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Pouchlý, Václav. "Slinování pokročilých keramických materiálů s využitím vysokoteplotní dilatometrie." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228398.
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This diploma work is focused on exploitation of high-temperature dilatometry in sintering of advanced ceramic materials. Newly developed software is presented in this diploma work. This software is able to calculate activation energy of sintering process via concept of Master Sintering Curve. In the second part of diploma work the software was verified by evaluation of sintering of four different ceramics materials. The following activation energies of sintering were calculated: 990kJ/mol for tetragonal ZrO2 (3mol% Y2O3), 620kJ/mol for cubic ZrO2 (8mol% Y2O3) and 640kJ/mol resp. 720kJ for Al2O3 with two different particle size.
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Solem, Benjamin. "Dilatometry Study of a High-Chromium Cast Iron." Thesis, KTH, Hållfasthetslära (Avd.), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232528.
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High-chromium cast irons are used in certain applications where the demand on abrasion resistance is high. Such applications can be found in the milling industry and in pumps for transport of abrasive particles in liquid suspension. Soft annealed high-chromium cast iron containing 2.6 % C and 24.7 % Cr was supplied by Xylem Water Solutions, Sundbyberg, and investigated by dilatometry. The heat treatments were inspired by induction hardening procedures. The purpose of the investigation was to evaluate the effect of maximum temperature reached during heat treatment on the final length of the test specimen. The aim with this was to find the treatment yielding the maximum possible length which should be profitable to create desirable compressive stresses in the surface hardened area. The experimental results were used to create a finite element model in COMSOL Multiphysics accommodating for the maximum temperature, simulating the phase changes occurring in a geometry based on the experimental test specimen. The experimental results did not reveal any clear correlation between the maximum temperature and the final length change. The hardness, however, increased with the increasing temperature in the treatment interval 900-1150 °C. The, by light optical microscopy, observed amount of secondary precipitated carbides decreased with increasing temperature. Martensite transformation was also affected; the transformation temperature decreased for increased treatment temperatures. From dilatometry it was also seen that the thermal strains were greatly affected by the direction of which the material was cut from the original cast material. Samples taken perpendicular to the mainly investigated direction showed lower coefficients of thermal expansion and the final strain was clearly positive compared to the slightly negative values found for the main direction. This phenomenon could possibly be explained by different macrostructures created during solidification of the melt causing anisotropy in the eutectic. The implementation in COMSOL by describing the phase transformation as ordinary differential equations did show partially good results in the simulation of thermal expansion. The difference in original material is noticeable in the dilatometry and the simulated martensite transformation deviates from the experimental results. The model needs to be validated against new intermediate test temperatures and the martensite transformation kinetics must be investigated further to yield better results to be able to combine the phase transformations with mechanical calculations.
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Matsubara, Daniel Bojikian. "Caracterização de chapa grossa de aço microligado temperado por meio da técnica de dilatometria." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-23102015-155738/.
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Foram coletadas amostras de uma chapa grossa temperada, de aço microligado ao boro com 8 mm de espessura. O aço foi produzido em aciaria do tipo LD, laminado na forma de chapa grossa em laminador de cadeira única reversível e finalmente recebeu tratamento de têmpera em forno de tubos radiantes e máquina de têmpera com fluxo de água. Todas as etapas de produção tiveram os parâmetros de processo controlados para obtenção das melhores propriedades possíveis. As amostras foram retiradas da região situada a um quarto da largura da chapa e submetidas a diversos ciclos térmicos em aparelho de dilatometria. Com auxílio de técnicas de microscopia ótica, microscopia eletrônica de varredura e medidas de dureza, o aço pôde ser caracterizado e foi possível levantar as curvas de resfriamento contínuo (TRC). As microestruturas revelaram a presença de múltiplos microconstituintes, principalmente em resfriamentos a partir de resfriamentos 25°C/s, quando surgem elementos aciculares como ferrita acicular e bainita misturados com ferrita poligonal e perlita. Acima desta taxa de resfriamento o campo perlítico é suprimido e a partir de 45°C/s surge a martensita. A 100°C/s a microestrutura é dominada predominantemente por martensita. As amostras resfriadas nas 3 taxas mais severas também revelaram a presença de austenita retida e constituinte MA, detectados por meio de difração de raios-x e ataque com reagente de Klemm.Samples were taken from a quenched plate with 8mm thickness and chemical composition consisting of carbon, manganese, silicon, aluminum, niobium, titanium and boron. The steel was produced in LD converter, rolled in a reversible single chair rolling mill and quenched in a radiating tube furnace and quenching machine with water flow. All production stages had the process parameters controlled to obtain the best possible properties. The samples were extracted from a position situated at one quarter of the plate´s width and submitted to various thermal cycles in dilatometry device. With the aid of optical microscopy, scanning electron microscopy and hardness measurements, the steel could be characterized and the continuous cooling transformation curves could (CCT) be plotted. The microstructures revealed the presence of multiple components, especially when cooling rates reach 25°C/s, where acicular elements, like acicular ferrite and bainite, are found along with polygonal ferrite and pearlite. Above this cooling rate the pearlite field is suppressed and starting at 45°C/s martensite was found. At 100°C/s the microstructure is mainly martensitic. The samples cooled at the 3 most severe rates also revealed the presence of retained austenite and MA constituent, which were detected by x-ray diffraction and attack using Klemm reagent.
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Abbas, Naseeba. "Analysis of phase transformations in hydrogenated titanium metals by non-isothermal dilatometry." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/12339.
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Includes bibliographical references (leaves 124-127).Hydrogen was used as a temporary alloying element in CP Ti and Ti-6AI-4V. The microstructural evolution and phase transformations were monitored, before, during and after hydrogenation with in-situ dilatometric testing. Wrought CP Ti and Ti-6AI-4V specimens were pre-annealed and experienced four consecutive thermal cycles (Cycles 1-4) i.e. hydrogenation, post-hydrogenation, dehydrogenation and post-dehydrogenation, during dilatometric testing. The specimen in each thermal cycle was heated to 1000°C, heating rate 1°C/min (with an isothermal hold at 1000°C for three hours for hydrogenation and dehydrogenation cycles) and then cooled to room temperature at cooling rate of 1°C/min.
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Pouchlý, Václav. "Slinování pokročilých keramických materiálů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-234142.
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Sintering is a one of the key step in a processing of bulk ceramic materials. New sintering methods were invented in the last years. These new sintering methods, according to their authors, can be used for obtaining finer final microstructure of ceramics only by modifying the heating schedule. This work is focused on an influence of the Two Step Sintering method on the final microstructure for oxide ceramics. Obtained experimental results have shown that the effectivity of the Two Step Sintering method is rising with crystallographic symmetry of used material. Thesis is also focused on a high-temperature dilatometry and concept of the Master Sintering Curve. This concept was used for calculation of the activation energy of sintering and finding different sintering mechanisms acting in the intermediate and final stage of sintering. Activation energy of sintering was compared with activation energy of grain growth with target to find the kinetic window. Kinetic window can allow a sintering without a grain growth. Master Sintering Curve method was also used in a pressure assisted unconventional sintering technique Spark Plasma Sintering. Master Sintering Curve applied to a Spark Plasma Sintering technique reveals and quantified different sintering mechanisms acting in Spark Plasma Sintering. These findings led to preparation of transparent tetragonal ZrO2.
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Spannagel, Ruven [Verfasser], Claus [Akademischer Betreuer] Braxmaier, Calus [Gutachter] Braxmaier, and Andreas [Gutachter] Rittweger. "Laser-interferometric dilatometry / Ruven Spannagel ; Gutachter: Calus Braxmaier, Andreas Rittweger ; Betreuer: Claus Braxmaier." Bremen : Staats- und Universitätsbibliothek Bremen, 2017. http://d-nb.info/1141862026/34.
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Mařák, Vojtěch. "Příprava a vlastnosti dopovaných piezokeramických materiálů na bázi BaTiO3." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417065.
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This diploma thesis deals with the preparation of doped piezoceramic materials based on BaTiO3 using electrophoretic deposition. Five rare earth oxides, i.e. Er2O3, Dy2O3, Eu2O3, Tb407 and CeO2, were used as dopants in amounts of 1, 3, and 5 wt. %. The prepared deposits were evaluated in terms of preparation methodology, high temperature dilatometry, X-ray diffraction analysis, relative density, mean grain size, hardness and fractographic analysis. The study of dilatometric curves described the sintering behavior and its changes at different material compositions. X-ray diffraction analysis revealed a tetragonal phase in all samples; the tetragonality of the BaTiO3 crystalline cell decreased with dopant content. By a suitable choice of dopant, it was possible to significantly increase the relative density of sintered samples, their hardness and at the same time prevent the samples from coarsening of the microstructure during heat treatment. A relative density up to 98 %, a mean grain size below 1 m and a hardness of over 10 GPa were achieved. Analysis of the fracture surfaces revealed that the fracture mode was transcrystalline for the most of studied materials; only the samples doped with cerium dioxide had fracture surfaces with both transcrystalline and intercrystalline fracture modes. Based on the obtained results, a suitable composition of the material for the intended use in a layered piezoceramic harvester was identified, which, in addition to the BaTiO3 layers, consists of functionally-protective Al2O3 and ZrO2 layers.
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Casarin, Samuel Jose. "Caracterização da temperabilidade de um aço C-Mn microligado ao boro, através de dilatometria e curvas de transformações de fases por resfriamento contínuo." Universidade de São Paulo, 1996. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-29012010-160947/.
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No presente trabalho, foi realizado um estudo sobre a influência da adição do boro em um aço C-Mn, nas transformações de fases por resfriamento contínuo, através da técnica dilatométrica. Para este estudo, utilizou-se dois aços de composição química semelhante: o aço 10B22 com 30 ppm de boro e o aço sem boro é o E1522, equivalente. Foram traçadas as curvas de CCT dos dois aços, onde analisou-se o efeito de temperabilidade do boro através das curvas de resfriamento. Os materiais foram ensaiados em um dilatômetro de resfriamento rápido, utilizando corpos de prova cilíndricos, resfriados por injeção de ar e hélio. Os resultados gráficos dos processos de resfriamento foram comparados com análises metalográficas ótica estruturais e quantitativas e também por medidas de dureza. Detalhes microestruturais, tais como, contagem de fases formadas em função das taxas de resfriamento, tamanho de grão, distribuição de inclusões e precipitados, foram extraídos, através de um sistema de análise de imagens. Complementando o trabalho, foi realizado uma completa documentação fotográfica das microestruturas, com uma indicação final do tratamento térmico mais adequado aos aços C-Mn microligados ao boro.This work presents a study about the influence of boron on phase transformation by continuous cooling in a C-Mn steel using the dilatometric technique. For this study two close chemical composition steels were applied: a 10B2 steel with 30 ppm of boron and a E1522 steel without boron. For both steels the CCT curves were obtained, where the effect of boron on hardenability was analysed throughout continuous cooling curves. Both materials were testedcin a high speed quenching dilatometer, using cilindricals samples quenched by helium blow on their surfaces. The graphics results of cooling processes were compared with microstructural and quantitative optical metallographic analysis and hardness measurements. Microstructural features as such phases fraction as a function of cooling rates, grain size, and distributions of inclusions and precipitates were obtained through an image analysis system. In addition, complete microstructural photography documentation was carried out where it was possible to indicate the best heat treatment to boron microalloyed C-Mn steels.
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Casarin, Samuel José. "Transformações de fases isotérmicas por dilatometria do aço SAE 1070: curva TTT." Universidade de São Paulo, 1993. http://www.teses.usp.br/teses/disponiveis/18/18136/tde-16092009-093825/.
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A proposta de desenvolvimento deste trabalho de dissertação veio de encontro com o objetivo de adaptar um laboratório para pesquisas em transformações de fases, utilizando o método dilatométrico, onde foram estudadas as reações no estado sólido que sofrem os materiais submetidos a ciclos térmicos. Para atingir este objetivo, instalou-se recentemente um dilatômetro de resfriamento rápido, modelo DT 1000 da Adamel Lhomargy. Completada a etapa de instalação do equipamento, o passo seguinte consistiu em explorar, através de ciclos térmicos variados, todos os recursos manipuláveis do dilatômetro. Aplicando a técnica dilatometrica em um aço de características termomecânicas conhecidas - SAE 1070 - possibilitou-se, a partir deste trabalho, que pesquisas mais complexas pudessem ser executadas com tal equipamento ou que o mesmo servisse como um instrumento complementar para estudos de transformações de fases. Nessa fase inicial de investigações estudou-se as curvas dilatométricas a fim de verificar os tempos de início e fim de transformação isotérmica em várias temperaturas de decomposição da austenita. Traçou-se as curvas de transformação isotérmica - curvas TTT - para o aço ensaiado (tratado termicamente), onde analisou-se a influência desse tratamento térmico prévio (recozimento) sobre a transformação \'alfa\' para \'gama\'. Finalizando a parte prática deste trabalho, comprovou-se as transformações de fases isotérmicas nas várias temperaturas ensaiadas, através de análise metalográfica e de medidas de microdureza dos produtos obtidos. A fim de solucionar eventuais problemas relacionados ao manuseio e manutenção do equipamento, com base na experiência adquirida ao longo do desenvolvimento deste trabalho, são dadas sugestões de possíveis aplicações do dilatômetro de têmpera rápida DT 1000 em pesquisas de transformações de fases.The purpose of this work comes together with the objective to adapt a phase transformation research laboratory using dilatometric method, where it will be possible to study the solid state reactions of materials submited to thermal cycles. To fulfil this purpose, it was installed a high speed quenching dilatometer, model DT 1000 manufactured by Adamel Lhomargy. After this stage, our next step was to explorer all equipment resources through variable thermal cycles. Appling dilatometric method to a well known thermomechanical steel - SAE 1070 - it becomes possible the accomplishment of more complex experiments with this equipment. This equipment, itself, may be a powerfull auxilliary instrument to phase transformations studies. In this first investigation, it was studied the dilatometric curves to find the beginning and the end times of isothermal phase transformation for several austenite decomposition temperatures - TTT diagram - for the tested steel (thermal treated). The effect of this previous heat treatment (annealing) on the \'alfa\' for \'gama\' transformation were observed. Finally, the isothermal phase transformation at the different tested temperatures could be confirmed through metallographic and microhardness analysis. In order to solve possible problems associated to the equipment use or maintenance, some suggestions of applications of the high speed quenching dilatometer are indicated for further works.
