Multifunctional superparamagnetic iron oxide nanoparticles (SPIONs) coated with silica are a promising research field for lots of biomedical applications. The scope of this work is a preparation of SPIONs and coating them with silica to form core-shell structured nanoparticles for nanomedicine applications. SPIONs were synthesized by two chemical methods – co-precipitation and thermal decomposition of organic iron precursor. Prepared nanoparticles were carefully characterized –average size, size distribution, morphology, crystallinity, colloidal stability and magnetic properties were studied. After comparing SPIONs synthetized by two routes the most suitable method for biomedical applicable nanoparticles preparation is determined. The nanomedicine requires nanoparticles of the highest quality. The next step was coating SPIONs with silica shell. For this purpose inverse microemulsion method was chosen. TEOS was used as a silica precursor. Mean size, size distribution, magnetic properties, structure of silica shell were studied.

Advanced High Strength Steel (AHSS) has become a popular steel grade among automakers to produce vehicle bodies. With improvements in strength and elongation, AHSS has evolved to its 2nd generation, including high manganese steel. Even though it has outstanding strength, the 2nd generation of AHSS faces some production problems due to its high alloying elements. With continual improvement, the 3rd generation of AHSS is currently in production. In this generation, the steel types still have a competitive strength and elongation like the 2nd generation of AHSS while having lower alloying element contents and production costs. One of the types of 3rd generation AHSS is medium manganese steel. Research related to the 2nd and 3rd generation of AHSS mainly focuses on their mechanical properties and microstructures. As there is a strong correlation between mechanical properties and inclusion characteristics, further investigation of the evolution of inclusions is still required. In this study, high-temperature experiments were conducted to investigate the effects of metal chemistry on the inclusion evolution in liquid steel. The concentrations of manganese, aluminum, and nitrogen were varied systematically. Two and three-dimensional analysis techniques were applied to study the number, composition, and size distribution of inclusions. Electrolysis extraction was used to identify the oxide, sulfide, and nitride inclusions, whereas an automated SEM with an ASPEX feature was used to detect a larger number of inclusions for better representation of the steel matrix. This work has established inclusion classification rules to distinguish nitride inclusions from oxide inclusions. To the best of the authors’ knowledge, this is the first discussion of this type of inclusion classification in the open literature. Based on the automated SEM (ASPEX Feature) analysis, the type of detected inclusions in medium and high manganese steels were Al2O3(pure), Al2O3-MnS, AlN(pure), AlN-MnS, AlON, AlON-MnS, and MnS inclusions. As the manganese content in the steel increased from 2% to 20%, the total amount of inclusions, especially AlN-contained inclusions, was raised. This phenomenon occurred due to the increase in nitrogen solubility with increased manganese content in the steel. The thermodynamic calculation also predicted that AlN inclusions would form when the steel was cooled or during the solidification. Moreover, AlN and MnS inclusions were observed to co-precipitate together. Similar to manganese, the increase in the aluminum content (Al = 0.5-6%) increased the total amount of inclusions in the steel, and the dominant inclusion type is AlN. AlN and Al2O3 inclusions can be heterogenous nucleation sites for MnS inclusions. Furthermore, Al2O3 inclusions also became heterogeneous nucleation sites for AlN inclusions. The experimental set-up was further modified to investigate the effect of nitrogen on the formation of inclusions in the medium manganese steels. The nitrogen was introduced by purging or injecting N2 gas into the steel system. Similar to the effect of manganese and aluminum, the increase in the nitrogen content also increased the total amount of inclusions. Once the nitrogen content in the steel exceeded the critical limit for the formation of