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Meta-talc Application in Inorganic Materials
Bednárek, Jan ; Rovnaník, Pavel (referee) ; Palou, Martin (referee) ; Havlica, Jaromír (advisor)
This thesis is focused at possibilities of preparation and characterization of XRD-amorphous delaminated and dehydroxylated talc phase – meta-talc, which can have its potential application and a starter material for a preparation of magnesium-silicate analogues of geopolymers. Changes in structure and morphology of talc ore were observed during this work. For the purposes of this research, two various talc ores – chloritic and dolomitic were examined. Whole process of meta-talc preparation was examined with whole scale of instrumental techniques such as X-ray diffraction, simultaneous thermogravimetric a differential thermal analysis, infrared spectroscopy, scanning electron microscopy or laser analysis of particle size. Meta-talc can be obtained via mechanochemical activation of talc ore with subsequent calcination. Mechanochemical treatment lead to destruction of original crystal structure and breaking of original bonds, i.e. the product of this treatment was almost amorphous and delaminated. Most of hydroxyl groups were converted to molecules of water which remained adsorbed or coordinated in ore structure. These molecules were removed during calcination step.
Modelling of Binary Nucleation in Laminar Co - Flow Tube.
Trávníčková, Tereza ; Havlica, Jaromír ; Hrubý, Jan ; Ždímal, Vladimír
Particle nucleation is one of the important phenomena encountered in both chemical engineering and environmental studies. The Laminar Co-Flow Tube (LCFT) was designed for experimental measurement of binary and ternary nucleation of mixtures of atmospheric aerosols at laboratory conditions, most often H2SO4 + H2O + amines (MEA, TEA)/terpenes (alfa-pinene, limonene). Two models were used for mathematical modeling of momentum and mass transfer in the LFDC. 2D axisymmetric CFD model and simplified 1D analytical model. A parametric study was carried out using both models and the influence of the individual simplifications of analytical model on overall behavior of the system was discussed.
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Indoor Particles of Outdoor Origin in Depositories.
Mašková, Ludmila ; Smolík, Jiří ; Trávníčková, Tereza ; Havlica, Jaromír ; Ondráček, Jakub ; Ondráčková, Lucie
Pollution in indoor environment can cause irreversible degradation of materials stored there. The air quality in depositories housed in historical buildings depends mainly on outdoor pollution infiltrated through the building envelope. There are several strategies to control the indoor air pollution. However, most of them including reconstruction, which is problematic in historical monuments. Thus detailed information about indoor air quality and factors influencing it is needed.
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Corrosion of Nonferrous Metal Materials
Ševčíková, Barbora ; Nový,, František (referee) ; Pacal, Bohumil (referee) ; Havlica, Jaromír (advisor)
In the presented dissertation thesis, I closely focused on corrosion resistance of non-ferrous metals. For full understanding of the possibilities for increasing corrosion resistance, it was vital to initially recognize the influences to the corrosion system of the samples and their surrounding environment. For this purpose, I focused on heat treatment, corrosion, and protective coatings, in the theoretical part of the thesis. For the subsequent research, it was necessary to define several constant variables, first. For this purpose, I have chosen a group of magnesium alloys, namely AZ91 Alloy and 3.5 % NaCl Electrolyte. AZ91 Alloy is of heterogenous structure formed by a solid solution of aluminum in magnesium, intermetallic phase in Mg17Al12, and their eutectic. Local microcells tend to occur in these heterogenities, which leads to faster corrosion. In order to increase corrosion resistance of the alloy, I used a combination of heat treatment and protective phosphate coating. For creating of the desired structure, which further affects compact coating formation, I selected a process involving solution heating with precipitation hardening T6. Secondary goals of the thesis involved optimization of standard technical procedures for the sake of increasing efficiency. With regard to this goal, I introduced optimized heat treatment T6 using accelerated cooling of a sample in water and liquid nitrogen. A modification besides the standard phosphating procedure was carried out with no activation step. For evaluation of corrosion resistance of the samples, I conducted water immersion tests using electrochemical methods; such as potenciodynamic curves combined with electrochemical impedance spectroscopy. In order to streamline the evaluation of the corrosion surface in technical practice, I used automatic detection. Substantial improvement of corrosion resistance of the above mentioned system, compared to heat-untreated samples, was proven through electrochemical methods. Due to accelerated cooling, a more homogeneous structure was achieved, which could be further utilized to create more uniform protective coating. For some phosphate coating, specifically manganese phosphate coating, I identified certain modifications that were in line with the set goals; i.e. skipping the activation phase, and using automatic detection for evaluation of uniform corrosion on the samples.
