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Zou, Yu. "Microstructural studies of cold sprayed pure nickel, copper and aluminum coatings." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92381.
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Leblanc, Robert Samuel. "Influence of Nozzle Material and Spray Parameters on Pure Aluminum and Aluminum 7075 coatings using Cold Gas Dynamic Spray." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34202.
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Commercial airplanes are still using aluminum alloys as their primary structural material. Even if the used carbon fiber reinforced polymers is becoming more popular due to their extremely high strength to weight ratio, the majority of the existing flying fleet is still made out of aluminum alloys. This material was primarily used due to its high strength to weight ratio, ease to machine, excellent corrosion resistance properties and its high crash energy absorption. Aircraft components made of aluminum alloys are subjected to high stresses and harsh environments during flight, potentially leading them to crack and/or corrode. Presently, there is no industrial approved method to repair these components. Recycling damaged aircraft parts by repairing them would result in large cost savings for the industry. The present study was motivated by the potential use of the cold gas dynamic spray (CGDS) process to repair damaged aluminum 7075-T6 aircraft components. Two feedstock materials were used to repair this alloy in this research: pure aluminum and aluminum 7075. Pure aluminum is used in the aircraft industry on non-bearing components due to its extremely high corrosion resistance properties. Aluminum 7075 is the material of choice for structural applications due to its high strength. The results of this study show that CGDS could be potentially used to repair aluminum components on aircrafts. However, this research demonstrated that new commercially available equipments need to be further developed to successfully produce repaired components that meet the industry standards.
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Mjali, Kadephi Vuyolwethu. "Laser bending of commercially pure grade 2 titanium alloy plates: mechanisms analysis and characterisation of mechanical properties." Thesis, Nelson Mandela Metropolitan University, 2014. http://hdl.handle.net/10948/d1021147.
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The processing of materials has become a specialist field and the industry will continue to grow due to rising costs in labour and raw materials which has forced many automotive industry suppliers to invest heavily in this field. In order to be relevant and competitive in today’s industrial world, companies in South Africa are now forced to dedicate billions of rands in profits to research and development. Metals like titanium are finding favour with automotive and aviation companies in pursuit of savings in fuel consumption. This saving is achieved by reducing weight on aircraft and automobiles yet still meeting acceptable and improved structural integrity. In-depth research into the behaviour of various materials under varying loading conditions is therefore essential. The study on the processing of commercially pure grade 2 titanium alloy plates focuses on the development of process parameters for bending the material using a 4kW Nd: YAG laser to an approximate radius of curvature of 120mm. The resulting mechanical properties of laser formed plates are then compared to those obtained from mechanically formed samples. The titanium parent material was used to benchmark the performance of formed samples. The effect of process parameters on the mechanical properties and structural integrity also formed part of this study. To obtain the bending parameters for laser forming, various combinations of processing speeds and laser powers were used. The line energy is dependent on the power and scanning velocity parameters and these are shown in table 1. The laser power, line energy and scanning velocity were the main parameters controlled in this study and the beam diameter remained unchanged. Residual stress analysis, micro-hardness and fatigue life testing were carried out to analyse mechanical properties and the structural integrity of the plate samples. Microstructural analysis was also done to observe changes in the material as a result of the forming processes. From the results it is evident that laser forming is beneficial to the hardness of titanium but detrimental to the fatigue life at higher line energies. Residual stress analysis showed the amount of stress within the study samples increased with each forming operation. This information was vital in the analysis of the fatigue life of titanium. A fatigue life prediction model was developed from this study and it shed some light on the behaviour of titanium in fatigue testing. The model could be used to predict fatigue life when no fatigue data is available for commercially pure grade 2 titanium alloy plates. In conclusion, this study helped establish parameters that could be used to bend titanium while the analysis of mechanical properties showed the limits of working with this alloy.
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Mjali, Kadephi Vuyolwethu. "Mechanisms, analysis and characterisation of mechanical properties of laser formed commercially pure grade 2 titanium alloy plates." Thesis, Nelson Mandela Metropolitan University, 2014. http://hdl.handle.net/10948/d1021083.
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The processing of materials has become a specialist field and the industry will continue to grow due to rising costs in labour and raw materials which has forced many automotive industry suppliers to invest heavily in this field. In order to be relevant and competitive in today’s industrial world, companies in South Africa are now forced to dedicate billions of rands in profits to research and development. Metals like titanium are finding favour with automotive and aviation companies in pursuit of savings in fuel consumption. This saving is achieved by reducing weight on aircraft and automobiles yet still meeting acceptable and improved structural integrity. In-depth research into the behaviour of various materials under varying loading conditions is therefore essential. The study on the processing of commercially pure grade 2 titanium alloy plates focuses on the development of process parameters for bending the material using a 4kW Nd: YAG laser to an approximate radius of curvature of 120mm. The resulting mechanical properties of laser formed plates are then compared to those obtained from mechanically formed samples. The titanium parent material was used to benchmark the performance of formed samples. The effect of process parameters on the mechanical properties and structural integrity also formed part of this study. To obtain the bending parameters for laser forming, various combinations of processing speeds and laser powers were used. The line energy is dependent on the power and scanning velocity parameters and these are shown in table 1. The laser power, line energy and scanning velocity were the main parameters controlled in this study and the beam diameter remained unchanged. Residual stress analysis, micro-hardness and fatigue life testing were carried out to analyse mechanical properties and the structural integrity of the plate samples. Microstructural analysis was also done to observe changes in the material as a result of the forming processes. From the results it is evident that laser forming is beneficial to the hardness of titanium but detrimental to the fatigue life at higher line energies. Residual stress analysis showed the amount of stress within the study samples increased with each forming operation. This information was vital in the analysis of the fatigue life of titanium. A fatigue life prediction model was developed from this study and it shed some light on the behaviour of titanium in fatigue testing. The model could be used to predict fatigue life when no fatigue data is available for commercially pure grade 2 titanium alloy plates. In conclusion, this study helped establish parameters that could be used to bend titanium while the analysis of mechanical properties showed the limits of working with this alloy.
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Krishnakumar, Rengan. "Passivation behavior of pure aluminum and sputtered non- equilibrium Al-Cr and Al-Ta alloy films /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487843688958645.
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Terhune, Shannon Derek. "An electron backscatter diffraction analysis of the microstructure of pure aluminum processed by equal-channel angular pressing." Thesis, Monterey, California. Naval Postgraduate School, 1998. http://hdl.handle.net/10945/8304.
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Equal-channel angular (ECA) pressing is a promising method to achieve refinement of grain size to 1.0 micrometer or less for aluminum and its alloys. Computer-aided electron backscatter diffraction (EBSD) analysis of high purity aluminum (99.99%) which had been subjected to one pass, four passes, and twelve passes through an ECA die was performed. Grain and subgrain size and boundary misorientation distributions during such large-strain deformation processing were of particular interest. A texture was present after one pressing and the boundary misorientation distribution had a peak at 5 deg - 10 deg although boundaries were present in all misorientation ranges. Fine equaixed grains were achieved after twelve passes through the ECA die, accompanied by random orientation and misorientation distributions
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Dunn, Darrell Scott. "Characterization and evaluation of anodized commercially pure titanium and titanium-aluminum-vanadium alloy surfaces for systemic antibiotic release." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/144641.
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Postoperative infections are one of the most feared complications following orthopedic implant procedures. Bacterial infections occur in approximately 1-2% of the patients who undergo orthopedic implant surgery. Treatment of these infections is typically done by administering antibiotics either locally or systemically. Systemic release of antibiotics from bone cement has been reasonably successful. However, it would also be desirable to develop a method of antibiotic release from porous coated implants designed for osseointegration. The principal objective of this research was to explore the feasibility of using anodizing (electrochemical oxidation) as a surface modification technique to facilitate the attachment of antibiotics to commercially pure titanium (CP Ti) and Ti-6Al-4V orthopedic implant materials. In particular the effect of anodizing conditions on the characteristics of the oxide coating such as thickness, composition and porosity has been investigated. Using microbiological methods, the efficacy of in-vitro attachment of antibiotics to anodized surfaces was determined.
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Xenikos, Dimitrios George. "Statics and dynamics of the mixed state in pure and aluminum-doped yttrium barium copper oxide high-temperature superconductors /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487856076412837.
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Nastic, Aleksandra. "Repair of Aluminum Alloy Aerospace Components and Cold Gas Dynamic Spray Flow Distribution Study." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32998.
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Aluminum alloys have been used for decades in aircraft as they offer a wide range of properties explicitly developed to provide a set of characteristics adapted to structural and non-structural components. However, aircraft components inevitably undergo degradation during service due to their extensive use and exposure to harsh environments. Typical repair methods are either not efficient for large scale repairs due to their low material growth rate, not suitable for field repair or involve the use of high process temperatures. The present research aims at evaluating the cold gas dynamic spray (CGDS) as a potential repair technology to restore Al7075-T6 nose landing gear steering actuator threads found on the Boeing 757 aircraft. Moreover, it studies the suitability of using cold spray to deposit Al2024 material. The influence of process parameters and substrate surface preparation on the material deposition efficiency and resulting microstructural and mechanical repair properties is also evaluated.
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Swaroop, N. R. Sathya. "Processing And High Temperature Deformation Of Pure And Magnesia Doped Alumina." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/180.
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Creep resistance is an important design criterion at high temperatures especially when continuous attempts are made to increase the efficiencies by increasing the operating temperatures. Alumina is an important high temperature material and in addition to that it is used in wide variety of applications such as substrates for electronic packaging, spark plugs, envelopes for sodium vapour lamps, cutting tools (when reinforced with silicon carbide) and in artificial joint prostheses.
Studies on creep in alumina. have started as early as 1961. There are differing mechanisms proposed to explain the creep behaviour of alumina in the literature, but until now there is no any unanimous decision as to what the rate controlling mechanism is. Magnesia doped at ppm levels can produce significant changes in the microstructure of alumina, the most important consequence of that being the grain growth inhibition, which renders alumina superplastic. However, in a stoichiometric oxide like alumina, small impurities can create extrinsic defects which would change the diffusivities and creep rates. Therefore the background impurities in alumina should be kept to a minimum, if small dopant effects have to be studied. The present study was undertaken making use of high purity alumina powder and comparing the grain growth and creep properties of pure and magnesia doped alumina, especially since no such investigation was carried out in the recent past with high purity alumina.
Pure alumina was processed by cold compaction followed by cold isostatic pressing (CIP) and pressureless sintering in air at 1773 K for 1 hour. Magnesia doped alumina was prepared by calcining a mixture of alumina and magnesium nitrate at 973 K for 2 hours followed by cold compaction, CIPing and pressureless sintering in air at 1773 K. Both pure and magnesia doped alumina were further annealed at 1873 K for various times to get grain sizes in the ranges of 1-5 μm.
