The project synthesizes phase pure Yttria particles using flame spray pyrolysis, and to experimentally determines the effect of various process parameters like residence time, adiabatic flame temperature and precursor droplet size on the phase of Yttria particles generated. Further, through experimentation and based on the understanding of the process, conditions that produce pure monoclinic Y2O3 particles were found. An ultrasonic atomization set-up was used to introduce precursor droplets (aqueous solution of yttrium nitrate hex hydrate) into the flame. A hydrogen-oxygen diffusion flame was used to realize the high temperature aerosol synthesis. The particles were collected on filters and analyzed using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Individual process parameters (flame temperature, residence time, precursor concentration, precursor droplet size) were varied in continuous trials, keeping the rest of the parameters constant. The effect of the varied parameter on the phase of the product Yttria particles was then analyzed. Pre-flame heating was undertaken using a nozzle heater at variable power. Precursor solution concentrations of 0.026 mol/L, 0.26 mol/L, and 0.65 mol/L were used. Residence time was varied by means of burner diameter (9.5 mm and 1.6 mm ID). Large precursor droplets were removed by means of an inertial impactor. The higher flame temperatures and precursor heating favor the formation of monoclinic yttrium oxide. The fraction of the cubic phase is closely related to the particle diameter. All particles larger than a critical size were of the cubic phase. Phase pure monoclinic yttrium oxide particles were successfully synthesized. The end conditions included a precursor concentration of 0.65 mol/L, a pure hydrogen-oxygen flame and a 1.6 mm burner. The precursor droplets entrained fuel gas was passed through a round jet impactor and preheated at full power (130 VA). The particles synthesized were in the size range of 0.350 to 1.7 µm.

The project synthesizes phase pure Yttria particles using flame spray pyrolysis, and to experimentally determines the effect of various process parameters like residence time, adiabatic flame temperature and precursor droplet size on the phase of Yttria particles generated. Further, through experimentation and based on the understanding of the process, conditions that produce pure monoclinic Y2O3 particles were found. An ultrasonic atomization set-up was used to introduce precursor droplets (aqueous solution of yttrium nitrate hex hydrate) into the flame. A hydrogen-oxygen diffusion flame was used to realize the high temperature aerosol synthesis. The particles were collected on filters and analyzed using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Individual process parameters (flame temperature, residence time, precursor concentration, precursor droplet size) were varied in continuous trials, keeping the rest of the parameters constant. The effect of the varied parameter on the phase of the product Yttria particles was then analyzed. Pre-flame heating was undertaken using a nozzle heater at variable power. Precursor solution concentrations of 0.026 mol/L, 0.26 mol/L, and 0.65 mol/L were used. Residence time was varied by means of burner diameter (9.5 mm and 1.6 mm ID). Large precursor droplets were removed by means of an inertial impactor. The higher flame temperatures and precursor heating favor the formation of monoclinic yttrium oxide. The fraction of the cubic phase is closely related to the particle diameter. All particles larger than a critical size were of the cubic phase. Phase pure monoclinic yttrium oxide particles were successfully synthesized. The end conditions included a precursor concentration of 0.65 mol/L, a pure hydrogen-oxygen flame and a 1.6 mm burner. The precursor droplets entrained fuel gas was passed through a round jet impactor and preheated at full power (130 VA). The particles synthesized were in the size range of 0.350 to 1.7 µm.

Y2O3:Eu particles are phosphors that have found wide applications. Flamesynthesized Y2O3:Eu particles may have either the cubic or the monoclinic structure. The effects of particle size and Eu doping concentration on crystal structure and the surface elemental composition of the flame-synthesized Y2O3:Eu particles had not been previously reported. In this study, a flame aerosol process was used to generate polydisperse Y2O3:Eu particle. H2 was used as the fuel gas, with either air or O2 gas as the oxidizer. The precursor was aqueous solutions of the metal nitrates, atomized using a 1.7-MHz ultrasonic atomizer. The product particles were analyzed by transmission electron microscopy (TEM), X-ray diffractometer (XRD), Selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), fluorescence spectrophotometer, and inductively coupled plasma mass spectrometer (ICP-MS). The Y2O3:Eu particles generated in H2/O2 flames were spherical and fully dense, with diameters in the range of 10~3000 nm. In particle samples with lower Eu doping concentrations, a critical particle diameter was found, whose value increased with increasing Eu doping concentration. Particles well below the critical diameter had the monoclinic structure; those well above the critical diameter had the cubic structure. At sufficiently high Eu doping concentrations, all Y2O3:Eu generated in H2/O2 flames had the monoclinic structure. On the other hand, all particles generated in the H2/air flames had the cubic structure. For the Y2O3:Eu particles generated in H2/O2 flames, XPS results showed that the surface Eu concentration was several times higher than the doping concentration. For Y2O3:Eu particles generated in H2/air flames, the surface Eu concentration was equal to the doping concentration. For both types of particles, the photoluminescence intensity reached a maximum corresponding to a surface Eu concentration 40~50%. The photoluminescence intensity then decreased rapidly with higher Eu doping concentration. The effect of particle size and Eu doping concentration on crystal structure may be explained by the interplay between surface energy and polymorphism. A mechanism for this surface enrichment phenomenon was proposed based on the binary Eu2O3-Y2O3 phase diagram.