AlN inclusions, AlN inclusions can be stable in the liquid steel. Moreover, regardless of the nitrogen content in the steel, AlN-MnS inclusions were formed in the slow-cooled steels. In terms of morphology, AlN inclusions can be formed of plate-like, needle, angular, agglomerate, or irregular shapes. Furthermore, a brief investigation on the addition of calcium and nitrogen to the medium manganese steels found that calcium led to the formation of other complex inclusions, such as CAx and CAS-Other inclusions. In the medium manganese steel composition in the present study, the number of CAS-Other inclusions was dominated by (Ca,Mn)S-Oxide inclusions after the addition of Ca. However, with time and after introducing N2 gas into the steel, the number of (Ca,Mn)S-Nitride inclusions also increased. The formation of (Ca,Mn)S-Nitride inclusions resulted from the co-precipitation of CaS, MnS, and AlN. The current work provides a better understanding of the formation mechanism of inclusions in medium manganese steels and high manganese steels. It presents complete information on the characteristics of inclusions, such as the number density, type, and morphology of inclusions. This knowledge can help steelmakers improve the steelmaking process to control the formation of inclusions, which can be problematic for the manufacture and performance of medium manganese steels and high manganese steels. / Dissertation / Doctor of Philosophy (PhD)

[pt] As nanopartículas magnéticas (NPMs) apresentam grande potencial em diversas aplicações tecnológicas e vem ganhando destaque na área da biomedicina devido suas propriedades superparamagnéticas. Para este trabalho foram sintetizadas nanopartículas de óxido de ferro (Fe3O4) pelo método de coprecipitação e recobertas com Pluronic F-127 (PL F-127), o qual se demonstrou, a partir de estudos anteriores, um surfactante com ótima estabilidade coloidal e alto grau de biocompatibilidade, sendo tais características relevantes para as aplicações na área da biomedicina. O método de produção se mostrou eficiente para produção de uma grande quantidade de amostra e baixo grau de oxidação, o que mantém a integridade dos resultados e do material para diversas análises no decorrer de longos períodos. A espectroscopia Raman e a difração de elétrons apontam para a composição majoritária de magnetita cristalina das amostras. As imagens obtidas através de microscopia de transmissão (MET) mostraram que o diâmetro médio das NPMs não é afetado pela concentração PL F-127 e está de acordo com os tamanhos obtidos pelas técnicas magnéticas. O MET também mostrou partículas monodispersas com formato esféricas. As técnicas de microscopia magnética de varredura (MMV), magnetômetro de amostra vibrante e de efeito Hall revelaram que o comportamento das NPMs é superparamagnético em temperatura ambiente e que a funcionalização não interferiu significativamente na magnetização de saturação. / [en] Magnetic nanoparticles (MNPs) have great potential in several technological applications and are gaining prominence in the biomedical area due to their superparamagnetic properties. For this work, iron oxide (Fe3O4) nanoparticles were synthesized by the coprecipitation method and coated with Pluronic F-127 (PL F127), which was demonstrated, from previus studies, a surfactante with excellent coloidal stability and high degree of biocompatibility, such characteristics being relevant for applications in the área of biomedicine. The production method proved to be efficient for producing a large amount of sample and a low degree of oxidation, which maintains the integrity of the results and material for several analyzes over long periods. Raman spectroscopy and eléctron diffraction indicate the samples are pure and crystalline magnetite. The images obtained through transmission eléctron microscopy (TEM) showed that the mean diameter of MNPs is not affected by the PL F-127 concentration and is in agreement with the sizes obtained by magnetic techniques. TEM also showed monodisperse particles with a spherical shape. Scanning magnetic microscopy (MMV), vibrating sample magnetometer and Hall effect techniques revealed that the behavior of NPMs is superparamagnetic at ambient temperature and that the functionalization did not significantly interfere in the saturation magnetization.

