Neste trabalho são apresentados resultados experimentais do processo de filtração tangencial de uma suspensão in natura (soro de leite) aplicada na retenção de bactérias do grupo coliforme. No estudo do processo de separação utilizaram-se tubos microporosos de -alumina (Al2O3) e membranas comerciais de tamanho médio de poros no valor de 0,8 e 1,2m. Os tubos microporosos cerâmicos foram sinterizados à temperatura entre 1400 e 1450ºC, os quais foram caracterizados pela técnica de porosimetria por intrusão de mercúrio, constatando o tamanho médio de poros de 0,3 a 0,5µm. Após a sinterização, os tubos cerâmicos foram sujeitos à impregnação com citrato de prata (material bactericida). As membranas comerciais também passaram pelo mesmo processo de impregnação. Com o uso da técnica de microscopia eletrônica de varredura (MEV) foi realizada uma caracterização da morfologia e da composição dos meios microporosos. Ensaios experimentais do processo de microfiltração foram realizados com soro de leite, com o objetivo de estudar a influência de parâmetros fluidodinâmicos tais como: número de Reynolds e pressão transmembrana, além de analisar a retenção da bactéria, Escherichia coli, em regime de escoamento para Reynolds entre 2700 e 32000 e pressões transmembrana entre 1 e 4 bar. O permeado foi analisado seguindo normas da 20ª. Edição dos Métodos Padrões para Análise de Água e Esgoto, e todos os experimentos seguiram padrões de segurança para minimizar a possibilidade de contaminação do meio junto à análise do material filtrado. A manutenção fisiológica das bactérias foi controlada com os parâmetros de pH e temperatura, respectivamente mantidos entre 6 e 7,0 e de 25 - 30ºC ± 1 ºC. Nestas condições de escoamento, da solução e do meio filtrante, o processo foi considerado satisfatório com vazões transmembrana entre 10 L/(h.m2) e 120 L/(h.m2). / This work reports experimental results of the crossflow microfiltration of emulsion (whey of milk) applied in the microrganism retention of the coliform group. In the study of the separation process were used micro-porous tubes of -alumina (Al2O3) and commercial membranes of average size pores of 0,8 and 1,2m. The micro-porous tubes were sinterised with temperature between 1400 and 1450 ºC and after, were characterized by technique of porosimetry for mercury intrusion, verifing average size of pores between 0,3 and 0,5µm. After the sintering, the ceramic tubes were treated with a citrate of silver solution (bactericidal substance), and submitted to synthesis for removed the organic matters. The commercial membranes were also impregnated by this process. With the scanning eletronic microscopy made the characterization of the morfology and micro-porous structures composition. Experimental tests of the crossflow microfiltration process were performed with whey of milk, with objective to study the influence of fluid dynamics parameters (Reynolds number and flux transmembrane) and to analyse the bacteria retention in turbulent regime, having Re between 2700 and 32000, transmembrane pressure (enters 1 to 4bar) and transmembrane flux between 0,5 and 300 L/h.m2. The permeate was analysed by the 20ª. Edition of the Standard Methods for Examination of Water, and all the experiments followed standards of security to restrict the possibility of contamination of the permeated and the atmosphere. The physiology of the bacteria was controlled by parameters of pH and temperature, respectively keeped between 6 and 7,0 and of 25 - 30ºC ± 1 ºC. In the conditions of flow, of the solution and system flow, the retention was considerated satisfactory with transmembrane flux between 10 L/(h.m2) and 120L/(h.m2).

