Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-02-21T21:32:47Z No. of bitstreams: 1 RicardoCesarDaSilvaRocha_TESE.pdf: 5309449 bytes, checksum: d6c6f63a7d0c3dd4a1a227198be68cee (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-02-23T18:57:37Z (GMT) No. of bitstreams: 1 RicardoCesarDaSilvaRocha_TESE.pdf: 5309449 bytes, checksum: d6c6f63a7d0c3dd4a1a227198be68cee (MD5) / Made available in DSpace on 2018-02-23T18:57:37Z (GMT). No. of bitstreams: 1 RicardoCesarDaSilvaRocha_TESE.pdf: 5309449 bytes, checksum: d6c6f63a7d0c3dd4a1a227198be68cee (MD5) Previous issue date: 2017-07-31 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Os processos de aspers?es t?rmica s?o utilizados para obten??o de revestimentos, com o objetivo, de reduzir o desgaste, minimizar os efeitos da corros?o ou para reparo de superf?cies, com aplica??es na ind?stria de petr?leo, aeroespacial e el?trica, dentre outras. O carbeto de ni?bio (NbC) tem se destacado na ind?stria mec?nica, na ?rea qu?mica e de microeletr?nica, por apresentar propriedades como elevada dureza, alto ponto de fus?o (3610?C), elevada condutividade t?rmica, grande estabilidade qu?mica, al?m de resist?ncia a radia??o. As propriedades dos revestimentos dependem da composi??o qu?mica e da microestrutura, que s?o influenciadas por sua vez pelos par?metros do processo. A t?cnica de deposi??o atrav?s de tocha de plasma por arco n?o transferido vem sendo estudada para o processamento de revestimentos. O Fe-NbC ? um novo produto desenvolvido para ser utilizado como refor?o por proporcionar melhoria nas propriedades mec?nicas de materiais met?licos. Apresenta-se neste trabalho os resultados de uma investiga??o sobre a forma??o, caracteriza??o e desempenho tribol?gico de camadas duras, obtidas por aspers?o t?rmica atrav?s de plasma de arco n?o transferido a partir de p?s de Fe-NbC, depositados em substrato de a?o ABNT 1020. Para a obten??o das camadas, foram variadas a corrente de trabalho e a vaz?o de g?s da tocha. Os revestimentos obtidos foram caracterizados por meio de an?lises de difra??o de Raios X, microscopia ?ptica, microscopia eletr?nica de varredura, an?lise qu?mica, rugosidade, microdureza Vickers e testes de pino sobre disco. Os resultados indicaram que as varia??es dos par?metros de deposi??o alteraram a dureza e o coeficiente de atrito devido a forma??o de fases de NbC e Fe3O4. / Thermal spraying processes are used to obtain coatings, which can reduce erosion, minimizing the effects of corrosion or for repairing surfaces, with applications in the petroleum, aerospace and electrical industries, among others. NbC carbide has been outstanding in the mechanical, chemical and microelectronic industries since it has properties such as high hardness, high melting point (3610 ? C), high thermal conductivity, high chemical stability, besides resistance to radiation. The properties of the coatings depend on the chemical composition and the microstructure, which are influenced by the process parameters. The technique of deposition through an untransferred arc plasma torch has been studied for coating processing. Fe-NbC is a new product developed to be used as reinforcement because it provides improvement in the mechanical properties of metallic materials. This work presents the results of an investigation on the formation, characterization and tribological performance of hard layers obtained by thermal spraying, using non-transferred arc plasma from Fe-NbC powders deposited on ABNT 1020 steel substrate. To get the layers, the working current and the gas flow of the torch were varied. The obtained coatings were characterized by X-ray diffraction analysis, optical microscopy, scanning electron microscopy, chemical analysis, roughness, Vickers microhardness and pin-to-disk tests. The results indicated that the variations of the deposition parameters have changed the hardness and the coefficient of friction due to the formation of NbC and Fe3O4 phases.