O desenvolvimento de materiais nanoestruturados tem se destacado devido a necessidade de miniaturização de dispositivos e a procura por novos efeitos físicos e químicos capazes de gerar novas tecnologias. Um importante composto com aplicações principalmente em óptica é o YAG (Y3Al5O12) presente no sistema cerâmico alumina-ítria (\'AL IND.2\'O IND.3\'-\'Y IND.2\'O IND.3\'). O YAG apresenta estrutura cristalina cúbica, expansão térmica isotrópica e não apresenta efeitos de birrefringência, o que possibilita a produção de cerâmica transparente para uso como material hospedeiro de íons terras-raras para o desenvolvimento de lasers de estado sólido. O ponto de partida em processamento cerâmico começa com o conhecimento das características físico-químicas do pó do composto. Em nosso trabalho, o objetivo foi o desenvolvimento de uma metodologia para a obtenção de nanopós de YAG de tamanhos médios diferenciados. Para isso foram realizados distintos processos químicos de síntese, e também, foram utilizados diferentes processos de separação, como a centrifugação e a sedimentação. Na produção das nanopartículas foram utilizados três métodos de síntese: Método de Pechini, Rota Glicerol e Método de Coprecipitação. No método de Pechini avaliou-se o efeito de diferentes valores de pH (1, 4, 7, 9 e 11) e procurou-se correlacionar com os tamanhos médios das nanopartículas. Após a obtenção do pó precursor foram realizadas medidas de decomposição térmica (DSC e TG), observando as principais transformações físico-químicas do material decorrentes dos diferentes métodos de síntese. A formação da fase cristalina do YAG foi determinada por difração de raios X e uma análise estrutural foi efetuada por espectroscopia de infravermelho. Medidas de área superficial específica (BET) foram usadas para avaliar o tamanho médio das partículas. Nanopós de YAG com diferentes intervalos de tamanhos foram produzidos, e o rendimento para cada intervalo de tamanho definido. / Nanostructured materials has emerged because the intense interest for miniaturization of devices and crescent demand for new physical and chemical effects that can generate new technologies. An important compound with applications mainly in optics is the YAG (Y3Al5O12). It\'s present in the alumina-yttria ceramic system (\'AL IND.2\'O IND.3\'-\'Y IND.2\'O IND.3\'). The YAG has a cubic crystaline structure, isotropic thermal expansion and it has no birefringence effects, which allows the production of transparent ceramics to use as host of solid-state lasers. The starting point in ceramic processing begins with the knowledge of the characteristics and physical and chemical properties of the powder. In our work, the goal was the development of a methodology for obtaining YAG nanopowders of different average sizes. To do this we performed distinct chemical synthesis, and we also used different separation processes such as centrifugation and sedimentation. For production of nanoparticles we used three synthesis methods: Pechini, glycerol route and coprecipitation. In the Pechini method we evaluated the effect of different pH values (1, 4, 7, 9 and 11) and tried to correlate with the average sizes of nanoparticles. After obtain the precursor powders we studied the decomposition thermal (DSC and TG) process, arising from the different synthesis methods. The crystalline phase of YAG was determined by x-ray diffraction and the structural analysis was carried out by infrared spectroscopy. Specific surface area measurements (BET) were used to evaluate the average particle size.YAG nanopowders with different average sizes were produced.

Les piles à combustibles à électrolyte solide de type SOFC permettent de transformer directement l’énergie de la réaction chimique de formation de l’eau à partir de l’hydrogène et de l’oxygène, en énergie électrique. De nos jours, les apatites de type silicates de terres rares présentent beaucoup d’intérêt comme électrolyte solide en raison de leurs propriétés de transport élevées avec une forte conductivité ionique et une faible énergie d'activation. Ils peuvent fonctionner de manière stable à une température intermédiaire sur une large plage de pression partielle d'oxygène en maintenant d'excellentes performances. Ils sont ainsi considérés comme de bons candidats pour les électrolytes de piles de type IT-SOFC. Parmi cette série de conducteurs, le type La-Si-O possède une conductivité plus élevée et leur performance serait modifiée par différents