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Tendo como vantagem a elevada resistência ao choque térmico da zircônia:magnésia e a alta condutividade iônica da zircônia:ítria, compósitos dessas cerâmicas foram preparados por meio da mistura, em diferentes concentrações, de eletrólitos sólidos de ZrO2: 8,6 mol% MgO e de ZrO2: 3 mol% Y2O3, compactação e sinterização. A caracterização microestrutural foi feita por meio de difração de raios X e microscopia eletrônica de varredura. A análise do comportamento térmico foi feita por dilatometria. As propriedades elétricas foram estudadas por meio de espectroscopia de impedância. Foi feita uma montagem experimental para monitorar a resposta elétrica gerada em função do teor de oxigênio a altas temperaturas. Os principais resultados mostram que os compósitos cerâmicos são parcialmente estabilizados nas fases monoclínica, cúbica e tetragonal, e apresentam comportamento térmico similar ao apresentado por eletrólitos sólidos de zircônia:magnésia de dispositivos sensores de oxigênio. Além disso, os resultados de análise de espectroscopia de impedância mostram que a adição da zircônia:ítria melhora o comportamento elétrico da zircônia:magnésia, e que resposta elétrica gerada é dependente do teor de oxigênio a 1000 °C, mostrando ser possível construir sensores de oxigênio utilizando compósitos cerâmicos. / Taking advantage of the high thermal shock resistance of zirconia-magnesia ceramics and the high oxide ion conductivity of zirconia-yttria ceramics, composites of these ceramics were prepared by mixing, pressing and sintering different relative concentrations of ZrO2: 8.6 mol% MgO and ZrO2: 3mol% Y2O3 solid electrolytes. Microstructural analysis of the composites was carried out by X-ray diffraction and scanning electron microscopy analyses. The thermal behavior was studied by dilatometric analysis. The electrical behavior was evaluated by the impedance spectroscopy technique. An experimental setup was designed for measurement the electrical signal generated as a function of the amount of oxygen at high temperatures. The main results show that these composites are partially stabilized (monoclinic, cubic and tetragonal) and the thermal behavior is similar to that of ZrO2: 8.6 mol% MgO materials used in disposable high temperature oxygen sensors. Moreover, the results of analysis of impedance spectroscopy show that the electrical conductivity of zirconia:magnesia is improved with zirconia-yttria addition and that the electrical signal depends on the amount of oxygen at 1000 °C, showing that the ceramic composites can be used in oxygen sensors.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-04-26T14:15:43Z No. of bitstreams: 1 jeansoaresmiranda.pdf: 6014272 bytes, checksum: a6aaf905414159a41b45b4d6a499eb38 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-05-02T00:50:50Z (GMT) No. of bitstreams: 1 jeansoaresmiranda.pdf: 6014272 bytes, checksum: a6aaf905414159a41b45b4d6a499eb38 (MD5) / Made available in DSpace on 2016-05-02T00:50:50Z (GMT). No. of bitstreams: 1 jeansoaresmiranda.pdf: 6014272 bytes, checksum: a6aaf905414159a41b45b4d6a499eb38 (MD5) Previous issue date: 2016-01-25 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo dessa pesquisa foi avaliar a influência do tempo de condicionamento com ácido fluorídrico a 10%, sobre a resistência de união entre uma cerâmica Y-TZP vitrificada e um cimento resinoso. Blocos pré-sinterizados de cerâmica Y-TZP (IPS e.max® ZirCAD - Ivoclar-Vivadent) foram cortados para obtenção de 40 amostras. Previamente à sinterização, os blocos foram regularizados com lixas d’água de granulação #180, #600 e #1200. Eles foram, então, divididos aleatoriamente em quatro grupos (n=10), sendo um o grupo controle no qual foi realizada a silicatização com Rocatec Soft (RS) e três grupos teste vitrificados