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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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Study on the transport of humic acids through the plant cuticles
Smilková, Marcela ; Záhora, Jaroslav (referee) ; Sedláček, Petr (advisor)
This diploma thesis is focused on foliar fertilization. It is nowadays one of the most widespread types of application of commercial fertilizers. Concern of this thesis is the study of plant cuticles as a thin layer on the leaves. These thin membranes are responsible for regulation of water transport and nutrients. Further function of plant cuticles is the mechanical protection of the outer part of the plant. Plant cuticles were characterized by fluorescence spectroscopy, classical optical microscopy and profilometry. The main aim of this thesis is the optimization and verification of experimental methodology aimed to the transport of commercial humic product through plant cuticles by simple diffusion techniques. The results obtained by presented diffusion techniques of humic product through plant cuticles were correlated with the same diffusion experiments through synthetic membranes with defined pore size and density. The study on transport of commercial humic product was realized in hydrogel medium by two different diffusion methods – non-stationary diffusion technique and diffusion couple. The important part of this diploma thesis is the characterization of supported hydrogel matrix by rheology tests, mercury intrusion porosimetry and scanned electron microscopy. Conclusions of this diploma thesis could be used for improving of efficiency of foliar fertilization.
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Diffusion processes in modified humic gels
Grunt, Jakub ; Sedláček, Petr (referee) ; Klučáková, Martina (advisor)
This bachelor thesis presents a study on diffusion of cupric ions in humic acid gels. A total of four types of samples were made during a modified preparation of gels. Humic acids were dissolved either in sodium hydroxide or in the solution of sodium triphosphate. Subsequently, hydrochloric acid and magnesium chlorid were used for "precipitation" of the gels. Gained samples differed particularly in the nature of interactions forming their gel structures. All the samples were subjected to diffusion experiments. Two different methods – constant-source diffusion and immediate planar source diffusion – were used to assign the diffusion coefficients. Both these methods were based on monitoring how the diffusion profiles of cupric ions in gels develop in time and on assigning the overall diffusion flow. The aim of the thesis was to assess the impact of gel preparation procedure and resultant structure on diffusion coefficients of cupric ions and their transport attributes in gels in general. Two different methods of diffusion inquiry were chosen particularly to assess the impact of cupric ion concentration on the diffusion coefficient.
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Experimental study on the release of active ingredients from gel matrices
Volhinava, Anastasiya ; Enev, Vojtěch (referee) ; Sedláček, Petr (advisor)
This thesis deals with the characterization of hydrogels containing humic substances and salicylic acid. Experimental study of the transport of active substances was performed from the gel matrix over the skin and synthetic membranes. During this work was writing literature review focused on the use of gels with humic substances in cosmetic, medical and pharmaceutical industries. The model humic hydrogels was prepared with salicylic acid and their characterization by basic methods of material analysis. These basic methods were and visual assessment of consistency during the preparation and rheology. The study of the release of active and humic substances was performed due to the vertical diffusion cells. The amount of released humic substance was characterized by UV-VIS method and the amount of released salicylic acid from gel matrix was determined by HPLC.
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First-principles studies of the electronic and structural properties of Lead Zirconate Titanate (PZT)
Planer, Jakub ; Friák, Martin (referee) ; Bartošík, Miroslav (advisor)
This work is focused on Density Functional Theory (DFT) calculations of oxygen vacancy diffusion barriers in mixed perovskite lead zirconate titanate and its pure counterparts. We found out that barrier heights are different in lead titanate and lead zirconate caused by the different localization of the excess electrons due to the oxygen vacancy formation. Diffusion barriers were also determined for titanium-rich mixed phases and compared to experimental values. This work contributes to clarify unusually low experimentally measured diffusion coefficients in PZT. We found out that the induced vacancy states are forming localized bonds to the lead atoms which causes the oxygen vacancies to become immobile due to the increase of the activation energy of the diffusion process.
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