Iron ore sinter is produced from fine-grained ore in order to provide a direct charge to the blast furnace. During the sinter production process fine sinter is produced that is not acceptable as feedstock for the blast furnace. This fine material is screened off and returned to the sinter plant to be recycled. The production of these recirculating fines therefore results in loss of revenue for the sinter producing facility. The aim of this study is to compare the composition and phase chemistry of the fine and normal sinter to determine if chemical or operational changes can be made to reduce the amount of fine sinter formed. This will be achieved through the analyses of real industrial sinter samples, synthetically produced lab-based samples and sinter test pot samples. Iron ore sinter was collected from the Vanderbijl Park sinter plant in South Africa. The samples were prepared for X-ray diffraction (XRD) and X-ray fluorescence (XRF) analysis to test the reproducibility of the equipment used as well as the reproducibility of the sample preparation method. The results obtained showed that the methods applied produced accurate results and the preparation method was then applied on all samples that were analyzed. The XRD analyses show that the sinter contains spinel (mainly magnetite with variable Mg), hematite, dicalcium silicate (C2S) and silico ferrite of calcium and aluminum (SFCA) and that there are distinct differences between the fine and normal sinter. Fine sinter contains more hematite and less SFCA than normal sinter. The presence of the SFCA is considered to be essential for the production of strong sinter. The XRF analyses show that there are no distinctive differences in the chemistry of fine and normal sinter. The samples were then analyzed with an electron microprobe. It was found that the compositions of some of the SFCA phases present in the samples do not correspond to those described in the literature. Optical microscopy combined with point counting was conducted on the fine and normal sinter in order to determine differences and to compare the point counting data to the XRD results. The point counting results showed that the hematite present in the fine sinter is largely relict or unreacted hematite. Sinter pot test samples were analyzed with XRD and XRF. It was found that the pot test samples exhibited similar trends as the samples taken at the sinter plant. This shows that it is not only plant parameters such as sample transport that result in the formation of fines, but that carbon addition, flame temperature and reaction time may also play a role in the formation of fine sinter material. It has been concluded that the production of fine sinter is a direct function of the amount of hematite present in the sinter. The proposed hypothesis for this phenomenon involves the incomplete reaction of the sinter material during processing. Suggestions to decrease the amount of fine sinter formed include: uniform heat distribution during ignition, pO2 alteration by reductant addition, lower ignition temperature, regulating the cooling regime and decreasing the grain size of lime. / Dissertation (MSc(Applied Science))--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / unrestricted

When the inorganic domain sizes in a composite are reduced to a level such that a "molecular composite" is formed, the hybrid materials are commonly referred to as "ceramers". Hybrid materials span from inorganically modified organic polymers to inorganic g1asses slightly modified by organic polymers. The incorporation of an inorganic phase into an organic polymer is done almost exclusively by the "sol-gel" process.

During this EngD project, two pigmented, anti-corrosion polymer/sol-gel hybrid coatings were developed with the aim of producing an eco-friendly alternative to conventional, toxic hexavalent chromate conversion and anodized anti-corrosion alloy treatments for the aircraft manufacturer; Airbus S.A.S. The polymer/sol-gel hybrid coatings were then tested and validated as anti-corrosion coatings on the AA2024-T3 aluminium aerospace alloy and in certain cases, their performance was compared against that of the hexavalent chromate benchmark (Alocrom 1200). The mechanisms of corrosion inhibition exhibited by the coatings were also studied in depth. The polymer/sol-gel hybrid coatings that were developed in this project are silane based and the first, designated as B2, has polyester-methacrylic functionality and the second, designated as CA/MM, has polyester-amide functionality. Certain inhibitor compounds which were incorporated in the polymer/sol-gel hybrid coatings were chosen by the split-cell technique. The microstructure and elemental compositions of the polymer/sol-gel hybrid coatings and of the AA2024-T3 aluminium alloy were determined by Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopic (SEM-EDS) analysis of the specimens. The anti-corrosion performance and the corrosion protection mechanisms of the polymer/sol-gel hybrid coatings were determined by salt-water and electrochemical testing of the coated alloy specimens. The thermal resistance of the polymer/sol-gel hybrid coatings was ascertained by thermogravimetric analysis (TGA) of the coatings. The polymer/sol-gel hybrid coatings were also analysed by Fourier Transform Infrared (FTIR), Micro-Raman and X-ray Photoelectron (XPS) spectroscopic techniques to determine whether the desired polymer and silane coating networks formed during coating processing. Anti-corrosion performance test results revealed that both polymer/sol-gel hybrid coatings are self-healing due to their ability to implement a precipitation mechanism of corrosion inhibition. Analysis of the polymer/sol-gel hybrid coatings by X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) after salt-water exposure suggested that the B2 coating precipitated the compound tungsten pyrophosphate, W(P2O7), within defects and that the CA/MM coating precipitated the compound iron carbide, Fe2C, within defects. However, anti-corrosion test results also shown that the anti-corrosion performance of the polymer/sol-gel hybrid coatings does not satisfy aerospace industry requirements. Therefore, it can be concluded that although the achievements of this project have not enabled Airbus to eliminate toxic chromium (VI) species from their operations, further optimisation of the polymer/sol-gel hybrid coatings developed during this project could potentially lead to a solution being found.

