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Tailoring of phase composition and microstructure of calcium phosphate scaffolds applied in regenerative medicine.
Pejchalová, Lucie ; Novotná, Lenka (referee) ; Salamon, David (advisor)
Vápenaté fosforečnany jsou nejčastěji využívané keramické materiály v medicíně pro regeneraci kostní tkáně. Vápenaté fosforečnany jsou biokompatibilní, bioaktivní a mezi sebou se odlišují především rozpustností a související degradací v organismu, proto jsou nejčastěji využívány k regeneraci malých defektů nebo jako vrstvy na kovových implantátech. U již zmíněné rozpustnosti materiálu po implantaci, hraje důležitou roli poměr zastoupení jednotlivých vápenatých fosforečnanů, od kterého se pak odvíjí rychlost degradace materiálu v organismu. Tato práce se zabývá vlivem tvarovacích metod na mikrostrukturu a zejména fázové složení vápenatých fosforečnanů. Výchozím materiálem pro pozorování změn ve fázovém složení byl komerční hydroxyapatit, který byl upraven kalcinací při 800 °C po dobu jedné hodiny. Při kalcinaci došlo k vytvoření dvoufázové směsi, obsahující hydroxyapatit a -fosforečnan vápenatý. Tato dvoufázová směs byla poté využita pro přípravu suspenze s plněním 15 obj.%, a také k přímé přípravě polotovarů s různou výslednou mikrostrukturou a fázovým složením. S cílem zjistit vliv procesu byly v této práci porovnány vzorky připravené pomocí metod: freeze-casting, izostatické lisování za studena, uniaxiální lisování a suspenzní odlévání. U polotovarů a slinutých vzorků byla provedena charakterizace mikrostruktury a analýza fázového složení. V práci se potvrdil vliv tvarovací metody na oba stanovené parametry – mikrostrukturu a fázové složení. Nově pak bylo zjištěno, že se zvyšující se hodnotou porozity a velikostí pórů se zvyšuje i zastoupení hydroxyapatitu ve vzorcích. Tento trend byl pozorován u vzorků vykazujících unimodální i bimodální zastoupení velikosti pórů.
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Bioceramic Materials for Advanced Medical Applications
Novotná, Lenka ; Lapčík,, Lubomír (referee) ; Drdlíková, Katarina (referee) ; Cihlář, Jaroslav (advisor)
Cílem disertační práce bylo připravit trojrozměrné biokeramické podpůrné systémy („skafoldy“), které by v budoucnu mohly pomoci při rekonstrukci a regeneraci poškozených kostních tkání. Porézní keramické pěny byly připraveny dvěma způsoby – replikační technikou a polymerizací in situ. Co se složení týče, byly studovány keramické materiály zejména na bázi oxidu hlinitého, zirkoničitého a kalcium fosfátů. Byl studován jednak vliv procesních parametrů jako je složení suspenzí a jejich viskozit, dále pak vliv tepelného zpracování na strukturu a výsledné vlastnosti připravených materiálů. U slinutých pěn byla pomocí rastrovací elektronové mikroskopie hodnocena zejména morfologie – velikost pórů, jejich propojenost a celková porozita, charakterizace mikrostruktury nebyla opomenuta. Dále bylo stanoveno fázové složení a pevnost v tlaku. Z biologických vlastností byla testována a diskutována bioaktivita a cytotoxicita materiálů. Disertační práce je členěna do několika částí. V literární rešerši je popsána stavba a vlastnosti kosti, požadavky kladené na kostní náhrady, výhody a nevýhody současně používaných materiálů a způsoby přípravy keramických pěn. Následuje experimentální část, kde byly nejprve studovány pěny připravené replikační technikou. Všechny takto vyrobené pěny měly propojené póry o velikostech 300 až 2000 m, celková porozita se pohybovala v rozmezí 50 – 99 %. Pevnost pěn na bázi kalcium fosfátů – 0,3 MPa (při celkové porozitě 80%) byla nedostatečná pro kostní náhrady, kde je požadována pevnost větší než 2 MPa. Kalcium fosfátové keramiky byly tedy zpevněny buďto inertním jádrem na bázi oxidu hlinitého nebo ATZ (oxidem zirkoničitým zhouževnatělým oxidem hlinitým). Dále byl přípraven částicový kompozit, ve kterým byl hydroxyapatit pojený oxidem křemičitým. Pevnost pěn se podařilo zvýšit až na více než 20 MPa. V poslední kapitole experimentální části byly studovány keramické pěny pěněné in situ, kde byly póry vytvářeny oxidem uhličitým unikajícím během reakce mezi diisokyanátem a polyalkoholem. Po vypálení polymerního pojiva měly pěny propojené póry o průměrné velikosti 80 až 550 m. Celková porozita se pohybovala v rozmezí 76 – 99%. Výhodou oproti replikační technice byly plné trámečky bez velké středové dutiny vznikající vypálením polymerní předlohy. Žádný ze studovaných materiálů nebyl pro buňky toxický, navíc všechny studované pěny vykazovaly bioaktivní chování. Z hlediska kostního tkáňového inženýrství se jako nejslibnější jeví kompozitní materiál zpevněný oxidem křemičitým.
