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Fast sintering of advanced ceramic materials
Prajzler, Vladimír ; Salamon, David (referee) ; Maca, Karel (advisor)
The bachelor thesis is dealing with fast sintering of advanced ceramic materials, such as tetragonal zirconia and alumina in conventional resistance furnace. This approach is made possible by special superkanthal furnace, which is capable to reach a heating rate of 200 °C/min. Samples obtained through fast sintering reached relative density higher than 93% for zirkonia and 97% for alumina, without forming any cracks in samples. Achieved relative density in the case of tetragonal zirconia was higher for samples with larger pores in the green body. This behavior is different of conventional sintering and leads to considerations of heat transfer mainly by radiation.
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Viscosity modulation by camphor during stereolithography printing of advanced ceramic materials
Sokola, Patrik ; Roleček, Jakub (referee) ; Salamon, David (advisor)
This bachelor's thesis deals with the preparation of printing suspensions containing ceramics, their subsequent printing and evaluation of the properties of sintered ceramics. In the preparation of the printing suspension using zirconium powder stabilized with yttrium, the influence of the viscosity modulator, in particular the camphor, on the properties of the suspension and the final microstructure of the extruded and sintered objects was investigated. Samples with different contents of ceramic particles were prepared and the effect of camphor on the rheological properties of the suspension was determined. It has been found that camphor always has a positive effect on reducing the viscosity of a selected volume of ceramic, and the maximum amount of zirconium powder in the epoxy resin has been determined to make the suspension usable for stereolithographic printing. After printing, the density of the samples, their porosity, particle size, defects in the microstructure, visual quality and percentage shrinkage were evaluated. The camphor samples showed better properties for different volumetric contents of zirconium ceramics for all the mentioned factors.
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Tailoring of cooling procedure during freeze-casting for bone replacement applications.
Šantavý, Tomáš ; Novotná, Lenka (referee) ; Salamon, David (advisor)
Bachelor thesis focuses on preparation of hydroxyapatite ceramics by freeze-casting. Hydroxyapatite is an important ceramic material, due to its biocompatibility, biodegradability and bioactivity it has a wide range of use in medicinal applications especially in replacement of bone material. The chosen method, freeze-casting, is flexible, eco-friendly and we are able to achieve a high level of porosity. The method includes freezing, freeze drying and sintering which creates a porous structure of the prepared material. Objective of this bachelor thesis was to find out the impact on the created porosity and mechanical properties of the final material. Freezing rates were applied 3, 4, 5, 6, 7 and 26 m/s. During the experimental part it was established that the freezing rate has a significant influence on the newly formed inner microstructure, it directly influences the interlamellar distances and mechanical property which is compressive strength. With liquid nitrogen with a speed of 26 m/s the achieved compressive strength was of 15 MPa as well as the shortest interlamellar distances of 14-22 µm. With slower freezing rate the average interlamellar distances were 40-150 µm and compressive strength of 2-4 MPa with comparable porosity.
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Preparation of ceramic-metal composites for ballistic protection
Hladík, Jakub ; Roleček, Jakub (referee) ; Salamon, David (advisor)
Cílem této práce je příprava keramicko-kovového kompozitu pro balistickou ochranu. Přičemž velká pozornost se klade na rozhraní obou materiálů. Práce popisuje jak vlastnosti používaných keramik a kovů, tak i aplikovatelné mechanické testy Kompozit na bázi oxidu hlinitého a hliníků byl experimentálně připraven metodou gravitačního lití / slinování hliníků, která vedla ke spojení s korundovými hexagony. K dosažení optimálního výsledku a co nejnižší teplotě lití bylo třeba vyzkoušet několik teplotních režimů. Připravené vzorky byly balisticky testovány na základě norem NIJ Standard- 0108.01 a NATO Standard STANAG 2280. Vlastnosti rozhraní byly ověřeny pomocí lomové analýzy vzorků, která zkoumala vzorky poškozené balistickým testováním. Za účelem zkoumání rozhraní byla připraveny speciální zkouška čtyřbodým ohybem. Dále bylo provedeno předběžné zkoumání mikrostruktury hliníku.
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Antibacterial properties of bioceramic materials
Achberger, Šimon ; Částková, Klára (referee) ; Salamon, David (advisor)
Implant surgery carries a risk of infection caused by bacterial contamination of the implant surface. An effective way to inhibit proliferation of bacteria is via antibacterial surfaces, however, their usage is medically and technologically difficult. Previous research shows that cicada wing topography exhibits unique bactericidal properties. In this thesis, various topographies were fabricated using heat treatment under hydrothermal conditions. The goal was to produce a surface covered by high aspect ratio structures with 60–215 nm width and 200–300 nm length. A relative density of 85%, 12 hrs long heat treatment and solution pH 4 and 5,6 had a positive effect on formation of thin surface structures. Quantity of morphological changes was proportional to -tricalcium phosphate content.
