Dissertations / Theses on the topic 'Zirconium oxide'
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Zhe, Xiaoli. "Novel zirconium oxide-based ceramic composites." Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366774.
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Meidell, J. "Control of microstructure in sintered zirconium oxide." Thesis, Staffordshire University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237830.
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Mangin, Stephan P. 1973. "Microstructural study of zirconium oxide grown on a zirconium alloy substrate for orthopaedic applications." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50372.
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Vemuri, Venkata Rama Sesha Ravi Kumar. "Fabrication and characterization of zirconium oxide thin films." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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McClellan, Kenneth James. "Structure/property relations in yttrium oxide-stabilized cubic zirconium oxide single crystals." Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1061395556.
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Cruz, César Roberto [UNESP]. "Desempenho de sondas Lambda no monitoramento de motores do ciclo Otto alimentados por etanol e GNV." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/132500.
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000854863.pdf: 5368324 bytes, checksum: f60f5de47f46c51ce3e51ec3e6e81da4 (MD5)Com aumento do número de veículos automotores em circulação, a quantidade de poluentes lançados no nosso planeta é muito significativa, sendo um risco real ao nosso meio ambiente. Vários avanços tecnológicos têm sido apreentados nos últimos anos, objetivando a redução destas emissões. As cerâmicas têm desempenhado um papel primordial neste cenário. Dentre estas, encontra-se o sensor de oxigênio que utiliza a zircônia (ZrO2) como eletrólito sólido, componente do sistema de gerencialmento eletrônico do motor do ciclo Otto, e elemento primordial na estratégia de reduzir as emissões e o consumo de combustível. Neste trabalho analisou-se o desempenho de quatro sensores de marcas líderes no mercado, com países de origem diferentes, originalmente desenvolvidos para operar com gasolina pura se comportam com combustível de uso alternativo, com composição química e fases distintas, Etanol (líquida) e GNV (gasosa). Instalados em um motor do ciclo Otto de 4 tempos, dotado de sistema de gerencialmento eletrônico multicombustível (Tetrafuel) original de fábrica, funcionando de forma autônoma ao veículo, operando em duas rotações predefinidas. Foram coletados e registrados os seguintes dados operacionais: sinal elétrico, tempo de resposta, temperatura de operação, e emissões de gases. Os valores obtidos nas etapas estipuladas foram tabulados e posteriormente analisados. Quando utilizado o Etanol como combustível, as tensões médias nas duas rotações foram menores que as observadas utilizando-se o GNV, a temperatura na região do sensor também se apresentou superior para o Etanol. O tempo médio de resposta para o Etanol foi superior ao GNV. Analisando as emissões geradas, concluímos que as mesmas estão de acordo com o preconizado na legislação vigente, indicando que o sistema de gerenciamento eletrônico do motor e consequentemente os sensores de oxigênio avaliados, cumprem plenamente e de forma adequada...
With the increasing number of motor vehicles in circulation, the amount of pollutantos released in the atmospheric air is very significant, being a real disk to our planet. People concerned about the consequences resulting from his problem have charged effective actions in order to minimize the impact of polluent generated and the preservaton of the life quality on our planet. Significant technological advances have been made in recent years, both in the forms of propulsion, when on reducing emissions by engines. The development and adoption of new materials, both in construction, or in the control of the several systems, is one of the bases of this major development. Among these materials, the ceramics have played a very important role in this scene, whose applications are enabling the achievement of the proposed objectives. This work focuses primarilly about the oxygen sensor using zirconia (ZrO2) as basic element. Also known as lambda sensor, it is used in automobiles to control along with the electronic management system of the engine, of air-fuel ratio, in orderto reduce the emissions and the fuel comsumption in internal combustion engines of Otto and Diesel cycles. It is installed in the exhaust gas system and aims to measure the residual oxygen content in gases produced by the engine. In this work we analyzed the performance of these sensors in measuring the concentration of residual oxygen content in the exhaust gases when installed on an Otto cycle engine, 4 stroke, endowed with electronic multi fuel management system (Tetrafuel), installed independently to the vehicle on a test bench, operating distinctly with liquid fuel (ethanol) and gas (CNG), in two predefined speeds. In this work, we will present is composition, construction, operating principles and performance in a real operating situation, of four sensors of different manufacturers allowing the understanding of its interaction with the electronic management system and the...
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Abdoulmoumine, Nourredine. "Sulfate and Hydroxide Supported on Zirconium Oxide Catalysts for Biodiesel Production." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/33873.
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Biodiesel is currently produced by homogeneous catalysis. More recently however, heterogeneous catalysis is being considered as a cheaper alternative to the homogeneous process. In this research project, heterogeneous catalysts of zirconium oxide were produced by impregnation.
Zirconium oxide impregnation with sulfuric acid produced acidic solid catalysts. It was determined that impregnation and calcination at 550oC (SO4/ZrO2-550oC) produced the best catalyst for palmitic acid esterification with 10 wt % as the optimum concentration in esterification of palmitic acid. SO4/ZrO2-550oC was successfully recycled for eight consecutive runs before permanent deactivation. Its sulfur content was 1.04 wt % using SEM-EDS and 2.05 wt % using XPS for characterization. BET surface area was 90.89 m2/g. The reaction mechanism over Brønsted acid (SO4/ZrO2-550oC) and Lewis acid (Al2O3) catalysts obeyed Eley-Rideal kinetics with palmitic acid and methanol adsorbed on the active site respectively.
Zirconium oxide was also impregnated with sodium hydroxide to produce basic catalysts. The best catalyst was produced when zirconium oxide was impregnated with 1.5 M NaOH and calcined at 600oC. Soybean oil was completely converted to biodiesel with 10 wt % catalyst and 1:6 oil to methanol. A mixture of the base catalyst with 30 wt % SO4/ZrO2-550oC effectively converted soybean oil containing 5% oleic acid indicating that this mixture could be used for waste oils. The reaction was first order with respect to triglyceride and second order with respect to methanol. The activation energy was 49.35 kJ/mol and the reaction mechanism obeyed Langmuir-Hinshelwood kinetics.Master of Science
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Bowen, Andrew. "Anodisation and study of oxide films formed on zirconium." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328407.
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Tewg, Jun-Yen. "Zirconium-doped tantalum oxide high-k gate dielectric films." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/1346.
