The possibility that iron and copper can ameliorate the effects of 2,4-dichlorophenoxy acetic acid (2,4-D) on the morphology and yield of plants has been investigated by Wort (64). A study of the literature indicates that although there is considerable variation among plant species and also parts of the same plant, 2,4-D concentrations below 50 p.p.m. promote or have no effect on respiration, while higher concentrations are generally inhibitory. Photosynthesis is generally inhibited. An experiment was planned and executed to determine whether iron and copper protect against the effects of 2,4-D on photosynthesis and respiration, and on fresh, dry and ash weights. Each treatment was replicated six times. Potato (Solanum tuberosum L.) plants were grown to the age required for treatment (4-7 weeks) in a hydroponic system. Treatment was applied either in the form of 'Attaclay' dust including growth substance and/or metal, or as aqueous spray in which the metal was applied two hours before the growth substance. At given intervals after treatment, photosynthesis and respiration in the leaflets were determined by the diethanolamine buffer method (60) on the Warburg apparatus. After the leaflets had been removed for the final determination of photosynthesis and respiration, the plants were harvested and their fresh, dry and ash weights were determined. A comparison was made of photosynthetic values based on both area and fresh weight. The results were analysed for statistical significance by the analysis of variance and Duncan's new multiple range test. Coefficients of variability (C.V.%) were calculated for the various measurements. In most cases the coefficients were shown to decrease by half during the course of the experiment. Results showed that 2,4-D was more inhibitory to gas exchange than its copper salt and also caused greater deformation of the plants. Further results indicated that application of iron with 2,4-D inhibited the effects measured for 2,4-D. Gas exchange values for the 2,4-D treated plants were frequently significantly different from those of plants treated two hours earlier with an iron spray. The iron spray when followed by 2,4-D application caused a significant height increase. This suggested that the effective concentration of 2,4-D had been lowered by the iron. These observations are discussed in the light of recent publications on the role of metal chelation in auxin action. / Science, Faculty of / Botany, Department of / Graduate

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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.

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / O presente trabalho consiste no estudo de revestimentos funcionais com aplicaÃÃo industrial nos setores metal-mecÃnico e energia. Para isto, foram estudados revestimentos de ZnAl, como camada protetora contra a corrosÃo, e realizado o desenvolvimento e a caracterizaÃÃo do revestimento (filme) semicondutor ZnTe para o aproveitamento da energia solar. Adicionalmente, foi desenvolvido um revestimento (filme fino) transparente condutor SnO2:F, depositado sobre vidro comum, para ser usado como substrato na eletrodeposiÃÃo do filme ZnTe. O estudo de corrosÃo do revestimento Zn-55Al (galvalume), depositado sobre substrato de aÃo carbono, foi feito como parte da caracterizaÃÃo de materiais tecnolÃgicos que estÃo sendo produzidos no Brasil. O filme semicondutor policristalino de ZnTe foi produzido por tÃcnica eletroquÃmica, bem como a sua caracterizaÃÃo bÃsica por voltametria cÃclica e cronoamperometria. O substrato transparente condutor foi produzido por spray pyrolysis a partir de parÃmetros operacionais definidos no prÃprio laboratÃrio. A produÃÃo do substrato transparente condutor foi feita por ser uma tÃcnica ainda inexistente em processos industriais e comerciais no Brasil, tendo que ser importado. Foram usadas tÃcnicas eletroquÃmicas para o estudo de corrosÃo do revestimento industrial Zn55Al, obtenÃÃo e caracterizaÃÃo do ZnTe e estabilidade quÃmica do SnO2:F. A caracterizaÃÃo morfolÃgica foi feita por Microscopia EletrÃnica de Varredura (MEV). Associada ao MEV pode-se citar a tÃcnica de Energia Dispersiva de raios-X (EDX) como uma tÃcnica semi-quantitativa e semi-qualitativa na complementaÃÃo