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Ceramic protection of anti-corrosion layers of 3-glycidyloxypropyl-triethoxysilane on steel
Pokorný, P.; Janata, Marek; Brožek, Vlastimil
2023 - English
There are various variations on the problem of steel reinforcement bond strength in concrete. Along with geometrical considerations, corrosion performance of steels with varying chemical compositions in interaction with variable chemical compositions of concrete are crucial. One approach is to cover steel surfaces with organosilane compounds, which increases the reinforcement resistance to corrosion in both acidic and alkaline conditions but, on the other hand, may weaken the reinforcement bond strength on concrete. The issue is resolved by intentionally forming a thin-walled, highly adhering corundum layer that is highly porous and impregnated with 3-glycidyloxypropyltriethoxysilane. This procedure also includes testing the adhesion properties between the ceramic and the metal and the cement prior to conducting a corrosion test in a chloride environment.
Keywords:
ceramic protection; 3-glycidyloxypropyl-triethoxysilane; steel
Fulltext is available at external website.
Ceramic protection of anti-corrosion layers of 3-glycidyloxypropyl-triethoxysilane on steel
There are various variations on the problem of steel reinforcement bond strength in concrete. Along with geometrical considerations, corrosion performance of steels with varying chemical compositions ...
Composite coatings containing nanometric constituents prepared by plasma spraying with liquid feedstocks
Mušálek, Radek; Tesař, Tomáš; Medřický, Jan; Čížek, Jan; Lukáč, František
2021 - English
Plasma spraying of liquid feedstocks allows deposition of materials with novel microstructures. Due to the combination of a liquid carrier and ultrafine powders (in case of suspensions) or in-situ formation of the final material in the plasma jet (in case of solutions), preparation of ultrafine composites is possible, typically in a form of coatings on the substrates. Moreover, both suspension and solution spraying routes can be easily combined, either together or even with conventional plasma spraying of coarse dry powders, thus merging benefits of “nanometric” and “micrometric” constituents in the final composite microstructure. As a consequence, liquid feedstock plasma spraying represents an industrially-relevant deposition process with wide variability, providing coatings with properties tailored for various applications ranging from compact wear-resistant layers, porous thermal barrier coatings, bio-compatible medical coatings, catalyst carriers, fuel-cells, etc. The paper introduces several examples of such ultrafine coatings recently deposited at IPP CAS using hybrid water-stabilized plasma torch.
Keywords:
Coatings; Functionally graded materials (FGMs); Liquid feedstock; Plasma spraying
Fulltext is available at external website.
Composite coatings containing nanometric constituents prepared by plasma spraying with liquid feedstocks
Plasma spraying of liquid feedstocks allows deposition of materials with novel microstructures. Due to the combination of a liquid carrier and ultrafine powders (in case of suspensions) or in-situ ...
Tungsten-steel and tungsten-chromium composites prepared by RF plasma spraying
Matějíček, Jiří; Klečka, Jakub; Čížek, Jan; Veverka, Jakub; Vilémová, Monika; Chráska, Tomáš; Ganesh, V.
2020 - English
For future fusion reactors, materials able to withstand harsh environments are needed. In particular, this concerns the plasma-facing components which are foreseen to consist of tungsten based plasma-facing armor and structural and cooling part made of steel. Currently, joining of these materials presents a significant challenge. The stress concentration at their interface, which arises due to thermal exposure and the difference in thermal and mechanical properties, can be reduced by composite/graded interlayers. Plasma spraying is among the prospective technologies for their preparation. In this work, tungsten-steel and tungsten-chromium composites were prepared by radio-frequency inductively coupled plasma (RF-ICP) spraying. Initial optimization of the spraying process for pure materials as well as their mixtures was carried out. Basic characterization of the layers for their structure, porosity and composition is presented.
Keywords:
tungsten; composites; RF plasma spraying
Fulltext is available at external website.
Tungsten-steel and tungsten-chromium composites prepared by RF plasma spraying
For future fusion reactors, materials able to withstand harsh environments are needed. In particular, this concerns the plasma-facing components which are foreseen to consist of tungsten based ...
Design of experimental device for testing of subcooled flow boilling
Gleitz, M.; Zacha, P.; Entler, Slavomír; Syblík, J.
2020 - English
The article presents the principle and function of the Hypervapotron and the current work progress on the realisation of the experimental loop. Hypervapotron is a heat exchanger operating in a two-phase flow regime, in which the latent heat of the water/steam phase transformation is used, which enables the transfer of large heat fluxes (up to tens of MW/m(2)). For this reason, it appears to be very promising for use in fusion reactors. The article describes the steps leading to the final design of the experimental loop selection of suitable mesh parameters in the Star-CCM+ code, geometry and used materials of the single elements of the heating system using electromagnetic induction. The effort of the experimental loop and the flow study in the Hypervapotron in general, is dimensional and material optimization of the geometry is suitable for a wide range of applications for which the benefits of subcooled boiling and Hypervapotron geometry can be applied.
Keywords:
Hypervapotron; Star-CCM; Fusion; Subcooled boiling; Induction heating
Fulltext is available at external website.
