Recobrimentos de Ni/NiO em substrato de alumínio têm sido utilizados para se desenvolverem superfícies seletivas com alto desempenho para aplicações fototérmicas. Industrialmente essas superfícies têm sido empregadas em coletores solares. No presente trabalho, amostras de alumínio foram recobertas com Ni/NiO por processos químico e eletrolítico seguidos de tratamento térmico para oxidação. Os filmes foram produzidos em camada dúplex, sendo a primeira constituída de Ni e a segunda de NiO, a camada de anti-reflexão (AR). As espessuras dos filmes depositados têm cerca de 1,0µm. As microestruturas das amostras foram examinadas ao microscópio eletrônico de varredura (MEV). Análises de difração de raios X (DRX) identificaram as fases presentes. As amostras foram caracterizadas quanto às propriedades óticas nas regiões do visível e do infravermelho próximo. A absortância solar média dos recobrimentos eletrolíticos oxidados atingiu picos de 97,5%, enquanto a refletância no infravermelho distante foi de 12%.

The investigation of Ni/NiO coatings in aluminum substrate has been realized to develop high performance selective surfaces for photothermal applications. These absorber surfaces have been designed for industrial production. The present work describes Ni/NiO coatings in aluminum substrate obtained by chemical and electrolytic processes. Thermal treatments were used for oxidation. The first layer is Ni, the second one is NiO, the layer is an antireflectant (AR). The layer thicknesses are 1.0µm. The microstructures of the samples were examined by scanning electronic microscope (MEV). The X-ray diffraction (XRD) was used to identify the present phases. The optical properties, in some regions of visible and near infrared, allowed peaks of 97,5% for solar absorption and reflection of 12% for the electrolytic process oxidation.

The effects of combustion thermal spraying parameters namely combustion pressure, feeding rate, and carrier gas on the wear resistance, friction coefficient, and Knoop hardness of poly (ethylene terephthalate) (PET) films were investigated. The PET coatings were characterized by measuring the wear coefficients by calowear-type testing, the friction coefficients by a pin-on-disk test, and Knoop hardness. The abrasive wear and friction coefficients of the coatings were compared with the values of a post consumer PET bottle chip reference sample. The structural characteristics of the coatings were investigated by X ray diffraction. Statistical analysis of the results allowed for the systematic characterization of the influence of the process variables mentioned above on the coating wear, friction, and microhardness values. Specifically, this study shows that the process parameters affect the wear coefficient and Knoop hardness significantly, but not the friction coefficient. The degree of crystallinity of the PET coatings varied from 20 to 26%.

Recobrimentos poliméricos vêm sendo utilizados como proteção contra a corrosão e o desgaste. O objetivo desse trabalho foi a produção de recobrimentos de poli (tereftalato de etileno), PET, pós-consumo, de um copolímero do etileno com o ácido metacrílico, EMAA, e de blendas PET-EMAA em substrato de aço carbono, usando-se as técnicas de aspersão térmica a combustão e refusão. A resistência à degradação do conjugado foi avaliada usando-se testes de intemperismo com exposição à radiação ultravioleta e umidade. As análises térmicas de calorimetria exploratória diferencial e testes de tração foram utilizados na caracterização das amostras antes e após os testes de degradação. A deformação na ruptura das amostras recobertas sofreu redução após o envelhecimento. A temperatura de transição vítrea dos recobrimentos de blendas poliméricas aumentou após exposição na câmara de intemperismo.

Polymer coatings have been used as protection against corrosion and wear. The aim of this work was to produce coated steel with a polymeric film using a low-speed-combustion thermal spraying and fusion technique, and to evaluate its chemical resistance to radiation and moisture. The substrate used was carbon steel, coated with a recycled poly (ethylene terephthalate), PET, and a copolymer of ethylene and methacrylic acid, EMAA, and PET-EMAA blends. The degradation resistance of the material was evaluated using an ultra-violet condensation-weathering test. The characterization of the composite was done using differential scanning calorimetry (DSC) and tensile measurements. The strain at the breakage of the coated samples decreased after aging. The glass transition temperature of the blended coatings increased after the aging process.

O mexilhão dourado ou Limnoperna fortunei é um organismo invasor que tem causado grandes prejuízos a sistemas de captação de água e usinas hidroelétricas, sendo que, mais recentemente, vem causando danos ao deslocamento de embarcações fluviais em águas do Pantanal Mato-Grossense. No presente trabalho, foi feito um estudo, em laboratório e em campo, de materiais antiincrustantes. A relação entre a força de desligamento do mexilhão dourado e a energia livre de superfície foi avaliada. Foram selecionados materiais com baixa energia de superfície como polímeros e alta energia de superfície como materiais metálicos. Qualitativamente, o desempenho do aço inoxidável e o desempenho do cobre, testados em laboratório e em campo, se apresentaram, relativamente, consistentes entre si e com dados da literatura. E, com os dados obtidos, percebe-se que há relação entre energia livre de superfície e o caráter antiicrustante do Limnoperna fortunei, mas, até o momento, não se pode afirmar que se trate de uma correlação linear, pois pode ser que outros fatores dos materiais estejam influenciando no comportamento dos organismos. Os dados sugerem, ainda, que a componente ligação de hidrogênio apresenta o principal efeito em termos de energia livre de superfície.

