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Influence of metal ions on microorganization of humic substances
Odehnalová, Nikola ; Krouská, Jitka (referee) ; Klučáková, Martina (advisor)
This bachelor thesis is focused on the study of influence of metal ions on microorganization of humic substances. This issue was studied on a sample od fulvic acid. Solution of cocentration 1 g/l was prepared from this sample. This solution was ten titrate with solutions of copper, calcium and magnesium ions. For this purpose, methods of dinamic and electrophoretic light scattering were used. The results obtained by these methods show that the solution of fulvic acid is the most made by associated molecules of fulvic acid. The size of molecules became larger and larger during titrations. Copper was sorpted the most.
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Preparation and Characterisation of Polyelectrolyte Complexes in the System Dextran-Surfactant
Klímová, Eliška ; Krouská, Jitka (referee) ; Kalina, Michal (advisor)
This bachelor thesis deals with the study on preparation and characterization of the polyelectrolyte complex formation in the dextran-surfactant system. The aim of the thesis was the investigation of the influence of the ionic strenght on the formation of the interactions in the studied system. For these purposes, components having opposite charges (DEAE-dextran hydrochloride and anion-active sodium dodecyl sulphate) were selected. For individual measurements mainly the methods of light scattering, dynamic and electrophoretic light scattering in particular, have been used. In the thesis have been studied interactions and aggregation concentrations of individual components having the potential to form polyelectrolyte complexes. It was verified in all the studied samples, by measuring the intensity of scattered light and the size of Z-diameter of particles, that the increase in sizes of particles is caused by the formation of these complexes. There were also measured additional characteristicts of the system such as pH or conductivity. Their dependences provide comprehensive view on the formation of complexes in studied system and can be utilized for other measurements and possible future applications, especially for purposes in medical applications.
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The influence of particle size and methods of preparation of calcium aluminate phases on their hydration
Ohaňka, Zdeněk ; Másilko, Jiří (referee) ; Koplík, Jan (advisor)
This work focuses on the hydration of four calcium aluminate phases – C3A, C12A7, CA and CA2. Above all, the influence of particle size and method of preparation on hydration behaviour were studied. Influence of these factors on hydration products were also investigated. Calcium aluminates were prepared by solid state synthesis and amorphous citrate method. Both methods were described in detail. The particle size was determined by laser diffraction. Isothermic calorimetry was used to investigate the process of hydration. Hydration products were identified by X-ray diffraction analysis and simultaneous thermogravimetric and differential thermal analysis.
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Morphology and hardness of particles of titanium powder prepared by cryogenic milling
Ibragimov, Ilya ; Stráský, Josef (advisor) ; Janeček, Miloš (referee)
The effect of cryogenic milling on morphology and microhardness of titanium powder was investigated. Initial powder of commercially pure titanium was subjected to cryogenic milling in liquid argon (LAr) using two different milling speeds. Prepared powders were subsequently cleaned by ethanol. The cleaning procedure was done in two ways: in the air and in the inert atmosphere in the glovebox. Particle size and morphology were investigated my scanning electron microscopy and subsequent automated image analysis. Microhardness of powder particles was determined by Vickers hardness measurement using small loads. The milling did not cause significant powder refiniment, while the shape of powder particles changes substantially. Milling speed affected particle shape and powder contamination. Application of stearic acid as the processing control agent prevented cold-welding of powder particles, but contaminated the powder by oxygen and hydrogen. Stearic acid could be successfully removed by cleaning in ethanol. The using of glovebox for cleaning did not have significant effect on the resultiing contamination.
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Titanium and titanium alloys prepared by cryogenic milling
Kozlík, Jiří ; Stráský, Josef (advisor) ; Janeček, Miloš (referee)
Ultra-fine grained materials are presently thoroughly investigated due to their enhanced mechanical properties. Cryogenic milling is one of the severe plastic deformation methods, which allow production of these materials. Titanium powder was processed by cryogenic milling in liquid nitrogen and argon and consequently consolidated via spark plasma sintering method. In this work, the influence of milling conditions (liquid nitrogen vs. liquid argon, material of balls, duration and speed of milling, usage of stearic acid) on size and shape of powder particles, contamination and mechanical properties was investigated. Particle size reduction was generally not observed, while their morphology changed significantly. Using liquid nitrogen as a cooling medium leads to strong contamination of prepared material and consequently to its hardening and embrittlement. Stearic acid supresses cold welding of particles during milling and enhances its efficiency. It is possible to eliminate stearic acid from powder by cleaning in acetone before sintering, to prevent contamination of processed material. Microhardness increased, depending on milling efficiency (in liquid argon), from original 178 HV to 200-300 HV range. Increase of yield and ultimate stength was observed in compression tests while maintaining ductility....
