Tesi sul tema "Oxide matrices"
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Frazier, Laura M. "Superabsorbent Nanofiber Matrices". University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1164646276.
Leite, Rubim Rafael. "Graphene oxide sheets confined within anisotropic fluid matrices". Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0209/document.
Since the discovery of graphene oxide (GO), the most accessible of the precursors of graphene, this material has been widely studied for applications in science and technology. The motivation of this work is to study with a fundamental perspective the coupling between amphiphilic bilayers, which can be seen as an anisotropic matrix formed of two-dimensional objects, and another two-dimensional object, namely the graphene oxide sheet when they are dispersed in a common solvent. The competition between the intrinsic elasticities of the bilayers and GO sheets, as well as between direct bilayer-bilayer, bilayer-GO and GO-GO interactions allows us to envisage a rich polymorphism, depending on the composition of the system. Following the development of a dedicated procedure for controlling in an extended range of GO content the binary GO-water system, the confined domain of aqueous GO dispersions was first investigated, and the ternary phase diagram then constructed. The obtained systems have been characterised, using techniques such as optical microscopy, light and x-ray scattering. Elastic and thermodynamic properties have been described by applying, and adapting to the scope of this study, models for two-component lamellar stacks
Desde sua descoberta, o grafeno oxidado (GO), o mais acessível dos precursores do grafeno,tem sido amplamente utilizado para aplicações na ciéncia e tecnologia. A motivação destetrabalho é de estudar, de um ponto de vista fundamental, o acoplamento entre bicamadas anfifílicas auto-organizadas (que podem ser vistas como uma matriz anisotrópica formada por objetos bidimensionais) e um objeto ele mesmo bidimensional, neste caso a folha de óxido de grafeno, quando estão dispersados em um solvente comum.A competição entre as elasticidades intrínsecas das bicamas e das folhas de GO, assimcomo as interaçãoes diretas bicamada-bicamada, bicamada-GO e GO-GO, permitem esperar um rico polimorfismo em função da composição do sistema. Seguindo o desenvolvimento de um procedimento destinado ao controle, em um intervalo extendido da quantidade de GO, o sistema binário GO-água, o domínio confinado de dispersões aquosas de GO foi explorado e, em seguida, o diagrama de fases ternário contruído.Os sistemas obtidos foram caracterizados por t_ecnicas como microscopia ótica, espalhamento dinâmico de luz e espalhamento de raios-x à baixos ângulos. As propriedadeselásticas e termodinâmicas foram descritas pela aplicação de modelos inicialmente concebidos para fases lamelares à dois constituintes e adaptados ao escopo deste estudo
Silva, Nuno João de Oliveira. "Structural and magnetic studies on iron oxide nanoparticles in hybrid matrices". Doctoral thesis, Universidade de Aveiro, 2006. http://hdl.handle.net/10773/8944.
Este trabalho aborda algumas propriedades magnéticas e estruturais de nanopartículas de óxidos e óxidos-hidróxidos de ferro crescidos em matrizes híbridas orgânicas-inorgânicas. As matrizes híbridas, denominadas di-ureasils e obtidas pelo processo sol-gel, são compostas por uma rede siliciosa ligada covalentemente por pontes ureia a cadeias orgânicas de diferente peso molecular. A estrutura local dos di-ureasils não dopados está modelada como grupos de domínios siliciosos com dimensões nanométricas, estruturalmente correlacionados no seio de uma matriz rica em polímero. Neste trabalho mostra-se que os di-ureasils permitem o crescimento controlado de óxidos e óxidos-hidróxidos de ferro, incluindo a magnetite, maguemite, oxihidroxinitrato de ferro e ferrihidrite. O crescimento das nanopartículas de ferrihidrite dá-se em condições ácidas à superfície dos domínios siliciosos, junto aos grupos carbonilo, que funcionam como pontos de nucleação. Desse modo dá-se uma nucleação heterogénea, onde o tamanho das nanopartículas depende da concentração de ferro (entre 1 e 6% em massa), sendo a concentração de partículas constante. As propriedades magnéticas das nanopartículas de ferrihidrite revelam a existência de interacções antiferromagnéticas e de momentos descompensados. A contribuição destas duas componentes nas curvas de magnetização em função do campo magnético pode ser separada usando um método aqui proposto, o que permite um adequado estudo da evolução do momento magnético com a temperatura. O estudo das propriedades magnéticas dinâmicas das partículas de ferrihidrite, através de susceptibilidade ac, medidas de relaxação e medidas de efeito Mossbauer, permitiu estudar a evolução das interacções dipolares em função da concentração de ferro, bem como determinar a distribuição de barreiras de energia de anisotropia no caso em que essas interacções são desprezáveis. É apresentado um novo método para comparação desta distribuição com a distribuição de tamanhos, que permitiu concluir que os momentos magnéticos descompensados estão aleatoriamente distribuídos em volume. Usando baixas concentrações de água, foi possível crescer fases de oxihidroxinitrato de ferro com diferentes graus de cristalinidade, sendo algumas precursoras da ferrihidrite (como observado noutros trabalhos) e sendo outras novas fases. O crescimento de nanopartículas de maguemite e magnetite acontece após incorporação de iões de Fe2+ e Fe3+ seguidos de tratamento básico e térmico. Estes sistemas apresentam propriedades magnéticas típicas de nanopartículas superparamagnéticas sem interacções dipolares. As propriedades magnéticas dependem criticamente da existência de grupos isocianato livres, que actuarão como pontos de nucleação.
The present work focus on the structure and the magnetic properties of iron oxide and iron oxide hydroxide nanoparticles grown in organic-inorganic hybrids. The sol-gel derived matrix, termed di-ureasils, is a siliceous network to which oligopolyoxyethilene chains with different molecular weight are grafted by means of urea cross-links. The di-ureasils local structure was modelled as groups of nanometric siloxane correlated domains embedded in a polymericrich media. In this thesis, the controlled growth of ferrihydrite, iron(III) oxyhydroxynitrate phases, maghemite and magnetite in di-ureasils is demonstrated. Ferrihydrite nanoparticles are formed at low pH on the siliceous surface, where the carbonyl groups act as nucleation points. This implies an heterogeneous nucleation, where the nanoparticles size depend on the amount of iron (in the 1 to 6% wt range) and the nanoparticles concentration is constant. The ferrihydrite nanoparticles have antiferromagnetic and uncompensated/canted moments, responsible for linear and saturation components in the dependence of the magnetization with field, respectively. These components can be separated by a new method here presented and an accurate dependence of the magnetic moment with temperature determined. The dynamic magnetic properties of ferrihydrite were studied by ac susceptibility, relaxation and Mossbauer measurements. These studies allowed the determination of the evolution of the dipolar interactions with the iron content and the determination of the anisotropy energy barrier distribution in cases where such interactions are negligible. Comparing the energy barrier distribution with the size distribution allowed to conclude that the uncompensated moments are randomly distributed in volume. This conclusion is based on a new method here presented, that uses distributions to investigate the power law relation between physical quantities. Antiferromagnetic iron(III) oxyhydroxynitrate phases with different degrees of crystallinity are formed when using low water concentrations in the sol-gel process. Some of these are precursors of ferrihydrite, as previously found in literature, but others constitute new phases. Maghemite and magnetite nanoparticles can be grown inside diureasils after the incorporation of Fe2+ and Fe3+ ions, followed by basic and thermal treatment. The magnetic properties show the existence of noninteracting superparamagnetic nanoparticles. Evidence for the possibility of tuning the magnetic properties of the system by allowing the existence of free isocyanate groups acting as nucleation sites was found.
Bowes, Sarah-Jane. "The study of Si-O bonds in low temperature matrices and in the gas phase". Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342658.
