Made available in DSpace on 2014-10-09T12:35:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:11Z (GMT). No. of bitstreams: 0 / O processo de conformação por spray é interessante devido à capacidade de conjugar, em apenas uma etapa do processo, a vantagem da técnica de solidificação rápida combinada com alta produtividade dos processos de fundição convencional. Este processo permite a obtenção de materiais livre de macrossegregações, livre de porosidades e com microestrutura refinada. A evolução recente das pesquisas está levando ao desenvolvimento de novas ligas e os resultados têm sido interessantes. O processo de solidificação rápida inerente da conformação por spray permite a produção de ligas com composições diferentes das obtidas pela fundição convencional. O objetivo deste trabalho foi o de caracterizar mecanicamente uma liga de alumínio AA-6082 conformada por spray. Os resultados de testes de dureza Vickers são apresentados para seções de um preformado em relação a sua altura (em um arranjo tridimensional). O material foi avaliado na condição como conformado por spray e após tratamento térmico de solubilização a 525 ºC por 1 h, seguido por envelhecimento a 125 ºC por períodos distintos de 1 h, 10 h, 100 h e 500 h. É mostrado que o a liga AA 6082 conformada por spray mostra uma boa estabilidade térmica em relação a variação da dureza durante o envelhecimento. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Orientador: Sandra Cristina dos Santos Rocha / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-04T05:32:13Z (GMT). No. of bitstreams: 1 Cunha_RobertoLuisGomesda_M.pdf: 4555527 bytes, checksum: c05f06e6d6afae91414137377cbe242d (MD5) Previous issue date: 2004 / Resumo: O recobrimento de materiais granulares é urna operação bastante utilizada pela industria Farmacêutica com diversas finalidades, que vão desde fatores estéticos ao controle da taxa de dissolução de substâncias químicas e incluem: facilitar a administração através da obtenção de uma super:ficie lisa, identificar o medicamento pelo emprego de cores, proteger a droga de agentes atmosféricos como, luz, oxigênio, entre outros. Neste trabalho estudou-se a fluido dinâmica e o recobrimento da celulose microcristalina - MICROCEL, que é o principal excipiente usado na indústria farmacêutica, com uma suspensão aquosa a base de Eudragit'1! / Abstract: The coating of granular materials is an operation widely used by tbe Pharrnaceutical industry with diverse purposes: to improve the product appearance, to obtain a product with controlled release of active components, to facilitate the administration through the artainrnent of a smooth surface, to identii)r the drug by colors, to prateet the drug ITom atmospheric agents as, light, oxygen, among others. ln this work, the fluid dy11aID.ics and the coating of microcrystalline cellulose - MICROCEL, which is the main excipient used in the pharmaceutical industry, was analyzed. An aqueous polymeric suspension of Eudragit@ was used as the coating liquid in a fluidized bed. The suspension was eontinuously sprayed on the granules by a double-fluid nome loeated at the top ofthe bed. The objeetive of this work was to analyze the fluid-dynamics of a fluidized bed during the coating process, using particles of type B according to Geldart classification, aiming at the identillcation of the bed saturation (instability andíor fluidized regime collapse) and relating it to the operating conditions. The independent variables analyzed were the flow rate of eoating suspension (Ws), for the values: 6.4, 11.0 and 18.0 glmin and the atomization pressure (pat) in the following levels: 10, 15 and 20 psig. The inlet aÍ! temperature of the bed was kept constant at 70°C, as well as the sÍZe of the particles, in the range of 0.30 - 0.42 mIn. A 32 factorial desígn was employed to evaluate the influences of the operating condítions on the responses: the process efficíeney, the partíc1es growth, the agglomerate formation and the instantaneous saturation until the bed collapse. The process efficiency varied ITom 51 to 99,7 %, the particles growth was characteristíc of a fi1m coating, the agglomerates índex varied ITom 0.38 to 6.28 % and the bed instantaneous saturation ITom 5.370.10-3 to 16.828.10-3 (min-l). During the experiments, i1 was observed that the fluidized regime collapse is related to the bed saturation, since the bed porosity decreases with the saturation increase, with consequent packing of the particles and collapse ofthe bed regime / Mestrado / Engenharia de Processos / Mestre em Engenharia Química

