xv, 153 p. : ill. (some col.) / Lead sulfide nanocrystals (PbS-NCs) are an important class of semiconductor nanomaterials that are active in the near-infrared and exhibit unique properties distinct from their bulk analogues, notably, size tunability of the band gap and solution processability. One factor influencing PbS-NC properties is the presence of an organic ligand shell, which forms the interface between the nanocrystal core and its environment. The specific focus of this dissertation is how ionic functionalization of the ligand shell alters the physical and chemical properties of the resulting PbS-NC/ligand complex. Short-chain ligands can improve photoconductivity in PbS-NC thin films, but there are few solution-based preparations available. Chapter II demonstrates how ionic groups can enable functionalization of PbS-NCs with two short- chain thiol ligands - sodium 3-mercaptopropanesulfonate (MT) and sodium 2,3-dimercaptopropanesulfonate (DT) - via a solution-phase exchange procedure. Despite a structural similarity, DT-functionalized PbS-NCs (PbS-DT) are more stable to oxidation than MT-functionalized PbS-NCs (PbS-MT). The relative stabilities are explained in terms of different binding modes to the nanocrystal surface (bidentate vs. monodentate) and oxidation pathways (intermolecular vs. intramolecular). Toxicology studies on nanomaterials have been limited by the availability of water-soluble samples with systematically controlled structures. As examples of such materials, PbS-DT and PbS-MT nanocrystals are studied in Chapter III for their toxicological impacts on embryonic zebrafish. PbS-DT solutions induce less toxicity than PbS-MT solutions, which is explained in terms of the relative stabilities of the nanocrystal solutions. Finally, Chapter IV investigates the hitherto unexplored effects of ionic functionalization on the optical/electrical properties of PbS-NC thin films, with an emphasis on understanding how counter ions affect the photoconductivity of PbS-DT thin films. Films containing small counter ions exhibit increased dark conductivity and responsivity with time under an applied bias, whereas films containing larger or multivalent counter ions show a suppression of this behavior. These results are discussed in terms of ion motion and ion-assisted carrier injection at the PbS-NC/electrode interface. This dissertation includes previously published and unpublished co-authored material. / Committee in charge: David R. Tyler, Chair; Mark C. Lonergan, Advisor; Catherine J. Page, Inside Member; Andrew Marcus, Inside Member; Hailin Wang, Outside Member

Prof. Dr. Derval dos Santos Rosa / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2016. / A grande quantidade de resíduos provenientes da agroindústria que são descartados no meio ambiente tem despertado o interesse de pesquisadores que os veem como fonte de matéria prima para aplicações em diversas áreas da ciência, como por exemplo a utilização como reforço de compósitos poliméricos biodegradáveis. Devido ao alto teor de celulose contido nesses resíduos, com várias formas de processamento e tamanho de partícula, é viável o estudo de novas metodologias de obtenção de nanocristais de celulose (CNC). Estes são muito versáteis nas diferentes aplicações em nanocompósitos. O desenvolvimento de metodologia de obtenção de CNC será o foco deste estudo, onde buscará obter partículas com dimensões em escala nanométrica. Os resíduos de folha de bananeira e palha de milho foram utilizados como matéria-prima do estudo. Inicialmente os resíduos foram submetidos ao processo 1, com apenas uma etapa de cada tratamento químico (mercerização, branqueamento e hidrólise) e diferentes concentrações de ácido sulfúrico (H2SO4) na hidrólise final, onde verificou-se a necessidade de melhorias nesse processo, gerando o processo 2, com várias etapas de branqueamento para cada resíduo e apenas uma concentração de H2SO4. Após todos os processos de tratamento aos quais foram submetidos, os cristais foram caracterizados por meio de análise de espectroscopia na região do infravermelho com transformada de Fourier (FTIR), análise termogravimétrica e sua derivada (TGA e DTG), difração de raio-X (DRX), determinação de teores de celulose, hemicelulose e lignina, microscopia eletrônica de varredura (MEV), espalhamento de luz dinâmico (DLS) e microscopia de força atômica (AFM), buscando verificar as suas composições, índice de cristalinidade, sua morfologia e o tamanho das partículas obtidas. Os resultados obtidos no processo 1, foram essenciais para a determinação da concentração de 30% v/v para a hidrólise ácida. Através dos resultados obtidos no processo 2, observou-se que a extração de hemicelulose e lignina foi mais eficaz com o segundo processo aplicado, assim como o uso de partículas virgens em tamanho milimétrico melhorou a ação dos tratamentos químicos. Os cristais de celulose obtidos apresentaram tamanho de partícula em escala nanométrica, embora a metodologia tenha se mostrado inviável para a aplicação em folha de bananeira, visto que há a necessidade de mais etapas de tratamento, gerando muito resíduo de processo. / The large amount of waste from the agricultural industry that discarded in the environment has aroused the researchers interest on it as a source of raw materials for applications on a wide science