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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Frittage ultra-rapide naturel : chauffage par micro-ondes et par induction / Ultrafast pressureless sintering : microwave or induction heating

Guyon, Audrey 11 July 2013 (has links)
Les techniques de frittage ultrarapide « naturel » (sans charge) comme le frittage par micro-ondes ou par induction présentent de nombreux avantages. Toutefois, le développement de ces techniques passe par une compréhension et une maitrise des mécanismes mis en jeu. A la fois similaires et complémentaires, ces procédés de chauffage-frittage ont été étudiées par une approche expérimentale afin d’approfondir les connaissances dans le domaine du Frittage Ultrarapide Naturel (FUN). Au cours de cette thèse, l’étude du frittage par micro-ondes de composites céramiques Al2O3-(Y)ZrO2 (3 à 40%vol.) a été menée parallèlement à celle du frittage par induction d’une poudre métallique micronique de nickel. La démarche expérimentale adoptée a consisté à réaliser des expériences de frittage à vitesses de chauffage imposées (de 25 à 1000°C/min) sur ces matériaux modèles et des pièces de petites dimensions, en se référant aux comportements en frittage conventionnel tant au niveau macroscopique qu’au niveau microscopique. / The techniques of ultrafast pressureless sintering as microwave or induction sintering offer manyadvantages. However, the development of these techniques requires an understanding and a control ofthe mechanisms involved. Both similar and complementary, these processes of heating-sintering havebeen studied by an experimental approach to increase knowledge in the field of Ultrafast PressurelessSintering.In this thesis, the study of microwave sintering of Al2O3-(Y)ZrO2 composites has been conductedin parallel with induction sintering of a submicronic nickel powder. The experimental approach usedconsisted in carrying out sintering experiments at imposed heating rates (from 25 to 1000°C/min) onchosen materials and small parts, referring to conventional sintering behavior at the macroscopic andmicroscopic scale.
82

Stress and Microstructural Evolution During the Growth of Transition Metal Oxide Thin Films by PVD

Narayanachari, K V L V January 2015 (has links) (PDF)
System on Chip (SoC) and System in Package (SiP) are two electronic technologies that involve integrating multiple functionalities onto a single platform. When the platform is a single wafer, as in SOC, it requires the ability to deposit various materials that enable the different functions on to an underlying substrate that can host the electronic circuitry. Transition metal oxides which have a wide range of properties are ideal candidates for the functional material. Si wafer on which micro-electronics technology is widely commercialized is the ideal host platform. Integrating oxides with Si, generally in the form of thin films as required by microelectronics technology, is however a challenge. It starts with the fact that the properties of crystalline oxides to be exploited in performing various functions are direction dependent. Thus, thin films of these oxides need to be deposited on Si in certain crystallographic orientations. Even if a suitably oriented Si wafer surface were available, it does not always provide for epitaxial growth a critical requirement for controlling the crystalline orientation of thin films. This is because Si surface is covered by an amorphous oxide of Si (SiOx). Thus, during growth of the functional oxide, an ambience in which the Si itself will not oxidize needs to be provided. In addition, during thin film growth on either Si or SiOx surface stresses are generated from various sources. Stress and its relaxation are also associated with the formation and evolution of defects. Both, stress and defects need to be managed in order to harness their beneficial effects and prevent detrimental ones. Given the requirement of SoC technology and the problem associated, the research work reported in this thesis was hence concerned with the precise controlling the stress and microstructure in oxide thin films deposited on Si substrates. In order to do so a versatile, ultra high vacuum (UHV) thin film with a base pressure of 10-9 Torr was designed and built as part of this study. The chamber is capable of depositing films by both sputtering (RF & DC) and pulsed laser ablation (PLD). The system has been designed to include an optical curvature measurement tool that enabled real-time stress measurement during growth. Doped zirconia, ZrO2, was chosen as the first oxide to be deposited, as it is among the few oxides that is more stable than SiOx. It is hence used as a buffer layer. It is shown in this thesis that a change in the growth rate at nucleation can lead to (100) or (111) textured films. These two are among the most commonly preferred orientation. Following nucleation a change in growth rate does not affect orientation but affects stress. Thus, independent selection of texture and stress is demonstrated in YSZ thin films on Si. A quantitative model based on the adatom motion on the growth surface and the anisotropic growth rates of the two orientations is used to explain these observations. This study was then subsequent extended to the growth on platinized Si another commonly used Si platform.. A knowledge of the stress and microstructure tailoring in cubic zirconia on Si was then extended to look at the effect of stress on electrical properties of zirconia on germanium for high-k dielectric applications. Ge channels are expected to play a key role in next generation n-MOS technology. Development of high-k dielectrics for channel control is hence essential. Interesting stress and property relations were analyzed in ZrO2/Ge. Stress and texture in pulsed laser deposited (PLD) oxides on silicon and SrTiO3 were studied. It is shown in this thesis that stress tuning is critical to achieve the highest possible dielectric constant. The effect of stress on dielectric constant is due to two reasons. The first one is an indirect effect involving the effect of stress on phase stability. The second one is the direct effect involving interatomic distance. By stress control an equivalent oxide thickness (EOT) of 0.8 nm was achieved in sputter deposited ZrO2/Ge films at 5 nm thickness. This is among the best reported till date. Finally, the effect of growth parameters and deposition geometry on the microstructural and stress evolution during deposition of SrTiO3 on Si and BaTiO3 on SrTiO3 by pulsed laser deposition is the same chamber is described.
83

