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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Sistema de pintura anticorrosiva monocomponente aplicado diretamente sobre o metal substituto ao sistema tradicional de três componentes - Desenvolvimento e avaliação de formulações de tinta base água / Anticorrosive one component paint system applied directly on metal in substitution to three components traditional system - Development and evaluation of water based paints

Álann de Oliveira Piagentini Bragatto 07 June 2018 (has links)
O trabalho desenvolvido tem como objetivo avaliar um sistema de pintura anticorrosiva aplicado diretamente sobre o metal, sistema DTM, em relação a um sistema tradicional, composto por Primer, Intermediário e Top Coating, ambos base solventes e destinados para aplicações arquitetônicas, e propor o desenvolvimento e avaliação de formulações base água substitutas à base solvente, procurando-se determinar a influência de determinados componentes presentes nas formulações, tais como o dióxido de titânio, fosfato de zinco, caulim, inibidor de corrosão orgânico e agente reticulante nas propriedades anticorrosivas da tinta. São realizadas avaliações das propriedades anticorrosivas das tintas por meio de medidas de potencial de circuito aberto (EOCP), espectroscopia de impedância eletroquímica (EIS) e ensaio acelerado de corrosão em câmara de névoa salina. Além das propriedades anticorrosivas, as tintas DTM base água formuladas são avaliadas comparativamente à tinta DTM base solvente em outras propriedades, particularmente em relação à resistência à água, por meio de medidas de absorção de água, permeabilidade ao vapor dágua e determinação do ângulo de contato, e em relação às propriedades estéticas, tais como o poder de cobertura de tinta úmida e seca. Os resultados demonstram que o sistema DTM basesolvente apresenta desempenho anticorrosivo equivalente ao sistema tradicional. Dentre as formulações base água avaliadas, verifica-se que o uso do fosfato de zinco como pigmento anticorrosivo e de um agente reticulante na formulação é fundamental para se obter um desempenho anticorrosivo satisfatório. Também é demonstrado que a resistência à água dos filmes é um fator fundamental a ser melhorado nas tintas base água para que se possa obter resultados satisfatórios em relação à resistência à corrosão para longos períodos de exposição como o obtido para o sistema base solvente. / The developed work aims to evaluate an anticorrosive paint system applied directly on metal, DTM system, in relation to a traditional three components paint system, composed by Primer, Intermediary Coating and Top Coating - both systems solvent based and intended to architectural applications. The work also aims to develop and evaluate water based DTM paint formulations in substitution to solvent based paint system, determining the influence of some components present in the formulations, such as titanium dioxide, zinc phosphate, kaolin, organic corrosion inhibitor and a crosslinker agent, in the anticorrosive properties of the paint. The anticorrosive properties of the paint are evaluated by open circuit potential measures (EOCP), electrochemical impedance spectroscopy (EIS) and accelerated corrosion test in the salt-spray chamber. Besides the anticorrosive paints properties, water based DTM formulated paints are compared to solvent borne DTM paint in other properties, particularly in relation to water resistance, by measures of water absorption, water vapor permeability and contact angle, and also in relation to aesthetic properties, such as dry and wet hiding power. The results demonstrated that anticorrosive performance of solvent borne DTM paint system is similar to the solvent borne traditional paint system. In relation to formulatedwater based DTM paints, it was observed that the use of zinc phosphate as an anticorrosive pigment and a crosslinker agent in the formulation is essential to obtain a satisfactory anticorrosive performance. It is also demonstrated that the paint films water resistance is a fundamental property to be improved in water based paints in order to obtain satisfactory results in relation to corrosion resistance for long periods of exposure, just as observed for solvent borne system.
