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Finite-volume methods have been used for modeling of fluidflows involved in forced convection electrochemical coating androtating spray painting systems. Electrodeposition on a singlecircular cylinder under forced convection for Reynolds numbers10 and 200 was simulated. Comparisons with earlier numericaland theoretical results are presented and it is shown that theunsteady wake that appears for Reynolds numbers greater than 50affects the mass transfer from the surface of the cylinder onlyin an average sense. This result is compared with a heattransfer case, where unsteadiness is much more manifest. Theeffect of application of circulation movement around thecylinder surface was considered, showing that the use ofoptimal values for circulation can create a recirculation zonearound the cylinder and result in a remarkable improvement ofthe deposit uniformity. The magnetoelectrolysis researchdiscipline is presented with focus on magnetic fields uses onmass transfer processes. A classification of the governingdimensionless parameters that control the phenomena isproposed. Application of magnetoelectrolysis on electroplatingprocesses is done for the first time. It is found that the useof an alternating magnetically induced force around thecylinder can result in interesting improvement of quality andproductivity. Application of numerical methods is also studiedin another field of the surface finishing industry, thepainting atomizers. A critical situation of "reverse flow" isanalyzed. Different parameters of this phenomenon are studiedand suggestions for atomizers design are given and tested. <b>Keywords:</b>mass transfer, electrochemical coating, iontransport, forced convection, diffusion, magnetoelectrolysis,electrolyte, limiting current, numerical simulation,finite-volume methods, paint atomization, Coanda effect.

<p>Finite-volume methods have been used for modeling of fluidflows involved in forced convection electrochemical coating androtating spray painting systems. Electrodeposition on a singlecircular cylinder under forced convection for Reynolds numbers10 and 200 was simulated. Comparisons with earlier numericaland theoretical results are presented and it is shown that theunsteady wake that appears for Reynolds numbers greater than 50affects the mass transfer from the surface of the cylinder onlyin an average sense. This result is compared with a heattransfer case, where unsteadiness is much more manifest. Theeffect of application of circulation movement around thecylinder surface was considered, showing that the use ofoptimal values for circulation can create a recirculation zonearound the cylinder and result in a remarkable improvement ofthe deposit uniformity. The magnetoelectrolysis researchdiscipline is presented with focus on magnetic fields uses onmass transfer processes. A classification of the governingdimensionless parameters that control the phenomena isproposed. Application of magnetoelectrolysis on electroplatingprocesses is done for the first time. It is found that the useof an alternating magnetically induced force around thecylinder can result in interesting improvement of quality andproductivity. Application of numerical methods is also studiedin another field of the surface finishing industry, thepainting atomizers. A critical situation of "reverse flow" isanalyzed. Different parameters of this phenomenon are studiedand suggestions for atomizers design are given and tested.</p><p><b>Keywords:</b>mass transfer, electrochemical coating, iontransport, forced convection, diffusion, magnetoelectrolysis,electrolyte, limiting current, numerical simulation,finite-volume methods, paint atomization, Coanda effect.</p>

Indium antimonide (InSb) and gallium antimonide (GaSb) are technologically important III-V semiconductor materials used in infrared detector systems. Yet, the application of these materials is to a certain extent limited, in that the techniques currently used for their growth are both expensive and problematic. Semiconductor electrochemical deposition, which has been successfully applied to the generation of II-VI semiconductor materials, may offer the prospect of overcoming such limitations. This work presents results that represent a significant contribution to the development of electrochemical methods for both InSb and GaSb thin film growth. The direct electrochemical co-deposition of InSb was achieved via the potentiostatic electrolysis of aqueous halide/citric acid electrolyte solutions, and for the first time, non-aqueous (ethylene glycol) electrolyte solutions containing the halides and tetraethylammonium chloride. This choice of solvents allowed the compound's deposition to be studied over a wide range of temperatures (RT to 185 &deg;C). A first report was also made of the direct potentiostatic co-deposition of GaSb from an aqueous solution containing Ga[2](SO[4])[3] and SbCl[3].An extensive study was carried out on the relationship between the technique's fundamental growth parameters (temperature, deposition potential, solution composition etc.) and the film's compositional, crystallographic and morphological properties. The material's characterisation showed that there was tendency for the films to be non-stoichiometric. X-Ray diffraction patterns obtained from InSb films deposited from aqueous electrolyte solutions showed