Dissertations / Theses on the topic 'Zn'

De nos jours, la galvanisation continue par immersion à chaud est largement utilisée dans les structures métalliques pour protéger les aciers contre la corrosion. Le zinc offre une barrière protectrice grâce à la formation d'un oxyde de surface et d'un effet de protection sacrificielle. Cependant, les procédés de fabrication de la structure ou les assemblages mécaniques par déformation plastique peuvent créer des dommages affectant les performances de corrosion du revêtement.L’objectif de ce travail était d’étudier la durabilité, en environnement agressif, par des essais d’immersion et en enceinte climatique, de revêtements galvanisés déformés à la suite d’une mise en forme. Trois revêtements différents ont été choisis. Un revêtement de zinc utilisé comme référence, un revêtement Zn-Al-Mg dans lequel l’ajout de magnésium et d’aluminium permet une meilleure tenue à la corrosion et enfin un revêtement Zn-55Al choisi pour sa très bonne durabilité en environnement agressif en raison de la quantité importante d’aluminium présente dans sa composition
Nowadays continuous hot-dip galvanizing is widely used in metallic structures to protect steels against corrosion. Zinc provides a protective barrier thanks to the for-mation of a surface oxide and a sacrificial protection effect. However, structure manufacturing processes or mechanical assemblies by plastic deformation can create damage affecting the corrosion performance of the coating.The objective of the present work is to study changes of corrosion resistance induced by plastic deformation using immersion and climatic chamber tests. Three different coatings were chosen. A zinc coating used as a reference, a Zn-Al-Mg coating in which the addition of magnesium and aluminum allows a better resistance to corrosion and finally a Zn-55Al coating chosen for its very good durability in aggressive environment in Because of the large amount of aluminum present in its composition

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The coffee tree is a demanding plant in micronutrients, especially Zn, and the P x Zn interaction is an important issue for the management of tropical soils, due to the use of high doses of P in soils with low availability of this nutrient. In this work was studied the seedlings response of Coffea arabica L. cv. Catuaí to doses of Zn and P, including the supply of P corresponding to a high availability of P, therefore, a high antagonism potential to the availability of Zn. The experiment was carried out in a greenhouse in the period between the October/2009 and January/2010 (122 days of conducting the experiment), using 4 × 4 factorial design, distributed in randomized blocks, with three replications, being four doses of Zn (0, 5, 15, and 45 mg / dm 3 of soil) and P (0, 200, 600 and 1,800 mg / dm 3 of soil). On the soil, having as a source ZnSO 4 .7 H 2O, the doses of Zn were applied trough a soil solution and P levels were incorporated, being the source the triple superphosphate. It was used samples of a Red Yellow sandy-loam originating from Três Marias - MG and coffee seedlings with four pairs of leaves, which were transplanted to pots (2 dm 3 of soil), maintaining soil moisture near to field capacity. It was evaluated the total content of Zn in plant parts (leaf, stem and root), the soluble fraction of Zn (leaf), the levels of total P (leaf, stem and root), the enzyme superoxide dismutase (SOD) , plant height, number of nodes per plant, average length of internodes and dry matter production (leaf, stem and root). There were no significant changes in levels of total Zn in leaves with increasing doses of P added to soil, although the levels of soluble Zn (active) have fallen, indicating, in this case, antagonistic interaction between the variables. The SOD activity was reduced with increasing doses of Zn added to soil. The growth of coffee seedlings was influenced by the interaction between P and Zn.
O cafeeiro é uma planta exigente em micronutrientes, especialmente, em Zn, e a interação P x Zn é uma questão importante para o manejo de solos tropicais, haja vista a utilização de altas doses de P em solos com baixa disponibilidade deste nutriente. Neste trabalho foi estudada a resposta de mudas de Coffea arabica L. cv. Catuaí às doses de Zn e P, incluindo-se o suprimento de P que correspondeu a uma alta disponibilidade de P, portanto, a um alto potencial de antagonismo em relação à disponibilidade de Zn. O experimento foi conduzido em casa-de-vegetação entre o período de outubro/2009 a janeiro/2010 (122 dias de condução do experimento), utilizando esquema fatorial 4 × 4, distribuído em blocos casualizados, com três repetições, sendo quatro doses de Zn (0, 5, 15, e 45 mg/dm3 de solo) e quatro doses de P (0, 200, 600 e 1.800 mg/dm3 de solo). No solo, tendo como fonte ZnSO4.7H2O, as doses de Zn foram aplicadas em solução via solo, e as doses de P foram incorporadas, sendo a fonte o superfosfato triplo. Utilizaram-se amostras de um Latossolo Vermelho Amarelo textura franco-arenosa originário de Três Marias – MG e mudas de café com quatro pares de folhas, que foram transplantadas para vasos (2 dm3 de solo), mantendo-se a umidade do solo próxima à capacidade de campo. Avaliaram-se o teor total de Zn nos órgãos das plantas (folha, caule e raiz) e a fração solúvel de Zn (folha), os teores totais de P (folha, caule e raiz), atividade da enzima superóxido dismutase (SOD), altura de plantas, número de nós por planta, comprimento médio dos entrenós e produção de matéria seca (folha, caule e raiz). Não houve alterações significativas nos teores de Zn total nas folhas com o aumento das doses de P adicionadas ao solo, embora os teores de Zn solúvel (ativo) tenham diminuído, indicando, neste caso, interação antagônica entre as variáveis. A atividade da SOD foi reduzida com o aumento nas doses de Zn adicionadas ao solo. O crescimento das mudas de café foi influenciado pela interação P e Zn.

L'objectif de cette thèse est d’analyser l'électrochimie des phases pures, composants des alliages de revêtement Zn-Al-Mg. Les données électrochimiques ont été utilisées pour prédire du comportement à la corrosion des revêtements d’alliage multiphasé. A cette fin, une base de données de courbes de polarisation élémentaire a été établie en fonction du pH en utilisant la spectroélectrochimie d'émission atomique (AESEC). Le désalliage de la phase intermétallique MgZn2 et de la phase α de Zn-Al (Zn-68Al) ont été étudiés à pH=10,1 représentent les extrêmes contiennent Mg et en Al dans le revêtement d'alliage Zn-Al-Mg, respectivement. Dans la polarisation cathodique, la couche enrichie en Zn (0) a été formée dans les deux cas par dissolution sélective de Mg et Al, respectivement. Cependant, l’influence de cette couche sur le désalliage cathodique différait : pour MgZn2, la dissolution sélective de Mg était restreinte par la couche désalliée, alors que pour Zn-68Al, la dissolution sélective de l'Al n'était pas affectée par cette couche. Il a été observé que le début de la dissolution active de Zn coïncidait avec une réduction de la vitesse de dissolution de l’Al, suggérant un effet inhibitif de la dissolution de Zn sur la dissolution de l’Al. Il a aussi été observé que la dissolution de l’Al dans des milieux alcalins était limitée par la vitesse de dissolution du film de Al(OH)3, mise en évidence par une dissolution de l’Al indépendante de potentiel. Les produits de corrosion les plus stables formés pendant des mesures électrochimiques, les solides précipités dans la solution pendant la titration et la simulation thermodynamique étaient raisonnablement cohérents entre eux. La plupart des espèces précipitées formées dans la solution correspondaient bien à celles prédites par la base de données thermodynamique. Il était en bon accord avec les produits de corrosion de l'alliage, caractérisés après les mesures électrochimiques. Par conséquent, on peut conclure que la base de données thermodynamique peut être utilisée pour prédire et éventuellement modéliser la situation de corrosion réelle
The objective of this Ph.D. project is to investigate the electrochemistry of the pure phases, components of the Zn-Al-Mg coating alloys. The electrochemical data was used as an input for the prediction of corrosion behavior of the multi-phase alloy coatings. To this end, a database of elemental polarization curves was established as a function of pH by using atomic emission spectroelectrochemistry (AESEC). Dealloying of the MgZn2 intermetallic and α-phase of Al-Zn (Zn-68Al) were investigated at pH=10.1 represent the extremes of Mg and Al content in the Zn-Al-Mg alloy coating, respectively. In the cathodic polarization, the Zn(0) enriched layer was formed in both cases by selective dissolution of Mg and Al, respectively. However, the influence of this layer on cathodic dealloying differed: for MgZn2, Mg selective dissolution was restrained by the dealloyed layer, whereas for Zn-68Al, Al selective dissolution was not affected by this layer. It was observed that the onset of active Zn dissolution coincided with a reduction in the Al dissolution rate, suggesting an inhibitive effect of Zn dissolution on Al dissolution. It was observed that Al dissolution in alkaline media was limited by the dissolution rate of the Al(OH)3 film, evidenced by potential independent Al dissolution. The most stable corrosion products formed by electrochemical measurements, precipitated species in the solution during titration experiment and the thermodynamic simulation were reasonably coherent with each other. Most of the precipitated species formed in the solution corresponded reasonably well to those predicted by thermodynamic database. It was in a good agreement with the corrosion products of the alloy, characterized after the electrochemical measurements. Therefore, it can be concluded that the thermodynamic database can be used to predict and eventually model the real corrosion situation

Introduction: The New Delhi metallo-β-lactamase (NDM-1) is an enzyme synthesized by bacterium which hydrolyses β-lactam antibiotics and inhibits their antibiotic effects. Its active site is highly diverse and the hydrolysis mechanism is not yet fully understood. So, there is currently no clinically useful inhibitor for this enzyme. Due to this β-lactam resistant characteristics and the ease of horizontal gene transfer between bacteria, NDM-1 producing bacteria poses a great threat to public health. Objective: Structural analysis on Zn-Zn distance in the active site of NDM-1 was carried out in order to gain a better insight on its hydrolysis mechanism. Method: Structures of NDM-1 were obtained from PDB database and were viewed on PyMOL. Out of 22 NDM-1 structures searched, 12 of them fulfilled the inclusion criterion and were included in this study. Zn-Zn distances were compared with different factors including pH and temperature during crystallization, presence of water in the active site and nature of ligand bound to active site. Results: A trend was observed when Zn-Zn distances were compared with pH. There was also a correlation between Zn-Zn distance and nature of ligand. Distance between the 2 zinc ions in the active site increased in acidic pH value of 6.5 or below and it favours substrate hydrolysis while neutral or alkaline pH shortened the distance between zinc ions leading to hydrolysis inhibition. Discussion: One NDM-1 structure can hydrolyse the substrate in the absence of water molecule. It suggested that there might be another alternative mechanism which does not involve water molecule as nucleophile. Future study can be carried out to verify this hypothesis. On the other hand, it was also suggested that a lower pH, likely to be a pH value of 6.5 or below, could lead to a relatively higher Zn-Zn distance, likely to be 4.00 Å or above. A Zn-Zn distance of 4.00 Å or above would facilitate the hydrolysis mechanism. In other words, a pH value lower than 6.5 might also promote the hydrolysis action against β-lactams. These give us a deeper understanding into the hydrolysis mechanism of NDM-1 and might be useful in future development of clinical inhibitor to tackle the public health threat brought by NDM-1.
published_or_final_version
Physiology
Master
Master of Medical Sciences

Ce travail porte sur la préparation et la caractérisation de catalyseurs bimétalliques Cu-Zn, Ni-Zn et Fe-Zn supportés sur TiO2 avec des rapports atomiques variables et sur l'étude de leurs propriétés catalytiques pour l'hydrogénation sélective d'hydrocarbures polyinsaturés. Les méthodes de co-dépôt-précipitation à l'urée (DPu) et co-dépôt-précipitation à pH fixe (DP8) ont été utilisées pour la préparation des matériaux. Les ions métalliques se déposent séquentiellement sur la surface de TiO2 (selon la séquence CuII < ZnII ?FeII
This work investigates the preparation and characterization of titania-supported non-noble bimetallic Cu-Zn, Ni-Zn and Fe-Zn catalysts with various atomic ratios and their catalytic properties for the selective hydrogenation of polyunsaturated hydrocarbons. Co-deposition-precipitation with urea (DPu) and co-deposition-precipitation at fixed pH (DP8) methods were employed for the samples preparation. The metal ions were sequentially deposited onto the TiO2 surface (the sequence of pH for ions deposition being CuII < ZnII ≈FeII < NiII) during the DPu, while they were simultaneously deposited using DP8 method. After sample reduction at proper temperature (350 °C for Cu-Zn, 450 °C for Ni-Zn and 500 °C for Fe-Zn), XRD and STEM-HAADF coupled with EDS showed that bimetallic nanoparticles were formed in Cu-Zn/TiO2 (Cu3Zn1 or Cu0.9Zn0.1 alloy) and Ni-Zn systems (Ni1Zn1 or Ni4Zn1 alloy) with average particle size smaller than 5 nm. Only metallic Fe was detected by XRD in Fe-Zn/TiO2. Zn is inactive for butadiene selective hydrogenation, and acts as a modifier of the monometallic catalysts whose activity follows the sequence: Cu < Fe < Ni. The addition of Zn slightly decreases the activity and influences the selectivity to butenes, but provides much more stable catalysts. The higher stability of the bimetallic catalysts was ascribed to the formation of lower amount of carbonaceous species during the reaction, resulting from the change in the size of the active metal surface ensembles by alloying with Zn

