To meet the growing energy world demands, and in conjunction, lower CO2 production levels, near zero emission energy sources must be pushed to the forefront as alternatives to fossil fuels. Photoelectrochemical (PEC) cells are a potential alternative to fossil fuels and have recently generated much interest because of their potential to electrolyze water into hydrogen fuel from sunlight. But in order to be competitive with fossil fuels, understanding the mass-transfer limitations in PEC systems is critical. This work focuses on the addressing the mass-transfer limitations in a conceptually novel PEC cell reactor, the Dual Bed Colloidal Suspension Reactor (DBCSR). Mass-transfer correlations for the DBCSR are presented. The correlations are based on experimental data obtained using two fabricated diffusion cells. The working correlation representative of both cells is given. An analysis of the orientation of the gas sparger suggests that the transport phenomena in both cells is not the same, and therefore using two correlations to represent similar systems is justified. An energy analysis is presented that shows that gas sparging is a low energy consumption option to mitigate mass-transfer limitations. Future work is suggested for better understanding the mass-transfer behavior in the DBCSR.

Composite materials are usually multi-phase materials, made up from two or more phases, which are combined to provide properties that the individual constituents cannot. This technology represents an economical way to improve product performances avoiding the use of expensive materials. Composite materials can be obtained as films by means of the electrolysis of electroplating solutions in which micrometre- or submicrometre-size particles are suspended: variable amounts of these particles become incorporated in the electrochemically produced solid phase, to which they impart enhanced properties. The main aims of the present work contributing to this thesis are the study of different parameters influencing the electroco-deposition process in order to promote and improve the applicability of such a technology in the high speed electroplating industry. Following a comprehensive review on the electroco-deposition of composite coatings, the phenomena have been analysed moving from a microscopic point of view i. e. the role of the metal ions present in the electrolyte and adsorption on the inert particles and their interactions with the growing metal layer, to a macroscopic point of view i. e. the electrolyte agitation, its influence on particle motion and all the issues related to the presence of particles in an electrolyte during electroplating. In particular the inert particle influence in terms of geometry, dimension and chemical nature (spherical polystyrene particles vs. irregular alumina particles with different dimensions), the metal matrix influence (nickel, copper and zinc), the influence of electrolyte agitation (using a Rotating Cylinder Electrode cell system) and the influence of the coating thickness on particle content in the final coating, using different deposition times, have been examined. The importance of the particle shape has been highlighted showing how incorporating irregular geometries gave higher particle incorporation densities than regular geometries. The influence of the substrate finishing in terms of imperfections has been related to the particle incorporation rate showing how small surface imperfections enhanced the incorporation of particles. Different hydrodynamic regimes have been analysed resulting three different regimes being discerned: laminar, transitional and turbulent. The consequence, in terms of particle incorporation levels, has been found showing how the amount of particles in the coating changed from one regime to another. Different rate-determining steps were related to the hydrodynamics: when the regime is laminar, particles were incorporated as agglomerates and the process was under particle transfer control, whilst in the turbulent zone, the rate determining step was the velocity of reduction of the ions adsorbed on the particle surface.

