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Ceramic dental restoration milling from stock based on ZrO2
Ščasnovič, Erik ; Spusta, Tomáš (referee) ; Kaštyl, Jaroslav (advisor)
In this bachelor thesis, the theoretical overview about the milling of the dental zirconia blanks was performed. The tests of biaxial flexural strength were evaluated in the experimental part, as well as the roughness and the grain size in sintered state and the linear shrinkage was determined. These tests were done for gel cast blanks from zirconia dioxide prepared in laboratories and also for two types of commercially available zirconia oxide blanks fabricated by cold isostatic pressing. The relationship between strength and grain size was shown. The samples prepared from gel cast blanks had statistically significantly higher strength than samples from commercial blanks. At the end of the thesis, the milling of dental crown was carried out based on real tooth model from gel cast zirconia blank studied in this thesis.
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Thermoplastic extrusion of ceramic materials with ionic and mixed conductivity
Kaštyl, Jaroslav ; Matoušek, Aleš (referee) ; Trunec, Martin (advisor)
In the bachelor thesis, an overview of the existing literature focused on thermoplastic extrusion method was worked out and based on the findings; the conditions for extrusion of mixtures with zirconia were optimized in order to produce rods. Great attention was paid to dimensional and shape precision of ceramic parts. Two methods were applied when preparing the ceramic mixtures – mixing and dissolving. These methods have been compared on the basis of the results achieved in rheological measurements of flow properties, microstructure and dimensional accuracy of the sintered rods. Having verified the efficiency of mixture dissolving, this method was used to prepare mixtures with different contents of cellulose and binder.
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Electrospinning and characterization of fibrous structure for piezoapplications
Svobodová, Anežka ; Kaštyl, Jaroslav (referee) ; Částková, Klára (advisor)
The master’s thesis deals with the preparation and characterization of PVDF-based composite fibrous layers prepared by electrospinning. Ceramic particles TiO2, BaTiO3 and BCZT were used as fillers. The fibers were prepared containing 10, 20, 30, 40 and 50% of these particles and then their morphology, piezoactive phase representation and dielectric characterization were characterized. The effect of the presence of particles on the fiber diameter and on the crystallinity fraction of the polymer was shown. Particle size significantly influenced their distribution in the fibers. Piezoelectric particles further influenced the content of electroactive phases beta and gamma. The highest proportion of electroactive phases was determined in BaTiO3 filled fibers, which reached up to 98%. For the BaTiO3 filled fibers, the dielectric constant values were also measured, which reached lower values than expected due to the high porosity of the prepared fibers The as-prepared fibers can be considered promising not only for piezoapplications, therefore, optimization of their preparation and measurement of electrical characteristics will be further studied.
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Core-Shell Ceramic Structures Prepared by Thermoplastic Co-Extrusion Method
Kaštyl, Jaroslav ; Pabst, Willi (referee) ; Hadraba, Hynek (referee) ; Trunec, Martin (advisor)
In the doctoral thesis, the bi-layer ceramic bodies with core-shell geometry were prepared by thermoplastic co-extrusion method and for these composite bodies the mechanical properties were studied. For study of co-extrusion and mechanical properties were designed two composite systems. First system ZTA-A combined the dense core ZTA (zirconia-toughened alumina) and the dense shell Al2O3. Second system ZST-Z consisted of porous core and dense shell made from ZrO2 for both cases. In the thesis, the rheology of ceramic thermoplastic suspensions and their mutual influence during co-extrusion was studied. Subsequently, the debinding process and sintering were studied, and based on the optimization of all process steps were obtained defect-free bodies with core-shell geometry. The mechanical properties (elastic modulus, hardness and bending strength) were determined for sintered bodies. To estimate the stress path in the core shell bodies loaded in bending, the relationship considering different elastic moduli of the core and the shell was used. For bodies of ZTA-A system was increased the strength in comparison with monolithic bodies of the individual components. Thus, bodies with high surface hardness of shell from Al2O3 and moreover having high fracture strength in bending were obtained. The effective elastic modulus was decreased for bodies of ZST-Z system up to 25 % in comparison with the elastic modulus of dense monolithic samples. The same effective modulus of elasticity was possible to achieve with core-shell bodies while maintaining significantly higher fracture strength than monolithic porous bodies or pipes.
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Applications of titanium alloys
Košťál, Jan ; Kaštyl, Jaroslav (referee) ; Němec, Karel (advisor)
This bachelor thesis will deal with titanium and titanium alloys, their properties and appropriate application in mechanical engineering and other branches. The first part is devoted to the pure titanium, describes technology of production, there are also briefly mentioned physical, chemical and mechanical properties, and according to them the position of titanium among other elements. The main part is focused on the different types of titanium alloys, their properties, production and processing. The conclusion is devoted to the use of pure titanium and its alloys in different industries.
