Le rôle de WO3 et de Fe2O3 dans l’amélioration de l'activité photocatalytique des dépôts de TiO2 a été étudié, à travers la dégradation de l'acide salicylique avec deux sources de lumière : UV et visible.Différentes procédures de couplage de semi-conducteurs ont été entreprises (imprégnation humide / mélange de semi-conducteurs à l'état solide / sol gel). Aussi différents substrats ont été testés (verre ordinaire, ITO).La spectrophotométrie UV-Visible (sans / avec sphère intégratrice), la diffraction des rayons X, la microscopie électronique à balayage et la caractérisation électrochimique ont été réalisées afin de mieux comprendre le comportement et le rôle des semi-conducteurs chargés.Des résultats prometteurs ont été trouvés pour les photocatalyseurs préparés par imprégnation humide et par mélange solide (addition de WO3): le gap d’énergie a diminué, l'activité sous la lumière visible a augmenté en conséquence (2,5% molaire de WO3) pour le premier cas. Une amélioration de 30% sous UV (0,5% WO3) a été atteinte pour le deuxième. La méthode Sol gel améliore le recouvrement sur le substrat de verre, elle semble être appropriée pour assurer un bon contact entre les semi-conducteurs et atteindre l’effet désiré : la séparation de charges. Le photocourant a été nettement augmenté avec l’addition de 4% de WO3 (substrat ITO), en cohérence avec le potentiel de circuit ouvert diminué. Cela confirme le rôle positif de WO3 dans la séparation de charges.Les dépôts Fe2O3-TiO2 préparés par imprégnation humide présentent une activité supérieure avec la lampe blanche comparant à la lampe UV (de 1 à 2% molaire de Fe2O3), l’effet positif de l’introduction du fer a également été observé avec la méthode sol gel. Le Fer sous sa forme ionique peut jouer un rôle positif dans le piégeage de charges, mais il peut former des phases allotropiques qui peuvent être des centres de recombinaison / The role of WO3 and Fe2O3 in enhancing the photocatalytic activity of TiO2 deposits has been investigated through the oxidation of salicylic acid using UV and vis-light irradiation. Different procedures of semiconductor loading (wet impregnation/mixing semiconductors in solid form/sol gel) and deposition were undertaken. Also different substrates were tested (ordinary glass, ITO).UV-Vis spectrophotometry (without/with Integrating sphere), X-ray powder diffraction, scanning electron microscopy and electrochemical characterization were done in order to better understand the behavior and the effective role of loaded semiconductors.Promising results were found for catalysts prepared by wet impregnation and mixing in solid form methods (WO3-loading): the bang gap energy decreased, activity under visible light increased consequently (at 2.5 % molar -WO3) for the first case. 30% improvement under UV (0.5 % -WO3) was reached for the second. Sol gel method enhances coverage on the glass substrate, it seems to be an appropriate method to ensure good contact between semiconductors and reach the charge separation desired effect. Enhanced photocurrent on the ITO substrate confirms the positive role of WO3 in charge separation, in coherence with open circuit potential which was found to be reduced with 4 % WO3 loading. Fe2O3-TiO2 coatings prepared by wet impregnation exhibit higher activity with white lamp comparing to UV lamp (loading from 1 to 2 % Fe2O3), also positive effect of iron introduction was observed with sol gel method. Iron under his ionic form can play positive role in trapping charge, but it can form allotropic phases which can be centers of recombination.Key words: TiO2; WO3; Fe2O3; band gap; salicylic acid; photocatalysis; sol gel