Des poudres céramiques multiéléments dans le système Si/C/N peuvent être obtenues avec le procédé de spray pyrolyse. Les paramètres de synthèse et leur influence sur la composition et la morphologie de poudres obtenues a fait l’objet de précédentes études. Toutefois, les mécanismes de décomposition et de recombinaison des espèces dans la zone de réaction restent inconnus. Cette étude vise à approfondir la compréhension du procédé, de la formation de l’aérosol jusqu’aux mécanismes de formation des particules solides. Ainsi, la caractérisation de l’aérosol par ombroscopie laser, couplée à la mise en place d’un modèle numérique du transport et traitement des gouttes du précurseur au sein du dispositif, a permis l’identification de distributions en taille de gouttes de type bimodal jusqu’à leur entrée en zone de réaction. Cette double approche a également permis de vérifier l’effet des phénomènes physiques et hydrodynamiques sur les distributions en taille des gouttelettes lors de leur transport vers la zone réactionnelle. L’introduction d’une distribution bimodale dans le four de pyrolyse permet d’envisager un mécanisme de décomposition du précurseur en deux étapes, lié à la taille des gouttelettes. Cette hypothèse combinée à l’étude de décomposition du précurseur Hexaméthyldisilazane à haute température a permis de proposer des mécanismes de formation de poudres dont la composition chimique varie selon l’atmosphère de synthèse utilisée. / Multielement ceramic powders in the Si/C/N system could be obtained by spray pyrolysis process. Synthesis parameters and their effect on powder chemical composition and morphology have been already studied. Nevertheless, the mechanisms of precursor decomposition and gas phase species recombination that take place in the reaction zone are still unknown. The aim of this study is the comprehension of the process, from the aerosol generation to the solid powders formation mechanisms. The shadowgraphy technique was used to characterize the spray, and coupled with the implementation of a numerical model of droplets transport and treatment through the device allowed to identify bimodal size distributions at the furnace entrance. This double approach let confirm the effect of physical and hydrodynamic phenomenon in drop size evolution. The introduction of a bimodal distribution into the pyrolysis furnace allows to consider a precursor decomposition mechanism in two steps, depending on the drop sizes. This hypothesis combined to the study of precursor decomposition at high temperature led to the proposal of powder formation mechanisms in which their chemical composition varies with the synthesis atmosphere.

