2026-03-14
00:01 |
Corrosion resistance of 10 425 csn/ s185 din prestressing steel with basalt coatings
Pokorný, P. ; Brožek, Vlastimil ; Janata, Marek ; Prodanovič, N. ; Steinerová, V. ; Mastný, L.
Corrosion damage to conventional prestressing steel reinforcement stimulated by chloride anions has recently caused a critical reduction in the load-bearing capacity and subsequent collapse of several important bridges and footbridges. The use of suitable protective coatings on the surface of the prestressing reinforcement can ensure a significant extension of the service life of these structures. The paper evaluates the corrosion barrier protection of a coating formed from basalt, classified according to QAPF with a high proportion of forsterite and diopsite when hot-dipping on conventional prestressing reinforcement by evaluating the porosity of the coating and exposures in solutions of HCl and NaCl. The roughness and phase composition of two variants of applied basalt coatings, melted at 1260°C on a preheated steel substrate and surface-applied by plasma spraying technology on a cold substrate using a WSP-H 500 water-stabilized plasma torch, were also evaluated. The differences are particularly evident in the increase in the proportion of amorphous silica phases, which ensure almost zero coating porosity and high adhesion even to the plain surface of the metal substrate.
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2025-12-16
16:40 |
CCU solutions vs. additional energy requirements
Šot, Ondřej ; Souček, I.
The issue of global warming and the role that fossil fuel emissions are playing is subject of political and technical disputes. This work is demonstrating the concept of elimination of CO2 emissions from fossil source emitting CO2. This CO2 could be converted to methanol. In order to convert CO2 to methanol, the green hydrogen production should be established. This amount of hydrogen could be produced by electrolyser with significantly high installed capacity. The interdependence of balance of production streams (water, hydrogen, CO2, oxygen for gas turbine operation and methanol) was analysed and balance model has been developed. This work identifies that green solution are significantly dependent on large amount of green electricity. Nevertheless, this concept could be used in situations of large access of the electricity from renewable sources converting CO2 it into products for final use or accumulating energy into products which are easy to store.
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2025-08-16
00:00 |
Local cohesion of splats in hybrid plasma spray coating as observed by in-situ experiment
Mušálek, Radek ; Tesař, Tomáš ; Minařík, Jakub ; Dudík, Jonáš
Hybrid plasma spraying combines spraying of dry coarse powders and liquids (suspensions and/or solutions). Introduction of secondary miniature phase from the liquid may provide new coating functionality but also may have a significant influence on the local coating cohesion – increasing or decreasing it, depending on the materials combination and deposition conditions. In this study, cohesion of dissimilar splats within the early-stage experimental hybrid thermal barrier coating (TBC) was evaluated by in-situ SEM three-point bending (3PB) observation coupled with high-resolution strain mapping. Loading was carried out on the annealed sample simulating in-service thermal exposure. Observed coating failure confirmed that the coating exhibits a rather high intersplat cohesion lowering its strain-tolerance, which was presumably the reason for the relatively low thermal cycling resistance of the deposit.
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2025-05-24
00:00 |
Influence of er doping level and post-growth plasma treatment on luminescence properties of zno nano- and microrods
Buryi, Maksym ; Sharma, Shelja ; Remeš, Zdeněk ; Mičová, J.
Paper deals with the important question of the influence of plasma treatment on the luminescence properties of the ZnO nano- and microrods especially after the annealing in air at 700 ℃. The annealing in air at 700 ℃ significantly suppresses excitonic luminescence (it is practically vanquished). However, hydrogen plasma treatment makes the excitonic luminescence to raise up again surpassing the initial level of intensity in the as grown sample. The influence of Er content on this effect has been studied. Temperature dependence of the excitonic band has been measured as well on example of the Er doping level at 0.25%. Interestingly, hydrogen plasma treatment applied after the annealing in air at 700 ℃ had strong influence on the excitonic intensity of the photon energy distribution as a function of temperature. Moreover, the effect of annealing in air and subsequent hydrogen plasma treatment on the allowed infrared 1.54 μm erbium transition is quite opposite. Exposure to hydrogen plasma leads after the annealing in air at 700 ℃ to the about double reduction of the 1.54 μm erbium transition. This phenomenon practically does not depend on Er content.
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2025-02-22
00:00 |
Surface degradation of tungsten for plasma-facing components after thermal loading
Petráš, R. ; Peterka, Matěj ; Matějíček, Jiří ; Hajíček, M. ; Havlík, P. ; Čížek, O. ; Zýka, J. ; Vála, L.
During the operation of fusion devices, plasma facing components (PFCs) are subjected to high thermal loads. These result in mechanical stresses and various forms of degradation and microstructural changes in the material volume. In order to assess the viability of the PFC candidate materials, tungsten samples were subjected to high heat flux tests simulating heat load pulses caused by plasma instabilities. The presented study includes also a thermal model developed in ANSYS Fluent software to simulate the temperature profile at different depths of the sample and its evolution during the tests. Thermal loading was performed using an electron beam facility. Short pulses (~1 s) of up to 40 MW/m2 thermal load were applied to the top surface of 10 mm wide cylindrical samples. Homogeneous heat flux distribution over the circular area was achieved by scanning the electron beam in a dense pattern. The temperature evolution during the tests was monitored using a thermocouple inserted into the sample along with the surface temperature measurement with a pyrometer. Scanning electron microscopy was used to document surface degradation. A dense net of intergranular cracks typically formed on the loaded surface of the studied material. As a result of a qualitative comparison of the measured temperature profiles during the experiments with the profiles issued from ANSYS simulations, the computational thermal model was verified.
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2025-02-22
00:00 |
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2024-04-01
22:21 |
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2024-02-18
00:07 |
Ceramic protection of anti-corrosion layers of 3-glycidyloxypropyl-triethoxysilane on steel
Pokorný, P. ; Janata, Marek ; Brožek, Vlastimil
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.
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2023-12-17
00:02 |
Ceramic protection of anti-corrosion layers of 3-glycidyloxypropyl-triethoxysilane on steel
Pokorný, P. ; Prodanović, N. ; Janata, Marek ; Brožek, Vlastimil
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.
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2023-01-29
22:31 |
Preparation of W-Cu composites by infiltration of w skeletons review
Matějíček, Jiří
Tungsten-copper composites feature high corrosion and erosion resistance, very good thermal and electrical conductivity, low thermal expansion and good mechanical properties. They are used in a variety of demanding applications, such as arc-resistant electrodes, high voltage electrical contacts, heat sinks for integrated circuits, etc. They are also foreseen for use in plasma-facing components of fusion reactors, e.g. as a transition layer between the (refractory) plasma-facing tungsten and the (highly conductive) copper-based cooling structure. In general, high density and good bonding of the tungsten and copper phases is desired. Molten copper infiltration into tungsten preforms is among the prospective fabrication technologies - the structure and properties of the resultant composites are dependent on the specific technological parameters. In this paper, the preparation of W-Cu composites by infiltration of W skeletons is reviewed and attention is paid to the influence of these particular parameters: infiltration temperature, time and atmosphere, tungsten preform porosity, orientation and chemistry (presence or absence of other elements). Optimum parameter combinations for achieving high density and proper bonding of copper and tungsten are identified.
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