Number of found documents: 507
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Combined coatings against mechanical wear and corrosion low carbon steel
Brožek, Vlastimil; Pokorný, P.; Kolísko, J.; Vokáč, M.; Mastný, L.; Stoulil, J.
2017 - English
In this study, special ceramic coatings were prepared on low carbon steel (1.0060 - EN 10027-2) via the plasma spraying technique using a WSP®-H plasma generator with output of up to 40 kg/h of aluminum oxide. Corundum coatings were deposited directly on the surface of steel plungers equipped with an anti-corrosion interlayer of zinc phosphate. Coating adhesion properties were tested using pin-off tests (modified ISO 4624) and reached a maximum value of 26 MPa. Corrosion resistance was evaluated by measurements of impedance spectra in the 100 kHz - 10 mHz range in a water solution of sodium sulfate. The capacity of electric double-layer varied depending on the porosity and thickness of the coating. Low-porosity coatings of >1.5 mm thickness had RCT 1.29·105 Ω·m2. The abrasive resistance of coatings was measured by rotary/machining test with SiC cutting knives, using a downforce of 50 kg·cm-2. Abrasion losses decreased with the quality of finish - starting at 0.00266 g cm-2 min-1 down to virtually zero losses after polishing the surface below Ra = 0.55 micro m. Keywords: Abrasion; Ceramic coatings; Corrosion resistance; Plasma spraying; Steel phosphating Available at various institutes of the ASCR
Combined coatings against mechanical wear and corrosion low carbon steel

In this study, special ceramic coatings were prepared on low carbon steel (1.0060 - EN 10027-2) via the plasma spraying technique using a WSP®-H plasma generator with output of up to 40 kg/h of ...

Brožek, Vlastimil; Pokorný, P.; Kolísko, J.; Vokáč, M.; Mastný, L.; Stoulil, J.
Ústav fyziky plazmatu, 2017

Suspension plasma spraying of sub-stoichiometric titania by hybrid water/argon stabilized plasma torch
Mušálek, Radek; Ctibor, Pavel; Medřický, Jan; Tesař, Tomáš; Kotlan, Jiří; Lukáč, František
2017 - English
In this study, suspension plasma spraying of sub-stoichiometric titania was attempted using hybrid water/argon stabilized plasma torch (WSP-H). Porous coatings with fine cauliflower-like columnar microstructure were successfully deposited in two separate experiments with different power levels of the plasma torch. In both cases, high solid-load content (40 wt. %) of the water-based suspension resulted in considerable coating thickness increase per deposition cycle. Coating annealing and partial remelting of the surface asperities were also achieved by additional pass of plasma torch in front of the coating surface. According to X-ray diffraction, all coatings consisted dominantly of rutile phase. Detailed microscopic observation of the as-sprayed and annealed deposits showed that the local coloration of the coating (ranging from dark blue to beige) was driven by the local overheating of the rough coating surface which could also promote the oxygen intake. Moreover, sample annealing was also observed to increase the sample reflectivity as observed by UV-VIS-NIR scanning spectrophotometry Keywords: Liquid feedstock; Plasma spraying; Suspension; Thermal spraying; Titania; WSP-H Available at various institutes of the ASCR
Suspension plasma spraying of sub-stoichiometric titania by hybrid water/argon stabilized plasma torch

In this study, suspension plasma spraying of sub-stoichiometric titania was attempted using hybrid water/argon stabilized plasma torch (WSP-H). Porous coatings with fine cauliflower-like columnar ...

Mušálek, Radek; Ctibor, Pavel; Medřický, Jan; Tesař, Tomáš; Kotlan, Jiří; Lukáč, František
Ústav fyziky plazmatu, 2017

XUV Spectra from High Current Nitrogen Z-Pinch Capillary Discharge.
Vrba, Pavel; Vrbová, M.
2017 - English
We have performed computer modeling of the pinching plasma of capillary discharge using the 1d NPINCH code, that considers ablation of the capillary wall. At high currents we have observed that, the ablation has significant effect on the plasma electron temperature evolution and on the rate of pinch decay. To estimate the emitted spectra in XUV range, the FLYCHK code was used as a post processor. The capillary wall ablation represents the principal obstacles of recombination pumping during pinch decay.\n Keywords: MHD and RMHD simulations of high current capillary discharge; Z-pinches; water window radiation; capillary wall ablation Available at various institutes of the ASCR
XUV Spectra from High Current Nitrogen Z-Pinch Capillary Discharge.

We have performed computer modeling of the pinching plasma of capillary discharge using the 1d NPINCH code, that considers ablation of the capillary wall. At high currents we have observed that, the ...