them to generally consist of two phases, the compound and, depending mostly on deposition potential, one of the elements. Films containing three phases, the compound and both elements, were deposited on Ti substrates from aqueous solutions and on to ITO substrates from non-aqueous solutions. These results were interpreted from both thermodynamic and kinetic viewpoints. This led to the conclusion that kinetic barriers to the formation of InSb still existed, even at the highest temperature used (~185 &deg;C). In respect of GaSb, the compound's formation was complicated by a side reaction involving the evolution of H[2].New studies involving Scanning Electron Microscopy of the electrodeposited materials showed that they exhibited a nodular morphology, which can be explained in terms of the film's limiting current growth conditions. Energy Dispersive X-Ray Analysis (EDX) and Glow Discharge Optical Emission Spectroscopy (GDOES) identified indium chloride as a major impurity in the InSb films, especially those deposited from non-aqueous solutions. A mechanism for the incorporation of indium chloride was proposed, based on the physical entrapment of a precipitate of the compound.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-11-11T09:51:24Z No. of bitstreams: 0 / Made available in DSpace on 2016-11-11T09:51:24Z (GMT). No. of bitstreams: 0 / PtBi/C e PdBi/C foram preparados em diferentes razões atômicas (100:0, 90:10, 80:20, 70:30, 60:40 e 50:50) pelo método de redução via borohidreto de sódio (com adição total da solução de borohidreto em uma única etapa) utilizando H2PtCl6.6H2O, Pd(NO3)2, (BiNO3)3.5H2O como fonte de metais, Vulcan® (XC72-Cabot) como suporte de carbono e com uma carga metálica correspondente a 20% em massa. Os eletrocatalisadores obtidos foram caracterizados por difração de raios-X (DRX), microscopia eletrônica de transmissão (MET) e voltametria cíclica (VC). A atividade dos diferentes materiais preparados para a oxidação eletroquímica do ácido fórmico foi realizada em eletrólito ácido e alcalino utilizando-se as técnicas de voltametria cíclica, e cronoamperometria. Para estes estudos foi utilizado a técnica do eletrodo de camada fina porosa. A caracterização eletroquímica permitiu comparar o desempenho eletroquímico da platina e paládio, além de avaliar o benefício da presença do bismuto nas razões atômicas propostas. Os difratogramas de raio-X (DRX) confirmaram para todos os compostos de PtBi/C e PdBi/C a formação da estrutura cúbica de face centrada (cfc) característicos da rede cristalina da platina e do Paládio respectivamente. Outros picos encontrados foram associados a presença de fases de óxido de bismuto em ambos os compostos, PtBi/C e PdBi/C. A microscopia eletrônica de transmissão (MET) indicou que a presença de maiores teores de bismuto não acarretaram em aumento do tamanho médio da partícula. Os resultados eletroquímicos em meio alcalino indicaram que ainda é necessário uma otimização da concentração de ácido fórmico para que possamos observar melhores resultados quanto à adição de bismuto na platina ou paládio, no entanto os estudos em meio ácido mostraram o efeito benéfico da adição de bismuto tanto para platina quanto para o paládio. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-10-09T19:31:24Z No. of bitstreams: 0 / Made available in DSpace on 2017-10-09T19:31:24Z (GMT). No. of bitstreams: 0 / A marcação por feixe laser em superfícies é utilizada para assegurar a identificação e a rastreabilidade em biomateriais. A texturização via feixe laser confere maior aderência às superfícies dos dispositivos médicos implantáveis. Este trabalho teve o objetivo de avaliar o comportamento da superfície do aço inoxidável austenítico ABNT NBR ISO 5832-1 submetido à marcação e texturização com feixe laser de fibra óptica, alterando-se a frequência dos pulsos; frente ao seu comportamento biomecânico, por meio de: ensaios de resistência à tração, fadiga e desgaste; verificar a susceptibilidade à corrosão localizada, por ensaios eletroquímicos em solução que simula os fluidos corpóreos; e caracterizar a sua microestrutura. Os tratamentos alteraram a rugosidade e a dureza dos biomateriais em função do aumento da frequência dos pulsos. A microestrutura e composição química das superfícies sofreram mudanças que afetaram diretamente a camada passiva dos aços inoxidáveis. Este efeito foi comprovado com o uso de SVET, XPS e caracterização de propriedades eletrônicas do filme passivo. Os dois tipos de tratamentos implicaram em aumento de susceptibilidade magnética das superfícies. Os parâmetros utilizados para as marcações e texturizações não causaram diminuição na viabilidade celular, de modo que não apresentou citotoxicidade mesmo após incubação prolongada. Este biomaterial mostrou-se adequado perante os ensaios biomecânicos, uma vez que os tratamentos a laser, nas condições utilizadas, não induziram a formação de tensões superficiais de magnitude capaz de levar à fratura por fadiga, indicando vida em fadiga infinita; tampouco se pôde relacionar a região de fratura por tração com as marcações a laser. O volume de desgaste diminuiu em função do aumento da dureza produzido pela elevação da frequência do pulso nas texturizações. O caráter visual das marcações e texturizações por feixe laser foi assegurado após a maioria dos ensaios realizados. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP