher temperatures for shorter holding times instead of heating at lower temperatures for longer holding times. Jander’s diffusion model was proposed for estimating the decarburization rate of Al2O3-C refractory in the SEN. The activation energy for Al2O3-C samples heated at AFR equal to 1.5, for air-fuel and oxygen-fuel combustions were found to be 84.5 KJ/mol and 95.5 KJ/mol respectively during non-isothermal heating in the temperature range 873 K to 1473 K. / QC 20101008

Im Gegensatz zu „festen Säuren“ sind „feste Basen“ wesentlich seltener Untersuchungsgegenstand in ihrer Anwendung als Katalysatoren in der heterogenen Katalyse. In der vorliegenden Promotionsarbeit wurden entgegen diesem Trend die Herstellung, Charakterisierung und Anwendung basischer Oxide sowie modifizierter Oxide in ihrer Eignung als feste Basen in der Katalyse untersucht. Zu diesen Katalysatoren gehören MgO, hergestellt nach unterschiedlichen Methoden, Kalium modifiziertes ZrO2, calcinierte Mg-Al Hydrotalcite und ein neuartiges Katalysatorsystem auf der Basis von Mg(O,F)-Kompositionen, die zum ersten Mal nach einem Sol-Gel-Fluorierungsverfahren hergestellt wurden. Die Katalysatoren wurden mittels N2 Adsorptions/Desorptionsuntersuchungen (BET), XRD, FTIR, XPS, TG-DTA-DTG und MAS NMR untersucht. Die Säure-Basen-Eigenschaften der Katalysatoren wurden durch TPD, FTIR Spektroskopie und Mikrokalorimetrie charakterisiert und mit den katalytischen Eigenschaften korreliert. Calcinierte Mg-Al Hydrotalcite und Mg(O,F) waren in diesem Zusammenhang am stärksten aktiv und auch selektiv wie für die Flüssigphasenreaktion der Michael-Addition von CH aciden Verbindungen mit Methylvinylketon gezeigt wurde. / In contrast to solid acid catalysts, much fewer efforts have been made to study solid base catalysts. In this thesis, preparation, characterization and application of oxides and modified oxide as solid base catalysts were studied. The catalysts include MgO prepared by different methods, potassium-modified ZrO2, calcined Mg-Al hydrotalcites, and a novel catalyst system Mg(O,F), which was prepared by sol-gel method for the first time. The catalysts were studied by N2 adsorption/desorption measurement, XRD, FTIR, XPS, TG-DTA-DTG and NMR. Acid-base properties of the catalysts were investigated by TPD, FTIR spectroscopy and microcalorimetry to correlate with the catalytic behavior. Calcined Mg-Al hydrotalcite and Mg(O,F) are found to be highly active and selective catalysts for liquid-phase Michael additions of CH-acid compounds with methyl vinyl ketone.

Made available in DSpace on 2014-12-17T15:42:31Z (GMT). No. of bitstreams: 1 AnneMichelleGPS.pdf: 4577671 bytes, checksum: 19f54b9da1543ee4a1008ce93d607ec1 (MD5) Previous issue date: 2007-10-04 / Bifunctional catalysts based on zircon oxide modified by tungsten (W = 10, 15 and 20 %) and by molybdenum oxide (Mo= 10, 15 e 20 %) containg platinum (Pt = 1%) were prepared by the polymeric precursor method. For comparison, catalysts the tungsten base was also prepared by the impregnation method. After calcinations at 600, 700 and 800 ?C, the catalysts were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, thermogravimetric and differential thermal analysis, nitrogen adsorption and scanning electron microscopy. The profile of metals reduction was determined by temperature programmed reduction. The synthesized catalysts were tested in n-heptane isomerization. X-ray diffractogram of the Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts revealed the presence of tetragonal ZrO2 and platinum metallic phases in all calcined samples. Diffraction peaks due WO3 and ZrO2 monoclinic also were observed in some samples of the Pt/WOx-ZrO2 catalysts. In the Pt/MoOx-ZrO2 catalysts also were observed diffraction peaks due ZrO2 monoclinic and Zr(MoO4)2 oxide. These phases contained on Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts varied in accordance with the W or Mo loading and in accordance with the calcination temperature. The infrared spectra showed absorption bands due O-W-O and W=O bonds in the Pt/WOx-ZrO2 catalysts and due O-Mo-O, Mo=O and Mo-O bonds in the Pt/MoOx-ZrO2 catalysts. Specific surface area for Pt/WOx-ZrO2 catalysts varied from 30-160 m2 g-1 and for the Pt/MoOx-ZrO2 catalysts varied from 10-120 m2 g-1. The metals loading (W or Mo) and the calcination temperature influence directly in the specific surface area of the samples. The reduction profile of Pt/WOx-ZrO2 catalysts showed two peaks at lower temperatures, which are attributed to platinum reduction. The reduction of WOx species was evidenced by two reduction peak at high temperatures. In the case of Pt/MoOx-ZrO2 catalysts, the reduction profile showed three reduction events, which are attributed to reduction of MoOx species deposited on the support and in some samples one of the peak is related