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Caractérisation de la sorption de gaz sur les charbons. Application au stockage géologique du dioxyde de carbone dans les veines de charbon / Characterisation of gas sorption on coals. Application of geological storage of CO2 on coal seamsCharrière, Delphine 06 October 2009 (has links)
La sorption de CO2 et de CH4 dans des charbons a été caractérisée au laboratoire afin d'étudier la faisabilité du stockage géologique de CO2 dans les veines de charbon. La diffusion et la sorption de CO2 et de CH4 sur des charbons du bassin de Lorraine et du bassin de Gardanne ont été étudiées par une méthode gravimétrique jusqu'à une pression de 5 MPa et pour des températures variant de 283 à 333 K. La cinétique de sorption dépend du gaz utilisé, de la granulométrie, de la pression en gaz et de la température. Elle peut être représentée par un modèle unipore basé sur la loi de Fick. Le coefficient de diffusion de CO2 dans le charbon est supérieur à celui du CH4 et est d'environ 10–12 m2 s–1, valeur de diffusion assez faible. A l'équilibre, la température, la pression, le gaz utilisé, la composition des charbons et la teneur en eau sont des paramètres qui influencent la capacité de sorption sur les charbons. Le charbon du bassin de Lorraine possède une plus grande capacité de sorption de CO2 (1,6 mmol g–1, soit ~ 36 m3 t–1) que celle du charbon du bassin de Gardanne. Le modèle de Dubinin-Astakhov basé sur un remplissage volumique des pores, rend mieux compte de la sorption de CO2 et CH4 que les modèles de Dubinin-Radushkevich et de Langmuir. Par ailleurs, les mécanismes de sorption de l'eau sur le charbon ont été mis en évidence, permettant de mieux interpréter l'influence de l'eau sur la capacité de sorption des gaz. A partir de l'ensemble des résultats, une évaluation des possibilités de stockage est discutée. Il en ressort la nécessité d'études complémentaires dans le but d'améliorer la perméabilité de la veine à l'échelle du site de stockage pour permettre une meilleure injectivité du gaz / The CO2 and CH4 sorption onto coals has been characterized in laboratory in order to study the feasibility of CO2 geological storage in coal seams. The diffusion and sorption of CO2 and CH4 on coals of Lorraine and Gardanne basins have been performed from a gravimetric method until a pressure of 5 MPa and for temperatures from 283 to 333 K. The kinetics of sorption depends on the nature of gas, the grain size of coal, the gas pressure and the temperature. It can be represented by a unipore model based on Fick's law. The CO2 diffusion coefficient on coal is higher than that of CH4 and is about 10–12 m2 s–1. At equilibrium, the temperature, pressure, nature of gas, composition of coal and water content are parameters that influence the sorption capacity of coals. The coal of Lorraine basin has a greater capacity for sorption of CO2 (1.6 mmol g–1, ~ 36 m3 t–1) than that of coal of Gardanne basin. The model of Dubinin-Astakhov based on a pore volume filling, has a best fit of sorption data that Dubinin-Radushkevich and Langmuir models. Finally, the different mechanisms of water sorption on coal have been identified and can better interpret the influence of moisture on the gas sorption capacity. From all results, an assessment of capacity storage is discussed. This indicates the need for further studies in order to improve the permeability of the coal seams across the storage site for better gas injectivity
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Impact of biochar manipulations on water and nitrogenUlyett, James January 2014 (has links)
A loss of soil organic matter (SOM), whether through natural means or management practices, results in soil degradation. Biochar as a soil amendment can alter soil properties, ultimately affecting the availability of nitrogen and water to plants and thus crop growth. The effects of biochar are not definitive, and often dependent on both the soil type and the biochar applied. Biochar properties can change according to the feedstock and production parameters, thus for their effective use further investigation is required to link biochar properties to its effects in soil. A high-temperature (600˚ C) biochar from a mixed-hardwood feedstock was investigated. The biochar increased the