Ces dernières années, la photocatalyse hétérogène a connu un essor important comme technique de dépollution de l'eau et de l'air. L'application de ce procédé sur des substrats organiques souples, comme les textiles, présente de nombreux challenges. Les revêtements doivent être photoactifs sans pour autant dégrader les supports. Avec l'utilisation du TiO2 comme photocatalyseur, une bonne fixation des particules est primordiale pour éviter tout relargage dans l'environnement. La structuration des matériaux est également un point important. La porosité des films favorise les interactions polluants/photocatalyseurs mais doit être obtenue à faibles températures pour ne pas décomposer les textiles. Pour se faire, nous avons choisi de synthétiser des revêtements composites en insérant des particules commerciales de TiO2 dans une matrice hybride silicatée, celle-ci servant à la fois de liant au substrat et de couche protectrice. La matrice est préparée par le procédé sol-gel qui permet d'insérer aisément des groupements organiques au réseau silicaté. Ces modifications permettent d'apporter de la flexibilité aux revêtements afin de conserver les propriétés mécaniques des supports. Notre étude s'est consacrée à l'élaboration et à l'optimisation de ces systèmes. Une première partie a été réalisée sur des supports inorganiques afin de définir des comportements modèles, avant de transférer la technologie sur les textiles. L'efficacité des revêtements a été évaluée en phase aqueuse et gazeuse par la dégradation de l'acide formique, du bleu de méthylène et du toluène. La stabilité des supports et des films par rapport aux UV a été suivie par plusieurs techniques analytiques (MEB, XPS, ToF-SIMS, RMN, angle de contact, IR, colorimétrie) en accélérant le photovieillissement des matériaux. Diverses caractérisations mécaniques (abrasion, arrachage, rigidité) sont venues compléter notre étude / Heterogeneous photocatalysis was widely developed these last years for water and air depollution. Applications on organic and flexible substrates, like textiles, induce many challenges. The coating must be photoactive without damaging the media. With the use of TiO2 as photocatalyst, a good fixation of the particles is essential to prevent their release into the environment. The material structuration is also an important point. Film porosity promotes pollutants/photocatalysts interactions but must be obtained at low temperatures to avoid textiles degradation. In this context, we chose to synthesize composite coatings inserting commercial TiO2 particles into a silica matrix used as binder and protective layer. The matrix is prepared by the sol-gel process that allows adding organic groups into the silicate network. Such modification of the structure provides flexibility to maintain the mechanical properties of the supports. Our study is devoted to the development and optimization of these systems. The first part was conducted on inorganic substrates to define models behavior before transferring the technology on textiles. Film efficiency was evaluated in gas and aqueous phase degrading formic acid, methylene blue and toluene. The UV stability of the media and the film was followed by several analytical techniques (SEM, XPS, ToF-SIMS, NMR, contact angle, IR, colorimetry) accelerating the photoaging of the materials. Various mechanical characterizations came to complete our study

Ce travail de thèse s'est inscrit dans le cadre d'un projet collaboratif à finalité industrielle ayant pour but de développer des matériaux composites à propriétés photocatalytiques (à base de nanoparticules de TiO2) obtenus par voie sol-gel pour une application sur substrats organiques (textiles et papiers) : intégration de nanoparticules de TiO2 dans une matrice sol-gel hybride (organique-inorganique) et dispersion de nanoparticules de TiO2 dans des microparticules de silice mésoporeuses. La contribution originale du travail de thèse a consisté à développer des caractérisations par analyse de surface (SEM, XPS et ToF-SIMS) et corréler ces résultats à ceux des tests photocatalytiques (suivi de la dégradation d'un polluant modèle (acide formique) en solution aqueuse sous irradiation UV). En complémentarité avec la question des différents niveaux de porosité des matrices utilisées, les techniques SEM, XPS et ToF-SIMS ont permis de définir différents critères tels que la