|
|
Machinable bioceramic foams prepared by gelcasting method
Šťastný, Přemysl ; Částková, Klára (referee) ; Trunec, Martin (advisor)
Diploma thesis is focused on development of method for preparation individualized bioscaffolds prepared by milling of HA foam prepared by gel casting method and consolidated via epoxy curing reaction. Diploma thesis continues in bachelor thesis Modern processing methods of porous bioceramics. Literature search is filled in the newest knowledge from the field of bioactivity enhancement of scaffolds. Experimental part of diploma thesis described development of system for individualized scaffold manufacturing from HA suspension preparation, preparation of ceramic blocks used as material for machining to final blocks machining. Pressure strength of foam were evaluated, too. Chosen samples were coated with calcium polyphosphate coating for biological response enhancement. Coated samples were given for in-vivo test to partner university in Beijing under the terms of project FP7-NMP-2013-EU-China: "Bioscaffolds"
|
|
|
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.
|
|
|
Transparent polycrystalline ceramics at visible and infrared wavelenghts
Veselý, Jan ; Maca, Karel (referee) ; Trunec, Martin (advisor)
his thesis deals with preparation of transparent ceramic sheets made out of sub-µm alumina powder. Green bodies are prepared by ultraviolet (UV) curing of UV curable resin containing ceramic powder followed by debinding of organic parts at elevated temperature. High relative density of green bodies is essential for reduction of shrinkage during subsequent sintering process. Therefore high solids loading dispersions containing > 57 vol% ceramic particles are used. To reach transparent behaviour, porosity within the sheets must be reduced completely. Therefore hot isostatic pressing (HIP) is used as a final operation. Finally, light transmission and hardness measurements are presented. Possibilities of making high resolution microstructures using maskless lithography and some suggestions for use of the UV curing technique for production of complex-shaped 3D structures are briefly mentioned.
|
|
|
Machinable bioceramics prepared by gelcasting method
Kolář, Martin ; Částková, Klára (referee) ; Trunec, Martin (advisor)
In the diploma thesis, overviews of the existing literature focused on the gelcasting method and based on the findings were prepared aqueous slurries of zirconium oxide for gelcasting method. These suspensions were examined for the influence of the content ceramics powder, type and content of dispersants and volume of initiator on viscosity of aqueous suspensions and process of polymerization. Optimum ceramic suspension had 45 vol.% of ceramic powder which was stabilized by 0,5 weight % of dispersant Dolapix CE 64. Polymerization running at room temperature was initiated by 0,175 weight % of ammonium persufate without accelerator. Microstructure of prepared ceramic blanks and sintered bodies was compared with body prepared by isostatic pressing. For the machining tests were prepared blanks in disc-shaped.
|
|
|
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.
|
|
|
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.
|
|
|
Lamination of ceramic tapes
Smiešková, Jana ; Pouchlý, Václav (referee) ; Trunec, Martin (advisor)
This master’s thesis deals with ways of lamination of ceramic tapes prepared by gel–tape casting method. The thesis is divided into two parts. The first part, a literary recherche, describes methods of production of thin ceramic layers. The main focus is on the tape casting method. The second, experimental, part of the thesis describes the preparation of ceramic suspensions, the fabrication of thin ceramic layers by gel–tape casting method, the preparation of laminated bodies from thick-walled discs and laminated tapes and it also shows a possibility of creating of ceramic layers by the spin coating method used on polycrystalline ceramic substrate.
|
|
|
Two-step sintering of advanced ceramic materials with various crystal structures
Žalud, Pavel ; Trunec, Martin (referee) ; Maca, Karel (advisor)
The influence of Two-Step Sintering (TSS) process on the final microstructure of oxide ceramics materials with two different crystal structures was studied. Tetragonal zirconia (stabilized with 3mol%Y2O3, particle size 90nm and 140nm ) and cubic zirconia (8mol%Y2O3, 70nm) powders were cold isostatically pressed and pressure less sintered with different heating schedules. The microstructures achieved with TSS method were compared with microstructures achieved with conventional Single-Step Sintering schedule (SSS). The results showed that the efficiency of the TSS of these oxide ceramics was more dependent on their crystal structure than on their particle size and green body microstructure. The method of TSS brought only negligible improvement of the microstructure of tetragonal zirconia ceramics. On the other hand, TSS was successful in the sintering of cubic zirconia ceramics; it led to a decrease in grain size by a factor of 2.
|
|
|
Ceramic materials with foam structure
Šenk, Vít ; Trunec, Martin (referee) ; Cihlář, Jaroslav (advisor)
Bachelor’s thesis is concerned to preparation ceramic materials with a foam structure suitable for supporting, catalytic and biological applications. A part of work is focused on preparation ceramic substrates such as alumina, zirconia and foam materials for catalytic applications based on perovskite materials. Process of preparation ceramic foam structures consists of stable ceramic slurry prepared by different methods, drying, thermal extraction and evaluating sintered structure.
|
|
|
Sintering of advanced ceramic materials
Průdek, Miloš ; Trunec, Martin (referee) ; Maca, Karel (advisor)
V předložené diplomové práci bylo studováno slinování hexagonálního Al2O3 a kubického MgAl2O4 pomocí slinovacích cyklů složených z beztlakého předslinutí metodou dvojstupňového slinování s následným doslinutím s využitím tlaku (HIPováním). Cílem bylo pokusit se snížit (při zachování vysoké dosažené hustoty) střední velikost zrn a tím zvýšit tvrdost keramiky popř. optickou transparenci. Hlavní úsilí bylo věnováno optimalizaci předslinutí pomocí různých slinovacích cyklů. Přestože bylo vyzkoušeno velké množství různých kombinací teplot a prodlev dvojstupňového slinování, nepodařilo se výrazným způsobem zvýšit výslednou tvrdost vzorků. V případě kubického MgAl2O4 bylo dosaženo hustot blížících se teoretické hustotě, což se projevilo v optické transparentnosti vzorků.
|
guest ::