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Coextrusion of laminated ceramic bodies
Kaštyl, Jaroslav ; Cihlář, Jaroslav (referee) ; Trunec, Martin (advisor)
In the diploma thesis, an overview of the existing literature focused on the thermoplastic co-extrusion method was worked out and based on the findings, extrusion of the monolayer and homogenous bodies from ZrO2, Al2O3, ZTA a ATZ was studied. For thermoplastic extrusion the capillary rheometer was modified and the nozzle was designed and fabricated. Applying the co-extrusion method, homogenous ceramic rods and monolayer rods in structure core/layer: ZrO2/Al2O3, ZrO2/ATZ and ZTA/Al2O3 were fabricated. In monolayer rods, the interface quality and defects that originate during preparation were evaluated. Technological parameters and properties of homogenous rods were used to rate the structure and defects in monolayer rods. Monolayer rods ZrO2/ATZ and ZTA/Al2O3 with 2.5 mm diameter and 45 mm length (containing small defects) were prepared by thermoplastic co-extrusion.
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Evolution of pores during sintering of advanced oxide ceramic materials
Spusta, Tomáš ; Kaštyl, Jaroslav (referee) ; Maca, Karel (advisor)
The goal of this bachelor’s thesis is to experimentally specify behaviour of pores in oxide ceramic materials (Al2O3, t-ZrO2, c-ZrO2), particularly to describe the transition from open to close porosity. Ceramics powders made by different producers and with different initial particle size (Al2O3 – AKP30, REYNOLDS, TAIMICRON; ZrO2 + 3 mol.% Y2O3 – TZ3Y, TZ3YSB; ZrO2 + 8 mol.% Y2O3 – TZ8Y, TZ8YSB) were used. Samples were pressed by cold isostatic pressing CIP at pressures of 100MPa and 300MPa, and pressureless sintered up to relative densities up to 88-96%. The obtained results show, that evolution is mainly affected by material, independently of size of initial particles neither by initial shaping pressure. Elimination of open pores occurs in cubic ZrO2 at 91-92 % of relative density, in tetragonal ZrO2 at 92-93 % of relative density and in Al2O3 at 94 % of relative density.
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Machining of ceramic bodies using CAD-CAM
Kaplan, Lukáš ; Částková, Klára (referee) ; Kaštyl, Jaroslav (advisor)
The literature part of bachelor's thesis deals with ceramic materials based on Al2O3 and ZrO2, methods of sample preparation for consequent machining, different methods of machining, especially the technology of CNC machining in non-sintered and sintered state with their comparison. The thesis presents possible examples of the use of ceramic parts. The experimental part of the thesis deals with the machining of ceramic based on ZrO2 using different types of ceramic powders, methods of preparation and the choice of the sintered temperature in relation to its properties. The best results were achieved with SZ-3Y ceramic material sintered at 1550 °C for 2 hours, strength values were 1203 MPa, roughness of surface Ra was 126 nm a grain size was 382 nm.
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Electrospinning of ceramic fibers
Nemčovský, Jakub ; Kaštyl, Jaroslav (referee) ; Částková, Klára (advisor)
This diploma thesis focuses on the fabrication of ceramic fibres by electrospinning. The theoretical part of the thesis summarizes the currently available information regarding ceramic fibres, their properties, applications and fabrication. The theoretical part also describes the process of electrospinning as one of the most frequently used methods of nanofibre fabrication, as well as the parametres influencing this process. The experimental part is aimed at the fabrication of ceramic fibres based on titania, pure non-doped zirconia and yttria-doped zirconia by electrospinning and at the characterization of thus fabricated fibres. Ceramic precursors based on propoxide and polyvinylpyrrolidone were subjected to electrospinning. The experimental part of this diploma thesis also describes the influence of precursor composition, process conditions and calcination temperature on the morphology and phase composition of the fibres. Precursors were characterized by viscosity measurements. Thermogravimetric analysis (TGA), Röntgen analysis (RTG) and scanning electron microscopy (SEM) were used to describe the fibres. By performing electrospinning of precursors based on titanium propoxide and subsequent calcination at 500-1300 °C, TiO2 fibres with thickness of 100-2500 nm were fabricated. The phase composition changed with calcination temperature from 500 °C from anatase phase through rutile blend to pure rutile at 900 °C. By performing electrospinning of precursors based on zirconium propoxide and subsequent calcination at 550-1100 °C, 0 – 8 mol% Y2O3 doped ZrO2 fibres with thickness of 50-1000 nm were fabricated. An analysis of fibres based on non-doped ZrO2, calcined at 550 °C showed a composition of predominantly monoclinic phase. An analysis of 3 or 8 mol% Y2O3 doped ZrO2 fibres calcined at 900 °C showed a composition of predominantly tetragonal phase or purely cubic phase, respectively. With the increasing calcination temperature, the morphology of the fibres changed from porous nanostructure to chain-like non-porous structure consisting of micrometer grains of TiO2 or ZrO2. The ZrO2 fibres calcined at 700 °C remained flexible as well as the spun ones, while their fragility increased with the increase in calcination temperature.
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