As cerâmicas porosas empregadas na substituição óssea, são utilizadas por apresentarem características como biocompatibilidade, ter estrutura tridimensional e apresentar alta porosidade. Nesse sentido, o objetivo desse trabalho foi obter e caracterizar cerâmicas porosas de Al2O3 e Al2O3 contendo 5% em volume de inclusões de ZrO2, produzidas pelo método da réplica. Essas cerâmicas porosas tiveram sua superfície tratada quimicamente com ácido fosfórico e foram recobertos, com fosfato de cálcio usando o método biomimético, em solução de SBF 5X (Simulated Body Fluid) por um período de incubação de 14 dias. Após o recobrimento, algumas cerâmicas porosas foram tratadas quimicamente para incorporação do Sr2+. Em seguida foram caracterizadas morfologicamente e estruturalmente usando ensaios de compressão axial, porosidade aparente, microscopia eletrônica de varredura (MEV), microtomografia de Raio X (µ-CT), difratometria de Raio X (DRX), Espectroscopia de Infravermelho Próximo (NIR), emissão óptica com plasma indutivamente acoplado (ICP-OES), Energia Dispersiva de Raio-X (EDS) e por Ensaios biológicos utilizando cultura de células para análise de viabilidade celular. As cerâmicas porosas de alumina e alumina-zircônia apresentaram, respectivamente, porosidade aparente de 80,93 % e 78,82 %, resistência à compressão axial, 2,93 MPa e 6,59 MPa, além de uma ampla faixa de tamanho de poros de, desejáveis para o favorecimento de interesses biológicos destinados à regeneração e formação de tecido ósseo. O recobrimento biomimético usando SBF 5X produziu a formação das fases α-TCP, β-TCP, TTCP e Hidroxiapatita, usando período de incubação de 14 dias. A incorporação de Sr2+ na estrutura dos fosfatos mostrou-se mais eficientes nos corpos porosos de alumina-zircônia. Os ensaios in vitro mostraram a biocompatibilidade das cerâmicas porosas estudadas, demonstrando a possibilidade de sua utilização como material para substituição ou preenchimento ósseo. / The porous ceramics used in bone substitution are used because they present characteristics as biocompatibility, have a three - dimensional structure and have high porosity. In this sense, the objective of this work was to obtain and characterize porous ceramics of Al2O3 and Al2O3 containing 5% by volume of ZrO2 inclusions, produced by the replica method. These porous ceramics were chemically treated with phosphoric acid and were coated with calcium phosphate using the biomimetic method in 5X SBF solution (Simulated Body Fluid) for a 14 day incubation period. After coating, some porous ceramics were chemically treated for Sr2+ incorporation. They were then characterized morphologically and structurally using axial compression, apparent porosity, scanning electron microscopy (SEM), microtomography (µ-CT), X-ray diffractometry (XRD), Near Infrared (NIR) Coupled (ICP-OES), X-ray Dispersive Energy (EDS) and Biological Assays using cell culture for cell viability analysis. The porous ceramics of alumina and alumina-zirconia showed, respectively, 80.93% and 78.82% apparent porosity, axial compression strength, 2.93 MPa and 6.59 MPa, as well as a wide range of pore size, desirable for the promotion of biological interests destined to the regeneration and formation of bone tissue. Biomimetic coated using SBF 5X produced the formation of α-TCP, β-TCP, TTCP and Hydroxyapatite phases using a 14-day incubation period. The incorporation of Sr2+ in the phosphate structure proved to be more efficient in porous alumina-zirconia bodies. The in vitro tests showed the biocompatibility of the porous ceramics studied, demonstrating the possibility of their use as material for bone replacement or filling.

No description available.

[pt] Sistemas Mo/Al2O3 e W/ZrO2 foram estudados a fim de evidenciar se a reação WO3+ZrO2 ocorre no estado sólido, e se a reação MoO3+Al2O3, também no estado sólido, ocorre com aluminas porosas. Para tanto, essas misturas foram preparadas utilizando-se dois teores de Mo e de W, respectivamente: 5 e 10 µmolMo/m2 de suporte alumina e 10 e 16 µmolW/m2 de suporte zircônia sendo tratadas a 773 K. Para o caso dos sistemas Mo/Al2O3, foram utilizadas três aluminas com diferentes propriedades, tais como: área específica, porosidade, grau de hidroxilação e distribuição de grupos OH superficiais. Para os sistemas W/ZrO2, verificou-se também o efeito de temperatura de tratamento mais elevada: 973 K. Todas as amostras obtidas foram caracterizadas pelas técnicas de: difração de raios-X, adsorção de N2, espectroscopia de absorção na região do infravermelho e de reflectância difusa no UV-visível. Considerando-se os sistemas Mo/Al2O3, verificou-se que o MoO3 reagiu com as três aluminas, apesar da maior dificuldade de difusão de massa devido à textura das aluminas porosas, formando estruturas de Mo diferentes do óxido original, sendo que a maior dispersão, sobre o suporte, das espécies de Mo geradas parece estar relacionada à presença de grupos