Thesis. (M.Tech. (Chemistry)) -- Vaal University of Technology, 2011. / Bis(acetylacetonato)oxovanadium(IV), Manganese(III) acetylacetonate, Co-Zn and Co-Al were prepared as catalyst precursors for the synthesis of carbon materials in a catalytic chemical vapor deposition (CCVD) reactor. The carbon materials produced were characterized with Raman spectroscopy, Scanning electron microscope (SEM), Energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), High resolution transmission electron microscopy (TEM) and Thermogravimetric analysis, (TGA). Carbon material prepared from bis(acetylacetonato)oxovanadium(IV) catalyst precursor showed the presence of carbon spheres with average diameter of 104μm together with small traces of carbon nanotubes or amorphous carbon. Synthesis of bis(acetylacetonato)oxovanadium(IV) catalyst precursor yielded approximately 92% of carbon material. Carbon material prepared from Manganese(III) acetylacetonate catalyst precursor showed the presence of carbon spheres with diameter of 87.5μm. Synthesis of Manganese(III) acetylacetonate catalyst precursor yielded approximately 97% of carbon material. Carbon material produced from Co-Zn and Co-Al catalyst precursors showed the presence of carbon nanotubes with small amounts of amorphous carbon. The use of Co-Zn catalyst precursor yielded approximately 80% of carbon nanotubes, whereas Co-Al catalyst precursor yielded approximately 98% of carbon nanotubes. / Vaal University of Technology; NRF; SASOL