to the reduction of Zr(MoO4)2 oxide. Pt/WOx-ZrO2 catalysts were active in the n-heptane isomerization with high selectivity to 3-methyl-hexane, 2,3- dimethyl-pentane, 2-methyl-hexane among other branched hydrocarbons. The Pt/MoOx-ZrO2 catalysts practically didn't present activity for the n-heptane isomerization, generating mainly products originating from the catalytic cracking / Catalisadores bifuncionais a base de ?xido de zirc?nio modificado por ?xidos de tungst?nio (W = 10, 15 e 20 %) ou molibd?nio (Mo= 10, 15 e 20 %) contendo platina (Pt = 1 %) foram preparados pelo m?todo dos precursores polim?ricos. Por compara??o, catalisadores a base de tungst?nio tamb?m foram preparados pelo m?todo de impregna??o. Ap?s calcina??es a 600, 700 e 800 ?C, os catalisadores foram caracterizados por difra??o de raios-X, espectroscopia de absor??o na regi?o do infravermelho, an?lise termogravim?trica, an?lise t?rmica diferencial, adsor??o de nitrog?nio e microscopia eletr?nica de varredura. Os perfis de redu??o dos metais foram determinados por redu??o a temperatura programada. Os catalisadores sintetizados foram testados na isomeriza??o do n-heptano. Os difratogramas de raios-X dos catalisadores Pt/WOx-ZrO2 e Pt/MoOx-ZrO2 revelaram a presen?a do ZrO2 tetragonal e da platina met?lica em todas as amostras calcinadas. Picos de difra??o referentes ao WO3 e ao ZrO2 monocl?nico tamb?m foram observados em algumas das amostras dos catalisadores Pt/WOx-ZrO2. Nos catalisadores do tipo Pt/MoOx-ZrO2 tamb?m foram observados picos de difra??o referente ao ZrO2 monocl?nico e ao ?xido Zr(MoO4)2. O aparecimento destas outras fases contidas nos catalisadores Pt/WOx-ZrO2 e Pt/MoOx-ZrO2 variaram de acordo com o teor de W ou Mo e de acordo com a temperatura de calcina??o. Os espectros de absor??o na regi?o do infravermelho exibiram bandas de absor??o referentes as liga??es O-W-O e W=O nos catalisadores Pt/WOx-ZrO2 e referentes as liga??es O-Mo-O, Mo=O e Mo-O nos catalisadores Pt/MoOx-ZrO2. A ?rea superficial espec?fica dos catalisadores Pt/WOx-ZrO2 variou de 30-160 m2 g-1 e para os catalisadores do tipo Pt/MoOx-ZrO2 variou de 10-120 m2 g-1. O teor de metais (W ou Mo) e a temperatura de calcina??o exercem uma influ?ncia direta no valor da ?rea superficial espec?fica das amostras. Os perfis de redu??o dos catalisadores Pt/WOx-ZrO2 exibiram dois picos a baixas temperaturas, os quais s?o atribu?dos a redu??o da platina. A redu??o das esp?cies WOx foi evidenciada por dois picos de redu??o a altas temperaturas. No caso dos catalisadores Pt/MoOx-ZrO2, os perfis de redu??o mostram tr?s eventos de redu??o, os quais s?o atribu?dos a redu??o das esp?cies MoOx depositadas no suporte e em algumas amostras um dos picos ? relacionado com a redu??o do ?xido Zr(MoO4)2. Os catalisadores Pt/WOx-ZrO2 foram ativos para a isomeriza??o do n-heptano com alta seletividade a 3-metil-hexano, 2,3-dimetil-pentano e 2-metil-hexano entre outros hidrocarbonetos ramificados. Os catalisadores Pt/MoOx- ZrO2 praticamente n?o apresentaram atividade para a isomeriza??o do n-heptano, gerando principalmente produtos oriundos do craqueamento catalitico

The continuous downscaling has enforced the device size and oxide thickness to few nanometers. After serving for several decades as an excellent gate oxide layer in complementary metal oxide semiconductor (CMOS) devices, the thickness of SiO2 layer has reached to its theoretical limits. Ultra-thin films of SiO2 can result in severe leakage currents due to direct tunneling as well as maintaining the homogeneity of the layers becomes an additional challenge. The use of a high- (HK) layer can solve these twin concerns of the semiconductor industry, which can also enhance the capacitance due to superior dielectric permittivity and reduce the leakage current by being thicker than the silicon dioxide. This thesis is concerned about the development of solution route fabricated high-k (TiO2, ZrO2 and HfO2) gate dielectrics and the investigation of high-/silicon interfaces by highly sensitive DLTS technique in MOS structures. The solution processing reduce the industrial fabrication cost and the DLTS method has the advantage to accurately measure the interface related defects parameters; such as interface trap density (Dit), capture cross-section (), activation energy (ET) and also distinguish between bulk and interface traps. In this thesis, HK films have been deposited by solution route, the material and electrical properties of the film and the HK/Si interface have been extensively evaluated. IN CHAPTER 1, we have summarized the history and evolution of transistor and it provides the background for the work presented in this thesis. IN CHAPTER 2, we have described the experimental method /technique used for the fabrication and characterization. The advantages and working principals of spin-coating