[pt] Oleos pesados são significativamente importantes no cenário brasileiro e internacional, sendo sua principal característica a alta viscosidade e consequente dificuldade de transporte. Além disso, durante o escoamento destes óleos ocorre a deposição de parafina nas paredes dos oleodutos, particularmente a baixas temperaturas. Esse tipo de petróleo possui características reológicas viscoplásticas, e sob certas condições ainda não muito bem conhecidas, apresentam o fenômeno do deslizamento aparente ao escoar internamente, tendo o potencial de reduzir substancialmente a perda de carga em um escoamento. Neste trabalho foi investigado experimentalmente o deslizamento aparente que ocorre em escoamentos de materiais viscoplásticos bem como foi determinada a tensão cisalhante necessária para descolar uma quantidade de parafina depositada sobre diferentes revestimentos. Devido a uma evidência experimental de que o grau de deslizamento depende de duas propriedades físicas da superfície interna do duto, foram determinadas também a rugosidade e a molhabilidade destas. Foi construída uma planta experimental na qual era possível variar as placas (diferentes revestimentos e rugosidades) que formavam as paredes do canal pelo qual o fluido era forçado a escoar, de forma a se obter a curva vazão x pressão para cada tipo de revestimento. Estes escoamentos foram simulados numericamente supondo ausência de deslizamento. A comparação entre as curvas experimentais e teóricas fornecem uma quantificação do deslizamento ocorrido nos experimentos. Utilizamos um fluido à base de água e um fluido à base de óleo. Foi observado que o deslizamento aparente, existente em escoamentos de materiais viscoplásticos, se manifesta na faixa de baixas tensões adimensionais e que os revestimentos possuem duas funções principais, a da redução da rugosidade e a do aumento da molhabilidade, ambas com o efeito de aumentar o nível de deslizamento e, consequentemente, reduzir a perda de carga, diminuindo os custos operacionais. / [en] Heavy oils are significantly important in the Brazilian and international scenario and its particularity is the high viscosity and consequent difficulty of transport. Also, during the flow of these oils occurs the deposition of paraffin on the pipelines walls especially at low temperatures. This type of oil has viscoplastic rheological characteristics, and under certain conditions not yet well understood, exhibits the phenomenon of apparent wall slip during internal flow, with the potential to substantially reduce the head-loss in a flow system. This study investigated experimentally the wall slip that occurs in the flow of viscoplastic liquids. Moreover, it was also determinated, the wall shear stresses necessary to unstick an amount of paraffin deposited on different coatings. Due to an experimental evidence, the amount of wall slip seems to depend on two physical properties of the internal surface of the pipeline, therefore it was determined also the roughness and wettability of these. A test section was designed and built. Plates with different coatings and roughness constitute the parallel channel which the fluid was forced through in order to obtain the curves of dimensionless average velocity versus dimensionless wall shear stress. These flows were also numerically solved referring to the case of no wall slip. Comparisons between the experimental and numerical results could quantify the amount of wall slip that occurs in the experiments. We used an aqueous solution and oil dispersion. It was observed that the wall slip, that occurs during the flow of viscoplastic materials, manifests itself in the range of low dimensionless wall shear stress and that the coatings have two main functions, reduction of the roughness and increase of the wettability, both with the effect of increasing the amount of wall slip and thus reduce the head-loss, diminishing operational costs.