Os compostos amônio quaternários (CAQ) e as nanopartículas de prata (AgNPs) são extensamente conhecidos por suas atividades antibacterianas. Neste contexto o silsesquioxano iônico contendo o grupo catiônico 1,4-diazôniabiciclo[2,2,2]octano (SiDb(NO3)2) foi utilizado como agente estabilizante de AgNPs em meio aquoso, possibilitando a obtenção de nanopartículas de prata estáveis na forma esféricas com diâmetros médios inferiores a 10 nm. Mesmo em concentrações baixas de prata (1.1 μg.mL-1), o sistema AgNPs/SiDb(NO3)2 apresenta excelente atividade antibacteriana contra as bactérias E. coli e S. aureus, como também baixa citotoxicidade. Também foram produzidos filmes finos, sobre substratos de vidro, com o sistema AgNPs/SiDb(NO3)2. Os filmes de AgNPs apresentaram excelentes atividades bacteriostática e bactericida contra as bactérias E. coli e S. aureus. Portanto, o sistema AgNPs/SiDb(NO3)2 é muito promissor para ser aplicado como agente antibacteriano na forma de dispersão aquosa ou de filme fino. / The quaternary ammonium compounds (QAC) and silver nanoparticles (AgNPs) are widely known for their antibacterial activities. In this context, the ionic silsesquioxane containing the cationic group 1,4- diazoniabicyclo [ 2,2,2 ] octane and the nitrate group as counter ion (SiDb(NO3)2) was used as a stabilizing agent of AgNPs in aqueous medium, making possible to obtain stable silver nanoparticles with spherical shape and average diameters below 10 nm. Even at low silver concentration (1.1 μg.mL-1), the AgNPs/SiDb(NO3)2 system shows excellent antibacterial activity against E. coli and S. aureus bacteria, as well as low cytotoxicity. Thin films of AgNPs/SiDb(NO3)2 system were made on glass substrates. The films of AgNPs showed excellent bacteriostatic and bactericidal activity against E. coli and S. aureus bacteria. Therefore, the AgNPs/SiDb(NO3)2 system is very promising to be applied as antibacterial agent as water dispersion or film form.

Orientador: Ulf Friedrich Schuchardt / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-07T20:41:43Z (GMT). No. of bitstreams: 1 RinaldiSobrinho_Roberto_D.pdf: 13717889 bytes, checksum: 44d71665f771669d5a379b692f3356c0 (MD5) Previous issue date: 2006 / Doutorado / Quimica Inorganica / Mestre em Química