Grain growth kinetics of pure and magnesia doped alumina were studied at 1823 and 1873 K. The parameter Kg which quantifies the mobility of the grain boundary was got. It was found that Kg had decreased in the magnesia doped alumina (in comparison with pure alumina) by a factor of about 3 to 4 which was marginal and insignificant. The grain sizes followed a log normal distribution in both the cases, indicative of normal grain growth.
Creep studies were conducted on pure and magnesia doped alumina in three modes, namely, constant stress, temperature jump and stress jump test. The temperature range used was 1673 to 1773 K and the stress range used was 10 to 100 MPa. The creep parameters were found to be n~1.6, p~3.7 and Q-545 kJ mol"1 for pure alumina and n~l .3, p~3.0 and Q~460 kJ mol-1 for magnesia doped alumina. The creep rates in the case of magnesia doped alumina were found to have increased by a factor of 2 to 3, in comparison with pure alumina. The increase in creep rates were found to be insignificant. The creep data were analyzed and the possibility of the dislocation and interface reaction controlled creep mechanisms were ruled out since they were inconsistent with the data. It was found, from creep parameters and the comparison of theoretical Coble and Nabarro-Herring creep rates with the experimental rates, that Coble creep might be rate controlling. The activation energy values suggested that aluminium ion diffusing along grain boundary might be the rate controlling species. However, when the theoretical creep rates considering various species were compared, the rate controlling species turned out to be oxygen ion diffusing along the grain boundary.
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Anyalebechi, P. N. "The solubility of hydrogen in pure aluminium and binary aluminium-lithium alloys." Thesis, Brunel University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354569.
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Almajdub, Musbah. "Structural studies of anodic films on pure aluminium." Thesis, University of Warwick, 1998. http://wrap.warwick.ac.uk/59556/.
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The morphology and composition of anodically formed alumina films on pure aluminium are well characterised, but their structure is not well known due to the long range order. Two systems have been looked at in this study; the nature of the structure of tungsten incorporated from tungstate electrolyte during polarisation of aluminium at 100 V, and the other system is the thin passivating layers formed anodically on aluminium surface by polarisation within the range -2.2 - +2.5 V in aqueous solutions at various pH's. Even though other techniques, such as, electron microscopy and XPS have been used to confirm the presence of anion species in alumina films only EXAFS can yield direct information about the structure of incorporated species. In this study, EXAFS has been used for the first time to resolve the structure of tungsten incorporated into anodic alumina. Accurate determination of structural parameters require the establishment of reliable phase shift. By fitting the EXAFS of tungsten foil and potassium tungstate, the reliability of the calculated phase shifts for oxygen and tungsten was established. Based on phase shift transferability, the phase shifts calculated for 0 and W were used in the fitting of fluorescence EXAFS of tungsten in alumina oxide films formed on aluminium in tungstate solution at 100V. The experimental EXAFS function was fitted to a single oxygen shell with four atoms at a distance of 1.79 ± 0.01 A. From the structural parameters for incorporated tungsten it is clear that it is in a W04 2- even though this can not be the entity which is outwardly mobile. It is suggested that the tungstate may be linked in some way to the alumina and that because aluminium cations are outwardly mobile so tungstate is dragged along. The other kind of anodic films on aluminium are those produced by polarising aluminium in aqueous solutions at various pH's to various voltages within the range -2.2 - + 2.5 V. In some instances, passivating films grow on aluminium causing aluminium protection against corrosion. The structure of these films is not defined and because of their existence on aluminium, and their small thickness, so their structure is not easy to be studied. Electron microscope and XPS techniques have been used to determine their morphology and composition. Some work on indirectly extracting the structure of these films from XPS data was reported and it was claimed that these films have a pseudoboehmite like structure. XPS results of these films reported in this study have confirmed that under open circuit conditions an oxide film forms, but to provide good corrosion protection aluminium is polarised at different potentials. The oxide film which forms in these conditions has been found to have both 4 and 6 coordiation. The Al K-edge EXAFS of these oxide films was fitted in the same way as those for the incorporated tungsten. In this case, the EXAFS of aluminium foil and alpha alumina was fitted by the use of phase shifts calculated in EXCURV92 for aluminium and oxygen. The oxygen and aluminium phase shifts calculated in EXCURV92 were reliable, so they were used to fit the EXAFS of the passivating films on aluminium of unknown structure. The EXAFS results in this study have confirmed that these oxides do not have a single phase crystalline structure like boehmite or any others. Their structure is of a short range order and it is characterised in terms of co-ordination number and shell distances. All of the results reported in the EXAFS section of this work indicate that these oxide films are relatively thin and that is indicated by a metallic aluminium signal present most of the time. The sampling depth of the x-ray photons is much greater than the thickness of the oxide film and for this reason a metallic signal was recorded. By comparing the bond length value to the relation between the bond length and co-ordination number, it is obvious that these oxides films have a mixture of 4 and 6 co-ordination. In some cases, like aluminium polarised to + 0.9 V in pH 10, most of the co-ordination of the oxide is 6 except a little of it in the 4 co-ordination. XANES spectra for the model compounds and those for oxide films on aluminium and their derivative have agreed with the EXAFS results about the structure of thin films formed on aluminium. Also these findings were complemented by the XPS data where the Al 2p of pseudoboehmite has a binding energy of 80.0 eV whilst that of the oxide films in general were - 74 eV. So, it is clear that the oxide films structure is not a psuedoboehmite, but it is a local one with different values for the bond length and as a consequence a mixture of different (4 and 6) co-ordination.
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Shirandasht, Jamshid. "Évaluation de la technique LiMCA II pour la mesure d'inclusions dans l'aluminium pur et l'alliage binaire Al-6%Si : rôle de la température de coulée /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
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Pereira, Cristian Guilherme Barbosa. "Fabricação e caracterização mecânica da alumina reforçada com grafeno /." Bauru, 2019. http://hdl.handle.net/11449/191509.
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Orientador: Cesar Renato FoschiniResumo: Os avanços na área da tecnologia e ciência dos materiais têm possibilitado grande evolução e contribuição para o desenvolvimento de materiais cerâmicos. Pesquisas associadas a esse tipo de material estão cada vez mais difundidas por apresentar características como: alta dureza, biocompatibilidade, estabilidade térmica, inércia química e resistência à corrosão. Entretanto, seu uso acaba sendo limitado por sua fragilidade. A utilização dos alótropos de carbono (grafeno, nanotubos e fulerenos) como material de reforço nas cerâmicas, têm sido muito estudados, no entanto, o desempenho desses alótropos está restrito a condições específicas de mistura e sinterização. Esta pesquisa trata da fabricação e caracterização mecânica do compósito Al2O3-MLG. Partindo de um pó cerâmico de Al2O3 e adicionando diferentes concentrações, 0,5%; 0,75%; 1,0% e 1,25%, em peso de MLG em sua matriz, corpos de prova foram fabricados através da mistura em meio úmido dos pós, secagem da mistura, compactação dos pós secos e posterior sinterização com atmosfera redutora. As amostras obtidas pelo método proposto foram submetidas a caracterização física, microestrutural e mecânica, sendo comparadas diretamente a amostra contendo apenas Al2O3. Foi verificado que a sinterização com atmosfera redutora, preservou a estrutura do MLG em matriz de Al2O3. A análise dos resultados indicou que a utilização de concentrações menores que 1,0% em peso de MLG, proporcionou a fabricação de compósitos com maior dispersão e me... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Advances in the area of technology and materials science have enabled major evolution and contribution to the development of ceramic materials. Research associated with this type of material is becoming more widespread due to characteristics such as: high hardness, biocompatibility, thermal stability, chemical inertia and corrosion resistance. However, its use ends up being limited by its fragility. The use of carbon allotropes (graphene, nanotubes and fullerenes) as reinforcement material in ceramics has been widely studied, however, the performance of these allotropes is restricted to specific mixing and sintering conditions. This research is about the fabrication and mechanical characterization of the Al2O3-MLG composite. Starting from an Al2O3 ceramic powder and adding different concentrations, 0,50%; 0,75%; 1,0% and 1,25% by weight of MLG in their matrix, samples were fabricated by wet powder mixing, drying of the mixture, dry powder compaction and subsequent sintering with reducing atmosphere. The samples obtained by the proposed method were subjected to physical, microstructural and mechanical characterization, being directly compared to the sample containing only Al2O3. It was verified that the sintering with reducing atmosphere preserved the structure of the MLG in Al2O3 matrix. The analysis of the results indicated that the use of concentrations lower than 1.0% by weight of MLG, allowed the fabrication of composites with greater dispersion and less formation of aggl... (Complete abstract click electronic access below)
Mestre
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Sande, Gunnar. "Softening Behaviour of Selected Commercially Pure Aluminium Model Alloys." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18897.
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A characterization of the softening behaviour of four different commercially pure aluminium alloys has been carried out. The work is related to the MOREAL project (Modelling towards value-added recycling friendly aluminium alloys), where the main goal is to quantify the effect of the elements in recyclable aluminium alloys on microstructure and mechanical properties during thermo-mechanical processing. Typical elements are iron (Fe), silicon (Si) and manganese (Mn), and the alloys studied in this work contain Fe and Si with different amount and ratio: alloy A1 with 0.15 wt% Fe and 0.05 wt% Si; alloy A2 with 0.15 wt% Fe and 0.15 wt% Si; alloy B1 with 0.5 wt% Fe and 0.05 wt% Si and alloy B2 with 0.5 wt% Fe and 0.15 wt% Si.The as-cast material of all four alloys were homogenized at 600 °C for 24 hours followed by a cooling sequence to 450 °C, implying a total dwell time of 160 hours. The alloys were then cold rolled to a strain of 2.6 and isothermally annealed at temperatures from 275 °C to 375 °C, and the physical and mechanical properties were followed with electrical conductivity and hardness measurements. The microstructure and texture has been investigated with electron backscattering diffraction (EBSD) in scanning electron microscope (SEM), optical light microscopy and orientation distribution functions (ODF) from X-ray diffraction. Alloy A1 and A2 where fully recrystallzed after 10 000 seconds when isothermally annealed at 300 °C. Alloy B1 and B2 are slightly faster to reach the fully recrystallized state than alloy A1 and A2. The decrease in mechanical properties during softening was nearly linear on a logarithmic time scale, especially for alloy B1 and B2, with the onset of recrystallization difficult to seperate from the recovery. Electrical conductivity measurements showed that there was minimal concurrent precipitation. Images of the microstructure of the samples annealed at 275 °C show a long recovery phase followed by recrystallization. Particle stimulated nucleation (PSN) sites seems to be an important nucleation mechanism as it is found that the initial grain size have little effect on the softening kinetics, indicating that nucleation on old grain boundaries is of little importance. The recrystallization texture is weak with the typical Cube orientation slightly rotated around the normal direction. The recrystallized grain size was found to be smaller in alloy B1 and B2 (16-20 μm) than in alloy A1 and A2 (21-27 μm), most likely due to more PSN sites in these alloys. The grain growth that followed after recrystallization was found to be slightly larger for alloy A1 and A2 than alloy B1 and B2, most likely due to the effect from solute drag.
