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Thin-film geopolymeric plasters for exterior application
Ručková, Jana ; Opravil, Tomáš (referee) ; Šoukal, František (advisor)
This thesis is dealing with preparation of exterior thin-layer geopolymer plaster where the effect of supplement of various types of superplasticizers in their different amounts on the quality of geopolymer plaster is studied. The objective of this work is to determine suitable type of superplasticizer which would improve rheological quality of fresh plaster mix, its adhesion to the surface and last but not least would preserve good mechanical qualities of geopolymer binder. In the experimental part initially test subject were prepared from meta-kaolin, water, water-glass, sand and with supplement of various types of superplasticizers in various amounts. These test subjects were tested for compressive and flexural strength. Further workability and adhesion to the surface of these plaster pastes was observed. Geopolymer pastes were also subjected to calorimetric comparison of kinetic processes occurring during solidification and hardening. In order to identify the exact composition of superplasticizers used as rheological modifiers, the infra-red spectrometry of these substances was performed. There was a need to specify the water-glass in more detail as well, elemental analysis was performed on it on radiographic fluorescent spectrometry. To closer identify the structure and distribution of superplasticizer in geopolymer paste the pictures of the mix which was the most suitable for use for exterior thin-layer geopolymer plasters were made on scanning electron microscope. On the same mix radiographic diffraction on the powder samples was also performed which served for phase analysis.
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Polymer-cement composites for refractory aplications
Zbončák, Marek ; Ptáček, Petr (referee) ; Šoukal, František (advisor)
This bachelor thesis deals with preparation of high-strength polymer-cement composites based on the calcium aluminate cement and polyvinylalcohol. MDF composites are interesting because of their mechanical properties which exceed strengths of the common materials based on the cement and inorganic binders. So they represent perspective kind of material which could be used for construction purposes. Thermal degradation of the polymer leads to structure changes of the composite and reduction of mechanical properties. Therefore thesis is aimed to characterize the influence of the temperature on mechanical properties, structural changes and material composition. Temperature dependence of flexural strength was examined during the work. Changes of composition and structure were characterized by XRD, DTA-TGA in combination with EGA, SEM and EDS analyses. Due to requirement of the material refractoriness there were also tested options of preparation of MDF composites based on phosphates binders which are used in refractory manufacture.
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The formation of gehlenite and anortite in the ceramics body.
Matysová, Dorota ; Šoukal, František (referee) ; Ptáček, Petr (advisor)
This bachelor thesis deals with the study of mechanism and kinetics of gehlenite and anorthite formation in the ceramic body. Methods used for this study were thermal analysis (TG-DTA-EGA), HT-XRD and heating microscopy. The Kissinger equation which belongs to the mechanism-free isoconversional methods was used for the determination of the activation energy, the pre-exponential factor and the Avrami coefficient. Characteristic of reactants kaoline Sedlec Ia and precipitated CaCO3 (Penta, p.a.) using IR spectrometry, thermal analysis (TG-DTA-EGA), SEM and heating microscopy is also included in this thesis.
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Preparation and characterization of concretes based on blended geopolymeric binder
Bulejko, Pavel ; Straka, Radek (referee) ; Šoukal, František (advisor)
This bachelor thesis focuses on preparation of concretes based on alkali activated binding systems (geopolymers). Finely ground blast-furnace slag was used as a basic aluminosilicate compound for preparation of an alkali activated binder. A mixture of sodium water glass and 50 % KOH solution, which was replaced by cement kiln dust in some cases, was used as an activator. The prepared testing samples (columns 40x40x160 mm) were mechanically tested for strength and the influence of the substitution of KOH solution by cement kiln dust on strength was observed. Then the work aims at structure analysis of binders prepared – the thermal analysis was carried out and the phase composition was explored with RTG diffraction.