Nos últimos anos, acentuou-se o interesse em materiais semicondutores com alto número atômico e larga banda de energia proibida para aplicações na detecção de radiação ionizante à temperatura ambiente, usando o método direto de detecção. Alguns materiais como o PbI2, HgI2, TlBr, CdTe and CdZnTe são bons fotocondutores e podem ser usados à temperatura ambiente. Como um bom candidato, o PbI2 apresenta uma banda de energia proibida acima de 2,0 eV, o qual quando operando à temperatura ambiente apresenta um baixo ruído, baixa corrente de fuga e alta coleta de cargas. O alto poder de frenamento da radiação ionizante é devido ao alto número atômico e alta densidade. Pesquisadores buscam métodos alternativos que minimizem o tempo de deposição e barateiem o custo dos filmes finos de materiais semicondutores candidatos em aplicações médicas, como detector de raios-X à temperatura ambiente para radiografias digitais. Neste sentido, apresentamos dois métodos para a deposição de filmes finos policristalinos de iodeto de chumbo (PbI2). As técnicas de spray pyrolysis (SP) e evaporação de solvente em estufa (ES) foram usadas para a fabricação de filmes finos de PbI2 com relativo baixo tempo de deposição. A técnica de SP foi adotada com o uso de água milli-Q e N.N-dimetilformamida (DMF) como solventes, variando os parâmetros de deposição. No primeiro caso, para uma deposição otimizada na temperatura de 225ºC e concentração de solução de PbI2 3,1 g/l, uma taxa de deposição de aproximadamente 3,3 Ås-1 foi obtida. O solvente orgânico DMF foi usado para dissolver o PbI2 com alta eficiência no crescimento do material, sendo que uma taxa de crescimento de 20Å/s até 50 Å/s foi obtida como uma função da taxa de solução e um comportamento linear foi observado. Posteriormente, usando a técnica de ES, foram depositados filmes finos usando DMF como solvente com concentração de 150 g/l. Filmes de 6 ?m de espessura foram obtidos com substratos completamente recobertos. Ambos os filmes depositados com DMF (spray pyrolysis e evaporação de solvente) apresentaram cristalização do politipo 4H. No entanto, a cristalização nessa forma se mostra com menor ocorrência nos filmes depositados por evaporação de solvente, indicando um maior grau de ordenamento cristalino nesse material. Em adição, os detectores produzidos com os filmes finos foram expostos aos raios-X na faixa de diagnóstico mamografico usando uma fonte de raios-X com anodo de molibdênio (Mo) com filtro de Al de 0,5 mm de espessura. A fotocorrente é comparada com a corrente no escuro e uma resposta linear foi observada em função da exposição. / In the last few years, great interest has been focused to high atomic number and wide band gap semiconductor materials for applications in room temperature ionizing radiation detection using the direct detection method. Some materials such as PbI2, HgI2, TlBr, CdTe and CdZnTe are good photoconductors and can be used at room temperature. As a good candidate, PbI2 presents a wide band gap (above 2.0 eV), what leads to low noise, low leakage current and large charge collection when the device is operated at room temperature. The high photon stopping power for ionizing radiation is due to the high atomic number and high density. Researchers seek alternative methods that minimize the time of deposition of thin films of promising semiconductor materials candidates for medical applications, such as room temperature X-rays detectors for digital radiography. For this application, large areas are also necessary. In this sense, we investigated two alternative methods for the deposition of polycrystalline thin films of lead iodide (PbI2). The spray pyrolysis (SP) and solution evaporation (ES) deposition techniques were used for fabrication of PbI2 thin films with relative low deposition time. The SP technique was adopted using milli-Q water and N.N-dimethylformamide (DMF) as solvents under varying deposition parameters. In the first case, for an optimized deposition temperature of 225ºC and concentration of PbI2 of 3.1 g/l a deposition rate of about 3.3 Å/s was obtained. The DMF organic solvent was used for dissolution of the PbI2 with higher efficiency on the growth of the film. A growth rate varying from 20 Å/s up to 50 Å/s was obtained as a function of solution rate and a linear behavior could be observed. After, using the ES technique, were obtained thin films deposited using DMF as solvent with concentration of 150 g/l. Thin films 6 ?m-thick were obtained with full coverage of the substrates. In addition, the detectors produced using the thin films were also exposed to X-ray in the range of mammography diagnosis, using as X-ray source a molybdenum (Mo) anode with 0.5 mm Al filtration. The photocurrent is compared to the dark current and a linear response was observed as a function of exposure.