fields, for example, the use as biodegradable polymer composites reinforcement. Due to the high cellulose content contained in these residues, with various processing forms and particle sizes, is viable the cellulose nanocrystals (CNC). These are very versatile in the different applications in nanocomposites. The development of CNC obtaining methodology will be the focus of this study, which will seek to obtain particles with dimensions on the nanoscale. The banana leaf and corn stover residues used as raw materials of this study. Initially the waste subjected to process 1, with one stage for each treatment (mercerizing, bleaching and hydrolysis) and different concentrations of sulfuric acid (H2SO4) in the final hydrolysis, where there is a need for improvements in the process, generating the process 2, with various bleaching stages for each residue and only a concentration of H2SO4. After all treatment processes to which it was subjected, the crystals were characterized by the Fourier Transform Infrared Spectroscopy Analysis (FTIR), Thermogravimetric Analysis and its derived (TGA e DTG), X-ray Diffraction (XRD), determining of cellulose, hemicellulose and lignin, Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM), seeking to verify their compositions, crystallinity index, morphology and size of the particles obtained. The results obtained in process 1, were essential for determining the concentration of 30% v/v to acid hydrolysis. By the results obtained in process 2, it observed that the hemicellulose and lignin extraction was more effective in the second process as well as the use of virgin particles millimeter size improved the action of chemical treatments. The obtained cellulose crystals had particle size in the nano-scale, although the method has proved impracticable for use in banana leaves, since there is the need for further processing steps, generating a lot of waste process.

L'objectif principal de cette thèse est de concevoir, fabriquer et caractériser les dispositifs plasmoniques basés sur les cavités métalliques bidimensionnelles monocristallines pour le transfert d'information et la réalisation d'opérations logiques. Les fonctionnalités ciblées émergent de l'ingénierie spatiale et spectrale de résonances plasmon d'ordre supérieur supportées par ces cavités prismatiques. Les nouveaux éléments étudiés dans cette thèse ouvrent la voie à de nouvelles stratégies de transfert et de traitement de l'information en optique intégrée et miniaturisée. Dans un premier temps, nous caractérisons la réponse optique des nanoplaquettes d'or ultra-fines et de taille submicronique (400 à 900 nm) par spectroscopie en champ sombre. La dispersion des résonances plasmoniques d'ordre supérieur de ces cavités est mesurée et comparée avec un bon accord aux simulations obtenues par la méthode des dyades de Green (GDM). En outre, nous présentons une analyse par décomposition lorentzienne des réponses spectrales de ces nanoprismes déposés sur des minces substrats métalliques. Nous avons, par ailleurs systématiquement étudié les effets qui pourraient modifier les résonances plasmoniques par microscopie de luminescence non-linéaire, qui s'est avérée un outil efficace pour observer la densité d'états locale des plasmons de surface (SPLDOS). En particulier, nous montrons que les caractéristiques spectrale et spatiale des résonances plasmoniques d'ordre supérieur peuvent être modulées par la modification du substrat (diélectrique ou métallique), par l'insertion contrôlée d'un défaut dans la cavité ou par le couplage électromagnétique, même faible, entre les deux cavités. L'ingénierie rationnelle de la répartition spatiale des résonances confinées 2D a été appliquée à la conception de dispositifs à transmittance accordable entre deux cavités connectées. Les géométries particulières sont produites par gravure au faisceau d'ions focalisé sur des plaquettes cristallines d'or. Les dispositifs sont caractérisés par cartographie de luminescence non-linéaire en microscopie confocale et en microscopie de fuites. Cette dernière méthode offre un moyen unique d'observer la propagation du signal plasmon dans la cavité. Nous démontrons la dépendance en polarisation de la transmission plasmonique dans les composants à symétrie et géométrie adéquates. Les résultats sont fidèlement reproduits par notre outil de simulation GDM adapté à la configuration de transmission. Enfin, notre approche est appliquée à la conception et à la fabrication d'une porte logique reconfigurable avec plusieurs entrées et sorties. Nous démontrons que dix des douze portes logiques possibles à 2 entrées et 1 sortie sont activable sur une même structure en choisissant les trois points d'entrée et de sortie et en ajustant le seuil de luminescence non-linéaire pour le signal de sortie. / The main objective of this PhD work is to design, fabricate and characterize plasmonic devices based on highly crystalline metallic cavities for the two-dimensional information transfer and logic gate operations. First, we thoroughly characterize the optical response of ultra-thin gold colloidal cavities of sub-micronic size (400 to 900 nm) by dark- field spectroscopy (Fig. 1a). The dispersion of the high order plasmonic resonances of the cavities is measured and compared with a good agreement to simulations obtained with a numerical based on the Green Dyadic Method (GDM). We further extend our experiments to systematically tune the spectral responses of these colloidal nanoprisms in vicinity of metallic thin film substrates. A comprehensive study of these sub-micronic size cavity in bowtie antenna configuration is performed. We show a polarization-dependent field enhancement and a nanoscale field confinement at specific locations in these bowtie antennas. We systematically study the effects that could potentially affect the plasmonic resonances by non-linear photon luminescence microscopy, which has proved to be an efficient tool to observe the surface plasmon local density of states (SPLDOS). Inparticular, we show that an effective spatially and spectrally tuning of the high order plasmonic resonances can be achieved by the modification of the substrate (dielectric or metallic), by the controlled insertion of a defect inside a cavity or by the weak electromagnetic coupling between two adjacent cavities. The rational tailoring of the spatial distribution of the 2D confined resonances was applied to the design of devices with tunable plasmon transmittance between two connected cavities. The specific geometries are produced by focused ion milling crystalline gold platelets. The devices are characterized by non-linear luminescence mapping in confocal and leakage radiation microscopy techniques. The latter offers a unique way to observe propagating SPP signal over a 2D plasmonic cavity. We demonstrate the polarization-dependent mode-mediated transmittance for devices withadequate symmetry. The results are faithfully reproduced with our simulation tool based on Green dyadic method. Finally, we extend our approach to the design and fabrication of a reconfigurable logic gate device with multiple inputs and outputs. We demonstrate that 10 out of the possible 12 2-input 1-output logic gates can be implemented on the same structure by choosing the two input and the one output points. We also demonstrate reconfiguration of the device by changing polarization of the incident beam, set of input locations and threshold of the non-linear luminescence readout signal.

abstract: The rapid progress of solution-phase synthesis has led colloidal nanocrystals one of the most versatile nanoscale materials, provided opportunities to tailor material's properties, and boosted related technological innovations. Colloidal nanocrystal-based materials have been demonstrated success in a variety of applications, such as LEDs, electronics, solar cells and thermoelectrics. In each of these applications, the thermal transport property plays a big role. An undesirable temperature rise due to inefficient heat dissipation could lead to deleterious effects on devices' performance and lifetime. Hence, the first project is focused on investigating the thermal transport in colloidal nanocrystal solids. This study answers the question that how the molecular structure of nanocrystals affect the thermal transport, and provides insights for future device designs. In particular, PbS nanocrystals is used as a monitoring system, and the core diameter, ligand length and ligand binding group are systematically varied to study the corresponding effect on thermal transport. Next, a fundamental study is presented on the phase stability and solid-liquid transformation of metallic (In, Sn and Bi) colloidal nanocrystals. Although the phase change of nanoparticles has been a long-standing research topic, the melting behavior of colloidal nanocrytstals is largely unexplored. In addition, this study is of practical importance to nanocrystal-based applications that operate at elevated temperatures. Embedding colloidal nanocrystals into thermally-stable polymer matrices allows preserving nanocrystal size throughout melt-freeze cycles, and therefore enabling observation of stable melting features. Size-dependent melting temperature, melting enthalpy and melting entropy have all been measured and discussed. In the next two chapters, focus has been switched to developing colloidal nanocrystal-based phase change composites for thermal energy storage applications. In Chapter 4, a polymer matrix phase change nanocomposite has been created. In this composite, the melting temperature and energy density could be independently controlled by tuning nanocrystal diameter and volume fractions. In Chapter 5, a solution-phase synthesis on metal matrix-metal nanocrytal composite is presented. This approach enables excellent morphological control over nanocrystals and demonstrated a phase change composite with a thermal conductivity 2 - 3 orders of magnitude greater than typical phase change materials, such as organics and molten salts. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2015

