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Studium vývoje mikrostruktury pokročilých keramických materiálů v poslední fázi slinování
Hrubý, Jan ; Salamon, David (oponent) ; Maca, Karel (vedoucí práce)
Tato diplomová práce se zabývá studiem vývoje mikrostruktury v poslední fázi slinování dvou keramických materiálů na bázi ZrO2 (tetragonálního ZrO2 dopovaného 3 mol% Y2O3 a kubického ZrO2 dopovaného 8 mol% Y2O3). Pro jejich slinování bylo použito konvenčního, mikrovlnného a SPS slinování. U slinutých materiálů byla hodnocena jejich dosažená relativní hustota a střední velikost zrn. Bylo zjištěno, že použité nekonvenční metody slinování umožňují v krátké době připravit keramický produkt se zlepšenou mikrostrukturou ve srovnání s konvenčním slinováním.
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Tvarování hydroxyapatitu na mikro úrovni pro přípravu kostních náhrad
Pejchalová, Lucie ; Novotná, Lenka (oponent) ; Salamon, David (vedoucí práce)
Vhledem k celosvětovému stárnutí populace, dochází k častější potřebě opravy pohybového aparátu. V některých případech je proto nutno přejít v konečné fázi k implantaci kostní náhrady. Nejčastěji je pro svoji biokompatibilitu a bioaktivitu využíván hydroxyapatit, který je v kostech přirozeně zastoupen. Využití hydroxyapatitu jako materiálu pro kostní náhrady je omezeno mechanickou stabilitou v porézních systémech. Metoda, při které bylo dosaženo nejlepšího poměru mechanické stability a porozity, se nazývá freeze – casting. Tato metoda využívá tvorbu ledu (v případě vodných suspenzí) ke tvorbě lamelární struktury během kontrolovaného mražení. Dalším krokem je odstranění ledových krystalů lyofilizací. Následně je výsledná porézní lamelární struktura zpevněna slinutím. Změnou složení suspenze nebo podmínek mražení lze dosáhnout různé mezilamelární vzdálenosti, spojení lamel a porozity. V této práci byly připraveny keramické suspenze v objemovém zastoupení hydroxyapatitu 7,5 %, 10 %, 15 % a 20 %, které byly použity při přípravě porézních kostních náhrad metodou freeze – casting. Během mražení byla do struktur implementována 3D mřížka, která posloužila jako šablona pro síť kanálků (v průměru cca 800 mikrometrů). Po lyofilizaci byly následným ohřevem odstraněny z materiálu organické látky, včetně 3D mřížky. Výsledná biokeramická struktura dosáhla porozity víc než 90 % a velmi dobrého poměru mechanické stability a porozity. Implementace 3D mřížky se ukázala být vhodnou metodou pro kontrolovanou tvorbu kanálků s dostatečným rozměrem, sloužící k zvýšení bioaktivity materiálu.
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Bioceramic materials bioactivity testing via simulated body fluid
Holbusová, Eva ; Novotná, Lenka (oponent) ; Salamon, David (vedoucí práce)
These days, there is a possibility of joint replacement implantation, more common dental implants, or regeneration of bone fractures using bone graft replacements is more accessible than in history. Bioceramic materials are used for these purposes. Bioceramics is a non-toxic ceramic material. It is characterized by its bioactivity and biocompatibility. Bioactivity testing of bioceramics is performed using simulated body fluid (SBF). In addition, the change in the concentration of calcium ions was investigated during the testing. The aim of the work was to determine whether the concentration of calcium ions changes between bioceramics and SBF. Bioceramic samples were prepared by two methods, namely freeze-casting and cold isostatic pressing. What was soaked in c-SBF was prepared according to Kokubo. The analysis of SBF was performed using a colorimetric method with a reagent of Murexide solution and reagent KIT. The concentration of calcium ions in the SBF after soaking samples in a testing cycle 0, 3, 7, 14, and 21 days was measured using a UV/VIS spectrophotometer. In addition, X-ray diffractometry was used to determine the phase composition of the material before soaking in SBF. The change in calcium ion concentration during the test cycle in the bioceramic – SBF system was confirmed with UV/VIS spectrophotometry. The most significant increase in concentration was recorded on the third day of soaking. The assumption of an apatite layer formation on the soaked bioceramic samples was supported by a change in the concentration of calcium ions SBF and the change in weight of the material after soaking. It was found that using indirect colorimetric determination delivered better results when the Murexide indicator was used instead of KIT.
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Preparation of thin wall ceramic hollow fibers by dip-coating
Gockert, Radek ; Maca, Karel (oponent) ; Salamon, David (vedoucí práce)
This master thesis deals with the production of ultrathin ceramic hollow fibers by dip-coating. Preparation of ceramic hollow fibres is nowadays limited by dimension of outer and inner diameter. Application of dip-coating for preparation of ultrathin hollow fibers is new and technologically demanding process that requires the choice of a suitable sacrificial template, while mastering the control of coating parameters. The basic materials selected with high application potential are hydroxyapatite and titanium dioxide. Self-supporting hollow fibers with wall thickness below 1 m were successfully prepared from both materials. Furthermore, dip-coating process of thin sacrificial templates was described. This method is unique because it allows the production of ultrathin ceramics fibers with an outside diameter below 100 m and a wall thickness below 1 m.