O iodeto de mercúrio(HgI2) vem sendo largamente estudado com o objetivo de utilizá-lo em detectores de radiação –X e –γ. Este material semicondutor apresenta propriedades interessantes que o tornam um grande candidato a esta aplicação em relação a outros materiais. Suas propriedades são gap óptico largo (2,13 eV), alto numero atômico (ZHg = 80; ZI = 53) e alto coeficiente de absorção para comprimentos de onda da ordem de energia do raios-X e -γ. Este, também, pode apresentar três fases quando sólido: fase vermelha (ou α-HgI2), fase amarela (ou β-HgI2) e fase laranja. Cada uma destas fases é associada com diferentes estruturas cristalinas. O α-HgI2 é tetragonal, o HgI2 laranja é também tetragonal,diferindo da fase vermelha somente na posição dos átomos de mercúrio, e β-HgI2 é ortorrômbico. Neste trabalho, estes materiais foram obtidos por duas técnicas: spray pyrolysis e evaporação de solvente. Nas duas técnicas os mais importantes parâmetros para a obtenção das diferentes estruturas são a temperatura e a taxa de evaporação do solvente. Através do método de spray pyrolysis foi possível obter filmes finos de HgI2 com duas estruturas diferentes, somente variando a temperatura do aquecedor de substratos e o solvente. Acima da temperatura de 100ºC com o solvente água foi possível obter filmes amarelados de HgI2. Por sua vez, a temperatura abaixo de 100ºC com o solvente etanol foi possível obter filmes avermelhados. Com a técnica de evaporação de solvente foi possível obter cristais e filmes laterais variando somente a taxa de evaporação de solvente. Variaram-se as taxas de evaporação entre rápida(~10ml/h), média(~0,5ml/h), lenta(~0,1ml/h) e super-lenta(~0,01ml/h). Para a taxa de evaporação média e lenta foram obtidos filmes laterais. Já para a taxa super-lenta foi possível obter cristais. Outro ponto estudado foi a influência da luz no crescimento dos cristais: no escuro obteve-se cristais maiores que os submetidos a luz ambiente. Todos os filmes foram caracterizados por difração de raios-X, microscopia eletrônica de varredura (MEV), e espectroscopia de dispersão de energia (EDS). Já os cristais foram caracterizados por difração de raios-X, MEV e espalhamento Raman. / Recently, attention has been devoted to the study of mercuric iodide (HgI2) because this material is a strong candidate for the development of X- and γ -ray detectors. This material has an optical gap of 2.13 eV, high atomic number (ZHg = 80; ZI = 53) and high absorption coefficient for radiation in the wavelength region of X- and γ –rays. When solid, three phases can be obtained: red (or α-HgI2), yellow (or β-HgI2) and orange. Each of these phases has a different crystalline structure: α-HgI2 is tetragonal, as it is the orange- HgI 2 (the difference is that for the last one the mercury atoms sits in different positions), while the β-HgI2 is orthorhombic. In this work we obtained these materials using two different techniques: spray pyrolysis and solvent evaporation. For both of them the most important parameters are the deposition temperature and solvent evaporation rate. Thin films with two different structures were obtained by spray pyrolysis varying the substrate temperature and the solvent. Using water as solvent and deposition temperature above 100ºC we obtained yellow HgI2. When the temperature is reduced below that value and the solvent is ethanol, red films were obtained. For the solvent evaporation technique, lateral films and millimeter-sized crystals were obtained by varying the solvent evaporation rate. For ethanol as solvent we used four evaporation rates named as fast(~10ml/h), medium (~0.5ml/h), slow (~0.1ml/h) and super-slow (~0.01ml/h). For the medium and slow evaporation rates lateral films were obtained on the wall of the reservoir. For the super-slow evaporation rate crystals were obtained at the bottom of the reservoir. We observed that light has a tremendous influence on crystal growth: bigger crystals are obtained in the dark than under ambient light illumination. As characterization techniques we used: X-rays diffraction, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Raman Scattering.

