The object of this research is to produce and characterise some coated powers for use in the powder metallurgy and related industries. The study introduces very briefly general powder metallurgy techniques and raw materials. A review of coating techniques is given, followed by a discussion of techniques for handling particulate substrates in chemical reaction systems. A discussion of the fluidised bed chemical reactor and electrode, and mechanically stirred vessels is presented.

This thesis describes investigations into a number of coating processes using experimental, analytical and computational techniques. The first problem, considered experimentally, is that of reverse roll coating with a liquid reservoir positioned directly above horizontally aligned rollers. Measurements of the film thickness as a function of the height of fluid in the reservoir and speed ratio are presented. When the wetting line is located downstream of the nip, either a decrease in the height of the associated hydrostatic head or an increase in the speed ratio causes a reduction in the thickness of the outgoing film. However, when the wetting line is located upstream of the nip the opposite is found to be true. The bead-break instability in forward meniscus coating is considered both experimentally and analytically. Agreement between predictions from a simple mathematical model of the stable bead and experimentally determined meniscus positions is seen to be excellent. A perturbation hypothesis is used to predict the onset of the bead-break instability, at which the upstream meniscus accelerates rapidly towards the downstream one, so the two collide and the bead collapses. The results from the model compare well with experiments. An outline of a method for using the bead-break instability as a design criterion is also presented. Typically in a slot, blade or knife coater the downstream meniscus is assumed to pin at a corner of the coating device. In chapter 5, a series of experiments and a corresponding computational study, are presented which illustrate that the meniscus can advance up the face of such coating devices (in this case a roll-flat plate system). Reducing the corner angle is seen to reduce the size of the climb region and the associated recirculation at this point at the downstream meniscus. It is also shown that the meniscus can detach from the corner and retreat into the gap, which can in turn give rise to the ribbing instability. An offset gravure coating arrangement is considered in chapter 6. The coating arrangement is split into two areas of study - the offset gravure nip and the kiss coating bead. An experimental investigation of the offset nip with the two rolls vertically aligned and running at the same speed in forward mode reveals two ways in which the metered film thickness can be influenced. Either increasing the nip force by pressing the two rolls together or decreasing the roll speeds causes a reduction in the metered film thickness. At higher speeds the metered film thickness is observed to asymptote to a limiting value, the value of which depends on the gravure pattern. The reverse mode kiss coating bead operating at speed ratios greater than one is also investigated. Experiments reveal that under these conditions, all the fluid is transferred from the roll surface to the web and the two make contact due to the generation of a sub-ambient pressure field within the bead. Two models based on lubrication theory are derived, one assuming an infinitely tensioned web and a second that incorporates the effect of web flexibility. The latter is found to give much better agreement with the experimental data. Finally a perturbation hypothesis is applied to these to models in order to predict the onset of the ribbing instability, both of which are found to give reasonable agreement with the experimental data. Finally, the results of a systematic experimental investigation of reverse mode direct gravure coating is reported, where the web runs directly over a gravure roll surface. This wide ranging parametric study illustrates the effect of the operating parameters on the final film thickness. Key findings are that speed ratio, fluid properties and cell shape and size can significantly influence the final film thickness. For a fixed roll speed it is observed that as the web speed is increased the gravure bead becomes unstable. This results in streaking on the web, and gives an upper limit to the speed ratio.

No description available.

No description available.