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A new high-k dielectric material, i.e., zirconium-doped tantalum oxide (Zr-doped TaOx), in the form of a sputter-deposited thin film with a thickness range of 5-100 nm, has been studied. Important applications of this new dielectric material include the gate dielectric layer for the next generation metal-oxide-semiconductor field effect transistor (MOSFET). Due to the aggressive device scaling in ultra-large-scale integrated circuitry (ULSI), the ultra-thin conventional gate oxide (SiO2) is unacceptable for many practical reasons. By replacing the SiO2 layer with a high dielectric constant material (high-k), many of the problems can be solved. In this study, a novel high-k dielectric thin film, i.e., TaOx doped with Zr, was deposited and studied. The films electrical, chemical, and structural properties were investigated experimentally. The Zr dopant concentration and the thermal treatment condition were studied with respect to gas composition, pressure, temperature, and annealing time. Interface layer formation and properties were studied with or without an inserted thin tantalum nitride (TaNx) layer. The gate electrode material influence on the dielectric properties was also investigated. Four types of gate materials, i.e., aluminum (Al), molybdenum (Mo), molybdenum nitride (MoN), and tungsten nitride (WN), were used in this study. The films were analyzed with ESCA, XRD, SIMS, and TEM. Films were made into MOS capacitors and characterized using I-V and C-V curves. Many promising results were obtained using this kind of high-k film. It is potentially applicable to future MOS devices.
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Muratore, Francesca. "Growth of porous anodic films on zirconium and zirconium alloys in glycerol/fluoride electrolytes." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/growth-of-porous-anodic-films-on-zirconium-and-zirconium-alloys-in-glycerolfluoride-electrolytes(ce98e6f6-e743-47b2-b1c4-7b0fd6797003).html.
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Anodic films have been produced on zirconium and zirconium alloys potentiostatically (at either 20 or 40 V) in 0.35 M ammonium fluoride in glycerol, with interest in the addition of small amounts of water (up to 5 vol.%) to the electrolyte on their growth, morphologies and compositions. Scanning and transmission electron microscopies have been employed to analyse morphologies of the films, which appeared to be porous under all the investigated conditions.Rutherford backscattering spectroscopy and nuclear reaction analysis, used as techniques to investigate film compositions, disclosed the presence of zirconium, oxygen, fluorine, carbon and nitrogen in the films. The contents of fluorine and oxygen in the films were found to increase and decrease respectively by decreasing the amount of water added to the electrolyte from 5 to 0 vol.%. Moreover, the content of fluorine increased by decreasing the applied formation voltage, from 40 to 20 V, for films formed in electrolytes containing similar amounts of added water.In order to get information on the distribution of the species in the films, cross-sections of selected specimens were produced by focused ion beam and analysed by analytical transmission electron microscopy. Oxide-rich nanotubes were revealed embedded in a fluoride-rich matrix, suggesting that the mechanism of growth of the anodic films is governed by different migration rates of the anionic species in the film base, with F- ions, being the fastest anions. The relative amounts of the oxide-rich and fluoride-rich materials were related to the composition of the electrolyte, with the fluoride regions being less extensive and the oxide-rich nanotubes being thicker-walled by adding small amounts of water. Moreover, nanotubes are constituted of two shells (an outer one surrounding the pores and an inner one located between the outer shell and the matrix), suggesting differences in the composition in these two regions, presumed to be due to the incorporation of carbon species, being the slowest migrating species, in the outer shell. The fluoride-rich matrix chemically dissolved following 1 h immersion of the specimens in the formation electrolytes, promoting the transition from porous to nanotubular morphologies. Ageing of the specimens in deionized water for similar times did not significantly influence the morphologies and compositions of the anodic films.
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Southon, Peter. "Structural evolution during the preparation and heating of nanophase zirconia gels /." Electronic version, 2000. http://adt.lib.uts.edu.au/public/adt-NTSM20040204.135030/index.html.
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Thesis (PhD.)--University of Technology, Sydney, 2000."A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy, University of Technology Sydney, November 2000" Includes bibliographic references.
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Proff, Christian. "Aspects microstructuraux de l'oxydation d'alliages de Zirconium." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00609232.
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Cette thèse est axée sur la caractérisation microstructurale des précipités dans les oxydes des alliages binaires de zirconium (1 wt.% Fe, Cr , Ni ou 0.6 wt.% Nb). La température d'oxydation est fixée au 415°C. Les échantillons sont oxydés dans l'air et dans l'autoclave sous des pressions différentes et dans un microscope électronique à balayages environnemental sous vapeur d'eau. Les résultats des recherches peuvent être résumés ci-dessous : -Deux types d'oxydation (retardée et non retardée) ont été observés pour les précipités. -Le facteur de Pilling-Bedworth des précipités est plus élevé par rapport à celui de zirconium. -Les précipités contenant du fer entrainent une formation des cristaux de l'oxyde de fer pur à la surface du matériau, quand les précipités sont à la surface ou à la proximité. Ces observations mènent à la conclusion que le comportement d'oxydation des précipités peut être corrélé à leurs compositions et à la tendance d'oxydation de leurs éléments constituants.
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Hudson, Daniel. "Zirconium oxidation on the atomic scale." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:bf3f8711-7930-4f5c-87c3-4d78565576eb.