Design of experimental device for testing of subcooled flow boilling
The article presents the principle and function of the Hypervapotron and the current work progress on the realisation of the experimental loop. Hypervapotron is a heat exchanger operating in a ...
High temperature corrosion studies of HVOF sprayed coatings in molten sulphate salts environment
Lencová, K.; Česánek, Z.; Houdková, Š.; Lukáč, František; Mušálek, Radek
2019 - English
The generally applied requirements on lowering of emission production in the field of power industry have led, among others, into the application of low-emission combustion process of coal fired power plants. Besides the emissions reduction, this process has led to an increase of boilers parts corrosion degradation due to the reducing atmosphere in low-emission boilers, responsible for sulphide corrosion and molten salt attack. In such environment, the protection of the exposed surfaces gains importance. Among others, the thermal spraying technology can offer a suitable way of surface corrosion protection. In the present work, the high temperature corrosion behaviour of CoCrAlYTaCSi and Cr3C2-25%NiCr High Pressure/High Velocity Oxygen Fuel (HP/HVOF) sprayed coatings is evaluated and compared to the behaviour of bare structural steel (SPT360) substrate. The specimens were exposed to a molten salt environment, i. e., 12% Na2SO4 + 82% Fe2(SO4)3 at 690 °C under cyclic condition, simulating the working environment in low-emission boilers of coal-fired power plants. The thermogravimetric method was used to establish the kinetics of corrosion. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyse the corrosion products and determine the corrosion mechanism. The thermogravimetric measurement shows high oxidation rate of SPT360 steel. Cr3C2-25%NiCr coating provides slightly better performance compared to CoCrAlYTaCSi coating. Based on the obtained results, both coatings were found to have higher corrosion resistance than the SPT360 steel substrate, offering a sufficient surface protection in a given environment.
Keywords:
Coal fired boilers; CoCrAlYTaCSi; Cr3C2-25%NiCr; High temperature corrosion; hvof; Low-emission boilers; Thermal spraying
Fulltext is available at external website.
High temperature corrosion studies of HVOF sprayed coatings in molten sulphate salts environment
The generally applied requirements on lowering of emission production in the field of power industry have led, among others, into the application of low-emission combustion process of coal fired power ...
Fluctuations in the scrape-off layer and edge plasma of the COMPASS tokamak
Seidl, Jakub; Jiráková, Kateřina; Adámek, Jiří; Grover, Ondřej; Horáček, Jan; Hron, Martin; Vondráček, Petr
2018 - English
We have identified two distinct types of turbulent fluctuations in COMPASS plasmas, the high-frequency edge oscillations and low-frequency SOL blobs. The transition region is localized in the near SOL, where both types spatially overlap and interact and the radial particle transport gradually transfers from high to low frequencies. Even though skewness of isat fluctuations is positive even inside LCFS, distinguishable Gamma-distributed PDF, formed by the low-frequency fluctuations, arises in the near SOL. This supports, together with turbulence spreading rate being positive in the near SOL but negative in the edge, the picture presented in [3] that most of the fluctuations that form a positive skewness in the edge region disappear around LCFS and new blobs are formed in the near SOL. Further, we cannot confirm the assumption that the blobs are generated randomly according to a Poisson process. Oscillations of all measured quantities, incl. radial particle flux, in the near SOL are peaked around ∼13 kHz. This seems to correspond to a poloidally rotating structure with a rather large poloidal wave-length ∼ 15 − 20 cm, that at least partly modulates blob generation. Nevertheless, we note that time separation of blobs becomes more random further in the SOL, possibly due to differences in their individual propagation. These observations hold for diverted plasmas, but the situation may be different in limited low-elongation plasmas where the radius of zero skewness was observed to be shifted significantly (several cm) inwards, compared to diverted configuration, and Gamma-like PDF is detected even inside the LCFS. Study of these plasmas is ongoing.
Keywords:
plasma; tokamak; turbulence
Fulltext is available at external website.
Fluctuations in the scrape-off layer and edge plasma of the COMPASS tokamak
We have identified two distinct types of turbulent fluctuations in COMPASS plasmas, the high-frequency edge oscillations and low-frequency SOL blobs. The transition region is localized in the near ...
OLGA – efficient full wave code for the coupling of LH grills
Preinhaelter, Josef; Hillairet, J.; Urban, Jakub
2018 - English
The full wave code OLGA, for determining the coupling of a single row lower hybrid launcher (waveguide grills) to the plasma, is extended to handle multirow multijunction active passive structures (like the C3 and C4 launchers on TORE SUPRA) by implementing the scattering matrix formalism. The extended code is still computationally fast because of the use of (i) 2D splines of the plasma surface admittance in the accessibility region of the k-space, (ii) high order Gaussian quadrature rules for the integration of the coupling elements and (iii) utilizing the symmetries of the coupling elements in the multiperiodic structures. The extended OLGA code is benchmarked against the ALOHA-1D, ALOHA-2D and TOPLHA codes for the coupling of the C3 and C4 TORE SUPRA launchers for several plasma configurations derived from reflectometry and interferometery. Unlike nearly all codes (except the ALOHA-1D code), OLGA does not require large computational resources and can be used for everyday usage in planning experimental runs. In particular, it is shown that the OLGA code correctly handles the coupling of the C3 and C4 launchers over a very wide range of plasma densities in front of the grill.
