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Synthesis of ceramic materials based on Ca-Co-O system
Žáková, Kateřina ; Švec, Jiří (referee) ; Bartoníčková, Eva (advisor)
In this work synthesis of structure cobaltites based on Ca-Co-O system is discussed. As major way of synthesis was chosen citric acid method. The document is devided into theoretical and experimental part and also into discussion of observed results. Main focus of literary research is general utilization and function of thermoelectric materials, related thermoeletric effects according to structural defects in crystals. Also topic of cobaltite ceramics is described. Due to the fact that calcium-cobalt oxides are conductive, their use is point of interest in high-temperature and energy applications. During experiments differential thermal and thermogravimetric analysis (TG-DTA), X-Ray diffraction, heat microscopy and scanning electron microscopy were used.
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Optimization of kaoline flocculation process
Kurťák, Marek ; Švec, Jiří (referee) ; Šoukal, František (advisor)
The bachelor thesis deals with flocculation of Karlove Vary area kaolin raw materials, their sedimentation rate and correlation of the flocculation, and sedimentation properties with composition of a particular material. The research was composed of sedimentation rate monitoring, execution of COD test, and subjecting the materials emission spectrometry with inductively coupled plasma, ion chromatography and roentgen diffraction.
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Alumina based refractories for noncement application
Böhm, Petr ; Dlabajová, Lucie (referee) ; Švec, Jiří (advisor)
The thesis deals with the possibility of bonding the ceramic mixture by a sol-gel method, Colloidal alumina was used as the sol and the gelation was performed by changing the ionic strength or pH. The influence of different gelling agents (NaCl, NH4Cl, NH3, MgO a CO(NH)) on the gellation time and on the course of the gelation was compared. The aim of the work is the preparation of refractory monolith with the highest packing desity possible, which was solved by modeling the granulometric curve of the solid part of the ceramic mixture based on alumina. The thesis also describes the behavior of prepared gels during thermal processing of ceramics. Subsequently the resulting structure of prepared ceramic bodies was monitored.
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Modification of polyvinylalcohol of lower saponification degree for preparation of MDF composites
Kotrla, Jan ; Švec, Jiří (referee) ; Šoukal, František (advisor)
The subject of the bachelor thesis is modification of polyvinylalcohol of lower saponification degree for preparation of MDF composites. MDF composites are characterized by their extreme mechanical properties. However, their low resistance to moisture is a significant disadvantage. Increased moisture resistance could be achieved by grafting suitable functional groups on the polymeric chain and the subsequent cross-linking. The study is focused on optimization of the number of functional groups and the cross-linking conditions. The number of grafted functional groups was determined by UV – VIS, XPS analysis and IR spectrophotometry. The solubility of the crosslinked samples was measured by rheological measurements.
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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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The study of sulfate depletion in cement binders
Jurko, Michal ; Švec, Jiří (referee) ; Novotný, Radoslav (advisor)
This bachelor thesis deals with the study of sulfate depletion in cement binders. Basic knowledge about cement binders is summarised at the beginning of the theoretical part. The theoretical part goes on to describe the hydration of Portland cement (PC) and to briefly describe the influence of different types of milling on PC particle size. In the experimental part, PC fractions of various average particle sizes were prepared on a planetary ball mill for wet conditions. On the prepared cement, their hydration was studied using isothermal calorimetry; especially sulfate depletion, portlandite precipitation, heat flow rate and induction period interval. n the thesis were also used analyzes for autogenous shrinkage, XRD and STA. The input raw materials are cement CEM I 42,5 R (grey, Českomoravský cement, a.s. – Mokrá, Czech Republic) and sulfate-resistant cement CEM I 52,5 R (white, Aalborg Portland, a.s. – Aalborg, Denmark). On the basis of the results analysis, a proposal was made to correct the presence of sulfate ions by adding gypsum in these cements. In the case of CEM I 52,5 R the correction is recommended and in the case of CEM I 42,5 R the correction is necessary.
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Floor systems based on secondary raw materials from power industry
Kalina, Martin ; Švec, Jiří (referee) ; Opravil, Tomáš (advisor)
This thesis deals with the possibility of using secondary raw materials from the energy industry especially the solid residues of high temperature combustion of coal. These materials should be now seen as a material with wide usage especially in the construction industry. One possibility of their usage is a replacement of binding parts in floor systems. The aim is to find the optimal composition of the mixture, which fits all the technical requirements and at the same time reduces the cost of its production. An advanced methods of powder X-ray diffraction analysis, particle size laser diffraction analysis and X-ray fluorescence analysis were used to determine the raw materials. Based on these analysis the experiments were designed focusing on the mechanical properties, the observation of the evolution of hydration’s heat in prepared mixtures and their time of setting and hardening.
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The possibilities of utilization of scoira from high-temperature combustion of coal
Dobeš, Jiří ; Švec, Jiří (referee) ; Opravil, Tomáš (advisor)
This thesis deals with the possibility of usage boiler slag in construction industry and related fields. Within this study is observed the influence of the amount of added boiler slag on the properties of pastes and mortars based on Portland cement. The influence of the addition of superplasticizer was further studied as well. The prepared samples were tested for mechanical properties such as tensile strength, bending and compression strength in the time dependence of the standard wet storage. The obtained data were further processed and evaluated.
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Modification of dry stuff with lime sludge
Švec, Jiří ; Kovářová, Alena (referee) ; Ptáček, Petr (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. Especially this can be use in following processing. After firing, where is necessary to set suitable temperature, arises a mixture of soft calcinated lime and remaining dehydrated mineral components. This calcinated mixture could partially replace used binders in dry stuffs.
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