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Inverse vulcanised sulphur as an electroactive material for lithium-sulphur and sodium-sulphur batteries
Trochta, David ; Kazda, Tomáš (referee) ; Čech, Ondřej (advisor)
This thesis deals with the study of lithium-sulfur and sodium-sulfur batteries, which are designed for use at room temperatures. Both of these systems are interesting mainly due to their high theoretical capacity and low environmental impact, thus greatly outperforming lithium-ion batteries. The weakness of these new technologies is their low lifespan and the associated rapid loss of battery capacity. To increase the lifespan, elemental sulfur in this work was replaced by sulfur with an amorphous structure, synthesized by an inverse vulcanization process that has been optimized in various ways. In addition to the optimization of the inverse vulcanization technology window, the effect of the addition of carbonaceous additives during the synthesis was also investigated. In this work, a series of samples of inverse vulcanized sulfur with different ratios of input precursors were prepared and also with different additives. X-ray diffraction was used to confirm the amorphous structure of the material, which also excludes the presence of crystalline sulphur. The results of Raman spectroscopy were also presented, demonstrating the possibility of using this method to determine semi-quantitative ratios of the input precursors. Electrodes for electrochemical cells were fabricated from selected samples. The homogeneity of the distribution of the electroactive material on the electrode was investigated using a scanning electron microscope and elemental mapping by energy dispersive spectroscopy technique. The electrochemical characterization of the inversely vulcanized sulfur electrodes was carried out by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic potential limited cycling.
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Effect of Organic Additives on Electrochemical Processes Influencing Zn-Air Battery parameters
Smejkal, Jan ; Čech, Ondřej (referee) ; Chladil, Ladislav (advisor)
The diploma thesis is focused on the study of the influence of selected organic additives on the properties and morphology of zinc deposit on the negative electrode when used in zinc-air accumulators. Organic additives have been selected based on the study of literature and previously done experiments. The deposition was made on the tin plate electrodes in a solution of 6 mol/l KOH saturated with ZnO with added additives. All chosen additives were studied with a focus on the morphology of zinc deposit and with regard to their ability to suppress dendritic growth. Zinc morphology was studied by using a Tescan Vega 3 electron microscope and a Rigaku MiniFlex HR 600 X-ray diffractometer.
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Wireless timekeeper for firefighting sport
Šlechta, Adam ; Chladil, Ladislav (referee) ; Čech, Ondřej (advisor)
This bachelor thesis deals with the analysis of timekeepers designed for firefighting sport. It presents the possibilities of solutions for these timekeepers and describes their problems. The thesis includes a review and evaluation of commercially available timekeepers. Furthermore, the thesis deals with the possibilities of solutions for wireless communication and remote time synchronization. The thesis describes the design and manufacture of a prototype timekeeper. The thesis also briefly defines the history and individual disciplines of firefighting.
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Preparation and characterisation of ceramic electroactive materials for Na-ion batteries
Vaněk, Martin ; Libich, Jiří (referee) ; Čech, Ondřej (advisor)
Hlavním cílem této práce je charakterizace vzorků titanátů, jako materiálů pro sodíko-iontové (Na-ion) akumulátory. Syntéza některých vzorků je součástí této práce. Charakterizace je zaměřena na elektrochemické vlastnosti, složení a morfologii použitých materiálů. První část se zabývá lithium-iontovými (Li-ion) akumulátory. Byly vybrány, protože jsou ve vědeckých článcích dobře popsány a základní funkční princip je aplikovatelný také na Na-ion akumulátory. Materiály používáné pro katody, anody a elektrolyty následují po krátké části shrnující parametry a konstrukci Li-ion akumulátorů. Následující kapitola je zaměřena na sodíko-iontové akumulátory. Srovnání sodíku a lithia je následováno materiály používanými pro elektrody a elektrolyty (s důrazem na anodové materiály). Třetí část popisuje analytické metody použité pro charakterizaci elektrod a materiálů. Jedná se o elektrochemickou charakterizaci (cyklická voltametrie a galvanostatické cyklování s potenciálovým omezením), morfologii (rastrovací elektronová mikroskopie) a složení (X-ray difrakční spektroskopie). Poslední dvě kapitoly obsahují syntézu a charakterizaci sodného titanátu a charakterizaci dvou vzorků TiO2. Výsledky této práce jsou shrnuty v závěru.
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Firearm Type Identification in an Image
Čech, Ondřej ; Drahanský, Martin (referee) ; Dvořák, Michal (advisor)
Main goal of this work is to design, implement and test an approach for classifying firearms in an image into categories with short and long fireams, and then with single shot, multi-barreled, repeating and semi-automatic/automatic firearms. This problem was solved using SVM classifier together with Harris corner detector, FREAK descriptor and Bag of Words method. Accuracy of final program is up to 13,3 %.
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Preparation and characterisation of electrode materials based on elementar sulphur for Li-ion cells
Jankulár, Tomáš ; Vondrák, Jiří (referee) ; Čech, Ondřej (advisor)
This thesis deals with the preparation and characterization of electrode materials for Li-ion batteries based on elemental sulfur. The theoretical part is focused on the characteristics of Li-ion batteries, electrochemical reactions, the process of electrochemical lithiation of sulfur and solubility properties of intermediate polysulfides. The practical part of the thesis deals with the preparation of cathode materials for Li-ion cells with an active substance in the form of elemental sulfur. The prepared electrodes were investigated using cyclic voltammetry and galvanostatic cycling. Physical characterization by SEM and XRD was provided.
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XRD characterization of electrodes and electrode materials for electrochemical power sources
Klvač, Ondřej ; Chladil, Ladislav (referee) ; Čech, Ondřej (advisor)
The thesis describes available choices of methods for research of electrochemical power source electrode strcture by x-ray diffraction spectroscopy. At first there is a theoretical computation of difractogram. Then there are discussed possibilities of in-situ and ex-situ techniques as background research. Practical part of thesis compares theoretical assumptions to measurements of lithium and sodium cells, including analyze of crystallographic phases and lattice constants. As a conclusion, there are discussed possibilities of subsequent research.
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Threading operations in the building industry
Čech, Ondřej ; Fiala, Zdeněk (referee) ; Kalivoda, Milan (advisor)
The aim of this bachelor thesis is the sumarization of common threads and thread joints used in construction industry complemented with illustrations of actual joints. On construction thread cutting possibilities, more precisely situations, where there is no possibility to use stanionary placed machinery. Mechanical engineering machinery overwiev. Technological regime of selected thread joints. This thesis is supplemented with description of specific machining and thread cutting work on heavy-duty part of hydropower plant.
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The influence of alcaline accumulators loading on their parameters
Čech, Ondřej ; Vrbický, Jiří (referee) ; Sedlaříková, Marie (advisor)
This master's thesis deals with alkaline battery characteristics and it has special consideration of nickel-cadmium cells. There are three main experimental parts in this paper. First one is concerned with positive electrode materials properties and is aimed to investigate impact of magnesium ions formed into nickel hydroxide electrode structure. Second part deals with battery charging/discharging and response measurement tool design. National Instruments hardware PXI modules for data acquisition was used and program in LabView environment was made. Last one is concerned with nickel-cadmium cell properties changes during increased temperature stressing. Investigation of cell self-charge changes during lithium hydroxide addition into electrolyte was made.
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