Made available in DSpace on 2017-07-21T18:53:10Z (GMT). No. of bitstreams: 1 Cleoci Beninca.pdf: 2151933 bytes, checksum: 349c3f1b536a4959c33dc9c6535f2af7 (MD5) Previous issue date: 2008-02-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Corn and cassava starches are used thoroughly in several industrial applications. Due to some intrinsic characteristics, chemical modifications in the structure of the starch granules have been developed. In this study, thermo-analytical techniques (TG/DTA and DSC), optical microscopy and X ray diffratometry were used in the analysis of acid-modified (0.15M HCl at temperatures of 30°C and 50 °C), oxidized with different hypochlorite concentrations (0.8; 2 e 5 g Cl/100 g starch) and native corn and cassava starches. The granules of native starches presented characteristic morphology. The morphology of the granules didn't show alteration after oxidative modification but they had alterations in the external morphology after acid treatment. Through the X ray diffraction, it was confirmed the typical crystallinity of cereals and tubers of the native corn and cassava starches, respectively. After modifications there were no differences in the crystallinity patterns. The corn starch enthalpy of gelatinization (ΔHgel) reduced after oxidative modification, the same didn't happen for cassava starch. In general, as larger the oxidation degree, larger the enthalpy of elatinization and more exothermic were the reactions of starch decomposition. The onset temperature (To), peak temperature (Tp) and the enthalpy of gelatinization (ΔHgel) reduced after acid modification for the starches of both botanical sources. / O amido é uma matéria-prima oriunda de diferentes origens botânicas. Amidos de milho e de mandioca são amplamente utilizados em diversos ramos industriais. Devido a algumas características intrínsecas dos amidos nativos, tem-se optado por realizar modificações químicas na estrutura dos grânulos. Neste estudo, foram empregadas técnicas termoanalíticas (TG/DTA e DSC) e de microscopia óptica na análise de amidos de milho e de mandioca nativos, ácido modificados por HCl 0,15M a 30°C e a 50°C e oxidados com diferentes concentrações de hipoclorito de sódio (0,8; 2 e 5 g Cl/100g de amido). A termogravimetria (TG) e a análise térmica diferencial (DTA) foram realizadas simultaneamente nas seguintes condições: massa da amostra de aproximadamente 9,0 mg em cadinho de α-Al2O3; atmosfera de ar sintético a uma vazão de 100 mL min-1; razão de aquecimento: 20 °C min-1, de 30 °C a 600 °C. Cada amostra levada à analise por calorimetria exploratória diferencial (DSC) foi misturada à água (proporção amido:água de 1:4) e foi deixada em repouso por pelo menos duas horas. Com auxílio de micro-pipeta, retirou-se 10 μL da suspensão que foi inserida em um microcadinho de alumínio posteriormente selado. A DSC foi realizada nas seguintes condições: atmosfera de ar sintético a 100 mL min-1; razão de aquecimento: 5 °C min-1, de 30 °C a 100 °C. Os grânulos de amido nativo de milho e de mandioca apresentaram morfologia característica e sofreram alterações na sua morfologia externa somente após tratamento ácido. Através da difratometria de raios X confirmou-se a cristalinidade típica de cereais e tuberosas dos amidos nativos de milho e de mandioca, respectivamente. Após as modificações não foi obtida diferença nos padrões de cristalinidade. As temperaturas onset (To) e de pico (Tp) e a entalpia de gelatinização (ΔHgel) reduziram após modificação ácida para os amidos de ambas as fontes botânicas estudadas. A entalpia de gelatinização do amido de milho reduziu após oxidação, o mesmo não ocorreu para o amido de mandioca. Em geral, quanto maior o grau de oxidação, maior a entalpia de gelatinização e mais exotérmicas foram as reações de decomposição dos amidos.

