|
|
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.
|
|
|
Polymer-cement composites of increased refractoriness
Ryšková, Martina ; Opravil, Tomáš (referee) ; Šoukal, František (advisor)
The subject of the diploma thesis is the preparation of macro-defect-free (MDF) composites based on calcium-aluminate cement and organic polymer polyvinylalcohol. Attention focused on the optimization of the dose, the degree of hydrolysis and molecular weight of the polymer with respect to the heat resistance of the material. Thermal degradation of polyvinyl alcohol leads to changes in the structure of MDF composite. The study was mainly focused on the characteristics of polyvinyl alcohol dosage associated with the resultant mechanical properties of the material. During the work were monitored for changes in the mechanical properties of samples were cured at 60 °C and subsequently fired at 180 °C, 600 °C, 1000 °C and 1400 °C. It was tested in flexural strength, heat microscopy, TGA-DTA-EGA and SEM analysis.
|
|
|
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.
|
|
|
Synthesis of foamed bioceramics for potential medical applications
Doboš, Petr ; Šoukal, František (referee) ; Palou, Martin (advisor)
Cílem práce byla příprava porézních vzorků HAP pro potenciálně medicínské aplikace. HAP byl připraven metodou sol-gel a precipitační. Vzorky HAP byly podrobeny analýze FTIR, XRD, SEM. Takto připravený HAP byl napěněn pomocí houbové metody s jasně definovanými póry a pomocí polymerního a skleněného expanzelu s různou distribucí a velikostí pórů. U výsledných napěněných vzorků byla vyhodnocena mikrostruktura a povrchová analýza pomocí SEM, zjištěna porozita pomocí Hg porozimetru a sledována bioaktivita in vitro v SBF. Byly zjištěny jasně definované makro, mezo a mikro póry při různé distribuci. U houbové metody pomocí sol-gel došlo k vytvoření jasně definovaných a pravidelných pórů s monodisperzní porozitou. Dominantní velikost póru byla stanovena v rozmezí 1–5 µm. Celková porozita byla stanovena na 63,5 % s celkovým povrchem 3,048 1 m/g. Precipitační metodou s polymerním expanzelem došlo k polydisperznímu rozložení pórů s třemi hlavními fázemi v rozmezí: 50–100 µm, 5–10 µm a 0,5–1 µm. Celková porozita byla stanovena na 67,6 % s celkovým povrchem 19,090 3 m/g. Bioaktivita výsledných napěněných vzorků in vitro byla sledována po dobu 7 dnů v připraveném SBF. Při napěnění sol-gel houbovou metodou nevznikla výsledná bioaktivní vrstva. U precipitační metody napěněné pomocí polymerního expanzelu vznikla nepravidelná bioaktivní vrstva. Výsledky byly naměřeny pomocí SEM analýzy.
|
|
|
Reduction of efflorescence in the geopolymer systems
Suchý, Rostislav ; Šoukal, František (referee) ; Kalina, Lukáš (advisor)
Alkali metal cations are weakly bound in the structure of alkali activated materials. This fact causes the formation of undesirable efflorescence in humid environment. In this work, the effect of fluoride additives, which significantly reduce the efflorescence, was investigated. The chemical mechanism of selected additive in the modified binder was studied based on XRD, SEM EDX and ICP OES analysis. Also the effect of the added fluorides on the mechanical properties of the final product was monitored.
|
|
|
Inhibition of hydrogen evolution in aluminum-phosphate refractory binders
Bednárek, Jan ; Kalina, Lukáš (referee) ; Šoukal, František (advisor)
The thesis deals with the possibilities of inhibition of the reaction of aluminium-phosphate binders with wear iron, which is contained in bauxite. This material is mixed with phosphate binders to form refractories. The hydrogen is produced by this reaction causing the mixture foaming. The amount of evaluated hydrogen was observed by the measuring by the Jank’s calcimeter. Also the shape of oxidation-reduction potential of the binders was measured before and after mixing with aggregate, using potentiometer. The influence of the addition of various cations on the hydrogen evolution and on the oxidation-reduction potential was observed. The effectiveness of the inhibitors was studied also visually by forming test elements.
|
|
|
Latexes modified cementitious materials
Vinter, Václav ; Krátký, Josef (referee) ; Šoukal, František (advisor)
In this thesis, the development of mechanical properties and structure of latex modified cementious materials during hydration was studied. Latex modified materials are composites of inorganic cement (portland cement) and organic polymer latex. Preparation, processing and fabrication of the polymer cement material based on portland cement was optimized with aim to reach the most compact structure of the product with the finest mechanical characters. The experimental part was pointed to observe influence of the type and amount of polymer latex with focus on mechanical characters and hydration kinetics with given filling as well as without it. In presented work, the possibility of compaction of the material by high-shear mixing within twin-roll mixer (the prototype for production of MDF composite) was verified. The second part of the labor was aimed to analysis of prepared polymer-cementitious material. For determination of influence of batching of added polymer latex on hydration of cement paste the thermal analysis (DTA/TGA) and infrared spectroscopy of composite was done. At last the microscopic observation by optical microscope was carried.
|
|
|
Modification of concrete elements for cooling towers
Mohelská, Lucie ; Šoukal, František (referee) ; Opravil, Tomáš (advisor)
This master´s thesis deals with the suppression of the growing of algae in cooling towers. Subject of the work is suggestion and testing surface modification of the existing mature concrete in order to suppress the growth of algae. In the frame surface modification, several commercially available and newly developed systems were tested. Testing systems are based on the basis of portland cement, geopolymers or formation of insoluble complex compounds containing metal elements (Zn, Cu). Experimental methods were applied in the real environment of cooling towers of Dukovany Nuclear power plant.
|
|
|
Possibilities of hexavalent chromium reduction within portland cement hydration
Mončeková, Miroslava ; Koplík, Jan (referee) ; Šoukal, František (advisor)
The issue of Hexavalent chromium toxicity to Portland cement hydration is a very actual these days. It takes much effort to obtain a cement containing Cr(VI) less than 2 ppm. The primary objective of this diploma theses is to find appropriate reducing substances and specify their efficiency, as well as to make an attempt to optimize their dosage. As reducing substances there were plumbed sulphites and tin(II) salts. The influence of reducing substances applied to the hydration and cement properties were validated by strenght tests, the calorimetric measurement and the volume-variation measurement. And also the changes in hydration products microstructure of Portland clinker after the gypsum replacement by sulphite ions were plumbed. The study of microstructure is based on SEM and XRD methods.
|
|
|
Mechanical activation of chemical reactions at interfaces of MDF composites
Matoušek, David ; Másilko, Jiří (referee) ; Šoukal, František (advisor)
The thesis deals with study of mechnochemical activation of chemical reactions at interphase of MDF composites. MDF composites are high-perspective composite materials on polymer-cement base. They excel especially in terms of flexural strengths. High flexural stregth is caused by binding interactions between the polymer and the cement. This interactions arise due to mechanochemical activation of raw material mixture at the stage of production. This work focuses on the creation of artificial cement-polymer interphase by contacting the surfaces of two molded tablets (polyvinyl alcohol and monocalcium aluminate), activation of chemical reactions at interphase by means of specially designed appartus, which achieves good plane-parallelism of activation surfaces and good definability of activation conditions (shear rate, pressure). After experiments under different conditions, the activated surfaces are analyzed by SEM, EDS, XPS and FT-IR.
|
guest ::
RSS feed.