|
|
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.
|
|
|
Determination of optimum sintering schedule of oxide ceramics
Průdek, Miloš ; Hadraba, Hynek (referee) ; Maca, Karel (advisor)
The sintering of cubic ZrO2 (stabilized with 8mol% Y2O3) by Single-Step sintering was studied in this bacherol‘s thesis. Two types of commercial powders with different particle size of 80nm and 140nm were used. It was studied whether the grain size of the sample sintered for shorter time at higher density is higher or smaller than after sintering for longer time at lower temperature. It was found taht for cubic zirconia the sintering for a longer time at lower temperature is advantageous from the point of view of decreasing the grain size fo cintered ceramics.
|
|
|
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.
|
|
|
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.
|
|
|
Laminated Ceramic Composites - Deposition, Structure and Properties
Drdlík, Daniel ; Maca, Karel (referee) ; Cihlář, Jaroslav (advisor)
The work was focused on the preparation of layered ceramic materials and their characterizations. The direct measurment of weight deposite for enhanced description of one component system was studied within this work. The kinetics of electrophoretic deposition obtained from theoretical calculation and from experimental values were confronted. It was prepared a lot of depositions for described kinetic of electrophoretic deposition with applied constant currents. The relative density and porosity were determined on the annealled and sintered bodies. The hardness measurments were performed on sintered bodies and then resulted values were confronted with the used currents. A ceramic composite based on Al2O3 and ZrO2 was prepared by using of precision describtion of electrophoretic deposition kinetic.
|
|
|
Composite Dental Biomaterials - Structure, Analysis and Properties
Matoušek, Aleš ; Vaněk,, Jiří (referee) ; Lapčík,, Lubomír (referee) ; Cihlář, Jaroslav (advisor)
The aim of this work is to define relations between grain size and bioaktivity of oxide ceramics, specifically ZrO2, Al2O3 and HA. Ceramic materials with grain size from 100 nm up to 10 m, with various surface roughness, were tested for its bioactivity. Ceramography analysis was performed for all tested materials to precisely describe microstructures. Biological properties of the ceramic materials were tested via dilation tests directly in-vitro and by in-vitro extraction. Three cell culturing lines: osteoblast MG63, fibroblast L929, and epithelioid HeLa, were used for our testing. An influence of the grain size on the biological response was only found for the ceramic materials which had been thermally etched. The thermally etched nanocrystalline samples had larger areas covered by cells than ceramics with coarse grain microstructure. Biological tests on layered composites Al2O3×ZrO2 showed the cell selection determined by the type of material, where ZrO2 surfaces were preferably covered. Improved biological response of nanocrystalline ZrO2 was demonstrated on ceramic ZrO2, Al2O3 and SiO2 substrates with nanocrystalline coating of ZrO2. In this work a novel technological process for the formation of defect-free coatings was developed. Sintered coatings were tested using in-vitro technique with cell line HeLa, L929 and MG63 for up to 72 hours. The results of the biological tests of nanocrystalline coatings were consistent with results from the bulk nanocrystalline thermally etched ZrO2 ceramics.
|
|
|
Influence of plasma activation of ceramic particles on ceramic technology and properties
Klevetová, Tereza ; Ráheľ,, Jozef (referee) ; Pouchlý, Václav (advisor)
This thesis is focused on the study of the influence of plasma activation of powder ceramic materials on sintered microstructure. In this experiment Diffuse Coplanar Surface Barrier Discharge (DSCBD) device was used for plasma treatment and two materials were chosen to be investigated – Al2O3 (TAI) and ZrO2 doped with 3 mol % Y2O3 (TZ). Two methods of powders dispergation in suspension were used – ultrasound and ball milling. The effect of using of DCSBD on alumina and zirconia powders was investigated by mercury intrusion porosimetry, dilatometry and by evaluation of final relative densities and grain sizes. Generally, was investigated that plasma surface activation of ceramic particles has measurable influence on the final microstructure. In comparison with the non-plasma treated alumina powders, plasma activated powders disperged with ultrasound and ball milling achieved lower values of grain size at comparable relative densities. In case of zirconia powders was observed that plasma treated powders achieve higher relative densities, if ultrasound was used. On the other hand, plasma treated zirconia powders disperged with ball milling achieve lower relative densities compared with non-plasma treated zirconia powders. Final sintering trajectory of plasma treated TZ powders disperged with ultrasound is comparable to the sintering trajectory of non-plasma treated zirconia powders disperged with ball milling and vice versa. Plasma surface treatment is the way of more ecological friendly preparation of suspension and its stabilization than the conventional stabilization methods using chemical additives.
|
|
|
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.
|
|
|
Microstructure revealing and analysis of partially sintered oxide ceramic materials
Jemelka, Marek ; Salamon, David (referee) ; Spusta, Tomáš (advisor)
The goal of this bachelor’s thesis is to experimentally determine appropriate etching conditions for etching of partially sintered advanced ceramic materials (Al2O3, ZrO2 + 3mol % Y2O3, ZrO2 + 8mol % Y2O3) with emphasis on minimal influence on the final surface microstructure. The obtained results show, that the optimal etching way of selected materials is thermal etching under conditions: Al2O3 (rel. 95,7 ± 0,9 %)- Te = 1015 C (Ts – 350 C), tetragon. ZrO2 (rel. 94,5 ± 0,6 %)- Te = 1005 C (Ts – 350 C), cubic. ZrO2 (rel. 94 ± 0,5 %)- Te = 1105 C (Ts – 350 C). The applying of chemical etching in H3PO4 for 60s led to revealing of the microstructure of Al2O3 and cubic ZrO2 in shorter times, but the procedure carries its difficulties of etching conditions determination and execution itself, which put it in the second place. Microstructure revealing via using focused ion beam was experimentally determined as inappropriate due to time and personnel demands.
|
|
|
The influence of heating rate on two step sintering of advanced ceramic materials
Klevetová, Tereza ; Maca, Karel (referee) ; Pouchlý, Václav (advisor)
Recently, there has been growing interest in new technologies and procedures to improve the microstructure of advanced ceramic materials. One of the most commonly used sintering methods is Two step sintering (TSS), Rapid rate sintering (RRS) and Spark plasma sintering (SPS). Within the framework of this bachelor thesis number of experiments were carried out for the research of the microstructure interconnecting the Two step sintering with the Rapid rate sintering and non-preassure Spark plasma sintering. The aim of this work was to determine the influence of the heating rate on the size of final relative density and the average grain size for ceramic materials based on ZrO2. The results of the study show that occurrence of the „core-shell“ structure on the ZrO2 doped by 3 mol.% Y2O3 (TZ-3Y) tend to production of non-homogenous microstructure with a fully compacted surface and a porous center. In the case of ZrO2 doped by 8 mol.% Y2O3 (TZ-8Y) this structure was detected only in several cases at higher heating rates. An the same time it was found that the final relative density decreases with increasing heating rate. Using cubic ZrO2 with larger grain size (TZ-8YSB), the „core-shell“ structure did not appear, however a lower relative densities of about 98 % t.d. was always achieved, regardless of the applied temperature profile. The best results were obtained with TZ-8Y using Spark plasma sintering and Rapid rate sintering. Smaller grain size was obtained as compared with conventional methods of other authors. The difference in grain size was just within the framework of the standart deviation. This work doesn’t show any positive influence of Rapid rate sintering on the resulting grain size.
|
guest ::