soil water retention, as demonstrated by a water release curve and field trials. This retention was predominant at higher water potentials, which was attributed to the greater number of meso (storage) pores in the biochar. Biochar did not affect the soil’s saturated hydraulic conductivity; this is thought to be due to the low number of macro (transmission) pores in the biochar. Thus there was no effect on the transmission rate in the soil. Biochar reduced gross ammonium levels in the soil via adsorption, but resulted in increased non-exchangeable ammonium levels, possibly due to physical entrapment. Where carbon was already abundant in the organically managed soil, the adsorbed ammonium reduced nitrification through lower substrate availability. The range of carbon fractions added as a result of the biochar amendment increased the total organic carbon (TOC) content of the soil, but this supplementary carbon was released by the microorganisms as carbon dioxide. Microorganisms in the relatively carbon poor conventionally managed soil (with lower TOC), assimilated the additional labile carbon increasing microbial biomass. The higher microbial biomass, combined with improvements in pH and the higher ammonium levels (as a result of the ammoniacal fertiliser) increased nitrification. These changes in water and nitrogen availability did not alter crop yields as measured in the glasshouse and field trials. The effects of this biochar in a sandy agricultural soil depended on the type and level of carbon and nitrogen present in the soil, thus consideration of these factors should be taken when applying.
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Imagerie par Résonance Magnétique pour la vélocimétrie d’un fluide en milieu poreux / Magnetic Resonance Imaging for velocimetry of a fluid in porous mediaSalameh, Wassim 07 June 2011 (has links)
Cette étude présente la mise au point de mesures de porosité et de vitesse d’écoulement faites par IRM dans des colonnes de billes de verre et de polymère de différentes granulométries saturées en eau. L’avantage des billes en polymère est qu’elles ne contiennent pas d’éléments ferro ou paramagnétiques, contrairement aux billes de verre qui perturbent le champ magnétique créant des artéfacts sur les images IRM. La séquence d’IRM utilisée pour l’étude des écoulements en milieu poreux a été préalablement paramétrée à l’aide d’une étude sur un écoulement de Poiseuille. Deux situations ont été examinées : d’une part, l’observation des écoulements interstitiels entre les billes permet de minimiser les effets de volume partiel et de faciliter la correction du phénomène de repliement de phase. D’autre part, la mesure de vitesses moyennes (Darcy) nécessite d’utiliser simultanément les images de vitesse et les images de porosité. Dans ce cas, il est préférable d’ajuster la puissance des gradients d’encodage de vitesse de façon à éviter tout phénomène de repliement de phase. La géométrie du dispositif utilisé a permis une comparaison rigoureuse des mesures de débit de façon intrinsèque uniquement par IRM (débit en milieu poreux et dans l’espace annulaire) et aussi à partir de la mesure directe du débit (pesée). / This study presents the development of measurement of porosity and velocity of flow made by MRI in packed beds with glass and polymer beads of various size saturated in water. The advantage of polymer beads is that they do not contain elements ferro or paramagnetics, contrary to the glass beads which disrupt the magnetic field creating artifacts on the MRI images. The calibration of the MRI velocity measurements was achieved from Poiseuille flow in a tube at different flow rates. Two situations were examined: first, the observation of interstitial flows between the beads minimizes partial volume effects and facilitates the correction of the phenomenon of phase aliasing. On the other hand, the measurement of average interstitial velocity (Darcy) requires using simultaneous velocity image and porosity image. In this case, it is preferable to adjust the strength of magnetic field gradient in the velocimetry sequence in a way to avoid any phase aliasing. The geometry of the flow cell was chosen to enable comparison by the MRI method between volume flow rates of water in the porous media and in the outer annulus.