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Mazraeh, Mohsen. "The resistance of flare stack coatings to corrosion." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251829.
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El-Mashri, Saleh M. "Structure of anodic-oxide and hydrated oxide films on pure aluminium." Thesis, University of Warwick, 1985. http://wrap.warwick.ac.uk/108759/.
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The technique of electron yield-EXAFS has been used to derive information about the different structures of amorphous films, formed anodically on pure aluminium when various electrolyte solutions are used. It has been found that the uniform non-porous (barrier-type) oxide films which are formed in neutralised sodium tartrate or sodium borate electrolyte are amorphous and have an average Al-0 bond length of 0.190 nm. The amorphous oxide produced in neutralised sodium oxalate gives an average Al-0 separation of 0.185 nm, while the porous oxides formed in strong aggressive electrolytes, chromic acid and phosphoric acid, have an average Al-0 bond length of 0.183 nm and 0.180 nm respectively. Both the non-porous and the porous types of films have also been examined by high resolution scanning electron microscopy. The films formed in neutralised electrolytes show a structureless morphology, while the films prepared in strong acid are shown to have a porous morphology. All these oxide films become hydrated when exposed to hot water at 85°C. The time for complete hydration varies according to whether the film is porous or not. Electron yield-EXAFS analysis of these hydrated films yields two well defined Al-0 distances, 0.205 nm and 0.280 nm, which appear to be associated with the formation of an oxy-hydroxide similar in structure to boehmite. The SEM observation of these hydrated films shows a narked change in the micromorphology during hydration. A "cornflake" structure is developed which is related to the oxy-hydroxide structure (boehmite-like phase). These measured Al—O bond lengths derived from the EXAFS differ, depending on the nature of the anodising treatment, which suggests different states of aluminium-oxygen coordination. A possible model for the structure of amorphous alumina, based on this information, is proposed. These results are also discussed in relation to the structural chemistry of the hydration process.
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Fortin, Guy. "Détermination du coéfficient transitoire de transfert de chaleur à l'interface moule/métal lors de la solidification de l'aluminium pur commercial /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1992. http://theses.uqac.ca.
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Mémoire (M.Sc.A.)-- Université du Québec à Chicoutimi, 1992.Résumé disponible sur Internet. CaQCU Bibliogr.: f. 158-160, 220-221. Document électronique également accessible en format PDF. CaQCU
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Fournier, Agathe. "Interactions of pure aluminium hydrolytic species Keggin polyoxocations and hydroxide with biologically relevant molecules." Thesis, Nottingham Trent University, 2008. http://irep.ntu.ac.uk/id/eprint/99/.
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The general purpose of this thesis is concerned with the intricate interactions of pure aluminium species with biomolecules. Pure aluminium reference systems (aluminium monomers, Keggin aluminium polyoxocations - Al13 and Al30, and aluminium hydroxide suspensions) were used for systematic mechanistic studies of the sol-gel transformation of aqueous solutions of aluminium-ions into aluminium (oxy) hydroxides induced by the addition of a 'soft base' - Trizma-base, which does not ionize fully in an aqueous solution. The conversion proceeds via forced hydrolysis-condensation of aluminium-ions into molecular clusters, structural conversion of aluminium Keggin-like polynuclear clusters into nanoparticles of aluminium (oxy) hydroxide, aggregation of primary nuclei of aluminium (oxy) hydroxide into larger clusters and finally the 'arrested growth' of the aggregates with the formation of the three-dimensional gel network. The next part of the study concentrated on the development and the optimisation of a potentiometric method for the determination of the 'formal' hydrolysis ratio of aluminium-containing solutions. The method made it possible to establish the aluminium speciation of the selected systems. The interactions of aluminium species with three model biomolecules - lactic acid, hen egg lysozyme and porcine mucin - were investigated. Aluminium and lactic acid underwent a strong coordination in aqueous solutions, with increasing concentrations of lactic acid appearing to force all the aluminium species initially introduced to convert into monomers and dimers as a result of an acidic hydrolysis. Subsequently, the resulting hydrolysed products formed new aluminium-lactate chelates. The evolution of both the inorganic and biomolecular phases of the lysozyme-aluminium systems demonstrated that specific charge-stabilised bioinorganic assemblies involving aluminium species and lysozyme formed. The chemical and structural alterations of the protein on interaction with the inorganic species showed that the interactions occurred. The interactions of aluminium with mucin appeared predominantly electrostatically driven. The formation of the aluminium-mucin entities modified the native conformation of the protein: initially organised into b-sheet structure, mucin, within the complexes, acquired a more compact organisation involving intermolecular bonding. Furthermore, in the case of the aluminium hydroxide systems, the established complexes were ordered into sheet-like structures. Although the level of concentrations of aluminium and biomolecules exceeded those normally found in the human body and environmental media, we believe that the better understanding of aluminium species-biomolecule interactions would be of benefit to those working in the biomedical and environmental sciences.
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Li, Chuanping. "Rheological Properties of Aqueous Nanometric Alumina Suspensions." Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/835308-5NQETg/webviewable/.
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Nehari, Abdeldjelil. "Étude et caractérisation de la synthèse de milli-billes d’alumine alpha et de la cristallogenèse du saphir pur et dopé titane (Ti3+)." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10334.
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Ce travail est consacré à l’étude de la croissance cristalline du saphir non dopé et dopé titane (Ti3+). Pour faire croître des cristaux ayant des performances optimisées, il est indispensable de maitriser l’alumine (Al2O3) de départ. Toute contamination de la charge initiale à fondre, dégrade l’état stationnaire de croissance, entraîne la propagation de défauts cristallins, provoque la corrosion des creusets, en particulier en molybdène, et affecte les propriétés physico-chimiques, optiques et laser du cristal. Dans la première partie de ce travail, un nouveau procédé industriel de synthèse de millibilles d’alumine alpha (Al2O3-α) de géométrie sphérique, de haute pureté, a été mis au point. Le procédé est basé sur l’écoulement goutte à goutte de l’alumine fondue à travers des filières situées sous le creuset. Le procédé est particulièrement complexe, les études menées ont néanmoins visé à des descriptions qualitatives et quantitatives des phénomènes. La simulation et la modélisation de la thermique autour du creuset en iridium ont permis de maitriser le système et le contrôle continu du procédé. Dans le but de valider la qualité des millibilles d’alumine obtenues, des cristaux de saphir ont été tirés en utilisant des installations de croissance du LPCML (Czochralski, micro-pulling down) et de la société RSA le Rubis (EFG) qui ont des paramètres de fonctionnement différents (chauffage, atmosphère, creuset). La deuxième partie de la thèse, concerne la croissance cristalline du saphir dopé titane (Ti3+) qui est un matériau de très haute technologie. La demande actuelle porte sur des cristaux de 200 mm de diamètre, leur contrôle et caractérisation, le contrôle de la matière première, la mise en œuvre de différents procédés de croissance, le développement de mesures spécifiques des propriétés structurales, optiques et laser des cristaux. L’incorporation de l’ion Ti3+ dans la matrice du saphir se fait par substitution de l’ion Al3+. La différence de rayons ioniques rend difficile l’incorporation du Ti3+, conduisant à une concentration réelle en titane inférieure à celle souhaitée. Il s’ensuit une ségrégation du titane entre le bain fondu et le cristal lors de la croissance cristalline, ce qui provoque des hétérogénéités qui dégradent la qualité des cristaux. Dans cette partie de thèse, nous avons travaillé sur :1-La croissance stable en bain fondu de cristaux de Ti: saphir de 100 mm. 2-L’amélioration des procédés de croissance pour produire de manière reproductible des cristaux plus homogènes (concentration constante en ions titane), de bonne qualité optique (exempt de défauts) et offrant de bonnes performances laser. 3-La caractérisation des propriétés structuralesThis PhD thesis is established to study undoped and titanium (Ti3+) doped sapphire single crystal growth. To grow crystals with optimized performances, it is necessary to control starting Alumina (Al2O3). Any contamination of initial charge to be melted, will affect the stationary crystal growth, causes defects propagation in the crystal, crucibles corrosion, particularly Molybdenum and affect the physical-chemistry, optics and laser properties of the crystal. In the first part of this work, a new industrial process to synthesize (Al2O3-) alpha alumina millibilles of spherical geometry, high purity has been developed. The process is based on drop flow from shaped crucible. The process is complex, the study involve description of qualitative and quantitative phenomena during the synthesis stage. The thermal modeling and simulation around iridium crucible have allowed controlling the system and continued process. In order to validate the quality of the obtained Alumina (millibilles), sapphire crystals have been pulled by crystal growth equipments (Czochralski, micro—pulling down) available in LPCML laboratory and (EFG) in RSA Le Rubis company which have different operating parameters. The second part concern titanium (Ti3+) doped sapphire single crystal growth, which is material for high technology. Current demand is for controlled 200 mm diameter crystals, characterization, starting material control, adjustment of crystal growth process, development of specific measurement of structure properties, optics and lasers of the crystals. The incorporation of Ti3+ in sapphire host, is realised by the substitution of Al3+ ion. Because of the difference of the ionic radii, the incorporation of Ti3+ is difficult and the real titanium concentration will be lower than the wishes one. Segregation of titanium during crystal growth causes heterogeneities which damage the crystal quality. In this PhD part we have worked on: 1-Stable melt crystal growth of Ti-sapphire of 100 mm in diameter. 2- Improvement of crystal growth process to produce reproducible homogeneous crystals ( constant ions titanium concentration), good optical quality ( defects free) and good laser performances. 3- Characterisation of structural, optics and laser crystals properties
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Ellis, Michael Martin. "Formation of pure polycrystalline alpha-alumina fibers from an organo-metallic sol-gel." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/20010.
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Li, Ping. "Low cycle fatique behaviour of pure aluminium and Al-Zn-Mg-Cu alloy between 20 and 260° C /." [S.l.] : [s.n.], 1988. http://library.epfl.ch/theses/?nr=735.
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McCracken, Leahanne. "The Thermo-Mechanical processing of commercially pure aluminium through the application of simple shear deformation and heat treatment." Thesis, University of Ulster, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489975.
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In an attempt to achieve the high strength requirements for modem applications, today's advanced metallic materials are enhanced through strengthening mechanisms such as solid solution strengthening or cold workmg. The disadvantage associated with these mechanisms is the subsequent loss in ductility. This reduction also has a significant effect on the formability of materials. For example this is a particular disadvantage in the aerospace industry were the curvature of sheet components are limited by their formability. This project investigates an alternative strengthening mechanism in an attempt to maintain ductility.
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Kenway, P. R. "Computer simulation of the pure and defective surface properties of α-aluminium oxide, lanthanum cuprate and neodymium cuprate." Thesis, University of Bath, 1991. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278199.
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Hassanabadi, Massoud. "Grain Refinement of Commercial EC Grade 1070 Aluminium Alloy for Electrical Application." Thesis, KTH, Materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-163402.
