National Repository of Grey Literature 130 records found  previous11 - 20nextend  jump to record: Search took 0.01 seconds. 
Synthesis, properties and product of hydration of strontium yttrite cement
Florian, Ondřej ; Šoukal, František (referee) ; Ptáček, Petr (advisor)
The master thesis is focused on the preparing a binder system based on strontium ytritte cement and examining the physicochemical properties of the obtained system. The course of the process was evaluated using methods calorimetry, thermal analysis, X-ray diffraction analysis and scanning electron microscopy.
Analysis of the Causes of Traffic Accidents Involving Vehicles and Pedestrians on Selected Pedestrian Crossings
Šimáková, Aneta ; Ptáček, Petr (referee) ; Maxera, Pavel (advisor)
A master’s thesis deals with a problem of traffic accidents on pedestrian crossings. A theoretical part describes causes and following responsibilities of all participants of the traffic accident. Furthermore, the theoretical part analyzes a traffic system and its individual parts. A practical part of this thesis describes all measuring tools used for collection of data during the analysis. The data was obtained during a real traffic on chosen pedestrian crossing in Brno A tool used for analysis is called eyetracer. Furthermore, an evaluation of collected data and following analysis were carried out. Eventually, results were compared with reports about accidents which happened on chosen pedestrian crossings.
Preparation and Characterization of Advanced Thermally-sprayed Coatings on Magnesium Alloys
Buchtík, Martin ; Hadzima, Branislav (referee) ; Fintová, Stanislava (referee) ; Ptáček, Petr (advisor)
The proposed dissertation thesis deals with the characterization of HVOF and APS-thermally sprayed coatings prepared on the AZ31 and AZ91 magnesium substrates. The theoretical part of the thesis describes in-detail Mg substrates used in the experimental part of the thesis. There are also characterized materials and coatings based on NiCrAlY and FeCrNiMoSiC metals, WC-CoCr cermets, and YSZ ceramic materials. At the end of the theoretical part, the literary research summarizing the characterization and analysis performed on thermally sprayed coatings on Mg alloys. Based on the theoretical knowledge, the characterization of Mg substrates and deposited coatings was performed in terms of the surface morphology, microstructure, and the chemical composition using the light microscopy (LM) and scanning electron microscopy with energy-dispersive spectroscopy (SEM+EDS). The phase composition of the coatings was analyzed using the X-ray diffraction (XRD). The diffractions corresponding to the sprayed coatings were compared with the feedstock powders, i.e. materials used for the spraying of the coatings. The characterization of the prepared coatings in terms of the mechanical and tribological properties was performed. The hardness and microhardness of the coatings as well as the coefficient of friction, and the wear rate were measured. The last chapter of the experimental part deals with the evaluation of the electrochemical corrosion properties by the potentiodynamic measurements in a 3.5% NaCl solution. In the case of exposed samples, the evaluation of the surface and coating/substrate interface was performed using LM and SEM with EDS. The mechanism of the corrosion attack and degradation was determined from the acquired knowledge and base on the results of the short-term measurements. Based on the measured results, it can be stated that the deposited coatings were successfully applied on the surface of both Mg alloys. All the coatings increase the surface hardness of the Mg alloys and significantly improve their tribological properties. However, except for FeCrNiMoSiC coatings, the corrosion properties of Mg alloys deteriorate due to the fact that the corrosion environment can pass through the coating to the less noble Mg substrate and the corrosion microcells are created.
Creation of database of heterogenous systems FT – IR spectra
Hajzler, Jan ; Ptáček, Petr (referee) ; Opravil, Tomáš (advisor)
The aim of this thesis was to create a FT – IR database of heterogenous inorganic samples. The contents of the theoretical part include an introduction to infrared radiation and display the theoretical basis for measurement in a concise form. The experimental part consists of two areas. The first area focuses on the measurement of IR spectra of chosen samples. The measured samples are mostly based on silicon dioxide. The second area of the experimental part studies the influence of the selected method of measurement on the results of the measurement. The experiment examines two methods of measurement of the IR spectra, one being carried out with the use of KBr tablets and the other using the ATR accesory. Both of these methods were measured in the middle infrared and far infrared region.
Mineral wool and binding agent interaction and behavior study
Fiala, Michal ; Šoukal, František (referee) ; Ptáček, Petr (advisor)
Diploma's thesis describes resolution of cause technological problems in mineral wool manufacturig in company Saint-Gobain Orsil. Main attention is paid to thermal and volatile process in mineral wool from filtration chamber and common commercial sales. Samples of mineral wool were characterizated by thermal analysis (simultaneous TG-DTA), effluent gas analysis (EGA), infrared spectroscopy (FT-IR), electron microscopy (SEM) and X-ray diffraction (XRD). Thermal analysis experiments was used to check thermal volatile processes. Technological problem of burning is linked with rise of isocyanic acid.
Sol-gel synthesis of a LAS glass ceramics and influence of additives on a phase transformation and crystallization.