This article presents nano composite TiO2.Fe2O3/laterite materials, which were successfully prepared by hydrometallurgical method. The materials were modified using urea as the nitrogen source. The particles size of the materials is from 20-30 nanometers. The obtained materials can not only absorb arsenic compounds but also enhance the ability of converting As (III) or As (V) into Aso, which is removed from solution. Arsenic removal efficiency of these materials is high. Using sunlight in a hydraulic retention time, about 180 minutes, the arsenic value at the inflow was about 10 mg/L but the outflow was negligible. Covering TiO2.Fe2O3 nano on laterite have brought high economical efficiency, on one hand, it saved material and on the other hand, it can be continuously operated without the centrifugal separation of the nano material. / Bài báo này giới thiệu về phương pháp điều chế vật liệu nano TiO2.Fe2O3 biến tính nitơ được phủtrên đá ong bằng phương pháp thủy luyện. Vật liệu nano thu được có kích thước 20-30 nm. Vật liệu thu được không những có khả năng hấp phụ các hợp chất của asen mà còn có khả năng khử As (III) hoặc As (V) thành Asokhi được chiếu sáng. Sử dụng ánh sáng mặt trời chiếu vào hệ thống xử lý trong thời gian 180 phút có thể loại bỏ được gần như hoàn toàn asen ra khỏi nước mặc dù hàm lượng đầu vào là 10 mg/l. Việc phủ vật liệu TiO2.Fe2O3 nano lên đá ong đã mang lại hiệu quả kinh tế cao, một mặt nó tiết kiệm được vật liệu, mặt khác, vật liệu có thể sử dụng một cách liên tục mà không cần phải tách bằng phương pháp ly tâm.

The thesis, entitled 'Investigation of the conversion of fuels in the presence of solid oxygen carriers and the development of a plasma-assisted chemical looping system for H2 production', presents the work of Yaoyao Zheng in the Department of Engineering, University of Cambridge, for the degree of Doctor of Philosophy. The thesis focused on chemical looping conversion of fuels, which employ oxygen carriers to supply oxygen, followed by the regeneration of the reduced oxygen carriers in air. Combustion of a Polish coal-derived char was first carried out in a fluidised bed reactor in the presence of Fe2O3 or ZrO2-supported Fe2O3. CO2 was introduced to the fluidised bed, to allow the char to be gasified in situ, prior to the reaction with the oxygen carriers. The presence of Fe2O3 did not alter the gasification step, given that the gasification of the char was free of external mass transfer limitation. A numerical model was developed to describe the gasification behaviour, as well as predicting the effect of CO on gasification. The inhibition effect of CO on char gasification was found more significant than expected. Combustion of biomass (wood pellets), by Fe2O3 or mayenite-supported CuO was studied in a fluidised bed. This was to understand how efficient the wood pellets were combusted by the oxygen carriers, as well as the distribution of the products. A tar measurement system, based on a plasma reactor, was first developed. With the developed measuring system, it was found that both Fe2O3 and mayenite-supported CuO were efficient for combusting wood pellets. Particularly, the CLOU nature of CuO makes mayenite-supported CuO a promising candidate for direct combustion, without introducing any reactive gaseous oxidant. The final part of the dissertation was focused on developing a plasma-assisted chemical looping system for H2-rich gas production (PCLH) from CH4 at mild temperatures (~ 673 K). SrFeO3-, Fe2O3, and Ni-doped SrFeO3- and Fe2O3 were investigated as the packing material. Total combustion of CH4 was observed in SrFeO3-. The addition of Ni onto SrFeO3- significantly improved the selectivity towards H2; whilst it was only active in the fresh cycle. Fe2O3 was found to be inert for converting CH4; however, the addition of Ni to form NiO/Fe2O3 dramatically improved H2 production and the reactivity maintained high for three redox cycles. The energy cost of such PCLH was comparable to that of water electrolysis.

Ces quinze dernières années, l'élaboration d'oxydes fonctionnels sous forme de couches minces a connu un essor important. En microélectronique, ainsi qu'en spintronique, il est important de pouvoir synthétiser des films cristallins avec une épaisseur nanométrique et une interface abrupte. Dans cette configuration, les propriétés des films diffèrent des propriétés du matériau massif, notamment de part l'importance des conditions à l'interface entre le film et le substrat. Cette étude est focalisée sur la croissance par MOCVD a injection pulsée d'oxydes a base de fer : Fe3O4, g-Fe2O3 et BiFeO3. L'originalité de ce travail découle des études in situ des premiers stades de la croissance des films par AFM (microscope a force atomique) sous ultravide.

No description available.