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Notions de petitesse, géométrie des espaces de Banach et hypercyclicitéMoreau, Pierre 15 June 2009 (has links)
Il existe de nombreuses notions de petitesse en analyse. On considère trois d'entre elles: la Haar-négligeabilité, la Gauss-négligeabilité et la sigma-porosité. On étudie à quelles conditions le cône positif d'une base de Schauder est Haar-négligeable, et ce que cela entraîne pour l'espace de Banach associé. On étudie également sous quelles conditions l'ensemble des vecteurs non-hypercycliques d'un opérateur hypercyclique est Haar-négligeable ou sigma-poreux. / There are many notions of smallness in Analysis. We will consider three of them: Haar-negligeability, Gauss-negligeability and sigma-porosity. We will study on which conditions the positive cone of a Schauder basis is Haar-null, and its consequence on the Banach space. We will also study on which conditions the set of non-hypercyclic vectors of an hypercyclic operator is Haar-null or sigma-porous.
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Korektorské vlastnosti sedimentárních hornin z karotážních měření / Well log analysis for sedimentary formation evaluationŠálek, Ondřej January 2013 (has links)
3 ABSTRACT The work is focused on analysis of five structural well profiles penetrating sediments of the Bohemian Cretaceous Basin and the underlying Upper Palaeozoic continental basins to the crystalline basement. The objectives of well profile analysis are sedimentary formation evaluation from well log analysis and statistical analysis and evaluation of some physical properties of sedimentary rocks, which have been determined by measurements of drill cores. The aim of the work is to verify the possibility of porosity evaluation from well log analysis in the Bohemian Cretaceous Basin and the underlying Upper Palaeozoic continental basins. The next aim is to compare different geological environments with respect to physical properties of rocks. The content of the work involves presentation of well log curves, computation of porosity values and comparison between the resulting values of porosity from resistivity log, acoustic log and neutron-neutron log and from laboratory measurements of drill core samples. Data from five deep structural wells are used. Different geological environments were compared by statistical methods with respect to physical properties of rocks measured on well core samples from these five wells. Porosity evaluation from well log analysis is difficult but it is possible provided that...
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Nouvelles voies de synthèses de carbones et céramiques non-oxydes à porosités contrôlées / New synthetic routes for carbons and non-oxyde ceramics with controlled porositiesSchlienger, Sébastien 09 December 2011 (has links)
Les matériaux nanoporeux (méso- et/ou micro-poreux) visent des applications en relation avec les phénomènes d’adsorption tels que la catalyse, la dépollution, le stockage de gaz ou d’énergie,… Récemment, différents types de synthèses ont donc été développés pour contrôler la porosité et l’adapter aux applications visées : synthèse par voie directe, procédé de nanomoulage, technique de réplication réactive. Pour la très grande majorité d’entre elles, elles servent à l’élaboration des matériaux oxydes méso- et micro-poreuses. L’objectif de ce travail de thèse a donc été d’étendre ces procédés à une gamme de matériaux plus large au niveau des compositions chimiques, tout en gardant un contrôle de la porosité. En effet, les oxydes poreux ont un champ d’application limité du fait, par exemple, de leur température maximale d’utilisation, de leur fragilité sous certaines atmosphères ou encore, dans certains cas, de leurs propriétés d’adsorption mal adaptées. Afin de réduire ces limitations, nous avons cherché à étendre la gamme de composition chimique des matériaux poreux dans le domaine non-oxyde (carbone, céramiques de type nitrure, …) tout en contrôlant leur porosité. Pour cela, différentes approches ont été utilisées. La première approche a consisté à étudier mécanisme de formation des matériaux carbonés mésostructurés obtenus directement par l’auto-assemblage d’un tensioactif et d’un polymère précurseur de carbone. Nous avons alors pu déterminer les