La gravure plasma de structures à fort rapport d’aspect dans le silicium est une étape clé dans la fabrication de microsystèmes et de composants de microélectronique de puissance. L’objectif de ce travail est de développer un procédé de gravure profonde du silicium, qui fonctionne à plus haute température de substrat que le procédé cryogénique en chimie plasma SF6/O2 et qui présente une meilleure stabilité en température et en concentration de gaz passivant(s). Dans ce but, de nouvelles voies de passivation non polymérisante ont été explorées. Nous avons évalué les possibilités de passivation par l’apport de SO2 en remplacement de O2. A température cryogénique, les propriétés de gravure sont semblables en plasma SF6/SO2 et SF6/O2 ; elles sont corrélées aux densités de neutres mesurées par spectrométrie de masse et actinométrie. La majeure partie des recherches a été consacrée à l’étude de la molécule SiCl4 comme précurseur de passivation. Nous avons au préalable analysé les interactions entre espèces générées en plasma SF6/SiCl4. Les expériences de caractérisation du plasma montrent que les réactions aux parois entre atomes F et espèces SiClx contrôlent la chimie du plasma et donc les propriétés de gravure du silicium. En mélange SF6/O2/SiCl4, ces réactions influent également sur la vitesse de gravure du substrat, mais l’ajout de SiCl4 à SF6/O2 a surtout pour effet de favoriser l’attaque chimique latérale. Nous avons finalement étudié la possibilité de former une couche de passivation par plasma SiCl4/O2 à température de substrat de -20 °C. Les résultats de cette étude permettent de proposer un nouveau procédé, basé sur l’alternance d’étapes de gravure par plasma SF6 et d’étapes de passivation par plasma SiCl4/O2. / Plasma etching of high aspect ratio structures in silicon is a key step for the fabrication of microsystems and power microelectronic devices. This thesis aimed to develop a silicon deep etching process, working at a higher substrate temperature than the cryogenic process in SF6/O2 plasma chemistry, and showing a better stability to drifts in temperature and passivating gas concentration. To this purpose, we investigated new methods of passivating the structure sidewalls by non polymerising chemistries. We studied the possibility of passivation by SO2 instead of O2. At cryogenic temperatures, etch properties are similar in SF6/SO2 and SF6/O2 plasmas. They are correlated to the neutral densities measured by mass spectrometry and actinometry. Most of the research was then dedicated to the study of SiCl4 as a passivation precursor. First we analysed the interactions between species generated in SF6/SiCl4 plasma. Characterisation experiments show that reactions on reactor walls between F radicals and SiClx species control the plasma chemistry, thereby the silicon etch properties. In SF6/O2/SiCl4 mixtures, these reactions also impact the substrate etch rate. However, the addition of SiCl4 to SF6/O2 mostly enhances lateral chemical etching. We finally studied the possibility of forming a passivation layer by SiCl4/O2 plasma at a substrate temperature of -20 °C. The results of this study enabled the development of a new process, based on alternating the etching steps in SF6 plasma with the passivation steps in SiCl4/O2 plasma.

The use of two online sensors, the S::CAN and the FLD, was used to evaluate the treatment of synthetic wastewater by UV/H₂O₂ advanced oxidation. The UV dose and intensity for the flow through reactor was also determined using H₂O₂ actinometry. The total power of the lamps in the reactor was determined to be 139 W which, with the absorbance of the water, produced a UV dose of 39.4 mJ/cm². It was determined that the S::CAN was unable to differentiate between treatment of a particular water, however it could differentiate between different test waters. The FLD was very sensitive and was able to detect minute variations in treatment of the test water.

Aerosols of nitrate solutions were irradiated in the presence of radical scavengers in an attempt to measure the yield of hydroxyl radical in both the aqueous phase and the gas phase. Carbon monoxide, benzoic acid, benzene and cyclohexane were used as scavengers to trap hydroxyl radical. The products from the reaction of these scavengers with hydroxyl radical were analysed with High Performance Liquid Chromatography and mass spectrometry. The radiant flux in the chamber was measured via ferrioxalate actinometry, both with bulk liquid and aerosol droplets. Many quantitative results were obtained but several anomalies were found. This suggests that Mie theory is not capable of predicting rates of photochemical reactions within droplets.

Aerosols of nitrate solutions were irradiated in the presence of radical scavengers in an attempt to measure the yield of hydroxyl radical in both the aqueous phase and the gas phase. Carbon monoxide, benzoic acid, benzene and cyclohexane were used as scavengers to trap hydroxyl radical. The products from the reaction of these scavengers with hydroxyl radical were analysed with High Performance Liquid Chromatography and mass spectrometry. The radiant flux in the chamber was measured via ferrioxalate actinometry, both with bulk liquid and aerosol droplets. Many quantitative results were obtained but several anomalies were found. This suggests that Mie theory is not capable of predicting rates of photochemical reactions within droplets.

