Number of found documents: 530
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COMPARISON OF S-CO2 POWER CYCLES FOR NUCLEAR ENERGY
Veselý, L.; Dostál, V.; Entler, Slavomír
2016 - English
The supercritical carbon dioxide (S-CO2) is a possible cooling system for the new generations of nuclear reactors and fusion reactors. The S-CO2 power cycles have several advantages over other possible coolants such as water and helium. The advantages are the compression work, which is lower than in the case of helium, near the critical point and the S-CO2 is more compact than water and helium. The disadvantage is so called Pinch point which occurs in the regenerative heat exchanger. The pinch point can be eliminated by an arrangement of the cycle or using a mixture of CO2. This paper describes the S-CO2 power cycles for nuclear fission and fusion reactors. Keywords: S-CO2; power cycle; fusion Available at various institutes of the ASCR
COMPARISON OF S-CO2 POWER CYCLES FOR NUCLEAR ENERGY

The supercritical carbon dioxide (S-CO2) is a possible cooling system for the new generations of nuclear reactors and fusion reactors. The S-CO2 power cycles have several advantages over other ...

Veselý, L.; Dostál, V.; Entler, Slavomír
Ústav fyziky plazmatu, 2016

Plazmové stříkání z kapalné fáze: interakce kapaliny s proudem plazmatu a vznik nástřiku
Tesař, Tomáš; Mušálek, Radek; Medřický, Jan; Lukáč, František
2016 - Czech
Plazmové stříkání z kapalné fáze je rychle se rozvíjejícím odvětvím žárového stříkání. Hybnou silou vývoje jsou unikátní vlastnosti, které vrstvy deponované z kapalné fáze nabízejí, jako je vysoká tvrdost, vysoká odolnost vůči tepelným šokům či nízká tepelná a elektrická vodivost. Klíčovým faktorem ovlivňujícím výsledný vzhled a vlastnosti vyrobeného nástřiku je zvolený vstupní materiál, kterým může být suspenze jemného prášku či roztok. Parametry dané suspenze (koncentrace pevné fáze, viskozita, povrchové napětí, chemické složení, atd.) či roztoku (zejména koncentrace) pak ovlivňují interakci s proudem plazmatu, která má na výslednou mikrostrukturu zásadní vliv. Tento příspěvek přibližuje problematiku interakce kapalného vstupního materiálu s plazmatem a ukazuje možnosti studia mechanismů růstu nástřiku. Plasma spraying from liquid feedstocks is a rapidly developing field of thermal spraying since the coatings prepared from liquids exhibit some unique features, such as high hardness, thermal shock resistance or low thermal and electric conductivity. The key factor influencing the final coating character and properties is the input material which may be in the form of a suspension or a solution. Parameters of the selected suspension (solids concentration, viscosity, surface tension, chemical composition, etc.) or solution (concentration, etc.) determine its interaction with the plasma jet which strongly influences the coating buildup. This proceeding introduces the problematics of the interaction between the liquid feedstock material with the plasma jet and presents the way of evaluation of the coating buildup. Keywords: suspension plasma spraying; liquid plasma interaction; atomization; coating buildup Available at various institutes of the ASCR
Plazmové stříkání z kapalné fáze: interakce kapaliny s proudem plazmatu a vznik nástřiku

Plazmové stříkání z kapalné fáze je rychle se rozvíjejícím odvětvím žárového stříkání. Hybnou silou vývoje jsou unikátní vlastnosti, které vrstvy deponované z kapalné fáze nabízejí, jako je vysoká ...

