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Light ceramic materials for ballistic protection
Greguš, Peter ; Pouchlý, Václav (oponent) ; Salamon, David (vedoucí práce)
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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Tailoring of phase composition and microstructure of calcium phosphate scaffolds applied in regenerative medicine.
Pejchalová, Lucie ; Novotná, Lenka (oponent) ; Salamon, David (vedoucí práce)
Calcium phosphates are the most used ceramic materials for bone regeneration. Calcium phosphates are biocompatible, bioactive and differ in solubility and related degradation in organism. Therefore, calcium phosphate materials are used to regenerate bone defects of small size and as coatings for metallic implants. The solubility of the used materials in body environment after implantation is determined by the ratio of individual calcium phosphates and related degradation rates. This thesis deals with the impact of shaping methods on microstructure and phase composition of calcium phosphates. Commercial hydroxyapatite powder was used as a starting ceramic powder and was treated by calcination at 800 °C for one hour. The biphasic mixture of hydroxyapatite and -tricalcium phosphate was formed during the calcination and this mixture was used for ceramic suspension preparation, with solid loading of 15 vol%, as well as for green bodies preparation. Samples were prepared using several shaping methods: freeze casting, cold isostatic pressing, uniaxial pressing, and slip-casting. Characterization of both, green bodies and sintered samples was performed and the impact of used shaping methods on microstructure and phase composition, was confirmed. It was also observed that the hydroxyapatite content is increasing with increasing porosity, and pore size. This trend applies for samples with unimodal pore size distribution as well as for samples with bimodal pore size distribution.
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Extremely fast sintering of advanced ceramic materials
Tan, Hua ; Chlup,, Zdeněk (oponent) ; Sedláček,, Jaroslav (oponent) ; Salamon, David (vedoucí práce)
Rapid sintering techniques, such as Spark Plasma Sintering (SPS), Flash Sintering (FS), Selective Laser Sintering (SLS), Induction Sintering (IS), and Microwave Sintering (MS), are designed to effectively and predictably control ceramic microstructure during the sintering process. Spark Plasma Sintering as one of the most novel rapid sintering technique has been studied for decades. There are three main features in SPS: direct Joule heating, pulsed direct current, and mechanical pressure. However, the mechanisms of these features are not clearly and fully addressed. This thesis was inspired by the increasing attention towards rapid sintering techniques and open scientific questions. The present study has four parts, investigation of ‘Field effect’, pulse pattern effect, pressure effect, and direct Joule heating. The results showed the negligible impact of the electromagnetic field during SPS according to the simulation as well as no ‘field effect’ was found during the experiments. While the effect of pulse pattern was significant, the TiO2 powder was sintered by pulse patterns 12:2 and 10:9 with the constant power input. Titania grain size increased one order of magnitude and 8% in density after application of the pulse pattern 10:9, while the amount of consumed energy remained constant. The variation of the effective power and contact resistance induced by the mechanical pulse are two main reasons accounting for the varying energy efficiency heating with different pulse patterns. The pressure timing effect also significantly influenced the SPS. The results showed that applying the pressure at 900 brought high density and small grain size of the sintered alumina nanopowder, leading to the best Vickers hardness. The interaction between pressure and vapor, leading to the different vapor transfer rate of the first sintering stage, was considered as a reason for the differences in microstructure (micropores, grain size, etc.). The timing of the mechanical pressure can also promote the densifying diffusion mechanisms during the second sintering stage, such as grain boundary diffusion and lattice diffusion. The direct Joule heating of the electrically conductive samples by direct electrical current passing through the sample leads to high internal and low measured temperature when sintering boron carbide (B4C) and its composites. Adding titanium alloy and silicon in B4C significantly increased the densification, which was the main reason for the change of mechanical properties. The sample doped by 1 vol. % of Ti alloy (B4C+1.0Ti) reached the hardness 3628.5 ± 452.6 HV1 (16.2% higher than pure boron carbide) with a fracture toughness 2.11 ± 0.25 MPam0.5. The sample doped by 0.5 vol. % of Si (B4C+0.5Si) achieved the hardness 3524.6 ± 207.8 HV1 (13.0% higher than pure boron carbide), the sample B4C+1.0Si achieved the highest fracture toughness 2.97 ± 0.03 MPam0.5 (15.6% higher than pure boron carbide). The grains of titanium doped composites became a bit larger and inhomogeneous compared with the pure boron carbide. In contrast, the grain size of silicon doped samples did not change compared with that of pure boron carbide. The secondary phase silicon carbide was well connected with the boron carbide matrix and showed a great strengthen effect on both the hardness and fracture toughness. This work examined various features of the SPS technique and their effect on ceramic materials, leading to a better understanding of this novel technique.
