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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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Influence of parameters of electrophoretic deposition on properties of ceramics
Husák, Roman ; Čelko, Ladislav (referee) ; Hadraba, Hynek (advisor)
Electrophoretic deposition is experimentally undemanding shaping method enabling preparation of ceramic material from stable suspension of ceramic particles by means of direct electric current. The aim of the work was to describe effect of electric current magnitude on velocity and final microstructural and mechanical properties of the ceramics. The alumina and zirconia layers were prepared by electrophoretic deposition from stable suspensions of ceramic particles in the isopropanol stabilised with monochloracetic acid. It was found that the real time dependance of particle deposition differs from the theoretical predisction for given electrical conditions. By precise measurement of kinetics of the electrophoretic deposition the actual electrophoretic mobility of the particles and the actual amount of particles taking part in the deposition process were found. It was found that with increasing the electrical current the actual electrophoretic mobility was decreased and actual amount of particles taking part in the deposition process was increased. The increasing velocity of particles under higher electrical currents led to the detorioration of particle arrangement in the elctrode and thus to the increasing of the pore sizes and final densities of the deposits. These microstructural changes reflected in the lowering of the hardness of the deposited ceramics of about 300HV5 in the case of alumina.
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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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Study of Sintering of Nanoceramic Materials
Dobšák, Petr ; Hanykýř, Vladimír (referee) ; Havlica, Jaromír (referee) ; Šída, Vladimír (referee) ; Cihlář, Jaroslav (advisor)
The topic of the Ph.D. thesis was focused on the process of sintering alumina and zirconia ceramic materials with the aim to compare kinetics of sintering sub-micro and nanoparticle systems. Zirconia ceramic powders stabilized by different amount of yttria addition in the concentration range of 0 – 8 mol% were used. The different crystal structure (secured by yttria stabilization) of zirconia, as found, did not play statistically proven role in the process of zirconia sintering. The possible influence was covered by other major factors as particle size and green body structure, which does affect sintering in general. According to the Herrings law, the formula predicting sintering temperature of materials with different particle size was defined. The predicted sintering temperatures were in good correlation with the experimental data for zirconia ceramic materials prepared from both, coarser submicrometer, and also nanometer powders. In case of alumina ceramics the predicted and experimentally observed sintering temperature values did not match very well. Mainly the nanoparticle alumina materials real sintering temperature values were markedly higher than predicted. The reason was, as shown in the work, strong agglomeration of the powders and strong irregularities of particle shape. The major role of green body microstructure in the sintering process was confirmed. The final density of ceramic materials was growing in spite of sintering temperature, which was decreasing together with pore - particle size ratio (materials with similar particle size were compared). Sintering temperature was increasing together with growing size of pores trapped in the green body structure. Clear message received from the above mentioned results was the importance of elimination of stable pores with high coordination number out off the green body microstructure during shaping ceramic green parts. Same sintering kinetics model was successfully applied on the sintering process of submicro- and also nanometer zirconia ceramics. Activation energy of nanometer zirconia was notably lower in comparison to submicrometer material. For the sintering of nanoparticle zirconia was typical so called “zero stage” of sintering, clearly visible on kinetic curves. It was found out, that processes running in zirconia “green” material during zero stage of sintering are heat activated and their activation energy was determined. Pores of submicrometer zirconia were growing in an open porosity stage of sintering just a slightly (1.3 times) compared to the nanoparticle zirconia, where the growth was much higher (5.5 times of the initial pore diameter). This difference was most probably caused by preferential sintering of agglomerates within the green bodies and by particle rearrangement processes which appears in the zero stage of sintering of nanoparticular ceramics. The technology of preparation of bulk dense ytria stabilized zirconia nanomaterial with high relative density of 99.6 % t.d. and average grain size 65nm was developed within the thesis research.
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Milling of pre-sintered ceramics using CAD / CAM
Ščasnovič, Erik ; Pouchlý, Václav (referee) ; Kaštyl, Jaroslav (advisor)
Diploma thesis is focused on determination of proper pre-sintering temperatures of zirconia ceramic blanks intended for CAD-CAM milling. Functional properties of milled and sintered samples are also discussed. Experimental part is aimed on determination of properties of blanks which affect directly the CAD-CAM process. Another solved issue is definition of mechanical and physical properties of sintered bodies. Final properties are compared with properties of ceramic blanks made from standard ceramic powder. Dental crown, dental three-unit bridge and partial knee joint were prepared successfully. The tests of geometric accuracy were performed on dental crown as well as on partial knee joint replacement with using 3D scanner.
