Uma série de amostras do sistema catalítico V2O5/TiO2 foi preparada pelo método sol-gel com diferentes teores da fase ativa (de 0 a 9% em massa de V2O5) e calcinada em diferentes temperaturas (de 250 a 6000C). Sistema similar foi obtido pelo método de impregnação para a comparação. Os catalisadores foram caracterizados quanto suas propriedades texturais e estruturais pelas técnicas de Adsorção de N2 a 77K, Difratometria de Raios-X (DRX), Espectroscopia Raman, Ressonância Paramagnética Eletrônica (EPR), Espectroscopia de Fotoelétrons Excitados por Raios-X (XPS) e Espectroscopia de Absorção de Raios-X (XAS). Testes catalíticos para a verificação da atividade e seletividade foram realizados frente à reação de conversão do metanol. O sistema obtido pelo método sol-gel apresentou elevada área superficial e porosidade, as quais foram ampliadas com o aumento do teor de vanádio e reduzidos com o aumento da temperatura de calcinação. O sistema preparado por impregnação apresentou as mesmas propriedades texturais do suporte comercial. A análise de DRX identificou a existência de TiO2 nas formas cristalográficas anatásio e rutilo, não foi identificada a presença de V2O5 na forma cristalina. No sistema preparado por impregnação a estrutura cristalográfica do suporte se mantém, independente do teor de vanádio, porém a partir de 6% de V2O5 foi identificado à presença de V2O5 cristalino. Os espectros de Raman mostraram a presença de dois grupos superficiais de vanádio, os vanadilos monoméricos e os vanadatos poliméricos mesmo em elevados teores de vanádio, nos sistemas preparados pelo processo sol-gel. Nos catalisadores obtidos por impregnação foram identificados modos vibracionais referentes ao V2O5 cristalino.Os resultados obtidos por XAS confirmaram os obtidos por DRX e indicaram a presença de vanádio V4+ e V5+, porém com simetria diferente da forma cristalina V2O5. A determinação da razão entre os átomos V/Ti superficiais feita por XPS mostrou ser crescente com o aumento do teor de vanádio. Os espectros de EPR indicaram a presença de pelo menos três famílias de íons V4+ em diferentes simetrias, duas delas inseridas na matriz da titânia na fase rutilo e a outra dispersa na superfície. O sistema obtido por impregnação apresentou poucos íons V4+. Os testes catalíticos revelaram que a atividade e seletividade catalítica foram praticamente as mesmas para os sistemas preparados pelos dois métodos. Entretanto, a estabilidade catalítica do sistema obtido via sol-gel foi superior ao sistema preparado por impregnação. / A series of samples of the catalytic system V2O5/TiO2 was prepared by the sol-gel method with different proportions of the active phase (from 0 to 9% in mass of V2O5) and calcined in different temperatures (from 250 to 6000C). A similar system was obtained by the impregnation method for comparison. The catalyst were characterized by their textural and structural properties by Adsorption of N2 at 77K, X-Ray Diffraction (XRD), Raman Spectroscopy, Electronic Paramagnetic Resonance (EPR), X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Absorption Spectroscopy (XAS). Catalytic tests for the verification of the activity and selectivity were performed by the conversion reaction of the methanol. The system obtained by the sol-gel method presented a high superficial area and porosity, which were enlarged by the increase of vanadium proportion and reduced with increase of the calcinations temperature. The system prepared by impregnation presented the same textural proprieties of the commercial support. XRD analysis identified the existence of TiO2 in two crystallographic forms, anatase and rutile. It was not identified the presence of V2O5 in the crystalline form. In the system prepared by impregnation the crystallographic structure of the support keeps, independent of the vanadium content, however starting from 6% of the vanadia was identified crystalline V2O5. Raman spectra showed the presence of two superficial groups of vanadium, the monomeric vanadyls and the polymeric vanadates even for elevated contents of vanadium, in the system prepared by the impregnation method vibrational modes were identified referring to V2O5 crystalline. The results obtained by XAS confirmed the obtained by XRD and indicated the presence of V4+ and V5+, however with different symmetry from the V2O5 in a crystalline form. The determination of the proportion between the surface V/Ti atoms determined by XPS showed to be increased with the increase of the vanadium content. EPR spectra indicated the presence of at least three V4+ion families in different symmetries; two of them inserted in the matrix of titania in the rutile phase and to other dispersed on the surface. The system obtained by impregnation presented few V4+ ions. The catalytic tests reveled that the catalytic activity and selectivity were practically the same for the systems prepared by both methods. However, the catalytic stability of the system obtained via sol-gel was superior to the system prepared by impregnation.