disponibilité du photocatalyseur (TiO2) en extrême surface mais aussi la modification de la matrice autour du TiO2. Ces critères ont contribué à mieux comprendre les différences de propriétés photocatalytiques des différents matériaux composites déposés en surface des substrats organiques / This thesis work is part of a collaborative project with an industrial purpose aiming at the development of composite materials with photocatalytic properties (composed of TiO2 nanoparticles) obtained by sol-gel process for application on organic substrates (textiles and paper): integration of TiO2 nanoparticles into a sol-gel hybrid (organic-inorganic) matrix and dispersion of TiO2 nanoparticles in mesoporous silica microparticles. The original contribution of this work was to develop characterization by surface analysis techniques (SEM, XPS and ToF-SIMS) and correlate these results to those from the photocatalytic tests (following the degradation of a model pollutant (formic acid) in aqueous solution under UV irradiation). Complementarily to the issue of matrices porosity, surface analysis techniques (SEM, XPS and ToF –SIMS) allowed to define criteria such as availability of photocatalyst (TiO2) at the outermost surface but also the modification of the matrix around the TiO2. These criteria were used to better understand the differences in photocatalytic properties of various composite materials deposited on the surface of organic substrates

Ce mémoire rapporte la préparation et l'étude de matériaux hybrides organiques-inorganiques à base de titane où les deux réseaux sont liés par des liaisons titane-carbone stables. Différents précurseurs dans lesquels deux groupes cyclopentadienyltitane sont reliés par des espaceurs variés ont été préparés. Ces espaceurs comprennent des groupes aromatiques et hétéroaromatiques linéaires ainsi que des groupes aromatiques disubstitués par des chaînes alkyle. Ces complexes dimétalliques, où le titane est aussi lié à trois groupes labiles, ont été ensuite hydrolysés dans les conditions du procédé sol-gel pour conduire à des hybrides de classe II. Le réseau organique y est lié au réseau inorganique par des liaisons stables titane-carbone. Ces matériaux sont organisés et leur mode d'organisation dépend de la nature de l'espaceur reliant les groupes cyclopentadienyle. Les espaceurs linéaires conduisent à des matériaux à structure en escalier dans lesquels les ligands sont associés par des liaisons p. La longueur des espaceurs n'a pas d'effet sur cette organisation. Par contre, les matériaux à espaceurs substitués latéralement sont organisés par les chaînes alkyle. La calcination de ces matériaux hybrides sous oxygène conduit à la formation de dioxyde de titane nanoporeux sous forme d'anatase dont la cristallinité et la surface spécifique dépendent de la température de calcination. D'une façon similaire des films de dioxyde de titane de même type sont obtenus par la calcination de films minces d'hybrides préparés par spin-coating. / This work aimed to the preparation of titanium-based organic-inorganic hybrid materials where both networks are linked through stable titanium-carbon bonds. The preparation of various di(cyclopentadienyltitanium) precursors in which various organic groups serve as a bridge between the two cyclopentadienyl groups while each titanium atom is equipped with three hydrolysable groups was first achieved. Then, these complexes were hydrolyzed in a sol-gel process that led to new self-assembled titanium-based class II hybrid materials in which the inorganic network is connected to the organic network through stable titanium-carbon bonds. The mode of organization of the nanostructures depends on the spacer bridging the cyclopentadienyl groups. Linear aromatic spacers led to materials having a stair-like structure in which the organic ligands are arranged via p-stacking. The length of the spacer has a little effect on the organization of the nanostructures. The structure of the materials obtained with spacers endowed with long lateral chains is governed by the side chains. The calcination of these materials under oxygen led to the formation of nanoporous anatase titanium dioxide the crystallinity and surface area of which depend on the calcination temperature. Similarly titanium dioxide thin films were prepared by the calcination of hybrid thin films prepared by spin coating.