Made available in DSpace on 2017-07-21T18:53:16Z (GMT). No. of bitstreams: 1 Fernanda Janaina Oliveira Gomes da Costa.pdf: 2530982 bytes, checksum: 65f2e845c0bdca1384a01a29d20c0298 (MD5) Previous issue date: 2010-02-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Starch is an abundant carbohydrate in nature, can be extracted from several botanical sources and has many industrial applications, mainly in the food sector.Due to some limitations of native starch, the production of modified starch has been an alternative to overcome these restrictions and promote increase in use of this polymer. This study used techniques thermoanalitycal TG, DTA and DSC for the evaluation of thermal properties (stability, gelatinization and enthalpy). Also has been applied optical microscopy and X-ray diffraction in samples of native cassava starch, extracted in laboratory and commercial sample wich were modified by action of H2O2 in different concentrations (1, 2 and 3%) with and without addition of the catalyst FeSO4 (0,01%). The results of thermal analysis showed that the onset temperature (To) and peak (Tp), and enthalpy of gelatinization (ΔHgel) vary with the degree of oxidation. The native starch granules showed characteristic morphology and only showed small changes in morphology after treatment with H2O2 in the concentration of 3%. Through X-ray diffraction can be seen the typical crystallinity of starches and were observed few changes in the patterns of crystallinity of the modified starches. / O amido é um carboidrato abundante na natureza, pode ser extraído de diversas fontes botânicas e possui muitas aplicações industriais, principalmente no ramo alimentício. Devido a algumas limitações dos amidos nativos, a produção de amidos modificados tem sido uma alternativa para superar tais restrições e promover o aumento da utilidade deste polímero. Neste estudo foram utilizadas técnicas termoanaliticas TG, DTA e DSC para a avaliação das propriedades térmicas (estabilidade, gelatinização e entalpia). Também foram aplicadas microscopia óptica e difratometria de raios X nas amostras de amido de mandioca nativo, tanto extraídos em laboratório quanto comercial, que foram modificados pela ação de H2O2 em diferentes concentrações (1, 2 e 3%) com ou sem a adição do catalisador FeSO4 (0,01%). Os resultados da análise térmica mostraram que as temperaturas onset (To) e de pico (Tp) e a entalpia de gelatinização (ΔHgel) variam de acordo com o grau de oxidação. Os grânulos do amido nativo apresentaram morfologia característica e somente apresentaram pequenas alterações após tratamento com H2O2 na concentração de 3%. Através da difratometria de raios X pode-se perceber a cristalinidade típica de amidos e para os amidos modificados foram observadas poucas alterações nos padrões de cristalinidade.

O presente estudo objetivou testar experimentalmente a existência da possível correlação entre a penetração de cimento nos túbulos dentinários e a qualidade do selamento. Foram utilizados 60 incisivos centrais superiores humanos que formaram um único grupo experimental. Após a eliminação das porções coronárias, as raízes foram padronizadas em 13 mm de comprimento. A instrumentação dos canais foi realizada no sentido coroa-ápice, e o comprimento de trabalho estabelecido a 1 mm aquém do forame apical. Como solução irrigadora foi empregado o NaOCl a 5,25% e ao final, EDTA a 17%. Em seguida, todos os canais foram obturados com guta-percha e cimento AH Plus marcado com um corante fluorescente. Para determinar a qualidade do selamento das obturações endodônticas, as amostras foram submetidas ao modelo de infiltração de glicose sob pressão. As raízes foram montadas em um dispositivo de dupla-câmara selada para permitir a infiltração da glicose. Como controle negativo foram utilizados 4 dentes hígidos, e como controle positivo, 2 dentes instrumentados porém, não obturados. Foram utilizados 0,75 mL de solução de glicose a 1 mol/L na câmara superior e 0,75 mL de água deionizada na câmara inferior. Os dispositivos foram conectados a um sistema de distribuição de pressão desenvolvido com o objetivo de permitir a infiltração de 32 amostras em uma mesma etapa. A solução de glicose foi forçada apicalmente sob uma pressão de 15 psi durante 1 hora. Uma alíquota de 50 L foi coletada da câmara inferior para quantificar a glicose infiltrada. A concentração de glicose foi determinada através de um método enzimático com o auxílio do Kit Glucose HK e de um espectrofotômetro em um comprimento de onda de 340 nm. Na sequência, as amostras foram desacopladas dos corpos de prova, embutidas em resina epóxi e cortadas em 3 secções transversais. Uma sequência de preparação metalográfica padrão foi realizada para permitir a observação da penetração de cimento nos túbulos dentinários por meio de microscopia confocal e óptica. Os dados obtidos nos 2 experimentos foram cruzados pelo teste de correlação de Spearman, o qual revelou a inexistência de qualquer possibilidade de correlação (r = 0,12). Com base nesses resultados, o presente