An Experimental Study of Submerged Entry Nozzles (SEN) Focusing on Decarburization and Clogging

Memarpour, Arashk January 2011 (has links)
The submerged entry nozzle (SEN) is used to transport the molten steel from a tundish to a mould. The main purpose of its usage is to prevent oxygen and nitrogen pick-up by molten steel from the gas. Furthermore, to achieve the desired flow conditions in the mould. Therefore, the SEN can be considered as a vital factor for a stable casting process and the steel quality. In addition, the steelmaking processes occur at high temperatures around 1873 K, so the interaction between the refractory materials of the SEN and molten steel is unavoidable. Therefore, the knowledge of the SEN behaviors during preheating and casting processes is necessary for the design of the steelmaking processes  The internal surfaces of modern SENs are coated with a glass/silicon powder layer to prevent the SEN graphite oxidation during preheating. The effects of the interaction between the coating layer and the SEN base refractory materials on clogging were studied. A large number of accretion samples formed inside alumina-graphite clogged SENs were examined using FEG-SEM-EDS and Feature analysis. The internal coated SENs were used for continuous casting of stainless steel grades alloyed with Rare Earth Metals (REM). The post-mortem study results clearly revealed the formation of a multi-layer accretion. A harmful effect of the SENs decarburization on the accretion thickness was also indicated. In addition, the results indicated a penetration of the formed alkaline-rich glaze into the alumina-graphite base refractory. More specifically, the alkaline-rich glaze reacts with graphite to form a carbon monoxide gas. Thereafter, dissociation of CO at the interface between SEN and molten metal takes place. This leads to reoxidation of dissolved alloying elements such as REM (Rare Earth Metal). This reoxidation forms the “In Situ” REM oxides at the interface between the SEN and the REM alloyed molten steel. Also, the interaction of the penetrated glaze with alumina in the SEN base refractory materials leads to the formation of a high-viscous alumina-rich glaze during the SEN preheating process. This, in turn, creates a very uneven surface at the SEN internal surface. Furthermore, these uneven areas react with dissolved REM in molten steel to form REM aluminates, REM silicates and REM alumina-silicates. The formation of the large “in-situ” REM oxides and the reaction of the REM alloying elements with the previously mentioned SEN´s uneven areas may provide a large REM-rich surface in contact with the primary inclusions in molten steel. This may facilitate the attraction and agglomeration of the primary REM oxide inclusions on the SEN internal surface and thereafter the clogging. The study revealed the disadvantages of the glass/silicon powder coating applications and the SEN decarburization. The decarburization behaviors of Al2O3-C, ZrO2-C and MgO-C refractory materials from a commercial Submerged Entry Nozzle (SEN), were also investigated for different gas atmospheres consisting of CO2, O2 and Ar. The gas ratio values were kept the same as it is in a propane combustion flue gas at different Air-Fuel-Ratio (AFR) values for both Air-Fuel and Oxygen-Fuel combustion systems. Laboratory experiments were carried out under nonisothermal conditions followed by isothermal heating. The decarburization ratio (α) values of all three refractory types were determined by measuring the real time weight losses of the samples. The results showed the higher decarburization ratio (α) values increasing for MgO-C refractory when changing the Air-Fuel combustion to Oxygen-Fuel combustion at the same AFR value. It substantiates the SEN preheating advantage at higher temperatures for shorter holding times compared to heating at lower temperatures during longer holding times for Al2O3-C samples. Diffusion models were proposed for estimation of the decarburization rate of an Al2O3-C refractory in the SEN. Two different methods were studied to prevent the SEN decarburization during preheating: The effect of an ZrSi2 antioxidant and the coexistence of an antioxidant additive and a (4B2O3 ·BaO) glass powder on carbon oxidation for non-isothermal and isothermal heating conditions in a controlled atmosphere. The coexistence of 8 wt% ZrSi2 and 15 wt% (4B2O3 ·BaO) glass powder of the total alumina-graphite refractory base materials, presented the most effective resistance to carbon oxidation. The 121% volume expansion due to the Zircon formation during heating and filling up the open pores by a (4B2O3 ·BaO) glaze during the green body sintering led to an excellent carbon oxidation resistance. The effects of the plasma spray-PVD coating of the Yttria Stabilized Zirconia (YSZ) powder on the carbon oxidation of the Al2O3-C coated samples were investigated. Trials were performed at non-isothermal heating conditions in a controlled atmosphere. Also, the applied temperature profile for the laboratory trials were defined based on the industrial preheating trials. The controlled atmospheres consisted of CO2, O2 and Ar. The thicknesses of the decarburized layers were measured and examined using light optic microscopy, FEG-SEM and EDS. A 250-290 μm YSZ coating is suggested to be an appropriate coating, as it provides both an even surface as well as prevention of the decarburization even during heating in air. In addition, the interactions between the YSZ coated alumina-graphite refractory base materials in contact with a cerium alloyed molten stainless steel were surveyed. The YSZ coating provided a total prevention of the alumina reduction by cerium. Therefore, the prevention of the first clogging product formed on the surface of the SEN refractory base materials. Therefore, the YSZ plasma-PVD coating can be recommended for coating of the hot surface of the commercial SENs. / <p>QC 20111014</p>
84