Tesař, Tomáš; Mušálek, Radek; Medřický, Jan; Lukáč, František
Ústav fyziky plazmatu, 2016

ELECTRON BEAM REMELTING OF PLASMA SPRAYED ALUMINA COATINGS
Matějíček, Jiří; Veverka, J.; Čížek, J.; Kouřil, J.
2016 - English
Plasma sprayed alumina coatings find numerous applications in various fields, where they enhance the properties of the base material. Examples include thermal barriers, wear resistance, electrical insulation, and diffusion and corrosion barriers. A typical structure of plasma sprayed coatings, containing a multitude of voids and imperfectly bonded interfaces, gives them unique properties - particularly low thermal conductivity, high strain tolerance, etc. However, for certain applications such as permeation barriers or wear resistance, these voids may be detrimental.\nThis paper reports on the first experiments with remelting of plasma sprayed alumina coatings by electron beam technology, with the purpose of densifying the coatings and thereby eliminating the voids. Throughout the study, several parameters of the e-beam device were varied - beam current, traverse velocity and number of passes. The treated coatings were observed by light and electron microscopy and the thickness, structure and surface morphology of the remelted layer were determined and correlated with the process parameters. Based on the first series of experiments, the e-beam settings leading to dense and smooth remelted layer of sufficient thickness were obtained. In this layer, a change of phase composition and a marked increase in hardness were observed.\n Keywords: Plasma sprayed coating; alumina; electron beam; remelting; post-treatment Available at various institutes of the ASCR
ELECTRON BEAM REMELTING OF PLASMA SPRAYED ALUMINA COATINGS

Plasma sprayed alumina coatings find numerous applications in various fields, where they enhance the properties of the base material. Examples include thermal barriers, wear resistance, electrical ...

Matějíček, Jiří; Veverka, J.; Čížek, J.; Kouřil, J.
Ústav fyziky plazmatu, 2016

Evolution of Point-To-Plane Nanosecond Discharge in Deionized Water
Šimek, Milan; Pongrác, Branislav; Člupek, Martin; Babický, Václav; Lukeš, Petr
2016 - English
We employed techniques of time-resolved ICCD microscopy and spectroscopy to register basic morphologic and emission fingerprints of micro-discharges produced in deionized water. Fast risetime high-voltage pulses (duration of 5 ns and amplitude of ~110 kV) applied in a point-to-plane electrode geometry produced micro-discharges either periodically or in a single-shot regime. Time resolved ICCD images evidence typical streamer-like branched filamentary morphology while emission spectra show a broad-band continuum evolving during the first few nanoseconds followed by the well-known HI/OI atomic lines (tens of ns). Keywords: nanosecond discharge; water; ICCD imaging Available at various institutes of the ASCR
Evolution of Point-To-Plane Nanosecond Discharge in Deionized Water

We employed techniques of time-resolved ICCD microscopy and spectroscopy to register basic morphologic and emission fingerprints of micro-discharges produced in deionized water. Fast risetime ...

Šimek, Milan; Pongrác, Branislav; Člupek, Martin; Babický, Václav; Lukeš, Petr
Ústav fyziky plazmatu, 2016

THE INVESTIGATION OF AN Al7075 ALLOY PREPARED BY SPARK PLASMA SINTERING OF MILLED POWDERS
Molnárová, O.; Málek, P.; Nemeth, G.; Kozlík, J.; Lukáč, František; Chráska, Tomáš; Cinert, Jakub
2016 - English
Atomized powder of an Al7075 alloy was high energy ball milled at room and cryogenic temperatures and compacted by spark plasma sintering (SPS) method. The influence of processing parameters on phase composition and microstructure was studied by X-ray diffraction, light and scanning electron microscopy. The mechanical properties were characterized by microhardness measurements. The atomized powder contained a large volume fraction of intermetallic phases located predominantly in continuous layers separating cells or dendrites in the interior of individual powder particles. Consolidation by SPS destroyed partially this morphology and replaced it by individual particles located at boundaries of original powder particles, at cell boundaries or arranged in chains in previous dendritic regions. High energy milling destroyed most intermetallic particles and enriched the matrix by solute atoms. The high deformation energy introduced into the powder during milling enhanced microhardness up to 220 HV. Consolidation of milled powders by SPS led to the formation of very fine-grained structure with the grain size even below 1 μm and with the fraction of high-angle boundaries about 0.9. Two main types of heterogeneously distributed precipitates were found. The irregularly shaped precipitates with a size about 1 μm seemed to encompass areas with rod like nano-precipitates in most samples. A drop in microhardness to 118HV was observed after SPS, predominantly due to a release of introduced deformation energy. Keywords: Cryo-milling; Spark plasma sintering; Ultrafine-grained materials; Milling Available at various institutes of the ASCR
THE INVESTIGATION OF AN Al7075 ALLOY PREPARED BY SPARK PLASMA SINTERING OF MILLED POWDERS