A presente tese fornece uma revisão bibliográfica dos trabalhos mais importantes sobre as reduções catódicas e anódicas do grupo carbonila em aldeídos, cetonas, dicetonas, cetonas α, β-insaturadas, cetoácidos, cetoésteres, e ésteres α, &#946 -insaturados. São descritas as sínteses por nós efetuadas de 13 hidroxi e cetoésteres metílicos, a saber: mandelato , 4-carbometoxi, 4-cloro, 4-nitro e 4-metoximandelatos, α-fenil-β-hidroxibutirato, fenilglioxilato, 4-carbometoxi, 4-cloro, 4-nitro e 4-metoxifenilglioxilatos,benzilpiruvato e piruvato. A pureza desses compostos foi testada por meio de espectroscopia no I.V .e R.M.N., cromatografia de gás ou em camada delgada e, em alguns casos, por análise elementar. 4-nitrofenilglioxilato, 4-carbometoxifenilglioxilato e 4-carbometoximandelato, compostos ainda não descritos na literatura, foram caracterizados e analisados. O trabalho fornece as eletrólises, com eletrodos de platina em metanol, de 10 cetoésteres que incluem, além dos acima enumerados, o α -cetobutirato de metila, 4-cetopimelato de etila e o cetomalonato de etila. Os produtos de reação obtidos foram identificados por métodos cromatográficos e espectroscópicos. São apresentadas dois tipos de experiências eletrolíticas: as simples e as que foram acompanhadas em tempos periódicos pela análise cromatográfica, sendo as primeiras, em alguns casos, repetidas, variando-se o tempo da eletrólise. Os resultados obtidos demonstram que são reduzidos aos hidroxiésteres correspondentes os seguintes cetoésteres contendo anel aromático: fenilglioxilato, 4-cloro e 4-carbometoxifenilglioxilatos e benzilpiruvato, como também, os 2 cetoésteres alifáticos -α -cetobutirato e piruvato. Entretanto, verifica-se que tanto 4-nitro e 4-metoxifenilglioxilatos como cetomalonato e 4-cetopimelato não sofrem redução. Estes resultados comparados com os anteriores do nosso laboratório, permitem sugerir a seguinte ordem de velocidade da redução: α -cetovalerato > α-cetobutirato > piruvato > fenilglioxilato) > 4-clorofenilglioxilato > 4-carbometoxifenilglioxilato. São fornecidas provas de que a falta de reatividade de 4-nitrofenilglioxilato e cetomalonato e a diminuição de reatividade de 4-cloro e 4-carbometoxifenilglioxilatos, como também, de piruvato são devidas à existência do equilíbrio cetoéster-semiacetaléster nestes compostos, em metanol. Finalmente, é apresenta.da uma discussão do mecanismo da redução de cetoésteres que justificaria a diminuição de reatividade de fenilglioxilato em relação aos α-cetoésteres alifáticos e a falta de reatividade. de 4-cetopimelato e 4-metoxifenilglioxilatonilglioxilato. / The present work describes the syntheses of some aliphatic and aromatic α-hydroxy - and α-keto-methyl esters and reports the electrolyses of the latter, in methanol, at a platinum cathode Some simple electrolytic experiments, varying the experimental conditions as well as those in which the transformations occurring during the electrolyses were followed by gas chromatography, are described. The reactivities towards cathodic reduction are reported and the following order of the relative rate for the reduction is suggested: α-oxovalerate > α-oxobutyrate > pyruvate> phenylglyoxylate > 4-chlorophenylglyoxylate > 4-methoxycarbonylphenylglyoxylate .No reduction is found to occur with 4-methoxyphenylglyoxylate 4-nitrophenylglyoxylate or 4-oxopymelate .An explanation for these differences in reactivities is suggested on the basis of electronic effects, steric inhibition of coplanarity, and hemiacetal formation

Filmes de benzotriazol (BTAH) formados sobre aços carbono e inoxidável 316L foram estudados em meios de ácido sulfúrico, ácido clorídrico e cloreto de sódio a 25°C. Os seguintes aspectos foram considerados: as condições de formação do filme, sua eficiência, sua resistência em meios não contendo o inibidor,a presença de aditivos e o efeito do transporte de massa sobre o mecanismo da reação. Foram empregadas como técnicas: transitórios de potencial de circuito aberto, ensaios gravimétricos, curvas de polarização potenciostáticas e potenciodinâmicas com eletrodo parado e de disco rotativo, cronoamperometria, espectroscopia de impedância eletroquímica, microscopia ótica, microscopia eletrônica de varredura e análise da superfície por dispersão de energia. O BTAH se mostrou inibidor na grande maioria dos meios para os dois materiais estudados. A resistência dos filmes formados não existe ou é parcial quando as superfícies metálicas revestidas com o filme são imersas nos meios estudados sem inibidor. A adição de Cu(II) aumenta a resistência dos filmes, para determinadas relações [BTAH]/[Cu(II)] que