La Cuenca Vasco-Cantábrica (CVC) se formó durante el episodio de rifting del Mesozoico entre las placas Europea e Ibérica (Vergès y García-Senz, 2001). El registro estratigráfico Mesozoico incluye rocas sedimentarias desde el Triásico hasta el Cretácico Superior. Durante el Cretácico Inferior, la intensa actividad tectónica dió como resultado la acumulación de una potente secuencia de sedimentos. En las regiones alrededor de los depocentros, las evaporitas del Triásico generaron estructuras diapíricas (García-Mondéjar et al., 1996), activas desde el Cretácico Inferior hasta el Campaniense. Posteriormente, se reactivaron durante la compresión Alpina (Paleoceno-Eoceno). En dos de estas estructuras, los diapiros de Murguía y Orduña, existen mineralizaciones de Zn-Pb. Encajan en sedimentos siliciclásticos del Albiense superior (Fm. Valmaseda), y rocas carbonatadas del Cenomaniense superior (Serie Rítmica Cenomaniense) y del Turoniense (Margas de Zuazo, Calizas de Gárate), así como en una franja de rocas carbonatadas en la zona de contacto que tienen afinidad con la litología conocida como cap rock. Las mineralizaciones consisten en filones y cuerpos estratoligados, constituidos por esfalerita, galena, pirita, barita, dolomita, calcita y cuarzo. Se ha reconocido la presencia de materia orgánica (betunes sólidos) asociada espacialmente a los sulfuros en prácticamente todas las localidades. Los fluidos mineralizantes consisten en salmueras de hasta un 26% en peso equivalente de NaCl, con unas relaciones de halógenos compatibles con disolución de halita (Grandia et al., 2003). Los datos microtermométricos de las inclusiones fluidas, la madurez de la materia orgánica y los geotermómetros isotópicos indican temperaturas de formación entre 160 y 200ºC. Los valores de δ34S en esfalerita y galena (+4,1 a +14,6‰) y barita (+16,2 a +24,3‰) son compatibles con la reducción de los sulfatos evaporíticos del Triásico (+13,5 a +17,4‰). En la pirita, la mayoría de los valores de δ34S están entre +3,4 y +28,8‰. Los carbonatos asociados a la mineralización presentan unos valores δ13C / δ18O menores respecto a los carbonatos marinos de la CVC. Los valores de δ13C más negativos (hasta -14‰) indican una fuente de carbono relacionada con materia orgánica, mientras que la variación de δ18O (de +17,7 a +27‰) se explica mediante la interacción de los fluidos con las distintas litologías encajantes (siliciclástica o carbonatada). En la zona de contacto del diapiro de Murguía, se ha identificado una franja de carbonatos brechificados, de hasta 50 m de potencia interpretada como un antiguo cap rock. Está constituida principalmente por dolomita, con unos valores de δ13C negativos (hasta -20‰) y una δ18O alrededor de +25‰. Sin embargo, estos valores isotópicos iniciales han sido modificados tras la circulación de los fluidos mineralizantes. Uno de los rasgos distintivos de las mineralizaciones peridiapíricas es la relación entre la formación del cap rock y los sulfuros Sin embargo, tanto las relaciones texturales entre la materia orgánica y los sulfuros como la composición isotópica de los carbonatos, sugieren que las mineralizaciones no están relacionadas con la génesis del cap rock. Las relaciones 87Sr/86Sr de las fases carbonatadas varían de 0,70801 a 0,70949 en las mineralizaciones encajadas en carbonatos y de 0,70986 a 0,71202 cuando el encajante es la Fm Valmaseda. Esta relación sugiere que los valores de 87Sr/86Sr en el fluido fueron tamponados por la litología del encajante. Los valores de los isótopos de plomo en galenas son homogéneos, y están dentro del rango de los depósitos MVT encajados en Cretácico de la CVC (Velasco et al., 1996) sugieriendo una fuente de los metales similar a escala de cuenca.
The Basque Cantabrian Basin (BCB) is related to rift systems that developed between the European and Iberian plates during the Mesozoic (Vergès and García-Senz, 2001). The Mesozoic stratigraphic record includes sedimentary rocks from Triassic up to Upper Cretaceous ages. The intense fault activity during the rifting led to the deposition of a very thick succession of sedimentary rocks, mainly during the Early Cretaceous. Evaporite diapirs consisting of Upper Triassic rocks developed in the regions surrounding the depocenter, and were active from Early Cretaceous to Campanian ages. During the Alpine compression (Palaeocene-Eocene) the halokinesis was reactivated. Stratabound Zn-Pb deposits are known to occur in association with the Orduña and Murguía diapirs, which are located SW of the BCB. The host rocks are sandstones of Upper Albian ages (Valmaseda Formation) and carbonates of Cenomanian and Turonian ages (Rhythmic Cenomanian Series, Zuazo Marls and Gárate Limestones). The mineralizations are also hosted in a carbonated rocks band in the diapiric contact, which are related to the cap rock lithology. The mineralizations consist on veins and stratabound bodies of sphalerite, galena, pyrite, barite, dolomite, calcite and quartz. Organic matter as solid bitumen is ubiquitous and spatially related to sulphide minerals. Sulphide stage fluid was a brine up to 26 wt % NaCl equivalent salinity with halogen ratios compatible with halite dissolution (Grandia et al., 2003). Thermal indicators (fluid inclusion, organic matter data and isotope geothermometry) show formation temperatures between 160ºC and 200ºC. δ34S values of sphalerite and galena (+4,1 a +14,6‰) and barite (+16,2 a +24,3‰) are compatible with evaporite sulphate reduction of Triassic age (+13,5 a +17,4‰). δ34S of most pyrite samples range between +3,4 and +28,8‰. Carbonates associated to sulphides show lower δ13C / δ18O values than the Mesozoic marine carbonates of the BCB. The low δ13C values (up to -14‰) indicate a carbon source related to organic matter, whereas variantions in δ18O (from +17,7 to +27‰) are explained from fluid interaction with different host rock lithologies (silicilastics and carbonates). In the Murguia diapir, a brecciated carbonate band (up to 50 m thick) at the contact zone has been interpreted as a cap rock-related lithology. Isotopic composition of carbonates shows δ13C negative values (up to -20‰) and a δ18O of about +25‰. Those original values have been modified to higher δ13C and lower δ18O values after the circulation of hydrothermal fluids, related to ore formation.. However, textural relationship between organic matter and sulphides and carbonate isotope data point to ore precipitation unrelated to cap rock formation. 87Sr/86Sr values of gangue carbonates range from 0,70801 a 0,70949 when host rocks are carbonates and from 0,70986 to 0,71202 when mineralizations are hosted in siliciclastics. This relationship suggests that 87Sr/86Sr ratios in the fluid was buffered by host lithologies, in agreement with the δ18O data conclusions. Pb isotope values in galena are homogeneous and fall within the Cretaceous field defined for other MVT deposits in the BCB (Velasco et al., 1996), pointing to similar source rocks for the metals at basin scale.

The focus of this thesis is physicochemical characterisation of Zn complex with a natural phytosiderophore ligand – 2’-deoxymugineic acids (DMA), in light of its possible role in the root Zn uptake in staple crop species, such as rice. Mechanisms behind efficient Zn acquisition in rice cultivars are not yet clearly identified. Yet, this information is vital for the progress of biofortification programs of staple food crops. The work shown in this thesis examines the stability of the [Zn(DMA)] complex in view of the required traits for the fulfillment of the phytosiderophore role. To this end, the ligand in question was synthesised in laboratory conditions. Subsequent tests have shown that the Zn binding affinity of DMA is substantial in comparison to the other rhizosphere present organic molecules. Therefore, solubilisation by DMA is a promising Zn acquisition mechanism in plants. The studies following this investigate stable isotope partitioning upon Zn complexation with DMA by means of experiments, as well as by using computational chemistry calculation methods. Both methods yielded the same conclusion: Zn complexation by DMA favours the heavy 66Zn isotope (∆66Zn ~0.3 ‰), and hence, can introduce a significant isotopic fractionation into the environment. The results of a study on field grown rice are also presented. In this study heavy isotopic enrichment is demonstrated under Zn-deficient conditions in two rice genotypes differing in their susceptibility to Zn-deficient soils; where A69-1 and IR26 are low-Zn tolerant and sensitive cultivars used, respectively. The heavy fractionation factors ((∆66Zn) 0.21 ‰ and ~0.30 ‰ for the tolerant and sensitive rice, respectively) are consistent with Zn solubilisation and uptake by phytosiderophore ligands, and the magnitude of the measured factors corresponds well with the values identified in the preceding experimental and theoretical studies.

La present Tesi té com objectiu l’estudi dels dipòsits de Zn a la zona de Riópar i les seves roques encaixants, que es localitzen just en el límit entre les zones del Prebètic Intern i l’Extern (Conca Bètica Mesozoica, SE d’Espanya). Això permetrà discernir el tipus i evolució dels fluids mineralitzants, així com els principals controls per la seva circulació, a partir de dades geològiques, petrogràfiques i geoquímiques. La zona de Riópar es caracteritza per presentar múltiples cossos dolomítics allotjats en carbonats de diferents edats. Les composicions isotòpiques de C-O dels cossos dolomítics en el Juràssic Inferior i Mitjà, així com en el Cretaci Superior (δ13C: +2,5 a +3,8‰; δ18O: +26,9 a +29,8‰), són similars a les composicions de les calcàries marines del Juràssic-Cretàcic (δ13C: +0.5 a +3.2‰; δ18O: +27.6 a +30.9‰), fet que suggereix una dolomitització per aigua marina a baixes temperatures. En contraposició, els estudis isotòpics de C-O i microtermomètrics desenvolupats en inclusions fluides de les dolomies allotjades en el Juràssic Superior-Cretàcic Inferior (δ13C: -2,3 a +0,8‰; δ18O: +25,1 a +27,6‰; Th: 150-250ºC) posen de manifest que aquestes dolomies varen ser formades per processos hidrotermals. Els dipòsits de Zn-(Fe-Pb) de Riópar es troben exclusivament en les dolomies d’origen hidrotermal, entre les falles de San Jorge i Socovos. Aquests jaciments es caracteritzen per presentar dos tipologies de mineralitzacions: i) hipogèniques de sulfurs de Zn-(Fe-Pb) de tipus Mississippí Valley (MVT), constituïdes per marcassita, esfalerita i galena; i ii) supergèniques de tipus calamina formades per smithsonita, hidrozincita i cerussita, així com oxi-hidròxids de Fe (hematites i goethita). Les dolomies hidrotermals i els sulfurs es varen formar per una mescla entre un fluid de baixa salinitat, probablement derivat del mar Cretàcic (Fluid A: ≤ 5% en pes eq. de NaCl), el qual va circular a través dels estrats Mesozoics, i una salmorra hidrotermal de conca (Fluid B: ≥ 25% en pes eq. de NaCl) amb metalls i sulfat, que va circular per el basament Paleozoic. Les relacions isotòpiques de Pb en cristalls de galena (206Pb/204Pb: 18,736-18,762; 207Pb/204Pb: 15,629-15,660; 208Pb/204Pb: 38,496-38,595) apunten a una única font de metall, segurament derivada de roques Paleozoiques. Per altre banda, les composicions isotòpiques de sofre dels sulfurs de metalls base (marcassita: -7,5 a -5,8‰ δ34S; esfalerita: -2,2 a +3,5‰ δ34S; galena: -2,8 a -2,4‰ δ34S), suggereixen que el sofre va derivar de sulfat Triàsic (marí y/o de dissolució d’evaporites). La reducció del sulfat (SO42-) a àcid sulfhídric (H2S) s’explica mitjançant reaccions termoquímiques amb compostos orgànic (ex., hidrocarburs, metà) en la zona de precipitació mineral. Les observacions de camp i els resultats de les simulacions de transport de calor i flux de fluid suggereixen que els fluids hidrotermals varen circular canalitzats predominantment a través de la falla de San Jorge, mentre que la falla de Socovos devia actuar com a barrera impedint la fuita del fluid hidrotermal cap el Prebètic Extern. Les composicions isotòpiques en C-O de la smithsonita (δ18O: 27,8 a 29,6 ‰; δ13C: -6,3 a +0,4‰), que constitueix la fase principal dels jaciments de calamina, posen de manifest que: i) el fluid oxidant era d’origen meteòric i va interactuar amb els sulfurs a temperatures de 12 a 19ºC, suggerint un procés de meteorització supergènica sota condicions de clima temperat; i ii) la font de carboni va resultar de la mescla entre dos components de CO2, un derivat de la dissolució de les roques carbonatades de caixa (font enriquida en 13C) i l’altre de la descomposició vegetal (font empobrida en 13C). Finalment, la combinació entre els estudis petrogràfics, isotòpics de C i O i microtermométrics seria la eina d’exploració més útil per identificar les dolomies que són favorables a allotjar mineralitzacions de Zn a la zona del Prebètic. Una de las àrees susceptibles a explorar es el bloc inferior de la falla de l’Alto-Guadalquivir.
La presente Tesis tiene como objetivo el estudio de los depósitos de Zn de la zona de Riópar y sus rocas encajantes, que se localizan justo en el límite entre las zonas del Prebético Interno y el Externo (Cuenca Bética Mesozoica, SE de España). Esto permitirá discernir el tipo y evolución de los fluidos mineralizantes, así como los principales controles para su circulación, a partir de datos geológicos, petrográficos y geoquímicos. La zona de Riópar se caracteriza por presentar múltiples cuerpos dolomíticos albergados en carbonatos de diferentes edades. Las composiciones isotópicas de C-O de los cuerpos dolomíticos en el Jurásico Inferior y Medio, así como en el Cretácico Superior (δ13C: +2,5 a +3,8‰; δ18O: +26,9 a +29,8‰), son similares a las composiciones de las calizas marinas del Jurásico-Cretácico (δ13C: +0,5 a +3,2‰; δ18O: +27,6 a +30,9‰), sugiriendo una dolomitización por agua marina a bajas temperaturas. En cambio, los estudios isotópicos de C-O y microtermométricos desarrollados en inclusiones fluidas de las dolomías alojadas en Jurásico Superior-Cretácico Inferior (δ13C: -2,3 a +0,8‰; δ18O: +25,1 a +27,6‰; Th: 150-250ºC) ponen de manifiesto que estas dolomías fueron formadas por procesos hidrotermales. Los depósitos de Zn-(Fe-Pb) de Riópar se encuentran exclusivamente en las dolomías de origen hidrotermal, entre las fallas de San Jorge y Socovos. Estos yacimientos se caracterizan por presentar dos tipologías de mineralizaciones: i) hipogénicas de sulfuros de Zn-(Fe-Pb) de tipo Mississippi Valley (MVT) constituidas por marcasita, esfalerita y galena; y ii) supergénicas de tipo calamina formadas principalmente por smithsonita, hidrocincita y cerusita, así como oxi-hidróxidos de Fe (hematita y goethita). Las dolomías hidrotermales y los sulfuros se formaron por una mezcla entre un fluido de baja salinidad, probablemente derivado del mar Cretácico (Fluido A: ≤ 5% en peso eq. de NaCl), el cual circuló a través de los estratos Mesozoicos, y una salmuera hidrotermal de cuenca (Fluido B: ≥ 25% en peso eq. de NaCl) con metales y sulfato, que circuló por el basamento Paleozoico. Las relaciones isotópicas de Pb en cristales de galena (206Pb/204Pb: 18,736-18,762; 207Pb/204Pb: 15,629-15,660; 208Pb/204Pb: 38,496-38,595) apuntan a una única fuente de metal, posiblemente derivada de rocas Paleozoicas. Por otra parte, las composiciones isotópicas de S de los sulfuros de metales base (marcasita: -7,5 a -5,8‰ δ34S; esfalerita: -2,2 a +3,5‰ δ34S; galena: -2,8 a -2,4‰ δ34S), sugieren que el azufre derivó de sulfato Triásico (marino y/o de disolución de evaporitas Triásicas). La reducción del sulfato (SO42-) a ácido sulfhídrico (H2S) se explica mediante reacciones termoquímicas con compuestos orgánicos (ej., hidrocarburos, metano) en la zona de precipitación mineral. Las observaciones de campo y los resultados de las simulaciones de transporte de calor y flujo de fluido sugieren que los fluidos hidrotermales circularon canalizados predominantemente a través de la falla de San Jorge, mientras que la falla de Socovos actuaría como barrera impidiendo el escape del fluido hidrotermal hacia el Prebético Externo. Las composiciones isotópicas en C-O de la smithsonita (δ18O: 27,8 a 29,6 ‰; δ13C: -6,3 a +0,4‰), que constituye las fase principal de los yacimientos de calamina, ponen de manifiesto que: i) el fluido oxidante era de origen meteórico e interaccionó con los sulfuros a temperaturas de 12 a 19ºC, sugiriendo un proceso de meteorización supergénica bajo condiciones de clima templado; y ii) la fuente de carbono resultó de la mezcla entres dos componentes de CO2, una derivada de la disolución de las rocas carbonatadas de caja (fuente enriquecida en 13C) y otra de la descomposición vegetal (fuente empobrecida en 13C). Finalmente, la combinación entre los estudios de petrográficos, isotópicos de C y O y microtermométricos sería la herramienta de exploración más útil para identificar las dolomías favorables a albergar mineralizaciones de Zn en la zona del Prebético. Una de las áreas susceptibles a explorar es el bloque inferior de la falla del Alto-Guadalquivir.
The aim of the present PhD Thesis is the study of the Zn ore deposits and their carbonate host rocks in the Riópar area, which is located in the limit between the Internal and External Prebetic Zones (Mesozoic Betic Basin, SE Spain). This study will constrain the type and evolution of mineralizing fluids and the main controls for fluid flow, from geological, petrographical and geochemical data. The Riópar zone is home to extensive outcrops of dolostone bodies, which are hosted within different age carbonates. The C-O isotopic compositions of the dolomitic bodies in Lower and Middle Jurassic, as well as in Upper Cretaceous (δ13C: +2.5 a +3.8‰; δ18O: +26.9 a +29.8‰), are within the range of Jurassic to Cretaceous marine limestones (δ13C: +0.5 a +3.2‰; δ18O: +27.6 a +30.9‰); this supports a seawater dolomitization model at low temperature. Nevertheless, the C-O isotopic and fluid inclusion microthermometric studies from dolostones hosted within Upper Jurassic and Lower Cretaceous carbonates (δ13C: -2.3 a +0.8‰; δ18O: +25.1 a +27.6‰; Th: 150-250ºC) suggest that these dolostones are formed by hydrothermal processes. The Riópar Zn-(Fe-Pb) deposits are enclosed within the hydrothermal dolostones, between San Jorge and Socovos faults. These deposits are characterized by two mineralization types: i) hypogenic Zn-(Fe-Pb) sulfides of Mississippi Valley type (MVT) constituted by marcasite, sphalerite and galena; and ii) supergenic non-sulfide deposits (calamine), formed by predominant smithsonite, hydrozincite and cerussite, as well as Fe-oxi-hydroxides (hematite and goethite). The hydrothermal dolostones and sulfides were formed by a mixing between a low salinity fluid, probably derived from Cretaceous seawater (Fluid A: ≤ 5 wt.% NaCl eq.), which flowed through Mesozoic strata, and a basinal brine (Fluid B: ≥ 25 wt.% NaCl eq.) with metals and sulfate, which flowed within the Paleozoic basement. The Pb isotopic ratios in galena crystals (206Pb/204Pb: 18.736-18.762; 207Pb/204Pb: 15.629-15.660; 208Pb/204Pb: 38.496-38.595) suggest a unique metal source, probably from within Paleozoic rocks. On the other hand, the S isotopic compositions from base metal sulfides (marcasite: -7.5 to -5.8‰ δ34S; sphalerite: -2.2 to +3.5‰ δ34S; galena: -2.8 to -2.4‰ δ34S), points to a sulfur source derived from Triassic sulfate (seawater and/or from dissolution of Triassic evaporites). The sulfate (SO42-) reduction to hydrogen sulfide (H2S) is explained by thermochemical reactions with organic compounds (e.g., hydrocarbons, methane) in the ore formation region. Field observations and results of heat transport and fluid flow simulations suggest that hydrothermal fluids must have flowed upwards predominantly along San Jorge fault, whereas the Socovos fault must have acted as a thermal barrier blocking the scape of fluid to the External Prebetic area. The C-O isotopic composition of smithsonite (δ18O: +27.8 to +29.6‰; δ13C: -6.3 to +0.4‰), which constitute the principal mineral phase of the calamine deposits, puts constrains on: i) the oxidizing fluid type, which was of meteoric origin and interacted with sulfides at temperatures of 12 to 19°C, suggesting a supergene weathering process for the calamine-ore formation under a temperate climate; and ii) the carbon source, that resulted from mixing between two CO2 components, one derived from the dissolution of the host-dolomite (13C-enriched source) and another form vegetation decomposition (13C-depleted component). Therefore, the combination of petrographical, C-O isotopes and microthermometrical studies can be used as an exploration tool to identify favorable dolostones to host Zn mineralizations in the Prebetic Zone. One of the susceptible areas to target is the footwall block of Alto-Guadalquivir fault.

