Orientador: Marcela Rocha de Oliveira Carrilho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-04T03:11:48Z (GMT). No. of bitstreams: 1 Malacarne-Zanon_Juliana_M.pdf: 636484 bytes, checksum: 6d6f6fb65dab84312134d942c458dc89 (MD5) Previous issue date: 2005 / Resumo: Este estudo avaliou o comportamento em água de sistemas adesivos com caráter hidrófilo diferentes. No primeiro estudo, a cinética de difusão da água foi avaliada a partir da mensuração da sorção, da solubilidade e do coeficiente de difusão da água em cada adesivo selecionado. Os materiais empregados foram: as resinas adesivas dos sistemas Clearfil SE (SE) e Scotchbond Multiuso (MP), e os adesivos simplificados Single Bond (SB) e Excite (EX). Cinco resinas experimentais com caráter hidrófilo estabelecido em função de seus respectivos parâmetros de solubilidade foram também avaliadas de modo que servissem como referência de materiais mais ou menos hidrófilos. Os materiais foram dispensados em matriz metálica e fotoativados por 40s (650mW/cm2). Para cada material, foram obtidos quinze espécimes em forma de disco (0,8mm x 5,8mm). Estes foram armazenados em câmara dessecante a 37°C até que não houvesse variação de sua massa seca (m1), aferida em balança analítica. Em seguida, dez destes foram armazenados em água destilada, e tiveram suas massas (m2), mensuradas após 1,2,3,4,5,6,7,14 e 28 dias, para avaliação da variação de massa ao longo do tempo. Ao final dos 28 dias, os espécimes foram novamente submetidos ao ciclo de dessecamento, para determinação da massa seca final (m3), e dos valores de sorção e solubilidade. Os cinco espécimes restantes foram também armazenados em água destilada, mas tiveram suas massas ¿úmidas¿ mensuradas em intervalos mais curtos para o cálculo do coeficiente de difusão da água em cada material. A composição e o caráter hidrófilo dos materiais influenciaram o trânsito de fluidos através dos mesmos. Dentre os adesivos comerciais, os sistemas mais hidrófilos (SB e EX) apresentaram valores de sorção, de solubilidade e de coeficiente de difusão da água significativamente maiores que dos adesivos menos hidrófilos (MP e SE) (p<0.05). Comportamento semelhante foi observado com a resina experimental mais hidrófila, R5. Com exceção da R1, todos os adesivos (comerciais e experimentais) apresentaram o maior aumento de massa no primeiro dia de armazenamento em água. Num segundo estudo, foi avaliado o efeito da armazenagem em água na resistência máxima à tração (RMT) dos adesivos comerciais referenciados. Para cada adesivo, foram obtidos 60 (±2) espécimes com área de secção transversal retangular de aproximadamente 1mm2. Estes foram armazenados em câmara dessecante a 37°C por 24 horas. Doze a treze espécimes de cada material foram submetidos ao ensaio de tração a 0,5mm/min tão logo foram removidos da câmara dessecante. Os demais foram armazenados em água destilada a 37°C e testados após 24h, 7 dias, 30 dias ou 180 dias. O armazenamento em água por 24h determinou a redução significativa da RMT de todos os adesivos (p<0,05). A armazenagem prolongada em água promoveu a queda dos valores de RMT apenas para o adesivo EX, após 180 dias (p<0,05). Com base nos resultados, é possível concluir que adesivos mais hidrófilos absorvem mais água num período mais curto de avaliação. A queda mais significativa nos valores de RMT ocorreu após as primeiras 24 horas de armazenamento em água, coincidindo com o período de maior absorção de água / Abstract: This study evaluated the effect of water storage on the kinetics of moieties diffusion and on the ultimate tensile strength of dental adhesives with different degree of hydrophilicity. In the first study, kinetics of moieties diffusion in commercial and experimental adhesives were evaluated using parameters as itswater sorption, solubility and water diffusion coefficient after ageing in distilled water. Four current dental adhesives were employed: the bonding resins of Clearfil SE Bond (SE) and Scotchbond Multi-Purpose (MP) systems, and the simplified ¿one-bottle¿ systems, Single Bond (SB) and Excite (EX). Five experimental resins with hidrophilicity recognizably different were used as reference. Specimen discs were prepared from each material by dispensing the uncured resin into a mould (5.8mm x 0.8mm). The