trabalho concluiu que, dentro das condições experimentais usadas, a quantidade de cimento presente dentro dos túbulos dentinários não teve relação com a qualidade do selamento produzido. / The purpose of the present study was to experimentally test the potential correlation between tubular dentin sealer penetration and sealability. Sixty human maxillary central incisors were selected in order to compose a single experimental group. After removing of crowns, the roots were standardized at 13 mm in length. A crown-down root canal instrumentation was performed 1mm short of the apical foramen (working length). How irrigating solution was used 5.25% NaOCl and final, 17% EDTA. Then, all root canals were filled with gutta percha and AH Plus sealer labeled with a fluorescent dye. To determine the sealability pattern, samples were submitted to glucose leakage model under pressure. Four intact teeth were used as negative control while further 2 instrumented but nonfilled teeth was used as positive control. The roots were mounted in a double-chamber apparatus where 0,75 mL of 1 mol/L glucose solution was placed into the superior chamber and 0,75 mL of deionized water was placed into the inferior chamber. The devices were connected to a pressure distribution system that was developed in order to allow testing 32 specimens at the same experimental stage. The glucose solution was forced apically under a pressure of 15 psi during 1 hour. A sample of 50 L was taken from the inferior chamber and the glucose concentration was measured following an enzymatic reaction using a Glucose HK Kit readed under spectrophotometry (wave-length of 340 nm). After that, the samples were removed from the apparatus, embedded in epoxy resin and cut into 3 sections. Standard metallographic preparation was performed prior the observation of the sealer penetration into dentinal tubules by confocal and optical microscopy. Data provided by the evaluations were submitted to Spearman correlation test which revealed a lack of correlation between the two variables (r = 0.12). Therefore, the present study concluded that there was no correlation between tubular sealer penetration and sealability in non-bonding conventional root-fillings.

nÃo hà / Nas Ãltimas dÃcadas, existiu uma crescente demanda por aproveitamento do potencial eÃlico mundial. Essa tendÃncia està transformando as pÃs eÃlicas em uma das mais importantes aplicaÃÃes dos materiais compÃsitos polimÃricos. Alguns componentes de uma turbina eÃlica sÃo confeccionados em materiais compÃsitos polimÃricos e suas pÃs eÃlicas representam o maior uso desse material. Este trabalho tem como objetivo a avaliaÃÃo dos efeitos do envelhecimento acelerado em amostras de materiais compÃsitos revestidos com poliuretano utilizados em aerogeradores. O compÃsito à constituÃdo de resina epÃxi, reforÃado com fibras de vidro e revestido com poliuretano. O envelhecimento acelerado simula de forma intensificada os intemperismos naturais (radiaÃÃo solar, umidade e temperatura). As placas compÃsitas foram caracterizadas por ensaios nÃo-destrutivos de ultrassom e emissÃo acÃstica; ensaios mecÃnicos de traÃÃo e Izod; anÃlises tÃrmicas de termogravimetria (TGA) e calorimetria diferencial de varredura (DSC); microscopia Ãptica e grau de empoamento.Devido ao alto coeficiente de atenuaÃÃo caracterÃstico de materiais com mais de um constituinte e a consequenteausÃncia de sinal acÃstico de retorno, o ensaio por ultrassomnÃo logrou Ãxito. Mediante os avanÃos da degradaÃÃo acelerada, houve estabilidade nos valores mÃdios da velocidade de propagaÃÃo da onda e do coeficiente de atenuaÃÃo nos compÃsitos, por meio do ensaio de emissÃo acÃstica. Os ensaios mecÃnicos de traÃÃo e Izod mostraram que o envelhecimento acelerado interferiunas seguintes propriedades: mÃdulo de elasticidade, tensÃo de ruptura, alongamento mÃximo e resistÃncia ao impactoIzod. Pela tÃcnica de TGA, houve alteraÃÃo na temperatura mÃxima de degradaÃÃo e estabilizaÃÃo na massa residual com os avanÃos da degradaÃÃo acelerada. Por DSC, foi possÃvel detectar diminuiÃÃo na temperatura de transiÃÃo vÃtrea (Tg). A microscopia Ãptica revelou que nÃo houve alteraÃÃes na superfÃcie do revestimento de poliuretano e na interface poliuretano-epÃxi e ocorreu degradaÃÃo na interface fibra-matriz (face exposta à radiaÃÃo) nos compÃsitos mediante os progressos de envelhecimento acelerado. Entretanto, a mediÃÃo do grau de empoamento apresentou deteriorizaÃÃosuperficial do revestimento de poliuretano. Diante de todos os resultados encontrados, conclui-se que o envelhecimento acelerado influenciou no desempenho dos materiais utilizados em aerogeradores. / In recent decades, there has been a growing demand for utilization of wind power worldwide. This trend is transforming wind blades in one of the most important applications of polymeric composites. Some components of a wind turbine are made of polymeric composites and wind blades represent the largest use of this material. This study aims to assess the effects of accelerated aging in samples of