Foodborne illnesses caused by Listeria monocytogenes have long been associated with ready-to-eat (RTE) meats contaminated after the primary thermal process has been applied. It is believed that brine solutions used to chill cooked RTE products may serve as a reservoir for L. monocytogenes becoming a potential point of post-processing contamination for RTE meats. Re-circulating ultraviolet light (UV) systems are being used to inactivate L. monocytogenes in chill brines; however very little has been reported on the dose response of healthy and stressed L. monocytogenes to UV in brine solutions. The objectives of this research were to determine 1) minimum dose of UV required to inactivate L. monocytogenes in distilled water, fresh brine, undiluted spent brine, and diluted spent brine, 2) if adaptation to food processing stresses affects the dose response, and 3) if the acquisition of antibiotic resistance mechanisms provides resistance to ultraviolet light 4) effect of stress adaptation on survival in brine solutions. After UV exposure, populations were reduced as follows from greatest to least: water > fresh brine > 5% spent brine > 35% spent brine > 55% spent brine > 100% spent brine (P ≤ 0.05). There were no population differences between acid stressed and antibiotic resistant or healthy and heat shocked (P > 0.05). However, acid-stressed and sulfanilamide-resistant were more resistant to UV light than healthy and heat shocked L. monocytogenes (P ≤ 0.05). Survival in brine solutions (no UV) followed the trend, from greatest to least (P ≤ 0.05): sulfanilamide-resistant > acid-stressed > healthy > heat-shocked. Population estimates decreased from initial inoculation to final sampling for each cell type suspended in spent brine (P ≤ 0.05), but only healthy and heat- shocked cells suspended in fresh brine were significantly reduced (P ≤ 0.05). Knowledge of UV dosing required to control L. monocytogenes in brines used during RTE meat processing, and a greater understanding of the interactions that may influence dose will aid manufacturers in establishing appropriate food safety interventions for these products. / Ph. D.

Nesta pesquisa estudou-se o emprego de radiação ultravioleta em reatores de batelada e em reator com escoamento contínuo (unidade comercial de alta intensidade), respectivamente em escala de laboratório e real. Os ensaios em batelada tiveram como finalidade monitoramento da potência radiante da lâmpada de baixa pressão de vapor de mercúrio durante a vida útil, determinação da intensidade média de radiação ultravioleta incidente no interior da câmara de desinfecção, obtenção dos coeficientes do modelo de Hom para coliformes totais, Escherichia coli e Clostridium perfringens e comparação da resistência à desinfecção desses microrganismos indicadores e colifagos. Os ensaios em sistema contínuo apresentaram como principal objetivo estudo da resistência dos microrganismos indicadores à desinfecção em condições de operação em escala real. Nos ensaios de desinfecção utilizou-se esgoto sanitário tratado em nível secundário. Os microrganismos indicadores apresentaram a seguinte ordem decrescente de resistência à desinfecção: C. perfringens, coliformes totais, E. coli e colifagos. As percentagens de inativação de C. perfringens, coliformes totais, E. coli e colifagos nos ensaios em batelada variaram de 0 a 99,882%, 36,3 a 99,999%, 21,8 a 100% e de 86,5 a 100%, respectivamente. Os resultados de inativação obtidos para coliformes totais e E. coli apresentaram ajustes pelo modelo de Hom com valores de R2 superiores a 0,81 e 0,76, respectivamente. Comprovou-se que a instalação contínua é inadequada para efluentes com elevadas concentrações de sólidos em suspensão e matéria orgânica. / In this research the use of ultraviolet radiation was studied in batch and continuous flow (high intensity commercial unit) reactors, respectively in laboratory and real scale. The batch assays were aimed to monitor the wattage of the low-pressure mercury lamp during its lifetime, to determine the mean ultraviolet radiation intensity inside disinfection chamber, to obtain Hom model coefficients for total coliforms, Escherichia coli and Clostridium perfringens and to compare the resistance to disinfection of these indicator microorganisms and coliphages. The assays in the continuous system presented as main objective to study the resistance of these indicator microorganisms to disinfection in real scale operational conditions. In the disinfection assays wastewater treated by a secondary level was used. The indicator microorganisms presented the following decreasing order of disinfection resistance: C. perfringens, total coliforms, E. coli and coliphages. C. perfringens, total coliforms, E. coli and coliphages inactivation percentages in batch assays varied from 0 to 99,882%, 36,3 to 99,999%, 21,8 to 100% and from 86,5 to 100%, respectively. The inactivation results obtained for total coliforms and E. coli presented adjustments by Hom model with R2 values above 0,81 and 0,76, respectively. It was proved that the installation of high intensity is not adequate for effluents with high concentration of suspended solids and organic matter.

