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1
Howard, P. "Precipitation and creep in an Al-Zn-Mg-Cu based alloy." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356709.
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Jackson, Adrian. "Homogenisation effects of the hot working of Al-Zn-Mg-Cu alloys." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319934.
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Solas, Denis. "Anisotropie des propriétés mécaniques et endommagement des alliages Al-Zn-Mg-Cu." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0226.
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Les toles fortes en alliage d'aluminium de la serie 7000 peuvent presenter une anisotropie des proprietes mecaniques (limite d'elasticite, ecrouissage et endommagement). Ces toles sont obtenues apres laminage a chaud, mise en solution, trempe, detensionnement et traitement de revenu. Dans un premier temps, nous avons caracterise la microstructure du materiau (structure granulaire, texture cristallographique, microstructure des joints de grains. . . ). L'anisotropie des proprietes mecaniques est determinee pour differents traitements de revenu par essai de traction. L'anisotropie de la limite d'elasticite est simulee a l'aide d'un modele autocoherent elastoplastique. Ce modele permet de prevoir et de prendre en compte les contraintes residuelles du deuxieme ordre generees par le detensionnement. En ce qui concerne l'endommagement et la rupture, plusieurs mecanismes ont ete identifies en fonction du traitement de revenu et de la direction de traction. En particulier, la rupture intergranulaire se produit pour une contrainte critique qui depend du mode de sollicitation des joints de grains (traction et cisaillement) et de leur microstructure.
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Caraher, Sally Kate 1974. "Clustering and precipitation processes in age-hardened Al-Zn-Mg-(Ag, Cu) alloys." Monash University, School of Physics and Materials Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/7803.
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Lamb, Justin. "Decomposition and its effects on mechanical properties in Al-Zn-Mg-Cu alloys." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/54931.
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The effects of variations in composition on the decomposition process in Al-Zn-Mg-Cu alloys (i.e. – 7xxx-series aluminum alloy) were studied emphasizing their effect on mechanical properties. Several experimental quaternary alloys were studied to compare their behavior with commercial 7xxx-series alloys. The investigation included studies on the effects of natural aging, artificial aging, quench sensitivity, precipitate free zone formation, and homogenization. Additionally, “true aging” curves (i.e. – hardness/strength vs. conductivity) were presented in order to visualize and quantify the entire precipitation process.
It is obvious that fluctuations in the main alloying elements/processing parameters can alter the precipitation process, but the purpose of this work was to quantify those changes using standard industrial techniques. It was found that natural aging was detrimental for strength in the T6 temper for alloys containing more than 1.0 wt.% Cu, and was shown to alter the coarsening kinetics in the over-aged condition (T7). Conversely, for alloys with Cu contents less than 0.5% natural aging was shown to be beneficial for strength. Altering the Zn:Mg ratio was also shown to effect natural aging response of an alloy in addition to introducing additional precipitation processes (T-phase). Therefore, this work is a blueprint for advanced alloy manufacturing that allows for the rapid production of new alloys and tempers by narrowing the research focus depending on an alloy’s composition.
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Cottignies, Laurent. "Propriétés mécaniques d'un alliage Al-Zn-Mg-Cu obtenu par voie Osprey(TM)." Grenoble INPG, 1993. http://www.theses.fr/1993INPG0077.
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Nous avons etudie la microstructure et les proprietes mecaniques statiques d'un alliage d'aluminium al-zn-mg-cu a haute teneur en zinc elabore par deposition en mode osprey. L'alliage a ete file et mis en solution de maniere conventionnelle. Nous avons suivi la cinetique de la precipitation structurale a 105 degres par diffusion centrale de rayons x in situ. Une etude des precipites en microscopie electronique a permis de mettre en evidence la presence de phases cubiques specifiques presentant avec la matrice cfc la relation d'orientation de kurdjumov et sachs. L'alliage possede une limite d'elasticite tres elevee pour un alliage d'aluminium. A l'aide de modeles de la metallurgie physique couples a un modele de deformation elastoplastique des polycristaux, nous avons etabli que la limite d'elasticite peut etre interpretee par des mecanismes de cisaillement des precipites. Les precipites ne sont pas distribues de maniere isotrope a l'interieur des grains ; ce phenomene est responsable d'une part de l'anisotropie de la limite d'elasticite. Les modes de rupture de l'alliage ont ete etudies en traction et en traction sous pression hydrostatique de confinement. Deux modes de ruine de materiau sont en competition : la decohesion des joints de grains et la propagation de bandes de cisaillement
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Криницький, А. В., and В. З. Барсуков. "Дослідження впливу легування (Zn та Zn+Cu) на корозійну стійкість (α-Al-Mg2Si) сплавів системи Al-Mg-Si." Thesis, КНУТД, 2016. https://er.knutd.edu.ua/handle/123456789/4543.
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Рожин, А. В. "Совершенствование процессов модифицирования и легирования алюминиевых сплавов на основе систем Al-Cu-Mg и Al-Zn-Mg-Cu : автореф. дис. … канд. техн. наук : 05.16.04." Thesis, б. и, 2013. http://hdl.handle.net/10995/20232.
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Yoon, Yuhchae. "Formation and breakdown on chromate conversion coatings on Al-Zn-Mg-Cu 7x75 alloys." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1101754567.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xxi, 282 p.; also includes graphics (some col.). Includes bibliographical references (p. 262-282).
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Rick, Cristiane Fonseca. "Estudo da liga base de Zn-Al-Cu-Mg aplicada na fabricação de jóias folhadas." Pontifícia Universidade Católica do Rio Grande do Sul, 2006. http://hdl.handle.net/10923/3377.
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Previous issue date: 2006The last years, the jewellery industrial sector is becoming of significance importance in the scenario of national and international economy. Brazil is one of the jewels biggest world producer, being the Rio Grande do Sul the leading among all Brazilian states, with a regional distinction for the city of Guaporé witch has more than a hundred jewel factories, where are produced gold and silver jewels and semijewels plated with gold and silver. In spite of it, there are very few literature related to scientific studies in the jewellery area, particularly nationwide. In this context, this research has as a main aim to investigate the Zn-Al- Cu-Mg alloy that has recently applied in fabrication of jewel-plated in order to obtain information about the properties of interest to fabrication and plated processes. The experimental methodology utilized in this work involved the following steps: analysis of superficial defects in gold and silver plated semi-jewel made with Zn-Al-Cu-Mg commercial alloy and as well as the determination of its microstructure and mechanical characteristics; compositional modification of this alloy by the addiction of extra Copper and Magnesium and study of their effects in the alloy properties; and as a final point the evaluation of gold plating capacity of the commercial alloy and the alloy modified with Copper and Magnesium. This study demonstrated that composition variations modified considerably the microstructure of the alloy and consequently its mechanical properties, as well as this plating capacity. The employed characterization techniques CA-CCA (Computer- Aided Cooling Curve Analysis), DTA (Differential Thermal Analysis), Dilatometry and optical and scanning electron microcopies where of fundamental importance to better understand the influence of chemical composition on the microstructure and properties of the Zn-Al-Cu-Mg alloy. However, it was observed that another factor of great influence in the quality of the superficial plated of this alloy is the procedure and quality of cleaning effectuated in the parts for posterior platting process.
Nos últimos anos, o setor Joalheiro vem demonstrando uma importância cada vez mais significativa no cenário econômico nacional e internacional. O Brasil aparece entre os maiores produtores de Jóias do mercado mundial, assim como, o Rio Grande do Sul entre os estados brasileiros, com destaque regional para o Município de Guaporé que têm mais de 100 fábricas, onde são produzidas peças em Folhado, Prata ou Ouro. Entretanto, vale enfatizar que a literatura disponível referente a estudos científicos voltados para o setor Joalheiro é escassa, particularmente em nível nacional. Nesse contexto, esta pesquisa tem como objetivo principal investigar a liga à base de Zn-Al-Cu-Mg que recentemente tem sido aplicada na fabricação de jóias folheadas, com a finalidade de obter informações sobre suas propriedades de interesse aos processos de fabricação e de revestimento. A metodologia experimental utilizada no desenvolvimento desse trabalho envolveu as seguintes etapas: análise dos defeitos de acabamento em semi-jóias folhadas com Ouro e Prata confeccionadas com a liga comercial à base de Zn-Al-Cu-Mg e determinação de suas características microestruturais e mecânicas; modificação composicional dessa liga pela adição extra de Cobre e Magnésio e estudo dos seus efeitos nas propriedades da mesma e por fim avaliação da capacidade de revestimento com Ouro da liga comercial e modificada pela adição de Cobre e Magnésio. Este estudo mostra que variações composicionais da liga Zn-Al-Cu-Mg modifica de forma significativa a microestrutura da referida liga e conseqüentemente suas propriedades mecânicas, bem como sua capacidade de revestimento. As técnicas de caracterização utilizadas, CA-CCA (Computer-Aided Cooling Curve Analysis), DTA (Differential Thermal Analysis), Dilatometria e Microscopias Óptica e Eletrônica de Varredura, foram fundamentais para entender melhor a influência da composição química na microestrutura e propriedades da liga à base de Zn-Al-Cu-Mg. Contudo, observou-se que um outro fator de grande influência na qualidade do revestimento dessa liga é o procedimento e qualidade de limpeza prévia efetuadas nas peças para o posterior folhamento.
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Ulansky, Sherry M. "Effect of fluctuations in pH on the availability of K, Mg, Cu, Mn, Zn, and Fe." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27677.
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An exploratory study was conducted to determine the effect of fluctuations in pH on the availability of K, Mg, Cu, Mn, Zn, and Fe. Two soils were selected for study which had differing buffering capacities based on their clay and organic matter contents. The pH of soil samples was manipulated with either HC1 or CaC03 and then allowed to incubate.
Mineralogical changes, as well as, chemical analysis indicated that fluctuations in pH may have a moderating effect on mineral weathering and precipitation reactions which in turn influences nutrient release, fixation, and availability. Changes in organic matter content with fluctuating pH appear to influence the behaviour of the trace metals and may be responsible for the development of pH-dependent charge CEC.Land and Food Systems, Faculty of
Graduate
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Mokgalaka, NS, T. Wondimu, and RI McCrindle. "Slurry nebulization ICP-OES for the determination of Cu, Fe, Mg, Mn and Zn in bovine liver." Chemical Society of Ethiopia, 2007. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000695.
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A method that involves analysis of bovine liver by slurry nebulization and ICP-OES has been
developed. This method permits rapid and accurate determination of Cu, Fe, Mg, Mn and Zn in bovine liver.
Aliquots of freeze-dried and powdered bovine liver sample were dispersed in 2.0 M HNO3 and sonicated to
homogenize the resulting slurries. Bovine liver samples were also microwave digested or subjected to aqueous
extraction for comparison of analytical results. Concentrations of Cu, Fe, Mg, Mn and Zn in aqueous slurries, the
digests, and aqueous extracts were determined by the ICP-OES using external calibration curves. A student’s ttest
showed that the results obtained using the slurry method were in good agreement at 95 % confidence level
(CL) with those of microwave digestion or aqueous extraction techniques, except for Fe. To check the accuracy
and precision of the slurry method, a bovine liver CRM was analyzed and good agreement was achieved with the
certified values at 95 % CL. The results demonstrate inefficiency of aqueous extraction technique for complete
removal of Fe in bovine liver sample.
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Rick, Cristiane Fonseca. "Estudo da liga ? base de Zn-Al-Cu-Mg aplicada na fabrica??o de j?ias folhadas." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2006. http://tede2.pucrs.br/tede2/handle/tede/3233.