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Balzer, Christian [Verfasser], Vladimir [Gutachter] Dyakonov, and Oskar [Gutachter] Paris. "Adsorption-Induced Deformation of Nanoporous Materials — in-situ Dilatometry and Modeling / Christian Balzer ; Gutachter: Vladimir Dyakonov, Oskar Paris." Würzburg : Universität Würzburg, 2018. http://d-nb.info/1151818690/34.
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Carvalho, Leandro Gomes de. "Estudo dilatométrico das transformações de fase em aços maraging M300 e M350." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-26032012-112344/.
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Os aços maraging são aços de baixo teor de carbono com estrutura martensítica (CCC), que são endurecidos pela precipitação de fases intermetálicas. O objetivo deste trabalho é estudar as transformações de fases desses aços: precipitação, reversão da martensita para a austenita e transformação martensítica. Nesse trabalho, foram caracterizadas uma corrida de aço maraging da série 300 e três corridas da série 350, usando diversas técnicas complementares: microscopia ótica, microscopia eletrônica de varredura com análise dispersiva de energia, microdurômetro, difração de raios-X, ferritoscópio e dilatometria. Os resultados obtidos mostraram que as corridas com maiores teores de cobalto e titânio apresentaram maiores valores de microdureza nos estados solubilizado e envelhecido. Por outro lado, medidas dilatométricas mostraram que há uma influência significativa tanto da composição química, quanto da taxa de aquecimento nas reações de precipitação e reversão da martensita para a austenita. No entanto, a transformação martensítica mostrou-se dependente apenas da taxa de aquecimento.Maraging steels are steels with a low carbon martensitic structure (BCC), which are hardened by precipitation of intermetallic phases. The aim of this work is to study the phase transformations of these steels: precipitation, martensite to austenite reversion and martensitic transformation. In this study, one cast of 300 grade and three casts of 350 grade were characterized using several complementary techniques: optical microscopy, scanning el ectron microscopy with energy dispersive analysis, microhardness, X-ray diffraction, ferritoscope and dilatometry. The results showed that the casts with higher concentrations of cobalt and titanium showed higher microhardness in the solution annealed and aged states. On the other hand, dilatometry measurements showed that there is a significant influence of both the chemical composition and the heating rate on the reactions of precipitation and reversion of martensite to austenite. However, the martensitic transformation was dependent solely on the heating rate.
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Ramírez, Mario Fernando González. "Influência da microestrutura nas propriedades mecânicas e na fragilização por hidrogênio em um aço microligado." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-19072013-170730/.
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A tecnologia dos aços microligados para transporte de gás natural e petróleo tem sido pressionada pelo descobrimento das novas jazidas e o aumento da demanda no mundo. As solicitações ambientais e de resistência mecânica são os parâmetros para o desenvolvimento de aços de alta resistência baixa liga para o transporte de gás e petróleo a menor custo e de forma segura. Neste contexto esta pesquisa investiga, em um aço microligado para tubos API 5L X80, o efeito das transformações de fase obtidas por resfriamentos controlados na fratura induzida por hidrogênio Hydrogen Induced Cracking-(HIC) e nas propriedades mecânicas. Os testes de HIC foram realizados no material como recebido, na espessura da chapa submetida a resfriamentos contínuos e em amostras do material tratadas de forma a simular as regiões de grão grosso da zona afetada pelo calor (GGZAC). Segundo o ciclo de resfriamento, os aços microligados têm microestruturas complexas, como é caso do aço microligado em estudo, onde sua microestrutura, estudada em trabalhos anteriores, é formada principalmente por ferrita, bainita, perlita e microconstituinte austenita/martensita (AM). A morfologia, tamanho, quantidade e distribuição dos produtos de transformação na chapa mudam as propriedades do aço. Esses fenômenos são de grande interesse tecnológico em aços microligados para a fabricação de tubos soldados para o transporte de gás e petróleo, tanto quando a solda é realizada em campo como também durante o encurvamento por indução; aqui as propriedades mecânicas do tubo decorrentes do processo de fabricação termomecânico podem ser degradadas pela ação do aquecimento e dos resfriamentos experimentados na zona afetada pelo calor (ZAC), principalmente na região de GGZAC. A simulação dos ciclos térmicos para o estudo da HIC na espessura da chapa foram realizados em CP austenitizados a 900ºC e submetidos a resfriamentos contínuos no dilatômetro de têmpera. Para simular os ciclos térmicos com resfriamentos controlados focados na GGZAC e a seguir obter CP de tamanho adequado para testes de tração e Charpy, foi necessário fazer os tratamentos térmicos a 1300ºC e resfriamentos contínuos em um simulador termomecânico e dilatômetro Gleeble. O maior tamanho da amostra tratada termicamente neste último equipamento permitiu extrair amostras para avaliar as propriedades mecânicas e a HIC do material, pois as diferentes regiões da ZAC em uma solda real são restritas e não permitem este tipo de ensaios em uma região específica da ZAC. Os resultados permitiram identificar a suscetibilidade de cada microestrutura produto da transformação da austenita na espessura da chapa, sendo a região central da chapa a mais sensível ao hidrogênio no aço como recebido e quando tratado a baixas taxas de resfriamento de 0,5°C/s após austenitizado a 900°C. As bandas grosseiras formadas por estruturas de maior dureza que a matriz na região central diminuíram a resistência à HIC. Da mesma forma nos corpos de prova que simulam a região GGZAC, a fratura induzida pelo hidrogênio foi localizada na região central da espessura embora apresente bainita e ferrita acicular. A falha possivelmente se deve aos elementos remanescentes segregados nesta região central e partição de carbono para os sub contornos de grão da bainita e ferrita que cresceram a partir a austenita primária. As inclusões e precipitados, segundo seu tipo, forma e localização na microestrutura, participam ou não da nucleação e propagação da trinca, sendo a posição mais crítica quando localizadas dentro das estruturas bandeadas. Não foi observada a nucleação de trincas na presença de hidrogênio em precipitados de Nb e Ti.The technology of microalloyed steels for the transportation of natural gas and oil has been pressed by the discovery of new deposits and the increased demand in the world. Environmental requests for safety and ever increasing mechanical strength are the parameters for the development of high strength low alloy steels for transporting gas and oil at lower cost and safely. In this context, this research investigates, in a microalloyed steel pipe API 5L X80, the effect of phase transformations obtained by controlled cooling on the behavior when loaded with hydrogen - Hydrogen Induced Cracking - (HIC) and in the mechanical properties. HIC tests were performed on as-received material, on samples extracted from the thickness of the plate and subjected to continuous cooling and on samples of the material treated to simulate the coarse-grained regions of heat affected zone (CGHAZ). According to the cooling cycle, the microalloyed steels have complex microstructures: in the steel under evaluation its microstructure, studied in a previous work, consists mainly of ferrite, bainite, pearlite and austenite/martensite constituent (AM). The morphology, size, quantity and distribution of the products of transformation change the properties of plate steel. These phenomena are of great technological interest in microalloyed steels for the fabrication of welded tubes for the transport of gas and oil, when the welding is performed in the field as well as during hot bending; here the mechanical properties of the tube from the process of thermomechanical fabrication can be degraded by the action of heating and cooling experienced in the heat affected zone (HAZ), mainly in the region of CGHAZ. Simulations of thermal cycles for the study of HIC on sheet thickness were performed in coupons subjected to austenitization at 900ºC followed by continuous cooling in the dilatometer. To simulate the thermal cycles with controlled cooling, focused in the CGHAZ, and getting suitable sample sizes for tensile testing and Charpy, it was necessary to austenitize at 1300ºC followed by continuous cooling using the thermal and thermomechanical simulator in a Gleeble dilatometer. Samples heat treated in this equipment were suitable to evaluate the mechanical properties and the HIC of the material for different regions of HAZ, while a real weld would not have enough material to allow this type of testing on a specific region of HAZ. The results showed the susceptibility of each microstructure product of austenite transformation and of the position on the plate thickness. The central region of the plate was more sensitive to hydrogen in the steel as-received and when treated at low cooling rates of 0.5°C/s after austenitization at 900°C. The bands formed by coarse structures of greater hardness than the matrix in the central region decreased the resistance to HIC. Likewise in coupons that simulate the CGHAZ region, the fracture induced by hydrogen was located in the central thickness line, even when the microstructure were bainite and acicular ferrite. Failure there was possibly due to remnants of segregated elements in this central region and carbon partition to the subboundaries of the bainite and ferrite grain that grew from the primary austenite. Inclusions and precipitates, according to their type, shape and location in the microstructure, participating or not in the nucleation and propagation of the crack, were more critical when located within the banded structures; crack nucleation in the presence of hydrogen was not observed at Nb and Ti precipitates.
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MELO, FRANCISCO C. L. de. "Efeito de aditivos na sinterizacao de carbeto de boro." reponame:Repositório Institucional do IPEN, 1994. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10407.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Peleška, Jan. "Kinetika koordinační polymerace 1-olefinů katalyzované diiminovými komplexy niklu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2012. http://www.nusl.cz/ntk/nusl-233353.
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This Ph.D. thesis is focused on kinetic study of propene and hex-1-ene coordination polymerizations initiated by complex [(2-tBuC6H4)N=C(1,8-naphtalenediyl)C=N(2-tBuC6H4)]NiBr2 activated by simple organoaluminium compounds and on product properties. In first three parts proper activators are chosen in model polymerizations. The attention is paid to the reproducibility of polymerizations and analytical methods. The fourth part is focused on propene polymerization kinetics with the aim to define optimal reaction conditions, especially polymerization temperature and time. The four part concerns also properties of polymers. The fifth and sixth parts deal with hex-1-ene polymerization kinetics conducted at various activator/initiator molar ratios and various catalytic precursor concentrations, to find out kinetic orders with respect to catalyst and cocatalyst concentration. Last part is oriented on detail mechanistic investigation of nickel diimine complexes activation process. Results of measurements in presence or absence of monomer enabled to propose new interpretation of UV-vis spectra based on concrete structures of absorbing species.
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O'Meara, Nicholas. "Developing material models for use in finite element predictions of residual stresses in ferritic steel welds." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/developing-material-models-for-use-in-finite-element-predictions-of-residual-stresses-in-ferritic-steel-welds(0f2cfa95-1d35-42be-b224-665252950efc).html.
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Nuclear reactor pressure vessels are constructed by welding low alloy steel forgings together. Welding processes can leave residual stresses which affect the RPV's resistance to fracture. Welding also induces microstructural changes and these changes have a number of associated consequences, including inelastic strains and altering mechanical properties. The extent to which these microstructural changes influence residual stress evolution during welding is not fully understood. The aim of this project is to characterise the microstructural and mechanical response of SA-508 Gr.3 Cl.1 pressure vessel steel to thermal cycles and develop representative models that can be used to determine how these effects influence stress predictions. There is insufficient materials data to inform the models used to predict how phase transformations influence residual stresses. Using the recently developed Gleeble thermo-mechanical simulator, previously unmeasured data characterising the response of the material to weld-like thermal cycles was generated. Variations in the kinetics of austenite formation and decomposition were investigated using dilatometry. It was found that when the steel is subjected to multiple thermal cycles that exceed the austenisation temperature, the behaviour during the first thermal cycle is different to that of subsequent cycles. In the subsequent thermal cycles, two observations were made: 1) the austenite formation rate increases on heating, and 2) for a given cooling rate, the austenite will decompose at lower temperatures into harder phases. It is explained how these changes in behaviour can affect the residual stress distribution in this thesis. Bainitic, austenitic and martensitic samples were generated. The stress-strain behaviour of these phases is presented and has been used to inform mechanical constitutive models. Finite element simulations of autogenous edge welded beams have shown how microstructural changes can affect the residual stress predictions. The extent of the transformed region of the HAZ and the yield stress of the material surrounding this region influences the location and magnitude of the peak tensile residual stress after a weld pass. Changes in mechanical properties induced by tempering bainitic and martensitic samples were quantified experimentally. The reductions in yield stress in bainite and martensite during short tempering heat treatments were found to be significant. A new approach to integrate the observed tempering behaviour into existing models is presented. The data and models presented in this thesis can provide guidance to structural integrity engineers and help produce more accurate and less conservative residual stress predictions for use in structural integrity assessments.