éléments dopants.L'objectif de cette thèse est d'étudier les effets des éléments de substitution / dopage ainsi que les méthodes de synthèse sur les propriétés structurales ainsi que sur la conductivité des apatites de type silicates de lanthane. Dans cette étude, nous utilisons une double approche: une approche de simulation et une approche expérimentale pour optimiser la pureté et les performances des matériaux d'électrolyte.Dans l'approche de simulation, le calcul basé sur la DFT (Théorie de la fonctionnelle de la densité) a été réalisée en vue d’étudier l'effet des positions de dopage: dopant Sr à La position de La et dopant Ge à la position de Si. Les résultats obtenus par le calcul concernant la conductivité ionique confirment ceux obtenus par l’expérience.Avec l’approche expérimentale, nous présentons la synthèse et la caractérisation de La10Si6O27 (LSO) dopé par Sr et élaboré par des procédés sol-gel. Les résultats montrent que la conductivité ionique est activé thermiquement et que les valeurs se situent entre 4,5 × 10-2 et 1 x 10-6 S·cm-1 à 873 K et dépend des conditions d’élaboration et de la composition de la poudre. / The Solid Oxide Fuel Cell (SOFC) defined by its ceramic and oxide electrolyte, is an electrochemical energy conversion device that produces electricity directly from the chemical reaction of fuel. Nowadays, apatite type rare earths silicates and germaniums attract many interests as the solid electrolyte due to the superior transport properties with high ionic conductivity and low activation energy. They can operate stably at intermediate temperature over a wide oxygen partial pressure range and maintain excellent performances, being considered as a candidate for IT-SOFC electrolytes. Among this series of conductors, the La-Si-O type has a higher conductivity and the performance would be modified by different doping elements.The objective of this thesis is to study the effects of element substitution/doping and synthesis methods on the structural and conductivity properties of apatite type lanthanum silicates. In this study, we use a double approach: a simulation approach and an experimental approach to optimize the electrolyte materials purity and performance.Using simulation approach, a first principle calculation based on DFT (Density Functional Theory) was carried out to investigate the effect on doping positions: Sr dopant at La position and Ge dopant at Si position. The calculation results give a connection to the ionic conductivity obtained by experiments.With experimental approach, we present the synthesis and characterization of Sr-doped La10Si6O27 (LSO) prepared through an optimized water-based sol-gel process. The results show that the ionic conductivity is thermally activated and values lies between 4.5×10-2 and 1×10-6 Scm-1 at 873 K as a function of the composition and powder preparation conditions.

Cyclodextrins (CD) are cyclic oligosaccharides composed of six to more than sixty glucose units. Large-ring cyclodextrins (LR-CD) are novel CD comprised of more than eight glucose units with cavity structures and sizes different from that of commercially available CD₆ – CD₈. LR-CD may offer unique molecular recognition properties and can be produced biocatalytically from starch using cyclodextrin glucanotransferase (CGTase, E.C. 2.4.1.19) in a short reaction time. LR-CD were isolated from glucose, CD₆ – CD₈ and other compounds by complexation of CD₆ – CD₈ as well as precipitation techniques. The yield of LR-CD (degree of polymerization from 9 to 21) was optimized using central composite design. Addition of polar organic solvents to the synthesis resulted in higher yields of LR-CD. LR-CD composed of 9 to 21 glucose units were successfully separated using reversed-phase of ODS-AQ chromatography and normal-phase of polyamine II chromatography. Maintaining optimized reaction conditions aided in a high yield of CD₉; it could be separated with reasonable yield using a single step of polyamine II chromatography. A co-grinding method helped to obtain higher solubilization levels of glibenclamide, vitamin A acetate and vitamin D₃ in CD₁₃, CD₁₀ and CD₁₁, respectively when compared to other CD. Vitamin K₁ was solubilized in distilled water with CD₆ – CD₁₃ using a co-precipitation method. When compared with other CD, CD₉ was seen to be the best solubilizer. The analysis of complexes using ESI MS showed spironolactone and glibenclamide complexed with CD₉ and CD₁₃, respectively.