The Golden Mussel or Limnoperna fortunei is an invading organism that has caused much damage to water supply systems and hydroeletric power plants, and more recently, it is also causing damage to boat transportation in the "Pantanal" waters of Mato Grosso. The present work, a laboratory and field study of the detachment force of the Golden Mussel, was carried on aiming at the understanding of its relationship with surface free energy and its components. The materials were chosen to cover an ample range of surface free energy, including materials with low surface energy, as polymers, and high surface energy, as the metallic materials. Qualitatively, the performance of stainless steel and copper, tested in the laboratory and field, are consistent with respect to literature results. A linear correlation between surface free energy and mussel detachement force was verified but with a poor correlation coefficient, the strongest effect being due to hydrogen bonds.

Thermal spraying allows the production of overlay protective coatings of a great variety of materials, almost without limitations as to its components, phases and constituents on a range of substrates. Wear and corrosion resistant coatings account for significant utilization of thermal spray processes. Besides being a means to evaluate the coating tribological performance, erosion testing allows also an assessment of the coating toughness and adhesion. Nevertheless, the relationship between the erosion behavior of thermal sprayed coatings and its microstructural features is not satisfactorily understood yet. This paper examines room temperature solid particle erosion of zirconia and alumina-based ceramic coatings, with different levels of porosity and varying microstrucutre and mechanical properties. The erosion tests were carried out by a stream of alumina particles with an average size of 50 µm at 70 m/s, carried by an air jet with impingement angle 90°. The results indicate that current erosion models based on hardness alone cannot account for experimental results, and, that there is a strong relationship between the erosion rate and the porosity.

The increase of the petroleum cost in the last decades revitalized the interest for lighter and more economic vehicles. Simultaneously, the demand for safe and unpolluted transports grows. The application of thermal barriers coatings (TBC) on combustion chamber and on flat surface of pistons reduces the thermal losses of the engines, resulting in higher temperatures in the combustion chamber. This fact contributes to the improvement of the thermal efficiency (performance) and for the reduction of incomplete combustion. Supported on these initial ideas, thermal barriers coatings constituted by CaO partially stabilized zirconia were produced and their microstructure examined. This coating still presents some drawbacks associated with thermal stresses and permeability to oxidizing gases, which will, eventually, lead to failure of the TBC by spallation. The failure may, in general, be associated to one of three factors: oxide growth at the ceramic-metal interface, formed during thermal cycling; stress build-up due to thermal cycling; and metal-oxide interface segregation, mainly of S. However, it is also relevant to understand the behavior of TBC's under isothermal oxidation. Therefore, this paper investigates the effect of oxidation on the adherence of thermal sprayed coatings. The adherence was measured by linear scratching tests, widely used for thin coatings. Plasma sprayed calcia partially stabilized zirconia was used as TBC and Ni-5%Al as bond coat, with Al substrates. Coated samples were submitted to heat treatments at 500 °C, for 50 h. The microstructures were examined by optical light microscopy, X-ray diffraction, profilometry and SEM.

Neste trabalho foram analisados recobrimentos de poli(tereftalato de etileno), PET, depositados em aço carbono através da técnica de aspersão térmica à combustão, e produzidos a partir de pós oriundos de processos de moagem, em moinho de bolas e de facas, de garrafas de PET pós-consumo. Algumas condições de moagem foram testadas, tendo-se obtido pós com diferentes características morfológicas. As características morfológicas dos pós e dos recobrimentos foram avaliadas por microscopia óptica e eletrônica, tendo-se observado que o recobrimento apresentava bolhas, provavelmente devido à degradação do polímero. Além disto, os recobrimentos produzidos, bem como as amostras de pó, foram caracterizados por espectroscopia na região do infravermelho, por calorimetria exploratória diferencial e através da determinação de viscosidade intrínseca em solução. Os resultados obtidos mostraram que é possível a produção de aço carbono recoberto com PET através da técnica de aspersão térmica, sendo que o grau de degradação, a morfologia e a distribuição granulométrica dos pós utilizados influenciaram significativamente as características e propriedades dos recobrimentos formados.

The main purpose of this work was to study the production of a thermal spray coated poly(ethyleneterephthalate) steel. Poly(ethylene terephthalate) coatings were made of a thin grinding waste produced by a PET recycling company, and of a PET powder, which was obtained by grinding post-consumer beverage bottles. Some grinding conditions, using a ceramic ball mill, were studied. Scanning Electronic Microscopy (SEM) and optical microscopy (OM) were used in the study of powder and coating morphologies, and this analysis showed that PET coating presents bubbles due to polymer degradation. PET powder and coating characteristics were investigated using Differential Scanning Calorimetry (DSC) and measurements of intrinsic viscosity. It was observed that the powder morphology and the degradation and the size distribution of the PET powder affect significantly the characteristics and properties of coatings.