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Ceramic materials and composites for advanced applications
Mařák, Vojtěch ; Částková, Klára (referee) ; Michálková,, Monika (referee) ; Drdlík, Daniel (advisor)
Tato dizertační práce se zaměřuje na pokročilou oxidovou keramiku a částicové a vrstevnaté kompozity. Studované materiály zahrnují biokeramický hydroxyapatit, termomiotický wolframan hlinitý a bezolovnaté piezoelektrické materiály na bázi titaničitanu barnatého. Příprava těchto keramik má několik omezení ovlivňující finální vlastnosti, zahrnující použití toxických stabilizátorů, nízké zhutnění, náchylnost k praskání, vznik nežádoucích chemických reakcí, nízké mechanické a elektrické vlastnosti. Tato práce řeší tyto problémy přizpůsobením jednotlivých kroků zpracování a použitím progresivních výrobních metod pro optimalizaci požadovaných funkčních vlastností materiálů. Úprava hydroxyapatitového prášku studenou plazmou umožnila elektroforetickou depozici bez toxických stabilizátorů, což vedlo k hutnějším povlakům bez trhlin. Praktický benefit tohoto přístupu byl demonstrován v případě bezdefektních hydroxyapatitových povlaků ortopedických šroubů. Termomiotický wolframan hlinitý, vyznačující se svým téměř nulovým koeficientem tepelné roztažnosti, byl syntetizován optimalizovanou koprecipitací za účelem zlepšení slinovatelnosti prášku. Rychlé beztlaké slinování a slinování plazmovou jiskrou byly použity ke zhutnění materiálu, přičemž bylo dosaženo dosud nejvyšších publikovaných hodnot hustot při nejnižší slinovací teplotě. Vývoj mikrostruktury piezokeramiky titaničitanu barnatého byl studován pomocí rychlého beztlakého slinování a slinování s pomocí radiace. Získané poznatky byly využity pro slinování částicových kompozitů na bázi titaničitanu barnatého vyztuženého oxidovými keramikami. Vysoká reaktivita mezi zvolenými materiály měla negativní vliv na vlastnosti kompozitů a jeden z reakčních produktů byl podrobněji charakterizován. Byly připraveny vrstvené kompozity střídáním vrstev na bázi titaničitanu barnatého a dielektrického oxidu zirkoničitého. Vysoká reaktivita piezoelektrických materiálů byla potlačena volbou slinovací strategie. Souhrnným cílem této disertační práce je posunout vědění v oblasti vlastností a zpracování keramických materiálů, poskytnout náhled na optimalizaci funkčnosti a řešit kritická omezení v různých aplikacích.
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Capsule-free Hot Isostatic Pressing of transparent structural and functional ceramic materials
Krupa, Filip ; Drdlík, Daniel (referee) ; Maca, Karel (advisor)
The presented work focused on evaluating the suitability of several types of cubic zirconia powders for preparing suspension with a high solid content (over 40 vol.%). The suspensions were doped with TiO2 nanopowder (0,1 – 0,5 at. %). The influence of the shaping method (casting the suspension and drying the suspension by spray drying, followed by shaping through pressinng) and subsequent pre-sintering to the closed porosity stage was investigated, focusing on comparing two sintering regimes (long – 1300 °C/120 min and short – 1560 °C/2 min). The microstructure of both the pre-sintered samples and the samples after hot isostatic pressing was then observed using an electron microscope. The presented work assessed the influence of TiO2 on relative density, average grain size, and pore size, as well as the optimal amount of TiO2 to achieve maximum photoluminescent properties.
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Advanced high-temperature resistant metal-ceramic composites based on TiB2 for cutting tools
Halmazňa, Jiří ; Drdlík, Daniel (referee) ; Chlup, Zdeněk (advisor)
This diploma thesis deals with the preparation of new high-temperature resistant cermets based on TiB2. The hard ceramic phase is bonded by NiW metallic alloy, which was prepared by mechanical alloying using a planetary ball mill. The first part of the thesis is targeted to the optimization of mixing of both powders in the planetary ball mill. The procedure of preparation of powders mixture with homogenous particles distribution of the NiW alloy was designed and verified with simultaneous particle size refinement. The second part is focused on the microstructure characterisation and mechanical properties evaluation of sintered materials. In this case both powders, TiB2 and NiW, were mixed in a tubular mill and consequently compacted by a rapid hot pressing method at four different sintering temperatures. The influence of the sintering temperature on the microstructure development characterized by the density, porosity and grain size was monitored. The elastic modulus, fracture toughness, flexural strength and hardness were measured on prepared test specimens. The results of conducted experiments show a significant dependence of the microstructure and mechanical properties on applied sintering temperatures. The higher sintering temperatures are used the better mechanical properties are observed. However, the sintering temperature of 1375°C seems to be an optimal one. The sintering temperature of 1400°C leads to the significant losses of the metal phase due to sublimation of nickel resulting in increased porosity in the metal phase regions.