paramètres pertinents à contrôler pour la reproductibilité des synthèses ayant lieu, aussi bien, en phase aqueuse que par évaporation de solvant. Des analogies avec les mécanismes de formation des matériaux siliciques ont pu être mises en évidence. [...] / Nanoporous materials (meso-and / or micro-porous) target applications in relation to the adsorption phenomena such as catalysis, waste removal, gas or energy storage.... Recently, various types of syntheses have been developed to control the porosity and adapted to applications: direct route synthesis, nanocasting process, reactive templating. For most of them, they are used for the preparation of meso-and micro-porous oxide materials. The objective of this thesis was therefore to extend these methods to a wider range of materials in chemical composition, while keeping control of the porosity. Indeed, the porous oxides have a limited scope because, for example, their maximum operating temperature, their fragility under certain atmospheres or in some cases, their adsorption properties, are unsuitable. To reduce these limitations, we searched to extend the range of chemical composition of porous materials in the non-oxide field (carbon, nitride ceramics,...) while controlling their porosity. For this, different approaches were used. The first approach consisted to study formation mechanism of mesostructured carbon materials obtained directly by the self-assembly of a surfactant and a polymer carbon precursor. We were then able to determine the relevant parameters to control syntheses reproducibility taking place both in aqueous phase and by solvent evaporation. Analogies with the formation mechanisms of siliceous materials have been identified. With a better understanding of the formation mechanisms, we declined in a second time this method of direct synthesis to other materials by varying the nature of the precursors. Thus, a "green" synthesis of a carbonaceous material with ordered mesoporosity was developed in the absence of all toxic reagents such as formaldehyde and phenol, by using a natural precursor, the mimosa tannin. [...]
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Simulação de transporte de massa de um soluto em meio poroso com auxílio do CFD (Computer Fluid Dynamics). / Solute mass transport simulation in a porous media with CFD\'s support (Computer Fluid Dynamics).Frankfurt, Ricardo 23 October 2008 (has links)
Com o avanço dos computadores pessoais, problemas técnicos complexos, antes restritos aos grandes centros de pesquisas internacionais, passam a ser acessíveis pelas mais diversas áreas do conhecimento, como as engenharias e em particular a Engenharia Química. Fenômenos físicos são representados matematicamente por equações diferenciais, que na maioria das vezes não possuem solução analítica possível. O CFD ( Computer Fluid Dynamics) é uma técnica numérica iterativa, que busca a solução destas equações diferenciais através da discretização do domínio estudado e das equações que governam o fenômeno envolvido. Neste trabalho, através de um software especialista de CFD, o ANSYS CFX 11.0, foi simulado o transporte de massa e momento de um soluto traçador, o Cloreto, presente no sal Cloreto de Sódio, em um meio poroso. Em seguida, os resultados desta simulação foram comparados e validados por um experimento de transporte de massa numa caixa de areia. / With the advance of the personal computers, complex technical problems, before restricted to the huge centers of international researches, have become more accessible by many areas of the knowledge, like the engineering and in particular the Chemical Engineering. Physical phenomena are represented mathematically by differentials equations, which most of the time do not have possible analytical solution. CFD (Computer Fluid Dynamics) is an iterative numeric technique, which search the solution of these differentials equations through both discretization of the studied domain and the equations that govern the involved phenomenon. In this work, through a CFD\'s specialist software, ANSYS CFX 11.0, it was simulated the mass and momentum transport of a solute tracer, Chloride, present in Sodium Chloride, in a porous media. After this, the simulations results were compared and validated in a mass transport experiment in a sand box.