Rodríguez, Martínez Yerila. "Plasmonic Cu nanoparticles inclusion in ZnO and Cu2O matrices for enhanced photoconversion of all-oxide optoelectronics". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0208.
In this work we present the results on in-situ growth of plasmonic copper (Cu) nanoparticles (NPs) into a p-Cu2O matrix by using reactive magnetron sputtering of a Cu target and adjusting the oxygen flowrate. It was possible to observe, for oxygen-poor conditions, the formation of CuNPs-Cu2O composites presenting the signature of the localized surface plasmon resonance (LSPR) phenomenon. Devices based on the studied nanocomposites interfaced with zinc oxide (ZnO) were characterized by J-V and spectral photocurrent measurements, showing a photocurrent density increase under optical illumination as a result of the plasmonic particles incorporation and consequent hot carriers injection. In the second part of the manuscript, the results about the rapid thermal annealing (RTA) of the CuNPs-Cu2O composites under oxygen-poor conditions and their properties evolution when temperature increases are presented. At temperature higher than 150 ºC it was possible to see a copper segregation towards the surface, increase in the crystal preferential orientation of Cu2O and improvement of the LSPR signal. Electrical response of devices constituted by the composite layers interfaced with ZnO and annealed at 200 ºC showed a further increase in the photocurrent resulting from the LSPR of Cu NPs at the devices surface. Finally, the synthesis of Cu nanoparticles through a gas aggregation source (GAS) and the subsequent fabrication of ZnO-CuNPs multilayer structure with plasmonic response were studied. The resulted composite revealed LSPR response and the presence of Cu particles acting as nucleation points for highly oriented ZnO conical grains
Xuankun, Li. "Effect of Surfactants on the Behaviors and Transport of Metal Oxide Nanomaterials in Aqueous Matrices and Porous Media". 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225578.
Thumma, Sridhar. "Characterization of water insoluble and water soluble drugs in hot-melt poly (ethylene oxide) matrices for oral transmucosal delivery /". Full text available from ProQuest UM Digital Dissertations, 2008. http://0-proquest.umi.com.umiss.lib.olemiss.edu/pqdweb?index=0&did=1850456491&SrchMode=1&sid=3&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1279304005&clientId=22256.
Typescript. Vita. "March 2008." Major professor: Dr. Michael Repka Includes bibliographical references (leaves 306-326). Also available online via ProQuest to authorized users.
Sim, Seok-Hoon. "Modifications of polyimides and polyimide-inorganic oxide hybrids with perfluoroether oligomers for use as matrices for carbon-fibre composites". Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/35624.
Vallerini, Barbosa Itália. "Nanocristaux oxydes luminescents pour le développement de nanosondes de température in vivo". Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALI125.
Biological thermal modifications are common events during abnormal cellular metabolic activities. Indeed, thermal aberrations – such as an increase in local tissue temperature – are directly related to the detection of inflamed areas, the presence of tumors, or other diseases. In addition to contributing to the diagnosis of diseases, the determination of local temperature in biological systems can also help with their treatment. For instance, in hyperthermia, the increase in temperature must be induced in tumor tissues up to cytotoxic levels in order to kill cancer cells and therefore, it assists in the cancer treatment. However, the increase in temperature must be carried out in a controlled and well-localized manner to target cancer cells, while avoiding overheating of surrounding healthy tissue. Furthermore, to determine such biological aberrations, temperature variations must be accurately determined. The thermometric performance of the nanothermometers was determined by calculating the relative thermal sensitivity (S_r) using the ratiometric luminescence intensity approach. Furthermore, our study made it possible to raise some hypotheses that can effectively contribute to the thermometric performance of thermal probes. We use the technique of the intensity ratio of two luminescence peaks for which the values of S_r can be optimized by co-doping the nanocrystals with two, or more, Ln3+ ions and by using oxide matrices presenting different phonon energies. Thus, due to its generic nature and synthesis flexibility, the Pechini method was chosen to synthesize several oxide matrices, Y2O3, Y2Ge2O7, Y3Al5O12 (YAG), Y3BO6 and YBO3. The nanocrystals were firstly monodoped with Nd3+ and posteriorly, codoped with Nd3+ -Yb3+ to improve the thermal probe properties within the biological windows of near infrared. In addition, we optimized the doping concentrations in the host matrices for greater efficiency in luminescence detection in biological organisms. We experimentally observed that Sr values are strongly impacted to the phonon energy of the matrix. We analyzed that by Nd3+ -Yb3+ codoping the thermometric performance of nanocrystals is improved compared to nanocrystals mono doped with Nd3+. Our study of different oxides shows that the YAG and Y2O3 matrices are the most promising matrices for the luminescence nanothermometry in vivo application. Lastly, YAG individual nanocrystals (non-agglomerated as in the case of Pechini syntheses) of size 60 nm and controlled morphology were obtained in solution by the solvothermal method to advance in further studies in biological applications. We observed that the YAG nanothermometers suitable for the purpose have a S_r equal to 0.47 %·K-1 and a thermal resolution of 0.3 K. In vivo experimental tests are required to validate the findings of this study; however, our results obtained on the performance of YAG: Nd3+ -Yb3+ nanocrystals has been showing high potential for in vivo applications of ratiometric luminescence nanothermometry
Molloy, James. "Argon and argon-chlorine plasma reactive ion etching and surface modification of transparent conductive tin oxide thin films for high resolution flat panel display electrode matrices". Thesis, University of Ulster, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243741.
Boutenel, Florian. "Comportement d’une matrice alumine-silice au cours de l’élaboration de composites à matrice céramique oxyde/oxyde". Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2020. http://www.theses.fr/2020EMAC0011.
Oxide/oxide ceramic matrix composites can be used for structural applications operating continuously at temperatures between 500°C and 900°C under oxidizing environments, such as in areas close to aircraft engines. In particular, composites based on a matrix combining alumina and silica are promising. In addition, the processing of these materials comprises several steps. Two of them are essential: the impregnation of the fibrous reinforcement with the suspension and the sintering of the matrix. This PhD thesis focuses on the processing of oxide/oxide ceramic matrix composites using an alumina-silica matrix. It is derived from an aqueous suspension in which the two species are initially present as particles. The aim of this work is to study the behaviour of such a system during the various stages of the manufacturing, i.e. to establish the relationships between processing/microstructure/properties, in order to propose an optimal composition of the matrix regarding the process and the required properties. In particular, the silica proportion will be a crucial parameter. Firstly, since the quality of the impregnation step is based on the ability of the suspension to flow within the fibrous structure, a rheological characterization of the oxide suspensions has been carried out. The rheological behavior has been interpreted on the basis of the domains of predominance of the different interactions within the suspension. Also, the influence of the various suspension characteristics, such as the solid fraction and the alumina-silica ratio, has been examined. Then, the behaviour of this system during the sintering has been studied since this thermal treatment should lead to a microporosity that respects the concept of weak matrix composites. The sintering mechanisms have been identified while the influence of the various parameters on the kinetics has been qualified. Also, relationships with the mechanical properties of the matrix have been established. Finally, composites with Nextel™ 610 reinforcements and a porous alumina-silica matrix have been fabricated and characterized
Kiselewsky, Michael. "Untersuchungen an Singulettcarbenen und Carbonyl-O-oxiden in kryogenen Matrizes". [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=961903201.
Ben, Ramdane Camélia. "Etude et modélisation du comportement mécanique de CMC oxyde/oxyde". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0077/document.