Les deux principales limitations des mémoires non-volatiles de type Flash à stockage de charges dans des nanocristaux en silicium sont la faible fenêtre mémoire et la dispersion des caractéristiques électriques due à la dispersion en taille des nanocristaux. Dans cette thèse, plusieurs solutions sont étudiées afin de remédier à ces deux défauts. Afin d'augmenter la fenêtre de programmation, une première approche consiste à augmenter la densité de stockage de charges grâce à l'utilisation d'une double couche de nanocristaux en silicium. Le fonctionnement et les performances électriques de ces dispositifs mémoires sont étudiés puis interprétés grâce à un modèle analytique. Une seconde approche, plus amont, consiste à utiliser des nanocristaux métalliques pour augmenter la quantité de charges piégées dans les nanocristaux. Le dépôt, la passivation et l'intégration de nanocristaux à caractère métallique (Pt, TiN, W) en tant que grille flottante dans un dispositif mémoire sont ainsi réalisés. Enfin, l'organisation « bottom-up » des nanocristaux est proposée comme une solution à la dispersion des caractéristiques électriques des dispositifs mémoires. Un procédé original de transfert et de gravure d'un masque auto-organisé à base de copolymères diblocs est développé. / The two main limitations of Flash nonvolatile memories charge storage in silicon nanocrystals are the small memory window and the dispersion of electrical characteristics due to the size dispersion of nanocrystals. In this thesis, several solutions are studied in order to remedy these defects. In order to increase the programming window, a first approach is to increase the density of charges stored in the device through the use of a double layer of silicon nanocrystals. The operation and electrical performance of these memory devices are studied and interpreted through an analytical model. A second approach, more upstream, is the use of metallic nanocrystals to increase the amount of trapped charges in the nanocrystals. Deposition, passivation and integration of metal nanocrystals (Pt, TiN, W) as a floating gate in a memory device have been realized. Finally, the "bottom-up" organisation of nanocrystals is proposed as a solution to the dispersion of electrical characteristics of memory devices. An original process for transferring a self-organized diblock copolymer mask into a hard mask is developed and used to etch nanocrystals with small size dispersion.

Pour que l'énergie photovoltaïque devienne compétitive, les coûts de production doivent être baissés et l'efficacité des cellules augmentée. Les cellules solaires à base de nanocristaux semi-conducteurs constituent une approche prometteuse pour remplir ces objectifs combinant une mise en œuvre par voie liquide avec la possibilité d'ajuster précisément la largeur de bande interdite et les niveaux électroniques. Aujourd'hui, les rendements de conversion des cellules constituées de nanocristaux de sulfure de plomb approchent les 7%. Seulement, à cause des normes européennes destinées à l'affranchissement du plomb du fait de ses risques pour la santé et l'environnement, de nouveaux matériaux doivent être trouvés. Cette thèse concerne la synthèse de nouveaux types de nanocristaux semi-conducteurs et leur application dans des cellules solaires. La synthèse des nanocristaux de CuInSe2 et de SnS de taille et de forme contrôlées a été effectuée, notamment par des voies de synthèses reproductibles dont le passage à grande échelle est facilement possible. Une analyse approfondie de la structure des nanocristaux de SnS par spectroscopie Mössbauer a montré que ces nanocristaux avaient une forte tendance à s'oxyder, ce qui limite leur utilisation dans des dispositifs électroniques après exposition à l'air. La constitution de couches minces continues ayant de bonnes propriétés électriques a été effectuée par le dépôt contrôlé de nanocristaux ainsi que l'échange de leurs ligands de surface. En particulier, un nouveau type de ligand inorganique a été utilisé qui a montré une augmentation de la conductivité des films multiplié par quatre ordres de grandeurs par rapport aux ligands initiaux. Enfin, la préparation de cellules solaires basées sur ces couches minces de nanocristaux a montré des résultats encourageants et notamment un clair effet photovoltaïque lorsque le dépôt est effectué sous atmosphère inerte. / In order to be cost-effective, photovoltaic energy conversion needs to improve the solar cell efficiencies while decreasing the production costs. Nanocrystal based solar cells could fulfil these requirements through solution-processing, band gap and energy level engineering. PbS nanocrystal thin films already proved their potential for use as solar cell active materials with power conversion efficiencies approaching 7%. However, since lead based compounds are not compatible with European regulations and present high risks for health and environment, semiconductor nanocrystals of alternative materials have to be developed. This thesis focuses on novel types of semiconductor nanocrystals and their application in photovoltaics. The first part of the study deals with the synthesis of size- and shape-controlled CuInSe2 and SnS nanocrystals. An in-depth investigation of the structure of SnS nanocrystals using Mössbauer spectroscopy revealed their high oxidation sensitivity, which limits their usability in optoelectronic devices after air exposure. The second part deals with the thin film preparation and the surface ligand exchange of the obtained nanocrystals. Using a fully inorganic nanocrystal-surface ligand system, the deposited films exhibited a current density improved by four orders of magnitude as compared to the initial ligands. Finally, solar cell devices based on nanocrystal thin films were fabricated, which showed encouraging results with a clear photovoltaic effect when processed under inert atmosphere.