specimens were placed in a desiccator at 37°C until a constant mass was obtained. After desiccation, the cured specimens were stored in distilled water and the kinetic of moieties diffusion was evaluated during the following times: 1,2,3,4,5,6,7,14 and 28 days. Shorter time intervals were used to calculate diffusion coefficient. After the 28 days, water sorption and solubility related to the entire period of storage were determined. Resin composition and hydrophilicity influenced water sorption, solubility and kinetics of moieties diffusion of both the commercial and experimental resins. Between commercial adhesives, the most hydrophilic systems (SB and EX) showed water sorption, solubility and diffusion coefficient values significantly greater than the least hydrophilic materials (SE and MP). The most hydrophilic experimental resin, R5, showed the highest values of water sorption, solubility and diffusion coefficient. Except for resin R1, all materials (commercial and experimental) presented the greatest mass gain at the first day of water storage. In a second study, the effect of water storage on the ultimate tensile strength (TS) of the same commercial was evaluated. I-shaped specimens were prepared by pouring the adhesives mentioned above into a brass mould. The adhesives were light-cured, removed from the mould and stored in a desiccator at 37°C for 24 hours. Afterwards, twelve to thirteen specimens of each adhesive were tested under tension at 0.05 mm/min, while the remaining specimens were stored in distilled water for 24 hours, 7, 30 and 180 days, before testing. In contrast to dry storage, water immersion produced significantly lower values of UTS for all materials (p<0.05), within the first 24 hours of storage. For the adhesives SE, MP and SB no significant changes in the UTS were observed along the whole period of ageing in water. However, a significant reduction in the UTS was detected after 180 days of water storage for the EX system (p<0.05). Based on the results brought about with these two studies, it can be concluded that more hydrophilic dental adhesives absorb more water within a short period of storage. The greatest decrease in UTS occurred after 24 hours of water storage; period in which was also observed the greatest amount of water uptake. Prolonged water storage had a detrimental effect on the UTS of the EX system, one of the most hydrophilic adhesives employed in the study / Mestrado / Materiais Dentarios / Mestre em Materiais Dentários

En suivant les tendances écologiques des dernières années, les innovations visant à réduire les empreintes énergétiques se multiplient. Parmi les nombreux domaines cherchant à développer des technologies écologiques, le génie se doit de proposer des solutions viables. Depuis longtemps, les composites renforcés de fibres sont intégrés à de nombreux produits. Toutefois, beaucoup d’efforts sont déployés afin d’améliorer ces produits en terme de densité, de coût et de recyclage. La solution privilégiée repose sur la substitution des fibres synthétiques par des fibres naturelles, moins chères et moins denses. Les fibres les plus couramment utilisées sont le bois, le lin et le chanvre. D’une part à cause de la culture de ces matières qui est déjà maitrisée, d’autre part à cause de leurs propriétés en termes de dimensions utilisables. Dans une optique écologique, le choix des fibres se doit d’être fait en fonction des matières à disposition afin de limiter les coûts de transports. Toutefois, cet échange ne se fait pas sans heurt, là où les fibres synthétiques étaient caractérisées par une forte durabilité, les fibres naturelles sont fortement sensibles à leurs environnements. L’utilisation de composés végétaux est délicate, car ils apportent une problématique sur la durabilité notamment à cause de complexité de leur structure et leur capacité à absorber l’eau. Les solutions appliquées consistent à traiter la surface de la fibre afin de limiter ce phénomène tout en renforçant l’interface avec la matrice. Ainsi la tenue des composites est améliorée de même que leurs propriétés. Au lieu de rendre la plante hydrophobe via des traitements, l’utilisation d’une plante présentant naturellement cette capacité serait un avantage. Les fibres produites dans la cosse de l’asclépiade