Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-01-21T10:14:57Z No. of bitstreams: 0 / Made available in DSpace on 2015-01-21T10:14:57Z (GMT). No. of bitstreams: 0 / O Processamento e Análise Digital de Imagens é utilizado cada vez mais para agilizar processos, aumentar a precisão, segurança e confiabilidade de dados extraídos de imagens nas mais diversas áreas de pesquisa. No entanto, muitas vezes é necessário que o pesquisador faça, ele próprio, o pré-processamento das imagens, mesmo não sendo um especialista nesta área. Isto coloca em risco o próprio objetivo do uso do Processamento e Análise Digital de Imagens. Este trabalho analisa a relação dos dados extraídos de uma imagem (micrografia) através do software livre ImageJ com relação ao seu processamento final desejado, avaliando assim, a necessidade ou não, de uma ou mais sequencias de pré-processamento para adequar a imagem para o processamento final, indicando ainda quais fatores de influência apresentam informações irrelevantes ou incompletas para o processamento final utilizando ferramentas da Lógica Paraconsistente Anotada. Os resultados obtidos mostram que esta abordagem carece de informações diversificadas sobre a imagem original capturada que possam subsidiar a tomada de decisão quanto aos procedimentos necessários e, para o pré-processamento adequado ao objetivo desejado. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Orientador: Rubens Caram Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-14T01:19:58Z (GMT). No. of bitstreams: 1 Contieri_RodrigoJose_M.pdf: 6106126 bytes, checksum: c0a763660f171b211110a4237cfd34db (MD5) Previous issue date: 2009 / Resumo: A aplicação de tratamentos térmicos de recozimento a materiais metálicos encruados pode resultar em fenômenos de recuperação, de recristalização e de crescimento de grãos. Tal tipo de tratamento térmico resulta na transformação da microestrutura e, portanto, das propriedades físicas e mecânicas do material. O objetivo deste trabalho é determinar parâmetros característicos do processo de recristalização e de crescimento de grãos do titânio comercialmente puro (Ti C.P.) por meio do desenvolvimento e aplicação de um modelo teórico baseado no algoritmo autômatos celulares e em experimentos. Esse modelo teórico considera a redução da energia interfacial nos contornos de grão a cada intervalo de tempo como força motriz do processo, assim como a influência de uma barreira de potencial. Objetivando validar os resultados teóricos obtidos e também obter informações necessárias à simulação, foram executados experimentos associados à laminação, a tratamentos térmicos e à caracterização de amostras de Ti C.P. Os resultados obtidos mostram que o modelo concebido é capaz de simular processos de recristalização e de crescimento de grãos. Observou-se a dependência da cinética de crescimento em relação à energia de ativação, temperatura e energia interfacial nos contornos. Por outro lado, concluiu-se que a recristalização do Ti C.P. laminado à temperatura ambiente pode ser investigada através de análises quantitativas de calorimetria diferencial de varredura (DSC) e de microdureza. Finalmente, informações obtidas da aplicação do modelo teórico exibem boa concordância com dados obtidos experimentalmente e com outros disponíveis na literatura / Abstract: Application of annealing heat treatments to strain hardened metallic materials may give rise to recuperation, recrystallization and grain growth phenomena. This heat treatment leads to microstructure transformation and hence, changes in physical and mechanical properties. The aim of this work is to determine parameters of recrystallization and grain growth processes of commercially pure titanium (C.P. Ti) by means of the development and application of a theoretical model based on Cellular Automata algorithm as well as on experiments. This model considers the decrease in the interfacial energy at grain boundaries every time step as the process driving force. In addition, it takes into account the influence of potential barrier. To validate theoretical results as well as to obtain essential information for the simulation, experiments related to rolling, heat treatments and characterization of C.P. Ti samples were carried out. The results obtained show the developed model is able to simulate recrystallization and grain growth processes. It was observed the growth kinetic depends on activation energy, temperature and interfacial energy at the boundaries. Also, it was concluded that recrystallization of the room temperature rolled C.P. Ti may be investigated by using results of differential scanning calorimetry and microhardness. Finally, information obtained by using the theoretical model well agrees with data experimentally obtained and with other available in literature / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

