Made available in DSpace on 2014-12-17T14:06:56Z (GMT). No. of bitstreams: 1 MarcianoF.pdf: 4534279 bytes, checksum: c57f1201db2e0c16d64c992932b57fc3 (MD5) Previous issue date: 2007-09-28 / Metal powder sintering appears to be promising option to achieve new physical and mechanical properties combining raw material with new processing improvements. It interest over many years and continue to gain wide industrial application. Stainless steel is a widely accepted material because high corrosion resistance. However stainless steels have poor sinterability and poor wear resistance due to their low hardness. Metal matrix composite (MMC) combining soft metallic matrix reinforced with carbides or oxides has attracted considerable attention for researchers to improve density and hardness in the bulk material. This thesis focuses on processing 316L stainless steel by addition of 3% wt niobium carbide to control grain growth and improve densification and hardness. The starting powder were water atomized stainless steel manufactured for H?gan?s (D 50 = 95.0 μm) and NbC produced in the UFRN and supplied by Aesar Alpha Johnson Matthey Company with medium crystallite size 16.39 nm and 80.35 nm respectively. Samples with addition up to 3% of each NbC were mixed and mechanically milled by 3 routes. The route1 (R1) milled in planetary by 2 hours. The routes 2 (R2) and 3 (R3) milled in a conventional mill by 24 and 48 hours. Each milled samples and pure sample were cold compacted uniaxially in a cylindrical steel die (? 5 .0 mm) at 700 MPa, carried out in a vacuum furnace, heated at 1290?C, heating rate 20?C stand by 30 and 60 minutes. The samples containing NbC present higher densities and hardness than those without reinforcement. The results show that nanosized NbC particles precipitate on grain boundary. Thus, promote densification eliminating pores, control grain growth and increase the hardness values / O presente trabalho apresenta uma contribui??o ao estudo da sinteriza??o s?lida de um a?o inoxid?vel 316L, com o objetivo de aumentar a sua densidade e dureza atrav?s da inclus?o de part?culas nanom?tricas de Carbeto de Ni?bio - NbC. O a?o inoxid?vel 316L ? uma liga largamente utilizada pela sua propriedade de alta resist?ncia ? corros?o. Contudo, sua aplica??o ? limitada pela baixa resist?ncia ao desgaste, conseq??ncia da sua baixa dureza. Al?m disso, apresenta baixa sinterabilidade e n?o pode ser endurecido pelos m?todos tradicionais de tratamentos t?rmicos, devido a sua estrutura austen?tica, c?bica de face centrada, estabilizada principalmente pela presen?a do N?quel. Os materiais de partida empregados neste trabalho foram o a?o inoxid?vel, austen?tico 316L atomizado a ?gua, com tamanho de part?culas (D50) equivalente a 95μm, e duas partidas diferentes de NbC, com tamanhos m?dios de cristalitos de 16,39 nm e 80,35 nm. Amostras de a?os adicionadas com 3% em peso de NbC (cada amostra com carbetos de partidas diferentes), seguiram rotas diferenciadas de moagem mec?nica. A rota 1 (R1) em um planet?rio por uma hora, a rota 2 (R2) e rota 3 (R3), em moinho convencional por 24 e 48 horas respectivamente. Cada uma das amostras resultantes, assim como amostras do a?o puro foram compactados a 700 MPa, a frio, sem nenhum aditivo, uniaxialmente, em uma matriz cil?ndrica de 5 mm de di?metro, em quantidade calculada para ter uma altura m?dia final do compactado de 5 mm. Posteriormente, foram sinterizadas em forno a v?cuo, em temperatura de at? 1290? C com incremento de 10 ?C por minuto, sendo mantidas neste patamar por 30 ou 60 minutos e resfriadas ? temperatura ambiente. As amostras sinterizadas foram submetidas aos ensaios para a medi??o da densidade e da micro-dureza. As amostras contendo o refor?o de NbC apresentaram maiores valores de densidade e um aumento significativo na sua dureza. As an?lises complementares no microsc?pio ?tico, no microsc?pio eletr?nico de varredura e no difrat?metro de raios-X, mostram que o NbC, na forma processada, contribuiu com o aumento da dureza, pela densifica??o, pela sua pr?pria dureza e pelo controle do crescimento dos gr?os da matriz met?lica, segregando-se nos seus contornos

Les performances de filtration d’un filtre à manche vis-à-vis de particules submicroniques et nanométriques ont été évaluées à l’échelle du laboratoire durant plusieurs cycles de colmatage/décolmatage. La distribution granulométrique des particules (aérosol de combustion) était représentative de celle rencontrée en incinération de nano-déchets en sortie de chambre de combustion à l’échelle du laboratoire. Le filtre à manche opérait en conditions réalistes, représentatives de celles rencontrées dans les lignes de traitement des fumées d’incinération de déchets en termes de température, humidité, vitesse de filtration, présence de réactifs et conditions de décolmatage. Le flux d’air et le filtre à manche étaient chauffés à 150°C, la teneur en eau était de 