Národní úložiště šedé literatury Nalezeno 13 záznamů.  1 - 10další  přejít na záznam: Hledání trvalo 0.01 vteřin. 
DEPOSITION OF PVP-PROTECTED PLATINUM NANOPARTICLES ON SEMICONDUCTOR SUBSTRATES FOR HYDROGEN SENSING
Černohorský, Ondřej ; Yatskiv, Roman ; Grym, Jan
High quality Schottky diode hydrogen sensors were prepared by the deposition of colloidal graphite on n-type InP substrates partly covered with PVP-protected Pt nanoparticles (NPs). A sub-monolayer of the Pt NPs was created by simple evaporation of the solvent in which Pt NPs were dispersed. The Pt NPs serve to dissociate hydrogen molecules into atomic hydrogen, which is absorbed at the metal-semiconductor interface. Hydrogen absorption leads to the formation of the dipole layer, which changes the Schottky barrier height and results in the increase of both forward and reverse current. The proposed hydrogen sensor showed high sensitivity response of similar to 10(6) to 1000 ppm H-2 in N-2 at room temperature
Use of iron nanoparticles for post-treatment of metal finishing wastewater
Matysíková, J. ; Sukopová, M. ; Škvoran, O. ; Holba, Marek
This study evaluated the efficiency of copper, nickel and zinc removal from industrial metal finishing wastewater using nZVI material in lab and pilot scale conditions. Initial concentrations of Cu, Ni and Zn in raw wastewater were 3.16 mg/L, 0.38 mg/L and 0.56 mg/L, respectively. All metals were presented in residual concentrations and difficult to remove. Copper concentration was lowered by 77.2% in lab scale and 85.2% in pilot scale test for nZVI dose of 400 mg/L after 3 hours of reaction. Removal efficiency of nickel was 51% in the lab scale and 85.2 % at the pilot scale. Decrease of zinc concentration was less significant and reached 35.4% and 40% in lab and pilot scale experiment, respectively. Increase of efficiency in pilot scale testing was caused by the application of nZVI under inert atmosphere which ensured the preservation of high iron reactivity. pH adjustment before the nZVI dosing had also significant influence for efficiency of reaction. No changes and fluctuations of temperature and conductivity were observed. Pilot-scale test with lower dose of nZVI was performed to reveal the surpluses of previous dose of iron. The dose of 300 mg nZVI/L was applied into the reactor under inert atmosphere with pH adjustment before iron dosing. Efficiency of metals removal dropped to the 70% and 70.1% for copper and nickel. Efficiency of zinc removal increased to the 60.5%. nZVI dose of 300 mg/L was sufficient for reaching of limits for wastewater discharge.
Microfltration nanofibrous membrane for wastewater treatment
Lev, J. ; Holba, Marek ; Došek, M. ; Kalhotka, L. ; Detvanová, L. ; Dostálová, L. ; Přichystalová, J. ; Vincent, I. ; Kimmer, D.
Pilot testing of nanofiber membrane module demonstrated long-term stability of the filtration process in activated sludge and showed the applicability in real-world conditions at the wastewater treatment plant. Microbial contamination of samples of the filtrate reached log removal 2 CFU/mL. Filtration in combination with UV irradiation resulted in a reduction of microbial contamination under required legislative standards. These results supported our assumptions to use nanofibre membranes in membrane bioreactor. Regeneration, optimization and antifouling surface treatment will be another step to increase the competitiveness of nanofiber membranes for water treatment.