12

Contribuição para diagnóstico e durabilidade de algumas edificações em estruturas de aço da cidade de Goiânia / Contribution to diagnosis and durability of some buildings in structures Goiânia city steel

Lima, Marcello Alencar 26 November 2015 (has links)
Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2016-04-20T11:51:59Z No. of bitstreams: 2 Dissertação - Marcello Alencar Lima - 2015.pdf: 14183931 bytes, checksum: 77b93f4d48465daec7bd845bade974f2 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-04-20T11:53:48Z (GMT) No. of bitstreams: 2 Dissertação - Marcello Alencar Lima - 2015.pdf: 14183931 bytes, checksum: 77b93f4d48465daec7bd845bade974f2 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2016-04-20T11:53:48Z (GMT). No. of bitstreams: 2 Dissertação - Marcello Alencar Lima - 2015.pdf: 14183931 bytes, checksum: 77b93f4d48465daec7bd845bade974f2 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-11-26 / Recently have been noticed a few buildings made of steel structures in the city of Goiania, have shown process and progressive corrosion in your structural systems, and partly, for example, trusses, beams, columns etc. Such succession was visually perceived due to the aggressiveness of conditions relating primarily to the internal microenvironment of buildings, rain and animal feces. The methodology that was used is the data collection in the field of measuring thickness of the paint protection of apparent metal structures and photographic record of the problems of works, such as pathological manifestations of steel, paint, water accumulation sites etc. With the obtained data, the spreadsheet will be filled, depending on the model suggested by Mortari, 2008. In completing the Check list, it is easier to diagnose the structure, mainly because the diagnosis is last. / Recentemente têm-se percebido que alguns edifícios construídos em estruturas de aço na Cidade de Goiânia, vêm mostrando um processo progressivo de corrosão em seus sistemas estruturais, e em parte, como por exemplo: treliças, vigas, pilares etc. Tal sucessão foi percebida visualmente, devido às condições de agressividades ligadas primordialmente ao microambiente interno das edificações, chuva e fezes de animais. A Metodologia que foi empregada é o levantamento dos dados em campo medição da espessura da tinta de proteção das estruturas metálicas aparentes e com registro fotográfico dos problemas das obras, tais como, manifestações patológicas do aço, pintura, locais de acumulo de água etc. Com os dados obtidos, será preenchida a planilha, conforme o modelo sugerido por MORTARI, 2008. Com preenchimento do Check list, fica mais fácil fazer o diagnóstico da estrutura, principalmente por que o diagnóstico está no final.
13

Valorisation d'espèces envahissantes des genres Xanthium et Senecio : caractérisation, variabilité chimique et activités des huiles essentielles / Valuation of invasive species and genera Xanthium Senecio : characterization, chemical variability and activities essential oils

Andreani, Stéphane 09 December 2014 (has links)
La prolifération d’espèces invasives est un problème mondial. Après la pollution et la destruction des habitats, l’introduction d’espèces exogènes est une des principales causes de la disparition de la biodiversité animale et végétale dans le monde. La Corse n’est pas épargnée par le phénomène ; en effet, chaque année nous dénombrons de plus en plus d’espèces végétales introduites, potentiellement envahissantes et dangereuses pour l’écosystème insulaire. Si elles ne sont pas contrôlées, ces plantes peuvent rapidement gagner du terrain et s’installer durablement en raison de leurs facultés d’adaptation à divers écosystèmes.C’est dans ce contexte que nous sommes intéressés à quatre plantes de la famille des Astéracées considérées comme envahissantes : deux espèces du genre Xanthium (Xanthium italicum et X. spinosum) et deux espèces du genre Senecio (Senecio angulatus et S. inaequidens). L’objectif principal était d’initier une possible voie de valorisation de ces espèces par la production d’huile essentielle ; cela permettrait d’une part de limiter la dissémination et d’autre part, de générer un débouché économique.Par ailleurs, nous avons étendu ce travail à Limbarda crithmoides et à six espèces du genre Senecio poussant à l’état spontané en Corse. Une approche chimiotaxonomique réalisée à partir de 180 échantillons d’huiles essentielles du genre Senecio a conduit à différencier les espèces dites halotolérantes (S. aquaticus, S. transiens et S. cineraria) des espèces plus « terrestres » (S. vulgaris, S. angulatus, S. inaequidens, S. serpentinicola et S. lividus). L’étude de la variabilité chimique intraspécifique a permis