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Tvarování biokeramiky metodou povlakování namáčením
Gockert, Radek ; Částková, Klára (oponent) ; Salamon, David (vedoucí práce)
Tato bakalářská práce se zabývá popisem základních tvarovacích metod biokeramických materiálů, speciálně popisem metody povlakování namáčením. Následně experimentální část prezentuje použití této metody k přípravě keramických mikro jednotek z hydroxyapatitu, obsahujících mikro kanálek vhodných pro transport médií v živé tkáni. V rámci této metody také popisuje možnosti modifikace tohoto procesu pro tvorbu kapek a stabilního filmu. V následném slinovacím procesu dává do souvislosti vliv teploty a kalcinaci výchozího prášku na výslednou mikrostrukturu, konkrétně porozitu a velikost zrna. V rámci práce byly připraveny mikro jednotky z hydroxyapatitu o velikosti od 50 µm do 1 mm s různou porozitou a velikostí mikro kanálku.
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Neural bioceramic scaffold prepared by freeze-casting
Vojníková, Michaela ; Pejchalová, Lucie (oponent) ; Salamon, David (vedoucí práce)
Several procedures have been investigated for the regeneration of injured nerves. However, the resulting axonal growth can be random or disorganized and has limitations reflected on patient recovery. Therefore, the novel freeze-casted scaffolds were manufactured with mechanical and microstructural properties suitable for the neural scaffold. Concretely, the bioceramic scaffolds were based on calcium phosphates, titania, and zirconia. The oriented microstructure was prepared by controlled ice growth in one direction. The observation with scanning electron microscopy confirmed linearly oriented pores (lamellar system) in which average pore size decreased with a higher freezing rate. According to the results, the scaffolds prepared by freezing in liquid nitrogen showed excellent mechanical properties, where flexural strength was in the range of 10–17 MPa. Interlamellar distances of these scaffolds were 10–30 µm, which are appropriate for neural scaffolds. Biocompatibility was evaluated with Schwann cells’ line in vitro, where the adhesion and growth in the lamellar direction were observed. Cytotoxic tests revealed a negative impact of a high calcium level on Schwann cell’ survival. The prepared scaffolds could form an apatite layer on its surface in the form of embryonic and nucleation centers and apatite itself. Calcium phosphate and titania scaffolds exhibited promising regenerative characteristics of adhesion and ingrowth through porous structures with outstanding mechanical properties.
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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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Highly porous ceramic materials prepared by Spark Plasma Sintering
Barančíková, Miriama ; Spusta, Tomáš (oponent) ; Salamon, David (vedoucí práce)
Porous ceramic materials are an interesting group of materials due to a wide range of physical properties, low density, and good permeability. Production of a monolith with a shape stability that would also have a high specific surface area and high porosity is a common problem with porous ceramics. The goal of this work was to maintain the high specific surface area and to produce a monolith with a shape stability. Two forms of porous silica nanofibers (as prepared and milled) were used and partially sintered using the Spark Plasma Sintering method (SPS). Different sintering times and temperatures for SPS were tested. The findings revealed that the best SPS conditions were as follows: temperature: 600 °C, sintering time: 5 minutes, pressure: 3 MPa, and the heating rate: 144 °C/min. These sintering conditions resulted in a stable silica based machinable monolith made from fibers or milled fibers. The monoliths have the specific surface area of up to 470 m^2/g and porosity of 72 %, or the specific surface area of up to 422 m^2/g and porosity of 69 % for as prepared fibers and milled fibers, respectively.
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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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Bioceramic materials bioactivity testing via simulated body fluid
Holbusová, Eva ; Novotná, Lenka (oponent) ; Salamon, David (vedoucí práce)
These days, there is a possibility of joint replacement implantation, more common dental implants, or regeneration of bone fractures using bone graft replacements is more accessible than in history. Bioceramic materials are used for these purposes. Bioceramics is a non-toxic ceramic material. It is characterized by its bioactivity and biocompatibility. Bioactivity testing of bioceramics is performed using simulated body fluid (SBF). In addition, the change in the concentration of calcium ions was investigated during the testing. The aim of the work was to determine whether the concentration of calcium ions changes between bioceramics and SBF. Bioceramic samples were prepared by two methods, namely freeze-casting and cold isostatic pressing. What was soaked in c-SBF was prepared according to Kokubo. The analysis of SBF was performed using a colorimetric method with a reagent of Murexide solution and reagent KIT. The concentration of calcium ions in the SBF after soaking samples in a testing cycle 0, 3, 7, 14, and 21 days was measured using a UV/VIS spectrophotometer. In addition, X-ray diffractometry was used to determine the phase composition of the material before soaking in SBF. The change in calcium ion concentration during the test cycle in the bioceramic – SBF system was confirmed with UV/VIS spectrophotometry. The most significant increase in concentration was recorded on the third day of soaking. The assumption of an apatite layer formation on the soaked bioceramic samples was supported by a change in the concentration of calcium ions SBF and the change in weight of the material after soaking. It was found that using indirect colorimetric determination delivered better results when the Murexide indicator was used instead of KIT.
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