RESPONSE OF SURFACE MORPHOLOGY IN COBALT-FULLERENE MIXTURE FILMS UPON VARIATION OF THE METAL CONTENT
Lavrentiev, Vasyl ; Lavrentieva, Inna ; Vacík, Jiří
The morphology and roughness of the films show great change around some critical composition x(c) of the mixture film (x(c) approximate to 3). The films with lower Co content (x < 3) is rather smooth and the roughness is rather low. However, if x >= 3, the roughness of the CoxC60 films dramatically increases and sharp protrusions appear on the surface that reflects an important phase transformation in the film structure. The obtained AFM results define the concentration interval of the Co solubility in solid C-60 (x < 3), which was found to be narrower than that evaluated from spectroscopic experiments (see the text). This interval suggests a formation of the Co1C60 and Co2C60 fullerides in the CoxC60 mixtures where the Co atoms occupy the tetrahedral holes in the fullerene lattice. The dramatic change of the surface morphology at x >= 3 reflects the pronounced Co clustering which likely occurs due to numerical filling the octahedral pores. Formation of the protrusions on the surface of the supersaturated CoxC60 mixture films (x > 3) is a consequence of the compressive stress arising in the film due to the Co clustering.
IMPEDANCE MEASUREMENT OF GAS SENSORS WITH NICKEL(II)-AND COPPER(II)-OXIDE ACTIVE LAYERS
Horák, Pavel ; Khun, J. ; Vrňata, M. ; Bejšovec, Václav ; Lavrentiev, Vasyl ; Vacík, Jiří
Thin layers (90 nm) of nickel(II)- and copper(II)- oxide were deposited onto ceramic sensor substrates equipped with interdigital electrodes for signal reading. The deposition was carried out in two or three steps: (i) sputtering by means of Ar ion beam from pure (99.99%) metal targets, (ii) following thermal oxidation (400 degrees C for 5 h) in air, (iii) in some cases - sputtering of Pd catalyst to the surface. Then the impedance response of produced sensors (NiO, NiO+Pd, CuO, CuO+Pd) to 1000 ppm of hydrogen and 1000 ppm of methanol vapor was measured. Impedance measurements were performed in the frequency range from 40 Hz to 100 MHz. The obtained data were depicted in Nyquist representation (i.e. imaginary vs. real part of complex impedance). These diagrams have a character of one complete and one incomplete semicircle, each of them corresponding to a parallel RC-element. It was proved, that both NiO and CuO behave like p-type semiconductors; the sensor impedance increases on exposure to reducing gases. The best sensitivity was achieved on NiO+Pd sensor - during detection of hydrogen (1000 ppm) the real part of complex impedance measured at 40 Hz increased from 120 to 350 Omega.
Tuning the Photophysical Properties of Anti-B18H22 [1]
Braborec, Jakub ; Černá, H. ; Benkocká, M. ; Kolská, Z. ; Londesborough, Michael Geoffrey Stephen
The tuning of the photophysical properties of the highly fluorescent boron hydride cluster anti-B18H22 (1), by straight-forward chemical substitution to produce 4,4'-(HS)(2)-anti-B18H20 (2), facilitates intersystem crossing from excited singlet states to a triplet manifold.[1] This subsequently enhances O-2((1)Delta(g)) singlet oxygen production from a quantum yield of Phi(Delta) similar to 0.008 in 1 to 0.59 in 2. This contribution describes the synthesis and full structural characterization of the new compound 4,4'-(HS) 2-anti-B18H20 (2) and uses UV-vis spectroscopy coupled with DFT and ab initio computational studies to delineate and explain its photophysical properties. Additionally, we will report on new fluorescent derivatives of anti-B18H22 and their immobilisation on solid nanostructured substrates.
Influence of inhaled manganese oxides nanoparticles on mass of internal organs in mice
Zeman, T. ; Dočekal, Bohumil ; Mikuška, Pavel ; Buchtová, Marcela ; Míšek, Ivan ; Šerý, Omar ; Večeřa, Zbyněk
Results of the statistical analysis of a long-term inhalation experiment on laboratory mice are presented. During 17 weeks of the experiment, the experimental group was exposed to inhaled manganese oxides nanoparticles. Manganese oxides (MnO.Mn2O3) nanoparticles (MnONPs) were synthesized continuously via aerosol route in a hot wall tube flow reactor using a thermal decomposition of metal organic precursor manganese(II)acetylacetonate in the flow tube reactor (in vertical position) at temperature 750 °C in the presence of 30 vol% of oxygen. The concentration of produced MnONPs at the reactor output was in the range 1-3 × 107 particles/cm3 and the size of generated nanoparticles MnO.Mn2O3 was in the range 7-50 nm. Before entering the inhalation chamber, MnONPs in the mixture of N2, O2 and air (at total flow rate of 3 L/min) were further diluted using filtrated humidified air (20 L/min) at temperature 21 °C resulting in the MnONPs concentration 2 × 106 particles/cm3. At regular time intervals the mass of selected internal organs of mice from both experimental and control group was assessed. It has been proven that inhaled nanoparticles are able to influence the mass of internal organs of mice. Statistically significantly lower mass of kidneys, liver and spleen and higher mass of pancreas have been found in the experimental group compared to the control group.