hidroxila mais básicos. Para os sistemas W/ZrO2, os resultados também evidenciaram que foram geradas espécies de tungstênio diferentes do WO3 original, sendo que a utilização da maior temperatura de calcinação levou à formação de mais espécies de W dispersas sobre o suporte. / [en] Mo/Al2O3 and W/ZrO2 systems have been studied in order to verify if the WO3+ZrO2 reaction occurs in solid state, and if the MoO3+Al2O3 reaction also occurs with porous alumina in the solid state. These mixtures were prepared using two Mo and W loadings: 5 and 10 µmolMo/m2 of support alumina and 10 and 16 µmolW/m2 of support zirconia, and they were calcined at 773 K. For Mo/Al2O3 systems three aluminas with different properties, such: specific area, porosity, hydroxylation degree, and OH groups distribution were used. For W/ZrO2 systems the effect of a higher treatment temperature: 973 K was also evaluated. All samples were characterized by the following techniques: X- ray diffraction, N2 adsorption, infrared absorption spectroscopy, and UV-vis diffuse reflectance spectroscopy. For Mo/Al2O3 systems it has been verified that molibdenum oxide reacted with the aluminas even though the mass transfer difficulties related to the porosity, forming Mo structures distinct from MoO3, which higher Mo dispersion may be related to more basic hydroxyl groups. For W/ZrO2 systems, the results have also shown that W species different from WO3 were obtained, and higher calcination temperature promoted the formation of more dispersed species onto the support.

The thesis deals with the possibility of bonding the ceramic mixture by a sol-gel method, Colloidal alumina was used as the sol and the gelation was performed by changing the ionic strength or pH. The influence of different gelling agents (NaCl, NH4Cl, NH3, MgO a CO(NH)) on the gellation time and on the course of the gelation was compared. The aim of the work is the preparation of refractory monolith with the highest packing desity possible, which was solved by modeling the granulometric curve of the solid part of the ceramic mixture based on alumina. The thesis also describes the behavior of prepared gels during thermal processing of ceramics. Subsequently the resulting structure of prepared ceramic bodies was monitored.

Tato diplomová práce je zaměřená na výrobu Au-PANI-Au nanodrátů. Prezentovaná výroba nanodrátů je založená na elektrochemické depozici různých kovů a polymerizaci polyanilínu do porézních šablon z porézní anodické aluminy připravených anodizací hliníku. Teoretická část pojednává o základech elektrochémie a porézní anodické aluminy.

No description available.

Aluminas have had some form of chemical and industrial use throughout history. For little over a century corundum (α-Al2O3) has been the most widely used and known of the aluminas. The emerging metastable aluminas, including the γ, δ, η, θ, κ, β, and χ polymorphs, have been growing in importance. In particular, γ-Al2O3 has received wide attention, with established use as a catalyst and catalyst support, and growing application in wear abrasives, structural composites, and as part of burner systems in miniature power supplies. It is also growing in importance as part of the feedstock for aluminium production in order to affect both the adsorption of hydrogen fluoride and the feedstock solubility in the electrolytic solution. However, much ambiguity surrounds the precise structure of γ-Al2O3. Without proper knowledge of the structure, understanding the properties, dynamics and applications will always be less than optimal. The aim of this research was to contribute towards settling this ambiguity. This work was achieved through extensive computer simulations of the structure, based on interatomic potentials with refinements of promising structures using density functional theory (DFT), and a wide range of supporting experiments. In addition to providing a more realistic representation of the structure, this research has also served to advance knowledge of the evolution of the structure with changing temperature and make new insights regarding the location of hydrogen in γ-Al2O3. / Both the molecular modelling and Rietveld refinements of neutron diffraction data showed that the traditional cubic spinel-based structure models, based on m Fd3 space group symmetry, do not accurately describe the defect structure of γ-Al2O3. A more accurate description of the structure was provided using supercells of the cubic and tetragonal unit cells with a significant number of cations on c symmetry positions. These c symmetry based structures exhibited diffraction patterns that were characteristic of γ-Al2O3. The first three chapters of this Thesis provide a review of the literature. Chapter One provides a general introduction, describing the uses and importance of the aluminas and the problems associated with determining the structure of γ-Al2O3. Chapter Two details the research that has been