>Magister Scientiae - MSc / In this thesis we report on the deposition of silicon nanostructures using a 3-zone thermal chemical vapour deposition process at atmospheric pressure. Nickel and gold thin films, deposited by DC sputtering on crystalline silicon substrates, were used as the catalyst material required for vapour-solid-liquid growth mechanism of the Si nanostructures. The core of this work is centred around the effect of catalyst type, substrate temperature and the source-to-substrate distance on the structural and optical properties of the resultant Si nanostructures, using argon as the carrier gas and Si powder as the source. The morphology and internal structure of the Si nanostructures was probed by using high resolution scanning and transmission electron microscopy, respectively. The crystallinity was measured by x-ray diffraction and the high resolution transmission electron microscopy. For composition and elemental analysis, Fourier transform infrared spectroscopy was used to quantify the bonding configuration, while electron energy-loss spectroscopy in conjunction with electron dispersion spectroscopy reveals the composition. Photoluminescence and UV-visible spectroscopy was used to extract the emission and reflection properties of the synthesized nanostructures.

Dependendo da característica da indústria, nem sempre, a operação de torneamento de aços é a que aparece com maior frequência. Geralmente a operação de furação destes materiais ocupa espaço relativo abaixo da operação citada. Entretanto, a Empresa Müller Metais Indústria e Comércio que decidiu colaborar de forma decisiva para a elaboração deste trabalho, é totalmente voltada para a usinagem de furos em chapas de grandes dimensões e de diversas espessuras. As chapas são geralmente de Aço Carbono, mas, também existe a incidência de furos em chapas de Aço Inoxidável. O número de furos pode variar entre 500 até 2500 por peça. As brocas possuem um suporte sobre o qual é fixado um inserto de geometria especialmente projetada para atender a qualidade exigida da superfície interna do furo. Os insertos são de metal duro classe ISO K15 e revestidos por PVD multicamadas à base de AlCr sobre o referido substrato. O critério para troca de ferramenta é baseado em um número de furos (vida) previamente adotado em função da experiência acumulada ao longo do tempo. A Empresa Müller Metais Indústria e Comércio vêm trabalhando no sentido de aumentar a produtividade para melhor fazer frente a demanda crescente por parte de clientes de diversas áreas que utilizam tais peças. O objetivo deste trabalho é analisar os mecanismos de desgastes ocorridos em brocas especiais com insertos intercambiáveis de metal duro visando melhorar o desempenho dos mesmos. Os insertos foram banhados por um produto antiatrito e em seguida mantidos em estufa à temperatura da ordem de 80C por 30 minutos provocando, desta forma, um tratamento termoquímico da superfície do inserto. / Depending on the characteristic of the industry, turning operation of steel is not always the one that appears most frequently. Generally drilling operation is less mentioned and used by industries. However, the company Müller Metals Industry and Trade that decided to collaborate decisively to the development of this work. They were fully geared for machining holes in large plates with various thicknesses. The plates are usually carbon steel, but there is also the incidence of holes in plates of stainless steel. The number of holes can vary from 500 to 2500. The drills have a support on which insert are fixed. The inserts are ISO K15 grade carbide and coated multilayer PVD -based AlCr on the carbide substrate. The Company Müller Metals Industry and Commerce has been working to increase productivity to better cope with increasing demand from clients in various areas using such parts. The objective of this study is to analyze wear mechanisms in special drills with interchangeable cemented carbide inserts to improve their behavior. To achieve this goal the drills should be treated by anti friction product at a temperature of about 80 C.

Thermal and chemical recovery processes are important EOR methods used often by the oil and gas industry to improve recovery of heavy oil and high viscous oil reservoirs. Knowledge of underlying mechanisms and their modeling in numerical simulation are crucial for a comprehensive study as well as for an evaluation of field treatment. EOS-compositional, thermal, and blackoil reservoir simulators can handle gas (or steam)/oil/water equilibrium for a compressible multiphase flow. Also, a few three-phase chemical flooding reservoir simulators that have been recently developed can model the oil/water/microemulsion equilibrium state. However, an accurate phase behavior and fluid flow formulations are absent in the literature for the thermal chemical processes to capture four-phase equilibrium. On the other hand, numerical simulation of such four-phase model with complex phase behavior in the equilibrium condition between coexisting phases (oil/water/microemulsion/gas or steam) is challenging. Inter-phase mass transfer between coexisting phases and adsorption of components on rock should properly be modeled at the different pressure and temperature to conserve volume balance (e.g. vaporization), mass balance (e.g. condensation), and energy balance (e.g. latent heat). Therefore, efforts to study and understand the performance of these EOR processes using numerical simulation treatments are quite necessary and of utmost importance in the petroleum industry. This research focuses on the development of a robust four-phase reservoir simulator with coupled phase behaviors and modeling of different mechanisms pertaining to thermal and chemical recovery methods. Development and implementation of a four-phase thermal-chemical reservoir simulator is quite important in the study as well as the evaluation of an individual or hybrid EOR methods. In this dissertation, a mathematical formulation of multi (pseudo) component, four-phase fluid flow in porous media is developed for mass conservation equation. Subsequently, a new volume balance equation is obtained for pressure of compressible real mixtures. Hence, the pressure equation is derived by extending a black oil model to a pseudo-compositional model for a wide range of components (water, oil, surfactant, polymer, anion, cation, alcohol, and gas). Mass balance equations are then solved for each component in order to compute volumetric concentrations. In this formulation, we consider interphase mass transfer between oil and gas (steam and water) as well as microemulsion and gas (microemulsion and steam). These formulations are derived at reservoir conditions. These new formulations are a set of coupled, nonlinear partial differential equations. The equations are approximated by finite difference methods implemented in a chemical flooding reservoir simulator (UTCHEM), which was a three-phase slightly compressible simulator, using an implicit pressure and an explicit concentration method. In our flow model, a comprehensive phase behavior is required for considering interphase mass transfer and phase tracking. Therefore, a four-phase behavior model is developed for gas (or steam)/ oil/water /microemulsion coexisting at equilibrium. This model represents coupling of the solution gas or steam table methods with Hand’s rule. Hand’s rule is used to capture the equilibrium between surfactant, oil, and water components as a function of salinity and concentrations for oil/water/microemulsion phases. Therefore, interphase mass transfer between gas/oil or steam/water in the presence of the microemulsion phase and the equilibrium between phases are calculated accurately. In this research, the conservation of energy equation is derived from the first law of thermodynamics based on a few assumptions and simplifications for a four-phase fluid flow model. This energy balance equation considers latent heat effect in solving for temperature due to phase change between water and steam. Accordingly, this equation is linearized and then a sequential implicit scheme is used for calculation of temperature. We also implemented the electrical Joule-heating process, where a heavy oil reservoir is heated in-situ by dissipation of electrical energy to reduce the viscosity of oil. In order to model the electrical Joule-heating in the presence of a four-phase fluid flow, Maxwell classical electromagnetism equations are used in this development. The equations are simplified and assumed for low frequency electric field to obtain the conservation of electrical current equation and the Ohm's law. The conservation of electrical current and the Ohm's law are implemented using a finite difference method in a four-phase chemical flooding reservoir simulator (UTCHEM). The Joule heating rate due to dissipation of electrical energy is calculated and added to the energy equation as a source term. Finally, we applied the developed model for solving different case studies. Our simulation results reveal that our models can accurately and successfully model the hybrid thermal chemical processes in comparison to existing models and simulators. / text