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The possibilities of use of sludges from limestone wash
Švec, Jiří ; Šoukal, František (referee) ; Opravil, Tomáš (advisor)
In modern point of view of waste management is desirable to effectively process the grates possible amount of wastes. Sediments from cleaning of mined lime stones contains a lot of clay components, but there is also indispensable share of soft calcite. This composition makes these sediments a promising material for preparation of hydraulic binders. Production of common hydraulic binders, especially Portland cement, is very energy-intensive plus loads environment with considerable amount of combustion gases, therefore it is necessary to explore possibilities of alternative low - energy binders production and usage.
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Preparation of yttrium based chemically bounded phosphate ceramics
Uher, Samuel ; Šiler, Pavel (referee) ; Švec, Jiří (advisor)
The thesis is focused first on the research of literature on the topic of phosphate ceramics and then on the search for a suitable synthesis of phosphate binder based on Y2O3-P2O5-H2O and characterization of the resulting products. Various types of syntheses were prepared with subsequent characterization of the phase and chemical composition of the final products. The samples were measured on an electron microscope to determine their surface morphology and also element maps were obtained. The samples were also analyzed by heat microscopy to determine the temperature behavior of the samples. After measurement on a heat microscope, the samples were measured again on an electron microscope, in order to detect changes caused by the action of high temperatures, in particular to assess the presence of binder or sintered phases.
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Mechanism and kinetics of gas-solid carbonation of portlandite
Valach, Jakub ; Švec, Jiří (referee) ; Ptáček, Petr (advisor)
The main goal of this work, is study of kinetics and mechanism of gas-solid carbonation of portlandit. The introduction part of the thesis acquaints the reader with basic theoretical information about the study of kinetics, mechanism and the analyses themselves. In the experimental part, the reader is acquainted with the methods and procedures used to evaluate the kinetics and mechanism. The last chapter interprets the results of the study, with discusion about results and analysis of the used sample.
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Optimization of the hardening and drying process of non-cement refractory castables based on colloidal SiO2
Zbíral, Roman ; Koplík, Jan (referee) ; Švec, Jiří (advisor)
Thesis deals with drying and its effect on refractory materials based on materials with zero cement content. Heat-resistant materials prepared by the sol-gel method, i.e., a process where the input raw materials are first formed into a colloidal solution, in our case already prepared by the manufacturer, and then a gel is formed with gelation reagent. This sol must be poured into a mold before gelation processes start and gel mesh formation occur. These materials can have better mechanical properties and better firing possibilities than standard cement materials, and a shorter preparation time. These refractory materials will be examined from the point of view of drying result gel, but also with the effect of subsequent firing and mechanical properties. Samples of sol, aluminate cement, model and real mixture will be analyzed using thermal methods (DSC, TG, DTA and thermal microscope). XRD technique was used to determine content of crystalline phases.
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Physico-Chemical Characterization of Suspensions Based on Zirconium Oxide for the Use in Stereolithographic Printing Systems
Sokola, Patrik ; Švec, Jiří (referee) ; Kalina, Michal (advisor)
The presented diploma thesis deals with the optimization and characterization of suspensions with zirconium oxide stabilized by trimolar yttrium (d50 = 300 nm) using Disperbyk – 103 and Disperbyk – 111 reagents. Kinetic stability and appropriate rheological properties are important prerequisites for successful stereolithographic printing. The main goal of the work was to find a suspension suitable for practical 3D applications, to find a correlation between the performed analyses and to confirm the suitability of the prepared suspensions by mechanical tests of high-temperature processed 3D printed bodies. As part of the optical analysis performed using Fourier transform infrared spectrometry (FTIR), it was confirmed that both types of agents are successfully adsorbed on the powder surface. As part of the kinetic stability of suspensions performed using an analytical centrifuge, it was found that the agent Disperbyk - 103 is a suitable candidate for the creation of highly stable ceramic suspensions. Considering the measured and published results, the stability analysis can be considered as a complementary analysis to the traditional analysis for the assessment of suspensions - rheological measurement. Particle size analysis confirmed that Disperbyk - 103 prevents agglomerations in the entire investigated range, while Disperbyk - 111 showed a decreasing trend in mean particle size with increasing agent content. Reagent Disperbyk – 103 showed values of dynamic viscosity suitable for 3D printing of ceramics (0.93 Pa·s) when filled with ceramics (30 vol.%), in contrast to Reagent Disperbyk – 111, which can no longer be considered suitable at the same filling for the preparation of suspensions, due to the higher value of dynamic viscosity (3.09 Pa·s). Stereolithographically printed and high-temperature processed samples for both types of reagents were subjected to mechanical tests, and samples containing the Disperbyk-103 reagent achieved high Vickers hardness (1299–1315 HV), relative density (98.2%) and low defectivity confirmed by scanning electron microscope images, which determined the given agent as a suitable adept for 3D printing. The samples containing Disperbyk – 111 could be assessed as defective already visually, while the defectiveness of the microstructure was also confirmed microscopically. In addition, they achieved lower Vickers hardness (951–1037 HV) and lower values of relative density (92.8%). The greatest contribution of the publication is the provision of a hitherto unpublished view of stability analysis as a useful tool for the assessment of ceramic suspensions.