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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 large and complex-shaped ceramics parts
Prehradná, Jana ; Pouchlý, Václav (referee) ; Trunec, Martin (advisor)
This bachelor’s thesis deals with research of ceramic materials in field of material engineering. The first part deals with biomaterials, especially bioceramics, its types, properties and its usage. The second part of this thesis deals with transparent ceramics and the third part includes the procedure and method of gel casting. The experimental part is dedicated to production of large and complex shaped components - knee joint, spherical cover and discs with transparent properties. The method of gelcasting was used for samples preparation of this type. The task was not only to produce these samples, but also to find suitable surrounding conditions for the proper course of the entire production process.
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Preparation and properties of machinable ceramic materials
Sláma, Martin ; Matoušek, Aleš (referee) ; Cihlář, Jaroslav (advisor)
The thesis is focused on studying the machinability of ceramic material in dependence on presintering temperature. Alumina was used as an experimental material. The machinability of alumina was observed on samples produced by uniaxial pressing. Presintered and not-presintered disks were machined by cutter. Disks were presintered at 700°C, 800°C, 900°C and 1000°C for one or two hours. Machinability of alumina was tested according to four levels of the milled depth and according to temperature and the effect of dwell.
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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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Bioceramic materials bioactivity testing via simulated body fluid
Holbusová, Eva ; Novotná, Lenka (referee) ; Salamon, David (advisor)
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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Study of bioceramic materials on the base of calcium phosphates
Kolář, Martin ; Maca, Karel (referee) ; Cihlář, Jaroslav (advisor)
The literature search on the topic of Bioceramic materials focused in layered materials based on calcium phosphates was written up. Based on knowledge obtained, experiments of preparation of calcium phosphates layered materials based on calcium phosphates by spin-coating method focused in optimalization of layer application conditions were designed and carried out. Experiments of preparation of hydroxyapatite bulk ceramics by uniaxial pressing followed by heat treatment were also performed. Prepared layered and bulk ceramics were characterized from bioactivity point of view by testing of their interaction with simulated body fluid.
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Shaping of bioceramics by dip-coating
Gockert, Radek ; Částková, Klára (referee) ; Salamon, David (advisor)
The presented bachelor thesis describes basic shaping methods of bioceramic materials, especially a description of the dip-coating method. Subsequently, the experimental part of the thesis presents the usage of this method for the preparation of ceramic micro units sintered from hydroxyapatite, and containing micro channel suitable for transporting media in living tissue. Tailoring of the process leads to the formation of variable droplets and films, subsequent sintering process used temperature control and calcination of the starting powder to achieve microstructure with controlled porosity and grain size. Micro units with diameter from 50 µm to 1 mm with variable porosity and micro channels were prepared from hydroxyapatite.
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Study of bioceramic composite based on hydroxyapatite and bioglass
Virágová, Eliška ; Hadraba, Hynek (referee) ; Drdlík, Daniel (advisor)
This bachelor thesis is focused on the bioceramic composite materials based on hydroxyapatite (HAp) and bioglass (BG). The wet shaping method, i.e. electrophoretic deposition (EPD), was chosen for the preparation of these materials. The methodology of preparation and its influence on kinetics, relative density and pore distribution in the prepared composites was evaluated. The sintering process of the prepared composites was studied using high temperature dilatometry with subsequent evaluation of their microstructural and mechanical features. It was found that EPD is an applicable method for successful preparation of the particle composites. The microstructural quality of particle composites was affected mainly by the electrical conductivity of the suspension. It was found during the study of EPD kinetics that the highest deposition rate was achieved in the suspension with the lowest electrical conductivity. Increasing amount of BG in HAp caused increase of the relative density and pore diameter whereas the volume of pores decreased. High temperature dilatometry showed a decrease of relative shrinkage, which was evident with increasing HAp amount in the structure. Observation of the microstructure revealed a crystalline structure of BG and an open porosity of HAp, which is desired for biocompatible materials. The phase composition of the materials was determined by X-ray diffraction analysis. In case of the mechanical properties it was found an increase of the hardness and Young’s modulus of elasticity with the increasing amount of BG in bioceramic composites. Based on the obtained results the suitable process and material composition for the planned preparation of the functionally graded material were identified.
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