Magíster en Ciencias de la Ingeniería, Mención Química. Ingeniero Civil Químico / Uno de los mayores desafíos para la ingeniería de tejidos óseos es el desarrollo de estructuras que puedan promover la formación de hueso y estimular la formación de nuevos vasos sanguíneos (angiogénesis). El biovidrio es un material prometedor en el área de regeneración ósea y corresponde a un vidrio cerámico que puede ser dopado con distintos elementos, permitiendo otorgarle nuevas funcionalidades. En particular se destacan los iones metálicos terapéuticos, tales como el cobalto, debido a su capacidad de mejorar la angiogénesis. Esta tesis pretende desarrollar vidrios dopados con cobalto mediante el método sol-gel y estudiar los efectos que tiene la incorporación de este ión en las propiedades finales del material. Se sintetizaron mediante 2 métodos sol-gel distintos vidrios bioactivos ternarios (60SiO2-36CaO-4P2O5 %mol) dopados con 1, 2 y 4%mol de CoO, buscando obtener micro y nanopartículas (método 1 y 2 respectivamente). El área específica, la nanotopografía y el rol del cobalto en la estructura, ya sea como óxido intermediario o modificador de red, de los materiales obtenidos dependen del método de síntesis. Todos presentaron una disminución de la bioactividad al incorporar cobalto, pero las micropartículas presentaron mejores propiedades de liberación de cobalto. Así también, las micropartículas presentaron mejores resultados de viabilidad celular en comparación con las nanopartículas, asociado a las mayores áreas superficiales y mayor liberación de calcio de estas últimas. Por otro lado, todos los materiales presentaron una capacidad alcalinizadora que afectó negativamente tanto a las células SaOS-2 como Ea.HY, durante los ensayos de citocompatibilidad y migración. Se prepararon mediante fundido compósitos de PDLLA con un 10% en peso de vidrios sintetizados por el método 1. Después de 28 días de inmersión en SBF no se observó la formación de apatita mediante SEM o DRX, pero el análisis EDS indica una razón Ca/P relacionada a esta fase mineral. Además, la incorporación de vidrio en una matriz polimérica permitió regular la liberación de iones, mitigando los efectos alcalinizadores. Los compósitos con biovidrios dopados con cobalto presentaron mayores migraciones que el compósito con vidrio ternario, pero faltan estudios de los factores angiogénicos para determinar el efecto terapéutico del cobalto. Los efectos del dopaje con cobalto y la incorporación de estos vidrios en matrices poliméricas descritos en este trabajo proporcionan información importante a la hora de decidir el uso de estos materiales en ingeniería de tejidos y regeneración ósea.

Linear alkylbenzenes (LAB) are key intermediates in the synthesis of linear alkylbenzene sulfonate surfactants that are used in the manufacture of detergents. Production of LAB with traditional Lewis acids as catalysts, such as hydrofluoric acid, results in the formation of large amounts of toxic wastes and corrosion of industrial equipment. Phosphotungstic acid (PTA) has gained much attention in recent years as a solid catalyst for various alkylation reactions. This research work aims to develop a novel material based on PTA-containing silica gel, which can effectively catalyze LAB synthesis. Sol-gel synthesis of silica gel in the presence of PTA and tetraethyl orthosilicate as precursors produced a mesoporous aterial containing covalently embedded PTA clusters. Obtained superacidic catalyst demonstrated high catalytic activity in liquid-phase alkylation of benzene by various alkenes. Covalent embedding of catalytically active HPA clusters prevents their leaching from the catalyst surface, which enabled its excellent catalytic properties.

Tesis para optar al grado de Doctora en Ciencias de la Ingeniería, Mención Ciencia de los Materiales / La contaminación del agua por arsénico (As) es un problema grave en los países en desarrollo. En agua contaminadas de forma natural con As, están presentes dos tipos de especies As (V) y As (III), siendo la última la más tóxica. En este trabajo, se preparó un innovador adsorbente basado en nanopartículas de CaTiO3 (CTO) mediante la técnica sol-gel para la eliminación de As (III) de soluciones acuosas. Esta forma de abatimiento de As es importante ya que permite simultáneamente adsorber y oxidar el As(III), sobre las perovskitas mediante procesos fotocatalíticos hasta con radiación visible. En tal sentido, con el presente trabajo se pretende estudiar las propiedades estructurales, ópticas y fotocatalíticas de nanopartículas de CaTiO3 y CaCu3Ti4O12, puras y dopadas. La tesis presentada está dividida en tres etapas, en la primera etapa se determinaron los parámetros de síntesis y la ruta de obtención de perovskitas puras y dopadas. Se propusieron dos métodos de síntesis sol-gel e hidrotermal. Con el método sol-gel, la introducción del agente reticulante en la síntesis, inhibió el crecimiento de los cristalitos de las perovskitas y en base a los resultados de la estructura cristalina y resultados calorimétricos, se logró obtener perovskitas a nivel nanométrico. El área superficial de las perovskitas fue afectada negativamente por los dopantes. En el caso de la síntesis hidrotermal, se estudió la influencia del tipo y concentración del mineralizador, temperatura y tiempo de reacción, para el caso de CaTiO3 se lograron partículas de forma poliédrica y tamaño entre 1 a 9 µm, para la obtención del CaCu3Ti4O12 por este método es necesario adicionar un proceso de calcinación para la obtención de la fase esperada, lo que implicó en el aumento del tamaño de partícula. En la segunda etapa, se evaluó el comportamiento en la remoción de As del agua con las perovskitas, destacando en eficiencia a la remoción de As el CaTiO3 sobre todas las perovskitas, mediante modelos matemáticos siguen un comportamiento de pseudo segundo orden, que resultó en un ajuste para la muestra a pH 3 fue de 0,99, alcanzando una capacidad máxima de adsorción de 11,12 mgg-1. Se demostró, que la coexistencia de otros iones no afecta considerablemente la remoción de As, también que la perovskita CaTiO3 puede reutilizarse hasta en cuatro ciclos de adsorción/desorción y en que en condiciones ácidas y básicas está perovskita mantiene su fase mineralógica. Se verificó que el As(III) está adsorbido en la superficie del CaTiO3 mediante XPS. En la tercera etapa se estudió en comportamiento fotocatalítico de las perovskitas puras y dopadas, sobre la oxidación de As(III) y la generación de As(V). Se demostró que al incrementar el dopaje en el CaTiO3 disminuye la brecha de energía prohibida. Se logró oxidar As(III) a As(V) hasta 55%, utilizando radiación UV con nanopartículas de CaTiO3 y con radiación visible se logró generar 40% de As(V) mediante CTO dopadas con 10% de Cu. Se evidenció que, en la superficie de las perovskitas fotocatalizadas están presentes las especies de As(III) y As(V), sin formar nuevos enlaces de ligadura, lo que indicaría que el As está fisisorbido en el CaTiO3.

