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Model of static recrystallization in the coarse-grained B2 iron aluminide
Schindler, I.; Šumšal, V.; Kopeček, Jaromír; Kawulok, P.; Jozwik, P.; Rusz, S.; Kawulok, R.; Opěla, P.
2014 - English
Microstructure of the laboratory castings made from Fe-40at.%Al-Zr-B alloy was homogenized by the multipass hot rolling in protective capsules and subsequent lannealing. Based on the isothermal hot compression tests and EBSD analysis, the sufficiently accurate model describing the static recrystalization kinetics of the such prepared coarse-grained B2 iron aluminide after strain 0.2 was developed. The independent variables in this model are temperature of deformation as well as annealing time equal to the deformation temperature. Unexpected effect of the previous strain value on the static softening was observed. Static recrystallization begins relatively easy in the studied alloy in the whole range of testing temperatures (900-1100 °C), but a very long-term annealing is quite necessary for the complete course of recrystallization.\n
Keywords:
iron aluminide; hot compression test; microstructure; EBSD; static recrystallization
Available at various institutes of the ASCR
Model of static recrystallization in the coarse-grained B2 iron aluminide
Microstructure of the laboratory castings made from Fe-40at.%Al-Zr-B alloy was homogenized by the multipass hot rolling in protective capsules and subsequent lannealing. Based on the isothermal hot ...
Nanopositioning with detection of a standing wave
Holá, M.; Hrabina, J.; Číp, O.; Fejfar, Antonín; Stuchlík, Jiří; Kočka, Jan; Oulehla, J.; Lazar, J.
2014 - English
A measuring technique is intended for displacement and position sensing over a limited range with detection of standing-wave pattern inside of a passive Fabry-Perot cavity. In this concept we consider locking of the laser optical frequency and the length of the Fabry-Perot cavity in resonance. Fixing the length of the cavity to e.g. a highly stable mechanical reference allows stabilizing wavelength of the laser in air and thus to eliminate especially the faster fluctuations of refractive index of air due to air flow and inhomogeneity. Detection of the interference maxima and minima within the Fabry-Perot cavity along the beam axis has been tested and proven with a low loss transparent photodetector with very low reflectivity. The transparent photodetector is based on a thin polycrystalline silicon layer. Reduction of losses was achieved thanks to a design as an optimized set of interference layers acting as an antireflection coating. The principle is demonstrated on an experimental setup.
Keywords:
nanometrology; nanopositioning; Fabry-Perot cavity; standing wave; interferometry
Available at various institutes of the ASCR
Nanopositioning with detection of a standing wave
A measuring technique is intended for displacement and position sensing over a limited range with detection of standing-wave pattern inside of a passive Fabry-Perot cavity. In this concept we consider ...
Characterisation of InAs/GaAs quantum dots by high resolution transmission electron microscopy
Zíková, Markéta; Hospodková, Alice; Pangrác, Jiří; Hulicius, Eduard; Komninou, Ph.; Kioseoglou, J.
2014 - English
The InAs/GaAs quantum dots (QDs) covered by GaAsSb strain reducing layer (SRL) have suitable properties for various applications. The GaAsSb SRL covering InAs QDs is used to improve the structure growth and the final parameters like QD density, QD size or photoluminesence. To obtain high-quality structure with required properties, the structure growth and final structure have to be deeply studied. Since the QDs and SRL system is surrounded by GaAs, the high resolution transmission electron microscopy (HRTEM) measurement was used to reveal the real material arrangement in a prepared sample. In this work we will discuss the results of following HRTEM measurements: flatness and thickness of prepared layers, QD size, atomic arrangement and composition of GaAsSb layer.
Keywords:
quantum dot; InAs; GaAsSb; high resolution transmission electron microscopy
Available at various institutes of the ASCR
Characterisation of InAs/GaAs quantum dots by high resolution transmission electron microscopy
The InAs/GaAs quantum dots (QDs) covered by GaAsSb strain reducing layer (SRL) have suitable properties for various applications. The GaAsSb SRL covering InAs QDs is used to improve the structure ...
