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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Synthesis And Characterization Of Semiconductor Thin Films For Photovoltaic Applications

Tezel, Tamer 01 September 2009 (has links) (PDF)
Cadmium sulfide (CdS) thin films are very attractive materials due to their tunable optical properties and potential applications in not only photovoltaic devices but also in electronics, bio-labeling and fluorescence imaging. Recently, there is a great interest in flexible photovoltaic devices due to their unique properties such as very low weight, mechanical durability and large area applications. Organic semiconductors and their heterojunctions with inorganic materials are the most promising candidates for flexible photovoltaic applications. Preparation of CdS and Polypyrrole (PPy) semiconducting thin films on flexible polyethyleneterephtalate (PET) substrates and investigation of their morphological, structural, optical and electrical properties are the main scopes of this thesis. In the first part of the study, CdS thin films were deposited on PET via electrodeposition method. Taking the advantages of electrodeposition methods, CdS thin films with good optical and electrical properties were produced. CdS thin films were also deposited on soda-lime glass substrates in order to observe substrate effect. Scanning electron microscopy equipped with energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD) and UV-vis spectrometry have been used to determine the structural and optical properties of the films deposited at various temperatures and for different deposition time intervals. For all samples, molecularly homogenous CdS films have been observed with atomic percent ratios of the Cd to S very close to 1:1. Thin films showed (002) hexagonal crystal structure around 26 (2) with average grain size 7.0 nm. CdS films have high transmittance for the wavelength greater than 500nm. Band gap energies of the films, which range between 2.74 and 2.68 eV, decreased with increasing both deposition temperature and time. For further characterization, photoelectrochemical performances and electrochemical impedance spectroscopy (EIS) of both as deposited and CuCl2 treated CdS thin films have been investigated. Later, following to the deposition of individual CdS thin films, polypyrrole thin films were produced and then heterojunctions of polypyrrole with CdS were examined. It has been observed that cadmium sulfide enhanced the photoelectrochemical properties of the polypyrrole film. Influence of the polypyrrole thin film deposition time on the photoelectrochemical properties has been also investigated in this study. Frequency dependent measurements revealed that type of charge carrier changes as a function of polypyrrole deposition time.
2

Synthesis And Characterization Of Semiconductor Nanowires Via Electrochemical Technique

Dogan, Bahadir 01 December 2009 (has links) (PDF)
This thesis aims to investigate structural, optical and photoelectrochemical behavior of CdS nanowires and their heterojunctions with CdTe and polypyrrole nanowires. In the first part, CdS nanowires have been synthesized via electrochemical template-based route. It has been observed that synthesis conditions, such as bias voltage and deposition time, affect the morphology, optical and photoelectrochemical characteristics of CdS nanowires. Depending on the deposition time, length of the CdS nanowires changed from 100-200 nm to 3-4 m. Also the diameter of the nanowires increased with increasing the deposition time. Structure of the CdS nanowires has been confirmed by X-ray diffraction spectrometry and EDX analysis. Phototelectrochemical performances of the CdS nanowires have been changed dramatically with bias voltage and deposition time.In the second part of this thesis, CdTe nanostructures have been deposited on CdS nanowires. Change in optical and photoelectrochemical behavior of CdS nanowires after CdTe deposition has been investigated. Organic semiconductors and their composites with inorganic materials have been gaining attention due to tunable optical, electrical and magnetic properties. Also, ease of fabrication techniques, and therefore, low cost made these materials attractive for lots of applications including photovoltaic devices and flexible electronics. In the last part of this thesis, heterojunctions of CdS and Polypyrrole (Ppy) nanowires have been synthesized. Like CdS/CdTe heteronanostructures, first the CdS nanowires have been electrochemically deposited in anodized alumina template and then Ppy has been successfully deposited on CdS nanowires. In order to investigate the effects of polypyrrole synthesis conditions on CdS/Ppy heteronanostructures, CdS nanowire synthesis conditions have been kept constant. It has been observed that morphology and photoelectrochemical behavior of the Ppy nanowires has been affected from Ppy synthesis conditions. The photoelectrochemical performance changes of CdS/Ppy heteronanostructures have been also investigated in this part.
3