nÃo hà / AÃos elÃtricos de grÃo nÃo orientado sÃo amplamente utilizados na fabricaÃÃo de nÃcleos para motores elÃtricos, sendo o desempenho destes equipamentos afetado pela textura cristalogrÃfica presente nesses materiais. Jà o tamanho de grÃo interfere consideravelmente nas perdas magnÃticas. A textura cristalogrÃfica e o tamanho de grÃo sÃo extremamente influenciados pelo tratamento tÃrmico de recozimento realizado apÃs o processo de laminaÃÃo a frio para obtenÃÃo de tiras metÃlicas desses aÃos. O recozimento promove estados de recristalizaÃÃo na microestrutura do material e esses estados estÃo intimamente relacionados com a textura cristalogrÃfica. O objetivo deste trabalho à avaliar a influÃncia da recristalizaÃÃo no comportamento da textura cristalogrÃfica e das perdas magnÃticas por histerese de um aÃo elÃtrico de grÃo nÃo orientado com 1,28% Si que foi laminado a frio industrialmente com reduÃÃes de 50 e 70%. Amostras do material nas condiÃÃes laminado a frio, parcialmente recristalizadas a 580, 585, 590, 595, 600, 605, 610, 615 e 620ÂC e recozidas a 730ÂC por 12 horas (recozimento em caixa) foram analisadas quanto à microestrutura, textura cristalogrÃfica e perdas magnÃticas por histerese. O material tambÃm foi submetido a tratamentos tÃrmicos para crescimento de grÃo e estes tambÃm foram avaliados com respeito à microestrutura e a textura cristalogrÃfica. Os resultados mostraram o inÃcio da recristalizaÃÃo primÃria nas condiÃÃes parcialmente recristalizadas e os tratamentos tÃrmicos para crescimento de grÃo provocaram a ocorrÃncia de recristalizaÃÃo secundÃria. A textura cristalogrÃfica foi modificada pelas condiÃÃes parcialmente recristalizadas, pelo recozimento em caixa e pela recristalizaÃÃo secundÃria. Quanto Ãs perdas magnÃticas por histerese, o recozimento em caixa promoveu uma diminuiÃÃo destas. / Non-oriented electrical steels are widely used in the manufacture of cores for electric motors being the performance of this equipment affected by the presence of crystallographic texture in these materials. In other hand, the grain size considerably affects the magnetic losses. The crystallographic texture and grain size are greatly influenced by the annealing process performed after cold rolling of these steels. Annealing promotes recrystallization in the microstructure of the material which is closely related with the crystallographic texture. The objective of this study is to evaluate the influence of recrystallization on the evolution of crystallographic texture and hysteresis magnetic losses by in non-oriented grain electrical steel with 1.28% Si that was cold rolled with reductions of 50 and 70% in an industrial plant. Samples of the material in the conditions cold rolled and partially recrystallized at 580, 585, 590, 595, 600, 605, 610, 615 and 620ÂC and annealed at 730ÂC for 12 hours (box annealing) were analyzed in the aspects of microstructure, crystallographic texture and magnetic hysteresis losses. The material was also subjected to heat treatment for grain growth and they were also evaluated with respect to the microstructure and crystallographic texture. The results showed the evolution of primary recrystallization and also the microstructure and texture when the material is subjected to final heat treatment that promotes grain growth and secondary recrystallization. The crystallographic texture has changed in the process of primary recrystallization occurred during box annealing and also in the process of secondary recrystallization after heat treatment simulating the final processing of the material. The evaluation of hysteresis magnetic losses showed that the box annealing promoted a reduction of these.