FundaÃÃo de Amparo à Pesquisa do Estado do CearÃ
Carried out an experiment under field conditions, in Russas, CE, in order to evaluate the response of papaya (Carica papaya L.) to phosphorus and zinc fertilization under irrigation for one year of cultivation. The experiment was a NEOSSOLO QUARTZARÃNICO, using a randomized block design in a factorial design with five doses of P2O5 (105, 157.5, 210, 315 and 420 kg / ha) and five Zn (0, 3.12, 6.24, 12.48 and 18.72 kilograms / ha), with four replications, totaling 25 treatments and 100 plots. The variables were: P and Zn in soil from 0 to 20 and 20 to 40 cm depth, content of P and Zn in the leaf (petiole), plant height, girth and productivity. The nutrient content in soil and leaf, plant height and stem diameter were evaluated after six months of planting. Productivity was assessed on the first six months of production (1 st year of cultivation). Aside from stem diameter, all other variables were influenced by the levels of P2O5 and Zn, with interaction between the two nutrients in their effect on plant height, concentration of P and Zn in the soil, P concentration in leaves and productivity. The plant height increased linearly with increasing fertilizer with phosphorus and zinc. Phosphorus decreased availability of soil Zn, but did not influence the levels of Zn in the plant. Since the Zn influenced the content of P in the soil and the leaf. The highest yield was related to doses of 293 kg / ha P2O5 and 9.83 kg / ha of Zn.
Realizou-se um experimento em condiÃÃes de campo, em Russas, CE, com o objetivo de avaliar a resposta do mamoeiro sob irrigaÃÃo (Carica Papaya L.) Ã adubaÃÃo com fÃsforo e zinco, durante um ano de cultivo em solo NEOSSOLO QUARTZARÃNICO. O delineamento experimental utilizado foi o de blocos ao acaso, em um esquema fatorial 5 x 5 (105; 157,5; 210; 315; e 420 kg de P2O5/ha) e (0; 3,12; 6,24; 12,48 e 18,72 kg de Zn/ha), com quatro repetiÃÃes. As variÃveis avaliadas foram: conteÃdos de P e Zn no solo nas camadas de 0 a 20 e 20 a 40 cm de profundidade, teor de P e Zn na folha (pecÃolo), altura da planta, circunferÃncia do caule e produtividade. Os teores dos nutrientes no solo e na folha, altura de planta e diÃmetro do caule foram avaliados apÃs seis meses do plantio. A produtividade avaliada foi referente aos seis primeiros meses de produÃÃo (1Â ano de cultivo). Com exceÃÃo do diÃmetro do caule, todas as outras variÃveis foram influenciadas P (P2O5) e Zn, havendo interaÃÃo entre os dois nutrientes no seu efeito sobre a altura da planta, concentraÃÃo de P e Zn no solo, teor de P na folha e produtividade. A altura da planta aumentou linearmente com o incremento da adubaÃÃo com fÃsforo e zinco. O fÃsforo diminuiu a disponibilidade de Zn no solo, porÃm nÃo influenciou os teores de Zn na planta. JÃ o Zn influenciou os conteÃdos de P tanto no solo como na folha. A mÃxima produtividade foi relacionada Ãs doses de 293 kg/ha de P (P2O5) e 9,83 kg/ha de Zn.

In the aerospace and automobile industries, many workpieces are required to have complex shapes and almost defect-free internal structures. These requirements are difficult to meet using traditional cold plastic processing or hot processing. Therefore, the superplastic forming (SPF) process was developed to meet the manufacturing requirements for these workpieces. However, superplastic deformation has long been considered a phenomenon that only occurs in high-temperature conditions. The denaturation temperature will mostly exceed that of half the melting point of the material (temperature in Kelvin). Under these conditions, the SPF process will consume significant energy, which will obviously limit the application of this effective process. Therefore, how to reduce the temperature of superplastic deformation to achieve low temperature superplasticity has become one of the most important issues in this field. In 2018, a special Al-Zn alloy was reported by Russian and Japanese scientists to have room-temperature superplasticity, but the explanation given for this outstanding property was not satisfactory. Therefore, this project will employ advanced in-situ scanning electron microscopy (SEM) testing and high-resolution transmission electron microscopy (TEM) technology to conduct a comprehensive study of the mechanism behind this material’s room-temperature superplasticity. These advanced methods have facilitated exploring the whole process of room-temperature superplasticity. This first chapter of this thesis summarises the SPF process and its development over the last 50 years. It also introduces the mechanisms and requirements for high-temperature superplasticity and the research process for room-temperature superplasticity. The second chapter describes the methods used in this project: X-ray diffraction (XRD), SEM, TEM, high-pressure torsion (HPT) and in-situ tensile test. It also explains the details of the study procedure. The third chapter lists most of the study’s experimental results achieved using the above-mentioned methods. The results of the in-situ SEM tensile test show the process of superplastic deformation at different stages; the results of the high-resolution transmission microscopy illustrate the changing process of Zn atoms during this deformation. Zn atoms will move in the Al matrix to continuously support superplasticity. These data are used to fully explore this material at different stages, from macroscale to microscale. The fourth chapter addresses the reasons for these uncommon results, discussing the movement of Zn atoms and the extraordinary effect of Zn atoms at grain boundaries. Most importantly, the chapter summarises the mechanisms of room-temperature superplasticity based on all these data. The last chapter states the major observations and conclusions of this project and notes some questions that require further investigation.

