Дисертації з теми "ZrOCl2"
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Pimenta, Jean Senise. "Metalização mecânica para brasagem de uniões ZrO2/metal e ZrO2/ZrO2." reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/94180.
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No presente trabalho empregou-se a técnica de metalização mecânica na produção de um revestimento de metal ativo (Ti ou Zr) para reduzir superficialmente a zircônia e favorecer o molhamento com ligas de adição convencionais. A interface resultante foi caracterizada por técnicas de análise microestrutural. Posteriormente, avaliou-se o desempenho de juntas brasadas estanques cerâmica/metal e cerâmica/cerâmica por meio de testes de microdureza e resistência mecânica à flexão-3p. A condição de molhamento foi analisada em substratos metalizados constituídos por zircônia (ZrO2) estabilizada com ítria ou magnésia, usando-se as ligas Ag-28Cu e Au-18Ni nos respectivos ciclos térmicos. Os melhores resultados dos testes de molhamento foram selecionados para os testes de brasagem indireta em forno de alto-vácuo (<3 10-5 mbar) e metalização com Ti. Os ângulos de contato medidos em decorrência da metalização prévia com Zr foram consideravelmente elevados, afetando a qualidade do molhamento das ligas fundidas. Juntas cerâmica/metal e cerâmica/cerâmica brasadas com a liga Ag-28Cu e metalização com Ti apresentaram ótima estanqueidade nos testes de detecção de vazamento de gás hélio a temperatura ambiente. Entretanto, nas juntas ZrO2/Ti-6Al-4V brasadas com a liga Au-18Ni verificou-se uma estanqueidade insatisfatória e a presença de microtrincamento na interface cerâmica/liga de adição. Perfis de microdureza feitos através da interface em juntas estanques não revelaram alteração brusca nesta propriedade mesmo onde a zircônia mostrou um típico escurecimento após o ciclo térmico de brasagem. Interações ocorridas entre os componentes individuais da junta brasada e, em particular, na camada escura de reação adjacente ao substrato metalizado foram investigadas por técnicas de análise microestrutural e análise EDX. A resistência mecânica à flexão-3p apresentou os melhores resultados nas juntas ZrO2/Ag-28Cu/Ti-6Al-4V (metalização com Ti). A ruptura se deu na interface cerâmica/liga, onde as superfícies de fratura mostraram arrancamento severo e alguma porção de material cerâmico aderido ao par metálico da união.
In the present study, the mechanical metallization technique was used in the production of an active metal coating (Ti or Zr) for superficial reduction of zirconia ceramic and increasing wetting in it using active-metal-free filler alloys. The resultant interface was characterized by microstructural analysis techniques. Afterwards, the performance of tight ceramic/metal and ceramic/ceramic brazed joints was evaluated by microhardness and three-point flexure tests. The wetting condition was analyzed in metallized substrates composed by stabilized zirconia with yttria or magnesia, using the conventional filler alloys Ag-28Cu and Au-18Ni with respective thermal cycles. Better wetting results were selected for indirect brazing tests in a high vacuum furnace (<3 10-5 mbar) using titanium metallization. Measured contact angles as a result of zirconium metallization were considerably high, which affected the wetting quality of molten filler alloys. Reliable vacuum tight ceramic/metal and ceramic/ceramic joints were produced using Ti metallization and the Ag-28Cu filler based on helium gas leak detection test at room temperature. However, the tightness for ZrO2/Au-18Ni/Ti-6Al-4V joints with Ti metallization was not satisfactory at all including the presence of microcracking was observed at the resultant interface. Microhardness profiles made across the tight joints interface did not reveal any severe change in this mechanical property, including also where zirconia undergone a typical darkening during brazing thermal cycle. Interactions between the individual members of the brazed joint assemble and, in particular, at the dark reaction layer that was formed closely to the metallized substrate were examined by microstructural analysis techniques and energy dispersive X-ray analysis. With regard to the mechanical strength by three-point flexure test better results were obtained for ZrO2/Ag-28Cu/Ti-6Al-4V joints (titanium metallization). The rupture occurred at the ceramic/filler interface whose fracture surfaces presented severe pulling up and some portion of ceramic material remained adhered to the metallic counterpart of the brazed joint.
Dressler, Martina [Verfasser]. "Kristallisationskinetik in TiO2/ZrO2, SnO2/ZrO2 und ZrO2-haltigen LAS-Glaskeramiken mittels der Hochtemperaturröntgenbeugung / Martina Dressler." München : Verlag Dr. Hut, 2012. http://d-nb.info/102878533X/34.
Повний текст джерелаDantz, Dirk. "Eigenspannungen in mikrowellengesinterten Ni/8Y-ZrO2 und NiCr8020/8Y-ZrO2 Gradientenwerkstoffen." Berlin : Hahn-Meitner-Inst, 2000. http://opus.kobv.de/tuberlin/volltexte/2000/74/.
Повний текст джерелаSalem, Raphael Euclides Prestes. "Desenvolvimento de ZrO2/Al2O3 e ZrO2/Al2O3-NbC usando sinterização convencional e não convencional." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/74/74133/tde-26022018-094441/.
Повний текст джерелаHigh performance ceramic composites have been the subject of frequent studies in recent decades, aiming at improving mechanical properties and increasing their range of applications in technological products. This work consisted in studying the preparation, the conventional and non-conventional sintering and the mechanical properties resulting from two t-ZrO2 matrix composites: the t-ZrO2/Al2O3 system and the t-ZrO2/Al2O3-NbC system. In the t-ZrO2/Al2O3 system, the compositions of 0, 5 and 15% by volume of Al2O3 using commercial powders were studied, while in the t-ZrO2/Al2O3-NbC system, an Al2O3-NbC nanocrystalline powder obtained by high energy reactive milling, deagglomerated, leached in HCl and added in the proportion of 5% by volume to the t-ZrO2 matrix. The obtained powders were uniaxially and isostatically pressed and sintered in conventional furnace and using flash sintering (t-ZrO2/Al2O3) and spark plasma sintering (SPS) (t-ZrO2/Al2O3-NbC). Conventionally sintered t-ZrO2/Al2O3 and conventionally sintered t-ZrO2/Al2O3-NbC composites were characterized by measurements of apparent density, dilatometry, SEM, and mechanical properties: hardness, Young\'s modulus and fracture toughness. The t-ZrO2/Al2O3 composites sintered by FS were characterized by measurements of apparent density, in situ dilatometry and SEM. t-ZrO2/Al2O3-NbC nanocomposites were also characterized for wear strength by the ball-in-disc method, using Al2O3 and WC-6%Co beads as countermaterials. The results showed that the high energy reactive milling was complete and effective in obtaining nanometric powders of Al2O3-NbC, with crystallite sizes equal to 9.1 and 9.7 nm, for Al2O3 and NbC, respectively. The deagglomeration after high energy reactive milling was effective in reducing the size of agglomerates. Conventionally sintered t-ZrO2/Al2O3 and t-ZrO2/Al2O3-NbC composites and SPS-sintered t-ZrO2/Al2O3-NbC showed high densification (> 97% TD), good dispersion of the inclusions in the matrix and good mechanical properties. The t-ZrO2/Al2O3 nanocomposites sintered by FS presented an ultrafast densification (<1 min) with linear shrinkage superior to the sintered samples in conventional furnace, occurring at temperatures lower than 1000°C, with relative densities higher than 90% TD in some compositions. The t-ZrO2/Al2O3-NbC nanocomposites presented competitive properties between conventionally sintered and SPS-sintered composites with higher hardness and fracture toughness than monolithic t-ZrO2. The wear resistance of these conventionally sintered nanocomposites, however, was markedly higher than those of SPS-sintered ones. The oxidation of NbC in the composites sintered conventionally influenced negatively the properties, leading to the suggestion of a \"window\" of temperatures in which the sintering of the t-ZrO2/Al2O3-NbC nanocomposite is interesting without the degradation of the mechanical properties. The results allowed concluding that the studied materials present potential for industrial applications that require high mechanical performance and wear resistance ceramics.
Asencios, Yvan Jesús Olortiga. "Reações de reforma de biogás sobre catalisadores de NiO-MgO-ZrO2 e NiO-Y2O3-ZrO2." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-11032013-093914/.
Повний текст джерелаThe anaerobic fermentation of the organic material produces a mixture of gases called biogas. This biogas contains CH4 and CO2 as major components. These two compounds are greenhouse gases and their use are very important from the environmental and economic point of view. The present study aimed to produce synthesis gas (H2/CO), a high-value raw material for the chemical industry, from the oxidative reforming of biogas using oxygen (1.5CH4 +1.0CO2+0.25O2) over NiO-MgO-ZrO2 and NiO-Y2O3-ZrO2 catalysts. These catalysts were prepared by the one-step polymerization method. The variation content of MgO and Y2O3 in each catalyst was studied. These materials were characterized by XRD, TPR, adsorption-desorption of N2, XPS, XAS, SEM and EDX; they were evaluated in the oxidative reforming reaction of a model biogas (molar composition: 1.5 CH4/1CO2) in the presence of oxygen at 750 °C and 1atm, aiming to produce synthesis gas.
The content of MgO in the NiO/MgO/ZrO2 system was varied ranging from 0-100% (0%, 4%, 20%, 40% and 100%mol in relation to ZrO2) , the same contents were used for the Y2O3 in the NiO/Y2O3/ZrO2 system. All catalysts had 20% wt of Ni. The XRD, TPR and XPS confirmed the formation of NiO-MgO and the MgO-ZrO2 solid solutions in the NiO-MgO-ZrO2 catalysts; and NiO-Y2O3 and Y2O3-ZrO2 solid solutions in the NiO-Y2O3-ZrO2 catalysts. These solid solutions together, in the corresponding catalysts, inproved the catalytic performance, leading to high conversion rates and low carbon deposition rates. The optimum MgO content was 20mol% for the NiO/MgO/ZrO2 system and 20% and 40mol% of Y2O3 for the NiO/Y2O3/ZrO2 system. In the NiO-MgO-ZrO2 catalysts, the NiO-MgO solid solution promoted primarily the dry reforming reaction of methane (CH4 + CO2), while in the NiO-Y2O3-ZrO2 catalysts, the Y2O3-ZrO2 solid solution primarily favored the partial oxidation of methane (CH4 + 1/2O2). The Ni20MZ and Ni20YZ catalysts showed promising results for the oxidative reforming of biogas in the presence of oxygen; these catalysts being better than a commercial catalysts (Ni/Al2O3; 20%wt Ni) tested under the same reaction conditions. The H2/CO ratio in the reaction products over the best catalysts was very close to 1.0, which allows its direct use in various processes such as Fischer-Tropsch process, Syngas-to-dimethyl-ether process (STD) and in the synthesis of formaldehyde.