Oxide/oxide CMCs are good candidates for thermostructural applications. Themechanical behaviour and damage mechanisms of two alumina/alumina composites with two andthree dimensional woven reinforcements were studied and compared. The microstructure of theseweak matrix CMCs was characterized by porosimetry and NDT methods, such as IR thermography,ultrasound scanning and X-ray tomography, which highlighted initial defects. The mechanicalbehaviour was studied through tensile tests, as well as compression tests in the case of the twodimensionalreinforced CMC. These tests were conducted at room temperature, in the fibres directionsand in the ±45° direction. In order to fully exploit these tests, several extensometry and damagemonitoring methods, such as IR thermography and acoustic emission, were used. Young’s moduli andmaximum stresses and strains of the two-dimensional reinforced CMC developed at Onera appearedto be higher than those available in the literature. The damage mechanisms of the materials weredetermined by post mortem SEM observations and in situ testing in a SEM, which made it possible toassess the nocivity of initial defects. Studying the mechanical behaviour of these composites finallyenabled the development of a three-dimensional damage model that will facilitate the furtherdevelopment of such materials, through finite element analysis. Finally, some improvements regardingthe manufacturing processes and the instrumentation for damage monitoring were suggested forfuture studies
Nualas, Florence. "Fonctionnement en oxydation de matériaux composites céramiques (CMC) dans des environnements aéronautiques". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00993488.
Klangsin, Junya. "Incorporations de nanoparticules de silicium dans des matrices obtenues par voie Sol-Gel : élaboration et caractérisations". Lyon 1, 2008. http://n2t.net/ark:/47881/m6p55kmn.
The optoelectronic properties of silicon nanoparticles are very different from those of bulk silicon. Their low sizes (a few nanometers) provide the quantum properties and they present a strong luminescence in the visible at ambient temperature. Therefore, they are very interesting for different applications (for example: light-emitting diode (LED) based on silicon only, non volatile memory, sensor, drugs transport, etc…). In general, these nanoparticles have to be integrated in the matrix in order to be able to exploit their properties. In this work, we have proposed to incorporate the silicon nanoparticles, obtained by electrochemical etching of a silicon substrate and then milling, in oxide matrices by using the Sol-Gel method. The principal advantages of these techniques are: low cost, simplicity, and various choices of matrix offered. Three matrices chosen herein (SiO2, ZrO2 and TiO2) allow us to sweep a wide range of band gap and dielectric constant. For each matrix, different concentrations of nanoparticles and annealing conditions were carried out. The obtained results are quite satisfactory. Structural studies confirm the presence of nanoparticles in every matrix. The compressive stress induced by their matrix is also observed. Photoluminescence studies show that the nanoparticles conserve their optical properties when they are incorporated in the SiO2 matrix and the ZrO2 matrix but not in the TiO2 matrix. The stability of the nanoparticles towards the influence of annealing temperature is more important for the SiO2 matrix. Besides, in photoluminescence study, the coupling effect among nanoparticles increasing with their concentration is observed
AKRAM, MUHAMMAD YASIR. "Giunzione di compositi a matrice ceramica a base ossidica". Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2751274.
Strauss, Mathias 1982. "Efeito da nanoestruturação de óxidos semicondutores suportados em matrizes mesoporosas sobre a atividade fotocatalítica". [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250546.
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Materiais baseados no óxido de titânio (TiO2) são bastante explorados no desenvolvimento de tecnologias ambientalmente amigáveis que utilizam a radiação solar para a remediação de poluentes atmosféricos e na água, bem como na geração de energia. Aspectos relacionados aos efeitos da nanoestruturação sobre a atividade fotocatalítica do TiO2 são amplamente discutidos na literatura. Dentro deste contexto, a presente tese teve como objetivos centrais estudar os efeitos da cristalinidade, tamanho de cristalito e dopagem com metais de transição de nanopartículas de TiO2 suportadas em sílicas mesoporosas sobre atividade fotocatalítica. Foram utilizados dois protocolos distintos de síntese: método sol-gel (para estudo do efeito da cristalinidade) e método de ciclos de impregnação-decomposição (para estudo do efeito do tamanho de cristalito e dopagem com metais de transição). As propriedades estruturais, ópticas e eletrônicas das nanopartículas de TiO2 foram caracterizadas principalmente por difratometria de raios X e espectroscopias Raman (aplicada ao Modelo de Confinamento de Fônons) e UV-vis (aplicada ao Modelo de Aproximação da Massa Efetiva). A atividade fotocatalítica dos materiais foi avaliada quanto à fotodescoloração de azul de metileno, fotodegradação de ácido salicílico, fotogeração de radicais hidroxila e/ou fotooxidação de iodeto. Os materiais sintetizados a partir da rota sol-gel seguida por tratamento térmico em diferentes temperaturas permitiram o entendimento dos efeitos da cristalinidade de nanopartículas de TiO2 de tamanho fixo sobre a atividade fotocatalítica. Nanopartículas de baixa cristalinidade apresentaram menor ordem e maior quantidade de defeitos estruturais que atuaram como sítios de aprisionamento e recombinação dos portadores de carga diminuindo a atividade fotocatalítica. Quanto a influência do tamanho de cristalito, o aumento no tamanho diminuiu o valor em energia da banda proibida e aumentou a faixa de absorção do espectro UV-vis dos materiais, o que aumentou a capacidade de fotogeração de radicais OH. Por outro lado, o aumento do tamanho das nanopartículas leva também a uma redução na razão aréa superficial/volume das nanopartículas de TiO2 que trouxe redução na atividade catalítica, frente as reações de fotodescoloração de azul de metileno e fotodegradação de ácido salicílico, deixando clara a dependência com os mecanismos de adsorção e dessorção dos reagentes e produtos na superfície do fotocatalisador. A dopagem das nanopartículas de TiO2 com diferentes metais de transição (Mn, Co, Zn, Ce, Cu, Mo, Ni e Sn) promoveu a redução no valor da banda proibida e aumento na absorção de luz na região do visível. A fotooxidação de I- pelas nanopartículas de TiO2 dopadas mostrou-se fortemente dependente da formação de defeitos pontuais e distorções estruturais que são responsáveis pelo aprisionamento e recombinação dos elétrons e buracos
Abstract: Titanium oxide (TiO2) based material are much explored in the development of environmental friendly technologies that use the solar radiation to mitigate atmospheric and water pollutants, and on energy generation. Aspects related to the nanostructure of the TiO2 over its photocatalytic activity had been widely discussed in the literature. In this context, this thesis has as main objective studing the effects of the cristallinity, cristallite size and transition metals doping of TiO2 nanoparticles supported in mesoporous silicas over the photocatalytic activity. Two distinct synthesis protocols were used: sol-gel method (to study the cristallinity effects) and the impregnation and decomposition cycles method (to study the cristallite size and transition metal doping effects). The structural, optical and electronic properties of the TiO2 nanoparticles were studied using mainly X ray diffractometry, and Raman (applied to the Phonons Confinament Model) and UV-vis (applied to the Effective Mass Approximation Model) spectroscopies. The photocatalytic activity of the materials were tested against the photodecolorization of methylene blue, photodegradation of salycilic acid, photogeneration of OH radicals and/or photooxidation of I-. The material synthesized using the sol-gel route followed by thermal treatment permitted the understanding of the cristallinity effects of size-fixed TiO2 nanoparticles over the photocatalytic activity. Nanoparticles with low cristallinity presented lower structural order and higher number of structural defects that acted as trapping and recombination sites lowering the photocatalytic activity. Regarding the influence of the crystallite size, the increase in size decreased the band gap energy value and enhanced the UV-vis absorption range of the materials, that resulted in an enhanced OH radicals photogeneration capacity. By the other side, the increase in the particle size lead also to a reduction of the surface area/volume ratio of the TiO2 nanoparticles that brought reduction in the catalytic activity at the photodecolorization of methylene blue and photodegradation of salycilic acid reactions, letting clear its dependency with the adsorption and dessorption mechanisms of the reagents and products on the photocatalyst surface. Doping the TiO2 nanoparticles with different transition metals (Mn, Co, Zn, Ce, Cu, Mo, Ni e Sn) resulted in band gap lowering and enhancement of the visible radiation absorption. The photooxidation of I- had shown strong dependence with the generation of punctual defects and structural distortions that are responsible for the electrons and holes trapping and recombination
Doutorado
Quimica Inorganica
Doutor em Ciências
Carles, Valérie. "Elaboration et caractérisation physico-chimique et électromagnétique de nanoparticules ferromagnétiques dispersées dans une matrice du type oxyde". Toulouse 3, 1995. http://www.theses.fr/1995TOU30227.