Abstract Yellow head virus (YHV) has caused mass mortalities in Penaeus monodon shrimp farmed throughout Southeast Asia since it was first discovered in the early 1990’s. YHV possesses a positive-sense, single-stranded RNA genome and a rod-shaped enveloped virion. Together with the closely related gill-associated virus (GAV) identified in P. monodon shrimp in Australia, it is classified in the genus Okavirus, family Roniviridae within the order Nidovirales. YHV particles contain only three structural proteins, a nucleocapsid (N) protein (p20) protein and two envelope glycoproteins gp116 and gp64. In this study, the glycosylation status of gp116 and gp64 extracted from YHV virions was characterized in detail, including the identification of active N-linked glycosylation sites and the nature of the attached carbohydrates. This was achieved by optimizing and applying a combination of methods that included SDS-PAGE followed by carbohydrate-specific staining of gels or probing of membrane-bound proteins using lectins with different carbohydrate specificities, enzymatic removal of N-linked carbohydrates and a variety of mass spectrometry techniques. In these analyses, it was found that N-linked glycans are the major contributor to the higher estimated mass of gp116 and gp64 by SDS-PAGE compared to those estimated from their deduced amino acid sequences. Neither gp116 nor gp64 were found to posses O-linked glycans. Mannose residues were identified to be the major glycan component of carbohydrates linked to gp116 and gp64 and are possibly the sole component of carbohydrate linked to gp64. Unlike gp64, other glycans such as terminal N-acetyl--D-galactosamine and N-acetyl--D-glucosamine were identified to be attached to gp116. Assuming that glycosylation processes in shrimp mimic those of vertebrates that are known in more detail, the nature of the glycans attached to gp116 suggests that they might be added and modified during the transportation of the protein from the endoplasmic reticulum (ER) to the trans-Golgi network (TGN). Mass spectrometry analyses of tryptic peptides derived from the native glycoproteins and following their enzymatic deglycosylation, generated approximately 81% (gp116) and 66% (gp64) coverage of their predicted amino acid sequences. Detailed mass spectrometry analyses of peptides derived from the deglycosylated proteins identified that most of the potential N-linked glycosylated site in the virion envelope glycoproteins, 6 of 7 present in gp116 and 3 of 4 present in gp64 were identified to be modified by glycans. In gp116, one site was not identified and in gp64 one site was not utilized. As phosphorylation has been shown to affect nucleocapsid protein (N) functioning in vertebrate nidoviruses, SDS-PAGE using two phosphoprotein-specific staining methods, as well as mass spectrometry methods, were employed to examine whether the YHV N protein present in virions is phosphorylated. The protein staining methods provided contradicting results and no phosphate-containing peptides were identified by mass spectrometry. The apparent absence of phosphate in the N protein was also supported by its isoelectric point (pI ~10) determined by isoelectric focusing and two-dimensional electrophoresis (2-DE) analysis, which was very similar to that predicted (pI = 9.98) from its deduced amino acid sequence. Taken together, the data suggest that the YHV N protein encapsulated within virions is not phosphorylated. The RNA-binding capability of the GAV N protein was assessed using an electrophoretic mobility shift assay (EMSA) technique. Full-length and variously truncated forms of the GAV N protein expressed in bacteria were assessed in the assays. It was found that the full-length recombinant N protein bound to RNA in a sequence non-specific manner. Analysis of the five truncated N protein constructs localized the RNA-binding domain to a 50 amino acid sequence in the N-terminal region residing between Met11 and Arg60. A motif rich in proline and arginine residues, which are commonly found in other RNA-binding proteins, occurred in first 18 amino acids of this region. Although RNA-binding was not sequence-specific, the data suggest that this region of the GAV N protein is the most likely site at which it interacts with and nucleates viral genomic RNA during nucleocapsid formation. A synthetic peptide spanning the 18 amino acid of the putative RNA-binding domain was shown to possess RNA-binding properties similar to the recombinant protein fragment. These results indicated that the 18 amino acid, proline and arginine rich motif (MPVRRPLPPQPPRNARLI) in the N-terminal region of the GAV N protein confers its RNA-binding function. Using an immuno-co-precipitation assay, a host protein was found to interact abundantly with the GAV N protein in infected lymphoid organ cells. Mass spectrometry analysis identified the protein as -actin. Immuno-histochemistical double-labeling methods in conjunction with observations made using confocal and electron microscopy revealed that actin and the N protein were co-located in cytoplasm of infected cells. Electron microscopy suggested that interaction of the two proteins occurs before nucleocapsid envelopment within virions, suggesting that -actin might be involved in transporting the N protein or the nucleocapsid from their sites of synthesis to the rough endoplasmic reticulum where the virion acquires its envelopes. In summary, the research described in this thesis has advanced understanding of the YHV/GAV proteome through the identification of the glycosylation sites in the envelope glycoproteins gp116 and gp64, and demonstrating that nucleocapsid protein encapsulated within virion is unlikely to be phosphorylated. Functional studies have also shown that the nucleocapsid protein binds RNA non-specifically through an 18 amino acid domain near its N-terminus and that it binds and co-localizes with -actin in infected cells, suggesting that -actin may play role in trafficking N protein in infected cells.

