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Use of finite element method for stress evaluation in layers for optical applications
Tesařová, Anežka ; Ohlídal, Miloslav (referee) ; Burša, Jiří (advisor)
This thesis is concerned with the mechanical stress generated in thin layers applied on a substrate. The application takes place at high temperatures and due to different coefficients of thermal expansion of materials, the sample is deformed, and thereby the stress is generated. The first part of the thesis includes the derivation of the Stoney formula for uniaxial and biaxial stress in a layer. Besides, analytical calculations of the normal stress in the layer for the simplified link model, and shear stress on the layer interface were evaluated. The main part of the work consists of solving the problem using FEM modeling. Because the actual temperature behavior during the application was not known, a fictitious temperature load was used as an input. For the samples, the coefficients of thermal expansion of the layer were then searched so that the thermal load resulting deflection corresponds to the experimental data. Three types of models were created, namely the link body model, the axisymmetric model, and the solid model. The axisymmetric model was used for the calculation of samples forming circular isolines during deformation and a volume model for samples forming elliptical isolines. The result of the FEM calculations was the normal stress in the applied layers, for which corresponding relationships were created using regression analysis.
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Gas molecule interaction with surfaces of oxides including vanadium
Krutel, Jozef ; Nehasil, Václav (advisor) ; Ševčíková, Klára (referee)
The project researches a thin vanadium layer model system. The samples were prepared by vapour-deposition of vanadium on support layer of cerium oxide. The surface composition of samples was monitored by X-ray photoelectron spectroscopy (XPS). The samples were exposed to CO and O2 molecular beams (MB), in order to measure gas adsorption and CO2 production. In the course of reaction measurements by quadrupole mass spectroscopy (QMS) exhibited no signs of oxidative reaction. The XPS spectra show the tendency of vanadium to interact with CO and O2 forming carbide and oxide.
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Photocatalytic activity of hybrid titanium dioxide layers treated by plasma
Koukolová, Anna ; Králová, Marcela (referee) ; Veselý, Michal (advisor)
The bachelor thesis deals with photocatalytic activity of thin layer of titanium dioxide deposited onto PET flexible foil treated by plasma. Photocatalytic activity is measured by two different methods, degradation of dye Acid Orange 7 and benzoic acid. Possible model compounds for evaluation of photocatalytic activity as well as deposition techniques for preparing thin layers of photocatalyst were discuss in the theoretical part. Changes of photocatalytic activity were found insignificant with plasma treatment. Evaluation used Acid Orange 7 is suitable. Unlike method with benzoic acid was discovered inappropriate for measuring of photocatalytic activity for photocatalyst deposited onto PET foil.
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Preparation of zinc oxide nanorods colloid from thin layers
Mičová, Júlia ; Remeš, Zdeněk ; Chang, Yu-Ying ; Neykova, Neda
The interest in ZnO (zinc oxide) nanoparticles is increasing due to low cost of their processing as well as the ability of fabricating ZnO nanostructures with controllable morphology such as size, shape and orientation. Our choice of method of the preparation of the nanostructured thin ZnO layers is the hydrothermal growth of ZnO nanorods on glass substrates coated by the nucleation layer deposited by the reactive magnetron sputtering. We have developed and optimized conditions of the thin layer growth with controllable dimensions of nanorods followed by the ultrasound peeling. The colloid of ZnO nanorods was characterized by measuring the size of particles using the dynamic light scattering (DLS) and the scanning electron microscopy (SEM). We found that the dynamic light scattering (DLS) can’t be directly used for size evaluation of ZnO nanorods due to their non- sperical shape. \n
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Energy harvester working on epidermis
Fecko, Peter ; Prášek, Jan (referee) ; Hubálek, Jaromír (advisor)
This work focuses on theoretical designing of a device harvesting energy from perspiration on human epidermis. Chemical composition of the human sweat was researched from articles and publications dealing with this problem. Following their results the approximate concentration values of ionic salts (and other substances) were established, also an adequate combination of electrode metals were examined, theoretically making the energy harvester functional. Next proposal described a draft and production procedures towards manufacturing the harvester. Evaluation of voltage stability and dependency was made on changes in ionic concentrations of the electrolyte, representing human sweat. Finally, the harvester cell was produced according to proposed manufacturing methods and the cell performance was measured.