Vrba, Pavel; Vrbová, M.
Ústav fyziky plazmatu, 2017

The investigation of an Al-Zr-Ti alloy prepared by spark plasma sintering of atomized powder
Molnárová, O.; Málek, P.; Lukáč, František; Chráska, Tomáš; Cinert, Jakub
2017 - English
The microstructure and mechanical properties of a powder metallurgical Al-Zr-Ti alloy was studied. Fine powder with a typical size below 50 ?m was prepared by gas atomization. The smallest powder particles with a diameter below 10 ?m exhibited a segregation free microstructure. Larger droplets were found to contain intermetallic particles rich in Zr and Ti. The gas atomized powder was consolidated by spark plasma sintering (SPS) at various temperatures ranging from 450 to 550 °C. During SPS the materials microstructure remained nearly unchanged and a fine grain size between 2 and 3 ?m was observed. All SPS samples exhibited a microhardness of around 90 HV. The annealing (1 h, 500 °C) of the sample sintered at the highest temperature (550 °C) resulted in a decrease of microhardness to 75 HV as a result of changes in the phase composition, the fine grain size was retained. Natural aging at room temperature was not observed. Keywords: Gas atomization; High strength alloy; Spark plasma sintering; Thermal stability Available at various institutes of the ASCR
The investigation of an Al-Zr-Ti alloy prepared by spark plasma sintering of atomized powder

The microstructure and mechanical properties of a powder metallurgical Al-Zr-Ti alloy was studied. Fine powder with a typical size below 50 ?m was prepared by gas atomization. The smallest powder ...

Molnárová, O.; Málek, P.; Lukáč, František; Chráska, Tomáš; Cinert, Jakub
Ústav fyziky plazmatu, 2017

Surface profilometry by digital holography
Psota, Pavel; Lédl, Vít; Kaván, František; Matoušek, O.; Mokrý, P.
2017 - English
This paper presents newly developed method for measurement of surface topography based on frequency scanning digital holography. Digital holography allows for direct computation of the phase field of the wavefront scattered by an object. A tuning of the light source optical frequency results in linear phase variation with respect to the optical frequency. Slope of the linear function in every single pixel corresponds to absolute measurement of optical path difference and thus topography map of the surface can be retrieved. Principle of this contactless method is introduced and experimentally verified. The method can be used for measurement of complex geometries of common manufacturing parts as well as for topography measurement of complex composite structures, and active acoustic metasurfaces. Keywords: Surface profilometry; Digital holography; Frequency scanning; Absolute measurement Available at various institutes of the ASCR
Surface profilometry by digital holography

This paper presents newly developed method for measurement of surface topography based on frequency scanning digital holography. Digital holography allows for direct computation of the phase field of ...

Psota, Pavel; Lédl, Vít; Kaván, František; Matoušek, O.; Mokrý, P.
Ústav fyziky plazmatu, 2017

Mechanical properties of plasma sprayed layers of NiAl10 and NiAl40 on AZ91 alloy
Kubatík, Tomáš František; Brodil, R.; Ctibor, Pavel; Průša, F.; Brožek, Vlastimil
2017 - English
In this work, plasma coatings of NiAl10 and NiAl40 on magnesium alloy AZ91 substrate were prepared by the hybrid plasma spraying system WSP®-H 500. The both plasma sprayed coatings of NiAl10 and NiAl40 have metallurgical bond. The thicknesses of microstructures in the cross-section of NiAl10 and NiAl40 plasma sprayed coatings prepared by 9 passes were 374 and 440 μm respectively. Adhesion test of plasma sprayed layers was performed using a modified ASTM C 633 standard. The tensile adhesion strength values are 24.7 MPa for NiAl10 coatings and 12.3 MPa for NiAl40 coatings. Abrasion resistance according to Slurry Abrasion Response (SAR) test of NiAl40 layers had similar values (0.12 g/cm2)in a comparison with the uncoated AZ91 (0.126 g/cm2). Layers NiAl10 had greater weight losses (0.175 g/cm2) than uncoated AZ91. Microhardness of plasma coating of NiAl40 is several times greater than microhardnesses of plasma coating of NiAl10 and uncoated substrate AZ91 Keywords: Adhesion strength; Nickel alloys; Plasma spraying; Wear resistance Available at various institutes of the ASCR
Mechanical properties of plasma sprayed layers of NiAl10 and NiAl40 on AZ91 alloy

In this work, plasma coatings of NiAl10 and NiAl40 on magnesium alloy AZ91 substrate were prepared by the hybrid plasma spraying system WSP®-H 500. The both plasma sprayed coatings of NiAl10 and ...

Kubatík, Tomáš František; Brodil, R.; Ctibor, Pavel; Průša, F.; Brožek, Vlastimil
Ústav fyziky plazmatu, 2017

Microwave reflectometry for density profile and turbulence measurements on the COMPASS tokamak.
Bogár, Ondrej; Bílková, Petra; Böhm, Petr; Hron, Martin; Pánek, Radomír; Silva, A.; Zajac, Jaromír; Varavin, Mykyta
2017 - English
Microwave reflectometry is an established radar technique to acquire various scientific results in plasma fusion research. Fast electron density profile measurements are crucial for the study of fusion plasmas and the operation of fusion devices. Operation capability and first results of the reflectometry on the COMPASS tokamak are presented in this contribution. Keywords: plasma; tokamak; COMPASS Fulltext is available at external website.
Microwave reflectometry for density profile and turbulence measurements on the COMPASS tokamak.

