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Preparation and Characterization of Fluoride Conversion Coatings on Biodegradable Magnesium Alloys
Drábiková, Juliána ; Hadzima, Branislav (referee) ; Brezinová,, Janette (referee) ; Ptáček, Petr (advisor)
The submitted work is aimed at the unconventional fluoride conversation coating preparation on the AZ31, AZ61, ZE10 and ZE41 magnesium alloys by their immersion in Na[BF4] molten salt. The influence of the preparation parameters (such as temperature and time) on the quality of the fluoride conversion coating is investigated. Methods of light and scanning electron microscopy were used for the evaluation of morphology, chemical composition and thickness of the coating. Short and long-term corrosion tests were executed to analyze the corrosion performance in simulated body fluid solution at 37 ± 2 °C with and without the fluoride conversion coating. The short-term behavior was evaluated by potentiodynamic tests, namely by the linear polarization. Long-term performance was assessed by electrochemical impedance spectroscopy or immersion tests. The coating preparation parameters influence on the character of the formed fluoride conversion coating was defined based on the obtained results. The next part of the thesis deals with the description of the possible mechanism of formation and kinetics of growth of the unconventional fluoride conversion coating on the selected AZ61 magnesium alloy. In this part, further detailed analyses were carried out to investigate the microstructure and chemical composition of the fluoride conversion coating using focused ion beam, transmission electron microscopy and X-ray photoelectron spectroscopy.
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Calandering of li-ion electrodes and its impact on the final capacity of lithium-ion cell
Svoboda, Lukáš ; Kazda, Tomáš (referee) ; Čech, Ondřej (advisor)
There is an effort to produce lithium-ion batteries with maximal density of energy, or higher capacity of cell with the same size. Calendaring of electrodes is important part of manufacturing of batteries. Its parameters, mainly the pressure of calendaring and with it related the final compression ratio of electrode layers, affect parameters of battery significantly. It is the process of pressing electrode material coated on current collector with certain pressure and it reduces its porosity and thickness. The aim of this bachelor thesis is determination of suitable level of calendaring that increases specific capacity, but does not reduce its cyclability.
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Electrochemical impedance spectroscopy as a nanostructured bioelectrodes characterization method
Vrbová, Eva ; Urbánková, Kateřina (referee) ; Hrdý, Radim (advisor)
Diploma thesis deals of nanostructured surfaces, nanoparticles and electrochemical characterization methods such as cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. The aim of this thesis is a theoretical research issues of production and characterization nanostructured modified electrodes. The practical part is the production of biomodified nanostructured electrodes by anodi- zation W/Al layers with galvanic deposition of gold or deposition of mercury, a modifi- cation of the electrodes by 11-mercaptoundecanoic acid and by bovine serum albumin (BSA). The thesis includes SEM images of nanostructured electrodes contact angle mea- surements of these electrodes and form an electrical circuit with subsequent simulation waveforms.
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Evaluation of electrochemical characteristics of AZ61 magnesium alloy processed by squeeze casting
Pikner, Jan ; Hadzima, Branislav (referee) ; Fintová, Stanislava (advisor)
Bachelor thesis deals with the characterization of electrochemical corrosion properties of AZ61 magnesium alloy prepared by squeeze casting method. The theoretical part of the work focuses on properties of AZ61 alloy, influence of alloying elements on magnesium alloys and corrosion. The practical part of the work deals with electrochemical characteristics of AZ61 alloy with different surface condition in of 0.1 M NaCl solution. Corrosion potential (Ekor) and corrosion current density (ikor) were determined by potentiodynamic test. Polarisation resistance was determined by electrochemical impedance spectroscopy. Based on the measured results was discussed the influence of production, chemical composition, structure and surface treatment (grinding and polishing) on corrosion characteristics of the alloy.
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Spray-coated working electrodes of electrochemical sensors
Lechner, Filip ; Majzlíková, Petra (referee) ; Prášek, Jan (advisor)
This thesis is about the selection of the better type of thick film working electrode for the detection of substances in aqueous solutions, modified by spray coated carbon nanotubes. The theoretical part of this thesis describes the technology of thick film, properties and production of carbon nanotubes, introduction to electrochemistry and electroanalytical methods for the detection of substances in aqueous solutions. The practical part is aimed to realization of the working electrodes by thick film technology and their modification by spray-coated layer consist of carbon nanotubes. Electrodes are characterized using voltammetric methods, electrochemical impedance spectroscopy and electron microscopy. In conclusions is selected the most suitable type of working electrodes for reproducible electrochemical analysis.