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This work was produced as part of a multidisciplinary study of the corrosion of zirconium alloys undertaken by a consortium of universities working in the MUZIC program; Oxford, Manchester and The Open University. The objective of the project as a whole was to further the understanding of the mechanisms of the breakaway oxidation process and to characterise these corrosion processes within a number of fuel rod cladding materials. This thesis describes laser 3D atom probe characterisation of the nano-scale chemical redistribution of oxygen and other solutes that occurs at the metal-oxide interface during corrosion, and a large body of technique development that was required to achieve this goal. The development of the metal-oxide interface of ZIRLO, a Zr-Nb-Sn-Fe-O alloy, is followed by generating 3D atomic scale reconstructions at four different stages of corrosion. The formation of a sub-oxide ZrO layer is seen during pre-transition oxide development. The ZrO interfacial layer is consumed by the rapid formation of oxide after the breakaway transition. After transition the chemistry of the interface is similar to the early pre-transition case, although an oxygen-saturated layer of metal adjacent to the interface formed during corrosion remains. The ZrO interfacial layer (Zr-ZrO-ZrO₂) and the region of oxygen-saturated material ahead of the metal-oxide interface alter the distribution of minor alloying additions such as niobium and iron. The ZrO layer increases the acceptance of niobium into the oxide, which is otherwise seen to be rejected at the Zr-ZrO2 interface along with iron. Niobium is seen to precipitate out of solution as nano-scale particles near the interface after around 100 days of corrosion. This is not seen in the bulk metal matrix of the corroded material due to the absence of other factors driving the process: the stress at the interface and a very high oxygen concentration in the metal ahead of the interface. The nano-scale niobium particles are found to be of a meta-stable composition. Iron is seen to redistribute in the corroded material and can be correlated with the local oxygen concentration. Similarities are seen in the behaviour of solutes within pre-transition ZIRLO and Zircaloy-4 (Zr-Sn-Fe-O). In both cases no redistribution of tin is seen at the metal-oxide interface. A Zr-Nb-Ti alloy with very poor corrosion resistance was also analysed in this way, and the similarities and differences with chemically-similar ZIRLO are discussed. The segregation of solutes to grain boundaries and solute clustering within the matrix are also examined before and after corrosion.
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Zhang, Qingyin. "Molecular simulation of transport in Yttria stabilized-zirconia and silica nanopore." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39557686.
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Cheng, Chi-kit Horace, and 鄭志傑. "Aspects of surface modification of zirconia with different zirconate coupling agents." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48334698.
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Wong, Dai-cheung Jonathan, and 黃大彰. "Effects of zirconate coupling agents on resin modified composites bonding to zirconia surfaces." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B4833473X.
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Liu, Dan, and 刘丹. "Some surface treatments for improving the durability of zirconia-based restorations." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206648.
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Zirconia has now been increasingly used in modern dental prosthetic practice due to its high mechanical strength, good esthetics, and excellent biocompatibility. However, the application of zirconia-based dental restorations is still constrained by its chemical inertness and the resultant relatively weak bonding properties, including porcelain to zirconia bonding, and resin to zirconia bonding. Therefore, many investigations have been carried out on the development of an effective method of surface modification on zirconia for improving its bonding ability. The aim of this laboratory study was to evaluate the effects of some new modified surface treatments on the adhesion durability of dental zirconia prosthetic system.
In Part I and Part II, the application of laser surface treatment was examined. Laser energy was utilized and applied on zirconia surface before porcelain veneering procedure. Its influence on porcelain zirconia integration interface was mechanically tested and compared with sandblasting treatment. The changes in porcelain zirconia shear bond strength and mechanical strength values of zirconia with the modulation of output energy were recorded. In Part III and Part IV, several types of coating treatment, such as tribochemical approach, silica powder coating, and zirconium silicate coating, were compared with their effects on resin zirconia bonding. The changes in resin zirconia shear bond strength under different aging conditions were observed. The elemental analysis was also performed for clarifying the chemical composition of zirconia surface.
The application of laser produced a flake-like micro-retentive structure on zirconia surface. Laser irradiation with the output energy higher than 11.3 W/cm2 was effective in increasing porcelain to zirconia bond strength values. The biaxial flexural strength of zirconia was not significantly affected by laser irradiation with the settings in this study. However, most of the laser treatments still demonstrated slightly lower flexural strength values compared with the control group. No changes in crystalline structure were detected after laser treatment with X-ray Diffraction (XRD) technique. Resin to zirconia shear bond strength was significantly increased after surface coatings. Without surface treatment the bonding between resin and zirconia was susceptible to artificial aging effects. Zirconia and silica-coating groups demonstrated the highest resistance to hydrolytic influence. On the other hand, the chemical changes of zirconia surface were still in need of clarification.
It was concluded that porcelain zirconia bonding could be effectively enhanced by applying both sandblasting and a new laser irradiation approach. Laser irradiation might be a potential approach as a surface treatment for improving the quality of porcelain zirconia bonding interface. The strong and reliable resin zirconia integration could not be achieved without appropriate surface pre-treatment. This coating treatment is a promising approach for strengthening resin to zirconia adhesion.published_or_final_version
Dentistry
Doctoral
Doctor of Philosophy
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Herodotou, Stephania. "Zirconium doped zinc oxide thin films deposited by atomic layer deposition." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2013045/.
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Doped zinc oxide is of interest as a transparent conductive oxide (TCO), due to the abundance of its major constituents, its low resistivity, high transparency and wide bandgap. The current work focuses on the properties required for TCO applications including resistivity of ≤10-3 Ω•cm, carrier density of ≥1020 cm-3, and transparency >80% in the visible light. Zirconium (Zr4+) was chosen as the dopant in the current work due to its abundance, comparable ionic size to Zn and because it can act as a double donor providing up to two extra free electrons per ion when substituted for Zn2+. The doping process can be controlled using atomic layer deposition (ALD), with the doped films resulting in an increased conductivity. The films in the current work resulted in a minimum resistivity of 1.44×10-3 Ω•cm and maximum carrier density of 3.81×1020 cm-3 for films <100 nm thickness, having 4.8 at.% Zr concentration. The resistivity was further reduced after reducing the interfacial and grain boundary scattering (i.e. increase grain size), by increasing the overall film thickness. The resistivity of 7.5×10-4 Ω•cm, carrier mobility of 19.6 cm2V‒1s-1 and carrier density of 4.2×1020 cm-3 were measured for a 250 nm thick film with 4.8 at.% doping. The tuning of the carrier density via doping offers control over the optical gap due to the net effect of Burstein-Moss effect and bandgap renormalisation. This resulted to an increase of the optical gap from 3.2 eV for the un-doped ZnO to 3.5 eV for 4.8 at.% Zr-doped films. The average optical transparency in the visible/near IR range was as high as 91% for 4.8 at.% doped films. The thickness increase also resulted in a grain orientation shift from perpendicular to the substrate (i.e. polar c-plane orientation) to parallel (i.e. non-polar m-plane) due to the strain increase that forced the films to grow at a low strain energy direction. This offers the possibility of growing non-polarised films that show no piezoelectric field charge observed in polar oriented films. Therefore, controlling the grain size through the number of ALD cycles can effectively result in mobility and preferred orientation control, while the doping concentration controls the resistivity, optical bandgap and transparency of the films.