Nos últimos anos, acentuou-se o interesse em materiais semicondutores com alto número atômico e larga banda de energia proibida para aplicações na detecção de radiação ionizante à temperatura ambiente, usando o método direto de detecção. Alguns materiais como o PbI2, HgI2, TlBr, CdTe and CdZnTe são bons fotocondutores e podem ser usados à temperatura ambiente. Como um bom candidato, o PbI2 apresenta uma banda de energia proibida acima de 2,0 eV, o qual quando operando à temperatura ambiente apresenta um baixo ruído, baixa corrente de fuga e alta coleta de cargas. O alto poder de frenamento da radiação ionizante é devido ao alto número atômico e alta densidade. Pesquisadores buscam métodos alternativos que minimizem o tempo de deposição e barateiem o custo dos filmes finos de materiais semicondutores candidatos em aplicações médicas, como detector de raios-X à temperatura ambiente para radiografias digitais. Neste sentido, apresentamos dois métodos para a deposição de filmes finos policristalinos de iodeto de chumbo (PbI2). As técnicas de spray pyrolysis (SP) e evaporação de solvente em estufa (ES) foram usadas para a fabricação de filmes finos de PbI2 com relativo baixo tempo de deposição. A técnica de SP foi adotada com o uso de água milli-Q e N.N-dimetilformamida (DMF) como solventes, variando os parâmetros de deposição. No primeiro caso, para uma deposição otimizada na temperatura de 225ºC e concentração de solução de PbI2 3,1 g/l, uma taxa de deposição de aproximadamente 3,3 Ås-1 foi obtida. O solvente orgânico DMF foi usado para dissolver o PbI2 com alta eficiência no crescimento do material, sendo que uma taxa de crescimento de 20Å/s até 50 Å/s foi obtida como uma função da taxa de solução e um comportamento linear foi observado. Posteriormente, usando a técnica de ES, foram depositados filmes finos usando DMF como solvente com concentração de 150 g/l. Filmes de 6 ?m de espessura foram obtidos com substratos completamente recobertos. Ambos os filmes depositados com DMF (spray pyrolysis e evaporação de solvente) apresentaram cristalização do politipo 4H. No entanto, a cristalização nessa forma se mostra com menor ocorrência nos filmes depositados por evaporação de solvente, indicando um maior grau de ordenamento cristalino nesse material. Em adição, os detectores produzidos com os filmes finos foram expostos aos raios-X na faixa de diagnóstico mamografico usando uma fonte de raios-X com anodo de molibdênio (Mo) com filtro de Al de 0,5 mm de espessura. A fotocorrente é comparada com a corrente no escuro e uma resposta linear foi observada em função da exposição. / In the last few years, great interest has been focused to high atomic number and wide band gap semiconductor materials for applications in room temperature ionizing radiation detection using the direct detection method. Some materials such as PbI2, HgI2, TlBr, CdTe and CdZnTe are good photoconductors and can be used at room temperature. As a good candidate, PbI2 presents a wide band gap (above 2.0 eV), what leads to low noise, low leakage current and large charge collection when the device is operated at room temperature. The high photon stopping power for ionizing radiation is due to the high atomic number and high density. Researchers seek alternative methods that minimize the time of deposition of thin films of promising semiconductor materials candidates for medical applications, such as room temperature X-rays detectors for digital radiography. For this application, large areas are also necessary. In this sense, we investigated two alternative methods for the deposition of polycrystalline thin films of lead iodide (PbI2). The spray pyrolysis (SP) and solution evaporation (ES) deposition techniques were used for fabrication of PbI2 thin films with relative low deposition time. The SP technique was adopted using milli-Q water and N.N-dimethylformamide (DMF) as solvents under varying deposition parameters. In the first case, for an optimized deposition temperature of 225ºC and concentration of PbI2 of 3.1 g/l a deposition rate of about 3.3 Å/s was obtained. The DMF organic solvent was used for dissolution of the PbI2 with higher efficiency on the growth of the film. A growth rate varying from 20 Å/s up to 50 Å/s was obtained as a function of solution rate and a linear behavior could be observed. After, using the ES technique, were obtained thin films deposited using DMF as solvent with concentration of 150 g/l. Thin films 6 ?m-thick were obtained with full coverage of the substrates. In addition, the detectors produced using the thin films were also exposed to X-ray in the range of mammography diagnosis, using as X-ray source a molybdenum (Mo) anode with 0.5 mm Al filtration. The photocurrent is compared to the dark current and a linear response was observed as a function of exposure.