O desgaste abrasivo de dois aços austeníticos ao manganês, materiais com grande utilização na mineração, foi estudado empregando metodologia multiescala (escalas: macro, meso e micro). Na macroescala foram estudados os mecanismos de dano e de desgaste de revestimento de britador utilizado em campo. Na mesoescala foram realizados ensaios de britador de mandíbula e de esclerometria linear. Na microescala o ensaio de esclerometria linear foi utilizado para avaliar os efeitos da camada encruada em campo e da orientação cristalográfica dos grãos austeníticos dos aços com 12 %Mn e 20 %Mn. As técnicas de caracterização utilizadas nesta pesquisa foram: macro e microdureza, nanodureza instrumentada, MO, MEV, DRX, EBSD, FIB e MET. A pesquisa foi dividida em três Capítulos, intitulados: \"Desgaste abrasivo dos aços austeníticos com 12 %Mn e 20 %Mn via ensaio de britador de mandíbula\"; \"Efeito do encruamento e da orientação cristalográfica no desgaste por riscamento dos aços austeníticos 12 %Mn e 20 %Mn\"; e \"Microestrutura da subsuperfície do aço austenítico com 12 %Mn deformado por desgaste abrasivo\". O primeiro Capítulo mostrou, a partir do ensaio de britador de mandíbulas (mesoescala), que o aço com 20 %Mn tem tendência de maior resistência ao desgaste que o aço com 12 %Mn. Este resultado foi obtido para a mandíbula fixa do britador, na qual a severidade de desgaste foi superior a mandíbula móvel, por apresentar microcorte e microsulcamento como micromecanismos predominantes, enquanto na mandíbula móvel o micromecanismo predominante foi a microendentação. No segundo Capítulo observou-se que o desgaste por riscamento (mesoescala e microescala) não depende do perfil de encruamento gerado em campo. Entretanto, foi identificado o efeito da orientação cristalográfica, planos (001), (111) e (101), no desgaste por riscamento dos aços com 12 %Mn e 20 %Mn. No último Capítulo a análise multiescala mostrou que a microestrutura deformada na subsuperfície sofre alterações semelhantes em diferentes intensidades. Nas três escalas de análise foram observadas uma camada com grãos ultrafinos (nanométricos), na subsuperfície, e uma de transição com maclas de deformação. A formação dos grãos ultrafinos foi associada à recristalização dinâmica por deformação plástica, na qual faz parte do mecanismo de auto reparação superficial. Além dos resultados apresentados, o desenvolvimento desta pesquisa de doutorado permitiu a elaboração de duas metodologias: i. análise do efeito da orientação cristalográfica no desgaste por microesclerometria; e ii. análise de microestrutura revelada por ataque iônico - FIB. / The abrasive wear of two manganese austenitic steels, materials broadly used in mining industry, was studied using multiscale methodology (scales: macro, meso and micro). In the macroscale the mechanisms of damage and wear of in-service crusher liner were studied. In the mesoscale, jaw crusher and linear scratch tests were performed. In the microscale the linear scratch test was used to evaluate the effects of the hardening layer and the crystallographic orientation of the austenitic grains of steels with 12 %Mn and 20 %Mn. The characterization techniques used in this research were: macro and microhardness, instrumented nanohardness, OM, MEV, DRX, EBSD, FIB and TEM. The research was divided into three chapters, entitled: \"Abrasive wear of steels with 12 %Mn and 20 %Mn via jaw crusher test\"; \"The effect of the in-service workhardening and crystallographic orientation on the micro-scratch wear of austenitic steels with 12 %Mn and 20 %Mn\"; and \"Subsurface microstructure of the deformed austenitic steel with 12 %Mn by abrasive wear\". The first chapter showed, from the jaw crusher tests (i.e. mesoscale), that the steel with 20 %Mn tends to be more wear resistant than the steel with 12 %Mn. This result was obtained to the fixed jaw crusher, in which the wear severity was superior to the movable jaw, since it presents microcutting and microploughing as predominant micromechanisms, whereas in the mobile jaw the predominant micromechanism was microendentation. In the second chapter, it was observed that scratch wear (i.e. meso and microscale) does not depend on the in-service work-hardening profile. However, it was identified the effect of crystallographic orientation, (001), (111) and (101) planes, on the scratch wear of the steels with 12% Mn and 20% Mn. In the last chapter, the multiscale analysis showed that the subsurface deformed microstructure changes with different intensities. At the three analysis scales, a layer with ultrafine grains was observed in the subsurface and mechanical twins. The formation of this layer, with nanometric grains, was associated with dynamic recrystallization by plastic deformation, in which it is part of the self healing effect. In addition to the results found, the development of this doctoral research allowed for the elaboration of two methodologies: i. Analysis of the effect of crystallographic orientation on the scratch wear; and ii. Microstructure analysis revealed by ion etching - FIB.