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The aluminium alloys for electrical conductivity applications are generally not grain refinedsince the addition of grain refiners drops the electrical conductivity by introducing impuritiesinto the melt. Non-grain refined aluminium may lead to bar fracture and cracks during themetalworking process. The present study focuses to find an optimum balance between the grain refiner addition andthe electrical conductivity of commercial EC grade 1070 aluminium alloy for electricalapplication. In order to reach this goal, the electrical conductivity and the macrostructure ofcommercial EC grade 1070 aluminium (commercial pure aluminium) have been studiedunder a series of controlled lab scale trails. Specific addition levels of different grain refiners(TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B) were added to the metal melt and sampleswere taken at specific time intervals. The collected samples were sectioned, ground andmacro-etched. Thereafter, the macrostructure was analysed by the use of a digital camera andthe electrical conductivity was measured at temperature. The obtained result was expressed asa percentage of the International Annealed Copper Standard (IACS %). The macro-structuralanalysis showed that TiBloy, Al-5Ti-1B, and Al-3Ti-1B, with the maximum addition level of0.1%, cannot grin refine commercial pure aluminium. However, at higher grain refiner levelsthe number of columnar grains increased and their size decreased. The Al-3Ti-0.15C master alloy, with the same addition level as the once chosen for the othergrain refiners (up to 0.1%), showed significantly better grain refining. By the addition of0.1% of this grain refiner the macrostructure became very equiaxed already after 30 minutesof grain refiner addition. The fading of the Al-3Ti-0.15 master alloy was, however, observedfor samples with a long holding time. Nevertheless, by maximum addition level (0.1%) and a90 minutes holding time the macrostructure remained as equiaxed grains. The electrical conductivity results showed that none of the applied grain refiners (TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B), with the maximum addition level of 0.1%, decreasedthe electrical conductivity of commercial pure aluminium.
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Subbarayan, Sapthagireesh. "Fabrication of a Novel Al/Mg Composite: : Processing and Characterization of Pure Aluminium, Al/AZ31 Alloy Bi-Metal and Aluminium based Sheet Composites by Severe Plastic Deformation." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23778.
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Siddiqui, Mohammad S. "Vacuum Brazing of Alumina Ceramic to Titanium Using Pure Gold as Filler Metal for Biomedical Implants." FIU Digital Commons, 2011. http://digitalcommons.fiu.edu/etd/497.
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One of the many promising applications of metal/ceramic joining is in biomedical implantable devices. This work is focused on vacuum brazing of C.P titanium to 96% alumina ceramic using pure gold as the filler metal. A novel method of brazing is developed where resistance heating of C.P titanium is done inside a thermal evaporator using a Ta heating electrode. The design of electrode is optimized using Ansys resistive heating simulations. The materials chosen in this study are biocompatible and have prior history in implantable devices approved by FDA. This research is part of Boston Retinal implant project to make a biocompatible implantable device (www.bostonretina.org).
Pure gold braze has been used in the construction of single terminal feedthrough in low density hermetic packages utilizing a single platinum pin brazed to an alumina or sapphire ceramic donut ( brazed to a titanium case or ferrule for many years in implantable pacemakers. Pure gold (99.99%) brazing of 96% alumina ceramic with CP titanium has been performed and evaluated in this dissertation. Brazing has been done by using electrical resistance heating. The 96% alumina ceramic disk was manufactured by high temperature cofired ceramic (HTCC) processing while the Ti ferrule and gold performs were purchased from outside. Hermetic joints having leak rate of the order of 1.6 X 10-8 atm-cc/ sec on a helium leak detector were measured.
Alumina ceramics made by HTCC processing were centreless grounded utilizing 800 grit diamond wheel to provide a smooth surface for sputtering of a thin film of Nb. Since pure alumina demonstrates no adhesion or wetting to gold, an adhesion layer must be used on the alumina surface. Niobium (Nb), Tantalum (Ta) and Tungsten (W) were chosen for evaluation since all are refractory (less dissolution into molten gold), all form stable oxides (necessary for adhesion to alumina) and all are readily thin film deposited as metals. Wetting studies are also performed to determine the wetting angle of pure gold to Ti, Ta, Nb and W substrates. Nano tribological scratch testing of thin film of Nb (which demonstrated the best wetting properties towards gold) on polished 96% alumina ceramic is performed to determine the adhesion strength of thin film to the substrate. The wetting studies also determined the thickness of the intermetallic compounds layers formed between Ti and gold, reaction microstructure and the dissolution of the metal into the molten gold.
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Bittencourt, Evandro. "Elaboração e caracterização de um cerâmico de alumina pura e de compósitos de alumina/carbeto de Silício." Universidade do Estado de Santa Catarina, 1997. http://tede.udesc.br/handle/handle/1797.
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Previous issue date: 1997-02-09Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Um estudo bibliográfico preliminar permitiu estabelecer um estado de conhecimento sobre as técnicas de elaboração e de reforçamento de materiais cerâmicos. Foram elaborados via técnicas barbotina um cerâmico de alumina, compósito alumina/SiCm e nanocompósito alumina/SiCn, com 5% EM VOLUME DE SiC. Os pós-obtidos da mistura mecânica foram pré compactados dentro de uma matriz em grafite à 40MPa, após a matriz foi colocada dentro de um forno de prensagem à quente para realização de sinterização a uma temperatura T2 = 1550 oC para alumina e a 1600 oC para o compósito e nanocompósito Al2O3/SiC. A incorporação de 5% em volume do pó de SiC nanométrico (d=20 30mm), conduziu a uma estabilização térmica da alumina, isto é, permitiu uma limitação do crescimento dos grãos de alumina alfa da matriz. Tendo sido levado em conta as observações, para os cerâmicos nanocompósitos Al2O3/SiC a prensagem à quente foi realizada a uma temperatura T2 = 1600 oC. As características mecânicas obtidas mostram que os valores do nanocompósito e compósito se apresentam superiores aos valores da alumina, embora, esta superioridade provavelmente foi devida a uma melhora na densificação, devido as diferenças na realização da sinterização do compósito e nanocompósito. Estes resultados foram explicados pelo estudo, através da técnica de microscopia eletrônica de varredura. As propriedades baixas obtidas, resultam em particular da má dispersão das partículas nanométricas de SiC na matriz e da contaminação dos pós ocorrida durante a preparação, resultado da fragmentação das esferas utilizadas no moinho de bolas.
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Djeroud, Sacia. "Contribution à l’étude de la viscoélasticité de l'aluminium pur à température ambiante par mesures de variations d’atténuation ultrasonore." Lyon, INSA, 1988. http://www.theses.fr/1988ISAL0012.
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Dans ce travail nous avons réalisé des mesures de variations d'atténuation et de vitesse des ondes ultrasonores lors d'un essai de type "dip-test" mis en œuvre au voisinage de la température ambiante. Lors de cet essai, les décréments de contrainte induisent généralement une augmentation d'atténuation qui est due au désancrage des dislocation à partir des défauts ponctuels. Ce mécanisme nous a permis d'évaluer les contraintes internes athermiques ressenties par les dislocations dans leur plan de glissement : cette détermination repose sur le fait que la densité de dislocations désancrables lors d'un décrément de contrainte et la variation d'atténuation qui en résulte sont maximales lorsque la contrainte effective agissant sur les dislocations au cours du palier de contrainte qui précède le décrément est minimale. Par ailleurs, dans le domaine où le fluage initial suit une loi puissance, le premier décrément de contrainte induit une diminution "anormale" de l'atténuation. Nous présentons un modèle qui montre que cette diminution pourrait être expliquée par une rupture au début de ce décrément, de l'équilibre dynamique, entre créations et annihilations de dislocations, qui tendait à s'établir lors de ce fluage transitoire. Enfin, à partir des caractéristiques microscopiques moyennes (longueurs libres et aires d'activation apparentes) nous discutons les mécanismes contrôlant la déformation viscoplastique correspondant aux deux modes de fluage mis en évidence.
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Alhamany, Abdelilah. "Contribution à l’étude de l'effet de la répartition hétérogène des dislocations sur la plasticité cyclique de l'aluminium pur monocristallin." Lyon, INSA, 1991. http://www.theses.fr/1991ISAL0099.
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Notre travail a pour but de contribuer à la connaissance des mécanismes microscopiques qui contrôlent la plasticité cyclique de l'aluminium pur. L'étude a été menée à température ambiante sur des monocristaux d'aluminium orientés pour un glissement simple à des amplitudes de déformation comprises entre 10-4 et quelques 10-3. L'aluminium ne présente pas de véritable saturation mécanique. Nous sommes en présence d'une séquence durcissement adoucissement durcissement secondaire. L'aluminium fatigué présente en outre un effet Bauschinger marqué dont l'amplitude évolue le long de la boucle de fatigue. La déformation se localise d~s la période d'adoucissement dans Ide courts segments des bandes de glissement du système primaire que l'on peut assimiler à des bandes de glissement persistante (BGP) de l'aluminium. La microstructure est constituée de bandes de cellules allongées, réparties dans une matrice de cellules équiaxées. Les contraintes à grande distance liées aux incompatibilités de déformation résultant de la répartition hétérogène des dislocations jouent un rôle prépondérant sur la plasticité cyclique et expliquent la présence de l'effet Bauschinger. L'effet plus ou moins marqué de ces contraintes de compatibilité lié à l’établissement progressif dans les bandes d'une structure cellulaire est à l'origine du durcissement secondaire observéThis work is concerned with the study of microscopic mechanisms which control the cyclic plasticity of pure aluminium. Fatigue test are performed on single slip oriented Al crystals at room temperature, at plastic shear strain amplitudes in the range of 10-4 ta 3 to-3. Mechanical saturation is not obtained. Instead, a hardening - softening - secondary hardening sequence is found. The Bauschinger effect which appears in aluminium deformed by cyclic straining, changes all along the fatigue loop and during the fatigue test. As soon as softening appear, deformations become located in short well defined band fragments of primary system which can be described as PSB of Aluminium fatigued at room temperature. The band microstructure contains cells elongated along the primary slip direction; bands are regularly distributed in an equiaxed cell matrix. The long range internal stress necessary to ensure the compatibility of deformation between hard and soft regions corresponding to an heterogeneous distribution of dislocations controls the cyclic plasticity and can explain the observed Bauschinger effect. These long range internal stresses due to cell structure in bands lead to the observed secondary hardening
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Almeida, Camargo Nelson Heriberto. "Elaboration et caractérisation de céramiques d'alumine sol-gel pure et de nanocomposites alumine sol-gel/carbure de silicium." Lyon, INSA, 1995. http://www.theses.fr/1995ISAL0051.