Les principaux objectifs de ces travaux de thèse sont d'une part d'optimiser le protocole d'élaboration des barrières thermiques (BT) issues de la voie sol-gel et d'autre part de caractériser l'adhérence de ces barrières thermiques mais aussi de proposer des pistes en vue d'augmenter la durée de vie de celles-ci. Tout d'abord, une première étude a porté sur le choix et la validation d'un nouvel agent dispersant pour optimiser la formulation du sol chargé permettant la mise en forme des barrières thermiques. Ainsi, ce changement de dispersant a généré une microstructure conduisant à une augmentation significative de la durée de vie du système en oxydation cyclique mais a aussi permis de simplifier le protocole d'élaboration puisque l'étape de colmatage, jusqu'alors nécessaire, a été supprimée. L'étude paramétrique de la microstructure surfacique des barrières thermiques a montré que le réseau de microfissures formé initialement restait stable en fonction du vieillissement avec la création d'un sous-réseau microfissuré. Pour comprendre les mécanismes d'endommagement des barrières thermiques sol-gel et les confronter à ceux des barrières thermiques industrielles EB-PVD, la méthode d'indentation interfaciale a été retenue pour sonder l'interface revêtement/substrat. Ainsi des valeurs de ténacités apparentes ont pu être déterminées afin de comparer les adhérences des BTSG et des BTEB-PVD. A partir de ces résultats, des modèles phénoménologiques d'endommagement ont été imaginés. Pour les BTEB-PVD, l'initiation et la propagation de fissures restent localisées à l'interface barrière thermique/sous-couche de liaison, d'un coté ou de l'autre de l'oxyde de croissance selon les conditions, alors que pour les BTSG, l'endommagement est induit par la libération d'énergie élastique stockée dans le système qui augmente en fonction du vieillissement. / The main objectives of this PhD are first to improve and optimise the elaboration protocol of thermal barrier coatings (TBC) manufactured by the sol-gel route and then to characterise their adhesion and investigate the possibility to enhance their lifetime. A preliminary study is focused on the selection and validation of a new dispersing agent to optimise the composite sol formulation before shaping TBC. Indeed, the new dispersant induced a microstructure allowing to significantly increase the cyclic oxidation lifetime of the system but also to simplify the elaboration process as the reinforcement step was suppressed. The parametric study of TBC surface microstructure proved that the initial micro-cracks network remained stable during ageing including the formation of a crack sub-network. To understand the damage mechanisms of sol-gel TBC and to compare them to those corresponding to industrial EB-PVD TBC, the method of interfacial indentation was developed to investigate the subtrate/top-coat interface. The apparent toughness values were determined to compare both BTSG and BTEB-PVD adhesions. From these results, phenomenological models for damage mechanisms were proposed. For BTEB-PVD, crack initiation and propagation are located at the top-coat/bond-coat interface, either on one side or the other side of the thermally grown oxide (TGO) depending of the conditions. For BTSG, the damage is a consequence of the release of the elastic strain energy stored in the system, increasing with the ageing temperature.

Résumé confidentiel / Résumé confidentiel

Cette thèse s’inscrit dans le développement et l’optimisation d’un panel de catalyseurs dopés ou non dopés pour le traitement des eaux usées par un Procédé d’Oxydation Avancée (POA), la photocatalyse hétérogène solaire. Ce procédé de traitement tertiaire pour la dépollution de molécules organiques biorécalcitrantes est limité par l’absorption des catalyseurs dans le domaine de l’UV ne représentant que 5 % du spectre solaire reçu à la surface de la Terre. L’objectif de ce travail est de comparer les efficacités photocatalytiques sous rayonnement UV, visible et solaire dans le but d’améliorer les efficacités dans le domaine de l’UV, de développer un catalyseur exploitant efficacement le rayonnement visible et de définir les paramètres clés régissant les réponses photocatalytiques. Dans cette optique, une étude a été menée sur les catalyseurs de ZnO dopés ou non dopés. L’ensemble des catalyseurs à base de ZnO ont été synthétisé par un seul et même procédé, le sol-gel couplé à un séchage en conditions supercritiques. Les caractérisations structurales, morphologiques, chimiques, optiques et optoélectroniques ont été réalisées en vue de définir leurs paramètres physico-chimiques pour maitriser les conditions de synthèses des catalyseurs. Elles ont également montré que le ZnO dopé décale sa bande d’absorption vers le domaine du visible. Les expérimentations photocatalytiques ont été conduites à l’aide d’un banc de mesure photocatalytique dans le domaine de l’UV, du visible