O iodeto de mercúrio(HgI2) vem sendo largamente estudado com o objetivo de utilizá-lo em detectores de radiação –X e –γ. Este material semicondutor apresenta propriedades interessantes que o tornam um grande candidato a esta aplicação em relação a outros materiais. Suas propriedades são gap óptico largo (2,13 eV), alto numero atômico (ZHg = 80; ZI = 53) e alto coeficiente de absorção para comprimentos de onda da ordem de energia do raios-X e -γ. Este, também, pode apresentar três fases quando sólido: fase vermelha (ou α-HgI2), fase amarela (ou β-HgI2) e fase laranja. Cada uma destas fases é associada com diferentes estruturas cristalinas. O α-HgI2 é tetragonal, o HgI2 laranja é também tetragonal,diferindo da fase vermelha somente na posição dos átomos de mercúrio, e β-HgI2 é ortorrômbico. Neste trabalho, estes materiais foram obtidos por duas técnicas: spray pyrolysis e evaporação de solvente. Nas duas técnicas os mais importantes parâmetros para a obtenção das diferentes estruturas são a temperatura e a taxa de evaporação do solvente. Através do método de spray pyrolysis foi possível obter filmes finos de HgI2 com duas estruturas diferentes, somente variando a temperatura do aquecedor de substratos e o solvente. Acima da temperatura de 100ºC com o solvente água foi possível obter filmes amarelados de HgI2. Por sua vez, a temperatura abaixo de 100ºC com o solvente etanol foi possível obter filmes avermelhados. Com a técnica de evaporação de solvente foi possível obter cristais e filmes laterais variando somente a taxa de evaporação de solvente. Variaram-se as taxas de evaporação entre rápida(~10ml/h), média(~0,5ml/h), lenta(~0,1ml/h) e super-lenta(~0,01ml/h). Para a taxa de evaporação média e lenta foram obtidos filmes laterais. Já para a taxa super-lenta foi possível obter cristais. Outro ponto estudado foi a influência da luz no crescimento dos cristais: no escuro obteve-se cristais maiores que os submetidos a luz ambiente. Todos os filmes foram caracterizados por difração de raios-X, microscopia eletrônica de varredura (MEV), e espectroscopia de dispersão de energia (EDS). Já os cristais foram caracterizados por difração de raios-X, MEV e espalhamento Raman. / Recently, attention has been devoted to the study of mercuric iodide (HgI2) because this material is a strong candidate for the development of X- and γ -ray detectors. This material has an optical gap of 2.13 eV, high atomic number (ZHg = 80; ZI = 53) and high absorption coefficient for radiation in the wavelength region of X- and γ –rays. When solid, three phases can be obtained: red (or α-HgI2), yellow (or β-HgI2) and orange. Each of these phases has a different crystalline structure: α-HgI2 is tetragonal, as it is the orange- HgI 2 (the difference is that for the last one the mercury atoms sits in different positions), while the β-HgI2 is orthorhombic. In this work we obtained these materials using two different techniques: spray pyrolysis and solvent evaporation. For both of them the most important parameters are the deposition temperature and solvent evaporation rate. Thin films with two different structures were obtained by spray pyrolysis varying the substrate temperature and the solvent. Using water as solvent and deposition temperature above 100ºC we obtained yellow HgI2. When the temperature is reduced below that value and the solvent is ethanol, red films were obtained. For the solvent evaporation technique, lateral films and millimeter-sized crystals were obtained by varying the solvent evaporation rate. For ethanol as solvent we used four evaporation rates named as fast(~10ml/h), medium (~0.5ml/h), slow (~0.1ml/h) and super-slow (~0.01ml/h). For the medium and slow evaporation rates lateral films were obtained on the wall of the reservoir. For the super-slow evaporation rate crystals were obtained at the bottom of the reservoir. We observed that light has a tremendous influence on crystal growth: bigger crystals are obtained in the dark than under ambient light illumination. As characterization techniques we used: X-rays diffraction, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Raman Scattering.

L’objet de cette thèse est la synthèse et la caractérisation de nouveaux filtres UV inorganiques nanostructurés, efficaces dans le domaine des UVA. Dans ce contexte, nous avons choisi d’étudier le dioxyde de cérium (CeO2) et l’hématite (α-Fe2O3) en raison notamment de leurs propriétés optiques d’absorption des UV. Deux méthodes de synthèse ont été sélectionnées pour l’élaboration de ces oxydes, purs ou dopés, sous la forme de poudre nanométrique: la co-précipitation et le spray-pyrolyse. Les conditions optimales de synthèse ont été déterminées grâce à de la diffraction des rayons X et de l’analyse thermique. La structure cristalline ainsi que la granulométrie des échantillons obtenus ont été caractérisées par diffraction des rayons X et microscopies électroniques. La granulométrie et la morphologie des échantillons sont reliées aux méthodes de synthèse, aux conditions opératoires (atmosphère et température de calcination), à la nature et à la concentration des éléments dopants. Les propriétés optiques des échantillons suspendus dans de l’éthanol ont été étudiées par spectroscopie d’absorption UV-visible. Elles sont reliées à la granulométrie des échantillons ainsi qu’à des phénomènes localisés au sein de la maille cristallographique (changements de valence, présence de défauts). Les échantillons à base de CeO2 et α-Fe2O3 ont finalement été incorporés en émulsion solaire, à la place de ZnO, afin de tester leurs performances anti-solaires (SPF et FP-UVA) par mesure in vitro. Les résultats montrent que le ZnO peut être positivement remplacé dans les produits de protection solaire par l’oxyde de cérium ou de fer qu’ils soient purs ou dopés. / The subject of this thesis is the synthesis and the characterization of new UVA-efficient nanostructured inorganic UV filters. In this context, we chose to study cerium dioxide (CeO2) and hematite (α-Fe2O3), most importantly because of their optical absorption properties. Two methods were selected to synthesise cerium dioxide and hematite in nanostructured powder form: the co-precipitation method and the spray-pyrolysis method. Cerium dioxide was studied in both non-doped and doped forms. Optimal synthesis conditions were determined by X-ray diffraction and thermal analysis. The crystalline structure and granulometry of the obtained samples were characterised by X-ray diffraction and electronic microscopy techniques. Granulometry and morphology of the samples are linked to: the synthesis method, the experimental conditions (atmosphere and temperature of calcinations), and the nature and concentrations of the dopes. The optical properties of ethanol suspended samples were studied by UV-visible absorption spectroscopy. They are linked to the samples’granulometry as well as localised phenomena in the crystallographic lattice (valence changes, defects presence). Cerium dioxide- and hematite-based samples were finally incorporated in emulsion, instead of ZnO, in order to test their photoprotection performance (SPF and PF-UVA) by measuring in vitro. Results show that ZnO can be positively replaced by pure or doped cerium or iron oxide in sunscreen, when these are associated with the inorganic filter TiO2.