conducted on the structure of vi γ-Al2O3 historically. Chapter Three describes the major principles behind the computational methods employed in this research. In Chapter Four, the specific experimental and computational techniques used to investigate the structure of γ-Al2O3 are described. All preparation conditions and parameters used are provided. Chapter Five describes the methodology employed in computational and experimental research. The examination of the ~ 1.47 billion spinel-based structural possibilities of γ-Al2O3, described using supercells, and the selection of ~ 122,000 candidates for computer simulation, is detailed. This chapter also contains a case study of the structure of κ-Al2O3, used to investigate the applicability of applying interatomic potentials to solving complex structures, where many possibilities are involved, and to develop a systematic procedure of computational investigation that could be applied to γ-Al2O3. Chapters Six to Nine present and discuss the results from the experimental studies. / Preliminary heating trials, performed to determine the appropriate preparation conditions for obtaining a highly crystalline boehmite precursor and an appropriate calcination procedure for the systematic study of γ-Al2O3, were presented in Chapter Six. Chapter Seven details the investigation of the structure from a singletemperature case. Several known structural models were investigated, including the possibility of a dual-phase model and the inclusion of hydrogen in the structure. It was demonstrated that an accurate structural model cannot be achieved for γ-Al2O3 if the cations are restricted to spinel positions. It was also found that electron diffraction patterns, typical for γ-Al2O3, could be indexed according to the I41/amd space group, which is a maximal subgroup of m Fd3 . Two models were presented which describe the structure more accurately; Cubic-16c, which describes cubic γ-Al2O3 and Tetragonal-8c, which describes tetragonal γ-Al2O3. The latter model was found to be a better description for the γ-Al2O3 samples studied. Chapter Eight describes the evolution of the structure with changing calcination temperature. Tetragonal γ-Al2O3 was found to be present between 450 and 750 °C. The structure showed a reduction in the tetragonal distortion with increasing temperature but at no stage was cubic γ-Al2O3 obtained. Examination of the progress of cation migration indicates the reduction in the tetragonal nature is due to ordering within inter-skeletal oxygen layers of the unit cell, left over from the breakdown of the hydroxide layers of boehmite when the transformation to γ-Al2O3 occurred. Above 750 °C, δ-Al2O3 was not observed, but a new phase was identified and designated γ.-Al2O3. / The structure of this phase was determined to be a triple cell of γ-Al2O3 and is herein described using the 2 4m P space group. Chapter Nine investigates the presence of hydrogen in the structure of γ-Al2O3. It was concluded that γ-Al2O3 derived from highly crystalline boehmite has a relatively well ordered bulk crystalline structure which contains no interstitial hydrogen and that hydrogen-containing species are located at the surface and within amorphous regions, which are located in the vicinity of pores. Expectedly, the specific surface area was found to decrease with increasing calcination temperature. This trend occurred concurrently with an increase in the mean pore and crystallite size and a reduction in the amount of hydrogen-containing species within the structure. It was also demonstrated that γ-Al2O3 derived from highly crystalline boehmite has a significantly higher surface area than expected, attributed to the presence of nano-pores and closed porosity. The results from the computational study are presented and discussed in Chapter Ten. Optimisation of the spinel-based structural models showed that structures with some non-spinel site occupancy were more energetically favourable. However, none of the structural models exhibited a configuration close to those determined from the experimental studies. Nor did any of the theoretical structures yield a diffraction pattern that was characteristic of γ-Al2O3. This discrepancy between the simulated and real structures means that the spinel-based starting structure models are not close enough to the true structure of γ-Al2O3 to facilitate the derivation of its representative configuration. / Large numbers of structures demonstrate migration of cations to c symmetry positions, providing strong evidence that c symmetry positions are inherent in the structure. This supports the Cubic-16c and Tetragonal-8c structure models presented in Chapter Seven and suggests that these models are universal for crystalline γ-Al2O3. Optimisation of c symmetry based structures, with starting configurations based on the experimental findings, resulted in simulated diffraction patterns that were characteristic of γ-Al2O3.