de mettre en évidence des corrélations entre la composition chimique des huiles essentielles et le polymorphisme des taxons et/ou des facteurs édaphiques. L’étude du genre Senecio a également conduit à la caractérisation de deux nouvelles molécules, l’oxyde d’acétoxybisabolène et le 8-acétoxybisabolène 1,9-diol, isolées de l’huile essentielle de S. transiens (espèce endémique de Corse).D’un point de vue plus appliqué, les mesures des activités anti-radicalaires et anticorrosives des huiles essentielles ont démontré le potentiel de certaines espèces comme sources d’anti-oxydants naturels (notamment, Xanthium italicum et X. spinosum) mais aussi le pouvoir anticorrosif de la cacalohastine, isolée de l’huile essentielle de S. inaequidens (espèce invasive). / The proliferation of invasive species is a global problem. The introduction of exogenous species is after pollution and habitat destruction a major cause of the disappearance of the worldwide plant and animal biodiversity. Corsica is not spare to the phenomenon and every year there are numerous dangerous species which are introduced to the island ecosystem.In this study, we have studied four invasive species of Asteraceae (X. italicum, X. spinosum, S. angulatus and S. inaequidens) from Corsica. The aim of this study is to initiate a possible valuation pathway of these species by production of their essential oils. For this purpose, we investigated the chemical variability of each essential oil and their antioxidant and anticorrosive activities. Then we have extended our investigations to the others species of Senecio genus and to Limbarda crithmoides, anciently parented taxa.GC and GC/MS analysis allowed the identification of 107 and 74 components which accounted for 98.7 and 93.5% of the X. italicum and X. spinosum essential oils, respectively. Essential oils of X. italicum and X. spinosum were dominated by hydrocarbon monoterpenes (66.2%) and oxygenated sesquiterpenes (41.5%), respectively. The same metabolomic pathways seem occur for both species during the vegetative cycle of the plant: oxygenated sesquiterpene-production was higher during the flowering stage. Moreover the study of 25 sample oils of X. italicum and X. spinosum showed that the chemical variability of both essential oils could be linked to morphological characters.A comprehensive work on the chemical variability of 180 sample oils of Senecio was carried out and 251 components were identified. Among them, using mono and bi-dimensional NMR the structures of 8-acetoxybisabolene-1,9-diol and 8-acetoxy-1,9-oxobisabolene, two new components of S. transiens essential oil were described for the first time. Corsican Senecio species exhibited interspecies chemical variability: the halotolerant Senecio species (S. transiens, S. cineraria and S. aquaticus erraticus) were characterized by essential oils dominated by non-terpenic compounds while the so-called “terrestrial” Senecio species (S. angulatus, S. ineaquidens, S. lividus, S. vulgaris and S. serpentinicola) exhibited terpenic component-rich oils. The study of intra-species chemical variability highlighted direct correlations between the plant-production of secondary metabolites and the nature of soils on which S. lividus, S. vulgaris and S. transiens grows. Hence essential oil compositions and morphological polymorphism are indirectly related. In the same way, the chemical variability of S. cineraria essential oils seems to be linked to the geology of the soils while the oil diversity of the invasive S. angulatus, could be linked to the both spots of introduction on Corsica Island. In addition, an original chiral-gas chromatographic method was improved and applied to the main components of the essential oils in order to complement the chemical composition of the Senecio sample oils.Furthermore the originality of Corsican Limbarda crithmoides essential was highlighted by the occurrence of two p-cymenene derivatives, never reported in the related studies from literature. The investigation of 25 Corsican L. crithmoides focuses on a direct correlation between the water salinities of the plant locations and the chemical compositions of the essential oils.Finally the antioxidant activities, anti-free radical and reducing power, were measured on some essential oils of the studied species. Essential oils of the Xanthium genus appeared to be most effectives. In addition, anticorrosion properties of the essential oils were investigated and the best corrosion inhibiting activity was exhibited by those of S. inaequidens . Anticorrosion activity could be attributed to the cacalohastine, a naphtalofuranic component, isolated form the whole essential oil after column chromatography.
