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Electrode Materials for Li-S Batteries
Jaššo, Kamil ; Almáši,, Miroslav (oponent) ; Syrový,, Tomáš (oponent) ; Kazda, Tomáš (vedoucí práce)
This thesis is focused on the research of electrode materials for lithium-sulphur (Li-S) batteries, with an emphasis on the optimization of the process of preparation of positive electrodes through the modification of the individual technical steps of the manufacturing process and the selection of a suitable binder. The theoretical part of the thesis is devoted to terminology and battery issues with emphasis on Li-S batteries, their working principle, shortcomings, critical parameters for commercialization and existing research in this field. The practical part of the thesis deals with the influence of the compression pressure used in the production of positive electrodes on the electrochemical properties of the resulting Li-S cells. In the next part of the thesis, the influence of the binder used on the resulting electrochemical properties is investigated. In the following sections, the influence of the thickness of the electrode material layer and the ratio of its individual components (C/S) on the resulting electrochemical properties of the Li-S cell is analyzed. On the basis of the measured results, the optimum conditions for the preparation of the positive electrodes of the Li-S cells have been identified with respect to the individual technical steps of the manufacturing process.
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The effect of salts on the hydrolytic stability of biopolymer carriers with antibacterial substances
Tertinská, Martina ; Brtníková, Jana (oponent) ; Vojtová, Lucy (vedoucí práce)
This diploma thesis deals with observing the effects of salt on the stability of biopolymer carriers made of protein and polysaccharide. The theoretical part is concerned with biomaterials and materials for sample preparation and also deals with the current situation of treatment of infected wounds with various materials. Within the experimental part, the carriers were prepared in two different buffers with different concentrations of sodium chloride in order to stabilize bioactive proteins, peptides or enzymes generally used for carrier entrapment. In every series of samples there were prepared both crosslinked and non-crosslinked samples. Properties like hydrolytic stability and swelling ratio were tested and the effect of salt concentration on sample stability was observed. Since the optimal salt concentration has been established, antibacterial enzyme was entrapped into all carriers and its release was monitored. Whereas at non-crosslinked samples significant differences between salt and salt-free samples both stability and enzyme release have been monitored, at crosslinked samples the differences were neglectable. However, in all cases the enzyme released from foamed samples according to first order kinetics, which is concentration dependent. Based on the results from disk diffusion test provided on different strains of S. aureus, the concentration of 325 mg/ml, have been chosen for my further work. Prepared carriers with antibacterial enzyme could be used as both- fast or prolonged releasing wound dressings for Staphylococcus aureus or methicillin-resistant Staphylococcus aureus (MRSA) infected tissue.
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The effect of organic and inorganic additives on the chemico-physical properties of biopolymer substrates for tissue engineering
Kohoutek, Martin ; Muchová, Johana (oponent) ; Brtníková, Jana (vedoucí práce)
This bachelor’s thesis deals with the preparation and characterization of composite collagenous scaffolds for possible applications in both bone and skin tissue engineering with an emphasis on their chemico-physical properties. In the theoretical part, the selected components for fabrication of the scaffolds are described and later were used to fabricate 3D porous composite scaffolds in the experimental part. Altogether, four different composite collagenous scaffold types and a reference pure collagen scaffold type were prepared using the freeze-drying fabrication technique. Two scaffold types were made by combining collagen with either oxidised cellulose (OC) or carboxymethyl cellulose (CMC). The other two types of scaffolds had the same biopolymeric origin enhanced with the addition of bioceramics based on the hydroxyapatite and tricalcium phosphates. The microstructure, porosity and pore size were assessed by the scanning electron microscopy. The highest porosity and pore size were achieved by the reference purely collagenous scaffolds, followed by the collagen composites with OC and CMC. Scaffolds with the content of bioceramics had the lowest porosity and pore size, especially those containing CMC. Swelling behaviour analysis and enzymatic degradation in vitro showed, that the hydrophilicity and mass loss in the degradation process correlate with each other. The scaffolds without bioceramics were more hydrophilic and achieved greater mass loss than the scaffolds containing bioceramics. The pure collagen was in the between the two groups. Scaffolds containing CMC achieved greater mass loss and hydrophilicity than their OC counterparts. In terms of mechanical properties, scaffolds with bioceramics achieved higher compressive strength in the wet state than the other three scaffold types. The mechanical properties were generally better for scaffolds with lower porosity and lower hydrophilicity.
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