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Previous issue date: 2006-07-14Nos ?ltimos anos, o setor Joalheiro vem demonstrando uma import?ncia cada vez mais significativa no cen?rio econ?mico nacional e internacional. O Brasil aparece entre os maiores produtores de J?ias do mercado mundial, assim como, o Rio Grande do Sul entre os estados brasileiros, com destaque regional para o Munic?pio de Guapor? que t?m mais de 100 f?bricas, onde s?o produzidas pe?as em Folhado, Prata ou Ouro. Entretanto, vale enfatizar que a literatura dispon?vel referente a estudos cient?ficos voltados para o setor Joalheiro ? escassa, particularmente em n?vel nacional. Nesse contexto, esta pesquisa tem como objetivo principal investigar a liga ? base de Zn-Al-Cu-Mg que recentemente tem sido aplicada na fabrica??o de j?ias folheadas, com a finalidade de obter informa??es sobre suas propriedades de interesse aos processos de fabrica??o e de revestimento. A metodologia experimental utilizada no desenvolvimento desse trabalho envolveu as seguintes etapas: an?lise dos defeitos de acabamento em semi-j?ias folhadas com Ouro e Prata confeccionadas com a liga comercial ? base de Zn-Al-Cu-Mg e determina??o de suas caracter?sticas microestruturais e mec?nicas; modifica??o composicional dessa liga pela adi??o extra de Cobre e Magn?sio e estudo dos seus efeitos nas propriedades da mesma e por fim avalia??o da capacidade de revestimento com Ouro da liga comercial e modificada pela adi??o de Cobre e Magn?sio. Este estudo mostra que varia??es composicionais da liga Zn-Al-Cu-Mg modifica de forma significativa a microestrutura da referida liga e conseq?entemente suas propriedades mec?nicas, bem como sua capacidade de revestimento. As t?cnicas de caracteriza??o utilizadas, CA-CCA (Computer-Aided Cooling Curve Analysis), DTA (Differential Thermal Analysis), Dilatometria e Microscopias ?ptica e Eletr?nica de Varredura, foram fundamentais para entender melhor a influ?ncia da composi??o qu?mica na microestrutura e propriedades da liga ? base de Zn-Al-Cu-Mg. Contudo, observou-se que um outro fator de grande influ?ncia na qualidade do revestimento dessa liga ? o procedimento e qualidade de limpeza pr?via efetuadas nas pe?as para o posterior folhamento.
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Nascimento, Angerson Nogueira do. "Especiação e biodisponibilidade de metaloproteínas de Ca, Cu, Fe, Mg, Zn em castanha de caju (Anacardium Ocidentale)." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-07022012-082107/.
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Este trabalho apresenta os estudos decorrentes da identificação de espécies moleculares associadas aos elementos Ca, Cu, Fe, Mg e Zn em amostras de castanha de caju (Anacardium Ocidentale), os quais foram realizados por: (1) digestão total da amostra, (2) digestão simulada in vitro, (3) extração de metais e proteínas empregando água, NaOH e Tampão Tris-HCl, (4) precipitação de proteínas com HCl ou acetona, (5) avaliação da associação entre espécies elementares e moleculares presentes nos diferentes meios extratores utilizando o acoplamento entre SEC-UV-SIMAAS e SEC-UV-ICP OES e (6) especiação de Fe em amostra de água de diálise empregando método espectrofotométrico. As determinações elementares nas amostras de castanha de caju demonstraram que os teores de Ca foram de (0,031 ± 0,001)%; Cu (19,1 ± 0,1) mg kg-1; Fe (53,5 ± 0,2) mg kg-1; Mg (0,22 ± 0,01) % e Zn (40 ± 3) mg kg-1, respectivamente. O emprego de soluções gástrica e intestinal simuladas revelou que 10% de Ca, 29% de Zn, 44% de Mg, 80% de Fe e 90% de Cu são extraídos durante a digestão. Após o processo de diálise, verificou-se que 100% do Zn e 90% do Ca, Fe e Mg passaram através da membrana de ester de celulose (tamanho de poro = 12 kDa). Porém, o cobre apresentou uma porcentagem de diálise de 70%. O processo de extração de proteínas indicou que a solução alcalina possui elevada capacidade de solubilização dos analitos, quando comparada com os demais extratos. A análise molecular das soluções extratoras demonstrou que em meio alcalino e tamponado há uma maior solubilização de compostos de alto peso molecular e o meio aquoso solubiliza espécies de baixo peso molecular. A precipitação realizada a partir dos extratos proteícos utilizando HCl propiciou uma alteração no perfil de distribuição molecular dos compostos presentes nos extratos aquoso e tamponado. Porém, o uso da precipitação em meio de acetona revela um perfil de separação diferente, pois em meio orgânico ocorre a seleção de compostos de baixo peso molecular (< 6,5 kDa). As análises por SEC-UV-ICP OES em soluções gastrointestinais revelou que os elementos estão distribuidos entre proteínas de alto e baixo peso molecular. Mas o processo de diálise demonstrou que algumas interações elementares e moleculares foram desfeitas após esta etapa de precipitação com HCl ou acetona. Porém, estes dados podem fornecer o primeiro indício da presença de metaloproteínas em amostras de castanha de caju. O monitoramento das espécies de ferro em amostras de água de diálise demonstra que apenas o íon trivalente (Fe3+) foi identificado. Sendo que, ao realizar a quantificação desta espécie, verifica-se que o teor de ferro livre presente na solução foi de 15%. Portanto, esta solução continha, aproximadamente, 85% de espécies químicas de ferro presentes no extrato gastrointestinal, as quais estão associadas a outros compostos presentes na amostraIn this work studies were done for the identification of molecular species associated to Ca, Cu, Fe, Mg and Zn in cashew nuts (Anacardium Occidental) using the following procedures: (1) sample acid digestion for total element determination; (2) in vitro digestion; (3) metals and proteins extraction using water, NaOH and Tris-HCl; (4) protein precipitation with HCl or acetone; (5) evaluation of association between elemental and molecular species in different extractors using SEC-UV-SIMAAS and SEC-UV-ICP OES and (6) iron speciation analysis in dialysis water using a spectrophotometric method. The elemental analysis showed that in cashew nuts there is a great quantity of Ca (0.031 ± 0.001) % and Mg (0.22 ± 0.01) %, but minor quantity of Cu (19.1 ± 0.1) mg kg-1, Fe (53.5 ± 0.2) mg kg-1 and Zn (40 ± 3) mg kg-1. The bioavailability studies reveal that Ca (10%), Zn (29%), Mg (44%), Fe (80%) and Cu (90%) were extracted during the in vitro digestion. After dialysis, 100% of Zn and 90% of Ca, Fe and Mg passed through the membrane, however, only 70% of Cu was dialysed in this step. The protein extraction procedures indicate that alkaline media has a great capacity for solubilization of analytes, if compared with other extracts. The molecular analysis of extracts showed that in alkaline and buffered media there is a presence of high molecular weight compounds and water extracted low molecular weight compounds. The HCl precipitation in water and buffered extractors change the molecular distribution profile and acetone precipitation selected low molecular weight compounds (< 6.5 kDa) for all extractors. The SEC-UV-ICP OES analysis in gastric intestinal solutions showed that the elements were distributed between high and low molecular weight compounds, but the dialysis procedure revealed the elemental and molecular correlations disappear to some metals. The monitoring of iron species by spectrophotometric method demonstrated that only 15% of trivalent iron was identified in the water dialysis. Therefore, this solution contain approximately 85% of iron species present in the gastrointestinal extract which are associated with others compounds in the sample.
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Li, Ping. "Low cycle fatique behaviour of pure aluminium and Al-Zn-Mg-Cu alloy between 20 and 260° C /." [S.l.] : [s.n.], 1988. http://library.epfl.ch/theses/?nr=735.
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Wu, Zhicheng [Verfasser], Sandra [Akademischer Betreuer] Korte-Kerzel, and Sebastian [Akademischer Betreuer] Münstermann. "Mechanical behaviour and deformation mechanisms of Zn-Al-Cu-Mg alloys / Zhicheng Wu ; Sandra Korte-Kerzel, Sebastian Münstermann." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1180542452/34.
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Gaquère-Leprêtre, Anne. "Synthèse et étude d'organométalliques (Li, Zn, Mg, Cu) en série hétérocyclique π-déficitaire (diazines, pyridine). Optimisation par sonication." Rouen, 2000. http://www.theses.fr/2000ROUES012.
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Ce travail décrit la préparation et l'étude d'organométalliques en série hétérocyclique azotée π-déficitaire, essentiellement en série diazinique. Des dérivés du zinc, du magnésium et du cuivre ont été préparés et leur réactivité a été étudiée soit en réaction de couplage croisé, soit vis-à-vis des électrophiles. En ce qui concerne les organozinciques, l'utilisation de la sonication a permis d'optimiser les réactions de couplage croisé de type Negishi. Une autre partie de ce travail a consisté en l'étude de la réaction de type Barbier sous ultrasons avec le lithium comme métal, ce travail a permis de fonctionnaliser les hétérocycles π-déficitaires avec des temps de réaction très courts mais surtout à température ambiante.
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Godard, David. "Influences de la précipitation sur le comportement thermomécanique lors de la trempe d'un alliage Al-Zn-Mg-Cu." Vandoeuvre-les-Nancy, INPL, 1999. http://www.theses.fr/1999INPL011N.
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La trempe est une opération critique lors de l'élaboration des alliages d'aluminium à durcissement structural. Les vitesses de refroidissement élevées nécessaires pour maintenir la solution solide sursaturée génèrent des contraintes internes. Dans le cas de la trempe de produits épais, la précipitation se développe cependant, car les vitesses de refroidissement peuvent être localement faibles. Elle modifie les propriétés mécaniques du matériau, et peut donc affecter les contraintes internes développées au refroidissement. Nous avons étudié ces différents effets pour un alliage al-zn-mg-cu. La précipitation se développant au refroidissement a été caractérisée à différentes échelles par trempe interrompue. Les sites de germination et les phases formées ont été étudiés par microscopie électronique. Les cinétiques de précipitation à haute température ont été suivies par resistivimetrie in-situ. L’évolution du rayon des précipités à basse temperature a été déterminée par diffusion centrale des rayons x aux petits angles. Le comportement mécanique au refroidissement a été identifié par trempe interrompue. Ses différentes caractéristiques ont été reliées à la température, ainsi qu'aux cinétiques de précipitation. La déplétion de la solution solide diminue la limite d'élasticité, alors que la précipitation homogène introduit un durcissement. Un modèle a été établi afin de décrire ces phénomènes. Les précipitations hétérogène et homogène sont prises en compte grâce à une approche moyenne. La germination est traitée à partir des théories statistiques classiques. L’équilibre local à l'interface des précipités permet de traiter la croissance. Une sursaturation en lacunes est introduite afin de traduire l'accélération de la diffusion. Le lien avec le comportement mécanique s'effectue grâce à des lois classiques de durcissement par solution solide et par précipitation cohérente. Ce modèle a été valide à chaque étape. Compte tenu des différentes hypothèses, l'accord entre simulation et expérience est satisfaisant. Ce modèle a été introduit dans le code de calcul thermomécanique marc afin d'appréhender les conséquences de la précipitation sur la genèse des contraintes internes dans une tôle forte. Seule la précipitation homogène influence au final le niveau des contraintes internes dans la zone en compression sous la surface. Ces calculs permettent également de décrire l'appauvrissement de la solution solide dans l'épaisseur de la tôle.
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Ma, Yu. "Effects of TiB2 nanoparticles on the interfacial precipitation and mechanical properties of Al-Zn-Mg-Cu matrix composites." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS252.