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Une céramique d'alumine pure a été élaborée par procédé sol-gel en utilisant un précurseur organo-minéral. La filiation Sol --> Gel--> Xérogel -->Alumine de transition (calcination à 900°C) - Alumine alpha (calcination à T1> l000°C) -->Céramique (pressage sous charge à T2 = 1550°C) a fait l'objet d'un analyse physico-chimique et microstructurale exhaustive. L'optimisation de la température a permis d'obtenir une céramique présentant une contrainte de rupture en flexion particulièrement performante (environ 700 MPa). Puis une poudre nanométrique de SiC (d = 20-30 nm) a été incorporée (5% Vol. ) au sol avant gélification, incorporation conduisant à une stabilisation thermique de l'alumine de transition. Ce phénomène a été expliqué sur la base d'une limitation des processus diffusionnels associés à la germination-croissance de l'alumine alpha, nécessitant ainsi une températures T1 sensiblement plus élevée pour former le corindon. Tenant compte de ces observations, des échantillons de céramique nano-composite Alumine/SiC ont été préparés par pressage à chaud à différentes température T2 de 155°C à 175°C. Les caractéristiques mécaniques obtenues restent toujours inférieures à celle de la matrice d'alumine pure et la fracture est transgranulaire, conséquence de l'établissement de contraintes internes élevées au cours du refroidissement du matériau. Ces résultats ont été expliqués par l'analyses de la micro- et de la nano-structure des matériaux en utilisant les techniques de microscopie électronique. Les propriétés assez moyennes obtenues, qui résultent en particulier de la mauvaise dispersion du renfort SiC dans la matrice, ont pu être sensiblement améliorées par une opération d'attrition du xérogel composite associée à un recuit qui limite les contraintes. Mais pour obtenir des caractéristiques performantes, de nombreux autres paramètres doivent être pris en compte. Une analyse de ces paramètres est présentéeA pure alumina ceramic matrix has been made by sol-gel route, using an organo-mineral precursor. The "Sol--> Gel--> Xerogel--> Transition alumina--> Alpha Alumina (calcination at Tl> 1000°C) -->Alumina ceramic (hot-pressing at T2 >Tl)" filiation was subjected to an exhauxtive physico-chemical and microstructural analysis. The optimization of the Tl temperature has allowed to obtain a ceramic body with particularly high flexural strength (about 700 MPa). Then, a nanometric SiC powder was dispersed into the sol before gellation, processing that leads to the thermal stabilization of the transition alumina. This phenomenon was explained on the basis o a limitation of diffusionnal processes associated with the nucleation growth of alpha alumina grains, what needs'to increase the T1 temperature of formation of corundum. Taking this observation into account, nano-composite Alumina/SiC bodies have been elaborated at different T2 temperatures from 1550°C to 1750°C. But mechanical characteristics of the samples obtained are always lower than those of the pure sol-gel alumina ceramic and the fracture is transgranular in type, a consequence of internal stresses that appear during cooling the samples. These results have been explained on the basis of an exhaustive analysis of both the nano- and the microstructure, using electron microscopy. The middle-sized strengths obtained, that also result from the bad dispersion of the SiC reinforcement in the matrix, have been sensitively improved by bali milling the xerogel and annealing the hot-pressed bodies to limit the internal stresses. But the obtention of high strength bodies must take into account the role of many other parameters that are discussed
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Loh, Wei Sun. "Studies of Avalanche Breakdown Characteristics in 4H-SiC and reliability of pure aluminium wire bonds for high power and high temperature applications." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500188.
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Louet, Nicolas Fantozzi Gilbert. "Influence du dopage à la silice ou à l'oxyde de calcium sur le frittage et sur l'évolution microstructurale d'une alumine-alpha ultra pure." Villeurbanne : Doc'INSA, 2005. http://docinsa.insa-lyon.fr/these/pont.php?id=louet.
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Louet, Nicolas. "Influence du dopage à la silice ou à l'oxyde de calcium sur le frittage et sur l'évolution microstructurale d'une alumine-alpha ultra pure." Lyon, INSA, 2003. http://theses.insa-lyon.fr/publication/2003ISAL0077/these.pdf.
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L'objectif de ce travail est d'étudier l'effet de SiO2 et Ca sur le frittage et sur la microstructure d'une alumine alpha ultra pure. De faibles quantités de dopants ont été ajoutées (additions successives de 500 ppm). SiO2 retarde la densification alors que Ca provoque l'effet contraire. L'étude du frittage sous différentes atmosphères et les essais de Thermoluminescence nous ont permis de comprendre le rôle des dopants, en accord avec les équations d'électroneutralité. Les observations au MEB attestent du lien entre la présence de ces impuretés et la croissance exagérée des grains. Cette croissance anormale des grains apparaît pour des températures qui correspondent aux eutectiques des diagrammes de phase respectifs. Les observations HRTEM montrent qu'en dessous de la température eutectique, un enrichissement en dopant est détecté près des joints de grains. Au dessus de cette température, des films amorphes et du CA6 sont détectés respectivement après dopage avec SiO2 et CaThe aim of this work is to investigate the effect of SiO2 or Ca on the sintering behavior and on the microstructure of an ultrapure alpha Al2O3. Very low amounts of impurities have been added (step of 500 ppm). SiO2 addition leads to a significant decrease in shrinkage rate whereas Ca leads to the opposite. The study of the densification under different atmospheres and Thermoluminescence measurements help us to explain the role of the dopants in agreement with electroneutrality equations. SEM investigations confirm the well know correlation between doping and heterogeneous microstructures. After doping with Ca or SiO2 abnormal grain growth appears at the temperature which corresponds to the lowest eutectic giving by the phase diagram. HRTEM observations show that below the critical temperature for abnormal grain growth, dopant enrichment is observed near grain boundaries. Above this temperature, glassy phase for SiO2-doping are present at grain boundaries
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IZIDORO, JULIANA de C. "Síntese e caracterização de Zeólita pura obtida a partir de cinzas volantes de carvão." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10180.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Cordeiro, Cristiane Italiano. "AVALIAÇÃO POR ESPECTROSCOPIA DE IMPEDÂNCIA ELETROQUÍMICA DO EFEITO CORROSIVO DE BIODIESEL PURO E MISTURAS EM ALUMÍNIO." Universidade Federal do Maranhão, 2013. http://tedebc.ufma.br:8080/jspui/handle/tede/976.
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Previous issue date: 2013-06-07FUNDAÇÃO DE AMPARO À PESQUISA E AO DESENVOLVIMENTO CIENTIFICO E TECNOLÓGICO DO MARANHÃO
The use of biodiesel as fuel has presented a great potential in the world, both for its contribution to the environment as well as for being a fuel derived from renewable sources. However, this fuel is causing serious problems of corrosion metallic in materials used in diesel engines, transport systems and storage. In this sense, the present work aims, evaluating the corrosive effect of biodiesel and mixtures in aluminum by means of electrochemical techniques, as the open circuit potential and impedance electrochemical spectroscopy. For such, were used aluminum blades immersed in samples of B100 biodiesel and mixtures of B5 and B4, was also used microemulsion samples for obtaining better answers in the electrochemical trials. The surface of the metalic material was evaluated, after immersion trials, by visualization the optical microscope, in order to identify the effect caused by corrosion. The results obtained for trials showed that aluminum presented a good corrosion resistance in contact with the fuel samples, as well as in samples microemulsion.
A utilização do biodiesel como combustível tem apresentado um grande potencial no mundo inteiro, tanto pela sua contribuição ao meio ambiente como por ser um combustível derivado de fontes renováveis. Entretanto, este combustível vem ocasionando sérios problemas de corrosão metálica nos materiais usados em motores a diesel, sistemas de transporte e armazenamento. Nesse sentido, o presente trabalho tem por objetivo, avaliar o efeito corrosivo do biodiesel e misturas em alumínio por meio de técnicas eletroquímicas, como o potencial de circuito aberto e a espectroscopia de impedância eletroquímica. Para tal, foram utilizadas lâminas de alumínio imersas em amostras de biodiesel B100 e misturas B5 e B4, utilizou-se também amostras microemulsionadas para obtenção de melhores respostas nos ensaios eletroquímicos. A superfície do material metálico foi avaliada, após ensaios de imersão, por meio da visualização no microscópio ótico, como forma de identificar o efeito causado pela corrosão. Os resultados obtidos para os ensaios mostraram que o alumínio apresentou uma boa resistência à corrosão em contato com as amostras de combustível, bem como nas amostras microemulsionadas.
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PETRI, ANNA R. "Medidas do primeiro coeficiente de Townsend de ionização no isobutano puro submetido a campos elétricos uniformes." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10198.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Pillonnet, Anne. "Étude structurale et optique de guides d'onde planaires d'alumine pure et dopée (chrome et europium) élaborés par voie sol-gel et par ablation laser." Lyon 1, 2002. http://www.theses.fr/2002LYO19001.
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Des guides d'onde planaires d'alumine pure et dopée par des ions chrome et europium ont été élaborés par deux méthodes différentes : le procédé Sol-Gel et le dépôt par ablation laser (Pulsed Laser Deposition : PLD) et ce à des fins de comparaisons. La corrélation entre les paramètres expérimentaux des films, leur propriétés physico-chimiques (composition, structure cristalline) et optiques en configuration guiée (indice de réfaction, coefficient d'atténuation) a été réalisée. L'analyse résolue en temps des propriétés de fluorescence des ions dopants chrome et europium dans les films a permis d'approfondir l'étude de la structure des guides à l'échelle nanomètrique
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Ferey, Frédérique. "Thermoluminescence et frittage de l'alumine alpha ultra-pure dopée par le zirconium, le thorium, le calcium, ou le cérium." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2002. http://tel.archives-ouvertes.fr/tel-00814282.
Full textAbstract:
La thermoluminescence est une technique de caractérisation des défauts ponctuels qui apparaissent dans un solide lors de son élaboration. Les paramètres de synthèse de l'alumine alpha considérés dans cette étude sont l'atmosphère de calcination (oxydante ou réductrice) et les différents dopants : Zirconium, thorium, calcium et cérium. L'objectif de ce travail est de relier les défauts ponctuels à la réactivité de la poudre, en particulier son frittage. Les mécanismes de TL du pic dosimétrique de l'alumine alpha, situé à 200°C, ont été clarifiés : Le défaut piège est une association de 2 défauts du type Schottky (VAl-V0), et le centre de recombinaison est le Cr3+. L'effet sensibilisateur du thorium, ou du cérium sous atmosphère réductrice, est expliqué par la présence d'une large bande d'émission bleue-verte. Le chrome est l'impureté principale à l'origine du pic E' (360°C) de l'alumine alpha. Il intervient comme défaut piège et comme centre de recombinaison. Un mécanisme de transfert d'énergie entre le Cr3+ et le Ti4+ est également proposé pour expliquer l'augmentation du signal de TL du pic E' lors du dopage par un cation tétravalent. Dans le cas du dopage par le calcium, la TL a permis de révéler la présence de la phase CaAl12O19. Un phénomène d'extinction par concentration a été observé sur les alumines dopées calcium ou dopées cérium et préparées sous atmosphère réductrice. Ce phénomène est expliqué par une teneur élevée en lacunes d'oxygène (Ca) et par la présence de Ce3+. Les alumines calcinées sous atmosphère réductrice présentent une cinétique de frittage perturbée, ainsi qu'un grossissement anormal des grains pour les alumines dopées. Cette cinétique irrégulière s'explique par une diminution de la concentration en lacunes d'aluminium sous atmosphère réductrice, ce qui augmente indirectement la ségrégation du Si4+ aux joints de grains, et conduit à l'apparition d'une phase liquide à la surface des grains. Ce phénomène est amplifié lors du dopage par le calcium.