O Grupo Vazante hospeda o maior depósito de Zn não-sulfetado, hipógeno, conhecido mundialmente, Vazante (>60 Mton @ 20% Zn), que ainda possui concentrações de Pb e Ag. A Mina de Vazante (VZT) e sua continuidade, a Mina de Extremo Norte (EN), são subdivididas em cinco domínios geo-mineralógicos, sendo três deles pertencentes à VZT: Lumiadeira 1 (LUM1); Lumiadeira 2 (LUM2); Sucuri (SUC) e dois à EN: Extremo Norte 1 (EN1) e Extremo Norte (EN2). Estudos de campo, amostragem sistemática, análises petrográficas e com uso de microscopia eletrônica de varredura, incluindo mineralogia automatizada por Mineral Liberation Analyzer, e microssonda eletrônica, e litoquímicas foram empregadas objetivando caracterizar detalhadamente cada domínio, relacionar aspectos geológicos e mineralógicos e apontar possíveis fatores responsáveis por mudanças na qualidade do minério frente aos processos de beneficiamento. Os corpos de minério de Zn não-sulfetado nas minas VZT e EN são compostos essencialmente por willemita (Zn2SiO4), possuem formas anastomosadas e são hospedados por brechas dolomíticas e subordidamente por rochas metapelíticas e metabásicas e brechas hematíticas. Corpos restritos ricos em sulfetos ocorrem, principalmente, imbricados em corpos de minério willemítico ou como veios e vênulas. Os cristais de willemita apresentam texturas de preenchimento, como coloforme e fibro-radiada (tipo I), de reequilíbrio, como granoblástica (tipo II), ou são finamente granulares e preenchem fissuras tardias (tipo III). Desse modo, registram complexa sequência de processos e condições para a geração do minério de Zn não-sulfetado. Zinco, Fe, C, Ca, SiO2, e Mg são os principais componentes químicos do minério. Na mina EN, o teor de Fe (<26,7%) no minério é, em média, mais elevado quando comparado à mina VZT, presente principalmente na forma de hematita. Chumbo e Ag, co-produtos da explotação de Zn, são principalmente encontrados na mina VZT, nos domínios LUM1 e SUC onde são concentrados em corpos ricos em sulfetos. Elementos terrígenos, tais como Al, K, Rb, Sc, Co, Th e La são positivamente anômalos no domínio LUM2 indicando maior presença de metapelitos no setor sul da mina VZT. Quando associado à metapelito, o minério willemítico pode conter até 15% de Zn-talco, podendo assim refletir em menores recuperações de Zn. Quando hospedado por rochas metabásicas, o principal mineral de zinco pode ser franklinita (<25%), mineral deletério para o processamento de minério. Caso hospedado por brechas hematíticas, característica do domínio EN2, a willemita apresenta-se comumente cominuída e os conteúdos de Fe e hematita podem ser limitantes para o beneficiamento. Em síntese, os resultados desse estudo mostram que cada domínio geo-mineralógico apresenta características específicas. Mostrou-se que espessura, formato e profundidade dos corpos, variação da natureza das rochas encaixantes e substituições minerais afetam diretamente a mineralogia e a qualidade do minério de Zn. Tais fatores refletem processos geológicos e características do ambiente formacional do depósito que podem ser restritos ou mais frequentes em determinado domínio, refletindo assinaturas específicas para o minério estudado, que podem ser espacializadas e monitoradas integrando um modelo geometalúrgico. / The Vazante Group hosts the major hypogene, nonsulfide Zn deposit known worldwide (e.g., Vazante; >60 Mton @ 20% Zn), which also contains Pb and Ag concentrations. The Vazante Mine (VZT) and its continuity, the North Extension Mine (EN), are subdivided into five geo-mineralogical domains, since three belonging to VZT: Lumiadeira 1 (LUM1); Lumiadeira 2 (LUM2); Sucuri (SUC), and two to EN: North Extension 1 (EN1); North Extension 2 (EN2). Field studies, systematic sampling, petrography, scanning electronic microscopy, automated mineralogy via Mineral Liberation Analyzer, and lithochemical analyses were carried out aiming to characterize each domain in detail, connect their geological and mineralogical aspects, and point to possible features responsible for changes on ore quality during ore beneficiation. The nonsulfide Zn orebodies at VZT and EN are anastomosed, composed of willemite (Zn2SiO4), and hosted by dolomite breccias and subordinately by metapelite, metabasic rocks, and hematite breccias. Minor sulfide-rich orebodies occur mainly imbricated within willemite orebodies or as veins and veinlets. The willemite crystals show infilling textures, such as colloform and fibrous-radiated (type I), reequilibrium texture, such as granoblastic (type II), or fine-grained textures, when controlled by late fissures (type III). Thus, willemite registers a complex sequence of processes and conditions responsible for the nonsulfide Zn ore generation. Zinc, Fe, C, Ca, SiO2, and Mg are the main chemical compounds of the ore. At EN, the Fe (<26.7%) and hematite contents in the ore are, on average, higher than those of VZT. Lead and Ag, co-products of Zn exploitation, are chiefly found at VZT, in the LUM1 and SUC domains, concentrated in sulfide-rich bodies. Terrigenous elements, such as Al, K, Rb, Sc, Co, Th, and La, are positively anomalous in the LUM2 domain indicating the influence of metapelite host in the south sector of VZT. In this case, willemite ore may contain up to 15% Zn-talc, related to lower Zn recoveries. If the willemite ore is hosted by metabasic rocks, franklinite, a deleterious phase into processing, might be the main Zn-bearing phase (<25%). If hosted by hematite breccias, characteristic of the EN2 domain, willemite is commonly comminuted and the Fe and hematite contents might be a limiting for beneficiation. The results herein presented show that each geo-mineralogical domain exhibits their own characteristics. Ore thickness, format, and depth of bodies, the nature of host rocks, and mineral replacements affect the mineralogy and quality of Zn ore directly. Those factors express geological processes and characteristics of the deposit environment that may be restricted or more frequent at a certain domain, thus creating specific signatures for the analyzed ore, which might be spatialized and monitored integrating a geometallurgical model.