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Praparation and characterization of calcium aluminate hydrates
Hubáček, Václav ; Švec, Jiří (referee) ; Koplík, Jan (advisor)
This thesis deals with the preparation of pure calcium aluminate phases, specifically CA, CA2, C3A and C12A7 by two different methods - the solid state synthesis and the amorphous citrate method. The hydration of these phases at different temperatures was also studied The effect of the phase preparation method used and the simultaneous effect of temperature were observed on the prepared hydrates, using suitable analytical methods. The characterization and identification of the prepared phases and their hydrates were studied by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and simultaneous thermogravimetric and differential thermal analysis. The prepared hydration products were mostly identified in accordance with the literature data. TGA/DTA of the prepared hydrates helped to clarify some of the hydrate decomposition processes, especially for the hexagonal hydrate CAH10 and the cubic hydrate C3AH6, which were prepared in a sufficiently pure form suitable for analysis.
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A study of the hydration of calcium aluminate cement in an excess of silica fume
Nehéz, Samuel Emil ; Švec, Jiří (referee) ; Novotný, Radoslav (advisor)
This thesis deals with the effect of silica fume (microsilica) on the hydration process of alumina cement (CAC). During the preparation of the samples, the effect of the amount of microsilica and the effect of the hydration temperature on the formation of hydration products were investigated. Microsilica was always in excess compared to alumina cement. The characterization of the raw materials was carried out using particle size measurement and calorimetry. In the case of the samples themselves, calorimetric measurements showed that the hydration process is divided into two separate events. Thanks to this, it was possible to stop the hydration at the desired time and examine the emerging hydration products. The presence of silica fume caused the formation of characteristic hydration products - strätlingite (C2ASH8). It was found that as the temperature of hydration increases, the resulting products form more quickly. Increased hydration temperature had a negative effect on mechanical properties. The properties and characterization of the prepared samples were further investigated using XRD, TG-DTA and scanning electron microscopy (SEM).
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Utilisation of already deposited energy by-products in cement production
Lukášek, David ; Švec, Jiří (referee) ; Opravil, Tomáš (advisor)
This bachelor thesis focuses at study of deposited high-temperatured fly ash and its utilization in production of cement. The theoretical part of the bachelor thesis deals with the production and division of cements. The individual advantages and disadvantages of high-temperature and fluid fly ash when added to cements are addressed. The theoretical knowledge was used to design subsequent experiments. The conclusion of the theoretical part of the work deals with pozzolans. The main content of the experimental part was the analysis of raw materials and subsequent analysis of the mechanical properties of the prepared mixtures. The experiments were designed in accordance with valid standards.
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Combined aluminium-silicon based sol-gel binding system for refractory
Taraba, Vojtěch ; Koplík, Jan (referee) ; Švec, Jiří (advisor)
The following piece of work deals with the use of a combined aluminium-silicon based sol-gel binding system for refractory. The effect of different gelling agents on the gelation process was observed and rheometric measurements were performed for MgO. After optimizating the drying process, the resulting gel was characterized by thermal analyses, based on which the firing temperatures were selected. Qualitative analysis of the gels fired to the selected temperatures was performed using FTIR. Using XRD, the semi-quantitative phase composition of the samples was monitored as a function of firing temperature. The topography of the test bodies prepared based on results of the previous analyses was later observed using a scanning electron microscope.
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Thermal analysis methods application for characterisation of sol-gel binding system for ceramic materials
Cesnek, Ľuboš ; Másilko, Jiří (referee) ; Švec, Jiří (advisor)
The master thesis deals with the study of the binder system of silica sol and its characterization mainly by methods of thermal analysis. The master thesis also uses method of rheology to determine the gelatinization time, method of TG/DTA do analyse the exo and endothermic effects during heating, the method of FT-IR to quickly determine the composition of samples, method of XRD to analyze phase composition of the samples and the method of SEM to observe the topography of the samples. MgO is used as a gelling agent, reactive alimina is used as a filler.
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