Propriedades termo-ópticas interfaciais e morfológicas de quitosana dopada com nanopartículas de prata / Thermo-optical properties and interfacial morphology of Chitosan doped with silver nanoparticles

Praxedes, Ana Paula Perdigão 25 September 2015 (has links)
The study of materials composed from the combination of chitosan and silver nanoparticles has attracted the interest of researchers from different areas due to large variety of applications of these systems, such as the development of electro-optical devices and the disease treatment like cancer. Despite the existence of several works devoted to the characterization of the biological activity of these materials, many physical properties have not been explored so far. In this work, we study thermo-optical, interfacial and morphological properties of fluids and lms based on chitosan, by considering the effects associated with the addition of silver nanoparticles. Using a large variety of experimental techniques, it is investigated how the concentration of silver nanoparticles modifies the heat diffusion, fluid adhesion and photodegradation process in chitosan samples. From the time-resolved z-scan measurements in solution of chitosan and silver nanoparticles, it is studied how the heat transport induced by the visible radiation is modifed by the insertion of the metallic nanoparticles. Our results show that thermo-optical coefficient and thermal diffusivity are sensible to the variation of colloids concentration. With respect to morphological properties of chitosan film doped with silver nanoparticles, it is observed that the introduction of guest particles tends to modify the superficial structure of the films, with the formation large clusters of nanoparticles. In relation to interfacial properties associated with wetting phenomenom, it is observed a non-monotonic behavior of the contact angle of castor oil droplets as the silver nanoparticles concentration is increased. The parameters related to wetting phenomenon are computed from the analysis of time-evolution of the droplet spreading, by using a molecular-kinetic theory. Further, the effects of silver concentration on the photodegradation of chitosan films are examined, when the films are exposed to the electromagnetic radiation in the visible and ultraviolet regions. The present results reveal that the photodegradation process of the films depends on the radiation wavelength and the used excitation regime. / O estudo de materiais formados pela associação da quitosana a nanopartículas de prata tem atraído a atenção de pesquisadores de diferentes áreas devido à grande variedade de aplicações destes sistemas, tais como a fabricação de dispositivos eletro-ópticos e o tratamento de doenças como câncer. Apesar da existência de inúmeros trabalhos voltados à caracterização da atividade biológica destes materiais, diversas propriedades físicas ainda não foram devidamente caracterizadas. Neste trabalho, estudaremos as propriedades termo-ópticas, interfaciais e morfológicas de fluidos e filmes baseados em quitosana, considerando os efeitos associados à adição de nanopartículas de prata. Usando uma grande variedade de técnicas experimentais, é investigado como a concentração de nanopartículas de prata altera os processos de difusão de calor, de adesão à fluidos e de fotodegradação nas amostras de quitosana. A partir de medidas de varredura Z resolvida no tempo em soluções de quitosana e nanopartículas de prata, é averiguado como o transporte de calor induzido pela radiação visível incidente é modificado pela inserção da nanopartículas metálicas. Nossos resultado mostram que o coeficiente termo-óptico e a difusidade térmica são sensíveis à variação da concentração de nanopartículas de prata. No que diz respeito às propriedades morfológicas de filmes de quitosana dopada com nanopartículas de prata, é observado que a introdução das partículas hóspedes tende a transformar a estrutura super cial dos lmes, com a formação de grandes aglomerados de nanopartículas. Com relação as propriedades de interfaciais associadas ao fenômeno de molhagem, é observado um comportamento não-monotônico do ângulo de contato de gotículas de óleo de mamona, à medida que a concentração de nanopartículas aumenta. Os parâmetros associados ao fenômeno de molhagem são calculados a partir da análise da evolução temporal do espalhamento das gotas, usando a teoria cinética-molecular. Além disso, os efeitos da concentração de nanopartículas sobre a fotodegradação dos filmes de quitosana dopada são verificados, quando submetidos à radiação eletromagnéticas nas regiões do visível e ultravioleta. Os presentes resultados revelam que o processo de fotodegradação dos filmes depende do comprimento de onda e do regime de excitação utilizado.
4