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Zavanelli, Ricardo Alexandre. "Influencia da soldagem a laser no titanio comercialmente puro e titanio-aluminio-vanadio sobre a fadiga-corrosão em diferentes meios." [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289188.
Full textAbstract:
Orientador : Guilherme Elias Pessanha HenriquesTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Aliado aos esforços cíclicos, determinados agentes à base de flúor podem atuar sobre as infra-estruturas de próteses, causando a fadiga. Assim, o propósito deste estudo foi avaliar, analisar e comparar a vida em fadiga-corrosão de amostras confeccionadas em titânio comercialmente puro e liga Ti-6AI-4V intactas e soldadas a laser, e ensaiadas em diferentes meios de armazenagem. Para cada metal, 60 amostras semelhantes a um halteres, com 2,3mm de diâmetro no segmento central, foram obtidas a partir do sistema de fundição Rematitan. Os ensaios de fadiga-corrosão foram realizados em máquina universal de ensaios (MTS - Test Star II) com carga 30% abaixo do limite de escoamento a 0,2% do deslocamento, e combinando três situações de armazenagem: sem imersão, com saliva artificial e com saliva artificial fluoretada. Após a fratura, o número de ciclos foi registrado e a superfície de fratura analisada em MEV. As amostras fraturadas foram subseqüentemente soldadas a laser, usinadas e ensaiadas novamente nas mesmas condições das amostras intactas. A análise de variância (ANOVA) e o teste de Tukey com 5% de probabilidade, indicaram redução no número de ciclos até a fratura (5674 - saliva artificial e 3948 ciclos - saliva fluoretada) quando as amostras foram ensaiadas na presença das soluções de armazenagem, com diferença estatisticamente significativa em relação às amostras ensaiadas sem os meios (16186 ciclos). O processo de soldagem a laser influenciou negativamente, diminuindo o número de ciclos até a fratura (6146 cicios), mostrando diferença estatisticamente significativa em relação às amostras intactas (11060 ciclos)
Abstract: Stress cyclic and some prophylactics agents could affect infrastructure of prosthesis causing fatigue. So, the aim of this study was to evaluate, analyze and compare the corrosion-fatigue lives of specimen obtained in commercially pure titanium and Ti-6AI-4V alloy intacted and laser welded, tested in different storage environments. For each metal, 60 dumbbell rods, 2,3mm in diameter at the central segment, were obtained and casted in Rematitan system. Corrosion-fatigue life was carried out through a universal testing machine (MTS Test Star II) with a load 30% lower than the 0,2% offset yield strength and combining tree different environments: in air at. room temperature, with synthetic saliva and with fluoride synthetic saliva. After failure, the number of cycles were recorded, and the fracture surface was examined with an SEM. The specimen were then laser welded, grounded and tested again in the same conditions of the intact specimen. ANOV A and Tukey's multiple comparison test indicated that the number of cycles decreased in wet environments (5674 - synthetic saliva and 3948 cycles - fluoride saliva), with significant differences between the specimen tested in air at room temperature (16186 cycles). The process of laser welding affected negatively the corrosion-fatigue strength (6146 cycles), reducing the number of cycles showing significant differences between the intact specimen (11060 cycles)
Doutorado
Protese Dental
Doutor em Clínica Odontológica
42
Nguyen, Hai Trung. "Transfert hydrique dans le milieu poreux réactif : Application à l’étude de séchage d’une pâte pure ettringitique au jeune âge." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI124/document.
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Les chapes autonivelantes sont souvent composées de ciment alumineux et de sulfate de calcium pour assurer une prise rapide. Le ciment alumineux est généralement à base de monocalcium aluminate (CA). Récemment, un nouveau ciment alumineux riche en mayénite (C12A7) a été conçu pour optimiser l’application des chapes par l’augmentation de la quantité d’ettringite formée. Le développement de l’hydratation au jeune âge (pendant les premières 24 heures) de ce type de produit est pourtant très peu connu. L’objectif principal de cette étude est d’évaluer l’interaction entre l’hydratation au jeune âge et le séchage naturel à travers un modèle de couplage. Ce modèle est appliqué à l’étude d’une pâte pure ettringitique composée de ciment riche en C12A7 et de plâtre alpha. Tout d’abord, un modèle cinétique d’hydratation, initialement développé en système dilué, a été proposé pour étudier l’hydratation d’une pâte pure ettringitique en condition endogène. Il permet de décrire l’évolution en fonction du temps de la porosité, de la teneur en eau, des quantités de phases (réactifs et hydrates). Un modèle de distribution de rayon de pores a été aussi proposé. Ce modèle permet d’obtenir la courbe de pression capillaire au jeune âge nécessaire pour la modélisation des transferts hydriques. Ensuite, une modélisation complète des transferts hydriques a été présentée. Elle a montré que l’hypothèse d’une pression de gaz constante conduit à une surestimation de perte de masse pour des matériaux à faible perméabilité. Pourtant, pour le cas des ciments alumineux, cette hypothèse peut être retenue pour simplifier le couplage avec le modèle cinétique d’hydratation. Enfin, une modélisation des couplages entre l’hydratation et la dessiccation a été développée. L’originalité de ce modèle porte sur l’intégration de la courbe isotherme issue du modèle de distribution poreuse dans la modélisation des transferts hydriques via une fonction Matlab. Le modèle a été capable de reproduire la cinétique de perte de masse d’un échantillon de pâte pure ettringite réactive soumis au séchage précoce. La nécessité de la prise en compte de l’évolution de température a été mise en évidence. De plus, le modèle a prévu un arrêt précoce de l’hydratation à la surface séchante après 10 heures d’hydratation. L’effet de la dessiccation atteint une profondeur de 5 mm sur un échantillon de 3 cm d’épaisseurSelf-leveling flooring compounds (SLC) are often composed of calcium aluminate cements (CAC) and calcium sulfate to ensure rapid setting. The mineral composition of calcium aluminate cements is usually designed around monocalcium aluminate (CA). Recently, a new cement with the main compound of mayenite (C12A7) has been designed to optimize the application of SLC by increasing the amount of ettringite in the hydration product. However, there is a lack of knowledge related to early-age hydration (during the first 24 hours) of this type of product. The main objective of this study is to evaluate the interaction between early-age hydration and natural drying through a coupling model. This model is applied to the study of an ettringite binder composed of cement rich in C12A7 and plaster First, a kinetic model of hydration, initially developed in a diluted system, has been proposed to study the hydration of an ettringite paste under endogenous conditions. It allows to describe the evolution as a function of time of the porosity, the water content, and the quantities of phases (reactants and hydrates). A model of pore size distribution has also been proposed. This model allows us to obtain the capillary pressure curve at early-age, which is necessary for the modeling of moisture transport. Then, a complete modeling of water transfers was presented. It has shown that the assumption of constant gas pressure leads to an overestimation of mass loss for weakly permeable materials. However, for the case of CAC, this hypothesis can be retained to simplify the coupling with the kinetic model of hydration. Finally, a modeling of the coupling between hydration and desiccation has been developed. The originality of this model concerns the integration of the isothermal curve resulting from the pore size distribution model in the modeling of water transfers via a Matlab function. The model was able to reproduce the kinetics of mass loss of a sample of ettringite binder subjected to early drying. The role of temperature was also elucidated. In addition, the model predicted an early stop of hydration on the drying surface after 10 hours of hydration. The effect of desiccation reaches a depth of 5 mm on a sample with a thickness of 3 cm
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Ruiz, Contreras Edwin Fernando. "Avaliação do desajuste marginal de coroas totais fundidas em titanio comercialmente puro e titanio-aluminio-vanadio antes e apos a eletroerosão." [s.n.], 2000. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289185.
Full textAbstract:
Orientador: Guilherme Elias Pessanha HenriquesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: O titânio e a liga titânio-alumínio-vanádio têm se tornado interessantes substitutos às ligas nobres, semi-nobres e básicas devido às características de biocompatibilidade, resistência à corrosão e propriedades mecânicas satisfatórias. Entretanto, a difícil fundição pode acarretar margens cervicais incompletas, fazendo com que o propósito deste estudo fosse: avaliar o ajuste marginal de coroas fundidas em titânio comercialmente puro e titânio-alumínio-vanádio; avaliar a efetividade da eletroerosão na redução do desajuste marginal; comparar os resultados obtidos, antes e após a eletroerosão, com os obtidos com coroas em paládio-prata. Dentes bovinos com preparos padronizados foram moldados pela técnica da dupla-mistura para obtenção de troquéis em gesso, sob os quais foram confeccionadas 45 coroas, sendo divididas em 3 grupos (paládio-prata, titânio comercialmente puro e titânio-alumínio-vanádio). O processo de eletroerosão foi usado no refinamento marginal das coroas em titânio comercialmente puro e titânio-alumínio-vanádio. O desajuste marginal foi medido em microscópio mensurador, antes e após a eletroerosão. Na análise estatística dos resultados utilizou-se os testes de Kruskal-Wallis e t-Student. Os valores médios de desajustes marginais encontrados foram: liga de paládio-prata (45,2¿mu'm); titânio comercialmente puro antes (83,9¿mu'm) e após (50,6¿mu'm) a eletroerosão; liga titânio-alumíniovanádio antes (50,8¿mu'm) e após (24,5¿mu'm) a eletroerosão. Concluiu-se que: as coroas em liga paládio-prata apresentaram-se com menor desajuste marginal logo após a fundição, sendo diferente estatisticamente somente das fundidas em titânio comercialmente puro; as coroas em titânio-alumínio-vanádio, após a eletroerosão, foram significativamente melhores que as obtidas em titânio comercialmente puro e liga de paládio-prata; a redução do desajuste marginal com a eletroerosão foi igualmente significativa em ambos os grupos
Abstract: Titanium and titanium-aluminum-vanadium alloy became interesting replacement for the existing alloys, due to their advantageous features, such as excellent biocompatibility, corrosion resistance and desirable mechanical properties. However, the cast difficult can resulting in margins of the crowns less complete. The proposition of this study was: to evaluate the marginal fit of commercially pure titanium and titanium-aluminum-vanadium alloys cast crowns; to evaluate the effectiveness of the spark erosion process in the decrease of unfitted margins; to compare the results obtained in both metais, before and after the spark erosion process, with the ones obtained in palladium-silver alloy cast crown. Double-mix impressions were taken from a standard prepared bovine teeth to obtain stone die, on the ones which were made 45 crowns, divided to 3 groups (palladium-silver, commercially pure titanium and titanium-aluminum-vanadium). The spark erosion process was used for marginal refining of the commercially pure titanium and titanium-aluminum-vanadium alloy cast crowns. The marginal unfit was measured with a microscope before and after the spark erosion processoIn the statistical analysis of the results the Kruskal-Wallis and t-Student tests were used. The mean values of marginal unfit were: to palladium-silver alloy (45,2¿mu¿m); to commercially pure titanium before (83,9¿mu¿m) and after (50,6¿mu¿m) the spark erosion process; to titaniumaluminum-vanadium before (50,8¿mu¿m) and after (24,5¿mu¿m)the spark erosion processo It was concluded: palladium-silver alloy cast crowns were statistically better than ones cast in commercially pure titanium, before the spark erosion; titanium-aluminum-vanadium alloy cast crowns were statistically better than ones cast in palladium-silver alloy and commercially pure titanium, after the spark erosion process; the decrease of the unfitted marginal of commercially pure titanium and titanium-aluminum-vanadium alloy cast crowns after the spark erosion process obtained was significant for both metais
Mestrado
Protese Dental
Mestre em Clínica Odontológica
44
Troia, Junior Manoel Gomes. "Avaliação da resistencia de união de uma porcelana de baixa fusão em combinação com o titanio comercialmente puro e liga titanio-aluminio-vanadio." [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289190.