Depuis quelques décennies, les nanomatériaux et tout particulièrement les nanoparticules d’oxyde de fer (magnétite/maghémite) superparamagnétiques ont connus un intérêt croissant en nano-médecine. Leur biocompatibilité et leurs propriétés magnétiques permettent notamment leur utilisation à des fins de diagnostic (IRM, Imagerie optique et nucléaire…) et de thérapie (Hyperthermie, nano vectorisation…). Au cours de cette thèse, la première étape a consisté à étudier en détails l’influence de plusieurs paramètres de synthèse sur les propriétés finales des nanoparticules d’oxyde de fer magnétique. Cette étude avait pour but de développer et d’optimiser une méthode de synthèse dérivée de la méthode de synthèse classique dite de co-précipitation mais modifiée par ajout de ligand citrates au cours de la synthèse. Des nanoparticules d’oxyde de fer d’une taille pouvant être contrôlée entre 4 et 13 nm recouvertes par une couronne de ligands citrates ont ainsi été synthétisées, celles-ci présentent une aimantation à saturation atteignant jusqu’à 75 emu/g d’oxyde de fer qui est une valeur particulièrement haute pour des nanoparticules de cette taille. Tout au long de ce travail, la caractérisation de ces nanoparticules par un panel étendu de techniques (MET, DRX, Mössbauer, IRTF, XPS, mesures magnétiques, DLS …) à permis notamment d’étudier de façon précise les relations existantes entre la taille, le taux de ligand, la composition et les propriétés magnétiques des nanoparticules synthétisées. Ces nanoparticules fonctionnalisées par des citrates ont ensuite été testées en milieu biologique afin d’évaluer leur internalisation dans les cellules et leur cytotoxicité. Dans un deuxième temps, d’autres travaux ont été menés sur les nanoparticules d’oxyde de fer. Notamment le remplacement des ligands citrates par un polymère bio-inspiré pouvant, selon les fonctions chimiques qui lui sont adjointes, avoir de multiples applications dans le domaine biomédical / From decades now, nanomaterials and especially superparamagnetic iron oxide nanoparticles are studied for their numerous applications in nanomedecine area. The biocompatibility and the magnetic properties of such nano-objects allow their utilization for diagnostic (MRI, optical imagery, PET…) and for therapy application (nanovectorization, hyperthermia…) During this thesis work, the first step was to study the influence of several synthesis parameters on the final properties of the magnetic iron oxide nanoparticles. The aim of this study was the development and the optimization of the widely used way of synthesis by co-precipitation modified by a ligand addition during the growth step of the synthesis. Citrate capped iron oxide nanoparticles with a controlled size between 4 and 13 nm have been synthesized, the saturation magnetization of these nanoparticles reach 75 emu/g of iron oxide, this value is particularly high for nanoparticles of such sizes. During this work, the large panel of characterizations performed on these nanoparticles (TEM, XRD, Mössbauer, FTIR, XPS, DLS, Magnetic measurement) allowed to study precisely the relations between size, ligand ratio, composition and magnetic properties of the synthesized nanoparticles. The interaction between the synthesized citrate capped nanoparticles and biological materials such as human cells have been investigated in-vitro notably to evaluate cells internalization and citotoxicity. In a second step, some additional works have been performed on the citrate capped iron oxide nanoparticles in order to replace the citrate ligand by a bio-inspired polymer (poly-oxazoline). This polymer can have multiple biomedical applications depending of the pendent chemical groups that have been fixed on it

