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Personal exposure measurement during dental nanocomposite grinding
Ždímal, Vladimír ; Ondráčková, Lucie ; Ondráček, Jakub ; Schwarz, Jaroslav ; Bradna, P. ; Roubíčková, A. ; Pelclová, D. ; Rössnerová, Andrea
The purpose of this study was to measure the personal exposure of each participant of the study and to compare the results with those of static monitoring. Personal nanoparticle sam-plers (PENS), which can simultaneously detect both nanoparticles (PM0.1) and respirable parti-cles (PMA), were used to determine personal exposure (Tsai et al., 2012). Area monitoring in-cluded measurement of mass concentrations using the Berner Low Pressure Impactor (BLPI 25/0.018 /2, Hauke GmbH, Gmunden, Austria) and the Low Volume Sampler (LV5, Sven Leckel Ingenieurbüro GmbH, Germany). The number concentrations and their size distributions were measured with the Scanning Mobility Particle Sizer (5MP5 3936, T5I Inc., USA) and the Aerody-namic Particle Sizer (APS 3321, TSI Inc., USA). Measurements with all of the above- mentioned instruments were performed in four shifts with six participants per shift. Each participant milled for 10 minutes and then remained in the room until the group finished the session, so the total exposure lasted about 70 minutes. Due to the high content of filler nanoparticles, the nanocom-posite Filtek Ultimate (body A2, 3M ESPE, USA) was selected for these measurements.
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Biomarkers of Oxidative Stress and Inflammation in Researches Exposed to Nanoparticles by Inhalation During the Handling of Nanocomposites.
Pelclová, D. ; Ždímal, Vladimír ; Schwarz, Jaroslav ; Komarc, M. ; Vlčková, Š. ; Fenclová, Z. ; Lischková, L. ; Dvořáčková, Š. ; Rössnerová, Andrea ; Rössner ml., Pavel
At present, little is known about the health effects in the workers processing nanocomposites. In our study, 20 researchers (41.8 +/- 11.4 y/o), handling nanocomposites for 17.8 +/- 10.0 years were examined pre-shift and post-shift, together with 21 controls (42.7 +/- 11.5 y/o). Biomarkers of oxidative stress derived from lipids, nucleic acids, proteins and markers of inflammation were analyzed in the exhaled breath condensate (EBC). Aerosol exposure was monitored during three nanoparticle generation operations: smelting, welding and nanocomposite machining. Mass concentrations during these operations ranged from 0.120 to 1.840 mg/m(3), and median particle number concentrations from 4.8x10(4) to 5.4x10(5) particles/cm(3). Nanoparticles accounted for 40 to 95 % of particles, with Fe and Mn prevailing. Significant elevations were already seen in most oxidative stress markers and in several inflammation markers in the pre-shift samples relative to the controls. Significant associations were found between working in nanocomposite synthesis and the majority of EBC biomarkers. Chronic bronchitis was more frequent in researchers. A minor, but significant post-shift decrease of lung function parameters was found. We conclude that workers in nanocomposite synthesis may be at risk of developing airway disorders with time. From all the markers analyzed in EBC, the following markers were most robust and could be recommended for preventive examinations: 8-hydroxy-2-deoxyguanosine (8-OHdG) and 5-hydroxymethyl uracil (5-OHMeU) from nucleic acids, o-tyrosine (o-Tyr) and 3-nitrotyrosine (3-NOTyr) from proteins, and malondialdehyde and aldehydes C6-C13 from lipids. Among the markers of inflammation, tumor necrosis factor (TNF) and leukotriene B4 appeared to be the most useful.
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Antimicrobial properties of photo-polymerized 3D printed nanocomposites
Matonohová, Zuzana ; Sevriugina, Veronika (referee) ; Lepcio, Petr (advisor)
This diploma thesis deals with the preparation and characterization of nanocomposites suitable for 3D printing by masking stereolithography (MSLA) and emphasis on the antimicrobial properties of prepared nanocomposites. The theoretical part of the work is devoted to research on additive production and 3D printing, materials suitable for 3D printing using the MSLA method and nanocomposites. The experimental part of the work then deals with the preparation of individual composites containing nanoparticles (ZnO, AZO, TiO2 and carbon nanotubes) and their subsequent testing. The printability of the material was monitored by Jacobson working curves and differential scanning photocalorimetry (photo-DSC), then the structure of the composite was evaluated by Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), mechanical properties were monitored by dynamic-mechanical analysis (DMA) and tensile tests. The main point of this work were antimicrobial tests, which were performed on printed composite samples and on the nanoparticles themselves.
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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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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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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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