Atualmente o ramo industrial tem voltado grande parte de suas atenções para situações ambientais. Um dos grandes problemas mundiais encontra-se no uso de cromo hexavalente, prejudicial à saúde humana, além de contaminar leitos e rios por ser solúvel em água e a fosfatização que é responsável pela eutrofização das águas. Novos processos sustentáveis têm sido estudados para reduzir os impactos ambientais causados por esses tratamentos, dentre os quais podemos citar os revestimentos chamados de nanocerâmicos, por formarem camadas nanoestruturadas de óxido de zircônio na superfície do substrato. Vários parâmetros influenciam na formação da camada (substrato, pH, concentração, tempo). O trabalho teve como objetivo o estudo da influência dos parâmetros no desempenho contra a corrosão do revestimento formado por camadas de conversão obtidas a base de ácido hexafluorzircônio em aço galvanizado. O comportamento eletroquímico foi analisado através dos ensaios de potencial de circuito aberto, espectroscopia de impedância eletroquímica e polarização potenciodinâmica. Também foram realizados ensaios de avaliação anticorrosiva com adição de um revestimento final (tinta comercial) sobre a camada de conversão para avaliar o comportamento como revestimento. A partir dos ensaios realizados chega-se a parâmetros que foram considerados ideais e com melhor desempenho. Com isso obtém-se um pré-tratamento capaz de fazer frente a processos convencionais de cromatização e fosfatização. / Currently, the industrial sector has turned much of their attention to environmental situations. One of the great global problems is the use of hexavalent chromium, harmful to human health and pollute rivers and beds being soluble in water and phosphate which is responsible for water eutrophication. New sustainable processes have been studied to reduce the environmental impacts caused by these treatments, among which we can mention the nanoceramic coatings called for forming nanostructured layers of zirconium oxide on the substrate surface. Several parameters influence the layer formation (substrate, pH, concentration, time). The work aims to study the influence of parameters on the performance against corrosion coating formed by conversion layers obtained acid based hexafluorzirconic on galvanized steel. The electrochemical behavior was analyzed through the trials of open circuit potential data, electrochemical impedance spectroscopy and polarization. Also evaluation trials were performed with addition of an anti-corrosive top coat (commercial ink) on the layer of conversion coating painted as to evaluate the corrosion resistance. From the tests to parameters that were considered ideal and best performance. Thus is obtained a pretreatment able to cope with the conventional processes chromate and phosphate.

Metais são bastante usados como materiais implantáveis, principalmente para dispositivos feitos na área de ortopedia. Há uma constante relação dos processos de corrosão nesse biomateriais com a agressividade do meio fisiológico. Usando quatro tipo de metais e ligas metálicas – titânio puro, liga de titânio, aço inoxidável de baixo carbono e liga de cobalto – o processo de corrosão foi estudado. Além disso, o desempenho desses materiais revestidos com nitreto de titânio foi avaliado. Dois processos de revestimento por PVD – evaporação e magnetron sputtering – foram executados, verificando a eficiência desses materiais em meio fisiológico - O melhor comportamento se deu para o revestimento obtido por evaporação. O mecanismo de corrosão predominante para as amostras foi indicado. / Metals are very much used as implantable materials mainly for the construction of devices orthopaedic area. There is a constant concern about the corrosion process in those metallic biomaterials due to the aggressiveness of the physiological environment. By using four types of metals and metallic alloys – pure titanium, titanium alloy, low carbon stainless steel and cobalt-chromium alloy – the corrosion process in physiologic environment has been studied. Also, the performance of such materials coated with titanium nitrate was evaluated. Two PVD coating methods – evaporation and magnetron sputtering – were performed, and the efficiency of those materials in physiologic medium was verified. The best behaviour was found by the evaporation coating method. The predominant corrosion mechanism for coated samples was suggested.