Made available in DSpace on 2015-03-03T15:02:47Z (GMT). No. of bitstreams: 1 AndarairGS_TESE.pdf: 4507597 bytes, checksum: 16de9c7e1586bd26c89356d656acea26 (MD5) Previous issue date: 2010-07-02 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / This thesis focuses on the coprecipitation synthesis method for preparation of ceramic materials with perovskite structure, their characterization and application as catalytic material in the reaction of converting CO to CO2 developing a methodological alternative route of synthesis from the middle via oxalate coprecipitation material SrCo0,8Fe0,2O3-d. In order to check the influence of this method, it was also synthesized using a combined citrate - EDTA complexing method. The material was characterized by: X-ray diffraction (XRD), Rietveld refinement method, thermogravimetry and differential thermo analysis (TG / DTA), scanning (SEM) and transmission (TEM) electron microscopy, particle size distribution and surface analysis method BET. Both methods led to post-phase synthesis, with pH as a relevant parameter. The synthesis based on the method via oxalate coprecipitation among particles led to the crystalline phase as those obtained using a combined citrate - EDTA complexing method under the same conditions of heat treatment. The nature of the reagent used via oxalate coprecipitation method produced a material with approximately 80 % lower than the average size of crystallites. Moreover, the via oxalate coprecipitation method precursors obtained in the solid state at low temperature (~ 26 oC), shorter synthesis, greater thermal stability and a higher yield of around 90-95 %, maintaining the same order of magnitude the crystallite size that the combined citrate - EDTA complexing method. For purposes of comparing the catalytic properties of the material was also synthesized by the using a combined citrate - EDTA complexing method. The evaluation of catalytic materials SrCo0,8Fe0,2O3-d LaNi0,3Co0,7O3-d was accompanied on the oxidation of CO to CO2 using a stainless steel tubular reactor in the temperature range of 75-300 oC. The conversion CO gas was evaluated in both materials on the results shaved that the firm conversion was loves for the material LaNi0,3Co0,7O3-d / Esta tese enfoca o m?todo de s?ntese de coprecipita??o para prepara??o de materiais cer?micos com estrutura perovsquita, suas caracteriza??es e aplica??o como material catal?tico na rea??o de convers?o de CO a CO2 desenvolvendo uma rota metodol?gica alternativa de s?ntese a partir da coprecipita??o via meio oxalato do material SrCo0,8Fe0,2O3-d. No intuito de verificar a influ?ncia desse m?todo o mesmo foi sintetizado tamb?m com base no m?todo de complexa??o combinando EDTA - Citrato. O material foi caracterizado por: difratometria de raios-X (DRX), refinamento pelo m?todo Rietveld, termogravimetria e termodiferencial (TG/DTA), Microscopia Eletr?nica de Varredura (MEV) e de transmiss?o (MET), distribui??o granulom?trica e analise superficial pelo m?todo BET. Ambos os m?todos de s?ntese permitiram obter p?s monof?sicos, tendo o pH como um par?metro relevante. A s?ntese com base no m?todo via coprecipita??o em meio oxalato permitiu obter tamanho de part?culas na mesma ordem de grandeza que os obtidos a partir do m?todo de complexa??o combinando EDTA - Citrato, nas mesmas condi??es de tratamento t?rmico. A natureza do reagente utilizado no m?todo via coprecipita??o em meio oxalato produziu um material com aproximadamente 80 % menor em rela??o ao tamanho m?dio de cristalito. Al?m disso, o m?todo via coprecipita??o em meio oxalato obteve precursores em estado s?lido, em baixa temperatura (~26 oC), menor tempo de s?ntese, maior estabilidade t?rmica e um rendimento maior da ordem 90 a 95 %, mantendo na mesma ordem de grandeza o tamanho m?dio de cristalito que o m?todo de complexa??o combinando EDTA - Citrato. Para fins comparativo das propriedades catal?ticas do material, a perovsquita LaNi0,3Co0,7O3-d foi tamb?m sintetizada pelo m?todo de complexa??o combinando EDTA Citrato. A avalia??o catal?tica dos materiais SrCo0,8Fe0,2O3-d e LaNi0,3Co0,7O3-d, foi acompanhada na rea??o de oxida??o do CO a CO2 utilizando um reator tubular de a?o inoxid?vel na faixa de temperatura de 75 300 oC. A convers?o foi avaliada cujos resultados mostraram que para ambos os materiais o CO foi completamente convertido por?m em menor tempo para o material LaNi0,3Co0,7O3-d

