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Influence of alloying elements on the solubility of titanium in magnesium alloys
Matocha, Martin ; Buchtík, Martin (referee) ; Březina, Matěj (advisor)
This bachelor's thesis examines the influence of alloying elements on the solubility of titanium in magnesium alloys. In the theoretical part, a literature review was conducted on the topics of the creation, composition, processing, and brief analysis possibilities of magnesium alloys, with an emphasis on the potential for alloying magnesium alloys with titanium. The experimental part focused on the preparation of systems with various compositions to achieve the integration of titanium into the magnesium alloy. After preparation of the samples of the given systems, their analysis was performed using SEM/EDS and XRD. Based on the ongoing results of the samples analysis, efforts were made to optimize the holding time of the samples of the given system at a temperature of 905°C. It was found that during the stabilization of the modification of titanium, it is possible to achieve mixing of titanium, zinc, and magnesium. The condition for the formation of the modification of titanium is the highest possible temperature allowed by the system. However, the temperature must exceed at least 881°C. The stability of the modification of titanium is also supported by the absence of alloying elements that promote the stability of the modification of titanium. The mixture of elements in the aforementioned system has not yet been described in the scientific literature.
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Immiscible alloy based on Fe-Cu system
Semerák, Petr ; Havlík, Petr (referee) ; Jan, Vít (advisor)
The aim of this work is the preparation of FeCuMn alloy in equimolar composition by melting and the analysis of the resulting microstructure. The theoretical part of the work deals with miscibility and the use of immiscible systems in practical applications. Furthermore, the influence of cooling rate and the effect of the ratio of the components of the immiscible Fe-Cu system on the resulting microstructure are described. The practical part of the work presents the microstructure of FeCuMn alloy, which was prepared by melting in an induction furnace under a protective atmosphere of argon. Furthermore, the practical part deals with the chemical composition of the individual phases and the shape of the resulting phases. For the FeCuMn alloy, the melting temperature of the phases is analysed, the material is also deformed, and the hardness of the deformed and undeformed material is evaluated. In the subsequent discussion, the results from the experimental part are related to published experimental results by other authors.
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Behaviour of humic acids in aqueous solutions
Čechová, Eva ; Barančíková, Gabriela (referee) ; Klučáková, Martina (advisor)
Tato práce se zabývá chováním huminových kyselin ve vodných roztocích a to především jejich disociací a rozpustností. Disociace huminových kyselin byla studovaná jejich částečným rozpuštěním ve vodě a v roztocích solí o různých iontových silách. Analyzované huminové kyseliny pocházely jak z lignitických tak i půdních zdrojů a jedna z nich byla upravena plazmatem. Metodami použitými při experimentech byla potenciometrie, konduktomerie a UV/VIS spektroskopie. Podle Henderson-Hasselbalchovy závislosti byly vypočítány zdánlivé disociační konstanty. Dále byly určeny zdánlivé aktivitní koeficienty kyselých funkčních skupin. Poté byla studovaná rozpustnost huminových kyselin ve vodných roztocích solí. Byly sestrojeny závislosti pH hodnot, vodivostí a absorbancí jak na obsahu huminových kyselin ve vzorku tak na iontové síle roztoku. Studována byla také kinetika disociace huminových kyselin. Získaná data byla srovnána s navrženou hypotézou předpokládající několikakrokový mechanismus disociace huminových kyselin. Chovaní všech vzorků huminových kyselin odpovídalo navrženému mechanismu. Bylo potvrzeno, že stupeň disociace huminových kyselin ve vodných roztocích klesá s rostoucím obsahem huminové kyseliny stejně tak jako ve vodných roztocích solí s rostoucí iontovou silou.
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Smart food polymer layers
Valíková, Michaela ; Kovalčík, Adriána (referee) ; Veselá, Mária (advisor)
Smart packaging represents a group of packaging with great potential when used in the food industry. Active packaging can have a positive effect on the condition of stored food and smart packaging can inform consumers about the condition of stored food. In the theoretical part, a search was made on the topic of packaging in the food industry, with emphasis on active and intelligent packaging, including the legislative framework. The substances from which smart packaging is made have been described. In the experimental part, partially water¬insoluble polymer layers were prepared from gelatin, glycerol, crosslinking agent and anthocyanin extract. Glutaraldehyde or tannic acid was used as a crosslinking agent. Anthocyanins were obtained by extraction from red cabbage. The total concentration of anthocyanins in the extract was determined by the difference method. For prepared layers, their water solubility was measured and the colour response to the pH environment was evaluated spectrophotometrically. The stability of the layers over time was also monitored. It was found that the prepared layers are able respond to changes in pH.
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Fractionation of humic acids isolated from lignite
Moťka, Pavel ; Barančíková, Gabriela (referee) ; Klučáková, Martina (advisor)
The diploma thesis deals with lignitic humic acids. Bibliographic search can be divided into three parts. The aim of the first part is characterization of humic substances, presence, composition, structure and exploitation especially of humic acids. The second part describes a division of heterogeneous mixture of humic acids into closed fractions with more specific properties. The final part is a study of solubility of humic acids. The experimental part of the diploma thesis is structured similarly. In this work, a gradual fractionation with pH is used. Obtained fractions were characterized by UV/VIS and FT-IR spectroscopy. We assessed the portion of ash and carboxyl groups have been identified. Subsequently, all fractions extracted by gradual fractionation as well as some soluble fractions obtained by direct fractionation have been analyzed in view of solubility and their behaviour in water environment. Both used methods were compared.
