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Study of Nanocomposites for Electrical Insulation
Klampár, Marián ; Mentlík, Václav (referee) ; Váry,, Michal (referee) ; Liedermann, Karel (advisor)
The dissertation thesis submitted deals with the study of dielectric properties of epoxy nanocomposites containing nanoparticles of inorganic oxides. These nanocomposites may have a promising technologic application for electric insulations in view of their higher resistance against partial discharges; yet information about their behavior in the course of ageing is not available. If at least a partial mass replacement of the currently used epoxy insulation with nanocomposite-based insulations is due to occur, the knowledge of the changes of their dielectric properties in the course of their operation will become indispensable. Within the framework of this dissertation, ensembles of samples of epoxy resins without fillers and with Al2O3, WO3, TiO2 and SiO2 fillers in the form of nanopowders, in concentrations up to 12 wt %, have been prepared. These ensembles have been measured prior to ageing and exposed to long-time (up to 5000 hours) ageing at increased temperatures 200, 250 and 300 °C and in a few cases also at 330 and 360 °C. Samples were measured in the course of ageing roughly in a logarithmic time series after 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000 and 5000 hours. The measured quantities included complex permittivity , internal resistivity i and loss factor tan at temperatures ranging from -153 °C to +167 °C and in the frequency range 10-2 – 106 Hz. Changes in nanocomposites have been investigated using not just dielectric spectroscopy measurements, but other methods, too, namely Fourier-transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The experiments have proved that materials with different fillers respond to the same concentrations of various fillers in different ways. The addition of nanoparticles, without the addition of microparticles, at a relatively low concentration (max 12 wt %), was not sufficient for reaching fundamental changes in dielectric spectrum; only smaller changes of dielectric strength and shifts of relaxations and in relaxation maps have occurred. Out of more pronounced changes, increase of concentration of the SiO2 filler in the epoxy matrix brings about a decrease of electrical conductivity in the resulting nanocomposite. The TiO2 filler had a different impact. Different TiO2 concentrations make their marked appearance in the region between the relaxation and relaxation. The TiO2-filled nanocomposites do not exhibit the unambiguous dependence of electrical conductivity on nanofiller concentration. It can be concluded that the mere addition of nanoparticles, without the addition of established microparticles, does not change the dielectric spectrum substantially. Generally, a serious problem was the production of the nanocomposite with a uniform distribution of nanoparticles. The preparation of such a nanocomposite was not trivial and, in industrial applications, this issue will require a specific focus, so as to avoid the formation of undesirable aggregates. Within the framework of this research, a methodology for the production of an epoxy nanocomposite has been developed with as high as possible uniformity of nanoparticle distribution.
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The relationship between kidney stone formation and the composition of food.
Zbořilová, Eliška ; Márová, Ivana (referee) ; Vránová, Dana (advisor)
This bachelor’s thesis deals with causes of formation and identification of urinary concrements. The theoretical part of this study includes basic definition of problems with urolithiasis, points to risk factors of formation of urinary concrements and deals with their classification in accordance to their chemical composition. Important part of this study has been devoted to dietary habits, because composition of ingested food and daily intake of liquids is very important for formation of concrement in urinary tract. Analysis of urinal concrement and following identification of its composition is absolutely unavoidable for definition of subsequent therapeutic method of treatment of urolithiasis. In the experimental part, infrared spectroscopy has been used for analysis of urinal concrements. The calibration lines of the most frequent two-component mixtures of urinary concrements have been scaled by this method
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DESIGN OF FIBER-OPTIC BIOSENSOR WITH NEAR-INFRARED SPECTRAL ANALYSIS
Křepelka, Pavel ; Jakubec,, Martin (referee) ; Skládal, Petr (referee) ; Mikulka, Jan (advisor)
This thesis deals with a measurement and interpretation of NIR spectra of bacterial cells and design of biosensor using this analytical technique. In the first chapter, there is introduction of current state of knowledge in the field of NIR spectroscopy in microbiology and technology of fiber optic biosensors. The summary of this chapter shows that NIR is a suitable technique for direct molecular analysis of bacteria, but it suffers from low sensitivity and insufficient interpretation of bacterial spectra. In the next part of the thesis, there is a theoretical background of spectral analysis techniques and technology of fiber optic sensors. In the practical part of this work, there is suggested the elimination of disadvantages of NIR spectroscopy in microbiology by a series of experiments used for interpretation of NIR spectra of bacteria and design of fiber optic sensor to increase sensitivity of this technique. In this work, spectral regions important for the identification of bacterial strains were determined and partially interpreted and the sensor for bacterial analysis capable of classifying strains based on 105 captured cells was designed. Therefore, the objectives of this work were fulfilled.
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Properties of novel magnetoelectric and multiferroic ceramic materials
Osička, Luděk ; Kachlík, Martin (referee) ; Maca, Karel (advisor)
Literature search about properties of magnetoelectric and multiferroic ceramic materials was made. Ferromagnetism and ferroelectricity and requirements for materials in which both of these properties can exist in the same phase were discussed. Further, multiferroics were classified by mechanism of ferroelectricity and by their crystal structure. Finally, multiferroic and magnetoelectric composites and some examples of strong magnetoelectric effect in multiferroics were described. In experimental part of this bachelor thesis preparation of specimens of magnetoelectric perovskite EuTiO3 was described. Prepared specimens had higher density than specimens described in literature and were phase-pure and they are suitable for research of magnetoelectric properties of EuTiO3 by infrared spectroscopy.