In this work we studied the dependence of two organic precursors, sucrose and glycerin, in the process to obtain CoFe2O4 nanoparticles by co-precipitation method. The samples were studied by different techniques of structural and magnetic characterization. X-ray diffraction Measurements associated with the Rietveld refinement analysis confirm that all samples obtained with and without the addition of organic precursors have a single phase identified in a cubic crystalline system belonging to the space group . The average crystallite size calculated by Scherrer's equation using the full width at half maximum (FWHM) for the samples synthesized without and with concentration of 0.020 mol.L-1 of glycerin and sucrose showed values approximately equal to 14(2), 8(1) and 5(1) nm, respectively. The Williamson-Hall curves show that both organic precursors used in this work influence on the homogeneity of the samples. Transmission electron microscopy analysis indicates that the inclusion of sucrose during the process of synthesis of these materials reduces the average size of the crystallite, it induces a narrowing in the size distribution and change in the particles shape. The X-ray absorption measurements performed in the Co and Fe K-edge of samples synthesized with sucrose and glycerin show a low variation in the density of unoccupied state in the p sublevel however reveal an increase in the interatomic distances between the absorber and the scattering atoms. Magnetization measurements as a function of temperature show a decrease in the blocking temperature (TB) even as a superparamagnetic behavior at room temperature for sample with 0.020 mol.L-1 of sucrose. / Neste trabalho foi realizado um estudo sobre a influência do uso de dois precursores orgânicos, sacarose e glicerina, no processo de obtenção de nanopartículas de ferrita de cobalto (CoFe2O4) pelo método de co-precipitação. As amostras foram estudadas através de diferentes técnicas de caracterização estrutural e magnética. As medidas de difração de raios X associadas às análises de refinamento Rietveld confirmaram que todas as amostras obtidas com e sem a adição de precursores orgânicos têm única fase identificadas em um sistema cristalino cúbico pertencente ao grupo de espaço . O tamanho médio de cristalito estimado pela equação de Scherrer, usando a largura a meia altura dos picos de difração, mostra que para as amostras sintetizadas sem e com concentração de 0,020 mol.L-1 de glicerina e de sacarose revelaram valores aproximadamente iguais a 14(2), 8(1) e 5(1) nm, respectivamente. As análises das curvas de Williamson-Hall mostram que ambos os precursores orgânicos utilizados neste trabalho influenciam na homogeneidade das amostras. As análises de microscopia eletrônica de transmissão indicam que a incorporação de sacarose durante o processo de síntese desses materiais reduz o tamanho médio do cristalito, assim como, induz um estreitamento na distribuição de tamanho, além de alterar a morfologia das amostras. Medidas de absorção de raios X realizadas nas bordas K do Co e Fe nas amostras sintetizadas com sacarose e glicerina apresentam uma baixa variação da densidade de estado desocupados no subnível p, no entanto revela um aumento na distância interatômica entre o átomo absorvedor e o espalhador. Medidas de magnetização como uma função da temperatura mostram uma diminuição na temperatura de bloqueio na amostra obtida com adição de sacarose, assim como, um comportamento superparamagnético à temperatura ambiente na amostra obtida com 0,020 mol.L-1 de sacarose.