com glaze spray (VITA Akzent Plus, Vita Zanhfabrik, Bad Sachingen, Alemanha), com diferentes tempos de condicionamento com ácido fluorídrico a 10% (Condac Porcelana, FMG, Brasil) executado na superfície destinado a adesão: por 20s (GS20s), 60s (GS60s) ou 100s (GS100s). Para cimentação foi utilizado um adesivo universal (Single Bond Universal, 3M ESPE) contendo monômero MDP em sua composição e um cimento resinoso dual (RelyX Ultimate, 3M ESPE). Em cada bloco foram obtidas duas colunas de cimento, totalizando 20 amostras por grupo. Após termociclagem, o teste de cisalhamento foi realizado (EMIC,DL 2000), a resistência de união foi registrada e utilizada para cálculo da resistência adesiva. Além disso, a análise de falha também foi realizada em todas as amostras com um estereomicroscópio (Stemi 2000-C). Uma amostra extra de cada grupo teve metade de sua superfície tratada para obtenção de imagens por perfilometria e microscopia eletrônica de varredura (MEV), além de realização de espectrometria por energia dispersiva (EDS). O teste de Kruskal-Wallis apresentou p valor igual a 0,001 e o teste de Dunn demostrou diferença apenas do grupo RS (22,10Mpa) para os grupos GS (GS20s: 8,10Mpa; GS60s: 10,49; GS100s: 7,53), porém não houve nenhuma diferença dentre os diferentes grupos GS. As imagens de perfilometria e MEV revelaram um padrão irregular de disposição do glaze após o condicionamento com HF 10%. Por meio da perfilometria foi possível aferir a espessura da camada do glaze remanescente (GS20s: 5 ± 1μm; GS60s: 4 ± 1μm; GS100s: 3 ± 1μm). Todas as falhas foram adesivas. E foi possível concluir que a resistência de união entre uma cerâmica Y-TZP vitrificada e um cimento resinoso com MDP não é influenciada por diferentes tempos de condicionamento com ácido fluorídrico. / The purpose of this research is to evaluate the influence of conditioning time with hydrofluoric acid on the bond strength of a Y-TZP glazed ceramics and a resin cement. Ceramic pre-sintered Y-TZP blocks (IPS e.max® ZirCAD - Ivoclar Vivadent-) were cut to obtain 40 samples. Prior to sintering the blocks were smoothed with sandpaper water granulation #180, #600 and #1200. They were then randomly divided into four groups (n = 10), one control group was performed silicatization with Rocatec Soft (RS) and three vitrified test groups with different acid conditioning times surface: GS20s, GS60s and GS100s (application hydrofluoric acid for 20, 60 and 100 seconds respectively). For cementation was used a universal adhesive containing the MDP monomer in its composition (Single Bond Universal, 3M ESPE) and a dual resin cement (RelyX Ultimate, 3M ESPE). In each block was obtained two cement columns, totaling 20 samples per group. After thermocycling, the shear test was performed (EMIC, DL 2000), the maximum force to fracture was recorded and used to calculate the bond strength. Furthermore, the failure analysis was also performed with a esteriomicroscópio (Stemi 2000-C). An extra sample of each group had half of its surface treated to obtain images by profilometry and scanning electron microscopy (SEM), as well as conducting energy dispersive spectrometry (EDS). The Kruskal-Wallis test showed ap value of 0.001 and the Dunn test demonstrated differences only the RS group (22,10Mpa) for GS groups (GS20s: 8,10Mpa; GS60s: 10.49; GS100s: 7.53 ), but there was no difference among different GS groups. The profilometry and SEM images revealed an irregular pattern of glaze layout after conditioning with HF 10%. By profilometry it was possible to measure the thickness of the remaining glaze layer (GS20s: 5 ± 1μm; GS60s: 4 ± 1μm; GS100s: 3 ± 1μm). All failures were adhesive. And it concluded that the bond strength between Y-TZP glazed pottery and a resin cement with MDP is not influenced by different conditioning times with hydrofluoric acid.

