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Effect of body fluids on setting, structure and mechanical properties of phosphate bone cements
Bednaříková, Vendula ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
Presented diploma thesis describes the preparation and characterization of composite calcium-phosphate bone cements (CPCs). In the literature review properties and structure of tricalcium phosphates (TCPs) are described, including their interaction with body environment. In the experimental work, first of all, sample preparation technique was determined by experiments with setting reactions provided in ultrapure water environment. Optimal technique of setting CPC samples included memory foam setting mold, ending setting reactions by absolute cold ethanol and vacuum drying procedures. Consequently, the work describes the sample preparation and process of TCP bone cement setting in both natural (pig blood) and simulated body fluids (physiological, Hank´s and Ringer´s solutions). Morphology study by Scanning Electron Microscopy (SEM) was performed for samples set for 1 day, 1 week, 2 weeks and 1 month, due to the significant change in crystalline structure proving as well by X-ray diffraction (XRD) analysis by determining -TCP conversion to calcium-deficient hydroxyapatite (CDHA). Porosity investigated by X-ray computed microtomography (-CT) was slightly higher at sample set in natural blood. Mechanical properties of CPC samples measured by mechanical compression tests showed stable cement strength set in physiological solution already after 1 day while cements set in blood has shown still increasing strength even at 1 month. On contrary, strength of cement samples rapidly decreased after 2 weeks of setting in both Hank´s and Ringer´s solutions probably due to its slightly acidic pH accelerating CPC disintegration. As a result, setting environment has significant effect on resulting CPC properties and natural blood in comparison to simulated plasma had shown better CPC properties while more closely imitating the in vivo conditions.
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Preparation and Characterization of Fluoride Conversion Coatings on Biodegradable Magnesium Alloys
Drábiková, Juliána ; Hadzima, Branislav (oponent) ; Brezinová,, Janette (oponent) ; Ptáček, Petr (vedoucí práce)
The submitted work is aimed at the unconventional fluoride conversation coating preparation on the AZ31, AZ61, ZE10 and ZE41 magnesium alloys by their immersion in Na[BF4] molten salt. The influence of the preparation parameters (such as temperature and time) on the quality of the fluoride conversion coating is investigated. Methods of light and scanning electron microscopy were used for the evaluation of morphology, chemical composition and thickness of the coating. Short and long-term corrosion tests were executed to analyze the corrosion performance in simulated body fluid solution at 37 ± 2 °C with and without the fluoride conversion coating. The short-term behavior was evaluated by potentiodynamic tests, namely by the linear polarization. Long-term performance was assessed by electrochemical impedance spectroscopy or immersion tests. The coating preparation parameters influence on the character of the formed fluoride conversion coating was defined based on the obtained results. The next part of the thesis deals with the description of the possible mechanism of formation and kinetics of growth of the unconventional fluoride conversion coating on the selected AZ61 magnesium alloy. In this part, further detailed analyses were carried out to investigate the microstructure and chemical composition of the fluoride conversion coating using focused ion beam, transmission electron microscopy and X-ray photoelectron spectroscopy.
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Effect of body fluids on setting, structure and mechanical properties of phosphate bone cements
Bednaříková, Vendula ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
Presented diploma thesis describes the preparation and characterization of composite calcium-phosphate bone cements (CPCs). In the literature review properties and structure of tricalcium phosphates (TCPs) are described, including their interaction with body environment. In the experimental work, first of all, sample preparation technique was determined by experiments with setting reactions provided in ultrapure water environment. Optimal technique of setting CPC samples included memory foam setting mold, ending setting reactions by absolute cold ethanol and vacuum drying procedures. Consequently, the work describes the sample preparation and process of TCP bone cement setting in both natural (pig blood) and simulated body fluids (physiological, Hank´s and Ringer´s solutions). Morphology study by Scanning Electron Microscopy (SEM) was performed for samples set for 1 day, 1 week, 2 weeks and 1 month, due to the significant change in crystalline structure proving as well by X-ray diffraction (XRD) analysis by determining -TCP conversion to calcium-deficient hydroxyapatite (CDHA). Porosity investigated by X-ray computed microtomography (-CT) was slightly higher at sample set in natural blood. Mechanical properties of CPC samples measured by mechanical compression tests showed stable cement strength set in physiological solution already after 1 day while cements set in blood has shown still increasing strength even at 1 month. On contrary, strength of cement samples rapidly decreased after 2 weeks of setting in both Hank´s and Ringer´s solutions probably due to its slightly acidic pH accelerating CPC disintegration. As a result, setting environment has significant effect on resulting CPC properties and natural blood in comparison to simulated plasma had shown better CPC properties while more closely imitating the in vivo conditions.
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Preparation and Characterization of Fluoride Conversion Coatings on Biodegradable Magnesium Alloys
Drábiková, Juliána ; Hadzima, Branislav (oponent) ; Brezinová,, Janette (oponent) ; Ptáček, Petr (vedoucí práce)
The submitted work is aimed at the unconventional fluoride conversation coating preparation on the AZ31, AZ61, ZE10 and ZE41 magnesium alloys by their immersion in Na[BF4] molten salt. The influence of the preparation parameters (such as temperature and time) on the quality of the fluoride conversion coating is investigated. Methods of light and scanning electron microscopy were used for the evaluation of morphology, chemical composition and thickness of the coating. Short and long-term corrosion tests were executed to analyze the corrosion performance in simulated body fluid solution at 37 ± 2 °C with and without the fluoride conversion coating. The short-term behavior was evaluated by potentiodynamic tests, namely by the linear polarization. Long-term performance was assessed by electrochemical impedance spectroscopy or immersion tests. The coating preparation parameters influence on the character of the formed fluoride conversion coating was defined based on the obtained results. The next part of the thesis deals with the description of the possible mechanism of formation and kinetics of growth of the unconventional fluoride conversion coating on the selected AZ61 magnesium alloy. In this part, further detailed analyses were carried out to investigate the microstructure and chemical composition of the fluoride conversion coating using focused ion beam, transmission electron microscopy and X-ray photoelectron spectroscopy.
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