O presente trabalho tem por objetivo investigar e propor uma metodologia rápida e eficaz de avaliação da reatividade do cimento Portland frente ao ataque por sulfatos. O método consiste na utilização de amostras de pasta de cimento hidratada em pó, colocadas em contato direto com soluções concentradas de Na2SO4 e MgSO4, em temperatura elevada (65ºC), para acelerar o ataque. Apesar dos cimentos estudados possuírem composição química parecida, os resultados de SO3 combinado mostraram que o cimento Classe G foi pouco menos suscetível ao ataque por sulfatos em função do maior teor de Fe2O3 presente. Da TG e DRX observou-se a formação de etringita no ataque por ambos os sais de sulfato; e formação de gipsita no ataque por MgSO4. Enquanto havia disponibilidade de portlandita na pasta hidratada, o cimento com adição mineral incorporada apresentou mesma taxa de ataque que os demais (sem adição), entretanto a partir do momento que toda a portlandita foi consumida, iniciou-se um processo de descalcificação do C-S-H, observado pela DRX. / The main point of this research is to propose a fast and effective method of evaluation of the cement reactivity to sulfate attack. Resistance to sulfate attack was measured by determining the combined sulfate in cement paste samples with exposure to Na2SO4 and MgSO4 solution, at high temperature (65°C). The samples of cement paste was triturated (powdered) in the proposed method. The results of combined SO3 showed that the Class G cement was little less susceptible to the sulfate attack because it has larger amount of Fe2O3. The ettringite formation was observed in the attack for both sulfate salts; and gypsum formation in the attack for MgSO4 (results of TG and XRD). The blended cement presented same results that the others, however when the Ca(OH)2 was totally consumed, it observed the decalcification of the C-S-H, by XRD.

Made available in DSpace on 2017-07-24T19:37:53Z (GMT). No. of bitstreams: 1 Caetano, Elenice Hass.pdf: 4149328 bytes, checksum: b6eb52279243079ec9a5d88b5028ae4c (MD5) Previous issue date: 2015-03-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Clay minerals are hydrated silicates of Aluminum, Iron and Magnesium that has lamellar structure (phyllosilicates) composed by continuous SiO4 tetrahedral layers connected to bi and tri metals hydroxide octahedral layers. The layers are continuous and hexagonally ordered regarding to crystallographic axis a and b. The arrange of clays minerals determines the type of clay mineral as 1:1 or 2:1. The 2:1 clays minerals are divided in groups: Vermiculite, Mica, Chlorite, Saponite, Paligorskita and the Smectite group. Among the Smetectite group stands out the Bentonite, the most abundant clay mineral and that shows 2:1 phyllosilicates structure composed by two silicate tetrahedral layers and one alumina octahedral layers, both connected by oxygen atoms in common. The great technological interest in these clay results of the high cation exchange capacity, swelling by water and low size of crystals. Such properties favor the clays modification to discovery new applications. Thus, the clays minerals are an essential step for the discovery of technological applications as well as the fundamental properties of clays. In this work, were characterized four samples of clays through of X-Ray Diffraction, X-Ray Fluorescence Spectroscopy, Fourier Transform Infrared Spectroscopy, 27Al NMR-MAS and Field Emission Scanning Electron Microscopy. The obtained results indicate the predominance of Smectite phase in clays due to high swelling capacity and cation exchange observed. The predominance of Smectite phase was confirmed by XRD, XRF and FTIR, which also indicates the presence of quartz and other minerals. Were also evaluated the presence of organic compounds in the interlayer space of modified clays