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Grosso, David. "Nanoparticles of scandium oxide, zirconium oxide and hafnium oxide in alcoholic medium, used for high index optical coatings at 351nm." Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/804420/.
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de, Carvalho Tomás Eduarda M. S. "Characterisation of the ceria and yttria co-doped scandia zirconia, produced by an innovative sol-gel and combustion process." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/931.
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In the last decade new materials appeared that are candidates to be used as an electrolyte in a Solid Oxide Fuel Cell, SOFC. Some materials show high ionic conductivity but lack in important properties, such as mechanical stability or chemical compatibility with other materials in the fuel cell. Scandia Stabilised Zirconia, SSZ, became a possibility when the scandia price dropped with the opening of the Chinese and Russian markets. In the starting system Ce[subscript(x)]Y[subscript(0.2-x)]Sc₀.₆Zr₃.₂O[subscript(8-δ)], (0≤x≤0.2), scandia is introduced to improve conductivity and stabilise the cubic phase; yttria is introduced to fully stabilise the cubic phase and ceria to enhance conductivity lost with the introduction of yttria. The aim of this project is to develop a reliable new method to produce quality ceramics that are not strongly composition dependent, then to prepare a range of compositions and compare intrinsic properties without having to be concerned that poor sintering dominates conduction properties. This project can be divided in two sections, the first section the powder production method, the characteristics of the powders and its final products are in focus. In the second section the relation between electric characteristics and microstructure of the material is reported. In the first section, the effect of different compositions of the system Ce[subscript(x)]Y[subscript(0.2-x)]Sc₀.₆Zr₃.₂O[subscript(8-δ)], (0≤x≤0.2) is studied, in terms of structure, phase and microstructure. The nature, size and shape of the powders are discussed, and their effect on the final product. The sol-gel and combustion method gives the formation of hard agglomerates (shells), during the combustion, a wide range of grain sizes, between less than 1µm and 200 µm, and the formation of grains with non spherical shape. In this project, the sol-gel and combustion process and solid state method are also compared. In the second section of this project, AC Impedance measurements, as a function of temperature, oxygen partial pressure and time are discussed. The Arrhenius plot for all compositions shows two regions (high and low temperature) and the change of region occurs at 580 °C. At low temperatures there is a slight difference between compositions but this difference is less at high temperatures. The obtained ionic conductivity, at 350 °C, varies from 3.84×10⁻⁶ to 5.53×10⁻⁵ S/cm; at 700 °C, ionic conductivity from 0.013 to 0.044 S/cm. At low temperatures, the activation energy associated with bulk process is generally lower than grain boundary process; for example, the composition Ce₀.₁Y₀.₁Sc₀.₆Zr₃.₂O₇.₆₅ has an activation energy, for the bulk process, of 1.05 eV and an activation energy, for the grain boundary process, of 1.17 eV. For compositions with higher ceria content, activation energy, for bulk and grain boundary, have similar values. The AC impedance as function of oxygen partial pressure show that the amount of ceria introduced as an effect on the conductivity at low oxygen partial pressure. For the sample with no ceria in its composition, Y₀.₂Sc₀.₆Zr₃.₂O₇.₆₀, the conductivity does not vary significantly as the oxygen partial pressure is decreased; for oxygen partial of 0.21 atm, conductivity is 0.018 S/cm and when oxygen partial pressure is approximately 10⁻²⁴ atm conductivity is 0.018 S/cm. For the sample with a higher content of ceria, Ce₀.₁₂Y₀.₀₈Sc₀.₆Zr₃.₂O₇.₆₆, there is a decrease in conductivity while oxygen partial pressure decreases; and there is also the appearance of a semi-circle for lower oxygen partial pressures. For oxygen partial pressure approximately 0.21 atm, conductivity is 0.019 S/cm, but when oxygen partial pressure is decreased to 10⁻²⁴ atm conductivity decreases to 0.011 S/cm. AC impedance measurements as a function of annealing time at 600 °C were performed. Total conductivity is fairly stable, for all compositions, until 1800 hours but after this time, conductivity slowly decreases. Some compositions show a second semi-circle in the AC impedance spectra, either from the beginning, time equals 0 hours, or after some working hours. Here, the changes in conduction and conduction processes with time are discussed.
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Zouari, Wiem. "Étude de la solubilité de l'oxyde de zirconium et de sa réactivité de surface en milieux aqueux." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2018. http://www.theses.fr/2018IMTA0117.
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L’oxyde de zirconium est un matériau prometteur pour le stockage des actinides en formation géologique profonde. Pour la sureté de stockage, la stabilité de ces matrices dans les milieux géologiques doit être examinée. Une connaissance approfondie de la solubilité des phases solides de confinement des déchets radioactifs s’avère donc nécessaire. La solubilité de ZrO2 est très faible aux pH neutres (<10-8M), et augmente aux pH acides et alcalins. Cependant, les valeurs de solubilités publiées varient de plus de 6 ordres de grandeurs. L’objectif de ces travaux de thèse est de comprendre les processus ayant lieu, à l’équilibre, à l’interface ZrO2/solution et d’étudier la réactivité de surface de ce matériau en contact avec des solutions aqueuses. La solubilité de ZrO2 monoclinique et cubique a été explorée en approchant l’équilibre depuis les conditions de sous-saturation. Un protocole expérimental robuste a été développé permettant de mesurer, au plus précis possible, les très faibles concentrations de zirconium en solution (limite de quantification [Zr] ~10-11M). Les phases solides ont été caractérisées par BET, XRD, SAXS,HR-TEM and STEM-HAADF avant et après l’atteinte de l’équilibre afin d’étudier la réactivité de surface des matériaux mis en contact avec les solutions aqueuses. En vue de comprendre les mécanismes se déroulant à l’interface aussi bien que la faible solubilité dans les milieux aqueux, l’hydrolyse des liaisons Zr-O-Zr par les molécules d’eau a été étudiée par la méthode DFT en utilisant le code VASP. Cette étude nous a permis de proposer un mécanisme de dissolution dont l’étape limitante, aux pH neutres, est la difficulté de former un complexe activé à l’interface ZrO2/solutionZirconium dioxide is a promising ceramic for the specific immobilization of actinides in a geological disposal vault. An appropriate knowledge of the solubility controlling solid phases confining radioactive waste is necessary if one wants to assess the stability of ZrO2 in a disposal environmental conditions. The solubility of zirconium oxide is very low at neutral pH (<10-8M), but increases at highly acidic and alkaline pH. Solubility values may differ by more than 6 orders of magnitude at a given pH, indicating high uncertainties. The objective of this work is to understand processes governing the equilibrium between zirconium oxide and water, and to study the surface reactivity of the material in contact with aqueous solutions. The solubility of monoclinic and of cubic ZrO2 in aqueous solutions were investigated, approaching equilibrium from under-saturated conditions.The low solubility of zirconia makes its measurement a challenging task. A reliable experimental procedure was developed to measure low concentrations of zirconium (limit of quantitation[Zr] ~10-11M). In order to examine the surface reactivity, solid phases were further characterized by BET, XRD, SAXS, HR-TEM and STEM-HAADFbefore and after reaching equilibrium. In order to understand the reaction mechanism taking place at the zirconia/water interface as well as the low solubility in aqueous phase, hydrolysis of Zr-O-Zr bonds by a single and multiple water molecule were studied using the periodic DFT code, with Vienna ab initio simulation package (VASP). This study led to the proposal of a dissolution mechanism whose limiting step, in the neutral pH range, is the difficulty of formation of an activated complex
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Gao, Yong. "Deposition, stabilization and characterization of zirconium oxide and hafnium oxide thin films for high k gate dielectrics." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290136.
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As the MOS devices continue to scale down in feature size, the gate oxide thickness is approaching the nanometer node. High leakage current densities caused by tunneling is becoming a serious problem. Replacing silicon oxide with a high kappa material as the gate dielectrics is becoming very critical. In recent years, research has been focused on a few promising candidates, such as ZrO₂, HfO₂, Al₂O₃, Ta₂O₅, and some silicates. However, unary metal oxides tend to crystallize at relatively low temperatures (less than 700°C). Crystallized films usually have a very small grain size and high leakage current due to the grain boundaries. The alternatives are high κ oxides which are single crystal or amorphous. Silicates remain amorphous at high temperatures, but have some problems such as phase separation, interface reaction, and lower κ value. In this work, we addressed the crystallization problems of zirconium oxide and hafnium oxide thin films. Both of these two thin films were deposited by DC reactive magnetron sputtering so that very dense films were deposited with little damage. A specially designed system was set up in order to have good control of the deposition process. The crystallization behavior of as-deposited amorphous ZrO₂ and HfO₂ films was studied. It was found that the films tended to have higher crystallization temperature when the films were thinner than a critical thickness of approximately 5 nm. However, it was still well below 900°C. The crystallization temperature was significantly increased by sandwiching the high kappa oxide layer between two silica layers. Ultra thin HfO₂ films of 5nm thickness remained amorphous up to 900°C. This is the highest crystallization temperature which has been reported. The mechanisms for this effect are proposed. Electrical properties of these high kappa dielectric films were also studied. It was found that ultra thin amorphous HfO₂ and ZrO₂ films had superior electrical properties to crystalline films. The leakage current density of ultra thin amorphous films was at least two orders of magnitude lower than that of crystallized films. Amorphous films also showed much less hysteresis in the capacitance-voltage curve than uncapped crystallized films. The mechanisms for the electrical property differences between ultra thin crystalline and amorphous films were studied. Due to successful control of the low dielectric interfacial layer thickness, an effective oxide thickness of 1.2 and 1.4 nm was obtained for HfO₂ and ZrO₂ films, respectively.
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Platt, Philip Michael. "Mechanical degradation in oxides formed on zirconium alloys." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/mechanical-degradation-in-oxides-formed-on-zirconium-alloys(290e5b3b-a07b-404f-9eca-a5301c472dab).html.
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The present work has been produced as part of an on-going collaboration between the University of Manchester and Amec, with the primary aim of furthering mechanistic understanding of corrosion processes in zirconium alloys out-of-reactor. Zirconium alloys are used as cladding material for nuclear fuel pellets, and correct understanding of the corrosion process in autoclave is essential to predicting material behaviour in-reactor. This EngD thesis is composed of five proposed papers that investigate observations and hypotheses under the theme of mechanical degradation in oxides formed on zirconium alloys in autoclave. First investigations concern observed stress relaxation in zirconium oxide. Finite element analysis is used to capture mechanical aspects of the corrosion process and apply this to stress behaviour determined previously using synchrotron x-ray diffraction. The results indicate that a mechanism other than creep or hydrogen induced lattice strain must be present to account for the observed stress relaxation. One such potential mechanism is crack formation; statistical analysis of scanning electron microscopy images has been used to identify a link between the development of roughness at the metal-oxide interface, crack formation in the oxide and transition points or acceleration in the corrosion kinetics. Parameters such as the median radius of curvature and profile slope (Rdq) have been applied, as these parameters do not require the definition of a periodic wavelength or amplitude. These and other parameters are related to information in literature to indicate that for samples of Zircaloy-4 and ZIRLOTM, which go through transition, the interface roughness changes in a way that would increase localised stress concentrations. The third material is an experimental low tin alloy, which under the same oxidation conditions, and during the same time period, does not appear to go through transition and does not develop an interface roughness in the same way. A critical assessment of finite element analysis applied to oxidising non-planar interfaces shows the significant limitations in the existing mechanism for representing oxidation expansion and stress formation. Autoclave oxidation experiments of artificially roughened samples of Zircaloy-4 were carried out to further understand the impact of out-of-plane stress generation. The results indicate a divergence based on surface roughness after ~86 days oxidation. SEM examination of images in cross section highlighted accelerated oxidation above surface roughness peaks, and an increased crack area in rougher samples. Finally, finite element analysis of the tetragonal to monoclinic phase transformation showed that biaxial compressive stress relaxation, or the tri-axial tensile stress associated with an advancing crack tip, could reduce the transformation strain energy and destabilise the tetragonal phase. The volumetric expansion and shear strain associated with the phase transformation produces stress in the surrounding oxide sufficient to generate nano-scale cracks perpendicular to the metal-oxide interface. This would allow fast ingress routes for oxygen containing species, and therefore acceleration in the corrosion kinetics.
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Lalgudi, Srinivas Bhadrinarayanan. "Experimental evalution of oxide growth in binary zirconium alloys along with pure zirconium and Zircaloy-2 by steam corrosion testing." Thesis, KTH, Fysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95310.