La fabrication de guides d’ondes à partir d’un matériau composite CFRP isolant, nécessite de rendre la surface interne conductrice électriquement. Cela peut s’effectuer par métallisation, mais des verrous technologiques apparaissent en raison de la géométrie complexe associée à une surface inerte. Le CFRP est composé d’époxy dont la température de transition vitreuse est de 216 °C, ce qui limite le choix des techniques de métallisation. De plus, l’énergie de surface du polymère qui compose la surface du CFRP est plutôt faible (20-40 mJ/m2) et non polaire, ce qui conduit à une adhérence faible des revêtements métalliques. Le procédé DLI-MOCVD est utilisé pour le dépôt du revêtement métallique car il combine un contrôle rigoureux des débits de réactifs, des vitesses de croissance élevées et il est adapté pour revêtir des substrats tridimensionnels. Le choix du métal (le cuivre) est basé sur un savoir-faire antérieur de l’équipe de recherche, pour la possibilité de le déposer à une température bien inférieure à 216 °C, et bien entendu pour son excellente conductivité électrique et sa résistance au vieillissement ambient. Le film de Cu est élaboré à partir du précurseur organométallique (hfac)Cu(MHY), développé par P. Doppelt au CNRS. Ce précurseur qui se présente sous forme liquide à Tambiante, est dilué dans de l’octane anhydre pour pouvoir être injecté par le système DLI. Après avoir implémenté un réacteur dédié au travaux de la thèse, une étude de cinétique chimique du dépôt à partir du précurseur a permis de définir les conditions expérimentales optimales ; notamment la température de dépôt fixée à 195 °C. Les revêtements obtenus sont partiellement couvrants et sont conducteurs. Leur adhérence avec le substrat est nulle. Par conséquent, on sélectionne puis on teste différents prétraitements du substrat afin de modifier la morphologie et la réactivité de la surface CFRP. On montre à travers six prétraitements que la formation de rugosité de surface favorisant l'ancrage mécanique est un caractère prépondérant pour l’amélioration de l’adhérence, par rapport à la modification chimique. Les deux prétraitements les plus performants sont le traitement par voie humide CircupositTM et le traitement in situ à l’O3 A ce stade, les films sont conducteurs et adhérents mais ils ne mouillent pas intégralement la surface du composite lors du dépôt. On démontre alors que l’injection d’un précurseur de cobalt (Co2(CO)5) en alternance avec le dépôt de Cu permet d’obtenir un revêtement de cuivre métallique, pur à plus de 98 %, couvrant, conducteur et adhérent. A ce stade, le rôle du précurseur de Co n’est pas clairement établi. Néanmoins, les études préliminaires d’industrialisation du procédé consistant à améliorer les rendements et vitesses de croissance sont entreprises. Notamment, les coûts sont abaissés en remplaçant le solvant octane. Avec ce solvant, le dépôt de Cu est adhérent sans prétraitement préalable de la surface du substrat. A noter que le précurseur de Co est toujours nécessaire pour assurer une couverture complète de la surface CFRP. C’est dans ces conditions de dépôt, et après quelques ajustements paramétriques que les premiers guides d’ondes de 60 mm sont revêtus. Les résultats des tests de cyclage thermique étant positifs, la longueur des guides d’ondes à revêtir est augmentée à 300 mm, dimension minimale pour pouvoir effectuer des tests de transmission des ondes radiofréquences : la propriété finale. Cette modification géométrique requière une phase d’optimisation plus complexe afin de garantir l’uniformité en épaisseur et en propriétés électriques sur toute la longueur. Les guides d’ondes de 300 mm métallisés passent les cyclages thermiques avec succès. Les tests radiofréquences indiquent un taux de transmission des ondes < 30 dB, ce qui est tout à fait acceptable d’un point de vue applicatif. En revanche, les pertes sont importantes en comparaison avec l’existant, mais de nombreuses pistes d’améliorations sont proposées. / The manufacturing of waveguides from insulating C fibers reinforced polymer composites necessitates to render internal surfaces electrically conductive. This can be achieved by metallization but technological bottlenecks arise due to the complex geometry and the chemical inertia of the surface. The CFRP matrix is composed of RTM6 epoxy whose glass-transition temperature equals 216 °C, limiting the choice of metallization techniques. Additionally, the surface energy of the polymer (constituting the surface of the CFRP) is low (20-40 mJ/m2) and non-polar, i.e. a poor adherence is expected for metallic coatings. A DLI-MOCVD process is used to form the metallic coating because it combines a good control of reactive fluxes, high deposition rates, and because it is relevant for the coating of three-dimensional substrates. The choice of the metal (Cu) is dictated by the anterior know-how of the research group, by the possibility to deposit at a temperature well below 216 °C, and because Cu shows an excellent electrical conductivity and a good resistance to ambient ageing. The Cu film is formed from the organometallic precursor (hfac)Cu(MHY), developed par P. Doppelt at CNRS (Paris). The precursor is diluted in anhydrous octane to make it injectable by DLI. After the mounting and implementation of the DLI-MOCVD