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L’influence des renforts nanoparticules de TiB2 (6 wt.%) sur la précipitation interfaciale de la phase (Zn1.5Cu0.5)Mg, la résistance à la traction et la fissuration sous chargement de fatigue (fatigue crack growth-FCG) des composites à matrice de Al-Zn-Mg-Cu ont été étudiées. Des échantillons de composites ont été obtenus par réaction in-situ pendant le moulage suivi d’un FSP (friction stir processing) et une extrusion à chaud. Seuls les échantillons moulés et extrudés ont été utilisés pour étude de FCG à cause de la limitation de la taille après FSP. Des observations au microscope électronique à balayage (SEM), avec la diffraction des électrons rétrodiffusés (SEM/EBSD) et au microscope électronique en transmission à haute résolution (HRSTEM) ont été réalisées pour caractériser la microstructure.Des échantillons présentent une structure des grains équi-axiaux et des nanoparticules de TiB2 sont distribuées de façon homogène dans la matrice. En état de solution solide, l’interface TiB2/Al est de nature semi-cohérente et très propre. En état de vieillissementou ou sur vieillissement, la précipitation interfacaile hétérogène de la phase (Zn1.5Cu0.5)Mg a été observée. La cinétique de la précipitation interfaciale a été discutée. Les interfaces entre Al/(Zn1.5Cu0.5)Mg/TiB2 sont quasi cohérentes et l’interface TiB2/Al a été renforcée grâce à la réduction de l’énergie de l’interface. Ce mécanisme de précipitation interfaciale peut expliquer l’effet de renforcement de l’interface contribuant simultanement l’augmentation de la résistance et de l’élongation des échatillons de composite.La majorité de nanoparticules TiB2 tentent de s’agglomérer le long des joints de grains dans des échantillons sans FSP. La vitesse de croissance de fissure a été augmentée à l’intérieur des grains avec un facteur d’intensité (ΔK) intermédiaire ou important à cause de l’affinement de grains. Cependant, la vitesse de croissance de fissure a été diminuée aux joints de grains avec (ΔK) faible ou intermédiaire à cause de la présence des clusters de TiB2 tandis que cette vitesse augmente avec (ΔK) important à cause de la coalescence des microporesThe influences of TiB2 reinforcement nanoparticles (6 wt.%) on the interfacial precipitation of (Zn1.5Cu0.5)Mg phase, the associated tensile and fatigue crack growth (FCG) properties of the Al-Zn-Mg-Cu matrix composites have been studied. The composite samples were produced by in-situ reaction during casting followed by friction stir processing (FSP) and hot extrusion, while only casted and extruded samples were used for evaluating FCG due to size limit of the nugget zone after FSP. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and high-resolution scanning transmission electron microscopy (HRSTEM) were employed for the microstructure characterization.The as-processed composite samples contain the fine equiaxed-grain structure, where TiB2 nanoparticles are homogenously distributed. At solid-solution state, the TiB2/Al interfaces are featured by the clean and semi-coherent nature. At the peak-aged and overaged states, the interface precipitate determined as (Zn1.5Cu0.5)Mg phase was formed, and the underlying heterogeneous interfacial precipitation kinetics was discussed. The Al/(Zn1.5Cu0.5)Mg/TiB2 multi-interfaces were revealed to be almost coherent, and the TiB2/Al interfaces were thus strengthened due to the greatly reduced coherency strains. This mechanism was proposed as precipitation assisted interface strengthening, which has contributed to the simultaneously enhanced tensile strength and uniform elongation of the as-processed composite.The majority of TiB2 nanoparticles tend to aggregate along grain boundaries (GBs) in the composite samples without FSP. The FCG rate is increased inside grains at intermediate and high stress intensity factor (ΔK) ranges due to the refined grain size. However, the FCG rate at the GBs is decreased at the low and intermediate ΔK ranges by fatigue crack deflection and trapping due to the presence of TiB2 clusters, while it increases at the high ΔK range due to microvoid coalescence
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Mazi, Wafa A. "FORMATION OF C-C COVALENT BOND ON THE SURFACE OF POLY (CHLOROTRIFLUOROETHYLENE) BY SUBSTITUTION." Miami University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1292027447.
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Д`яченко, Олексій Вікторович, Алексей Викторович Дьяченко, and Oleksii Viktorovych Diachenko. "Оптимізація структурних, електричних та оптичних характеристик шарів тонкоплівкових сонячних елементів на основі оксидів Mg, Zn, Cu, отриманих спрей-піролізом." Thesis, Сумський державний університет, 2019. http://essuir.sumdu.edu.ua/handle/123456789/73163.
Full textAbstract:
Дисертаційна робота присвячена визначенню ефективності та основних
фотоелектричних характеристик (зовнішнього і внутрішнього квантових виходів,
напруги холостого ходу, густини струму короткого замикання, фактора заповнення
ВАХ) сонячних елементів (СЕ) на основі гетеропереходу (ГП) n-Zn1-xMgxO / p-CuxO з фронтальними струмознімальними прозорими шарами n-ITO, ZnO:Al залежно від
конструктивних особливостей приладів за допомогою моделювання фізичних
процесів у ФЕП; оптимізації конструкції таких приладів шляхом мінімізації оптичних
і рекомбінаційних втрат у СЕ; дослідженню впливу фізико-технологічних умов
нанесення функціональних шарів MgO, ZnO, Zn1-xMgxO, CuO методом пульсуючого
спрей-піролізу на їх структурні, субструктурні, оптичні та електрофізичні властивості
для оптимізації характеристик із метою подальшого використання як базових шарів
ФЕП; створенню прототипу приладу на основі ГП n-Zn1-xMgxO / p-CuO та визначенню його електричних властивостей. Встановлені взаємозв’язки між фізико- і хіміко-технологічними умовами нанесення плівок оксидів металів та їх структурними, субструктурними, оптичними властивостями, елементним складом можуть бути використані для подальшого створення приладів опто- та мікроелектроніки, геліоенергетики і сенсорики з покращеними характеристиками.Диссертационная работа посвящена определению эффективности и основных фотоэлектрических характеристик (внешнего и внутреннего квантовых выходов, напряжения холостого хода, плотности тока короткого замыкания, фактора заполнения ВАХ) солнечных елементов (СЭ) на основе гетероперехода (ГП) n-Zn1-xMgxO / p-CuxO с фронтальными токосъемными прозрачными слоями n-ITO, ZnO:Al в зависимости от конструктивных особенностей приборов с помощью моделирования физических процессов в ФЭП; оптимизации их конструкции путем минимизации оптических и рекомбинационных потерь в СЭ; исследованию влияния физико-технологических условий нанесения функциональных слоев MgO, ZnO, Zn1-xMgxO , CuO методом пульсирующего спрей-пиролиза на их структурные, субструктурные, оптические и электрофизические свойства для оптимизации их характеристик с целью дальнейшего использования в качестве базовых слоев ФЭП; созданию прототипа прибора на основе ГП n-Zn1-xMgxO / p-CuO и определению его электрических свойств. Установленные взаимосвязи между физико- и химико-технологическими условиями нанесения пленок оксидов металов и их структурными, субструктурными, оптическими свойствами, элементным составом могут быть использованы для дальнейшего создания приборов опто- и микроэлектроники, гелиоэнергетики и сенсорики с улучшенными характеристиками.
PhD thesis is devoted to determining the efficiency η and the main photoelectric characteristics (external and internal quantum yield, open circuit voltage, short-circuit current density, fill factor) of solar cells based on n-Zn1-xMgxO / p-CuxO heterojunctions with frontal transparent contacts n-ITO, ZnO:Al, depending on the design features of the devices by modelling the physical processes in the solar cells; to optimization of the design of such solar cells by minimizing optical and recombination losses in such devices; to the study of influence of the physical conditions of deposition of functional layers of MgO, ZnO, Zn1-xMgxO, CuO by the spray pyrolysis method on their structural, substructural, optical, and electrical properties in order to optimize their characteristics with a view to further its usage as the base layers of solar cells; to creating a prototype device based on n-Zn1-xMgxO / p-CuO heterojunction and determining its electrical properties. The established relationships between the MgO, ZnO, CuO films growth conditions and Zn1-xMgxO nanocrystals synthesis conditions and structural, substructural, optical properties, chemical composition could be used to further development of photovoltaic devices with the enhanced characteristics. The prototype of the solar cell with the ITO / n- Zn1-xMgxO / p-CuO / Cu structure was created.
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Hultqvist, Adam. "Cadmium Free Buffer Layers and the Influence of their Material Properties on the Performance of Cu(In,Ga)Se2 Solar Cells." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-133112.
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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
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Renauld, Elisabeth. "Etude de la fissuration par corrosion sous contrainte de l'alliage d'aluminium 7010 (Al-Zn-Mg-Cu) : Influence du traitement thermique." Bordeaux 1, 1994. http://www.theses.fr/1994BOR10574.
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Les alliages d'aluminium Al-Zn-Mg-Cu sont particulièrement intéressants pour l'insdustrie aéronautique mais peuvent s'avérer sensibles à la corrosion sous contrainte (CSC) dans certains états métallurgiques. Ce travail s'articule autour des trois paramètres permettant à la CSC d'exister : à savoir, les facteurs métallurgiques, environnementaux et mécaniques. Ainsi, le matériau est d'abord décrit sur le plan microstructural et mécanique pour chaque état (T351, T651 et T7451). Puis, son comportement électrochimique ainsi que son endommagement macroscopique et microscopique après essai de traction lente en milieu corrosif sont étudiés. Le rôle de la microstructure a été mis en évidence tant sur le plan mécanique que sur la sensibilité à la CSC, et en particulier le comportement fragile des particules intermétalliques Al7Cu2Fe. Pour essayer d'établir le rôle possible de l'hydrogène, différentes démarches expérimentales sont mises en oeuvre. Il apparaît que la dissolution anodique et les effets de l'hydrogène interviennent conjointement mais les résultats ne permettent pas de déterminer la part respective de chacun.
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Zhao, Huan [Verfasser], Dierk [Akademischer Betreuer] Raabe, and Brita Daniela [Akademischer Betreuer] Zander. "Segregation and precipitation at interfaces in a model Al-Zn-Mg-Cu alloy / Huan Zhao ; Dierk Raabe, Brita Daniela Zander." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1216040680/34.
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Mortensen, Magnus. "Method for quantification of Ca, Cu, Fe, Mg, Sr and Zn in low concentrated whole blood samples using ICP-AES." Thesis, Uppsala universitet, Institutionen för kemi - BMC, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-386069.
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Platzer-Björkman, Charlotte. "Band Alignment Between ZnO-Based and Cu(In,Ga)Se2 Thin Films for High Efficiency Solar Cells." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6263.
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Thin-film solar cells based on Cu(In,Ga)Se2 contain a thin buffer layer of CdS in their standard configuration. In order to avoid cadmium in the device for environmental reasons, Cd-free alternatives are investigated. In this thesis, ZnO-based films, containing Mg or S, grown by atomic layer deposition (ALD), are shown to be viable alternatives to CdS. The CdS is an n-type semiconductor, which together with the n-type ZnO top-contact layers form the pn-junction with the p-type Cu(In,Ga)Se2. From device modeling it is known that a buffer layer conduction band (CB) position of 0-0.4 eV above that of the Cu(In,Ga)Se2 layer is consistent with high photovoltaic performance. For the Cu(In,Ga)Se2/ZnO interface this position is measured by photoelectron spectroscopy and optical methods to –0.2 eV, resulting in increased interface recombination. By including sulfur into ZnO, a favorable CB position to Cu(In,Ga)Se2 can be obtained for appropriate sulfur contents, and device efficiencies of up to 16.4% are demonstrated in this work. From theoretical calculations and photoelectron spectroscopy measurements, the shift in the valence and conduction bands of Zn(O,S) are shown to be non-linear with respect to the sulfur content, resulting in a large band gap bowing. ALD is a suitable technique for buffer layer deposition since conformal coverage can be obtained even for very thin films and at low deposition temperatures. However, deposition of Zn(O,S) is shown to deviate from an ideal ALD process with much larger sulfur content in the films than expected from the precursor pulsing ratios and with a clear increase of sulfur towards the Cu(In,Ga)Se2 layer. For (Zn,Mg)O, single-phase ZnO-type films are obtained for Mg/(Zn+Mg) < 0.2. In this region, the band gap increases almost linearly with the Mg content resulting in an improved CB alignment at the heterojunction interface with Cu(In,Ga)Se2 and high device efficiencies of up to 14.1%.
