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Preparation and characterization of nanostructured III-V semiconductor materials
Maniš, Jaroslav ; Kostelník,, Petr (referee) ; Hospodková,, Alice (referee) ; Šikola, Tomáš (advisor)
Předkládaná dizertační práce se zabývá výrobou a analýzou gallium nitridových (GaN) nanostruktur ve třech odlišných formách. V prvním případě byl zkoumám trojdimenzionální GaN ve formě nanokrystalů rostených na grafenu. Nanokrystaly byly připraveny s využitím techniky droplet epitaxy, která mimo jiné umožňuje růst nanostruktur za nízké teploty substrátu (T = 200°C). Studium se zaměřovalo jak na charakterizaci kvality připravených nanokrystalů, tak na statistický popis růstu. V dalším kroku byly připravené struktury využity pro výrobu fotodektoru citlivého na ultrafialové světlo. Výroba fotodektoru a jeho úspěšné použití slouží jako základ pro navazující výzkum. Ve druhém případě byly studovány dvoudimenzionální GaN nanostruktury, které byly rovněž připraveny za nízké teploty křemíkového substrátu. Následná analýza se soustředila na popis krystalové struktury a prvkovou analýzu, neboť byly takovéto struktury pozorovány vůbec poprvé. Další rozvoj možností přípravy těchto nanostruktur je předmětem navazujícího výzkumu. Ve třetím případě byly zkoumány jednodimenzionální GaN nanodráty připravené na safírovém substrátu. Účelem tohoto projektu bylo získání datasetu pro ověření teoretického modelu, který popisuje růst horizontálních nanodrátů. Na základě sběru a analýzy dat se podařilo modelovat růstovou dynamiku GaN nanodrátů, která byly v souladu s teoretickým modelem.
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Influence of particle size of cosmetic pigments on final properties product
Obručová, Kateřina ; Hurčíková, Andrea (referee) ; Zemanová, Jana (advisor)
This diploma thesis is focused on the study of the influence of the of size cosmetics pigments on the properties of the final product. This effect was studied on samples of make-up given by industry partner. Make-up samples were measured by the rheology method and the yield stress of all samples was determined. Scanning electron microscopy was used to determine the size and shape of the pigment particles. Particle size was also measured by dynamic light scattering, but the results were influenced by forming aggregates. To easier determination of the types of pigments in the sample was determined elemental composition of the pigments (Ti, Fe, O, Al) by EDS detector. Due to the unknown composition of make-up, the information was supplemented by X-ray powder diffraction (XRD) analysis, and it was possible to determine the compounds TiO2 (anatase and rutile), FeOOH and Fe2O3. The results obtained by these methods showed what pigments can be found in make-up samples, what their sizes and shapes are. It has been shown that the smaller the pigments are, the higher the viscosity and yield stress of the final product. The higher these quantities, the harder it is to handle the product.
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Utilization of biosurfactants for incorporation of hydrophobic domains into modern controlled-release systems
Nešpor, Tomáš ; Pekař, Miloslav (referee) ; Sedláček, Petr (advisor)
This work deals with the current topic of carrier systems. Since the biggest problem is the passage of hydrophobic drugs through the bloodstream, or through universal body barriers (eg blood-brain), it is necessary to chemically modify these carriers in order to be able to administer hydrophobic substances effectively. Based on a literature search, several systems are designed and subsequently studied, in which there is a presumption of possible use for carrier systems and at the same time they have biosurfactants incorporated in them due to their ability to solubilize hydrophobic molecules. The theoretical part of this work will describe the individual biosurfactants, the process of their production, their physicochemical properties, and the possibility of their use in carrier systems. At the same time, the individual carrier systems, the procedure of their preparation, the possibilities of their use are described, and their advantages and disadvantages are also compared. In the practical part, the screening of both individual substances and their mutual interactions, as well as methods used to study the emerging structures is then performed. The study of molecular interactions is primarily performed using the technique of dynamic light scattering. The next part describes the optimization of hydrogel formation with incorporated biosurfactants in their structure and then the formed gels are subjected to rheological and solubilization tests. The study of the internal structure of these gels is performed using a scanning electron microscope.
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Microscopy: tool for material analysis
Pleskalová, Kateřina ; Řehořek, Lukáš (referee) ; Čupera, Jan (advisor)
This thesis deals with description of the microscopic techniques that are used to analyse materials. The introductory part briefly summarizes the history of microscopy. The first part of the thesis is focused on light microscopy and the confocal microscopy technique is more elaborated here. The second part of the thesis is focused on basic techniques of electron microscopy, which means transmission electron microscopy and scanning electron microscopy. At the end of each chapter, there is summarization of limits and advantages of these techniques. The preparation of metallographic samples is also briefly described for these microscopic techniques.