O uso de pinturas \"frias\", em coberturas e fachadas, é uma estratégia utilizada para melhorar a sensação térmica dos usuários por meio do aumento desempenho térmico das edificações, potencializar a eficiência energética e mitigar ilhas de calor. Por outro lado, a exposição ao longo do tempo pode alterar a capacidade refletiva dessas superfícies, devido à deposição de sujidades e crescimento microbiológico. Esse estudo tem o objetivo de avaliar a manutenção da capacidade refletiva, a alteração da cor, do aspecto e da emissividade de pinturas expostas por três anos ao envelhecimento natural. Para esse estudo foram produzidos, em laboratório, dois grupos de tintas tipo premium, para uso em superfícies externas de fachadas e coberturas, com dois acabamentos: acetinado (PVC 30%) e fosco (PVC 50%), nas cores: branco, cinza, amarelo e marrom, que são cores usualmente utilizadas em fachadas e coberturas no Brasil. Um grupo é composto por tintas convencionais, formuladas com pigmentos inorgânicos naturais e orgânicos. O outro grupo é composto por tintas formuladas com pigmentos, com alta capacidade de refletância solar na região do infravermelho próximo, conhecidos como pigmentos \"frios\". Ainda há um terceiro grupo de tintas que foi coletado do mercado e utilizado como referência. Na exposição ao envelhecimento natural o microclima é um dos fatores determinantes no tipo de degradação da pintura, por isso esse estudo contempla os três microclimas predominantes do Estado de São Paulo: rural (Pirassununga), urbano (São Paulo) e costeiro (Ubatuba). Nesse trabalho estão sendo apresentados os resultados obtidos com três anos de exposição e já foi possível observar redução da refletância inicial, alteração de cor (diminuição do índice L luminosidade) e indícios de crescimento microbiológico. / The application of cool paints, on roofs and facades components, is a strategy to improve indoor thermal comfort for users in rooms that are not air conditioned. Increasing the thermal performance of buildings, enhance thermal efficiency and mitigate urban heat island. On the other hand, the exposure of paints over time can change reflectance capability of the surface, due to dirty deposition and microbiological colonization. The objectives of this study is evaluate the level of maintenance of reflectance, emissivity, color and visual aspects of paints after three years of natural aging exposure. Two groups of \"premium\" type paints, formulation recommended for applications on facades and roofs, we prepared in laboratory. Each group of paints was produced with two sheen type, two ratios pigment to binder, gloss finish (PVC 30%) and silk finish (PVC 50%), for the colors white, yellow, grey and brown, which are the most used colors in facades and roofs in Brazil. One group, the standard paint, was produced with natural inorganic and organic pigments and the other group was produced with cool pigments, which has high solar reflectance capacity in the near-infrared spectrum. Additionally, a third group of paints was acquired from the market and used as reference data. The microclimate is one of the key factors for paint degradation by natural aging, so in this study was considered three major microclimates of São Paulo State: rural (Pirassununga City),urban (São Paulo city) and oceanic climate (Ubatuba). The present study shows the results of the paints after three years exposure, which was observed significant reduction in reflectance, color change (reduction of the luminance L index) and evidences of microbiological colonization.

O uso de pinturas \"frias\", em coberturas e fachadas, é uma estratégia utilizada para melhorar a sensação térmica dos usuários por meio do aumento desempenho térmico das edificações, potencializar a eficiência energética e mitigar ilhas de calor. Por outro lado, a exposição ao longo do tempo pode alterar a capacidade refletiva dessas superfícies, devido à deposição de sujidades e crescimento microbiológico. Esse estudo tem o objetivo de avaliar a manutenção da capacidade refletiva, a alteração da cor, do aspecto e da emissividade de pinturas expostas por três anos ao envelhecimento natural. Para esse estudo foram produzidos, em laboratório, dois grupos de tintas tipo premium, para uso em superfícies externas de fachadas e coberturas, com dois acabamentos: acetinado (PVC 30%) e fosco (PVC 50%), nas cores: branco, cinza, amarelo e marrom, que são cores usualmente utilizadas em fachadas e coberturas no Brasil. Um grupo é composto por tintas convencionais, formuladas com pigmentos inorgânicos naturais e orgânicos. O outro grupo é composto por tintas formuladas com pigmentos, com alta capacidade de refletância solar na região do infravermelho próximo, conhecidos como pigmentos \"frios\". Ainda há um terceiro grupo de tintas que foi coletado do mercado e utilizado como referência. Na exposição ao envelhecimento natural o microclima é um dos fatores determinantes no tipo de degradação da pintura, por isso esse estudo contempla os três microclimas predominantes do Estado de São Paulo: rural (Pirassununga), urbano (São Paulo) e costeiro (Ubatuba). Nesse trabalho estão sendo apresentados os resultados obtidos com três anos de exposição e já foi possível observar redução da refletância inicial, alteração de cor (diminuição do índice L luminosidade) e indícios de crescimento microbiológico. / The application of cool paints, on roofs and facades components, is a strategy to improve indoor thermal comfort for users in rooms that are not air conditioned. Increasing the thermal performance of buildings, enhance thermal efficiency and mitigate urban heat island. On the other hand, the