et du solaire. Une attention particulière est portée sur un polluant modèle, le pyriméthanil. En parallèle, ces expérimentations ont été couplées à un modèle cinétique. Les nanoparticules de Zn1-xMxO (M : Ca, Al, Li, V, In, Co, P…) présentent des réponses photocatalytiques prometteuses dans le domaine du visible. Une corrélation a également été mise en évidence entre les propriétés physico-chimiques des catalyseurs et l’efficacité à produire des radicaux. Par ailleurs, une étude plus approfondie a été menée sur le Zn0,90Ca0,10O. Cette étude révèle la présence de défauts structuraux jouant un rôle essentiel sur les réponses photocatalytiques. / This thesis is part of the development and optimization of a doped and undoped panel of catalysts for the treatment of waste water based on an Advanced Oxidation Process (AOP), solar heterogeneous photocatalysis. This tertiary process for bio-recalcitrant organic molecules clean up is limited by the catalysts absorption in the UV range which represent only 5 % of the solar spectrum received on the earth surface. The aim is to compare photocatalytic efficiency under UV, visible and solar irradiation in order to improve efficiency in the UV range, to develop a catalyst which operates effectively under visible irradiation and to define key parameters governing the photocatalytic activities. In this context, a study is performed on doped or undoped ZnO based catalysts. All of ZnO based catalysts are synthesized by the same process, the sol-gel process under supercritical drying conditions. Structural, morphological, chemical, optical and optoelectronical characterizations is carried out to define their physico-chemical parameters in order to control the synthesis conditions of these catalysts. Doped ZnO also showed an absorption edge shift toward the visible range. Photocatalytic experiments are carried out with a photocatalysis optical bench in the UV, visible and solar range. Particular attention is paid on a model pollutant, pyrimethanil. In parallel, these experiments are coupled to a kinetic model. Nanoparticles of Zn1-xMxO (M : Ca, Al, Li, V, In, Co, P…) showed encouraging photocatalytic activities in the visible range. A correlation is showed between the physico-chemical properties of the catalysts and the radicals production efficiency. Furthermore, an extensive study is done on Zn0,90Ca0,10O. This study reveals the presence of structural defects playing a main role on the photocatalytic activities.

La synthèse d'acide polyamique (APA) comportant des blocs élastomères de type oligo-oxyéthylène et -oxypropylène et des polyimides correspondants (PEI) a été étudiée et leurs propriétés de perméation gazeuse déterminées pour He, N2, O2, H2, CH4 et CO2. Il a été montré que la présence de la phase élastomère augmentait de façon très importante les coefficients de perméabilité au gaz comparativement aux polyimides aromatiques conventionnels. La perméabilité du CO2, augmentée de façon préférentielle par rapport celles de tous les autres gaz, conduit à des sélectivités idéales tout à fait remarquables, en particulier vis-à-vis de N2 (≈40). L’incorporation de nanoparticules de silice dans les PEI (de 1 à 15% en masse) a été effectuée lors de l’étape de cyclo-déshydratation de l'APA, soit par ajout de silice hydrophobes (16 nm) ou hydrophiles (12 nm), soit par méthode Sol-Gel à partir de précurseurs alcoxysilanes (TMOS et TEOS). L'influence des charges SiO2 sur les propriétés de perméation gazeuse a été étudiée par la méthode du temps de retard (time-lag) essentiellement sur la série préparée avec des particules préformées. On a observé que les nano-charges de silice ne semblent pas interférer dans le processus de cyclisation et que les propriétés mécaniques sont renforcées ; la perméabilité aux gaz varie surtout selon la quantité de charges incorporées mais aucune augmentation spectaculaire de perméabilité n’a pu être observée. On peut en déduire que, vraisemblablement, c’est la phase élastomère qui est le lieu d’incorporation des particules de SiO2. Ces résultats montrent l’intérêt des membranes PEI et PEI/SiO2 dans des applications industrielles de séparation de gaz, notamment pour la séparation de mélanges CO2/N2 / The synthesis of polyamic acids (PAA) with oligo-oxyethylene and -oxypropylene rubbery blocks and the related polyimides (PEI) has been studied and their gas permeation properties determined for He, N2, O2, H2, CH4 and CO2. It was shown that the rubbery phase dramatically increased the gas permeability coefficients compared to conventional aromatic polyimides. The permeability of CO2 is preferentially increased in comparison to all other gases, leading to remarkable ideal selectivities, especially for the N2 mixture (≈40). The incorporation of silica nanoparticles in PEI (from 1 to 15 wt%) was carried out during the cyclo-dehydration of the PAA by adding fumed hydrophobic (16 nm) or hydrophilic (12 nm) silica, or by Sol-Gel approach using alkoxysilane precursors (TMOS and TEOS). The effect of SiO2-fillers on the properties of gas permeation has been studied by the time-lag method mainly on the series prepared with fumed silica. It was observed that nano-particles of silica do not seem to disturb the PAA cyclization process and that the mechanical properties are improved; the gas permeability varies essentially depending on the amount of fillers incorporated but no spectacular increase in permeability could be shown due to the nano-particles amounts. Apparently, it can be deduced that it is the rubbery phase which accommodates the SiO2 particles. These results showed the value of PEI and PEI/SiO2 membranes in industrial applications of gas separation, especially for the separation of CO2/N2 mixtures

Orientadora: Profa. Dra. Juliana Marchi / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, Santo André, 2018. / A hipertermia e uma terapia de tratamento de cancer que consiste em aumentar a temperatura do tecido biologico contendo celulas cancerigenas a temperaturas ate 43¿C, a qual afeta as celulas cancerigenas e causa minimos danos a celulas saudaveis. Este trabalho visou sintetizar, pelo metodo sol-gel, vidros bioativos do sistema SiO2-CaO-P2O5 contendo fases magneticas de oxido de ferro a fim de obter um material com propriedades magneticas promissoras para hipertermia e com propriedades osteocondutoras favoraveis para regeneracao ossea, podendo assim ser utilizado no tratamento de cancer osseo. As fases magneticas foram introduzidas por dois diferentes metodos: I) cristalizacao por reacoes de estado solido (Parte I); II) dispersao de nanoparticulas de magnetita na matriz vitrea (Parte II). Na Parte I do trabalho, uma rota alternativa de sintese foi desenvolvida e validada para possibilitar a obtencao de vidros contendo fases superparamagneticas nucleadas por cristalizacao. Os materiais foram caracterizados por difracao de raios X (DRX), espectroscopia de infravermelho na transformada de Fourier, calorimetria diferencial de varredura (DSC) e magnetometro de amostra vibrante (VSM-SQUID). Os resultados indicaram que vidros obtidos pela metodologia modificada da Parte I apresentam estrutura quimica similar aos vidros obtidos pelo metodo convencional, i.e. uma fase vitrea contendo fase secundaria cristalina de hidroxiapatita. Foi possivel obter vidros contendo ferro, cuja incorporacao ocasiona uma conversao 3Q2 ¨ 2Q3 na estrutura vitrea, sugerindo um efeito de ion intermediario em relacao ao ferro. O tratamento termico de vidros contendo ferro a 670¿C induziu a nucleacao de nanocristais de hematita, fazendo que os vidros exibissem comportamento superparamagnetico. Na segunda parte deste trabalho (Parte II) os vidros foram obtidos pelo metodo quick-alkali onde as nanoparticulas de magnetita foram dispersas durante a sintese. Os materiais foram caracterizados por DRX, DSC, espectroscopia Raman, microscopia eletronica de varredura por emissao de campo e VSM-SQUID. Os resultados da Parte II indicaram que vidros contendo nanoparticulas de magnetita com propriedades superparamagneticas foram obtidos. Foi observado um efeito de aglomeracao das nanoparticulas, o qual afetou as interacoes dipolares entre as particulas. O processo da sintese induziu uma oxidacao das nanoparticulas de magnetita, levando a uma diminuicao do momento de saturacao, porem ainda com valores adequados para sejam empregados em tratamentos por hipertermia. Os resultados de ambas as Partes (I e II) indicam que materiais promissores para aplicacoes em hipertermia foram obtidos. / Hyperthermia is a cancer treatment therapy that consists of increasing the cancerous tissue temperature up to 45¿C, majorly affecting cancer cells, and minimally damaging healthy ones. The aim of this work was to synthesize, through the sol-gel method, bioactive glasses based on the SiO2-CaO-P2O5 and containing magnetic phases of iron oxide in order to achieve materials with suitable magnetic properties for hyperthermia, and desired biological properties for bone regeneration. Therefore, such material can be used in treatment of bone cancer. The magnetic phases were added in the glass structure by two different methodologies: I) crystallization through solid state reactions (Part I); II) dispersion of magnetite nanoparticles within the glass matrix (Part II). In Part I, an alternative synthesis route was developed and validated to obtain glasses containing superparamagnetic phases nucleated by crystallization.The prepared materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM-SQUID). The results showed that glasses obtained by the adapted synthesis of Part I showed chemical structure similar to those glasses obtained by the conventional quick-alkali route, i.e., a glassy phase contenting hydroxyapatite crystals as residues. Iron-containing glasses were also obtained, and it was verified