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Preparation of hybrid ceramic materials by ice-templating
Roleček, Jakub ; Lenčéš,, Zoltán (oponent) ; Jankovský,, Ondřej (oponent) ; Salamon, David (vedoucí práce)
Ice-templating, also known as freeze-casting, is a relatively simple, inexpensive, and very versatile technique to fabricate porous ceramic scaffolds with the controlled microstructure. The prepared scaffolds are used for preparation of hybrid ceramic composites or as bioceramic scaffolds. Hybrid ceramic composites are based on mimicking the architecture of natural/biological materials and structures. The motivation is to emulate nature’s toughening mechanisms by infiltration of polymers into ceramic structures. However, the main problem for an application is size of the prepared scaffolds. Preparation of large scaffolds by ice-templating method requires achieving controlled ice crystals growth throughout the whole sample volume. Thus it is necessary to precisely control the ice-templating process to obtain the well-defined lamellar architecture. Biological activity of bioceramic materials depends on a combination of physical and chemical characteristics that are strongly related to their microstructure. The scaffold porosity has to be interconnected with a sufficiently large pore size for successful bone tissue growth within the whole volume of an implant. Presented Ph.D. dissertation work was focused on scale up of the ceramic scaffolds prepared by ice-templating, creation of multiscale porosity inside the scaffolds, and preparation of hybrid ceramic composites for a ballistic protection. Ceramic suspensions for ice-templating were successfully prepared from different powders (mainly hydroxyapatite and alumina) with different solid loadings of ceramic powder from 7.5 vol.% up to 45 vol.%. The influence of suspension additives on formation of lamellar roughness and interlamellar bridging, and impact of these microstructural elements was studied. Hybrid alumina/polymer composites were successfully designed and prepared from ice-templated alumina plates with lamella length up to 70 mm and various polymeric resins. Mechanical performance of hybrid alumina/epoxy resin composites was tested and the results showed that ice-templating reveals to be the robust method for production of hybrid ceramic-polymer composites with good strength/density ratio. However ballistic tests of ice-templated alumina/polymer hybrid composites revealed that majority of composites presented in this work were not able to efficiently stop armor piercing projectiles. Combination of ice-templating and indirect rapid prototyping has been shown to enable manufacturing of bioceramic scaffolds for bone replacement from hydroxyapatite with multiscale porosity which could prove to be beneficial for the development of highly porous bioactive scaffolds with enhanced biological performance. Ice-templating also significantly modified the phase composition change during the sintering of hydroxyapatite scaffolds.
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Nanášení kovové vrstvy na keramické substráty pro úpravu povrchových vlastností
Dvorský, Vojtěch ; Kachlík,, Martin (oponent) ; Salamon, David (vedoucí práce)
Práce se soustředí na přípravu povlaku niklu na keramický (Al2O3) substrát. Depozice niklu byla provedena technikou bezproudého pokovování v lázni za různých kinetických podmínek. Rovněž byl zkoumán vliv rozměrů, tvarů a drsností povrchu keramických substrátů. Cílem bylo optimalizovat experimentální podmínky lázně pro přípravu tenkých homogenních kovových vrstev. Připravené povlaky niklu byly charakterizovány pomocí rastrovací elektronové mikroskopie, EDX analýzy, mechanické profilometrie a pokovovací lázeň byla analyzována metodou UV-VIS spektrofotometrie. Modifikací procesu depozice bylo dosaženo souvislých povlaků niklu na keramickém substrátu a byl popsán kinetický mechanismus sledovaného experimentálního systému lázně.
