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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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Synthesis and fabrication of lead-free piezoceramics
Řeháková, Bára ; Pouchlý, Václav (referee) ; Částková, Klára (advisor)
The topic of this thesis is synthesis and preparation of lead-free pizoceramic with perovskite structure, in particular potassium-sodium niobate (KNN). In theoretical part are described possibilities of KNN synthesis and of it’s shaping and sintering. Experimental part deals with three types of synthesis described in the theretical part – solid state reaction, hydrothermal synthesis, sol-gel synthesis, and subconsequentional shaping of prepared powders by uniaxial pressing, cold isostatic pressure method, sintering (classical in oven, in some cases SPS – spark plasma sintering) of such green body and their following properties like relative density, grain size or charge constant. Preparation of KNN powder by each described method took place, followed by shaping and sintering. Best properties were shown by SPS sintered samples, which reached the highest density and lowest grain growth.
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Preparation and application of metal and semiconductor nanostructures
Hrubý, Jakub ; Kolíbal, Miroslav (referee) ; Šimšíková, Michaela (advisor)
Tato práce se zabývá teoretickými základy přípravy, charakterizace a možnými aplikací nanostruktur. V experimentální části je nastíněna syntéza a charakterizace nanostruktur. Ušlechtilé kovy jsou zastoupeny zlatem a stříbrem. Oxid zinečnatý jakožto II--VI polovodič a kompozit oxidu zinečnatého a oxidu měďnatého byly také syntetizovány bottom-up metodou. Připravené částice tvořily různé tvary, jako například kuličky, tyčinky, dlaždičky a takzvané nanokytičky. Částice byly posléze charakterizovány. Optickou mikroskopií byl proveden přibližný odhad morfologie. Skenovací elektronový mikroskop byl použit pro detailní pohled do struktury vzorku. Další charakterizační metody jako fotoluminiscence a absorbance byly využity u CuO/ZnO kompozitu.
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Hydrothermal synthesis and characterization of calcium phosphate-based coatings on AZ31 magnesium alloy
Knoflíčková, Lenka ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
The aim of this diploma thesis was to summarize all necessary knowledge needed for preparation of a quality CaP coating on AZ31 wrought magnesium alloys, and to implement its optimization for use in simulated body fluids. The theoretical part discusses biomaterials and their classification. Subsequently, the potential of magnesium alloys, their corrosion, and the possibility of surface treatment for in vivo applications are described in detail. The theoretical part concludes with the mechanism of deposition of CaP coatings on magnesium alloys and methods to evaluate their corrosion resistance. The experimental part includes the process of optimization of Mg alloy pretreatment and optimization of CaP coatings preparation, where the quality evaluation criteria were the appearance of the coating and its electrochemical and corrosion properties. These were evaluated by potentiodynamic tests. The microstructure and the chemical composition of deposited coating were observed and measured by optical and scanning electron microscopy. Long-term corrosion tests using electrochemical impedance spectroscopy (EIS) were performed on the optimized CaP coatings and these results were then compared with the corrosion properties of the uncoated AZ31 alloy.