O objetivo deste trabalho é realizar um estudo comparativo da recristalização de dois aços rápidos, AISI M2 (Werkstoffnummer 1.3343) e ABC III (Werkstoffnummer 1.3333), após o encruamento resultante do processo de laminação a frio de chapas planas utilizadas para a confecção de serras fitas. Estudar a recristalização estática nesta classe de aços é relevante, pois eles freqüentemente são laminados a frio e recozidos na etapa final de processamento, antes da confecção da peça ou componente. Inicialmente, foi realizada a caracterização das amostras no estado como recebido, ou seja \'\'laminado a quente\'\'. A caracterização envolveu análise química, ensaios mecânicos, microscopia óptica, microscopia eletrônica de varredura, medidas de dureza e dilatometria. Em seguida, as amostras sofreram deformação a frio da ordem de até 50% de redução em espessura para determinação das curvas de endurecimento por deformação. Amostras com 25% de redução foram recozidas entre 100ºC e 750ºC, durante 1 hora e os resultados de dureza foram utilizadas para determinar as curvas isócronas de amolecimento. Amostras com 25% redução foram recozidas entre 600ºC e 750ºC, entre 15 e 480 minutos para cada uma das temperaturas, para determinação curvas isotérmicas de amolecimento. Resultados da análise microestrutural mostraram que o aço rápido AISI M2 apresenta uma distribuição mais homogênea de carbonetos. Esses carbonetos são mais finos em relação aos do aço ABC III, que apresenta uma distribuição mais heterogênea. Os dois aços apresentaram curvas muito similares de endurecimento por deformação. Após recozimento das amostras encruadas, foi verificado que o aço AISI M2 apresenta recuperação e recristalização levemente mais rápidas quando comparado com o ABC III. Ainda na etapa de recuperação e antes da recristalização, notou-se nos dois aços um pequeno aumento de dureza, principalmente entre 30 e 60 minutos de recozimento, na faixa de 650 ºC e 700ºC. Utilizando-se análises por difração de elétrons retroespalhados (microtextura e mesotextura) observou-se que o aço ABC III apresenta maior resistência para a recristalização se completar que o aço AISI M2. / This work aims at the comparative study of the recrystallization of two high-speed steels, namely AISI M2 (Werkstoffnummer 1.3343) and ABC III (Werkstoffnummer 1.3333), hardened by cold rolling of sheets employed in the production of band saws. Studying static recrystallization in this class of steels is relevant, since frequently they are cold rolled and annealed in their final processing stage, prior to the actual work piece manufacturing. Initially, samples have been characterized in the as-received condition, i.e. hot rolled. Characterization involved chemical analysis, tensile testing, optical metallography, scanning electron microscopy, hardness measurements and dilatometry. Following, samples have been cold worked with a 50% thickness reduction in order to evaluate the cold work hardening curves. Samples with 25% reduction have been annealed at temperatures in the 100oC to 750oC range, for one hour and hardness results have been used to determine the isochronous softening curves. Samples with 25% reduction have been annealed between 600 oC and 750oC for 15 to 480 minutes, for each one of the temperatures, to determine the isothermal softening curves. The microstructural analysis has shown that the AISI M2 steel presents a homogeneous carbide distribution. These carbides were fine when compared to those of the ABCIII steel that presented a heterogeneous distribution. Both steels presented similar work-hardening curves. After annealing the cold worked samples, it has been observed that the AISI M2 steel presented a slightly faster recovery and recrystallization than the ABCIII steel. Still in the recovery stage, prior to recrystallization, both steels showed a small hardness increase, mainly on annealing during 30 to 60 minutes in the 650oC to 700oC temperature range. Using electron backscattered diffraction analysis (microtexture and mesotexture) it has been observed that the ABCIII steel presented higher resistance to complete recrystallization than the AISI M2 steel.