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Gas sensor based on carbon nanoparticles
Morávek, Petr ; Pytlíček, Zdeněk (referee) ; Prášek, Jan (advisor)
This thesis deals with characterization of gas sensors based on carbon nanomaterials. In the theoretical chapter, the basic terms connected with the gas detection field, properties of different carbon nanoparticles and methods of their preparation are described. Practical experiments include the evaluation of samples` responses to ammonia, influence of annealing on their response and comparison of pure samples and their modifications.
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THIN LUBRICANT FILMS STUDY USING SPECTROSCOPIC REFLECTOMETRY
Čudek, Vladimír ; Dzimko, Marián (referee) ; Navrátil, Karel (referee) ; Dobeš, Petr (referee) ; Křupka, Ivan (advisor)
ectroscopic reflectometry is measurement technique that enables the study of the thickness and refractive index of thin layers. This thesis deals with its use for the study of lubrication films within EHD contact and verifies a new approach suggested in recent publications. It is focused on the development of an optical arrangement and mathematical model for the lubrication film thickness measurement within the entire EHD contact. This technique brings the possibility to study the pressure distribution within the contact area through the evaluation of changes in lubricant refractive index.
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Thin Film Electrodes for Electrochromic Devices
Macalík, Michal ; Kadlec, Jaromír (referee) ; Nováková,, Sabina (referee) ; Sedlaříková, Marie (advisor)
The work deals with the deposition of layers for electrochromic device with different methods. Transparent electrically conductive layer of SnO2 was deposited by pyrolytic decomposition of peroxostannate solution. Hydrogen peroxide in starting solution contributes to the oxidation process of growth layers and to increase the electrical conductivity. Active electrochromic layer of WO3 was electrolytic deposited from the peroxotungstic acid solution. Optimal deposition time and the optimal annealing temperature of deposited layers were found. Passive electrochromic layer of V2O5 was deposited using dip-coating method from peroxovanadate solution. A contribution of solution diluted with distilled water was investigated. Found results were used to construct complete electrochromic device with polymer gel electrolyte.
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Optimization of production of thin films of metallic materials
Čejka, Marek ; Kadlec, Michal (referee) ; Šubarda, Jiří (advisor)
The present thesis deals with optimization of the formation of thin layers of metallic materials. In the theoretical part was elaborated overview of the implementation of the formation of thin- film structures, particularly using vacuum techniques. Chemical and physical vapor deposition. They were described methods of pretreatment of thin layers. The findings were discussed methods of controlling the pre-treated surface, quality control and mutual adhesion of coating layers. In the experimental part of the pre-treatment methods were selected and applied to selected substrates. Pretreatments were evaluated using a control surface by wetting angles and by atomic force microscopy. Then, the metal structure formed of copper on the pretreated substrates. Implementation by means of magnetron sputtering. Adhesion layers was checked by testing the surface lattice method. The quality was observed by scanning electron microscopy. The results were used to design the technological process of making metal layers.
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Diagnostics of thin film barrier properties
Horák, Jakub ; Mazánková, Věra (referee) ; Přikryl, Radek (advisor)
This thesis is focused on characterization of the SiOx thin layers properties prepared by plasma enhanced chemical vapour deposition (PECVD). The layers were characterized with regard to its future possible use for the protection of the museum archives against the corrosion. Liquid hexamethyldisiloxane was used as a precursor. Polypropylene foils and silica wafers were used as substrates for thin film preparation. Metal sheets were chosen for corrosion tests. Methods such as permeation rate measurement (oxygen transmission rate - OTR), Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ellipsometry and simple corrosion tests of steel sheets coated and uncoated by SiOx thin layer were used for the layer properties characterization.
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