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Nanopatterned alumina-based materials for electrochemical sensors and biosensors
Kynclová, Hana ; Hynek, David (referee) ; Trnková, Libuše (referee) ; Prášek, Jan (advisor)
The doctoral thesis is focused on basic research and development of nanostructured surfaces prepared using anodic alumina material. Various types of gold nanostructured surfaces and nanoporous aluminum membranes for electrochemical sensors and biosensors were prepared using the anodic oxidation method. Nanostructured surfaces were prepared by electrochemical anodization of aluminum material to form hexagonally arranged nanopores. Gold was then deposited into the nanoporous masks by electrochemical reduction from potassium dicyanoaurate solution using a pulse deposition method. The prepared nanostructured gold surfaces were electrochemically characterized by electrochemical impedance spectroscopy and voltammetry. Temperature stability and the effect of annealing on their electrochemical behavior at atmospheric pressure as well as in the vacuum were investigated. Then, gold nanostructures of various dimensions were prepared and the influence of their shape and dimensions on the electrochemical behavior was studied. Nanostructured surfaces were also modified with 11–mercaptoundecanoic acid, and the effect of this modification on the electrochemical results was studied. In the last part of the work, nanoporous aluminum membranes were prepared, and their permeability was studied.
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Measurement module based on electrochemical impedance spectroscopy intended for hydrogen fuel cell research
Přecechtěl, Vít ; Pazdera, Ivo (referee) ; Procházka, Petr (advisor)
This thesis deals with diagnostic fuel-cell parameters using electrochemical impedance spectroscopy. The document begins with brief explanation of fuel-cell operation and its basic principles. Thesis continues with description of fuel-cell voltage generation and influence of charge dual-layer on impedance. After that electrochemical impedance spectroscopy, signals used for perturbation and evaluation of impedance spectrum using Bode a Nyquist plot is described. Next part explains measurement of impedance spectrum using potentiostat in combination with lock-in amplifier or frequency response analyzer. Practical part of thesis is dedicated to electric circuit design of EIS module and software designed for automatic measurement of impedance spectrum. Last part shows results of EIS module testing.
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Optimalisation of coposite materials for civil engineering
Kazda, Tomáš ; Chladil, Ladislav (referee) ; Novák, Vítězslav (advisor)
This work is focused on optimalisation of coposite materials for civil engineering. In the theoretical part of the project is introduction of the composite materials and materials which are used for their production. There are also concerned their properties and possible application areas. In conclusion of theoretical part this project is a summary of the possible use of composite materials. The practical part compares the characteristics of the different types of composites made in terms of conductivity and the rate of corrosion.
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Impedance spectroscopy characterization of perovskite solar cell materials
Křečková, Jitka ; Vanýsek, Petr (referee) ; Novák, Vítězslav (advisor)
The Master‘s thesis deals with the topic of perovskite solar cells with the main focus on the materials used for the active layer. In the introductory part, the electrical and optical properties of halide perovskites are described and specific examples of perovskite crystals are introduced. The description of impedance and photoimpedance measurement methods used for characterization of perovskite solar cells is also included in the thesis. The measurement of electrochemical impedance spectroscopy was conducted on four perovskite crystals and equivalent circuit was formed to fit the obtained data. Parameters of the circuit elements were acquired using the fitting method and were further evaluated in experimental part of this thesis.
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Study of intercalation properties of electrode materials based on expanded graphite
Vencelides, Lukáš ; Máca, Josef (referee) ; Libich, Jiří (advisor)
The diploma thesis deals with the issue of electrochemical cells and deals in detail with lithium-ion batteries. The thesis describes the history of development of lithium-ion batteries, basic information about lithium and basic types of electrochemical cells. The work is devoted in detail to the description of characteristics and operating principle of lithium-ion batteries with emphasis on the negative electrode and negative electrode materials. Of the negative electrode materials, both the most widely used material graphite and modern materials with a great potential for the future are described. In the measurement methods the work describes methods CV, GCPL and EIS. Great emphasis is placed on the explanation of the principle of the function of electrochemical impedance spectroscopy and its application in measurement of electrochemical properties of materials used in lithium-ion batteries. There is also described the procedure of calculation of diffusion coefficients using the results of electrochemical impedance spectroscopy. In the practical part, two methods are used to calculate the diffusion coefficients of lithium ions into the negative electrode made of expanded flake graphite using the results of a series of electrochemical measurements.
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