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High Temperature Processes in Silicon Solar Cells Production
Frantík, Ondřej ; Hudec, Lubomír (referee) ; Banský,, Juraj (referee) ; Szendiuch, Ivan (advisor)
The thesis is focused on high temperature processes in crystalline solar cells production. Main topic is diffusion of traditional dopants phosphorus and boron. Diffusion processes for creating solar cells are different from classical diffusion in semiconductor industrial. It is reason why the thesis describes crated layers in detail. Knowledge of diffusion processes is used for creating bifacial solar cells and development of a new phosphorus emitter for conventional solar cells. Bifacial cells are a new type of cells. Developed new emitter increases efficiency and decreases cost of solar cells production. Another part the thesis is devoted to the prediction of diffusion processes. New models of phosphorus and boron diffusion for photovoltaic industrial are created in software SILVACO. Models correspond with real results.
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Investigation and Modelling of Concrete Carbonation
Rovnaníková, Markéta ; Keršner, Zbyněk (referee) ; Bajza, Adolf (referee) ; Havlica, Jaromír (advisor)
The corrosion of steel reinforcement is probably the most frequent type of degradation of reinforced concrete structures. Reinforcing bars are protected from corrosion by a thin iron oxide layer which is formed on their surface due to a high alkalinity of the surrounding concrete. Corrosion may start when this layer is destroyed (i) either by chloride ion penetration (when the concentration of dissolved chloride at the depth of the reinforcing steel exceeds a critical value) or (ii) by a reduction in the pH value of pore solution to values below 9.5. Such a reduction in alkalinity is the result of carbonation of the Ca(OH)2 in the concrete mass, i.e. of its reaction with the atmospheric CO2. The main aim of this work is an experimental investigation and modelling of carbonation process. The effect of relative humidity, curing period and replacement of Portland cement by supplementary cementing materials (SCM - fly ash, blast furnace slag and metakaolin) on carbonation process has been studied. Calcium hydroxide content in the presence of SCM and their pozzolanic activities have been also determined. Furthermore, lots of parametric studies and comparison of carbonation models have been provided. The software tools based on the introduced models and considering the input data to be statistically independent random variables have been described and used for other parametric studies.
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Verification of durability of ash concrete in the environment XF
Kušiak, Petr ; Hela,, Vlastimil (referee) ; Hela, Rudolf (advisor)
Fly ash is now much used as an admixture to concrete. This master´s thesis focuses on the use of fly ash as an active admixture in concrete environment for XF. The thesis has two parts. The first part collected theoretical information about the origin and behavior of fly ash in fresh and hardened concrete. In the second part was experimental verification of these characteristics. The purpouse of this thesis is to demonstrate that the fly ash attribute to meet all environmental XF.
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Conductive ceramic as additive in the lead-acid accumulators
Šrut, Martin ; Křivík, Petr (referee) ; Bača, Petr (advisor)
Lead-acid batteries are most used secondary electrochemical power sources. Their basic principle has remained the same for several years; only the operating parameters are in development. Lead-acid batteries are used in hybrid electric vehicles (HEV), which operates in the partial charge PSoC. Sulphation is one of the possible failures lead-acid batteries in the HEV, especially the negative electrode. By adding additives to the negative active mass can reduce the rate of sulphation and increase ability to accept an electrical charge by negative electrode.
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Influence of temperature on lead acid batteries lifetime
Kopečný, Martin ; Bača, Petr (referee) ; Neoral, Jiří (advisor)
Lead –acid batteries are the most common type of secondary cells used in automotive industry. This diploma thesis deals with the influence of temperature on their lifetime. In the preamble of this work is shortly described their history, division, construction and processes during battery operation. There are noted unfavorable phenomena which have an impact on increasing the temperature inside the battery. The first experimental part is devoted to evaluation the effects of addition on the temperature rise during charging. The second part is focused on conditions simulation in hot areas at the temperature above 30 °C and effects of this temperature on the function of lead – acid batteries.
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Investigation size effect of negative active mass additive on service life lead-acid accumulator.