The Effect of Collision Parameters and Particle Diameter on Dynamics and Mixing Process of Granular Material by using Discrete Element Method.
Kozakovič, M. ; Paříková, A. ; Trávníčková, Tereza ; Kohout, M. ; Havlica, Jaromír
This contribution is focused on mixing dynamics and homogenization process of the granular material via Discrete Element Method. The simulation is conducted by using open-source code LIGGGHTS. The mixing process of approximately forty-two thousand monodisperse spherical particles is simulated in a vertical cylindrical mixer with two opposed flat blades. The rake angle of blades is 45°. The mixing process was studied with varying blade rotational speed (from 15 rpm to 540 rpm), coefficient of friction (from 0.05 to 0.9), coefficient of restitution (0.1 to 1.0), Poisson’s ratio (0.1 to 0.45) and particle diameter (2mm, 4 mm). Each of simulated processes was performed for 80 stirrer revolutions.\n\n\n\n
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Nucleation of H2SO4-H2O in Laminar co-Flow Tube: CFD Simulations and Analytical Modelling.
Trávníčková, Tereza ; Havlica, Jaromír ; Hrubý, Jan ; Ždímal, Vladimír
In this work the validity of two mathematical models differing in the complexity of flow dynamics is tested on two new nucleation isotherms measured by LCFT device. The first model is CFD and commercial software Fluent 16.2 is used for hydrodynamics evaluation. The second one is analytical programmed in the Matlab (Coflow).
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Possibilities of application of phosphate bond in brick abrasion dust treatment
Tmejová, Jana ; Havlica, Jaromír (referee) ; Opravil, Tomáš (advisor)
This bachelor´s thesis deals with possibilities of application of phosphate bond in brick abrasion dust treatment. Brick abrasion dust is produced as a secondary product of brick production during brick grinding. Brick abrasion dust is a relatively fine powder of the same composition as a burnt brick fragment. Since the brick abrasion contains an insufficient amount of the aluminum component, which is crucial for the formation of phosphate bond, the work is primarily concerned with finding a suitable aluminum dopant. The aim of the thesis is to find a suitable admixture that has a sufficient content of aluminum to form a phosphate bond and to determine the ideal amount to be added. Alternative sources of the aluminum component are tested in combination with a commercially available phosphate bond (Alufos 50).
Breaking of Rod-shaped Model Material during Compression.
Kulaviak, Lukáš ; Pěnkavová, Věra ; Růžička, Marek ; Punčochář, Miroslav ; Zámostný, P. ; Grof, Z. ; Štěpánek, F. ; Schöngut, M. ; Havlica, Jaromír
The breakage of a model anisometric dry granular material caused by uniaxial compression was studied. The bed of uniform rod-like pasta particles (8 mm long, aspect ratio 1:8) was compressed (Gamlen Tablet Press) and their size distribution was measured after each run (Dynamic Image Analysing). The compression dynamics was recorded and the effect of several parameters was tested (rate of compression, volume of granular bed, pressure magnitude and mode of application). Besides the experiments, numerical modelling of the compressed breakable material was performed as well, employing the DEM approach (Discrete Element Method). The comparison between the data and the model looks promising.
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