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Dissociation behaviour of humic acids
Karbanová, Kateřina ; Kratochvílová, Romana (referee) ; Klučáková, Martina (advisor)
Humic acids are substances of natural origin and form the finest part of humic substances. They are formed by biochemical transformations of organic residues (mainly plants). They act as a weakly acidic polyelectrolytes with not exactly described structure. Their solubility is affected by pH value. The higher the pH value is the higher the solubility is. They are almost insoluble in acids. Bachelor thesis deals with the study of the dissociation behaviour of humic acids. Dissociation constant of humic acids is determined by three different methods – conductometric, spectrophotometric and combination of measurment pH and the content of acidic functional groups in Na2SO4. On the basis of results the methods are compared.
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Bioinformatics Tool for Prediction of Protein Solubility
Hronský, Patrik ; Burgetová, Ivana (referee) ; Martínek, Tomáš (advisor)
This master's thesis addresses the solubility of recombinant proteins and its prediction. It describes the subject of protein synthesis, as well as the process of recombinant protein creation. Recombinant protein synthesis is of great importance for example to pharmacologic industry. This synthesis is not a simple task and it does not always produce viable proteins. Protein solubility is an important factor, determining the viability of the resulting proteins. It is of course favourable for companies, that take part in recombinant protein synthesis, to focus their effort and their resources on proteins, that will be viable in the end. In this regard, bioinformatics is of great help, as it is capable, with the help of machine learning, of predicting the solubility of proteins, for example based on their sequences. This thesis introduces the reader to the basic principles of machine learning and presents several machine learning methods, used in the field of protein solubility prediction. It deals with the definition of a dataset, which is later used to test selected predictors, as well as to train the ensemble predictor, which is the main focus of this thesis. It also focuses on several specific protein solubility predictors and explains the basic principles upon which they are built, as well as the results of their testing. In the end, it presents the ensemble predictor of protein solubility.
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Determination of content of humic acids in solutions chronopotentiometrically
Viktorinová, Jana ; Kislinger, Jiří (referee) ; Klučáková, Martina (advisor)
Humic acids are part of humic substances, which are substances of natural origin occurring in soil, peats, sediments and young coal. These substances are mixture of compounds with different molecular weight and structures. Humic acids are only partially soluble in aqueous solutions and their solubility is growing up with icreasing pH value. Bachelor thesis uses method of chronopotentiometric titration, which has not been used yet for humic research. This bachelor thesis is trying to check possibility of exercise this method for assessment concentration of soluble humic acid. Especially trace amounts of analyt are measured by this method. Results obtained by chronopotentiometric titration are compared with results in common used method as UV/VIS spetctromerty and potentiometry.
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Solubility of polypropylene in hydrocarbon solvents
Urbánková, Radka ; Kučera, Jaroslav (referee) ; Kratochvíla, Jan (advisor)
Polypropylene, on a mass-scale produced polyolefin, shows an excellent combination of end-use properties, eco-friendliness, easy recyclability, and a good processability by different technologies. Key structural parameters of polypropylene are its stereoregularity, molecular weight, and its distribution. A theoretical part of this work compiles a bibliographic search and an experimental part deals with extraction and solubility of polypropylene powder prepared on a highly active Ziegler-Natta polymerization catalyst. Extractions at a boiling point temperature of solvents (pentane - hexane - cyclohexane - hex-1-ene - benzene - heptane - octane - ethylbenzene) resulted in a progressive increase of extracted portions with temperature of extraction. Solvents used within this work were characterised by their physical properties, and steric and electronic parameters such as molecular weight, density, boiling point temperature, dipole moment, refractive index, and Hildebrand´s solubility parameter. Extraction PP at a constant temperature 36°C (boiling point of pentane) at a saturated vapour pressure in a series of hydrocarbon solvents (pentane – hexane – heptane – octane) resulted in practically the same results. Boiling octane extractable fraction at a temperature 36°C was nearly 100 % higher than fractions extracted by the other solvents. The origin of this phenomenon has not been revealed. Polypropylene solubility was determined by a complete dissolving the sample at 140°C in a series of aliphatic and aromatic solvents (pentane - hexane - cyclohexane - hex-1-ene - benzene - heptane - octane - toluene - ethylbenzene - o-xylene - m-xylene - p-xylene - decalin - chlorbenzene - 1,2-dichlorbenzene), followed by cooling the solution down to a laboratory temperature, and separating a soluble fraction, and an insoluble one. The stereoregularity of soluble fractions was characterised by a 13C NMR method, the crystallinity by a DSC method, and a molecular weight distribution by a GPC method. As a result, polypropylene solubility decreases with increasing the Hildebrand solubility parameter of the solvent that corresponds with theoretical expectations. Moreover, PP solubility correlates strongly with a refractive index, and a density of solvent.
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