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3d shaping of UV curable ceramic feedstock
Mišák, Jiří ; Salamon, David (referee) ; Graule, Thomas (advisor)
Diplomová práce je zaměřena na přípravu koloidních suspenzí, vytvrditelných UV zářením, jenž jsou určeny k 3D tisku komplexních keramických vláknových struktur. Rovněž jsou v práci představeny techniky následného tvarování vytisknutých a vytvrzených struktur. Z hydroxyapatitu ve formě prášku a komponent, vytvrditelných UV zářením, byly vytvořeny pasty, určené k 3D tisku komplexních keramických vláknových struktur a multivrstev. U takto vytisknutých a vytvrzených struktur bylo navíc dosaženo zlepšení kvality povrchu a soudržnosti vláken. Pro výrobu past, určených k 3D tisku, s vhodnými reologickými vlastnostmi je nezbytné důkladné pochopení interakcí mezi částicemi, surfaktantem a monomerní/oligomerní směsí. Za použití lineárních a zesíťujících oligomerů jako disperzního média vznikají po tisku a UV vytvrzení velmi flexibilní vláknové mřížky, které lze dále tvarovat a takto vytvářet rozmanité struktury. Tyto struktury jsou následně slinuty, bez významných vad na povrchu či delaminace vrstev, za vzniku složitých keramických těles. Vysoké kvality povrchu je dosaženo UV vytvrzením vytisknutých struktur v argonové atmosféře, která brání kyslíkové inhibici radikálů v blízkosti povrchu vláken. Výhody kombinace 3D tisku s UV vytvrzováním jsou demonstrovány v této práci za užití dvouvrstvých flexibilních struktur, určených k následným metodám 3D tvarování. Takto vytvořených složitých 3D struktur je jen velmi obtížné, ne-li nemožné, dosáhnout pouze užitím přímého 3D tisku. Na základě této práce může být v budoucnu odvozena univerzální teorie k přípravě past, určených k 3D tisku komplexních keramických struktur pro různé aplikace.
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Light ceramic materials for ballistic protection
Greguš, Peter ; Pouchlý, Václav (referee) ; Salamon, David (advisor)
This thesis gives a comprehensive characterization of lightweight non-oxide ceramic materials for ballistic applications, an overview of production technologies and processing of boron carbide B4C and its ceramic-based composites. A framework for evaluating the ballistic resistance of the material based on mechanical properties is shown there. It can be used in experiments without normalized equipment. The experiments including B4C + Si, B4C + Ti composites, and application of Spark plasma sintering (SPS) were designed according to outputs from the theoretical part. The volume fractions of Si, Ti dopants were optimized based on ongoing chemical reactions during sintering. The obtained samples were subjects of mechanical testing which results were compared to identify the ideal ratio of matrix and reinforcement. As the best suited material for ballistic protection, B4C + 1,0 obj. % reaches these values of parameters; hardness = 3502 ± 122 HV1; fracture toughness KIC = 2,97 ± 0,03 MPam^0,5.
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Study of microstructure evolution during final stage of sintering of advanced ceramic materials
Hrubý, Jan ; Salamon, David (referee) ; Maca, Karel (advisor)
This diploma thesis deals with the study of microstructure development during the final stage of sintering of two zirconia based ceramic materials (tetragonal ZrO2 doped with 3 mol% of Y2O3 and cubic ZrO2 doped with 8 mol% of Y2O3). Conventional, microwave and SPS sintering methods were used. Achieved relative densities and mean grain sizes were evaluated for sintered materials. It was found that the non-conventional sintering methods are capable of rapid processing of ceramics with improved microstructure compared to conventional sintering.
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Shaping of bioceramic hydroxyapatite scaffolds on micro level
Pejchalová, Lucie ; Novotná, Lenka (referee) ; Salamon, David (advisor)
Due to increasing average age of population around the world, there are more patients who need surgery of musculoskeletal system. In some cases, it is even necessary to implant new bone scaffold or replace joints. Hydroxyapatite is the most frequently used material for its biocompatibility and bioactivity. On the other hand, mechanical properties constraints its use in porous scaffolds. The method providing both good mechanical stability and high porosity is freeze – casting. This method utilises controlled freezing to form lamellar structure. During freezing of slurry, ice crystals grow in direction of temperature gradient. In next step, ice crystals are removed by lyophilisation and lamellar structure is revealed. This structure is relatively unstable and needs to be reinforced by sintering. There are many aspects affecting resulting structure – freezing schedule, slurry concentration etc. We used water/ceramic slurries in various concentrations of hydroxyapatite (7,5 % vol., 10 % vol., 15 % vol. and 20 % vol.). These slurries were used for preparation of porous bone scaffolds. We tried to add 3D mash to form net of channels and we observed favourable changes in porosity. 3D mash was removed during sintering. Resulting bioceramics structure was highly porous (up to 90 %). These scaffolds had an acceptable ration between porosity and mechanical stability, too. We considered, adding of 3D mash, as good way to form channels of desired properties.
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