14

S?ntese e avalia??o da atividade anticorrosiva de cloretos de 1,3,4-tiadiaz?lio-2-fenilaminas e 1,3,4-triaz?lio-2-tiolatos em meio ?cido / Synthesis and evaluation of the anticorrosion activity of 1,3,4-thiadiazolium-2-phenylamine chlorides and 1,3,4-triazolium-2-thiolates chlorides in acidic medium

SANTOS, Cristiane Frauches dos 25 September 2017 (has links)
Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2018-08-29T19:26:49Z No. of bitstreams: 1 2017 - Cristiane Frauches dos Santos.pdf: 7660831 bytes, checksum: d9f6418f111957d4be1789ee9411cc8f (MD5) / Made available in DSpace on 2018-08-29T19:26:49Z (GMT). No. of bitstreams: 1 2017 - Cristiane Frauches dos Santos.pdf: 7660831 bytes, checksum: d9f6418f111957d4be1789ee9411cc8f (MD5) Previous issue date: 2017-09-25 / CAPES / CNPq / FAPERJ / Petrobr?s / Corrosion is one of the serious problems faced in industrial processes, generating enormous financial losses. Several techniques are used to prevent or remedy corrosion in the different materials it affects. Among them, the use of organic or inorganic inhibitors has been widely used. Thus, in this thesis were synthesized 34 heterocyclic compounds, 18 chlorides of 1,3,4-thiadiazolium-2-phenylamines, (11 unpublished), and the other 16 compounds belonging to the class of mesoionic 1,3,4-triazolium -2-thiolate, (15 unpublished), with the objective of evaluating its efficiency as inhibitors of corrosion in acidic corrosion. Derivatives of the class 1,3,4-thiadiazolium-2-phenylamines were obtained with satisfactory purity and yields in the range of 42-96% and, in the class of 1,3,4-triazolium-2-thiolates in 20 -97%. All compounds were characterized by IR, 1H and 13C NMR spectroscopies. The theoretical study was conducted using the SPARTAN-PRO program in the semi-empirical method with the Hamiltonian AM1, to determine its structural and electronic properties of 1,3,4-thiadiazolium-2-phenylamines that could contribute to the efficiency of inhibition of corrosion. The compounds of 1,3,4-thiadiazolium-2-phenylamine class were tested against corrosion of AISI 1020 carbon steel in 0.5 mol L-1HCl and in 0.5 mol L-1 H2SO4. For this evaluation, the electrochemical techniques of Potenciodynamic Polarization (PP), Resistance to Linear Polarization (RPL) and Electrochemical Impedance Spectroscopy (EIS) were used. The results showed significant percentages of corrosion inhibition in both acidic solutions, reaching the rate of up to 95% efficiency for the compound 4-phenyl-5-(3'-methoxy-phenyl)-1,3,4-thiadiazolium-2-phenylamine chloride in the concentration of 3.5x10-4 mol L-1 for the HCl solution, and 99% efficiency for the 2'-chloro and 2'-fluorosubstituted compounds in the concentration of3.5x10-4 mol L-1 for the H2SO4 solution. In addition to the electrochemical techniques, the gravimetric technique was used, which presented 99% of anticorrosive efficiency for the 2'-trifluoromethyl-substituted 1,3,4-thiadiazolium-2-phenylamine derivative, showed the best inhibitory effect in HCl solution. However, the 2'-trifluoromethyl-substituted 1,3,4-triazolium-2-thiol derivative showed less corrosion efficiency than its corresponding isomer. The methodologies used to evaluate the corrosion activity (PP, RPL and EIE), including the theoretical evaluation by molecular modeling, indicated the mesoionic chloridrates as efficient mixed corrosion inhibitors. / S?ntese e avalia??o da atividade anticorrosiva de cloretos de 1,3,4-tiadiaz?lio-2-fenilaminas e 1,3,4-triaz?lio-2-tiolatos em meio ?cido. 2017. 