estabilizem o intermediário Cu(I). A presença de íons provenientes da dissolução do aço inoxidável 304 em H2SO4 0,50 mol.L-1 contendo BTAH, eleva significativamente a resistência dos filmes formados, quando estes são expostos aos meios sem inibidor. O cloreto de trimetildodecil amônio exerce sinergismo sobre a ação do BTAH como inibidor de corrosão do aço carbono 1010 em meios ácidos. Superfícies de aço carbono previamente reduzidas são mais eficientes na formação de filmes resistentes aos meios sem inibidor. O transporte de massa do BTAH é uma etapa cinética importante no mecanismo de formação do filme sobre aço inoxidável 316L em meio de HCI 2,0 mol.L-1. O BTAH se mostrou inibidor para a corrosão do aço quando revestido pelo \"primer\" da tinta epóxi, quando adicionado à tinta ou quando o filme é formado antes da aplicação do \"primer\". / Benzotriazole (BTAH) films formed on carbon steel and 316L stainless steel have been studied in sulfuric and chloridric acids and in sodium choride solutionsat 25°C. Different aspects were considered: the film formation conditions, its efficiency, its resistance, the presence of additives and the effect of mass transport on the reaction mechanism. Open circuit potential measurements, weight loss experiments, potenciostatic and potentiadynamic polarization curves using stationary and rotating disc electrode, chronoamperometry, electrochemical impedance spectroscopy, optical and scanning electron microscopies and energy dispersive surface analysis have been used as techniques. BTAH have shown inhibitive effect over the majority of the systems studied. The film resistance depends on the presence of the inhibitor in the solution but the result is different if the film is formed in solution containing additives as copper (II) ions or cations obtained from 304 SS dissolution in H2SO4 media; in this case the films resist to chloridric acid media without BTAH. Dodecyltrimetilammonium chloride presents synergism on the inhibitive BTAH action forcarbon steel in acid solution. The BTAH mass transport represents an important step on the film formation mechanism. BTAH is also an effective inhibitor for carbon steel covered by epoxy primer when it is added to the primer or when the film is formed on the carbon steel surface from a H2SO4 solution containing BTAH.

Orientador: Nilson Cristino da Cruz / Resumo: O alumínio é um dos materiais mais utilizados em vários setores da indústria. Devido ao baixo custo, se comparado ao cobre, e considerando sua abundância de oferta, o interesse nas propriedades térmicas do alumínio tem aumentado. Neste contexto, a proposta desta pesquisa é avaliar as propriedades térmicas de amostras de alumínio tratadas por oxidação eletrolítica plasmática (PEO), em eletrólitos de silicato de sódio, utilizando espectroscopia fotoacústica. A rugosidade, morfologia e a composição química dos revestimentos foram analisados, respectivamente, por perfilometria, Microscopia Eletrônica de Varredura (MEV) e Espectroscopia de Energia Dispersiva (EDS). A porosidade da camada superficial do revestimento foi estimada pelo software de processamento de imagem digital, utilizando imagens da análise de MEV, enquanto difração de Raios X (DRX) foi utilizada para determinar a estrutura cristalina das superfícies tratadas. Os resultados das análises demonstraram que os revestimentos, predominantemente constituídos por γ-Al2O3, são rugosos, com superfícies porosas e apresentam boa resistência mecânica. A espectroscopia de absorção de UV-VIS demonstrou que a amostra tratada absorveu em média 18% mais radiação na região infravermelha quando comparada com amostras sem tratamento. Em consequência, como revelado pela espectroscopia fotoacústica a difusividade térmica das amostras tratadas é pelo menos 30% maior se comparada ao alumínio não tratado e 700% maior do que a alumina conven... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Aluminum is one of the most widely used materials in several areas of the industry. Owing to lower cost, if compared to copper, and considering its abundance, the interest on the thermal properties of aluminum has increased. In this context, the proposal of this research is to evaluate the thermal properties of aluminum samples treated by Plasma electrolytic oxidation (PEO), in sodium silicate electrolytes, using photoacoustic spectroscopy. Roughness, morphology and chemical composition of the coatings have been analyzed, respectively, by profilometry, scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). The porosity of the surface layer was estimated by digital image processing using SEM micrographs while X-ray diffraction (XRD) was used for determining the crystalline structure of the treated surfaces. The results of the analyses have shown that the coatings, predominantly constituted by γ-Al2O3, are rough, with porous surfaces and present good mechanical resistance. UV-Vis absorption spectroscopy has shown that the treated sample absorbed on average 18% more radiation in the infrared region than the pristine samples. In consequence, as revealed by photoacoustic spectroscopy the thermal diffusivity of the treated samples is at least 30% larger if compared to untreated aluminum and 700% larger than that of conventional Alumina / Mestre