A Comparison of Different Measurement Method of Mechanical Properties of Al Thin Film
Truhlář, M. ; Buršíková, V. ; Sobota, Jaroslav ; Kruml, Tomáš
The paper compares two different methods for testing of metallic thin films: microcompression test and nanoindentation. Microcompression test is one possibility how to perform mechanical tests on a very small scale. This method requires preparation of a small cylindrical specimen (micropillar) of micrometric size by FIB and execution of a compression test using nanoindenter device equipped with a flat diamond punch. Stressstrain curves of the thin films were obtained from such tests. Nanoindentation tests were then conducted to compare the results on the same films. Two different metal thin films – AlCuW, AlCuSi with thickness 2 .mu.m and grain size 3.8 .mu.m in average were prepared by PVD method. In this paper, we announce the results of measurements, a comparison of the results obtained by each method and identify advantages and limitations of the methods.
E-beam Nano-patterning for Electroforming Replication
Krátký, Stanislav ; Kolařík, Vladimír ; Urbánek, Michal ; Paták, Aleš ; Horáček, Miroslav ; Matějka, Milan
This contribution deals with nano-patterning by the way of electron beam lithography with satisfying requirements for electroforming replication of desired patterns. Electron beam lithography can be used for creating nano graphics (images, text etc.) due to its very high resolution and precision. However, patterns created by electron beam lithography cannot be applied for mass production directly because of resist material soft nature (usually a polymer material). Because of that, hard printing plate must be produced. Nickel plate prepared by electroforming is one of the ways to accomplish that. Prior to the production of nickel plate by electroforming, the surface of polymer material has to be covered by a sufficiently thick layer of metal. This procedure can lead to a partial destruction of the motif (completely covered by metal) thus the decreasing of nano graphics resolution. In this paper several nano graphics (images and text with various resolutions) are prepared in positive resist PMMA (thickness of 2000 nm) by e-beam lithography. Chemical developer (pentyl acetate) was used for wet developing of prepared patterns. The sputtering of silver (100 nm) was carried out to achieve sufficient thickness of conductive layer for electroforming. Electron scanning microscope was used for evaluation, which one of the images and texts are still recognizable.
Some Other Gratings: Benchmarks for Large-Area E-Beam Nanopatterning
Meluzín, Petr ; Horáček, Miroslav ; Urbánek, Michal ; Bok, Jan ; Krátký, Stanislav ; Matějka, Milan ; Chlumská, Jana ; Kolařík, Vladimír
E-beam lithography is a flexible technology for diffraction gratings origination. Nevertheless, requirements of the high optical quality of large area diffractive structures imply various severe challenges to e-beam delineating processes. This paper summarizes the e-beam process parameters that influence the quality of large area grating structures. Next, we propose some new methods to prepare diffraction gratings that were found to be useful for testing and benchmarking purposes. Those methods include single line gratings, labyrinth structures, fractional structures, tiling patterns, quasi regular filling structures and forked line structures. Various samples were prepared with the standard and newly developed e-beam patterning processes using both e-beam writers available: one with the Gaussian beam at 100 keV and another one with the shaped beam at 15 keV. Some of the results are presented further in this paper, their variants and parameters are discussed as well as their usefulness as benchmarking e-beam patterns for large area optical structures, elements and devices.

Národní úložiště šedé literatury : Nalezeno 13 záznamů.   1 - 10další  přejít na záznam: