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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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Antibacterial properties of bioceramic materials
Achberger, Šimon ; Částková, Klára (referee) ; Salamon, David (advisor)
Implant surgery carries a risk of infection caused by bacterial contamination of the implant surface. An effective way to inhibit proliferation of bacteria is via antibacterial surfaces, however, their usage is medically and technologically difficult. Previous research shows that cicada wing topography exhibits unique bactericidal properties. In this thesis, various topographies were fabricated using heat treatment under hydrothermal conditions. The goal was to produce a surface covered by high aspect ratio structures with 60–215 nm width and 200–300 nm length. A relative density of 85%, 12 hrs long heat treatment and solution pH 4 and 5,6 had a positive effect on formation of thin surface structures. Quantity of morphological changes was proportional to -tricalcium phosphate content.
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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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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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Antibacterial properties of bioceramic materials
Achberger, Šimon ; Částková, Klára (referee) ; Salamon, David (advisor)
Implant surgery carries a risk of infection caused by bacterial contamination of the implant surface. An effective way to inhibit proliferation of bacteria is via antibacterial surfaces, however, their usage is medically and technologically difficult. Previous research shows that cicada wing topography exhibits unique bactericidal properties. In this thesis, various topographies were fabricated using heat treatment under hydrothermal conditions. The goal was to produce a surface covered by high aspect ratio structures with 60–215 nm width and 200–300 nm length. A relative density of 85%, 12 hrs long heat treatment and solution pH 4 and 5,6 had a positive effect on formation of thin surface structures. Quantity of morphological changes was proportional to -tricalcium phosphate content.
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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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