Propriedades óticas e elétricas de filmes de óxido de titânio dopados com nióbio / Optical and electrical properties of titanium oxide films doped with niobium

Stryhalski, Joel 07 August 2015 (has links)
Made available in DSpace on 2016-12-08T15:56:18Z (GMT). No. of bitstreams: 1 Jeol Stryhalski.pdf: 4312921 bytes, checksum: b338c848a830e15dee64928b0bf1545c (MD5) Previous issue date: 2015-08-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Titanium oxide films doped with niobium were deposited by sputtering, using triode magnetron sputtering technique. The Nb:TixOy films, as deposited, displays an interesting combination of properties: transparency and electrical conductivity. The sputtering of titanium and niobium was carried out from a titanium target with niobium inserts arranged in the erosion area. Films containing different ratios of [Nb/Ti], and deposited under different substrate bias, were characterized by the following techniques: atomic force microscopy; transmittance and reflectance measurements, Hall resistivity, x-ray diffraction (XRD), energy dispersive fluorescence of x-ray (EDX) and contact angle. It was not observed any peak of niobium oxide in the XRD pattern of Nb:TixOy, indicating that the Nb atoms are substitutional atoms in sites of Ti. Transmittance and reflectance measurements and simulations using the Tauc-Lorentz model allow us to obtain intrinsic optical properties such as refractive index and extinction coefficient. The transmittance depends on the percentage of niobium and type of substrate bias ( pulsed bias or DC bias ). Results of transmittance measurements of Nb:TixOy films (as deposited, without annealing) reached values up to 60%. Electrical resistivity measurements using the method of four points probe (ASTM F43-99) through van der Pauw technique indicate values around 10-2 Ωcm. The electrical properties were also calculated by using optical properties. It indicates a reduction in the resistivity due to the Nb incorporation and pulsed bias. The contact angle indicates that films deposited on glass substrates using pulsed bias and high content of Nb has smaller contact angles (high surface free energy). Another effect due to the Nb is the reduction of grain size (nano grains) and the production of smoother surface of the Nb:TixOy films. / Filmes de óxido de titânio dopados com nióbio foram obtidos através de pulverização catódica, utilizando o sistema Triodo Magnetron Sputtering. A pulverização catódica de titânio e nióbio foi feita a partir de um alvo de titânio com insertos de nióbio dispostos na zona de erosão. Filmes contendo diferentes proporções de [Nb/Ti], e depositados sob diferentes polarizações do substrato. Foram caracterizados pelas seguintes técnicas: microscopia de força atômica, medidas de transmitância e refletância, resistividade através de efeito Hall difração de raios X (DRX), espectroscopia de energia dispersiva por fluorescência de raios X (EDX) e ângulo de contato. Os resultados mostram que não há formação de óxido de nióbio, indicando que os átomos de Nb se alojam na estrutura do TixOy como átomos substitucionais nos sítios do Ti. Medidas de transmitância e refletância e simulações usando o modelo de Tauc-Lorentz permitiram a obtenção de propriedades óticas intrínsecas, como índice de refração e coeficiente de extinção. A transmitância depende do percentual de nióbio e do tipo de polarização do substrato (pulsado ou DC). A transmitância de filmes sem recozimento (na condição como depositado ) alcançam 60% na região do visível. A resistividade elétrica, medida pelo método de quatro pontas (norma ASTM F43-99) com a técnica de Van der Pauw, indicam valores da ordem de 10-2 Ωcm. As propriedades elétricas também foram calculadas por meio das propriedades óticas e indicam uma redução na resistividade com a presença de Nb e com a polarização pulsada. O ângulo de contato indica que filmes depositados com polarização pulsada e com maior concentração de Nb tem os menores ângulos de contato (maior energia livre de superfície). Outro efeito causado pela incorporação de Nb é a redução do tamanho de grão dos filmes e da nanorugosidade superficial dos filmes.
5

Ação da radiação de alta energia nas propriedades mecânicas de compostos elastoméricos a base de SBR carregados com barita

