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Effect of glucose on the corrosion behaviour of AZ31 magnesium alloy in saline solution
Faltýnková, Denisa ; Hasoňová, Michaela (referee) ; Doskočil, Leoš (advisor)
This bachelor thesis deals with the influence of glucose concentration on corrosion behaviour of magnesium alloy AZ31 in saline solution. The theoretical part briefly summarises the use of magnesium and its alloys in biomedical applications and offers insight into the current state of knowledge of the effect of glucose on corrosion of these materials. In the experimental part, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to evaluate the electrochemical behaviour of AZ31 alloy in saline solution with varying concentrations of glucose. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterise post-corrosion surface of the alloy. The corrosion environment was analysed by measurement of conductivity, pH, inductively coupled plasma atomic emission spectroscopy (ICP-OES) and liquid chromatography with conductivity detector. Results showed that glucose, depending on concentration, impairs corrosion resistance of AZ31 alloy in 0.9% NaCl. Three organic acids were identified in the corrosion environment, of which gluconic acid is the most abundant.
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Sorption of metal ions mixture on natural lignite
Doskočil, Leoš ; Taraba, Boleslav (referee) ; Pekař, Miloslav (advisor)
Sorption of quaternary metal ions (Pb2+, Cu2+, Cd2+ and Zn2+) was carried out on lignite from the South Moravia. Following experiments were tested: kinetic sorption, dependence of sorption on pH, initial concentration, temperature, effect of electrolytes (KNO3 and NaCl) and desorption in deionized water. Sorption studies was carried out in quaternary mixtures and in the case of inicial concentration effect additional in a single-component solution. The batch sorption experiments was used. Sorption time was 24 hour, although concentration of ions was a near equilibrium after two hour. As the optimal pH was determined pH 5. The order of affinity by lignite was obtained Pb >> Cd > Zn > Cu for the sorption of metals in the single-component solution and the order was Pb > Cu > Zn > Cd for the sorption of mixture of metals. The maximum adsorptium capacities from single solutions were for Pb 97,82 mg/g, Cd 60,34 mg/g, Zn 49,88 mg/g and Cu 30,28 mg/g and in the case of ones from mixture solutions were for Pb 39,03 mg/g, Cu 25,94 mg/g, Zn 15,21 mg/g and Cd 5,18 mg/g. Experimental data have been analysed using Langmuir and Freundlich model. Thermodynamic values H°, S° and G° were calculated. Desorption test showed that desorption efficiency is 0–3 %. NaCl had the greatest influence on sorption from electrolytes. On the basis obtained results we can say that metals are binding to lignite in particular due to chemical interactions. Lignite is s suitable as a sorption material for metal ions especially in the field of low concentrations.
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Quality evaluation of unprocessed steels for corrosion
Holubářová, Michaela ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
This bachelor thesis is based on quality evaluation of unprocessed steels for corrosion. Visual control of the steel quality by a microscope is not sufficient, as this method of resistance assessment lacks quantified values. Current instruments are already able to provide specific corrosion values and therefore the SmartCET has been used to electrochemically characterize the supplied steel materials. The theoretical part includes general description and basic division of steel and corrosion. It also contains a summary of thermodynamic and kinetic corrosion aspects and methods of metal resistance evaluation. The experimental part deals with the measurements and evaluation of electrochemical characteristics (general corrosion rate, pitting factor and B value) over time compared to visual control.
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Stability of Soil Organic Matter
Heldesová, Michaela ; Doskočil, Leoš (referee) ; Kalina, Michal (advisor)
This bachelor thesis summarizes available information about current research of soil organic matter stability and it divides them into two logical units. The first part includes environmental, physical and chemical factors, including human activities, which affect the stability or decomposition of soil organic matter. The methods used for the study of organic matter in the soil are summarized in the second part of this thesis. There the attention is paid to the accumulation of organic matter in specific pools, the ways of extraction of organic compounds and the use of quantitative and qualitative analytical methods to describe various characteristic of organic matter.
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Application of thin layer chromatography (TLC) for fractionation of humic substances.
Hegrová, Nela ; Doskočil, Leoš (referee) ; Enev, Vojtěch (advisor)
The main aim of this Bachelor thesis was to suggest and optimize a method of fractionation of organic matter of humic substances using thin-layer chromatography (TLC). HS Pahokee Peat standards have been characterized by thermochemical and spectrometric techniques such as thermogravimetry, elemental analysis, UV-Vis and Fourier-transform infrared spectrometry. Molecular absorption spectrometry in the ultraviolet and visible range of electromagnetic radiation and steady-state fluorescence spectrometry were used for physicochemical characterization of organic fractions. Using fluorescence spectrometry, humic substances were found to be composed of fluorophores of humic and non-humic (protein) character. Organic fractions corresponding to the humic fluorphores were characterized by a higher aromaticity, average molecular weight and higher content of oxygen substituents on the aromatic nucleus. In contrast, the organic fractions corresponding to the protein constitutional units were distinguished by low values of the humification index. These tell us about microbial origin of these organic substances during the genesis of HS Pahokee Peat.