Le traitement de la corrosion constitue un enjeu économique, environnemental et de sécurité sanitaire. Plus largement utilisée à l’échelle industrielle, la protection par revêtements consiste à isoler le métal du milieu agressif par une couche adhérente, continue et imperméable. Ils doivent répondre à trois propriétés majeures : 1) être fortement adhérent au substrat métallique, 2) posséder de bonnes propriétés barrière pour limiter la pénétration de l’eau et des espèces agressives et 3) apporter un rôle d’inhibition de la corrosion. Cependant, la protection des surfaces métalliques par les techniques actuelles génère une pollution notable liée à l’usage de chromates. L’utilisation de polymères biosourcés et solubles en milieu aqueux serait un challenge et contribuerait à préserver l’environnement. Les polysaccharides comme le chitosane sont des macromolécules biodégradables et respectueuses de l'environnement possédant des propriétés d’anticorrosion et sont donc des alternatives envisageables. Ces travaux de thèse portent sur le développement de revêtements anticorrosion à base de chitosane. Le chitosane possède deux points faibles pour être utilisé comme revêtement contre la corrosion : 1) une adhésion insuffisante sur la surface des matériaux et 2) un caractère hydrophile. En conséquence, le chitosane a été modifié chimiquement afin d’augmenter son adhésion et ses propriétés barrières. Afin d’améliorer son adhésion sur des substrats métalliques, des groupements de type acide phosphonique ont été ajoutés via la réaction de Kabachnik-Fields sur le chitosane. L’élaboration d’un chitosane possédant des fonctions catéchol a été également discutée. Dans un premier temps, le chitosane modifié a été testé et caractérisé par spectroscopie d’impédance électrochimique (SIE) en tant qu’inhibiteur de corrosion puis des revêtements à partir de ce même chitosane ont été réalisés et leurs protections contre la corrosion ont été évaluées. Deux approches de mise en forme des revêtements ont été testées : par dip-coating et par la technique Layer-by-Layer (LbL). Différentes voies de fonctionnalisation du chitosane ont également été présenté afin d’augmenter les propriétés barrière du revêtement. La chimie de phthaloylation du chitosane a été décrite puis le greffage de chaînes hydrophobes a été étudié. / Corrosion treatment is an economic, environmental and health safety issue. More widely used on an industrial scale, coating protection consists in isolating the metal from the aggressive medium by an adherent, continuous and impermeable layer. They must have three major properties: 1) be strongly adherent to the metallic substrate, 2) have good barrier properties to limit the penetration of water and aggressive species and 3) provide a role in inhibiting corrosion. However, the protection of metal surfaces by current techniques generates significant pollution due to the use of chromates. The use of bio-based and soluble polymers in aqueous media would be a challenge and would contribute to preserving the environment. Polysaccharides such as chitosan are biodegradable and environmentally friendly macromolecules with anticorrosive properties and are therefore possible alternatives. These theses focus on the development of anticorrosion coatings based on chitosan. Chitosan has two weak points for use as a coating against corrosion: 1) insufficient adhesion on the surface of the materials and 2) hydrophilicity. As a result, chitosan has been chemically modified to increase its adhesion and barrier properties. In order to improve its adhesion on metal substrates, phosphonic acid groups have been added via the Kabachnik-Fields reaction on chitosan. The development of a chitosan with catechol functions was also discussed. Initially, the modified chitosan was tested and characterized by electrochemical impedance spectroscopy (EIS) as a corrosion inhibitor and coatings based on the same chitosan were made and their corrosion protection evaluated. Two approaches of coating elaborations were tested: dip-coating and Layer-by-Layer (LbL). Different ways of functionalizing chitosan have also been presented to increase the barrier properties of the coating. Phthaloylation chemistry of chitosan was described and hydrophobic chain grafting was studied.

<p>Development of durable icephobic coating and reduction of ice accumulation on the product surfaces has proven to be a challenging task in the past decade. Considering the challenges posted during ice storms and existing limitations to the state of the art, development of durable icephobic coating which can provide low ice adhesion strength and less ice weight increase is a critical milestone for industries and research communities. To obtain durable icephobic coating, high temperature and weather resistance Fluoro-Ethylene-Alkyl-Vinyl-Ether (FEVE) binder was selected to design a smooth and superhydrophobic coatings. These coatings were benchmarked against commercially available silicone epoxy and superhydrophobic coatings and validated its surface roughness, surface wettability and icephobic performance such as ice adhesion strength and ice accumulation. To evaluate coatings thermal durability, targeting power transmission line application, these coatings were exposed to extreme thermal ageing conditions (200 ^oC for 60 days) and retention of icephobic performance were measured. Though, commercial coatings have provided better icephobicity at unaged condition, after high temperature heat ageing these coatings icephobic performance were deteriorated significantly. However, FEVE based coating had retained its surface characteristics and icephobic properties after aggressive thermal ageing.</p>