In this work, a high-performance hybrid supercapacitor is assembled with N-doped reduced graphene oxide (N-rGO) decorated with Fe2O3 (Fe2O3/N-rGO) as the anode, and NiCo layered double hydroxide integrated with conductive Co(OH)2 (NiCo LDH/Co(OH)2) as the cathode. The two main pseudo-capacitive materials are modified by different materials (N-rGO and Co(OH)2) to enhance the conductivity. For anode, the Fe2O3 nanoparticles are uniformly dispersed on N-rGO via a facile solvent-thermal method. The highly conductive Fe2O3/N-rGO exhibits a superior capacitance of 912.9F/g at 1 A/g and retains 84% at 30 A/g. The NiCo LDH/Co(OH)2 cathode also synthesized by a convenient solvent-thermal method delivers a high specific capacitance of 2220.0F/g at 1 A/g and retains 70% at a high current density of 50 A/g. Utilizing these electrodes, we successfully fabricate a hybrid battery-like supercapacitor with an excellent energy density of 103.3 Wh/kg at an outstanding power density of 790 W/kg, an excellent capacitance of 296.3F/g at 1 A/g and a remarkable cyclic stability with 92% retention after 1000 cycles at 10 A/g. Due to the elaborately designed electrode materials, the battery-like supercapacitor exhibits excellent electrochemical properties and is an inspiration for future energy storage devices.

No description available.

Cette thèse décrit une stratégie de synthèse de nouvelles générations des nanoparticules (NPs) pour applications biomédicales, visant à une amélioration de leurs performances pour l’imagerie, le diagnostic thérapeutique. Ces NPs présentent plusieurs fonctionnalités leur permettant de réaliser des tâches multiples. Deux types de sondes bimodales ont été développés et étudiés afin d'évaluer leur potentiel comme agents (1) de contraste en IRM et (2) luminescents. Ces objetscombinent les propriétés des complexes de lanthanide (Ln3+) et celles des NPs de silice ou de type coeur-écorce Fe2O3@SiO2 pour une imagerie bimodale. Ces NPs testées sur des cellules vivantes ont permis d’illustrer la preuve du concept aussi bien en IRM avec une augmentation d'intensité des images et un impact significatif sur les relaxivities r1, r2 et r2* qu’en photoluminescence. L’étude du système coeur-écorce a montré que l’influence du contrôle fin de l’écorce autour du noyau d'oxyde de fer a pu être modélisée. / This thesis describes a strategy of synthesis of new generations of nanoparticles (NPs) for biomedical applications, aiming at an improvement of their performances for the imaging, and the therapeutic diagnosis. These NPs present several functionalities enabling them to carry out multiple tasks. Two types of bimodal probes were developed and studied so as to evaluate their potential as contrast agents (1) in MRI and (2) and luminescence. These objects combine the properties of the lanthanide complexes (Ln3+) and those of NPs of silica or core/shell Fe2O3@SiO2 for a bimodal imaging. These NPs tested on living cells were able to illustrate the proof of the concept not only in MRI with an increase of intensity of the images and a significant impact on the relaxivities r1, r 2 and r2* but also in photoluminescence. The study of the core/shell system showed that the influence of the fine control of the shell around the iron oxide core could be modeled.