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Evaluation of the effect of chelating agents on the properties of phosphate coatings on AZ31 magnesium alloy prepared by hydrothermal method
Molva, Vojtěch ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
The aim of this bachelor thesis was to evaluate the influence of chelating agents on the properties of CaP coatings deposited on the AZ31 magnesium alloy by hydrothermal method. The theoretical part deals with magnesium and its alloys useful not only in biomedicine. Subsequently, the possibilities of surface treatments in the field of biomedical applications are described, with a focus on calcium phosphate (CaP) coatings. The theoretical part further discusses these coatings and the influence of selected chelating agents on the formation of CaP coatings. The theoretical part is concluded with a review of the experiments already carried out for the preparation of CaP coatings on Mg alloys. The experimental part includes the preparation and analysis of the protective Mg(OH)2 layer necessary for the deposition of CaP coatings. Within the experimental part, the influence of chelating agents (Chelaton III, citric acid, magnesium gluconate hydrate) at concentrations of 5, 50, and 500 mM at different pH of the reaction mixture on the structure, morphology, composition, and quality of the prepared CaP coatings was studied. The morphology, structure, and composition of the deposited coatings were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Based on these analyses, an assessment of the quality of the coatings was performed. In terms of coating quality, the coating prepared with the addition of 50 mM of Chelaton III at pH 7 and with the addition of 5 mM of magnesium gluconate hydrate at pH 5 appeared to be the best. The corrosion resistance was investigated by potentiodynamic tests in 0.15M NaCl, always with the sample from each batch that showed the best quality. The corrosion potential (Ecorr) and current corrosion density (icorr) values were determined from the polarization curves using the Tafel extrapolation method. Based on the measurements made, the most corrosion-resistant coated sample was the one with the addition of 5 mM magnesium gluconate hydrate at pH 5.
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Effect of complexing agents on the preparation of phosphate coatings on AZ31 magnesium alloy
Wolanský, Petr ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
The bachelor thesis deals with the characterization of the effect of complexing agents on the preparation of phosphate (CaP) coatings deposited on AZ31 magnesium alloy. The theoretical part presents the basic characterization of magnesium alloys with emphasis on AZ31 and their corrosion properties. Furthermore, attention is paid to CaP coatings, their preparation with a focus on the chosen hydrothermal synthesis and the influence of complexing agents on the preparation of CaP coatings. In the experimental part the preparation of CaP coatings on AZ31 alloy with Mg(OH)2 interlayer is presented. Surface analysis of CaP coatings was performed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). Chemical analysis of CaP coatings was performed using Fourier transform infrared spectroscopy. To assess the corrosion resistance of the coatings, potentiodynamic tests were performed in 0.15M NaCl. For all the selected reagents, the best corrosion properties were obtained at the lowest concentrations, while the lowest value of icorr was observed for the sample with 0.0175M EDTA, this value corresponded to the icorr of the pretreated Mg(OH)2 sample. The preparation of CaP coatings resulted in better corrosion properties than that of pure AZ31 alloy. In all samples, the presence of hydroxyapatite (HA) as the main phase in the coating was identified. From the results obtained, it can be clearly determined that the presence of complexing agents and their concentrations affect the morphology of CaP coatings and can alter the corrosion resistance. It seems that the corrosion resistance was mainly due to the Mg(OH)2 interlayer rather than the prepared CaP coatings, which could provide higher biocompatibility of the materials.
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Tracking the evolution and stability of metal nanoparticles in zeolites by in-situ heating electron microscopy
Krakl, František ; Mazur, Michal (advisor) ; Knotková, Kateřina (referee)
Zeolites, with their unique characteristics, such as microporosity, thermal stability, and shape selectivity, are used as a support for metal nanoparticles to enhance their catalytic properties. Metal nanoparticles have a large attainable surface in relation to their mass, thus volume. There are several ways of supporting metal on zeolites, such as ion-exchange, impregnation, or direct encapsulation during synthesis. The latter method provides the stability of metal, however, even the zeolite-encapsulated nanoparticles are not fully sinter-resistant, especially at high temperatures. Insights into the sintering mechanism is crucial for improvement of stability of supported metal catalysts. In this work platinum nanoparticles were directly introduced into chabazite (CHA) zeolite during hydrothermal synthesis. The goal of this thesis was to understand metal nanoparticle sintering mechanisms. the role of aluminium content in zeolite framework in the stabilisation of metal nanoparticles was described. The structure of prepared materials was confirmed by powder X-ray diffraction. Inductively coupled plasma mass spectrometry was used to determine the elemental composition of the materials and their distribution in crystals was mapped by energy dispersive X-ray spectroscopy in a scanning transmission...