Atomized powder of an Al7075 alloy was high energy ball milled at room and cryogenic temperatures and compacted by spark plasma sintering (SPS) method. The influence of processing parameters on phase ...

Molnárová, O.; Málek, P.; Nemeth, G.; Kozlík, J.; Lukáč, František; Chráska, Tomáš; Cinert, Jakub
Ústav fyziky plazmatu, 2016

ATMOSPHERIC JET BASED ON SURFACE STREAMER DIELECTRIC BARRIER DISCHARGE
Šimek, Milan; Prukner, Václav
2016 - English
We designed novel axisymmetric atmospheric jet formed by effluents produced by surface streamers suitable for various applications. Filamentary streamers are produced by the amplitude-modulated AC surface dielectric barrier discharge. The SDBD-based jet makes use of the tangential injection of the working gas into a cylindrical chamber that induces a fast vortex flow through the discharge zone and expells excited/ionized/reactive species out of the discharge area through the axial orifice in the form of a jet spinning around its axis. The jet may be easily used to treat surfaces, expose biological samples or even be injected in liquids. Keywords: atmospheric pressure; jet; surface barrier discharge Available at various institutes of the ASCR
ATMOSPHERIC JET BASED ON SURFACE STREAMER DIELECTRIC BARRIER DISCHARGE

We designed novel axisymmetric atmospheric jet formed by effluents produced by surface streamers suitable for various applications. Filamentary streamers are produced by the amplitude-modulated AC ...

Šimek, Milan; Prukner, Václav
Ústav fyziky plazmatu, 2016

Youngův modul na rozhraní elastického a elastoplastického materiálu
Kocmanová, Lenka; Haušild, P.; Materna, A.; Matějíček, Jiří
2015 - Czech
Příspěvek je zaměřený na určování Youngova modulu na ostrém rozhraní mezi dvěma materiály, kde jeden materiál je elastický a druhý elasto-plastický. K určení Youngova modulu byl použit 3D numerický model nanoindentace s kuželovým indentorem. Rozhraní mezi materiály je rovina s normálou kolmou ke směru vtisku. Cílem je simulovat spojení kovových a keramických materiálů.\nHodnoty Youngova modulu v závislosti na normované vzdálenosti od rozhraní jsou aproximovány inverzní beta distribucí a je určena závislost parametrů inverzní beta distribuce na velikost oblasti ovlivněné druhou fází. \n The paper is aimed at determining the Young's modulus at the sharp interface between two materials, where one material is elastic and the other elastic-plastic. To determine the Young's modulus was used 3D numerical model of nanoindentation with conical indenter. The interface between the materials with the normal plane perpendicular to the direction of penetration. The goal is to simulate the combination of metal and ceramic materials.\n Young modulus according to the standardized distance from the interface are approximated inverse beta distribution and is determined by the relation between parameters inverse beta distribution of the size of the area affected by the second phase Keywords: instrumented indentation; tungsten; steel; composites; finite element modelling Available at various institutes of the ASCR
Youngův modul na rozhraní elastického a elastoplastického materiálu

Příspěvek je zaměřený na určování Youngova modulu na ostrém rozhraní mezi dvěma materiály, kde jeden materiál je elastický a druhý elasto-plastický. K určení Youngova modulu byl použit 3D numerický ...