LIMA, F. M. Preparação e caracterização de filmes condutores: óxidos de estanho e cobre para uso em célula solar fotovoltaica sensibilizada por corante. 2017. 183 f. Tese (Doutorado em Engenharia e Ciência de Materiais)-Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by Pós-Graduação Ciência de Materiais (materiais@metalmat.ufc.br) on 2017-11-17T19:06:20Z No. of bitstreams: 1 2017_tes_fmlima.pdf: 6913544 bytes, checksum: e045a84e3ad90408c35dff5100654a78 (MD5) / Rejected by Marlene Sousa (mmarlene@ufc.br), reason: Favor trocar arquivo completo, por arquivo que contenha só as partes que o autor deseja disponibilizar. Fico aguardando. Marlene on 2017-11-20T12:26:07Z (GMT) / Submitted by Pós-Graduação Ciência de Materiais (materiais@metalmat.ufc.br) on 2017-11-30T13:03:56Z No. of bitstreams: 1 2017_tes_fmlima.pdf: 6913544 bytes, checksum: e045a84e3ad90408c35dff5100654a78 (MD5) / Approved for entry into archive by Marlene Sousa (mmarlene@ufc.br) on 2017-11-30T13:35:02Z (GMT) No. of bitstreams: 1 2017_tes_fmlima.pdf: 6913544 bytes, checksum: e045a84e3ad90408c35dff5100654a78 (MD5) / Made available in DSpace on 2017-11-30T13:35:02Z (GMT). No. of bitstreams: 1 2017_tes_fmlima.pdf: 6913544 bytes, checksum: e045a84e3ad90408c35dff5100654a78 (MD5) Previous issue date: 2017 / The transparent conductor oxide films are a class important of materials because exhibit both transparency and electronic conductivity simultaneously. Although a large number of works on preparation using acid and characterization on that materials have seen reported over the years, but there seems not a single work on the theme. In the present work was developed a systematic process for the preparation of transparent conductor oxide films (number patent BR1020160302633) and characterization. Together, the materials here described were composed of a group of two different films, one with fluorine doped tin oxide and other with addition of copper. All films were tailored on face of preheated glass substrates at 600oC. The spray pyrolysis technique was used. The experimental arrangement was a furnace with ceramic ohmic heater, glass substrates, and precursor solutions, spray nozzle and air compressor. The precursor solutions with tin chloride dehydrate, ammonium fluorine and deionized water were used for obtain fluorine doped tin oxide films. While that from of the tin chloride dehydrate, ammonium fluorine, copper chloride dehydrate deionized water was tailored the other type. Thus, fluorine doped tin oxide films were prepared with different amount of deionized water, in range about 7 - 10 mL, which the amount of source for tin and fluorine was constant. After to find the optimum amount of water, it was fixed constant in the preparation of fluorine doped tin oxide films with different amount of copper. On the characterization, the discussion was in direction of both solution concentration and copper effects on the electrical, optical and structural properties of the fluorine doped tin oxide films. The mean characterization of films was sheet resistance, ultraviolet-visible transmittance and Mott-Schottky method measurements. In the complementary characterization was used optical thickness and band gap, scan electronic microscopy, X-rays diffraction and energy edge. From 500 nm up to 800 nm, the transmittance range was about 60 - 80% for all samples of films. From the electrical measurement, it was determined that sheet resistance range about 17.60 - 19.40 Ω/ □ on influence of solution concentration and 20.20 - 35.80 Ω/ □ in function of copper concentration. The Mott- Schottky showed all the films as n-type semiconductors. Scan electronic microscopy showed that the experimental variations lead to morphologic range. From X-rays diffraction, all the films have only characteristic peaks of the tin dioxide, it was understood that possibly the amounts of fluorine and copper were as doping. Aftercharacterization, the products two were