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Efeito da incorporação de agentes antifúngicos na resistência à tração e porosidade de materiais resilientes temporários para base de próteses / Effect of incorporation of antifungal agents on the ultimate tensile strength and porosity of temporary soft denture linersLima, Jozely Francisca Mello 10 February 2017 (has links)
Este estudo investigou a resistência à tração (ou limite de resistência à tração- LRT) e a porosidade de reembasadores resilientes temporários modificados por concentrações inibitórias mínimas (CIMs) de agentes antifúngicos para o biofilme Candida albicans (SC5314). Para os testes de LRT, corpos de prova em forma de halteres (n=7) com uma área transversal de 33 mm x 6 mm x 3 mm foram produzidos para os materiais resilientes (Trusoft e Softone) sem (controle) ou com incorporação de cinco fármacos em suas CIMs: nistatina- 0,032 g; diacetato de clorexidina- 0,064; cetoconazol- 0,128 g; miconazol- 0,256 g; itraconazol-0,256 g (grama de fármaco por grama de pó de material resiliente). Após a plastificação, as amostras foram imersas em água destilada a 37°C durante 24 h, 7 e 14 dias e, então, testadas em tensão em uma máquina universal de ensaios (EMIC DL-500 MF) a 40 mm/min. A porosidade foi mensurada por absorção de água, com base na exclusão do efeito plastificante. Inicialmente, determinou-se por isotermas de sorção, que a solução de armazenagem adequada para os corpos de prova (65 mm x 10 mm x 3,3 mm) de ambos os materiais foi o cloreto de cálcio anidro a 50% (S50). Assim, o fator de porosidade (FP) foi calculado para os grupos de estudo (n=10) formados por espécimes sem (controle) ou com incorporação de fármaco em suas CIMs (nistatina, clorexidina ou cetoconazol) após a armazenagem em água destilada ou S50 por 24 h, 7 e 14 dias. Os dados de resistência à tração (MPa) e percentagem de alongamento (%) foram submetidos à ANOVA de 3 fatores seguida pelo teste de Tukey (=0,05). Os dados de porosidade foram analisados estatisticamente por ANOVA de medidas repetidas para 4 fatores e teste de Tukey (=0,05). Ao final de 14 dias, a resistência à tração para ambos os materiais foi significativamente menor nos grupos modificados pelo miconazol e itraconazol em relação aos outros grupos (P<0,0001), que não mostraram diferenças significativas entre si (P>0,05). Após 7 e 14 dias em água, o miconazol e itraconazol adicionados a ambos os materiais resultaram em percentagens significativamente menores de alongamento em comparação com os outros fármacos e ao controle (P<0,0001), que foram semelhantes entre si (P>0,05). O cetoconazol não resultou em alterações significativas no FP para ambos os materiais resilientes em água ao longo de 14 dias (P>0,05). Em comparação aos controles, houve aumento dos FPs do Softone e Trusoft aos 14 dias de imersão em água somente após a adição de nistatina e clorexidina e de clorexidina, respectivamente (P<0,05). Ambos os materiais não apresentaram alterações significativas no FP em até 14 dias de imersão na S50, em comparação aos controles (P>0,05). Em todas as condições experimentais, os FPs do Softone e Trusoft foram significativamente menores quando imersos em S50 em comparação com a água destilada (P<0,05). Concluiu-se que a adição de nistatina, clorexidina e cetoconazol nas CIMs para o biofilme de C. albicans não resultou em efeitos deletérios na resistência à tração e na percentagem de alongamento dos materiais resilientes temporários para base de prótese até o período de 14 dias. A adição de antifúngicos nas CIMs não resultou em efeitos adversos à porosidade de ambos os materiais resilientes temporários em diferentes períodos de imersão em água, com exceção da clorexidina e nistatina no Softone e clorexidina no Trusoft aos 14 dias. Não foram observados efeitos deletérios para a porosidade de ambos os materiais resilientes modificados com as CIMs dos fármacos durante os 14 dias de imersão na S50. / This study investigated the tensile strength (ultimate tensile strength- UTS) and porosity of temporary soft denture liners modified by minimum inhibitory concentrations (MICs) of antifungal agents for Candida albicans biofilm (SC5314). For UTS tests, dumbbell-shaped specimens (n=7) with a central cross-sectional area of 33 mm x 6 mm x 3 mm were produced by resilient materials (Trusoft and Softone) without (control) or with incorporation of five drugs at MICs: nystatin- 0.032 g; chlorhexidine diacetate-0.064 g; ketoconazole- 0.128 g; miconazole- 