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Ceramic nanofiber-reinforced composites
Bocian, Luboš ; Přikryl, Radek (referee) ; Poláček, Petr (advisor)
This thesis investigated how the addition of unsilanized and silanized ceramic SiO2 nanofibers into particle reinforced composite affects flexural strength, fracture toughness, total fracture work and temperature dependence of viscoelastic properties. Fracture surfaces were analyzed with SEM. Flexural strength always decreased with addition of nanofibers. Composites with silanized nanofibers showed higher flexural strength than those with unsilanized nanofibers. Fracture toughness was higher with addition of nanofibers. Fracture toughness of composites with silanized nanofibers was always lower than that of systems with unsilanized nanofibers. Total fracture work was lower with addition of nanofibers, but sharply increased in composites with 5 % of nanofibers. Glass transition temperature almost always increased with addition of nanofibers. Storage modulus increased with addition of nanofibers. Storage modulus was always lower in composites with silanized nanofibers.
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Nanostructured surfaces for biomedical applications
Kratochvíl, Jiří ; Kylián, Ondřej (advisor) ; Baroch, Pavel (referee) ; Čech, Vladimír (referee)
Nanostructured thin films deposited by magnetron sputtering and gas aggregation sources of nanoparticles are studied especially with regards to their use in biomedical applications. The possibility of using plasma polymers for the preparation of antibacterial coatings is tested first. It is presented that sputtered nylon 6,6 films may be impregnated by antibiotics. The subsequent release of antibiotics from such prepared reservoirs may be tuned by their thickness, chemical composition, or by an additional barrier layer. The second studied type of antibacterial coatings is based on metallic nanoparticles overcoated with sputtered PTFE. It is shown that by a proper choice of the number of nanoparticles and thickness of fluorocarbon overlayer, a significant antibacterial effect can be achieved while maintaining the biocompatibility of produced nanocomposite coatings. The possibility to enhance the antibacterial effect by impregnation of plasma polymer/nanoparticle nanocomposites by antibiotics is also verified. Nanoparticle sources are used to study two-component films with 2D gradient character, too. A simple analytical model is developed allowing description and design of such nanomaterials. Its suitability is experimentally verified on 2D gradients combining Ag and Cu nanoparticles. Finally, an original...
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Quantum-mechanical study of magnetic properties of superalloy nanocomposite phase Fe2AlTi
Slávik, Anton ; Miháliková, Ivana ; Friák, Martin ; Všianská, Monika ; Šob, Mojmír
The L21-structure Fe2AlTi intermetallic compound is one of the two phases identified in Fe-Al-Ti superalloy nanocomposites. Experimental data related to low-temperature magnetic properties of this Heusler compound indicate that magnetic moment is about 0.1 Bohr magneton per formula unit. In contrast, previous quantum-mechanical calculations predicted Fe2AlTi to have much higher magnetic moment, 0.9 Bohr magneton per formula unit. In order to solve this discrepancy between the theory and experiment we have performed a series of quantum-mechanical fix-spin-moment calculations and compared our results with those for non-magnetic state. It turns out that the total energy of the non-magnetic state is only by 10.73 meV/atom higher than that of the magnetic state. When applying Boltzmann statistics to this very small energy difference we predict that the non-magnetic state appears at non-zero temperatures with significant probabilities (for instance, 22.36 % at T = 100 K) and reduces the overall magnetic moment. As another mechanism lowering the magnetization we studied selected shape deformations, in particular trigonal shearing. Fe2AlTi exhibits a compression-tension asymmetry with respect to these strains and, for example, the strain 0.08 destabilizes the spin-polarized state, leaving the non-magnetic state as the only stable one.
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First-principles study of interface energies in Fe-Al-based superalloy nanocomposites
Miháliková, Ivana ; Slávik, Anton ; Friák, Martin ; Všianská, Monika ; Koutná, N. ; Holec, David ; Šob, Mojmír
Fe-Al-based nanocomposites with a superalloy-type of microstructure constitute a very promising class of materials. They possess a great potential as an alternative to the currently used steel grades in high temperature applications. Intermetallics-containing nanocomposites, such as those with the Fe3Al compound being one of the phases, may open a way towards future automotive and energy-conversion technologies with lower fuel consumption and reduced environmental impact. We employ quantum-mechanical calculations to analyze relations between ordering tendencies of Al atoms in the disordered Fe-18.75at.%Al phase on one hand and thermodynamic, structural and magnetic properties of Fe-Al-based nanocomposites on the other. When comparing supercells modeling disordered Fe-Al phase with different atomic distribution of atoms we find out that the supercell without 1st and 2nd nearest neighbor Al-Al pairs has a lower energy than that mimicking a perfect disorder (a special quasi-random structure, SQS). Further, coherent interfaces with (001), (110) and (1-10) crystallographic orientations between Fe3Al compound and SQS Fe-Al phase have higher energies than those exhibiting atomic distribution without 1st and 2nd nearest neighbor Al-Al pairs.