Sacrificial metallic coatings, such as those based on Zn and Cd are used to protect steel components against corrosion. Growing environmental and health concerns have limited the use of Cd in any form since Cd plating bath is cyanide based and Cd compounds are carcinogenic. This thesis investigates Zn-Ni as a potential replacement for Cd and Cd based alloy coatings used in aerospace industries and Zn in automotive industries with respect to their tribological, corrosion and tribocorrosion resistance and hydrogen embrittlement susceptibility. In situ tribometry and additional ex situ analyses revealed that Zn-Ni coatings had superior resistance to adhesive wear compared to cadmium coatings. The microhardness of Zn-Ni coatings was higher than Zn and Cd coatings. Hardness on the wear track of Zn-Ni coatings showed the formation of strain hardened tribo layer. Zn-Ni coatings had higher polarization resistance after wear testing as compared to zinc and cadmium coatings. The mass loss due to wear enhanced corrosion was less with Zn-Ni than with Zn and Cd coatings. Zn-Ni coatings are a suitable replacement to Cd coatings when the surfaces are subjected to simultaneous wear and corrosion. Zn-Ni coatings had higher polarization resistance after the 24 hour immersion tests compared to zinc and cadmium coatings. Zn-Ni coatings offer better sacrificial corrosion protection because of low corrosion rates, and are a suitable replacement for Cd coatings. The Passivated Zn-Ni coatings showed lower corrosion resistance when heat treated due to localized damage of passive films while there was no effect of heat treatment on corrosion resistance of as plated Zn-Ni coatings. During the electrodeposition of metals, hydrogen is evolved due to electrolysis. The evolved hydrogen may diffuse outward and become trapped in the substrate/coating interface or migrate inward into the steel lattice causing delayed embrittlement when the component is subjected to stress. This study reports two principal variables for Zn, Zn-Ni, and Cd coatings: (i) quantity of hydrogen absorbed by the coating and substrate, by vacuum thermal desorption (ii) permeability of the coating material to hydrogen, by electrochemical permeation. The findings were analyzed in correlation with microstructural characteristics of both the coating material and the coating/substrate interface. With Zn-Ni, both coating process and coating material combined to significantly reduce the risk of internal hydrogen embrittlement by: (i) introducing the least amount hydrogen during the electrodeposition process, and (ii) by the ease with which hydrogen can be extracted by baking due to the presence of cracks in the coating.Keywords: Zn-Ni, Cd, Cd-Ti, Zn, EIS, insitu tribology, tribocorrosion, hydrogen permeation, TDS
Les revêtements métalliques sacrificiels à base de zinc et cadmium sont utilisés pour protéger les composants en acier contre la corrosion. Les préoccupations environnementales et de la santé ont limité l'utilisation du cadmium car les bains de d'électrodéposition au Cd sont normalement à base de cyanure et en plus le Cd est cancérigène. Cette thèse examine le revêtement Zn-Ni pour remplacer le Cd et les revêtements à base de Cd pour utilisation dans l'industrie aérospatiale, ainsi que pour remplacer le Zn dans l'industrie automobile. Les caractéristiques étudiées sont les propriétés tribologique, la résistance à la corrosion et la tribocorrosion, ainsi que la susceptibilité à la fragilisation par l'hydrogène.La tribométrie in situ a révélé que les revêtements Zn-Ni on une résistance supérieure à l'usure adhésive par rapport aux revêtements cadmium. La micro-dureté des revêtements Zn-Ni était plus élevé que les celle des revêtements Zn et Cd. La dureté de la piste d'usure des revêtements Zn-Ni témoigne la formation d'une tribo-couche écrouie.Les revêtements Zn-Ni ont une plus grande résistance à polarisation après l'essai d'usure comparés aux revêtements Zn et Cd. La perte de masse due à l'usure améliorée à la corrosion était moins que pour les revêtements Zn et Cd. Les revêtements Zn-Ni sont un substitut approprié pour les revêtements Cd lorsque les surfaces sont soumises à l'usure et la corrosion simultanée. L'effet du traitement thermique et de la passivation au chrome trivalent sur la corrosion des revêtements Zn-Ni est également décrit. Les revêtements Zn-Ni démontrent une plus grande résistance à la polarisation lors des essais d'immersion comparés aux revêtements Cd. Les revêtements Zn-Ni offrent une meilleure protection à la corrosion sacrificielle en raison des faibles taux de corrosion, et sont de ce point de vue un substitut approprié de revêtements Cd.Au cours de l'électrodéposition de métaux, l'hydrogène se dégage par électrolyse. L'hydrogène peut soit diffuser vers l'extérieur et se piéger à l'interface entre le substrat en acier et le revêtement, soit migrer vers l'intérieur dans l'acier provoquant une fragilisation retardée lorsque le composant est soumis à une contrainte. Cette étude rapporte deux variables principales pour le Zn, Zn-Ni, et les revêtements Cd: (i) la quantité d'hydrogène absorbé par le revêtement et le substrat, mesurée par désorption thermique sous vide, et (ii) la perméabilité du matériau de revêtement à l'hydrogène, mesurée par perméation électrochimique. Les résultats sont analysés en corrélant les caractéristiques de la microstructure du matériau de revêtement et de l'interface entre le revêtement et le substrat en acier. Pour le Zn-Ni, le procès de revêtement ainsi que le matériau de revêtement, ensemble diminuent le risque de fragilisation par l'hydrogène en: (i) introduisant une quantité minimum d'hydrogène lors du processus d'électrodéposition, et (ii) par la facilité avec laquelle l'hydrogène peut être extrait par traitement thermique grâce à la présence de fissures dans le revêtement.Mots-clés: Zn-Ni, Cd, Cd-Ti, Zn, tribologie in situ, tribocorrosion, perméation de l'hydrogène.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O zinco é um micronutriente considerado limitante à produção do milho no Brasil, sendo a sua deficiência muito comum em todas as regiões do país. Com o objetivo de avaliar os efeitos de doses e fontes de Zn nas concentrações do micronutriente no solo, na planta e na produção de matéria seca da parte aérea do milho, foi conduzido um experimento em casa de vegetação, empregando-se amostra de um Latossolo Vermelho textura média. O delineamento experimental foi inteiramente casualizado, com três repetições, segundo um arranjo fatorial 6 x 3 (seis doses de Zn e três fontes). Foram empregadas as seguintes doses de Zn: 0; 0,5; 1; 2; 4 e 6 mg kg-1, utilizando-se as fontes: Zn-EDTA, Zn-lignosulfonato (Zn-LS) e sulfato de zinco. Verificou-se que a aplicação de Zn, independentemente da fonte considerada, aumentou significativamente a produção de matéria seca da parte aérea de milho e as concentrações do micronutriente no solo e na planta. A fonte Zn-LS proporcionou concentrações de Zn no solo e na planta significativamente superiores, particularmente em relação à fonte inorgânica. As fontes de Zn apresentaram um comportamento semelhante em termos de produção de matéria seca. Os níveis críticos de Zn no solo e na parte aérea da planta foram respectivamente, 0,9 e 16 mg kg-1.
The zinc is a micronutrient that limits the production of the maize in Brazil, being its very common deficiency in all the regions of the country. With the objective of evaluating the effect of the zinc rates in micronutrients concentration in soil, in plants and maize shoot dry matter production, an experiment in pots containing Haplustox (Latossolo Vermelho). It was used a complete randomized design, with three replications of treatments, in a factorial arrangement 6 x 3 (six rates of zinc and three sources). It was used following rates of zinc: 0; 0.5; 1; 2; 4 e 6 mg kg-1, and sources: Zn-EDTA, Zn-lignosulfonate (Zn-LS) and zinc sulfate. It was observed zinc application, own the sources, increased corn shoot dry matter and the micronutrient concentration in soil and plant. The source Zn-LS provided more Zn concentration in soil and plant than inorganic source. The zinc sources showed the same performance in dry matter production. The Zn level critic in soil and plant were respectively 0.9 mg kg-1 and 16 mg kg-1.

The goals of this thesis were to synthesize nanocrystalline Zn, to study the mechanical properties of bulk nanocrystalline Zn and try to reveal the deformation mechanisms in nanocrystalline materials. Nanocrystalline Zn powder has been synthesized by a cryomilling method. The average grain size decreased exponentially with the cryomilling time and reached a minimum average grain size of around 17nm. Large numbers of small grains (2~6nm) have been found in the very early stages of cryomilling. Dynamic recrystallization (DRX) was used to explain the observed phenomena. Differential scanning calorimetry (DSC), x-ray diffraction and transmission electron microscopy (TEM) were used to study the structural changes and grain size distribution with milling time and subsequent annealing. Maxima in both stored enthalpy (for the low temperature DSC peak) and lattice strain on the Zn basal planes were observed at the same milling time. Dislocation density on the basal planes is proposed as a major source for lattice strain and the measured stored enthalpy. The released enthalpy that might be due to grain growth is very small. These cryomilled nanocrystalline Zn powders were consolidated into disks with a density of nearly theoretical density by uniaxial compression at room temperature. Cyclic variation of microhardness with milling time has been observed in cryomilled nanocrystalline Zn. Evidence from transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) suggests that the variation of dislocation density and grain size distributions determine the hardness behavior. A model, based on a kinetic reaction-rate model for cyclic amorphous-to-crystalline phase transformations observed during ball milling, simulates the experimental results very well. The model confirms the effect of DRX on modulated cyclic variation of microhardness. Dislocation strain hardening and recrystallization effects are superposed linearly with the intrinsic grain boundary hardening during the simulation. A dislocation density on the order of 10/sup 16/m /sup -2/ is predicted to be necessary to trigger DRX from the model. This prediction is evidenced by HRTEM observation of dislocation density on the same order and consistent with the estimation from thermodynamic calculation. The activation energy for rate controlling step in DRX estimated from the model is around 50 kJ/mol. This estimation indicates that a grain boundary diffusion controlled mechanism could dominate in DRX. Ductility of cryomilled nanocrystalline Zn has been studied by MDBT. The yield strength obtained from MDBT shows modulated cyclic variations with cryomilling time. Three times yield strength is consistent with the microhardness values for the same Zn samples. Ductility of CM2h and CM4h samples are much better than other cryomilled samples as indicated by a much larger ratio of normalized displacement than other cryomilled nanocrystalline Zn samples. However, the ductility of all cryomilled Zn samples is poor or very limited. The poor ductility of cryomilled Zn is presumably due to the remaining flaws as a result of incomplete bonding between particles. The Young?s modulus measured from MDBT barely changes for all tested samples. Bulk (spherical balls) ultra-fine-grained (UFG) or nanostructured Zn via in situ consolidation of powders are produced by mechanical attrition at room temperature. The size of these spherical balls increased with the increase of ball milling time. The grain size decreased rapidly to around 80nm after 1h of ball milling and then increased to around 240nm at 3h. The grain size decreased gradually thereafter with the increase of milling time. An average gain size of around 23nm was achieved for Zn bulk samples ball milled for 25h. In situ consolidation of metal powders during mechanical attrition may be a promising method to produce bulk UFG or nanostructured materials with full density and less contamination. The hardness, yield stress measured from MDBT, and tensile tests are consistent with one another. The hardness increased almost linearly with the decrease of grain size. The positive Hall-Petch slope is much smaller compared to the slope for coarse-grained Zn. Except for BM1h Zn sample, all other samples possess good ductility as evidenced from miniaturized disk bend test (MDBT) results and from the observations of fracture surfaces studied by FESEM. A bulged hat shape sample is usually obtained after MDBT test. The Young?s modulus almost keeps the same as for conventional coarse-grained Zn. The low temperature ball milling proves to be more efficient in reducing the grain size. A maximum elongation of around 110% is achieved for UFG Zn (around 240nm) under uniaxial tension test, which discloses a superplastic deformation in UFG Zn at room temperature. The elongation of room temperature ball milled Zn decreases with the decrease of grain size. Around 20% elongation is observed for Zn with an average grain size of around 23nm. Tension tests at elevated temperature result in a reduction of yield stress. The significant drop of yield stress at 200 centigrade degree or above may be due to recovery or recrystallization as evidenced from FESEM images. A strain rate sensitivity value of around 0.14 is usually found for Zn tested at 20 centigrade degree - 40 centigrade degree.

Ces travaux concernent la caractérisation microstructurale d'alliages Zn-Ni d'origine industrielle, électrodéposés sur des tôles d'acier. Deux techniques sont principalement utilisées : la microscopie électronique en transmission sur des sections tranverses et la diffraction des rayons X en incidence rasante. Le MET renseigne notamment sur les particularités structurales susceptibles de constituer des sites privilégiés de corrosion, stratification induite par le procédé d'élaboration, ancrage du dépôt au substrat et couche de prétraitement, taille et morphologie des grains, fissures d'origines diverses. La diffraction X permet d'identifier les phases présentes dans les revêtements et de lever l'incertitude portant sur la cristallographie de la phase delta ZnNi par l'analyse d'alliages de synthèse et de couples de diffusion. Sur des revêtements spéciaux électrodéposés en cellule pilote, on apprécie l'influence de la densité de courant et de la vitesse relative entre la tôle et l'électrolyte sur la microstructure et la stratification. Le troisième volet de cette thèse est axé sur l'évaluation de la tenue en corrosion des aciers revêtus ZnNi et comporte noatmment une étude par spectroscopie d'impédance électrochimique.

Bibliography: leaves 137-174. This thesis describes research which aims to develop analytical methodology to assist in the determination of metal-chelate complexes in soil solutions and plant fluids, to resolve the process involved in chelate-assisted cadmium and zinc phytoextraction, and also to determine the possible effects of chelation processes on the quantity of phytoavailable Cd and Zn in polluted soils.

Thermogravimétrie, spectroscopies SPX et AUGER, mesures cinétiques ont été utilisées pour caractériser très finement différents catalyseurs Cu-Zn-Al-O couramment utilisés en synthèse du méthanol. A l'état réduit à 523 k, les principaux éléments dégagés de notre étude sont : 1) la présence de cuivre métal et d'une fraction de cuivre à l'état partiellement oxyde et inséré dans le réseau Zn-Al-O ; 2) la présence d'une espèce hydrogène extractible, localisée dans le réseau des oxydes résiduels ; 3) l'existence d'ions hydroxyles relativement mobiles auxquels nous avons attribué un phénomène de blocage des sites hydrogénants. La prise en compte de ces différents points associée à une étude cinétique d'hydrogénation de l'isoprène en l'absence d'hydrogène nous ont amené à établir un modèle de sites actifs et un modèle cinétique d'extraction des espèces hydrogène. Ces modèles sont transposables à toute une classe de catalyseurs à base de cuivre. Le modèle cinétique a permis d'évaluer la quantité d'espèces hydrogène localisées à la surface et qui interviennent dans la détermination des aires métalliques et dans le processus catalytique d'hydrogénation. Enfin, l'influence de la nature des phases sur les caractéristiques et performances des catalyseurs a été discutée.

Orientador: Edson Luiz Mendes Coutinho
Banca: Salatier Buzetti
Banca: Mara Cristina Pessôa da Cruz
Resumo: O zinco é um micronutriente considerado limitante à produção do milho no Brasil, sendo a sua deficiência muito comum em todas as regiões do país. Com o objetivo de avaliar os efeitos de doses e fontes de Zn nas concentrações do micronutriente no solo, na planta e na produção de matéria seca da parte aérea do milho, foi conduzido um experimento em casa de vegetação, empregando-se amostra de um Latossolo Vermelho textura média. O delineamento experimental foi inteiramente casualizado, com três repetições, segundo um arranjo fatorial 6 x 3 (seis doses de Zn e três fontes). Foram empregadas as seguintes doses de Zn: 0; 0,5; 1; 2; 4 e 6 mg kg-1, utilizando-se as fontes: Zn-EDTA, Zn-lignosulfonato (Zn-LS) e sulfato de zinco. Verificou-se que a aplicação de Zn, independentemente da fonte considerada, aumentou significativamente a produção de matéria seca da parte aérea de milho e as concentrações do micronutriente no solo e na planta. A fonte Zn-LS proporcionou concentrações de Zn no solo e na planta significativamente superiores, particularmente em relação à fonte inorgânica. As fontes de Zn apresentaram um comportamento semelhante em termos de produção de matéria seca. Os níveis críticos de Zn no solo e na parte aérea da planta foram respectivamente, 0,9 e 16 mg kg-1.
Abstract: The zinc is a micronutrient that limits the production of the maize in Brazil, being its very common deficiency in all the regions of the country. With the objective of evaluating the effect of the zinc rates in micronutrients concentration in soil, in plants and maize shoot dry matter production, an experiment in pots containing Haplustox (Latossolo Vermelho). It was used a complete randomized design, with three replications of treatments, in a factorial arrangement 6 x 3 (six rates of zinc and three sources). It was used following rates of zinc: 0; 0.5; 1; 2; 4 e 6 mg kg-1, and sources: Zn-EDTA, Zn-lignosulfonate (Zn-LS) and zinc sulfate. It was observed zinc application, own the sources, increased corn shoot dry matter and the micronutrient concentration in soil and plant. The source Zn-LS provided more Zn concentration in soil and plant than inorganic source. The zinc sources showed the same performance in dry matter production. The Zn level critic in soil and plant were respectively 0.9 mg kg-1 and 16 mg kg-1.
Mestre