251p Tese (Doutorado em Qu?mica, Ci?ncia exatas, s?ntese org?nica). Departamento de qu?mica, Universidade Federal Rural do Rio de Janeiro, Serop?dica, RJ, 2017. A corros?o ? um dos s?rios problemas enfrentados nos processos industriais, gerando enormes preju?zos financeiros. Diversas t?cnicas s?o utilizadas para evitar ou remediar a corros?o nos diferentes materiais que ela afeta. Dentre elas o uso de agentes inibidores org?nicos ou inorg?nicos tem sido muito utilizado. Assim, neste trabalho de tese foram sintetizados 34 compostos heteroc?clicos, sendo 18 cloretos de 1,3,4-tiadiaz?lio-2-fenilaminas (11 in?ditos) e os outros 16 compostos pertencentes ? classe dos mesoi?nicos 1,3,4-triaz?lio-2-tiolato (15 in?ditos), com o objetivo de avaliar sua efici?ncia como inibidores de corros?o em meio ?cido. Os derivados sintetizados da classe 1,3,4-tiadiaz?lio-2-fenilaminas foram obtidos com grau de pureza e rendimentos satisfat?rios na faixa de 42-96% e, da classe dos 1,3,4-triaz?lio-2-tiolatos em 20-97%. Todos os compostos foram caracterizados por espectroscopia de IV, RMN de 1H e13C. Foi realizado o estudo de modelagem molecular, utilizando o programa SPARTAN-PRO com o m?todo semi-emp?rico, hamiltoniano AM1, para determina??o das propriedades estruturais e eletr?nicas dos 1,3,4-tiadiaz?lio-2-fenilaminas que pudessem contribuir para a efici?ncia de inibi??o da corros?o. Os cloridratos mesoi?nicos da classe 1,3,4-tiadiaz?lio-2-fenilaminas foram testados frente ? corros?o de a?o carbono AISI 1020 em solu??o de HCl 0,5 mol L-1 e em H2SO4 0,5 mol L-1. Para tal avalia??o foram utilizadas as t?cnicas eletroqu?micas de Polariza??o potenciodin?mica (PP), Resist?ncia ? polariza??o linear (RPL) e Espectroscopia de imped?ncia eletroqu?mica (EIE). Os resultados mostraram percentuais significativos de inibi??o da corros?o em ambas solu??es ?cidas, alcan?ando o ?ndice de at? 95% de efici?ncia para o composto cloreto de 4-fenil-5-(3?-met?xi-fenil)-1,3,4-tiadiaz?lio-2-fenilamina na concentra??o de 3,5x10-4 mol L-1 para a solu??o de HCl e, 99% de efici?ncia para os compostos 2?-cloro e 2?-fluor-substitu?dos na concentra??o de 3,5x10-4 mol L-1 para a solu??o de H2SO4. Al?m das t?cnicas eletroqu?micas, foi utilizada a t?cnica gravim?trica que apresentou 99% de efici?ncia anticorrosiva para o derivado 2?-trifluormetil-substitu?do da classe 1,3,4-tiadiaz?lio-2-fenilamina que mostrou o melhor efeito inibidor em solu??o HCl. No entanto, o derivado 2?-trifluormetil-substitu?do da classe 1,3,4-triaz?lio-2-tiol apresentou menor efici?ncia anticorrosiva do que seu is?mero correspondente. As metodologias utilizadas para avalia??o da atividade anticorrosiva (PP, RPL e EIE), incluindo a avalia??o te?rica por modelagem molecular, indicaram os cloridratos mesoi?nicos como eficientes inibidores de corros?o mistos.