Made available in DSpace on 2016-06-02T19:55:32Z (GMT). No. of bitstreams: 1 4381.pdf: 2748711 bytes, checksum: 4ba9831d0665b24b6f48f775d30927d2 (MD5) Previous issue date: 2012-04-13 / Universidade Federal de Minas Gerais / The minimization of the emissions of nitrogen oxides (NOx) is a subject of crucial interest, since them cause serious environmental problems which affect human health, vegetation and fauna. With the purpose to abate NOx, processes involving their catalytic reduction show strong potential. In the case of the reduction of NO with CO a meaningful advantage arises, once both pollutants are removed simultaneously. In order to obtain efficient and stable catalysts for this reaction, many studies have been done with the aim to improve the catalytic activity by achieving a better favorable metal-support interaction to the occurrence of the reaction and a better distribution of the active phases on the support. In this context, the objective of this study was to prepare Cu, Fe and Co based catalysts supported on TiO2, CeO2 and ZrO2 to be applied in the abatement of NO with CO. The addition of the precursors of the active phases was made during the synthesis of the support via the sol-gel method (in situ addition). Furthermore, catalysts with the same composition were prepared by conventional methods. Results from the N2 adsorption/desorption measurements show that the sol-gel method was efficient to prepare supports with improved textural properties. H2-TPR and UVVIS-DRS data evidenced the presence of Cu, Fe or Co oxides in the respective catalysts, which mostly did not show characteristic X-ray diffraction peaks of those oxide phases, suggesting their high dispersion on the supports. In general, results of the reduction of NO to N2 with CO revealed that the catalysts prepared via sol-gel are as active as those prepared by conventional routes, which demonstrate the great potential of the catalysts preparation via the sol-gel in situ procedure, which diminishes the number of the synthesis steps saving time and energy. In general, among the studied supports, ceria presented a more favorable metal-support interaction. In the presence of O2, SO2 and water steam, catalysts 6,5Cu/CeP, 5,5CuZrSG and 8,4Fe/TiC showed no significant changes in their activity and selectivity, indicating that they present high stability to be used under the severe conditions of real processes. / A minimização das emissões de óxidos de nitrogênio (NOx) é assunto de interesse crucial, pois geram graves problemas ambientais que afetam à saúde humana, à flora e à fauna. Para abater os NOx, processos envolvendo à sua redução catalítica apresentam forte potencial. No caso da redução catalítica de NO com CO, tem-se a vantagem adicional de minimizar as emissões de ambos poluentes. Para a obtenção de catalisadores eficientes e estáveis para essa reação, muitos estudos têm sido desenvolvidos no sentido de aumentar a atividade por meio de uma interação metalsuporte mais favorável ao processo reativo e de se conseguir uma melhor distribuição da fase ativa no suporte. Nesse contexto, o objetivo do presente estudo foi preparar catalisadores para a redução de NO com CO à base de óxido de Cu, Fe ou Co, suportados em TiO2, CeO2 ou ZrO2, com a adição do precursor da fase ativa durante a preparação do suporte via processo sol-gel (adição in situ). Além disso, catalisadores de mesma composição foram preparados por rotas convencionais. Resultados de medidas de adsorção/dessorção de N2 dos suportes mostram que o método sol-gel utilizado é mais eficiente no preparo de suportes com propriedades texturais melhoradas. Análises de RTP-H2 e ERD-UVVIS evidenciaram a presença dos óxidos de Cu, Fe ou Co em todos os catalisadores, os quais, em sua maioria, não apresentaram picos de difração de raios X característicos dessas fases, o que sugeriu sua alta dispersão no suporte. Em geral, os resultados da redução de NO a N2 com CO mostraram que os catalisadores preparados pelo método sol-gel in situ são tão ativos quanto os catalisadores preparados por métodos convencionais, o que demonstra o forte potencial desse procedimento, que resulta no uso de um número menor de etapas na preparação do catalisador, com a consequente economia de tempo e energia. De maneira geral, dentre os suportes estudados a céria mostrou uma relação metal-suporte mais favorável ao processo de óxidoredução. Os catalisadores 6,5Cu/CeP, 5,5Cu-ZrSG e 8,4Fe/TiC, na presença de O2, SO2 e vapor de água não apresentaram alteração significativa da sua atividade e seletividade, mostrando uma alta estabilidade para atuar sob as drásticas condições dos processos reais.

This thesis deals with the combined ultra-high vacuum (UHV) and electrochemical (EC) studies of selected iron oxide surfaces, namely Fe3O4(001) and -Fe2O3(012). The state-of- the-art knowledge regarding these surfaces is briefly reviewed, and importance of understanding these materials in the electrochemical environment is discussed. The design of the transfer system between UHV and EC environment is presented; individual features of the system are thoroughly discussed and the system is used for testing the stability of the Fe3O4(001) (2×2)R45° surface reconstruction in ambient conditions. The experimental results presented in this thesis show that the Fe3O4(001) (2×2)R45° reconstruction, utilized as an adatom array for single atom catalysis studies, survives both exposure to air and to liquid water, if the exposure is achieved in well-controlled fashion. Further, this thesis presents the first-ever atomic scale scanning tunneling microscopy (STM) study of the -Fe2O3(012) surface, which is important for photoelectrochemical water splitting. STM images of two surface reconstructions of the -Fe2O3(012) surface known to date are presented. A bulk terminated model of the (1×1) reconstruction is confirmed and a novel surface structure model for the (2×1) reconstructed surface is proposed. Adsorption studies of H2O and O2 on the (2×1) reconstructed surface are documented by timelapse STM.