Microwave reflectometry is an established radar technique to acquire various scientific results in plasma fusion research. Fast electron density profile measurements are crucial for the study of ...

Bogár, Ondrej; Bílková, Petra; Böhm, Petr; Hron, Martin; Pánek, Radomír; Silva, A.; Zajac, Jaromír; Varavin, Mykyta
Ústav fyziky plazmatu, 2017

Large displacement and deformation measurement by frequency sweeping digital holography
Psota, P.; Lédl, Vít; Kaván, František; Matoušek, O.; Doleček, R.
2017 - English
Recently, a digital holographic method called Frequency Sweeping Digital Holography (FSDH) for high precision measurements of surface topography of mechanical parts has been introduced. The greatest advantage of the presented FSDH is the fact that the measurement is absolute. i.e. optical path difference is independently retrieved in every single pixel. This approach can therefore be used also for measurement of large displacements and deformation. FSDH is particularly suitable in cases where the common digital holographic methods fail due to e.g. 2π unambiguity problem or speckle decorrelation. Measurement method principles, setup details, an some features of the method are discussed.\n Keywords: Digital holography; Digital holographic interferometry; Displacement measurement; Absolute measurements Available at various institutes of the ASCR
Large displacement and deformation measurement by frequency sweeping digital holography

Recently, a digital holographic method called Frequency Sweeping Digital Holography (FSDH) for high precision measurements of surface topography of mechanical parts has been introduced. The greatest ...

Psota, P.; Lédl, Vít; Kaván, František; Matoušek, O.; Doleček, R.
Ústav fyziky plazmatu, 2017

Virtuální zobrazení vzdálených objektů dlouhofokálními spojkami a konkávními zrcadly
Rail, Zdeněk; Vápenka, David
2016 - Czech
Dlouhofokální spojky a konkávní zrcadla mohou sloužit jako optické prvky, úhlově zvětšující rozměry vzdálených objektů podobně jako dalekohledy. Tyto jejich vlastnosti mohly být pravděpodobně používány pozorovateli dávno před objevem dalekohledu. Naše práce přináší optickou analýzu a výsledky astronomických pozorování soustavou dlouhofokální positivní čočky a lidského oka. The longfocal positive lenses and concave mirrors can serve as optical elements increasing the angular dimensions of the distant objects similarly to telescope.\nThese properties could be probably used by ancient observers before the discovery of telescope.\nOur paper brings optical analysis and results of visual astronomical observations with the longfocal positive lens. Keywords: Real and virtual imaging; Angular magnification; Ibn al-Haytham; Benjamin of Tudela; Roger Bacon; Giambattista della Porta; Johann Lippershey; Galileo; Kepler; Longfocal lens; Lighthouse on Pharos island; Ancient lenses; Šolc mirror; Camera obscura; Longfocal lens observation Available at various institutes of the ASCR
Virtuální zobrazení vzdálených objektů dlouhofokálními spojkami a konkávními zrcadly

Dlouhofokální spojky a konkávní zrcadla mohou sloužit jako optické prvky, úhlově zvětšující rozměry vzdálených objektů podobně jako dalekohledy. Tyto jejich vlastnosti mohly být pravděpodobně ...

Rail, Zdeněk; Vápenka, David
Ústav fyziky plazmatu, 2016

Black Chromia Plating for the Solar Radiation Absorbers
Brožek, Vlastimil; Březina, Václav; Brom, Petr; Kubatík, Tomáš František; Vilémová, Monika; Mastný, L.; Novák, M.
2016 - English
Black chromia layers were produced on copper, zirconium and aluminium substrates. These layers are aimed to serve as solar collectors. Efficiency of the layers during UV-VIS, UV radiation and WSP® plasma torch radiation is described. The chromia layers were prepared by a new procedure, i.e. deposition of ammonium dichromate solution using plasma torch or so called Liquid Precursor Plasma Spraying (LPPS). Solution of ammonium dichromate is fed into plasma stream, where dissociation takes place under temperatures of 4000 K – 25000 K. Up to nanometric oxide particles can be produced; the resulting size is dependent on solution concentration and feeding nozzle diameter. The particles impact on substrate and form coating. Using 2 wt.% to 5 wt.% solution of ammonium dichromate and feeding nozzle of 0.2 mm in diameter is the size of produced chromia particles about 6 µm which results in formation of 2 µm to 3 µm thick coating, i.e. according to the theory an optimal thickness 2.5 um for absorption layers, necessary condition for formation energy traps for IR radiation emitters up to 100°C. Moreover, black chromia coating is a suitable corrosion barrier of metallic substrates. \n\n Keywords: Solar collector; black chromia; plasma spraying; ceramic coatings Available at various institutes of the ASCR
Black Chromia Plating for the Solar Radiation Absorbers

Black chromia layers were produced on copper, zirconium and aluminium substrates. These layers are aimed to serve as solar collectors. Efficiency of the layers during UV-VIS, UV radiation and WSP® ...

Brožek, Vlastimil; Březina, Václav; Brom, Petr; Kubatík, Tomáš František; Vilémová, Monika; Mastný, L.; Novák, M.
Ústav fyziky plazmatu, 2016

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