0.256 g; itraconazole- 0.256 g (each per gram of soft liner powder). After plasticization, specimens were immersed in distilled water at 37°C for 24 h, 7 and 14 days, and then tested in tension in a universal testing machine (EMIC DL-500 MF) at 40 mm/min. The porosity was measured by water absorption, based on exclusion of the plasticizer effect. Initially, it was determined by sorption isotherms that the adequate storage solution for specimens (65 mm x 10 mm x 3.3 mm) of both materials was 50% anhydrous calcium chloride (S50). Then, the porosity factor (PF) was calculated for the study groups (n=10) formed by specimens without (control) or with drug incorporation at MICs (nystatin, chlorhexidine or ketoconazole) after storage in distilled water or S50 for 24 h, 7 and 14 days. Data of tensile strength (MPa) and elongation percentage (%) were submitted to 3-way ANOVA followed by Tukey\'s test (=0.05). Data of porosity were statistically analyzed by 4-way repeated measures ANOVA and Tukeys test (=0.05). At the end of 14 days, the tensile strength for both materials was significantly lower in the groups modified by miconazole and itraconazole compared to the other groups (P<0.0001), which showed no significant difference between them (P>0.05). After 7 and 14 days in water, miconazole and itraconazole added into both materials result in significant lower elongation percentages compared to the other drugs and control (P<.0001), which were similar to each other (P>0.05). Ketoconazole resulted in no significant changes in PF for both liners in water over 14 days (P>0.05). Compared to the controls, Softone and Trusoft PFs were increased at 14-day water immersion only after addition of nystatin and chlorhexidine, and chlorhexidine, respectively (P<0.05). Both materials showed no significant changes in PF in up to 14 days of S50 immersion, compared to the controls (P>0.05). In all experimental conditions, Softone and Trusoft PFs were significantly lower when immersed in S50 compared to distilled water (P<0.05). It was concluded that the addition of the nystatin, chlorhexidine and ketoconazole at MICs for C. albicans biofilm resulted in no harmful effects on the ultimate tensile strength and elongation percentage of the temporary soft denture liners up to 14-day period. The addition of antifungals at MICs resulted in no detrimental effects for the porosity of both temporary soft liners in different periods of water immersion, except for chlorhexidine and nystatin in Softone and chlorhexidine in Trusoft at 14 days. No deleterious effect was observed for the porosity of both soft liners modified by the drugs at MICs over 14 days of S50 immersion.
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Fronteira e horizontalidade na Amazonia: as cidades gêmeas de Tabatinga (Brasil) e Leticia (Colômbia) / Boundary and horizontality in the Amazon: the twin cities of Tabatinga (Brazil) and Leticia (Colombia)Euzebio, Emerson Flavio 28 February 2012 (has links)
As cidades situadas na fronteira ocidental da Amazônia constituem rica área a ser estudada. Nas últimas três décadas a estrutura urbana e populacional da Amazônia sofreu modificações significativas. A população urbana passou de 59% para 79% (IBGE, 2010). Nesse movimento destaca-se a centralidade que vem se desenvolvendo em torno das cidades gêmeas fronteiriças: Tabatinga (Brasil) e Leticia (Colômbia) situadas na tríplice fronteira Brasil, Colômbia e Peru. O objetivo da pesquisa é compreender a dinâmica territorial criada em torno do subespaço das cidades gêmeas Tabatinga-Leticia, partindo da análise da densidade de fixos, fluxos e normas, e do significado das horizontalidades presentes no subespaço. A pesquisa fundamenta-se com informações obtidas em fontes estatísticas brasileiras e colombianas e em trabalhos de campo, que incluem coleta de dados primários e secundários; entrevistas em órgão oficiais, instituições públicas e entidades privadas localizadas no subespaço. O inventário dos fixos, levantamento da densidade normativa e análise dos fluxos associado ao estudo da fomação sócioespacial das sociedades nacionais envolvidas nos permitiu compreender como a fluidez territorial e porosidade territorial têm contribuído para a consolidação de uma horizontalidade interurbana que tem se traduzido em uma melhoria das condições de vida da população e vem conformando uma centralidade regional. / The towns located in the occidental boundary of Amazon constitute a rich area to be studied. In the last