Frente ao aumento populacional e consequente incremento na demanda por alimentos, é importante estabelecer um melhor aproveitamento da área de cultivo, objetivando a colheita de produtos agrícolas em maior quantidade e de melhor qualidade. O aumento da concentração de micronutrientes nos produtos colhidos, especialmente de zinco é um desafio crescente para a agricultura, com possibilidade de trazer benefícios à saúde humana e à produtividade da cultura. Nesse sentido, a aplicação foliar de zinco realizada periodicamente, à partir da antese floral, é uma técnica capaz de incrementar o teor do micronutriente nas sementes e biofortificar os grãos de feijão e trigo, causando melhoria de aspectos agronômicos (crescimento vegetativo e produtividade da cultura) de plantas provenientes dessas sementes, além de resultar proveitos para a saúde humana daqueles que se alimentam de produtos biofortificados, e ainda com potencial para produzir grãos e sementes como produtos de maior valor comercial no mercado, valendo-se de inovação tecnológica. Porém, atualmente pouco se conhece sobre os diversos aspectos desta técnica. Assim sendo, objetivou-se: (i) elucidar o efeito da aplicação foliar de zinco, à partir da antese floral, como método para incrementar o teor do micronutriente nos grãos de feijão (Phaseolus vulgaris L.) e de trigo (Triticum aestivum L.), em substrato com teor adequado do micronutriente (ii) utilização de diferentes fontes de zinco aplicadas via foliar visando estabelecer a melhor fonte para o aumento do teor do micronutriente no grão de feijoeiro e (iii) determinação das doses de zinco mais adequadas a serem aplicadas através de pulverização foliar visando o aumento do teor do nutriente no grão de plantas de feijão e de trigo. Com base nos resultados obtidos, concluiu-se que (i) a aplicação foliar de zinco realizada periodicamente, à partir da antese floral é capaz de aumentar o teor do micronutriente em grãos de feijão e de trigo; (ii) a fonte mais viável para o enriquecimento de grãos de feijão é o sulfato de zinco; (iii) e todas as doses testadas (125, 250, 375 e 500 g Zn ha-1) aplicadas via foliar na forma de sulfato de zinco foram efetivas para o enriquecimento de grãos de feijão e de trigo, em relação ao controle (0 g Zn ha-1).
In view of the population increase and consequent growth of food demand, it is important to establish a better utilization of the cultivation area, aiming the harvest of agricultural products in greater quantity and of better quality. The increased concentration of micronutrients in products harvested, especially zinc, is a growing challenge for agriculture, with potential to bring benefits to human health and crop productivity. In this matter, the foliar zinc application performed periodically starting at floral anthesis is a technique capable of increasing the micronutrient content in the seeds and biofortifying grains of common bean and wheat, causing agronomic aspects improvement (vegetative growth and crop productivity) of plants derived from these seeds, in addition to bringing benefits to human health of those who feed on biofortified products, and still with potential to produce grains and seeds as products of greater commercial value in the market, being a technological innovation. However, currently little is known about the aspects that circumvent this technique. The objective of this study was: (i) elucidate the effect of foliar application of zinc, starting at floral anthesis, as a method to increase the micronutrient content of common bean (Phaseolus vulgaris L.) and wheat (Triticum aestivum L.) (ii) the use of different sources of zinc applied in a foliar way, in order to establish the best source for increasing the micronutrient content in common bean grains, and (iii) the determination of the most suitable zinc doses, applied by foliar spraying to increase the nutrient content of common bean and wheat plants. Based on the results obtained, it was concluded that (i) the periodic application of zinc foliar application starting at floral anthesis is capable of increasing the micronutrient content in common bean and wheat grains; (ii) the most viable source for the enrichment of bean grains is zinc sulphate; (iii) and all the doses tested (125, 250, 375 and 500 g Zn ha-1) applied via foliar in the form of zinc sulfate were effective for the enrichment of common bean and wheat grains, in relation to the control (0g Zn ha-1).

Les métallo-β-lactamases sont des enzymes qui confèrent aux bactéries qui les synthétisent une résistance aux antibiotiques. La classe B représente les β-lactamases, dans lesquelles le site actif contenant un ou deux atomes de Zn favoriserait l'hydrolyse des antibiotiques. La dégradation des antibiotiques par les enzymes bactériennes est un mécanisme majeur de résistance. L’objectif de ce travail de thèse est de mettre en œuvre des outils de modélisation fondés sur des méthodes de mécanique quantique en vue de déterminer les structures de métallo-β-lactamases avec des inihibiteurs, étape nécessaire pour comprendre ultérieurement quels sont les mécanismes de réaction favorisant la dégradation d’un inhibiteur par des métallo-β-lactamases et fournir des informations qui serviront à mieux interpréter les phénomènes biologiques.Nous avons tout d’abord déterminé les géométries et la stabilité de complexes de coordinations métalliques de systèmes modèles contenant du Zn, comme dans les sites métalliques des métallo-β-lactamases, ou du Cu, complexés à des histidines coordonnées par les Nπ ou Nτ, afin de voir s’il y a une préférence géométrique pour l’une ou l’autre des deux coordinations et voir l’influence de ces différentes coordinations possibles sur les paramètres géométriques au niveau du site métallique. Enfin la présence d’eau et l’influence du solvant aqueux a été étudiée. Grâce à ces méthodes de chimie quantique fondées sur la théorie de la fonctionnelle de la densité, nous avons montré comment ces méthodes permettent d’avoir des informations structurales sur la symétrie adoptée par les centres métalliques, du Zn2+ et du Cu2+. Cette étude structurale nous a permis de mettre en évidence des différences structurales entre ces deux ions métalliques et de déterminer les spectres vibrationnels. Ces investigations nous ont permis de mettre en évidence la nature des liaisons métal-ligand grâce à des approches topologiques. Nous avons montré que ces études préliminaires nous ont permis de choisir la meilleure méthode de calculs DFT pour étudier des centres à zinc dans des structures de β-lactamases.Pour compléter l’étude de structures de métallo-β-lactamases, nous avons déterminé la structure de l’enzyme native L1 (β-lactamase) qui a permis de reproduire les paramètres géométriques des structures expérimentales de L1. Nous avons montré que l’approche combinant des études quantiques et classiques (QM/MM) permet de reproduire avec une très bonne confiance les paramètres structuraux de sites actifs de l’enzyme L1.Enfin, nous avons déterminé les structures de certains sites actifs de la famille B3 des Métallo-β lactamases (Enzyme L1) pour comparer les affinités de différentes familles d’inhibiteurs synthétisées à l’IBM de Montpellier (Institut des Biomolécules de Montpellier) et prédire la structure possible de L1 avec différents inhibiteurs par des méthodes QM/MM pour voir si cette stratégie pourra être appliquée à d’autres inhibiteurs pour des métallo-β-lactamases
Metallo-β-lactamases are enzymes that give the bacteria that synthesize them antibiotic resistance. B Class represents the beta-lactamases, wherein one or two Zn atom(s) promote(s) β-lactams (antibiotics) hydrolysis. The major resistance mechanism is the degradation of the β-lactams by bacterial enzymes called β-lactamases. One major approach to overcome this resistance deals with combination therapy in which a β-lactam drug is given along with a β-lactamase inhibitor, which protects the former from inactivation. The objective of this thesis is to implement modeling tools based on quantum mechanical methods to determine metallo-β-lactamase structures with inhibitors, a step necessary to understand at a later stage the mechanisms of response to the degradation of the inhibitor by β-lactamases and to provide information that will serve to better interpret biological phenomena.We have first determined the geometries and the stability of metal coordination complexes of model systems containing Zn, as in the metallo-β-lactamase metal sites, or Cu, complexed to histidines coordinated by Nπ or Nτ, in order to see if there is a geometric preference for one or the other of the two coordination’s and to see the influence of these different possible coordination’s on the geometrical parameters at the metallic site. Finally, the presence of water and the influence of the aqueous solvent were studied. Using these methods of quantum chemistry based on the density functional theory, we have shown how these methods provide structural information on the symmetry adopted by the metallic centers of Zn2 + and Cu2 +. This structural study allows us to demonstrate structural differences between these two metal ions and to determine the vibrational spectra. These investigations were able to demonstrate the nature of the metal-ligand bonds through topological approaches. We have shown that these preliminary studies have conducted us to choose the best method of DFT calculations for studying zinc centers in β-lactamase structures.To complete the study of metallo-β-lactamase structures, we have determined the structure of the native enzyme L1 (β-lactamase) which permitted to reproduce the geometric parameters of the experimental structures of L1. We have shown that the combination of quantum and classical approaches (QM/MM) allows to reproduce with very good confidence the structural parameters of the L1 enzyme active sites.Finally, we have determined the structures of certain active sites in the B3 family of Metallo-β lactamases (Enzyme L1) to compare the affinities of different families synthesized at IBM in Montpellier (Institute of Biomolecules of Montpellier) and to predict the possible structure of L1 with different inhibitors by QM / MM methods to see if this strategy can be applied to other inhibitors for metallo-β-lactamases

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The squeeze casting process is a casting process in which the cast metal in the liquid state is solidified under pressure in a metal mold closed off by a punch. In general components manufactured by squeeze casting have fine grained, high surface finish and almost free of porosity, may be the same of different sizes and shapes, the mechanical properties are enhanced significantly in comparison with the traditional method of casting and, in addition, parts manufactured by squeeze casting possess superior weldability and are able to heat treatment, and finally compared to the common casting parts manufactured by squeeze casting are formed in one operation with a lower energy consumption. The objective of this study is to analyze the influence of pressure as well as the zinc content of the alloys in the secondary dendrite spacing, the hardness and tensile strength limit, and correlate the microstructures with the mechanical properties and process parameters. For this purpose we used the mass compositions Al-Zn 1% Al-Zn 3% and Al-Zn 5% solidified with the squeeze casting process using the pressure 50 MPa, 100 MPa and 150 MPa, and the pressing time of 5 seconds. It is observed that the increase in pressure causes a reduction in dendrite spacing until 100 MPa, pressure variations from this point up to 150 MPa causes a increase in the secondary dendrite spacing, was also observed that the Vickers hardness and the tensile strength limit have a relationship with the secondary dendrite spacing.
O processo squeeze casting é um processo de fundição, no qual o metal vazado no estado liquido, é solidificado sob pressão dentro de um molde metálico fechado por um punção. Em geral componentes fabricadas por squeeze casting possuem granulação fina, excelente acabamento de superfície e quase livre de porosidade, os mesmo podem ser de diferentes tamanhos e formatos, as propriedades mecânicas são aumentadas significantemente, em comparação ao método tradicional de fundição e, além disso, peças fabricadas por squeeze casting possuem soldabilidade superior e são aptas a tratamentos térmicos, e finalmente em comparação com a fundição comum peças fabricadas por squeeze casting são formadas em uma só operação com um menor consumo de energia. O objetivo deste trabalho é analisar a influencia da pressão assim como do teor de zinco das ligas no espaçamento dendrítico secundário, na microdureza e no limite de resistência à tração, e correlacionar as microestruturas com as propriedades mecânicas e com os parâmetros de processo. Para tal foram utilizadas as composições Al-1%Zn , Al-3%Zn e Al-5%Zn em massa, solidificadas com o processo squeeze casting usando as pressões 0 MPa, 50 MPa, 100 MPa e 150 MPa, com o tempo de prensagem de 5 segundos. Observa-se que o aumento da pressão causa uma diminuição no espaçamento dendrítico até a pressão 100MPa, a partir deste ponto variações até 150 MPa causam aumento no espaçamento dendrítico secundário, observou-se também que a microdureza vickers assim como o limite de resistência à tração apresentam uma relação com o espaçamento dendrítico secundário.

Des electrodepots d'alliage zinc-nickel sur acier, utilises comme revetement sacrificiel, ont ete elabores par courant pulse. L'utilisation de signaux de courant discontinus contribue a une modification des caracteristiques physicochimiques des revetements, dont la plus importante semble etre l'augmentation de la teneur en nickel des alliages. La structure des alliages electrodeposes en courant continu ou pulse est conditionnee par leur composition chimique. Nous proposons un diagramme de phases des depots zinc-nickel entre 0 et 15% de nickel, ou la phase delta, observee a l'equilibre thermodynamique, est absente. En courant continu, les depots sont constitues de la phase eta jusqu'a 7,5% de nickel, des phases eta et gamma de 7,5% et 12,5% et enfin de la phase gamma jusqu'a 15%. En courant pulse, le domaine de coexistence des phases eta et gamma est deplace vers les plus hautes teneurs en nickel (14,5%). La morphologie de surface des depots obtenus en courant continu evolue en fonction de leur structure: les grains sont en forme de plaquettes pour un depot de zinc pur puis deviennent progressivement hexagonaux jusqu'a 7,5% de nickel. Au-dela, ils sont dendritiques et ne deviennent lisses qu'a partir de 12,5% de nickel. Sous courant pulse, un effet nivelant et un affinement des grains similaires a ceux d'un additif organique sont constates. L'etude du comportement en corrosion marine des depots par dissolution intentiostatique et impedance electrochimique a revele que la nature des produits et le type de corrosion different suivant la structure des depots. Lorsque l'alliage est sous la forme de la phase eta, il y a formation de piqures et de produits de corrosion constitues essentiellement d'oxyde et d'hydroxyde de zinc. Lorsque l'alliage est sous la forme de la phase gamma, la corrosion se developpe suivant des lignes de contraintes du depot avec formation d'un reseau dense de fissures. Les produits de corrosion sont dans ce cas majoritairement composes d'hydroxychlorure et d'hydroxyde de zinc