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Lee, Yunmi. "Site- and Enantioselective C-C and C-B Bond Forming Reactions Catalyzed by Cu-, Mg-, Zn-, or Al-based N-Heterocyclic Carbene Complexes." Thesis, Boston College, 2010. http://hdl.handle.net/2345/1165.
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Thesis advisor: Amir H. HoveydaChapter 1. In this chapter, the ability of chiral bidentate N-heterocyclic carbenes (NHCs) to activate alkylmetal reagents directly in order to promote C‒C bond forming reactions in the absence of a Cu salt is presented. Highly regio- and enantioselective Cu-free allylic alkylation reactions of di- and trisubstituted allylic substrates with organomagnesium, organozinc, and organoaluminum reagents are demonstrated. Chiral bidentate sulfonate-bearing NHC-Zn and NHC-Al complexes are isolated and fully characterized. Based on crystal structures of these catalytic complexes, mechanistic details regarding Cu-free allylic alkylations with alkylmetal reagents are proposed. Chapter 2. New methods for efficient and highly enantioselective Cu-catalyzed allylic alkylation reactions of a variety of trisubstituted allylic substrates with alkylmagnesium and alkyl-, aryl-, 2-furyl-, and 2-thiophenylaluminum reagents are presented. Transformations are promoted by a chiral NHC complex in the presence of commercially available, inexpensive and air stable CuCl2*H2O. Enantiomerically enriched compounds containing difficult-to-access all-carbon quaternary stereogenic centers are obtained. Chapter 3. New methods for highly site- and enantioselective Cu-catalyzed allylic alkylation reactions of allylic phosphates with vinylaluminum reagents are presented. The requisite vinylaluminums are prepared by reaction of readily accessible terminal alkynes with DIBAL-H and used directly without further purification. Vinyl additions are promoted in the presence of a chiral bidentate sulfonate-based NHC complex and a Cu salt. The desired SN2' products are obtained in >98% E selectivities, >98% SN2' selectivities, >98% group selectivities (<2% i-Bu addition) and high enantioselectivities. The enantioselective total synthesis of the natural product bakuchiol highlights the versatility of the one-pot hydroalumination/Cu-catalyzed enantioselective allylic vinylation process. Chapter 4. Efficient and highly site-selective Cu-catalyzed hydroboration reactions of 1,2-disubstituted aryl olefins with bis(pinacolato)diboron (B2(pin)2) are presented. Transformations are promoted by an NHC-Cu complex in the presence of MeOH, affording only secondary β-boronate isomers. A Cu-catalyzed method for the synthesis of enantiomerically enriched secondary alkylboronates promoted by chiral NHC complexes is disclosed. Chapter 5. A new method for efficient and site-selective tandem Cu-catalyzed copper-boron additions to terminal alkynes with B2(pin)2 in the presence of an NHC-Cu complex is demonstrated. In a one-pot process, Cu-catalyzed hydroboration of alkynes provides vinylboronates in situ, which undergo a second site-selective hydroboration to afford vicinal diboronates. Highly Enantiomerically enriched diboronates obtained through Cu-catalyzed enantioselective dihydroboration in the presence of chiral bidentate sulfonate-based NHC-Cu complex are obtained. The control of site selectivity in the first-stage hydroboration of alkynes is critical for efficient and highly enantioselective reactions in the tandem dihydroboration. Functionalizations of the vicinal diboronates described herein underline the significance of the current method
Thesis (PhD) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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Ben, Ali Neji. "Caractérisation et modélisation micromécanique de la propagation de fissures fragiles par effet de l'hydrogène dans les alliages AA 7xxx." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2011. http://tel.archives-ouvertes.fr/tel-00648428.
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Nous étudions la fragilisation par l'hydrogène de l'alliage d'aluminium 7108. Une technique expérimentale spécifique a été développée : Un pré-chargement en hydrogène des échantillons, à travers un dépôt de nickel de quelques dizaines de microns, qui empêche la dissolution du substrat d'aluminium, est utilisé. Il permet la comparaison de la résistance à la fragilisation de différentes microstructures modèles. Nous étudions l'effet du traitement thermique et de la précipitation sur la sensibilité à l'hydrogène pour des vitesses de déformation macroscopiques imposées variables. Différents modes de rupture sont observés ainsi que des transitions entre eux. Au moyen de simulations numériques à l'échelle mésoscopique, l'effet de taille des précipités intergranulaires pré-fragilisés sur la ténacité des joints de grains est estimé, en utilisant un modèle de zone cohésive. Nous analysons la compétition entre la diffusion de l'hydrogène vers la pointe de la fissure et la vitesse de fissuration par un couplage mécanique - diffusion basé sur la diffusion de l'hydrogène assistée par la contrainte hydrostatique. Une vitesse critique au-delà de laquelle l'hydrogène ne peut plus suivre la fissure, est mise en évidence. L'influence de la microstructure du joint de grains sur cette vitesse est analysée. La valeur est comparée à une estimation des vitesses de propagation expérimentales obtenues pour différentes vitesses de déformation macroscopiques. Nous analysons l'effet du piégeage de l'hydrogène par les précipités intergranulaires et la désorption sur la répartition de l'hydrogène le long du joint de grains en imposant un flux au niveau de l'interface précipités - matrice.
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Santos, Mellina Damasceno Rachid. "Avaliação de hidrocarbonetos policíclicos aromáticos e metais (Cu, Cd, Pb e Zn) em sedimentos do rio Paraibuna, Juiz de Fora, MG." Universidade Federal de Juiz de Fora (UFJF), 2014. https://repositorio.ufjf.br/jspui/handle/ufjf/4317.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
O sedimento possui uma grande importância ambiental devido a sua capacidade de adsorver e acumular substâncias tais como hidrocarbonetos policíclicos aromáticos (HPAs) e metais, os quais podem ser redissolvidos para a coluna d’água ou absorvidos pela biota. No presente trabalho determinou-se os níveis de concentração de HPAs e dos metais Cu, Cd, Pb e Zn em sedimentos superficiais do rio Paraibuna, em Juiz de Fora (MG). Foi proposta uma metodologia para determinação de HPAs em sedimentos de rio aplicando extração assistida por ultrassom e quantificação por GC/MS. Para otimizar o processo de extração de HPAs foram delineados experimentos através do planejamento Box-Behnken 33 com triplicata no ponto central, cujas variáveis estudadas foram proporção de n-hexano (n-HEX) e diclorometano (DCM) na mistura de solventes, volume desta mistura e tempo de sonicação. A condição ótima de extração selecionada através da metodologia de superfície de resposta consistiu em três etapas de sonicação de 15 minutos utilizando 10 mL de mistura de solventes composta por n-HEX/DCM (55:45). Esta condição foi avaliada pela percentagem de recuperação obtida através da extração do branco e amostra fortificados utilizando como mistura de solvente n-HEX/DCM (55:45) e n-HEX/acetona (55:45). Esta última foi selecionada por apresentar menor desvio padrão relativo e maior eficiência no processo de extração. Os valores de limites de detecção e quantificação variaram de 0,005 a 0,015 mg L-1 e de 0,016 a 0,050 mg L-1, respectivamente. Assim, a metodologia de extração e quantificação de HPAs desenvolvida foi aplicada em amostras de sedimento do rio Paraibuna, Juiz de Fora. As concentrações de HPAs totais variaram de 10,40 a 246,36 ng g-1 de peso seco, e as concentrações de HPAs prioritários variaram de 7,34 a 187,56 ng g-1 de peso seco. As relações Flu/Flu+Pir e InP/InP+BghiP indicaram uma introdução de origem pirolítica, seja por queima de combustível fóssil ou de biomassa. Para a determinação dos metais, as amostras de sedimento foram tratadas conforme o método de extração 3050B descrito pela EPA e analisadas por F AAS. As faixas de concentração encontradas foram de 4,95 a 40,20 µg g-1 peso seco para o Cu, de 1,84 a 4,99 µg g-1 peso seco para o Cd, de 4,41 a 40,04 µg g-1 peso seco para o Pb, e de 39,35 a 344,27 µg g-1 peso seco para o Zn. Algumas amostras de sedimento do rio Paraibuna apresentaram concentrações de Zn e Cd acima dos valores estabelecidos pela Agência Canadense de Proteção Ambiental com prováveis efeitos adversos à biota (PEL).
Sediments have a great environmental importance due to their ability to adsorb and accumulate substances such as polycyclic aromatic hydrocarbons (PAHs) and metals, which can be later redissolved to the water column or absorbed by the biota. In the present study, concentration levels of PAH and Cu, Cd, Pb and Zn metals were determined at surface sediments of the Paraibuna river, Juiz de Fora (MG). A method for the determination of PAHs at river sediments applying an ultrasound assisted extraction followed by GC/MS quantification, was proposed. Box Behnken 33 planning, with triplicates at the central point, was delineated in order to optimize the extraction process of PAHs, in which the proportion of n-hexane (n-HEX) and dichloromethane (DCM) at the solvents mixture, this mixture volume and sonication time were chosen as variables. The optimum extraction conditions, selected through a response surface methodology study, consisted in a three steps sonication for 15 minutes using a 10 mL solvent mixture, composed by n-HEX/DCM (55:45). This condition was evaluated by means of the recovery percentage obtained for the extraction of a spiked blank and sample using as solvent mixture n-HEX/DCM (55:45) and n-HEX/acetone (55:45). The n-HEX/acetone (55:45) mixture was chosen since it presented a lower relative standard deviation and a greater efficiency at the extraction process.Detection and quantitation limits values ranged from 0.005 mg L-1 to 0.015 mg L-1 and from 0.016 to 0.050 mg L-1, respectively.Thus, the extraction and quantification methodologies were then applied for PAHs at Paraibuna’s river sediment samples. The total PAH concentrations ranged from 10.40 to 246.36 ng g-1 of dry weight, and priority PAH concentrations ranged from 7.34 to 187.56 ng g-1 of dry weight. Flu/ Flu+Pyr and InP/InP+BghiP relationship indicated an introduction by pyrolytic origin, either by combustion of fossil fuel or biomass. For metals determination, sediment samples were treated by the 3050B extraction methodology, described by EPA, and then analyzed by F AAS. Concentration ranges between 4.95 to 40.20 µg g-1 of dry weight for Cu, 1.84 to 4.99 µg g-1 of dry weight for Cd, 4.41 to 40.04 µg g-1 of dry weight for Pb and 39.35 to 344.27 µg g-1 of dry weight for Zn, were obtained. Some Paraibuna river sediment samples showed Zn and Cd concentrations above the established values by the Canadian Environmental Protection Agency, with some probable adverse effects to the biota (PEL).
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Deschamps, Alexis. "Influence de la prédéformation et des traitements thermiques sur la microstructure et les propriétés mécaniques des alliages Al-Zn-Mg-Cu." Phd thesis, Grenoble INPG, 1997. http://tel.archives-ouvertes.fr/tel-00370760.
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Nous avons étudié l'influence du traitement thermomécanique des alliages Al-Zn-Mg-Cu sur leur microstructure et leurs propriétés mécaniques. Plus spécifiquement, nous avons étudié comment les mécanismes de précipitation et de durcissement structural sont modifiés lorsqu'on introduit des dislocations par détensionnement préalablement au traitement de revenu.La première approche de ce problème est expérimentale. Le but était d'obtenir des relations entre les microstructures développées suivant les différents traitements thermomécaniques et les propriétés mécaniques qui en résultent. Pour cela, nous avons utilisé de nombreuses techniques d'investigation complémentaires: microscopie optique et électronique en transmission, calorimétrie différentielle, diffusion centrale des rayons X, tomographie atomique, résistivité, microdureté et essais de traction.