Kocmanová, Lenka; Haušild, P.; Materna, A.; Matějíček, Jiří
Ústav fyziky plazmatu, 2015

Konstrukce spektroskopu pro pozorování hvězdných spekter
Rail, Zdeněk; Jareš, Daniel; Pintr, Pavel; Vápenka, David
2015 - Czech
Tento článek předkládá návod na konstrukci přístroje - spektroskopu pro vizuální pozorování hvězdných spekter. K jeho stavbě je použito běžně prodávaných součástek. Samotné sestavení přístroje lze provést bez pomoci obráběcích strojů ve spartánsky vybavené dílně. This paper presents the construction list of a spectroscope for visual observation of stellar spectra. The device consists of parts easily accessible on market. Assembly of the spectroscope does not require exceptionally equipped workshop and can be made in very spartan conditions. Keywords: Spectrograph; Star spectral line; Newton telescope; Barlow lens; Difraction grating; Colimator lens; Toroidal lens; StarAnalyzer grating Fulltext is available at external website.
Konstrukce spektroskopu pro pozorování hvězdných spekter

Tento článek předkládá návod na konstrukci přístroje - spektroskopu pro vizuální pozorování hvězdných spekter. K jeho stavbě je použito běžně prodávaných součástek. Samotné sestavení přístroje lze ...

Rail, Zdeněk; Jareš, Daniel; Pintr, Pavel; Vápenka, David
Ústav fyziky plazmatu, 2015

SPARK PLASMA SINTERING OF BALL MILLED AND ATOMIZED POWDER BASED ON Fe-Al
Šíma, V.; Minárik, P.; Chráska, Tomáš
2015 - English
High-quality compacts were prepared using the spark plasma sintering (SPS) method from powders of similar composition Fe-Al-Zr-B. The properties of the sintered compacts are strongly dependent on the morphology and properties of the feedstock powder. The first powder was obtained by ball milling of the as cast alloy and the second was prepared by atomization under argon atmosphere. The morphology and structure of the two powders are compared and mechanical properties and microstructure of compacts prepared under the same conditions of the SPS procedure are discussed. The milled powder has an irregular morphology and shape of the polycrystalline particles, which have a completely disordered BCC structure with considerable internal stresses, high concentration of structural defects and the presence of aluminum oxide. The atomized powder particles are nearly spherical, polycrystalline with ordered B2 structure, with no significant signs of internal stresses and oxidation. Microhardness of particles of both powders was measured and compared with the microhardness of compact materials, the results of compression tests of compacts at room temperature were compared and discussed. Keywords: Iron aluminides; spark plasma sintering; metallic powders; mechanical properties; microstructure Available at various institutes of the ASCR
SPARK PLASMA SINTERING OF BALL MILLED AND ATOMIZED POWDER BASED ON Fe-Al

High-quality compacts were prepared using the spark plasma sintering (SPS) method from powders of similar composition Fe-Al-Zr-B. The properties of the sintered compacts are strongly dependent on the ...

Šíma, V.; Minárik, P.; Chráska, Tomáš
Ústav fyziky plazmatu, 2015

Synthesis and applications of Intermetallics
Novák, P.; Salvetr, P.; Kříž, J.; Kubatík, Tomáš František
2015 - English
Intermetallic compounds, intermetallics, are characterized by interesting properties, such as e.g. excellent high -temperature oxidation resistance, shape memory or ability to store hydrogen reversibly. Their positive, but also negative, properties are a combination of the behaviour of metals and ceramics. Their wider application in industry is limited due to low room-temperature ductility and problematic production, associated with high melting points of many intermetallics, high reactivity of metals at high temperatures and problematic processing. In this paper, the overview of the methods for synthesis of intermetallic compounds is presented, ranging from conventional casting processes to modern powder metallurgy technologies. Selected interesting applications from industry and medicine, where their unique properties are used Keywords: Intermetallic compounds; powder metallurgy technologies Fulltext is available at external website.
Synthesis and applications of Intermetallics

Intermetallic compounds, intermetallics, are characterized by interesting properties, such as e.g. excellent high -temperature oxidation resistance, shape memory or ability to store hydrogen ...

Novák, P.; Salvetr, P.; Kříž, J.; Kubatík, Tomáš František
Ústav fyziky plazmatu, 2015

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