exposure of paints over time can change reflectance capability of the surface, due to dirty deposition and microbiological colonization. The objectives of this study is evaluate the level of maintenance of reflectance, emissivity, color and visual aspects of paints after three years of natural aging exposure. Two groups of \"premium\" type paints, formulation recommended for applications on facades and roofs, we prepared in laboratory. Each group of paints was produced with two sheen type, two ratios pigment to binder, gloss finish (PVC 30%) and silk finish (PVC 50%), for the colors white, yellow, grey and brown, which are the most used colors in facades and roofs in Brazil. One group, the standard paint, was produced with natural inorganic and organic pigments and the other group was produced with cool pigments, which has high solar reflectance capacity in the near-infrared spectrum. Additionally, a third group of paints was acquired from the market and used as reference data. The microclimate is one of the key factors for paint degradation by natural aging, so in this study was considered three major microclimates of São Paulo State: rural (Pirassununga City),urban (São Paulo city) and oceanic climate (Ubatuba). The present study shows the results of the paints after three years exposure, which was observed significant reduction in reflectance, color change (reduction of the luminance L index) and evidences of microbiological colonization.

Sais quaternários de amônio são amplamente usados como agentes antissépticos, desinfetantes, detergentes e preservantes. Além disso, sais quaternários de amônio são frequentemente utilizados como algicidas, sendo o cloreto de dodecil dimetil benzil amônio (Cloreto de benzalcônio) o mais efetivo contra estes microorganismos. No entanto sua aplicação como algicida de superfícies é limitada, devido a sua alta hidrofilicidade, ocasionando uma alta lixiviação deste composto quando a superfície é exposta à alta umidade e intempéries de clima tropical. Atualmente compostos como Diuron e S-Triazina são empregados como algicidas, considerados de baixa lixiviação. No entanto, altos níveis de concentração destes biocidas foram detectados em regiões costeiras evidenciando a lixiviação destes biocidas, quando utilizados em tintas para casco de navio. Assim surge a necessidade do desenvolvimento de um algicida para suprir as deficiências de lixiviação dos compostos empregados atualmente. Materiais como as argilas organofílicas são uma excelente alternativa, pois são altamente hidrofóbicas. Portanto sintetizou-se neste trabalho uma argila organofílica utilizando-se cloreto de benzalcônio, a qual foi utilizada em uma formulação de tinta imobiliária. O material foi caracterizado pelas técnicas de difração de Raios X e análise termogravimétrica. Um filme de tinta foi submetido a uma câmara de lixiviação, simulando a ação da chuva. Após a lixiviação o filme de tinta seguiu para testes microbiológicos, para verificar se a superfície ainda possui proteção microbiana. As algas testadas foram das espécies Phormidium cebenense, Trentepohlia odorata, Chlorella sp e Scenedesmus quadricauda colocadas num pool de algas. Através das análises de Difração de Raios X e termogravimétrica é possível determinar a estrutura e quantificar o teor cloreto de benzalcônio no material, respectivamente. Os testes microbiológicos e de lixiviação avaliaram a capacidade biocida assim como a resistência à intempérie do material. O novo composto sintetizado neste trabalho apresentou um alto potencial para uso como agente microbiano em tintas. / Quaternary ammonium compounds are widely used as antiseptic agents, disinfectants, detergents and preservatives. In addition, quaternary ammonium compounds are often used as algaecides, and dodecyl dimethyl benzyl ammonium chloride (benzalkonium chloride) is the most effective against these microorganisms. However benzalkonium chloride is not used as surface algaecide compound due its high hydrophilic, bring on high leaching of this compound when the surface is exposed to high humidity and severe weather from tropical climate. Currently, compounds such as diuron and s-triazine are used as microbial agent, considered low leaching. However diuron and s-triazine were detected in coastal regions in high levels concentration showing the leaching of these biocides when used in antifouling paints in ships. Considering these, it can be observed the necessity to develop a new algaecide to overcome the failings of leaching of the compounds used nowadays. Material as organoclay is an excellent alternative because they are highly hydrophobic. Therefore in this work was synthesized a new nanomaterial using benzalkonium chloride, which was applied in a house paint formulation. The material was characterized by the techniques of X-ray diffraction and thermogravimetric analysis. A film coating was placed in a leaching chamber, simulating the action of rain. After leaching the coating film was applied to microbiological tests to check if the surface still had microbial protection against the following algae species: Phormidium cebenense, Trentepohlia odorata, Chlorella sp and Scenedesmus quadricauda; placed in a pool of algae. It was possible to determine the structure and quantify the amount of benzalkonium chloride in the material through X-ray Diffraction and Thermogravimetric analysis, respectively. The biocide capabilities as well as the resistance to weathering of coating with the material were analyzed by microbiological and leaching test, respectively. The new compound developed in this study has a high potential to be used as microbial agent in paints.