Etude des dépôts par plasma ALD de diélectriques à forte permittivité diélectrique (dits « High-K ») pour les applications capacités MIM

Monnier, D. 09 April 2010 (has links) (PDF)
La miniaturisation des composants dans la micorélectronique touche maintenant les composants passifs comme les capacités MIM (Métal/Isolant/Métal). Pour augmenter la densité de capacité des capacités MIM, les diélectriques conventionnels (SiO2, ε = 3.9) sont remplacés par des diélectriques à haute permittivité diélectrique dits « high-k » comme ZrO2. Sa permittivité ε est égale à 47 lorsqu'il se trouve sous la phase tétragonale. Le procédé de dépôt de ZrO2 est la méthode PEALD. Nous avons étudié le procédé de dépôt de ZrO2 avec les précurseurs TEMAZ et ZyALD. Les propriétés thermodynamiques du TEMAZ ont été analysées par spectrométrie de masse. L'influence des paramètres du procédé PEALD et de post-traitements sur les mécanismes de formation de la zircone tétragonale a été étudiée. De nombreuses méthodes de caractérisation (XRD, Raman, TEM, SIMS, XPS, caractérisations électriques...) ont été employées afin d'établir un optimum propriétés des films de ZrO2 / performance du procédé de dépôt.
85

Brownian Motion, Cleaving, Healing and Interdiffusioninduced Nanopores and Defect Clusters in Ni1-xO-Co1-xO-ZrO2 System