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Macaigne, Rodolphe. "Frittage micro-ondes du matériau spinelle MgAl2O4 : vers des céramiques transparentes." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC236/document.
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Les conditions nécessaires pour obtenir des céramiques transparentes (absence de porosité, absence de seconde phase) requièrent une totale maitrise de chacune des étapes (synthèse, mise en forme, frittage) intervenant dans le processus, ce qui rend encore difficile l'industrialisation d'un procédé d'élaboration reproductible. Dans ce contexte, ce travail de thèse s’est focalisé à développer et évaluer la capacité du procédé de frittage micro-ondes à améliorer la robustesse du processus d'élaboration de spinelle transparent. La mise en place d'un dispositif de dilatométrie optique et une nouvelle technique de calibration originale, basée sur la fusion d'oxyde, ont permis de caractériser le frittage micro-ondes du spinelle pur avec une plus grande confiance. Même si aucun effet lié au procédé micro-onde n’a pu être mis en évidence pour le frittage du spinelle pur (trajectoire de frittage, mécanisme de densification et évolution de la porosité identiques), ces travaux ont démontré que l’impact de dopants pouvait être amplifié en présence du rayonnement micro-ondes. Ainsi, un décalage des courbes de retrait vers les basses températures a été observé lors du frittage micro-ondes du spinelle dopé avec TiO2 et MgO. L'existence d'un couplage particulier entre les défauts ponctuels chargés (lacunes, cations interstitiels) et le champ électrique pourrait être à l'origine de ce phénomène. Ces travaux de thèse ont également démontré la faisabilité de fritter des pièces de spinelle carrées de grandes dimensions (< 65 mm) compatibles avec un post-traitement HIP, en vue d'obtenir des pièces transparentes. Pour cela, un four micro-ondes monomode 915 MHz a été automatisé et une cellule de frittage adaptée a été développée. A l'issue du traitement HIP, les pièces ont présenté une transparence et des propriétés mécaniques (dureté; ténacité) comparables à celles des pièces pré frittées par voie conventionnelleThe elaboration of transparent ceramics (no porosity, no second phase) requires a strict control of all steps of the process (synthesis, shaping, sintering). As a result, the industrialization of a reproducible process is still difficult to achieve. In this context, this thesis has focused on developing and evaluating the ability of the microwave sintering process to improve the robustness of the transparent spinel elaboration process.The set-up of an optical dilatometer and a new original calibration method, based of melting of different oxides, allowed to characterize the microwave sintering with a greater confidence. Even if no microwave effect has been observed on the sintering of pure spinel (identical sintering trajectory, densification mechanism and porosity evolution), this work has shown an amplification of the impact of dopants during microwave sintering. A shift of the shrinkage curves towards the low temperatures was observed during the microwave sintering of the spinel doped with TiO2 and MgO. The existence of a particular interaction between charged point defects (vacancies, interstitial cations) and the electric field could explain this phenomenon.This work thesis has shown also the feasibility of sintering of large square spinel pieces (< 65 mm) compatible with post treatment HIP in order to produce transparent ceramics. For this purpose, the microwave system working at 915 MHz was automatized and a new sintering configuration was developed. After a post-treatment, the transparency and mechanical properties (hardness; tenacity) of microwave pre-sintered samples were comparable with those of samples sintered by conventional heating
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Rose, Kyle. "Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1703275/.
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An in-depth study of Al2W3O12 negative thermal expansion (NTE) ceramic was performed, focused on synthesis, phase mappings, and the underlying mechanisms shown to be responsible for NTE. Review of the literature has shown inconsistencies in reported values of the dilatometry measured coefficients of thermal expansion, and the temperature for the known monoclinic to orthorhombic phase transition. Two synthesis techniques are introduced: an ionic-liquid non-hydrolytic sol-gel synthesis route; and a low temperature solid state reaction synthesis for Al2W3O12. X-ray diffraction, Raman spectroscopy, and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) were used to verify the techniques. Two differential scanning calorimetry (DSC) experiments (high and low temperature) were performed on the material showing the transition between -5 and -20 °C and no other phase changes until a reported degradation above 1100 °C. Extensive dilatometry on the material led to the discovery of elastic transitions occurring in the polycrystalline sample capable of explaining the inconsistencies in reported dilatometry results. This is further developed into a proposed model defining the regions between these transitions. Each region has a different thermal expansion as well as a direct effect on the reaction of the material upon cooling. This proposed model may allow more consistent reporting of dilatometry results for NTE materials. Raman spectroscopy was performed from 25-725 °C on the material showing both a joining in the tungsten-oxygen bending modes as well as a broadening in the tungsten-oxygen stretching modes. This is consistent with Al-O-W angle changes along the same temperature range reported in literature as well as the transverse vibrational modes responsible for NTE.
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Neher, Roland. "Phasenbeziehungen und kinetische Modellierung von flüssigphasengesintertem SiC mit oxidischen und nitridischen Additiven." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-148121.
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In the present dissertation the formation of microstructure, the kinetics of densification and the formation of surface layers developing during liquid phase sintering of silicon carbide are studied. The focus is on the additive systems Al2O3 plus Y2O3 and AlN plus Y2O3.
Phase and especially liquid phase formation in both of the systems SiC, Al2O3 , Y2O3 and AlN, Al2O3 , Y2O3 are investigated in detail examining 12 espectively 17 different compositions per system. Melting temperatures have been determined by TG/DTA, in both systems for the first time. Phase composition of samples was analysed by the combination of XRD, SEM and EDX. In the system SiC, Al2O3 , Y2O3 the formation of the phases expected from the quasibinary Al2O3 , Y2O3 could be observed thus silicon carbide has to be in equilibrium with the oxide additives. The low solubility of SiC in the oxide melt, which was suggested by Hoffmann and Nader, could be confirmed. In the system AlN, Al2O3 , Y2O3 the formation of phases as stated by Medraj was confirmed, except for the dimension of the stability region of the γ- spinel and YAG which is wider in the present work.
For the first time diffusion coefficients of the species Y3+ and Al3+ in the oxide melt formed by Al2O3 and Y2O3 at temperatures above 1825 ◦ C were determined. The values are in the order of 2 · 10−6 cm2 /s which results in a diffusion length of 14.1 μm for a diffusion time of one second. This allows the fast equilibration of Y and Al deficiencies.
Kinetics of densification was modeled by kinetic field, master curve and thermokinetic method, based on detailed experimental investigation of the shrinkage during liquid phase sintering of SiC. It could be proved that the first 30 − 40 % of densification are controlled by solid phase reactions which accelerate particle rearrangement without presence of a liquid phase. During the remaining 60 − 70 % of densification a liquid is present, resulting in the predominance of mechanisms of liquid phase sintering. The models deliver activation energies in the range from 608 KJ/mol to 1668 kJ/mol and allow, within the scope of validity of each method the prediction of densification during liquid phase sintering of silicon carbide.
When sintering silicon carbide with Al2O3 plus Y2O3 the formation of several surface layers, depending on atmosphere, maximum temperature, dwelling time and amount and composition of additives was observed. In nitrogen atmosphere with low partial pressures a surface layer consisting of AlN is forming whilst at high partial pressures SiAlON- polytypes occur. After sintering in Argon or Ar-CO- atmosphere three main types of surface layers are present. One consists of alumina, one contains only YAG and one shows highly porous, additive depleted regions. An explanation for the formation of the several surface layers could be given by the combination of the determined diffusion coefficients with the results achieved in the thermodynamics part.
The results achieved in this work can be a contribution to the knowledge based design of the production process of liquid phase sintering of silicon carbide.
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Ruiz, Alberto Ibañez. "A presença do nióbio em um ferro fundido branco de cromo-molibdênio: traçado da curva transformação-tempo-temperatura." Universidade de São Paulo, 1996. http://www.teses.usp.br/teses/disponiveis/18/18136/tde-09102017-142618/.
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Avaliou-se experimentalmente o ferro fundido branco de alto-cromo-molibdênio ao qual foi adicionado nióbio, a respeito de sua temperabilidade. Dilatometricamente traçou-se a curva TTT desse material, bem como a de um ferro fundido branco de alto cromo para efeito comparativo. Constatou-se por essa comparação e pelos resultados da literatura a alta temperabilidade obtida pela liga experimental. A partir da temperatura de austenitização utilizada, podem-se usar taxas de resfriamento de até 0,12°C/s sem transformação de fase, enquanto que na liga comparativa essa taxa aumenta para 5,8°C/s. Foram realizadas análises de desgaste abrasivo, de dureza e microdureza, de difração por raios-X , de fase magnética e de microanálise como forma de caracterizar as transformações de fase observadas por dilatometria. As variações estruturais decorrentes dos tratamentos térmicos realizados nas duas ligas foram acompanhados por microscopia ótica. É indicativo pelo presente trabalho que tal material além de suas características inerentes de resistência à abrasão e à corrosão oferece maior flexibilidade nos projetos que envolvam paredes espessas.In this work we studied the hardenability of high chromium- molibdenum white cast iron with niobium. By dilatometry we obtained the TTT curve of this material as well as the high chromium white cast iron for comparison. This comparison and available results in literature confirm the high temperability of experimental material. We can use slow rate cooling 0,12°C/s or higher without phase transformation, while in the comparative alloy this rate is around 5,8°C/s or higher from specific used austenitic abrasive temperature. We also realized analysis of abrasive wear, hardness and microhardness, raios-X difraction, magnetic phase and microanalyse for verifing the phase transformation as observed by dilatometry. The structure variation as function of termic treatment in both alloys is monitored by optical microscope. The present work indicate that the material under study can offer more flexibility for projects with thick materials apart from intrinsic characteristics of abrasive wear and corrosion.
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Conti, Elaine Cristina Guerbach [UNESP]. "Estudo da interface titânio/porcelana, com três porcelanas de ultra baixa fusão, empregando-se microscopia eletrônica de varredura e dilatometria." Universidade Estadual Paulista (UNESP), 2002. http://hdl.handle.net/11449/89679.
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conti_ecg_me_arafo.pdf: 2274247 bytes, checksum: bd8fd8849fb076ead7d056ec179f83a2 (MD5)O objetivo deste trabalho foi caracterizar química e metalograficamente o Ti.c.p. antes e após a fundição por Plasma-Skull, e estudar as interfaces entre esse metal e as porcelanas Vitatitankeramik, Triceram e Noritake TI22, empregando-se M.E.V., EDS, Mapeamento Elementar e Dilatometria. Trinta e cinco placas nas dimensões de 25mm x 3mm x 1mm foram fundidas pela máquina nacional Discovery - Plasma, EDG Equipamentos, sendo 5 amostras empregadas para a análise química e metalográfica e as 30 restantes, utilizadas para aplicação das porcelanas, sendo divididas em 3 grupos de 10 placas cada. O tratamento da superfície do metal, bem como a aplicação e as cocções das porcelanas foram realizadas segundo as recomendações de cada fabricante. Posteriormente, as amostras tiveram uma de suas faces laterais lixadas, até a exposição da interface e preparadas para análise por M.E.V. Para os ensaios de Dilatometria, 2 amostras de Ti c.p. e 2 para cada sistema de porcelanas foram confeccionadas na forma de cilindro com 12 mm de comprimento x 2 mm de diâmetro, e em cada amostra foi soldado um termopar de cromel-alumel, para medida de temperatura dos ensaios. As curvas de expansão térmica do Ti c.p. e das três porcelanas, foram levantadas para estudar a compatibilidade entre os conjuntos metalocerâmicos. Os resultados da análise química e das imagens obtidas por Microscopia Óptica, demonstram que o Ti c.p. após a fundição apresenta condições físico-químicas adequadas para receber a aplicação da porcelana. Dos resultados de M.E.V., observa-se que todos os sistemas apresentaram integridade nas interfaces Ti/Bonder, livre de fendas ou poros, com um bom contato entre a porcelana e o metal, confirmado pelas imagens do Mapeamento Elementar, sugerindo uma adequada interação entre esses materiais. Da análise das imagens do EDS... .
The aim of this work was to perform a chemical na metalographical characterization of the commercially pure titanium before and after melting by the Plasma-Skull method, and to study the interfaces between this metal and the porcelains Vitatitankeramik, Triceram e Noritake TI22, using SEM, EDS, elementary mapping and dilatometry. Thirty five samples with dimensions 25mm x 3mm x 1mm were melted in a national Discovery-Plasma, EDG Equipaments, five of which were used for chemical analysis and metalography and the remaining thirty, divided in three groups, were used for applications of the porcelains. The metal surface treatment, as well as the applications and firing of the porcelains, were performed according to the recommendations of each manufacturer. Subsequently, one of the lateral surfaces of the samples was polished until the interfaces was exposed and then was prepared for the SEM analysis. Two samples of commercially pure titanium and other two for each system of porcelains were cylindrically shaped with lengths of 12mm and 2mm of diameter, and in each sample Chromel-Alumel thermocouple was welded to measure the temperature of the tests. The thermal expansion curves of the commercially pure titanium and porcelains were measured to study the compatibility of the metal-ceramic systems. The chemical analysis and optical microscopy results show that the commercially pure titanium after the melting exhibits appropriate physical and chemical conditions for the application of the porcelain. The SEM results indicate that all the systems exhibits integrity of the Ti/bonder interface, free of gap and porous, with good contact between metal and porcelain, which was confirmed by the elementary mapping images, suggesting and adequate interaction between these materials. From the analysis of the EDS images... (Complete abstract, click electronic address below).