As superligas à base de cobalto são bem conhecidas por sua excelente resistência ao desgaste. Muitas pesquisas reportadas na literatura abordam o comportamento do desgaste destas ligas, seja no desgaste por deslizamento, erosivo ou abrasivo. Não obstante, o desgaste microabrasivo destas ligas não tem sido muito investigado, apesar dos danos causados por este tipo de solicitação. O comportamento do desgaste microabrasivo de três superligas à base de cobalto: a) 48% Co, 29 %Cr, 19 % Fe; b) uma liga com composição química próxima à da liga comercial Tribaloy T400 (Co 56 %, Cr 8.5%, Mo 29% Si 3.3 %) e c) uma liga com composição próxima à da liga comercial Stellite 6 (Co 64%, Cr 24 %, W 4.2 %, C 2,3%) foram investigadas. Os ensaios de microabrasão foram conduzidos com três abrasivos SiO2, Al2O3, e SiC em suspensão em água destilada, com concentração de 0,1 g/cm3. A carga aplicada foi de 0,3 N, a velocidade angular 20 rpm e a distância total de deslizamento, 48 metros. A análise das superfícies desgastadas por microscopia óptica, eletrônica de varredura e por perfilometria de contato mostraram que o tamanho, forma e dureza dos abrasivos podem influenciar significativamente os coeficientes de desgaste. Os ensaios conduzidos com partículas abrasivas de SiC e Al2O3 apresentaram maiores coeficientes de desgaste que os conduzidos com partículas de SiO2. A Liga Co-Cr-Fe mostrou os maiores coeficientes de desgaste quando comparada com as demais ligas, devido à baixa fração volumétrica de partículas de segunda fase, duras, precipitadas em sua microestrutura. Durante os ensaios, as três ligas, ensaiadas com os três diferentes abrasivos, apresentaram coeficientes de desgaste crescentes com o aumento da dureza do abrasivo; observou-se uma variação linear dos coeficientes de desgaste com a razão entre a dureza do abrasivo (Ha) e a dureza composta da liga (Hs), com R2 = 0.74. O micromecanismo dominante em todos os ensaios foi o desgaste abrasivo a dois corpos (grooving wear). A liga com composição próxima à da liga comercial Tribaloy T400, contendo fases de Laves dispersas em sua microestrutura, apresentou uma transição de micromecanismo de desgaste dúctil para frágil, quando submetida a ensaios com partículas abrasivas de Al2O3. Assim sendo, o volume de material removido nesta liga foi ligeiramente maior que o observado no ensaio com partículas de SiC. Na liga contendo baixa fração volumétrica de partículas de segunda fase, com matriz constituída por Co (CFC), observou-se uma camada subsuperficial nanocristalina de aproximadamente 1 µm de espessura, severamente deformada, imediatamente abaixo da superfície desgastada. Concluiu-se que o desgaste microabrasivo induziu a recristalização a frio do material encruado, com formação de grãos equiaxiais de dimensões nanométricas. / Cobalt alloys are well known for their excellent wear resistance. Many investigations are reported in literature related to the behavior of erosive, abrasive or sliding wear of these alloys. Nevertheless, the micro-abrasive wear of these alloys has not been thoroughly investigated, despite the damage caused by this type of wear. The microabrasive wear behavior of three cobalt alloys: a) 48 wt.% Co, 29 wt.% Cr, 19 wt.% Fe; b) an alloy with chemical composition close to Tribaloy T400 (56 wt.% Co, 8.5 wt.% Cr, 29% wt. Mo, 3.3 wt. %Si) and c) an alloy with chemical composition close to Stellite 6 (64wt.% Co 24 wt.% Cr, 4.2 wt.% W, 2,3 wt.% C were investigated. The tests were carried out using three 0,1 g/cm3 slurries composed by SiO2, Al2O3, and SiC particles, in suspension in distilled water. The applied load was 0.3 N, the rotational speed 20 rpm and the total sliding distance 48 m. Analysis of the worn surfaces of the tested alloys by Optical Microscopy, Scanning Electron Microscopy and Contact Stylus Profilometry showed that abrasive size, shape and hardness could significantly influence the wear coefficients. The tests carried out with SiC and Al2O3 slurries resulted in greater wear rates than those carried out in SiO2 slurry. Stellite 250, showed the greatest wear coefficient, compared to the two other experimental alloys, due to a very low volume fraction of hard second phase particles in the microstructure. Wear coefficients decreased with increasing abrasive particles hardness. An approximate linear correlation with the ratio between the hardness of the abrasives (Ha) and the compound hardness of the alloys (Ha) with a correlation factor R2= 0.74. The dominant wear micromechanism observed in all tests was two-body abrasion (grooving wear). The modified T400 alloy, containing Laves phase showed a transition from ductile to brittle wear mechanisms when testing with alumina slurries. The worn volume was slightly greater than the one observed with SiC. A severely deformed nanocrystalline layer was identified, immediately below the worn surface. It was concluded that cold recrystallization of the work-hardened material occurred, with the formation of nano sized equiaxed grains.