Billard, Romain. "Mise au point d’un composite à fibre oxyde et matrice d’aluminosilicate de baryum modifiée". Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0291/document.
The main purpose of the present work is to propose a new BaAl2Si2O8 (BAS) composite reinforced with alumina fibers exhibiting similar physical properties but a higher refractoriness than SiO2 / SiO2 composites. The hexagonal crystal form of BAS is the stable one at high temperatures. However, it is metastable below 1590 °C and it is therefore necessary to stabilize it in order to prevent crystalline transformations. The stabilization of the hexagonal form by atomic substitution, including rubidium at 5 atomic % has been chosen. Regarding the matrix BAS composite, the alumina fibers selection has been justified by their low physical and chemical reactivity with this material. Several elaboration methods of the BAS matrix and of the BAS / alumina composite have been investigated. The development by "reactive spark plasma sintering" (R-SPS) brings an important benefit in terms of reduced elaboration time and yield. This saving time thus limits the BAS exposure to high temperatures and the risk of transformation into monoclinic. Nevertheless, the SPS shaping of oxide materials, including the BAS, is confronted with the presence of important thermal gradient within the sample. This is why shaping in a heating mold is currently in progress, as an alternative to the SPS. This system should allow the use the same thermal cycles as for SPS, but with lower thermal gradient
Silva, Rondes Ferreira da [UNESP]. "Sistemas de liberação controlada de óxido nítrico baseados em ditiocarbamatos". Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/94502.
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O óxido nítrico (NO) é um radical livre com inúmeras funções fisiológicas, tais como regulação da pressão sanguínea e sistema nervoso. O desenvolvimento de Sistemas de Liberação Controlada (SLC) de NO no organismo são de grande importância em tratamentos de diversas patologias, bem como para a indústria farmacêutica. A espectroscopia de ressonância paramagnética (RPE) foi utilizada para detecção e caracterização da taxa de liberação de NO. Esta é uma técnica amplamente utilizada no estudo de entes paramagnéticos existentes em sistemas biológicos. Os SLCs de NO foram desenvolvidos a partir da incorporação do agente aprisionador de NO, FeDETC, nas matrizes biocompatíveis de látex e siloxanopoli(oxipropileno) (PPO). O foco deste trabalho é obter membranas para liberação controlada de NO que sejam capazes de liberar NO localmente através de estímulos externos. A matriz de PPO apresentou forte sinal de NO, resistência mecânica e estabilidade igual às melhores matrizes sólidas já obtidas em nosso laboratório. Mantendo a matriz de PPO em ambiente sem iluminação e à temperatura ambiente, o NO permanece aprisionado ao FeDETC por até 45 dias nas primeiras sínteses e 33 dias nas últimas sínteses. Em experimentos feitos com a matriz de látex foi observado que o NO permanece complexado ao FeDETC até 61 dias e 45 dias para amostras estocadas no escuro à temperatura ambiente e sob temperatura de 50C. Em ambas matrizes, foi observado que a taxa de liberação de NO do sistema pode também ser acelerada através da aplicação de um campo magnético ou através do aumento de temperatura. Estas características fazem do PPO e látex , matrizes ideais para construção de SLCs de NO.
Nitric oxide (NO) is a free radical species with multiples physiological functions, such as the regulation of blood pressure and nervous system. The development of drug delivery systems (DDS) of NO in the body are of great importante in the treatment of varios diseases, as well as for the pharmaceutical industry. Electron Paramagnetic Resonance (EPR) technique, was used for NO detection and characterization of the NO delivery kinetics. This is a technique widely used in the study of paramagnetic entities existing in biological systems. NO DDSs were developed based in trap FeDETC incorporated in siloxane–poly(oxypropylene) (PPO) and latex biocompatible matrix. The focus of this work is to obtain membranes for controlled release of NO that are able to release NO locally by external stimuli. The PPO400 and PPO2000 DDS presents a stronger EPR signal, strength and highest stability, equal to the best solid matrices already obtained in our laboratory, e. g. latex matrix. Keeping the matrix in PPO enviromment without lighting and temperature, the NO remains trapped in FeDETC for up to 45 days in the first synthesis and summaries for the last 33 days. In experiments made with the latex matrix was observed that NO remains trapped in FeDETC until 61 or 45 days for samples stored in the dark at room temperature and samples left at the greenhouse 50C. In both matrices was observed that the kinetics of NO release of NO release of the system can also be accelerated by applying modulated magnetic field of 40G or by increasing temperature. These characteristics make the PPO and latex, matrices ideal for building DDS NO.
Lahalle, Marie-Pierre. "Étude des propriétés spectroscopiques du neptunium IV dans les matrices monocristallines ThSiO₄ et ThO₂". Paris 11, 1986. http://www.theses.fr/1986PA112206.
This thesis is concerned, in a first time, with the spectroscopy of the Np4+ ion diluted in the single crystal of ThSi04. Crystals of ThSi04 with a tetragonal structure, doped with neptunium 237 were grown by the flux method (the rate of Np included in these crystals being about 0. 16 %). The crystallographic structure of the obtained crystals has been confirmed at room temperature by X-rays diffraction. Raman diffusion experiments performed between 300 K and 4,2 K have shown that no phase transition occurs at low temperature. Then, the site symmetry of Np4+ in ThSi04 remains D2d at 4. 2 K (temperature of the recorded optical spectra). On the optical polarized absorption spectra of ThSi04:Np4+, most of the excitated Stark levels coming from the first J states 4r11/2' 4p3/2 and 4r1V2 have been assigned. Moreover, fluorescence experiments have permitted to identify two of the Stark components of the lower multiplet 4r9/2 On the whole, 29 energy levels have been used for the spectroscopie parameter calculations: pk, s and Bkq which defined the crystal field interaction. In order to enlarge the spectroscopy knowledge of Np4+, the optical analysis of Np4+ in Th02 have been performed in a second time. The cubic structure of the thorium dioxide provides an Oh symmetry for the Np4+ ions. Owing to the existence of an inversion center in such a symmetry, the pure dipolar electric transitions are theoretically forbidden and only the vibronic transitions are allowed. This results in a more difficult analysis than for ThSi04. The combined analysis of the spectra recorder at 4. 2 K and higher temperatures allows us to deduce the pure electronic transitions. A first interpretation has permitted to identify about fifteen excitated Stark levels of Np4+. The comparison of the spectroscopie parameters obtained in ThSi04:Np4+ and Th02:Np4+ allows us to deduce threlative covalent effect between Np4+ and these two crystalline environments
Nguyen, Thi Thu Thuy. "Etude des transistors en couches minces à base d’IGZO pour leur application aux écrans plats à matrice active LCD et OLED". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT060/document.