and was noted that have not changes in their crystalline structures, based on FTIR and 27Al NMR-MAS results. The SEM-FEG micrography confirms the irregularity of cluster size, according to expect to bentonite clays. The performed characterizations for these clays minerals determine its elementary composition and makes possible distinguish the four samples according to its place of origin by the amount of impurities, as well as the prevalence of smectite phase. The characterization analysis were used to quantification of fundamental properties and to evaluated the organic compounds presence in interlayer space through of delocalization of the most intense peak in 2θ angle. The obtained results are useful for the benefit of industrial areas such as pharmaceutical, food, environmental and others, once the mineral clays properties can be improved when properly identified and quantized. / Argilas são materiais naturais, terrosos, considerados finos grãos que contém partículas com diâmetro inferior a 2 μm e, quando umedecidos com água, apresentam plasticidade. São constituídas essencialmente por argilominerais (filossilicatos) e por matéria orgânica, sais solúveis, minerais como calcita, pirita, gibsita, quartzo entre outras impurezas. Bentonita, conhecida como o argilomineral mais abundante do grupo da esmectita, pertence ao grupo dos filossilicatos 2:1, sua estrutura cristalina é constituída por duas folhas tetraédricas de sílica com uma folha central octaédrica de alumina, ambas unidas por átomos de oxigênio em comum. O grande interesse tecnológico nessa argila está ligado à sua alta capacidade de troca catiônica, intumescimento pela água e às pequenas dimensões dos cristais, cujos fatores favorecem a modificação das argilas para a descoberta de novas aplicações. Para tanto, a caracterização da argila é uma etapa primordial para aplicações tecnológicas bem como suas propriedades fundamentais como alta adsortividade, alta capacidade de troca catiônica, capacidade de inchamento e alta propriedade de barreira. No presente trabalho, foram caracterizadas quatro amostras de argilas Bentonítas de diferentes procedências, sendo duas na sua forma pura e duas organofílicas pelas respectivas técnicas: difração de raios X, fluorescência de raios X, Espectroscopia Vibracional de Absorção na Região do Infravermelho, Ressonância Magnética Nuclear do estado sólido - 27Al RMN-MAS, Microscopia Eletrônica de Varredura com Efeito de Campo. Os resultados obtidos indicaram a predominância da fase esmectita evidenciada pela alta capacidade de inchamento e alta capacidade de troca catiônica. Além disso, os resultados de DRX, FRX e FTIR também evidenciaram a predominância da fase esmectita, bem como a presença de quartzo e outros minerais. Também foi possível avaliar a presença de compostos orgânicos no espaço interlamelar das argilas organofílicas e notou-se que não houve alterações em suas estruturas cristalinas, informações estas corroboradas pelas técnicas de FTIR e 27Al RMN-MAS. As micrografias obtidas por MEV-FEG puderam confirmar a irregularidade de tamanho dos aglomerados de partículas típico de bentonitas. As Caracterizações obtidas para as argilas determinaram sua composição elementar, sendo possível distinguir argilas de diferentes procedências pela quantidade de impurezas, bem como a predominância da fase esmectita. Além disso, por meio da caracterização também foi possível determinar a quantificação de suas propriedades fundamentais, e também confirmar a presença de composto orgânico no espaço interlamelar por meio do deslocamento do pico de maior intensidade do ângulo 2θ. Essas caracterizações podem ser utilizadas em benefício das áreas industriais, como farmacêutica, alimentícia, ambientais entre outras, podendo ser aprimoradas as propriedades quando bem identificadas e quantizadas.

