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Optimisation of polyethylene glycol hydrogels preparation by polymerisation and their subsequent characterisation
Fornůsek, Jakub ; Trudičová, Monika (referee) ; Smilek, Jiří (advisor)
The goal of this bachelor’s thesis was the optimization of the preparation of polyethyleneglycol hydrogels by radical polymerization and their subsequent characterization by the means of rheometry, swelling experiments and examination of transport properties through the absorption of an active substance and its subsequent desorption. To examine these hydrogels, UV photopolymerization was chosen due to its simplicity and reproducibility. As part of the optimalization, hydrogels were prepared under varying conditions and then characterised by the previously mentioned methods. The effect of the presence of the cross-linking agent ethylenglycol dimethacrylate on the properties of the resulting hydrogels was also investigated. These examined gels represent a new type of chemically cross-linked hydrogels, which are part of a basic research project applications by GAČR. From rheometric measurements, it was confirmed that a higher molecular weight of the measured sample corresponded to lower values of viscoelastic moduli. The effect of the cross-linking agent on these values was negligible. The mesh density played a significant role in swelling and transport experiments. As its value increased, the swelling capacity of the hydrogel decreased and therefore a smaller amount of water was absorbed. The presence of the cross-linking agent was also noticeable, as it contributed to a creation of higher density polymer networks.
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Investigation of transport processes in humic systems using computer modelling
Zeman, Matěj ; Sedláček, Petr (referee) ; Smilek, Jiří (advisor)
This bachelor’s thesis deals with issue of humic acid diffusion. The main goal of this work is to obtain a simple mathematical model that simulates the dialysis of a dye and humic acid and thus to investigate the bonding properties of humic acids as a sorption agent. This model was simplified enough to be used as a basis for the next modelling. The COMSOL Multiphysics program was used to create the model, especially the „Transport od Diluted Species“ and „Chemistry“ modules, which enable simulation of the mentioned processes. The results showed that it is possible to monitor dialysis over time using this model and at the same time the sorption properties of these substances can be observed.
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Migration of pharmaceuticals in soil systems
Janebová, Denisa ; Pekař, Miloslav (referee) ; Klučáková, Martina (advisor)
The increasing use of drugs leads to their frequent occurrence in the environment, which poses a risk not only because it can lead to the proliferation of antibiotic-resistant bacterial strains, but also because it can threaten human health. Therefore, this work focuses on the issue of the occurrence and behaviour of two antibiotics in soil, specifically tetracycline and sulfamethoxazole. Due to the presence of soil organic matter, it is believed that the soil can partially prevent the spread of drugs that enter the environment. The diploma thesis involved conducting diffusion experiments in soil columns under real conditions to determine the effective diffusion coefficients of tetracycline and sulfamethoxazole in three extraction agents. Sorption and desorption processes were also conducted in the individual layers of the soil column. The concentrations of the leachates were measured using UVVis spectrometry and liquid chromatography, while FTIR spectrometry was used to confirm the presence of the bound drug in the soil column.
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Transport and mechanical properties of hybrid hydrogel networks based on gellan
Sokolínský, Jan ; Pekař, Miloslav (referee) ; Kalina, Michal (advisor)
This diploma thesis deals with the characterization of the mechanical and transport properties of gellan based hybrid hydrogels. As part of this work, the process of optimizing the preparation of gellan-poly(vinylalcohol) IPN hydrogel was first studied with an emphasis on the repeatability of the preparation due to the preservation of mechanical properties of the hydrogel. Then, both on the gellan hydrogels themselves and on selected IPN compositions, the effect of various additives was studied (specifically, the effect of the addition of a plasticizer and the effect of cross-linking by polyvalent ions). Based on these tests, a set of samples was selected, on which dynamic mechanical analysis, swelling and drying experiments were additionally measured. At the end of this diploma thesis, the transport properties of selected hydrogel compositions were also studied. The tests conducted in this thesis revealed that both the formation of a dual network and the addition of the mentioned additives allow us to influence the studied properties.
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Difuzní vlastnosti OSB desek v důsledku zasažení nadměrnou vlhkostí.
Žižková, Lucie ; Vertal', Marián (referee) ; Chybík, Josef (referee) ; Bečkovský, David (advisor)
The presented dissertation focuses on the change of diffusion properties in oriented strand board (OSB) panels after exposure to excessive moisture. OSB panels undergo a change in their diffusion properties after being affected by excessive moisture and subsequently dried, causing them to deviate from the original design of the wooden wall structure. The aim of this study is to describe the experimentally measured change in diffusion properties and incorporate it into the composition of a real wooden wall structure, evaluating its performance through computer simulation. The introduction of the dissertation provides the theoretical basis for the experimental section, which includes measurements of water absorption, diffusion properties, and the risk of mold growth. The experimental section describes the approaches and methods used to achieve the objectives of the dissertation. The measurements were conducted on test samples of OSB panels in the laboratories of the Institute of Civil Engineering. After being exposed to excessive moisture, the test samples were dried using two drying methods. The dried test samples were placed in testing assemblies, where diffusion was measured using the dry cup method. The measurements were carried out in two stages, with more than 80 samples measured in each research stage. In the final part, the measurements are evaluated through graphs. The change in diffusion properties was then incorporated into the composition of a real wooden wall structure and assessed using computer simulation, which is more commonly used in practice according to ČSN 73 0540 (Czech Technical Standard).