A presença de metais pesados tóxicos em fertilizantes tem sido motivo de preocupação e apontada como um dos obstáculos à produção sustentável de alimentos. Por outro lado, há uma crescente busca por produtos agrícolas de melhor qualidade, com maior teor de micronutrientes e menos fatores antinutricionais, como os metais pesados tóxicos. No Brasil, há poucos trabalhos relacionando fertilização e qualidade dos produtos agrícolas, em termos de micronutrientes e metais pesados tóxicos. Neste contexto, no presente trabalho foram realizados quatro experimentos tendo como objetivos avaliar: 1) a eficiência de métodos de extração e de quantificação simultânea de micronutrientes e de metais pesados tóxicos em fertilizantes; 2) a influência da fertilização nos teores de micronutrientes e metais pesados tóxicos no solo, nos indicadores microbiológicos, nas atividades enzimáticas em plantas e na qualidade dos produtos agrícolas; 3) a variação genotípica para teor de Cd, micronutrientes e suas relações em 35 cultivares de arroz de terras altas do Brasil; 4) a influência do estado nutricional e genotípica nos teores de Cd e 70Zn no arroz. Quando se usa reagentes e água de alta pureza, a análise de metais pesados tóxicos em amostras de fertilizantes pode ser realizada por micro-ondas ou sistema aberto, sendo que as quantificações dos elementos por ICP-MS e ICP-AES produzem resultados semelhantes. Porém, na análise dos teores naturais de Cd, Cr e Pb apenas a quantificação por ICP-MS foi adequada. Nas condições deste trabalho, tanto os subprodutos e rocha fosfática quanto os fertilizantes foram capazes de fornecer nutrientes às plantas, sem causar aumentos excessivos de metais pesados tóxicos nos solos e nos produtos agrícolas. Os indicadores microbiológicos do solo e as atividades enzimáticas em plantas de alface reagiram positivamente à fertilização. Foram identificadas variedades de arroz de terras altas com baixo e alto teor de Cd nos grãos. Os teores de Fe, Zn e Se apresentaram relações inversas ao teor de Cd. Observou-se interação entre estado nutricional da planta e genótipo no teor de Cd em grãos de arroz de terras altas cultivado em solução nutritiva. Concluiu-se que, com manejo adequado, a fertilização aumenta a produtividade e melhorar qualidade dos produtos agrícolas para alimentação humana e animal / The presence of toxic heavy metals in fertilizers has been a big concern. It has been indicated as one of the obstacles to sustainable food production. On the other hand, there is a growing demand for better-quality products, with high micronutrient content and low malnutrition factors, such as toxic heavy metals. In Brazil there are scarce number of studies regarding fertilization and the quality of agricultural products for micronutrients and toxic heavy metals. In this context, the present study, involving four experiments, was conducted with the objectives: 1) to assess the efficiency of methods to extract and quantify micronutrients and toxic heavy metals in fertilizers; 2) to study the influence of fertilization on the levels of micronutrients and toxic heavy metals in agricultural products; 3) to evaluate the genotypic variation in response to the content of Cd, micronutrients and their relations in 35 upland rice cultivars from Brazil; and 4) to determine the influence of the nutritional status and genotype on the levels of Cd and 70Zn in rice plant. The results showed that with the use of reagents and water of high purity, toxic heavy metals can be extracted for analysis by microwave or an open air system, and that quantification of the elements by ICP-MS and ICP-AES yields similar results. However, for the analysis of natural contents of Cd, Cr and Pb only ICP-MS quantification was appropriate. Further, both by-products and phosphate rock, as fertilizers were able to supply nutrients to the plants without causing excessive increases of toxic heavy metals in soil and agricultural products. Microbiological soil indicators and enzyme activities in plants responded positively to fertilization. Furthermore, results also showed that there were upland rice cultivars with low and high Cd content in the grains, and the levels of Fe, Zn and Se showed inverse relations with the Cd content. There was an interaction between plants the nutritional status and genotype for Cd content in grains of upland rice cultivars. Based on the results, it can be concluded that with adequate management, fertilization can increase crop yields and improve the quality of agricultural products for human and animal consumption