>Magister Scientiae - MSc / Without reverting to encapsulation, organic bulk - heterojunction solar cells can be protected from the oxidation of the highly reactive low work function cathode metal electrode, by the deposition of metal oxide buffer layers onto an indium-tin oxide (ITO) substrate. The zinc-oxide (ZnO) or titanium dioxide (TiO2) layer can serve as an electron collecting contact. In such a case the ordering of layer deposition is inverted from the traditional layer sequencing, using an additional effect of the metal oxide layer acting as a hole blocking contact

Microbial cross-contamination remains an on-going challenge in the food sector despite implemented sanitation programs. Antimicrobial coatings with inherent self-sanitizing properties have been explored to enhance current cleaning practice and support food safety. Prior work has demonstrated successful incorporation of dual antimicrobial characters, cationic polymers and N-halamines, into one coating system. In addition to the rechargeable nature of N-halamines, the coating was reported to exhibit biocidal effects due to the inherently antimicrobial cationic moieties and the chlorinated N-halamines. However, while these polymer coatings were able to retain antimicrobial activity after repeated chlorination, signs of hydrolysis was observed for the N-halamine bonds, indicating potential issues for long-term usage. Herein, we introduced varied molecular weight cross-linkers in an adaption of the established fabrication method to evaluate cross-linker molecular weight (styrene maleic anhydride (SMA) of 6, 8, 120, 250 kDa) influence on surface properties of the coating. All antimicrobial polymer coatings exhibited similar FTIR spectra, with a prominent absorption band at ~1650 cm-1 suggesting successful cross-link of the polyethyleneimine and SMA. Surface concentration of primary amines ranged from 350-900 nmol/cm2, and N-halamines from 90-130 nmol/cm2. Surface energy decreased with increasing molecular weight of SMA, but were not statistically different from one another. In the end, optimal cross-linker molecular weight was determined based on antimicrobial performance, where the coated PPs with 6 kDa SMAs demonstrated enhanced biocidal effects against E. coli O157:H7 in its chlorinated form. Further, the antimicrobial coating demonstrated efficacy of ~3 to >5 log reductions of microbial load in its unchlorinated and chlorinated form against E. coli O157:H7, L. monocytogenes, and P. fluorescens. Storage studies support the stability of the chlorinated halamines, with full retention of chlorinated N-halamines over a 24 h study (representative of time between sanitation cycles). These results support the potential application of this antimicrobial polymer coating in food processing and handling operations, in support of reducing cross-contamination of spoilage and pathogenic microorganisms.

No description available.

The aim of this master's thesis is to deal with main thread production methods and to study the influence of coatings on tap cutting performance. The high-speed steel cutting taps with different PVD coatings (Physical Vapour Deposition) were tested, while the same cutting conditions were set. Cutting torques were measured and analysed, which together with the results of evaluation of tool wear led to conclusion.

The diploma thesis in the first part deals with a theoretical description of coating technologies, textile materials used in coatings, types of coated polymers and properties of coatings - especially adhesion. The experimental part of the work is devoted to the preparation of textile coatings from polyester fabric and coating based on addition silicone. Using the developed method of sample preparation for T-peel testing of the adhesive strength, the improvement of the adhesion of the coating by chemical adhesion with the support of adhesive agents was studied. The second method studied the change in compactness and adhesion of the coating to the fabric after shaking as a function of breathability. The influence of side reactions of reagents on silicone cohesion was studied by preparing dogbones for testing tensile-deformation properties. The research also included the characterization of silicone samples using ATR-FTIR, monitoring the weight gain and thickness of the fabric after coating, the feel and color stability of the applied fabric and observing the coating under an optical microscope.

The master´s thesis deals with a process called cold kinetic deposition technology. Using this technology, a copper layer was formed on a sample with an aluminium base by high-pressure cold spraying at a pressure of 25 bar. In the experimental part, the influence of corrosion degradation in the salt chamber was assessed at the time cycles of 100 h, 200 h and 300h, where changes in internal and surface resistances before and after corrosion were measured. Subsequently, the analysis of corrosion products was performed, where the extent of corrosion attack was determined using an electron microscope. These methods led to a final evaluation of the boundary limits of the applied coating layer by cold kinetic deposition, after the effect of corrosion. Finally, a theoretical application of this technology was suggested. It was discovered that the sample placed and left in the corrosion chamber for the longest time was the most affected by corrosion. Finally, a theoretical application of cold kinetic deposition was proposed.