Marr, Robert A. (Robert Allen) 1965. "The Na2O-ZrO2-SiO2 and CaO-ZrO2-SiO2 systems : theoretical petrogenetic grids and synthesis experiments." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56671.
Повний текст джерелаThe observed replacement of armstrongite by gittinsite + quartz in the Strange Lake peralkaline complex, Canada, suggests that the preferred topology for the $ rm SiO sb2$-$ rm CaZrO sb3$-$ rm H sb2O$ system may be the one in which the calcium catapleiite-, quartz- and calciohilairite-absent invariant points are stable.
Synthesis experiments in the $ rm SiO sb2$-$ rm CaZrO sb3$-$ rm H sb2O$ system resulted in the formation of the compound $ rm{Ca sb2 ZrSi sb4 O sb{12}}$ as well as zircon, baddeleyite, xonotlite and wollastonite under various conditions, but synthesis of naturally-occurring Ca-zirconosilicates remained elusive.
Dantz, Dirk [Verfasser]. "Eigenspannungen in mikrowellengesinterten Ni/8Y-ZrO2 und NiCr8020/8Y-ZrO2 Gradientenwerkstoffen / vorgelegt von Dirk Dantz." Berlin : Hahn-Meitner-Inst, 2000. http://d-nb.info/96029242X/34.
Повний текст джерелаNova, Cássia Vanessa [UNESP]. "Síntese, caracterização e avaliação antimicrobiana de nanopartículas de ZrO2 e ZrO2:Ag por Método Hidrotermal." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/144429.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O aumento de doenças infecciosas vem perturbando as economias mundiais e a saúde pública. As bactérias que contribuem para essa preocupação são as Escherichia coli, Gram-negativa e a Staphyloccocus aureus, Gram-positiva. Essas bactérias podem provocar infecções graves, principalmente quando presentes em água, alimentos e ambientes hospitalares. Nanopartículas estão sendo desenvolvidas para o tratamento e prevenção dessas estirpes biológicas. Nanoestruturas de ZrO2 apresentam propriedades, ópticas, fungicidas e bactericidas. Quando os metais são suportados nas estruturas, como, Ag, suas propriedades bactericidas são potencializadas. Os materiais foram produzidos por síntese hidrotermal e caracterizados por DRX, UV-Vis, FTIR, MEV, TEM e TG. Para avaliar as nanopartículas sintetizadas, foram realizados testes de atividade antimicrobiana com as bactérias Escherichia coli e Staphylococcus aureus (cepas sensíveis e resistentes à meticilina). A eficiência da avaliação antimicrobiana foi mensurada por cinética de crescimento e estatística, por ensaio colorimétrico de viabilidade e MEV. Os resultados das caracterizações mostraram a metodologia de produção de nanopartículas por rota hidrotermal que foram eficientes na produção de nanomateriais cristalinos com morfologia esférica para a zircônia tetragonal, com tamanhos entre 7 e 10 nm e prata cúbica, com tamanho médio entre 40 e 50 nm. As técnicas de TG e FTIR indicaram e permitiram quantificar e identificar a presença de matéria orgânica residual do processo de síntese. Os biotestes revelaram que as nanopartículas de dióxido de zircônio com e sem prata foram eficientes na inibição das bactérias.
Nova, Cássia Vanessa. "Síntese, caracterização e avaliação antimicrobiana de nanopartículas de ZrO2 e ZrO2:Ag por Método Hidrotermal /." Bauru, 2016. http://hdl.handle.net/11449/144429.
Повний текст джерелаCo-orientador: James Venturini
Banca: Alejandra Hortencia Miranda González
Banca: Aroldo Geraldo Magdalena
Banca: Vinicius Carvalho Porto
Banca: Willian Zambuzzi
Resumo: O aumento de doenças infecciosas vem perturbando as economias mundiais e a saúde pública. As bactérias que contribuem para essa preocupação são as Escherichia coli, Gram-negativa e a Staphyloccocus aureus, Gram-positiva. Essas bactérias podem provocar infecções graves, principalmente quando presentes em água, alimentos e ambientes hospitalares. Nanopartículas estão sendo desenvolvidas para o tratamento e prevenção dessas estirpes biológicas. Nanoestruturas de ZrO2 apresentam propriedades, ópticas, fungicidas e bactericidas. Quando os metais são suportados nas estruturas, como, Ag, suas propriedades bactericidas são potencializadas. Os materiais foram produzidos por síntese hidrotermal e caracterizados por DRX, UV-Vis, FTIR, MEV, TEM e TG. Para avaliar as nanopartículas sintetizadas, foram realizados testes de atividade antimicrobiana com as bactérias Escherichia coli e Staphylococcus aureus (cepas sensíveis e resistentes à meticilina). A eficiência da avaliação antimicrobiana foi mensurada por cinética de crescimento e estatística, por ensaio colorimétrico de viabilidade e MEV. Os resultados das caracterizações mostraram a metodologia de produção de nanopartículas por rota hidrotermal que foram eficientes na produção de nanomateriais cristalinos com morfologia esférica para a zircônia tetragonal, com tamanhos entre 7 e 10 nm e prata cúbica, com tamanho médio entre 40 e 50 nm. As técnicas de TG e FTIR indicaram e permitiram quantificar e identificar a presença de matéria orgâ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The increase in infectious diseases is disrupting the world's economies and public health. The bacteria that contribute to this concern are Escherichia coli, one Gram-negative bacilli and Staphylococcus aureus, Gram-positive. These bacteria can cause serious infections, especially when present in water, food and hospital environments. Nanoparticles are being developed for the treatment and prevention of these biological strains. ZrO2 nanostructures have properties such as optical, fungicides and bactericides. When metals are supported in the compound, such as, Ag, its bactericidal properties are enhanced. The materials were produced by hydrothermal synthesis and characterized by XRD, UV-Vis, FTIR, SEM, TEM and TG. To evaluate the synthesized nanoparticles Antimicrobial activity tests were performed using Escherichia coli and strains of methicillin-resistant and methicillin-sensitive Staphylococcus aureus. Evaluation of antimicrobial activity was determined by kinetic of growth, vaibility assay and SEM. The results of the characterization showed the nanoparticles production methodology by hydrothermal route that were efficient in the production of crystalline nanomaterials with sherical morphology for tetragonal zirconia with sizes between 7 and 10 nm and cubic silver, with an average size between 40 and 50 nm. TG techniques and FTIR indicated and allowed to quantify and identify the presence of residual organic matter in the synthesis process
Doutor
Vieluf, M. "Hochauflösende Rutherford-Streuspektrometrie zur Untersuchung von ZrO2-Schichtwachstum im Anfangsstadium." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-61469.
Повний текст джерелаStrey, Nathan Fantecelle. "Tribologia de cerâmicos dissimilares no deslizamento em água. Estudos de caso : Si3N4-SiC, Si3N4-Al2O3, Si3N4-ZTA, Al2O3-SiC, ZrO2-SiC, ZrO2-Al2O3 e ZrO2-ZTA." reponame:Repositório Institucional da UFES, 2015. http://repositorio.ufes.br/handle/10/1642.
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Sob determinadas condições, o deslizamento de cerâmicos lubrificados com água apresenta ultrabaixo coeficiente de atrito (μ<0,01), o que caracteriza um estado de superlubricidade. A elevada capacidade de carga e eficiência energética destes tribossistemas, além do reduzido impacto ambiental, são características superiores aos tradicionais pares tribológicos metálicos lubrificados a óleo. Pares similares de nitreto de silício (Si3N4) ou carbeto de silício (SiC) foram amplamente estudados e são apontados como os de melhor performance tribológica, enquanto que pares similares de cerâmicos óxidos, como alumina (Al2O3) e zircônia (ZrO2), geralmente apresentam baixo desempenho (baixa capacidade de carga e alto coeficiente de atrito) em condições de lubrificação com água. A literatura é escassa no que se refere aos pares cerâmicos dissimilares deslizando em água e, também, quanto à natureza do fenômeno de superlubricidade. Neste contexto, uma investigação do comportamento tribológico de sete diferentes combinações de cerâmicos dissimilares, óxidos (Al2O3, ZrO2 e alumina tenacificada por zircônia - ZTA) e não-óxidos (Si3N4 e SiC), na configuração esfera sobre disco foi realizada com o objetivo de identificar pares de materiais e condições operacionais onde superlubricidade ocorre, assim como determinar mecanismos de desgaste e regimes de lubrificação vigentes. No estudo de lubrificação, a verificação experimental de um modelo que considera efeitos da topografia superficial e de forças interfaciais de dupla camada elétrica foi realizado. Dos sete pares estudados, cinco apresentaram superlubricidade (Si3N4-SiC, Si3N4- Al2O3, Si3N4-ZTA, Al2O3-SiC e ZrO2-SiC), sendo que para os últimos três não havia relatos na literatura. Em uma ampla faixa de cargas e velocidades, os dois outros pares (ZrO2-Al2O3 e ZrO2-ZTA) apresentaram transições entre regimes de desgaste moderado e severo, com respectivas transições no comportamento do atrito. Quanto à pressão média de contato, parâmetro que pode ser interpretado como a capacidade de carga de um mancal, o par ZrO2-SiC foi superior, com a magnitude pelo menos duas vezes maior que os demais pares. Da verificação do modelo de lubrificação, concluiu-se que todos os pares que apresentaram superlubricidade operaram em regime de lubrificação mista. De modo geral, a sustentação hidrodinâmica, auxiliada por efeitos da topografia superficial, foi importante na capacidade de carga do filme lubrificante, enquanto que forças eletrocinéticas de dupla camada elétrica foram desprezíveis. Para estes pares, mecanismos de desgaste triboquímicos propiciaram a formação de tribofilmes nas superfícies em deslizamento. A manutenção de coeficientes de atrito tão baixos, mesmo em regime de lubrificação mista, suporta a ideia de que tribofilmes são imprescindíveis para a ocorrência do fenômeno.