Ce travail de thèse s’inscrit dans un projet de grande envergure piloté par l’IRT M2P, intitulé « Hard Chrome by Trivalent Chromium » qui regroupe 15 partenaires industriels et 2 partenaires académiques. L’objectif principal est de substituer les composés du chrome hexavalent par des électrolytes à base de chrome trivalent dans les procédés de chromage « dur », en réponse à l’application du règlement européen REACH en septembre 2017, même si des demandes d’autorisations temporaires sont en cours. Dans le cadre de cette thèse, des études électrochimiques ont été réalisées sur des bains commercial et synthétique. Celles-ci ont conduit au choix d’un matériau jouant le rôle d’anode, à une meilleure compréhension des mécanismes mis en jeu et de ce fait à une optimisation des conditions d’utilisation du bain commercial. D’autre part, une étude approfondie des courbes transitoires permet de mieux appréhender le comportement des électrolytes de chrome trivalent vis-à-vis des courants pulsés. Ainsi, un plan d’expérience sur les paramètres des pulses avec pour sortie de multiples caractérisations des dépôts de chrome montre que les courants pulsés influent sur plusieurs propriétés telles que : la teneur en carbone, la structure cristalline, la microdureté, la morphologie de surface et la microfissuration. Grâce au traitement des données issues du plan d’expériences, l’optimisation des paramètres de polarisation aboutit à l’élaboration de séquences de pulses optimisées. L’utilisation de celles-ci, employées seules ou en combinaison avec d’autres séquences de pulses issues également du plan d’expériences, aboutit à l’obtention de dépôts de chrome trivalent dont les propriétés sont modulables en fonction des paramètres procédés. Dans l’optique de la mise en place d’une nouvelle stratégie de choix des paramètres de l’impulsion anodique, un dispositif permettant la mesure du pH local en fonction des séquences et à proximité immédiate de la surface a été élaboré. Les premières tendances confirment les modes d’action des courants pulsés, et les choix qui ont été faits pour l’optimisation. / This thesis work is part of an ambitious project handled by IRT M2P, named “Hard Chrome by Trivalent Chromium” which gathers 15 industrials partners but also 2 academic partners. The main objective is to substitute the hexavalent chromium compounds in hard chromium electroplating process before there ban by European instances (REACH, ECHA) in September 2017, excepted for those authorized. As part of this thesis, electrochemical studies were realized on commercial and synthetic baths. Thanks to this studies, a material has been chosen to act as an anode for the making of the trivalent chromium coatings ; furthermore, the utilization conditions of the commercial bath has been optimized. Moreover, another study based on transient curves allows a better comprehension of the behaviour of the trivalent chromium electrolytes regarding pulsed current. This work permitted the elaboration of pulse sequences in the form of an experimental design. The realization and characterization of trivalent chromium coatings as a part of the experimental design show that pulsed current have an effect on several properties of the coatings such as carbon content, crystalline structure, microhardness, surface morphologies an microcracking. Thanks to the analyses of the results from the experimental design, an optimization of pulsed current has been made to obtain optimized pulse sequences. The utilization of those pulse sequences, used alone or combine with some pulse sequences of the experimental design lead to the elaboration of trivalent chromium coatings which properties are adjustables depending on the set parameters of the process. To further optimize the properties of the coatings, the basis of an analysis tool based on local pH measurements are developed; this analysis tool must make it possible to select the most interesting pulse sequences for the realization of trivalent chromium coatings.

