Orientador: Abner de Siervo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-31T16:48:10Z (GMT). No. of bitstreams: 1 Ferreira_RodrigoCezardeCampos_M.pdf: 12900994 bytes, checksum: 7f4ff602b7e6aae7e2d8890e9f8d0a2b (MD5) Previous issue date: 2016 / Resumo: O grafeno é um alótropo bidimensional do carbono com hibridização do tipo sp2. Suas notáveis propriedades eletrônicas e estruturais provocaram um enorme interesse científico e tecnológico para o material na última década. Grafeno pode ser crescido em certos metais de transição através da técnica bem conhecida Chemical Vapor Deposition (CVD). A estabilidade do grafeno nesses substratos é garantida, porém as interações químicas entre eles modificam suas exóticas propriedades eletrônicas e estruturais. É possível sintetizar grafeno sobre Ir(111) sem defeitos estruturais substanciais e em um único domínio, quando realizado sob condições específicas de temperatura do substrato e da pressão do gás precursor (propileno). Na tentativa de isolar o grafeno do substrato, seja fisicamente ou eletricamente, existe a possibilidade da intercalação de diversas espécies, tais como gases, metais ou nanopartículas. Realizando tal procedimento, além da suspensão do material, é possível também dopar a banda eletrônica ou induzir abertura de gap. Neste contexto, o objetivo deste trabalho é estudar a dinâmica de crescimento e intercalação do ferro em Gr/Ir(111), seguindo os parâmetros termodinâmicos envolvidos e observando principalmente os deslocamentos químicos usando espectroscopia de fotoelétrons de raio-x (XPS) de alta resolução com síncrotron. Em paralelo, também usamos o microscópio de varredura por tunelamento (STM) para acompanhar a formação e intercalação das estruturas na superfície durante os ciclos de evaporação do ferro. Os resultados mostraram que, com o substrato à temperatura ambiente, o Fe interage fortemente com o grafeno e ocorre intercalação parcial. No caso de evaporação à temperaturas moderadas, houve intercalação total do Fe que permaneceu protegido pela folha de grafeno, indicando ser possível crescer um filme fino intercalado na superfície / Abstract: Graphene is a 2D carbon allotrope having sp2 hybridized atoms in a single-layer. Its remarkable electronic and structural properties attract an enormous scientific and technological interest to the material in the last decade. Graphene can be grown on certain transition metals by the well-known Chemical Vapor Deposition (CVD) technique. The stability of graphene in these substrates is guaranteed, but the chemical interactions between them modify its exotic electronic and structural properties. It is possible to grow graphene on the Ir(111) surface without substantial structural defects and withsingle domain, whenspecific conditions of substrate temperature and pressure of the precursor gas (propylene) are applied. While trying to retrieve the characteristic properties, the scientific community has been trying to isolate graphene from the metallic substrate, either physically or electrically, by intercalation of various species such as gases, metals or nanoparticles. By performing such procedures, it is possible, besides the desired suspension of the material, to induce changes such as gap opening and doping of the electronic band structures. In this context, the aim of this work is to study the dynamics of iron growth and intercalation in Gr/Ir(111), following the thermodynamic parameters involved and observing mainly the chemical shifts using high resolution x-ray photoelectron spectroscopy (XPS). In parallel, we also used the scanning tunneling microscope (STM) to follow the formation of Fe surface structures during the evaporation cycles and intercalation. The results show that at room temperature, Fe interacts strongly with graphene with partial intercalation. In the case of evaporation at moderate temperatures, there was full intercalation of Fe which remained protected by the graphene sheet / Mestrado / Física / Mestre em Física / 1423605/2014 / CAPES

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"This study considers the flammability hazard associated with the pouring of gasoline from a portable gasoline container (PGC) in an area containing a potential ignition source. In this scenario a flame may propagate into the PGC and cause an explosion if a flammable environment exists along the length of the pour spout and into the PGC headspace. In order to quantify this hazard, experiments are conducted to measure the flammable vapor concentration within this area under various conditions of temperature, liquid volume, and container pour angle. It is found that liquid fuel volumes as high as 30 mL in a 5-gallon PGC are capable of producing a flammable vapors within the PGC headspace. Finally, a mathematical model is presented to predict the flammability hazard under various conditions."

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Dissertação (Mestrado em Engenharia Química) - Centro Universitário FEI, São Bernardo do Campo, 2017

Estágio realizado na Galp Energia e orientado pelo Eng.º Manuel Leão Tavares / Tese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 2008

Tese de mestrado. Construção de Edifícios. 1997. Faculdade de Engenharia. Universidade do Porto

Estágio realizado na Petrogal - Petróleos de Portugal, S.A. e orientado pelo Eng.ª Maria do Céu M. P. M. Barros / Tese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 2009

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The main objective of this thesis is to find optimum discharge conditions in plasma reactors to realize controlled synthesis of various carbon-based materials with desired properties. Experimental conditions including substrate biasing, substrate pretreatment, gas flow rate, catalyst coating, and the type of carbon source, play important roles in controlling the nucleation and growth of carbon-based materials. In this Ph.D. work, the effects of various processing factors on nucleation and growth of carbon based materials were systematically investigated. The work has led to a better understanding of how each experimental parameter affects the carbon-based materials growth. Optimization of experiment conditions based on this understanding is beneficial for the controlled synthesis of carbon-based materials with desired properties. In addition, the controlled synthesis of tungsten-based nanostructures using a hot filament reactor was studied.<p>The main results presented in this thesis are: <p>(1) Synthesis of well-aligned carbon nanotube or carbon nanocone films with a glow discharge under a negative substrate biasing. The electric field in the plasma sheath above the substrate has been found to play an important role in controlling the alignment and orientation of nanotubes or nanocones. <p>(2) Synthesis of high purity diamond films using solid graphite as the carbon source by graphite etching. The technique provides a route to realizing deposition of high quality diamond films at low substrate temperatures (typically as low as 350 ℃). <p>(3) Successful synthesis of high quality diamond films on aluminum-coated steels using a graphite etching technique. The aluminum interlayer effectively reduces the graphitization which occurs on a steel substrate. <p>(4) Synthesis of nanocrystalline diamond films with smooth surfaces under high gas flow rates with a positive substrate biasing. Both high gas flow rate and positive biasing effectively increase the nucleation density of diamond and therefore reduce the diamond grain size. <p>(5) Synthesis of high purity crystalline tungsten or tungsten oxide nanorod films by optimizing the filament temperature in a hot filament reactor.