Under certain conditions, the sliding of ceramic materials under water lubrication shows ultra-low friction coefficient (μ<0,01), which characterizes a state of superlubricity. The high load capacity and energetic efficiency of these tribosystems, together with its reduced ambiental impact, are superior characteristics if compared to the traditional oil-lubricated metallic tribological pairs. Similar pairs of silicon nitride (Si3N4) or silicon carbide (SiC) were widely studied and are pointed as having the greatest tribological performance, while similar pairs of oxide ceramics, such as alumina (Al2O3) and zirconia (ZrO2), usually show poor performance (low load capacity and high friction coefficient) in water-lubricated conditions. Literature is scarce concerning to dissimilar ceramic pairs sliding in water and in explanations about the nature of the superlubricity phenomenon. In that context, an investigation of the tribological behavior of seven different combinations of dissimilar ceramic materials, oxide (Al2O3, ZrO2 and zirconia-toughened alumina – ZTA) and non-oxide (Si3N4 and SiC), using ballon- disc test configuration was performed with the objective of identifying pair of materials and operational conditions where superlubricity occurs as well as to determine present wear mechanisms and lubrication regimes. In the study of lubrication, an experimental verification of a model that incorporates effects from surface topography and electrical double layer forces was done. Of the seven studied pairs, five showed superlubricity (Si3N4-SiC, Si3N4- Al2O3, Si3N4-ZTA, Al2O3-SiC and ZrO2-SiC), noting that for the last three listed there were no previous reports in the literature. For a wide range of normal loads and sliding speeds, the other two pairs (ZrO2-Al2O3 and ZrO2-ZTA) showed transitions between mild and severe wear regimes, with respective transitions on frictional behavior. Regarding to mean contact pressure, a parameter that can be interpreted as the load capacity of a bearing, the pair ZrO2-SiC was superior, with the magnitude at least two times greater than the others. From the verification of the lubrication model, the conclusion was that every pair that showed superlubricity operated at a regime of mixed lubrication. In a general way, hydrodynamic pressure, assisted by effects of the surface topography, was important in determining the load capacity of the lubricating fluid film, while electrokinetic forces were negligible. For these pairs, tribochemical wear mechanisms led to the formation of tribofilms on the sliding surfaces. Maintaining ultra-low friction coefficients, even in mixed lubrication regime, support the idea that the tribofilms are vital for the occurrence of the phenomenon.
STREY, N. F. "TRIBOLOGIA de Cerâmicos Dissimilares no Deslizamento em Água estudos de Caso: Si3n4-sic, Si3n4-al2o3, Si3n4-zta, Al2o3-sic, Zro2-sic, Zro2-al2o3 e Zro2-zta." Universidade Federal do Espírito Santo, 2015. http://repositorio.ufes.br/handle/10/9803.
Повний текст джерелаSob determinadas condições, o deslizamento de cerâmicos lubrificados com água apresenta ultrabaixo coeficiente de atrito (μ<0,01), o que caracteriza um estado de superlubricidade. A elevada capacidade de carga e eficiência energética destes tribossistemas, além do reduzido impacto ambiental, são características superiores aos tradicionais pares tribológicos metálicos lubrificados a óleo. Pares similares de nitreto de silício (Si3N4) ou carbeto de silício (SiC) foram amplamente estudados e são apontados como os de melhor performance tribológica, enquanto que pares similares de cerâmicos óxidos, como alumina (Al2O3) e zircônia (ZrO2), geralmente apresentam baixo desempenho (baixa capacidade de carga e alto coeficiente de atrito) em condições de lubrificação com água. A literatura é escassa no que se refere aos pares cerâmicos dissimilares deslizando em água e, também, quanto à natureza do fenômeno de superlubricidade. Neste contexto, uma investigação do comportamento tribológico de sete diferentes combinações de cerâmicos dissimilares, óxidos (Al2O3, ZrO2 e alumina tenacificada por zircônia - ZTA) e não-óxidos (Si3N4 e SiC), na configuração esfera sobre disco foi realizada com o objetivo de identificar pares de materiais e condições operacionais onde superlubricidade ocorre, assim como determinar mecanismos de desgaste e regimes de lubrificação vigentes. No estudo de lubrificação, a verificação experimental de um modelo que considera efeitos da topografia superficial e de forças interfaciais de dupla camada elétrica foi realizado. Dos sete pares estudados, cinco apresentaram superlubricidade (Si3N4-SiC, Si3N4- Al2O3, Si3N4-ZTA, Al2O3-SiC e ZrO2-SiC), sendo que para os últimos três não havia relatos na literatura. Em uma ampla faixa de cargas e velocidades, os dois outros pares (ZrO2-Al2O3 e ZrO2-ZTA) apresentaram transições entre regimes de desgaste moderado e severo, com respectivas transições no comportamento do atrito. Quanto à pressão média de contato, parâmetro que pode ser interpretado como a capacidade de carga de um mancal, o par ZrO2-SiC foi superior, com a magnitude pelo menos duas vezes maior que os demais pares. Da verificação do modelo de lubrificação, concluiu-se que todos os pares que apresentaram superlubricidade operaram em regime de lubrificação mista. De modo geral, a sustentação hidrodinâmica, auxiliada por efeitos da topografia superficial, foi importante na capacidade de carga do filme lubrificante, enquanto que forças eletrocinéticas de dupla camada elétrica foram desprezíveis. Para estes pares, mecanismos de desgaste triboquímicos propiciaram a formação de tribofilmes nas superfícies em deslizamento. A manutenção de coeficientes de atrito tão baixos, mesmo em regime de lubrificação mista, suporta a ideia de que tribofilmes são imprescindíveis para a ocorrência do fenômeno.
Palmeira, Alexandre Alvarenga. "Estudo da sinterização de pós nanocristalinos de ZrO2 tetragonal estabilizado com Y2O3." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/97/97134/tde-02102013-104354/.
Повний текст джерелаWe studied the sintering of nanoparticles of yttria stabilized zirconia, ZrO2-Y2O3. Powders of ZrO2-Y2O3 3 mol% with nanometric sizes and specific surface area of 16.2 m2/g, were uniaxially compacted at pressures ranging between 12.3 MPa and 73.5 MPa. Such pressures, the compressed samples reached the green density between 33% and 44.3%. The compacts were sintered by dilatometry up 1.400ºC and the results indicated that the onset temperature of densification is next to 1.000ºC, regardless of the compaction pressure applied. Temperatures of 1.400ºC are required to complete the densification of the compact. Compared microparticulate powders of ZrO2-Y2O3 3 mol% (specific surface area of 7.0 m2/g) were compressed to 73.5 MPa and green density reached 44.2%. This material exhibited the beginning of the next retraction 1.200ºC, suggesting that the use of powder nanopatticulados reduced sintering temperature of 200ºC. The conventional sintering of nanoparticle powders was undertaken at temperatures between 1.400ºC and 1.250ºC, with levels between 2 and 16h. The microparticulate powders were subjected to sintering at temperatures up to 1.600ºC with the same levels. The results indicated that under all conditions, and sintering the powder used interchangeably, only tetragonal ZrO2 phase was found. Furthermore, the relative density (RD) of nanoparticles ranged from 92% (1.250ºC- 0h) and greater than 99% (above 1.350ºC-4h). Microstructural analysis indicated the presence of refined grains with average size of 0.18 ? m (DR = 92%) for nanoparticles sintered at 1.250ºC-0h, and average size of 0.95 ?m (DR = 100%, 1.400ºC -16h). The powders were micron average grain size of 0.39 ?m (DR = 98.8%) to the sintered ceramic 1.530ºC-0h and the average grain size of 1.84 ?m (DR = 100%) of sintered ceramics the 1.600 ºC-0h. The grain growth exponents calculated were the order of 2.8 and 2.3 for nanoparticles and microparticles, respectively, and indicating that the mechanism of grain boundary diffusion was predominant in the studied materials. The values of activation energy for the grain growth were calculated 141.3 kJ/mol and 244.7 kJ/mol, respectively indicating that the powder micrometric require more energy to promote grain growth. The results are discussed in terms of the associated phenomena of densification and grain growth in the particle size used.
Mucelini, Johnatan. "Estudo ab initio da adsorção de átomos de zircônio sobre superfícies de óxido de cério: Zrn/CeO2(111)." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-23102018-161515/.
Повний текст джерелаCerium oxides (CeOx, 3/2≤ x ≤ 2) based catalysts are employed in several reactions with high economic interest, such as the reaction in three-way-catalysts. It is well know that is possible to improve the ceria catalytic properties, by mixing with zirconium oxide and adding metallic particles over the material surface. Meanwhile, the deposition of Zr atoms over CeO2(111) is little explored although it has already been used for synthesis Ag nanoparticles of controlled size. One of the particularities of the Zr/CeO2(111) systems is to form islands of height between 1,5 and 3,0 Å on the surface of the ceria, which are suggested in the literature to be Zr-O and O-Zr-O layers. However, the nature and magnitudes of interactions between Zr and CeO2 surface are little know, as well as the CeO2 modifications induced by Zr and the mechanisms for Zr oxidation and ZrO2 formation over the surface. Aiming to understand the Zr-CeO2(111) interactions and the ZrO2 formation over the CeO2(111), this mastering project perform a theoretical study of n (1 ≤ n ≤ 4) Zr adatoms absorption over CeO2(111), and the ZrO2 formation over CeO2(111). The charge analysis indicated charge transfer from Zr adatons to the surface together with change in species oxidation state. The Zr oxidize to Zr4+ and interact with surface O2- , where four Ce4+ cations reduce to Ce3+. Energetic analysis pointed out that the process is very stabilizing, more than 10 eV per Zr adatom. With the increase of quantity n of Zr adatoms over the surface, it is observer 4 × n Ce4+ reductions and O2- migrations from inside surface to close the Zr4+, forming ZrO2 aggregates over the surface. The O migration occurs because of two reasons, the O2- interaction with Zr4+ in the agregate is more stabilizer than the interaction of O2- with Ce3+ inside the surface, and the O migration decrease the strain produced bue to the radius of Ce3+ being greater than the Ce4+ radius. In addition, was found a stability trend for Zr4+ to migrate to inside surface Ce sites, due of the more Zr-O coordinations and release of the strain induced by Ce3+.
Hrubý, Jan. "Studium vývoje mikrostruktury pokročilých keramických materiálů v poslední fázi slinování." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231433.
Повний текст джерелаKratschmer, Tim. "Flammgespritzte Schichten im System Al2O3-TiO2-ZrO2." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2011. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-63845.
Повний текст джерелаMaia, Thaísa Aparecida. "Desenvolvimento de catalisadores de cobalto suportados em matrizes de Al2O3,CeO2, e ZrO2 para produção de hidrogênio a partir da reforma a vapor e oxidativa do etanol." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-14092007-110208/.
Повний текст джерелаCobalt supported in yAl2O3, CeO2, 20%CeO2-yAl2O3 and CexZr1-xO2 (0<= x <= 1) solid solution, were prepared by impregnation and applied in steam and oxidative reforming of ethanol. In the preparation of the catalysts was used 20wt.% of cobalt with yAl2O3, CeO2 and 20%CeO2-yAl2O3 supports and 10wt.% with CexZr1-xO2 supports. The solids were characterized by X-Ray Dispersive Spectroscopy; Temperature Programmed of Reduction with H2 (TPR- H2); X-Ray Diffraction (XRD); Nitrogen Adsorption by B.E.T. method; Ultraviolet and Visible Spectroscopy. The ethanol steam reforming was carried out at 400, 500 and 600oC with molar rates H2O/Ethanol= 3/1 and 4/1. The ethanol oxidative reforming was carried out at 500 °C with molar rates H2O/Ethanol/O2 = 3/1/0.16 e 3/1/0.20. XRD and TPR-H2 results showed the formation of Co3O4 phase for all catalysts. For the catalysts supported in y-Al2O3 and 20%CeO2-y-Al2O3 was still observed the formation of the CoO-Al2O3 phase. In the ethanol steam reforming the higher conversion was obtained at 600°C and the best H2 selectivity was observed with the H2O/Etanol=3/1 molar ratio. The higher CO2/CO ratio was observed at 500oC with Co/Ce0,4Zr0,6O2 catalyst. Already, the addition of oxygen caused a decrease in the carbon deposition.
Andrianainarivelo, Mahandrimanana. "Homogénéité d'oxydes mixtes SiO2-ZrO2, SiO2-TiO2, TiO2-ZrO2, Al2O3-TiO2 et Al2O3-SiO2 préparés par sol-gel non hydrolytiques." Montpellier 2, 1996. http://www.theses.fr/1996MON20077.
Повний текст джерелаHagen, Volker. "Die selektive Hydrierung von Carbonsäureestern mit ZrO2-Katalysatoren." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=960162992.
Повний текст джерелаMöller, Andreas. "Modellierung der Dispergierbarkeit nanokristalliner Al2O3- und ZrO2-Pulver." [S.l. : s.n.], 2000. http://elib.tu-darmstadt.de/diss/000067/versfin.pdf.
Повний текст джерелаMaciel, Sara Alves. "Preparação e cracterização de compósitos de CoFe2O4/ZrO2." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/5738.
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In this work, structural, morphological and magnetic properties of cobalt ferrite/zirconium oxide composites prepared via mechanical mixing of the powders were evaluated. Cobalt ferrite powders were obtained by coprecipitation, and some synthesis parameters were optimized, such as the speed of stirring , the concentration of base and metal solutions, in order to obtain stoichiometric ferrites (Fe3+/Co2+ = 2: 1) or near to it. Zirconium oxide powders were synthesized via sol-gel. The composites were analyzed by Atomic Absorption, Field Emission Scanning Electron Microscopy and Spectroscopy Dispersive Energy, Diffraction of X-rays, Infrared Spectroscopy and Vibranting Sample Magnetometry. It was observed the migration of cations between the ferrite and zirconia structures as a result of high diffusion between phases due to heat treatment. The analysis by Field Emission Scanning Electron Microscopy and Spectroscopy Dispersive Energy showed the different microstructures of aggregates present in the composites and the average diameter of the grains. The insertion of a magnetic phase on a non-magnetic matrix caused an increase in the saturation magnetization and the remanent magnetization, and decrease in coercivity as the cobalt ferrite content increases.
Neste trabalho, foram avaliadas propriedades estruturais, morfológicas e magnéticas de compósitos de ferrita de cobalto/óxido de zircônio, preparados via mistura mecânica dos pós. Os pós de ferrita de cobalto foram obtidos pelo método da coprecipitação, tendo seus parâmetros de síntese otimizados, tais como velocidade de agitação, concentração das soluções de base e dos metais, a fim de se obter ferritas estequiométricas (Fe3+/Co2+ = 2:1) ou próximas disso. Os pós de óxido de zircônio foram sintetizados via sol-gel. Os compósitos foram analisados por Absorção Atômica, Microscopia Eletrônica de Varredura com Emissão de Campo e Espectroscopia por Energia Dispersiva, Difratometria de Raios X, Espectroscopia na Região do Infravermelho e por Magnetometria de Amostra Vibrante. Foi observada a migração de cátions entre as estruturas da ferrita e da zircônia como consequência da alta difusão entre as fases devido ao tratamento térmico. A análise por Microscopia Eletrônica de Varredura com Emissão de Campo e Espectroscopia por Energia Dispersiva permitiu verificar as diferentes microestruturas dos agregados presentes nos compósitos e o diâmetro médio dos grãos. A inserção de uma fase magnética em uma matriz não magnética provocou aumento na magnetização de saturação e na magnetização remanescente, além de uma diminuição na coercividade à medida que o teor de ferrita de cobalto aumenta.
Pereira, Altair Soria. "Estabilidade de fases de ZrO2 sob altas pressões." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1995. http://hdl.handle.net/10183/31454.
Повний текст джерелаIn this work the pressure driven monoclinic/orthorhombic-I phase transition in ZrO2 was used to study the problem of martensitic nucleation in that material, mainly the role played by defects in the nucleation process. The main characteristics of the monoclinic/orthorhombic-I transformation were reviewed and its martensitic nature was established. The choice of a pressure driven transition was taken in advantage to use the temperature as an independent way to change the state of defects of samples in the monoclinic phase (stable at room conditions). The effect of treatments at the temperatures of 120°C, 300°C, and 500°C, during 24h in water, on the phase stability of a nanometric powder (particle size < 30 nm) was investigated. This powder was submitted to pressures up to 12 GPa, using a diamond anvil cell, and the transformed fraction from the monoclinic to the orthorhombic- I phase was monitored by in situ X-ray diffraction. A sample treated at 300°C/24h in vacuum, was also studied to investigate a possible environment influence. The behavior of the vacuum treated sample was almost the same as a non-treated sample, but the powder treated in water needed higher pressures to have the same transformed fraction. The pressure behavior of the transformed fraction was properly described by the Statistical Heterogeneous Nucleation Model. In order to do that, this model was adapted to the case of pressure driven martensitic transformations and the isothermal equations of state of both the phases were determined. The results obtained in the high pressure experiments were taken as a consequence of a change in the state of surface defects promoted by the treatments in water. This is in agreement with results of transmission electron mycroscopy of the samples. The existence of an intrinsic nucleation regime in nanometric particles points for a non-classic nucleation mechanism in ZrO2. This is confirmed by the finding of a relaxation effect in the monoclinic—wrthorhombic-I transition pressure of single crystals kept at room temperature. The role of the environment in the change of the ZrO2 properties was also confirmed by the detection of indentation creep in single crystals kept in wetted environments. All these environment effects seem to be related to some stress relaxation process associated to the rupture of Zr-O bonds by dissociative reactions with H2O.
Pereira, Altair Soria. "Estudo de nucleação martensitica em ZrO2 sob pressão." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1987. http://hdl.handle.net/10183/135440.
Повний текст джерелаCheah, Wei Li. "Theory and simulation of ZrO2/SrTiO3 multilayer structures." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/10744.
Повний текст джерелаGambe, Jess. "Non-hydrolytic synthesis and structure of ZrO2 nanoparticles." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0011/document.
Повний текст джерелаThis work deals with the synthesis and the structural characterization of zirconium oxide nanoparticles (ZrO2) as well as their size/structure relationships. We elaborated nanoparticles with a size inferior to 5 nm and a narrow size distribution using a non-hydrolytic solvothermal sol-gel route. Classical X-ray diffraction was used to evaluate the crystallite size via Rietveld refinement and X-ray total scattering to extract the pair distribution functions (PDF) of the samples for structural analysis.We succeeded in synthesizing crystalline nanoparticles of ZrO2 with a size of about 3 nm and quasi mono-dispersed. We showed that an adjusted addition of sodium hydroxide into the reaction mixture was pertinent to obtain a well crystallized and single-phase nanoparticles exhibiting an average monoclinic or tetragonal structure in benzaldehyde or in benzyl alcohol, respectively. Finally, the dilution of benzyl alcohol by anisole, an inert solvent, lead to the fine tuning of average crystallite size of the nanoparticles from 3.2 nm to 2 nm according to the TEM investigation.Those three major samples prepared in alkalinized benzaldehyde, benzyl alcohol, or anisole were subjected to complete structural analysis. According to their PDF analysis, these three samples offer an insight to the understanding of structural properties of such small particles.The experimental PDF of the benzaldehyde-prepared sample coincide with the refined PDF of a monoclinic structural model. However, the experimental PDF of the benzyl alcohol-prepared sample does not conform to any of the known polymorphs of ZrO2 having a fluorite-derived structure but rather it has an average tetragonal structure and a monoclinic distortion at the short-range order. Lastly, the experimental PDF of the anisole-prepared sample has large structural distortion at the medium-range order but has monoclinic structural features at the short-range order. We then subjected the anisole-prepared sample by thermally assisted ageing (3 to 24 days) and addition of varied amounts ex-situ water (0.3 to 5% volume content). We observed that the nanoparticles evolve from a phase containing high disorder (3 days) to a state of higher structural order (24 days) that fits with the average tetragonal structure while maintaining a monoclinic distortion at the short-range order. Similarly, the addition of ex-situ water onto the reaction mixture promoted a faster crystallization and promotes the onset of peaks that aligns with the monoclinic structure. However, the formation of monoclinic phases was inhibited by the presence of sodium hydroxide but limited to about 2% volume water content and higher than this amount lead to the formation of large particles with monoclinic structure
Sláma, Martin. "Studium přípravy a vlastností biokeramických kompozitů na bázi Ca-fosfátů a ZrO2." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231718.
Повний текст джерелаŽaludek, Jakub. "Příprava dopovaných bezolovnatých pieozokeramik pomocí nekonvenčních slinovacích metod." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-442601.
Повний текст джерелаFinsel, Maik [Verfasser], and Tobias [Akademischer Betreuer] Vossmeyer. "Synthesis of ZrO2/YSZ-Al2O3 composite and ZrO2/YSZSiO2 coreshell microparticles for high-temperature photonic applications / Maik Finsel ; Betreuer: Tobias Vossmeyer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2019. http://d-nb.info/1197801510/34.
Повний текст джерелаSilva, Jo?o Moreno Vilas Boas de Souza. "Metaliza??o mec?nica de ZrO2 com Ti para brasagem ZrO2/A?o com ligas de adi??o sem metal ativo." Universidade Federal do Rio Grande do Norte, 2011. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15581.
Повний текст джерелаMetal/ceramic interfaces using zirconia have dominated the industrial applications in the last decade, due to the high mechanical strength and fracture toughness of zirconia, especially at temperatures below 300 ?C. Also noteworthy is the good ionic conductivity in high temperatures of this component. In this work joining between ZrO2 Y-TZP and ZrO2 Mg-PSZ with austenitic stainless steel was studied. These joints were brazed at high-vacuum after mechanical metallization with Ti using filler alloys composed by Ag-Cu and Ag-Cu-Ni. The influence of the metallization, and the affinity between the different groups (ceramic / filler alloys) was evaluated, in order to achieve strong metal/ceramic joints. Evaluation of joints and interfaces, also the characterization of base materials was implemented using various techniques, such as: x-ray diffraction, leak test, three-point flexural test and scanning electron microscopy with chemical analysis. The microstructural analysis revealed physical and chemical bonds in the metal/ceramic interfaces, providing superior leak proof joints and stress cracking, in order to a good joint in all brazed samples. Precipitation zones and reaction layers with eutetic characteristics were observed between the steel and the filler metal
As interfaces metal/cer?micas utilizando zirc?nia t?m dominado as aplica??es industriais na ?ltima d?cada, em virtude da alta resist?ncia mec?nica e tenacidade ? fratura da zirc?nia, especialmente em temperaturas abaixo de 300 ?C. Destaca-se tamb?m a boa condutividade i?nica em temperaturas elevadas deste componente. No presente trabalho, estudou-se as uni?es entre ZrO2 Y-TZP e ZrO2 Mg-PSZ com o a?o inox austen?tico 304. Estas jun??es foram produzidas por brasagem a alto-v?cuo ap?s a metaliza??o mec?nica com Ti utilizandose ligas de adi??o compostas por Ag-Cu e Ag-Cu-Ni. Avaliou-se a influ?ncia da metaliza??o, bem como a afinidade entre os diversos grupos (cer?mica / liga de adi??o) com o intuito de se conseguir a melhor uni?o metal/cer?mica. A avalia??o das uni?es e interfaces, bem como a caracteriza??o dos materiais de base foi feita com recurso de diversas t?cnicas, tais como: difra??o de raios-x, ensaios de estanqueidade, flex?o em 3- pontos e microscopia eletr?nica de varredura com microan?lise por espectroscopia de energia dispersiva de raios-x. A an?lise microestrutural revelou liga??es f?sicas e qu?micas na interface metal/cer?mica, proporcionando boa estanqueidade e tens?o de ruptura e, consequentemente, uma boa uni?o em todas as amostras brasadas. Foram observadas zonas de precipita??o e camadas de rea??o com caracter?sticas eut?ticas entre o a?o e o metal de adi??o
Cangani, Maxwell Pereira. "Caracterização microestrutural de ZrO2 estabilizada com Y2O3 sinterizada a partir de pós nanocristalinos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/97/97134/tde-22082013-172245/.
Повний текст джерелаCeramic materials obtained from nanocrystalline powders enable the obtaining of excellent properties after sintering, due to the possibility of reducing the final sintering temperature with consequent microstructural refinement and excellent densification. In this context, tetragonal zirconia (ZrO2 (t)) has an important role, since their intrinsic characteristics, such as the martensitic transformation (ZrO2 (t-m)), allow the development of excellent properties, highlighting the high tenacity to fracture and resistance to bending, making it a differentiated material aiming noble applications where mechanical properties and reliability are prerequirements. In order to optimize these applications, it is necessary to know the correlations between the mechanical properties and microstructure. Thus, it is extremely important to promote the microstructural disclosure of these materials, in a standardized manner and with statistical representativeness, which requires care with the ceramographic preparation techniques. This work aims to microstructurally characterize ceramics based on nanometric ZrO2(Y2O3), looking for the study of the effects of the sintering temperature and time on the graingrowth kinetics. It was defined a route for ceramographic preparation and analysis proposing a sequence of sandpapers and polishing cloths, as well as loads and times at each stage. The samples were thermally etched and micrographs were obtained. The micrographs were processed through routines of digital image analysis, aiming the definition of standards for the determination of microstructural parameters of interest, such as distribution of grain sizes, density of grains per unit of area, aspect ration, and others. It was studied the effects of the sintering conditions (final temperature and time of isotherm) on the grain growth.
Badenes, March Jose Antonio. "Estudio de los sistemas Pr-ZrSiO4 y Pr-ZrO2." Doctoral thesis, Universitat Jaume I, 2000. http://hdl.handle.net/10803/10544.
Повний текст джерелаLos sistemas pigmentantes estudiados son el amarillo de Pr-ZrSiO4, el sistema Pr-ZrO2 y el sistema Pr-(Ca-ZrO2).
El pigmento amarillo de Pr-ZrSiO4 se estudia el mecanismo de síntesis de dicho pigmento mediante la utilización de métodos de síntesis no convencionales, haciendo énfasis en los procedimientos sol-gel.
En el sistema Pr-ZrO2 y Pr-(Ca-ZrO2) se pretende optimizar el pigmento amarillo con dicha red huésped en función de los precursores, métodos y polimorfo de circona estabilizado.
El praseodimio no estabiliza a temperatura ambiente la circona cúbica/tetragonal.
La circona cúbica estabilizada con óxido de calcio y dopada con praseodimio presenta una coloración amarilla, en la que el praseodimio sustituyendo a un ion estructural: formación de una disolución sólida.
En la segunda parte de la tesis se estudia el efecto del praseodimio sobre la estabilización, reactividad y sinterizabilidad de circonas tetragonales y cúbicas estabilizadas en función del método de síntesis: cerámica, coloide, resina de citratos y gel polimérico.
En el sistema Pr-(Ca-ZrO2) se siguen dos tratamientos: estabilización-sinterización simultánea y estabilización-sinterización sucesiva. Los resultados indican que para obtener buenos densificados y un adecuado control composicional los mejores polvos son los del tipo citrato o coloide tratados por el procedimiento de estabilización sinterización simultánea.
En función de lo comentado anteriormente se compararon diferentes sistemas estabilizantes (Ca, Y, Mg) cuando son tratados por el procedimiento simultáneo.
Por último, dichos materiales son caracterizados desde el punto de vista mecánico, microestructural y de propiedades eléctricas.
Grzebielucka, Edson Cezar. "Obtenção e sinterização de nanopartículas de ZrO2-4,5%Y2O3." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2009. http://tede2.uepg.br/jspui/handle/prefix/1394.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
The powders synthesis of yttria-stabilized zirconia by chemical methods has enabled the reduction in particle size for the submicrometer-sized scale. This reduction is to improve the electrical and mechanical responses of electrolyte fuel cells. Contributing in this research, this work was to study the effects of temperature elimination of organic phases, to obtain powder of yttria stabilized zirconia, and the effect of time and sintering temperature on grain size of sintered bodies. The powders were obtained by two chemical routes: Pechini and PEG / AF, using 4.5 mol% of Y2O3 as a dopant. The properties of powders were made by X-ray Diffraction, Scanning Electron Microscopy and Infrared Spectroscopy and the sintered bodies were characterized by X-ray diffraction, scanning electron microscopy and density. It was observed that the coordination of metal ions with the polymer occurs through different ways, depending on the process used to obtain the post. The final microstructure has a greater influence than the sintering of treatments for removal of organics. The method of production of powders, temperature and calcination time change the size of the crystallites formed, and the largest variation in size occurs when increasing the calcination temperature. The final size of the grains obtained after sintering was about 1μm not influenced by the method or by the firing conditions for obtaining the post. Crystallite size obtained by Scherrer equation reported values between 5 and 8nm, and that the crystallite size tends to increase with time and temperature of heat treatment.