A síndrome cólica equina (SCE) é a emergência mais frequente em equinos. Sua etiopatogenia é diversificada, dificultando o diagnóstico e comprometendo a aplicação do tratamento apropriado em cada caso. Sendo assim, este estudo visa ampliar os conhecimentos nesta área, tendo como foco diferenciar as alterações hemogasométricas entre segmentos intestinais acometidos, tipos e grau de lesão. Para tanto, foram avaliados 30 equinos separados em três grupos (G1 = animais que apresentavam lesôes no intestino delgado; G2 = animais que apresentavam lesões no intestino grosso e G3 = controle) e reorganizados novamente em três grupos de acordo com o tipo e grau de lesão (GA = isquemia severa com necessidade de enterectomia; GB = congestão/isquemia leve e GC = sem lesões; controle) observados na laparotomia. Os animais foram acompanhados durante o atendimento clínico-cirúrgico e tiveram avaliados por hemogasometria: sódio (Na+), potássio (K+), cloreto (Cl-), nitrogênio ureico sanguíneo (BUN), glicose (Glu), hematócrito, hemoglobina, pH(v), pressão parcial do dióxido de carbono do sangue venoso (pCO2(v)), concentração total de dióxido de carbono no plasma sanguíneo (ctCO2(v)), bicarbonato (HCO3-), excesso de base (BE) e anion gap (AnGap). As amostras foram coletadas anaerobicamente, através de punção jugular, no instante da chegada dos animais ao centro clínico, pré-tratamento. Não foram observadas alterações nos níveis plasmáticos de Na+, K+, Cl-, pCO2(v) e AnGap independente da etiopatogenia da SCE. Foi constatado que indivíduos com lesões presentes no intestino delgado apresentam níveis elevados de ctCO2(v), BUN e HCO3- em relação aos animais com lesões no intestino grosso e controle (p< 0,05), sendo que a comparação do HCO3- G1xG3 apresentou p< 0,001, assim como valores de glicose e BE em relação ao controle (p< 0,05). Verificou-se que os animais com lesões isquêmicas severas e que necessitaram de enterectomia apresentaram valores de glicose, hematócrito e hemoglobina superiores aos animais dos grupos que apresentavam lesões brandas tais como, congestão e/ou isquemia discreta (p< 0,01) e ao controle (glicose = p< 0,01; hematócrito e hemoglobina = p< 0,001). Evidenciou-se também que estes os equinos com lesões isquêmicas severas apresentaram valores superiores de pH(v), HCO3- e BE em relação aos animais do grupo controle (p< 0,01). Equinos com lesões isquêmicas severas localizadas no intestino delgado e/ou lesões isquêmicas severas apresentam variações laboratoriais importantes na avaliação do paciente. / Equine colic syndrome presents very diverse etiopathogenesis, making its diagnosis and treatment difficult. Thus, this study aims to increase knowledge in this area, distinguishing hemogasometric changes among affected body regions and injury types. For this, 30 horses were assessed, divided into three groups according to the affected body regions (G1 = small intestine; G2 = large intestine; G3 = control) and then reorganized into three groups according to the injury types (GA = severe ischemia and need for enterectomy; GB = congestion/mild ischemia; GC = no injuries). Sodium (Na+), potassium (K+), chloride (Cl-), blood urea nitrogen (BUN), glucose (Glu), hematocrit (Ht), hemoglobin (Hb), pH, blood carbon dioxide partial pressure (pCO2), total carbon dioxide concentration in blood (ctCO2), bicarbonate (HCO3-), base excess (BE) and anion gap (AG) were measured. Samples were collected by jugular puncture, before treatment. No significant changes were found in plasma levels of Na+, K+, Cl-, pCO2 and AG in any etiopathogenesis of equine colic syndrome. Horses with small intestine injuries presented higher levels of ctCO2 (p< 0,05), BUN (p< 0,05) and HCO3- (p< 0,001), compared to those with large intestine injuries and to the control group, as well as higher levels (p< 0,05) of Glu and BE than the control group. Animals with severe ischemic injuries presented higher levels of Glu, Ht and Hb than the ones with mild congestion injuries and/or mild ischemia (p< 0,01) and those without injuries (Glu p< 0,01, Ht and Hb p< 0,001). Horses with severe ischemic injuries presented higher pH, HCO3- and BE compared to control ones (p< 0,01). Therefore, it was possible to conclude that horses with small intestine injuries and with severe ischemic injuries show variations of parameters which can be observed through hemogasometry.