do estudo morfolÃgico. A tÃcnica de difraÃÃo de raios-X (DRX) foi utilizada como tÃcnica qualitativa e estrutural que esclareÃam as informaÃÃes obtidas por MEV e EDX. A xii caracterizaÃÃo Ãtica dos filmes SnO2:F e ZnTe foi feita por transmitÃncia na faixa do visÃvel, que à a faixa de operaÃÃo para sistemas fotovoltaicos. Foi observado que o revestimento Zn55Al, mesmo com um potencial de corrosÃo menor que o zinco puro, apresentou maior resistÃncia à corrosÃo devido à formaÃÃo de camada passivante e que o processo de corrosÃo inicia-se nas regiÃes interdendrÃticas, ricas em zinco com formaÃÃo microrrachaduras. Este comportamento foi comparativo entre os testes acelerados em meio aquoso, em atmosfera marinha e avaliaÃÃo por perda de massa. Na obtenÃÃo dos filmes ZnTe, foi observado que no pH = 4,5 ocorre a formaÃÃo do filme de estequiometria 1:1 a um potencial â0,60V (versus Ag/AgCl), e temperatura de 60oC, ao abrigo da luz visÃvel (escuro). Adicionalmente, por medidas de transmitÃncia, foi determinado o gap de energia (Eg) de 2,44 eV, com lmÃx = 702,3nm, condiÃÃo satisfatÃria para o uso em janelas de conversÃo fotovoltaica. Os filmes de SnO2:F apresentaram transmitÃncia mÃxima de 92,27% em l = 682nm e resistÃncia mÃdia de superfÃcie de 30Â10 W/ . Por outro lado, foi observado por volttametria cÃclica, uma boa estabilidade eletroquÃmica em meio Ãcido (pH = 1) por voltametria cÃclica. / The present work consists of the functional coatings study with industrial application in the sectors metal-mechanic and energy. For this, coatings of ZnAl had been studied, as protective layer against the corrosion and carried through the development and the characterization of the coatings (film) ZnTe semiconductor for use to advantage of the solar energy. Additionally, an coatings was developed (fine film) transparent SnO2:F conductor, deposited on common glass, to be used as substratum in the electroplating of the ZnTe film. The study of corrosion of the Zn5Al coatings (galvalume), deposited on steel, it was made as part of the characterization of technological materials that are being produced in Brazil. The film polycrystalline semiconductor of ZnTe was produced by electrochemical technique as well as its basic characterization by cyclic voltammetry and chronoamperometry. The conducting transparent substratum was produced by spray pyrolysis from defined operational parameters in our laboratory. The production of the conducting transparent substratum was made by being one still inexistent technique in industrial and commercial processes in Brazil, having that to be mattered. They had been used electrochemical techniques for the study of corrosion of the industrial coatings Zn5Al, attainment and characterization of the ZnTe and chemical stability of the SnO2:F. The morphologic characterization was made by scanning electron microscopy (MEV), and the compositional measurements by EDX to complementation of the morphologic study. The technique of DRX, was used as qualitative and structural studies to complement the information gotten for MEV and EDX. The characterization optics of the films SnO2:F and ZnTe was made by transmittance in the band of the visible, that it is the band of operation for photovoltaic systems. It was observed that the Zn5Al coatings, with a less potential of corrosion then pure zinc, presented greater resistance to the corrosion due formation of passiveness xiv layer and the corrosion process initiated in the interdendritics regions, rich in zinc with cracks formation. This behaviour was comparative as well as immersion tests and sea atmospheric tests and evaluation for loss of mass. An stoichiometric ZnTe films, it was observed that in pH = 4.5 the formation of the film of stoichiometry 1:1 at -0,60V (vs. Ag/AgCl), and temperature of 60ÂC, on the absence of the visible light. Additionally, by measures of transmittance was determined the energy gap of 2.4 eV, with lmÃx = 702.3nm, satisfactory condition for the use in windows of photovoltaic conversion. The films of SnO2:F had presented maximum transmittance of 92.27% in l =682 nm and average resistance of surface of 30Â10 W/ . On the other hand, it was observed an electrochemical stability in acid medium (pH = 1) by cyclic voltammetry.