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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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Cold sintering of dielectric materials
Kocman, Lukáš ; Prajzler, Vladimír (referee) ; Salamon, David (advisor)
CSP (Cold Sintering Process) is an innovative production route due to the dramatic reduction in sintering temperature and processing time, which leads to a reduction in energy and production costs. During this low temperature process, the ceramic powder is compacted using a liquid phase under intense uniaxial external pressure and limited heating conditions (typically below 400 °C). Barium titanate BaTiO3 has gained worldwide interest from the scientific community due to its excellent dielectric, ferroelectric and piezoelectric properties. In particular, it is a suitable candidate for dielectric ceramic materials for energy storage. Barium titanate can be prepared by various methods, where the synthesis depends on the desired properties for the final application. The method used has a significant effect on the structure and properties of the materials. In the experimental part of the work, BaTiO3 samples were prepared by the cold sintering method and the possibility of doping ceramic materials during the cold sintering process was investigated. Furthermore, various factors and influences such as heating rate, temperature, dwell time, maximal pressure or sintering flux on the compaction and dielectric properties of the material were discussed.
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3D printing of ceramic materials based on barium titanate with crystallographic preferred orientation
Pišťák, Jan ; Drdlík, Daniel (referee) ; Částková, Klára (advisor)
In this work, textured barium titanate (BTO) ceramics were prepared using 3D ceramic printing technology. We achieved preferential grain growth in polycrystalline ceramics by using template grain growth on the platelet particles. Firstly, we prepared platelet particles with preferential crystalline orientation in the [001] direction by molten salt synthesis and topochemical microconversion. Subsequently, an acrylate-based photosensitive suspension was optimised for use with BaTiO3 ceramic powder. Samples with different amounts of platelets were printed from these suspensions. The overall crystallographic texture of the sintered ceramics increased with increasing amounts of platelets in the suspension. The maximum value of Lodgering factor was achieved after adding 5 wt. % of the platelets (F001 = 42%). It was further found that the addition of platelets resulted in a decrease in the grain size of the sintered texture. The particle size reduction did not affect the porosity and, regardless of the amount of platelet particles added, relative densities in the range of 96-98 % of the theoretical density were achieved. The feasibility of preparing textured barium titanate materials by 3D printing using template grain growth was confirmed.
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Improving Efficiency Concept of Machining Technology of Chimney Liner
Kubů, Marek ; Kyncl, Jiří (referee) ; Sedlák, Josef (advisor)
Diploma thesis contains introduction of a company P-D Refractories CZ a. s., where the manufacture of ceramic chimney liners is. Followed by a description and analysis of the product in the entire production cycle, material and product spectrum. Based on the results of current production is created proposal to streamline the machining technology with a view to increase productivity and reduce defective products, which means determine the material of a tool and the method of machining. The work is finished by technical-economic assessment, where the summary and recommendation of the proposed solution are.
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On the milling of ceramic materials
Rudel, Václav ; Slaný, Martin (referee) ; Píška, Miroslav (advisor)
In the diploma thesis dividing of ceramic materials is made, their bonds and other attributions, which define ceramic materials. There is also described how ceramic materials are manufactured and the thesis is including information about machining ceramic materials. In the experimental part sample of ceramic material R-S67K was machined by milling. During the experiment cutting forces were measured and roughness of surface after finishing, these data were finally evaluated.
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Semiconducting ceramics for thermoelectric application
Jebavá, Alžběta ; Koplík, Jan (referee) ; Bartoníčková, Eva (advisor)
This diploma thesis focuses on the syhnthesis of multicomponent ceramic system based on Ca-(Mn,Co)-O. The thesis is devided in theoretical and experimental part. The theoretical part is describing ceramic materials for thermoelectric application, preparation and synthesis of these materials and their processing. The experimental part is dealing with synthesis of ceramic powder which is processed to the porous ceramics. The properties of prepared porous ceramics are observed.
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Effective machining of advanced structural ceramics
Jurán, Antonín ; Prokop, Jaroslav (referee) ; Humár, Anton (advisor)
The objective of this diploma thesis are new design materials in a view of their structure, properties, manufacture,partitions, applications and possibili-ties of effective machining them Ceramics are used in the field of design applications more often than before. They are in form of compact parts and in form of thin coatings on the surface of metal parts. Fast development of constructive applications requires the same progress rate of machining ma-chines innovations and development of new methods of effective machining these materials, too. The aim is to produce parts of demanded shapes, dimensions and surface quality at affordable costs. Ceramics guarantee long terming durability and reliability. The evaluation of ceramics grinding tests from the point of view of cutting forces and surface quality of the machined faces are presented in the last part of the diploma thesis.
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A study on the grinding of ceramic materials
Kresa, Jakub ; Sliwková, Petra (referee) ; Píška, Miroslav (advisor)
This thesis is focused on ceramics materials in terms of their partition, properties, structure, manufacture and methods of their possible machining. The first part of this thesis is devoted to the distribution of ceramics materials, their structure, properties, and methods of production. Currently, ceramics materials are increasingly used in structural (engineering) applications therefore we deal with methods of effective machining of ceramic materials, to achieve part of the required shape, dimensions and surface quality. The evaluation of ceramic grinding test from the point of view of cutting forces and surface quality of the machined faces are presented in the last part of the thesis. The tested materials have been provided by company SEEIF Ceramics a.s.
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