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Crystallization of microbial polyesters - methods and biological consequences
Liczka, Jan ; Kalina, Michal (referee) ; Sedláček, Petr (advisor)
The aim of this bachelor thesis was to test suitable methods for preparation of amorphous form of microbial polyesters and to perform model experiment to study a kinetics of crystallization of prepared polyesters. The theoretical part deals with PHA characteristics and various methods of isolating PHB granules from bacterial cells. In the experimental part, measuring techniques such as analytical centrifugation, dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FTIR) were tested to characterize the properties of PHB granules. Furthermore, an experiment was performed to isolate native PHB granules from Cupriavidus necator using lysozyme, deoxyribonuclease and cell disruption by ultrasonification. The results of the analyzes showed that the granules were either isolated amorphous only in the wet and crystallized upon drying, or that the granules were completely amorphous but not isolated from the bacterial cell.
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Analytical methods for hyaluronan
Černá, Lucie ; Mravec, Filip (referee) ; Pekař, Miloslav (advisor)
This thesis deals with of simple methods for determining the concentration of hyaluronan in aqueous solution and compares the performance of each selected methods such as UV -VIS spectroscopy, IR spectroscopy and the method of determination by alcian blue. These methods were chosen for their simplicity and low cost of the assay. As the most reliable of these three methods, seems to be the method of IR spectroscopy. Determination of the concentration of HA by this method is relatively accurate at concentrations above 0.4 % in deionized water. The method of UV-VIS spectroscopy is based on a linear calibration curve determination, but no characteristic peak was detected, which means that this determination could be influenced by other components of the aqueous solution. Weak ionic strength and molecular weight of HA does not affect the determination. In the method with alcian blue, the results were quite unsatisfactory and does not correspond with the literature. Therefore, this method is not applicable in this form for determining the concentration of HA. Another option for determining the concentration of the HA is ELISA method. These are commercially produced kits suitable for determining low concentrations in low volumes. Its price is higher than the above- mentioned methods.
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Preparation of organic semiconducting thin films by vacuum evaporation
Schön, Martin ; David, Jan (referee) ; Salyk, Ota (advisor)
This thesis deals with preparation of organic molecular thin film compounds and its properties like morphology and purity. The vapour deposition was used for thin films preparation, because used materials are very few soluble. Thin films properties were characterized with the infrared spectroscopy (FTIR) and scanning electron microscope. There are described basics of infrared spectroscopy, spectra measurement and interpretation in the theoretical part. Process of thin film preparation is also described in this part. In the experimental part are described used vacuum technology and measuring instruments, process of sample measurement and there is the list of studied materials. 12 derivates of diketopyrrolopyrrols (DPP) were studied in this thesis. Diketopyrrolopyrroles (DPP) and its derivates have interesting chemical and physical properties, expecting wide range of applications, especially in electronics industry.
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Occurance of urinary stones in the CR and simulation of conditions of their rise.
Zbořilová, Eliška ; Márová, Ivana (referee) ; Vránová, Dana (advisor)
The aim of this diploma thesis was identification of urinary concrements by the infrared spectroscopy and study of conditions of formation of the most frequent urinary stones (calcium oxalates) by the thermodynamic simulation. The theoretical part of this study includes basic information about problems with urolithiasis and technique of identification of urinary concrements. Important part has been devoted to the thermodynamic simulation of formation of calcium oxalate concrements and on this simulation were determinated the conditions for formation of urinary stones. The experimental part contains analysis of real urinary concrements by the infrared spectroscopy and statistical evaluation of the file of 50 149 samples, which were analysed in years 1994 - 2010.
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Breath Alcohol Tester
Pagáč, Patrik ; Kolář, Radim (referee) ; Chmelař, Milan (advisor)
The theme of bachlor’s project is design of simply breath alkohol tester. A breath alcohol test determines how much alcohol is in your blood by measuring the amount of alcohol in the air you breathe out (exhale).My task is interpret the possibility of measuring the alcohol content in the body. Describe the different methods and compare their accuracy and useability for practical measurements and also used in law enforcement.
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Testing of commercial rubber sealing components exposed to different ambient conditions
Jančaříková, Marie ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
Diploma thesis studies the effect of temperature (75 and 105 °C) and the effect of 3 kinds of liquids (silicone and hydraulic oil and coolant) at room temperature and at 105 °C on change of the structure of 3 species butadiene-acrylonitrile (NBR) seals (o-ring and two types of bolts). The seals are inspected by the thermogravimetric analysis, differential scanning calorimetry and infrared spectroscopy, the influence of 105 °C on the o-rings is also evaluated in terms of changes in tensile properties. The greatest changes in the composition and structure are observed on o-rings particularly due to temperature of 105 °C, there was a significant reduction in dilatability and an increase in stiffness and glass transition temperature. The root cause is the surface and centre additive decomposition and oxidation. The bolts have suffered from decomposition of the protective surface layer and the additives in the centre, structural change was minor. Exposure to 75 °C has resulted in a gradual loss of low molecular weight substances. Liquids at room temperature didn‘t affect the structure of the seals, at 105 °C it caused a loss of weight due to decomposition of the protective surface layer and release of additives and the products of their decomposition. Results showed that the common use of the NBR seals at 105 °C is unsuitable, at 75 °C it leads to gradual changes, loss in mechanical and sealing properties.
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