Spark plasma sintering (SPS), also known as direct current sintering (DCS) is an advanced sintering technique that and uses a continuous pulsed direct current to rapidly process materials through Joule heating and offers significant advantages and versatility over conventional sintering methods. The technique features in energy saving owing to high heating rates and is very suitable for consolidation as well as diffusion bonding of electrical conductive advanced ceramic materials such as ultra high temperature ceramics (UHTCs). However, cooling rate in SPS also plays an important role as it directly influences the generation of residual stress especially for specimens consist of dissimilar phases such as composites and laminates primarily due to CTE mismatch. Therefore, in order to produce high quality materials, a zirconium diboride with addition of silicon carbide (ZrB2-SiC) ultra high temperature ceramic composite is selected to investigate the effect of cooling rate in SPS on microstructure and mechanical properties. After being densified at the target temperature, ZrB2-25vol%SiC specimens are cooled from 1800°C using controlled cooling rates of 10 °C/minute to ~225.5 °C/minute (free cooling). A time dependent finite element analysis (FEA) model is used to simulate the temperature gradients across the specimens at dwell times and during the cooling processes. The residual stress within the specimens are experimentally verified using X-ray diffraction (XRD) and Raman spectrometry, and found maximum residual stress within the specimen cooled at 225.5 °C/minute. Peak Hardness and moderate elastic modulus is found for specimen sintered at 1800 °C and cooled at 100 °C/minute, which make this temperature and cooling rate appropriate conditions for future fabrication of UHTCs with similar thermal and electrical properties. These materials are of great interest for their excellent high-temperature capabilities, wear and corrosion resistance, and are regarded as material candidates for engineering applications in extreme environments. Therefore, development of an effective joining technique is important since near-net shape fabrication is challenging, and joints formed by brazing or conventional solid-state diffusion bonding limit the mechanical strength and high temperature applications of the base materials. Using SPS we have rapidly and successfully joined ZrB2 to hafnium diboride (HfB2) at 1750 and 1800 °C within a minute through electric current assisted solid-state diffusion bonding. The electric current enables localized Joule heating as well as plastic deformation of the mating surface asperities, and enhances the elemental interdiffusion process at the HfB2/ZrB2 interfaces owing to electromigration, which leads to the formation of ZrxHf1-xB2 solid solution. A series of characterization and analytical techniques including scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS), electron backscatter diffraction (EBSD), and scanning transmission electron microscopy (S/TEM) are employed to study the microstructure and chemical composition at of the HfB2/ZrB2 interfaces. Apart from enhanced diffusion as a result of electromigration, the applied electric current can also be use to promote plastic deformation in ZrB2, which does not go through gross plastic deformation due to its extremely high melting point and brittle nature even when elevated temperature and pressure are applied. Through “electroplastic effect” (an effect based on electromigration) the mobility and multiplication of the existing dislocations in ZrB2 is enhanced, and a “metal-like” primary recrystallization phenomenon in the ZrB2 is observed meaning the material has experienced a sufficient amount of plastic deformation and reached the critical dislocation density and configuration for nucleation of “strain-free” grains. The average grain size of the recrystallized grain is only ½ of its original value. These findings suggest great potentials in microstructural tailoring and grain refinement of conductive advanced ceramics using SPS, and provide promising ideas for future fabrications and applications.