and DLTS techniques are summarized. IN CHAPTER 3, we have presented the preparation and optimization of TiO2 based HK layer. Structural, surface morphology, optical electrical and dielectric properties are discussed in details. A high- 34 value is achieved for the 36 nm TiO2 films. IN CHAPTER 4, we presented the technologically relevant Si/TiO2 interface study by DLTS technique. The DLTS analysis reveals a small capture cross-section of the interface with acceptable interface state density. IN CHAPTER 5, we have focused on the fabrication of amorphous ZrO2 films on p-Si substrate. The advantage of amorphous dielectric layer is summarized as first dielectric reported SiO2 is used in its amorphous phase. The moderate-15 with low leakage current density is achieved. IN CHAPTER 6, the HfO2 films are prepared using hafnium isopropoxide and a high value of dielectric constant 23 is optimized with low leakage current density. The current conduction mechanisms are discussed in details. IN CHAPTER 7, we have probed the oxygen vacancy related sub-band-gap states in HfO2 by DLTS technique. IN CHAPTER 8, we have presented the summary of the dissertation and the prospect research directions are suggested. In summary, we have studied the group IVB transition metal elemental oxides (TMEO); TiO2, ZrO2 and HfO2 thin films in the MOS structure, as a possible replacement of SiO2 gate dielectric. For the TMEO films deposition a low-cost and simple method spin-coating was utilized. The film thicknesses are in the range of 35 – 39 nm, which was measured by ellipsometry and confirmed with the cross-sectional SEM. A rough surface of gate dielectric layer can trap the charge carrier and may cause the Fermi level pinning, which can cause the threshold voltage instabilities. Hence, surface roughness of oxide layer play an important role in CMOS device operation. We have achieved quite good flat surfaces (RMS surface roughness’s are 0.2 – 2.43 nm) for the films deposited in this work. The TiO2 based MOS gate stack shows an optimized high dielectric constant ( 34) with low leakage current density (3.710-7 A.cm-2 at 1 V). A moderate dielectric constant ( 15) with low leakage current density (4.710-9 A.cm-2 at 1 V) has been observed for the amorphous ZrO2 thin films. While, HfO2 based MOS gate stack shows reasonably high dielectric constant ( 23) with low leakage current density (1.410-8 A.cm-2 at 1 V). We have investigated the dominating current conduction mechanism and found that the current is mainly governed by space charge limited conduction (SCLC) mechanism for the high bias voltages, while low and intermediate bias voltages show the (Poole – Frenkel) PF and (Fowler – Nordheim) FN tunneling, respectively. For the HfO2 MOS device band alignment is drawn from the UPS and J-V measurements. The band gap and electron affinity of HfO2 films are estimated 5.9 eV and 3 eV, respectively, which gives a reasonable conduction band offset (1.05 eV) with respect to Si. A TMEO film suffers from a large number of intrinsic defects, which are mostly oxygen vacancies. These defects can create deep levels below the conduction band of high- dielectric material, which can act like a hole and electron traps. In addition to that, interface between Si and high- is an additional concern. These defect states in the band gap of high- or at the Si/ high- interface might lead to the threshold voltage shifts, lower carrier mobility in transistor channel, Fermi level pinning and various other reliability issues. Hence, we also studied bulk and interfacial defects present in the high- films on Si and their interface with Si by a very sensitive DLTS technique. The capture cross-sections are measured by insufficient filling DLTS (IF – DLTS). The defects present at the interface are Si dandling bond and defect in the bulk are mostly oxygen vacancies related defects present in various charge states. The interface states (Dit) are in the range of 2×1011 to 9×1011 eV-1cm-2, which are higher than the Al/SiO2/Si MOS devices (Dit in Al/SiO2/Si is the benchmark and in the order of 1010 eV-1cm-2). Still this is an acceptable value for Si/high-k (non-native oxide) MOS devices and consistent with other deposition methods. The capture cross-sections are found to be quite low in the order of 10-18 to 10-19 cm2, which indicate a minor impact on the device operation. The small value of capture cross-sections are attributed to the involvement of tunneling, to and from the bulk traps to the interface. In conclusion, the low cost solution processed high- thin films obtained are of high quality and find their importance as a potential dielectric layer. DLTS study will be helpful to reveal various interesting facts observed in high- such as resistive switching, magnetism and leakage current problems mediated by oxygen vacancy related defects