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GIOFFREDI, EMILIA. "Polymer Crystallization: Micro- and Nano- Filler Effects on Isotactic Polypropylene." Doctoral thesis, Politecnico di Torino, 2012. http://hdl.handle.net/11583/2500104.
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Isotactic polypropylene (iPP) is one of the commodities used in the largest quantity today. Its good mechanical properties and relatively low price result in continuous growth of pro-duction and expansion of its market. The continuously increasing application accelerates research on all related fields, including the preparation of iPP-based composites and blends.
The preparation of polymer blends is an important technique in order to modify the target property of an individual polymer according to the requirement of the application field. Since the features of semi-crystalline polymers depend on the crystallinity degree and crystallite morphology, studies about the effects of fillers on the crystallization behavior of composites are of great interest.
Nucleated crystallization has been the subject of several studies over the last 50 years or so [Cormia et al. 1962, Binsbergen 1970, Mercier 1990].
In the relative simple case of isothermal crystallization, the presence of a nucleating agent (NA) shortens the induction time as well as enhances the overall rate of transformation from the molten state to the crystalline solid state. A shortening of the induction time due to a NA is obviously understandable since the polymer melt does not have to form its own seeds to initiate crystallization (self-nucleation being a time-dependent phenomenon as it results from the statistical fluctuations in the local order). In the processing of polypropylene, a nucleating agent is usually used for reducing the size of the iPP spherulites, improving the optical clarity, decreasing the cycle time of the process and enhancing the mechanical properties.
Therefore, the main goal of this work is the investigation of the effects of different mi-cro- and nano- fillers on the isotactic polypropylene crystallization behavior, both in quies-cent and in flow-induced conditions.
To this aim, two types of isotactic polypropylene were mixed with maleic anhydride grafted polypropylene (PP-MA) as compatibilizer and various micro- (talc, carbon fibres) and nano- (montmorillonites, carbon nanofibres and carbon nanotubes) fillers were added. In order to keep the same matrix, the micro- and nano- composites were prepared by in-creasing the filler loading at a fixed iPP/PP-MA ratio (13.2).
Structural characterization was carried out by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses and the materials behavior in the molten state was studied by means of rheological measurements in small-amplitude oscillatory shear (SAOS) with a rotational rheometer (plate-plate configuration).
Differential Scanning Calorimetry (DSC) was employed to investigate the crystallization in quiescent conditions of the prepared micro- and nano- composites. Both the quiescent and flow-induced crystallization were evaluated using SAOS techniques (dynamic time sweep tests).
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SANTOS, THAIS da S. "Micro-nanocompósitos de Al2O3/ NbC/ WC e Al2O3/ NbC/ TaC." reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23599.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Case, Sandra Lynn. "Fundamental Importance of Fillers, Cure Condition, and Crosslink Density on Model Epoxy Properties." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28059.
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The influence of silane treated amorphous fumed silica fillers on properties of the cured epoxy was examined in the first part of the study. Silica particles were treated with 3- aminopropyldiethoxymethylsilane (APDS) and 3-aminopropyltriethoxysilane (APTS) coupling agents. The filler and coupling agents decreased the mobility of the polymer chains in the vicinity of the filler leading to an increase in the activation energy for the glass transition and an increase in cooperativity. Fumed silica did not significantly affect moisture diffusion properties.
Next, a linear dilatometer was used to investigate the effects of cure conditions, mold types, and the presence of filler in the model epoxy. These studies revealed that there was substantial shrinkage in the cured epoxy on heating it through its glass transition region. The shrinkage was determined to be the result of stress in the epoxy generated during cure and could be minimized by curing at lower temperatures, followed by a postcuring heat treatment. Additional free volume in the sample increased the magnitude of the shrinkage by allowing increased stress release through increased network mobility.
Decreasing the polymer mobility by adding fillers decreased the observed shrinkage. The influence of the model epoxy crosslink density was examined by varying the content of 1,4-butanediol in the model system. Addition of 1,4-butanediol led to a decrease in the modulus and glass transition temperature, which resulted in a reduction in residual stress and subsequent shrinkage. Moisture uptake increased with the addition of 1,4-butanediol due to an increase in the free volume of the epoxy. However, even with greater moisture uptake, the addition of 1,4-butanediol to the epoxy increased its adhesion to quartz by promoting lower residual stress and increased energy dissipation. These results indicate that bulk diffusion of water is not the controlling factor in adhesive degradation in this system.Ph. D.
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Gyhlesten, Back Jessica. "Modelling and Characterisation of the Martensite Formation in Low Alloyed Carbon Steels." Licentiate thesis, Luleå tekniska universitet, Material- och solidmekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62369.
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The current work contains experimental and theoretical work about the formation of martensite from the austenitic state of the steel Hardox 450. Simulation of rolling and subsequent quenching of martensitic steel plates requires a model that can account for previous deformation, current stresses and the temperature history, therefore dilatometry experiments were performed, with and without deformation. Two austenitization schedules were used and in the standard dilatometry the cooling rates varied between 5-100 °C/s, in order to find the minimum cooling rate that gives a fully martensitic microstructure. Cooling rates larger than 40°C/s gave a fully martensitic microstructure. The cooling rate of 100 °C/s was used in the deformation dilatometry tests where the uniaxial deformation varied from 5-50 %. The theoretical work involved modelling of the martensite formation and the thermal/transformation strains they cause in the steel. Characterizations were done using light optical microscopy, hardness tests and electron backscatter diffraction technique. The parent austenite grains of the martensitic structure were reconstructed using the orientation relationship between the parent austenite and the martensite. Kurdjumov-Sachs orientation relationships have previously been proven to work well for low-carbon steels and was therefore selected. The standard implementation of the Koistinen-Marburger equation for martensite formation and a more convenient approach were compared. The latter approach does not require the storage of initial austenite fraction at start of martensite formation. The comparison shows that the latter model works equally well for the martensite formation. The results showed that the use of martensite start and finish temperatures calibrated versus experiments for Hardox 450 works better when computing thermal expansion than use of general relations based on the chemistry of the steel. The results from deformation dilatometry showed that deformation by compressive uniaxial stresses impedes the martensite transformation. The simplified incremental model works well for deformation with 5 % and 10 %. However, the waviness in the experimental curve for deformation 50 % does not fit the model due vi to large barrelling effect and the large relative expansion for the material that the sample holders are made of. Crystallographic reconstruction of parent austenite grains were performed on a hot-rolled as-received reference sample and dilatometry samples cooled with 60 °C/s and 100 °C/s. The misorientation results showed that the samples match with the Kurdjumov-Sachs orientation relationship in both hot rolled product and dilatometry samples. When misorientation between adjacent pixels are between 15° and 48°, then the boundary between them was considered as a parent austenite grain. The austenitic grain boundaries of the sample cooled at 100 °C/s is in general identical with the hot rolled sample when considering high angle boundaries (15°-48°). The results from the hardness tests showed that the rolled product exhibits higher hardness as compared to samples cooled by 100 °C/s and 60 °C/s. This can be attributed to the formation of transition-iron-carbides in the hot rolled product due to longer exposure of coiling temperature.
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Singh, Jagat. "Commissioning of an Arc-Melting/Vacuum Quench Furnace Facility for Fabrication of Ni-Ti-Fe Shape Memory Alloys, and the Characterization." Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2104.
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Shape memory alloys when deformed can produce strains as high as 8%. Heating results in a phase transformation and associated recovery of all the accumulated strain, a phenomenon known as shape memory. This strain recovery can occur against large forces, resulting in their use as actuators. The goal of this project is to lower the operating temperature range of shape memory alloys in order for them to be used in cryogenic switches, seals, valves, fluid-line repair and self-healing gaskets for space related technologies. The Ni-Ti-Fe alloy system, previously used in Grumman F-14 aircrafts and activated at 120 K, is further developed through arc-melting a range of compositions and subsequent thermo-mechanical processing. A controlled atmosphere arc-melting facility and vertical vacuum quench furnace facility was commissioned to fabricate these alloys. The facility can create a vacuum of 10-7 Torr and heat treat samples up to 977 °C. High purity powders of Ni, Ti and Fe in varying ratios were mixed and arc-melted into small buttons weighing 0.010 kg to 0.025 kg. The alloys were subjected to solutionizing and aging treatments. A combination of rolling, electro-discharge machining and low-speed cutting techniques were used to produce strips. Successful rolling experiments highlighted the workability of these alloys. The shape memory effect was successfully demonstrated at liquid nitrogen temperatures through a constrained recovery experiment that generated stresses of over 40 MPa. Differential scanning calorimetry (DSC) and a dilatometry setup was used to characterize the fabricated materials and determine relationships between composition, thermo-mechanical processing parameters and transformation temperatures.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Conti, Elaine Cristina Guerbach. "Estudo da interface titânio/porcelana, com três porcelanas de ultra baixa fusão, empregando-se microscopia eletrônica de varredura e dilatometria /." Araraquara : [s.n.], 2002. http://hdl.handle.net/11449/89679.
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Resumo: O objetivo deste trabalho foi caracterizar química e metalograficamente o Ti.c.p. antes e após a fundição por Plasma-Skull, e estudar as interfaces entre esse metal e as porcelanas Vitatitankeramik, Triceram e Noritake TI22, empregando-se M.E.V., EDS, Mapeamento Elementar e Dilatometria. Trinta e cinco placas nas dimensões de 25mm x 3mm x 1mm foram fundidas pela máquina nacional Discovery - Plasma, EDG Equipamentos, sendo 5 amostras empregadas para a análise química e metalográfica e as 30 restantes, utilizadas para aplicação das porcelanas, sendo divididas em 3 grupos de 10 placas cada. O tratamento da superfície do metal, bem como a aplicação e as cocções das porcelanas foram realizadas segundo as recomendações de cada fabricante. Posteriormente, as amostras tiveram uma de suas faces laterais lixadas, até a exposição da interface e preparadas para análise por M.E.V. Para os ensaios de Dilatometria, 2 amostras de Ti c.p. e 2 para cada sistema de porcelanas foram confeccionadas na forma de cilindro com 12 mm de comprimento x 2 mm de diâmetro, e em cada amostra foi soldado um termopar de cromel-alumel, para medida de temperatura dos ensaios. As curvas de expansão térmica do Ti c.p. e das três porcelanas, foram levantadas para estudar a compatibilidade entre os conjuntos metalocerâmicos. Os resultados da análise química e das imagens obtidas por Microscopia Óptica, demonstram que o Ti c.p. após a fundição apresenta condições físico-químicas adequadas para receber a aplicação da porcelana. Dos resultados de M.E.V., observa-se que todos os sistemas apresentaram integridade nas interfaces Ti/Bonder, livre de fendas ou poros, com um bom contato entre a porcelana e o metal, confirmado pelas imagens do Mapeamento Elementar, sugerindo uma adequada interação entre esses materiais. Da análise das imagens do EDS... (Resumo completo, clicar acesso eletrônico abaixo).Abstract: The aim of this work was to perform a chemical na metalographical characterization of the commercially pure titanium before and after melting by the Plasma-Skull method, and to study the interfaces between this metal and the porcelains Vitatitankeramik, Triceram e Noritake TI22, using SEM, EDS, elementary mapping and dilatometry. Thirty five samples with dimensions 25mm x 3mm x 1mm were melted in a national Discovery-Plasma, EDG Equipaments, five of which were used for chemical analysis and metalography and the remaining thirty, divided in three groups, were used for applications of the porcelains. The metal surface treatment, as well as the applications and firing of the porcelains, were performed according to the recommendations of each manufacturer. Subsequently, one of the lateral surfaces of the samples was polished until the interfaces was exposed and then was prepared for the SEM analysis. Two samples of commercially pure titanium and other two for each system of porcelains were cylindrically shaped with lengths of 12mm and 2mm of diameter, and in each sample Chromel-Alumel thermocouple was welded to measure the temperature of the tests. The thermal expansion curves of the commercially pure titanium and porcelains were measured to study the compatibility of the metal-ceramic systems. The chemical analysis and optical microscopy results show that the commercially pure titanium after the melting exhibits appropriate physical and chemical conditions for the application of the porcelain. The SEM results indicate that all the systems exhibits integrity of the Ti/bonder interface, free of gap and porous, with good contact between metal and porcelain, which was confirmed by the elementary mapping images, suggesting and adequate interaction between these materials. From the analysis of the EDS images... (Complete abstract, click electronic address below).
Orientador: José Roberto Cury Saad
Coorientador: Antônio Carlos Guastaldi
Banca: Marcelo Ferrarezi de Andrade
Banca: Silvio José Mauro
Mestre
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Vilela, Rivelino Cunha. "Estudo de transições de fase em cristais de l-alanina + ácido oxálico." reponame:Repositório Institucional da UFC, 2013. http://www.repositorio.ufc.br/handle/riufc/13883.