Arsenic contamination of groundwater associated with mining operations is a widespread problem across the globe. The release of arsenic (As) into the environment occurs naturally by oxidation of exposed sulfide minerals. In the case of gold ores, the mining and beneficiation may also produce As-bearing wastes and this can accelerate the natural mechanisms of As mobilization. The Bakyrchik is the largest gold deposit in Kazakhstan and one of the largest in the world. Gold (Au) is dispersed in pyrite and arsenopyrite in the form of microscopic inclusions. Despite the fact that only 10% of gold ore has been mined to date, it has left behind a dangerous As-containing legacy. Speciation of As has been determined for samples from Bakyrchik to understand the post-processing environment and the mobility of arsenic in the mining-influenced area. As(III) and As(V) have been detected in water samples using HPLC-ICP-MS. The variability of As species across the narrow pH and Eh range indicates that biogeochemical processes can play a role in the speciation of As in water at the study site. In order to understand processes controlling As mobilization in water, the solid phase speciation of As in Bakyrchik sediments, soil, and metallurgical processing products has been investigated using XRD and EPMA. This revealed arsenopyrite, As-bearing pyrite, and their alteration products containing up to 25% As, iron oxides and oxyhydroxides (with up to 2.5% As), haidingerite, and calcium arsenate in studied samples. Sequential extraction demonstrated that in soil and sediment samples As is associated mainly with Al and amorphous Fe oxyhydroxides. Results suggest that the main mechanisms controlling As mobility in Bakyrchik are dilution with regional waters, adsorption onto iron and aluminium oxyhydroxides, and co-precipitation of dissolved As with alteration products of sulfide minerals. Assessment of As bioaccessibility through inhalation demonstrates its strong dependence on the mineralogy rather than on total As content of the solid samples. Calculated cancer and non-cancer risks of inhalation exposure imply that all samples are highly hazardous for human health. With the depletion of the oxide lode ore deposits, gold extraction is moving towards the mining of technologically difficult ores, such as those found at Bakyrchik. A new method of Au recovery from double refractory Au-As-bearing concentrates has been developed, allowing recovery of 97% of Au, and the conversion of up to 95% As into iron-arsenic alloy. Fe-As alloy can contain up to 40% As, and do not require further solidification/stabilisation prior to disposal. The method has been published as a patent with the Patent Office of the Republic of Kazakhstan. Quantitative phase composition of the Fe-As alloy, has been determined by EPMA, QEMSCAN, X-ray and neutron diffraction. Toxicity and solubility of Fe-As alloy in aqueous solutions have been characterised. High-temperature structural behaviour of Fe-As alloy and Fe$_{2}$As in inert atmosphere has been determined by $\textit{in situ}$ synchrotron XRD. Results of the study support the development of the new method as an efficient alternative for processing double refractory Au-As-bearing concentrates.

Argilominerais são componentes abundantes nas frações < 2 &mu;m solos, com grande papel no controle de processos geoquímicos e de formação de solos. Nos manguezais brasileiros, apesar das caracterizações gerais já realizadas, há ausência de estudos cristaloquímicos detalhados que possam evidenciar mecanismos de formação/transformação envolvendo essas fases. Este trabalho se propõe, através de dois estudos comparativos, aprofundar a caracterização cristaloqímica das frações 2-0,2 &mu;m e < 0,2 &mu;m, sugerir processos de transformação envolvendo os argilominerais dos manguezais e entender quais atributos ambientais estão associados a essas transformações. Esta caracterização se baseia nas técnicas de modelagem de DRX, decomposição de picos 060 de padrões não-orientados de DRX, FTIR, espectroscopia Mössbauer, análises térmicas, análise química da água intersticial e modelagem geoquímica dos componentes químicos em solução. Os resultados, que serão detalhados nos capítulos 2 e 3, sugerem uma série de transformações minerais, via fases interestratificadas, que devem ter importantes implicações para a compreensão dos processos pedogenéticos envolvendo argilominerais, do seu papel no ciclo biogeoquímico dos elementos associados à sua gênese e relação indireta ou direta com componentes bióticos do ecossistema, que podem influenciar nas transformações que envolvem os minerais. / Clay minerals are ubiquitous components in < 2 &mu;m size fraction of soils, having an important role in the control of geochemical processes and soil genesis. Despite of the general characterizations performed in Brazilian mangroves soils there is a lack of a detailed crystal chemical study able to evidence mechanisms of formation/transformation of such minerals. This study aims (by two different comparative works) to enhance the crystal chemical characterization of mineral phases in the 2-0,2 &mu;m and < 0,2 &mu;m size fractions of mangrove soils, suggesting the existence of mineral transformation involving clay phases and comprehending what environmental settings are related to these transformations. This characterization is based on XRD modelling of oriented patterns, peak fitting of 060 peaks in randomly XRD patterns, Mössbauer spectroscopy, thermal analysis, chemical analysis of soil pore water and geochemical modelling of inorganic soluble compounds. The results, which are described in chapters 2 and 3 indicate a sequence of mineral transformations, via mixed-layered clays, which may have important consequences for the comprehension of soil genesis processes involving clay minerals, their role in the biogeochemical cycles of structural elements of clays and a straight relationship with biotic components of mangrove ecosystem.

