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Preparation of calcium-aluminate phases
Ohaňka, Zdeněk ; Novotný, Radoslav (referee) ; Koplík, Jan (advisor)
This work focuses on the preparation of calcium aluminates by solid state synthesis and by sol-gel method. Phases prepared were monocalcium aluminate (CA), dodecacalcium heptaaluminate (C12A7), tricalcium aluminate (C3A) and calcium dialuminate (CA2). Two modifications of sol-gel method were used – the difference between them was in the addition of EDTA. Each method was closely described and results were compared according to the achieved purity of prepared phases. X-ray diffraction analysis was used to determine the purity of prepared calcium-aluminates.
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Options of preparation of tobermorite
Dlabajová, Lucie ; Másilko, Jiří (referee) ; Opravil, Tomáš (advisor)
The bachelor thesis deals with options of preparation of tobermorite. Tobermorite is a mineral, which, thanks to its composition and properties, is an important phase in aerated concrete. On the field of science and research, an attention has been drawn on tobermorite as an ion ex-changer. Synthesis of a pure mineral can cause problems with testing and improving its properties. Tobermorite crystallizes together with other calcium silicate hydrates from system CaO-SiO2-H2O during a hydrothermal reaction. This thesis mainly focuses on influence of choosing starting materials and their treatment before the hydrothermal synthesis. Other influences which are studied are conditions of hydrothermal processes and their influence on final products of hydrothermal synthesis. Phase composition of prepared samples was characterized by XRD and TG-DTA. As an additional analyze was used scanning electron microscopy (SEM).
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Optimization depozition variables during material printing of titania coatings
Mlčkovová, Hana ; Králová, Marcela (referee) ; Dzik, Petr (advisor)
This thesis studies the effect of conditions in the printing material layers of titanium dioxi-de sol-gel formulations for the print properties of the resulting films – TiO2, which were pre-pared from a precursor of titanium tetraisopropoxide (TTIP). Thin films were deposited on the printing material soda lime glass and the layer thickness was controlled by repeatedly apply-ing. Prepared films were subjected to observation under an optical microscope, and the thic-kness of the layers was measured by mechanical profilometry.
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Synthesis of foamed bioceramics for potential medical applications
Doboš, Petr ; Šoukal, František (referee) ; Palou, Martin (advisor)
Cílem práce byla příprava porézních vzorků HAP pro potenciálně medicínské aplikace. HAP byl připraven metodou sol-gel a precipitační. Vzorky HAP byly podrobeny analýze FTIR, XRD, SEM. Takto připravený HAP byl napěněn pomocí houbové metody s jasně definovanými póry a pomocí polymerního a skleněného expanzelu s různou distribucí a velikostí pórů. U výsledných napěněných vzorků byla vyhodnocena mikrostruktura a povrchová analýza pomocí SEM, zjištěna porozita pomocí Hg porozimetru a sledována bioaktivita in vitro v SBF. Byly zjištěny jasně definované makro, mezo a mikro póry při různé distribuci. U houbové metody pomocí sol-gel došlo k vytvoření jasně definovaných a pravidelných pórů s monodisperzní porozitou. Dominantní velikost póru byla stanovena v rozmezí 1–5 µm. Celková porozita byla stanovena na 63,5 % s celkovým povrchem 3,048 1 m/g. Precipitační metodou s polymerním expanzelem došlo k polydisperznímu rozložení pórů s třemi hlavními fázemi v rozmezí: 50–100 µm, 5–10 µm a 0,5–1 µm. Celková porozita byla stanovena na 67,6 % s celkovým povrchem 19,090 3 m/g. Bioaktivita výsledných napěněných vzorků in vitro byla sledována po dobu 7 dnů v připraveném SBF. Při napěnění sol-gel houbovou metodou nevznikla výsledná bioaktivní vrstva. U precipitační metody napěněné pomocí polymerního expanzelu vznikla nepravidelná bioaktivní vrstva. Výsledky byly naměřeny pomocí SEM analýzy.
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Application of Sol-Gel Method for Preparation of Dicalcium Silicate and its Solid Solutions
Baráček, Jan ; Živica, Vladimír (referee) ; Rovnaníková, Markéta (referee) ; Palou, Martin (advisor)
The subject of this doctoral thesis was to elucidate the mechanism of reaction leading to the formation of dicalcium silicate (C2S), its solid solutions and other phosphatic calcium silicate phases using the sol-gel method of synthesis. SiO2 (Tosil A), CaO (calcium nitrate tetra-hydrate) and H3PO4 (as a source of P2O5) were used as starting materials. Series of samples with different content of P2O5 were synthesized. The characterization of Tosil A and samples was based on the following methods: DTA/TGA and EGA, XRD and SEM and EDS analy-ses. It is known, that phosphorous oxide can enter the structure of C2S and possibly form solid solutions and different phosphatic calcium silicate phases in C2S–C3P system. Depending on the P2O5 concentration in mixtures, three distinct phases are formed: larnite (2CaO•SiO2), Ca14,92(PO4)2,35(SiO4)5,65 and 5CaO•SiO2•P2O5, as detected by XRD. Local microanalysis de-monstrated the presence of calcium phosphate epicenters (C3P) containing SiO2, calcium sili-cate (C2S) zones with minimum content of P2O5 and intermediary areas of various phosphatic calcium silicates. The formation of two distinct islets of C2S and C3P is due the affinity of acid oxides (SiO2, P2O5) towards the basic one (CaO) during the sol-gel process. Then, the formation of various phosphatic calcium silicates results from the diffusion of P2O5 and SiO2 towards calcium silicate and calcium phosphate, respectively.