Almeida, Jademir Jesus Pirapora de 30 March 2012 (has links)
Made available in DSpace on 2016-03-15T19:36:37Z (GMT). No. of bitstreams: 1 Jademir Jesus Pirapora de Almeida.pdf: 6328511 bytes, checksum: a6b516ba7f4098781189faf6cc895d92 (MD5) Previous issue date: 2012-03-30 / Universidade Presbiteriana Mackenzie / In this work were studied the action of ionizing radiation on the physical-mechanical properties in elastomeric compounds based on styrene-butadiene rubber (SBR) filled with barite, opening way for application of these composites in the protection and shield against high-energy radiation, in the form of aprons. These aprons come to substitute the elastomeric ones with lead filler in ergonomic and economically advantageous conditions. The effect of high-energy radiation was studied on SBR compounds filled with barite at 50, 75, 100, 125, and 150phr (phr = parts per hundred rubber) of barite concentrations, exposed to ionizing radiation at 0, 100, 200, 500 and 1000kGy doses. The samples were characterized by physic-mechanical tests as rheometry, tensile strength, resilience, hardness, wear resistance, oil absorption, permanent deformation under compression (compression set) and dynamic mechanical thermal analysis. The morphological characteristics were determined by scanning electron microscopy. The results showed that the radiation causes an increase in tensile strength and elongation, the tear strength and hardness, and a decrease in fluid absorção and deformation under compression. / Neste trabalho foi estudada a ação da radiação ionizante nas propriedades físico-mecânicas nos compostos elastoméricos a base de estireno-butadieno (SBR) carregados com barita, abrindo caminho para aplicação destes compostos na proteção e blindagem contra a radiação alta energia, na forma de aventais, vindo substituir os aventais a base de elastômero carregado com chumbo em condições ergonômicas e economicamente vantajosas. Foi estudado o efeito da radiação ionizante em compostos a base de SBR carregado com barita nas concentrações de 50, 75, 100, 125, e 150phr (phr = partes por cem de borracha) de barita expostos à radiação ionizante nas doses de 0, 100, 200, 500 e 1000kGy. As amostras foram caracterizadas por meio de ensaios físico-mecânicos de reometria, de resistência à tração, resiliência, dureza, resistência ao rasgo, absorção de óleo, deformação permanente sob compressão (compression set) e ensaios de análise térmica dinâmico-mecânica. As características morfológicas dos compositos foram determinadas por meio de microscopia eletrônica de varredura. Os resultados mostraram que a radiação provoca um aumento da resistência à tração, do alongamento sob tração, da resistência ao rasgamento e da dureza; e um decréscimo na absorção de fluido e na deformação sob compressão.
6

Strukturiranje kompozitnih materijala na osnovu poli(laktida) i ugljeničnih nanocevi / Structuring of composite materials based on poly(lactide) and carbon nanotubes