composite materials coated with polyurethane used in wind turbines. The composite is made of epoxy resin reinforced with glass fibers and coated with polyurethane. The accelerated aging test simulates an enhanced form natural weathering (solar radiation, humidity and temperature). The composite plates were characterized by non-destructive testing of ultrasonic waves and acoustic emission; tensile tests and Izod; thermal analyzes thermogravimetricanalysis (TGA) and differential scanning calorimetry (DSC); optical microscopy and the degree of chalking. Because of the high attenuation coefficient characteristic of materials with more than one constituency and the consequent absence of acoustic feedback, the ultrasound test didn`t succeed. Through the advances in accelerated degradation was stable on mean average velocity of wave propagation and attenuation coefficient of the composite by means of acoustic emission test. The tensile tests and Izod showed that the accelerated aging interfered with the following properties: modulus of elasticity, tensile strength,ultimate elongation and Izod impact. By the technique of TGA, there was change in maximum temperature of degradation and stabilization in the residual mass with the advances in accelerated degradation. By DSC it was possible to detect a decrease in glass transition temperature (Tg). The optical microscope demonstrated that no changes in the surface of the coating polyurethane and polyurethane-epoxy interface and degradation occurred in the fiber-matrix interface (the exposed radiation face) in the composite by the progress of accelerated aging. However, measuring the degree of deterioration showed chalking surface of the polyurethane coating. With all the results, these studies conclude that the accelerated aging affect the performance of materials used in wind turbines.

A Terapia Fotodinâmica é um tratamento promissor no cura de várias doenças oftalmológicas e dermatológicas, assim como tumores. Este tratamento utiliza a combinação de luz e um composto fotossensível na presença de oxigênio. Neste trabalho objetivamos entender mecanismos de fotossensibilização em membranas. Para isso, estudamos os efeitos de irradiação em Vesículas Unilamelares Gigantes (GUVs) compostas de POPC e Cardiolipina (CL) e POPC e Colesterol (Col), contendo uma molécula fotoativa (diC12-porf) ancorada à superfície dessas membranas. GUVs compostas por POPC e POPC:Col na presença da molécula fotoativa reagem ao estímulo da luz exibindo um aumento de área seguido de flutuações. O mesmo foi observado para membranas de POPC contendo menos que 50mol% de CL. Já para composições contendo 50mol% de CL, a membrana passa a formar domínios lipídicos podendo ou não ser destruída durante a irradiação. Estes domínios podem ser suprimidos com a adição de EDTA (agente quelante de íons divalentes) na solução. Ao adicionarmos CaCl2 ao meio externo das GUVs contendo EDTA, percebemos que o efeito dos domínios e destruição da membrana reaparece. Tal fato evidencia que íons Ca++ presentes em solução devem complexar com as cargas da CL, levando à formação de domínios lipídicos. Ao quantificar o aumento de área sofrido pelas membranas percebemos que a presença de CL na membrana de POPC inibe o aumento de área para concentrações acima de 40mol% de CL. Já a presença de Col na membrana parece não contribuir significativamente para o aumento de área, embora o mesmo sofra oxidação. Além disso, evidenciou-se que na presença de CL/Col o tempo de fotoclareamento de diC12-porf é muito maior do que na ausência destes. Estes resultados evidenciam que a inclusão de CL na membrana oferece um número maior de sítios de reação para o oxigênio singlete reduzindo a foto-degradação da molécula fotoativa. Já a inclusão de Col aumenta o tempo de vida da molécula fotoativa provavelmente devido ao fato da dupla ligação do Col estar mais próxima ao centro produtor de oxigênio singlete do que a dupla ligação do POPC. / Photodynamic Therapy is a promising treatment for the cure of many diseases, like tumors. This treatment uses a combination of light and a photosensitive molecule in the presence of oxygen. In this way, our objective is to understand photosensibilization mechanisms on membranes. For this purpose, we studied the effects of irradiation in Giant Unilamelar Vesicles (GUVs) composed of POPC and Cardiolipin (CL) and POPC and Cholesterol (Chol) in the presence of a photosensitive molecule (diC12-porf). When the GUVs composed of POPC or POPC and Cholesterol (Chol) in the presence of the photosensitive molecule were irradiated, increase in surface area followed by fluctuations was observed. For GUVs composed of low concentrations of CL, the membrane photo-response was similar to that observed for pure POPC. For GUVs composed of 50 mol% CL different responses to light irradiation were observed. Some lipid domains appear for GUVs in water under irradiation and the GUV might be destroyed. When the irradiation was done in the presence of EDTA (chelant agent), the formation of the domains was