This thesis aims to study thin-film transistors (TFTs) based on Indium Gallium Zinc Oxide (IGZO) in the framework of applications in active matrix flat panel LCD and OLED display. The TFT fabrication process and the characterization of IGZO deposited film are two key studies in this thesis in order to obtain TFT electrical characteristics close to the state-of-the-art. We have also studied the passivation which is identified as crucial for stabilizing the TFT and achieving good performance.The deposition of the active layer and the fabrication process of TFT are firstly studied. Smooth surface of deposited films is demonstrated by AFM and the absence of the crystalline peak of the material is shown by X-ray diffraction. The density of charge carriers decreases with the increase of oxygen flow rate. The active layer deposited at 200°C and at 4 sccm of oxygen flow has a carrier density in the order of 1E17 cm-3 which is suitable for TFT operation. This condition is chosen to fabricate IGZO-based TFT in this thesis.In a second step, we have evaluated the influence of annealing condition on TFTs' electrical characteristics. Annealing in oxygen leads to operational TFTs while doing the same under nitrogen or the absence of annealing suppresses field-effect behavior. Our studies have also shown that annealing temperature of 300°C is suitable to obtain good performance of the transistors. From this study, we have obtained TFTs with high mobility (between 5 and 15 cm2/Vs), high ION/IOFF ratios (about 1E7), and reasonable sub threshold slope (about 0.3 V/decade). The threshold voltage (VT) however remains low (between -4 and -2 V) and needs to be improved.Finally, we have investigated the impact of a passivation layer on the performance of IGZO TFTs. SiO2 film (deposited by PECVD) and Al2O3 film (formed by ALD) were studied. We have observed that such passivation can degrade the TFTs rather than protecting them. Concretely, VT shifts in negative direction when increasing the Al2O3 layer thickness or the silane flow during SiO2 deposition. Principal reason for this shift is the presence of hydrogen which is generated during passivation. We have evaluated some solutions to reduce the degradation during deposition and ensure a good protection of the TFTs
Delerue, Johann. "Matrices de bolomètres supraconducteurs à haute température critique pour l'infrarouge : matériaux, technologies et caractérisations optiques". Paris 6, 2002. http://www.theses.fr/2002PA066098.
DANTAS, ELIZABETH S. K. "Estudo para a determinacao de impurezas de terras raras em matrizes de oxidos de samario, terbio e disprosio por espectrometria de absorcao atomica". reponame:Repositório Institucional do IPEN, 1990. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10224.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
Tingaud, David. "Contribution au contrôle du frittage SHS de composites à matrice intermétallique et de céramiques de type oxyde". Limoges, 2006. http://www.theses.fr/2006LIMOA001.
Lefebvre, Dominique. "Hexagallates de lanthanide pour matrices laser et substrats d'épitaxie : élaboration, étude cristallographique et spectroscopique". Paris 6, 1986. http://www.theses.fr/1986PA066415.
Trad, Fatme. "Influence de l'insertion de bore et de phosphore sur les propriétés optiques et structurales des nanocristaux de silicium dans une matrice de silice". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0012.
In order to contribute to the in-depth understanding of doping at the nanoscale, we have studied the influence of the insertion of boron and phosphorus atoms on the optical and structural properties of silicon nanocrystals. Using the ultra-vacuum evaporation technique, we prepared silicon nanocrystals inserted in a silica matrix with two types of layers: thin films of silicon oxides SiO1.5 and SiO/SiO2 multilayers containing boron or phosphorus impurities with different and controlled concentrations. While phosphorus facilitates the demixing of silicon oxide, which has led to an increase in the size of silicon nanocrystals, boron seems to have no measurable influence on the appearance and growth of nanocrystals. The evolution of the photoluminescence of nanocrystals with doping has been explained by the existence of structural defects as well as by a passivating role of the phosphorus atoms. Finally, transmission electron microscopy and atomic tomographic probe techniques have shown that, unlike boron atoms, phosphorus atoms are preferentially located within nanocrystals
Kalinke, Lucas Hoffmann Greghi. "Materiais compósitos obtidos a partir da interação de complexos hetero-bimetálicos em matrizes porosas e lamelares". Universidade Federal de Goiás, 2014. http://repositorio.bc.ufg.br/tede/handle/tede/3688.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The composite materials studies have been treated in many fields of science, in order to obtain materials with improved properties compared to isolated constituents. There are several matrices, and dispersed phases, that can be used to build composite materials. From the reduced particle size materials point of view, the matrix can act restricting the particles growth. In this work, the procedure used to obtain composites was precursor metal oxamate complexes by wet impregnation followed the in situ reaction to obtain hetero bimetallic complexes within the matrix. The matrices used were the layered double hydroxides, mesoporous silica and porous Vycor glass (PVG). The composites prepared into PVG matrix was thermal decomposition to obtain de mixed oxides CuO-CeO2 and NiO-CeO2. The structural, optical, magnetic and electronic properties was studied by X ray powder diffraction, infrared spectroscopy, UV-vis spectroscopy, Raman spectroscopy, magnetic measurements and transmission electron microscopy. It was possible to observe the magnetic and electronic properties dependence due the confinement of the materials in the matrix. The molecular magnets built into LDH matrix, Mcu(opba)@HDL, where M= Co(II), Mn(II) and Ni(II), showed magnetic behavior the suggest the magnetic isolation of the materials through matrix layer. The material CoCu(opba)@SX, where X= 1, 2, 3 and 4; showed the size dependence of the chain size with the pore volume of the silica matrix. The composites CeCu@PVGX and CeNi@PVGX, where X= 2, 4, 6, 8 and 10; presented phase segregation oxides and formation of the oxides solid solution confined into PVG matrix.
Os estudos de materiais compósitos têm sido tratados nas diversas áreas da ciência, no intuito de produzir materiais com propriedades melhoradas em relação aos constituintes isolados. Diversas são as matrizes e fases que podem ser utilizadas para construir materiais compósitos. Do ponto de vista da construção de materiais com tamanho reduzido de partículas, a matriz do compósito pode atuar restringindo o crescimento dessas partículas. Neste trabalho, a metodologia empregada para preparação dos compósitos foi a impregnação por via úmida de complexos precursores de metais de transição, com o ligante ponte oxamato, e posterior reação in situ, para obtenção dos complexos hetero-bimetálicos na matriz. As matrizes utilizadas foram hidróxidos duplos lamelares, sílica mesoporosa e vidro poroso Vycor®. Os compósitos preparados na matriz do vidro poroso Vycor foram submetidos a decomposição térmica para síntese dos óxidos mistos do metais CuO-CeO2 e NiO-CeO2. As propriedades estruturais, ópticas, magnéticas e eletrônicas foram estudadas por difratometria de raios X, espectroscopia vibracional na região do infravermelho, espectroscopia na região do UV-vis, espectroscopia Raman, análises magnéticas e microscopia eletrônica de transmissão. Foi possível observar a dependência das propriedades magnéticas e elétricas dos materiais devido ao confinamento nas matrizes. Os materiais magnéticos moleculares construídos na matriz HDL, MCu(opba)@HDL, onde M= Co(II), Mn(II) e Ni(II), apresentaram comportamento magnético que sugere um isolamento magnético dos materiais através das lamelas da matriz. Os materiais CoCu(opba)@SX, onde X= 1, 2, 3 e 4, mostram a dependência do tamanho da cadeia bimetálica com o volume de poro da matriz de sílica. Os compósitos CeCu@PVGX e CeNi@PVGX, onde X= 2, 4, 6, 8 e 10 apresentaram segregação de fases dos óxidos e a formação de solução sólida dos óxidos confinados na matriz PVG.
Benazzouk, Louiza. "Approche du comportement dynamique d'un oxyde liquide dans un matériau composite autocicatrisant " MAC "". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00984446.
Miedzinski, Rafal. "Etude des effets optiques photo-induits dans les métallo-composites et analyse de leurs caractéristiques surfaciques par microscopie à force atomique". Reims, 2009. http://theses.univ-reims.fr/sciences/2009REIMS038.pdf.