Vukić Nevena 02 November 2019 (has links)
<p>U ovom radu, izvr&scaron;ena je sinteza i karakterizacija bionanokompozitnih materijala na osnovu poli(laktida) i vi&scaron;eslojnih ugljeničnih nanocevi. Ispitivan je uticaj različitih tehnika funkcionalizacije nanocevi, kao i izbor uslova sinteze i odnosa polaznih komponenti sistema, na svojstva dobijenih kompozitnih materijala na osnovu poli(L-laktida). Radi postizanja uniformne raspodele nanopunila u kompozitima, vi&scaron;eslojne ugljenične nanocevi su modifikovane hemijskom i radijacionom funkcionalizacijom. Izvr&scaron;ena je karakterizacija ugljeničnih nanocevi, sa ciljem utvrđivanja uspe&scaron;nosti primenjenih tehnika modifikacije na njihova svojstva i stepen funkcionalizacije. Metodom in situ polimerizacije L-laktida sa povr&scaron;ina modifikovanih nanocevi, pripremljene su serije uzoraka kompozitnih materijala sa različitim sadrţajem funkcionalizovanih nanocevi. Detaljno je ispitan uticaj funkcionalizovanih nanocevi na toplotna, kristalna, morfolo&scaron;ka, mehanička i električna svojstva sintetisanih kompozitnih materijala. Postignuta homogena disperzija nanocevi unutar biorazgradive, biokompatibilne matrice polimera koji se dobija iz obnovljivih sirovina, uticala je na pobolj&scaron;anje svojstava, kao i na uspostavljanje novih funkcionalnosti dobijenih materijala. Značajno pobolj&scaron;anje toplotnih i mehaničkih svojstva sintetisanih materijala, zajedno sa postignutom električnom provodljivo&scaron;ću, omogućava pro&scaron;irenje oblasti primene kompozita na osnovu poli(laktida) i ugljeničnih nanocevi.</p> / <p>In this thesis, bionanocomposites based on poly(lactide) and multi-walled carbon nanotubes were synthesized and characterised. Poly(L-lactide) was used as a matrix for the composite synthesis; the influence of nanofillers content, the methods of their functionalization, as well as the synthesis parameters, on the properties of obtained materials were investigated. In order to achieve a uniform dispersion of nanofillers in composite materials, multi-walled carbon nanotubes were modified using chemical and radiation functionalization. Characterization of carbon nanotubes was performed in order to determine the influence of applied modification techniques on their properties and degree of functionalization. A series of composite materials with different content of modified nanotubes were prepared by in situ polymerization of L-lactide from the surface of functionalized nanotubes. The influence of functionalized nanotubes on the thermal, crystal, morphological, mechanical and electrical properties of synthesized composites was investigated in detail. The homogeneous dispersion of carbon nanotubes within the biodegradable, biocompatible, biobased polymer matrix, has influenced the improvement of the properties, as well as the acquiring of new functionalities of synthesized materials. The significant improvement of thermal and mechanical properties of composites, and the achievement of its electrical conductivity, allow the field of application of composites based on poly(lactide) and carbon nanotubes to be expanded.</p>
7

Filage du chitosane pour l’élaboration de textiles biomédicaux innovants / Chitosan fiber-spinning for the elaboration of innovative biomedical textiles

Desorme, Mylène 20 June 2011 (has links)
Ce travail concerne le développement de nouvelles méthodes de filage du chitosane ainsi que l’étude des propriétés morphologiques, mécaniques et biologiques des fibres obtenues, en vue de leur utilisation sous forme de fils et textiles dans des applications biomédicales (en particulier, la constitution de prothèses pariétales pour la chirurgie viscérale et de pansements pour le traitement des plaies chroniques). Les monofilaments sont élaborés à partir de solutions hydroalcooliques de chitosane. Les deux procédés décrits sont basés sur la gélification physique du polymère sans utiliser d’agent réticulant externe. L’étude systématique des paramètres physico-chimiques mis en jeu au cours de la formation des fibres a permis de déterminer les paramètres clés permettant le contrôle de la morphologie cristalline des fibres, notamment les fractions cristalline anhydre et hydratée. Les propriétés mécaniques des fibres de chitosane sont stables au moins jusqu'à 6 mois de stockage à l'ambiante, et ont pu être optimisées en jouant à la fois sur des paramètres « procédé » (étirages du filament aux différentes étapes du procédé d’élaboration) et sur des paramètres physicochimiques (concentration en chitosane dans le collodion, masse moléculaire du polymère et composition du solvant hydroalcoolique). L’observation de la morphologie des fibres à différentes échelles par diffusion/diffraction des rayons X et microscopie électronique en relation avec les propriétés mécaniques a permis d’appréhender l'évolution microstructurale au cours de l'étirage, notamment le mécanisme de formation de fibrilles d'une part, et les échelles clés pour l'interprétation du comportement à rupture des fibres (morphologie en agrégats de 100-300 nm). Enfin, une implantation en souscutané chez le rat de fibres de chitosane possédant différentes morphologies cristallines (anhydre et hydratée) a validé le potentiel de ces fibres pour leurs applications biologiques avec une excellente tolérance des biomatériaux implantés (réponses inflammatoire et tissulaire très limitées) et une faible biodégradabilité après 90 jours d'implantation / This work deals with the development of new chitosan fiber spinning processes and the study of morphological, mechanical and biological properties of obtained fibers, in the perspective of their use as yarns or textiles in biomedical applications (in particular, the design of abdominal reinforcement meshes for visceral surgery and wound dressings for the treatment of chronic wounds). The monofilaments were elaborated from hydroalcoholic chitosan solutions. The two processes that we described are based on the physical gelation of the polymer without using any external crosslinking agent. The systematic study of physico-chemical parameters occurring during the fiber formation allowed to determine the key parameters controlling the crystalline morphology of fibers, especially the anhydrous and hydrated crystalline fractions. The mechanical properties of chitosan fibers are stable at least up to 6 months of storage at ambient atmosphere, and were optimized by acting on processing parameters (filament stretching at different steps of its elaboration) and physico-chemical parameters (chitosan concentration in the dope, molecular weight of the polymer and composition of the hydroalcoholic solvent). The observation of the fiber morphology at different length scales by X-ray diffusion/diffraction and electronic microscopy in relation to their mechanical properties allowed us to comprehend the microstructural evolution during fiber stretching, including the mechanism of fibril formation and the key length scales to understand the behaviour at break of fibers (100-300 nm aggregate morphology). Finally, a subcutaneous implantation of chitosan fibers with different crystalline morphologies (anhydrous and hydrated) validated the potential of these fibers in their biological applications with an excellent tolerance of implanted biomaterials (very low inflammatory and tissue reactions) and a low biodegradability after 90 days of implantation
8

