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Effect of polymer type on the properties of 3D printed auxetic structures
Zbíral, Roman ; Štaffová, Martina (referee) ; Jančář, Josef (advisor)
This thesis deals with special structures such as optical, acoustic and mechanic metamaterials, which has their own specific properties. Auxetic materials as subgroup of mechanical metamaterials has its own special arrangement of sub-cells, that is bound to negative Poisson’s ratio. With mechanical load auxetic materials change its own density, geometry of structure and in thrust only change its internal structure instead of breaking. Most of these materials are made using additive technologies such as 3D print which allows better quality of produced structure and are made of special polymers which provide expected properties.
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Study of phytic acid-based organic conversion coatings on magnesium alloys
Zbíral, Roman ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
This thesis deals with organic conversion coatings based on phytic acid, on the magnesium alloys. In theoretical part it deals with corrosion properties of magnesium and magnesium alloys, usage of magnesium alloys for biomedicine applications. There are also summarized information’s about usage of phytic acid, it’s reactions with magnesium and magnesium alloys. At the end of theoretical part is search about phytic acid conversion coatings deposited on magnesium alloys. There are studied optimal conditions for application of phytic acid coatings such as pH, concentration, time of deposition, etc. Based on the knowledge from the theoretical part, a layer based on phytic acid was deposited on the surface of Mg alloy AZ31. The coating was evaluated in the experimental part in terms of its morphology and structure, chemical and corrosion behaviour. Scanning electron microscope (SEM) images showed the presence of microcracks in the dried coating. The chemical nature of the phytic acid-based conversion coating was investigated by energy dispersive spectroscopy (EDS) techniques in combination with Fourier transform infrared spectroscopy (FTIR). The electrochemical corrosion behaviour of Mg alloy AZ31 and coated Mg alloy was investigated by potentiodynamic polarization in Hank's solutions. Based on the obtained values of the corrosion potential and the corrosion current density, it can be stated that the applied layer of the conversion coating leads to an improvement of the corrosion properties. From the results of SEM analysis of samples after exposure in a corrosive environment, it was found that during potentiodynamic measurements no significant manifestation of corrosion attack was observed in coated samples, as was the case with Mg alloy AZ31.
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Optimization of the hardening and drying process of non-cement refractory castables based on colloidal SiO2
Zbíral, Roman ; Koplík, Jan (referee) ; Švec, Jiří (advisor)
Thesis deals with drying and its effect on refractory materials based on materials with zero cement content. Heat-resistant materials prepared by the sol-gel method, i.e., a process where the input raw materials are first formed into a colloidal solution, in our case already prepared by the manufacturer, and then a gel is formed with gelation reagent. This sol must be poured into a mold before gelation processes start and gel mesh formation occur. These materials can have better mechanical properties and better firing possibilities than standard cement materials, and a shorter preparation time. These refractory materials will be examined from the point of view of drying result gel, but also with the effect of subsequent firing and mechanical properties. Samples of sol, aluminate cement, model and real mixture will be analyzed using thermal methods (DSC, TG, DTA and thermal microscope). XRD technique was used to determine content of crystalline phases.
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Study of phytic acid-based organic conversion coatings on magnesium alloys
Zbíral, Roman ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
This thesis deals with organic conversion coatings based on phytic acid, on the magnesium alloys. In theoretical part it deals with corrosion properties of magnesium and magnesium alloys, usage of magnesium alloys for biomedicine applications. There are also summarized information’s about usage of phytic acid, it’s reactions with magnesium and magnesium alloys. At the end of theoretical part is search about phytic acid conversion coatings deposited on magnesium alloys. There are studied optimal conditions for application of phytic acid coatings such as pH, concentration, time of deposition, etc. Based on the knowledge from the theoretical part, a layer based on phytic acid was deposited on the surface of Mg alloy AZ31. The coating was evaluated in the experimental part in terms of its morphology and structure, chemical and corrosion behaviour. Scanning electron microscope (SEM) images showed the presence of microcracks in the dried coating. The chemical nature of the phytic acid-based conversion coating was investigated by energy dispersive spectroscopy (EDS) techniques in combination with Fourier transform infrared spectroscopy (FTIR). The electrochemical corrosion behaviour of Mg alloy AZ31 and coated Mg alloy was investigated by potentiodynamic polarization in Hank's solutions. Based on the obtained values of the corrosion potential and the corrosion current density, it can be stated that the applied layer of the conversion coating leads to an improvement of the corrosion properties. From the results of SEM analysis of samples after exposure in a corrosive environment, it was found that during potentiodynamic measurements no significant manifestation of corrosion attack was observed in coated samples, as was the case with Mg alloy AZ31.
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Effect of polymer type on the properties of 3D printed auxetic structures
Zbíral, Roman ; Štaffová, Martina (referee) ; Jančář, Josef (advisor)
This thesis deals with special structures such as optical, acoustic and mechanic metamaterials, which has their own specific properties. Auxetic materials as subgroup of mechanical metamaterials has its own special arrangement of sub-cells, that is bound to negative Poisson’s ratio. With mechanical load auxetic materials change its own density, geometry of structure and in thrust only change its internal structure instead of breaking. Most of these materials are made using additive technologies such as 3D print which allows better quality of produced structure and are made of special polymers which provide expected properties.
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