Electrical and thermal conductivities of the yttria-stabilised zirconia/alumina (YSZ/Al2O3) composites and the yttria-zirconia-ceria (YSZ-CeO2) solid solutions are studied in this thesis. The electrical conductivity of the YSZ/Al2O3 composites decreases with an increase in the volume fraction of Al2O3 and exhibits typical percolation behaviour. The electrical conductivity of the YSZ/Al2O3 interface is higher than that of the YSZ grain boundary, but lower than that of the YSZ grains. The thermal conductivity of the YSZ/Al2O3 composites increases with an increase in the Al2O3 volume fraction, and it can be fitted well to the Maxwell theoretical model, which indicates the absence of obvious interfacial thermal resistances in the composites. The low interfacial thermal resistance of the YSZ/Al2O3 interface is due to the 'clean' and coherent nature of the YSZ/Al2O3 interface, along with the small difference between the elastic properties of YSZ and Al2O3. The electrical conductivity of the [(ZrO2)1-x(CeO2)x]0.92(Y2O3)0.08 (0 ≤ x ≤ 1) solid solutions has a 'V-shape' variation as a function of the mole ratio of CeO2 (x). In the ZrO2-rich region (x < 0.5), CeO2 doping increases the concentration of defect associates which limits the mobility of the oxygen vacancies; in the CeO2-rich region (x > 0.5), the increase of x increases the lattice parameter, which enlarges the free channel for oxygen vacancy migration. A comparison of the YSZ-CeO2 solid solutions with the YSZ-HfO2 series indicates the ionic radius of the tetravalent dopant determines the composition dependence of the ionic conductivity of the solid solutions.The thermal conductivity of the [(ZrO2)1-x(CeO2)x]0.92(Y2O3)0.08 (0 ≤ x ≤ 1) solid solutions also has a 'V-shape' variation as a function of the mole ratio of CeO2 (x), which indicates an incorporation of Zr4+ and Ce4+ can effectively decrease the thermal conductivity of the end members YSZ and yttria-doped ceria (YDC). In the ZrO2-rich region (0 ≤ x ≤ 0.5), the thermal conductivity is almost temperature independent; in the CeO2-rich region (0.5 ≤ x ≤ 1), it decreases obviously with increasing temperature. By calculating the phonon scattering coefficients, it is concluded that the composition dependence of the thermal conductivity in the ternary solid solutions is dominated by the mass difference between Zr and Ce at the cation sites, whereas the temperature dependence is determined by the order/disorder of oxygen vacancies at the anion sites.

Orientador: Cecilia Amélia de Carvalho Zavaglia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T21:01:51Z (GMT). No. of bitstreams: 1 Santana_Marcio_M.pdf: 2241450 bytes, checksum: 6a2d73eb696ed813c03446c21f1f74e3 (MD5) Previous issue date: 2015 / Resumo: Neste trabalho foram pesquisados as cerâmicas óxido de alumínio e óxido de zircônio na forma de compósito para aplicação em próteses odontológicas mais especificamente como pilar de fixação (Abutment). A alumina, em sua fase alfa, é uma cerâmica que apresenta excelentes propriedades mecânicas e é biocompatível, porém tem como restrição a sua baixa tenacidade à fratura o que a impede de ser utilizada com mais regularidade em aplicações estruturais. O óxido de zircônio também possui excelentes propriedades mecânicas, maior tenacidade à fratura das cerâmicas avançadas e é biocompatível, entretanto apresenta uma restrição à sua aplicação em meios fisiológicos abaixo de 300º C quando o material se degrada, inicia um processo de propagação de trinca e se rompe depois de um determinado período. O compósito alumina-zircônia apresenta melhores propriedades mecânicas e maior tenacidade à fratura para aplicação estrutural, portanto melhores condições de ser aplicado em uma prótese dentária. Foram estudadas e caracterizadas 3 composições (30, 40, 50% em vol. de zircônia na matriz de alumina) deste compósito sub-microestruturado. Foram realizados ensaios para avaliar as propriedades de cada composição e sua morfologia no intuito de analisar qual a composição é a mais adequada para a construção de um pilar de fixação. Os resultados apontados indicam uma melhora nas propriedades mecânicas do compósito com 30% de zircônia quando comparado à alumina e