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VILELA, Rivelino Cunha. Estudo de transições de fase em cristais de l-alanina + ácido oxálico. 2013. 113 f. Tese (Doutorado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2013.Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-10-29T21:51:24Z No. of bitstreams: 1 2013_tese_rcvilela.pdf: 12577577 bytes, checksum: 4dc32419c1bbdde79375612c04227181 (MD5)
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In the present word we have studied the effect of temperature on the Raman spectra of crystals of L-alanine + oxalic acid, C3H8NO2+.C2HO4-. Raman spectroscopy measurements were performed on polycrystalline samples at different temperatures varying in the range from room temperature to T = 20 K; a tentative assignment of all normal modes was furnished. In order to help the understanding of the crystal behavior we have also obtained X-ray diffractograms and studied the dependence of lattice parameters through dilatometry as a function of temperature in the 290 K – 93 K range. The three different techniques allowed us to construct a picture of the material under low temperature conditions. As a consequence we have realized that L-alanine + oxalic acid crystal undergoes three phase transitions at low temperatures. The splitting of a band at 90 cm-1 and an anomaly in one of the lattice parameters are the signature for the first phase transition that is observed at 250 K. At 150 K it was observed the appearance of two new bands in the Raman spectrum and, simultaneously, it was observed change in the curves of a and c lattice parameters. Additionally, it was verified the appearance of new peaks in the X-ray diffractogram at the same temperature, characterizing the second phase transition. At a temperature even lower, at about 43 K, it was verified the occurrence of the third phase transition that has as main characteristic the splitting of two bands that are associated to the lattice modes. Changes in the modes associated with CH3 and NH3+ during the cooling is discussed. An important behavior of the crystal with the cooling process was the red shift of the band of lower frequency, similar to the soft-mode vibration of ferroelectric materials, although the frequency of the mode in L-alanine + oxalic acid does not goes to zero. Based on the results on Raman spectroscopy, dilatometry and X-ray diffraction, and on the possible symmetry sites occupied by the molecules through the O=CC group in the various phases, it is suggested the following sequence of phase transitions D24 C2h5 Cs3 C23, which should occur at 250 K, 150 K and 43 K.
Neste trabalho, estudou-se o efeito da temperatura nos espectros Raman de cristais de L-alanina + ácido oxálico, C3H8NO2+.C2HO4-. Foram realizadas medidas de espectroscopia Raman em policristais a diferentes temperaturas no intervalo compreendido entre a temperatura ambiente e a temperatura de 20 K, sendo fornecida uma identificação tentativa para todos os modos normais de vibração observados. Para auxiliar o entendimento do comportamento do cristal também foram obtidos os difratogramas de raios-X bem como estudada a dependência dos parâmetros de rede em função da temperatura através de dilatometria no intervalo entre 290 K e 93 K. As três técnicas utilizadas em conjunto permitiram mostrar o comportamento estrutural do material em baixas temperaturas. Deste quadro foi possível inferir que os cristais de L-alanina + ácido oxálico apresentam três diferentes transições de fase durante o resfriamento. Em 250 K o aparecimento de um dubleto em 90 cm-1 e a anomalia num dos parâmetros de rede apontam para a ocorrência da primeira transição de fase. Em 150 K surgem pelo menos duas novas bandas no espectro Raman, ao mesmo tempo em que ocorrem bruscas mudanças de inclinação nas curvas que representam as dimensões dos eixos a e c do cristal. Também se verifica que, de forma semelhante ao que ocorre com os espectros Raman, aparecem novos picos no difratograma de raios-X em torno desta temperatura, caracterizando assim a segunda transição de fase. A uma temperatura ainda mais baixa, em torno de 43 K, foi verificada a ocorrência da terceira transição de fase, que tem como principal característica a separação de dois modos Raman associados a modos da rede. Mudanças nos ambientes dos grupos CH3 e do NH3+ durante o resfriamento são discutidas. Um importante aspecto apresentado pelos espectros Raman com o resfriamento da amostra foi o deslocamento da banda de mais baixa energia para menores valores de frequências, semelhantemente ao que ocorre com vibrações do tipo soft-mode em materiais ferroelétricos, embora a frequência do modo no cristal de L-alanina + ácido oxálico não tenha ido à zero. Baseado nos resultados acima e nos possíveis sítios de simetria ocupados pelas moléculas através do grupo O=CC nas diversas fases, sugere-se a seguinte sequência de transições de fase D24 para C2h5 para Cs3 para C23, que aconteceriam, respectivamente, nas temperaturas de 250 K, 150 K e 43 K.
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Silva, Cloir Salatiel da. "Análise microestrutural em altas temperaturas de um ferro fundido branco de alto cromo com molibdênio e nióbio." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-14092016-124243/.
Full textAbstract:
As mudanças microestruturais, causadas pela adição de elementos de liga e pelos tratamentos térmicos, modificam as propriedades mecânicas e tribológicas dos materiais. Foi desenvolvido então um estudo em amostras de um ferro fundido branco de alto cromo com molidbênio e nióbio, procurando determinar os efeitos dos elementos de liga molibdênio e nióbio, na microestrutura deste material, através de medidas de dureza, dilatometria, ataque químico, microscopia eletrônica de varredura e,principalmente, a utilização de metalografia em altas temperaturas. A técnica de metalografia em altas temperaturas permite o estudo das mudanças microestruturais durante os ciclos térmicos, que foram programados, tendo como referência a curva TTT previamente traçada para este material, focalizando regiões onde não ocorrem mudanças de fase. Deste modo foram obtidas as aparências metalográficas em altas temperaturas e feito um estudo comparativo com as outras técnicas usadas. Com isto é possível melhorar o conhecimento sobre a microestrutura do material em questão e obter ligas com propriedades pré-determinadas.The microstructural changes caused by the addition of alloying elements and by thermal treatments modify the mechanical and tribological properties of the materials. A study was develop on samples of molybdenum and niobium high chromium white cast iron, trying to determine the effects of molybdenum and niobium alloys elements on microstructure of this material through hardness measurements, dilatometry, chemical etching, scanning electron microscopy, and mainly, utilizing metallography at high temperatures. The metallography at high temperatures technic allows the study of microstructural changes during the thermal cyc1es, which were scheduled, having as reference the TTT curve previously traced to this material, focusing regions where changes of fase don\'t occur. So the metallographic appearances at high temperatures were obtained and it was done a comparative study using other technics. Because of that is possible to improve the knowledge of the material microstructure, which it has been studied, and to obtain alloys with predetermined properties.
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Vilela, Rivelino Cunha. "ESTUDO DE TRANSIÃÃES DE FASE EM CRISTAIS DE L-ALANINA + ÃCIDO OXÃLICO." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=10397.
Full textAbstract:
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorNeste trabalho, estudou-se o efeito da temperatura nos espectros Raman de cristais de L-alanina + Ãcido oxÃlico, C3H8NO2+.C2HO4-. Foram realizadas medidas de espectroscopia Raman em policristais a diferentes temperaturas no intervalo compreendido entre a temperatura ambiente e a temperatura de 20 K, sendo fornecida uma identificaÃÃo tentativa para todos os modos normais de vibraÃÃo observados. Para auxiliar o entendimento do comportamento do cristal tambÃm foram obtidos os difratogramas de raios-X bem como estudada a dependÃncia dos parÃmetros de rede em funÃÃo da temperatura atravÃs de dilatometria no intervalo entre 290 K e 93 K. As trÃs tÃcnicas utilizadas em conjunto permitiram mostrar o comportamento estrutural do material em baixas temperaturas. Deste quadro foi possÃvel inferir que os cristais de L-alanina + Ãcido oxÃlico apresentam trÃs diferentes transiÃÃes de fase durante o resfriamento. Em 250 K o aparecimento de um dubleto em 90 cm-1 e a anomalia num dos parÃmetros de rede apontam para a ocorrÃncia da primeira transiÃÃo de fase. Em 150 K surgem pelo menos duas novas bandas no espectro Raman, ao mesmo tempo em que ocorrem bruscas mudanÃas de inclinaÃÃo nas curvas que representam as dimensÃes dos eixos a e c do cristal. TambÃm se verifica que, de forma semelhante ao que ocorre com os espectros Raman, aparecem novos picos no difratograma de raios-X em torno desta temperatura, caracterizando assim a segunda transiÃÃo de fase. A uma temperatura ainda mais baixa, em torno de 43 K, foi verificada a ocorrÃncia da terceira transiÃÃo de fase, que tem como principal caracterÃstica a separaÃÃo de dois modos Raman associados a modos da rede. MudanÃas nos ambientes dos grupos CH3 e do NH3+ durante o resfriamento sÃo discutidas. Um importante aspecto apresentado pelos espectros Raman com o resfriamento da amostra foi o deslocamento da banda de mais baixa energia para menores valores de frequÃncias, semelhantemente ao que ocorre com vibraÃÃes do tipo soft-mode em materiais ferroelÃtricos, embora a frequÃncia do modo no cristal de L-alanina + Ãcido oxÃlico nÃo tenha ido à zero. Baseado nos resultados acima e nos possÃveis sÃtios de simetria ocupados pelas molÃculas atravÃs do grupo O=CC nas diversas fases, sugere-se a seguinte sequÃncia de transiÃÃes de fase D24 para C2h5 para Cs3 para C23, que aconteceriam, respectivamente, nas temperaturas de 250 K, 150 K e 43 K.
In the present word we have studied the effect of temperature on the Raman spectra of crystals of L-alanine + oxalic acid, C3H8NO2+.C2HO4-. Raman spectroscopy measurements were performed on polycrystalline samples at different temperatures varying in the range from room temperature to T = 20 K; a tentative assignment of all normal modes was furnished. In order to help the understanding of the crystal behavior we have also obtained X-ray diffractograms and studied the dependence of lattice parameters through dilatometry as a function of temperature in the 290 K â 93 K range. The three different techniques allowed us to construct a picture of the material under low temperature conditions. As a consequence we have realized that L-alanine + oxalic acid crystal undergoes three phase transitions at low temperatures. The splitting of a band at 90 cm-1 and an anomaly in one of the lattice parameters are the signature for the first phase transition that is observed at 250 K. At 150 K it was observed the appearance of two new bands in the Raman spectrum and, simultaneously, it was observed change in the curves of a and c lattice parameters. Additionally, it was verified the appearance of new peaks in the X-ray diffractogram at the same temperature, characterizing the second phase transition. At a temperature even lower, at about 43 K, it was verified the occurrence of the third phase transition that has as main characteristic the splitting of two bands that are associated to the lattice modes. Changes in the modes associated with CH3 and NH3+ during the cooling is discussed. An important behavior of the crystal with the cooling process was the red shift of the band of lower frequency, similar to the soft-mode vibration of ferroelectric materials, although the frequency of the mode in L-alanine + oxalic acid does not goes to zero. Based on the results on Raman spectroscopy, dilatometry and X-ray diffraction, and on the possible symmetry sites occupied by the molecules through the O=CC group in the various phases, it is suggested the following sequence of phase transitions D24 C2h5 Cs3 C23, which should occur at 250 K, 150 K and 43 K.
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Schuldt, Thilo. "An optical readout for the LISA gravitational reference sensor." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16241.
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Der weltraumgestützte Gravitationswellendetektor LISA (Laser Interferometer Space Antenna) besteht aus drei identischen Satelliten an Bord derer sich jeweils zwei frei schwebende Testmassen befinden. Die Lage der einzelnen Testmassen in Bezug auf die zugehörige optische Bank muss mit einer Genauigkeit besser 1 pm/sqrt(Hz) in der Abstands- und besser 10 nrad/sqrt(Hz) in der Winkelmessung erfolgen. In der vorliegenden Arbeit wird ein kompaktes optisches Auslesesystem präsentiert, welches als Prototyp für diese Abstands- und Winkelmetrologie dient. Das dafür entwickelte polarisierende Heterodyn-Interferometer mit räumlich getrennten Frequenzen basiert auf einem hoch-symmetrischen Design, bei dem zur optimalen Gleichtakt-Unterdrückung Mess- und Referenzarm die gleiche Polarisation und Frequenz sowie annähernd gleiche optische Pfade haben. Für die Winkelmessung wird die Methode der differentiellen Wellenfrontmessung eingesetzt. In einem ersten Prototyp-Aufbau wird ein Rauschniveau von weniger als 100 pm/sqrt(Hz) in der Translations- und von weniger als 100 nrad/sqrt(Hz) in der Winkelmessung (beides für Frequenzen oberhalb 0.1 Hz) demonstriert. In einem zweiten Prototyp-Aufbau werden zusätzlich eine Intensitätsstabilisierung und ein Phasenlock der beiden Frequenzen implementiert. Die analoge Phasenmessung ist durch eine digitale, FPGA basierte, ersetzt. Mit diesem Aufbau wird ein Rauschen kleiner 5 pm/sqrt(Hz) in der Translationsmessung und kleiner 10 nrad/sqrt(Hz) in der Winkelmessung, beides für Frequenzen größer 0.01 Hz, erreicht. Eine Rausch-Analyse wurde durchgeführt und die Nichtlinearitäten des Interferometers bestimmt. Das Interferometer wurde im Hinblick auf die LISA Mission entwickelt, findet seine Anwendung aber auch bei der Charakterisierung der dimensionalen Stabilität von ultra-stabilen Materialien sowie in der optischen Profilometrie. Die Adaptierung des Interferometers dazu sowie erste Resultate zu beiden Anwendungen werden in dieser Arbeit präsentiert.The space-based gravitational wave detector LISA (Laser Interferometer Space Antenna) consists of three identical satellites. Each satellite accommodates two free-flying proof masses whose distance and tilt with respect to its corresponding optical bench must be measured with at least 1 pm/sqrt(Hz) sensitivity in translation and at least 10 nrad/sqrt(Hz) sensitivity in tilt measurement. In this thesis, a compact optical readout system is presented, which serves as a prototype for the LISA proof mass attitude metrology. We developed a polarizing heterodyne interferometer with spatially separated frequencies. For optimum common mode rejection, it is based on a highly symmetric design, where measurement and reference beam have the same frequency and polarization, and similar optical pathlengths. The method of differential wavefront sensing (DWS) is utilized for the tilt measurement. In a first prototype setup noise levels below 100 pm/sqrt(Hz) in translation and below 100 nrad/sqrt(Hz) in tilt measurement (both for frequencies above 0.1 Hz) are achieved. A second prototype was developed with additional intensity stabilization and phaselock of the two heterodyne frequencies. The analog phase measurement is replaced by a digital one, based on a Field Programmable Gate Array (FPGA). With this setup, noise levels below 5 pm/sqrt(Hz) in translation measurement and below 10 nrad/sqrt(Hz) in tilt measurement, both for frequencies above 0.01Hz, are demonstrated. A noise analysis was carried out and the nonlinearities of the interferometer were measured. The interferometer was developed for the LISA mission, but it also finds its application in characterizing the dimensional stability of ultra-stable materials such as carbon-fiber reinforced plastic (CFRP) and in optical profilometry. The adaptation of the interferometer and first results in both applications are presented in this work.
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Nuruddin, Ibrahim K. "Effect of welding thermal cycles on the heat affected zone microstructure and toughness of multi-pass welded pipeline steels." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7755.
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This research is aimed at understanding the effect of thermal cycles on the metallurgical and microstructural characteristics of the heat affected zone of a multi-pass pipeline weld. Continuous Cooling Transformation (CCT) diagrams of the pipeline steel grades studied (X65, X70 and X100) were generated using a thermo mechanical simulator (Gleeble 3500) and 10 mm diameter by 100 mm length samples. The volume change during phase transformation was studied by a dilatometer, this is to understand the thermodynamics and kinetics of phase formation when subjected to such varying cooling rates. Samples were heated rapidly at a rate of 400°C/s and the cooling rates were varied between t8/5 of 5.34°C/s to 1000°C/s. The transformation lines were identified using the dilatometric data, metallographic analysis and the micro hardness of the heat treated samples. Two welding processes, submerged arc welding (SAW) and tandem Metal Inert Gas (MIG) Welding, with vastly different heat inputs were studied. An API-5L grades X65, X70 and X100 pipeline steels with a narrow groove bevel were experimented with both welding processes. The welding thermal cycles during multi-pass welding were recorded using thermocouples. The microstructural characteristics and metallurgical phase formation was studied and correlated with the fracture toughness behaviour as determined through the Crack Tip Opening Displacement (CTOD) tests on the welded specimens. It was observed that SAW process is more susceptible to generate undesirable martensite-austenite (M-A) phase which induce formation of localised brittle zones (LBZ) which can adversely affect the CTOD performance. Superimposition of the multiple thermal cycles, measured in-situ from the different welding processes on the derived CCTs, helped in understanding the mechanism of formation of localised brittle zones. Charpy impact samples were machined from the two X65 and X70 grades, for use in thermal simulation experiments using thermo mechanical simulator (Gleeble). The real thermal cycles recorded from the HAZ of the SAW were used for the thermal simulations, in terms of heating and cooling rates. This is to reproduce the microstructures of the welds HAZ in bulk on a charpy impact sample which was used for impact toughness testing, hardness and metallurgical characterisation. The three materials used were showing different response in terms of the applied thermal cycles and the corresponding toughness behaviours. The X65 (a) i.e. the seamless pipe was showing a complete loss of toughness when subjected to the single, double and triple thermal cycles, while the X65 (b), which is a TMCP material was showing excellent toughness in most cases when subjected to the same thermal cycles at different test temperatures. The X70 TMCP as well was showing a loss of toughness as compared to the X65 (b). From the continuous cooling transformation diagrams and the thermally simulated samples results it could be established that different materials subjected to similar thermal cycle can produce different metallurgical phases depending on the composition, processing route and the starting microstructure.
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Canto, Rodrigo Bresciani. "Estudo teórico e experimental dos processos de compactação e sinterização do politetrafluoretileno (PTFE)." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18135/tde-10022017-123542/.
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Este trabalho apresenta um estudo dos processos de prensagem e sinterização do politetrafluoretileno (PTFE) com o objetivo principal de investigar a influência dos parâmetros desses processos na microestrutura e nas propriedades mecânicas do material após sinterização. O PTFE faz parte do grupo dos termoplásticos, mas assim como outros polímeros de alto peso molecular, apresenta elevada viscosidade no estado fundido que impede sua utilização em moldagem por injeção, e seu processamento é realizado por compactação a frio do pó polimérico seguida de sinterização. No processo de sinterização é aplicado um tratamento térmico acima da temperatura de fusão do material que é responsável por grandes deformações anisotrópicas que, por sua vez, são dependentes do histórico de carregamentos induzidos na fase de compactação. Com o objetivo de desenvolver modelos de comportamento termomecânicos para realizar simulações computacionais dessas etapas de fabricação, ensaios experimentais foram realizados para se investigar os diferentes mecanismos de evolução microestrutural e de deformações nas etapas de compactação e sinterização. O estudo experimental do processo de compactação compreendeu a realização de ensaios de compactação uniaxial (oedométrico), de compactação hidrostática em prensa isostática e ensaios triaxiais verdadeiros em um dispositivo original acoplado numa prensa triaxial com seis atuadores eletrohidráulicos. Através dos resultados obtidos dos ensaios de compactação foi possível identificar os parâmetros do modelo de Drucker-Prager/cap, disponível na biblioteca de leis de comportamento do programa de cálculo pelo método dos elementos finitos ABAQUSTM, que permitiu de simular numericamente alguns casos simples. O estudo experimental do processo de sinterização foi realizado com o auxílio de ensaios de termogravimetria (TGA), calorimetria exploratória diferencial (DSC) e ensaios de dilatometria em corpos-de-prova isótropos e anisótropos com diferentes índices de vazios. Através dos resultados obtidos destes ensaios foi possível identificar que a deformação global de sinterização é composta por uma deformação térmica reversível, uma deformação devido à mudança de fase cristalina em fase amorfa -ou vice-versa-, uma deformação devido ao fechamento dos vazios e uma deformação de recuperação. Este estudo foi realizado em dois tipos de materiais, sendo o PTFE puro e o PTFE reforçado com 5wt% de EkonolTM e 5wt% de fibras de carbono, respectivamente comercializados pelos nomes de TeflonTM 6407 e TeflonTM 6507.The main objective of this work is to study the influence the process parameters on the microstructure and the mechanical properties of components manufactured by compaction at room temperature and sintering of polytetrafluorethylene (PTFE). Similary to other High Molecular Weight Polymers and although it belongs to the group of thermoplastic polymers, since it cannot be processed in the melt state because its very high viscosity, PTFE, is powder processed -that consists in sintering compacted powder-. Sintering corresponds to a heat treatment up to temperatures higher than the melting temprature, inducing finite deformations that are generally anistropic and dependent on the mechanical loading the material has been submitted to during the pre-compaction at room temperature. In order to develop thermo-mechanical constitutive equations that could be used during predictive numerical simulations of the whole process, different tests have been performed to study the different mechanisms that are responsible for microstructural evolutions and deformations during compaction and sintering. The experimental study of the compaction has been performed via uniaxial (oedometric) compaction tests, hydrostatic compaction tests that were made with an isostatic hydraulic press and triaxial tests that were made with and original device installed on an electrohydraulic testing machine six actuators. A \"Drucker-Prager/cap\" type elasto-plastic model -as available in the constitutiveequations library of ABAQUSTM industrial finite element software- has been identified from the results of these tests, so that a few simple cases have been numerically simulated. The experimental study of the sintering process has been performed via Thermo-Gravimetric Analyses (TGA), Differential Scanning Calorimetric analyses (DSC) and dilatometry tests that were performed on isotropic or anisotropic specimens with different values of the porosity From the results of these tests it has been possible to decompose the sintering deformation into different mechanisms, viz. a reversible thermal expansion, a strain that is linked to the transition from the crystalline phase to the amorphous phase -or vice versa-, a pore closure strain and a recovery strain. This study has been performed on a powder made of pure PTFE and a powder of PTFE filed with 5wt% EkonolTM and 5wt% of carbon fibres, respectively available as TeflonTM 6407 and TeflonTM 6507.
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CARVALHO, SABRINA G. de M. "Inclusão e remoção térmica de NaCl, KI e grafite para obtenção de cerâmicas porosas de zircônia estabilizada com ítria." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10553.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Granbom, Ylva. "Structure and mechanical properties of dual phase steels : An experimental and theoretical analysis." Doctoral thesis, KTH, Mekanisk metallografi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-24869.
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The key to the understanding of the mechanical behavior of dual phase (DP) steels is to a large extent to be found in the microstructure. The microstructure is in its turn a result of the chemical composition and the process parameters during its production. In this thesis the connection between microstructure and mechanical properties is studied, with focus on the microstructure development during annealing in a continuous annealing line. In-line trials as well as the lab simulations have been carried out in order to investigate the impact of alloying elements and process parameters on the microstructure. Further, a dislocation model has been developed in order to analyze the work hardening behavior of DP steels during plastic deformation. From the in-line trials it was concluded that there is an inheritance from the hot rolling process both on the microstructure and properties of the cold rolled and annealed product. Despite large cold rolling reductions, recrystallization and phase transformations, the final dual phase steel is still effected by process parameters far back in the production chain, such as the coiling temperature following the hot rolling. Lab simulations showed that the microstructure and consequently the mechanical properties are impacted not only by the chemical composition of the steel but also by a large number of process parameters such as soaking temperature, cooling rate prior to quenching, quench and temper annealing temperature.QC 20101004
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Lebrun, Jean-Marie. "Etude des mécanismes d'oxydation et de frittage de poudres de silicium en vue d'applications photovoltaïques." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENI054/document.
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La conversion photovoltaïque présente de nombreux avantages. Actuellement, les technologiesbasées sur l’élaboration de wafers de silicium cristallins dominent le marché, mais sont responsablesde pertes de matières importantes, très néfastes au coût de production des cellules. Le défi à releverest donc la réalisation de matériaux bas coûts en silicium par un procédé de métallurgie des poudres.Cependant, le frittage du silicium est dominé par des mécanismes de grossissement de grains quirendent la densification difficile par frittage naturel. Dans la littérature, l’identification de cesmécanismes est sujette à controverse. En particulier, le rôle de la couche d’oxyde natif (SiO2) à lasurface des particules de silicium reste inexploré. Dans ce manuscrit, l’influence de l’atmosphère surla réduction de cette couche de silice au cours du frittage est étudiée par analysethermogravimétrique. Les cinétiques de réduction sont en accord avec un modèle thermochimiqueprenant en compte, les quantités d’oxygène initialement présentes dans poudre, la pression partielleen espèces oxydantes autour de l’échantillon et l’évolution de la porosité du fritté. Pour la premièrefois, des données expérimentales permettent de montrer que la couche de silice inhibe legrossissement de grain. Des nouveaux procédés, basés sur un contrôle de l’atmosphère enmonoxyde de silicium (SiO(g)) autour de l’échantillon, sont alors proposés afin de maitriser la stabilitéde cette couche. Bien que la couche d’oxyde retarde les cinétiques de diffusion en volume, sonmaintien à des températures de 1300 – 1400 °C permet d’améliorer significativement la densification.Dans ces conditions, le comportement au frittage du silicium peut être séparé en deux étapes,clairement mises en évidences par la présence de deux pics de retrait sur les courbes de dilatométrie.Ce résultat est inhabituel compte tenu de l’aspect monophasé du matériau étudié. Cependant, il peutêtre expliqué à l’aide d’un modèle cinétique de frittage, basé sur des simplifications géométriques enaccord avec l’évolution microstructurale du matériauPhotovoltaic conversion is a promising energy resource. Bulk crystalline silicon technologies currentlydominate the market but suffer from high material losses that are highly detrimental to solar cellproduction costs. The challenge is then the elaboration of low cost silicon materials through a powdermetallurgy route. However, silicon sintering is dominated by grain coarsening mechanisms thatpreclude densification. Identification of these mechanisms is controversial in the literature. Especially,the role of the native oxide layer (SiO2) at the powder particle surfaces has remained unexplored yet.In this manuscript, the influence of the atmosphere on the reduction of this silica layer is studied usingthermogravimetric analysis. Reduction kinetics is consistent with a thermochemical model taking intoaccount the powder oxygen content, the partial pressure of oxidizing species and the pore morphologyof the sintered material. For the first time, experimental evidences support the idea that the silica layerinhibits grain coarsening. New sintering processes, involving a control of the silicon monoxideatmosphere (SiO(g)) surrounding the sample are then proposed and investigated in order to monitorthe stability of this layer. Stabilization of the silica layer at temperatures as high as 1300 – 1400 °C isshown to enhance densification although it retards lattice diffusion kinetics. In these conditions, thesintering behavior can be divided into two sequential stages marked by two shrinkage peaks on thedilatometric curves. This result is unusual for the sintering of single-phase materials. However, it canbe explained with help of a kinetic model using appropriate geometrical simplifications andobservations of the sample microstructures
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Nobrega, Paixao Formiga Franklin Giovanna. "Etudes operando par SECM, ECD, et EQCM de matériaux pour le stockage électrochimique de l'énergie." Electronic Thesis or Diss., Toulouse 3, 2023. http://www.theses.fr/2023TOU30267.
