|
|
Příprava keramických vláken elektrostatickým zvlákňováním
Nemčovský, Jakub ; Kaštyl, Jaroslav (oponent) ; Částková, Klára (vedoucí práce)
Diplomová práca je zameraná na prípravu keramických vlákien elektrostatickým zvlákňovaním. Teoretická časť diplomovej práce zhrňuje doposiaľ známe informácie v oblasti keramických vlákien, ich vlastností, aplikácií a výroby. Teoretická časť tiež popisuje proces elektrostatického zvlákňovania ako jednu z najpoužívanejších metód výroby nanovlákien a parametre, ktoré tento proces ovplyvňujú. Experimentálna časť je zameraná na prípravu keramických vlákien na báze oxidu titaničitého, čistého nedopovaného oxidu zirkoničitého a ytriom dopovaného oxidu zirkoničitého metódou elektrostatického zvlákňovania a na charakterizáciu takto pripravených vlákien. Zvlákňované boli keramické prekurzory zložené z propoxidu a polyvinylpyrolidonu. Experimentálna časť diplomovej práce tiež popisuje vplyv zloženia prekurzoru, procesných podmienok a teploty kalcinácie na morfológiu a fázové zloženie vlákien. Prekurzory boli charakterizované pomocou merania viskozity. K popisu vlákien bola použitá termogravimetrická analýza (TGA), röntgenová analýza (RTG) a elektrónová rastrovacia mikroskopia (SEM). Elektrostatickým zvlákňovaním prekurzorov na báze propoxidu titaničitého a následnou kalcináciou pri teplote 500 až 1300 °C boli pripravené TiO2 vlákna s hrúbkou 100 až 2500 nm, pričom sa fázové zloženie s kalcinačnou teplotou menilo od anatasovej fázy, cez zmes s rutilom až po čistý rutil. Elektrostatickým zvlákňovaním prekurzorov na báze propoxidu zirkoničitého a následnou kalcináciou pri teplotách 550 až 1100 °C boli pripravené ZrO2 vlákna dopované 0 – 8 mol.% Y2O3 s hrúbkou v rozmedzí 50 až 1000 nm. Analýza vlákien na báze nedopovaného ZrO2 kalcinovaných na teplotu 550 °C ukázala prevažujúce zloženie monoklinickej fáze. Analýza 3 resp. 8 mol.% Y2O3 dopovaného ZrO2 kalcinovaných na teplotu 900 °C ukázala zloženie prevažujúcej tetragonálnej fáze resp. zloženie čisto kubickej fáze. V závislosti na zvyšujúcej sa teplote kalcinácie dochádzalo ku zmene morfológie vlákien od poréznej nanoštruktúry po retiazkovitú neporéznu štruktúru, ktorá bola tvorená mikrometrovými zrnami TiO2, resp. ZrO2. Vlákna ZrO2 po kalcinácii na teplotu 700 °C zostávali stále pružné, rovnako ako tie zvláknené (as spun), pričom so zvyšujúcou sa teplotou kalcinácie sa zvyšovala aj ich krehkosť.
|
|
|
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.
|
|
|
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.
|
|
|
Application of Electronic Continuum Correction to Molecular Simulations of Nano/Bio Interfaces
BIRIUKOV, Denys
Nowadays it is almost impossible to imagine our life without nanotechnologies. They are present in smartphones and many other gadgets we use every day, while advanced nanoparticle-based devises are currently indispensable in medicine, engineering, and science. In the case of biomedical applications, the knowledge how a specific nanomaterial behaves and changes its properties in complex physiological medium is essential to guarantee the accomplishment of all specific goals facing a scientist or engineer. Some of physical and chemical processes occurring when a nanodevice enters biological environment are yet very difficult to fully detail without accurate computer simulations, so special attention needs to be focused on theoretical studies of nano-bio interactions. In this thesis, molecular simulations were used to investigate the interactions between different nanomaterials (titanium dioxide, silicon dioxide, and gold) and aqueous solutions, which contain ions, organic molecules, and amino acids. The importance of this scope and particularly selected for this study materials and compounds is given in Introduction. To model nano/bio interfaces, we adopted and integrated recent theoretical approaches, which together with basic principles of molecular simulations are described in Methods. Obtained results are divided in four parts and address several important issues that are vital in deciphering molecular mechanisms, through which nanoparticles identify and bind various biomolecules. The simulation data are thoroughly discussed, compared to experiments, and used to explain some of experimental observations. Additionally, outcomes of this thesis serve as a springboard for further theoretical studies aimed to advance our understanding of nano-bio interactions.
|
|
|
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.