Dans un deuxième temps, nous avons développé un modèle de précipitation compétitive homogène / hétérogène sur les dislocations. Ce modèle intègre continûment les différentes étapes de la précipitation (germination, croissance et coalescence) et du durcissement structural (cisaillement, contournement). Nous avons pu retrouver les principaux résultats expérimentaux à l'aide de ce modèle.
Enfin, nous avons étudié les propriétés plastiques de nos matériaux, suivant l'état de précipitation. Plus particulièrement, nous avons pu mettre en évidence la présence d'une précipitation dynamique lors d'essais de traction dans des états sursaturés, apportant un écrouissge très élevé.
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Deschamps, Alexis. "Influence de la prédéformation et des traitements thermiques sur la microstructure et les propriétés mécaniques des alliages Al-Zn-Mg-Cu." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0067.
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Nous avons etudie l'influence du traitement thermomecanique des alliages al-zn-mg-cu sur leur microstructure et leurs proprietes mecaniques. Plus specifiquement, nous avons etudie comment les mecanismes de precipitation et de durcissement structural sont modifies lorsqu'on introduit des dislocations par detensionnement prealablement au traitement de revenu. La premiere approche de ce probleme est experimentale : le but etait d'obtenir des relations entre les microstructures developpees suivant les differents traitements thermomecaniques et les proprietes mecaniques qui en resultent. Pour cela nous avons utilise de nombreuses techniques d'investigation complementaires : microscopie optique et electronique en transmission, calorimetrie differentielle, diffusion centrale des rayons x, tomographie atomique, resistivite, microdurete et essais de traction. Dans un deuxieme temps, nous avons developpe un modele de precipitation competitive homogene/heterogene sur les dislocations. Ce modele integre continument les differentes etapes de la precipitation (germination, croissance et coalescence) et du durcissement structural (cisaillement, contournement). Nous avons pu retrouver les principaux resultats experimentaux a l'aide de ce modele. Enfin, nous avons etudie les proprietes plastiques de nos materiaux, suivant l'etat de precipitation. Plus particulierement, nous avons pu mettre en evidence la presence d'une precipitation dynamique lors d'essais de traction dans des etats sursatures, apportant un ecrouissage tres eleve.
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Brockman, John Douglas. "Investigation of K₀ neutron activation analysis at MURR and investigation of the toenail as a biomonitor for Mg, Zn, Cu, Se and Hg." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/5890.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 13, 2007) Vita. Includes bibliographical references.
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Rebiere, Michel. "De la corrosion sous contrainte à la fatigue-corrosion : mécanismes d'amorçage des fissures dans les alliages Al-Zn-Mg et Al-Li-Cu." Grenoble INPG, 1989. http://www.theses.fr/1989INPG4205.
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L'analyse de la resistance la fatigue corrosion (dans le domaine de la fatigue oligocyclique) en milieu chlorure aqueux au potentiel de corrosion libre d'alliages d'aluminium a durcissement structural (al-zn-mg et al-li-cu) a permis de montrer l'existence de relations entre les mecanismes d'amorcage des fissures et la vitesse de deformation. Ainsi la corrosion sous contrainte est generatrice de fissures aux basses vitesses de deformation. Par contre, l'amorcage des fissures resultant de l'action combinee de la localisation de la deformation et de la rupture du film passif est observe aux vitesses de deformation elevees. La sensibilite a la piquration de l'aluminium-lithium en milieu chlorure est a l'origine de deux types d'amorcages rencontres aux vitesses de deformation intermediaires, la taille et la distribution des piqures agissent alors sur la duree de vie en fatigue-corrosion. Une polarisation cathodique peut induire une fragilisation par l'hydrogene dans ces deux alliages s'il existe des sites favorables a une decharge localisee de l'hydrogene
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Venieri, Andrea. "Sistemi catalitici per la reazione di water - gas shift a media temperatura." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5758/.
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Negli ultimi anni l’interesse nei confronti dell’H2 è cresciuto notevolmente per l’aumento della richiesta energetica mondiale. Uno dei processi più importanti per la produzione di H2 utilizza la reazione di Water-Gas Shift (WGS) per il trattamento delle correnti in uscita dai processi di steam reforming o di ossidazione parziale catalitica.
CO + H2O CO2 + H2 ∆H0298 = -41,2 KJ/mol
Sono quindi stati sviluppati sistemi catalitici attivi nella reazione di WGS a media temperatura (circa 300 °C). Partendo da sistemi catalitici a base di Cu/Zn/Al, ottenuti da precursori idrotalcitici e sviluppati in lavori di tesi precedenti, sono state effettuate modifiche nella composizione al fine di aumentarne l’attività e la stabilità.
L’aggiunta di piccole quantità di Mg ha un effetto positivo sull’attività dei sistemi catalitici, con effetti più evidenti a 250 °C. Tuttavia, l’aumento del contenuto di Mg, sebbene migliori le proprietà fisiche del catalizzatore (area superficiale e dispersione del Cu) sia del campione calcinato che di quello scaricato dopo reazione, peggiora drasticamente l’attività catalitica. L’aggiunta di piccole quantità di Mg sembra portare alla stabilizzazione della specie attiva Cu+ e promuovere un meccanismo redox superficiale (Cu0 e Cu+). E’ possibile correlare la conversione del CO con il rapporto ZnO/Cu, confermando il ruolo nella reazione di WGS dell’interazione Cu0/ZnO libero. La sostituzione di Mg con Ba comporta un miglioramento delle prestazioni catalitiche, in particolare nelle condizioni MTS (300 °C), suggerendo una più facile dissociazione dell’acqua legata alla stabilizzazione degli ossidrili da parte dei siti basici. È però accompagnato da una diminuzione della stabilità nelle condizioni di reazione.
L’aggiunta di piccole quantità di La, Ce o Zr (con un rapporto Al/R = 50 mol/mol) incrementa la stabilità termica, sia in termini di proprietà fisiche che di attività catalitica. A seguito dei cicli termici di invecchiamento accelerato, infatti, non si riscontrano importanti diminuzioni di attività catalitica, evidenziando un’elevata stabilità della fase attiva.
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VALLASCAS, ELISABETTA. "Sangue, urina e capelli: bioindicatori per il monitoraggio di esposizione umana all'As, Pb e U nei bambini dei comuni di Perdasdefogu e Jerzu." Doctoral thesis, Università degli Studi di Cagliari, 2008. http://hdl.handle.net/11584/266026.
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Il continuo incremento del carico inquinante sulle popolazioni non esposte, sia nelle società avanzate sia nelle società in via di sviluppo, è diventato un problema
rilevante per quanto concerne la salvaguardia dello stato di salute. Per tali ragioni sono stati effettuati numerosi studi volti a determinare quali siano le metodiche e le
metodologie più appropriate per la determinazione dei livelli dei metalli pesanti nelle popolazioni umane.
È noto che un eccessivo livello di elementi tossici con un contemporaneo deficit di metalli essenziali, quali Mg, Zn, Cu, Ca ed altri biolementi, possa determinare dei disordini metaboloci, una diminuita efficienza dell’organismo un declino dei processi immunologici e quindi la comparsa di varie malattie e persino la morte dell’individuo (Lech, 2002).
Gli effetti tossici dei metalli pesanti risultano particolarmente dannosi per i soggetti in accrescimento. I bambini costituiscono la parte della popolazione maggiormente a rischio, rispetto agli adulti, per gli effetti dei metalli pesanti in quanto hanno maggiori probabilità di essere esposti all’inquinamento non occupazionale e di ingerire sostanze non commestibili contenenti metalli pesanti.
Infatti, la polvere contenente gli inquinanti ricade dall’atmosfera sui giocattoli, sui mobili e su altre superfici di zone destinate al gioco, da cui può,facilmente, essere ingerita (Schell, 1991a).
I bambini inoltre assorbono, in genere, una maggiore quantità di metalli pesanti rispetto agli adulti, in quanto presentano oltre che una maggiore attività metabolica e
fisica, anche un maggiore assorbimento e ritenzione nel tratto gastrointestinale(Annest et al., 1982; Chilsom, 1987; Schell, 1991a; Fitzgerald et al., 1998; Al-Saleh
et al., 1999).
È ancora oggetto di dibattito se anche dei moderati livelli di alcuni metalli pesanti nei bambini possano causare loro delle patologie (Pirkle et al., 1985; Fulton et al.,
1987; Cavalleri, 1988; McMichel et al., 1988; Abbritti et al., 1989; Morisi et al.,1989; Factor-Litvak et al., 1999; Canfield et al., 2003; CDC, 2004), oltre che influire
negativamente sulla crescita (Schwartz et al., 1986; Frisancho e Ryan, 1991; Ballowet al., 1999; Factor-Litvak et al., 1999; Rahman et al., 2002) e causare una riduzione
del QI (Schwartz, 1994; Factor-Litvak et al., 1999;Campbell et al., 2000; Rahman et al., 2002); risulta pertanto necessario un monitoraggio continuo dell’accrescimento e
dunque dello stato di salute nelle popolazioni potenzialmente esposte all’inquinamento da metalli pesanti.
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Menezes, Eveline de Abreu. "Determinação da disponibilidade de Ca, Cu, Fe, Mg e Zn em amostras de carnes bovinas, suínas e de frango In natura e processadas termicamente." Universidade Federal de São Carlos, 2010. https://repositorio.ufscar.br/handle/ufscar/6169.
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In this work, the availability of Ca, Cu, Fe, Mg, and Zn in bovine, pork and chicken meat samples raw and after thermal treatments: water boiled, grilled, microwave, convention oven I 180 oC (FCI) and conventional oven II 60 min and 180 oC was evaluated. Total determination of Ca, Cu, Fe, Mg and Zn in bovine and pork samples was performed by inductively coupled plasma optical emission spectrometry (ICP OES), and Cu in chicken samples was determined by graphite furnace atomic absorption spectrometry (GFAAS), after digestion assisted by microwave radiation. Total protein determination was performed based on total nitrogen determination and the protein digestibility determination was determined by using the method proposed by Akeson and Stahman, in which the sample is digested with digestive enzymes in an acidic medium, simulanting in vitro conditions. To the mineral availability evaluation, an in vitro procedure, simulated gastric fluid was applied. Independent of the procedure of cooking, similar behavior was observed for all meat sample evaluated. Increasing temperature and exposition time of food to heat, decreases in proteins availability was observed, probably due to proteins denaturation. The bovine meat presented about 20% of Cu, Fe, and Zn availability, that became this kind of food an important source of these nutrients in human nutrition. When the meat was water boiled, it was observed increase in nutrients availability. For all samples, the use of conventional oven during 60 min at 180oC (FCII) presented reduces in nutrients and proteins availability, indicating that this thermal treatment can change the digestibility and mineral absorption of the evaluated meat samples.
