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Utilization possibilities of industry gypsum and secondary materials containing for preparation of composites
Weiglová, Jana ; Šoukal, František (referee) ; Opravil, Tomáš (advisor)
The work studies the possibilities of the utilization of secondary raw materials produced by power industry. It addresses mainly the gypsum by-products and fluidized coal combustion ash. As for the secondary raw materials the content of sulphites is observed and the dependences of their transformation to sulphides via natural oxidation by air oxygen or by addition of adequate oxidant are studied. The work follows with describing the effect of sulphides contained in raw materials on the mechanical properties of composites prepared from several various matrices such as alumina or portland cement, lime or portland clinker. As for pure portland clinker the ability to retard the setting is also observed. The amount of contained sulphites is measured volumetrically via indirect titration of iodine surplus by sodium thiosulphate with the starch size as the indicator.
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Reduction of hexavalent chromium in cement binders
Hrubý, Petr ; Šoukal, František (referee) ; Kalina, Lukáš (advisor)
The issue of hexavalent chromium contained in cement binders and the possibilities of its reduction are very current, due to the toxicity of Cr (VI) and constantly stricter regulations of the EU. The effort of achieving a cement binder with Cr (VI) concentration lower than 2 ppm and keeping this concentration unchanged during the long term storage is a frequently studied issue which needs to be solved. Requirements are put on the low cost for industrial use and without inducing changes of final properties of cement binders. A reducing agents based on iron (II) sulphate monohydrate potentially combined with some additives were studied in this study. The efficiency of reducing agents was analysed by commonly used UV-VIS spectrophotometry technique which uses 1,5-diphenylcarbazide as an indicator. The influence of added reducing agent on the mechanical properties was noticed by compressive strength test.
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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.
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Preparation of bioceramic materials for medical applications
Doboš, Petr ; Šoukal, František (referee) ; Palou, Martin (advisor)
The aim of this work was to prepare hydroxyapatite powder by sol-gel and precipitation method. Then, the powders were pressed and sintered at 500 °C, 800 °C and 1100 °C. These samples of HAP were analyzed by FTIR, XRD, SEM methods. The microstructure measurement by SEM indicates that the size HAP particles varies from micro to nano meter. The average size of dominant particles is determined around 5 – 8 µm with surrounding fine particles of 1 µm size. The in vitro bioactivity of HAP samples was investigated by immersing them in Simulated Blood Fluid for 4 weeks. The work reports the result of mikrostructure analysis of samples after immersion. The bioactivity was influenced by the sintering temperature. It is evident, that the layer of the new hydroxyapatite phase formed during immersion on the surface of initial HAP samples changes with temperatures.
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The study of hydration of RPC (Reactive Powder Concretes) in hydrothermal condition
Dvořáková, Tereza ; Koplík, Jan (referee) ; Šoukal, František (advisor)
The diploma thesis deals with the study of hydration of reactive powder concrete under hydrotermal conditions. The theoretical part describes the properties of materials and additives used for the preparation of mixtures. The following describes the principles and requiments for the materials for preparing the reactive powder concrete. The practical part is studied design method mix and the impact of materials to the consistency of paste. The effect of cample placement on flexural and compressive strength of the prepared mixtures was observed. The samples were stored under standart laboratory conditions and under hydrothermal conditions. The phase composition of the samples was monitored by X-ray diffraction analysis and the mocrostructure by scanning electron microscopy.
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Local tests of mechanical properties of materials
Wasserbauer, Jaromír ; Šoukal, František (referee) ; Zmrzlý, Martin (advisor)
This thesis deals with measurement of hardness and microhardness in relation to structure of homogeneous and heterogeneous materials. In the introduction basic theoretical background is commented, i.e. definitions, terminology, principles of measuring techniques for estimation of hardness, microhardness, tensile strength, compressive strength and bending strength. Follows a brief review of present research results focused on use of described principles in materials engineering. Then the experimental equipment and sample preparation is described. The crucial part of the thesis is summary of achieved results of original measurement and discussion of their relations to each other. Finally, the groundbreaking estimation is described, showing the correlation of chemical composition gradient and mechanical properties in interfacial zone of geopolymeric material.
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The influence of triaxial deformation of aggregates on properties of concrete
Fójcik, Tomáš ; Kalina, Lukáš (referee) ; Šoukal, František (advisor)
This diploma work takes focus in elastic modulus of unbound granular aggregates, which was determined by repeat load triaxial test and in deformation behaviour of unbound granular aggregates - elastic and plastic deformation. It was examine the propriety of this aggregate for its service as underlying granular material in pavement. Further, there was observed the influence of elastic modulus of unbound granular aggregates on concrete characteristics - compressive and bending strength. Finally, it was observed the influence of individual fractions of aggregates on its elastic modulus and strength of concrete.
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Preparation of geopolymeric binders for toxic metals inhibition
Jevická, Lucie ; Kalina, Lukáš (referee) ; Šoukal, František (advisor)
This thesis deals with preparation of geopolymeric binders for inhibition of toxic elements, especially arsenic. It studies influence of content progress of different phases in prepared binders on leachability of As during the setting. The aim of this study is to determine the type of inhibition or the cause of leachability of As in prepared binders respectively. Fly ash from high-temperature coal combustion, slag, cement kiln dust and sodium hydroxide solution were used for experimental works. FT-IR, TG-DTA, XRD analyses after different hydration times were used. The leachates were analyzed by ICP-MS. Calorimetric measurements of tested mixtures fresh pastes were implemented to learn about setting process. Hardened binder specimens were tested for bending and compressive strength.
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The influence of barium oxide on the formation and properties of portland clinker
Zezulová, Anežka ; Šoukal, František (referee) ; Opravil, Tomáš (advisor)
Portland clinker is thanks to its large-scale production a continuously studied topic. Clinker, or Portland cement, is used for construction purposes, or for insulation and special applications. One of these special applications could be shielding of different types of radiation by making use of the content of barium ions. The present master’s thesis examines the influence of barium oxide on the formation and properties of Portland clinker, which could be, by incorporation of barium ions into the system, used as a binder for buildings resistant to various types of radiation. Barium sulfate and barium carbonate were added to the raw meal in order to prepare clinkers with different content of barium oxide. The effect of barium on the formation of clinker phases was studied (by XRD – Rietveld analysis and by the microscopic point integration), as well as the effects on the variations of temperature of the phase formation (TG-DTA) and the rate of alite formation under isothermal conditions. Furthermore, the ability of barium to become a part of clinker minerals was studied by SEM with EDS, and the solubility of barium phases by ICP-OES. The hydration of clinker minerals containing barium was studied by isothermal calorimetry.
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The possibilities of use of sludges from limestone wash
Švec, Jiří ; Šoukal, František (referee) ; Opravil, Tomáš (advisor)
In modern point of view of waste management is desirable to effectively process the grates possible amount of wastes. Sediments from cleaning of mined lime stones contains a lot of clay components, but there is also indispensable share of soft calcite. This composition makes these sediments a promising material for preparation of hydraulic binders. Production of common hydraulic binders, especially Portland cement, is very energy-intensive plus loads environment with considerable amount of combustion gases, therefore it is necessary to explore possibilities of alternative low - energy binders production and usage.
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