Full textAbstract:
Orientador: Guilherme Elias Pessanha HenriquesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Embora tenha propriedades satisfatórias, o titânio apresenta problemas quanto a resistência de união em combinações com porcelanas, sendo algumas destas, susceptíveis à termociclagem. Adicionalmente, não há estudos que avaliem a resistência de união da liga Ti-6AI-4V quando combinada às porcelanas. O propósito deste estudo foi avaliar a influência de dois substratos metálicos (Ti c.p. e Ti-6AI-4V) na resistência de união a uma porcelana para titânio, mediante ensaio de flexão, além de analisar a influência de um protocolo de termociclagem sobre as combinações, e comparar os resultados com a combinação liga Pd-Ag e porcelana convencional. Para tanto, foram confeccionadas tiras metálicas medindo 25x3xO,5mm. No centro de uma das faces das tiras, foi aplicada porcelana restrita às dimensões de 8x3xlmm, obtendo-se 24 cOrPos-de-prova em Ti c.p. e 24 corpos-de-prova em Ti-6AI - 4V, combinados à porcelana Vita Titankeramik. Como grupo controle, foram confeccionados 20 corpos-de-prova em Pd-Ag combinados com porcelana Duceram. Metade dos corpos-de-prova de cada grupo foi termociclada de 4°C (:!::2°C) a 55°C (:f:2°C), sendo que a totalidade dos mesmos foi submetida a ensaio de flexão de três pontos. Os valores obtidos foram submetidos à análise das médias e comparação de variáveis significativas pelo teste de Análise de Variância (Anova) e Tukey, ao nível de 5% de probabilidade. Amostras representativas foram submetidas a Microscopia Eletrônica de Varredura, para caracterizar o tipo e a morfologia das fraturas. Os resultados mostraram que o efeito do protocolo de tennociclagem não foi significativo para todos os grupos. No tocante à resistência de união, o grupo controle Pd-Ag/Duceram obteve valores médios de 47 ,98MPa para o grupo não termociclado e 45,30MPa para o grupo tennociclado, sendo estes, cerca de 50% maiores e significativamente superiores aos apresentados pelos grupos Ti c.p./Titankeramik (24,99MPa e 23,60MPa respectivamente) e Ti-6AI-4V /Titankeramik (25,60MPa e 24,98MPa respectivamente). Tanto o grupo Ti c.p./Titankeramik como o grupo Ti-6AI-4V/Titankeramik não diferiram estatisticamente entre SI. A análise da MEV indicou fraturas predominantemente adesivas para os grupos Ti c.p. e liga Ti-6AI-4V /Titankeramik e fraturas predominantemente coesivas para a liga de Pd-Ag/Duceram
Abstract: Although the satisfactory properties, titanium alloys present weak bond strength with porcelains, being suceptible to thermocycling. In addition, there are no studies evaluating the bond strength between Ti-6AI-4V and porcelains. The purpose of this study was to evaluate the influence of diferent metallic substrats (Ti c.p. and Ti-6AI-4V) in bond strength between porcelain and titanium, by three point bending strength, to evaluate the influence of thermocycling on the samples, and to compare the results whit a Pd-Ag alloy bonded to convencional porcelain. For this purpose, mettalic ribbons measuring 25x3xO.5mm were made. In the center of one of the ribbon's faces, porcelains measuring 8x3xlmm were applied, obtaining 24 samples of Ti c.p. and 24 samples of Ti-6AI-4V, all of them bonded with Vita Titankeramik porcelain. Twenty samples of Pd-Ag bonded to Duceram porcelain were the control group. Half ofthe samples of each group was thermocycled form 4°C to 55°C, and all of them were submitted to the three point flexure test. The obtained values were submited to analysis ofthe averages and comparision of significant variables with one way analysis ofvariance (Anova) and Tukey, at the leveI of 50/0 of probability. The results showed that termocycling effect 1was not significant for all the groups. The bond strength on the control group Pd-AglDuceram obtained medi um values of 47.98Mpa for the non thermocycled group and 45.30MPa for the thermocycled group, being 50% larger and superior when compared to the Ti c.p./Titankeramik groups (24.991
Mestrado
Protese Dental
Mestre em Clínica Odontológica
45
Guilherme, Aderico Santana. "Influencia da rugosidade superficial apos polimento eletrolitico ou convencional sobre a resistencia a fadiga do titanio comercialmente puro e liga titanio aluminio vanadio." [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289189.
Full textAbstract:
Orientador : Guilherme Elias Pessanha HenriquesTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: A qualidade superficial está diretamente ligada ao desempenho em fadiga de estruturas metálicas. Heterogeneidades superficiais remanescentes do acabamento e polimento ou provocadas por agentes corrosivos afetam substancialmente a vida média das estruturas. A indefinição quanto ao correto protocolo de polimento de artefatos de titânio, além da possibilidade deste metal ser afetado pelo meio bucal fizeram com que os propósitos deste estudo fossem: avaliar a rugosidade superficial de amostras obtidas em titânio comercialmente puro (Ti c.p.) e liga de titânioalumínio-vanádio (Ti-6AI-4V), submetidas ao polimento convencional ou eletrolítico; correlacionar os resultados da rugosidade com a resistência à fadiga, mediante ensaio cíclico de flexão e comparar os resultados do ensaio mecânico das amostras na presença de saliva artificial fluoretada. Quarenta amostras para cada material, semelhantes a halteres, com 2,3 mm de diâmetro na porção central foram obtidas por fundição (Rematitan Dentaurum J.P. Winkelstroeter KG - Pforzhein - Alemanha). O polimento convencional foi executado como preconizado pelo fabricante e o eletrolítico, a partir de uma fonte elétrica de corrente contínua e imersão em solução eletrolítica contendo 5% de ácido fluorídrico, 35% de ácido nítrico e 60% de água destilada. A rugosidade superficial - Ra (em µm) - foi realizada em rugosímetro digital (SurfCorder SE 1700 - Kosaka Ltd Tóquio - Japão) e ensaio de resistência à fadiga, numa máquina de ensaios universal (MTS - Test Star 11). Os valores numéricos de rugosidade e ciclos prévios à fratura foram sujeitos à análise de variância e as médias significativas comparadas pelo teste de Tukey (p< 0,05). Verificou-se que: para ambos os materiais, o polimento eletrolítico trouxe valores de rugosidade superficial significativamente menores que o polimento convencional; independente do polimento utilizado, a rugosidade superficial da liga Ti-6AI-4V foi significativamente menor que a do Ti c.p.; não houve diferença significativa no desempenho em fadiga dos materiais avaliados ao ar livre; a liga Ti-6AI-4V não foi influenciada pela ação do meio de armazenagem enquanto que o desempenho do Ti c.p. foi significativamente menor quando solicitado sob ação do meio; e, para os valores de rugosidade obtidos, não houve correlação entre o desempenho em fadiga e a rugosidade
Abstract: Surface roughness of metallic components influences their fatigue properties. Surface heterogeneous after finishing and polishing or caused by corrosive agents affects the life of metallic structures. The lack of definition on the correct titanium polishing protocol and the possibility of a negative effect of fluoride on the titanium surfaces motivated this study, which evaluated the surface roughness of commercially pure titanium (cp Ti) and Ti-6AI-4V alloy submitted to conventional and eletrolitic polishing; the possible correlation of surface roughness and fatigue life using a fatigue strength test; and the influence fluoride environment on fatigue strength. Forty haltered-shape rods 2.3 mm in diameter were cast for each metal in Rematitan-System (Rematitan-Dentaurum J.P.Winkelstroeter KG-Germany). Conventional polishing was performed according to manufacturer' s instructions and electrolytic polishing was carried out with a continuous eletric current source and immersion in a solution containing 5% of fluoride acid, 35% of nitric acid and 60% of distilled water. Surface roughness values - Ra (/-lm) - were obtained after three measurements using a digital surface roughness measuring instrument (SurfCorder SE 1700-Kosaka Ltd - Tokyo - Japan). Fatigue strength was performed with an universal testing machine (MTS - Test Star 11). After failure, the cycles before failure were recorded and fracture surfaces were examined under scanning electron microscopy (SEM). The surface roughness values and cycles prior to failure were submitted to the analysis of variance (ANOVA) and values with significant differences were evaluated using Tukey's multiple comparison test with 5% (p<0.O5) of probability leveI. The surface roughness was significantly lower after electrolytic polishing than after conventional polishing; after polishing, the surface roughness of Ti-6AI-4V alloy was significantly lower than cp Ti; when tested in air without a storage media, there were no significant differences in fatigue strength for both materiais; the Ti-6AI-4V alloy was not influenced by storage environment, while the performance of cp Ti was significantly lower when solution was presentedo The correlation between surface roughness and fatigue performance was not valid
Doutorado
Protese Dental
Doutor em Clínica Odontológica
46
Orlianges, Jean-Christophe. "Optimisation du dépôt par ablation laser de films minces d'alumine et de carbone tétraédrique amorphe pure et dopé; propriétés des couches et intégration dans le fabrication de composants MEMS RF." Phd thesis, Université de Limoges, 2003. http://tel.archives-ouvertes.fr/tel-00006701.
