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Ceramic materials based on spinel MgAl2O4 for optical applications
Rychnovský, Daniel ; Maca, Karel (referee) ; Drdlík, Daniel (advisor)
This diploma thesis deals with preparation of transparent ceramics based on spinel MgAl2O4 and effect of Cr3+, Tb3+ doping on optical properties. Preparation of samples was optimized using several ways to prepare non-defect ceramic samples with the highest relative density of green body. The final step of the processing included hot isostatic pressing resulting in transparent undoped and doped spinel ceramics. The highest values of RIT (real in- line transmittance) of undoped and doped samples were measured between 77–79 %. It was found by measuring photoluminescence properties of prepared samples that increasing concentration of Cr3+ resulted to higher peak intensities. The most intense emission peak was measured in red spectral area at wavelength of 685 nm. In the case of Tb3+-doped spinel, the maximum peak intensities were measured at concentration of 0.075 at. % and the most intense emission peak was measured in green spectral area at wavelength of 545 nm.
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Research on the content of risk elements in the material of PET bottles
Kryštofová, Petra ; Řezáčová, Veronika (referee) ; Komendová, Renata (advisor)
This thesis deals with the research of the content of risk elements in the material of rPET (recycled polyethylene terephthalate), supplied from various countries, and the study of different factors (type of liquid, temperature) on the migration of antimony from this material. The recycling process has the potential to increase the content of unwanted substances and promote the formation of degradation products of chemical additives and by-products of polymerization, thus contributing to higher migration of these substances into food or food simulants [1]. The supplied rPET samples were subjected to total decomposition in an environment of concentrated sulfuric and nitric acid under the influence of microwave radiation prior to analysis. Prepared samples were analyzed by atomic absorption spectroscopy (AAS) techniques. The contents of Sb and Zn were determined by flame atomic absorption spectrometry (FAAS), and the concentrations of Pb, Cu, Zn, Cd, Cr, and Ni were determined by electrothermal atomic absorption spectrometry (ETAAS). Additionally, the concentrations of Sb were determined by this method in migration experiments. This thesis builds upon the author's bachelor's thesis, which included pilot experiments.
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Low-temperature plastic deformation of BCC metals with internal magnetic order
Holzer, Jakub ; Máthis,, Kristián (referee) ; Mrověc, Matouš (referee) ; Gröger, Roman (advisor)
Přestože plastická deformace kovů s prostorově střeďenou kubickou mřížkou za nízkých teplot je dnes dobře vysvětlena, vliv vnitřního magnetického uspořádání na mechanické vlastnosti a vliv plastické deformace na vnitřní magnetické uspořádání zůstávají z větší časti nevysvětleny. Cílem této práce je popsat nízkoteplotní plastickou deformaci -železa a chromu pomocí analýzy skluzových čar, elektronovou zpětně odraženou difrakcí a transmisní elektronovou mikroskopií (TEM). Vnitřní magnetické uspořádání chromu je zkoumáno pomocí magnetické neutronové difrakce v neutronovém centru na Institutu Paula Scherrera ve Švýcarsku. Vibrační magnetometrie je využita pro hledání změn v hmotnostní susceptibilitě, aby byly rozeznány různé magnetické stavy. Anomální skluz byl poprvé pozorován v deformovaném vzorku chromu. Dislokační síť zodpovědná za anomální skluz je charakterizována pomocí g·b analýzy v TEM. Síť protínajících se 1/2111 šroubových dislokací a jejich 100 spoje se tvoří na nízkozatížených {110} rovinách. Dvojčata vytvořená antidvojčatovým smykem byla pozorována v chromu, ale nikoliv v -železe. Tento jev je vysvětlen pomocí atomárních simulací využívajících semiempirické interakční potenciály. Magnetické domény v -železe byly studovány pomocí Kerrovy mikroskopie. Výsledky ukazují, že dvojčata mohou efektivně blokovat pohyb doménových stěn a nukleovat nové.
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Speciation analysis of chromium in particulate matter of urban dust
Rybínová, Marcela ; Rychlovský, Petr (advisor) ; Hraníček, Jakub (referee)
Anion-exchange chromatography with inductively coupled plasma - atomic emission spectrometry (ICP-AES) has been used for the speciation of chromium (Cr). Chromium speciation has attracted attention because of the different toxicity, Cr(III) is relatively non-toxic and Cr(VI) has been classified as a human carcinogen. The aim of the present study was to develop simple method for the speciation analysis of Cr (Cr(III) and Cr(VI)) in particulate matter of urban dust. A combination of 2% KOH + 3% Na2CO3 has been chosen as the optimal reagent for the extraction of chromium from particular matter. It was found that there was no conversion of Cr(VI) into Cr(III). The effect of separation parameters such as acidity of mobile phase was also studied. The detection limit for Cr(VI) was about 12 ng.ml-1 . Results for the determination of Cr(VI) were confirmed by the analysis of standard reference material (BCR CRM 545, Cr(VI) in welding dust loaded on a filter) with good agreement between certified (40,16 ± 0,60 μg.g-1 ) and found (37,83 ± 1,14 μg.g-1 ) values.