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Les avancées dans les technologies de stockage de l'énergie jouent un rôle essentiel dans notre société qui cherche activement des solutions durables et efficaces. Les enjeux associés à la gestion des ressources énergétiques renouvelables, telles que l'énergie solaire et éolienne, ainsi que la nécessité de répondre à une demande croissante en énergie, soulignent l'importance accrue du développement de matériaux de stockage d'énergie de haute performance. Cette thèse s'inscrit dans cette dynamique en se focalisant sur une analyse approfondie de divers matériaux largement utilisés dans l'stockage d'énergie. Cependant, elle va au-delà de l'approche de caractérisation classique déjà validée. Son objectif principal est d'acquérir une compréhension plus approfondie des mécanismes de transfert de charge propres à ces matériaux, tout en explorant l'influence de leur structure et de leur charge de surface. Plusieurs techniques puissantes d'analyse ont été employées, notamment la Scanning Electrochemical Microscopy (SECM), le dilatomètre électrochimique (ECD), et l'Electrochemical Quartz Crystal Microbalance (EQCM), permettant ainsi d'obtenir une vision globale et locale de la pertinence de ces matériaux pour le stockage d'énergie. Enfin, en consolidant ces techniques, une combinaison d'approches operando a été employée pour analyser le TiS2, un matériau puissant mais complexe à comprendre en ce qui concerne son processus de lithiation. Cette méthode nous a permis d'approfondir notre compréhension des deux phases de lithiation du TiS2. En somme, l'objectif de la thèse vise à fournir des informations plus précieuses et à éclairer davantage sur la pertinence de ces matériaux pour les applications de stockage d'énergie, contribuant ainsi à l'avancement crucial de ce domaineAdvancements in energy storage technologies play a crucial role in our society's quest for sustainable and efficient solutions. The challenges associated with managing renewable energy resources, such as solar and wind power, along with the increasing demand for energy, underscore the growing importance of developing high-performance energy storage materials. This thesis aligns with this dynamic by focusing on a comprehensive analysis of various materials widely used in energy storage. However, it goes beyond the conventional characterization approach that has already been validated. Its primary objective is to gain a deeper understanding of the charge transfer mechanisms specific to these materials while exploring the influence of their structure and surface charge. Several powerful analytical techniques were employed, including Scanning Electrochemical Microscopy (SECM), electrochemical dilatometry (ECD), and the Electrochemical Quartz Crystal Microbalance (EQCM), providing both a global and local perspective on the relevance of these materials for energy storage. Finally, by consolidating these techniques, a combination of operando approaches was used to analyze TiS2, a powerful yet complex material concerning its lithiation process. This method allowed us to delve deeper into our understanding of TiS2's two lithiation phases. In summary, the thesis aims to provide more valuable insights and shed further light on the suitability of these materials for energy storage applications, thus contributing significantly to the advancement of this critical field
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Hanemayer, Vincent C. (Vincent Cornelius) Carleton University Dissertation Engineering Civil. "Dilatometer tests using a model plate." Ottawa, 1989.
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Milhet, Gayraud Nathalie. "Étude expérimentale et modélisation de la précipitation [gamma]' dans le superalliage N18." Grenoble INPG, 1994. http://www.theses.fr/1994INPG0035.
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Les excellentes proprietes mecaniques des superalliages leurs sont conferees par la precipitation de la phase gamma prime issue des divers traitements thermiques. L'etape de trempe qui succede a l'elaboration par metallurgie des poudres des disques de turboreacteur en superalliage a base de nickel, conditionne fortement l'etat mecanique et microstructural final du materiau. L'objectif de ce travail est de developper et de valider un modele qui decrit la cinetique de precipitation de la phase gamma prime afin d'optimiser la microstructure resultant de cette trempe. Une serie de demarches experimentales a permis d'analyser et d'identifier le comportement du materiau au cours de ce traitement thermique. L'influence de la vitesse de refroidissement sur la microstructure finale et sur l'allure de la fraction volumique transformee est etudiee experimentalement par dilatometrie de trempe et observation electronique a transmission. Ces observations montrent que la coalescence s'effectue suivant la loi de lsw et que l'on retrouve la sequence de transformation morphologique sphere cube octocube dendrite observee dans le cas des transformations anisothermes. La dilatometrie permet egalement de mettre en evidence le domaine de precipitation de la phase gamma prime. De la meme facon, l'influence de la temperature de mise en solution sur la microstructure et sur la fraction volumique f#v est analysee. De plus, les enregistrements dilatometriques permettent d'apprecier la dissolution de la phase gamma prime en cours de chauffage a partir de microstructures variees. Enfin, la microstructure du n18 en cours de refroidissement est suivie par hyper-trempe a environ 10#5 k/s dans un four concu specialement pour cette etude. Une famille tres fine de phase gamma prime est mise en evidence par met et diffusion de neutrons aux petits angles. L'ensemble des resultats obtenus permettent de valider le modele base sur la theorie classique de nucleation et les lois de coalescence de lsw et permet de rendre compte de la capacite du calcul a decrire la precipitation intragranulaire (secondaire et tertiaire) au cours de traitements thermiques divers
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REIS, SHIRLEY L. dos. "Crescimento de graos e condutividade eletrica da ceria-samaria usando o metodo de sinterizacao e duas etapas." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9540.
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Dissertacao (Mestrado)
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Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Smith, Michael Gregory. "A laboratory study of the Marchetti dilatometer." Thesis, University of Oxford, 1993. http://ora.ox.ac.uk/objects/uuid:91016f8e-e3b0-42d7-a51c-894ce0ff73ab.
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The purpose of this study was twofold: to design, construct and commission a testing chamber for the calibration of in-situ devices in clay and to use the chamber to carry out a programme of research into the factors affecting the results of the Marchetti dilatometer test. A calibration chamber system was developed which was capable of producing one metre high by one metre diameter cylindrical beds of clay. The preparation technique involved an initial phase of one-dimensional consolidation in a rigid tube, followed by a second phase of consolidation in a chamber with independent stress control. The stress control was achieved through water-filled flexible membranes in the side and at the base of the chamber. Reasonably uniform distributions of the water content and the undrained strength were obtained from investigations carried out in each clay bed after they had been tested. The Marchetti dilatometer is an in-situ testing device the results of which have been interpreted chiefly through empirical correlations based on the results of field tests. The interpretation has mainly involved the use of two readings, and , though recently a third reading , has been introduced. Dilatometer tests were carried out in nine clay beds. The stress history and stress state of each clay bed were systematically varied in the test programme to allow their individual effects on the dilatometer readings to be assessed. The study revealed that in clay the dilatometer reading is controlled by the undrained strength and the horizontal stress and was independent of the degree of overconsolidation. Through use of this result it was shown that the applicability of many of the empirical correlations presently used to evaluate the dilatometer readings is restricted to deposits with one-dimensional stress histories. It was also found that was dependent on the undrained strength and that the reading was close to the total horizontal stress of the sample though the latter finding does not appear to be supported by the few field results that are available. The results have highlighted the redundancy of the reading for property evaluation. It was found that a timed sequence of , and readings could be used to detect the variation of the consolidation properties between clay beds. In addition to the tests in clay, the results of 31 dilatometer tests carried out in a calibration chamber for sand have also been analysed. An inter-relationship between , and was found suggesting that they were all measuring the same soil response; that of the pressure required to open a cavity in the sand. The reading was shown to be dependent on the horizontal stress and the state parameter, though this dependence could not be exploited to back calculate the horizontal stress. Overconsolidation of the sand specimens had no significant influence on the readings.
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Lolla, Sri Venkata Tapasvi. "Understanding the Role of Initial Microstructure on Intercritically Reheated Heat Affected Zone Microstructure and Properties of Multi-Pass Welds." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397826410.
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Britton, Karen J. "Automation of a capacitance dilatometer using distributed control." Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/13975.
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A comprehensive and novel system of automatic control has been designed and constructed using distributed intelligence techniques to control a complex item of equipment for the measurement of linear thermal expansion over the temperature range 1.5K - 300K. The system is designed to perform its own self-calibration automatically before the experiment commences. The low temperature dllatometer developed for this research project incorporates the most sensitive length change sensor available; a three-terminal capacitance transducer. This transducer technique has been refined to resolve length changes of 10-5A and more importantly, measure length against temperature profiles to better than 10-2A. The period of time required to collect a full set of data measurements on any particular specimen was in excess of 100 hours. Forming the heart of the automated control system is an assembly of Intel MCS-Sl single chip microcontrollers connected together on a serial link consisting of a simple pair of wires. The approach has been to divide the system automation into a number of specific control tasks and to allocate a different task to each controller. The Instrument has been used as a diagnostic tool to investigate the properties of lead glasses, and in particular to study the possibility of negative thermal expansion existing at low temperatures. Thermal expansion measurements were also performed to observe the phase change within single crystals of polydiacetylene and to research into low temperature phenomena occurlng within the crystal.
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Kinkelaar, Mark Richard. "Dilatometric study of low profile unsaturated polyester resins /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487848078450146.
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Tranchot, Alix. "Etude par émission acoustique et dilatométrie d'électrodes à base de silicium pour batteries Li-ion." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI101/document.
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Afin d’augmenter la densité d’énergie des batteries Li-ion, en particulier pour le marché des véhicules électriques, il est nécessaire de développer des matériaux d’électrode plus performants. Le silicium, dont la capacité spécifique (3579mAh/g) est dix fois supérieure à celle du graphite, est un matériau particulièrement prometteur. Néanmoins, lors de sa lithiation, il subit une forte expansion volumique (280% contre 10% pour le graphite) conduisant à la décrépitation des particules de Si et à la fissuration/décohésion de l’électrode. Il en résulte une diminution notable de la durée de vie de l’anode. Pour améliorer la tenue au cyclage des électrodes, il est nécessaire de bien comprendre/quantifier leur dégradation morphologique, ce que permettent difficilement des analyses post mortem conventionnelles. Notre objectif est d’utiliser et de développer des outils permettant d'étudier in operando la dégradation de ces électrodes. Nous avons mis en œuvre des protocoles de caractérisation in operando couplant des mesures électrochimiques à l’émission acoustique d’une part et à la dilatométrie d’autre part. Le suivi de l’activité acoustique au cours du cyclage de l’électrode a montré que les particules de Si micrométrique constituant cette électrode se fracturent dès le début de la lithiation, et que la fissuration de l’électrode se produit progressivement tout au long de la 1ère lithiation. Peu d’activité acoustique est détectée par la suite. Par l’analyse des signaux acoustiques, trois types de signaux ont été identifiés, se différenciant principalement selon leur fréquence de pic. Les signaux de hautes fréquences sont associés principalement aux micro-fractures des particules en début de lithiation, et les signaux à moyennes et basses fréquences sont respectivement attribuées à la fissuration de l’électrode et aux macro-fractures des particules de Si en fin de lithiation. L’étude dilatométrique a montré une expansion volumique maximale de ~170% avec une encre tamponnée à pH3 versus 300% si l’électrode est préparée à pH7. Cette différence s’explique par la formation de liaisons cohésives entre le liant CMC et les particules de Si lorsque l’électrode est préparée à pH 3, améliorant sa résistance mécanique. Ce qui a été confirmé par des mesures d’indentation. Ainsi, l’électrode formulée à pH 3 montre une meilleure cyclabilité. Enfin, nous avons démontré qu’une diminution notable de la durée de vie de l’électrode est observée lorsque la taille initiale des particules de Si est réduite de 230 à 85nm. Nous expliquons ce résultat inattendu par une quantité insuffisante de CMC par rapport à la surface spécifique plus élevée des particules de taille plus faible. De fait, sa résistance mécanique est insuffisante et conduit à une fissuration et une exfoliation importantes de l’électrode. Ceci est appuyé par les mesures de dilatométrie, d’émission acoustique et des observations MEBTo increase the energy density of Li-ion batteries, especially for the electric vehicle market, the development of new electrode materials is required. Silicon is a particularly interesting material, thanks to its high specific capacity (3579mAh/g, ten times higher than the capacity of graphite). Nevertheless, upon lithiation, silicon undergoes an important expansion (300% vs 10% for graphite). This leads to the cracking of the Si particles and fracturing of the electrode film. These induces electrical disconnections upon cycling, resulting in a poor cycle life. To improve the cyclability of the Si based electrodes, it is important to better understand/quantify their mechanical degradation. Conventional post mortem analyses are insufficient for that purpose. The objective of this work is to develop and use in operando analyses techniques. Therefore, we established protocols to characterize composite electrodes by electrochemical measurements coupled with either acoustic emission (AE) or dilatometry measurements. The evolution of the acoustic activity upon cycling showed that the cracking of the micrometric Si particles and of the composite film mainly occurs during the first cycle and is initiated in the early stage of the lithiation. Very few AE signals are detected in the following cycles. The signal analysis leads to the identification of three types of signals depending to their peak frequency. High frequency signals were associated with surface micro-cracking of the Si particles at the beginning of lithiation. Medium and low frequency signals were respectively attributed to the fracturing of the electrode film and bulk macro-cracking of the Si particles at the end of lithiation. An electrode thickness expansion of 170% was measured by electrochemical dilatometry for our electrodes prepared at pH3 versus 300% for electrodes prepared at pH7. The different mechanical behavior is explained by the formation of covalent bonds between the CMC binder and Si particles at pH3, which increases the mechanical stability of electrodes. This was confirmed by the measurement of their hardness and Young’s modulus. Therefore, pH3 electrodes display a higher capacity retention. It was also demonstrated that a decrease of the Si particle size does not necessarily lead to an improvement of the electrode cycle life. Indeed, we observed a significant decrease of the electrode cycle life when the Si particle size is decreased from 230 to 85 nm. This can be explained by a lack of CMC binder in relation with the higher surface area of the smaller Si particles, leading to a lower mechanical resistance of the electrode film. Within the first cycles, Si 85 nm based electrodes suffer from important cracking and exfoliation. This was confirmed by in operando dilatometry and acoustic measurements, and post mortem SEM observations
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McPherson, Ian Duncan. "An evaluation of the flat dilatometer as an insitu testing device." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25116.