A síntese de pós de zircônia estabilizada com ítria por métodos químicos tem possibilitado a redução nos tamanhos de partículas para a escala submicrométrica. Esta redução visa melhorar as respostas elétricas e mecânicas dos eletrólitos de células a combustível. Contribuindo nesta linha de pesquisa, este trabalho teve como objetivo estudar os efeitos das temperaturas de eliminação das fases orgânicas, na obtenção de pós de zircônia estabilizada com ítria, e o efeito do tempo e temperatura de sinterização no tamanho de grão dos corpos sinterizados. Os pós foram obtidos por duas rotas químicas: Pechini e PEG/AF, utilizando 4,5% em mol de Y2O3 como dopante. As caracterizações dos pós foram feitas por Difração de raios X, Microscopia Eletrônica de Varredura e Espectroscopia no infravermelho e os corpos sinterizados foram caracterizados por Difração de raios X, Microscopia Eletrônica Varredura e Densidade Aparente. Observou-se que a coordenação dos íons metálicos com o meio polimérico ocorre de maneiras diferentes, dependendo do processo utilizado para a obtenção dos pós. A microestrutura final sofreu uma maior influência da sinterização do que dos tratamentos para eliminação dos orgânicos. O método de obtenção dos pós, a temperatura e o tempo de calcinação alteram o tamanho do cristalito formado, sendo que a maior variação de tamanho ocorre quando se aumenta a temperatura de calcinação. O tamanho final dos grãos após sinterização obtidos foi da ordem de 1μm não sendo influenciado pelo método ou pelas condições de calcinação para a obtenção dos pós. Os tamanhos de cristalitos obtidos através da equação de Scherrer reportaram valores entre 5 e 8nm, e que o tamanho de cristalito tende a aumentar com o tempo e temperatura de tratamento térmico.
Silva, P. D. G. "Síntese e caracterização do core-shell ZrO2:Y3+@TiO2." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/6453.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Since the early 90's researchers have investigated the combination of nanocomposites comprised of multilayers, which have better efficiency than their corresponding individual particles, may present in certain cases, new properties. The resulting structure is called a core-shell. In this study, were synthesized ZrO2:Y 3+ coated with TiO2, obtaining nanocomposites ZrO2:Y 3+ @TiO2 with a thickness of 10, 20 and 50% shell. The photoluminescent property (FL) of the nanocomposites was studied. Such interest is due to the fact that the order/disorder structural at the interface of the core-shell type systems may be possible recombination processes responsible for the photoluminescence emission of these materials. Nanoparticles of the core and the shell were obtained by the Method of Polymeric Precursors. The samples were characterized by X-ray diffraction (XRD) to identify the formation of the nanocomposite and evaluate the structural order in the synthesized materials. The core was obtained with tetragonal structure and the shell with anatase structure. From the diffractograms have been carried out calculations of the crystallite size and lattice parameters. The characterization by Transmission Electron Microscopy (TEM), it was not possible to differentiate the core of the shell by the images, since both are structurally ordered, requiring analysis by Energy Dispersive X-ray (EDX), which was verified the presence of Zr and Ti elements that comprise the core-shell nanocomposite. The FL emission results were explained as a function of the shell thickness, as well as the effect of calcination temperature on the order-disorder structural material. To evaluate the performance of the FL issuing nanocomposites were calculated chromaticity coordinates, based on the FL emission spectra.
Desde o início da década de 90 pesquisadores vêm investigando a combinação de nanocompósitos constituídos por multicamadas, os quais apresentam melhor eficiência do que suas partículas individuais correspondentes, podendo apresentar em alguns casos, novas propriedades. A estrutura obtida é denominada core shell. No presente trabalho, foram sintetizados ZrO2:Y 3+ recobertos com TiO2, obtendo nanocompósitos ZrO2:Y 3+ @TiO2 com espessura de 10, 20 e 50% de shell. Foi estudada a propriedade fotoluminescente (FL) dos nanocompósitos. Tal interesse deve-se ao fato de que a ordem/desordem estrutural na interface dos sistemas do tipo core-shell pode ser possibilitar processos de recombinação responsáveis pela emissão fotoluminescente destes materiais. As nanopartículas do core e do shell foram obtidos pelo Método dos Precursores Poliméricos. As amostras foram caracterizadas por difração de Raios X (DRX) a fim de se identificar a formação do nanocompósito e avaliar a ordem estrutural nos materiais sintetizados. O core foi obtido com estrutura tetragonal e o shell com estrutura anatase. A partir dos difratogramas foram realizados cálculos do tamanho de cristalito e parâmetros de rede. Na caracterização por Microscopia Eletrônica de Transmissão (MET), não foi possível diferenciar o core do shell pelas imagens, uma vez que ambos encontram-se estruturalmente ordenados, sendo necessária a análise por Energia Dispersiva de Raios X (EDX), na qual verificou-se a presença dos elementos Zr e Ti que compõem o nanocompósito core-shell. Os resultados de emissão FL foram explicados em função da espessura do shell, bem como pelo efeito da temperatura de calcinação na ordem-desordem estrutural do material. Para avaliar o desempenho da emissão FL dos nanocompósitos foram calculadas as coordenadas de cromaticidade, baseado nos espectros de emissão FL.
Justo, Luciene Fernandes. "Desenvolvimento de conjugados cerâmicos no sistema A12O3-ZrO2-CeO2." Instituto Tecnológico de Aeronáutica, 1991. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=1828.
Повний текст джерелаRhouta, Benaïssa. "Caractérisation microstructurale de barrières thermiques NiCoCrAIY-ZrO2 partiellement stabilisée." Toulouse, INPT, 1991. http://www.theses.fr/1991INPT035G.
Повний текст джерелаCeballos, Sanchez Oscar. "Stabilité thermique de structures de type TiN/ZrO2/InGaAs." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY027/document.
Повний текст джерелаIII-V compound semiconductors, in particular InGaAs, are considered attractivealternative channel materials to replace Si in complementary metal-oxidesemiconductor(MOS) devices. Its high mobility and tunable band gap, requirementsfor high performance device design, have placed InGaAs as a promising candidate.However, the interfacial thermal stability and chemistry of high-k dielectrics on InGaAsis far more complex than those on Si. While most studies are focused on variouspassivation methods, such as the growth of interfacial passivation layers (Si, Ge, andSi/Ge) and/or chemical treatments to improve the quality of high-k/InGaAs interface,phenomena such as the out-diffusion of atomic species from the substrate as aconsequence of the thermal treatments have not been carefully studied. The thermaltreatments, which are related with integration processes of source and drain (S/D),lead to structural changes that degrade the electrical performance of the MOS device.A proper characterization of the structural alterations associated with the out-diffusionof elements from the substrate is important for understanding failure mechanisms. Inthis work it is presented an analysis of the structure and thermal stability ofTiN/ZrO2/InGaAs stacks by angle-resolved x-ray photoelectron spectroscopy (ARXPS).Through a non-destructive analysis method, it was possible to observe subtle effectssuch as the diffusion of substrate atomic species through the dielectric layer as aconsequence of thermal annealing. The knowledge of the film structure allowed forassessing the In and Ga depth profiles by means of the scenarios-method. For the asdeposited sample, In-O and Ga-O are located at the oxide-semiconductor interface. Byassuming different scenarios for their distribution, it was quantitatively shown thatannealing causes the diffusion of In and Ga up to the TiO2 layer. For the sampleannealed at 500 °C, only the diffusion of indium was clearly observed, while for thesample annealed at 700 °C the diffusion of both In and Ga to the TiO2 layer wasevident. The quantitative analysis showed smaller diffusion of gallium (~ 0.12 ML) thanof indium (~ 0.26 ML) at 700 °C/10 s. Since the quantification was done at differenttemperatures, it was possible to obtain an approximate value of the activation energyfor the diffusion of indium through zirconia. The value resulted to be very similar topreviously reported values for indium diffusion through alumina and through hafnia.~ vi ~Complementary techniques as high resolution transmission electron microscopy (HRTEM),energy dispersive x-ray spectroscopy (EDX) and time of flight secondary ion massspectrometry (TOF-SIMS) were used to complement the results obtained with ARXPS.Specially, TOF-SIMS highlighted the phenomenon of diffusion of the substrate atomicspecies to the surface
Compuestos semiconductores III-V, en particular InxGa1-xAs, son consideradosmateriales atractivos para reemplazar el silicio en estructuras metal-oxidosemiconductor(MOS). Su alta movilidad y flexible ancho de banda, requisitos para eldiseño de dispositivos de alto rendimiento, han colocado al InxGa1-xAs como uncandidato prometedor. Sin embargo, la estabilidad térmica en la interfazdieléctrico/InxGa1-xAs es mucho más compleja que aquella formada en la estructuraSiO2/Si. Mientras que la mayoría de los estudios se centran en diversos métodos depasivación tales como el crecimiento de las capas intermedias (Si, Ge y Si/Ge) y/otratamientos químicos para mejorar la calidad de la interfaz, fenómenos como ladifusión de las especies atómicas del sustrato como consecuencia del recocido no hansido cuidadosamente estudiados. Los tratamientos térmicos, los cuales estánrelacionados con los procesos de integración de la fuente y el drenador (S/D) en undispositivo MOSFET, conducen a cambios estructurales que degradan el rendimientoeléctrico de un dispositivo MOS. Una caracterización apropiada de las alteracionesestructurales asociadas con la difusión de los elementos del substrato hacia las capassuperiores es importante para entender cuáles son los mecanismos de falla en undispositivo MOS. En este trabajo se presenta un análisis de la estructura y laestabilidad térmica de la estructura TiN/ZrO2/InGaAs por la espectroscopía defotoelectrones por rayos X con resolución angular (ARXPS). A través de un método deanálisis no destructivo, fue posible observar efectos sutiles tales como la difusión delas especies atómicas del sustrato a través del dieléctrico como consecuencia delrecocido. El conocimiento detallado de la estructura permitió evaluar los perfiles deprofundidad para las componentes de In-O y Ga-O por medio del método deescenarios. Para la muestra en estado como se depositó, las componentes de In-O yGa-O fueron localizadas en la interfaz óxido-semiconductor. Después del recocido, semuestra cuantitativamente que éste causa la difusión de átomos de In y Ga hacia a lascapas superiores. Asumiendo diferentes escenarios para su distribución, se muestraque el recocido provoca la difusión de In y Ga hasta la capa de TiO2. Para la muestrarecocida a 500 °C, se observó claramente la difusión de indio, mientras que para lamuestra recocida a 700 °C tanto In y Ga difunden a la capa de TiO2. El análisis~ iv ~cuantitativo mostró que existe menor difusión de átomos de galio (0.12 ML) que deindio (0.26 ML) a 700 °C/10 s. Puesto que el análisis sobre la cantidad de materialdifundido se realizó a diferentes temperaturas, fue posible obtener un valoraproximado para la energía de activación del indio a través del ZrO2. El valor resultóser muy similar a los valores reportados previamente para la difusión de indio a travésde Al2O3 y a través de HfO2. Con el fin de correlacionar los resultados obtenidos porARXPS, se emplearon técnicas complementarias como la microscopía electrónica detransmisión (TEM), la espectroscopía de energía dispersiva (EDX) y la espectrometríade masas de iones secundarios por tiempo de vuelo (SIMS-TOF). Particularmente, TOFSIMSdestacó el fenómeno de difusión de las especies atómicas sustrato hacia lasuperficie
Chang, Tzu-Jung, and 張慈容. "Physical Properties of ZrOCl2 Blended Nafion Solutions and the Preparation of PTFE-Nafion-Zr(HPO4)2 Composite Membranes." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/94850451582028603521.