prevented. Further addition of CaCl2 to this solution induced the formation of domains again leading eventually to membrane disruption. These results suggest that divalent cations have effect on the binding to CL negative polar heads, favoring lipid domain formation. We quantified the area increase obtained for the GUVs. For GUVs composed of CL we observed that until 40mol% of CL, the maximum expansion reached by the membrane area was similar to that obtained for pure POPC. For 50mol% of CL the increase of area is smaller than that found for GUVs composed only by POPC. For GUVs composed of Chol the behavior of the area is similar to that found for POPC. This means that the increase of area is mainly related to POPC peroxidation, although Chol hydroperoxide must be concomitantly formed too. Further, we observed that the diC12-porf photobleaching characteristic time for GUVs composed of CL/Chol is greater than that noted for GUVs composed of POPC. This means that when we introduce CL we are increasing the possibilities of reaction of the singlet oxygen and the photosensitive molecule is protected. The insertion of Chol in the membrane also protects the photosensitive molecule.

O NbAl3 e algumas ligas intermetálicas do sistema Nb-Ni-AI foram sintetizadas por combustão a partir dos pós de seus elementos constituintes. O efeito de variáveis de processo, como o tamanho de partícula dos pós, a composição química, a pressão de compactação, o tratamento de desgaseificação e a taxa de aquecimento, foram investigados na síntese do NbAl3 na forma de pastilhas cilíndricas. A síntese de ligas do sistema Nb-Ni-AI foi realizada a partir de misturas com as composições Nb10Ni70AI, Nb20Ni65AI e Nb30Ni60AI. A microestrutura das amostras reagidas foi caracterizada por microscopia óptica, microscopia eletrônica de varredura, EDS e difração de raios-X (método de Rietveld). Foram obtidas pastilhas de NbAl3 com 98,5 % da densidade teórica, superior ao valor encontrado na literatura (95%), mediante o controle de variáveis de processo. Nas pastilhas contendo níquel, a combustão ocorreu nas pastilhas de todas as composições. Fases metaestáveis, presentes na microestrutura das pastilhas baitas de reação, foram transformadas após tratamento térmico, originando ligas trifásicas com diferentes concentrações de fases (NbAl3, NiAI e NbNiAI), conforme a composição inicial do compactado. Algumas propriedades mecânicas de amostras brutas de reação e tratadas termicamente foram determinadas pela técnica da impressão (microdureza e tenacidade). Os resultados obtidos são comparáveis aos da literatura, salvo algumas discrepâncias atribuídas a processos de fabricação distintos. As etapas de reação da síntese do NbAl3 e de ligas Nb-Ni-AI foram posteriormente investigadas mediante interrupção da reação durante sua propagação ao longo de barras paralelepipédicas compactadas. Verificou-se que a síntese do NbAl3 ocorre pela dissolução de nióbio no alumínio fundido, seguida da precipitação do NbAl3. Nas amostras contendo níquel, a síntese ocorre em dois estágios: no primeiro estágio formam-se o Ni2Al3 ou o NiAl3, em quantidades relativas dependentes da composição geral. As reações deste primeiro estágio podem disparar as reações do segundo estágio, referentes à síntese do NbAl3. / NbAl3 and Nb-Ni-AI intermetallic alloys have been obtained by pressureless combustion synthesis from elemental powders. The effects of process variables as powder particle size, composition, compaction pressure (green density), degassing treatment and heating rate on the combustion (thermal explosion mode) of NbAl3 cylindrical pellets were studied. Combustion synthesis of Nb-Ni-AI alloys was performed on powder mixtures with nominal compositions Nb10Ni70AI, Nb20Ni65AI and Nb30NI60AI. The microstructure of reacted samples was characterized by optical microscopy, scanning electron microscopy, EDS and X-ray diffraction (Rietveld method). It was shown that careful control of the processing conditions allowed near full (98,5%) dense pellets of NbAl3. In the nickel containing pellets, reaction occurred for all the compositions investigated. Metastable phases were seen to be present in the as reacted pellets, which were transformed after a heat treatment, producing a three phase alloy (NbAl3, NiAI and NbNiAI) with different phase concentrations, depending on the initial compact composition. Some mechanical properties, like microhardness and tenacity were measured by microidentation technique on the as reacted and heat-treated samples. The results are comparable with the literature, excepted for some discrepancies caused by different fabrication processes. The reaction sequence for both cases (NbAl3 and Nb-Ni-AI alloys) was further investigated by DSC analysis and also by interrupting the reaction during its propagation along compacted parallelopipedal bars. It was found that the NbAl3 synthesis occurs through niobium dissolution in molten aluminum and precipitation of NbAl3. In the nickel containing samples, synthesis occurs as two-stage reaction: Ni2Al3 or NiAl3 are formed in the first stage, with relative amounts depending on the general composition. This first stage reaction can trigger the second one, related to the formation of NbAl3.