Nesta pesquisa estudou-se o emprego de radiação ultravioleta em reatores de batelada e em reator com escoamento contínuo (unidade comercial de alta intensidade), respectivamente em escala de laboratório e real. Os ensaios em batelada tiveram como finalidade monitoramento da potência radiante da lâmpada de baixa pressão de vapor de mercúrio durante a vida útil, determinação da intensidade média de radiação ultravioleta incidente no interior da câmara de desinfecção, obtenção dos coeficientes do modelo de Hom para coliformes totais, Escherichia coli e Clostridium perfringens e comparação da resistência à desinfecção desses microrganismos indicadores e colifagos. Os ensaios em sistema contínuo apresentaram como principal objetivo estudo da resistência dos microrganismos indicadores à desinfecção em condições de operação em escala real. Nos ensaios de desinfecção utilizou-se esgoto sanitário tratado em nível secundário. Os microrganismos indicadores apresentaram a seguinte ordem decrescente de resistência à desinfecção: C. perfringens, coliformes totais, E. coli e colifagos. As percentagens de inativação de C. perfringens, coliformes totais, E. coli e colifagos nos ensaios em batelada variaram de 0 a 99,882%, 36,3 a 99,999%, 21,8 a 100% e de 86,5 a 100%, respectivamente. Os resultados de inativação obtidos para coliformes totais e E. coli apresentaram ajustes pelo modelo de Hom com valores de R2 superiores a 0,81 e 0,76, respectivamente. Comprovou-se que a instalação contínua é inadequada para efluentes com elevadas concentrações de sólidos em suspensão e matéria orgânica. / In this research the use of ultraviolet radiation was studied in batch and continuous flow (high intensity commercial unit) reactors, respectively in laboratory and real scale. The batch assays were aimed to monitor the wattage of the low-pressure mercury lamp during its lifetime, to determine the mean ultraviolet radiation intensity inside disinfection chamber, to obtain Hom model coefficients for total coliforms, Escherichia coli and Clostridium perfringens and to compare the resistance to disinfection of these indicator microorganisms and coliphages. The assays in the continuous system presented as main objective to study the resistance of these indicator microorganisms to disinfection in real scale operational conditions. In the disinfection assays wastewater treated by a secondary level was used. The indicator microorganisms presented the following decreasing order of disinfection resistance: C. perfringens, total coliforms, E. coli and coliphages. C. perfringens, total coliforms, E. coli and coliphages inactivation percentages in batch assays varied from 0 to 99,882%, 36,3 to 99,999%, 21,8 to 100% and from 86,5 to 100%, respectively. The inactivation results obtained for total coliforms and E. coli presented adjustments by Hom model with R2 values above 0,81 and 0,76, respectively. It was proved that the installation of high intensity is not adequate for effluents with high concentration of suspended solids and organic matter.

Ziel der vorliegenden Arbeit war die Herstellung, der Einsatz und die Bewertung von Durchfluss-Photoreaktoren für online Prüfungen zur photochemischen Stabilität im HPLC-System (hn- HPLC). Neben der Anfertigung eines für dieses Anforderungsprofil geeigneten Reaktors war es von Interesse, Strahlungsintensitäten zu bestimmen, die Photostabilität von UV-Filtern zu bewerten, sowie analytische Verfahren zu optimieren. Als wichtigste Ergebnisse dieser Arbeit sind: (1) erstmalig aktinometrische Messungen im Durchfluss durchgeführt worden, (2) die eingestrahlten Intensität im Durchfluss-Reaktor mit dem Standard-Sonnenspektrum (COLIPA) verglichen worden, (3) die Bestimmung von 4-Aminobenzoesäure (PABA) und 4-Acetamidobenzoesäure (PAABA) mittels HPLC-hn optimiert und (4) photochemische Umsätze an folgenden UV-Filtern festgestellt worden: 4-Methoxy-zimtsäure-2-ethyl-hexylester, 3-(4'-Methyl)benzyliden-bornan-2-on,1-(4-tert.-Butylphenyl)-3-(4-methoxyphenyl)propan-1.3-dion und 4-Aminobenzoesäure. / The aim of the present thesis was the construction and evaluation of an on-line photochemical reactor for photochemical stability tests in an HPLC-system (hn- HPLC). The work was focused on the production of a functional and effective photochemical reactor, the determination of radiation intensities and the optimisation of analytical methods. Furthermore the stability of UV-filters under exposure to UV-radiation was investigated. The main results of these thesis are presented in the following: (1) the determination of radiation intensities in online photochemical reactors, (2) the comparison of spectra with standard-sun spectra (COLIPA), (3) the optimisation of the determination of 4-aminobenzoic acid (PABA) and 4-acetamidobenzoic acid (PAABA) with an HPLC-hn method (4) the characterisation of photochemical changes of UV-filters: p-methoxy-cinnamic acid-2-ethyl-hexyl ester, 3-(4'-methyl)benzylidene-bornan-2-on,1-(4-tert.-butylphenyl)-3-(4-methoxyphenyl)propan-1,3-dion and p-aminobenzoic acid.