|
|
|
Suspension plasma spraying of sub-stoichiometric titania by hybrid water/argon stabilized plasma torch
Mušálek, Radek ; Ctibor, Pavel ; Medřický, Jan ; Tesař, Tomáš ; Kotlan, Jiří ; Lukáč, František
In this study, suspension plasma spraying of sub-stoichiometric titania was attempted using hybrid water/argon stabilized plasma torch (WSP-H). Porous coatings with fine cauliflower-like columnar microstructure were successfully deposited in two separate experiments with different power levels of the plasma torch. In both cases, high solid-load content (40 wt. %) of the water-based suspension resulted in considerable coating thickness increase per deposition cycle. Coating annealing and partial remelting of the surface asperities were also achieved by additional pass of plasma torch in front of the coating surface. According to X-ray diffraction, all coatings consisted dominantly of rutile phase. Detailed microscopic observation of the as-sprayed and annealed deposits showed that the local coloration of the coating (ranging from dark blue to beige) was driven by the local overheating of the rough coating surface which could also promote the oxygen intake. Moreover, sample annealing was also observed to increase the sample reflectivity as observed by UV-VIS-NIR scanning spectrophotometry
|
|
|
Příprava keramických vláken elektrostatickým zvlákňováním
Nemčovský, Jakub ; Kaštyl, Jaroslav (oponent) ; Částková, Klára (vedoucí práce)
Diplomová práca je zameraná na prípravu keramických vlákien elektrostatickým zvlákňovaním. Teoretická časť diplomovej práce zhrňuje doposiaľ známe informácie v oblasti keramických vlákien, ich vlastností, aplikácií a výroby. Teoretická časť tiež popisuje proces elektrostatického zvlákňovania ako jednu z najpoužívanejších metód výroby nanovlákien a parametre, ktoré tento proces ovplyvňujú. Experimentálna časť je zameraná na prípravu keramických vlákien na báze oxidu titaničitého, čistého nedopovaného oxidu zirkoničitého a ytriom dopovaného oxidu zirkoničitého metódou elektrostatického zvlákňovania a na charakterizáciu takto pripravených vlákien. Zvlákňované boli keramické prekurzory zložené z propoxidu a polyvinylpyrolidonu. Experimentálna časť diplomovej práce tiež popisuje vplyv zloženia prekurzoru, procesných podmienok a teploty kalcinácie na morfológiu a fázové zloženie vlákien. Prekurzory boli charakterizované pomocou merania viskozity. K popisu vlákien bola použitá termogravimetrická analýza (TGA), röntgenová analýza (RTG) a elektrónová rastrovacia mikroskopia (SEM). Elektrostatickým zvlákňovaním prekurzorov na báze propoxidu titaničitého a následnou kalcináciou pri teplote 500 až 1300 °C boli pripravené TiO2 vlákna s hrúbkou 100 až 2500 nm, pričom sa fázové zloženie s kalcinačnou teplotou menilo od anatasovej fázy, cez zmes s rutilom až po čistý rutil. Elektrostatickým zvlákňovaním prekurzorov na báze propoxidu zirkoničitého a následnou kalcináciou pri teplotách 550 až 1100 °C boli pripravené ZrO2 vlákna dopované 0 – 8 mol.% Y2O3 s hrúbkou v rozmedzí 50 až 1000 nm. Analýza vlákien na báze nedopovaného ZrO2 kalcinovaných na teplotu 550 °C ukázala prevažujúce zloženie monoklinickej fáze. Analýza 3 resp. 8 mol.% Y2O3 dopovaného ZrO2 kalcinovaných na teplotu 900 °C ukázala zloženie prevažujúcej tetragonálnej fáze resp. zloženie čisto kubickej fáze. V závislosti na zvyšujúcej sa teplote kalcinácie dochádzalo ku zmene morfológie vlákien od poréznej nanoštruktúry po retiazkovitú neporéznu štruktúru, ktorá bola tvorená mikrometrovými zrnami TiO2, resp. ZrO2. Vlákna ZrO2 po kalcinácii na teplotu 700 °C zostávali stále pružné, rovnako ako tie zvláknené (as spun), pričom so zvyšujúcou sa teplotou kalcinácie sa zvyšovala aj ich krehkosť.
|
|
|
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.
|
|
|
Deposition of Titania from Solution by Hybrid Water-Stabilized Plasma Torch
Mušálek, Radek ; Medřický, Jan ; Tesař, Tomáš ; Kotlan, Jiří ; Lukáč, František
Thermal spraying with liquid feedstock presents a novel route for deposition of functional coatings. In this study, possibility of preparation of titania coatings from solution by hybrid water stabilized plasma torch is presented. Coatings were prepared from solution of titanium isopropoxide Ti[OCH(CH3)2]4 in anhydrous ethanol. Fragmentation of feedstock stream in the plasma jet was monitored by shadowgraphy. Deposition was carried out on steel samples mounted to the cooled rotating carousel. Cross-sectional images from SEM microscope showed successful formation of the deposit with dual morphology consisting of fine feather-like features combined with bigger droplets. X-ray diffraction revealed formation of nanometric rutile crystallites.
|
|
| |
host ::
RSS.