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Synthesis and Characterization of Perovskite Nanostructures
Hricov, Štefan ; Zákutná, Dominika (advisor) ; Kalbáčová Vejpravová, Jana (referee)
The present Bachelor's thesis is focused on the improvement of the hydrothermal condi- tions for BaTiO3 nanoparticles synthesis to obtain better morphology, narrow size distri- bution, and high purity of the prepared product. Particular emphasis is on the influence of different parameters in reaction, such as co-solvent, co-surfactant, the ratio between oleic acid to oleylamine, and ex-situ sodium oleate, on the resulting structure and morphology of BaTiO3 nanoparticles. The structural purity was examined with powder X-ray diffraction with Rietveld refinement to obtain and follow changes in lattice parameters and coherent domain sizes. Moreover, from the refinement of PXRD patterns, the rough estimate of a synthesis by-product (BaCO3) abundance was extracted. Furthermore, implementing the spherical harmonics function within the Rietveld refinement allowed us to access the average nanocrystallite shapes with direction-dependent crystallite sizes. The crystallite shapes and sizes were compared with the physical nanoparticle size obtained from trans- mission electron microscopy experiments. The thesis is completed with attenuated total reflectance Fourier-transform infrared spectroscopy spectra, which gave us insight into the attachment of the oleic acid at the nanoparticle surface. Keywords: BaTiO3,...
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Nanosponge MFI zeolites functionalized with metal nanoparticles for catalysis
Laštovičková, Anna ; Mazur, Michal (advisor) ; Vyskočilová, Eliška (referee)
Metal nanoparticles immobilized at various supports have outstanding catalytic activity in hydrogenation reactions. Zeolites are used as supports, mainly due to their porous structure. In this work, metal nanoparticles were immobilized on MFI nanosponge zeolites. Zeolite nanosponges (pure silica and degallated) were impregnated with pure platinum and platinum mixed with rare-earth elements (cerium, lanthanum, and yttrium) to form alloys. The main aim of this work was to investigate the activity of bimetallic nanoparticles immobilized on zeolite nanosponges in hydrogenation of cinnamaldehyde. It is a versatile model reaction to investigate catalysts, due to the presence of three different reducible groups (C=C bond, C=O bond and benzene ring) in the cinnamaldehyde molecule. The objective was to focus on selectivity effects of various catalyst towards three possible products of cinnamaldehyde hydrogenation (hydrocinnamaldehyde, cinnamyl alcohol and hydrocinnamyl alcohol). The metal alloys evolution is more feasible on the degallated zeolites due to the defects in the structure called silanol nests. These defects stabilize bimetallic nanoparticles. Moreover, samples prepared with use of degallated support showed larger surface areas. Pure-silica zeolites impregnated with metals were also prepared for...
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Hydrothermal synthesis and characterization of calcium phosphate-based coatings on AZ31 magnesium alloy
Knoflíčková, Lenka ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
The aim of this diploma thesis was to summarize all necessary knowledge needed for preparation of a quality CaP coating on AZ31 wrought magnesium alloys, and to implement its optimization for use in simulated body fluids. The theoretical part discusses biomaterials and their classification. Subsequently, the potential of magnesium alloys, their corrosion, and the possibility of surface treatment for in vivo applications are described in detail. The theoretical part concludes with the mechanism of deposition of CaP coatings on magnesium alloys and methods to evaluate their corrosion resistance. The experimental part includes the process of optimization of Mg alloy pretreatment and optimization of CaP coatings preparation, where the quality evaluation criteria were the appearance of the coating and its electrochemical and corrosion properties. These were evaluated by potentiodynamic tests. The microstructure and the chemical composition of deposited coating were observed and measured by optical and scanning electron microscopy. Long-term corrosion tests using electrochemical impedance spectroscopy (EIS) were performed on the optimized CaP coatings and these results were then compared with the corrosion properties of the uncoated AZ31 alloy.
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