Li, Ming-yen 12 July 2005 (has links)
Abstract This research is designed to investigate the occurrence of interdiffusion-induced mesopores, Brownian motion, cleaving and healing and defect clusters in three binary composites, i.e. Ni1-xO/Co1-xO, Ni1-xO/ZrO2 and Co1-xO/ZrO2 of the Ni1-xO-Co1-xO-ZrO2 system. Firstly, the (NimCo1-m)1-£_O/Ni-doped Co3-dO4 composites prepared by reactive sintering Ni1-xO and Co1-xO powders (1:2 molar ratio, denoted as N1C2) at 1000oC with or without further annealing at 720oC in air were studied by X-ray diffraction and electron microscopy to clarify the formation mechanism of mesoporous spinel precipitates. Submicron-sized inter- and intragranular pores, due to incomplete sintering and grain boundary detachment, prevails in (Ni0.33Co0.67)1-£_O protoxide with rock salt structure; whereas nanosize pores due to Kirkendall effect were restricted to the spinel precipitates having Ni component progressively expelled upon annealing. A rapid net vacancy flux and a tensile misfit stress perpendicular to the protoxide/spinel interface caused the formation of elongated and aligned {100}-faceted mesopores in the spinel precipitates with a relatively low equilibrium vacancy concentration. Aligned mesopores in diffusion zone of nonstoichiometric metal oxides have potential applications on thermal barrier bond coating and mass-transport limited heterogeneous catalysis. Also, this thesis deals with the reorientation and shape change of low-crystal-symmetry (non-cubic) ZrO2 within the high-crystal-symmetry grains of Co1-xO/Ni1-xO cubic rock salt-type structure. ZrO2/Co1-xO composites 1:99 and ZrO2/Ni1-xO composites 1:9 in molar ratio were sintered and then annealed at 1650oC for 24 and 100 h in air to induce reorientation of the embedded particles. Transmission electron microscopic observations in both systems indicated that the submicron tetragonal/monoclinic (t/m) ZrO2 particles fell into three topotaxial relationships with respect to the host Co1-xO/Ni1-xO grain: (1) parallel topotaxy, (2) ¡§eutectic¡¨ topotaxy i.e. [100]Z//[111]C,N, [010]Z//[0 1]C,N and (3) ¡§occasional¡¨ topotaxy [100]Z//[111]C,N, [01 ]Z//[0 1]C,N. The parallel topotaxy has a beneficial low energy for the family of {100}Z/C,N and {111}Z/C,N interfaces. The change from the occasional topotaxy to an energetically more favorable eutectic topotaxy was likely achieved by a rotation of the ZrO2 particles over a specific (100)Z/(111)C,N interface. Brownian-type rotation is probable for the embedded t-ZrO2 particles in terms of anchorage release at the interphase interface with the Co1-xO/Ni1-xO host. Detachment or bypassing of rock salt type grain boundaries could also cause orientation as well as shape changes of intergranular ZrO2 particles. Zirconia-polymorphism-induced cleaving and spontaneous healing by precipitation was studied in Co1-xO polycrystals containing a dispersion of ZrO2 particles. Conventional, analytical, and high-resolution transmission electron microscopy indicated that the Co1-xO matrix cleaves parallel to {100} and {110} planes and heals itself by co-precipitation of parallel-topotaxial ZrO2/Co3-£_O4 particles upon cooling. Due to size effect and matrix constraint, nanometer-size ZrO2 precipitates at cleavages were able to retain tetragonality upon further cooling to room temperature. Paracrystalline array of defect cluster was shown to form in Zr-doped Ni1-xO and Co1-xO polycrystals while prepared by sintering at relative high temperature, i.e., 1650oC to increase the defect concentration. Paracrystalline array of defect clusters in Co3-£_O4 spinel structure also occurred when doped with Zr4+ at high temperature or cooled below 900oC to activate oxy-precipitation of Co3-dO4 at dislocations. transmission electron microscopic observations indicated the spinel precipitate and its paracrystal predominantly formed at the ZrO2/Co1-xO interface and the cleavages/dislocations of the Co1-xO host. Defect chemistry consideration suggests the paracrystal is due to the assembly of charge- and volume-compensating defects of the 4:1 type with four octahedral vacant sites surrounding one Co3+-filled tetrahedral interstitial site. The spacing of paracrystalline distribution is 3.3, 2.9 and 4.9 times the lattice parameter for Zr-doped Ni1-xO, Zr-doped Co1-xO and Zr-doped Co3-dO4. This spacing between defect clusters is about 0.98 times that of the previously studied undoped Co3-dO4. There is much larger (3.4 times difference) paracrystalline spacing for Zr-doped Co3-£_O4 than its parent phase of Zr-doped Co1-xO.
86

An Experimental Study of Submerged Entry Nozzles (SEN) Focusing on Decarburization and Clogging