Doutoramento em Engenharia Mecânica
In this work, the R&D work mainly focused on the mechanical and microstructural analysis of severe plastic deformation (SPD) of Al–Zn alloys and the development of microstructure–based models to explain the observed behaviors is presented. Evolution of the microstructure and mechanical properties of Al–30wt% Zn alloy after the SPD by the high–pressure torsion (HPT) has been investigated in detail regarding the increasing amount of deformation. SPD leads to the gradual grain refinement and decomposition of the Al–based supersaturated solid solution. The initial microstructure of the Al–30wt% Zn alloy contains Al and Zn phases with grains sizes respectively of 15 and 1 micron. The SPD in compression leads to a gradual decrease of the Al and Zn phase grain sizes down to 4 microns and 252 nm, respectively, until a plastic strain of 0.25 is reached. At the same time, the average size of the Zn particles in the bulk of the Al grains increases from 20 to 60 nm and that of the Zn precipitates near or at the grain boundaries increases as well. This microstructure transformation is accompanied at the macroscopic scale by a marked softening of the alloy. The SPD produced by HPT is conducted up to a shear strain of 314. The final Al and Zn grains refine down to the nanoscale with sizes of 370 nm and 170 nm, respectively. As a result of HPT, the Zn–rich (Al) supersaturated solid solution decomposes completely and reaches the equilibrium state corresponding to room temperature and its leads to the material softening. A new microstructure–based model is proposed to describe the softening process occurring during the compression of the supersaturated Al–30wt% Zn alloy. The model successfully describes the above–mentioned phenomena based on a new evolution law expressing the dislocation mean free path as a function of the plastic strain. The softening of the material behavior during HPT process is captured very well by the proposed model that takes into consideration the effects of solid solution hardening and its decomposition, Orowan looping and dislocation density evolution. In particular, it is demonstrated that the softening process that occurs during HPT can be attributed mainly to the decomposition of the supersaturated solid solution and, in a lesser extent, to the evolution of the dislocation mean free path with plastic strain.
Este trabalho foi dedicado à análise mecânica e microestrutural de uma liga Al–Zn submetida a um processo de deformação plástica severa (SPD) e ao desenvolvimento de modelos microestruturais para descrever os comportamentos observados. Foi investigada detalhadamente a evolução das propriedades mecânicas e da microestrutura da liga Al–30wt% Zn, após ensaios de torção a alta pressão (HPT), em função do grau de deformação. A SPD promoveu o refinamento gradual do grão e a decomposição da solução sólida de base Al sobressaturada. A microestrutura inicial da liga Al–30wt% Zn continha fases de Al e Zn com grãos de tamanhos 15 e 1 m, respetivamente. A deformação plástica até 0.25, em compressão, promoveu a diminuição gradual do tamanho dos grãos de Al e Zn até 4 m e 252 nm, respetivamente. Simultaneamente, o tamanho médio das partículas de Zn na rede cristalina de grãos de Al aumentou de 20 para 60 nm e, de forma idêntica, também aumentaram os precipitados de Zn na proximidade ou nos contornos de grão. Esta transformação microestrutural foi acompanhada, à escala macroscópica, por um forte amaciamento da liga. Os ensaios HPT foram conduzidos até uma deformação de corte de 314. Com esta SPD, as dimensões dos grãos de Al e Zn diminuiram até à nanoescala; para 370 nm e 170 nm, respetivamente. Como resultado do ensaio HPT, a solução sólida sobressaturada de Al rica em Zn decompôs–se completamente e atingiu o estado de equilíbrio à temperatura ambiente, com o consequente amaciamento do material. Foi criado um novo modelo, baseado na microestrutura do material, que permite descrever o processo de amaciamento que ocorre durante a forte compressão da liga Al–30wt% Zn. O fenómeno foi definido por uma nova lei que relaciona o caminho livre médio das deslocações com a deformação plástica. O modelo proposto permite prever muito bem o amaciamento do material durante o processo HPT, tendo em consideração os efeitos do endurecimento por solução sólida e sua decomposição, o mecanismo de Orowan e a evolução da densidade de deslocações. Em particular, ficou demonstrado que o processo de amaciamento que ocorre durante o ensaio HPT pode ser atribuído principalmente à decomposição da solução sólida sobressaturada e, em menor medida, à evolução do caminho livre médio das deslocações com a deformação plástica.

Wheat plants (Triticum aestivum L. cv. Gamenya) were grown for up to 40 days in a complete culture solution containing 1000 uM phosphate (Pi) with zinc (Zn) added (Zn+) or no Zn added (Zno). Plants were grown under various light regimes with either natural or artificial light. In some experiments, the root system was split into equal halves for either a long term growth period or a short term experimental period with each half root system was bathed in a separate solution. The effects of Zn treatment on dry matter, P content, P concentration, and Pi absorption rates were studied in an attempt to elucidate the mechanism by which Zn functions in relation to P accumulation in wheat plants. The effects of other factors, such as light, localised Zn supply, and pH of solution, were studied to determine how these may affect the response of P accumulation to Zn treatment. Decreasing total light irradiation, either by decreasing intensity or daylength, generally delayed growth but did not directly affect the response to Zn treatment. Thus, omitting Zn generally depressed growth when Zn concentration in the youngest emerged blade (YEB) had fallen to 10 to 12 µg/g dry matter irrespective of the light treatment imposed. Several days after Zn deficiency had depressed growth, Zn deficient plants developed necrotic symptoms in the mid to basal region of the young leaf blades. In addition to inducing these symptoms, Zn deficiency enhanced P concentrations in older leaves to 2% dry matter or greater. Under conditions of high light intensity, it also enhanced the necrotic symptoms of the leaf tips and margins attributed to P toxicity. Although it enhanced P concentration in shoots, Zn deficiency depressed P concentration in roots and generally depressed or had no effect on the rate of Pi absorption (Pi absorbed per unit root weight per unit time) or total P content of wheat plants. On the rare occasions that Z n deficiency enhanced Pi absorption rate or P content, its effect was only transient. When Zn was omitted from only one half of a paired root system, plants appeared identical to those with Z n supplied to both root systems even though omitting Zn from both root systems had severely depressed growth. Although not affecting dry matter of roots or shoots, omitting Zn from only one half root system slightly depressed the rate of Pi absorption by that root system. That omitting Zn from the root environment depressed Pi absorption rate by that root and did not enhance P concentration in shoots suggests that the effect of Zn in roots may be independent of its effect in shoots in relation to P accumulation. In separate experiments, radioactive phosphate (32Pi) was either painted on the oldest leaf blade or supplied to one half of a paired root system. These short term studies suggested that developing Zn deficiency enhanced accumulation of P in old leaves as a result of enhanced gross transport of P to shoots and depressed export of P out of these leaves. This effect of Zn on P movement is discussed in relation to the reported effects of Zn deficiency on auxin concentration. When Zn adequate plants were grown in culture solution with ammonium (NH4+), they lowered their culture solution pH to approximately 3.2. However, Zn deficient plants failed to lower the pH of their culture solution to t he same extent as Zn adequate plants. Indeed, Z n deficient plants raised the pH of their culture solution in spite of the presence of NH4+. This suggests that Zn may have a function in integrity of root membranes. When it was strictly controlled at differing levels, increasing the pH of the culture solution markedly enhanced subsequent short term absorption rate of 3 2 Pi . The effect of pH was much greater than the effect of either the Zn treatment or the nitrogen source supplied to wheat plants. This effect of long term pH treatment was consistent with other long term studies on the effects of pH on P content of plants but was inconsistent with the short term effects of pH on Pi absorption rate which have been previously reported. These results indicate that the pH at which wheat plants were grown was of far greater importance in determining Pi absorption rate than the pH of the solution from which Pi was absorbed. Failure to recognise the long term effect of pH on subsequent short term Pi absorption rate explains why previously published results for short term 32Pi absorption rates conflict with those for long term P accumulation in plants. Zn deficiency affected rhizosphere pH and this may, in turn, affect Pi absorption rate. However, in experiments in which culture solution pH was maintained at near constant levels, this effect of Zn on rhizosphere pH would probably have been of little importance in determining Pi absorption rate. Thus, the effect of Zn deficiency in enhancing P concentration to toxic levels in wheat leaves in the experiments presented in this thesis, can not be attributed to an enhanced Pi absorption rate as has been shown for other species. However, its effect in enhancing P concentration in emerged leaves can be explained by its effects on the distribution and translocation of P within wheat plants. As Zn deficiency became more severe, its effects on dry matter distribution accentuated its effects on P concentration.

CdS is conventionally used as a buffer layer in Cu(In,Ga)Se2, CIGS, solar cells. The aim of this thesis is to substitute CdS with cadmium-free, more transparent and environmentally benign alternative buffer layers and to analyze how the material properties of alternative layers affect the solar cell performance. The alternative buffer layers have been deposited using Atomic Layer Deposition, ALD. A theoretical explanation for the success of CdS is that its conduction band, Ec, forms a small positive offset with that of CIGS. In one of the studies in this thesis the theory is tested experimentally by changing both the Ec position of the CIGS and of Zn(O,S) buffer layers through changing their gallium and sulfur contents respectively. Surprisingly, the top performing solar cells for all gallium contents have Zn(O,S) buffer layers with the same sulfur content and properties in spite of predicted unfavorable Ec offsets. An explanation is proposed based on observed non-homogenous composition in the buffer layer. This thesis also shows that the solar cell performance is strongly related to the resistivity of alternative buffer layers made of (Zn,Mg)O. A tentative explanation is that a high resistivity reduces the influence of shunt paths at the buffer layer/absorber interface. For devices in operation however, it seems beneficial to induce persistent photoconductivity, by light soaking, which can reduce the effective Ec barrier at the interface and thereby improve the fill factor of the solar cells. Zn-Sn-O is introduced as a new buffer layer in this thesis. The initial studies show that solar cells with Zn-Sn-O buffer layers have comparable performance to the CdS reference devices. While an intrinsic ZnO layer is required for a high reproducibility and performance of solar cells with CdS buffer layers it is shown in this thesis that it can be thinned if Zn(O,S) or omitted if (Zn,Mg)O buffer layers are used instead. As a result, a top conversion efficiency of 18.1 % was achieved with an (Zn,Mg)O buffer layer, a record for a cadmium and sulfur free CIGS solar cell.
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 717

Les revêtements galvanisés alliés sont produits par immersion à chaud d’une bande d'acier dans un bain de zinc fondu à environ 460 °C, saturé en fer et contenant de faibles quantités d'aluminium (de 0,1 à 0,135% poids), suivie d’un traitement thermique (jusqu'à des températures voisines de 500-530 °C pendant environ 10 s) afin de déclencher les réactions d'alliation entre le fer et le zinc. La microstructure finale de ce type de revêtement est composée d'une succession de couches stratifiées de phases Fe-Zn et ses propriétés d'usage sont directement liées à la distribution de ces phases dans le revêtement. Les paramètres process à appliquer sur ligne industrielle doivent donc être optimisés pour obtenir la microstructure de revêtement souhaitée avec des coûts minimaux. Le développement d'un tel revêtement passe par différentes réactions complexes : la formation de la couche d'inhibition, la rupture de cette couche, la consommation du zinc liquide et l'enrichissement en fer du revêtement solide. Les cinétiques de ces réactions doivent être étudiées et modélisées séparément afin de contrôler avec précision l'évolution du revêtement au cours du cycle thermique. Dans ce travail, les deux premières réactions ont été étudiées dans le cas des aciers IF Ti. La cinétique de formation de la couche d'inhibition est extrêmement rapide et n’a par conséquent pas été étudiée. L'attention a été portée sur la nature de cette couche et sur les mécanismes responsables de sa formation. Il a été démontré que la couche d'inhibition formée dans des bains classiques pour la production de ces revêtements est composée d'une première couche très mince de Fe2Al5Znx (20-30 nm) sur la surface de l’acier et d’une seconde couche plus épaisse de δ (FeZn7) (environ 200 nm) au-dessus. Lorsque l'acier est immergé dans le bain de zinc, la dissolution du premier dans le second conduit à une sursaturation en fer à l'interface solide / liquide. Une très fine couche de Fe2Al5Znx métastable germe alors sur la surface de l'acier favorisée par des relations préférentielles d’épitaxie avec la ferrite. Par la suite, une couche de δ germe sur la couche de Fe2Al5Znx ce qui permet à la microstructure finale de devenir thermodynamiquement stable. L'effet de la teneur en aluminium du bain sur la nature de la couche d'inhibition a également été étudié. Quand la teneur en aluminium du bain diminue, la couche de Fe2Al5Znx devient discontinue car cette phase devient plus métastable et sa germination sur la surface de l'acier moins probable. Cette étape d’inhibition n'est que transitoire et un traitement thermique prolongé conduira à la rupture de la couche d'inhibition et au développement des réactions Fe-Zn. Le mécanisme de rupture, contrôlé par la diffusion du zinc dans les joints de grains de l'acier, peut être expliqué à l'aide du diagramme de phase ternaire Al-Fe-Zn et résumé en deux étapes : la disparition de la couche de Fe2Al5Znx à l'interface couche d’inhibition / acier résultant de l’enrichissement de cette interface en zinc, et la germination de la phase Г (Fe3Zn10) aux joints de grains de l'acier lorsque la concentration en zinc y devient suffisante. C’est cette germination qui va provoquer localement la rupture de la couche d’inhibition. La cinétique de cette réaction dépend fortement de la composition chimique de l'acier IF Ti et de la teneur en aluminium du bain. D'une part, il apparaît que l'effet de la composition chimique de l'acier sur la cinétique de rupture d'inhibition est contrôlé par la compétition entre deux phénomènes opposés : la vitesse de diffusion du zinc dans les joints de grains de l'acier et la capacité de l'acier à y accumuler les atomes de zinc. D'autre part, la diminution de la teneur en aluminium du bain favorise la discontinuité de la couche de Fe2Al5Znx, ce qui accélère la rupture de la couche d'inhibition car le zinc est supposé diffuser plus rapidement dans δ que dans Fe2Al5Znx
Hot-Dip GalvAnnealed (HDGA) coatings are produced by the immersion of the steel strip into an iron-saturated liquid zinc bath at around 460 °C containing small amounts of aluminium (from 0.1 to 0.135 wt.%, normally) and its subsequent heating (up to temperatures around 500-530 °C for about 10 s, typically) in order to trigger the alloying reactions between iron and zinc. The final microstructure of this kind of coatings is composed of a sequence of stratified Fe-Zn phase layers and its in-use properties are directly related to the phase distribution within the coating. The process parameters to be performed in industrial lines must therefore be optimized in order to obtain a successful coating microstructure with the minimum costs. The development of such a coating passes through different and complex reactions: the inhibition layer formation, the inhibition layer breakdown, the liquid zinc consumption and the iron enrichment of the solid coating. The kinetics accounting for these reactions must be studied and modelled separately in order to accurately control the evolution of the coating along the heat treatment performed in the industrial line. In the present work, the two first reactions were investigated in the case of Ti IF steel grades. The kinetics of the inhibition layer formation is extremely fast and has therefore not been investigated in detail. Concerning this reaction, the focus was given to the nature of this inhibition layer and to the mechanisms accounting for its formation. It has been found that the inhibition layer formed in typical baths for galvannealed coatings production is composed of a very thin layer of the Fe2Al5Znx phase (20-30 nm) on the steel surface and a thicker layer of the δ (FeZn7) phase (around 200 nm) on its top. As the steel strip enters the zinc bath, iron dissolution from the former into the latter leads to an iron supersaturation at the solid / liquid interface. As a result, a very thin layer of metastable Fe2Al5Znx nucleates on the steel surface favoured by preferential epitaxial relationships with ferrite. Subsequently, δ nucleates on the Fe2Al5Znx layer allowing the final microstructure of the inhibition layer to become thermodynamically stable. The effect of the bath aluminium content on the nature of this inhibiting structure has also been studied. As the bath aluminium content is lowered, the Fe2Al5Znx layer becomes discontinuous: the lower the bath aluminium content is, the higher the metastability of Fe2Al5Znx is and the less probable its nucleation on the steel surface is. The inhibition state is only transient and continued heat treatment will lead to the inhibition layer breakdown and the development of the further Fe-Zn alloying reactions. The breakdown mechanism, controlled by the diffusion of zinc towards the steel grain boundaries, can be explained using the Al-Fe-Zn ternary phase diagram and summarized in two steps: the disappearance of the Fe2Al5Znx layer at the inhibition layer / steel interface as a result of the enrichment of this interface in zinc, and the local nucleation of the Г (Fe3Zn10) phase at the steel grain boundaries, breaking the inhibition layer off, when the zinc concentration at these locations becomes high enough. The kinetics accounting for this reaction strongly depends on the Ti IF steel chemical composition and the bath aluminium content. On the one hand, it has been found that the effect of the steel chemical composition on the inhibition layer breakdown kinetics would be ruled by the competition between two opposite phenomena: the rate of zinc diffusion at the steel grain boundaries and the ability of the steel to accumulate the zinc atoms at these locations On the other hand, decreasing the bath aluminium content favours the discontinuity of Fe2Al5Znx, which accelerates the inhibition layer breakdown as zinc is expected to diffuse faster through δ than through Fe2Al5Znx