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Application of Atomic Absorption Spectrometry for Determination of Selected Elements from Potential Ecological Burden Area
Juránková, Lada ; Hraníček, Jakub (advisor) ; Šíma, Jan (referee)
This work is focused on the determination of selected (chemical) elements (Fe, Mn, Zn, Cr, Na, K, Mg a Ca) in a potential ecological burden area using flame atomic absorption spectrometry as a detection technique. A potential ecological burden is represented by tires which are used as a construction material or as an environment surrounding for growing decorative and consumable plants. Analytes were determined in plant origin samples. Firstly, the samples were dried in a laboratory electric dryer. The weighted amount of a dried sample (approximately 0.2 g) was digested inside a microwave decomposition device with an addition of nitric acid and hydrogen peroxide. An optimization of experimental parameters was done for each of the elements before sample measuring. A burner height was optimized and 8 mm height was chosen as a optimum for most elements. Under the optimum condition basic characteristics were measured for each element separately. These characteristics included limits of detection that were: 0.05; 0.01; 0.08; 0.21; 0.02; 0.01; 0.01; 0.01 mg L-1 for the following elements: Fe, Mn, Zn, Cr, K, Ca, Mg and Na, respectively. The limits of quantification, sensitivity and repeatability were determined for each element as well. A significant attention was paid to the content of zinc in the studied...
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Processing and properties of transparent polycrystalline ceramic materials
Tásler, Jan ; Pouchlý, Václav (referee) ; Maca, Karel (advisor)
The presented diploma thesis is focused on the preparation and properties of transparent polycrystalline ceramic materials based on Al2O3. Theoretically, the most important technological aspects of the processing of these materials are presented. Detailed attention is given to transparent Al2O3 polycrystalline ceramics doped with rare earth elements. The influence of microstructural parameters on the optical properties (represented by RIT) is investigated on Al2O3 samples doped and codoped with dysprosium, terbium and chromium. A significant effect of the average grain size on the light transmittance of all samples is observed. The highest RIT = 55 % (measured by a laser beam with a wavelength of 632,8 nm) was achieved by an optimized preparation process for a sample doped with 0,05 at. % of dysprosium. For all samples photoluminescent properties are also analysed. The photoluminescent emission spectra correspond to the activation of doping elements. In case of the terbium and chromium codoped samples, the differences in the activation of individual dopants depending on different excitation wavelengths were demonstrated, resulting in different colour emissions for different excitation wavelengths.
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The pilot plant scale of the electrochemical elimination of Cr and Ni
Krušinová, Zuzana ; Klusoň, Petr (advisor) ; Žebrák, Radim (referee)
Electrocoagulation is a progressive yet not thoroughly understood method used to purify water contaminated by toxic elements and compounds. This bachelor thesis is focused on pilot scale testing of the electrochemical elimination of chromium and nickel from groundwater, realized on the premises of the company Velobel in Zlaté Hory. Firstly, it was essential to optimize the electrocoagulation process according to the parameters and composition of the groundwater. Secondly, it was necessary to test a continuous long-term operation that would make possible complete decontamination of the site. The electrocoagulation process was followed by addition of flocculant which was used to promote the sedimentation of the sludge. Lime solution was added simultaneously to change pH and to help eliminate nickel. This was followed by sedimentation and the purified water was led away by an overflow. The sludge was treated by a filter-press. Hexavalent chromium content in water samples was analysed spectrophotometrically with diphenylcarbazide, whereas trivalent chromium, nickel, zinc and manganese were analysed in a laboratory using ICP-OES (inductively coupled plasma - optical emission spectrometry). It was discovered that the tested technology is very successful in real conditions, with metal removal efficacies...
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Leachability of Ba and Cr from alkali-activated matrices
Cába, Vladislav ; Hajzler, Jan (referee) ; Koplík, Jan (advisor)
The aim of this work is to determine the usability of alkaline activated matrices made from ashes to inhibition of barium and chrome. Ashes – fly ashes and ashes from fluidized bed combustion – were compared with cement used for inhibition. By using inductively coupled plasma atomic emmission spectrometer were determined concentrations of barium and chrome in leachates based on norm ČSN EN – 12457-4. In addition, images were taken on the scanning electron microscope and crystallographic spectra from X-ray crystalography were obtained to determine structure. The results show that ashes from fluidized bed combustion are suitable for inhibition of both barium and chrome, whereas fly ashes can not sustain these elements with such success.
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Taxonomic position, phylogenetic relationships and metal resistance of green algae dominating in phytoplankton of two acid lakes
Barcyte, Dovile ; Nedbalová, Linda (advisor) ; Hašler, Petr (referee)
The aim of this diploma thesis was to reveal the taxonomic position and phylogenetic relationships of the dominant planktonic algae in two acid metal-rich lakes (Hromnice Lake and Plešné Lake, Czech Republic) and to compare these isolates with other closely related strains with the focus on the tolerance to various toxic metals (Cr, Al, Cu, Mn, Zn, Hg). The phylogenetic analyses showed that both strains belong to species Coccomyxa simplex. It was the first evidence that specifically this species is capable to become the dominant phytoplankton alga in the extreme environment of acid lakes with increased supply of phosphorus. Based on 18S rDNA analysis, four independent phylogenetic lineages were revealed within the genus Coccomyxa with three of them containing isolates from acid freshwaters. Furthermore, new strains of the recently described species Coccomyxa polymorpha were found growing in various chemical solutions. The toxicity test revealed that Coccomyxa simplex strains isolated from Hromnice and Plešné lakes did not show any peculiar resistance to increased metal concentrations. A significantly strain-specific response was recorded in case of aluminum, however, it was not related to the concentration of this metal in the original habitat. The ability to thrive in extreme habitats is probably...
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