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Preparation of calcium-aluminate phases
Ohaňka, Zdeněk ; Novotný, Radoslav (referee) ; Koplík, Jan (advisor)
This work focuses on the preparation of calcium aluminates by solid state synthesis and by sol-gel method. Phases prepared were monocalcium aluminate (CA), dodecacalcium heptaaluminate (C12A7), tricalcium aluminate (C3A) and calcium dialuminate (CA2). Two modifications of sol-gel method were used – the difference between them was in the addition of EDTA. Each method was closely described and results were compared according to the achieved purity of prepared phases. X-ray diffraction analysis was used to determine the purity of prepared calcium-aluminates.
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Heat insulating moulded refractory materials
Novotný, Radoslav ; Lang, Karel (referee) ; Raschman,, Pavel (referee) ; Havlica, Jaromír (advisor)
Doctoral thesis is focused on the study, research and development of heat insulating moulded refractory materials. The replacement of shaped instead of unshaped refractories is recently and strongly industrially demanded and belongs to ongoing research topics. With the increasing demand of energy savings, the excellent insulation properties are essential. The insulating properties of castables are the result of targeted porosity formation. The porosity is coming from the controlled air intrusion into material resulted to foamed structure. The foaming process was achieved by mixing of separately prepared aqueous foam into raw castable slurry or by in situ foaming of intensively mixed castable slurry with the surfactant additive. Nevertheless, the study of foam behaviour and the influence of additives on binder hydration and setting processes (i.e. calciumaluminate cement) was substantial for successful preparation of the experimental samples. The two types of the experimental samples were prepared. The first one was based on mixing of kaolin slurry with pre-prepared aqueous foam, whereas the de-aglomeration ability of kaolin specie was utilized to water-particle film formation. In situ foaming of multicomponent system is the second one. The both processes brought some negative attributes, so the optimal properties of prepared castables were achieved by their combination.
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Influence of fumed silica on the properties of ultra-high performace cement composite
Hrbáčová, Markéta ; Švec, Jiří (referee) ; Novotný, Radoslav (advisor)
This diploma thesis deals with the properties of concrete based on reactive powdered materials. Pyrogenic nanosilica (Aerosil 200, Aerosil 380) was added to the concrete in various volume ratios. The aim was to design and prepare a series of samples in order to determine their basic properties, and to determine the behavior of selected samples during penetration by a high-speed projectile compared to the reference sample. In order to determine the strength of the samples, compression and tensile bending tests were performed. The so-called multihit test was used to determine ballistic resistance. The differential effect factor was also determined experimentally and compared with the reference sample. An electron microscope was used to monitor the behavior of the fibers in the binder as well as the binder itself. Hydration curves for individual samples were generated using calorimetric measurements. The bulk density of the samples and the spills during their preparation were also monitored. The resulting strength of the nanosilica samples did not show higher values compared to the reference sample. The results of the multihit test did not show considerable changes compared to the reference composite.
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Recyclation of dust from production of dry mortar blends
Ondrůšková, Nela ; Novotný, Radoslav (referee) ; Šoukal, František (advisor)
The work deals with the problem of disposal of ever-increasing waste (dust) from the production of building materials and examines the possibility of recycling dust dust into cement repair mortar. The aim of this work was to determine the composition of individual dust particles from the production of cement mixtures and to determine their mechanical properties, as well as to determine the ideal ratio of dust particles to each other when mixing the dust mixture and its mechanical properties. This mixture consisted mainly of dust from products based on Portland cement, aluminous cement, gypsum and lime hydrate. The mixture further replaced part of the cementitious mortar and the impact of the additive on the mechanical properties of the cementitious mortar was determined. X-ray fluorescence spectrometry was used to determine the elemental composition, and X-ray diffraction analysis was used to determine the mineralogical composition. Test specimens were prepared according to the ČSN EN 12390 standard. Mechanical strength tests were performed on the test specimens. A large part of the test specimens could not be subjected to mechanical tests because the test specimen did not solidify even after a long time. The individual measurements that could be made show that the mechanical properties of the dust samples show values which have shown that the dust cannot be recycled into the product due to its instability. Dust particles have too diverse composition and in combination with cementitious repair mortar do not have the required properties. The problem is especially the sampling from the data, which did not solidify at all and thus excluded the remaining samples with already good properties of the same sample. When designing the method of recycling, it was necessary to take into account which product of the company is most in demand, where recycling would also make economic sense, which is also an important indicator for the operation of the company today. Dust particles could prove successful in another product, but it would not be advantageous for the company now, so now the recycling of dust particles will not start and they will be further disposed of in the same way.