Memarpour, Arashk January 2011 (has links)
The submerged entry nozzle (SEN) is used to transport the molten steel from a tundish to a mould. The main purpose of its usage is to prevent oxygen and nitrogen pick-up by molten steel from the gas. Furthermore, to achieve the desired flow conditions in the mould. Therefore, the SEN can be considered as a vital factor for a stable casting process and the steel quality. In addition, the steelmaking processes occur at high temperatures around 1873 K, so the interaction between the refractory materials of the SEN and molten steel is unavoidable. Therefore, the knowledge of the SEN behaviors during preheating and casting processes is necessary for the design of the steelmaking processes  The internal surfaces of modern SENs are coated with a glass/silicon powder layer to prevent the SEN graphite oxidation during preheating. The effects of the interaction between the coating layer and the SEN base refractory materials on clogging were studied. A large number of accretion samples formed inside alumina-graphite clogged SENs were examined using FEG-SEM-EDS and Feature analysis. The internal coated SENs were used for continuous casting of stainless steel grades alloyed with Rare Earth Metals (REM). The post-mortem study results clearly revealed the formation of a multi-layer accretion. A harmful effect of the SENs decarburization on the accretion thickness was also indicated. In addition, the results indicated a penetration of the formed alkaline-rich glaze into the alumina-graphite base refractory. More specifically, the alkaline-rich glaze reacts with graphite to form a carbon monoxide gas. Thereafter, dissociation of CO at the interface between SEN and molten metal takes place. This leads to reoxidation of dissolved alloying elements such as REM (Rare Earth Metal). This reoxidation forms the “In Situ” REM oxides at the interface between the SEN and the REM alloyed molten steel. Also, the interaction of the penetrated glaze with alumina in the SEN base refractory materials leads to the formation of a high-viscous alumina-rich glaze during the SEN preheating process. This, in turn, creates a very uneven surface at the SEN internal surface. Furthermore, these uneven areas react with dissolved REM in molten steel to form REM aluminates, REM silicates and REM alumina-silicates. The formation of the large “in-situ” REM oxides and the reaction of the REM alloying elements with the previously mentioned SEN´s uneven areas may provide a large REM-rich surface in contact with the primary inclusions in molten steel. This may facilitate the attraction and agglomeration of the primary REM oxide inclusions on the SEN internal surface and thereafter the clogging. The study revealed the disadvantages of the glass/silicon powder coating applications and the SEN decarburization. The decarburization behaviors of Al2O3-C, ZrO2-C and MgO-C refractory materials from a commercial Submerged Entry Nozzle (SEN), were also investigated for different gas atmospheres consisting of CO2, O2 and Ar. The gas ratio values were kept the same as it is in a propane combustion flue gas at different Air-Fuel-Ratio (AFR) values for both Air-Fuel and Oxygen-Fuel combustion systems. Laboratory experiments were carried out under nonisothermal conditions followed by isothermal heating. The decarburization ratio (α) values of all three refractory types were determined by measuring the real time weight losses of the samples. The results showed the higher decarburization ratio (α) values increasing for MgO-C refractory when changing the Air-Fuel combustion to Oxygen-Fuel combustion at the same AFR value. It substantiates the SEN preheating advantage at higher temperatures for shorter holding times compared to heating at lower temperatures during longer holding times for Al2O3-C samples. Diffusion models were proposed for estimation of the decarburization rate of an Al2O3-C refractory in the SEN. Two different methods were studied to prevent the SEN decarburization during preheating: The effect of an ZrSi2 antioxidant and the coexistence of an antioxidant additive and a (4B2O3 ·BaO) glass powder on carbon oxidation for non-isothermal and isothermal heating conditions in a controlled atmosphere. The coexistence of 8 wt% ZrSi2 and 15 wt% (4B2O3 ·BaO) glass powder of the total alumina-graphite refractory base materials, presented the most effective resistance to carbon oxidation. The 121% volume expansion due to the Zircon formation during heating and filling up the open pores by a (4B2O3 ·BaO) glaze during the green body sintering led to an excellent carbon oxidation resistance. The effects of the plasma spray-PVD coating of the Yttria Stabilized Zirconia (YSZ) powder on the carbon oxidation of the Al2O3-C coated samples were investigated. Trials were performed at non-isothermal heating conditions in a controlled atmosphere. Also, the applied temperature profile for the laboratory trials were defined based on the industrial preheating trials. The controlled atmospheres consisted of CO2, O2 and Ar. The thicknesses of the decarburized layers were measured and examined using light optic microscopy, FEG-SEM and EDS. A 250-290 μm YSZ coating is suggested to be an appropriate coating, as it provides both an even surface as well as prevention of the decarburization even during heating in air. In addition, the interactions between the YSZ coated alumina-graphite refractory base materials in contact with a cerium alloyed molten stainless steel were surveyed. The YSZ coating provided a total prevention of the alumina reduction by cerium. Therefore, the prevention of the first clogging product formed on the surface of the SEN refractory base materials. Therefore, the YSZ plasma-PVD coating can be recommended for coating of the hot surface of the commercial SENs.
87