Este estudo apresenta a modelagem fluidodinâmica de um reator solar utilizado para Processos Oxidativos Avançados (POA). Desenvolveu-se um modelo que considera a fluidodinâmica, o campo de radiação e cinética da reação de actinometria química (ferrioxalato), em regime transiente. Essa modelagem foi feita utilizando-se o código de fluidodinâmica computacional PHOENICS. Para análise dos resultados de simulações com o modelo, consideraram-se os dados experimentais de actinometria química para um trecho do reator, constituído de dois tubos (hairpin), e de distribuição de tempos de residência (DTR), para o reator completo, constituído de dez tubos. Os dados experimentais foram obtidos por RIBEIRO (2009). O resultado da análise da distribuição do tempo de residência do reator completo mostrou que o modelo baseado em escoamento laminar apresentou uma maior aderência aos dados experimentais de DTR. Como os experimentos de actinometria foram realizados em trecho com dois tubos do reator, construiu-se a geometria do hairpin que apresentou uma DTR mais aderente aos modelos teóricos. Outra simplificação foi necessária para a modelagem do campo de radiação de forma mais precisa, adaptando-se o hairpin para um tubo reto simples. A partir dos resultados de actinometria química foi possível estimar, pelo modelo, a taxa de fótons incidentes na parede do reator. / This study consists of the fluid dynamic modeling of a solar reactor used in Advanced Oxidation Processes (AOP). The model was developed by considering fluid dynamics, radiation field and the kinetics of the chemical actinometry reaction (ferrioxalate) in transient regime. This modeling was developed using computational fluid dynamics (CFD) in PHOENICS. Simulation results based on the model were analyzed by comparing them with a set of chemical actinometry experimental data obtained by RIBEIRO (2009). This considered a reactor section constituted by two pipes (hairpin), and the residence time distribution (RTD) of the complete reactor, composed of ten pipes. Residence time distribution results showed that the laminar flow model presented a better fitting to experimental data. Since the actinometry experiments were carried out in a reactor section with two pipes, a new geometry was designed, which resulted in a better fitting of RTD results with theoretical models. In order to obtain a more precise radiation field model, another simplification was necessary, which consisted of assuming a straight cylindrical pipe geometry. The use of the chemical actinometry and the radiation field model enabled the estimation of the incident photons rate at reactor wall.

Este estudo apresenta a modelagem fluidodinâmica de um reator solar utilizado para Processos Oxidativos Avançados (POA). Desenvolveu-se um modelo que considera a fluidodinâmica, o campo de radiação e cinética da reação de actinometria química (ferrioxalato), em regime transiente. Essa modelagem foi feita utilizando-se o código de fluidodinâmica computacional PHOENICS. Para análise dos resultados de simulações com o modelo, consideraram-se os dados experimentais de actinometria química para um trecho do reator, constituído de dois tubos (hairpin), e de distribuição de tempos de residência (DTR), para o reator completo, constituído de dez tubos. Os dados experimentais foram obtidos por RIBEIRO (2009). O resultado da análise da distribuição do tempo de residência do reator completo mostrou que o modelo baseado em escoamento laminar apresentou uma maior aderência aos dados experimentais de DTR. Como os experimentos de actinometria foram realizados em trecho com dois tubos do reator, construiu-se a geometria do hairpin que apresentou uma DTR mais aderente aos modelos teóricos. Outra simplificação foi necessária para a modelagem do campo de radiação de forma mais precisa, adaptando-se o hairpin para um tubo reto simples. A partir dos resultados de actinometria química foi possível estimar, pelo modelo, a taxa de fótons incidentes na parede do reator. / This study consists of the fluid dynamic modeling of a solar reactor used in Advanced Oxidation Processes (AOP). The model was developed by considering fluid dynamics, radiation field and the kinetics of the chemical actinometry reaction (ferrioxalate) in transient regime. This modeling was developed using computational fluid dynamics (CFD) in PHOENICS. Simulation results based on the model were analyzed by comparing them with a set of chemical actinometry experimental data obtained by RIBEIRO (2009). This considered a reactor section constituted by two pipes (hairpin), and the residence time distribution (RTD) of the complete reactor, composed of ten pipes. Residence time distribution results showed that the laminar flow model presented a better fitting to experimental data. Since the actinometry experiments were carried out in a reactor section with two pipes, a new geometry was designed, which resulted in a better fitting of RTD results with theoretical models. In order to obtain a more precise radiation field model, another simplification was necessary, which consisted of assuming a straight cylindrical pipe geometry. The use of the chemical actinometry and the radiation field model enabled the estimation of the incident photons rate at reactor wall.