Applications of self-assembled 2D polystyrene nanosphere arrays
Domonkos, Mária; Ižák, Tibor; Demo, Pavel; Kromka, Alexander
2014 - English
In this study nanosphere lithography (NSL) is demonstrated to be a low-cost, parallel and material independent fabrication process for creating periodic arrays of nanostructures using self-assembled nanospheres as templates. SA is the most feasible way to fabricate 2D or 3D colloidal crystals on large areas. After the mask preparation NSL uses different steps of plasma etching and deposition processes. The resulting patterned nanostructures have a wide range of applications in many important areas such as photonics, antireflection, surface wetting, biological and chemical sensing, solar cells, etc. This study focuses on an overview of applications of 2D colloidal crystals. First, structuring of substrate surfaces and the creation of various nano-objects (nanotips, nanopillars, nanocones) is shown. Next, direct growth of patterned structures (graphene nanomesh and diamond structures) is pointed out.
Keywords:
nanosphere lithography; nanostructuring; polystyrene microspheres; reactive ion etching
Available at various institutes of the ASCR
Applications of self-assembled 2D polystyrene nanosphere arrays
In this study nanosphere lithography (NSL) is demonstrated to be a low-cost, parallel and material independent fabrication process for creating periodic arrays of nanostructures using self-assembled ...
Photocatalytic activity of ZnxCd.sub.1-x./sub.S quantum dots in dependence on their composition
Praus, P.; Svoboda, L.; Hospodková, Alice; Mamulová-Kutláková, K.
2014 - English
ZnxCd1-xS quantum dots (QDs) with the different composition x were prepared by precipitation of Zn and Cd acetates with sodium sulphide from aqueous colloid dispersions. Transition energies of these QDs were determined from UV-VIS spectra of the QDs colloid dispersions and consequently used for calculation of the QDs sizes according to the Schrödinger equation. The ZnCdS QDs size was found to be significantly influenced by their composition, decreased with increasing the Zn content. The QDs were also characterized by TEM, X-ray powder diffraction and PL. The photocatalytic activity of the QDs was studied using the methylene blue decomposition under UV irradiation with the maximum intensity of 365 nm. Different photocatalytic activity depending on the composition x was observed. Quantum levels of the QDs have important influence on their photocatalytic activity as a result of quantum size effect. The maximal photocatalytic activity was achieved for x=0.6.
Keywords:
quantum dots; ZnCdS; photocatalysis
Available at various institutes of the ASCR
Photocatalytic activity of ZnxCd.sub.1-x./sub.S quantum dots in dependence on their composition
ZnxCd1-xS quantum dots (QDs) with the different composition x were prepared by precipitation of Zn and Cd acetates with sodium sulphide from aqueous colloid dispersions. Transition energies of these ...
Production of nitrogen vacancy centers in nanocrystalline diamond thin film for quantum biosensing applications
Jakl Krečmarová, Marie; Gulka, Michal; Fekete, Ladislav; Remeš, Zdeněk; Petráková, Vladimíra; Mortet, Vincent; Nesládek, M.
2014 - English
Due to its excellent properties such as chemical stability and biocompatibility, diamond is an ideal material for bio sensing application. In particular, nitrogen vacancy (NV) centres in diamond are promising candidates for optical bio-sensing application in nanodiamond particles and single crystal diamond by irradiation (electron, proton, neutron, particles) followed by annealing has been recently developer. Production of NV centres in CVD diamond thin film is important for fabrication of new bio sensor.
Keywords:
nanocrystalline diamond; nitrogen vacancy centre; nitrogen doping; MW PECVD; photoluminescence
Available at various institutes of the ASCR
Production of nitrogen vacancy centers in nanocrystalline diamond thin film for quantum biosensing applications
Due to its excellent properties such as chemical stability and biocompatibility, diamond is an ideal material for bio sensing application. In particular, nitrogen vacancy (NV) centres in diamond are ...
Silver catalysed nanoscale silicon etching in water vapour
Křížek, Filip; Pikna, Peter; Fejfar, Antonín
2014 - English
N+-doped silicon substrates were etched by water vapour under the silver nanoparticles acting as a catalyst. Thin silver layer was deposited on two silicon wafers, where one of them was thermally annealed in nitrogen to create silver nanoparticles. Subsequently, both samples were annealed in water vapour and afterwards analysed by Scanning Electron Microscope. The images have shown that the annealed silver nanoparticles burrowed into the silicon substrate in the case of both samples. This new method of silicon etching introduces an alternative way of manufacturing nanohole arrays in silicon substrates.\n
Keywords:
silicon etching; water vapour; silver nanoparticles; thermal annealing
Available at various institutes of the ASCR
Silver catalysed nanoscale silicon etching in water vapour
N+-doped silicon substrates were etched by water vapour under the silver nanoparticles acting as a catalyst. Thin silver layer was deposited on two silicon wafers, where one of them was thermally ...