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Ho, Beatrice Jane, and 何沛枝. "Effects of sandblasting on resin composite bonding to zirconia and titanium." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/194577.
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Youssef, Mostafa Youssef Mahmoud. "Predicting the equilibria of point defects in zirconium oxide : a route to understand the corrosion and hydrogen pickup of zirconium alloys." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87492.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 172-178).
The performance of zirconium alloys in nuclear reactors is compromised by corrosion and hydrogen pickup. The thermodynamics and kinetics of these two processes are governed by the behavior of point defects in the ZrO₂ layer that grows natively on these alloys. In this thesis, we developed a general, broadly applicable framework to predict the equilibria of point defects in a metal oxide. The framework is informed by density functional theory and relies on notions of statistical mechanics. Validation was performed on the tetragonal and monoclinic phases of ZrO₂ by comparison with prior conductivity experiments. The framework was applied to four fundamental problems for understanding the corrosion and hydrogen pickup of zirconium alloys. First, by coupling the predicted concentrations of oxygen defects in tetragonal ZrO₂ with their calculated migration barriers, we determined oxygen self-diffusivity in a wide range of thermodynamic conditions spanning from the metal-oxide interface to the oxide-water interface. This facilitates future macro-scale modeling of the oxide layer growth kinetics on zirconium alloys. Second, using the computed defect equilibria of the tetragonal and monoclinic phases, we constructed a temperature-oxygen partial pressure phase diagram for ZrO₂. The diagram showed that the tetragonal phase can be stabilized below its atmospheric transition-temperature by lowering the oxygen chemical potential. This work adds a new explanation to the stabilization of the tetragonal phase at the metal-oxide interface where the oxygen partial pressure is low. Third, using the developed framework, we modeled co-doping of monoclinic ZrO₂ with hydrogen and a transition metal. Our modeling predicted a volcano-like dependence of hydrogen (proton) solubility on the first-row transition metals, which is consistent with a set of systematic experiments from the nuclear industry. We discovered that the reason behind this behavior is the ability of the transition metal to p-type-dope ZrO₂ and hence lower the chemical potential of electron. Therefore, the peak of the hydrogen solubility in monoclinic ZrO₂ also corresponds to an increased barrier for hydrogen gas evolution on the surface. This explanation opens the door to physics-based design of resistant zirconium alloys, and qualitatively consistent with the monoclinic ZrO₂. Finally, we uncovered the interplay between certain hydrogen defects and planar compressive stress which tetragonal ZrO₂ experiences on zirconium alloys. The stress enhances the abundance of these defects, while these same defects tend to relax the stress. This interplay was used to propose an oxide fracture mechanism by which hydrogen is picked up.
by Mostafa Youssef Mahmoud Youssef.
Ph. D.
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GARCIA, RAFAEL H. L. "Síntese e processamento de compósitos de zircônia-alumina para aplicação como eletrólito em células a combustível de óxido sólido." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11554.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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SANTANA, LEONARDO de P. "Estudo de conformacao de ceramicas a base de zirconia para aplicacao em celulas a combustivel do tipo oxido solido." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11727.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Manhique, A. J. (Arao Joao). "Optimisation of alkali-fusion process for zircon sands: A kinetic study of the process." Diss., University of Pretoria, 2003. http://hdl.handle.net/2263/27817.
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Garner, Alistair John. "Investigating the effect of oxide texture on the corrosion performance of zirconium alloys." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/investigating-the-effect-of-oxide-texture-on-the-corrosion-performance-of-zirconium-alloys(c98f3395-4ee7-42c5-b9f3-2a55e7923c14).html.
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This work was performed as part of the MUZIC-2 (Mechanical Understanding of Zirconium Corrosion) collaboration, established with the goal of understanding the mechanism of hydrogen pickup in zirconium alloys. Hydrogen pickup is one of the least understood and most significant degradation mechanisms affecting zirconium alloys in nuclear reactors. These alloys are used as cladding and structural materials in the reactor core, mainly due to their low thermal neutron absorption cross section and excellent corrosion resistance. This project aims to investigate the effect of oxide texture (i.e. the degree of preferred orientation) on the corrosion performance of zirconium alloys. The texture of the oxide is expected to affect the microstructural development of the oxide, the grain boundary distribution and the stress state. It is therefore considered to be one of the most important factors in determining how the corrosion process occurs, and why different alloys exhibit significantly different corrosion performance. It is hoped that this project will add to the current knowledge of the corrosion process, and in particular hydrogen pickup, so that the route of hydrogen through the protective oxide can be identified. This will lead to the development of a new generation of alloys that provide improved oxidation and hydrogen pickup performance, whilst maintaining the required mechanical properties. This work focuses on four zirconium alloys; Zircaloy-4, ZIRLO™, low-Sn ZIRLO™ and Zr-1.0Nb-0.1Fe. The alloys all have different chemical compositions and therefore exhibit different corrosion performance. The macrotexture of the oxide formed on different alloys was measured by glancing angle X-ray diffraction (XRD) and Electron Backscatter Diffraction (EBSD). A fibre texture was formed in all cases, with the (10-3) to (10-5) planes oriented parallel to the metal-oxide interface for the monoclinic phase. The major orientation was found to be independent of alloy chemistry, substrate orientation and oxidation conditions. The monoclinic texture strength was found to be weakened with increasing oxidation temperature, The major orientation of the tetragonal phase was also found to be a fibre texture, with the (001) planes oriented approximately parallel with the interface. Although significant variation from this texture component was observed. It is suggested that the main driving force for oxide texture development is the transformation stress induced by the Zr-ZrO2 transformation. The microtexture of the oxides was measured using two novel techniques, Transmission Kikuchi Diffraction (TKD) and automated crystal orientation mapping with transmission electron microscopy (TEM). The techniques revealed an oxide microstructure consisting of an outer layer of equiaxed grains with a large range of orientations and an inner layer consisting of well-aligned columnar monoclinic grains. This layer of equiaxed grains was observed to form again after the transition in corrosion kinetics. A large fraction of transformation twin boundaries were observed throughout the oxides. Some of these boundaries were observed to surround large monoclinic grains, providing evidence that the tetragonal grains from which they transformed had grown considerably larger than the critical grain size for stabilisation. Without the presence of Sn, larger monoclinic grains were observed to form with a greater degree of preferred orientation, and with a lower fraction of transformation twin boundaries than Sn-containing alloys. In addition, an increased number of well-oriented tetragonal grains was correlated with the presence of Sn. It is therefore concluded that a reduction in Sn will lead to the formation of an oxide microstructure that is more resistant to both oxidation and hydrogen pickup. An analysis of the crystallography and morphology of a ZrO phase present at the metal-oxide interface was also performed. Finally, the observations have been used to construct a model of the corrosion process.