Neste trabalho estudou-se a disponibilidade dos nutrientes Ca, Cu, Fe, Mg e Zn em amostras de carnes bovina, suína e de frango in natura e após os seguintes tratamentos térmicos: Cozido em água, grelhado, micro-ondas, forno convencional I 45 min 180 oC e forno convencional II 60 min e 180 oC. A determinação dos teores totais de Ca, Cu, Fe, Mg e Zn para amostras de carnes bovina e suína foi realizada por espectrometria de emissão óptica com plasma acoplado indutivamente (ICP OES), enquanto que a determinação de Cu para as amostras de carne de frango foi feita por espectrometria de absorção atômica com atomização eletrotérmica em forno de grafite (GFAAS), após digestão das amostras em forno de micro-ondas com cavidade. A determinação da proteína bruta foi realizada a partir da determinação do teor de nitrogênio total e para a determinação da digestibilidade da proteína foi empregado o método proposto por Akeson e Stahman, no qual a amostra é digerida com enzimas digestivas em meio ácido, simulando in vitro as condições existentes no trato gastrointestinal humano. Para avaliação da disponibilidade dos minerais foi empregado procedimento in vitro, utilizando fluido gástrico simulado. Indiferente ao procedimento de cocção, comportamento similar foi observado para os diferentes tipos de carne. A elevação da temperatura e do tempo de exposição do alimento ao calor provocam diminuição da disponibilidade das proteínas, provavelmente em função da desnaturação das mesmas. A carne bovina apresentou cerca de 20% de disponibilidade de Cu, Fe e Zn o que a torna fonte importante desses nutrientes na nutrição humana. Quando a carne foi cozida em água maior eficiência foi observada, em relação à disponibilidade de nutrientes. Para todas as amostras, o processamento que empregou forno convencional por 60 min e 180 oC mostrou uma baixa disponibilidade de nutrientes e proteínas, o que indica que esse processo de aquecimento térmico pode ter alterado a digestibilidade e a absorção dos minerais nas amostras aqui estudadas.
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DEIDA, MOHAMED FADEL. "Interactions de huit cations d'interet biologique (mn, fe, co, ni, cu, zn, mg et ca) avec des hydroxamates aromatiques : 2-hydroxypyridine-n-oxyde et derives." Reims, 1992. http://www.theses.fr/1992REIMS012.
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Les interactions de huit cations d'interet biologique (ca, mg, mn, fe, co, ni, cu, zn) ont ete etudiees avec trois hydroxamates aromatiques: 2-hydroxypyridine-n-oxyde (hpno), 2-mercaptopyridine-n-oxyde (mpno) et 3,4-dihydro-3-hydroxy-4-oxo-1,2,3 benzotriazine (dhob). Les pka de ces ligands bidentates, monoprotiques ont ete determines par protometrie et spectrophotometrie, les acidites croissant dans l'ordre hpno
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Carr, Hilda P. "The accumulation of aluminium and it's effect on the uptake and distribution of Ca, Mg, K, Mn, Fe, Cu and Zn in Camellia sinesis (L.)." HKBU Institutional Repository, 2001. http://repository.hkbu.edu.hk/etd_ra/287.
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Marlaud, Thorsten. "Microstructures de précipitation et mécanismes de corrosion feuilletante dans les alliages d'aluminium de la série 7000 à très hautes caractéristiques mécaniques." Phd thesis, Grenoble INPG, 2008. http://www.theses.fr/2008INPG0031.
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Les alliages d’aluminium de la série 7000 à hautes caractéristiques mécaniques, constitués principalement des éléments d’addition Zn, Mg, et Cu, sont notamment utilisés dans l’industrie aéronautique civile. Néanmoins, les traitements thermiques et/ou thermomécaniques appliqués pour maximiser les propriétés mécaniques de ces alliages, peuvent les sensibiliser à divers modes de corrosion structurale dont la corrosion feuilletante, dont les mécanismes sont encore mal compris. En outre, les nouvelles générations d’alliages, développées en vue d’augmenter les propriétés mécaniques, contiennent toujours plus d’éléments d’addition, ce qui est susceptible de modifier leur sensibilité à ce phénomène. Ce travail s’attache à faire progresser la compréhension des mécanismes de corrosion feuilletante des alliages 7000, en cherchant à identifier le rôle des principaux éléments d’alliage. Pour cela nous avons caractérisé finement les états de précipitation d’un grand nombre de microstructures, comme la composition des précipités durcissants nanométriques et de la matrice, par ASAXS et 3DAP. En parallèle, nous avons développé de nouvelles techniques électrochimiques permettant de quantifier la sensibilité de ces mêmes microstructures à la corrosion feuilletante. Les résultats de l’étude mettent en évidence l’existence de deux mécanismes de corrosion : endommagement par dissolution intergranulaire et par rupture intergranulaire, dont la prédominance dépend de la composition de l’alliage et du traitement thermique. Nous proposons une explication au comportement en corrosion des différentes microstructures, faisant intervenir la composition chimique des différentes entités microstructuralesHigh strength 7XXX series aluminium alloys, composed of the major alloying elements Zn, Mg, and Cu, are used especially for aircraft applications. However, the ageing process, maximizing the mechanical properties, returns alloys sensitive to structural corrosion, and particularly to exfoliation corrosion. New developments in high strength alloys, for strength optimization, lead an overall increase in solute saturation, which could modify their corrosion susceptibility. The objective of the study is to progress in the understanding of the exfoliation corrosion mechanisms of high-strength 7000 series aluminium alloys, by attempting especially to identify the role of the main alloying elements. By leaning on a quantitative precipitation characterisation of a large number of microstructures, we notably measured the composition of nanometric hardening precipitates and of the matrix, by ASAXS and 3DAP. In parallel, we developed new electrochemical techniques providing quantitative results on the exfoliation corrosion sensitivity of microstructuresTheses results show the existence of two operating corrosion mechanisms: damages by " intergranular dissolution " and by intergranular ruptures. The ascendancy of which depends on the composition of the alloy. We propose an explanation of the corrosion susceptibility of the various microstructures, based on the chemical composition of the microstructural entities and of the alloy
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Mandaji, Debora dos Santos. "Emissário submarino de Santos: contribuição nos sedimentos de fundo para Al, Mg, K, Ca, Fe, Ti, Na, Si, Ba, Cu, Zn, Cr, Mn, Co, Ni e S." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/44/44142/tde-02092008-163850/.
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Após a construção do Emissário Submarino de Esgoto de Santos, todo efluente da cidade de Santos e parte de São Vicente passou a ser descartado na Baía de Santos após Pré-condicionamento. Diante desse aspecto a CETESB iniciou monitoramento de controle sobre os materiais que estão sendo lançados pelo emissário. Nessa dissertação foram estudadas amostras de sedimentos no entorno dessa malha de monitoramento. A partir de duas coletas em períodos distintos - Abril de 2004 e Outubro de 2004 - obtiveram-se 20 amostras de sedimentos. Nessas amostras foram realizadas análises granulométricas e químicas (elementos maiores e traços determinados por DRX e ICPOES para 16 elementos com predomínio de metais). Os resultados granulométricos obtidos nas amostras de sedimentos mostraram serem esses constituídos predominantemente por areias e sedimentos em suspensão. A dispersão dessas frações sofre influência direta do fluxo dos materiais descartados pelo emissário. Dos diversos elementos analisados detectou-se que o Cobalto (Co) e Enxofre (S) ultrapassaram os limites de referência utilizados. O elemento Bário exibiu sempre concentrações elevadas nas análises realizadas. Foi notado, por outro lado, que a distribuição dos elementos Cu, Zn, Cr, Mn e Ni, sempre exibiu maiores concentrações no período de maior pluviosidade. Esses resultados corroboram para a indicação que alguns desses elementos químicos (Cu, Zn, Cr, Mn e Ni) devem provir de materiais intemperizados de rochas do entorno e que outros elementos (Co e S) possuem uma contribuição antropogênica sobre os sedimentos depositados pelo emissário. A determinação das razões C/N e C/S não permitiu determinar se a carga de efluentes do emissário contribui para o aumento do teor de matéria orgânica. Os resultados obtidos e interpretações realizadas conduzem a confirmar a influência do emissário sobre os sedimentos de fundo do seu entorno. Esses diversos resultados apontam para uma indicação de que o tratamento dos efluentes na Estação de Pré-Condicionamento de Esgoto de Santos não é o ideal, visto que alguns elementos considerados poluentes encontram-se depositados nos sedimentos analisados.After the construction of the Ocean Outfall of Santos\'s sewage, all of Santos\'s and part of São Vicente\'s effluents started to be discarded in the Santos Bay after Preconditioning. In light of that aspect, CETESB began a monitoring control of the materials dumped through the emissary. In this dissertation sediments samples in the environment of that monitoring mesh. From two collections in different periods - April 2004 and October 2004 - 20 samples of sediments were obtained. Granulometric and chemical analyses (larger and trace elements for DRX and ICP-OES for 16 elements with prevalence of metals) were developed. The granulometric results obtained in the sediment samples showed that those were predominantly constituted by sands and sediments in suspension. The dispersion of the prior fractions suffers direct influence of the flow of discarded materials by the emissary. Of the several analyzed elements, it was detected that the Cobalt (Co) and Sulfur (S) concentrations surplused the reference limits. The element Barium (Ba) was always highly concentrated in analysis. It was noticed, on the other hand, that the distribution of the elements Copper (Cu), Zinc (Zn), Chromium (Cr), Manganese (Mn) and Nickel (Ni), always exhibited larger concentrations in the period of greater rainfall. Those results corroborate the indicators that some of those chemical elements (Cu, Zn, Cr, Mn and Ni) comes from materials of naturally eroded rocks and that other elements (Co and S) were deposited by the emissary, constituting anthropogenic actions. The determination of the Carbon/Nitrogen (C/N) and Carbon/Sulfur (C/S) reasons didn\'t determine if the deposit of the emissary\'s effluents contributes in the increase of the concentration of organic matter. The results and interpretations obtained in the experiments confirm the emissary\'s influence on the environment\'s bottom sediments. Those results point that the effluent treatment in the Sewer\'s Pre-conditioning Station in Santos is not ideal, because some elements, considered pollutants, are found in deposits in the analyzed sediments.
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Marlaud, Thorsten. "Microstructures de précipitation et mécanismes de corrosion feuilletante dans les alliages d'aluminium de la série 7000 à très hautes caractéristiques mécaniques." Phd thesis, Grenoble INPG, 2008. http://tel.archives-ouvertes.fr/tel-00282987.
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Les alliages d'aluminium de la série 7000 à hautes caractéristiques mécaniques, constitués principalement des éléments d'addition Zn, Mg, et Cu, sont notamment utilisés dans l'industrie aéronautique civile. Néanmoins, les traitements thermiques et/ou thermomécaniques appliqués pour maximiser les propriétés mécaniques de ces alliages, peuvent les sensibiliser à divers modes de corrosion structurale dont la corrosion feuilletante, dont les mécanismes sont encore mal compris. En outre, les nouvelles générations d'alliages, développées en vue d'augmenter les propriétés mécaniques, contiennent toujours plus d'éléments d'addition, ce qui est susceptible de modifier leur sensibilité à ce phénomène. Ce travail s'attache à faire progresser la compréhension des mécanismes de corrosion feuilletante des alliages 7000, en cherchant à identifier le rôle des principaux éléments d'alliage. Pour cela nous avons caractérisé finement les états de précipitation d'un grand nombre de microstructures, comme la composition des précipités durcissants nanométriques et de la matrice, par ASAXS et 3DAP. En parallèle, nous avons développé de nouvelles techniques électrochimiques permettant de quantifier la sensibilité de ces mêmes microstructures à la corrosion feuilletante.
Les résultats de l'étude mettent en évidence l'existence de deux mécanismes de corrosion : endommagement par dissolution intergranulaire et par rupture intergranulaire, dont la prédominance dépend de la composition de l'alliage et du traitement thermique. Nous proposons une explication au comportement en corrosion des différentes microstructures, faisant intervenir la composition chimique des différentes entités microstructurales.
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Imbernon, Rosely Aparecida Liguori. "Os chapéus de ferro associados aos depósitos de Canoas (Pb-Zn-Ag), Adrianópolis (PR) e O\'Toolle (Cu-Ni-EGP), Fortaleza de Minas (MG) - caracterização textural, mineralógica e geoquímica." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/44/44134/tde-18112015-164006/.