Cette thèse s’est focalisée sur le développement de nanocristaux semi-conducteurs luminescents, i.e. des boîtes quantiques (quantum dots, QDs), pour des applications photo-induites. Ces nanomatériaux possèdent des propriétés optiques très intéressantes qui dépendent de leur taille et sont prometteurs pour des applications dans divers domaines.Les QD sont généralement hydrophobes mais de nombreuses applications intéressantes requiert une compatibilité avec l'eau ou du moins avec un environnement polaire. Cela, nécessite donc un traitement post-synthétique afin de modifier leur solubilité.Au cours de cette thèse, une nouvelle méthode pour transférer les QDs d'un solvant apolaire vers un solvant polaire a été développée en les fonctionnalisant avec l'acide lipoïque, un tensioactif complexant.L'acide lipoïque est une molécule chirale générant donc un effet de dichroïsme induit qui a pu être étudier, ainsi que sa dépendance vis-à-vis la taille des nanocristaux.Un objectif clef de ces recherches était le développement de QDs présentant un transfert d'énergie électronique réversible (REET). Il s’agit d’un transfert d'énergie bidirectionnel entre les QDs photoexcités et des unités chromophores appropriées fixées sur leur surface, dont la conséquence la plus importante est l'allongement de la durée de vie de luminescence du QD.Enfin, un nouveau protocole pour le dépôt de QDs chargés sur un substrat vitreux localement polarisé a été développé en collaboration avec le Dr Marc Dussauze de l'Université de Bordeaux. / This thesis focuses on the development of luminescent semiconductor nanocrystals quantum dots (QDs) for photoinduced applications. QDs are promising nanomaterials with size-dependent optical properties and are attractive for applications in several fields.However, QDs are commonly hydrophobic and many interesting applications require their compatibility with water or at least with a polar environment, meaning a post-synthetic treatment is required to confer a different solubility.During these studies, a new method for transferring QDs from an apolar solvent to another one polar has been successfully developed, by exploiting lipoic acid, as a versatile surface capping agent. Moreover, lipoic acid is a chiral molecule so a possible induced dichroism effect has been also investigated, as well as its dependence on the size of nanocrystals.A major aim of this research was the development of QDs exhibiting reversible electronic energy transfer (REET). Such a process is a bidirectional energy transfer between the photoexcited QDs and suitable chromophoric units attached on their surface, whose most important consequence is the elongation of the luminescence lifetime of the QD. Strong experimental evidence for REET and accompanying modifications of the photophysical properties has been obtained. Such a process to our knowledge has never been observed in QD-based systems.Finally, a novel protocol for depositing charged QDs on a locally polarized glassy substrate has been developed in collaboration with Dr. Marc Dussauze of the University of Bordeaux.