a zircônia puras. Os resultados para o compósito de 30% de zircônia de dureza foi de 14,73 GPa, de tenacidade a fratura foi 8,64 MPa.m1/2 e de compressão diametral foi de 252,41 MPa / Abstract: The present work was researched the alumina oxide and zirconia oxide ceramic in the form of composite for application in dental prostheses specifically abutment. Alumina in its Alpha stage is a ceramic that presents excellent mechanical properties and is biocompatible, however your low fracture toughness has the restriction which prevents it from being used more regularly in structural applications. The zirconia oxide also has excellent mechanical properties, is biocompatible and has higher fracture toughness than Alumina, although presents hidrothermal degradation in physiological environment below 300° C that causes cracks and breakage after a period of time. The alumina-zirconia composite have better mechanical properties and fracture toughness higher for structural application, so better able to apply in a dental prosthesis. Were studied and characterized three compositions (30, 40 50% vol. Zirconia Alumina in the matrix) of this sub-microstructured composite through tests to evaluate the properties, exam in SEM Microscopy of each composition and compare the final results to selected a best composition to construction of a dental abutment. The results presented so far indicates an improvement in the mechanical properties of the composite with 30% of zirconia when compared to other compositions and pure alumina and zirconia. The results for the 30% zirconia composite for micro-hardness was 14,73 GPa, fracture toughness was 8,64 MPa.m1/2 and testing for diametral compression for 252,41 MPa / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第22796号 / エネ博第410号 / 新制||エネ||78(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 坂口 浩司, 教授 佐川 尚, 准教授 高井 茂臣 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

No description available.

OBJECTIVES: To evaluate accelerated and real time aging effect on microstructure and mechanical properties of different types of zirconia’s with various surface treatments. METHODS: In this in-vitro study 830 discs were prepared from four Y-TZP based materials. These materials were TZ-3YSB-E, ZPex®, ZPex® Smile (Tosoh Corporation, Japan), and Cercon®xt extra translucent zirconia (Dentsply-Sirona). Final dimensions of each specimen disc were about 15 mm in diameter and 1.5 mm thick. An accelerated aging process for 5, 24, and 168 hours of steam aging at 134°C under a pressure of 0.2 MPa was applied to the specimens. Real time aging was performed for one year in normal saline solution at 37°C in an incubator. Sandblasting was performed using a PrepStar® system with Al2O3 50μm particle size at pressure of 60 psi, rate 4.2 gram/minute. Grinding with a Buehler AutoMet 250 was performed using a 240 μm diamond disc with a 0.0034 kg/mm2 load and speed of 120 rpm for two minutes. Bruker D8 advance diffractometer was used for the acquisition of X-ray diffraction (XRD) spectrum. Biaxial flexural strength was determined using a ball-on-three-balls configuration in a universal testing machine. Scanning Electron Microscopy (SEM) was used to examine the sample's surface topography. RESULTS: The results of this study show that the zirconia materials with smaller grain size have higher flexural strength. Sandblasting and grinding treatment increases the tensile flexural strength of TZ-3YSB-E and ZPex® compared to the controlled group of the same material. XRD analysis shows that TZ-3YSB-E at room temperature does not have any monoclinic phase before surface treatment and it increased after aging, sandblasting and grinding. Cercon®xt has the highest amount of cubic phase and it increases with surface treatment. CONCLUSION: Sandblasting surface treatment should not be applied to all types of zirconia and it has to be material specific. Within the scope of this study, accelerated aging process did not affect the grain size of all materials control groups. The smaller grain size of zirconia is correlated to higher flexural strength of the material. The smaller amount of cubic phase present is correlated to higher biaxial flexural strength.