Made available in DSpace on 2014-12-17T14:06:50Z (GMT). No. of bitstreams: 1 GustavoPD.pdf: 1290134 bytes, checksum: a233e53c4a04f17b6a39b7b4ef196218 (MD5) Previous issue date: 2008-08-22 / The main objective is to analyze the abrasive wear resistance to the low stress of the elements that make up the organs of road machinery that are exposed directly to contact with abrasives. These samples were analyzed after these elements are coated superficially by the process of welding electrode coated with (SAER) and the manual process of coating type LVOF thermal spraying. As well, is to provide suggestions for a better recovery and return of these elements, which are reducing costs and avoiding downtime in the fronts of service. The samples were made from a substrate of carbon ABNT 1045 tempered steel, following the same specifications and composition of metals and alloys of constituents was followed the standard governing the dimensions of these samples and in accordance with the corresponding size. The results were evaluated by testing the hardness, abrasion resistance to wear by the low stress and the loss of volume involving the microstructure of coatings analyzed / O objetivo principal do trabalho ? analisar a resist?ncia ao desgaste abrasivo ? baixa tens?o dos elementos que comp?em os ?rg?os de m?quinas rodovi?rias que est?o expostos diretamente ao contato com abrasivos. Estas an?lises foram efetuadas ap?s estes elementos serem revestidos superficialmente pelo processo de soldagem com eletrodo revestido (SAER) manual e pelo processo de revestimento por aspers?o t?rmica tipo LVOF. Como tamb?m visa apresentar sugest?es para um melhor aproveitamento e rendimento destes elementos, quais sejam, diminuindo custos e evitando paralisa??es nas frentes de servi?o. Os corpos-de-prova foram confeccionados a partir de um substrato de a?o carbono ABNT 1045 temperado, seguindo as mesmas especifica??es e composi??es dos metais constituintes das ligas e foi seguida a norma que regulamenta as dimens?es destas amostras e de acordo com a grandeza correspondente. Os resultados foram avaliados por meio de ensaios de dureza, resist?ncia ao desgaste por abras?o ? baixa tens?o e pela perda de volume associando a microestrutura dos revestimentos analisados

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-07-03T12:42:01Z No. of bitstreams: 1 EdilsonDoValeJunior_DISSERT.pdf: 1539679 bytes, checksum: 4a56d1012ec29d3c011274d08b737e16 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-07-06T14:12:27Z (GMT) No. of bitstreams: 1 EdilsonDoValeJunior_DISSERT.pdf: 1539679 bytes, checksum: 4a56d1012ec29d3c011274d08b737e16 (MD5) / Made available in DSpace on 2017-07-06T14:12:27Z (GMT). No. of bitstreams: 1 EdilsonDoValeJunior_DISSERT.pdf: 1539679 bytes, checksum: 4a56d1012ec29d3c011274d08b737e16 (MD5) Previous issue date: 2016-11-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A oxida??o an?dica ? um tipo de processo eletroqu?mico oxidativo avan?ado, no qual possibilita a degrada??o e mineraliza??o de compostos org?nicos. Essa mineraliza??o ocorre preferencialmente de duas formas. A primeira acontece devido a transfer?ncia de carga diretamente na superf?cie do ?nodo e a segunda ocorre atrav?s de uma oxida??o indireta mediante a gera??o de esp?cies fortemente oxidantes, as quais podem ser fisicamente adsorvidas na forma de radicais hidroxila (?OH), ou quimicamente adsorvidas, na superf?cie do eletrodo. Uma maior taxa de tratamento ? obtida quando os radicais est?o fisicamente adsorvidos, as rea??es que possibilitam a degrada??o do substrato org?nico de interesse. Na literatura, dois materiais catal?ticos se destacam para a degrada??o e mineraliza??o de compostos org?nicos, s?o eles os eletrodos de diamante dopado com boro (DDB) e platina (Pt). Por?m ambos apresentam algumas limita??es que inviabilizam o so da tecnologia eletroqu?mica em escala industrial. Logo, v?rios pesquisadores t?m dedicado grandes esfor?os para identificar materiais eletr?dicos mais acess?veis como uma alternativa para reduzir o investimento inicial e os custos operacionais. Este ? o caso de ?nodos dimensionais est?veis e outros ?nodos met?licos. Neste contexto, ligas baseadas em estanho foram consideradas como uma alternativa interessante, utilizando-as como ?nodos, para o processo de oxida??o an?dica. Portanto, neste trabalho, um ?nodo formado por uma liga de Sn-Cu Sb (Babbitt) foi sintetizado a partir da tecnologia de aspers?o t?rmica a frio para avaliar a sua potencial aplica??o para tratamentos eletroqu?micos, como um novo material ?nodico m?dico e est?vel. As propriedades eletrocatal?ticas do ?nodo sintetizado foram testadas na redu??o da descolora??o e da demanda qu?mica de oxig?nio (DQO) do corante az?ico Azul ?cido 29. Al?m disso, a evolu??o de esp?cies inorg?nicas nitrogenadas e ?cidos carbox?licos gerados pela quebra da mol?cula pela oxida??o foi avaliada por meio de an?lise por HPLC. / Anodic oxidation is a type of advanced oxidative electrochemical process, in which it allows the degradation and mineralization of organic compounds. This mineralization occurs preferably in two ways. The first occurs due to the transfer of charge directly on the surface of the anode and the second occurs through indirect oxidation through the generation of strongly oxidizing species, which can be physically adsorbed in the form of hydroxyl (OH) radicals or chemically adsorbed, On the surface of the electrode. A higher rate of treatment is obtained when the radicals are physically adsorbed, the reactions that allow the degradation of the organic substrate of interest. In the literature, two catalytic materials stand out for the degradation and mineralization of organic compounds, such as boron doped diamond (DDB) and platinum (Pt) electrodes. But both have some limitations that prevent so the electrochemical technology on an industrial scale. Therefore, many researchers have devoted great efforts to identify more affordable electrodic materials as an alternative to reduce the initial investment and operating costs. This is the case of dimensional stable anodes and other metal anodes. In this context, tin-based alloys were considered as an interesting alternative, using them as anodes, for the anodic oxidation process. Therefore, in this work, an anode formed by a Sn-Cu Sb alloy (Babbitt) was synthesized from the cold gas spray technology to evaluate its potential application for electrochemical treatments, such as a new cheap and stable anode material. The electrocatalytic properties of the synthesized anode were tested to reduce the decolorization and chemical oxygen demand (COD) of azido blue Acid 29. Moreover, the evolution of nitrogenous inorganic species and carboxylic acids generated by the breakdown of the molecule by oxidation was evaluated by means of HPLC analysis.