présentent cette capacité. Présentes à l’état sauvage sous différentes variétés à travers le monde, toutes ces espèces présentent la même fibre creuse et hydrophobe. Cette fibre est encore mal connue et la littérature nébuleuse sur plusieurs aspects, mais son potentiel est certain. L’objectif de l’utilisation de cette fibre est de proposer une alternative aux fibres synthétiques dans différents domaines qui ne sont pas nécessairement limités au génie civil. Cette fibre peut être utilisée comme isolant thermique dans le textile, absorbant pétrolier ou en panneaux pour l’isolation acoustique et thermique. Pour cela, la caractérisation de la fibre est nécessaire afin de mieux comprendre ses propriétés. Cela se traduit par une étude chimique de l’espèce considérée, Aslépias syriaca L., et une étude morphologique afin comprendre ses propriétés. Les résultats montrent que sa composition diffère de celle d’autres plantes usuelles, son fort taux de cire et de lignines influeraient son hydrophobicité. La principale difficulté d’utilisation est celle de la mise en forme, car sa nature de fibre creuse et courte la rend fragile et sensible aux agressions chimiques. Toutefois, la formation de voiles non tissés permet de créer un matériau léger, souple et pouvant être adapté à plusieurs applications. À partir de ce matériau mêlant fibre synthétique et fibres d’asclépiade, il est possible de former des composites par thermocompression. Ces derniers présentent des propriétés comparables à ceux pouvant être trouvés dans l’industrie automobile actuellement tout en étant moins denses. Finalement, les fibres d’asclépiade peuvent être utilisées en tant qu’absorbant pétrolier. Les tests préliminaires montrant une forte capacité d’absorption.

The gas-absorption/chemical-reaction (GACR) method used in chemical engineering to quantify gas-liquid interfacial area in reactor systems is adapted for the first time to measure the effective air-water interfacial area of natural porous media. Experiments were conducted with the GACR method, and two standard methods (X-ray microtomographic imaging and interfacial partitioning tracer tests) for comparison, using model glass beads and a natural sand. The results of a series of experiments conducted under identical conditions demonstrated that the GACR method exhibited excellent repeatability for measurement of interfacial area (A(ia)). Coefficients of variation for A(ia) were 3.5% for the glass beads and 11% for the sand. Extrapolated maximum interfacial areas (A(m)) obtained with the GACR method were statistically identical to independent measures of the specific solid surface areas of the media. For example, the A(m) for the glass beads is 29 (1) cm(-1), compared to 32 (3), 30 (2), and 31 (2) cm(-1) determined from geometric calculation, N2/BET measurement, and microtomographic measurement, respectively. This indicates that the method produced accurate measures of interfacial area. Interfacial areas determined with the GACR method were similar to those obtained with the standard methods. For example, A(ia)s of 47 and 44 cm(-1) were measured with the GACR and XMT methods, respectively, for the sand at a water saturation of 0.57. The results of the study indicate that the GACR method is a viable alternative for measuring air-water interfacial areas. The method is relatively quick, inexpensive, and requires no specialized instrumentation compared to the standard methods.

L'objectif de ce travail est de réaliser des substrats pour l’effet SEIRA (surface enhanced IR absorption) pour mesurer de faibles volumes de gaz ambiants possédant une signature moléculaire de 3,3 μm à 5,1 μm en exploitant la forte amplification de champ électrique due à la résonance plasmon de surface localisés. A cette fin, nous avons démontré la modulation des résonances de plasmon de surface localisées MIR (LSPR) dans les nanocristaux de ZnO dopés (NCs) dopés à Ga ou Al ainsi que dans des nanofils (NWs) de ZnO dopés Ga (GZO) et dans des nanofils coeur/coquille de ZnO/GZO. En ce qui concerne l’accordabilité de MIR LSPR dans les NC, nous avons modulé la résonance plasmon de surface dans des NC de ZnO dopés Ga et Al, de 3 à 5 μm en faisant varier la teneur en Al et en Ga de 3 à 9 at.