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Drisko, Glenna L. "Template synthesis and surface modification of metal oxides /." Connect to thesis, 2010. http://repository.unimelb.edu.au/10187/7090.
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Holmgreen, Erik Michael. "Nitrogen dioxide reduction with methane over palladium-based sulfated zirconia catalysts a componant [i.e. component] of a lean exhaust aftertreatement system /." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1155739813.
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Romano, Esteban Javier. "A surface science approach to understanding emission control catalyst deactivation due to sulfation of ceria-zirconia mixed-metal oxides." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-03252004-162922.
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Zhang, Qingyin, and 張慶印. "Molecular simulation of transport in Yttria stabilized-zirconia and silica nanopore." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557686.
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Zhang, Yue, and 张悦. "Synthesis and characterization of zirconia based solid acid catalysts for biodiesel production." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49858828.
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Biodiesel is a promising renewable alternative fuel to fossil energy. For the biodiesel production from low-cost feedstock, a pretreatment step is essential, which is the esterification of free fatty acids (e.g. oleic acid) in the feedstock in order to avoid soap formation and minimize catalyst deactivation. Sulfuric acid modified zirconia (H2SO4-ZrO2) is known as an effective heterogeneous catalyst for esterification. However, due to rapid 〖SO〗_4^(2-) leaching, its reusability is low and its practical use is thus largely hindered.
Zirconia supported on silica (ZrO2-SiO2) serves as a kind of non-sulfated zirconia catalyst against the leaching of the active species. Moreover, the silica support offers a large surface area and excellent thermal stability, which can accommodate a number of active zirconia species. Furthermore, there are Zr-O-Si bondings at the contact area between ZrO2 and SiO2, which might result in the formation of a new strong acid species and induce an increase of the zirconia acidity accordingly. Herein, two types of ZrO2-SiO2 catalysts were prepared, by using the reverse microemulsion method and sol-gel-hydrothermal method, denoted as ZrO2-SiO2-ME and ZrO2-SiO2-SG, respectively. The as synthesized ZrO2-SiO2 were characterized by TEM, SEM, EDX, XRD, BET and IR. ZrO2-SiO2-ME demonstrated a good dispersion of ZrO2 nanoparticles, encapsulating in the monodispersed SiO2 host matrix, while ZrO2-SiO2-SG possessed the SiO2 support with a mesoporous structure, with an average pore size of ~7 nm and a surface area of 418 m2/g. The catalysts both exhibited excellent catalytic activity and stable performance in the esterification of oleic acid.
Besides non-sulfated zirconia, sulfated zirconia catalysts other than traditional H2SO4-ZrO2 were also developed as solid acid catalysts for biodiesel production. Two sulfur-containing strong acids, chlorosulfonic acid (HClSO3) and (NH4)2SO4, were employed to acidify ZrO2, and two sulfated zirconia catalysts were prepared accordingly, namely HClSO3-ZrO2 and S-ZrO2. They were characterized by SEM, EDX, XRD, BET, IR, TGA and NH3-TPD. Comparing with H2SO4-ZrO2, HClSO3-ZrO2 and S-ZrO2 contained higher sulfur content and more acid sites. More importantly, both HClSO3-ZrO2 and S-ZrO2 demonstrated high catalytic activity and excellent durability in the esterification of oleic acid.
It is known that consecutive esterification and transesterification reactions are suitable for direct biodiesel production and acetylation of glycerol enables the conversion of this biodiesel byproduct to a biofuel additive. Therefore, all the above mentioned catalysts were examined to compare their catalytic abilities in these reactions. Among the four catalysts, HClSO3-ZrO2 exhibited the highest catalytic activity in both reactions under optimal conditions.
The thesis work here described the preparation and characterization of four types of ZrO2-based solid acid catalysts. Their catalytic activities were thoroughly investigated upon the several essential steps in biodiesel production. In addition, the synthesis condition-activity relation was studied and the synthesis and reaction conditions were delicately tuned.published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
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Romano, Esteban Javier. "In-situ surface science studies of the interaction between sulfur dioxide and two-dimensional palladium loaded-cerium/zirconium mixed metal oxide model catalysts." Diss., Mississippi State : Mississippi State University, 2005. http://library.msstate.edu/etd/show.asp?etd=etd-04062005-093500.
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McCoy, Tammy Michelle. "Extension of the master sintering curve for constant heating rate modeling." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22532.
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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Joe K. Cochran; Committee Co-Chair: Dr. Thomas H. Sanders; Committee Member: Dr. John Elton; Committee Member: Dr. Meilin Liu; Committee Member: Dr. Robert F. Speyer.
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Hui, Shiqiang. "Evaluation of yttrium-doped SrTiO3 as a solid oxide fuel cell anode /." *McMaster only, 2001.
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Yang, Jiun-Chan. "Nanoporous zeolite and solid-state electrochemical devices for nitrogen-oxide sensing." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1167408350.
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Godfrey, Shelli Heather. "Concentration and composition effects in combustion chemical vapor deposited yttria-zirconia." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/20046.
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Griffin, Jack M. "Combustion chemical vapor deposition of α-alumina, YSZ and multilayer α-alumina/YSZ films." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/20047.
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Lukich, Svetlana. "Vibrational and mechanical properties of 10 mol % Sc₂O₃-1 mol % CeO₂- ZrO₂ electrolyte ceramics for solid oxide fuel cells." Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002914.
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Shi, Jingyu. "Oxide nanoparticles and nanostructured coatings by wet chemical processing." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1148318139.