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Os chapéus de ferro associados ao depósito de Canoas mineralizado em Zn-Pb, em Adrianópolis (PR) e ao depósito de O\'Toole mineralizado em Ni-Cu, em Fortaleza de Minas (MG), contém concentrações anômalas desses metais base. O intemperismo químico do minério sulfetado produziu uma série de feições mineralógicas e geoquímicas características que são diagnóstico para a prospecção mineral e identificação do tipo de depósito mineral. Análises por espectrometria de raios X para elementos maiores e traços, difratometria de raios X, espectroscopia Mössbauer, análises microssituadas, foram utilizadas para este estudo. No depósito de Canoas existem três ocorrências de chapéus de ferro, Canoas 1, Salvador 1 e Salvador 2, os quais apresentam diferenças nos teores de metais base dosados que pode estar relacionado ao tipo de minério e maturidade do chapéu de ferro. O chapéu de ferro de Canoas 1 ocorre sobre o minério primário e assemelha-se a uma zona de sulfato-carbonato. Os chapéus de ferro de Salvador 1 e Salvador 2 apresentam feições e mineralogia características de chapéus de ferro maduros. A associação jarosita-goethita e em menor proporção hematita é a principal feição mineralógica dos chapéus de ferro de Canoas. As jarositas são uma fase transitória e armadilhas para o Pb. No depósito de O\'Toole o intemperismo e alteração supérgena dos sulfetos primários de Ni-Cu evoluíram para uma zona de pentlandita-violarita ou zona de cimentação ou transição. O chapéu de ferro ocorre sobre a zona de transição e tem feições, texturas e mineralogia típicas de um chapéu de ferro maduro e evoluído. Durante os processos de lixiviação dos sulfetos, metais tais como Pb, Zn, Cu, Ni e Co são dissolvidos e podem ser co-precipitados com compostos de Fe ou serem adsorvidos em duas superfícies. No primeiro caso eles são incorporados na estrutura dos minerais de Fe por substituição isomórfica, causando distorções nas dimensões da cela (continua) (dependendo) unitária, dependendo das diferenças entre os raios iônicos. No chapéu de ferro de Canoas a incorporação de Pb e Zn na estrutura da goethita não ficou claramente demonstrada. Para as amostras de chapéu de ferro de O\'Toole as análises sugerem que o Cu e Ni foram incorporados estruturalmente na goethita.Gossans associated with the Canoas zinc-lead ore deposits, in Adranópolis (PR), and O\'Toole nickel-copper ore deposit, in Fortaleza de Minas (MG), contain anomalous concentrations of these base metal. The chemical weathering of sulfide lodes has produced a series of characteristic mineralogical and geochemical features that are diagnostic for mineral prospection and identification of ore body type. X-ray spectrumetrie analysis of major and trace elements, difractrometry of the X-ray, Mössbauer spectroscopy, microprobe analysis, were used in this study. In the Canoas deposit there are three gossan occurrences, Canoas 1, Salvador 1 and Salvador 2, which have differences in accumulation that may be related to the ore type and gossan maturity. The Canoas 1 gossan is over the primary ore and appears to be a sulphate-carbonate zone. The Salvador 1 and Salvador 2 gossans presented features and mineralogy that are characteristics of the mature gossans. The jarosite-goethite association and to a lesser extent hematite is the principal mineralogical feature of the Canoas gossans. The jarosites are the transitory Pb-bearing phases. In the O\'Toole deposit the weathering and supergene alteration of primary nickel-cooper sulphides evolved to the pentiandite-violarite zone or cementation zone. The gossans is over the cementation zone and has features, textures and mineralogy typical of mature evolved gossans. During the sulphide leaching processes, metals such as Pb, Zn, Cu, Ni and Co are dissolved and can either co-precipitate with Fe compounds or be adsorbed onto their surfaces. In the first case they are incorporated into the Fe-mineral structurs by isomorphous substitution, causing distortions in the unit-cell dimensions, depending on the ionic radii differences. In the Canoas gossan incorporation of the Pb and Zn into the goethite structure are not clearly demonstrated. For the O\'Toole gossan samples the analysis suggests that Cu and Ni structurally incorporated in the goethite lattice.
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Dauga, Christine. "Impact de l'épandage d'une boue residuaire industrielle, riche en Mg, Mn, Cu, Pb et Zn sur une couverture ferralitique en climat tropical (SP, Brésil) : minéralogie, pétrologie et transferts géochimiques." Aix-Marseille 3, 2000. http://www.theses.fr/2000AIX30027.
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Ce doctorat porte sur l'impact sur l'environnement de l'epandage d'un dechet industriel solide, riche en mg, zn, cu, mn et pb, soumis a une alteration tropicale (bresil) et les mecanismes de transfert des metaux lourds. Une caracterisation chimique, mineralogique et petrographique du dechet, des sols impliques et un suivi qualitatif et quantitatif des eaux circulant dans le systeme (eaux de pluie et de percolation du sol) ont ete realises. Le dechet forme une dalle compacte de 25 cm et ses principaux mineraux sont des silicates, hydroxyde et carbonate de mg bien cristalises. Les metaux ne sont generalement pas associes a ces mineraux, mais restent concentres dans des zones localisees, sous forme d'oxy-hydroxydes ou sulfates. Bien que les sols de la region (latosol rouge-jaune) aient une porosite elevee (40%), la circulation verticale des eaux de percolation est assez lente. Resultant des fortes concentrations de la pluie en zn, les premiers centimetres de ces sols presentent des teneurs anormales en cet element. Par contre, le profil lateritique sous-jacent au dechet n'est pas contamine, ce qui est du a la compaction du sol ayant eu lieu lors de l'epandage, et au role impermeabilisant du dechet compacte. Sur le versant aval, la surface des profils est contaminee, se traduisant par l'existence des colluvions riches en particules du dechet apportees par erosion et qui correspond a un taux de 0,4cm/an de dechet erode. Dans les horizons lateritiques plus profonds, une migration verticale des metaux est observee et s'explique par la dissolution de ces particules sous l'action des fluides d'alteration aux ph plus acides et aux conditions plus oxydantes que ceux rencontres dans le dechet. Dans le latosol contamine, les metaux ont plus d'affinite avec la fraction <20m mais aucune avec les oxyhydroxydes de fe naturels, de mn originaires du dechet ou la matiere organique. Les zn, cu et mn anthropogeniques seraient lies a la kaolinite par des phenomenes de surface.
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Billard, Vincent. "Biofortification des plantes en Fe, Mg, Cu et Zn : études de l’effet de biostimulants sur leur absorption et caractérisation de leur remobilisation foliaire en condition de carence chez Brassica napus." Caen, 2014. http://www.theses.fr/2014CAEN2031.
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La biofortification des cultures vise, selon différentes méthodes, à augmenter la teneur de certains éléments minéraux tels que Fe, Zn, Mg et Cu dans les tissus récoltés. Dans ce cadre, nous avons tenté de déterminer le potentiel de biofortification chez le colza (Brassica napus L. ) de deux biostimulants dérivés d’algues ou d’acides humiques. Un deuxième objectif de recherche consistait à déterminer l’existence de processus de remobilisation foliaire du Cu, Mg et du Zn, chez la même espèce en situation de carence (Cu, Mg ou Zn), tout en identifiant des interactions potentielles entre éléments minéraux. Les principaux résultats obtenus montrent que ces deux biostimulants augmentent l’absorption du Mg et du Cu ainsi que la translocation du Zn et du Fe des racines vers les feuilles. Après 25 jours de carence (Cu, Zn ou Mg), 61,4% du Cu foliaire et 50,5% du Mg foliaire sont remobilisés vers les jeunes feuilles en croissance. A l’inverse, le Zn n’est pas remobilisé. Dans ces conditions, la remobilisation du Cu et du Mg semblent indépendante des mécanismes associés à la sénescence. Enfin des analyses élémentaires et protéomiques révèlent des variations importantes de l ‘absorption de certains éléments (tel que le Mo lors d’une carence en Cu, ou le Mo et le Mn lors d’une carence en Zn), ainsi qu’une perturbation des métabolismes chloroplastiques des feuilles qui remobilisent (avec par exemple une surexpression de la ferrédoxine et de la rhodanese). L’ensemble des résultats montre que les deux biostimulants testés présentent un potentiel de biofortification alors qu’à plus long terme, une sélection variétale prenant en compte l’efficacité de remobilisation du Mg et du Cu vers les tissus récoltés pourrait constituer une stratégie supplémentaireUsing different methods, plant biofortification aims to increase the concentration of mineral nutrients, such as Fe, Zn, Mg and Cu, in edible tissues. The first objective of this work was to evaluate the biofortification potential in Brassica napus of two biostimulants, derived from algae or humic acids. The second objective was to investigate and quantify a putative foliar remobilization of Cu, Zn and Mg in the same species, as well as the potential interactions between mineral nutrient uptake during deficiency (Cu, Mg or Zn). The main results show that these two biostimulants increased the Cu and Mg uptake, as well as the translocation from root to shoot of Zn and Fe. After 25 days of deficiency (Cu, Mg or Zn), 61. 4% of foliar Cu and 50. 5% of foliar Mg were remobilized to young expending leaves, while we did not find any evidence of Zn remobilization. Under these conditions of deficiency, the Cu and Mg remobilization seems to be independent of the processes associated with senescence. Finally, mineral and proteomics analyses revealed important variations of the uptake of some mineral nutrients (such as Mo in Cu depleted plants, or Mo and Mn in Zn depleted plants), and a disturbance of chloroplastic metabolisms in remobilizing leaves (with an overexpression of ferredoxin and rhodanese, as an example). Overall, these results show that the two tested biostimulants have a potential for plant biofortification, while in the long term a varietal selection relying on the remobilization efficiency of Cu and Mg to harvest tissues could constitute an alternative strategy
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Cerqueira, Marcos Rodrigues Facchini. "Avaliação da concentração de metais pesados (Zn, Cd, Pb e Cu) em água de chuva visando sua aplicação como fonte alternativa de água potável na cidade de Juiz de Fora/MG." Universidade Federal de Juiz de Fora, 2012. https://repositorio.ufjf.br/jspui/handle/ufjf/1758.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais
Muitas pessoas sofrem da falta crônica de água potável para necessidades pessoais e, nesse contexto, a água de chuva surge como uma possível fonte alternativa. Em cima disso, foi proposto um método simples e efetivo para a determinação de cobre(II), cádmio(II), zinco(II) e chumbo(II) em 64 amostras de água de chuva de Juiz de Fora/MG/Brasil utilizando a técnica de redissolução potenciométrica. Um potenciostato μ-AUTOLAB foi utilizado para a aquisição dos dados e a célula eletroquímica consistia de um eletrodo de trabalho de carbono vítreo modificado com filme de mercúrio, um eletrodo de Ag/AgCl(sat) como eletrodo de referência e um de eletrodo de platina como eletrodo auxiliar. Foi realizada uma avaliação do pH do meio variando de 0-3 para uma determinação simultânea de Cd, Pb e Cu e de 0-6 para a determinação de Zn. Um Planejamento Estrela 22 foi realizado para a otimização das condições eletroquímicas das determinações. Para as determinações de Cd, Pb e Cu foram estudados níveis entre -1,06 e -0,64 V para o potencial de deposição (Ed), com tempo de deposição (td) entre 239 s e 662 s. Para a determinação de Zn os níveis estudados para o Ed foram entre -1,70 V e -1,10 V, com td entre 239 s e 662 s. A condição ótima encontrada para o pH do meio foi de pH = 4 para a determinação de Zn e um pH = 0 para a determinação de Cd, Pb e Cu. De acordo com as superfícies de resposta obtidas, foi estipulado para a determinação de Zn um Ed = -1,40 V e um td = 300 s e para a determinação de Cd, Pb e Cu um Ed = -1,00 V e um td = 300 s. Foram construídas curvas analíticas para verificar a linearidade do método. Os limites de detecção e quantificação foram de 1,26 e 3,83 μg L-1 para Zn, 0,38 e 1,26 μg L-1 para Cd, 0,41 e 1,36 μg L-1 para Pb e 0,96 e 3,20 μg L-1 para Cu, respectivamente. O método mostrou valores de recuperação entre 86 e 113%. As amostras de água de chuva também foram analisadas por espectroscopia de absorção atômica em forno de grafite (GFAAS), como método de referência, demonstrando uma boa correlação entre os resultados. Foram encontrados valores entre 3,93 e 13,8 μg L-1 de Zn, 3,11 e 7,51 μg L-1 de Cu, enquanto que nenhuma concentração significativa foi observada para Pb e Cd. Conforme os valores estipulados na Portaria nº 2914, de 12 de dezembro de 2011, do Ministério da Saúde, a água de chuva da região de Juiz de Fora pode ser considerada como potável com relação os parâmetros avaliados.