Повний текст джерела元智大學
化學工程與材料科學學系
95
In this study, there are three system. First, we chose the addition of ZrOCl2•8H2O (Aldrich) to DuPont 5 wt% Nafion solution. Then we used dynamic viscoelasticity analyzer to study physical properties. Second, we added ZrOCl2•8H2O to 1 wt% DuPont Nafion solution that was diluted with MeOH/H2O (weight ratio 4 / 1) before. And we used dynamic viscoelasticity analyzer, Zeta potential and dynamic light scattering to study physical properties, particle size and flocculation properties. Third, we selected five ZrOCl2/Nafion wt ratio to prepare of PTFE-Nafion-Zr(HPO4)2 composite membranes. First system, the viscoelasticity data reveal polyelectrolyte behavior of Zr-N-48、Zr-N-72 solution. Second system, the viscoelasticity data reveal polyelectrolyte behavior of all these solution. The Zeta potential data of the 1 wt% Nafion/MeOH/H2O solution without ZrOCl2 is smaller and Particle size is larger than others. Third, the performance of single cell was the best when the ZrOCl2/Nafion wt ratio was 0.0391,and achieved 1045 mA/cm2 at 0.4 V, 110 ℃(RH=51.7 %); 790 mA/cm2 at 0.4 V, 120 ℃(RH=38.2 %) and 525 mA/cm2 at 0.4 V, 130 ℃(RH=28.8 %) base on H2/O2 and at a pressure of 1 atm.
Lo, Guang-Yu, and 羅廣鈺. "First-principles Calculations of ZrO2/Silicene/ZrO2 Sandwich Structures." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/2z65k8.
Повний текст джерела國立交通大學
電子研究所
106
As the state-of-the-art technology in semiconductor industry drives devices toward remarkably tiny dimension, the traditional Si-based MOSFETs will soon approach their scaling limits. An emerging development in this field is to find a replacement for the Si channel. A two-dimensional material consists of only a single atomic layer, being a good candidate of the MOSFET channel upon the ongoing scaling down. A two-dimensional silicon allotrope, silicene has its great advantage in being significantly compatible with the Si-based process. Silicene has a mobility two order of magnitude higher than bulk semiconductors and is expected to maintain a satisfactory device on-current. Yet there are also two major challenges to make it a feasible device. A stress-free stand-alone silicene, like graphene, has a gapless Dirac-cone band dispersion and needs additional treatments to open its gap. Besides, the silicene π bonds are chemically active, making it unstable in the air. In this thesis, I perform first-principles calculations to look for the strain-induced energy gap of silicene and how its electronic structures, especially the mobility, are affected when being sandwiched between dielectric materials. I find the energy gap is opened up to 0.17eV among the strains I have applied. We also calculate the electron and hole mobility of silicene under a particular strain to be 16.6 and 14.4m2V-1s-1, respectively, preserving the same order of magnitude of the free-standing mobility. I choose ZrO2/silicene/ZrO2 to be my model sandwich structure, where ZrO2 is a widely used high-k material in conventional semiconductor devices. I have considered both unpassivated and H-passivated interfaces of the above sandwich structure, and find that the former has no Dirac cone while the latter contains a Dirac cone and have indirect gap closing. I further apply a strain to the silicene in the H-passivated case such that the silicene restores its stand-alone symmetry, and find that the gap is re-opened. The symmetry-breaking mechanism of the unstrained (relaxed) silicene in a H-passivated sandwich is very likely due to the electrostatic charge that is transferred from ZrO2 to silicene, as calculated by the Bader analysis. In summary, my first-principles calculations show that silicene can have strain-induced gaps, and the ZrO2/silicene/ZrO2 sandwich structure needs both the H passivation (preserving the π bonds) and the silicene-symmetry restoration to open the gap. The mobility is also calculated from first principles and are found to maintain a high value in the order 10m2V-1s-1. These results provide preliminary guidance to develop silicene-based transistors.
Li, Han-siang, and 栗漢翔. "Unipolar Resistive Switching Investigation of ZrO2 and ZrO2-NiO Dielectric Layer." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/11334396072891422012.
Повний текст джерела國立臺灣科技大學
材料科學與工程系
100
This thesis focuses on the investigation of RRAM (Resistive Switching Random Accessing Memory) using ZrO2 and ZrO2-NiO thin films as dielectric layer and Al as bottom and top electrodes. Performance of the RRAM can be improved by adjusting the amount of oxygen or NiO in the dielectric thin film. Through the manipulation of the oxygen content and the thickness of ZrO2 thin films, voltage of forming process could be reduced. Studying of conducting mechanism shows that the forming process might be related with the presence of native oxide of Al bottom electrode. Al/ZrO2/Al could successfully achieve resistive switching using variety of oxygen contents, However, the difference of the high and low resistance in repeated resistive switching would be reduced using the lowest content of oxygen content in this experiment. Vset and Vreset are overlapped no mater what oxygen content were used in the ZrO2 films. The problem of overlapping of Vset and Vreset could be solved when Al/ZrO2-NiO/Al were prepared by mixing up NiO with ZrO2. The difference of the high and low resistance in repeated resistive switching would be reduced, and it is solved by using higher oxygen content. Furthermore, NiO may be present in conducting path and change the conducting mechanism.
Lu, Jer-han, and 盧哲瀚. "Exsolution of ZrO2-dissolved Al2O3 and early stage sintering of nanosized ZrO2." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/f8ygqq.
Повний текст джерелаEmiliano, José Vitório. "Ligações ZrO2/Ti e ZrO2/Ti-6Al-4V por difusão e brasagem." Doctoral thesis, 1995. http://hdl.handle.net/10773/33106.
Повний текст джерелаCNPq
Programa Doutoral em Ciência e Engenharia de Materiais
Linck, Christoph. "Keramische SiCN/ZrO2- und SiOC/ZrO2-Nanokomposite - Synthese, thermochemische und thermomechanische Eigenschaften." Phd thesis, 2016. https://tuprints.ulb.tu-darmstadt.de/5856/1/Dissertation_final_SiCNZrO2_SiOCZrO2.pdf.
Повний текст джерелаtw, wenpei_lin@yahoo com, and 林雯珮. "Effect of ZrO2 Content on the Oxidation Behavior of SiC/Al2O3/ZrO2 Composites." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/93512085299515031635.
Повний текст джерела國立交通大學
材料科學與工程系
91
The composites contented 30 vol% SiC was fabricated by hot pressing. It wilth different volume percent of zirconia and alumina in matrix, expressed as AZxx (xx meaned the percentage of zirconia in matrix). The composites represented as AZxx/SiC. Composites were exposed in air at 1000℃~1350℃,and the microstructures of the oxidized samples of various composites after exposured at a temperature of 1350℃, were studied using X-ray diffraction, SEM, TEM, and energy-dispersive spectroscopy ( EDS ). The result showed the oxidation weight gain increase with the raise of zirconia content. Because of the raise of zircon content caused the increase of diffusion rate. The oxidation rate was dramatically increased beyond the critical volume fraction, and displayed a different oxidation behavior. AZ0/SiC and AZ10/SiC were characterized by a small oxidation depth as well as a relatively large gradient, which exhibited oxidation behavior of Mode I. AZ20/SiC and AZ50/SiC were characterized by a large oxidation depth as well as a relatively small gradient demonstrated the oxidation behavior of Mode II. AZ0/SiC、AZ10/SiC、AZ20/SiC formed cristobalite and zircon, but without mullite under the oxidation of 1200℃. The solution and reprecipitation between silica and alumina resulted in a newly phase mullite after AZ0/SiC exposured in air at the temperature of 1350℃ for 200h. AZ10/SiC and AZ20/SiC formed zircon and mullite at the first stage of oxidation at the temperature 1350℃, resulted from the reaction between silica and zirconia, silica and alumina. After a long term oxidation, zircon reacted with alumina and produced zirconia and mullite. AZ50/SiC exposured at 1350℃ prefer to formed zirconia through the reaction between silica and zirconia.
Wei, Chen Chih, and 陳志維. "The hydrogenation of 1-methylnaphthalene over Pt/TiO2-ZrO2 d Pd/TiO2-ZrO2." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/57807637152606122928.