The objective of this work was to synthesize functionalized mesoporous silsesquioxanes with high concentrations of amine groups. During typical sol-gel syntheses, these materials are obtained by co-condensation of organic precursors with suitable linkers, such as tetraethoxysilane, necessary to prevent the mesoporous structure from collapsing. Thus, concentrations of amine groups in organosilicas usually do not exceed 2.7-3.4 mmol g -1. The use of bridged bis-trimethoxysilanes, however, allowed formation of mesoporous materials with no linker. Polycondensation of bis-trimethoxysilanes containing amine groups was conducted in acidic, neutral and basic media, resulting in high yields of solid bridged silsesquioxanes. Gelation occurred quickly if no acid or base was added to the reaction mixture. The hybrid organic/ inorganic nature of obtained materials was confirmed by FT-IR and MAS CP NMR spectroscopy. Elemental analysis showed that amino group concentration in the products was 3.3-4.1 mmol g -1. Measurement of particle size distribution confirmed that choice of reaction media significantly affects particle sizes and agglomeration degrees, with the largest agglomerates (up to 50 μm) formed in basic media. A morphology study, using smallangle X-Ray scattering, displayed two-level fractal structures composed of aggregated 6.5-10.5 nm particles. Reactions in the presence of a surfactant resulted in formation of mesoporous structures. Furthermore, the obtained bridged silsesquioxanes were thermally stable down to 260 °C, but could reversibly absorb water and CO 2 at temperatures below 120 °C. Thus, condensation of the bridged precursor without a linker resulted in formation of a highly functionalized mesoporous material.

Abstract: Silica gels containing embedded heteropolyacids were synthesized in acidic media by co-condensation of tetraethoxysilane with phosphotungstic or phosphomolybdic acids using the sol-gel technique. Surfactants dodecylamine, sodium dodecylsulfate, trimethylstearylammonium chloride, and Pluronic P123 were used as templates. The effect of the synthesis conditions on their structure and morphology was studied. All materials were mesoporous but contained micropores in their structures. Presence of bands of Keggin structures in fourier transform infrared spectroscopy spectra along with absence of X-ray diffraction patterns of crystalline heteropolyacids confirmed their fine incorporation into silica network. Particle sizes of modified materials were 500–1100 nm except for the W-containing sample obtained with trimethylstearylammonium chloride, which was significantly lower. This unusual effect was attributed to stabilization of primary silica nanoparticles by interactions between the surfactant and heteropolyacid. High ratio heteropolyacid/tetraethoxysilane resulted in partial loss of porosity. Obtained results might be used for optimization of synthesis of effective catalysts and adsorbents containing heteropolyacids in mesoporous structure. Graphical Abstract: [InlineMediaObject not available: see fulltext.]