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The results from the use of the dilatometer (Marchetti 1975, 1980) at 4 sites in British Columbia are presented. Comparisons are drawn between the dilatometer and other insitu test devices, including the piezo-friction cone, self-boring and Menard pressuremeters and field vane. Soils tested included saturated deltaic deposits, a sensitive plastic clay and a saturated, hydraulically placed fill.
Overall the dilatometer proved to be an extremely effective device. It had a low capital cost, required a minimum of support equipment and was simple to use. The data was repeatable and easily reduced using a computer programme. Computer output, both graphical and tabular, is easily amenable to interpretation to an engineer in the field.
For the most part the results in this thesis support Marchetti's empirical correlations with the following exceptions:
( i) determination of K0 in sands,
( ii) determination of a deformation modulus in clay,
and
(iii) in overconsolidated silts where it is believed that abnormal pore pressures caused the empirical correlations to breakdown.
The dilatometer is an insitu, total stress, penetration device which cannot be analysed in a fundamental manner. Elastic theory is inapplicable because of plastic straining during blade penetration and probably during membrane expansion. To more critically evaluate the dilatometer, the author designed an electronic research device with exactly the same external dimensions as Marchetti's dilatometer. The aim of the electronic dilatometer is to greatly improve understanding of the simple Marchetti dilatometer by allowing:
( i) a better understanding of the operational characteristics of Marchetti's dilatometer,
( ii) direct measurement of stress on, and deformation of, the membrane,
(iii) measurement of pore water pressure before and after halting penetration and during membrane expansion, and ( iv) measurement of the pushing force on the blade.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Tsang, Clifford Hing-Cheung. "Research dilatometer testing in sands and in clayey deposits." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26749.
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The development of Marchetti's flat dilatometer, method of testing, changes of Marchetti's (1980,1981) original correlations and Schmertmann's (1982,1983) proposed correlations are briefly described.
Factors affecting results of the dilatometer test (DMT) are discussed. In order to improve the understanding of the Marchetti dilatometer test (DMT), an electronic research dilatometer was developed at UBC. The research dilatometer can measure; pore pressure at the center of the membrane, membrane displacement, applied pressure, pushing force and verticality.
Test results obtained from the research dilatometer in sand and in clayey deposits at 4 sites in the Lower Mainland of B.C. are presented. Soil parameters interpretated using Marchetti's (1980,1981) and Schmertmann's (1982,1983) correlations are discussed. Comparison is made to other in-situ testing methods such as cone penetration test, vane shear test and pressuremeter test.
Based on a better understanding of the DMT, future potential methods of improving or checking the existing correlations are proposed.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Avila, de oliveira silva Lais. "Investigation de l’effet du gradient microstructural généré pendant le patentage sur les propriétés mécaniques finales des fils d’acier perlitiques." Electronic Thesis or Diss., Centrale Lille Institut, 2022. http://www.theses.fr/2022CLIL0007.
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Les aciers perlitiques pourraient apparaître comme une microstructure simple, de composition eutectoïde contenant deux phases (cémentite et ferrite) arrangées en lamelles. Cependant, ils présentent une microstructure hiérarchisée, composée de nodules de même cristallographie semblables à des grains. Ces nodules comprennent des colonies formées de lamelles parallèles de ferrite et de cémentite à l'échelle nanométrique. Dès lors, les aciers perlitiques offrent une résistance et une ductilité élevées à un coût raisonnable, en accord avec les applications telles que câbles de pont, ressorts… Bien que les aciers perlitiques soient connus et largement étudiés depuis plus de 150 ans, il pourrait paraître provoquant de proposer de nos jours des voies d’amélioration de leurs propriétés mécaniques.Cependant, certaines options n'ont pas encore été envisagées comme le gradient microstructural ou le contrôle des morphologies de la perlite. Le concept de gradient microstructural a été largement exploré pour des microstructures simples d’aciers (ferritique ou austénitique),mais sa transposition vers les aciers perlitiques est plus compliquée. Ce travail de thèse vise à étudier la faisabilité de produire un gradient microstructural dans des aciers perlitiques et de contrôler la morphologie de la perlite. Il repose sur la compréhension des mécanismes métallurgiques impliqués et l'impact sur les propriétés mécaniques, en particulier la fatigue, compte tenu de l'application finale de ce matériau. Le contrôle de la microstructure et du gradient est basé sur la transformation de l'austénite en perlite et, par conséquent, tous les paramètres pouvant influencer cette transformation doivent être étudiés. Cela comprend des paramètres de traitement thermique (vitesse de chauffage, vitesse de refroidissement, mode de refroidissement, température de transformation) et des matériaux (espacement interlamellaire entre ferrite et cémentite initial, état de déformation de la perlite). L'espacement interlamellaire, connu pour contrôler les propriétés mécaniques des aciers perlitiques, varie avec la température de transformation, donnant lieu à une perlite grossière et fine lors qu'elle est transformée à températures élevée ou basse, respectivement. Nous montrons qu’il est possible de créer un gradient microstructural d'espacement interlamellaire mais ce gradient est limité par le diamètre du fil. A partir d’essais utilisant un dilatomètre, ces gradients ont été obtenus avec succès dans des fils de diamètre 6 et 12 mm. Ces fils à gradient microstructural ont ensuite été tréfilés et les propriétés mécaniques avant et après tréfilage ont été comparées afin de s'assurer que les gradients formés lors du traitement thermique sur des fils de diamètre 6 mm sont toujours présents sur les fils de diamètre final 2,25 mm. La morphologie de la perlite a également été modifiée par la maîtrise des traitements thermiques utilisant un refroidissement continu et isotherme. Des perlites divorcées, connectées et bien alignées de même distance interlamellaire ont été produites. Il s'avère que la morphologie de la perlite dans des échantillons monolithiques a un impact plus important sur la plasticité cyclique que la présence d'un gradient. Les résultats obtenus dans ce doctorat ont donné lieu à discuter de la transformation perlitique lors d’un refroidissement continu et isotherme, des mécanismes contrôlant la morphologie de la perlite (surtout divorcée ou lamellaire), des phénomènes métallurgiques se produisant lors du chauffage (recristallisation,restauration et sphéroïdisation), ainsi que des mécanismes de plasticité de la perlite. Enfin, la possibilité de réaliser des gradients microstructuraux avec les moyens de refroidissement utilisés sur des lignes de tréfilage et de traitements thermiques a aussi été étudiée.L’obtention de gradients par des technologies de refroidissement alternatives autre que le plomb est un réel succès compte tenu des contraintes environnementales: Pearlitic steels could appear to be a simple and classic microstructure, with a rather simple eutectoid composition containing twophases (cementite and ferrite) in a lamellar distribution. However, they feature a hierarchical microstructure, which is composed of nodulesthat present the same crystallography and are grain-equivalent, then the nodules comprise the colonies that contain the parallel ferrite andcementite lamellas at a nanometric scale. As a result, pearlitic steels offer high strength and ductility at a reasonable cost, which fits verywell for various structural and reinforcement applications, e.g., steel core, bridge cables, wire ropes, springs…Although pearlitic steels areknown and vastly studied for over 150 years, it could appear outrageous to still propose manners of improving their mechanical properties.However, some options have not yet been considered such as the microstructural gradient or the control of the pearlite morphologies. Themicrostructural gradient concept has been widely explored in simple microstructure in steels, such as ferrite or austenite, but it is morecomplicated to export it in the pearlitic steel. The present Ph.D. aims to investigate the feasibility of producing a microstructural gradient infully pearlitic steels and of controlling the pearlite morphology. It is sought the understanding of the involved metallurgical mechanisms andthe impact on the mechanical properties, especially fatigue, considering the final application of this material. The control of themicrostructure and the gradient is based on the transformation of austenite into pearlite and, therefore, all the parameters that couldinfluence this transformation must be studied. It includes heat treatment parameters (heating rates, cooling rates, cooling modes,temperature of transformation…) and materials ones (initial interlamellar spacing, deformation state of pearlite…). The spacing between theferrite and cementite lamella, known to govern the mechanical properties of pearlitic steels, varies with the transformation temperature,which results in coarse and fine pearlite when transformed at high or low temperatures, respectively. It is found that a microstructuralgradient of interlamellar spacing is possible to be formed but is limited by the rod diameter. Using the dilatometer, it was successfullyprocessed in a 6 and 12 mm diameter rod. The gradient-containing wires were then drawn and the mechanical properties before and afterdrawing are compared to assure that the gradients formed during the heat treatment of the 6 mm diameter wires are still present on the2.25 mm final diameter wires. The morphology of pearlite has also been modified by control of heat treatments using continuous andisotherm cooling. Divorced, connected and well-aligned perfect pearlites with the same interlamellar distance have been processed. It turnsout that the morphology of the monolithic pearlite specimen has a higher impact on cyclic plasticity than the presence of a gradient. Theresults obtained in this Ph.D. gave rise to discussions on the pearlitic transformation under continuous and isotherm cooling, on themechanisms controlling the morphology of pearlite (mostly divorced or lamellar), on the phenomena happening during heating,(recrystallization, recovery, and spheroidization), and also on the mechanisms of plasticity of pearlite. Finally, the feasibility of the productionof the gradients by real cooling technologies is assessed by transforming the wires in a pilot line. It is of most interest that the gradients areproduced by alternative cooling technologies since the lead patenting technique is not the most environmentally friendly, although the mostwidely used
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Chiu, Chung-fai. "A modified flat dilatometer for field measurement of non-linear soil behaviour at small strains /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1806176X.
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Rivera, Cruz Ivan. "An evaluation of seismic flat dilatometer and lateral stress seismic piezocone." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/3890.
Full textAbstract:
The flat dilatometer (DMT) and piezocone penetration (CPTU) tests are likely to be among the most
widely used in situ testing methods for soil characterization and indirect determination of geotechnical
design parameters such as: strength, stiffness, permeability and compressibility. The flat dilatometer has
proved to be a reliable, robust and adaptable tool, and the data obtained with this instrument is very
repeatable, and easy to reduce and process. Furthermore, the addition of a seismic module to the standard
flat dilatometer (SDMT) to measure the shear wave velocity (Vs) significantly complements the set of
data typically obtained with a standard DMT test. Nonetheless, the experience in interpreting the
combination between Vs and DMT data is fairly limited due to the recent introduction of the SDMT for
commercial applications. Additionally, the estimation of the coefficient of earth pressure at rest (K₀) has
been the most important application of the DMT since its introduction. However, a potential weakness of
the DMT is that the derivation of K₀ is based upon empirical correlations developed some time ago and
neither improvement work nor upgrade of these approaches has been performed in the last 10 years.
Throughout the years several additional sensors have been developed in order to supplement the data
collected with the CPTU test. Among the wide variety of sensor developed, the lateral stress module
mounted behind a piezocone represents a promising tool for estimation of in situ lateral stress conditions
from the interpretation of lateral stress penetration data. However, the popularity of the so called lateral
stress cone has declined over the years due to constraints in both the instrumentation and the
interpretation of measured data. Also, the application of this instrument remains limited to specific soils
conditions and specific projects. However, the valuable experience gained throughout the years in the
development and application of several lateral stress cones in combination with developments in
electronics and understanding of soil behaviour allow the improvement of this type of technology.
This thesis presents the results of a comprehensive laboratory and field testing programs performed by the
author at several research sites located in the Lower Mainland of BC, undertaken in order to assess the
performance of the seismic flat dilatometer and lateral stress seismic piezocone (LSSCPTU), built and
develop at UBC. Firstly, the analysis of field measurements with the SDMT collected at several sites have
demonstrated the potential for an improved soil characterization through the combination of DMT
parameters and the small strain shear modulus (G₀). Additionally the usefulness of the DMT-C closing
pressure for soil identification is shown. On the basis of several relationships identified from this data, a
new soil type behaviour system based upon SDMT measurements is proposed. Furthermore, empirical
correlations based upon fairly large and updated databases have been developed to estimate K₀ and Vs
values from DMT parameters.
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Baier, Falko. "Atomare Leerstellen in Quasikristallen : eine spezifische Studie mit Positronen und Dilatometrie /." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9815627.
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