reactor dedicated to the PhD work, a study of the chemical kinetics of the deposition from this precursor helped in the definition of the optimal conditions; noticeably the deposition temperature fixed at 195 °C. The coatings are partially covering and interfacial adherence is poor, but they are conductive. Consecutively, we identify, develop and test several pretreatments in order to modify the topography and reactivity of the CFRP surface. Based on 6 recipes, we show that mechanical anchorage is preponderant over the chemical reactivity to improve the adherence. The two best pretreatments are the solution chemistry treatment CircupositTM, and the in situ treatment with O3. At this stage of the work, Cu films are conductive and adherent but they do not wet the entire composite surface, even after long deposition duration. We then demonstrate that the injection of a Co precursor (Co2(CO)5) alternating with the Cu deposition leads to the formation of a pure metallic Cu film (> 98%) which is covering, conductive and adherent. The role of the Co precursor is not yet established. Nevertheless, we start the preliminary process industrialization studies consisting in the improvement of the growth rate and the yield. Noticeably, costs are decreased by replacing the octane solvent. With it, the Cu coating is adherent without any pretreatment of the substrate surface! The Co precursor is still necessary to ensure the proper covering of the entire surface, though. In these conditions, and after adjustments of some parameters, the first 60 mmlong waveguides are coated. The thermal cycling resistance is excellent. Therefore, waveguides length is increased to 300 mm, the minimum dimension for the radiofrequency transmission tests (final property) to be correct. The increase of length causes a complex adaptation of the process in order to guarantee the deposition of a uniform coating over the length, in terms of thickness and electrical properties. Radiofrequency tests result in a stationary waves rate < 30 dB, which is acceptable at the industrial level. Yet, losses are too important in comparison with current waveguides, but many proposals are formulated to improve our solution.

La protection contre la corrosion par des films ultramince (≤50 nm) d'alumine déposées par ALD sur le cuivre et l'aluminium à 250°C a été étudiée dans une solution aqueuse 0,5 M de NaCl en combinant méthodes d'analyse électrochimique et de surface. L'étude de l'alumine ALD sur un substrat Cu comprend l'effet de l'épaisseur du revêtement, l'effet de l'oxyde interfacial, l'effet de la préparation de la surface et la durabilité du revêtement. Pour le substrat Al, le travail a porté sur l'examen de l'effet de l'épaisseur du revêtement. Les revêtements ont montré d'excellentes propriétés de corrosion sur des substrats Cu électropoli, tandis qu'ils ont échoué à protéger le substrat recuit, de fait d'une mauvaise adhérence à une surface lissée. L'amélioration de la résistance à la corrosion d'alumine ALD sur le substrat Cu est obtenue en l'absence de vieillissement de l'oxyde natif interfacial, et sa modification par un prétraitement. En dépit de remarquables propriétés d'étanchéité sur un substrat Cu électropoli, la protection contre la corrosion de l'alumine ALD n'est pas durable. Le revêtement du substrat Al avec l'alumine ALD conduit à l'augmentation significative de la résistance à la corrosion. Le potentiel de piqûration est augmenté en présence des revêtements l'épaisseur de 20 et 50 nm, ce qui n'a pas été obtenus avec 10 nm en raison de sa faible épaisseur. Cette étude est une étude préliminaire pour l'application de revêtements d'alumine ALD pour la protection contre la corrosion des alliages Al-Cu en combinaison avec d'autres compositions ALD. / Corrosion protection by ultrathin (≤ 50 nm) alumina films deposited by atomic layer deposition (ALD) on copper and aluminium at 250°C was studied in 0.5 M NaCl aqueous solution by combining electrochemical and surface analytical methods. The study of ALD Al2O3 on Cu substrate included investigation of the effect of the coating thickness, the effect of an interfacial oxide, the effect of surface preparation and the durability of the coating. For ALD Al2O3 on Al substrate, the work focused on the examination of the effect of the deposited coating thickness. ALD alumina coatings showed excellent corrosion properties on electropolished copper substrates, while they failed to protect the annealed substrate, as a result of poor adhesion to a smoothened surface. Modification of interfacial native copper oxide by its pre-treatment led to better corrosion protection of ALD alumina on copper substrate. Despite its remarkable sealing properties on electropolished Cu substrate, corrosion protection of ALD alumina was not durable. Coating of Al substrate with ALD Al2O3 led to significant increase of polarization resistance. Better performance was obtained for 10 and 20 nm coatings on Al than on Cu. Apart from significant decrease of current, the pitting potential was increased in presence of 20 and 50 nm coatings, which was not achieved with 10 nm due to its low thickness. This study was a preliminary study for application of ALD alumina coatings for corrosion protection of Al-Cu alloys in combination with other ALD compositions.