Following an earlier study of different coloured pigments used in Roman wall-plaster paintings, this research project investigates the use of the synthetic pigment commonly known as Egyptian Blue in Romano-British wall-plaster paintings. Samples of Egyptian Blue pellets were obtained from excavations at the Romano-British sites of Fishbourne Roman Palace, near Chichester, Piddington near Northampton, Turners Hall Farm, near St Albans, and from excavations at Verulamium (Roman St Albans). The aim of this study is to determine the chemical composition, fabric and texture of each pellet as well as attempting a textural and geochemical classification of the pellets, using well established analytical techniques, particularly LA-ICP-MS and SEM-EDAX. The colour of the pellets was examined and identified using the Munsell Book of Color (Matte Finish Collection) 1973. The results of the analysis of the Egyptian Blue pellets found on Romano-British sites showed that differing amounts of silica, copper, calcium, as well as smaller amounts of other elements, were used in their manufacture. Most of the pellets examined appear to have been manufactured locally, though some were almost certainly imported. Experimental work was undertaken, both in the laboratory and out in-the-field where a reconstructed Bronze Age Clamp Kiln and an Iron Age Belgic Kiln were used, to reproduce the synthetic pigment Egyptian Blue, using a recipe similar to that used by earlier investigators. Such recently manufactured Egyptian Blue pellets were applied, as a pigment, to damp lime mortar, in an attempt to correlate the achieved colour with the firing time. Similar techniques were used in an attempt to ascertain the nature of the pigments used on the small fragments of painted wall-plaster found in a back filled trench, from Wheeler's 1930 - 33 excavations at Verulamium. On two of the fragments gas chromatographic analysis was applied to determine the nature of the binding material that might have been used. This study is thought to be the first in-depth investigation of Romano-British Egyptian Blue pellets and thereby contributes to the art history and archaeological knowledge of this period.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Esse trabalho à o inÃcio de uma nova linha de pesquisa do laboratÃrio de eletroquÃmica da UFC que busca desenvolver tintas com alternativas de utilizaÃÃo de pigmentos tÃxicos e matÃrias-primas ditas ecologicamente corretas. Neste sentido este trabalho descreve o desenvolvimento e estudo de tintas ecologicamente corretas formuladas usando fosfato de zinco (ZP), molibdato de zinco (ZM), molibdato de zinco e cÃlcio (ZCM), fosfomolibdato de zinco (ZMP) e fosfomolibdato de zinco e cÃlcio (ZCMP), como alternativas seguras aos pigmentos anticorrosivos tradicionais (chumbo, cromo e outros metais pesados). Adicionalmente, consideraÃÃes ambientais tÃm limitado o uso de tintas organossolÃveis devido estas contribuÃrem para a poluiÃÃo atmosfÃrica e problemas de saÃde. Assim, resinas epÃxis hidrossolÃveis foram usadas na formulaÃÃo das tintas epÃxis anticorrosivas. O principal objetivo deste trabalho à empregar pigmentos de molibdatos para avaliar sua eficiÃncia contra corrosÃo em tintas hidrossolÃveis. As propriedades inibidoras dos pigmentos foram avaliadas por curvas de polarizaÃÃo potenciodinÃmica, monitoramento do potencial de circuito aberto e perda de massa por imersÃo de substratos ferrosos (SAE 1010) em soluÃÃo saturada dos pigmentos em 10-2 mol dm-3 NaCl. A caracterizaÃÃo fÃsico-quÃmica dos produtos de corrosÃo foi avaliada por microscopia eletrÃnica de varredura, energia dispersiva de raios-X e difraÃÃo de raios-X. Todos os testes mostraram que os pigmentos fosfomolibdatos apresentaram as melhores propriedades inibidoras de corrosÃo. Todas as tintas foram formuladas com 