No (399)
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399
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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 ...
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 ...
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 ...
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 ...
Investigation of Anode Attachment Area in Water/Argon Stabilized Plasma Arc
Ondáč, Peter; Mašláni, Alan; Hrabovský, Milan
2015 - English
Arc-anode attachment in a DC plasma arc stabilized by water vortex and argon, influences power distribution in the plasma, lifetime of the anode and also flow structure of the plasma jet. A movement of the attachment and the surrounding plasma has been directly observed by using a high-speed camera (max. 1,080,000 fps). The observations were compared with cathode–anode voltage measurements (sample rate 80 MHz). More than one attachment was observed in one frame with exposure time 0.25 μs or 0.29 μs. We have directly measured average velocities of the attachments and hydrodynamic waves above them, as well as the characteristic dwell times and dwell frequencies of the attachments
Keywords:
Arc-anode; plasma arc
Available at various institutes of the ASCR
Investigation of Anode Attachment Area in Water/Argon Stabilized Plasma Arc
Arc-anode attachment in a DC plasma arc stabilized by water vortex and argon, influences power distribution in the plasma, lifetime of the anode and also flow structure of the plasma jet. A movement ...
TOMOGRAPHICAL APPROACH IN 3-D TEMEPEARTURE DISTRIBUTION MEASUREMENT BY DIGITAL HOLOGRAPHY
Psota, Pavel; Doleček, Roman; Lédl, Vít; Vojtíšek, Petr; Vít, T.; Matoušek, Ondřej
2015 - English
This paper presents a digital holographic method for measurement and visualization of temperature distribution in 3-D space. It is based on measurement of phase information along various projections followed by a tomographic reconstruction of the 3-D temperature distribution. The method is experimentally proved and some results are presented in this paper.
Keywords:
digital holography; holographic interferometry; temperature; 3-D measurement; tomography
Available at various institutes of the ASCR
TOMOGRAPHICAL APPROACH IN 3-D TEMEPEARTURE DISTRIBUTION MEASUREMENT BY DIGITAL HOLOGRAPHY
This paper presents a digital holographic method for measurement and visualization of temperature distribution in 3-D space. It is based on measurement of phase information along various projections ...
Deposition of Fluorocarbon Plasma Polymer Nanoparticles and their Basic Properties
Serov, Anton; Choukourov, A.; Artemenko, A.; Kuzminova, A.; Biederman, H.; Hrabovský, Milan
2015 - English
Fluorocarbon plasma polymer nanoparticles have been fabricated using gas aggregation cluster source (GAS) equipped with a planar magnetron with PTFE target. A beam of nanoparticles 20 – 200 nm in diameter was generated. Fluorocarbon nanoparticle films have shown very good water repellent properties. Films immersed in ethanol for two hours exhibited excellent stability that was also good in case of water. Measurements using a deflection system showed the presence of both neutral and charged nanoparticles.
Keywords:
poly(tetrafluoroethylene); magnetron sputtering; plasma polymerization; superhydrophobic
Available at various institutes of the ASCR
Deposition of Fluorocarbon Plasma Polymer Nanoparticles and their Basic Properties
Fluorocarbon plasma polymer nanoparticles have been fabricated using gas aggregation cluster source (GAS) equipped with a planar magnetron with PTFE target. A beam of nanoparticles 20 – 200 nm in ...
P3-TOP-TN-15001 Achievable microroughness of ASPIICS optical glass elements
Bartoníček, Jiří; Budasz, Jiří; Hadincová, Ivana; Horodyská, Petra; Kaucká, Iva; Kovačičinová, Jana; Lédl, Vít; Melich, Radek; Pleštil, Jan; Poláková, Ivana; Procháska, František; Psota, Pavel; Rail, Zdeněk; Šípová, Gabriela; Šrajer, Bohdan; Ulrichová, Iva; Václavík, Jan; Vápenka, David; Vít, Tomáš
2015 - English
The scope of this document is describe a test that investigates an achievable micro-roughness realized on different types of optical glasses [R1] that are planned to be employed for realization of PROBA3 coronagraph telescope. The test is realized with respect to the technological manufacturing possibilities of optical elements at TOPTEC facility.
Keywords:
optical glass; microroughness; PROBA3; ASPIICS
Available at various institutes of the ASCR
P3-TOP-TN-15001 Achievable microroughness of ASPIICS optical glass elements
The scope of this document is describe a test that investigates an achievable micro-roughness realized on different types of optical glasses [R1] that are planned to be employed for realization of ...
Process development and prototype realization of non-symmetrical aspherical lenses
Melich, Radek; Pintr, Pavel; Pleštil, Jan; Poláková, Ivana; Procháska, František; Rail, Zdeněk; Václavík, Jan; Vápenka, David; Vít, Tomáš
2015 - English
The aim of the study is to develop a process chain and realize prototype lenses of non-symmetrical apherical lenses of given tolerances.
Keywords:
non-symmetrical; aspherica lens
Available at various institutes of the ASCR
Process development and prototype realization of non-symmetrical aspherical lenses
The aim of the study is to develop a process chain and realize prototype lenses of non-symmetrical apherical lenses of given tolerances.
Nanostructuring of solid surfaces by discharge-pumped xuv laser source
Schmidt, Jiří; Štraus, Jaroslav; Koláček, Karel; Frolov, Oleksandr
2015 - English
The experimental results of interaction of focused XUV laser beam (wavelength 46.9 nm) with Polymethylmethacrylate (PMMA) and GaAs samples will be presented. Proximity-standing golden grid showed on naturally-generated diffraction pattern that direct nanostructuring is possible
Keywords:
XUV laser; laser ablation; diffraction pattern
Available at various institutes of the ASCR
Nanostructuring of solid surfaces by discharge-pumped xuv laser source
The experimental results of interaction of focused XUV laser beam (wavelength 46.9 nm) with Polymethylmethacrylate (PMMA) and GaAs samples will be presented. Proximity-standing golden grid showed on ...
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