This thesis describes applications of advanced multinuclear solid-state nuclear magnetic resonance (NMR) experiments to the characterisation of industrially-relevant catalyst materials. Experiments on γ-Al₂O₃ introduce the use of solid-state NMR spectroscopy for the investigation of disordered solids. The existence of Al(V) sites on the surface of this material is demonstrated, showing that removal of adsorbed H₂O may facilitate a rearrangement effect in γ-Al₂O₃ that promotes the formation of these Al environments. A range of aluminium oxide-based supported metal catalysts has been investigated. Studies of these systems by ¹H and ²⁷Al solid-state NMR spectroscopy indicate that a metal-support interaction (MSI) exists between surface cobalt oxide crystallites and the γ-Al₂O₃ support, and is strongest for materials containing small, well dispersed Co oxide crystallites. It is shown that the hygroscopic nature of γ-Al₂O₃ allows the extent of the MSI to be visualised by ¹H MAS NMR, by observing the extent of the proton-metal oxide interaction resulting from the presence of adventitious adsorbed H₂O. The surface/bulk chemistry of Co spinel aluminate materials is also investigated. ¹H, ²⁹Si, ²⁷Al and ¹⁷O solid-state NMR techniques are used to gain insight into the structural nature of silicated alumina catalysts. The combination of isotopic enrichment and dynamic nuclear polarisation (DNP) surface-enhanced NMR spectroscopy can provide a definitive and fully quantitative description of the surface structure of Si-γ-Al₂O₃ (1.5 wt% Si), and the role of adventitious surface water is highlighted. Analysis of silicated aluminas prepared by “sequential grafting” and “single shot” approaches shows that silica growth on γ-Al₂O₃ follows two distinct morphologies. ¹⁷O gas exchange enrichment is also shown to be successful in facilitating ¹⁷O solid-state NMR studies of these materials. It is demonstrated that double (²⁹Si and ¹⁷O) enrichment of Si-γ-Al₂O₃ (1.5 wt% Si) can facilitate access to ²⁹Si-¹⁷O 2D correlation experiments, even at low silica loading. An exploratory investigation of Ti-alumina model catalysts has also been carried out using ¹H, ²⁷Al and ¹⁷O solid-state NMR spectroscopy. These studies indicate that Ti-γ-Al₂O₃ and Ti-Al M50 may be structurally distinct materials.

Made available in DSpace on 2014-07-29T15:07:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-26 / In this work we investigated the encapsulation of magnetite nanoparticles into the nanopores of anodic alumina membranes using atomic force microscopy (AFM), vibrating sample magnetometer (VSM) and electron magnetic resonance (EMR). Three biocompatible magnetic fluids, with different nanoparticle diameters, stably dispersed in water at physiological conditions, were used. The nanoparticles were obtained through the coprecipitation method and characterized by X-ray diffraction, from which we obtained the nanoparticle size and confirmed the crystal structure. The Scherrer´s relation revealed a nanoparticle diameter of 10.1nm, 12.3nm and 13.8nm. The alumina membrane were prepared through anodization process. The nanopores were arranged on a hexagonal lattice with an alumina thickness of 4 μm, a distance between pores (center to center) of 105 nm, and samples containing nanopores with diameter of 35 nm or 80 nm. The method of encapsulation of nanoparticles consisted of depositing a drop of magnetic fluid into the surface of alumina. The fluid enters the nanopores through capillarity carrying the nanoparticles into it. AFM images prove that we had success in encapsulating nanoparticles only for the alumina samples with nanopores with a size of 80 nm. Magnetization data of the alumina sample containing nanoparticles with a diameter of 13.8nm encapsulated into nanopores of 80 nm, revealed an increase, with respect to the first procedure of encapsulation, of 48 % of the nanoparticles internalized into the nanopore after the second process of encapsulation. Further, different from all the samples investigated, EMR data for the alumina containing nanopores of 80 nm and nanoparticles of 13.8 nm, after the first procedure of encapsulation, had shown perpendicular magnetization with respect to the alumina surface. The EMR spetra were curve fitted using two Gaussian lines, one representing the nanoparticles with magnetization parallel to the surface and the other perpendicular. AFM images suggest, in our sample, that residues on the alumina surface