Größenkontrollierte Herstellung von Ge-Nanokristallen in Hoch-Epsilon-Dielektrika auf Basis von ZrO2

Lehninger, David 08 December 2018 (has links)
Nanokristalle werden beispielsweise für eine Anwendung in Solarzellen, Lichtemittern und nichtflüchtigen Datenspeichern diskutiert. Damit diese Anwendungen funktionieren können, ist eine genaue Kontrolle der Kristallitgröße sowie der Flächendichte und Lage der Kristallite in der Matrix wichtig. Zudem sollte die Matrix amorph sein, da amorphe Matrixmaterialien die Nanokristall-Oberfläche besser passivieren und beständiger gegen Leckströme sind. In dieser Arbeit werden Ge-Nanokristalle in die Hoch-Epsilon-Dielektrika ZrO2 und TaZrOx eingebettet. Im System Ge/ZrO2 kristallisieren die Ge-Cluster und die ZrO2-Matrix bei der gleichen Temperatur. Aufgrund der kristallinen Matrix weicht die Form der Ge-Nanokristalle von einer Kugel ab, worunter unter anderem die Größenkontrolle leidet. Die Beimischung von Ta2O5 stabilisiert die amorphe Phase des ZrO2 und verhindert dadurch die gemeinsame Kristallisation. Dadurch wird es im System Ge/TaZrOx möglich, kugelförmige Ge-Nanokristalle im Größenbereich von 3 nm bis 6 nm positionskontrolliert in eine amorphe Matrix einzubetten. Für die Untersuchung einer möglichen Anwendung des Materialsystems wurden Speicherzellen eines nichtflüchtigen Datenspeichers auf Basis von Ge-Nanokristallen hergestellt. Dabei zeigte sich, dass das System Ge/TaZrOx überdurchschnittlich viele Ladungen speichert und daher für diese Anwendung vielversprechend ist. Zudem stabilisiert die Beimischung von Ta2O5 eine extrem seltene orthorhombische Modifikation des ZrO2. Für ferroelektrische Datenspeicher könnte diese Phase eine aussichtsreiche Alternative zum HfO2 sein.
88

Электрохимический синтез и люминесцентные свойства нанотубулярных структур диоксида циркония : магистерская диссертация / Electrochemical synthesis and luminescent properties of zirconium dioxide nanotubular structures

Кожевина, А. В., Kozhevina, A. V. January 2017 (has links)
Объект исследования – анодированный диоксид циркония. Цель работы – электрохимический синтез нанотубулярных структур диоксида циркония и исследование их люминесцентных и абсорбционных свойств. Методы исследования – растровая электронная микроскопия, рентгенофазовый анализ, абсорбционная и фотолюминесцентная спектроскопия. Новизна работы – исследована фотолюминесценция анодированного диоксида циркония в диапазоне температур 6.2-700 К. Показано, что интенсивность свечения в области 375 – 600 нм возрастает с уменьшением температуры до 30 К. Спектры свечения описываются двумя пиками гауссовой формы с максимумами Emax = 2.28 и 2.75 эВ и полуширинами ω = 0.77 и 0.67 эВ, соответственно. Измерены спектры диффузного отражения образцов до и после отжига. Посредством построения Тауца рассчитана энергия края оптического поглощения нанотубулярного диоксида циркония Eg = 5.4 ± 0.1 эВ. Возможная область применения анодированного диоксида циркония – матрицы солнечных батарей и фотокатализаторы. / The object of investigation is anodized zirconia. The aim of the work is the electrochemical synthesis of nanotubular zirconia structures and the study of their luminescence and absorption properties. The methods of investigation are scanning electron microscopy, X-ray phase analysis, absorption and photoluminescence spectroscopy. The novelty of the work is the photoluminescence of anodized zirconia in the temperature range of 6.2-700 K. It is shown that the luminescence intensity increases with decreasing temperature to 30 K. The emission spectra are described by two peaks of a Gaussian shape with maxima Emax = 2.28 and 2.75 eV and halfwidths ω = 0.77 and 0.67 eV, respectively. A possible field of application of anodized zirconia is the matrix of solar cells and photocatalysts. Spectra of diffuse reflection of samples before and after annealing were measured. By means of the Tauc plot, the energy of the edge of the optical absorption of nanotubular zirconium dioxide Eg = 5.4 ± 0.1 eV is calculated. A possible field of application of anodized zirconia is the matrix of solar cells and photocatalysts.
89