De, Rancourt Yoann. "Dispersion de charges d'oxydes de terres rares, Er2O3 et Pr6O11, dans une matrice polymère". Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20202.
This thesis focuses on the incorporation of mineral fillers of erbium oxide, Er2O3, and praseodymium oxide, Pr6O11, in an elastomeric polymer matrix, in the context of an industrial project to replace the lead in radiation protection equipment. The actual purpose of this thesis was to improve the dispersion of the fillers in the matrix through chemical treatment processes of these particles. Various types of surface functionalization were used to compatibilize them with an organic matrix, in particular by grafting compounds such as phosphonic acids. Hence, several phosphonic acids have been successfully used for the functionalization of both types of fillers. The characterization of these functionalizations is an important part of this project. Innovative analysis techniques, both direct and indirect have been used for this purpose, namely Py-GC/MS to detect the chemical compounds anchored to the surface of the fillers, X-ray fluorescence and FTIR spectroscopy with a quantification target, but also a study of sedimentation kinetics of the fillers in an organic medium. Finally, composites were obtained by mixing the fillers, untreated and treated, with a polyurethane matrix. Tensile tests have clearly shown an improvement of mechanical properties for some of the composites, due to the functionalization of the fillers by phosphonic acids
Silva, Carolina Aparecida de Sousa. "Desenvolvimento de uma metodologia para determinação de Pb2+ em matrizes aquosas utilizando nanopartículas magnéticas". Universidade Federal de Goiás, 2018. http://repositorio.bc.ufg.br/tede/handle/tede/8464.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The iron oxide (Fe3O4) nanoparticles are promising adsorbents and, in this work, they were synthesized, characterized and applied as adsorbents in the adsorption of lead ions (Pb2+) using solid phase magnetic extraction (MSPE). The iron oxide was synthesized by the coprecipitation method and the obtained nanoparticles presented the crystalline phase of the oxide, being proved by the characterization by X-Ray Diffraction, X-ray Dispersive Energy and Absorption Spectroscopy in the Infrared region. In order to obtain information on the surface charge of the synthesized material, the pH at the zero loading point (pHPCZ) was determined indicating that the oxide surface is negatively charged at pH values above 9.4. Once the best pH (9.0) for adsorption was defined, the influence of the variables agitation time and mass of the adsorbent were evaluated, fixing them in 4 min and 3.0 mg respectively, in order to obtain the best conditions of the adsorption. adsorption process. The maximum adsorption capacity was obtained by the construction of adsorption isotherms, and a value of 31.60 mg.g1 was found. Through the kinetic study, it was observed that the adsorption obeys a pseudo-first-order kinetics. After the adsorption was optimized, the best desorption parameters were evaluated, aiming the development of an extraction/preconcentration method. Thus, 500μL of 0.5 mol.L-1 nitric acid was used as the eluent. The analytical performance was evaluated by means of the parameters, limit of detection (L.D.), limit of quantification (L.Q.), precision (D.P.R) and values found were 5.44 μg.L-1 ; 16.48 μg.L-1 and 0.25%, respectively, with the linear range of the method being 16.48 -500 μg.L-1 . Finally, the accuracy of the method was evaluated from recovery tests on samples of mineral water, micellar water and facial makeup with recovery values in the range of 95.94 - 118%. In addition, analyzes of certified water reference material (APS-1071) were also made to verify the accuracy of the proposed method.
As nanopartículas de óxido de ferro (Fe3O4) são adsorventes promissores e, neste trabalho foram sintetizadas, caracterizadas e aplicadas como adsorvente na adsorção de íons chumbo (Pb2+) utilizando extração magnética em fase sólida (MSPE). O óxido de ferro foi sintetizado pelo método de coprecipitação e as nanopartículas obtidas apresentaram a fase cristalina do óxido, sendo comprovado através da caracterização por Difração de Raio X, Energia Dispersiva de Raio X e Espectroscopia de Absorção na região do Infravermelho. A fim de se obter informações sobre a carga superficial do material sintetizado, o pH no ponto de carga zero (pHPCZ) foi determinado indicando que a superfície do óxido se encontra carregada negativamente em valores de pH acima de 9,4. Uma vez definido o melhor pH (9,0) para adsorção, a influência das variáveis tempo de agitação e massa do adsorvente foram avaliadas, fixando-as em 4 min e 3,0 mg respectivamente, a fim de se obter as melhores condições do processo de adsorção. A capacidade de adsorção máxima foi obtida pela construção de isotermas de adsorção, tendo sido encontrado um valor de 31,60 mg.g-1 . Através do estudo cinético, observou-se que a adsorção obedece uma cinética de pseudo-primeira-ordem. Após ter a adsorção otimizada, foram avaliados os melhores parâmetros para dessorção, visando o desenvolvimento de um método de extração/pré-concentração. Assim, 500µL de ácido nítrico 0,5 mol.L-1 foram utilizados como eluente. O desempenho analítico foi avaliado por meio dos parâmetros, limite de detecção (L.D.), limite de quantificação (L.Q.), precisão (D.P.R) e os valores encontrados foram 5,44 μg.L-1 ; 16,48 μg.L-1 e 0,25%, respectivamente, sendo a faixa linear do método igual a 16,48 –500 μg.L-1 . Por fim, a exatidão do método foi avaliada a partir de testes de recuperação em amostras de água mineral, água micelar e demaquilante facial com valores de recuperação na faixa de 95,94 – 118%. Além disso, análises de material certificado de referência de água (APS-1071) também foram feitas para constatar a exatidão do método proposto.
Frada, Jean-Michel. "Contribution à l'étude des multimatériaux acier-polymère-acier : caractérisation chimique et structurale des interphases dans des systèmes métal-oxyde-polymère". Nancy 1, 1992. http://docnum.univ-lorraine.fr/public/SCD_T_1992_0408_FRADA.pdf.
Lorenc, Aleš. "Studium vlastností kompozitních materiálů plněných nanočásticemi". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217835.
Barguet, Laurianne. "Contrôle acoustique et vibratoire de la mécano-synthèse des matériaux composites à matrice métallique nanostructurés". Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1027/document.
During the ODS steel (Oxide Dispersion Strengthened) synthesis, the first stage consists in an active milling between original materials, which are metallic powder and oxide to obtain reinforced micro/nanoscale dispersions. This process, known as mechanical alloying, could be realized by balls milling composed by a cylindrical tank rotating around its main axis, within which steel beads are introduced. The grinding results from different combinations of collisions between beads and powders on the tank walls, that lead to morphological grain powder evolution (grain size and shape). The first part of this thesis proposes an ultrasonic method to characterize the metallic powder. An experimental method, which consists in acoustic probing for measuring linear acoustic parameters (longitudinal wave velocity and elastic modulus) of a slab of powder sample, appears to be suitable to follow different mechanical alloying stages. A dependence of the acoustic parameters on the morphological characteristics of metallic powder (grain shape and grain size distribution) is shown with the same sample preparation and the same confining pressure. In the second part, optimization process by identification of ball milling optimal rotation speed is researched in a first step. Correlation between acoustic or vibration signals and bead motion versus rotation speed, shows that acoustic and vibration energy are good indicators that can be used to find the optimal rotation speed. In a second step, acoustic and vibration measures are used to follow grain material properties evolution during a grinding (for a period of 176hrs) and to identify powder clogging mechanism on a milling tank
Morais, Lidiane Alves de. "S?ntese, caracteriza??o e estudo das propriedades fotocatal?ticas de compostos de ni?bio em matrizes ambientais". PROGRAMA DE P?S-GRADUA??O EM QU?MICA, 2016. https://repositorio.ufrn.br/jspui/handle/123456789/21542.