used in the dye-sensitized solar cells assembly. The photovoltaic characterizations of cells were made by current density versus voltage curves and Francisco Mott-Schottky (number patent BR1020160302617). The results showed that good transparency can be achieved in the fluorine doped tin oxide films by the addition of cooper. But, ability to create multication films without significantly degrading the electronic conductivity can not be achieved. Possibly, low electronic conductivity in the multication films was due degradation in the electrical transport parameters. But, the multication films showed potential for photovoltaic application. / Filmes de óxidos transparentes e condutores apresentando simultaneamente condutividade e transparência são materiais importantes. Embora existam vários trabalhos sobre métodos de preparação por via ácida e caracterização, aqui não foi uma simples abordagem sobre o tema. Neste trabalho, um processo foi desenvolvido para fabricação de filmes de óxidos transparentes e condutores (patente BR1020160302633) e caracterização. Os filmes produzidos foram divididos em duas categorias. Primeira, filmes de óxido de estanho dopado com flúor. A adição de cobre ao material resultou na segunda categoria. Todos os filmes foram depositados sobre vidros aquecidos a 600 oC via técnica spray pyrolysis. Também, forno com resistência encapsulada em massa cerâmica, substratos de vidro, soluções fontes, bico de spray e compressor de ar foram usados. Os filmes de óxido de estanho dopado com flúor foram obtidos usando solução fonte contendo cloreto de estanho dihidratado, fluoreto de amônio e água deionizada. Enquanto que o uso cloreto de cobre dihidratado e água deionizada e da primeira solução resultou nos materiais da segunda categoria. Filmes de óxido de estanho dopado com flúor foram preparados a partir de diferentes volumes de água, entre 7 - 10 mL, sendo as quantidades das fontes de estanho e flúor constantes. Após achar a quantidade adequada de volume de água foi variada a quantidade de cobre para obtenção de óxido de estanho dopado com flúor e cobre. Na caracterização, a discussão foi sobre as influências da concentração da solução e de átomos de cobre nas propriedades elétrica, óptica e estrutural dos filmes de óxido de estanho dopado com flúor. A caracterização principal foi via resistência elétrica de folha, transmitância no ultravioleta-visível e método Mott-Schottky. Também foi realizada caracterização complementar composta por medidas óptica da espessura e banda proibida, microscopia eletrônica de varredura, difração de raios-X e nível de energia. A transmitância variou entre 60 - 80% para todos os filmes depositados para a variação de 500 - 800 nm. As resistências de folha variaram entre 17,60 - 19,40 Ω/ □ e 20,20 - 35,80 Ω/ □ em função da concentração da solução e da quantidade de átomos de cobre, respectivamente. A análise via Mott-Schottk indicou predominância de semicondutor tipo n nas amostras. A microscopia eletrônica de varredura mostrou a dependência da morfologia em função das condições experimentais. A partir da difração de raios-X foi identificado picos de dióxido de estanho em todas as amostras. Isso foi atribuído ao fato dos átomos de flúor e cobre atuarem possivelmente como dopantes. Após a caracterização, duas amostras foram usadas para a construção decélulas solares sensibilizadas por corante. A caracterização fotovoltaica das células foi feita por meio da curva densidade de corrente versus voltagem e Francisco Mott-Schottky (patente BR1020160302617). Os resultados indicaram que a adição de cobre a filmes de óxido de estanho dopado com flúor pode produzir filmes com boa transparência. No entanto, nos filmes com multicátions a resistência elétrica foi incrementada. Possivelmente, a baixa condutividade pode ser atribuída à minimização dos carreadores de carga móvel. Contudo, os filmes multicátions apresentaram potencial para aplicação fotovoltaica.