Coatings are widely used to mitigate corrosion of structural steel in aggressive humid environments. However, the service life is often diminished in aggressive environments. Repair of coatings can be costly due to materials, labor and environmental controls. So, in search for novel coatings, Chemically Bonded Phosphate Ceramic (CBPC) coating was investigated for marine bridge application. The research on CBPC coating considered various exposure environments such as inland, beach, salt-fog, wet and alternate wet and dry exposure to identify the degradation mechanism. To assess the corrosion damage, the coating was evaluated by visual inspection, thickness, adhesion, microscopy and X-ray diffraction. The CBPC coating degraded initially due to alternate wet and dry exposure. The unreacted coating constituent reacted further in moist environment to form magnesium phosphate hydrate and enhanced bulk coating porosity. That facilitated moisture to the coating substrate and formed apparent protective iron phosphate hydrate by interaction with steel substrate to the coating constituents. Passive-like conditions were observed in wet test of chloride-free solutions for the formation of hydration product of magnesium but that type of hydrate was not identified in chloride solution for the apparent high solubility. The resolved coating impedance parameters were introduced to characterize the bulk ceramic degradation. The solution resistance did show a decrease for all samples due to leaching of minerals from the bulk material. The resolved pore resistance did not show any distinct change, though there was an indication of bulk coating degradation by MIP. Water saturation level during exposure was also calculated from the resolved capacitance. An approach was proposed to transfer the pre-exponential term, Yo to coating capacitance, CC for ceramic coating. The estimated value of the coating capacitance from the developed technique indicated early saturation with water during exposure due to the porosity. So, the extent of CBPC coating permeability and degradation could not be resolved only by conventional analysis approaches. However, the formation of iron hydrogen phosphate hydrate and iron phosphate hydrate from reaction of unreacted coating constituents was thought to provide apparent enhanced corrosion protection but there is a probability of steel substrate corrosion in extended exposure in humid environment.

No description available.

The optical properties of the absorber pipe in a parabolic trough collector isessential for the performance of the solar collector. The desirable propertiesare high absorptance (α) of solar radiation and low emittance (ε) of thermalradiation. A surface with these properties is known as a solar selective surface. There are several techniques used to produce selective surfaces, but one of the most common ones is electroplating. Research done by Vargas, indicates that optical properties of α = 0.98 and ε = 0.03 [1], which is superior to the best commercial alternatives (α = 0.95 and ε = 0.04 [2]), can be achieved by electroplating a Co-Cr coating on a stainless steel substrate. Additionally, Vargas used an electrolyte of trivalent chromium dissolved in a deep eutectic solvent, as opposed to the traditionally used aqueous electrolytes containing hexavalent chromium, which is toxic and carcinogenic. In this project, a coating of Co-Cr was electroplated on a stainless steel substratewith a method similar to that of Vargas in order to obtain a solar selective surface. The electrolyte was composed of ethylene glycol, choline chloride, CrCl3•6H2O and CoCl2•6H2O in a molar ratio of 16:1:0.4:0.2. The plating process was conducted using chronoamperometric electrodeposition with an applied potential of -1.2 V (against an Ag/AgCl reference electrode) for 15 min. The system was investigated using Cyclic Voltammetry (CV). The total absorptance was measured using UV-Vis spectroscopy, while the emittance was measured using an IR-thermometer. The microstructure and chemical composition was investigated using Scanning ElectronMicroscopy (SEM), Focused Ion Beam (FIB), Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. The thermal stability of the coating was investigated by exposingit to 400°C in air for 24 h. The electroplated coating is approximately 2.8 μm thick and exhibits a porousstructure with a surface of fine fiber-like flakes. The coating consists largely of Co hydroxides with low concentrations of Cr compounds, Co oxides and metallic Co. Hence, a satisfactory co-deposition was not accomplished, as the Cr concentration is low. The coating is not thermally stable up to 400°C, exhibiting signs of at least partially melting in the annealing process. The compounds in the coating were largely oxidized in the process. The electroplated surface does however exhibits strong selectivity, with a total solar absorptance of α = 0.952 and total emittance of ε = 0.32 at 160°C.