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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
Um dos materiais que atualmente est? em destaque s?o os compostos de ni?bio, por apresentarem caracter?sticas como acidez, propriedades oxidativas e fotocatal?ticas e por ser um dos metais mais abundantes do pa?s, sendo o Brasil o maior produtor mundial. Este trabalho avaliou a efici?ncia da fotocat?lise heterog?nea de materiais de ni?bio na oxida??o de metanol e na inativa??o do microrganismo Escherichia Coli. Foram sintetizados catalisadores a base de ni?bio Nb2O5 e foram feitas imobiliza??es (coating) utilizando ?xido de ni?bio. Diante das caracteriza??es, foi poss?vel verificar a forma??o de esp?cies de ?xido de ni?bio e niobatos de s?dio dependendo da metodologia de s?ntese adotada. Esses materiais foram avaliados na oxida??o de metanol em diferentes concentra??es de catalisadores e apresentaram uma efici?ncia na forma??o do formalde?do proveniente da oxida??o, esta efici?ncia est? diretamente relacionada com a concentra??o dos catalisadores, sendo o material de niobato de s?dio o que apresentou maior efici?ncia, devido as suas propriedades texturais, ?pticas, sendo este um material promissor no ramo da fotocat?lise. Para os sistemas de imobiliza??o (coating), verificou-se que o revestimento ideal ? obtido com tr?s imobiliza??es, estes materiais foram analisados na oxida??o de metanol e na inativa??o de microrganismo Escherichia Coli. Estes sistemas (coating) mostram uma boa atividade na oxida??o de metanol, apesar de apresentar resultados inferiores quando comparados aos materiais em suspens?o de ?xido de ni?bio, por?m a grande vantagem dos sistemas imobilizados em rela??o ao de suspens?es s?o a sua reutiliza??o. Em rela??o ? inativa??o da Escherichia Coli, foi verificado que os sistemas imobilizados n?o s?o muitos ativos e que o microrganismo ? bastante dependendo do meio em que se encontra.
One of the materials that is currently highlighted are the compounds of niobium, because they have features like acidity, oxidative and photocatalytic properties and for being one of the most abundant metals in the country, Brazil is the world's largest producer. In this scenario, the work has to evaluate the efficiency of heterogeneous photocatalysis niobium materials in the oxidation of methanol and the inactivation of Escherichia coli using immobilization systems ?coating? and suspension. Commercial niobium oxide (Nb2O5) was evaluated in suspension and immobilization in different systems (tubes and rings) for photocatalytic processes for water treatment (methanol oxidation and inactivation of Escherichia coli). From the results of the commercial Nb2O5 characterizations was observed the presence of an amorphous structure with heat thermal treatment at temperatures above 550 ?C becomes crystalline phases, however, this fact produce a significant aggregation of the particles which reduced the specific area and the photocatalytic activity. The not calcined Nb2O5 material showed a higher activity, for both oxidation of methanol as for the inactivation of bacterial tests, the latter being very sensitive to the chemical composition water. Immobilization of the photocatalyst reactor walls prevents the need for removal of Nb2O5 particles after treatment, but significantly reduction its activity. In contrast, immobilization in a fixed-bed (rings) led to a moderate reduction in activity, which is counteracted by improvement in the long-term stability of the material. Niobium catalysts were synthesized using a refluxing method with and without the use of NaOH in different conditions of synthesis and characterized by different techniques in order to verify the phase formation of niobium. From the results of X-ray diffraction for the synthesized materials were recorded forming of species niobium oxide and sodium niobates depending on the adopted synthesis methodology. The catalytic activity of these materials was evaluated in the oxidation of methanol in relation to the amount of catalyst in which the activities have different behaviors have been dependent on the structure, surface and morphological parameters. Materials with sodium niobate structure have a lineal tendency of activity in relation to the mass of catalysts, while the materials niobium oxide structure have an abrupt loss of their catalytic activity at higher catalyst concentrations, indicating that the dispersion of the light is higher in these catalysts as increases the amount of particles in suspension. Among the materials synthesized and analyzed in the oxidation of methanol, which was more efficient, was the material of sodium niobate NaNbO3 to their textural properties, optical, which is a promising material for photocatalysis.
MOUCHON, EMMANUELLE. "Composites ceramiques a matrice oxyde renforcee par des fibres longues tissees a proprietes thermiques et electromagnetiques specifiques : interet d'une voie d'elaboration sol-gel". Paris 6, 1993. http://www.theses.fr/1993PA066187.
Besse, Marie. "Caractérisation des interactions des nanoparticules de dyoxyde de titane avec les interfaces biologiques". Compiègne, 2012. http://www.theses.fr/2012COMP2039.
Nanoparticles (NPs) have unique properties due to their small size (less than 100 nm). Titanium dioxide NPs (TiO2 NPs) are widely used by the industrial sector for the manufacture of products such as sunscreens, paints, chocolates and air filters. Nowadays, it is known that Human are daily exposed to TiO2 NPs but their impact on health and potential toxicity mechanisms still unclear. Therefore, we studied the TiO2 NPs interaction with the biological interfaces and their components, i. E. Proteins and lipids. Biological membranes were studied using model membranes mimicking the lipid composition of the pulmonary surfactant and the cell membrane. Our results showed that TiO2 NPs deeply disturb the lipid distribution and increase the membrane order which lead to a modification of the physical state of the membrane. This could seriously disturb the membrane dynamic and function. Our work on TiO2 NPs interaction with proteins adsorbed on a surface revealed that proteins from the extracellular matrix (ECM) catch a lot more TiO2 NPs than serum proteins. Then, cell experiments showed that the presence of TiO2 NPs on a fibronectine layer (a major ECM protein) inhibits the adhesion of preosteoblastic cells. The adhesion step is required for various cell processes such as differentiation and proliferation. These conclusions are very important to consider since TiO2 NPs could be released from titanium bone implants into the surrounding tissue
Chayani, Moncef. "Spéficité structurale et propriété d'oxyde de silicium déposé par procédé plasma". Toulouse 3, 2003. http://www.theses.fr/2003TOU30091.
Fontaine, Florian. "Composites à matrice carbone-oxyde et carbone-nitrure : thermodynamique de l'élaboration et son impact sur les propriétés physico-chimiques, thermiques et mécaniques des composites". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14217/document.
Carbon/carbon composites exhibit excellent mechanical and thermal properties at high temperature that make them espe-cially suitable for ablation or friction pieces. Their sensitivity toward oxidation above 400°C has lead to the will of doping them with refractory ceramics that are nonoxidizable or with a high oxidation temperature. The sol-gel process allowed to introduce 1 % in volume of titanium or aluminum oxide or nitride in the matrix. Nitrides are obtained by carbothermal nitridation of the oxide films. Two types of sols were used: the “standard” ones and those with extra sucrose. Sucrose is added to prevent pyrocarbon consumption during the nitridation. Furthermore, it was shown that it has an impact on the nitridation rate. Charged composites are then densified by Chemical Vapor Infiltration, which induces phases transforma-tions that were predicted by thermodynamics: titanium nitride films are partially carburized (formation of titanium carbonitride) and titanium dioxide films are reduced (formation of titanium oxycarbide). Aluminum-based films are more stable and don’t undergo any transformation. Thermal diffusivity of the as-synthesized composites is not much modified by the addition of these ceramics while the tensile and compressive strength are slightly increased. By the way, composites are hardened. Their oxidation kinetics is slowed down. Aluminum-rich composites exhibit a weight loss divided by two compared to the C/C reference. All those properties are directly, or not, linked to the composition of the sols, in particular to their sucrose content. Indeed, it was shown that sucrose-containing sols rather jellify on the surface of the composite, thus preventing the diffusion of precursor gases to the heart of the pieces. The final porosity is then modified. The porosity has an important impact on the compressive strength, thermal diffusivity and oxidation kinetics of the synthesized composites
Cinausero, Nicolas. "Etude de la dégradation thermique et de la réaction au feu de nanocomposites à matrice PMMA et PS". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2009. http://tel.archives-ouvertes.fr/tel-00382965.