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Complex physicochemical analysis of natural medicinal water
Machátová, Nikol ; Doskočil, Leoš (referee) ; Enev, Vojtěch (advisor)
This bachelor thesis is focused on the study of the content humic substances in natural medicinal water. Humic substances extracted from this water were characterized by UV-VIS and FTIR spectroscopy, hereafter microbiological tests were performed. The main aim was determine the content HS using the norm ČSN 75 7536 and the calibration curves of standard fulvic acid Suwannee River. Another part of this bachelor thesis was focused on spectrometric characterization HS after different degree of purification. Humic substances were characterized by absorption coefficients and FTIR spectroscopy.
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Characterization of electrochemical properties of magnesium batteries in electrolyte modification
Honč, Jiří ; Doskočil, Leoš (referee) ; Wasserbauer, Jaromír (advisor)
This thesis deals with novel electrolytes for magnesium batteries. Prepared electrolytes were composed of affordable solvents and chemicals, which can be handled at normal laboratory conditions. Specifically, solutions of tetrahydrofurane and dimethylsulfoxide with magnesium chloride, aluminium chloride, nitrilotriacetic acid and disodium ethylenediaminetetraacetic acid, were prepared. To determine electrolyte ability of magnesium stripping and deposition, the cyclic voltammetry was used. The kinetics of electrochemical reactions in terms of polarization resistance was studied by electrochemical impedance spectroscopy. Based on scanning electron microscopy and EDS analysis, the effect of atmospheric oxygen and humidity on magnesium electrode corrosion during cycling was discussed.
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Characterization of cosmetic dispersion by centrifugal analyser
Tumová, Šárka ; Bokrová, Jitka (referee) ; Doskočil, Leoš (advisor)
Cosmetic products are widely used nowadays. These products are mostly emulsion systems, in which processes that lower physical stability can take place. This can leads among others to the shortening of the expiration date or to the reduction of the efficacy of the product. So, in the cosmetic practice, the physical stability is monitoring by tests. There are more types of these tests and they can be realized under different conditions. This Bachelor Thesis is focused on monitoring the physical stability of samples of cosmetics products by using an analytical centrifuge LUMiSizer and by using methods that are commonly used in a cosmetic practice and development. The aim of this study is to compare single results and to verify the suitability of the use of LUMiSizer for accelerated determine of the physical stability of cosmetic products. The stability of samples over time and the effect of the temperature on the stability of samples were monitoring by using the LUMiSizer device. Freeze-Thaw cycles and the conventional method of testing the stability of samples were applied as well. There was also determined the effectiveness of the stability test, mentioned by the literature, in this work. Based upon the results of experiments that were carried out and upon information given by manufacturers of samples that were used, the LUMiSizer device was evaluated as a useful tool for assessing the stability of samples although results obtained by the LUMiSizer device are not exactly the same as results of the conventional method. Although the application of additional methods is recommended.
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Sequential fractionation of organic matter of humic acid isolated from Leonardite
Krist, Tomáš ; Doskočil, Leoš (referee) ; Enev, Vojtěch (advisor)
The aim of the diploma thesis was to optimize the sequential fractionation method of organic matter to be used for physico-chemical characterization of extracted fractions. Humic acid isolated from oxidized brown coal of Leonardite was used as a source matrix of organic matter. An eluotropic series was assembled and sequential fractionation was performed by extraction on a Soxhlet apparatus. The original humic acid and fractions were characterized by elemental analysis (EA) and thermogravimetric analysis (TGA), followed by Fourier transform infrared spectrometry (FTIR), molecular absorption spectrometry (UV/VIS), fluorescence spectrometry and potentiometric titration. Atomic ratios were determined from the results of the elemental analysis. From the measured UV/Vis and fluorescence excitation and emission spectra, the absorption coefficients, resp. fluorescence coefficients. Used fractionation method proved to be a suitable method for studying HA structure. A total of 62 wt. % of initial materiál was extracted, indiivdual fraction amounted from 0.36–30.92 wt. %. From the results of the structural analysis, it is clear that with increasing polarity of the organic solvent, fractions with long aliphatic chains were first isolated and their aromaticity graddualy increased. Non-polar organic solvents were suitable for the extraction of lipid-like coumpounds, while the most polar organic fractions were rich in polar groups and their structual parameters were close to the original humic acid. The fraction extracted with acetonitrile was the most unique fraction. This fraction was rich on nitrogen and amine groups and was similar to protein-like structures. In the last two fractions, extracted with alcohols, a significant bathochromic shift typical of fluorophore type V was observed. Among other things, they were also characterized by a higher content of plant carbohydrate residues.
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Effect of hyaluronic acid on the corrosion of AZ31 magnesium alloy
Holubářová, Michaela ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
Magnesium and its alloys are interesting materials due to their many physical properties. They have considerable potential, especially in medical applications, where they can serve as a material for the production of orthopedic and cardiovascular implants. The disadvantage of these materials is their sensitivity to corrosion. As a result, it is necessary to know the corrosive properties of magnesium and its alloys in contact with substances that occur in the human body. Hyaluronan is a polysaccharide that is naturally present in the human body and can interact with implants. This master's thesis deals with the influence of low molecular weight (80–130 kDa) and high molecular weight (1 500–1 750 kDa) hyaluronan on the corrosion properties of magnesium alloy AZ31 in the environment of two simulated physiological solutions (0,9 % NaCl and synovial fluid). Potentiodynamic polarization (PD) and electrical impedance spectroscopy (EIS) were used for electrochemical tests. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to reveal the chemical composition of the corrosion products and the surface morphology after corrosion.
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