Depuis quelques années la demande en gazole dépasse la production des raffineries européennes et inversement pour les essences. L'objectif de cette thèse est de valoriser l'excédent d'essences et de satisfaire la demande en diesel en utilisant le procédé d'oligomérisation des oléfines. Nous nous sommes intéressés à l'oligomérisation du pentène qui, au contact d'un catalyseur solide acide, s'oligomérise en molécules plus lourdes de 10 à 25/30 atomes de carbone. Nous avons choisi les zéolithes et la mordénite en particulier comme catalyseur de la réaction. Afin d'améliorer le transport des molécules aux sites actifs nous avons modifié la texture des mordénites par la création d'un réseau secondaire de mésopores au sein de leurs cristaux, en utilisant deux traitements post-synthèse différents : la dessilication et la recristallisation. La dessilication génère des mésopores intra et inter-cristallins (de 10 nm à 100 nm de diamètre) par dissolution partielle de la zéolithe en présence d'une solution basique. La recristallisation conduit à une mésoporosité organisée et monodispersée en taille (petits mésopores de 4 nm) grâce à l'utilisation d'un agent structurant sous conditions hydrothermiques. Nous avons ainsi obtenu des mordénites micro-mésoporeuses de texture, porosité et acidité différentes en fonction du traitement appliqué. Finalement, après l'élaboration du micro-pilote expérimental, nous avons comparé les performances de nos catalyseurs optimisés de mordénites micro-mésoporeuses à celles des catalyseurs de référence (conversion, stabilité, sélectivité, rendement en oligomères C15-C20+, degré de branchement des produits) afin d'établir les relations structure-acidité-performances catalytiques. Nous avons mis en évidence l'impact positif de l'insertion de mésopores dans le catalyseur sur la conversion, la stabilité et le rendement en oligomères C15-C20+. Une méthodologie de caractérisation du degré de branchement des produits de réaction a également été mise au point pour compléter l'analyse des performances catalytiques. / Recently the demand in diesel has been exceeding the production of European refineries and, inversely for gasoline. The objective of this thesis is to increase the value of the gasoline excess and meet the demand in diesel using the olefin oligomerization process. We focused on the oligomerization of pentene, which can transform into heavier molecules from 10 to 25/30 carbon atoms in contact with a solid acid catalyst . We chose zeolites as catalysts and more specifically mordenite. To improve the molecular transport to the active sites we have modified the mordenite texture by creating a secondary mesoporous framework inside the crystals, using two different post-synthesis treatments: desilication and recrystallization. Desilication treatment generates intra and inter-crystalline mesopores (from 10 nm to 100 nm diameter) by partial dissolution of the zeolite in the presence of a basic solution. Recrystallization creates a well-organized mesoporosity with a uniform diameter (small mesopores of 4 nm) due to the use of an organic template of mesopores under hydrothermal conditions. Starting from the same parent mordenite we obtained micro-mesoporous mordenites with different textures, porosity and acidity properties depending on the treatment. Finally, after the development of the experimental pilot, we compared the performance (conversion, stability, selectivity, yield in oligomers C15-C20+, branching degree of the products) of our optimized catalysts of micro-mesoporous mordenite with some reference catalysts in order to establish relations between structure-acidity and catalytic performance. We highlighted the positive impact of the introduction of mesopores in the catalyst on the conversion, stability and yield in oligomers C15-C20+. A methodology to characterize the branching degree of the products has also been developed for completing the analysis of catalytic performances.

