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MINOR PHASES IN TIN-RICH HISTORICAL MATERIALS
Michalcová, A. ; Msallamová, Š. ; Fink, D. ; Friák, Martin
The historical organ pipes used to be manufactured from tin and tin-lead alloys. The tin-rich organ pipes usually contained copper as alloying elements, which make them similar to modern lead free soldering materials. The historical organ pipe materials can be used as model materials for natural ageing of soldering materials. Tin pest is a term for modification from white tin to grey tin, which leads to degradation of tin or tin-rich alloys. The influence of individual alloying elements has not been reliably described, yet. Not only on the concentration of the alloying element, but also the distribution may play the important role. In dependence on heat-treatment, the Cu can be in the Sn matrix present in these forms: i) as large intermetallic particles after casting (Cu6Sn5), ii) as solid solution after homogenization annealing and iii) as fine precipitates after ageing. The microstructure of the real historical organ-pipes material was studied and it was proven that contradictionary to the equilibrium phase diagram the Cu enriched was observed.
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EFFECT OF OXIDE DISPERSION ON ELECTRIC CONDUCTIVITY OF ROTARY SWAGED POWDER-BASED COPPER COMPOSITES
Kunčická, Lenka ; Benč, Marek ; Kačor, P. ; Marek, M.
Copper is a very popular electro-conductive material, however, the mechanical properties of pure Cu are low. They can be typically improved by (micro)alloying, or via structure modifications introduced by optimized deformation and thermomechanical treatments. Designing a Cu-based composite, possibly strengthened by a dispersion of fine oxides, is another way how to favourably improve the strength properties of Cu. In this study, we performed mechanical alloying of a Cu powder with a powder of Al2O3 oxide, which is known to have strengthening effects on metallic materials. After mixing, we sealed the powder mixture into evacuated tubular Cu containers (i.e. cans). As for the consolidation procedure, we applied direct consolidation of the canned powders via the intensive plastic deformation method of rotary swaging, performed under warm conditions. Subsequently, we subjected the swaged conductors to measurements of electric conductivity and detailed structure observations. The results revealed that the applied swaging ratio was sufficient to fully consolidate the canned powders as the final conductor was unrecognizable from a cast alloy from the viewpoints of visual and structure assessment. In other words, the structure did not exhibit any voids or remnants of unconsolidated powder particles. The observed fine grains with homogeneous dispersion of Al2O3 oxide particles provided improvement of the mechanical properties, as proven by microhardness measurements. Moreover, the electric properties remained favourable.
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Interaction of 7,8-dihydroxyflavone with physiological metals
Streďanská, Aneta ; Mladěnka, Přemysl (advisor) ; Červený, Lukáš (referee)
Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmacology and Toxicology Student: Aneta Streďanská Supervisor: prof. Přemysl Mladěnka, Pharm.D., PhD. Consultant: Zuzana Lomozová, Pharm.D., PhD. Title of thesis: Interactions of 7,8-dihydroxyflavone with physiological metals 7,8-dihydroxyflavone belongs to the phenolic substances collectively referred to as flavonoids. Flavonoids are bioactive components abundantly distributed in the daily diet with the ability to modulate health and disease through miscellaneous mechanisms including their antioxidant activity. However, they can also exhibit prooxidative effects under certain conditions. Due to this fact, which is related to individual factors, i.e. presence of various substitutions on the flavonoid come, it is therefore essential to understand the redox behavior based on the relationship between structure and effect and to understand their physiological, pharmacological and thus also potential toxic properties. The interaction with physiological metals is determined by the structure of the molecule through the dihydroxy moiety in positions 7 and 8. These mentioned metals are essential for many biochemical processes in biological systems. Their homeostasis is strictly regulated in the human body and disruption of this...
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Model diffusion experiment in alloys
Valúch, Adam ; Doubrava, Marek (referee) ; Kičmerová, Dina (advisor)
This bachelor's thesis deals with the process of diffusion in alloys, for a better understanding of the properties and microstructure. In the theoretical part, the nature of diffusion is described, brass and copper are used for different diffusion rates at different temperatures and times. In the experimental part, methods such as annealing in a vacuum furnace, polishing, and grinding are used. With subsequent observation under a SM, SEM microscope. The main goals were to prove the Kirkendall phenomenon and the previously mentioned microstructure and thickness of the diffusion layer.
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Analysis of hazardous metals in rPET granulate
Souček, Elena ; Řezáčová, Veronika (referee) ; Komendová, Renata (advisor)
Production of polymer products has increased rapidly in recent decades. Especially in food industry as a packaging it gained a dominant position when it replaced previously used materials. Due to the direct risk for human health it is necessary to be careful and pay attention to their composition. It is also necessary to develop methods to properly recycle and reuse already used material, not only produce new products. This thesis deals with the study of the content of risk elements in PET regranulate. The samples were completely decomposed by microwave radiation in an environment of concentrated sulfuric and nitric acid. They were subsequently analyzed by atomic absorption spectrometry (AAS). Flame atomization technique (FAAS) was used to determine Sb and Zn and electrothermal atomization (ETAAS) to determine Cd, Cr, Pb, Cu and Ni. This method was also used to study migration of antimony from samples to food simulant under different conditions (temperature, pH). This thesis follows up on the thesis of Mrs. Kryštofová who studied recycled PET flakes.