The research programme studied the cure reaction of a phenolic novolak resin and the effects of various additives and fillers on the reaction. The programme utilised the recently developed thermal analysis technique of temperature-modulated differential scanning calorimetry (TMDSC) performed in conjunction with other available thermal analysis techniques. TMDSC enables the signal for the heat of reaction to be separated from the underlying specific heat change in the resin. This meant that the reaction could be studied without interference from any physical changes in the resin. The manufacture of composite brake materials required the use of numerous additives and fillers to produce the desired properties. The influence of such additives on the cure rate and final properties of the resin was known to occur but had not previously been measured due to the difficulties presented by the presence of opaque additives. Some additives also underwent thermally induced physical changes in the temperature range of the cure. The final properties and the processing of new brake materials undergoing development often required trial and error adjustments to compensate for changes in cure rate. An understanding of the influence of additives would enable more rapid commercial development of brake materials through an improvement in the ability to predict both the properties of the product and the optimal processing parameters. Processing efficiency could also be improved through detailed knowledge of the kinetics. Moulding cycle times and post-baking times and temperatures were longer than necessary in order to ensure adequate cure at the end of each stage because of the lack of kinetic data. The cure of phenolic resin has been shown to be highly complicated with numerous alternate and competing reactions. For the manufacture of composite materials, knowledge of the kinetic parameters of individual reactions is not considered to be important; rather the overall kinetic parameters are required for prediction. Therefore the kinetic model parameters that best described the observed behaviour were chosen even though the model had no basis in the molecular interaction theory of reaction. Rather it served as a convenient tool for predictions. Characterisation of the resin proved to be difficult due to the presence of overlapping peaks, and volatile reaction products. TMDSC was successfully used to determine the reaction kinetics of the pure resin and the influence of certain additives on the reaction kinetics. The determination of the kinetic parameters using TMDSC agreed well with the traditional Differential Scanning Calorimetry isothermal and non-isothermal techniques. Both the Perkin-Elmer and TA Instruments were utilised for the research and were found to provide reasonably good agreement with each other. The capabilities and limitations of the individual instruments were critically examined, frequently beyond the manufacturers' specifications. TMDSC suffers from a limitation in the heating rate of the sample compared to DSC. However, it was observed that valuable information could still be obtained from TMDSC despite using heating rates that were higher than specified by manufacturers. Hot Stage Microscopy and thermogravimetry were additional experimental techniques used to aid in the characterisation of the resin. Some inhomogeneity of the resin was identified as well as differences in the behaviour of the cure between open (constant pressure) and closed (constant volume) environments were observed. A novel method of determining the orders of the cure reactions and their kinetic parameters was utilised. Reaction models for the overall cure reactions were postulated and tested by fitment to sections of experimental data in temperature regions which appeared to be free of interference from overlapping peaks. Once an individual peak was reasonably well modelled, adjacent overlapping peaks were able to be modelled both individually and in combinations by fitment to experimental data. The Solver function in Microsoft Excel was utilised to find the best fitting model parameters for the experimental data. The model parameters were able to be refined as overlapping peaks were progressively incorporated into the calculations. This method produced results that agreed well with the traditional method of analysing reaction peak temperatures at multiple scanning rates. Model fitment was shown to be of benefit where overlapping reactions occur. Various model scenarios could be tested and optimised to particular sections of experimental data. This enabled the researcher to easily identify areas of possible anomalies and postulate alternative scenarios. The accuracy of the postulated model was able to be determined by its successful fitment to experimental data from experiments run under different conditions.