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Interaction of Lanthanide trichlorides with the construction materials of a purification apparatus
Novotný, Radoslav ; Zmrzlý, Martin (referee) ; Richtera, Lukáš (advisor)
Lanthanide halides LnX3 are the base material for preparation a different compounds, but also the pure metals. Our faculty is used for the syntesis organometallic catalyst. This compounds are very sensitive to the presence of moisture and oxygen. Lanthanide halides are commercially available in anhydrous or hydrated form. This thesis is devided eight chapters and deals with matherial of the apparatus, which is designed to sublimation of anhydrous lanthanide halides. Initial chapters described the properties and preparation this substances. Following are on the sublimation and corrosion materials. In the last chapter is the skeleton sketch, layout and a availability parts of construction. The aim of this work was to create theoretical basis of construction aparatus and commissioning.
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Setting control of alkali-activated systems
Komosná, Kateřina ; Novotný, Radoslav (referee) ; Kalina, Lukáš (advisor)
This thesis is focused on the possibilities of setting control of alkali-activated systems based on blast furnace slag. The aim of this work is finding the suitable retarder that most extends the time of setting and also preserves the mechanical properties of alkali-activated material. In experimental section were prepared samples of blast furnace slag, water glass, water and additives in various weight addition. Testing samples have undergone of flexural and compressive strength tests. Then the setting time was determined using the Vicat device. The samples were measured calorimetrically because of monitoring the setting process. Finally the mixtures were observed using scanning electron microscope for a closer view on the structure of samples and distribution of setting retarder.
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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.
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Utilization of fluidized bed combustion solid residues in the production of refractories
Tvrdý, Michal ; Novotný, Radoslav (referee) ; Opravil, Tomáš (advisor)
The thesis deals with the preparation, study and analysis of refractory ceramics, namely fireclay mortars for stove purposes with the addition of fluid ash. The mixtures for preparation of refractory ceramics were doped with different content of fly and bed fluid ash in order to reduce the consumption of the original raw materials for the preparation of these materials. Fired slate clay, refractory clay, fly and bed fluid ash were used for preparation the samples. Input raw materials and fired fireclay mixtures were characterized by XRD, TG-DTA-EGA, TDA, SEM-EDS, heat microscopy, isothermal calorimetry, ICP-OES. The mechanical properties, i.e. compressive strength and tensile bending, were also determined on fired fireclay mortars. The results showed that the properties of the fireclay mortar containing fly ash are comparable to the starting mortar to a specific ash dosage. It has also been found that bed fluid ash is not suitable for the production of refractory materials.
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Chemical wall clamp based on fast-setting geopolymeric binders
Novotný, Radoslav ; Kalina, Lukáš (referee) ; Šoukal, František (advisor)
The aim of this work is to develope fast-setting geopolymeric binders applicable in the chemical wall clamp. This clamping systems are big trend because of easy application, ability to transfer big forces and short setting time. Binders of this systems are based on polymeric resin. Their raw materials are expensive, toxic and flammable substances. Based on this consideration an anorganic fast-setting geopolymeric binder was developed. This binders consist of mixture of metakaolin and precipitated silica activated by potassium hydroxide. Binder were characterized by suitable analytic methods (XRD, SEM, DTA). The results of this metods were used for optimalization of binder properties.
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Issues of stopping the hydration of alkali-activated slag using organic substances
Chadima, Jan ; Novotný, Radoslav (referee) ; Bílek, Vlastimil (advisor)
This thesis deals with the stopping of hydration of alkali activated slag by organic solvents and investigates to what extent the selected organic solvent affects the results of the analyses. The solvents used were acetone, diethyl ether, ethanol, isopropanol and methanol, and this is because these are the most commonly used organic solvents in practice. Thermogravimetric analysis along with differential thermal analysis was used to assess the degree of influence of organic solvents on the alkali activated slag and Portland cement samples. Methanol and acetone affected the samples the most and the longer the sample was stored in the solvent, the more it reacted with the organic solvent. The adverse interaction of organic solvent was greatest for the Portland cement samples. Samples that were rinsed with diethyl ether prior to analysis had lower mass losses than samples that were not rinsed. In the case of alkali activated slag, it was found that the way in which the thermogravimetric results were affected by organic solvents was highly dependent on the activator used, with the smallest effect observed for Na2CO3 activation, while the largest effect was observed for NaOH activation at temperatures below 600 °C, and for higher temperatures for water glass activation.
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