16% (v/v) de resina epÃxi, 7,5% (v/v) de pigmentos anticorrosivos, e demais componentes e aditivos para manter a relaÃÃo de PVC/CPVC em 0,8. A espessura da pelÃcula seca de tinta nos painÃis ficou em aproximadamente 120 μm. O desempenho das tintas foi monitorado por impedÃncia eletroquÃmica durante os testes de imersÃo, de exposiÃÃo atmosfÃrica e de cÃmara acelerado de nÃvoa salina. A estabilidade tÃrmica foi estudada por anÃlise tÃrmica e calorimetria exploratÃria diferencial. Os diagramas de impedÃncia de todas as tintas mostraram somente um arco capacitivo, com os valores de impedÃncia maiores que 109 Ωcm2. os valores de capacitÃncia variaram entre 10-6 e 10-10 Fcm-2. Os resultados sugerem que a combinaÃÃo do molibdato e fosfato fornecem as melhores propriedades inibidoras Ãs tintas. Em relaÃÃo Ãs anÃlises tÃrmicas foi possÃvel concluir que os pigmentos de molibdatos e fosfomolibdatos apresentaram o melhor desempenho tanto em relaÃÃo à estabilidade tÃrmica da resina epÃxi, uma vez que estes pigmentos mostraram maior interaÃÃo entre pigmento-resina, assim como em relaÃÃo à energia envolvida no processo de cura do filme polimÃrico, pois estes pigmentos demonstraram que contribuem para a diminuiÃÃo do calor envolvido no processo de cura. / This work describes the development and study of environmental friendly epoxies anticorrosives paints, which were formulated using zinc phosphate (ZP), zinc molybdate (ZM), zinc and calcium molybdate (ZCM), zinc phosphomolybdate (ZMP) and zinc and calcium phosphomolybdate (MZAP), as safe alternative to more traditional anticorrosive pigments (lead, chromium and other heavy metals). Additionally, environmental considerations are limiting the use of solvent-borne paints because it contibutes to atmospheric pollution and empairs health problems. Thus, hydrosoluble epoxy resin was used in the formulation of the water-borne paints. The aim od this research is to employ molybdate-based pigments in order to check their efficiency in water borne paints. Inhibitive properties of the pigments were evaluated by potentiodynamic polarization curves, open ciricuit potential (Eoc) and mass loss monitoring during 30 days in immersion test of SAE 1010 steel in aqueous saturated pigment solutions with 10-2 mol dm-3 NaCl. The physical chemical characterization of the corrosion products was carried out by scanning electron microscopy, energy dispersive X-ray and X-ray diffraction techniques. All the tests showed that the phosphomolybdate pigments presented the better corrosion inhibiting properties. All the paints were formulated with 16% (v/v) epoxy resin, 7.5 % (v/v) anticorrosive pigment, and additives and fillers in order to maintain the PVC/CPVC ration equal to 0.8. the dry thickness of the painted samples was approximately 120 μm. The paint performance was monitored by electrochemical impedance spectroscopy (EIS) during immersion tests, of the atmospheric exposition and accelerated ensay of salt spray. The thermal stability of the paintings was also studied by thermal gravimetry and differential scanning calorimetry. The impedance diagrams of all painted samples showed only one capacitive loop, with impedance values higher than 109 Ωcm2. Capacitance values varied between 10-6 and 10-10 Fcm-2. The results suggest that the combination of the molybdate and phosphate gives the best inhibitive properties. About the thermal analyses were observed that the molybdates and phosphomolybdates pigments showed the better performances thus in the thermal stability of epoxy resin, because theses pigments showed higher interaction between pigment-resin; just as in the relation the energy involved in the cure process of polymeric film, because these pigments contribued to reduce the heat involved in the cure process.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references.