This thesis examines and exploits the optical properties of pairs of MNPs. Pairs of MNPs offer two further parameters not existent at single MNPs, which both affect the local optical fields in their vicinity: the distance between them, and their relative orientation with respect to the polarisation of the excitation light. These properties are subject of three chapters: One section examines the distance-dependent and orientation-sensitive scattering cross section (SCS) of two equally sized MNPs. Both near- and far-field interactions affect the spectral position and spectral width of the SCS. Far-field coupling affects the SCS even in such a way that a two-particle system may show both a blue- and redshifted SCS, depending only on the distance between the two MNPs. The maximum distance for this effect is the coherence length of the illumination source – a fact of importance for SCS-based experiments using laser sources. Another part of this thesis examines the near-field between two MNPs and the dependence of the locally enhanced field on the relative particle orientation with respect to the polarisation of the excitation light. To attain a figure of merit, the intensity of fluorescence light from dye molecules in the surrounding medium was measured at various directions of polarisation. The field enhancement was turned into fluorescence enhancement, even providing a means for sensing the presence of very small MNPs of 12 nm in diameter. In order to quantify the near-field experimentally, a different technique is devised in a third section of this thesis – scanning particle-enhanced Raman microscopy (SPRM). This device comprises a scanning probe carrying an MNP which in turn is coated with a molecule of known Raman signature. By manoeuvring this outfit MNP into the vicinity of an illuminated second MNP and by measuring the Raman signal intensity, a spatial mapping of the field enhancement was possible. / Diese Dissertation untersucht und nutzt die optischen Eigenschaften von Paaren von Metall-Nanopartikeln (MNP). MNP-Paare bieten gegenüber einzelnen MNP zwei weitere Parameter, welche beide auf das optische Nahfeld der zwei MNPs wirken: zum Einen der Abstand der zwei MNPs zueinander, zum Anderen die relative Ausrichtung des Paares bezüglich der Polarisation des anregenden Lichts. Diese Eigenschaften sind Thema der Arbeit: Ein Abschnitt untersucht den abstands- und orientierungsabhängigen Streuquerschnitt (SQS) zweier gleichgroßer MNPs. Die spektrale Position und die Breite des SQS wird von Wechselwirkungen sowohl im Nah- als auch im Fernfeld beeinflusst. Der Einfluß der Fernfeld-Wechselwirkung geht so weit, daß ein Zwei-MNP-System sowohl einen blau- als auch einen rotverschobenen SQS haben kann – dies hängt lediglich vom Abstand der zwei MNPs ab. Die Reichweite dieser Fernfeld-Wechselwirkung wird durch die Kohärenzlänge der Beleuchtungsquelle bestimmt – eine wichtige Tatsache für SQS-Untersuchungen, welche Laserquellen verwenden. Ein weiterer Teil der Dissertation untersucht das Nahfeld zwischen zwei MNPs. Insbesondere wird dargestellt, inwieweit die Überhöhung des Nahfelds von der Orientierung des Partikelpaares bezüglich der Polarisation des Anregungslichts abhängt. Um den Effekt quantifizieren zu können, wurde die Intensität der Fluoreszenz des umgebenden Mediums für verschiedene Polarisationsrichtungen gemessen. Die lokale Feldverstärkung konnte in eine Fluoreszenzverstärkung gewandelt werden, mit deren Hilfe sich sogar die Anwesenheit sehr kleiner MNPs von nur 12 nm Durchmesser nachweisen ließ. Wie Nahfeld-Intensitäten experimentell quantifiziert werden können, stellt ein dritter Abschnitt dieser Dissertation vor – per MNP-verstärkter Raman-Rastersonden-Mikroskopie. Diese Technik besteht aus einer Rastersonde, welcher ein MNP anheftet, welches wiederum mit einem Molekül bekannter Ramansignatur überzogen ist. Indem solch eine Sonde in die unmittelbare Nähe eines zweiten, beleuchteten MNPs gebracht wurde und dabei die Intensität des Raman-Signals aufgezeichnet wurde, ließ sich die räumliche Verteilung der Ramanverstärkung vermessen.