that iron diffusion the glass structure led to a 3Q2 ¨ 2Q3 silicate population conversion, suggesting an intermediate role for iron ions. Thermal treatment in the iron-containing glasses up to 670¿C induced to a hematite nanocrystals nucleation, which makes the glasses to exhibit superparamagnetic properties. .In Part II, the glasses were obtained through quick-alkali route, where magnetic nanoparticles were dispersed during the synthesis. The obtained materials were characterized by XRD, DSC, Raman spectroscopy and field-emission gun scanning electron microscopy and VSM-SQUID. Part II results highlighted that glasses containing magnetite nanoparticles exhibiting superparamagnetic properties were obtained. It was noted that a clustering effect of the magnetite nanoparticles affected dipole-dipole interactions. In addition, along the synthesis, magnetite underwent oxidation, which diminished the saturation moment, but it does not prevent the use of such materials for hyperthermia purposes. Finally, the overall results of both parts (I and II) indicated that promising materials for hyperthermia applications were obtained.

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / In the present work, Dy3+ co-doped SrAl2O4:Eu3+ was produced via proteic sol-gel method, a modified sol-gel route which allows the formation of oxides at lower temperatures than other methods. CO2 laser sintering was used as a method for heat treatment, effective in reducing trivalent europium ions in doped samples. Thermal analysis of the precursors, performed by TG and DTA, revealed that the crystallization of SrAl2O4 phase occurs at approximately 1060 °C. By X-ray diffractometry of the samples characterized before and after sintering was verified monoclinic and hexagonal phases formation. DLS technique revealed the presence of nanosized and micrometric particles, and particle agglomerates, result which was confirmed by SEM images before and after sintering. Micrographs of the fracture surface of a sintered pellet revealed a high degree of densification caused by heat treatment. Photoluminescence measurements showed that the samples after synthesis and before the heat treatment with laser have reddish emission, composed of characteristic narrow emission lines from Eu3+ and more intense emission when the samples are excited at 265 nm. The laser treatment promotes the reduction of Eu3+ to Eu2+ and this effect is confirmed by the presence of a wide emission band in the green region of the spectrum with a maximum emission obtained after excitation at 350 nm. The luminescent decay time of the thermally treated sample was approximately 100 minutes. Via XRF measurements of acquired frits, DTA and TG of the frits, of the pigment and of mixtures of both, and via applications of the mixtures on ceramic plates it was noticed good compatibility in terms of thermal processes, that indicates that the pigment have a potential to be used in ceramic floor tiles. / No presente trabalho, pós cerâmicos de SrAl2O4:Eu3+, Dy3+ foram produzidos pelo método solgel proteico, uma rota de sol-gel modificada, que permite a formação do óxido em temperaturas mais baixas comparativamente a outros métodos. A sinterização a laser de CO2 foi utilizada como método para tratamento térmico, eficiente na redução dos íons trivalentes de európio das amostras dopadas. A análise térmica dos precursores, realizada por meio de DTA e TG, revelou que a cristalização da fase SrAl2O4 acontece em aproximadamente 1060 °C. Por difratometria de raios X verificou-se a formação de fase monoclínica e hexagonal nas amostras caracterizadas antes e após a sinterização. A técnica de EDL revelou a presença de partículas nanométricas, micrométricas e aglomerados de partículas, resultado este que foi confirmado por imagens de MEV de amostras antes e após a sinterização. Micrografias da superfície de fratura de uma pastilha sinterizada a laser revelaram o alto grau de densificação possibilitado pelo tratamento térmico. Medidas de fotoluminescência revelaram que as amostras após a síntese e antes do tratamento térmico a laser apresentam emissão com coloração avermelhada, composta de picos estreitos de emissão característicos do Eu3+ e com emissão mais intensa quando as amostras são excitadas em 265 nm. O tratamento a laser promove a redução do Eu3+ para Eu2+ e este efeito é confirmado pela presença de uma banda larga de emissão na região verde do espectro, com máximo de emissão obtido após excitação em 350 nm. O tempo de decaimento luminescente da amostra tratada termicamente chegou a alcançar aproximadamente 100 minutos. Por meio de medidas de FRX de fritas adquiridas, de DTA e TG de fritas, do pigmento e de misturas entre os dois, e da aplicação das misturas em placas cerâmicas foi possível observar boa compatibilidade em termos dos processos térmicos, o que aponta para um potencial uso do pigmento em placas de revestimento cerâmico.