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High-strength macrodefect-free composites for refractory applications
Ryšková, Martina ; Másilko, Jiří (referee) ; Šoukal, František (advisor)
The subject of the bachelor thesis is the study of heat-resistant macrodefect-free (MDF) cements based on calcium-aluminate cement and organic polymer polyvinylalcohol. Macrodefect-free cements are particularly important in excellent mechanical parameters, which include tensile strength in bending. These materials are characterized by their low porosity and the absence of microcracks. The main role of the MDF cements takes binding and non-flush interaction with polymer cement, which affect the chemical and physical-mechanical properties. The main problem in applying the MDF cements is the low water resistance. To prepare macrodefect-free samples were used calcium-aluminate cement (SECAR 51, SECAR 71) and polymer polyvinyl Gohsenol GH 17S. They were observed changes in mechanical properties depend on the type of curing samples were cured at laboratory temperature and 70°C. Samples annealed at 1000 ° C and then tested for tensile strength in bending before and after annealing, compared to mechanical properties. Thermal stress was tested by doping a microscope TGA-DTA-EGA and TMA analysis.
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Solubility of power plant fly ashes in high-alkali environment
Kejík, Pavel ; Opravil, Tomáš (referee) ; Šoukal, František (advisor)
This work deals with study of alkali activated ashes from high-temperature and fluidized bed coal combustion in thirteen powerplants in Czech republic. A solution of 50% sodium hydroxide was used as an alkali activator in this case. Because the two main elements of these secondary raw materials are silica and aluminum, the main part of the work is study of their evolution to solution and dissolve time dependence. The second part is comparing of the phase composition of powerplant ashes before alkali activation and after that.
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Preparation of bioceramic materials for medical applications
Doboš, Petr ; Šoukal, František (referee) ; Palou, Martin (advisor)
The aim of this work was to prepare hydroxyapatite powder by sol-gel and precipitation method. Then, the powders were pressed and sintered at 500 °C, 800 °C and 1100 °C. These samples of HAP were analyzed by FTIR, XRD, SEM methods. The microstructure measurement by SEM indicates that the size HAP particles varies from micro to nano meter. The average size of dominant particles is determined around 5 – 8 µm with surrounding fine particles of 1 µm size. The in vitro bioactivity of HAP samples was investigated by immersing them in Simulated Blood Fluid for 4 weeks. The work reports the result of mikrostructure analysis of samples after immersion. The bioactivity was influenced by the sintering temperature. It is evident, that the layer of the new hydroxyapatite phase formed during immersion on the surface of initial HAP samples changes with temperatures.
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Preparation of geopolymeric binders based on power plant fly ashes
Jevická, Lucie ; Opravil, Tomáš (referee) ; Šoukal, František (advisor)
This thesis deals with preparation of geopolymeric binders based on power plant fly ashes by alkali activation. It studies influence of different types ashes content in pastes on setting and final properties of geopolymeric binders. The aim of study is determination of optimal ratio of raw materials to reach the best possible characteristics of final binder. Ashes from high-temperature and fluidized bed coal combustion were used for experimental works. Mass content of ashes in tested mixtures and total ratio of oxides crucial for polycondensation and geopolymeric structure formation were chosen as major input parameters. Calorimetric measurements of tested mixtures fresh pastes were implemented to learn about setting process. Hardened binder specimens were tested for bending and compressive strength.
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TiO2 pillared clay for photocatalytic purposes
Fiala, Michal ; Šoukal, František (referee) ; Ptáček, Petr (advisor)
Bachelor’s thesis describes preparation of mixed catalytic systems kaolin/ TiO2 and metakaolin/ TiO2. Samples were prepared via hydrolysis of TiCl4 in kaolin suspension. Catalyst metakaolin/ TiO2 was prepared by calcination of this material under static oven atmosphere at 600 °C. Thermal analysis (simultaneous TG-DTA), infrared spectroscopy (FT-IR) and electron microscopy (REM) were used for samples characterization. Catalytic efficiency of mixture kaolin (Sedlec Ia) or metakaolin with TiO2 (anatase) was compared with pure kaolin. Experiment is based on oxidation of ethylalcohol, which was introduced in to reactor in flow of inert gas (argon). Amount of decomposed ethylalcohol is proportion to concentration of oxygen in gas product outputting from reactor. System kaolin/ TiO2 show higher catalytic performance than metakaolin/ TiO2 catalyst.
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