Mikoláš, Jiří ; Novák, Vítězslav (referee) ; Bača, Petr (advisor)
The task of research work is to study new mechanisms and to minimize disturbance of lead batteries for hybrid electric vehicles. Those arising under the PSoC (Partial State of Charge) and is linked to irreversible sulphation mainly negative electrodes. As one solution to prevent sulphation of the negative electrode appears to be the active ingredients in a negative matter. In the investigated electrodes is verified the influence of carbon, titanium dioxide and silica on the grain size of the order of nanometers.
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Infusorial Earth - Reactive Admixture for Cement Composites
Zimmermann, Štěpán ; Žižková, Nikol (referee) ; Rovnaníková, Pavla (advisor)
The aims of this bachelor´s thesis are the properties and the use of diatomaceous earth as a partial replacement of cement in concrete. It provides information about the origin of diatomaceous earth, sedimentation of dead diatoms and variety of algae, including chemical and physical properties of the diatoms according to origin. The paper also contains information about significant deposits of diatoms, the manner and intensity of mining, including treatment of raw diatomaceous earth for further use. The main use of diatomaceous earth is in the filtration, which represents more than half of total consumption. An important factor for use in building is a high content of amorphous SiO2 and associated pozzolana activity of diatomaceous earth. The experimental part was carried out research on the influence of diatomaceous earth as pozzolanic admixtures on the properties of cement mortars. Tested specimens were obtained by adding 10% diatomaceous earth by weight of cement in the cement mortars. As admixtures were use three diatomaceous earth of different chemical composition, particle size and pozzolanic activity. The evaluated parameters were mortar density, flexural and compressive strength. The microsture of mortars were also observed. Test results were compared with those determined by reference mortars.
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Development of structural concrete with power plant ash
Ťažký, Martin ; Sokol, Pavel (referee) ; Hela, Rudolf (advisor)
Worldwide production of concrete is increasing, what has a negative environmental load of cement production. That is due to effort in building construction, also concrete production, greater use of the secondary raw materials. Fly ash is the most commonly used secondary raw material. His used has a very good impact on the economy and ecology of production and positively affects on the properties of concrete in both the fresh and hardened state. The aim of this bachelor's thesis was to improve its use in concrete, using a minimum void fraction of dry mix cement-fly ash.
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SCC with secondary raw materials
Ťažká, Lucia ; Ťažký, Tomáš (referee) ; Hela, Rudolf (advisor)
Bachelor thesis is focused on the possibility of using secondary raw materials and their application to the production of SCC. Large part deals with impurities of type I and its application results mainly from abroad. Furthermore, this work examines the impact of different types of impurities on the resulting concrete durability in various aggressive environments. The practical part is focused on the use of chemically non-reactive additives of type I instead of the commonly used additives of type II which are used to replace part of cement and the resulting design and manufacture of low-strength SCC using appropriate additives.
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Pozzolanic Activity of Silicon Dioxide
Barek, Jaroslav ; Žižková, Nikol (referee) ; Rovnaníková, Pavla (advisor)
The aim of this bachelor's thesis is to investigate and identify the present status of resources with dominant amorphous silicon dioxide content and summarize feasible test methods to assess pozzolanic activity. The use of pozzolan as a partial replacement of Portland cement reduces the carbon dioxide emitted per tonne of product and can also improve various physical properties of the resulting cementitious composites. Assessment of the pozzolanic activity of cement replacement materials is increasingly important because of the economic sustainability of cementing materials. The pozzolanic activity of wheat straw ash, silica fume, nanosilica, two diatomites, glass powder and expanded perlite have been investigated and compared using the strength activity index test, the modified Chapelle test and the pozzolanicity test in accordance with the European Standard EN 196-5. From an experimental investigation of seven different pozzolans, the following main conclusions can be drawn. In the case of an acid-base titration (determination of [OH–], the procedure specified in EN 196-5) is better to use Tashiro (mixed indicator) instead of required methyl orange, Tashiro changes color at the endpoint of a titration distinctly. Strength activity index: the procedure used was based on EN 450-1. In its current form, this procedure is misleading because of two other significant properties of the pozzolan, namely its density and its water-reducing/increasing capabilities. Based on the results of our experimental investigation, the current testing procedure is evaluated against an alternative in which the 25% pozzolan replacement for cement is performed on a volumetric basis and the volume fraction of water is held constant.
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