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
The influence of glycerol additive on the electrodeposition process of Zn-Mn on Pt substrate from acid baths by means of cyclic voltammetry and the characteristics of the coatings by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometry (EDS) and of X-ray diffraction (XRD) have been studied. The voltammograms for deposition of Zn-Mn obtained with 0 to 0.63 M glycerol and boric acid 0.080 M or 0.24 M, were, in general similar (presence of the cathodic wave c0, two cathodic peaks c1 and c2, an anodic peak a1 and a2 region formed by an anodic waves). The efficiency of the process of electrodeposition of Zn-Mn increased with the concentration of glycerol and was it lower than 100%. The analyses of the coatings by SEM showed that those obtained in the deposition potential of -1.19 V were not uniform, consisting of crystallites of different sizes. The only exception was for the deposit obtained with GLY 0.32 M which was more uniform and covered all the substrate of Pt. The electrodeposit analysis obtained by EDX did not indicate this Edep codeposition of Mn with Zn for most of the coatings while for some we cannot assure the presence of Mn. Those obtained at Edep= - 1.53 V from baths containing 0.080 M - 0.48 M GLY were dendritic, while the ones obtained in the presence of 0.63 M GLY were refined showing that this concentration of glycerol acted as a brightener. The XRD analyses showed that the electrodeposits were formed from Zn, Mn, oxides and alloys of different compositions. The smaller size of the glycerol molecule related to boric-sorbitol complex did not prevent the codeposition of Zn and Mn did not lead to a more compact deposit and did not significantly alter the composition of phases.
Estudou-se a influência do aditivo glicerol no processo de eletrodeposição de Zn-Mn sobre substrato de Pt a partir de banhos ácidos, por meio da voltametria cíclica e nas características dos eletrodepósitos por Microscopia Eletrônica de Varredura, Espectroscopia de Dispersão de Raios-X e Espectroscopia de Difração de Raios-X. Os voltamogramas de deposição de Zn-Mn obtidos com 0-0,63M de glicerol e ácido bórico 0,080 M ou 0,24 M, de modo geral, foram similares (presença de onda catódica c0, dois picos catódicos c1 e c2, um pico anódico a1 e uma região a2 formada por ondas anódicas). A eficiência do processo de eletrodeposição de Zn-Mn aumentou com a concentração do glicerol e foi menor que 100%. As análises dos eletrodepósitos por MEV mostraram que os obtidos no potencial de deposição de -1,19 V não foram uniformes, sendo formados por cristalitos de diferentes tamanhos. Exceto para o depósito obtido com GLI 0,32M o qual foi mais uniforme e recobriu totalmente o substrato de Pt. A análise dos eletrodepósitos por EDX obtidos neste Edep não indicou codeposição de Mn com Zn para a maioria dos eletrodepósitos enquanto que para alguns não se pode afirmar a presença de Mn. Os obtidos em Edep=-1,53V a partir dos banhos contendo [0,080M - 0,48M] GLI foram dendríticos. Já os obtidos na presença de 0,63M GLI foram refinados mostrando que para esta concentração o glicerol agiu como abrilhantador. As análises por DRX indicou que os eletrodepósitos foram formados de Zn, Mn, óxidos e diferentes composições de ligas. O menor tamanho da molécula de glicerol com relação ao complexo bórico-sorbitol não impediu a codeposição de Zn e Mn, não levou a um depósito mais compacto e não alterou significativamente a composição de fases.
FAPESP: 2009/01665-0

L'objectif principal de ce travail est de comprendre les phénomènes de dissolution sélective et de cartographier la dissolution sélective des alliages Zn-Al et des alliages Zn-Mg-Al dans une moindre mesure en fonction du pH et de potentiel. Cela aidera à construire un modèle prédictif de couplage galvanique qui est une préoccupation majeure de l'industrie automobile. Pour s'approcher de la cible, nous utilisons la spectroélectrochimie d'émission atomique (AESEC) qui est une combinaison de méthodes électrochimiques et analytiques. Cette technique nous permet de quantifier en temps réel et séparément les taux de dissolution de zinc et d'aluminium à partir des alliages Zn-Al au potentiel de circuit ouvert et du potentiel appliqué dans différentes solutions. Dissolution sélective de zinc et d'aluminium à partir des alliages Zn-Al est ensuite tracée dans les gammes du pH et de potentiel. Les explications relatives à la dissolution sélective et les phénomènes d'inhibition survenant au cours d'expériences sont également donnés grâce à des résultats complémentaires de certains autres méthodes de caractérisation de surface (DRX, MEB / EDS, IR et XPS).

Conventional liquid lubricants are faced with limitations under extreme cyclic operating conditions, such as in applications that require lubrication when changing from atmospheric pressure to ultrahigh vacuum and ambient air to dry nitrogen (e.g., satellite components), and room to elevated (>500°C) temperatures (e.g., aerospace bearings). Alternatively, solid lubricant coatings can be used in conditions where synthetic liquid lubricants and greases are not applicable; however, individual solid lubricant phases usually perform best only for a limited range of operating conditions. Therefore, solid lubricants that can adequately perform over a wider range of environmental conditions are needed, especially during thermal cycling with temperatures exceeding 500°C. One potential material class investigated in this dissertation is lubricious oxides, because unlike other solid lubricant coatings they are typically thermodynamically stable in air and at elevated temperatures. While past studies have been focused on binary metal oxide coatings, such as ZnO, there have been very few ternary oxide and no reported quaternary oxide investigations. The premise behind the addition of the third and fourth refractory metals Ti and Zr is to increase the number of hard and wear resistant phases while maintaining solid lubrication with ZnO. Therefore, the major focus of this dissertation is to investigate the processing-structure-tribological property relations of composite ZnO, TiO2 and ZrO2 phases that form ternary (ZnTi)xOy and quaternary (ZnTiZr)xOy nanocrystalline coatings. The coatings were processed by atomic layer deposition (ALD) using a selective variation of ALD parameters. The growth structure and chemical composition of as-deposited and ex situ annealed ternary and quaternary oxide coatings were studied by combined x-ray diffraction/focused ion beam microscopy/cross-sectional transmission electron microscopy, and x-ray photoelectron spectroscopy/Auger electron spectroscopy, respectively. It was determined that the structure varied from purely nanocrystalline (ternary oxides) to composite amorphous/nanocrystalline (quaternary oxides) depending on ALD parameters and annealing temperatures. In particular, the ZnTiO3 ilmenite phase with (104) textured nanocolumnar grains, exhibiting high stacking fault/partial dislocation densities >1012/cm2, was responsible for the excellent tribological behavior. Steady-state sliding friction coefficients down to 0.12 in humid air and 0.2 in dry nitrogen were measured along with sliding and fretting wear factors in the range of 10-6 to 10-7 mm3/N·m, even after ex situ annealing to 550°C. Additionally, the quaternary oxide phase Zn(Ti,Zr)O3 in solid solution exhibited a low fretting wear rate of 1x10-6 mm3/N·m. In contrast, certain phases, such as Zn2TiO4 cubic spinel, that form at annealing temperatures >550°C were responsible for high friction and wear. Mechanistic studies using the above techniques revealed low friction and wear-reducing surfaces and subsurfaces were due to different velocity accommodation modes (VAM). In the case of the ternary system, sliding-induced plastic deformation was possible when ZnTiO3 (104) stacking faults, bordered by partial dislocations, serve as a pathway for the dislocations to glide parallel to the sliding direction and hence achieve low friction and wear via an intrafilm shear VAM. It was evident that the individual nanocolumnar ZnTiO3 grains were plastically sheared as opposed to being fractured during wear. Conversely for the quaternary system, an interfacial sliding VAM between the counterface and a mechanically mixed layer (tribofilm) composed of the refined coating and counterface material, that also served as a source for the formation of cylindrical rolls, was responsible for wear reduction. Therefore, these lubricious oxides are a potential candidate for solid lubrication at high temperatures (up to 550 °C) and in space environments.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Alquilfenilselenetos são intermediários sintéticos versáteis especialmente para a formação de duplas ligações carbono-carbono em condições suaves. Um método alternativo aos métodos tradicionais foi desenvolvido por Lothar Bieber e colaboradores, a partir da reação do PhSeSePh com haletos orgânicos na presença de zinco em pó em meio aquoso, abrangendo uma ampla classe de substratos. A falta de precedentes em termos do entendimento desta nova reação algumas vezes acarreta na escolha de condições desfavoráveis à obtenção dos melhores resultados. Isso impulsionou a realização de uma investigação que possibilite um entendimento mais detalhado da reação, culminando com a formulação de um mecanismo para a mesma. O estudo consiste na utilização do relógio radicalar ciclopropilcarbinil, muito difundido em investigações mecanísticas que objetivam a determinação do envolvimento de intermediários radicalares. Para isso utiliza-se halometilciclopropanos (precursor deste relógio radicalar) na reação tipo Barbier com o disseleneto de difenila (PhSeSePh) na presença de zinco em meio aquoso. Na reação realizada com iodometilciclopropano verificou-se a formação do produto de substituição sem rearranjo, o (metilciclopropil)-fenilseleneto (produto 1) e do produto de substituição após rearranjo o (3-butenil)-fenilseleneto (produto 2), sempre em menor proporção que o produto (1). As proporções entre os produtos mostraram-se dependentes do pH do meio, da concentração de PhSeSePh e da granulação do zinco e por outro lado pouco sensível ao uso de promotores radicalares; já nas reações em que se utilizou o cloro- ou o bromometilciclopropano observou-se a formação quase exclusiva do produto (1), com a proporção entre os produtos permanecendo praticamente inalterada com variação do pH ou da concentração do PhSeSePh. Mecanismos clássicos, tais como substituição nucleofílica e substituição homolítica, foram descartados devido à incapacidade destes mecanismos de esclarecer completamente todos os efeitos observados na reação, embora a presença de alguns aspectos característicos a ambos os mecanismos seja inegável

