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Sensoric Properties of Organic Materials
Tmejová, Kateřina ; Zmeškal, Oldřich (referee) ; Kratochvílová, Irena (referee) ; Nešpůrek, Stanislav (advisor)
The first part of the work is aimed to the study of changes of electrical properties of substituted phthalocyanines under the influence of humidity. Thin films were prepared by spin coating technique. During the influenece of humidity electrical conductivity increases. Sorption and desorption and the changes in electrical properties under the repated humidity exposure were investigated as well. Impedance spectroscopy was used for the studies. The second part of this work consists of optical studies and changes of optical parametrsunder the influence of different alcohols (methanol, ethanol, 2-propanol) exposures. The investigated samples were prepared by vacuum evaporation a glow-discharge-induced sublimation. The changes of optical reflectances of the films upon exposure to alcoholvapour-containg atmospheres were studied as a function of alcohol concetration and exposure time.
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Study of electrical and dielectric properties of ionic liquids
Maráčková, Lucie ; Nešpůrek, Stanislav (referee) ; Zmeškal, Oldřich (advisor)
This bachelor´s thesis is focused on a study of electrical and dielectric properties of ionic liquids in the form of solution and thin layers. The values of breakdown voltage have been determined from current-voltage characteristics in solutions. Frequency dependencies have been also observed and used for calculation of values of parallel conductivity and capacity of ionic liquid. It was found that solutions is contained by model with one parallel combination of conductivity and capacity. Thin layers have been created by mixing up PEDOT:PSS with two ionic liquids: 1-butyl-3- methylimidazolium trifluoromethanesulfonate and 1-ethyl-3-methylimidazolium tetrafluoroborate. These layers have created electrochemical battery as is evident from current-voltage characteristics. Frequency dependencies are more complex, a model contained two or respectively three parallel conductivities and capacities which have been influenced by PEDOT:PSS and by ionic liquids characteristics.
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Impedance Spectroscope
Sliž, Jiří ; Pikula, Stanislav (referee) ; Beneš, Petr (advisor)
The aim of this thesis is to design a measuring instrument intended for impedance spectroscopy. There are definitions of the terms impedance and impedance spectroscopy and methods of its measurement. The integrated circuit AD5933 from Analog Devices was used for measurement. The measuring device is controlled by a microcontroller PIC32MX460F512L, which communicates with the measuring circuit, controls the actual measurement and communication with the control PC via the USB interface. The work also includes the creation of the control program, which ensures calibration, measurement, storage data, and data visualization. Device has also the possibility of repeated measurements and automatic switching of multiple inputs. Finally, the proposed device has been tested on two microbiological experiments. Impedance change depending on the concentration of bacteria in the measured solution was proved in first experiment. The aim of the second experiment is to distinguish bacterial strains of Staphylococcus epidermidis which creates biofilm and which not. With PLS was created validation model that can be used as a detector strains forming biofilm.
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Influence of carbon on possitive electrode of Ni-Cd accumulators
Janečka, Marek ; Dvořák, Petr (referee) ; Chladil, Ladislav (advisor)
Master’s thesis is deals with the effect of carbon additives on the positive electrode in the NiCd batteries. It examines whether the positive electrode material enrichment of carbon additives to achieve improved internal parameters of conductivity and better contact with the electrode materials in a discharged. Galvanostatic cycling and electro-chemical impedance spectroscopy (EIS) are used for evaluation of graphite aditives.
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Properties study of gel polymer electrolytes for lithium-ion batteries
Zítka, Jan ; Dvořák, Petr (referee) ; Musil, Michal (advisor)
The present work deals with the research and development of gel polymer electrolytes and their applications. Thesis talks about the mechanisms that take place in gel electro-lytes. It also discusses the electroanalytical methods used in assessing the gel electro-lytes. The main focus of the work is the preparation of gel polymer electrolytes and compared their properties using methods of impedance spectroscopy, cyclic voltam-metry and methods of measurement of transference numbers. KEYWORDS
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Characterization of the perovskit photovoltaic cells
Kaliyev, Alexey ; Jandová, Kristýna (referee) ; Novák, Vítězslav (advisor)
The work is focused on problems of perovskite photovoltaic cells. The theoretical part describes the properties of perovskite structure, its composition and use in solar cells. There is also a brief information on silicon-based solar cells, which is followed by a comparison of the two systems. The measurement methods, which this stated and described here are used to understand problematics photovoltaic, determination of efficiency, stability and durability of the solar cell. In the practical part will focus on the application of these methods, discussion and evaluation of results.
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Gel polymer electrolytes with nanoparticles
Szotkowski, Radek ; Sedlaříková, Marie (referee) ; Jahn, Michal (advisor)
This master‘s thesis concerns gel polymer electrolytes formed on a methyl methacrylate base with selected types of nanoparticles. In the thesis are also analyzed the methods for measuring electrochemical properties. The practical portion deals with sample preparations of gel polymer electrolytes with different contents of alkaline salt in a solvent, creating gels with different nanoparticle content and comparing gel polymer electrolytes polymerized with heat and UV radiation. The thesis deals with the evaluation of these samples from the viewpoint of electrical conductivity and potential windows as well as thermal analysis of selected samples.
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Study of Electric and Thermal Properties of Building Materials with Conductive Additives
Veselá, Jana ; Krouská, Jitka (referee) ; Zmeškal, Oldřich (advisor)
This work focuses on study of electric, dielectric and thermal properties of composite electrically conductive building materials composed of magnesium oxychloride cement and small amount of graphene and graphite admixtures. The aim of this work was to determine thermal properties of materials and create a model of electric current conduction mechanism in material. Electric and dielectric properties were determined with using of transient direct current measurement of resistivity and impedance spectroscopy. Thermal properties were investigated using transient step-wise method and fractal analysis of thermocamera data. Electrical resistivities of materials are determined from the direct current measurements. Model of transport of electrical charge carriers was evaluated by fitting impedance data to an equivalent electrical circuit model. Thermal conductivities and thermal capacities were determined by means of thermal measurements. The presented properties for example can be used for assessment of suitability for specific construction applications.
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