Digital in-line holographic microscopy (DIHM) has been incorporated as an additional simultaneous in situ optical technique with ellipsomicroscopy for surface imaging and microscopy to study metastable pitting corrosion on stainless steel 316LVM in simulated biological solutions. DIHM adds microscopic volume imaging, allows one to detect local changes of the index of refraction in the vicinity of a pitting event, and allows one to track tracer particles and/or material ejected from the pitting sites. To improve the pitting corrosion resistance of stainless steel 316LVM, a simple surface treatment was tested and the aforementioned imaging techniques were used to verify that pitting occurred only on the wire face. Treatments consisted of polishing the samples to remove the passive layer, then immersing the wires in 90 C nanopure water for several hours. Treated wires show a marked increase in pitting corrosion resistance over untreated wires: the pit initiation potential increases by a minimum of 200 mV. Additional testing with scanning electron microscopy and energy dispersive X-ray spectroscopy indicate that the removal of sulphide inclusions from the surface is the most probable cause of this enhancement. To increase holographic reconstruction performance, Graphics Processing Units (GPUs) have been used; 4 Mpixel holograms are reconstructed using the dot product approximation of the Kirchhoff-Fresnel integral in 60 ms on a Tesla c1060 GPU. Errors in sizes and positions can easily be as large as 5 to 10 % for regions where the dot product approximation is not valid, so algorithms with fewer or no approximations are also required. Reconstructions for arbitrary holographic geometries using the full Kirchhoff-Fresnel integral take approximately 1 hour (compared to 1 week on a quad-core CPU), and reconstructions using convolution methods, in which the results of 256 reconstructions at 4096 x 4096 pixels in one plane are combined, take 17 s. This method is almost exact, with approximations only in the obliquity factor.

In the last decade there has been increasing research interest in the value of bio-sourced materials from lignocellulosic biomass. The dissolution of cellulose by ionic liquids (ILs) has led to investigations including the dissolution of cellulose, lignin, and complete biomass samples and the in situ processing of cellulose. Rapid quantitative measurement of cellulose dissolution in ILs is difficult. In this work, Fourier transform infrared spectroscopy (FTIR) spectra of cellulose dissolved in 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) were subjected to partial least squares (PLS) regression to model dissolved cellulose content. PLS regression was used due to the ease in developing predictive models with this technique in addition to linear regression being ineffectual for modeling when applied to potentially thousands of variables. Applying a normalization data treatment, before regression, generated a model that estimated cellulose content within 0.533 wt%. The methods described provided the basis for a rapid methodology to determine dissolved cellulose content. Development of rapid and facile screening techniques to determine the effectiveness of various ILs as solvents for cellulose or lignin will aid in the development of lignocellulosic based bioproducts. In this work, optical microscopy with and without the use of cross-polarized lenses, was used to monitor cellulose and lignin dissolution in two imidazolium-based and two phosphonium-based ILs as well as n,n-dimethylacetamide/lithium chloride (DMAc/LiCl), demonstrating that this technique could be applied more broadly than solely for ILs. The described optical microscopy methodology was more rapid and sensitive than more traditional techniques, such as visual inspection. The viscosity of [emim][OAc] (162 cP) is 100 times that of water at 20°C and could inhibit its use as a solvent for cellulose. There is a need for simple, low-cost and environmentally benign methods to reduce the viscosity of ILs to aid in cellulose dissolution. In this work, 4 wt% cellulose dissolved in [emim][OAc] was subjected to 50 psi CO2 and 20 psi N2, as a control environment, at both 50°C and 75°C. After 24 hours a nearly 2-fold increase in dissolved cellulose over the N2 control was demonstrated through the application of a 50 psi CO2 environment for cellulose dissolution in [emim][OAc] at 50°C. / Thesis (Master, Chemical Engineering) -- Queen's University, 2011-05-25 22:58:17.744