%. L’incorporation des dopants s’est révélée homogène jusqu’à 6%. Au-delà (9%), l’incorporation était fortement hétérogène, révélant que la limite de solubilité était atteinte. Les NC présentent une faible activation des impuretés. L'activation était aussi faible que 8%. Les LSPR présentaient également un fort élargissement (largeur-à-mi-hauteur FWHM). Pour accroitre l'activation des dopants, nous avons synthétisés les NC dans des conditions pauvres en O et en passivant les NC synthétisés dans des conditions riches en O (en les isolant dans des matrices telles que Al2O3 et SiO2). Nous avons ainsi augmenté l'activation de 8% à 20% pour les deux stratégies. De plus, l'incorporation des NC dans les matrices a réduit l'élargissement spectral de moitié (de 2200 cm-1 pour les NC déposés à 1100 cm-1 pour les NC noyés en matrice). En correspondance, les effets d’auto-assemblage des nanocristaux sur leur LSPR ont été modélisés par simulation FDTD. Cela a fourni des indications quant aux mécanismes responsable de l’élargissement inhomogènes des LSPR de nanocristaux de GZO. Outre les nanoparticules, nous avons étudié des nanofils ZnO dopés Ga (GZO) et coeur/coquille (ZnO/GZO) synthétisés par CVD d’organométalliques . La première conclusion importante est que le gallium produit un fort effet surfacatnt lors de la croissance MOCVD de GZO. Au lieu de former des nanofils de section hexagonale, l’introduction de Ga modifie nettement l’énergie de surface des faces latérales et conduit à al formation de structures de type « sapins de Noël ». Ce constat est aussi valable pour les coquilles de GZO déposées sur coeur de ZnO. Dans ce cas, les coquilles démouillent et forment des structures hiérarchiques en branches. Concernant les propriétés optiques de ces objets, les mesures de FTIR-photo acoustiques ont démontré une signature d’absorption reliée à la présence de Ga et pouvant être accordée selon la teneur en Ga. Cette absorption reproduit le comportement d’une résonance plasmon de surface. Cette résonance a pu être accordée de 1600 à 1900 cm-1. / The scope of this thesis is about developing SEIRA (surface enhanced IR absorption) platform to probe low volumes of environmental gases that possess molecular signature from 3.3 μm to 5.1 μm leveraging the high field amplification of localised surface plasmon resonance (LSPR). To realise SEIRA, we demonstrated tuning MIR LSPR in Al or Ga doped ZnO nanocrystals (NCs) as well as in GZO or core-shell (ZnO/GZO) nanowires (NWs). Regarding tuning MIR LSPR in NCs, we demonstrated tunable MIR LSPR in Ga and Al doped ZnO NCs from 3 to 5 μm varying the Al or Ga content from 3 to 9 at.%. The incorporation of dopant was homogeneous up to 6%. At 9% dopant concentration, the incorporation was inhomogeneous, revealing the solubility limit has been reached. However, the NCs exhibited low activation of impurities. The activation was as low as 8%. The LSPR were characterised by large broadening as well. In order to enhance the dopant activation, we synthesized the NCs in O-poor conditions as well as passivated the NCs fabricated in O-rich condictions (by isolating and embedding them in matrices such as Al2O3 and SiO2 matrices). Both strategies improved the dopant activation from 8% up to 20%. Moreover, for assemblies of NCs dispersed in matrices, the broadening (FWHM) of the LSPR was reduced by half (from 2200 cm-1 in as-deposited NCs to 1100 cm-1 in embedded NCs). Correspondingly, the effect of the self-assembly of the nanocrystals on their LSPR was modeled by FDTD simulation and provided hindsight into the mechanisms responsible for the heterogeneous broadening of the LSPR. Finally, we have studied Ga-doped ZnO (GZO) and core-shell (ZnO/GZO) NW synthesized by MOCVD. The first important conclusion is that Ga plays a major surfactant role during the MOCVD growth of GZO. Instead of leading to hexagonal NWs, the introduction of Ga during the synthesis led to faceted “Christmas-tree” like architectures. The same observation held for core-shell ZnO-GZO nanowires; in the latter case, the GZO shell resulted in a dewetting branched architecture. Regarding their optical properties, photo-acoustic FTIR measurements revealed an absorption feature related to the Ga content, likely to be assigned to a plasmonic effect. This resonance could be tuned from 1600 to 1900 cm.