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Self-assembling hybrid nanomaterials
Rodzeń, Krzysztof ; Strachota, Adam (advisor) ; Svoboda, Jan (referee) ; Matějíček, Pavel (referee)
Organic-inorganic polymer hybrids containing butyl stannoxane dodecamer cages (Sn_POSS) as nano-building blocks were prepared and investigated. Sn_POSS was employed as a linear, crosslinking or non-bonding molecularly blended unit. For this purpose, it was synthesized with two acrylamido, primary- or secondary amino, or with two additional non- functional groups, which were attached via ionic-bonded sulfonate substituents. The nano- building block was then incorporated in matrices such as PS, PAOS, PETA, PEMA, PHEMA and PPO-based epoxies (the latter with different mesh sizes). Sn_POSS reinforces the studied matrixes by filler-filler interactions (self-assembly to nano-domains). Specific interactions of the ionic bonds of Sn_POSS with suitable pendant groups of the matrixes also can generate reinforcement and suppress filler aggregation. Moreover, the Sn_POSS can undergo several types of chemical reactions like heat-induced oligomerization, dissociation of the ionic substituents, acidolysis of the Sn-butyl bonds, as well as radical reactions of the latter. The influence of ionically bonded cages on the hybrids' morphology, as well as their ability of dissociation and short-distance migration in the polymer network at elevated temperature, was evaluated by TEM, IR and NMR analyses. The mechanical...
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Nanoclusters coatings for biomedical applications
Divín, Radek ; Kylián, Ondřej (advisor) ; Hanuš, Jan (referee)
Title: Nanoclusters coatings for biomedical applications Author: Radek Divín Department: Department of Macromolecular Physics (110. 32-KMF) Supervisor: RNDr. Ondřej Kylián, Ph.D. Abstract: The copper nanocluster films were prepared with the aid of the gas cluster aggregation source based on the principle of material sputtering from the magnetron target to the relatively high pressure of the working gas (Ar). The nanocluster films prepared in this way were subsequently overlapped with the layer of plasma polymer deposited by RF magnetron sputtering from the nylon polymer target in the atmosphere of the working gas (Ar, 2 Pa). A repetition of this procedure enabled to prepare nanocomposite layers having a multilayer character. These layers were subsequently investigated with regard to their morphology, chemical composition, surface wettability and optical properties. The chemical composition of the surface layer formed by nanocomposite films was determined by the X-ray photoelectron spectroscopy (XPS). It turned out that the chemical surface composition of prepared nanocomposites was not markedly influenced by the presence of the Cu nanoclusters. The morphology of prepared films was studied by the scanning electron microscopy (SEM) and the atomic force microscopy (AFM), which showed that the resulting...
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Ultrathin films deposited by means of magnetron sputtering and their characterization
Petr, Martin ; Kylián, Ondřej (advisor) ; Straňák, Vítězslav (referee) ; Tichý, Milan (referee)
Presented work is focused on the deposition and characterization of thin and ultrathin plasma polymer films, then also on the preparation of nanocomposites metal/plasma polymer. The characterization of plasma polymer films was partly done in-situ without exposing the samples to the atmosphere. The thickness of prepared films was measured by spectral ellipsometry, the chemical composition was measured by XPS. The morphology and optical properties of deposited films were measured ex-situ. It is shown that during the initial stages of growth the properties of plasma polymer films depend on their thickness and also on the material of the substrate. Many interesting applications were explored for prepared nanocomposites metal/plasma polymer. They can be used as superhydrophobic coatings, gradient coatings, substrates for Raman spectroscopy or as antibacterial coatings. Moreover, special optical properties of prepared nanocomposites were studied in detail. Presented work has an experimental character.
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Study of electric properties of nanocomposit material
Ovsík, Jiří ; Rozsívalová, Zdenka (referee) ; Polsterová, Helena (advisor)
This work deals with the electrical properties of nanocomposite materials. Samples for the experiment are made of epoxy resin as matrix and titanium dioxide TiO2 as nanofillers in varying percentage performance. Measurements are temperature dependent components of the permittivity, dissipation factor and resistivity. Furthermore, the internal resistivity is observed with regard to the percentage performance of a sample of nanoparticles.
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Structure and Properties of Collagen/HAP Nanocomposite Networks
Kopuletá, Ema ; Lehocký,, Marián (referee) ; Amler,, Evžen (referee) ; Jančář, Josef (advisor)
Polymerní biomateriály jsou jedním ze současných populárních témat vzhledem k možnosti potenciální aplikace v tkáňovém inženýrství a řízeného dávkování léčiv v organismech. Kolagen je jako jeden z nejčastěji se vyskytujících proteinů zvláště zajímavý díky svým rozmanitým vlastnostem bez imunoreakce organismu příjemce. Tato práce je zaměřena na samouspořádávací procesy, kinetiku, obecné zákonitosti řídící proces samouspořádání a mechanické vlastnosti kolagenních roztoků. Dále je zkoumán efekt hydroxyapatitových nanočástic na samouspořádávání kolagenu a mechanické vlastnosti výsledných nanokompozitních hydrogelů. Jsou objasněny možné mechanismy interakcí mezi kolagenem I a hydroxyapatitem spolu s popisem vývoje struktury a vlastností na různých úrovních struktury. Byly měřeny a molekulárně interpretovány závislosti viskoelastických veličin na smykové rychlosti spolu s viskoelastickým chováním. Dále byla studována struktura kolagenních scaffoldů a určen vliv HAP a síťování. Závěrem byly diskutovány výsledky v souvislosti s jejich aplikovatelností v tkáňovém inženýrství chrupavek tvrdých tkání a v regenerativní medicíně.
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Study of electric properties of nanocomposites
Libra, Miroslav ; Rozsívalová, Zdenka (referee) ; Polsterová, Helena (advisor)
The present master´s thesis deals with the electrical properties of nanocomposite materials. Samples for the experiment are made epoxi resin and oxides TiO2 and Al2O3 as nanofillers in different percent performace. The samples nanocomposites are measured temperature dependence of the resistivity inside, dissipation factor and relative permittivity. It discusses the effect of the filler on the resulting electrical properties of the polymer.
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