10-12% (soit 3% d’humidité relative HR), et la vitesse de filtration était fixée à 1,9 cm.s⁻¹. Un mélange de particules de taille submicronique de charbon actif et de bicarbonate de sodium, utilisées dans les lignes de traitement des fumées d’incinération pour l’abattement des dioxines/furanes et des gaz acides, était généré simultanément avec l’aérosol de combustion. L’étude s’est centrée sur les performances de filtration au début de la durée de vie du filtre à manche, avant stabilisation de la perte de charge résiduelle du filtre résultant des précédents cycles de filtration. La perte de charge maximale du filtre était fixée à 150 Pa pour tous les cycles de filtration avant décolmatage par rétro-soufflage à air comprimé. Les performances du filtre à manche ont été évaluées en termes d’évolution de sa perte de charge et de son efficacité de collecte (totale et fractionnelle) au cours des cycles de colmatage/décolmatage. De plus, des études expérimentales et théoriques ont été menées afin d’étudier l’influence de divers paramètres sur les performances de filtration du filtre en configuration manche ou plane, tels que l’humidité de l’air (3% HR versus 0% HR à 150°C), la température (150°C versus 24°C), la vitesse de filtration (1,9 cm.s⁻¹ versus 1,4 cm.s⁻¹) et l’influence de l’injection de réactifs. Les principaux résultats de cette étude sont : (i) importante efficacité de capture des particules du filtre à manche en conditions représentatives des lignes de traitement des fumées d’incinération : efficacité minimale de collecte de 98,5% mesurée pour des particules de taille 74 ± 15 nm (diamètre de mobilité électrique), (ii) influence du gâteau résiduel de particules au début de chaque cycle de filtration sur les performances de traitement, (iii) influence significative de l’humidité de l’air sur la structure du gâteau de particules probablement due à l’augmentation des forces d’adhésion entre les particules en présence d’humidité (150°C – 3% HR soit environ 100 g d’eau par kg d’air sec) ; augmentation plus rapide de la perte de charge du filtre à manche en présence d’humidité (150°C – 3% HR) qu’en conditions d’air sec (150°C – 0% HR). / Filtration performance of a pulse-jet bag filter was evaluated at the laboratory-scale regarding submicronic particles with a nanosized fraction during clogging/unclogging cycles. The particle size distribution was representative to those encountered at the outlet of a nano-waste incineration device at laboratory-scale. The bag filter was operated in conditions as similar as possible to those found in flue gas treatment of waste incineration plants, in terms of temperature, humidity, filtration velocity, injection of sorbent reagents and unclogging conditions. The air flow and the bag filter were heated to 150°C, the water content was maintained in the air flow in the range of 10-12% (3% of relative humidity RH), and filtration velocity throughout the bag filter was fixed at 1.9 cm.s⁻¹. A mixture of submicronic suspended particles of activated carbon and sodium bicarbonate, both used in flue gas treatment systems mainly for the removal of dioxins/furans and acid gases, was generated simultaneously with the aerosol representative of combustion emissions.The study focused on the filtration performance at the beginning of the bag filter’s lifetime filter for the 11 first clogging-unclogging cycles before stabilizing the residual pressure drop reached after pulse-jet unclogging. The maximum pressure drop was set at 150 Pa for all filtration cycles. Once the maximum pressure drop was reached, the filter was unclogged using the pulse-jet system. The performance of the bag filter was evaluated in terms of the evolution of pressure drop, fractional and total particle collection efficiencies, during the clogging/unclogging cycles.Moreover, an experimental and theoretical study was carried out on the influence of different parameters on the filtration performance of bag filter and flat filter, such as influence of humidity (3% RH versus 0% RH at 150°C), temperature (150°C versus 24°C), filtration velocity (1.9 cm.s⁻¹ versus 1.4 cm.s⁻¹) and the influence of the injection of sorbent reagents.The main results of this study are: (i) high collection efficiency of the bag filter in representative conditions of flue gas treatment of waste incineration: minimun particle collection efficiency of 98.5% for particle diameter of 74 ± 15 nm (electrical mobility diameter), (ii) influence of residual particle cake at the beginning of the filtration cycles on the bag filter performance, (iii) significant influence of humidity on the porosity of the particle cake due to the capillary condensation of water between the particles in presence of humidity (150°C - 3% RH i.e. almost 100 g of water per kg of dry air). Faster increase of bag filter pressure drop in presence of humidiy (150°C - 3% RH) as compared to the dry conditions (150°C - 0% RH).