Kalinová, Helena ; Opravil, Tomáš (referee) ; Ptáček, Petr (advisor)
Course of synthesis of Li2O – Al2O3 – SiO2 (LAS) ceramic via sol – gel process made precursor was investigated. Powder precursor containing LAS components in molar ratio 1:1:4 were prepared by polycondensation technique in aqueous medium using lithium chloride (LiCl), hydrated aluminium nitrate (Al(NO3)39H2O) and silica sol (tosil), respectively. Heated sol was transformed into gel. The resulting gel was dried at temperature 105 °C and xerogel was next calcinated at 750°C. Further was evaluated influence of sintering additives (MgO, ZnO, Ca5(PO4)3OH) on the length of sintering interval. All of them have been stabilized spodumene in the solid solution. The properties of ceramic body prepared by sintering of precursor and grinded Li2CO2, Al2O3 a SiO2 powders were compared. Simultaneous thermogravimety and differential thermal analysis (TG-DTA), X-ray diffractions and heating microscopy were used to study sintering process of LAS ceramic.
Crash-Test Data Analysis - Side Impacts
Tillhonová, Veronika ; Ptáček, Petr (referee) ; Bradáč, Albert (advisor)
The diploma thesis deals with crash tests. Many international organizations specialize directly in conducting crash tests. Impact test simulates vehicle collision. The three most common test are front, side, and backstreets. The diploma thesis focuses on side conflicts. Side clashes are characterized by the fact that the first vehicle is damaged at the front and the second in the side. The measured data from these tests was evaluated to obtain the deformation energy consumed for permanent damage to vehicles. Deformation energy was calculated as equivalent to the individual speed of individual vehicles. EES values have been evaluated by various methods used in expert practice and compared. The impact tests were simulated to clarify assistance to experts in the analysis of traffic accidents.
Ash – the raw material base for the future
Marko, Michal ; Ptáček, Petr (referee) ; Opravil, Tomáš (advisor)
This master’s thesis responds to the worldwide problem concerning in the search of new material base for the future usage. Solid residues from high temperature or fluid coal combustion could be one of many alternatives to the raw materials. The study deals with the analysis of side energy products produced by power plant industry in the Czech Republic. Based on the fly ash chemical composition, possibilities of aluminium and even iron and titanium separation were proposed and then proved in the laboratory scale. Extracted components were separated selectively using apropriate methods. Then a couple of sintering reactions leading to improvement the leachability of selected elements from the fly ash matrix were carried out. Appropriate input material modification by high-temperature sintering reaction combined with extraction process in the sulfuric acid solution leads in dissolution up to 99 % of aluminium from the fluid and high-temperature fly ash.
Study of usabiliti of sands for preparation of aeroconcrete in hydrotermal condition
Straka, Radek ; Ptáček, Petr (referee) ; Opravil, Tomáš (advisor)
A building industry is expanding branch all the time and it intervenes in the life of everyone. Aeroconcrete is very attractive and actual subject nowadays because economy is important point of view of production. This material finds a wide-spread use thanks to its specific properties. The good manipulation and great thermal insulating properties are secured by its porous structure. Furthermore, proper material selection provides a saving of power of house for every customer demands. Due to aeroconcrete's sufficient compressive strength it is useful for both constructions and internal walls. Fundamental and very important for final material properties is raw material composition of aeroconcrete. A relationship between composition of filler (quartz sand) and resultant properties of aeroconcrete is an objective of the thesis.
Influence of anticorrosive surface treatment of steel reinforcement fibers on the properties of ultrahigh-performace cement composite
Bocian, Luboš ; Ptáček, Petr (referee) ; Novotný, Radoslav (advisor)
This thesis characterized surface layer of brass on commercially available steel microfibers. Subsequently, it was studied how to remove this surface layer of brass off these microfibers. Additionally, this thesis investigated influence of removal of brass surface layer on mechanical and ballistic properties of RPC composites. It was also studied how previously mentioned surface layer of brass influences interface between steel microfibers and matrix. It was found out that the surface layer of brass on commercially available steel microfibers is uneven and that the brass fills scratches present on steel underneath the surface layer of brass. It was also found out that conc. HNO3 and mixture of NH3 and H2O2 in volume proportion of 3 : 1 can be used to remove the surface layer of brass. The only thing to consider is that steel microfibers from conc. HNO3 corrode. Flexural strength of composite made with fibers from mixture of NH3 and H2O2 is higher than flexural strength of composite made with commercially available steel microfibers with surface layer of brass after 28 and 95 days. Compression strength wasn’t significantly affected in any composite used in this thesis after 28 and 95 days. Composite made with fibers from mixture od NH3 and H2O2 showed slightly better ballistic resistance than composite made with commercially available steel microfibers with surface layer of brass. In terms of SEM analysis of interface between matrix and steel fibers of certain composite, it was found out that there was no evidence of infiltration of components of brass into matrix.

National Repository of Grey Literature : 130 records found   previous11 - 20nextend  jump to record:
See also: similar author names
1 Ptáček, Patrik
12 Ptáček, Pavel
1 Ptáček, Petr Bc.
1 Ptáček, Přemysl
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