Les travaux de recherche présentés dans cette thèse concernent la mise au point et l’étude de résines polysiloxanes et de matériaux sol-gel hybrides permettant de développer de nouveaux revêtements de protection pour des applications spatiales. Il s’agit notamment d’assurer le contrôle thermique des véhicules spatiaux et la protection des polymères vis-à-vis de l’oxygène atomique pour les applications en orbite basse. Outre la stabilité en environnement spatial et les contraintes de mise en œuvre, les revêtements doivent présenter des caractéristiques innovantes (température de polymérisation modérée) et être élaborés à partir de matières premières facilement approvisionnables pour éviter tout risque d’obsolescence. / This work presents the formulation and the study of polysiloxane resins and hybrid sol-gel materials to develop new protective coatings resistant to space environment. Spacecraft thermal control and polymer protection towards atomic oxygen are required in Low Earth Orbit applications. Besides the stability in the space environment and the process requirements, the coatings have to exhibit innovative properties (such as a low curing temperature) and be composed of raw materials with easy supply in order to avoid any risk of obsolescence.

Trivalent chromium conversion coatings formed on Al and Al-Cu alloys has been investigated using high-resolution, analytical electron microscopy, atomic force microscopy, ion beam analysis, glow discharge optical emission spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, potentiodynamic polarization and electrochemical noise analysis. These coatings on the electropolished Al and sputtering-deposed Al consist of a chromium- and zirconium-rich outer layer and a thinner, aluminium-rich inner layer. Zirconium and chromium are presented in chemical states consistent with ZrO2, Cr(OH)3, Cr2(SO4)3, CrF3 and CrO3 or CrO42-. However, negligible amounts of hexavalent chromium species occurred in both coatings formed in de-aerated solution. On AA2024-T351 alloys, the coating above the second phase particles was thicker than that on the matrix due to the increased localized alkalinity. Moreover, the localized corrosion and copper enrichment of the matrix occurred at the coating base. The presence of copper resulted in a thinner coating at the matrix compared with superpure aluminium. An Fe(III)-containing D30 desmutter can effectively remove the protruded particles generated by alkaline etching. Moreover, a thinner oxide film on the D30-treated surface was evidenced to promote the coating initiation on the matrix. Further, the coating comprised the concentrated zirconium oxyfluorides and decreased contents of aluminium and copper. Coated alloys displayed a significantly enhanced corrosion protection, especially the cathoidc inhibition. In terms of coating post-treatments, the water immersion (40 ºC, pH 5) soon after conversion treatment revealed a simple but effective process to improve the fluoride enrichment in coatings and to enhance corrosion protection of freshly-developed coatings. Increasing concentration of solid-solution copper in sputtering-deposited alloys, in a range of 2, 24, 40 and 64 at.%Cu, significantly promotes the coating growth kinetics and an evident and a thicker corrosion layer by substrate dissolution was observed on Al-40 at.%Cu alloys. In addition, the relationship of copper-rich deposits with Cr(VI) transformation was demonstrated by Raman spectroscopy.