Made available in DSpace on 2016-06-02T19:56:40Z (GMT). No. of bitstreams: 1 3212.pdf: 9900982 bytes, checksum: fc5dfc8df72c2309a4e30ed6039ec097 (MD5) Previous issue date: 2010-07-21 / Universidade Federal de Minas Gerais / The FAU zeolite was obtained using different amounts of water. Both at higher levels as the lowest amount of water the intensities of the diffraction peaks are less intense. The results of physisorption of these samples suggest the presence of material not yet crystallized in this product. The scanning micrographs show large spherical particles with apparent roughness, suggesting the formation of aggregates of smaller particles. For transmission electron microscopy the results show very dense clusters, with indicative that the particles are very cohesive. The crystallization curve shows that the stabilization of the phase occurs at 8 h of synthesis at 100 ° C, be interesting to work on shorter times to prevent the growth of particles. The aging of the mixture facilitated the crystallization of the material by decreasing the induction time and particle size. In high alkalinity can be observed a decrease in the intensity of diffraction peaks and size of particles observed by SEM. Long crystallization times produce materials with high external area, about 40% higher than a commercial sample. The variation of aging time of the samples with high alkalinity shows that with three days are obtained clusters of about 100 nm are formed by crystals even smaller. Therefore, was developed a method to obtain nanocrystals of zeolite FAU, without the presence of template and using silica and alumina sources with reduced cost. / A zeólita FAU foi obtida em diferentes quantidades de água. Nos níveis mais altos e baixos de quantidade de água as intensidades dos picos de difração tornam-se menos intensos. O resultado de fisissorção dessas amostras sugere a presença de material não cristalizado ainda presente no produto. As micrografias de varredura mostram grandes partículas com contornos esféricos e aparente rugosidade, sugerindo a formação de agregados de partículas menores. Por microscopia eletrônica de transmissão os resultados mostram aglomerados bastante densos, indicando que as partículas estão bastante coesas. A curva de cristalização mostra que a estabilização da fase ocorre em 8 h de síntese a 100 °C, sendo interessante trabalhar em tempos inferiores para evitar o crescimento das partículas. O envelhecimento da mistura reacional facilitou a cristalização do material diminuindo o tempo de indução e o tamanho da partícula. Em alta alcalinidade pode ser observada a diminuição na intensidade dos picos de difração e no tamanho das partículas observadas por MEV. Maiores tempos de cristalização produzem materiais com elevada área externa, cerca de 40 % maior que uma amostra USY. A variação do tempo de envelhecimento das amostras com elevada alcalinidade mostra que com três dias são obtidos aglomerados de cerca de 100 nm formado por cristais ainda menores. Assim, foi desenvolvido um método para a obtenção de cristais nanométricos de zeólita FAU, sem a presença de direcionador orgânico e usando fontes de sílica e alumina de custo reduzido.

Orientador: José Antônio Malmonge / Resumo: Compósitos particulados de conectividade 0-3 obtidos a partir de cerâmicas ferroelétricas são objetos de inúmeros estudos científicos. Tal fato decorre da necessidade da indústria eletrônica de materiais com altas constantes dielétricas e densidade de energia, para fabricação de componentes passivos integrados em circuitos impressos e fabricação de dispositivos de armazenamento de energia. Por outro lado, a constante dielétrica dessa combinação se limita a baixos níveis para algumas aplicações. A fabricação de compósitos trifásicos vem ganhando atenção devido às elevadas constantes dielétricas obtidas com a inserção de uma terceira fase condutiva. A literatura apresenta tais compósitos com um perfil bem comportado baseado na regra das misturas e na teoria da percolação. Por outro lado, em alguns casos as interações das fases de preenchimento com a matriz, bem como a possível geração de cargas durante o processo de fabricação impedem um comportamento previsível considerando a distribuição não aleatória das fases. Este trabalho teve como objetivo a obtenção e caracterização de compósitos trifásicos empregando-se como matriz o poliuretano a base de água, como segunda fase Titanato Zirconato de Chumbo (PZT) e como terceira fase, para efeito de comparativo, negro de fumo (NF) ou nanocristais de celulose (CNC). Os compósitos trifásicos foram preparados a partir da mistura dos componentes em solução aquosa de PU, e suas propriedades comparadas àquelas obtidas para compósitos bifásic... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Particulate polymeric composite with connectivity 0-3 obtained using ferroelectric ceramics as a filler are objects of numerous scientific studies. This is due to the need of the electronics industry materials with high dielectric constants and high energy density, for the manufacture of integrated passive components in printed circuits and manufacturing energy storage devices. On the other hand, the dielectric constant of this combination is limited to low levels for some applications. The manufacture of three-phase composite has gained attention due to the high dielectric constant obtained by inserting a third conductive phase. The literature shows such composites with a well behaved profile based on the rule of mixtures and percolation theory. Moreover, in some cases the interactions of the filling phase with the matrix, as well as the possible generation of charges during the manufacturing process prevents a predictable behavior considering the non-random distribution of phases. This study aimed to obtain and characterize three-phase composites employing as matrix water-based polyurethane, and as a second phase Lead titanate zirconate (PZT) and as a third phase, for comparative purposes, carbon black (NF) or cellulose nanocrystals (CNC). The three-phase composites were prepared adding the fillers in aqueous PU, and their properties compared with those obtained for biphasic composites PU_PZT, PU_NF and PU_CNC. The characterizations were performed by Scanning Electron Micro... (Complete abstract click electronic access below) / Doutor

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2015-11-27T15:18:54Z No. of bitstreams: 1 BrismarkGoesDaRocha_TESE.pdf: 14655007 bytes, checksum: f132218e797f47b22250ea1afea1399e (MD5) / Approved for entry into archive by Elisangela Moura (lilaalves@gmail.com) on 2015-11-30T21:25:07Z (GMT) No. of bitstreams: 1 BrismarkGoesDaRocha_TESE.pdf: 14655007 bytes, checksum: f132218e797f47b22250ea1afea1399e (MD5) / Made available in DSpace on 2015-11-30T21:25:07Z (GMT). No. of bitstreams: 1 BrismarkGoesDaRocha_TESE.pdf: 14655007 bytes, checksum: f132218e797f47b22250ea1afea1399e (MD5) Previous issue date: 2014-07-30 / O presente trabalho tem como objetivos extrair a fibra da folha do abacaxizeiro tipo P?rola para obter bast?es (?whiskers) de celulose destas fibras tratadas quimicamente, para utiliza??o como refor?o na fabrica??o de filmes de Biocomp?sito com Poli ?lcool Vin?lico (PVA) e Poli (?cido l?tico) (PLA) como matrizes. As amostras foram caracterizadas utilizando an?lises como TGA, FTIR e DSC. Tamb?m foram realizados ensaios das folhas para a identifica??o de macro e micro nutrientes. As amostras dos filmes de biocomp?sitos foram usadas para ensaios mec?nicos de tra??o nos filmes e o teste de biodegrada??o aer?bica, bem como nos filmes de 100% de PVA e PLA. A extra??o da fibra foi efetuada numa desfibradeira autom?tica, e em seguida as fibras extra?das foram lavadas v?rias vezes para remover as impurezas e foram tratadas com NaOH (hidr?xido de s?dio) e NaClO (hipoclorito de s?dio), para remover as impurezas inerentes ?s fibras e a cor natural, respectivamente. Em seguida, as fibras tratadas foram submetidas a um processo de hidr?lise com ?cido sulf?rico a 13,5%, para obten??o de bast?es de celulose. Foram produzidos filmes biocomp?sitos de PVA e PLA com bast?es de celulose nas concentra??es de 0%, 1%, 3%, 6%, 9% e 12%. ?gua destilada a 80?C ? 5 na dilui??o de PVA e diclorometano para a dilui??o do PLA na temperatura ambiente. Na prepara??o dos filmes foi utilizado o m?todo de ?casting?. Posteriormente foram realizados os testes de absor??o de ?gua pelos filmes produzidos. Para o ensaio mec?nico de tra??o dos filmes foi utilizada a norma ASTM D638-10 com velocidade de 50 mm/min. O teste estat?stico Qui-quadrado foi empregado para a verifica??o da exist?ncia de diferen?as significativas em n?vel de 0,05: comprimentos das folhas do abacaxizeiro e dos bast?es, procedimentos utilizados para filtra??o em filtro utilizando seringa de 0,2 ?m e filtragem atrav?s de centrifuga??o. Foi realizado estudo de hidrofilidade dos filmes com base no ?ngulo de contato. Tamb?m foi aplicado o teste Estat?stico T-Student com n?vel de signific?ncia (0,05) para comparar as espessuras dos filmes de PVA e PLA e das propriedades mec?nicas (tra??o). Na avalia??o da biodegradabilidade dos biocomp?sitos, bem como os filmes de 100% das matrizes de PVA e PLA, foi utilizado