Étude des propriétés chimique et morphologique de composites hybrides de type (co)polymère plasma / métal / Study of the chemical and morphological properties of plasma (co)polymer/metal hybrid composites

Mansour, Agapy 18 January 2019 (has links)
Les nanocomposites constitués de nanoparticules métalliques finement dispersées dans une matrice isolante suscitent un grand intérêt en raison de leurs propriétés optiques, électriques ou antibactériennes permettant une variété d'applications technologiques. Dans ce travail, nous nous intéressons aux composites hybrides à base d’ une matrice polymère élaborée par polymérisation par plasma froid (PECVD), imprégnée par la suite avec une solution de sel métallique qui est finalement réduit. Ces nanocomposites sont essentiellement étudiés pour leurs applications et peu d’ études portent sur leur structure chimique et morphologique.Dans ce travail de thèse, notre objectif est ainsi d’ étudier la dépendance des propriétés chimiques et morphologiques de tels matériaux composites vis-à-vis de la structure chimique du polymère plasma, de la nature des nanoparticules métalliques et des fonctions chimiques du polymère impliquées dans les interactions polymère / métal. La matrice sera aussi bien un polymère plasma qu’ un mélange de deux polymères plasma. L'objectif est alors de mieux comprendre la formation de ces nanocomposites, et de montrer leur intérêt dans différentes applications et notamment la détection d'ammoniac. / Nanocomposites consisting of finely dispersed metal nanoparticles into insulating matrix are the focus of much attention because of their optical, electrical or antibacterial properties, allowing a variety of technological applications. In this work, we are interested in hybrid composites based on a polymer matrix synthesized by cold plasma polymerization (PECVD), subsequently impregnated with a solution of metal salt which is finally reduced. These nanocomposites are mainly studied for their applications and less focused on their chemical and morphological structure. In this work, our goal is to study the dependence of chemical and morphological properties of such composite materials on the chemical structure of the plasma polymer, the nature of the metal nanoparticles and the chemical functions of the polymer involved with the polymer / metal interactions. The matrix will be both a plasma polymer and a mixture of two plasma polymers. The objective is then to better understand the nanocomposites formation, and to show their interest in different applications particularly in the detection of ammonia gas.
9

Obtenção e caracterização de compostos elastoméricos a base de EPDM carregados com barita para serem empregados na fabricação de vestimentas para proteção radiológica