Neste trabalho, foi realizada a síntese de compostos do sistema PbO CrO3, em especial as composições PbCrO4 e Pb2CrO5, pelo método dos precursores poliméricos, avaliando sua aplicação como pigmentos. Para eliminar o aspecto negativo quanto à toxicidade dos materiais envolvidos, foi realizada a dispersão dos mesmos em SiO2, pelo método sol-gel. As amostras foram caracterizadas estruturalmente por difração de raios X, espectroscopia Raman e por microscopia eletrônica de varredura e transmissão. Pelos resultados de difratometria de raios X e espectroscopia Raman, foi verificado que o método dos precursores poliméricos possibilita a formação de Pb2CrO5 e PbCrO4 monofásicos para ambas as estequiometrias estudadas. Contudo, as imagens de microscopia eletrônica de varredura mostram que as partículas das duas composições apresentam forte coalescência e aglomeração. A caracterização óptica foi realizada pela técnica de reflectância difusa e coordenadas colorimétricas, em que foi determinado que as amostras de PbCrO4 possuem coloração verde-amarelada e que as amostras de Pb2CrO5 possuem coloração que varia do laranja escuro ao vermelho. A dispersão em SiO2 das partículas de Pb2CrO5 foi alcançada, no entanto, este processo provocou a formação de diferentes fases cristalinas, além de alterações na cor, as quais têm uma contribuição significativa da própria matriz SiO2, fato confirmado pela teoria de Kubelka-Munk. A incorporação dessas partículas em uma matriz polimérica de um copolímero de etileno e acetato de vinila (EVA) resultou em uma coloração homogênea da mesma, confirmando a eficácia destas partículas como pigmentos. / In this work, the synthesis of particles from the PbO-CrO3 system, in particular the PbCrO4 and Pb2CrO5 compositions were accomplished, by a polymeric precursor method, evaluating its application as pigments. In order to eliminate the negative toxic aspect of these materials, the dispersion of the same in SiO2 was achieved, by the sol-gel method. The samples were characterized structurally by X-Ray diffraction, Raman spectroscopy and scanning and transmission electron microscopy. From X-Ray diffraction and Raman spectra results it was verified that the polymeric precursors method is able to form single phase Pb2CrO5 and PbCrO4 for both studied stoichiometries. Although, scanning electron microscope images revealed that both compositions present strong coalescence and agglomeration of the particles. Optical characterization was carried out by diffuse reflectance technique and colorimetric coordinates. It was verified that the PbCrO4 samples possess green-yellowish coloration and the Pb2CrO5 samples presents coloration that varies from dark orange to red. The dispersion of Pb2CrO5 particles in SiO2 was reached, however, this process causes the formation of different crystalline phases, besides alteration in color, which have a significant contribution from the SiO2 matrix, confirmed by Kubelka-Munk theory. The incorporation of these particles in a polymeric matrix of ethylene vinyl acetate copolymer (EVA) resulted in the coloration of the same, confirming the efficiency of these particles as pigments.