Keywords:
lower hybrid waves; coupling; large multirow multijunction grills; tokamak; full-wave
Fulltext is available at external website.
OLGA – efficient full wave code for the coupling of LH grills
The full wave code OLGA, for determining the coupling of a single row lower hybrid launcher (waveguide grills) to the plasma, is extended to handle multirow multijunction active passive structures ...
Relativistic effects in plasma produced with sub-nanosecond 3-TW laser
Krása, J.; Klír, Daniel; Řezáč, Karel; Cikhardt, Jakub; Krůs, Miroslav; Velyhan, Andriy; Pfeifer, Miroslav; Dostál, Jan; Dudžák, Roman; Krupka, Michal; Kaufman, J.; Pisarczyk, T.; Kalinowska, Z.; Chodukowski, T.
2018 - English
This contribution deals with observations of relativistic electrons produced in a laser plasma interaction experiment at the PALS laser system operated at the Institute of Plasma Physics in Prague. The PALS laser is a near-infrared 3-TW iodine laser designed to deliver irradiance on target of 1016 Wcm2- in≈300 ps pulses at the wavelength of 1.315 μm. Various foils of 6 500 μm in thickness were irradiated with Iλ2 ≈5×1016 W cm-2 μm2 Under these conditions we have observed relativistic electrons expanding into the vacuum with maximum energy going beyond 4 MeV. The relativistically accelerated forward electrons escaping from the rear target surface were observed with the use of electron energy analysers. The observed electron energy spectra indicate that the applied laser intensity was increased by the thermal and relativistic self-focusing. The application of a unique femtosecond interferometry technique allowed us to observe bunches of thermal electrons occurring in the plasma expanding against the focused laser beam.
Keywords:
laser-produced plasma; relativistic electrons
Fulltext is available at external website.
Relativistic effects in plasma produced with sub-nanosecond 3-TW laser
This contribution deals with observations of relativistic electrons produced in a laser plasma interaction experiment at the PALS laser system operated at the Institute of Plasma Physics in Prague. ...
Fluctuations in the scrape-off layer and edge plasma of the COMPASS tokamak
Seidl, Jakub; Jiráková, Kateřina; Adámek, Jiří; Grover, Ondřej; Horáček, Jan; Hron, Martin; Vondráček, Petr
2018 - English
In this work we study properties of turbulent structures in the scrape-off layer (SOL) and edge plasma of the COMPASS tokamak. Two distinct types of coherent oscillations are observed: a) broadband high frequency branch rotating in the electron diamagnetic direction, appearing mainly in the confined region but protruding also to the SOL b) low-frequency blobs rotating in an opposite poloidal direction, formed in the vicinity of the radius of zero electric field. The transition region is localized in the near SOL, where both types spatially overlap and interact and the radial particle transport gradually transfers from high to low frequencies. Even though skewness of fluctuations of the ion saturation current is positive even inside LCFS, distinguishable Gamma-distributed PDF, formed by the low-frequency fluctuations, arises in the near SOL and most of the fluctuations that form a positive skewness in the edge region disappear around LCFS.
Keywords:
plasma; tokamak; turbulence
Fulltext is available at external website.
Fluctuations in the scrape-off layer and edge plasma of the COMPASS tokamak
In this work we study properties of turbulent structures in the scrape-off layer (SOL) and edge plasma of the COMPASS tokamak. Two distinct types of coherent oscillations are observed: a) broadband ...
Properties of hydroxyapatite surface deposited by plasma spray technologies
Matějková, M.; Čížek, Jan; Mušálek, Radek; Dlouhý, I.
2017 - English
The surface properties of hydroxyapatite (HA) deposited on the Ti-6Al-4V substrates by plasma spraying were studied. Two different plasma spray technologies (hybrid plasma spray system (WSP-H) and conventional atmospheric plasma spray technology (APS)) and two various feedstock (suspension for WSP-H and powder for APS) were used for deposition of HA layers potentially suitable for bio-applications. The layers properties (thickness, chemical and phase composition) and coating-substrate interface quality were analyzed. The XRD analysis showed formation of small amount of new phases (TTCP and CaO) in layers deposited by WSP-H. Better coating-substrate interface quality of samples prepared by WSP-H was observed. The results showed the deposition of HA through liquid feedstock via WSP-H as a promising route, complementing the traditional APS powder deposition in the near future.
Keywords:
hydroxyapatite; hybrid water-stabilized plasma spray; atmospheric plasma spray technology
Fulltext is available at external website.
Properties of hydroxyapatite surface deposited by plasma spray technologies
The surface properties of hydroxyapatite (HA) deposited on the Ti-6Al-4V substrates by plasma spraying were studied. Two different plasma spray technologies (hybrid plasma spray system (WSP-H) and ...
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