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Effects of structural and processing parameters on th eproperties of polymer nanocomposites
Zárybnická, Klára ; Žídek, Jan (referee) ; Jančář, Josef (advisor)
The work deals mainly with preparation protocol of nanocomposites. The task of this work is to study structural and procedural parameteres that control the dispersion of nanoparticles in polymer solution to be able to prepare desired spatial organization of nanoparticles. The work resolves the effect of various components such as polymer matrices, nanoparticles and solvent, in which matrices and nanoparticles are blended. Used components control final dispersion state of nanoparticles and it influences also properties of investigated materials such as glass transition temperature, stiffness and rheological properties.
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Study possibilities of nanotechnology in cement composites
Kardošová, Romana ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
The aim of this paper is to summarize and assess the possibility of using nanoparticles as additives in concrete. These particles have the ability to improve the mechanical and physical properties of cement composites or even gave them brand new ones. Industrial use is hampered by effective incorporation of nanoparticles into the matrix, the health and environmental risks and, last but not least, the financial costs. The experimental part of the thesis deals with the dispersing nanosilica and nanometakaolin particles in aqueous solution and their subsequent integration into the structure of cement mortar.
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Influence of nanoparticles on polymer chains in solution.
Bayer, Adam ; Chamradová, Ivana (referee) ; Jančář, Josef (advisor)
High surface area of used nanoparticles and their comparable size with polymer chains, are the most important characteristics of fillers in the preparation of non-Newtonian suspensions. Such structures at different concentrations have major influence on the rheological behavior of polymer solution in solvent. With increasing volume fraction of nanofiller, there is pseudoplastic or dilatant behavior present in the dissolved elastomers. Diploma thesis studies the influence of the concentration of different elastomers (SBR and SEBS copolymers) and nanofiller (hydrophobic nanosilica) in suspension, of rheological properties.
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Effect of colloidal silicon dioxide on selected properties of cement pastes and mortars
Barek, Jaroslav ; Žižková, Nikol (referee) ; Rovnaníková, Pavla (advisor)
The presented diploma thesis deals with the potential use of colloidal silica in cement composites. Investigation is focused primarily on selected properties of cement pastes and mortars with colloidal silica content. Two selected types of colloidal silica (particles with average size of 14 nm) have been used as a cement addition and partial replacement of cement, respectively. The experimental program for cement pastes with colloidal silica included tests for isothermal calorimetry (the study of cement hydration) and thermal analysis (determining the portlandite content). Hardened cement pastes have been studied through measurements of compressive strength. The microstructure was examined by scanning electron microscopy. Hardened mortars with colloidal silica have been studied through measurements of compressive strength, flexural strength, modulus of elasticity and fracture mechanics parameters. Fracture mechanics tests show that 5 % and 20 % addition of colloidal silica can enhance after 28 days of curing fracture energy up to 18,4 % and 32,7 %, respectively. For the compressive strength enhancing effect of colloidal silica, it was found to be more pronounced in the early age, while rate of strength gain can be lower than the control in the later ages. Our investigations revealed that the silica sol will coagulate immediately when the cement is mixed into the water containing sol. The ionic composition of pore fluid significantly influences the stability of colloidal silica and lead to their aggregation. After additional tests it has been found that small addition of calcium hydroxide greatly improved the compressive strength of the resulting cement pastes with colloidal silica content. Addition of calcium hydroxide in conjunction with modified cement paste preparation can enhance compressive strength after 3 days of curing up to 64,4 % in comparison with the blank paste.
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Concretes with high temperature fly ash activated by nanoparticles.
Labaj, Martin ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
The aim of this thesis is to summarize the knowledge regarding reduction of negative impact of high volumes of fly ash in HVFA concretes using nanotechnology and experimentally verify the findings. To compensate the inferior early-age properties, it is possible to use active nanoparticles, such as nanosilica or nanolimestone. The first step of the experiment was the production of stable nanoparticle’s dispersions using ultrasonic homogenization and UV/Vis spectroscopy. In subsequent steps the influence of nanoparticle’s presence on cementitious materials’ properties was verified on cement pastes and mortars with 40 a 60 % of fly ash. The best variant was then used to produce nano-modified HVFA concretes. Even at a minimum dose, the positive effect on early-age properties indicates the usefulness of nanoparticles in technology of concrete. An important contribution of this thesis is also the acquired knowledge related to the nanoparticle’s behavior and handling.
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The influence of nanoparticles on isothermal crystallization rate of isotactic polypropylene
Miškolci, Michal ; Jančář, Josef (referee) ; Bálková, Radka (advisor)
This diploma thesis deals with the study of isothermal crystallization of nanocomposite materials based on isotactic polypropylene (iPP) and nanosilica, depending on the volume fraction (0, 2, 4 and 6 %) and type of silica and the crystallization temperature. Fumed silica and four types of silica with different surface treatment were used as filler. The crystallization performed at temperatures 136, 138, 140 and 142 °C has been studied in-situ using polarized optical microscope and the crystallization rate was evaluated from the growing radius of spherulites. It can be stated that particles of silica have been inbuilt into the spherulites due to the linear growth of spherulites of all composite materials. The most significant increase of the crystallization rate of iPP was caused by fumed silica, the most significant decrease was caused by silica TS-720 at volume fraction 4 %. The crystallization rate (G) has been slightly increased with the increasing volume fraction of filler at 136 °C, the G slightly decreased at 138 °C and there was no trend of G for two higher temperatures. Also, it was not possible to exactly evaluate the influence of the surface treatments. The reason is the most probably uneven (non-homogenous) distribution of nanosilica as revealed thermogravimetric analysis. The crystallization kinetics was evaluated according to the Lauritzen-Hoffmann theory. The morphological part of the study showed that iPP was in ? and ß-structure and spherulites of ? phase were of the type I, II and mixed.
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Studying the properties of high strength concrete using micro and nano admixtures
Gabko, Miroslav ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
The objective of this bachelor thesis is to examine the properties of high strength concretes with the main focus on application of mikro or nano admixtures. In theoretical part their production, the properties and the influence on fresh and hardened properties of cement composites are described. In addition, it explores the influence of plasticizer type, some properties of aggregate and cement types. The practical part focuses on testing cement mortars in which fine cements were added. The compressive and flexural strengths were examined after 7 and 28 days of curing, moreover, rheological properties and heat hydration of cements were also observed. Furthermore, the influence of high speed mixing on cement mortars properties was studied.
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High-grade concrete using nanoparticles
Labaj, Martin ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
The aim of this paper is to summarize and assess the possibility of using nanoparticles as additives in high performance concrete. These particles have the ability to improve the mechanical and physical properties of cement composites or even gave them brand new ones. Industrial use, however, is hampered by several obstacles. In particular, it is the task of effective incorporation of nanoparticles into the matrix, the health and environmental risks and, last but not least, the financial costs. The experimental part of the work deals with the first-mentioned problem, namely with dispersing carbon nanotubes in aqueous solution and their subsequent integration into the structure of cement mortar.
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Polymer nanocomposites for interior car body parts
Miškolci, Michal ; Bálková, Radka (referee) ; Jančář, Josef (advisor)
This bachelor’s thesis is interested in the problem of scratch resistance of interior car body parts. In this thesis, the solution is seen in using polycarbonate – based nanocomposites. In theoretical part, a literature search of this theme was made. In experimental part, the samples based on polycarbonate were prepared, and their tensile modulus was tested, as one of the main parameter affecting the scratch resistance.
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