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NOBREGA, SHAYENNE D. da. "Fabricação e testes de células a combustível de óxido sólido a etanol direto usando camada catalítica." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10184.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Graves-Brook, Melissa Kaye. "Synthesis and characterization methods of palladium-doped ceria-zirconia compounds." Master's thesis, Mississippi State : Mississippi State University, 2005. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
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Cau, Camille. "Influence de la méthode de synthèse sur les propriétés structurales et catalytiques d'oxydes mixtes cérium-zirconium." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20192/document.
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Les oxydes mixtes de cérium-zirconium sont au cœur de nombreux sujets de recherche. En effet, ces matériaux sont utilisés dans différents domaines d'application, et tout particulièrement en catalyse, dans les catalyseurs trois voies en automobile ou pour l'oxydation de polluants organiques. L'intérêt pour ce composé réside dans ses propriétés remarquables d'oxydoréduction, sa capacité de stockage de l'oxygène et sa résistance au frittage. En conséquence, un nombre important de méthodes de synthèse ont été mises au point et soulignent la grande sensibilité de cet oxyde mixte à la voie de préparation employée. Dans le cadre de ce travail deux grandes voies de synthèses ont été utilisées, la co-précipitation (milieu aqueux) et la dégradation des -dicétonates métalliques (milieu non aqueux). Ces synthèses ont été réalisées à l'aide de plusieurs techniques que sont (i) le chauffage à pression atmosphérique, (ii) le traitement hydrothermal, (iii) la sonolyse et (iv) la combinaison de la sonolyse et du traitement hydrothermal, de façon successive ou en simultané. Afin de pouvoir réaliser cette dernière méthode de synthèse innovante, un réacteur permettant de réaliser un traitement sonochimique en température et sous pression a été développé (réacteur sonothermal). L'activité chimique des ultrasons dans ces conditions a pu être mise en évidence lors de la sonolyse de l'eau (légère ou lourde) et de celle d'un hydrocarbure. Au cours de la préparation de (Ce,Zr)O2, des paramètres autres que le dispositif de synthèse ont été étudiés, comme la présence d'un surfactant ou la longueur de chaine du solvant. Ainsi, il a pu être démontré que, dans le cas de la voie aqueuse, l'utilisation du réacteur sonothermal a une réelle incidence sur la surface spécifique du matériau final en comparaison de la réalisation successive des traitements sonochimique et hydrothermal. Les oxydes présentant les propriétés structurales les plus intéressantes ont été sélectionnés afin d'être employé en tant que support de métal noble dans des catalyseurs de type Pt/(Ce,Zr)O2. L'évaluation de l'activité catalytique de ces matériaux, lors de l'oxydation catalytique à l'air humide de l'acide formique, a montré que celle-ci dépend non seulement du mode de synthèse de l'oxyde mixte, mais également de la voie de dépôt du platine et du couple méthode de dépôt du platine/méthode de synthèse du supportCerium-zirconium mixed oxides are at the heart of numerous research subjects. Indeed, these materials are used in different fields of application, and particularly in catalysis in three-way catalyst for automobile or for organic pollutant oxidation. The interest for this compound resides in its remarkable oxidoreduction properties, its oxygen storage capacity and its resistance to sintering. Consequently, numerous preparation methods have been developed and underline the high sensitivity of these oxides to the synthesis way. In the present work, two main synthesis have been employed, coprecipitation (aqueous medium) and diketonate degradation (non-aqueous medium). These syntheses have been realized with several techniques which are (i) heating at atmospheric pressure, (ii) hydrothermal treatment, (iii) sonolysis and (iv) combination of sonolysis and hydrothermal treatments, in a successive or simultaneous way. In order to realize this last and innovative method, a reactor allowing sonochemical treatment under high temperature and pressure has been developed. Under these conditions, the ultrasounds chemical activity has been proved during light or heavy water or hydrocarbon sonolysis. During the (Ce,Zr)O2 preparation, other parameters than the synthesis technique have been studied such as the surfactant presence or the solvent chain length. Thus, it has been shown that, in the case of aqueous synthesis, the use of the sonothermal reactor has a real effect on the specific surface area of the material in comparison of successive realization of sonochemical and hydrothermal treatments. Oxides with the more interesting structural properties have been selected for being used as supports of noble metal in the Pt/(Ce,Zr)O2 catalysts. The evaluation of the catalytic activity of these materials, during the catalytic wet air oxidation of formic acid, showed that it not only depends on the synthesis method, but also on the platinum deposition method and the pair platinum deposition method/support synthesis method
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Amirsardari, Z., and M. Salavati-Niasari. "Study on Microstructure and Ablation Properties of Graphene Oxide/Zirconium Diboride Nanoparticle/Carbon Fiber/Resol Nanocomposites." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42604.
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.The development of compatible additives for hot corrosion inhibition in high temperature application requires test methods which yield significant results on a short time scale. The present study aims at the evaluation of the effect of hot corrosion inhibiting model additives on the performance of an ablative phenolic resin using oxy-acetylene torch test which measure different properties. Thermogravimetric analysis (TGA) and field‐emission scanning electron microscopy (FESEM) in combination with energy disperse Xray (EDX) are used. Two kinds of corrosion inhibiting additives are employed: an inorganic inhibitor based on graphene oxide sheets (GO); a ceramic nanoparticle (ZrB2) with inhibiting properties. The results obtained show that hot corrosion inhibiting additives drastically modify the ablation and thermal stability. The experimental approach described in this paper should be useful for additive development in carbon fiber/phenolic composite because it yields a more durable product than can be obtained by neat composite of how a given additive affects the ablation performance in a hot corrosive environment.
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Strothers, Susan Diane Hlavin. "Processing/microstructure/mechanical property relationships in iron aluminum zirconium boron with and without an oxide dispersion." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055341996.
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Bakradze, Georgijs [Verfasser], and Eric J. [Akademischer Betreuer] Mittemeijer. "Initial oxidation of zirconium : oxide-film growth kinetics and mechanisms / Georgijs Bakradze. Betreuer: Eric Jan Mittemeijer." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2011. http://d-nb.info/1018420975/34.
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Şahin, Erdem Çiftçioğlu Muhsin. "Synthesis and characterization of hydroxyapatite-alumina-zirconia biocomposites/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000548.pdf.
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Thesis (Master)--İzmir Institute Of Technology, İzmir, 2006.Keywords: Hydroxiapatites, alumina ceramic, zirconium oxide, urea, precipitations. Includes bibliographical references (leaves. 73-75).