15

Investiga??o da resist?ncia ? corros?o do a?o aisi 1020 em meio ?cido na presen?a de tiossemicarbazonas, extratos vegetais e suas formula??es

ALMEIDA, Mariana de Albuquerque 10 May 2017 (has links)
Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-11-09T17:58:22Z No. of bitstreams: 1 2017 - Mariana de Albuquerque Almeida.pdf: 2619920 bytes, checksum: 48c00262629bac9a7779fc4ea9ec94a6 (MD5) / Made available in DSpace on 2017-11-09T17:58:22Z (GMT). No. of bitstreams: 1 2017 - Mariana de Albuquerque Almeida.pdf: 2619920 bytes, checksum: 48c00262629bac9a7779fc4ea9ec94a6 (MD5) Previous issue date: 2017-05-10 / CAPES / This dissertation presents the evaluation of four thiosemicarbazones, from extracts of species of vegetables Talinum triangulare, Physalis angulata e Theobroma cacao L. besides formulation obtained from the combination extract of thiosemicarbazones vegetables as corrosion inhibitor in the presence of carbon steel AISI 1020. Thiosemicarbazones were obtained with good level of purity, satisfactory throughput and identified by NMR of 1H and 13C. The watery extract of Talinum triangulare was obtained using ultrasound device. The extracts of Physalis angulata species were obtained by maceration in water and the other one in ethyl acetate. The watery extracts of Theobroma cacao L. species were obtained using ultrasound device and decoction and hydroalcoholic extract was obtained by maceration in ethanol:water (80:20). The thiosemicarbazones, the vegetable extracts and their formulation were tested in the presence of corrosion of carbon steel AISI 1020 in solution 1 mol. L-1 of HCl. For this evaluation it was used the gravimetric techinique of weight loss and electrochemical techiniques of potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that the presence of thiosemicarbazones, as well as, the formulation increased significantly the resistence of carbon steel AISI 1020 in acidic medium. The results obtained in different used essays (weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy) show that these techniques are complementary in relation to the evaluation of corrosion inhibition. The best anti-corrosion efficiency was observed for thiosemicarbazone chloro and hydroxy-substituted and its formulations with the extract of T. triangulare achieving 88% and 87% of efficiency, by electrochemical impedance spectroscopy, respectively. / Nesta Tese ? apresentada a avalia??o de quatro tiossemicarbazonas, dos extratos das esp?cies vegetais Talinum triangulare, Physalis angulata e Theobroma cacao L., al?m de formula??es obtidas pela combina??o extrato vegetal:tiossemicarbazonas, como inibidores de corros?o frente ao a?o carbono AISI 1020 em meio de ?cido cloridr?co. As tiossemicarbazonas foram obtidas com bom grau de pureza, em rendimentos satisfat?rios e, caracterizadas por IV, RMN de ^1H e ^13C. O extrato aquoso de Talinum triangulare foi obtido em aparelho de ultrassom, os extratos da esp?cie Physalis angulata, foram obtidos sob macera??o em ?gua e o outro em acetato de etila; j? os extratos aquosos da esp?cie Theobroma cacao L. foram obtidos em aparelho de ultrassom e decoc??o e, finalmente, o extrato hidroalco?lico foi obtido por macera??o em etanol:?gua (80:20). As tiossemicarbazonas, os extratos vegetais e suas formula??es foram testadas frente ? corros?o de a?o carbono AISI 1020 em solu??o 1mol.L-1 de HCl. Para tal avalia??o foi utilizada a t?cnica gravim?trica de Perda de Massa e as t?cnicas eletroqu?micas de Polariza??o Potenciodin?mica e Espectroscopia de Imped?ncia Eletroqu?mica. Os resultados mostraram que a presen?a de tiossemicarbazonas, bem como, das formula??es aumentam significativamente a resist?ncia do a?o carbono AISI 1020 em ?cido. Os resultados obtidos nos diferentes ensaios utilizados (Perda de Massa, Polariza??o Potenciodin?mica e Espectroscopia de Imped?ncia Eletroqu?mica) mostraram que estas t?cnicas s?o complementares quanto a avalia??o da inibi??o da corros?o. A melhor efici?ncia anticorrosiva foi observada para as tiossemicarbazonas cloro e hidroxi-substitu?das e, para suas formula??es com o extrato da T. triangulare obtendo-se 88% e 87% de efici?ncia por espectroscopia de imped?ncia eletroqu?mica, respectivamente.

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