National Repository of Grey Literature 70 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Mechanism and kinetics of gas-solid carbonation of portlandite
Valach, Jakub ; Švec, Jiří (referee) ; Ptáček, Petr (advisor)
The main goal of this work, is study of kinetics and mechanism of gas-solid carbonation of portlandit. The introduction part of the thesis acquaints the reader with basic theoretical information about the study of kinetics, mechanism and the analyses themselves. In the experimental part, the reader is acquainted with the methods and procedures used to evaluate the kinetics and mechanism. The last chapter interprets the results of the study, with discusion about results and analysis of the used sample.
Possibilities of the hydrometallurgical process for the recovery of light metals
Skalík, Martin ; Ptáček, Petr (referee) ; Opravil, Tomáš (advisor)
This bachelor thesis focuses on the assembly of individual stages of the hydrometallurgical process for recovery of lithium, magnesium and aluminum from mica. The main focus was the primary process of hydrometallurgy, i.e. leaching of mica in order to obtain an leachate enriched with lithium, magnesium and aluminum ions. The concentration of metal ions in the leachate was assessed by F-AAS analysis to determine efficiency of the temperature while leaching, leaching time, leaching agent concentration and calcitantion of the input mica.
Possibilities of reducing zinc losses during heat treatment of ferrite ceramics
Buday, Patrik ; Šoukal, František (referee) ; Ptáček, Petr (advisor)
The diploma thesis is focused on the study of the influence of sintering temperature on the evaporation of zinc from Mn-Zn-ferrite ceramics. The main focus of the study is on the reaction kinetics of the zinc evaporation process, at the same time the aim of this work is to propose and verify a method that would limit the evaporation of zinc. The theoretical part summarizes the basic knowledge about the properties, classification, application, and production of Mn-Zn-ferrites. The end of the theoretical part describes the loss of zinc and a possible solution to this undesirable phonomenon. The beginning of the experimental part contains a summary of the principles of infrared spectroscopy, electron scanning microscopy, and X-ray crystallography. The experimental part of the diploma thesis is focused on the description of the production of ferrite samples, the characterization of the input material and the determination of the reaction kinetics of the sintering, and its comparison with the kinetics of the sample treated with a protective layer.
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.
Modern fungicides and mechanism of their action
Zaleš, František ; Gabriel, Jiří (advisor) ; Ptáček, Petr (referee)
Fungicides are compounds, which are able to kill a fungi (they are therefore fungicidal), or they are able to slow or stop growth of a fungi (they are therefore fungistatic). Some fungicides also have insecticidal properties and can offer dual protection. This bachelor thesis is mainly dealing with fungicides, which are used to protect wood and wooden constructions from wood decaying fungi. Part of this bachelor thesis is a brief overview of wood decaying fungi and also an insight into the history of fungicides, but the main goal of this thesis is to offer a survey of currently used fungicides for wood protection against wood decaying fungi and also describe the mechanism of their action. Keywords: fungi, fungicides, buildings, general threat, wood decay, mode of action
The impact of physical methods and new chemical preparations based on nanoparticles on selected wood-rotting fungi invading wooden structures - possibilities and limitations of modern techniques of prevention
Švec, Karel ; Gabriel, Jiří (advisor) ; Ptáček, Petr (referee)
83 Abstract The work focuses on the physiology of wood-rotting fungi and the possibilities of their inhibition by physical methods (microwave and gamma irradiations, dry heat) or newly developed chemical preparatives contaning metallic nanoparticles. The effect of abovementioned treatments on mycelial growth, activities of extracellular enzymes responsible for wood degradation and on spore germination or viability was studied in selected strains of wood-rotting fungi obtained from culture collection (Coniophora puteana, Fibroporia vaillantii, Gloeophyllum sepiarium) or isolated from infected buildings (Serpula lacrymans).
The influence of barium and its compounds on the formation and properties of Portland clinker
Zezulová, Anežka ; Rovnaníková, Pavla (referee) ; Palou, Martin (referee) ; Ptáček, Petr (advisor)
The work deals with the study of barium cement. Barium cements are used to prepare concrete that protects against ionizing radiation. Barium can be also present in a conventional Portland cement clinker as an impurity from alternative fuels or raw materials, which are increasingly used for clinker production, and thus change the structure and properties of the product. Various methods of preparation of this cement were studied in this work. Barium cements were prepared from raw meals of different composition, but always with the same procedure and burning temperature. Using suitable analytical methods, the work describes the influence of individual admixtures of raw meal on the phase composition of the resulting clinker. Furthermore, the work deals with monitoring the form and location of barium in the prepared clinker. Several experiments are focused on the study of hydration of prepared barium clinkers, the phase transformation is monitored by XRD and supplemented by analyses of hydration products. In this way, it was possible to obtain the data needed to describe the preparation, burning, and hydration of barium cements with different compositions. The work also deals in detail with the real use of barium cements. The ability of pastes and mortars from prepared barium cements to shield various types of ionizing radiation was tested and described experimentally. The results are presented in comparison with reference samples, which were prepared from commonly used Portland cement.
Influence of zinc loss during the sintering on permeability/inductance of ferrite ceramics
Kvapilová, Vendula ; Ptáček, Petr (referee) ; Šoukal, František (advisor)
The diploma thesis is focused on the investigation of the effect of zinc release during ferritic sintering on the permeability/inductance of ferrite ceramics. The theoretical part deals with the position of ferrites among other ceramic materials. It describes the basic characteristics of ferrites, their crystal structure and finally the problems that are directly related to their production and which fundamentally affect the magnetic properties of ferrites. In the second part of the work, the influence of the temperature and time of sintering and the position of the cores in the furnace during firing on the loss of zinc from the sample and subsequently on the electromagnetic properties of the prepared test specimens from industrial raw material mixtures was investigated. These are initial experiments, which will be followed by further research aimed at eliminating the problem of zinc loss in the production of Mn-Zn ferrites.
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.

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1 Ptáček, Patrik
6 Ptáček, Pavel
1 Ptáček, Petr Bc.
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