Повний текст джерелаWANG, KUO-HAO, and 王國豪. "Fabrication and characteristics of ZrO2 fiber and Ce2O3-ZrO2 fiber mats via electrospinning." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/26223829498857649576.
Повний текст джерела遠東科技大學
機械工程研究所
99
We have successfully to fabricate the metal oxide fibers via electrospinning method. Precursor of the fiber is a sol-gel which is made use of electrospinning installation to make into composite fibers. These composite fibers were calcined on atmosphere to decompose organic polymer and furthermore to from metal oxide fibers. There are two topics in this thesis. The first topic: We use Zirconium butylate and Zirconyl(IV) nitrate hydrate are two different Zirconium precursor by polyvinyl pyrrolidone (PVP) assisted electrospinning into nano-composite fibers. and then calcined to remove organic matter form zirconia oxide fiber by high-temperature. A Zirconium butylate precursor as long as the small amount of PVP of about 250 nm in diameter electrospinning symmetrical composite fibers, Zirconia fibers by calcined about 200 nm in diameter. Zirconyl(IV) nitrate hydrate as precursor amount of PVP to need more electrospinning about 200 to 500 nm in diameter symmetrical composite fiber. and then through calcined zirconia oxide fiber diameter of about 100 to 400 nm, using SEM, TG-DTA, FT-IR analysis and comparison of the two composite fiber characteristics and differences. The second topic: We use Zirconyl(IV) nitrate hydrate and Cerium(Ⅲ) nitrate hexahydrate precursor compound produced by polyvinyl pyrrolidone (PVP) assisted electrospinning into nano-composite fibers, and then through calcination to remove organic matter from metal composite oxide fiber diameter of about 600 nm ~ 2 µm. calcined 700℃ ~ 800℃ can get a little hollow fiber, and the use of SEM, TG-DTA , FT-IR analysis of the characteristics and type of nano-composite fibers.
HUANG, JIAN-MIN, and 黃見明. "Preparation of ZrO2 -based slurries and ZrO2 -Al2 O3 composites by colloidal mixing process." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/51495576958805705965.
Повний текст джерелаWang, Ming-Jia, and 王銘嘉. "The Study of Electrolytic MgO/ZrO2 and CaP/ZrO2 Coatings on AZ91D Magnesium Alloy." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/23890726632339458661.
Повний текст джерела國立中興大學
材料科學與工程學系所
102
In order to promote the corrosion resistance of magnesium alloy, an MgO/ZrO2 duplex-layer coating has been prepared on AZ91D magnesium alloy as a protective film against corrosion by a two-step fabrication process of electrodeposition and annealing treatment in the study. Owing to the chemical bonding formed after the condensation of precursory hydroxides, the adhesion strength, thickness and compactness of MgO coating on the substrate are significantly enhanced by the intermediate ZrO2 layer which prevents the formation of corrosion product Mg2(OH)3Cl·4H2O. As a result, the MgO/ZrO2 duplex-layer coated specimen reveals relatively high corrosion resistance and superior stability in 3.5 wt % NaCl solution with respect to the MgO single-layer coated specimen. Recently, magnesium alloys have been further proposed as a new class of biodegradable metallic biomaterials. However, their corrosion resistance restricts further applications in medical devices. In order to control the degradation rate and enhance the biocompatibility of magnesium alloys, calcium phosphate (CaP) top layer with ZrO2 interlayer composing CaP/ZrO2 coating was carried out on AZ91D magnesium alloy by electrodeposition and annealing. ZrO2 interlayer makes unstable dicalcium phosphate anhydrous (DCPA) for CaP single layer transform into stable hydroxyapatite (HA) for CaP/ZrO2 composite coating and enhance the adhesion strength of CaP from 12.1 to 24.4 MPa, owing to OH bonds provided by the precursory of intermediate layer Zr(OH)4 condensed with OH bonds in HA and on Mg alloy surface after annealing, also leading to a dense and compact under layer which effectively reduces the corrosion current density from 84.30 to 0.49 μA/cm2 in potentiodynamic polarization tests and weight increase in immersion tests. Besides, the in vitro cell assays demonstrate that CaP/ZrO2 and ZrO2 coatings can enhance more cell adhesion and proliferation whereas cell numbers on uncoated specimen decreases with culture time due to the corrosion accompanied with evolution of hydrogen, the rise in Mg2+ and pH of solution near the specimen surface, and the formation of corrosion products, revealing that CaP/ZrO2 or ZrO2 coated AZ91D magnesium alloy can be a promising candidate as a biodegradable implant.
Chou, Bang-Yen, and 周邦彥. "Plasma-Sprayed Hydroxyapatite Coating on Titanium Alloy With ZrO2 Second Phase and ZrO2 Intermediate Layer." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/47979693137028746634.
Повний текст джерела國立成功大學
材料科學及工程學系
90
In the thesis, the first two chapters, Chapter 1 and Chapter 2, are about introduction and theory foundation, respectively. From the literature, plasma-sprayed hydroxyapatite (HA) — coated Ti alloy surgical implant exhibits both excellent biocompatibility and satisfactory mechanical properties. The aim of this study was to strengthen the HA coating by adding dispersed ZrO2 particles in the HA matrix (HA+ZrO2) and introducing ZrO2 intermediate layer between HA coating and Ti alloy substrate as a bond coat (HA/ZrO2). In this study, the strengthening mechanisms of both coating systems were investigated as well as the transformation mechanisms of the interaction between HA and ZrO2 during spraying. In Chapter 3, the microstructural characteristics of plasma-sprayed HA+ZrO2 coating on Ti alloy were investigated by using X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The results reveal that the cubic phase of ZrO2 in HA+ZrO2 powders before coating maintains during plasma spraying and ZrO2 particle apparently bonds well to the calcium phosphate matrix with local crystallographic relationship. Furthermore, reaction of calcium phosphate and ZrO2 occurs to transform ZrO2 into CaZrO3. In addition, the mechanism of phase transformation in plasma-sprayed HA+ZrO2 coating is explored in Chapter 3. The changes in phase and chemistry of the coatings were characterized by XRD with lattice constant measurement (Cohen’s method), and by TEM. Experimental results show an evidence of the diffusion of calcium ion from the hydroxyapatite matrix, in liquid state, into the ZrO2. It results in the following structural features in the composite coating: (a) a CaO-doped ZrO2 solid solution (ZrO2-7.7 mol% Y2O3-4.4 mol% CaO); (b) a mixture of ZrO2 and CaZrO3 having crystal-orientation relationship; (c) an amorphous phase containing elements of Ca, P, Zr and Y; and (d) a remaining CaO-poor HA matrix (Ca10-x(HPO4)x(PO4)6-x(OH)2-x, x = 0.06). In Chapter 4, the mechanical properties and strengthening mechanisms between HA+ZrO2 and HA/ZrO2 coatings are compared. The bonding strength of coating is measured per ASTM C633-79. Results indicate that the bonding strength of the HA coatings increases from 28.6 3.2 MPa for HA coating to 32.5 4.2 MPa and 36.2 3.0 MPa for HA+ ZrO2 and HA/ZrO2 coatings, respectively. The cross-sectional microstructure of HA/ZrO2 coating of both HA/ZrO2 and ZrO2/Ti alloy interfaces was investigated by TEM. Elemental diffusion was found at HA/ZrO2 interface. In Chapter 5, HA coatings were plasma sprayed on the Ti alloy substrates with and without an intermediate ZrO2 layer, meanwhile the temperatures of substrates were varied at 90, 140 and 200°C. The purpose of the investigation was to study the effects of those processing variables on the bonding strength, residual stress and failure behavior of the system. It is found that the bonding strengths of HA/ZrO2 and HA coatings generally decrease with increasing substrate temperature, except for the HA/ZrO2 coating deposited at 200°C. The rationale of the results is attributed to the residual stress generated in the coating. Introducing ZrO2 bond coat is found to significantly promote the bonding strength of HA coating. The possible strengthening mechanism is the rougher surface of ZrO2 bond coat and the higher toughness of ZrO2, which provide the mechanical strengthening effects. The slightly denser HA in 200°C-deposited HA coating cannot explain the high bonding strength of the HA/ZrO2 coating. It is believed that a stronger diffusion bonding is formed at the interface of HA and ZrO2, which increases the bonding between them chemically.
LIN, ZHENG-GUO, and 林正國. "ZrO2 -based ceramic shell mold preparation." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/99460082486470619081.
Повний текст джерелаPai, Chin-tung, and 白謹通. "Preparation of dispersible c-ZrO2 nanocrystals." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/72736827583410076072.
Повний текст джерела國立中央大學
化學工程與材料工程研究所
100
The purpose of this experiment was formatted the dispersible c-ZrO2 nanocrystals with digestion. The organic acid grafted c-ZrO2 nanocrystals can be stabilized in different solvents. This synthesis route is relatively simple and has been developed into large-scale. In this study, we discussed the condition of the reactant, ion exchange and modification of the synthesis process. We used zirconium basic carbonate as the raw materials for the synthesis of zirconia nanocrystals. We adjusted the reactant ratio of zirconium dioxide, NaOH and water, controlling the particle size of zirconia nanoparticles. After reaction we used ammonium bicarbonate solution to ion exchange, the Na+ on zirconia nanoparticles surface would reduce. This precipitate can be modified with different organic acids and the organic acid grafted ZrO2 can dried into powders. The modified powders can disperse in different solvent. The particular sample was prepared by the 110oC/6 hours digestion of a mixture having 22.3 wt % ZrO2 equivalent and 22 wt% NaOH. It can obtained the cubic zirconia nanocrystals of 3.1 nm. The dispersion of BA grafted ZrO2 in toluene at 50 wt% had the transparency 82 % at visible wavelength of 600 nm. The average particle size is 15.6 nm from DLS. The density of BA-ZrO2 powder was 2.5 g/cm3 and refractive indexes was 1.7.