Les whiskers, filaments métalliques qui poussent sur des surfaces métalliques, sont unproblème très important pour la fiabilité des composants électroniques. Depuis ces dernièresannées, il y a eu un regain d’intérêts industriels dans le domaine de la croissance des whiskers,principalement en raison de la miniaturisation des dispositifs électroniques et des réglementationsenvironnementales interdisant l'utilisation du plomb.Alors que la plupart des recherches concernent les whiskers d'étain, il y a encore peu detravaux sur les whiskers de zinc. Les revêtements d’électrodéposés de zinc sont utilisés commeprotection anticorrosion pour les aciers faiblement alliés dans diverses industries, commel'automobile, l'aéronautique ou l'énergie, ainsi que dans les structures de soutien ou les planchersfaux plafonds dans les centres de données informatiques. Afin d'atténuer, de prévenir et deprédire les défaillances causées par les whiskers de zinc, les mécanismes de sa croissance doiventêtre compris.Grâce à des tests de stockage accéléré et à des observations par microscopie électronique àbalayage (MEB), la cinétique de croissance des whiskers de zinc a été étudiée sur des tôles d'acierau carbone faiblement allié, galvanisé et chromé. Afin de comprendre les mécanismes de lacroissance des whiskers de zinc, la caractérisation quantitative ainsi que les excroissances (densité,volume et vitesse de croissance) ont été reliées aux paramètres suivants: la température, le bainpour l’électrodéposition du zinc, la chromatation, l’épaisseur du substrat d’acier, l’épaisseur durevêtement de zinc ainsi que la contrainte résiduelle.En outre, la microstructure et la cristallographie du revêtement de zinc, des racines deswhiskers ainsi que des whiskers elles-mêmes ont été étudiées par diffraction des électronsrétrodiffusés (EBSD), microscopie électronique à transmission (MET), microanalyse par rayon X(EDX) et le dispositif ASTAR pour l'orientation locale des grains; la préparation des échantillonsa été réalisée à l’aide d’un faisceau d'ions focalisés (FIB). La recristallisation ainsi que lesdislocations dans les whiskers et les excroissances ont été observés; aucun composéintermétallique n’a été observé que ce soit dans les échantillons issus de différents bainsélectrolytes ou encore dans les films / whiskers.Il a été montré que la relaxation de contrainte de compression résiduelle et la croissance deswhiskers sont deux phénomènes différents mais fortement reliés et thermiquement activés.Chacun d'entre eux suit un mécanisme différent; les énergies d'activation apparentes des deuxphénomènes ont été établies, et la diffusion aux joints de grains est proposée comme le principalmécanisme de diffusion pour la croissance des whiskers.Des cinétiques de la croissance des whiskers, à la fois analytique et phénoménologique sontproposées. Une bonne estimation de la croissance des whiskers et de leur vitesse de croissance àdes températures proches des conditions de fonctionnement est obtenue par comparaison avecles données expérimentales
Whiskers, conductive metallic filaments that grow from metallic surfaces, are a very importantissue for reliability of electronic components. Through recent years, there has been a renewedindustrial interest on whisker growth, mainly due to the miniaturization of electronic devices andthe environmental regulations forbidding the use of lead.While most of the research has been focused on tin whiskers, there is still little reference tozinc whiskers. Electroplated zinc coatings are actually used as anticorrosive protection for lowalloy steels in diverse industries such as automotive, aerospace or energy, as well as for supportstructures or raised-floor tiles in computer data centers. In order to mitigate, prevent and predictthe failures caused by the zinc whiskers, the mechanisms of growth must be understood.By accelerated storage tests and Scanning Electron Microscopy (SEM) observation, kinetics ofgrowth of zinc whiskers was studied on low alloy chromed electroplated carbon steel.Quantitative characterization of both whisker and hillocks (density, volume and growth rate) wasrelated with the parameters temperature, electroplating electrolyte, presence of chrome, steelsubstrate thickness, zinc coating thickness and residual stress, in order to understand themechanisms of growth.Additionally, both microstructure and crystallography of zinc coating, whisker roots and actualwhiskers were studied by Electron Backscatter Diffraction (EBSD), Transmission ElectronMicroscopy (TEM), Energy-dispersive X-ray spectroscopy (EDX) and local grain orientationwith ASTAR setup, using Focused Ion Beam (FIB) for samples preparation. Recrystallization aswell as dislocations were observed in both whiskers and hillocks; no intermetallic compoundswere seen in neither electroplated nor whiskers.It is found that compressive residual stress relaxation and whiskers growth are two differentbut strongly interconnected phenomena both thermally activated, an each of them follows adifferent mechanism; apparent activation energies of the two phenomena are calculated, andgrain boundary diffusion is established as the main diffusion mechanism for whiskers growth.Whiskers growth kinetics, both analytical and phenomenological is proposed. Goodestimation of whiskers growth and whiskers growth rate at temperatures close to operationconditions is obtained when compared with experimental data
Whiskers, filamentos metálicos que crecen en superficies metálicas, son un problema muyimportante para la fiabilidad de componentes electrónicos. Durante los últimos años, ha habidoun renovado interés industrial en el crecimiento de whiskers, debido principalmente a laminiaturización de dispositivos electrónicos y a las regulaciones ambientales que prohíben lautilización de plomo.La mayoría de las investigaciones se concentran en los whiskers de estaño y hay todavía pocostrabajos sobre los whiskers de zinc. Los recubrimientos de zinc electrodepositado son utilizadoscomo protección anticorrosión para los aceros de baja aleación en diversas industrias, comoautomotriz, aeronáutica o energética, así como en la estructuras de soporte o tejas de techosfalsos en los centros de datos informáticos. Para atenuar, prevenir y predecir las fallas causadaspor los whiskers de zinc, los mecanismos de crecimiento deben ser comprendidos.Gracias a experimentos de almacenamiento de muestras y a observaciones por microscopíaelectrónica de barrido (SEM), la cinética de crecimiento de whiskers de zinc ha sido estudiada enaceros de baja aleación recubiertos de zinc y cromados. Para comprender los mecanismos decrecimiento de whiskers de zinc, la caracterización cuantitativa de whiskers y de protuberancias(densidad, volumen y velocidad de crecimiento) fue relacionada con los parámetros siguientes:temperatura, electrolito usado en la electrodeposición de zinc, cromado, espesor del substrato deacero, espesor del recubrimiento de zinc al igual que el estrés residual.Adicionalmente, microestructura y cristalografía del recubrimiento de zinc, de raíces dewhiskers así como de los propios whiskers fueron estudiadas por medio de la difracción deelectrones por retrodispersión (EBSD), microscopía electrónica de transmisión (TEM),microanálisis por rayos X (EDX) y el dispositivo ASTAR para la orientación local de granos; lapreparación de muestras fue realizada con la ayuda de un haz de iones localizados (FIB). Larecristalización así como las dislocaciones en whiskers y protuberancias fueron observadas;ningún compuesto intermetálico ha sido observado en los recubrimientos ni en los whiskers.Se determinó que la relajación del estrés residual de compresión y el crecimiento de whiskersson dos fenómenos diferentes pero fuertemente interconectados y térmicamente activados. Cadauno de ellos sigue un mecanismo diferente; las energías de activación aparentes de los dosfenómenos han sido establecidas, y la difusión por bordes de grano es propuesta como elprincipal mecanismo de difusión para el crecimiento de whiskers.Cinéticas de crecimiento de whiskers, a la vez analíticas y fenomenológicas son propuestas.Una buena estimación del crecimiento de whiskers y su velocidad de crecimiento a temperaturascercanas a las condiciones de operación es obtenida por comparación con los datosexperimentales

L'analyse thermodynamique des systemes binaires zn-te, cd-te et cd-cu a ete realisee par les methodes de calcul, base sur l'optimisation des coefficients d'enthalpies libres des phases de chaque systeme. L'etude experimentale a ete effectuee par les methodes d'analyse thermique differentielle, d'analyse calorimetrique differentielle, la radiocristallographie sur poudre et la metallographie. Nous avons mis en evidence la zone de demixtion dans la region riche en zinc du systeme binaire zn-te, la reaction monotectique est observee a 1207c. Les coefficients de l'enthalpie libre de chaque phase des systemes zn-te, cd-te et cd-cu ont ete obtenues, la coherence entre les resultats de calculs et nos donnees experimentales ainsi que ceux de la litterature sont illustres par les differentes courbes calculees. L'influence de la pression sur la forme des diagrammes de phases des systemes zn-te et cd-te a ete aussi examinee. Le systeme ternaire cd-te-zn a fait l'objet de peu de travaux experimentaux par contre, le calcul de ce systeme a attire de nombreux chercheurs. Les quelques informations experimentales dont nous disposons montrent que ce systeme presente une solution solide continue entre les composes cdte et znte. La zone de demixtion liquide-liquide dans la region riche en zinc a ete predit par les moyens de calcul et la lacune de miscibilite a l'etat solide par observation en microscopy electronique. L'etude experimentale de ce systeme a mis en evidence en plus de la presence de la solution solide continue, la lacune de miscibilite a l'etat solide. La zone de demixtion liquide-liquide qui part de la demixtion binaire du systeme zn-te et se renferme sur elle meme. Cette zone depasse legerement l'isoplethe a 10 atomes % de cadmium. Un eutectique ternaire a ete aussi observe a la temperature de 265c dans le quadrilatere cd-zn-znte-cdte. Cette etude ne revele l'existence d'aucun compose defini ternaire

Etude de la porosite des revetements electrolytiques de zn, ni et zn-12% ni par une methode basee sur les mesures du potentiel et de la vitesse de corrosion et par une methode basee sur les mesures d'impedance electrochimique. Comparaison du comportement des differents revetements en milieu neutre et en milieu acide

Neste trabalho, foram depositadas sobre lâminas de silício camadas de zeólitos cristalinos, formados por cadeias de átomos de zinco e bases conjugadas do imidazol (ZIF: Zeolitic Imidazolate Framework), com o objetivo de avaliar os processos de adsorção e absorção do CO2 e aplicar essas camadas como pré-concentradores para a detecção de CO2. Para a deposição das camadas ZIF através dos processos Spinning e casting, foi proposta uma solução química alternativa que emprega etanol como solvente em vez de metanol como reportado na literatura, a fim de proporcionar um processo menos tóxico ao ser humano e viabilizar o armazenamento de CO2 para aplicações envolvendo não apenas a sua detecção mas também a sua remoção do ambiente. As camadas ZIF foram depositadas utilizando uma solução obtida a partir da mistura de nitrato de zinco (4,3g) e 2-metilimidazol (9,7g) em etanol com diversas diluições com a finalidade de variar o pH na faixa de 7,2 a 8,2. Como resultado, verificou-se que as camadas obtidas apresentaram estrutura cristalina ZIF-8 ou ZIF-90 apenas na situação de pH próximo de 7. Além disso, as camadas depositadas através da técnica Spinning apresentaram baixa aderência sobre lâminas de silício e não foi possível depositar camadas com espessuras na faixa de micrômetros. Por outro lado, camadas repetitivas com aproximadamente 7, 5µm de espessura foram depositadas nas lâminas de silício através do processo casting em solução de pH = 7,2 (50ml). Após o recozimento dessas camadas na temperatura de 150 ºC por 48h em ambiente de nitrogênio ultrapuro, obtiveram-se distribuições repetitivas de nanocristais com tamanhos na faixa de 5 a 400nm e estrutura cristalina tipo ZIF-90. Das medidas de espectroscopia IR nas camadas de ZIF-90, observou-se que a banda localizada em 2337cm-1 intensifica com o aumento da pressão do CO2 e com o tempo em que a pressão é mantida. Além da banda em 2337cm-1, foi observada uma segunda banda em 2360cm-1, indicando dois diferentes tipos de resposta: (i) a banda em 2337cm-1 foi associada a uma porção substancial de moléculas de CO2 absorvidas dentro da camada junto aos contornos dos nanocristais ou dentro da sua estrutura cristalina, e (ii) a banda em 2360cm-1 foi atribuída à porção de moléculas de CO2 adsorvidas na superfície. Além disso, se o tempo de exposição da camada de ZIF-90 ao CO2, na pressão atmosférica for de pelomenos 2h, atinge-se sensibilidade de 100ppm ao CO2, considerando a leitura mínima de absorbância como sendo igual a 0,02 para 0,5 l/min de CO2 fluindo sobre a amostra.
In this work, layers of crystalline zeolites formed by chains of zinc atoms and conjugate bases of the imidazole (ZIF: zeolitic Imidazolate Framework) were deposited to evaluate the desorption and absorption of CO2 and apply these layers as pre-concentrators for CO2 detection. For the deposition of ZIF layers by means of spinning or casting, it was proposed an alternative chemical solution which employs ethanol as solvent instead of methanol, as reported in the literature, to provide a less toxic process to humans and allow one the CO2 storage applications involving not just detection but also its removal from the environment. The ZIF layers were deposited using a solution prepared from a mixture of zinc nitrate (4.3g) and 2-methylimidazole (9.7g) with several dilutions in ethanol to vary the pH in the range of 7.2 to 8.2. As a result, the crystalline structure of the layers was ZIF-8 or ZIF-90 only for pH next to 7. Furthermore, the layers deposited by spinning showed low adhesion to the silicon wafers and it was not possible to deposit layers for thickness in the micrometer range. Moreover, repetitive layers of approximately 7.5µm in thickness were deposited on the silicon wafers by casting for pH = 7.2 (50ml). After annealing these layers at a temperature of 150 ºC for 48h in ultra-pure nitrogen, it was obtained repetitive nanocrystals with size distributions in the range of 5 to 400 nm having a ZIF-90 crystal structure. From infrared (IR) measurements of the ZIF-90 layers, it was observed a band located at 2337cm-1 that increases with the increase of the CO2 pressure and with the exposure time to this pressure. In addition to the band at 2337cm-1, it was observed a second band at 2360cm-1 indicating two different responses: (i) the band at 2337cm-1 is related to a substantial portion of the CO2 molecules absorbed into the layer along the contours of the nanocrystals or within the crystal structure and (ii) the band at 2360cm-1 is related to the portion of CO2 molecules adsorbed on the surface. Also, if the ZIF-90 layer is exposed to CO2 at atmospheric pressure for at least 2h, a 100ppm sensitivity to CO2 is achieved considering the minimum absorbance as being 0.02 when 0.5 l/min of CO2 is flowing on the sample.

Les travaux présentés dans ce mémoire ont pour but de mieux comprendre l’électrodéposition de revêtements nanocomposites et d’approfondir leur caractérisation. Le système étudié est un revêtement de zinc renforcé par des nanoparticules de cérine. Les dépôts de zinc sont élaborés par électrodéposition en courant continu et pulsé dans un bain ammonium chlorure dans lequel sont introduites des nanoparticules de cérine commerciales de 50 nm de diamètre. A l’issue d’une phase d’optimisation, des conditions de bain particulières caractérisées par un pH basique et l’utilisation d’un surfactant anionique ont ainsi été sélectionnées afin de s’assurer d’une suffisante stabilité de la suspension. L’influence des nanoparticules sur les mécanismes et rendements d’électrodéposition est étudiée. Une caractérisation précise des revêtements élaborés en courant continu a été développée au moyen de diverses techniques (MEB-EDS, DRX, SIMS, SDL, MET). Cette approche multi-disciplinaire a pour but d’évaluer l’incorporation de cérine dans le composite et localiser celle-ci dans l’épaisseur, approche originale et novatrice dans le domaine des revêtements composites à matrice zinc. Les nanoparticules influencent les propriétés des revêtements, avec une augmentation de dureté jusqu’à quarante pourcents. L’impact sur le comportement à la corrosion est mineur mais une amélioration en immersion longue durée est observée. Dans le but d’augmenter plus drastiquement l’incorporation et donc les propriétés, une modification de la morphologie du zinc parait indispensable. Dans cette optique, une démarche d’élaboration en courants pulsés a été conduite avec des résultats limités du fait de la forte influence des particules sur les mécanismes de germination/croissance en pulsés. L’utilisation d’un élément d’alliage tel le nickel est une perspective encourageante pour obtenir des revêtements composites aux propriétés optimisées
The work presented within this thesis aims to better understand the electrodeposition of nanocomposite coatings and to improve their characterization. The system studied is a zinc coating reinforced by nanoparticles of ceria (50 nm in size). Zinc coatings are produced by DC and PC electroplating from an ammonium chloride bath in which the commercial ceria nanoparticles were introduced. Following an optimization stage, specific bath conditions with a alcaline pH and the use of an anionic surfactant have been selected to ensure sufficient stability of the suspension. The influence of nanoparticles on the mechanisms and plating efficiency is studied. A deep characterization of coatings was performed using various techniques (SEM-EDS, XRD, SIMS, GDOES, TEM). This plural approach aims to assess the dispersion of ceria in the composite surface and bulk, which leads to an original and innovative approach in the field of zinc matrix composite coatings. Nanoparticles influence the properties of coatings, increasing hardness up to forty percent. The impact on the corrosion behavior is minor but a slight improvement in long-term immersion is observed. In order to increase more drastically the incorporation of ceria and therefore properties of the resulting coating, change in the morphology of the zinc seems essential. In this context, an approach developed towards pulsed currents was conducted with limited results because of the strong influence of particles on the mechanisms of germination / growth. The use of an alloying element such as nickel is a promising prospect for composite coatings with optimal properties

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
In this works we will study G-graded algebras and G-graded polynomial identities, where G is an additive group. For main result we will describe a finite basis for Zn-graded polynomial identities of the matrix algebra of order n x n, with entries in a field F, This study will be divided into two stages: when the field F has characteristic zero and when the field F is infinite. These results were described by Vasilovsky [18] in 1999 and Azevedo [2] in 2006.
Nesta dissertação estudaremos álgebras G-graduadas e identidades polinomiais G-graduadas, onde G é um grupo aditivo. Como resultado principal descreveremos uma base finita para as identidades polinomiais Zn-graduadas da álgebra das matrizes n x n, com entradas em um corpo F, Este estudo será subdividido em duas etapas: quando o corpo F for de característica zero e quando o corpo F for infinito. Estes resultados foram descritos por Vasilovsky [18] em 1999 e por Azevedo [2] em 2006