The objectives of this project were to evaluate the efficacies of electrolyzed oxidizing (EO) and ozonated waters as antimicrobial agents for enhancing the microbiological safety of fresh strawberries (Fragaria x ananassa). The influence of sodium chloride (NaCl) concentrations used for preparing EO water was evaluated on their bactericidal activities against naturally occurring aerobic mesophiles on strawberries with a contact time of 5, 10, or 15 min. EO water and ozonated water containing about 1.90 ppm ozone were evaluated and compared with sodium hypochlorite (NaOCl) solution on their capabilities to inactivate and control the growth of Listeria monocytogenes and Escherichia coli O157:H7 inoculated onto strawberries stored at 4 ± 1 °C for up to 15 d, respectively. Post-treatment neutralization of fruit surfaces by washing was also investigated. More than 2 log₁₀ CFU/g reduction of mesophilic aerobic bacteria was achieved in samples washed for 10 or 15 min in EO water prepared from 0.10% (w/v) NaCl solution. Bactericidal activity of treatment solutions against L. monocytogenes and E. coli O157:H7 was not affected by post-treatment neutralization, and their effectiveness against both pathogens in whole fruit tissues did not significantly increase with increasing exposure time. The EO water had an equivalent antibacterial effect as compare with NaOCl in eliminating L. monocytogenes and E. coli O157:H7 on whole strawberry tissues. Fruit surfaces washing with distilled water resulted in 1.90 and 1.27 log₁₀ CFU/ml of rinse fluid reduction of L. monocytogenes and E. coli O157:H7, respectively, whereas ≥ 2.60 log₁₀ CFU/ml of rinse fluid reduction of L. monocytogenes and up to 2.35 and 3.12 log reduction of E. coli O157:H7 were observed on fruit surfaces washed with EO water and NaOCl solution, respectively. However, EO water and NaOCl solution treatments did not exhibit a higher microbicidal activity than water treatment during refrigeration storage. The ozone treatment on inoculated strawberries was not remarkably effective in removing and eliminating pathogens on the whole fruit tissues, but the populations of L. monocytogenes and E. coli O157:H7 were significantly decreased after ozone treatment regardless of the exposure time. The number of L. monocytogenes and E. coli O157:H7 on fruit surfaces was decreased by 2.17 and 2.02 log₁₀ CFU/ml of rinse fluid, respectively, after washing with ozonated water for 10 min. / Graduation date: 2008

M. Tech. Metallurgical Engineering. / Studies the tribological and electrochemical behaviour of various WC-Co, WC-Co-Cr and CrC-NiCr based thermal sprayed coatings in synthetic mine water environment. The research aims to achieve the following objectives. 1. Characterize commercially available cermet powders used during thermal spray process. 2. Explore and understand the relationship between feedstock powder parameters, the phases and microstructures generated during thermal spray process. Study the interrelationship of feedstock powder chemistry and method of powder synthesis on wear and corrosion behavior of thermally sprayed coatings. Assess the joint actions of wear and corrosion behaviour of the coatings in synthetic mine water environment.

Pressure tubes pick up hydrogen while they are in service within CANDU reactors. Sufficiently high hydrogen concentration can lead to hydride precipitation during reactor shutdown/repair at flaws, resulting in the potential for eventual rupture of the pressure tubes by a process called Delayed Hydride Cracking (DHC). The threshold stress intensity factor (KIH) below which the cracks will not grow by delayed hydride cracking of Zr-2.5Nb micro pressure tubes (MPTs) has been determined using a load increasing mode (LIM) method at different temperatures. MPTs have been used to allow easy study of the impact of properties like texture and grain size on DHC. Previous studies on MPTs have focused on creep and effects of stress on hydride orientation; here the use of MPTs for DHC studies is confirmed for the first time. Micro pressure tube samples were hydrided to a target hydrogen content of 100 ppm using an electrolytic method. For DHC testing, 3 mm thick half ring samples were cut out from the tubes using Electrical Discharge Machining (EDM) with a notch at the center. A sharp notch with a root radius of 15 µm was introduced by broaching to facilitate crack initiation. The direct current potential drop method was used to monitor crack growth during the DHC tests. For the temperature range tested the threshold stress intensity factors for the micro pressure tube used were found to be 6.5-10.5 MPa.m1/2 with the value increasing with increasing temperature. The average DHC velocities obtained for the three different test temperatures 180, 230 and 250oC were 2.64, 10.87 and 8.45 x 10-8 m/s, respectively. The DHC data obtained from the MPTs are comparable to the data published in the literature for full sized CANDU pressure tubes. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-04-24 12:55:36.917