The object of the present investigation has been to relate the mechanical properties of a high strength Mg-Y-Gd alloy to alloy composition, extrusion parameters and microstructure. Three alloys with various Y: Gd ratios, of similar total solute content (at %) to Elektron 675, have been investigated in this study:9122: Mg – 6.5 wt % Y – 7.6 wt % Gd – 0.4 wt % Zr 9123: Mg – 8.2 wt % Y – 4.8 wt % Gd – 0.4 wt % Zr9124: Mg – 2.6 wt % Y – 13.1 wt % Gd – 0.4 wt % ZrThe three alloys were extruded at 425 and 475 °C with extrusion ratio 17: 1 to give two samples from each alloy, group a and b. Alloy 9122 was also extruded at 460 and 500 °C with extrusion ratio 10: 1 to give another two samples c and d. The as-cast microstructure of the three alloys comprised equiaxed α-magnesium grains and regions of eutectic decorating some grain boundaries formed during solidification of the ingot. Variation of extrusion parameters has resulted in a dispersion of different volume fractions of second phase particles in different groups of samples. The chemistry of second phase particles was determined by in-situ bulk energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD); magnesium yttrium was identified for near-equiaxed particles and yttrium hydride was proposed as a possible identification for cuboids. The composition of these compounds varied with variation of Y: Gd in the three alloys. Variation of extrusion ratio and extrusion temperature had a clear effect on the evolution of the extruded microstructure and the development of crystallographic texture as characterized by optical microscopy, electron backscattered diffraction (EBSD) and inverse pole figures. The microstructure of the extruded samples was refined during extrusion through dynamic recrystallization (DRX). Samples of groups a, b and c exhibited a microstructure in which bands of fine, equiaxed grains in association with stringers of second phase particles (running along the extrusion direction) were formed between bands of coarse, equiaxed grains. Sample d contained only small volume fraction of second phase particles; only a few alternating bands were formed and considerable grain growth occurred. A random texture was developed during extrusion in samples of groups a, b and c; a wide spread of orientations accompanied by a (new) previously unreported texture component in which basal poles of some grains are aligned nearly parallel to the extrusion direction was developed. The new texture component was weak in sample c and entirely suppressed in sample d. The asymmetry in tensile and compressive yield stress commonly associated with magnesium extrusions was nearly eliminated in samples of group a and b. The new basal texture component was likely to be a result of nucleation of DRX on sites rotating into this orientation. This is proposed to be a result of deformation in those regions in grains was accomodated by basal, prismatic and pyramidal slip. The grains nucleated in this orientation appear to have developed a form of preferred growth which led to strengthening of this new component following solution treatment. The effect of varying solute content (Y & Gd) and different ageing temperatures 150, 200, 250 and 300 °C (T5 & T6) on the ageing response and precipitation reaction were investigated using hardness measurements and transmission electron microscopy (TEM). Alloy 9122 showed the highest ageing response of the three alloys at 150, 200 and 250 °C (T5 & T6); specimens aged in the T5 gave higher hardness than the T6 treatment, a contribution of fine grain size. The three alloys did not respond to ageing at 300 °C. The precipitation reactions that occurred in alloy 9122 (at under, peak and overageing) and alloys 9123 and 9124 (at peak ageing) at 250 °C have been characterized. The precipitation sequence observed in sample 9122a can be described as: . The microstructure of peak aged specimens of alloys 9122 and 9124 were similar; both contained a homogeneous dispersion of precipitates and some metastable precipitates. Alloy 9123 contained only a homogeneous dispersion of precipitates and remnants of precipitates and no precipitates. The enhanced thermal stability of and phases are most likely responsible for the superior elevated temperature properties of Elektron 675. The effect of varying solute content (Y & Gd) and extrusion parameters on the mechanical properties were determined using tensile testing. Alloys 9122 and 9124 exhibited higher 0.2 % proof stress and UTS than alloy 9123 and alloy 9122 was the hardest alloy. Alloy 9122 exhibited the worst ductiliy (T5 and T6) among 9123 and 9124, and this was attributed to the higher volume fraction of second phase particles. The ductility of samples a, b and c in the as-extruded & T5 conditions, particularly in the transverse direction, was limited by stringers of second phase particles, whereas ductility and failure in sample d was governed by grain size and texture. The ductility and failure of all samples aged in the T6 treatment, irrespective of the extrusion history, was controlled by texture and grain size rather than stringers of second phase particles.

The goal of our research is to generate cryopreservation agents derived from antifreeze glycoproteins. One postulated mechanism of cell cryo-injury is ice recrystallization. It is known that simple saccharides and cryopreservation agents (DMSO) display ice recrystallization inhibition (IRI). This study assessed the cytotoxicity and cryopreservation ability of these sugars in relation to their IRI. It was determined that compounds with greater IRI have increased cytotoxicity yet confer cryoprotection. To further investigate how structure is affecting IRI activity, several galactopyranoside derivatives were synthesized. A series of deoxy and α-Callyl- deoxy galactopyranoses were prepared. Testing determined that removal of any hydroxyl group removes IRI. 3-deoxy-β-thiophenyl galactose was also synthesized and had surprisingly better IRI than β-thiophenylgalactose. Also, 6-azido galactose had similar IRI to 6-deoxy galactose. Lastly, a series of β- thioalkylgalactosides was synthesized and testing gave contradicting results which suggest that predicting IRI based on hydrophilicity is more complicated than initially hypothesized.