o teste de Sturm norma D5209. Os resultados indicam a presen?a de bast?es de celulose com comprimentos variandos de 7,33 nm a 186,17 nm. As espessuras em m?dia dos filmes de PVA e PLA eram de 0,153 ?m e 0,210 ?m, respectivamente. Foi observada uma forte correla??o linear diretamente proporcional entre a tra??o dos filmes de PVA e a concentra??o de bast?es de celulose nos filmes (0,7336), da espessura do filme de 0,1404. Juntos, a porcentagem de bast?es de celulose e a espessura dos filmes, correlacionaram 0,8740. No caso dos filmes de PLA, a correla??o entre o teor dos bast?es de celulose e a tra??o foi fraca, inversamente proporcional (-0,0057) e a espessura em -0,2602, totalizando -0,2659, isto ?, os bast?es de celulose n?o aderiram totalmente ao PLA. Na compara??o dos resultados da tra??o das duas matrizes polim?ricas, os bast?es de celulose contribu?ram na melhoria das propriedades mec?nicas no caso de PVA, mas h? uma diferen?a com rela??o a PLA. Nos testes de biodegradabilidade, foi observado a degrada??o total do filme de PVA ap?s 27 dias, enquanto o filme de PLA degradou em 20 dias, o que comprova que os filmes produzidos s?o biodegrad?veis. / This work has the main objective to obtain nano and microcrystals of cellulose, extracted from the pineapple leaf fibres (PALF), as reinforcement for the manufacture of biocomposite films with polymeric matrices of Poly(vinyl alcohol) (PVA) and Poly(lactic acid) (PLA). The polymer matrices and the nano and microcrystals of cellulose were characterised by means of TGA, FTIR and DSC. The analysis was performed on the pineapple leaves to identify the macro and micronutrients. The fibers of the leaves of the pineapple were extracted in a desfibradeira mechanical. The PALF extracted were washed to remove washable impurities and subsequently treated with sodium hydroxide (NaOH) and sodium hypochlorite (NaClO) in the removal of impurities, such as fat, grease, pectates, pectin and lignin. The processed PALF fibers were hydrolysed in sulfuric acid (H2SO4) at a concentration of 13.5 %, to obtain nano and microcrystals of cellulose. In the manufacture of biocomposite films, concentrations of cellulose, 0 %, 1 %, 3 %, 6 %, 9% and 12% were used as reinforcement to the matrices of PVA and PLA. The PVA was dissolved in distilled water at 80 ? 5 oC and the PLA was dissolved in dichloromethane at room temperature. The manufacture of biocomp?sitos in the form of films was carried out by "casting". Tests were carried out to study the water absorption by the films and mechanical test of resistance to traction according to ASTM D638-10 with a velocity of 50 mm/min.. Chi-square statistical test was used to check for the existence of significant differences in the level of 0.05: the lengths of the PALF, lengths of the nano and microcrystals of cellulose and the procedures used for the filtration using filter syringe of 0.2 ?m or filtration and centrifugation. The hydrophilicity of biocomp?sitos was analysed by measuring the contact angle and the thickness of biocomp?sitos were compared as well as the results of tests of traction. Statistical T test - Student was also applied with the significance level (0.05). In biodegradation, Sturm test of standard D5209 was used. Nano and microcrystals of cellulose with lengths ranging from 7.33 nm to 186.17 nm were found. The PVA films showed average thicknesses of 0.153 ?m and PLA 0.210 ?m. There is a strong linear correlation directly proportional between the traction of the films of PVA and the concentration of cellulose in the films (composite) (0,7336), while the thickness of the film was correlated in 0.1404. Nano and microcrystals of cellulose and thickness together, correlated to 0.8740. While the correlation between the cellulose content and tensile strength was weak and inversely proportional (- 0,0057) and thickness in -0.2602, totaling -0,2659 in PLA films. This can be attributed to the nano and microcrystals of cellulose not fully adsorbed to the PLA matrix. In the comparison of the results of the traction of the two polymer matrices, the nano and microcrystals have helped in reducing the traction of the films (composite) of PLA. There was still the degradation of the film of PVA, within a period of 20 days, which was not seen in the PLA film, on the other hand, the observations made in the literature, the average time to start the degradation is above 60 days. What can be said that the films are biodegradable composites, with hydrophilicity and the nano and microcrystals of cellulose, contribute positively in the improvement of the results of polymer matrices used.