In a study to investigate the fate of the applied P in soils, a red-sandy clayey soil (Ferric Luvisols) from Rustenburg (high P fixing) and a red-sandy loam soil (Ferric Acrisols) from Loskop (low P fixing) were used. Sequential P fractionations were used to determine the content of the different P pools to show which pool the applied P was transformed to. The soils treatments consisted of different Prates (0, 25, 50, 100, 150, and 200 mg kg-1), and incubation periods (1, 60, 120, 180, and 240 days) under a laboratory conditions. The sequential P fractionation procedure consisted of extraction with hydrous ferric oxide in a dialysis membrane tube (DMT-HFO), 0.5M NaHC03, O.1M NaOH-P, 1.0M HCI, concentrated HCI, and concentrated H2S04 + H2O2. Approximately 30 to 60 % of the added P were transformed into less labile P pools within one day and 80-90 % after 60 days. This transformation was faster in the Rustenburg than in the Loskop soil showing a higher P fixation capacity. A major part of the P transformation was to the -OH-P1 pool with a recovery of about 30%. In the second experiment an attempt was made to determine P desorption rates by successive DMT-HFO extractions (1, 7, 14, 28, and 56 days) after the transformations of the applied P. This was followed by the sequential extractions to determine the changes and distribution of the added P into different P pools as well as which pools the P was des orbed from. The Rustenburg and Loskop soils were treated to different Prates (0, 25, 50, 100, and 200 mg P kg-1) and incubation periods (1, 120, and 240 days). The cumulative DMT -HFO extraction curves for 56 days showed that desorption could continue for a much longer period. This property is important in the economical management of fertilizer applications rates. Results showed the transformations and distribution of the applied P during incubation periods and proved that all the stable soil P pools contributed to the labile P pool by different proportions after prolonged successive DMT-HFO extractions. Although Rustenburg soil is considered a high P fixing soil, the P release rates under laboratory conditions were high enough to meet the requirements of cotton and tobacco crops. Root systems of these crops do not exploit 100 % soil volume as this laboratory method, which could explain why these crops experience P deficiencies. It is envisage that by using this method the P releasing properties of a soil could be used to develop a P desorption model to determine how much extractable P, with a specific extractant, in a particular soil, should be available at the beginning of a growing season to sustain a high enough P releasing rate to meet the requirements of a certain crop up to the end of the growing season. To do this, a model to describe root development that represents the percentage of the soil exploited P desorption rates that simulate P uptake by plant roots will be necessary. / Thesis (DPhil (Plant Production: Horticulture))--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

M.Sc. / The metallurgical industrial losses of base metals with waste solutions are an environmental threat to water sources, hence these metal ions must be removed prior to discharge into receiving bodies. In this study, Southern African clinoptilolite’s capability as an ion-exchanger with respect to Cu2+ and Co2+ was investigated in order to consider its application in metal cation removal from aqueous solutions. The clinoptilolite was characterised with X-ray powder diffraction (XRD), X-ray fluorescence (XRF), FTIR, thermogravimetric analyser (TGA) and SEM-EDS. The clinoptilolite was found to be a thermally stable alumino-silicate with calcite, dolomite and quartz as the main minerals. Investigations of Co2+ and Cu2+ uptake were first performed on non-mixed solutions of these cations. It was found that Cu2+ was removed faster than Co2+ with removal efficiencies of 79% and 63% respectively. The column method was used in the cation-exchange processes with synthetic solutions of 0.0020 M, 0.0698 M and 0.2000 M of Co2+ and Cu2+ concentrations which were measured using atomic absorption spectroscopy (AAS). The effects of Co2+ and Cu2+ ions on one another’s removal efficiency were investigated on Co/Cu mixed synthetic solutions by varying their concentration ratios in solution. The Cu2+ was generally found to be removed at lower rates than the Co2+. Investigations on added impurities in the form of Si4+ and Fe2+ in the mixed Co/Cu synthetic solutions were carried out to determine their effect on the removal efficiencies of the targeted metals. It was found that both Si4+ and Fe2+ greatly reduced the removal efficiency of Cu2+, especially with increased amounts of Si4+ in the Co/Cu solution.

M.Sc. (Instrumental Chemical Analysis) / Please refer to full text to view abstract

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