H2O2 generated by alveolar macrophages has been linked to the development pulmonary fibrosis, but little is known about its source, mechanism of production and exact role upon alveolar macrophage activation. In this study, we found that alveolar macrophages from asbestosis patients spontaneously produce high levels of H2O2 and have high expression of Cu,Zn-SOD. Cu,Zn-SOD localized to the mitochondrial intermembrane space (IMS) in asbestosis patients and asbestos induced translocation of Cu,Zn-SOD to the IMS. This process was unique to macrophages and dependent on functional mitochondrial respiration. The presence of at least one of the conserved cysteines was required for disulfide bond formation and mitochondrial translocation. These conserved cysteine residues were also necessary for enzyme activation and H2O2 generation. Cu,Zn-SOD-mediated H2O2 generation was inhibited by knockdown of the iron-sulfur protein, Rieske, in complex III. The role of Cu,Zn-SOD was biologically relevant as Cu,Zn-SOD-/- mice generated significantly less H2O2, had less oxidative stress, and were protected from developing pulmonary fibrosis. This protective mechanism is closely related to the alveolar macrophage activation and polarization in Cu,Zn-SOD-/- mice, as they had a dominant pro-inflammatory phenotype. Macrophages not only initiate and accentuate inflammation after tissue injury, but they are also involved in resolution and repair. The pro-inflammatory M1 macrophages have microbicidal and tumoricidal activity, whereas the M2 macrophages are involved in tumor progression and tissue remodeling, and can be pro-fibrotic in certain settings. We demonstrate that overexpression of Cu,Zn-SOD promoted macrophages polarization into an M2 phenotype. Furthermore, overexpression of Cu,Zn-SOD in mice resulted in a pro-fibrotic environment and accelerated the development of pulmonary fibrosis. The mechanism which Cu,Zn-SOD-mediated H2O2 utilizes to modulate macrophage M2 polarization is through redox regulation of a critical cysteine in STAT6. The polarization process, at least partially, was regulated by epigenetic modulation. We show that STAT6 was indispensable for Cu,Zn-SOD-mediated M2 polarization. STAT6 upregulated Jmjd3, a histone H3 lysine 27 demethylase, and initiated M2 gene transcriptional activation. Targeting STAT6 with leflunomide, which can reduce cellular ROS production and inhibit STAT6 phosphorylation, abolished M2 polarization and ameliorated the fibrotic development. Taken together, these observations provide a novel mechanism for the pathogenesis of pulmonary fibrosis whereby the antioxidant enzyme Cu,Zn-SOD plays a paradoxical role. The study highlights the importance of mitochondrial Cu,Zn-SOD and redox signals in macrophage polarization and fibrosis development. These observations demonstrate that the Cu,Zn-SOD-STAT6-Jmjd3 pathway is a novel regulatory mechanism for M2 polarization and that leflunomide is a potential therapeutic agent in the treatment of pulmonary fibrosis.

Le soudage des alliages Al-Zn-Mg est de plus en plus utilisé dans l'industrie du transport. Les variations brutales de température induites par le soudage à l'arc provoquent des modifications importantes de la microstructure dans la zone dite affectée thermiquement.<br />Cette étude porte sur l'évolution de la précipitation suite à ce procédé de l'alliage 7108.50 présentant différentes microstructures initiales. Une caractérisation fine des précipités durcissants dans la zone affectée thermiquement a été menée par SAXS, MET et DSC juste après soudage et après traitements thermiques post-soudage. Afin de mieux cerner les mécanismes influençant la précipitation au cours de ce procédé anisotherme, des traitements thermiques contrôlés, de type réversion ou rampes de montée en température, ont également été étudiés.<br />Un modèle basé sur l'évolution d'une distribution en taille de particules a été développé afin de prédire l'état de précipitation après divers traitements thermiques, dont le soudage.

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.

Les alliages d'aluminium de la série 7xxx sont des alliages à durcissement structural, principalement utilisés dans des applications aéronautiques en raison de leurs propriétés mécaniques spécifiques élevées. Le composant principal de leur résistance mécanique est leur microstructure de précipitation, obtenue par le biais de traitements thermomécaniques complexes. Ceux-ci induisent cependant des contraintes internes à longue distance, susceptibles de générer des distorsions sévères dans les pièces aéronautiques. Certains traitements thermomécaniques comme le grenaillage (shot peening), le formage laser (laser forming) et le formage revenu (age-forming), des procédés respectivement purement mécanique, purement thermique et thermomécanique, permettent de réduire les distorsions de pièces usinées. Ils modifient cependant la microstructure, et, par conséquent, les propriétés mécaniques. La présente étude, portant sur les couplages entre ces traitements thermomécaniques, la microstructure et les propriétés mécaniques d'un alliage 7xxx, comprend un travail de caractérisation expérimentale et de modélisation à base physique. L'effet de la précipitation sur l'écrouissage du matériau est ainsi examiné, et un modèle d'écrouissage destiné à être implémenté dans un modèle éléments finis de simulation du grenaillage est proposé. L'étude du formage laser aboutit quant à elle à un modèle prédictif de l'état de précipitation et des propriétés mécaniques locales induits par ce procédé. La dernière partie est consacrée à l'étude de l'effet du formage revenu – procédé combinant déformation plastique et traitement thermique simultanés – sur la précipitation.

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