The deposition of amorphous and amorphous hydrogenated silicon with embedded cubic Mg.sub.2./sub.Si nanoparticles
Stuchlíková, The-Ha; Stuchlík, Jiří; Remeš, Zdeněk; Fajgar, Radek; Galkin, N.G.; Galkin, K.N.; Chernev, I.M.
2014 - English
We study possibilities how to increase a by usage of magnesium silicide nanoparticles (Mg2Si-NPs) in structure of Si: H. In this paper we introduce two technics -combination of PECVD and Vacuum Evaporation (VE) and Reactive Laser Ablation (RLA) -for preparation of cubic structure of Mg2Si-NPs in amorphous (a-Si) or amorphous hydrogenated (a-Si: H) silicon matrix. Formation of Mg2Si-NPs was proved by Raman spectroscopy. Likewise we introduce optical changes measured at absorption edge and the first results on realized NIP structures.
Keywords:
Mg.sub.2./sub.Si nanoparticles; a-Si/a-Si:H matrix; RDA; PECVD; RLA
Available at various institutes of the ASCR
The deposition of amorphous and amorphous hydrogenated silicon with embedded cubic Mg.sub.2./sub.Si nanoparticles
We study possibilities how to increase a by usage of magnesium silicide nanoparticles (Mg2Si-NPs) in structure of Si: H. In this paper we introduce two technics -combination of PECVD and Vacuum ...
Influence of dispersed particles on utility properties od polyvinyl alcohol-based nanotextiles: macromechanical properties
Rácová, Z.; Nežerka, V.; Ryparová, Pavla; Kromka, Alexander; Tesárek, Pavel
2014 - English
The paper deals with the influence of different dispersed particles on utility properties of polyvinyl-alcohol (PVA) based nanofiber textiles. The purpose of the dispersed particles was to produce textiles of antibacterial character, and these were added into water-polymer solution, which was used for electrospinning in two various ways: in form of copper and silver ions, or in form of diamond nanoparticles. In order to assess the strength of textiles, macromechanical testing of modified PVA-based nanofiber textiles was carried out on samples with variable weight per area in range between 0.5 and 5 g/m(2). The obtained results were compared with the results of measurements on plain reference samples. The study revealed that the addition of silver ions causes the strength and stiffness reduction, the addition of copper ions has an opposite effect, while the diamond nanoparticles did not have any significant influence on the mechanical properties.\n
Keywords:
macromechanical properties; polymer nanofibers; dispersed particles; stiffness; tensile strength
Available at various institutes of the ASCR
Influence of dispersed particles on utility properties od polyvinyl alcohol-based nanotextiles: macromechanical properties
The paper deals with the influence of different dispersed particles on utility properties of polyvinyl-alcohol (PVA) based nanofiber textiles. The purpose of the dispersed particles was to produce ...
Effect of H- and O-termination of nanocrystalline diamond films on cell adhesion and osteogenic differentiation
Lišková, Jana; Babchenko, Oleg; Varga, Marián; Kromka, Alexander; Hadraba, Daniel; Švindrych, Zdeněk; Bačáková, Lucie
2014 - English
In order to control the hydrophobic or hydrophilic character, the NCD film surfaces were grafted by hydrogen atoms (H-termination) or by oxygen atoms (O-termination). Human mesenchymal stem cells and primary human osteoblasts were used for biological studies on H- and O-terminated NCD films. We found that cells cultivated on O-terminated NCD films exhibit better adhesion than H-terminated NCD films. In addition, the expression of osteogenic cell markers collagen and alkaline phosphatase analysed by Realtime PCR and immunostaining was higher on O-terminated films.
Keywords:
nanocrystalline diamond film; osteoblast; MSC; type I collagen; paxillin
Available at various institutes of the ASCR
Effect of H- and O-termination of nanocrystalline diamond films on cell adhesion and osteogenic differentiation
In order to control the hydrophobic or hydrophilic character, the NCD film surfaces were grafted by hydrogen atoms (H-termination) or by oxygen atoms (O-termination). Human mesenchymal stem cells and ...
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