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Synthesis and properties of transition metal carbides
Nedvědová Šolcová, Pavlína ; Tyrpekl, Václav (advisor) ; Zákutná, Dominika (referee)
This master thesis is a follow-up of my bachelor's project, where the goal was to prepare high entropy carbide (HEC), namely (Ti, Zr, Hf, Nb, Ta)C, by the sol-gel method followed by carbothermal reduction using spark plasma sintering facility (SPS). In this work, the first aim is to substitute SPS with ultra-fast high-temperature sintering (UHS) for the same HEC, (Ti, Zr, Hf, Nb, Ta)C. The advantages of UHS compared to SPS are a thousand times lower consumption of electricity and simpler set-up. The second aim is the adaptation of the synthesis for the preparation of HEC of different compositions, (Cr, Mn, Fe, Co, Ni)C. The third aim is the testing of the presented sol-gel technique on the production of borides, while the initial experiments were focused on boro- carbothermal reduction. Keywords: high entropy carbides, high entropy borides, transition metals, carbothermal reduction, high-temperature ceramics, sol-gel method
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Nonconventional synthesis of high entropy carbides
Šolcová, Pavlína ; Tyrpekl, Václav (advisor) ; Havlíček, David (referee)
This thesis aimed to streamline the method of the preparation of high entropy carbides. The simplification of synthesis and expends reduction were achieved using sol-gel method instead of using commercial starting powders. As precursors of transition metals, the chlorides (TiCl3, TaCl4, HfCl4 a NbCl5) and chlor-oxide (ZrOCl2) were used. The source of carbon was citric acid. All reactants were mixed in solution and dried to gel. The pyrolysis at 800 řC afterwards leads to creation of the amorphous carbon, which embedded the transition metal oxide nanoparticles. The carbothermal synthesis was completed in Spark plasma sintering device at 1400 řC, 1600 řřC and 1900 řC. Formation of high entropy carbide phase was achieved at 1600řC, which is almost 400 řC less than previously reported in literature. Intermediate and final products were characterized with powder X-Ray diffraction, scanning electron microscopy and products, in addition, were characterized with transmission electron microscopy and elements mapping. Key words: high entropy carbides, carbothermal reduction, high temperature ceramics, sol-gel method,
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Synthesis of bioactive glass for medical application
Wiederová, Kristýna ; Galvánková, Lucie (referee) ; Bartoníčková, Eva (advisor)
In this bachelor’s thesis, the 45S5 bioactive glass was synthesized via sol-gel method. Alternative precursors as colloidal silicas as a silicon source and phosphorous acid, ammonium hydrogenphosphate and ALUFOS were used. Three dierent gel ageing procedures were tested. The nine dierent samples were synthesized and analyzed. The dependence of the fnal properties of the products on the type of precursors has been confrmed. The dependence on the preparation process has not been confrmed within this thesis.
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Preparation of calcium-aluminate phases
Ohaňka, Zdeněk ; Novotný, Radoslav (referee) ; Koplík, Jan (advisor)
This work focuses on the preparation of calcium aluminates by solid state synthesis and by sol-gel method. Phases prepared were monocalcium aluminate (CA), dodecacalcium heptaaluminate (C12A7), tricalcium aluminate (C3A) and calcium dialuminate (CA2). Two modifications of sol-gel method were used – the difference between them was in the addition of EDTA. Each method was closely described and results were compared according to the achieved purity of prepared phases. X-ray diffraction analysis was used to determine the purity of prepared calcium-aluminates.
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Application of Sol-Gel Method for Preparation of Dicalcium Silicate and its Solid Solutions
Baráček, Jan ; Živica, Vladimír (referee) ; Rovnaníková, Markéta (referee) ; Palou, Martin (advisor)
The subject of this doctoral thesis was to elucidate the mechanism of reaction leading to the formation of dicalcium silicate (C2S), its solid solutions and other phosphatic calcium silicate phases using the sol-gel method of synthesis. SiO2 (Tosil A), CaO (calcium nitrate tetra-hydrate) and H3PO4 (as a source of P2O5) were used as starting materials. Series of samples with different content of P2O5 were synthesized. The characterization of Tosil A and samples was based on the following methods: DTA/TGA and EGA, XRD and SEM and EDS analy-ses. It is known, that phosphorous oxide can enter the structure of C2S and possibly form solid solutions and different phosphatic calcium silicate phases in C2S–C3P system. Depending on the P2O5 concentration in mixtures, three distinct phases are formed: larnite (2CaO•SiO2), Ca14,92(PO4)2,35(SiO4)5,65 and 5CaO•SiO2•P2O5, as detected by XRD. Local microanalysis de-monstrated the presence of calcium phosphate epicenters (C3P) containing SiO2, calcium sili-cate (C2S) zones with minimum content of P2O5 and intermediary areas of various phosphatic calcium silicates. The formation of two distinct islets of C2S and C3P is due the affinity of acid oxides (SiO2, P2O5) towards the basic one (CaO) during the sol-gel process. Then, the formation of various phosphatic calcium silicates results from the diffusion of P2O5 and SiO2 towards calcium silicate and calcium phosphate, respectively.
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