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Practical applications of superconductivity
Mádrová, Tereza ; Langerová, Petra (referee) ; Baumgartnerová, Alena (advisor)
Předložená bakalářská práce je zaměřena na zpracování souhrnného přehledu využití supravodivosti v technických řešeních a aplikacích, čímž se rozumí nikoliv experimentální využití, nýbrž využití v reálném technickém řešení. Tato práce se věnuje zejména popisu, v první části základním atributům supravodivosti, bez nichž není možné princip supravodivosti pochopit a jsou tudíž nezbytnou součástí práce, ve druhé části rozdělení do kategorií supravodičů podle určitých kritérií, a v poslední části popisuje příklady aplikací supravodivosti tak, jak se s nimi můžeme setkat v každodenním životě.
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Nuclear magnetic resonance study of multiferroic perovskites
Adamec, Martin ; Chlan, Vojtěch (advisor) ; Kouřil, Karel (referee)
The aim of this Bachelor thesis is to study the oxide Pb(FeNb)0.5O3 by means of nuclear magnetic structure spectroscopy. Studied material has perovskite structure and belongs to a class of materials exhibiting magnetoelectric behavior. Temperatures of phase transitions are among others affected by selection of cations and their arrangement. To examine the structural properties, nuclear magnetic resonance was utilized, since this method is sensitive to electron and magnetic structure. Temperature dependence (in the range of 12 to 296K) of 207 Pb and 93 Nb spectra sample Pb (FeNb)0.5O3 was measured in external magnetic field 9.4T. The spectra show frequency shifts and resonance-line width increase with decreasing temperature. 57 Fe spectrum was measured in zero external field at 4.2 K. Multiple signals were detected, indicating the presence of more than one type of Fe atom in the structure. The experimental results are interpreted and discussed in relation to phase transitions and to cation arrangement in the sample.
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Study of Perovskite Type Oxide Catalysts for Partial Oxidation of Methane
Cihlář, Jaroslav ; Hanykýř, Vladimír (referee) ; Čapek,, Libor (referee) ; Čičmanec,, Pavel (advisor)
Research was curried out on the perovskite systems with general formula A1-xA‘xB1-yB‘yO3± (where A=La, Sm, A´=Ca, B´=Al, B=Co,Fe,Mn and Cr). Perovskite oxides were sythesized by polymerisation methods and characterised by RTG analysis, BET method, SEM and EDX. TPD spectra and catalyst testing were measured in high temperature plug flow reactor and products were analysed by mass spectrometry. It was found, that metane oxidation at ratio O2/CH40,5 depended on the temperature. Total oxidation proceeded at the temperature betwen 300-700oC to the carbon dioxide and water, while the partial oxidation of metane (POM) occured at above 700oC to the hydrogen and carbon oxid (syngas). This was ascribed by equilibrium of O2 betwen gas phase and solid perovskite. There was used 12 perovskite systems, which catalysed methane oxidation by the same way. Dry reforming of methane run above temperature 700oC. Cobaltite and ferite type perovskites were found as the most active catalytic systems. On the base of obtained results the Mars van Krevelen mechanism was established for explanation of oxidation and reformation of methane by perovskite systems. It was showed, that POM was running by two steps mechanism. Products of total oxidation was occured in the first step, which were passed over to the syngas (H2+CO) in the second step.
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Synthesis and Analysis of Composite Oxide Ceramics in Presence of Nonconventional Energetic Fields
Bartoníčková, Eva ; Lapčík, Ĺubomír (referee) ; Zmeškal, Oldřich (referee) ; Cihlář, Jaroslav (advisor)
Synthesis and bulk analysis of composite ceramic oxide materials and materials with perovskite-defect structure is presented within this work. Syntheses of these advanced ceramics materials were carroed out by using of nonconventional techniques (microwave-assisted hydrothermal synthesis and polycondensation techniques) and by conventional mechanochemical activation followed by high temperature solid state reaction. X-Ray difraction (XRD), Rietveld analysis, scaning microscopy (SEM), microalysis EDS-SEM, thermal analysis (TG), infrared spectroscopy (IR), determination of particles size and specific surface area were used for description of synthesized products. In case of perovskite system based on La-Sr-Fe-Ti-O electrochemical properties were studied. Part of work was focused on chemical analysis of synthesized composite oxide materials and decomposition hard structured products by using of nonconventional fields.