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High Temperature Processes in Silicon Solar Cells Production
Frantík, Ondřej ; Hudec, Lubomír (referee) ; Banský,, Juraj (referee) ; Szendiuch, Ivan (advisor)
The thesis is focused on high temperature processes in crystalline solar cells production. Main topic is diffusion of traditional dopants phosphorus and boron. Diffusion processes for creating solar cells are different from classical diffusion in semiconductor industrial. It is reason why the thesis describes crated layers in detail. Knowledge of diffusion processes is used for creating bifacial solar cells and development of a new phosphorus emitter for conventional solar cells. Bifacial cells are a new type of cells. Developed new emitter increases efficiency and decreases cost of solar cells production. Another part the thesis is devoted to the prediction of diffusion processes. New models of phosphorus and boron diffusion for photovoltaic industrial are created in software SILVACO. Models correspond with real results.
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The influence of humic acids methylation on the interaction of surface active agents
Bělušová, Anna ; Weidlich, Tomáš (referee) ; Smilek, Jiří (advisor)
The presented diploma thesis deals with the study of interactions between humic acids as the main component of soil organic matter with a model organic pollutant presented by cationic surfactant Septonex (which was expected to interact positively with humic acids due to its charge) through unconventional combination of dialysis and diffusion techniques realized in diffusion cells together with isothermal titration calorimetry capable of elucidating the nature of ongoing reactions from a thermodynamic point of view. The experiments were performed with a humic acid isolated by standard isolation procedure from Leonardite (1S104H) purchased from the International Society for Humic Substances, with humic acids isolated from lignite as well as modal chernozem. The aim of the submited diploma thesis is to assess the influence of carboxyl functional groups in the structure of humic acids to interactions with Septonex. For this reason, said samples of humic acids have been modified by selective methylation of their carboxyl functional groups, which can no longer participate in interactions with ionic substances. Results from diffusion cells and isothermal titration calorimetry confirmed the assumption that Septonex interacted with all types of unmodified humic acids more than with their methylated derivatives. Despite the available literature, it was surprising that the differences in the interaction of humic acids with Septonex were not diametrically different when comparing unmodified humic acids with their methylated derivatives. The extent of these interactions was assessed through the apparent equilibrium constant Kapp determined in the diffusion (dialysis) experiments and from the course of enthalpy curves from isothermal titration calorimetry. After the experiments and their evaluation, it can be concluded that humic acids and Septonex in their interactions, due to their structures, probably apply not only electrostatic interactions, especially through available carboxyl functional groups of humic acids and positively charged hydrophilic parts of Septonex molecules, but also a significant role have a hydrophobic effect, hydrogen bonds and Van der Waals forces.
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Reactivity-mapping studies on biopolymers in hydrogel forms
Smilek, Jiří ; Kislinger, Jiří (referee) ; Sedláček, Petr (advisor)
The diploma thesis is focused on the study of interactions between biopolymers and model probes in a hydrogel media utilizing diffusion processes. The main aim was to test and to optimize selected combination of diffusion methods (diffusion cells and unsteady diffusion) in study of interactions between biopolymers and organic dyes. Anionic (humic acids) and cationic (chitosan) representatives of biopolymers were utilized and methylene blue and methylene orange were used as a reactivity probe in the case of humic acids and chitosan, respectively. Another appreciable part of the work is represented by in-depth characterization of applied biopolymers and hydrogel samples by a wide range of analytical and physico-chemical methods (rheometry, UV-VIS, FT-IR etc.). Besides particular experimental results on studied systems, the diploma thesis provides both theoretical and practical background for subsequent applications of the innovative and full-automated method for reactivity mapping of biopolymers.
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Reaction synthesis of bulk intermetallic materials from cold spray deposits from binary powders containing iron
Dyčková, Lucie ; Krajňáková, Petra (referee) ; Jan, Vít (advisor)
This thesis deals with reaction synthesis of materials Fe–Al, Fe–Cu and Fe–Ni from cold spray. In literature analysis are introduced these systems and for each system there is brief description of binary equilibrium diagram. Furthermore here are some short explanations of diffusion, Kirkendall effect and other possible processing technologies of intermetallic materials. In experimental part, samples of sprayed materials were annealed and then microstructural changes were investigated. This thesis contains photographs of microstructure, results from scanning electron microscopy, X-ray, and measurements of microhardness.
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