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Study of the content of risk elements in river sediments of the Váh River
Držíková, Klára ; Zlámalová Gargošová, Helena (referee) ; Komendová, Renata (advisor)
This bachelor thesis deals with the analysis of selected heavy metals in the river sediment of the Váh River. The elements were selected based on their relatively frequent occurrence and adverse effects on humans, fauna, and flora. Also due to their ability of good accumulation and persistence in sediments. The selected elements have a chalcophile character, which plays a significant role in the occurrence of the elements at the sampling sites. The analysis of the collected sediment samples was carried out using atomic absorption spectroscopy. The highest concentration of zinc (386.58 mg/kg), followed by copper (57.67 mg/kg), lead (42.24 mg/kg), and the lowest concentration of mercury (0.332 mg/kg) was measured in the sediments. Sediments are used in agriculture and forestry to improve soil properties. Their application to soils is regulated by Slovak legislation, which sets limit values for risk elements in the concerned sediment and soil. These established limits were not exceeded in any of the sediment samples.
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The study of PET bottles in terms of the content of risk elements
Kryštofová, Petra ; Řezáčová, Veronika (referee) ; Komendová, Renata (advisor)
This bachelor thesis deals with the issue of PET bottles in terms of the possible content of risk elements. The contents of antimony, copper and lead were determined in the PET packaging material and in the beverages contained in the bottles. A total of 15 samples of bottled still and infant water available in the Czech sales network were analyzed. The PET material was decomposed in an acidic medium under the action of microwave radiation under optimized conditions. Atomic absorption spectrometric methods with flame or graphite cuvette atomization were used to determine selected risk elements based on the predicted analyte concentrations. In the PET packaging material, 159.35 to 265.68 mgkg-1 of antimony were determined, the determined values of lead concentration were in the range of 10.96-20.23 mg·kg-1 and the copper concentration in the range of 0.11-7,52 mg·kg-1. In bottled water and in bottled infant water, antimony was identified only in samples labeled 6a, 8a, 9a and 15a, all lead concentrations were measured below LODPb, copper was determined only in samples 2a, 6a and 8a. In none of the samples did the concentrations given by the valid legislation be exceeded. The limits of these metals are not set in legislation in the packaging materials, only specific migration limits and they have not been exceeded. However, the high concentration of antimony in PET poses a potential risk of contamination of the contents of these packages.
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Temperature Profile in Reflow Soldering and Influence of Different PCBś and ComponentsThermal Capacities
Procházka, Martin ; Špinka, Jiří (referee) ; Starý, Jiří (advisor)
This thesis mainly deals with the prediction of temperature on the components and the PCB during reflow soldering. The theoretical part describes the particular solder reflow process, types of heat transfer and temperature profiles. The practical part is divided into forecasting temperatures if the conveyor is stopped and the temperature predictions when the conveyor is in motion. In both parts of the measured temperature is compared with the predicted temperatures, which show the success rate of prediction. The last part of this work is part of the simulation, which helps in proper understanding of the issues discussed.
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The study of vertical mobility of heavy metals and their transfer to mushrooms
Jurnečka, Roman ; Doležalová Weissmannová, Helena (referee) ; Komendová, Renata (advisor)
This bachelor thesis deals with the issue of contamination of forest soils and edible mushrooms with lead, cadmium, copper and zinc in the Jeseníky Mountains, specifically in the Domašov and Vápenná forests. Sampling took place at 12 localities, divided into spruce and beech stands. Atomic absorption spectrometry AAS ContrAA 800D was chosen to determine the content of selected heavy metals. Based on the measured values of the concentrations of the studied metals and other soil properties, dependences were created to determine the vertical mobility of selected metals in the soil profile. Vertical mobility depends on the physico-chemical properties of the soil (pH, C and S content). The dependence of the content of selected heavy metals in the soil on the pH value of the soil was found. In the case of lead, the sorption capacity of the soil organic component was confirmed. The risk and above-limit content of Pb, Cd and Cu was found on the yellow-boletus mushroom. Cadmium shows the highest bioavailability. Lead was evaluated as the element with the lowest mobility.
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Creation of Logistic Concept in the Selected Company
Kapusta, Vladimír ; Lahučký, Martin (referee) ; Jurová, Marie (advisor)
Master thesis named „Creation of logistic concept in the selected company“ is focused on detailed analysis of material flow of waste in manufacturing company. The main objective of thesis is proposal of new logistic concept of handling with copper waste, which is created during the manufacturing processes, which function will be to remove defects in material flow, to shorten the handling time with copper waste and more accurate information flow, considering work safety, costs and time.
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