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Impact of macro channels on mechanical stability of bone scaffolds during indirect 3D printing
Vojníková, Michaela ; Novotná, Lenka (oponent) ; Salamon, David (vedoucí práce)
Porous materials are currently subject to the great interest of tissue engineering. They provide unique properties such as bioactivity, biodegradability, osteoconductivity, and vascularization. Particularly, ceramic porous systems show appreciable potential in medical applications. However, there is a crucial problem with the porous scaffold on account of their bad mechanic properties and therefore they are presently used only at low-load locations. This thesis focuses on the preparation of the scaffolds made of hydroxyapatite by using the freeze-casting method where the indirect 3D printing was applied to get open channels with the size over 200 µm. It also compares the mechanical properties of the scaffolds with different internal structures and monitors how the implementation of different types of grids affects the resulting stability. The scaffolds were prepared with a different arrangement of macro-channel in the internal structure, but they had equal dimensions as common property. The 3D grid was implemented before freezing into the mold and afterward the grid was eliminated by sintering, leaving only a channel system with the size 540-600 µm in the final scaffold. The influence of the type of the 3D grid on the resulting mechanical stability of the scaffold was determined. Rotation of this grid does not have a significant effect on the result, while it only helps with cracking in the direction of the helix. The combination of these methods reports very good controllability with directed macro-channels in the resulting scaffold and therefore it is suitable for the preparation of the bone-implants with different structures.
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Tailoring of cooling procedure during freeze-casting for bone replacement applications.
Šantavý, Tomáš ; Novotná, Lenka (oponent) ; Salamon, David (vedoucí práce)
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 (oponent) ; Salamon, David (vedoucí práce)
Aim of this bachelor thesis is fabrication of ceramic-metal composite for ballistic protection, the main focus is on the materials interface. Properties of used ceramic and metal materials are described as well as applicable mechanical tests. Alumina / aluminum composite was prepared experimentally by gravity casting/sintering of aluminium among the alumina hexagons. Various temperature conditions were tested to achieve the optimal casting conditions at the lowest possible temperature. Prepared composite was tested by a ballistic impact according to NIJ Standard-0108.01 and NATO Standard STANAG 2280. Properties of the aluminium/alumina interface were verified by the fracture analysis of damaged samples and by a special version of four-point beam bending test. Also, a brief examination of aluminium microstructure was made.
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Využití 3D tisku k přípravě pokročilých keramických materiálů
Klusáček, Martin ; Kachlík, Martin (oponent) ; Salamon, David (vedoucí práce)
V této závěrečné práci jsou shrnuty hlavní metody 3D tisku sloužící ke tvarování pokročilé keramiky, vzájemné srovnání a zmínění jejich předností a nevýhod. V experimentální části byly připraveny dva druhy keramických suspenzí, které byly použity k ověřování možnosti využití komerčně dostupné 3D tiskárny k automatizovanému odlévání do silikonových forem a k přímému tisku 2D tvaru. Následně byly analyzovány výsledky na základě reprodukovatelnosti metody a relativních hustot vzorků. Z hlediska hmotností jednotlivých odlitků bylo dosaženo přesnosti 5,3 % a bylo zjištěno, že lze dosáhnout relativní hustoty vzorků přes 98 % s přesností 1 %.
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Zviditelnění a analýza mikrostruktury částečně slinutých oxidových keramických materiálů
Jemelka, Marek ; Salamon, David (oponent) ; Spusta, Tomáš (vedoucí práce)
Bakalářská práce má za úlohu experimentálně stanovit vhodné parametry leptacích procedur pro leptání částečně zhutnělých keramických materiálů (Al2O3, ZrO2 + 3mol. % Y2O3, ZrO2 + 8mol. % Y2O3) s důrazem na minimální ovlivnění výsledné mikrostruktury. Z výsledků vyplývá, že optimální leptací procedurou pro zvolené materiály je termální leptání za podmínek: Al2O3 (rel. 95,7 ± 0,9 %)- Tlept. = 1015 C (Ts – 350 C), tetragon. ZrO2 (rel. 94,5 ± 0,6 %)- Tlept. = 1005 C (Ts – 350 C), kubic. ZrO2 (rel. 94 ± 0,5 %)- Tlept. = 1105 C (Ts – 350 C). Užitím chemického leptání v prostředí H3PO4 s výdrží 60s je u Al2O3 a kubického ZrO2 možné dosáhnout naleptaného stavu povrchu v kratších časech, nicméně náročnost provedení a volby vhodných parametrů řadí tuto proceduru až za leptání termální. Zviditelnění mikrostruktury vybraných materiálů pomocí iontového svazku bylo experimentálně stanoveno jako nevhodné z důvodu časové a personální náročnosti metody.
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