Made available in DSpace on 2014-12-17T14:07:05Z (GMT). No. of bitstreams: 1 MarcioWDM_TESE.pdf: 5811012 bytes, checksum: feda974076398f5c8fbcb84ae56af460 (MD5) Previous issue date: 2010-09-17 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Metal substrates were coated by thermal spraying plasma torch, they were positioned at a distance of 4 and 5 cm from the nozzle exit of the plasma jet. The starting materials were used for deposition of tantalum oxide powder and aluminium. These two materials were mixed and ground into high-energy mill, then immersed in the torch for the production of alumina coating infused with particles of tantalum with nano and micrometric size. The spraying equipment used is a plasma torch arc not transferred, which operating in the range of 250 A and 80 V, was able to produce enough heat to ignite aluminothermic between Ta2O5 and aluminum. Upon reaching the plasma jet, the mixing powders react with the heat of the blaze, which provides sufficient energy for melting aluminum particles. This energy is transferred through mechanisms of self-propagating to the oxide, beginning a reduction reaction, which then hits on the surface of the substrate and forms a coating on which a composite is formed by a junction metal - ceramic (Ta +Al2O3). The phases and quantification of each were obtained respectively by X-ray diffraction and the Rietveld method. Morphology by scanning electron microscopy and chemical analysis by energy dispersive spectroscopy EDS. It was also performed measurements of the substrate roughness, Vickers microhardness measurements in sprays and determination of the electron temperature of the plasma jet by optical emission spectroscopy EEO. The results confirmed the expectation generated around the end product of spraying the mixture Ta2O5 + Al, both in the formation of nano-sized particles and in their final form. The electron excitation temperature was consistent with the purpose of work, in addition, the thermodynamic temperature was efficient for the reduction process of Ta2O5. The electron excitation temperature showed values of 3000, 4500 and 8000 K for flows10, 20 and 30 l / min respectively, these values were taken at the nozzle exit of the plasma jet. The thermodynamic temperature around 1200 ? C, was effective in the reduction process of Ta2O5 / Substratos met?licos de a?o inox 416 foram revestidos por aspers?o t?rmica em tocha de plasma. Eles foram posicionados a uma dist?ncia de 4 e 5 cm em rela??o ao bocal de sa?da do jato de plasma. Os materiais de partida utilizados para as deposi??es foram p?s de ?xido de t?ntalo e alum?nio. Esses dois p?s foram misturados e mo?dos em moinho de alta energia, em seguida, imersos na tocha para produ??o de revestimento de alumina impregnada com part?culas de t?ntalo com tamanho nano e microm?tricos. O equipamento de aspers?o utilizado foi uma tocha de plasma de arco n?o transferido que opera na faixa de 250 A e 30 V. Ao atingirem o jato de plasma, os p?s da mistura aquecem at? a temperatura de igni??o da rea??o aluminot?rmica. O calor gerado fornece energia suficiente para a fus?o do produto da rea??o. Esse produto fundido ao chocar-se na superf?cie do substrato forma um revestimento composto por uma jun??o metal cer?mica (Ta + Al2O3). A identifica??o das fases e sua quantifica??o foram obtidas respectivamente por difra??o de raios X e pelo m?todo de Rietveld. Para determina??o da morfologia e composi??o das part?culas foram utilizados microscopia eletr?nica de varredura e an?lise qu?mica por espectroscopia de energia dispersiva EDS, respectivamente. Tamb?m foram executadas medidas de rugosidades no substrato, medi??es de microdureza Vickers nas aspers?es e determina??o da temperatura eletr?nica do jato de plasma por espectroscopia de emiss?o ?tica EEO. Os resultados obtidos confirmaram a expectativa gerada em torno do produto final da aspers?o da mistura Ta2O5 + Al, tanto na forma??o de part?culas nanom?tricas de t?ntalo quanto no formato final delas. A temperatura de excita??o dos el?trons apresentou valores de 3000, 4500 e 8000 K para fluxos de 10, 20 e 30 l/min respectivamente, esses valores foram tomados na sa?da do bocal do jato de plasma. A temperatura termodin?mica, em torno de 1200 ?C mostrou-se eficiente para o processo de redu??o do Ta2O5