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Influence of humidity on total sterilisation effect of dielectric barrier discharge
Kramárová, Petra ; Bartlová, Milada (referee) ; Kozáková, Zdenka (advisor)
The main subject of this diploma thesis is the study of the effect of humidity on the total sterilization effect of the dielectric barrier discharge. Sterilization is a process which can eliminate all forms of life. The plasma sterilization is one of the methods that are suitable for sterilization of temperature and chemical sensitive materials. This sterilization method was proved to be effective on the wide spectrum of procaryotic and eucaryotic microorganisms. Basically, the main inactivation factors for cells exposed to plasma are heat, UV radiation and various reactive species. Dielectric barrier discharge (DBD) operating at atmospheric pressure was used for the sterilization of the samples. The discharge was generated in dry air and in humid air. The plasma power densities were 2 160 mW.cm-3, 2 279 mW.cm-3 and 2 760 mW.cm-3 (dry air) or 2 326 mW.cm-3 and 2 850 mW.cm-3 (humid air). Humidity of air was achieved using a wash bottle filled with water through which air flowed into the DBD reactor. Fungi spores of Aspergillus niger were used as model microorganisms. Whatman paper No. 1 was used as the carrying medium. When comparing sterilization efficiency of humid and dry air operating at the same conditions, the higher sterilization effect was observed in humid air. The sterilization effect of the DBD generated in air was compared with results obtained during plasma generation in argon and nitrogen. At the same conditions, the highest sterilization effect was observed in argon, followed by humid air, nitrogen and dry air. It was found out that in our experimental setup the active species are probably the main inactivation mechanism. The influence of temperature on the inactivation of microorganisms was completely negligible. The discharge parameters were studied by means of the optical emission spectroscopy (OES). Plasma treated samples were analyzed employing scanning electron microscopy (SEM). Damage of the microorganisms due to the effect of plasma as well as plasma effect on the structure of the carrying medium was evaluated.
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Welding of heterogeneous joints by laser
Charvátová, Eliška ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
This diploma thesis deals with welding of two dissimilar materials by laser. The samples were welded by direct beam guidance and wobbling, with and without using high alloy filler material and with the use of a diffusion barrier in the form of nickel. Welding was done with different shielding atmospheres. Nondestructive (VT, PT, UT-PA, RT) and destructive tests were performer (tensile test at room and elevated temperatures, microhrardness). Metalography was suplemented by EDX analysis of selected elements.
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Generation of metallic nanoparticles by non-thermal plasma in liquids
Čechová, Ludmila ; Blahová, Lucie (referee) ; Kozáková, Zdenka (advisor)
This thesis focuses on the process of nanoparticle generation using new source of nonthermal plasma combining corona and pin-hole discharge in liquids. The theoretical part is focused on generation of metallic nanoparticles using various types of plasma discharge, the properties of metallic nanoparticles, their preparation by other methods and methods of characterization of nanoparticles. The experimental part deals with the preparation of copper, silver and gold nanoparticles from solutions of their precursors. The influence of experimental conditions, such as the influence of voltage polarity, effect of precursor concentration, effect of added electrolyte or reducing agent were investigated. All samples were analyzed by UV-VIS spectroscopy. Dynamic light scattering was used to determine the sice of nanoparticles. To confirm the presence of nanoparticles, samples were analyzed using scanning microscope with and energy dispersion spectrometer for elemental analysis.
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Influencing the hydration of high-performance composites using zinc ions
Všetečka, Tomáš ; Hajzler, Jan (referee) ; Novotný, Radoslav (advisor)
The bachelor thesis is focused on the influence of hydration of high-performance cementitious composites, more specifically reactive powder composites. Zinc ions were supplied by the compounds of zinc oxide and zinc sulphate heptahydrate. Zinc ions were added by weight content to cement at concentrations of 0.2; 0.5 and 1.0 wt. %. The development of properties depending on the content of zinc ions and the type of compound used was monitored in this work. The measured values were compared with reference values that did not contain zinc ions. The highest compressive strengths were obtained with a sample containing 1.0% Zn in the form of zinc oxide. However, this sample is associated with a longer setting time due to the retarding effect of zinc ions on hydration. The retardation effect was monitored using isothermal calorimetry. For samples containing zinc ions, a negative effect on the brass layer of steel fibers, which was used as reinforcement, was observed. Due to the addition of zinc ions, dezincification and subsequent removal of brass from the surface of the fibers took place. Therefore, these specimens had lower tensile strengths. A positive effect on the differential ballistic protection efficiency factor was observed for a sample containing 1% Zn in the form of zinc oxide.
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The Rheological Behavior of Polymer Solutions Suitable for Electrospinning
Divínová, Nikol ; Voráč,, Zbyněk (referee) ; Chamradová, Ivana (advisor)
This diploma thesis deals with preparation and characterization of aqueous solutions of polyvinyl alcohol suitable for electrospinning. In the theoretical part method of electrospinning is described, including parameters which influence this process. Literary research also includes a chapter about rheology, which deals with the rheological properties of polymers, specifically PVA. The experimental part describes the preparation and rheological study of of aqueous solutions of polyvinyl alcohol, which were then spun. The morphology of prepared nanofibers was studied by using scanning electron microscopy (SEM). The effect of molecular weight, the solvent, concentration of solution, rheological properties, electrical conductivity and surface tension on the spinability, diameter and morphology of nanofibers is discussed.
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Techniques using beam of charged particles for imaging and material analysis
Lamborová, Leona ; Kičmerová, Dina (referee) ; Čupera, Jan (advisor)
This bachelor´s thesis deals with techniques using beam of charged particles for imaging and material analysis. There are two types of charged particles that are used for this purpose, electrons and ions. This research study is divided into principles of electron optics and principles of ion optics. Further, there is mentioned function, construction and detectors used for imaging and chemical analysis of scanning electron microscopy, transmission electron microscopy and focused ion beam.
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