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Study on the Supramolecular Structure of Humic Acids
Širůček, David ; Pekař, Miloslav (referee) ; Kalina, Michal (advisor)
This bachelor thesis is focused on the study of supramolecular structure of humic acids. This issue was studied on a number of HA samples which differed in source matrix (lignite, leonardite, soil, peat and compost). For these purposes, methods of size exclusion chromatography, dynamic and electrophoretic light scattering and UV-VIS spektrometry were used. In order to better understand the formation of the supramolecular structure of HA, the ways of its stabilization and how it was influenced by the change in pH, individual HA samples were studied in three pH-varying mediums (3,5; 7 and 12). The results obtained on a wide range of used humic acids are in accordance with the supramolecular theory of the structure of humic acids in aqueous solutions which describes them as freely-bound supramolecular associates of relatively small molecules having both polar and nonpolar parts and can be formed into more complex supramolecular aggregates depending on the conditions in the solution (pH, content of low molecular weight ions, etc.).
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Effects of hyaluronan on properties of Opthalmo-Septonex eye drops
Chromá, Kateřina ; Němcová, Andrea (referee) ; Pekař, Miloslav (advisor)
Modification of eye drops using hyaluronan to increase retention time on the eye surface. Using modification of Mahrous method have been determined concentration of Septonex in water. Than using gradual addition of hyaluronan into Opthalmo-Septonex eye drops was investigated appropriate concentration for membrane dialysis. With membrane dialysis was observed interaction hyaluronan-septonex. Than was determined size and charge of particles.
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The study of sedimentation of MR fluids for space applications
Vančurová, Martina ; Strecker, Zbyněk (referee) ; Roupec, Jakub (advisor)
This bachelor thesis deals with experimental determination of the effect of iron particle size on the sedimentation rate of magnetorheological (MR) fluids. MR fluids from three producers are examined here: Liquids Research Limited (Great Britain), HaoHua (China) a LORD Corporation (USA). Particles describing the effect of MR fluids’ different attributes on their sedimentation are summarized in an overview of current knowledge. The development of the Matlab script, that detects and measures the size of particles in the input electron microscope images, is presented. The particles are also measured manually in some images, which is partly used as a reference measurement for the developed script. The particle size measurement results are then compared with the sedimentation behavior of examined MR fluids.
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The Study of Aggregation of Humic Acids in Different Xenobiotic Environments
Hronová, Aneta ; Smilek, Jiří (referee) ; Kalina, Michal (advisor)
Theme of the presented bachelor thesis is the study of the aggregation behavior of the humic acids (HA) in the environment of extraneous substances. As extraneous substances, three cationic surfactants were selected (CTAB, TTAB and Septonex). In the experimental part of the thesis, the humic acids were characterized in detail using different methods (elemental analysis, ash content determination, titration acidity determination). The experimental part of the thesis is dealing with the structure of created HA-surfactant systems. These systems were characterized using the results of the elemental analysis and FT-IR spectroscopy. The key part of the experimental part of the study is represented by the selection of proper methods and by determination of the critical aggregation concentration of the humic acids in the surfactant environment. For these purposes, two key methods were selected in the frame of the presented bachelor thesis: isothermal titration calorimetry and dynamic light scattering. The first method is sensitive owing to the energetic fluctuations, in the case of the dynamic light scattering we are able to detect well the changes in the particle size caused by mutual interactions of particular substances in the system.
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The effect of particles size on the properties of mortars.
Sehnal, Tomáš ; Krátký, Josef (referee) ; Šiler, Pavel (advisor)
The consumption of concrete as a building material is still increasing over the world. Concrete production is closely associated with CO2 and other greenhouse gases emissions. The reduction of these emissions can be achieved by a higher utilization of secondary raw materials in cement mixtures. This bachelor work is focused on the using of secondary raw material, finely ground granulated blast furnace slag and fly ash from fluidized bed combustion and high temperature combustion. The properties of milling pure cement and cement mortars with addition of secondary raw material will be measured. Compressive strength, flexural strength, and calorimetric measurement will be performed for these prepared mortars.
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