Bahloul, Walid. "Génération in situ de dioxyde de titane par réactions d’hydrolysecondensations dans une matrice polymère fondu". Electronic Thesis or Diss., Lyon 1, 2010. http://www.theses.fr/2010LYO10124.
Polypropylene/Titanium dioxide (PP/TiO2) nanocomposites were prepared from an original method based on the hydrolysis-condensation reactions of titanium alkoxide inorganic precursor premixed with PP under molten conditions. The synthesis is based on sol-gel method without solvent through extrusion process. A second treatment in hot water was applied in order to improve final conversion degree. First, hydrolysis-condensation reactions of titanium n-butoxide precursor were studied in model medium. Based on a kinetic equation carried out in the model medium, then the synthesis of titanium dioxide particles was transposed and modelled in polypropylene medium with high molar mass. Chemical, structural and morphological analyses highlight the in situ synthesis of bactericides PP/TiO2 nanocomposites andpresenting a particular morphological and rheological behaviour
Rul, Sébastien. "Synthèse de composites nanotubes de carbone - métal - oxyde à partir de mousses céramiques". Toulouse 3, 2002. http://www.theses.fr/2002TOU30189.
Coanga, Jean-Maurice. "Caractéristiques vibrationnelles du chlorure de nitryle, du diméthyl-éther et de l'oxyde d'éthylène absorbés sur la surface de la glace ou piégés dans son volume entre 10 et 170 K : Etude de leur photodissociation à 30 K en matrices, phase solide et dans la glace". Paris 6, 2003. http://www.theses.fr/2003PA066062.
ZUBAIR, USMAN. "High-energy sustainable Lithium sulfur batteries for electrical vehicles and renewable energy applications ¿ Development of innovative electrodes". Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2730619.
Leon, Perez Edgar. "Matrice de nanofils piézoélectriques interconnectés pour des applications capteur haute résolution : défis et solutions technologiques". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT015/document.
This thesis project deals with the question of heterogeneous integration of interconnected nanowires on microelectronics chips in a view to MEMS and NEMS type devices. These devices aim to address the global problematic of “More than Moore”, that is the transformation of classical CMOS microelectronics processes to enable the development of new integrated micro and nanocomponents.In particular, over the past few years, a variety of nanomaterial-based devices have arisen, revealing micro-actuators and micro-sensors with new functionalities and/or improved performances, e.g. in terms of resolution, sensitivity, selectivity. Here we will focus on a certain type of nanostructures, Zinc Oxide (ZnO) nanowires, which have mostly been used so far to design devices whose working principle exploits the piezoelectric effect, often judiciously combined with their semiconducting properties. Indeed, when submitted to a mechanical constraint or displacement, piezoelectric nanowires generate an electrical potential (piezopotential). If, in addition to this, nanowires are also semiconducting, the piezopotential can be exploited to control an external current as a function of the mechanical constraint imposed to the nanowire (piezotronic effect). The advantage of using one-dimensional nanostructures lies into the modularity of both their mechanical and piezoelectric properties, in comparison with the bulk material. Moreover, their integration is now possible thanks to growth processes compatible with microelectronic processes (CMOS/MEMS). All these considerations make it possible to design very high performance devices combining the very small dimension of their functional unit elements (hence a high integration density which implies a high spatial resolution) and their sensitivity to nanoscale phenomena.In this project, we will adopt a very technology-oriented vision of the design of vertically-aligned ZnO-piezoelectric-nanowire matrix-type sensors. Relying on theoretical performance predictions and technological choices to solve device design and fabrication issues, this study aims to produce proof-of-concept prototypes of these high performance devices. First of all, the design process is elaborated based on finite element multiphysics models (FEM) of the piezoelectric response of a single bent nanowire, which we upgraded towards complete pixels, representative of an interconnected nanowire within a matrix. Following these considerations, we have imagined means of characterization of the piezoelectric response of a wire, then of a pixel. The implemented characterization experiment highlighted the complexity of carrying out a systematic, calibrated piezoelectric measurement, decorrelated from the environment of the pixel. Adequate technological solutions could then be implemented through the fabrication of elementary pixels suitable for characterization and whose piezoelectric response could be predictively modeled.This technological part of the work encompassed several development stages, including the chemical growth of ZnO nanowires and the design of the electrode matrix contacting the nanowires individually. The former splits into two steps: first choosing a clean-room compatible seed layer which will favor growth on a Silicon chip; secondly developing a selective growth process enabling the localization of nanowires within a predefined matrix of electrodes. The second part of the fabrication work focused on defining and optimizing the technological stack with respect to all the above mentioned considerations, and implementing the technological processes yielding the final targeted matrix
Shishido, Silvia Mika. "Fotoquimica de doadores de oxido nitrico (NO) : decomposição do nitroprussiato de sodio e da S-nitroso-L-cisteina em matrizes de agua e de poli (etileno glicol)". [s.n.], 1998. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248514.
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Mestrado
Cordier, Anne. "Élaboration de mousses nanocomposites nanotubes de carbone-métal-oxyde par synthèse CCVD de NTC in-situ dans des mousses céramiques". Toulouse 3, 2005. http://www.theses.fr/2005TOU30264.
The CCVD synthesis of CNT consists on selectively reduced a solid solution at a high temperature, in H2-CH4 atmosphere, in order to produce metal nanoparticules which immediately catalyse the decomposition of CH4 and allows the formation of CNT. The conditions of a-Al1. 8Fe0. 2O3 combustion synthesis were correlated to the oxide powders characteristics. The CNT were prepared by CCVD of a self-supported a-Al1. 8Fe0. 2O3 foam. The carbon quality was improved by Mo addition to the catalytic material during its synthesis or by Mo impregnation of a ceramic foam. It was shown that Mo favours the catalytic decomposition of CH4. The introduction under pressure of a viscous slurry of a-Al1. 8Fe0. 2O3 into consolidated commercial foams was developed. The NTC quantity is increased using a slurry of Mg0. 9(Co0. 75Mo0. 25)0. 1O1+e. They offer a specific surface area of 15 m2/g of composite material, making it attractive as a support of nanoparticules
Legorreta, Garcia Felipe. "Nanocomposites nanotubes de carbone-métal-oxyde : synthèse par CCVD et frittage par SPS". Toulouse 3, 2007. http://www.theses.fr/2007TOU30117.
The first objective was to study the preparation of CNT-metal-ZrO2 nanocomposite powders by the carbon nanotubes (CNT) in situ synthesis method. The conditions for the combustion synthesis of solid solutions between zirconia and one or several oxides of iron, cobalt, molybdenum or yttrium have been established. All solid solutions were obtained in stabilised form, either tetragonal or cubic, but yttrium incorporation was necessary to ensure a suitable thermal stability. Their selective reduction in either H2, or H2-CH4 or H2-C2H4 was studied in order to form metal-ZrO2 powders or CNT-metal-ZrO2 powders, respectively. The second objective was to study the consolidation and densification by spark-plasma-sintering of the ZrO2-matrix nanocomposite powders and of double-walled CNT-Co/Mo-MgO model powders. The mechanical properties and the electrical conductibility were measured
Shishido, Silvia Mika. "Liberação termica e fotoquimica de oxido nitrico a partir de S-nitrosotiois incorporados em matrizes de poli(etileno glicol) e em hidrogel de copolimero em bloco PEO-PPO-PEO". [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248522.
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Doutorado