three decades the population and urban structure in Amazon has suffered significant modifications. The urban population turned from 59% to 79% (IBGE, 2010). By this process is possible to highlight the concentration that is being developed in the surrounds of the twin cities of the frontier: Tabatinga (Brazil) and Leticia (Colombia) located at the triple frontier Brazil-Colombia-Peru. The goal of this research is to understand the territorial dynamic process created around the sub-space of the twin cities Tabatinga-Leticia, starting with the analysis of the density of infrastructures, flows and norms, and with information obtained from Brazilian and Colombian statistic sources and by fieldworks, which includes primary and secondary data collection; interviews in official organs, public institutions and private foundations located in the sub-space. The inventory of the infrastructures, collection of the normative density and the flows analysis associated to the studies of the social-spatial formation of the national societies involved has allowed the comprehension of how the territorial flowing and territorial porosity has contributed to the consolidation of an intercity horizontality, which has been brought to an improvement of life conditions and has been turned into a regional center.
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Estudo sobre a incidência das porosidades e sua identificação em uma liga de alumínio A356. / Study of porosity and identification in A356 alloy.Cardoso, Roberto 03 November 2007 (has links)
Este trabalho procurou identificar o defeito que ocorria no teste de estanqueidade de uma peça e apresentar a correlação entre o nível de porosidade encontrado no produto fundido com a liga de alumínio A356 e os processos de fusão e de manutenção sob temperaturas controladas, o teor de hidrogênio, o sistema de enchimento e de alimentação, obedecendo ao princípio de solidificação direcional e o posicionamento do modelo em relação à linha de divisão. Foram efetuadas algumas experiências com diferentes tempos de introdução de nitrogênio para a purificação do metal, com a inversão do modelo em relação ao plano de partição do molde, com a modificação das dimensões do sistema de enchimento, com a substituição dos massalotes laterais por outros com luvas exotérmicas e utilizando-se resfriadores. Tentou-se verificar os benefícios que os filtros cerâmicos proporcionam aos fundidos, principalmente quanto à diminuição do nível de porosidade, menor turbulência e maior capacidade de reter as inclusões e parte dos filmes de óxidos. Para comprová-los, propôs-se a fundição de peças, em moldes confeccionados pelo processo de areia à verde, com diferentes tipos de filtros cerâmicos nos canais de distribuição. As amostras foram analisadas no Laboratório Metalográfico do Departamento de Engenharia Metalúrgica e de Materiais da Escola Politécnica da Universidade de São Paulo e no Laboratório de Metalurgia e de Materiais Cerâmicos do Instituto de Pesquisas Tecnológicas de São Paulo. Após a análise dos resultados em microscópio óptico, microscópio eletrônico de varredura e em espectrômetro por emissão de energia observou-se que o problema está relacionado principalmente com a alimentação e a solidificação direcional e não somente com o teor de hidrogênio. / The objective of this work is to study the type of defect identified during the pressure tightness test of aluminum parts and to establish a relationship between porosity level of an A356 aluminum alloy and the production processes, hydrogen level, feeding system, and directional solidification. Different nitrogen blowing times, inversion of the mould pattern, relative to the partition line, changing of the feeding system dimensions, replacement of the lateral feeding by exothermic gloves and the use of chills where tested. Ceramic filters were also tested, in order to evaluate their influence on the formation of porosities and on the porosity level, through a decrease of turbulence and an increase in the capacity of retaining non-metallic inclusions and part of the oxide films. Casting was performed by the green sand process using different ceramic filters. The obtained parts were metallographicaly analyzed through optical and scanning electronic microscopy using also EDS analysis. The results showed that porosity is related with the feeding conditions and directional solidification besides the hydrogen content of the alloys.
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