Etude ab initio des propriétés physiques des matériaux

Vast, Nathalie 13 July 2009 (has links) (PDF)
Mon activité de recherche fondamentale dans le groupe de théorie du Laboratoire des Solides Irradiés concerne l'étude des propriétés des matériaux d'intérêt pour le CEA, dans les domaines du nucléaire ou de la nanoélectronique. Elle a pour objectif d'atteindre une description théorique -sans paramètre ajustable- des processus contrôlant l'excitation électronique, ainsi que la relaxation -ou désexcitation- électronique, et couvre: - Les propriétés de la matière hors excitation - l'état fondamental; - Les propriétés de l'état excité, abordées sous l'angle de la spectroscopie pour les électrons de valence; - Les vibrations collectives des atomes, leur couplage avec les électrons, et leurs effets sur le transport électronique ou la relaxation électronique. Ces études requièrent un environnement de calcul intensif et l'accès aux ordinateurs du Grand Equipement National de Calcul Intensif GENCI. Dans ce manuscrit, est d'abord rappelé comment calculer la fonction diélectrique inverse en théorie de la fonctionnelle de la densité dépendante du temps, et quel est le lien avec la fonction de perte électronique observée. Des résultats théoriques sur la fonction diélectrique inverse dans des oxydes non corrélés représentés par le dioxyde de titane TiO$_2$ et la zircone ZrO$_2$ sont décrits. Ensuite sont donnés les principaux résultats théoriques pour les calculs de spectres d'absorption optique pour l'oxyde de cuivre Cu$_2$O et la zircone ZrO$_2$. J'y présente une nouvelle interprétation de travail sur le noyau permettant de modéliser les effets excitoniques en théorie de la fonctionnelle de la densité dépendante du temps. Enfin, les derniers calculs menés sur les carbures de bore sont rappelés.
90

Kompozitní stomatologické biomateriály - struktura, analýza a vlastnosti / Composite Dental Biomaterials - Structure, Analysis and Properties

Matoušek, Aleš January 2012 (has links)
The aim of this work is to define relations between grain size and bioaktivity of oxide ceramics, specifically ZrO2, Al2O3 and HA. Ceramic materials with grain size from 100 nm up to 10 m, with various surface roughness, were tested for its bioactivity. Ceramography analysis was performed for all tested materials to precisely describe microstructures. Biological properties of the ceramic materials were tested via dilation tests directly in-vitro and by in-vitro extraction. Three cell culturing lines: osteoblast MG63, fibroblast L929, and epithelioid HeLa, were used for our testing. An influence of the grain size on the biological response was only found for the ceramic materials which had been thermally etched. The thermally etched nanocrystalline samples had larger areas covered by cells than ceramics with coarse grain microstructure. Biological tests on layered composites Al2O3×ZrO2 showed the cell selection determined by the type of material, where ZrO2 surfaces were preferably covered. Improved biological response of nanocrystalline ZrO2 was demonstrated on ceramic ZrO2, Al2O3 and SiO2 substrates with nanocrystalline coating of ZrO2. In this work a novel technological process for the formation of defect-free coatings was developed. Sintered coatings were tested using in-vitro technique with cell line HeLa, L929 and MG63 for up to 72 hours. The results of the biological tests of nanocrystalline coatings were consistent with results from the bulk nanocrystalline thermally etched ZrO2 ceramics.

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