are responsible for the parallel component. The magnetic resonance field data, for the perpendicular contribution, were analyzed taking into account in the energy density terms with uniaxial and cubic symmetry. The uniaxial energy contribution had a term due to magnetic dipolar interaction, between nanoparticles forming a linear chain, a magnetostatic term, due to the nanostructures self-organization, and also a magnetoelastic contribution, which came from the stress generated by the packing of nanoparticles, whose origin were related to the dipolar interaction between nanoparticles forming the linear chain. Indeed, the theoretical analysis allowed us to conclude that the mean size of the chain could vary from 4 to 9.5 nanoparticles. Finally, after heating the alumina, at 300°C for one hour, which contained nanoparticles with a size of 10.1 nm, and dissolving it in NaOH aqueous solution, AFM data were obtained. The AFM images confirmed the existence of nanowires. The diameter distribution, obtained from the AFM images, were curve fitted with a lognormal distribution revealing a modal diameter for the nanowires of 25,8 0, ± 4nm and diameter dispersity of 0,30 ± 0,02nm . / Neste trabalho investigamos o encapsulamento de nanopartículas de magnetita (Fe3O4) em nanoporos de alumina anódica utilizando as técnicas de Microscopia de Força Atômica (AFM), Magnetometria de Amostra Vibrante (VSM) e Ressonância Magnética Eletrônica (RME). Utilizamos três fluidos magnéticos com nanopartículas de diâmetros diferentes dispersas em solução fisiológica. As nanopartículas foram sintetizadas pelo método da coprecipitação e foram caracterizadas por difração de raios-x, de onde confirmamos sua estrutura cristalina e obtivemos o diâmetro. A relação de Scherrer forneceu os seguintes diâmetros: DRX=10,1nm, DRX=12,3nm e DRX=13,8nm. As membranas de alumina foram preparadas pelo método da anodização de um filme de alumínio puro, gerando nanoporos em um arranjo hexagonal, sendo a espessura da alumina de 4μm com distância entre poros centro a centro de 105nm e amostras contendo diâmetros de nanoporos de 35nm ou 80nm. O método de encapsulamento das nanopartículas consistiu em depositar uma gota do fluido magnético sobre a alumina, que penetra nos nanoporos por capilaridade, carreando as nanopartículas. Imagens de AFM mostraram que obtivemos sucesso no encapsulamento das nanopartículas em alumina somente nas amostras com nanoporos de 80nm. Uma comparação entre as curvas de magnetização da amostra com nanopartículas de DRX=13,8nm em nanoporos de 80nm, encapsuladas uma vez e duas vezes, mostrou um acréscimo de 48% no número de nanopartículas encapsuladas do primeiro para o segundo processo de encapsulamento. Além disso, diferentemente de todas as outras amostras estudadas, os dados de RME para alumina com nanoporos de 80 nm e nanopartículas com diâmetro de 13,8 nm, após o primeiro processo de encapsulamento, apresentaram magnetização perpendicular ao plano da membrana de alumina. O espectro de RME foi ajustado por duas gaussianas, uma representando uma componente com magnetização paralela e outra perpendicular. Imagens de AFM sugerem, na nossa amostra, que resíduos na superfície são responsáveis pela componente paralela. A análise dos dados do campo de ressonância para a componente perpendicular foram ajustados considerando termos de simetria uniaxial e cúbica para a densidade de energia. Na contribução uniaxial foi explicitado o termo devido à interação dipolar magnética, entre nanopartículas formando uma cadeia linear, o termo magnetostático, devido à autoorganização das nanoestruturas, e um magnetoelástico, proveniente do stress gerado pelo empacotamento das nanopartículas, cuja origem foi atribuída à interação dipolar entre as nanoestruturas formando a cadeia. A análise teórica permitiu, ainda, concluir que o tamanho médio das cadeias lineares formadas no interior dos nanoporos corresponde a 6,0 nanopartículas, podendo variar entre 4 e 11. Essas cadeias podem existir não somente em nanoporos diferentes, mas também no interior de um mesmo nanoporo. Por fim, após aquecermos a membrana de alumina, a 300°C por 1 hora, que continha nanopartículas com DRX=10,1nm e a dissolvermos em uma solução aquosa de NaOH, obtivemos imagens de AFM dos nanofios. Uma distribuição de tamanho construída a partir das imagens e ajustada por uma lognormal nos forneceu um diâmetro modal para os nanofios de 25,8 0, ± 4nm e uma dispersidade de 0,30 ± 0,02nm.