Many people suffer from a chronicle lack of potable water for their personal needs and, in this context, the rainwater arises as a possible alternative source. Upon this, an effective and simple method to determine copper(II), cadmium(II), zinc(II) and lead(II) in 64 rainwater samples from Juiz de Fora/MG/Brazil, using potentiometric stripping analysis (PSA), is proposed. A μ-AUTOLAB potentiostat was used for data acquisition and the electrochemical cell consisted of a working glassy carbon electrode modified with a thin mercury film, an Ag/AgCl(sat) as reference electrode and a platinum as auxiliary electrode. The pH of the medium was evaluated in the range of 0-3 for the simultaneous determination of Cd, Pb and Cu, and in the range of 0-6 for Zn. A 22 Star Design was run to optimize the analytical conditions. For Cd, Pb and Cu determination the studied levels for deposition potential (Ed) were between -1.06 V and -0.64 V, with deposition time (td) between 239 s and 662 s. For Zn determination the studied levels for Ed were between -1.70 V and -1.10 V, with td between 239 s and 662 s. The optimum medium pH conditions found were of pH = 4 for Zn determination and pH = 0 for Cd, Pb and Cu determination. According to the obtained response surfaces it was stipulated for Zn determination a Ed = -1.40 V and a td = 300 s and for Cu, Pb and Cd determination a Ed = -1.00 V and a td = 300 s. Analytical curves were constructed to verify the method linearity. The detection and quantification limits were of 1.26 and 3.83 μg L-1 for Zn, 0.378 and 1.26 μg L-1 for Cd, 0.407 and 1.36 μg L-1 for Pb and 0.960 and 3.20 μg L-1 for Cu, respectively. The method showed recovery values between 86 and 113%. The rainwater samples were also analyzed by graphite furnace atomic absorption spectrometry (GFAAS), as reference method, showing a good correlation between the results. Values between 3.93 and 13.8 μg L-1 of Zn, 3.11 and 7.51 μg L-1 of Cu were found, while no significant concentrations of Pb and Cd were found. According to the stipulated values on Portaria nº 2914, of december 12 of 2011, from Ministério da Saúde, the Juiz de Fora region rainwater can be considered potable, with respect to the evaluated parameters.
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Dauga, Christine. "Impacto da disposição de um resíduo industrial rico em metais pesados (Mn, Cu, Pb, Zn) e Mg sobre uma cobertura ferralítica em clima tropical (SP, Brasil): mineralogia, petrologia e transferências geoquímicas." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/44/44134/tde-03112015-125034/.
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Esta tese de doutorado focaliza a contaminação de um sitio localizado em um ambiente tropical úmido, após disposição de um resíduo industrial solido, rico em Mg, Zn, Cu, Mn e Pb. O objetivo principal é determinar o impacto da disposição sobre o meio natural e os mecanismos de transferência dos metais pesados. Para tanto, foram realizados estudos visando determinar a caracterização química, mineralógica e petrografica do resíduo e dos solos implicados, assim como foi efetuado um monitoramento qualitativo e quantitativo das águas circulantes no sistema (águas de chuva e de percolação do solo). O resíduo contaminante apresenta-se sob a forma de uma camada compacta, com estrutura heterogênea e espessura de 20 a 25 cm. Apresenta varias fase minerais (silicatos, hidróxidos e carbonatos de Mg) bem cristalizados. Os metais acima mencionados não se encontram associados a estes minerais, mas sim concentram-se em zonas localizadas, sob a forma de oxídos, hidróxidos ou sulfatos. O solo da região, um latossolo vermelho amarelo, formado por processos de lateritização, é bastante poroso (~40%) e constituído essencialmente por caolinita, oxi-hidroxidos de ferro e quartzo. Apesar da alta porosidade, as águas de percolação circulam lentamente na vertical. Resultado das fortes concentrações em Zn das precipitações, os primeiros centímetros dos solos do sitio apresentam teores anômalos em Zn. Entretanto, o perfil laterítico subjacente ao resíduo não exibe nenhuma contaminação, o que se explica pela compactação do solo realizada durante a disposição e pelo papel impermeabilizante do resíduo compactado. Na vertente, a jusante, os horizontes de superfície e os horizontes lateríticos mais profundos estão contaminados. A contaminação de superfície se traduz pela existência de coluvios ricos em partículas do resíduo, trazidas por transferência lateral. A erosão correspondente é de 0,4cm/ano. A migração vertical dos metais pesados se explica por dissolução destas partículas sob a ação dos fluidos de alteração com pH mais ácidos e condições redox mais oxidentes que a encontrados no resíduo. A realização de testes experimentais de reatividade com o resíduo (montagem soxhlet) corrobora a importância do pH e Eh na mobilidade dos metais. No latossolo, os metais possuem mais afinidade com a fração <20\'mü\'m, mas nenhuma com os oxi-hidroxídos de Fe naturais, de Mn originários do resíduo ou com a matéria orgânica. Os Zn, Cu e Mn antropogenicos estariam ligados a caolinita por fenômenos de superfície.This work presents a study about contamination due to a solid industrial waste deposit, rich in Mg, Zn, Cu, Mn and Pb, that is undergoing tropical alteration (Brazil). The objectives are to determine the impact on the environment due to heavy metals deposition and their transfer mechanisms within the soils. A chemical, mineralogical and petrographical characterisation, as well as a quantitative and qualitative monitoring of the waters that circulate within the soil system (rain and soil drainage waters), were performed. The waste forms a compact layer of 20-25cm thick, presenting heterogeneous structure. Its principal mineral phases are well-crystallised silicates, hydroxides and carbonate of Mg. As a general feature, the metals are not associated with these minerals, but they are found as oxides, hydroxides or sulphates forms, concentrated in localised zones. The soils in the area are mainly red-yellow ferrasol, constituted by kaolinite, iron oxyhydroxides and quartz. Although the soil presents high porosity (c.a 40%), the water drainage movement is low. A high amount of Zn in the first 5 cm of the soils is observed, which is attributed to the high Zn input through rainfall. However, in the soil profile underneath the waste, no contamination is observed, what can be explained by the soil compaction, due to the disposition procedure, and by the waterproofing role of the compacted waste. Over the slope below the waste deposit, the surface horizons and the deeper lateritic horizons are contaminated. The surface contamination is forming colluvions rich in waste particles that were transported downhill, which corresponds to an erosion rate of 0,4cm/year on the waste top. In the deeper lateritic horizons, a heavy metals migration is observed and can bee explained by the dissolution of these particles. The dissolution occurs under more acidic and redox conditions than those existed into the waste. Reactivity experimental tests (soxhlet) performed on the waste, confirms the importance of pH and Eh conditions for the metals mobility. In the contaminated ferrasol, the metals show high affinity with the <20\'mü\'m fraction, but none with the natural Fe oxyhydroxides, nor with waste Mn oxyhydroxides or with the organic matter. The anthropogenic Zn, Cu and Mn seemingly bond to the kaolinite by surface phenomena.
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Persaud-Sharma, Dharam. "An Assessment of Novel Biodegradable Magnesium Alloys for Endovascular Biomaterial Applications." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/950.
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Magnesium alloys have been widely explored as potential biomaterials, but several limitations to using these materials have prevented their widespread use, such as uncontrollable degradation kinetics which alter their mechanical properties. In an attempt to further the applicability of magnesium and its alloys for biomedical purposes, two novel magnesium alloys Mg-Zn-Cu and Mg-Zn-Se were developed with the expectation of improving upon the unfavorable qualities shown by similar magnesium based materials that have previously been explored. The overall performance of these novel magnesium alloys has been assessesed in three distinct phases of research: 1) analysing the mechanical properties of the as-cast magnesium alloys, 2) evaluating the biocompatibility of the as-cast magnesium alloys through the use of in-vitro cellular studies, and 3) profiling the degradation kinetics of the as-cast magnesium alloys through the use of electrochemical potentiodynamic polarization techqnique as well as gravimetric weight-loss methods. As compared to currently available shape memory alloys and degradable as-cast alloys, these experimental alloys possess superior as-cast mechanical properties with elongation at failure values of 12% and 13% for the Mg-Zn-Se and Mg-Zn-Se alloys, respectively. This is substantially higher than other as-cast magnesium alloys that have elongation at failure values that range from 7-10%. Biocompatibility tests revealed that both the Mg-Zn-Se and Mg-Zn-Cu alloys exhibit low cytotoxicity levels which are suitable for biomaterial applications. Gravimetric and electrochemical testing was indicative of the weight loss and initial corrosion behavior of the alloys once immersed within a simulated body fluid. The development of these novel as-cast magnesium alloys provide an advancement to the field of degradable metallic materials, while experimental results indicate their potential as cost-effective medical devices.
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Najjar, Denis. "Compétition entre les mécanismes de dissolution anodique et de fragilisation par l'hydrogène dans le processus de fissuration par corrosion sous contrainte de l'alliage Al-Zn-Mg-Cu 7150 sollicité en traction lente en milieu chlorure (NaCl 3)." Lille 1, 1994. http://www.theses.fr/1994LIL10098.
Full textAbstract:
Les alliages d'aluminium alznmg(cu) de la serie 7000 utilises dans l'industrie aeronautique ont fait l'objet de nombreuses etudes en corrosion sous contrainte (csc). Neanmoins, le mecanisme de fissuration est toujours sujet a controverses: dissolution anodique et fragilisation par l'hydrogene sont souvent proposes de maniere mutuellement exclusive. Le principal objectif de ce travail est de faire la part des choses entre ces deux grandes familles de mecanismes lors de la fissuration par csc de l'alliage 7150 sollicite en traction lente en milieu chlorure (nacl 3%). En couplant des essais mecaniques discriminatoires a des observations en microscopie electronique a balayage, nous montrons que dissolution anodique et fragilisation par l'hydrogene operent conjointement. L'influence relative de ces deux mecanismes depend des principaux parametres qui gouvernent la fissuration: l'etat microstructural, le potentiel electrochimique et la vitesse de deformation. En consequence, seule une modelisation qui considere cette influence relative semble appropriee pour rendre compte des resultats experimentaux. Jusqu'a presente, seule la phase de propagation avait fait l'objet d'etudes approfondies et nous proposons d'introduire la notion de defaut critique pour decrire la phase d'amorcage.
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Hacht, Brahim. "Etude des equilibres de coordination du facteur thymique serique (fts) avec les ions zn(ii), cu(ii), ca(ii), mg(ii), al(iii) et ga(iii) dans les conditions physiologiques et simulations quantitatives sur l'importance biol. Des complexes correspondants." Toulouse 3, 1987. http://www.theses.fr/1987TOU30105.
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Hacht, Brahim. "Etude des équilibres de coordination du facteur thymique sérique (FTS) avec les ions Zn(II), Cu(II), Ca(II), Mg(II), Al(III) et Ga(III) dans les conditions physiologiques, et simulations quantitatives sur l'importance biologique des complexes correspondants." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376060851.
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