During drilling at Borg, ca. 5 km southwest of central Norrköping, an unidentified fine-grained grey rock was encountered in contact with dark red granitic gneiss at 35m depth. The fine-grained grey rock occurs above the red granitic gneiss. Our understanding prior to testing is that the rock may have been formed by fluid alteration of a mafic rock, as neither metamorphic nor sedimentary textures were observed. Understanding this rock and the formation processes related to it, is of interest for the general understanding of the region and of geotechnical importance since fracture fillings may affect the stability of the rock during and after construction projects. This study uses the methods petrography, XRD and XRF to define the fine-grained mafic rock, black vein in the fine-grained mafic rock, the contact zone and the granitic gneiss. Results show that the fine-grained grey rock has a composition of muscovite (36.1%), quartz (24.6%), albite (20.8%), sericite (10.8) and montmorillonite (0.5%). The contact is mainly made of quartz veins and calcite veins. The protolith of the fine-grained mafic rock is suggested to be iron-rich. Further testing on additional unaltered mafic rock samples from the area would provide a more accurate picture of the protolith evolution.

En vue de la réduction des problèmes engendrés par les phénomènes de retrait-gonflement des sols dans la dépression de la Lama au Sud du Bénin, nous avons entrepris des recherches dans le but de maîtriser le comportement de ces sols. Six échantillons de sols fins dont quatre argileux de cette région ont été prélevés. Différents essais ont été réalisés : une caractérisation macroscopique concernant les propriétés mécaniques et géotechniques et les essais microscopiques prenant en compte les analyses chimiques, thermiques, minéralogiques et microstructurales. Les sols étudiés sont constitués de différents minéraux argileux. Celle à structure fibreuse est à l'origine d’un comportement macroscopique particulier décelé par l’essai de gonflement libre. Les essais ont confirmé le fort potentiel de gonflement et de retrait de certains sols qui sont donc à l'origine des fortes dégradations rencontrées.Les résultats montrent que les sols traités se distinguent par les performances mécaniques acquises et peuvent être utilisés à différents niveaux de la chaussée selon leur teneur en liant.Les différentes méthodes utilisées ont révélé des facettes particulières de l'étude de traitement des sols fins. Principalement, nous avons noté que les informations apportées par les observations au Microscope Electronique à Balayage, les analyses thermiques et les analyses de Diffraction aux Rayons X ont permis de compléter l’analyse des résultats géotechniques. En somme, les méthodes de caractérisation géotechnique permettent d’avoir une idée générale du potentiel de gonflement, mais pour les études d’envergure, la réalisation d’études microscopiques est primordiale. / To help reduce the problems caused by phenomena due to the shrink-swell soil in the depression of the Lama in southern Benin, we have undertaken research in order to control the behavior of these soils. Six soil samples, including four clay from this area were taken. Different types of tests were performed: a macroscopic characterization concerning mainly mechanical and geotechnical properties and microscopic tests taking into account the chemical, thermal, microstructural and mineralogical analysis. The soils studied consist of different clay minerals. The fibrous structure is at the origin of a particular macroscopic behavior detected by the free swell test. The tests confirmed the potential for swelling and shrinking of some soils that are causing heavy damage.Three soils treated with different contents at Binder Hydraulic Road, were subjected to several tests. The results show that these soils are distinguished by the acquired mechanical performance and may be used at different levels of the floor according to binder content.Also, the different methods revealed specific facets of fine soil treatment study. Mainly, we noted that the information provided by the observations scanning electron microscope, thermal analysis and the analysis of diffraction X-Ray are very important and helped complete the analysis of geotechnical results for soil treatment. In sum, geotechnical characterization methods used to get a general idea of the swelling potential, but for large-scale studies, conducting microscopic studies is paramount.