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Ce travail consiste en l'optimisation des conditions de dépôt par ablation laser à température ambiante du carbone et de l'alumine. Il se divise en huit parties principales. Le premier chapitre est une présentation du contexte de l'émergence des couches de carbone et d'alumine par ablation laser. le deuxième chapitre décrit les dispositifs expérimentaux et modes opératoires mis en œuvre, qu'ils concernent l'élaboration des films aussi bien que la détermination de leurs propriétés. Les deux chapitres suivants s'intéressent à résoudre les principaux défauts de l'ablation laser à savoir : La projection de particules solides lors du dépôt (chapitre 3) L'inhomogénéité en épaisseur des couches réalisées sur sustrat fixe (chapitre 4) le cinquième chapitre est consacré à l'étude des propriétés structurelles, électriques et mécaniques des couches de ta-C en fonction des conditiond de dépôt. Ce travail s'appuie sur une étude de l'énergie des ions dans le panache plasma (spectroscopie, imagerie résolue temporellement et spectralement) et leur rôle dans la croissance des films de ta-C (analyses Raman, XPS, MET...). le sixième chapitre reprend une étude similaire à ce qui a été présenté dans le chapitre précédent en l'applicant aux couches minces d'alumine par ablation laser. Enfin le dernier chapitre est consacré à l'intégration, dans les composants MEMS RF, des films d'alumine et de ta-C déposés par ablation laser. Ce chapitre rapporte les résultats de la collaboration menée avec l'IRCOM pour réaliser des composants fonctionnels (microcommutateurs RF, filtres accordables ...) à base de couches minces déposées par ablation laser.
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HALLOPEAU, XAVIER. "Etude de l'efficacite inhibitrice d'oxoanions de type xo#y#n#- sur la corrosion du magnesium pur et d'alliages magnesium-aluminium en milieux aqueux de ph neutre ou basique." Paris 11, 1996. http://www.theses.fr/1996PA112479.
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La premiere partie du travail est consacree a l'etude des mecanismes de corrosion du magnesium pur et des alliages magnesium-aluminium en fonction du ph du milieu sulfate de sodium (6 < ph 13). Les methodes electrochimiques, stationnaires et transitoires, ont permis de definir differents domaines de ph, chacun delimitant un comportement propre du magnesium pur et de ses alliages. Le domaine i (6 < ph 10,5) est un domaine ou la vitesse de corrosion generalisee est importante. L'addition d'aluminium au magnesium modifie les mecanismes reactionnels. Le domaine ii, de ph moyennement alcalin (10,5 < ph 12), correspond a une vitesse de corrosion plus faible, et a l'apparition d'un phenomene de corrosion localisee. Le domaine iii (ph = 13), correspond a une tres faible vitesse de corrosion. La caracterisation et l'analyse des couches de surface a permis de mettre en evidence l'etroite correlation entre le ph du milieu et la stabilite des couches formees. La deuxieme partie est consacree a l'etude de l'efficacite inhibitrice d'oxoanions de type xo#y#n#- sur la corrosion du magnesium pur et d'alliages magnesium-aluminium. Les inhibiteurs etudies peuvent se grouper en deux classes en fonction du ph des solutions. Les resultats, obtenus par voie electrochimique, ont montre que parmi les inhibiteurs fonctionnant en milieu neutre, molybdate de sodium et chromate de potassium, seul l'anion chromate est efficace: il agit par adsorption sur la surface du magnesium et a tendance a former, pour les alliages, un film passivant avec l'aluminium sous polarisation anodique. Parmi les inhibiteurs fonctionnant en milieu basique, phosphate trisodique et metasilicate de sodium, seul l'anion metasilicate est efficace: il agit par formation d'un film protecteur compose de metasilicate de magnesium et/ou d'aluminium qui renforce la couche de surface. Pour des concentrations superieures a 10#-#2m, on remarque meme l'apparition d'un palier anodique de passivation
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Yao, Yuan. "Performance and mechanism on a high durable silica alumina based cementitious material composed of coal refuse and coal combustion byproducts." Scholarly Commons, 2012. https://scholarlycommons.pacific.edu/uop_etds/155.
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Coal refuse and combustion byproducts as industrial solid waste stockpiles have become great threats to the environment. Recycling is one practical solution to utilize this huge amount of solid waste through activation as substitute for ordinary Portland cement. The central goal of this dissertation is to investigate and develop a new silica-alumina based cementitious material largely using coal refuse as a constituent that will be ideal for durable construction, mine backfill, mine sealing and waste disposal stabilization applications. This new material is an environment-friendly alternative to ordinary Portland cement. The main constituents of the new material are coal refuse and other coal wastes including coal sludge and coal combustion products (CCPs). Compared with conventional cement production, successful development of this new technology could potentially save energy and reduce greenhouse gas emissions, recycle vast amount of coal wastes, and significantly reduce production cost. A systematic research has been conducted to seek for an optimal solution for enhancing pozzolanic reactivity of the relatively inert solid waste-coal refuse in order to improve the utilization efficiency and economy benefit for construction and building materials. The results show that thermal activation temperature ranging from 20°C to 950°C significantly increases the workability and pozzolanic property of the coal refuse. The optimal activation condition is between 700°C to 800°C within a period of 30 to 60 minutes. Microanalysis illustrates that the improved pozzolanic reactivity contributes to the generated amorphous materials from parts of inert aluminosilicate minerals by destroying the crystallize structure during the thermal activation. In the coal refuse, kaolinite begins to transfer into metakaol in at 550°C, the chlorite minerals disappear at 750°C, and muscovite 2M 1 gradually dehydroxylates to muscovite HT. Furthermore, this research examines the environmental acceptance and economic feasibility of this technology and found that this silica alumina-based cementitious material not only meets EPA requirements but also shows several advantages in industrial application.
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Correa, Giovani de Oliveira. "Influencia da soldagem laser e ciclos de cocção da porcelana no desajuste marginal de infra-estruturas de proteses fixas em titanio comercialmente puro e titanio-aluminio-vanadio fundidos pelas tecnicas convencional e sobre-modelo refratario." [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289589.
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Orientador: Lourenço Correr SobrinhoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
Made available in DSpace on 2018-08-04T19:03:33Z (GMT). No. of bitstreams: 1 Correa_GiovanideOliveira_D.pdf: 622152 bytes, checksum: a395604ad381cd7abfdc99e9110c1421 (MD5) Previous issue date: 2005
Resumo: A soldagem é uma alternativa para a obtenção de melhor ajuste marginal de retentores metálicos de próteses fixas de três ou mais elementos aos respectivos pilares, em detrimento da fundição tipo monobloco (peça única). No entanto, há a possibilidade de defeitos nas uniões soldadas ou distorções de todo o conjunto. Embora a adaptação não esteja assegurada, as fundições tipo monobloco são vantajosas quanto à economia de tempo, resistência e durabilidade da infra-estrutura. O propósito desse estudo foi a avaliar a soldagem laser na redução do desajuste marginal de infra-estruturas fundidas em titânio comercialmente puro e titânio-alumínio-vanádio; os efeitos do ciclo de cocção da porcelana no desajuste marginal em infra-estruturas de próteses fixas fundidas em monoblocos sobre-modelo refratário, comparando os resultados com a técnica convencional de fundição de próteses fixas. Inicialmente confeccionou-se uma matriz metálica, sendo esta moldada em silicona por adição para a obtenção dos modelos de trabalho. Sobre os modelos foram encerados os padrões simulando infra-estruturas de próteses fixas, correspondendo às fundições convencionais nas duas ligas avaliadas. Para a fundição sobre-modelo, a matriz metálica foi duplicada e modelos em revestimento Rematitan Plus foram obtidos. Sobre os modelos de revestimento foram encerados os padrões simulando as infra-estruturas protéticas, sendo o conjunto padrões/modelo refratário, incluído para a realização das fundições. As infra-estruturas fundidas foram jateadas com óxido de alumínio, ajustadas internamente e acabadas por fresas. Os desajustes marginais foram medidos em microscópio mensurador (Olympus - Japão) com aumento de 50 X. Após a aplicação dos respectivos tratamentos, as infra-estruturas foram submetidas à simulação dos ciclos de cocção (bonder; opaco; corpo e; glaze). As mensurações foram realizadas após todas as fases do estudo, os dados foram tabulados e submetidos a Análise de variância com parcela subdividida e ao teste de Tukey em nível de 5% de significância. Concluiu-se que: a soldagem a laser foi eficaz na redução dos desajustes nas infra-estruturas em ambas as ligas; a etapa bonder interferiu no desajuste nas infra-estruturas
Abstract: Soldering has been an alternative for achieving acceptable marginal fit of metallic crowns of 3-unit fixed frameworks to the respective abutments, in detriment of the single-piece casting. However, defects at the joined areas or distortions of the entire frame are frequent. Although adaptation can not be assured, single-piece casting presents advantages such as time saving, strength and strength of the framework. The purpose of this study was to evaluate: the laser-welding in the decrease of unfitted frameworks margins of commercially pure titanium and titanium-aluminum-vanadium alloy; the effects of the ceramic firing cycle over the unfitted frameworks margins using the method of single-piece casting using a refractory die, comparing the results with the conventional casting technique for fixed prosthodontics. Initially a metallic cast was prepared and duplicated using addition silicone for making working casts. For the conventional technique, the 3-unit simulated frameworks were waxed over the working casts. For the single-piece casting, the metallic cast was duplicated and investment dies were made (Rematitan Plus ¿ c.p. Ti and Ti-6Al-4V). The frameworks were waxed on the investment casts that were invested for the castings. After casting, the frameworks were air-abraded with aluminum oxide particles, adjusted and finished with the aid of wheels. The marginal fit was measured under a measurer microscope (Olympus ¿ Japan) with X50 magnification. After laser welding, frameworks were submitted to firing cycle (bonder, opaque, dentin and glaze). The marginal fit was measured after the studies¿ steps. ANOVA and Tukey¿s tests were used in the statistical analysis of the results (P<0.05). It was concluded that the laser-welding was effective in the decrease of marginal unfit of the frameworks on both alloys; the bonder application did not interfere on the marginal fit of the frameworks
Doutorado
Doutor em Materiais Dentários
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Orlianges, Jean-Christophe. "Optimisation du dépôt par ablation laser de films minces d'alumine et de carbone tétraedrique amorphe pur et dopé : propriété des couches et intégration dans la fabrication de composants MEMS RF." Limoges, 2003. http://aurore.unilim.fr/theses/nxfile/default/adf9ac52-17e8-4476-98bb-50098b522ec8/blobholder:0/2003LIMO0032.pdf.
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La première partie de ce travail est consacrée au procédé. Il y est question des principaux problèmes rencontrés lors du dépôt par ablasion laser, à savoir la projection de particules solides lors du dépôt et l'homogénéi͏̈té en épaisseur des couches réalisées sur substrat fixe. La seconde partie est consacrée à l'étude des propriétés des films minces d'alumine et de carbone tétraédrique amorphe déposés à température ambiante ainsi qu'à la réalisation de multicouches et de dopages. Enfin nous présenterons les résultats de l'intégration, dans les composants MEMS RF, des films d'alumine et de TA-C déposés par ablation laserThe fist part of this work is devoted to the pulsed laser deposition process. We propose solutions for the two main problems of PLD : the jection of micron-sized particles and the non uniformity of film thickness profile. In the second part, we study the properties of alumina and pure and doped tetrahedral amorphous carbon deposited by laser ablation under high vacuum and at room temperature. In the last part, we present the insertion of these two materials in radio frequency micro electro mechanical system