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Study of the synthesis and structure of ceramic perovskite materials for energy applications
Strejček, Josef ; Bartoníčková, Eva (referee) ; Cihlář, Jaroslav (advisor)
Method, so called “glycin- nitrate process”, combined with high temperature solid state reaction, of preparation multi- component ceramic perovskite materials was studied. Two types of perovskite systems were prepared by this method. Firs one, based on LaNiO3 doped by calcium and aluminium and second one, based on SmFeO3 doped by calcium and nickel or cobalt. This method made possible preparation of one phase perovskite or perovskites with few percent of nickel in form of oxide. In systems containing both nickel and calcium another phases rich in calcium and nickel appeared.
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The study of preparation and catalytic activity of doped ABO3 perovskites for hydrogen synthesis
Dobeš, Jiří ; Cihlář, Jaroslav (referee) ; Cihlář, Jaroslav (advisor)
The Master´s thesis deals with the preparation of perovskite oxides by glycine synthesis with following characterization and analysis of catalytic activity. Especially is discussed crystallographic structure. In the theoretical part were first summarized the available information of the properties and usage of perovskite oxides. In the experimental part of the work was carried out the preparation of perovskite oxides and were made chemical analysis. Moreover a catalytic activity of selected perovskites has been studied and have been illustrated their crystal structure.
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Study of preparation of ceramic membranes
Matějková, Michaela ; Částková, Klára (referee) ; Bartoníčková, Eva (advisor)
In this bachelor thesis the literature retrieval concerning the preparation of ceramic membranes suitable for power applications (membrane reactors, fuel cells) and materials suitable for their preparation, was summarised. Based on that literature retrieval the glycine-nitrate syntheses of selected ceramic materials were performed. As starting material was chosen zirconate structure (Zr-Ba-O), which was doped by cerium, iron, aluminium and manganese ions. The resulting powders were further processed to solid membranes by unaxial pressing and sintering (density of sintered bodies about 93 % t. d.). Then the influence of dopants on the properties of the powders and ceramic membranes were studied. The evaluation of properties (as phase composition, powders morphology and microstructure of ceramic bodies) was performed by x-ray analysis, scanning electron microscopy, a specific surface analysis and simultaneous thermal analysis.
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Synthesis of functional ceramic powder materials
Čípová, Eva ; Maca, Karel (referee) ; Částková, Klára (advisor)
The theme of the work is electroceramic materials, particularly materials based on perovskites. The theoretical part describes electroceramic materials, their applications and possibilities of their synthesis. The experimental part focuses on the synthesis methods in liquid media and solid phase of barium strontium titanate. The prepared powders were characterized by morphology, phase composition and particle sinterability. It was found that weakly agglomerated particles with a single phase composition, perspective for the preparation of dense bulk ceramics, were prepared by the metod in liquid phase, especially by precipitation.
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Catalytic behaviour of ceramic catalytic materials
Schlosser, Radek ; Cihlář, Jaroslav (referee) ; Cihlář, Jaroslav (advisor)
In this bachelor’s thesis the methods of preparation of ceramic perovskite-like membranes for heterogenous catalysis and reformation reactions of carbohydrates were studied. The syntetic La-Ca-Fe-Ti-O type and commercial La-Ca-Fe-Co-O type powders were used. The properties such as phase purity, specific surface area and morphology of used powders were determined. Technology of processing included powder uniaxial pressing, membrane sintering and polishing their surface. Conditions for uniaxial pressing were optimized. The dependence of grain size and amount of titanium was determined.
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Synthesis and Properties of Ceramic Photocatalytic Materials
Strejček, Josef ; Maca, Karel (referee) ; Cihlář, Jaroslav (advisor)
Two methods of synthesis of ceramic catalytic perovskite materials for fotochemical decomposition of water and partial oxidation of methane were studied. The method based on mechanochemical activation of oxide reactants followed high temperature solid state reaction made possible preparation of almost one phase perovskites of InVO4, InNbO4, InTaO4, EuVO4, EuNbO4 a EuTaO4. Pseudo sol-gel synthesis combined with high temperature solid state reaction lead to one phase perovskites or products with more than 90% of perovskites phase of the Sm-Ca-Co-Al-O type.
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