Câmara, Jéssica Rodrigues 18 March 2011 (has links)
Made available in DSpace on 2016-03-15T19:36:30Z (GMT). No. of bitstreams: 1 Jessica Rodrigues Camara.pdf: 4063408 bytes, checksum: d160fbb4a019fe268fcee175023d69fd (MD5) Previous issue date: 2011-03-18 / In this work, it was studied the physical-mechanical properties of elastomers based on ethylene-propylene-diene monomer copolymer (EPDM) with barite addition, witch is a filler in powder form, opening way for application of these composites in the protection and shield against X radiation, in the form of aprons. These aprons come to substitute the elastomeric ones with lead filler in ergonomic and economically advantageous conditions. Elastomeric composites with different barite concentrations were studied: 50, 75, 100, 125 and 150phr (parts per hundred of ruber). Among the studied properties are distinguished: tensile strength, module strength, tear strength, compression set, hardness, fluid absorption, morphologic analysis, X-ray attenuation and equivalent thickness of attenuation in Pb. The results showed that all the compositions present a good dispersion of the filler in the matrix. It was observed that the increase of the barite concentration provokes an increase in the X-ray attenuation, equivalent thickness of attenuation in Pb, hardness, tensile strength, elasticity module, tear strength and in the compression set of composites, as well as a decrease in the oil absorption. / Neste trabalho estudou-se as propriedades dos elastômeros a base do copolímero de etilenopropileno-dieno monômero (EPDM) com a adição de barita, que é uma carga em pó, abrindo caminho para aplicação destes compostos na proteção e blindagem contra a radiação X, na forma de aventais, em substituição dos aventais a base de elastômero carregado com chumbo em condições. Foram estudados compostos elastoméricos com diferentes concentrações de barita: 50, 75, 100, 125 e 150phr (partes por 100 partes de borracha). Entre as propriedades estudadas destacam-se: resistência à tração, módulo sob tração, resistência ao rasgo, deformação permanente à compressão, dureza, absorção de fluído, análise morfológica, atenuação de raios X e espessura equivalente de atenuação em Pb. Os resultados mostraram que todas as composições apresentam uma boa dispersão da carga na matriz. Observou-se que com o aumento da concentração de barita há um aumento na atenuação de raios X, na espessura equivalente de atenuação em Pb, na dureza, na resistência à tração, no módulo de elasticidade, na resistência ao rasgo, na deformação permanente sob compressão dos compostos, bem como um decréscimo na absorção de óleo.
10

Caractérisation spectrale locale à l'aide de la microscopie interférométrique : simulations et mesures / Local spectral characterization using coherence scanning interferometry : simulations and measurements

Claveau, Rémy 08 December 2017 (has links)
La microscopie interférométrique est une méthode de mesure qui repose sur l’acquisition et le traitement du signal issu de l’interaction de deux ondes, dites ondes « objet » et de « référence ». Ces ondes proviennent des réflexions de la lumière sur un miroir de référence et sur l’échantillon étudié. Bien qu’étant généralement utilisées pour les analyses topographiques ou tomographiques d’un échantillon, les données interférométriques peuvent être exploitées pour réaliser des caractérisations spectrales locales résolues dans les trois directions de l’espace. Dans ce projet, nous avons étudié les performances de cette technique ainsi que ses limitations lorsque l’échantillon se complexifie (dégradation du signal d’interférences). L’analyse a été appliquée à des matériaux réfléchissants pour des mesures en surface puis à des couches transparentes et diffusantes pour aller sonder le milieu en profondeur et extraire la réponse spectrale individuelle de structures localisées dans ce milieu. / White light interference microscopy is a measurement method based on the acquisition and processing of the signal coming from the interaction between two wave fronts, known as the “object” and “reference” wave-fronts. These waves come from the reflection of the light on a reference mirror and the sample studied. Usually used for topographic or tomographic analysis of a sample, the interferometric data can be exploited for spectroscopic purposes. The resulting spectral characterizations are spatially resolved in the three directions of space. In this project, we have studied the performance of this technique, as well as the associated limitations when the sample becomes more complex (degradation of the interferometric signal). The analysis has been first applied to reflective materials for surface measurements and subsequently to transparent and scattering layers for probing within the depth of the medium and then extracting the individual spectral response of the buried structures.

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