<p>The principles of dye-sensitized solar cells were studied and are outlined in this thesis. An overview of the basic steps needed to create a DSC isfollowed by detailed experimental information on how to assemble the solar cells that were fabricated in this project. They were based on synthesizednanocrystalline ZnO thin films sensitized by chlorophyll a as well as isolated photopigments from spinach leaves. The nanocrystals werestudied using XRD, and it was confirmed that three different methods of synthesis resulted in ZnO crystals of a few nanometers. The solar cellswere assembled with Au electrodes in a sandwich configuration and their photovoltaic properties were measured. Overall light-to-electricity conversionwas low with the highest efficiency being 0.21 %. An astonishingly low efficiency of 0.0003 % was noted for a thin film which was not thermallytreated, and it is suggested that heat-treatment is of great importance. It was also found that photopigments from spinach can be extractedeasily and used as molecular sensitizer without any demanding purification steps.</p>

<p>Nanomaterials have attracted great interest in recent years, and are now also being considered for battery applications. Reducing the particle size of some electrode materials can increase battery performance considerably, especially with regard to capacity, power and rate capability. This thesis presents a study focused on the performance of such a material, vanadium oxide nanotubes, as cathode material for rechargeable lithium batteries.</p><p>These nanotubes were synthesized by a sol-gel process followed by hydrothermal treatment. They consist of vanadium oxide layers separated by structure-directing agents, normally amines or metal ions, e.g., Na⁺, Ca²⁺, Mn²⁺ and Cu²⁺. The layers are arranged in a scroll-like manner, allowing the interlayer structure to expand and contract, depending on the size of the embedded guest. This tubular form of vanadium oxide was able to insert lithium ions reversibly, making it a candidate cathode material. The structural and electrochemical response to lithium ion insertion was carefully studied to define optimal performance criteria and probe the lithium insertion mechanism. This was done using several characterization techniques, including X-ray diffraction, a variety of spectroscopic methods and electrochemical testing. Galvanostatic measurements show that the material can be charged and discharged reversibly for >100 cycles with a capacity of 150-200 mAh/g. The electrochemical performance is, however, dependent on the electrode film preparation technique, the choice of salt in the electrolyte and the nature of the embedded guest. Results from photoelectron spectroscopy, and soft X-ray emission and absorption spectroscopy confirm that vanadium is reduced during lithium insertion and that three oxidation states (V⁵⁺, V⁴⁺and V³⁺) co-exist at potentials below 2.0 V. <i>In situ</i> X-ray diffraction, performed during potential stepping, identifies two separate processes during lithium insertion: a fast decrease of the interlayer distance followed by a slow two-dimensional relaxation of the vanadium oxide layers. </p>

Nanomaterials have attracted great interest in recent years, and are now also being considered for battery applications. Reducing the particle size of some electrode materials can increase battery performance considerably, especially with regard to capacity, power and rate capability. This thesis presents a study focused on the performance of such a material, vanadium oxide nanotubes, as cathode material for rechargeable lithium batteries. These nanotubes were synthesized by a sol-gel process followed by hydrothermal treatment. They consist of vanadium oxide layers separated by structure-directing agents, normally amines or metal ions, e.g., Na+, Ca2+, Mn2+ and Cu2+. The layers are arranged in a scroll-like manner, allowing the interlayer structure to expand and contract, depending on the size of the embedded guest. This tubular form of vanadium oxide was able to insert lithium ions reversibly, making it a candidate cathode material. The structural and electrochemical response to lithium ion insertion was carefully studied to define optimal performance criteria and probe the lithium insertion mechanism. This was done using several characterization techniques, including X-ray diffraction, a variety of spectroscopic methods and electrochemical testing. Galvanostatic measurements show that the material can be charged and discharged reversibly for &gt;100 cycles with a capacity of 150-200 mAh/g. The electrochemical performance is, however, dependent on the electrode film preparation technique, the choice of salt in the electrolyte and the nature of the embedded guest. Results from photoelectron spectroscopy, and soft X-ray emission and absorption spectroscopy confirm that vanadium is reduced during lithium insertion and that three oxidation states (V5+, V4+ and V3+) co-exist at potentials below 2.0 V. In situ X-ray diffraction, performed during potential stepping, identifies two separate processes during lithium insertion: a fast decrease of the interlayer distance followed by a slow two-dimensional relaxation of the vanadium oxide layers.