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Flexible ceramic sheets based on ziconium dioxide
Hliničan, Jan ; Částková, Klára (referee) ; Šťastný, Přemysl (advisor)
The diploma thesis is focused on preparation of thin and highly flexible ceramic tapes from zirconia with a thickness from 70 to 200 m. The thesis is divided into two parts. The first part presents a literary research that focuses on the properties of zirconium dioxide, the preparation of thin ceramic foils and the evaluation of the mechanical properties of ceramic materials. The second part is experimental. It deals with the preparation of thin ceramic foils from colloidal ceramic suspensions produced by epoxy gel-tape casting method. The suspensions were prepared from zirconium dioxide stabilized by 2 and 3 mol.% of yttrium oxide. The maximum deflection and strength was determined on sintered foils. The maximum biaxial strength of 1806 MPa was achieved for 3Y-PC 75 foils with a thickness of 190 m. The maximum deflection of 10.5 mm at a ceramic foil thickness of 75 m was achieved in a 3-point bend with a support span of 30 mm on 3Y-PC 75 samples. At a support distance of 50 mm, the samples were pushed through the gap without damage. These results indicate excellent mechanical properties of the prepared ceramic foils.
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Bioceramic Materials and Their Biocopatibility with Bone Tissues
Novotná, Lenka ; Trunec, Martin (referee) ; Cihlář, Jaroslav (advisor)
The thesis concerns the study of ceramic coatings of zirconia nanoparticles deposited on alumina, zirconia and glass substrates by ultrasonic spraying. The quality of deposits was investigated in dependence on the type of substrate (composition, temperature, roughness) and concentration of ceramic suspension. The best results were received by the deposition of suspension of low concentration on rough substrates at low temperatures. The biocompatibility was tested in vitro. Good cytocompatibility of ceramics with nanostructure coatings was found.
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Neural bioceramic scaffold prepared by freeze-casting
Vojníková, Michaela ; Pejchalová, Lucie (referee) ; Salamon, David (advisor)
Pre regeneráciu a rast poranených nervových vlákien bolo preskúmaných mnoho postupov, no výsledný rast axónov je často náhodný až dezorganizovaný a odráža sa na zložitejšom zotavovaní pacienta. V tejto práci boli vyrobené nové skafoldy s mikroštruktúrnymi a mechanickými vlastnosťami nervového skafoldu pomocou metódy freeze-casting. Konkrétne boli vyrobené biokeramické skafoldy na báze fosforečnanov vápenatých, oxidu titaničitého alebo oxidu zirkoničitého. Pomocou kontrolovaného rastu ľadu v jednom smere bola pripravená orientovaná mikroštruktúra. Pozorovanie pomocou skenovacej elektrónovej mikroskopie potvrdilo lineárne orientované póry (lamelárny systém), v ktorých priemerná veľkosť pórov klesala so zvyšujúcou sa rýchlosťou mrazenia. Skafoldy pripravené pomocou mrazenia v tekutom dusíku vykazovali vynikajúce mechanické vlastnosti, kde pevnosť v ohybe bola získaná v rozmedzí 10–17 MPa. Tie isté skafoldy mali vzdialenosť medzilamelamelárnych priestorov 10–30 µm, ktorých parametre sú vhodné pre nervové skafoldy. Biokompatibilita bola vyhodnotená pomocou Schwannových buniek in vitro, kde bola pozorovaná adhézia a rast v lamelárnom smere. Cytotoxické testy odhalili negatívny vplyv vyššej koncentrácie vápnika na prežitie Schwannových buniek. Pripravené skafoldy mali schopnosť tvorby apatitu na povrchu v podobe embryonálnych a nukleačných centier a apatitu samotného. Skafoldy na báze fosforečnanov vápenatých a oxidu titaničitého vykazovali sľubné regeneračné vlastnosti, konkrétne adhéziu a rast prostredníctvom pórovitej štruktúry a taktiež vynikajúce mechanické vlastnosti.
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Study of bioceramic materials for dental applications
Lokvenc, Martin ; Matoušek, Aleš (referee) ; Novotná, Lenka (advisor)
This thesis deals with bioceramics used in dentistry. The biocompatibility, which is the characteristic property of biomaterials, is described in the opening chapter of the thesis. Advantages and disadvantages of advanced ceramics are also discussed. The main attention was paid particularly to the dental bioceramics, which can be divided according to different criteria. The used classification was based on microstructure, which significantly influences behaviour and properties of biomaterials. The ceramic is viewed as a composite material, where the glass matrix is filled with different amount of crystal phase. The thesis also includes the use of the individual types of bioceramics for the manufacture of dental restorations.
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Milling of pre-sintered ceramics using CAD / CAM
Ščasnovič, Erik ; Pouchlý, Václav (referee) ; Kaštyl, Jaroslav (advisor)
Diploma thesis is focused on determination of proper pre-sintering temperatures of zirconia ceramic blanks intended for CAD-CAM milling. Functional properties of milled and sintered samples are also discussed. Experimental part is aimed on determination of properties of blanks which affect directly the CAD-CAM process. Another solved issue is definition of mechanical and physical properties of sintered bodies. Final properties are compared with properties of ceramic blanks made from standard ceramic powder. Dental crown, dental three-unit bridge and partial knee joint were prepared successfully. The tests of geometric accuracy were performed on dental crown as well as on partial knee joint replacement with using 3D scanner.
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