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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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Lining of the induction furnaces
Kopečný, Vendelín ; Pernica, Vítězslav (referee) ; Myška, Martin (advisor)
This work deals with lining of electric induction furnaces. The first part describes the preparation of lining, its function during the running of furnace and also its tearing down at the end of work process. In the thesis is also discussed the use of rammed crucibles. The materials used for lining and rammed crucibles are described also in the sense of their chemical properties in connection with the possibilities of their use under different conditions. The practical part of the thesis describes the process of lining the electric induction furnace, which was realized by the author under the supervision of the supervisor.
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Synthesis and sintering of zirconia based ceramics for biomedical applications
Jahodová, Daniela ; Novotná, Lenka (referee) ; Částková, Klára (advisor)
The present thesis focuses on the preparation of tetragonal zirconia doped with yttria oxide, ceric dioxide, and magnesium oxide. In its theoretical part the thesis covers the characteristics of doped ceramics, the possible methods of powders preparation and of their further processing. The experimental part describes the precipitation synthesis of zirconia in base environment and further processing for ceramics. Also studied were the influences of dopant and of the processing technique used on the phase composition and microstructure of the resulting ceramics. To describe the powder structure, the thermal, dilatometric, surface area, and x-ray analyses were performed; as well as both the scanning and transmission electron microscopy employed. Dry processed ceramics showed the average grain size of 87–94 nm and the relative density in the range of 84,0–99,3 %. In comparison, the ceramics produced of hydrothermally synthesised powders proved the average grain size of 75–85 nm and the relative density between 92,7-99,9 %. As the next step, samples were subjected to low-temperature degradation for the time of 5 and 15 hours. Samples consisting of pure tetragonal ZrO2 were resistant to 5 and 15 hours of low-temperature degradation at 180 °C.
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Kinetics of Heterogeneous Processes in Silicate Technologies -Dehydroxylation and Disolution of Clay Minerals
Křečková, Magdaléna ; Kutzendörfer, Jaroslav (referee) ; Kuřitka, Ivo (referee) ; Havlica, Jaromír (advisor)
The first part of the thesis discuss general characterization of heterogeneous processes in silicates. This part is focused on kinetics of heterogeneous processes and mathematical description of reactions time behavior. The other part describes important technologies in silicate industry such as sintering, solid matter decomposition, transition modification, etc. Another chapter deals mineralogy, structure and properties of eminent silicate raw materials. Emphases is given to characterization of clay minerals and their utilising. The experimental part handle the analytic techniques used for investigation of thermal decompostion, dehydroxylation, crystalization of Al-Si spinel phase and sintering process of washed kaolin Sedlec Ia from the region Carlsbad (Czech Republic). Concluding chapter reports on results of experimental work.
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Preparation and properties of porous zinc material
Ryšťák, Jaroslav ; Fintová, Stanislava (referee) ; Doležal, Pavel (advisor)
Bachelor thesis is focused on preparation of bulk material prepared from zinc powder by cold pressing followed by sintering. Topic of the work includes characterization of prepared material depending on the choice of the compaction process conditions. Bulk material is characterized by physical-mechanical tests, structure and porosity. Thesis solving and focuses on study and control of processes during bulk material preparation and description of the processes from physically-chemical point of view of the structure creation and final material properties.
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Powder metalurgically prepared materials based on Zn and Ca
Morcinek, Tomáš ; Hasoňová, Michaela (referee) ; Doležal, Pavel (advisor)
The topic of this bachelor thesis is a process of preparation and characterization of bulk material from zinc and calcium powder mixture by hot pressing. Materials thus prepared were evaluated in terms of their microstructure and physical-mechanical properties. The influence of calcium content in the material on physical-mechanical properties of the resulting structure was observed. The solution is focused on exploration of the influence of material composition in the process of preparation of bulk material, and description of these processes from the physical-chemical point of view on the structure formation and the resulting properties of the material.
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Preparation processes and properties of porous zinc material
Moleková, Kristína ; Březina, Matěj (referee) ; Hasoňová, Michaela (advisor)
Bachelor thesis occupy with preparation of porous material from zinc powder by cold pressing, cold pressing followed by sintering and hot pressing. This thesis contain both preparation of bulk material, and charakterization of materials based on the compaction process conditions. Impact of pressing process on subsequent progress of sintering and final attributes of materials is evaluated. Bulk material is characterized considering to structure, porosity, and physical-mechanical properties. Properties of final metarial will serve to optimize conditions for process of pressing and sintering.
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