Národní úložiště šedé literatury Nalezeno 76 záznamů.  1 - 10dalšíkonec  přejít na záznam: Hledání trvalo 0.00 vteřin. 
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.
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.
Likvidace antibiotik z odpadních vod
Mastný, L. ; Brožek, Vlastimil ; Slavětínská, R.
Práce je zaměřena na odstranění širokospektrálního tetracyklinového antibiotika určeného khromadné léčebné a preventivní aplikaci u zvířat. Veterinární léčivo, které obsahuje tetracyklin a jeho deriváty, se po dokončení výrobní kampaně dostává ve vysoké koncentraci do odpadních vod. K likvidaci organických částí odpadů je použita metoda založená na oxidaci antibiotika okyseleným roztokem manganistanu draselného. Metoda likvidace bude zavedena ve firmě TEKRO, spol. sr.o.
Mechanical properties of plasma sprayed layers of NiAl10 and NiAl40 on AZ91 alloy
Kubatík, Tomáš František ; Brodil, R. ; Ctibor, Pavel ; Průša, F. ; Brožek, Vlastimil
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
Combined coatings against mechanical wear and corrosion low carbon steel
Brožek, Vlastimil ; Pokorný, P. ; Kolísko, J. ; Vokáč, M. ; Mastný, L. ; Stoulil, J.
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.
Material design problems of plasma-chemical reactors for disposal perfluorinated compounds
Brožek, Vlastimil ; Březina, Václav ; Mastný, L. ; Kubatík, Tomáš František ; Živný, Oldřich
Reduction of perfluorinated gases emissions from semiconductor industry has recently introduced a serious problem from both technological and economic side. With respect to chemistry of the decomposition reactions the most effective abatement techniques developed up to now consists in the interaction of those gaseous pollutants with several types of plasmas. In the framework of Czech-Taiwanese bilateral project No. 17-10246J 'Decomposition of Perfluorinated Compounds and Fluorinated Ozone Depleting Substances' a new plasmochemical reactor design is to be solved. In this reactor the plasma abatement process consisting of interaction of the plasma generated by unique watter stabilized H-WSP plasma torch at temperatures ranging\nfrom 2000 K up to 25,000 K with the treated gases will be carried out. However, the main product generated in the reactor during the steam plasma abatement process is hydrogen fluoride which causes corrosion of almost every construction material. The aim pursued by the work presented is to search for the materials resistant to exposition of HF even at high temperatures. To investigate corrosion resistance of construction materials with thermal stability within temperature interval 2700-3000 °C titan nitride, boron nitride, and silicon carbide have been selected. The samples of those materials have been prepared by spark plasma sintering method and exposed to concentrated solution of hydrofluoric acid for which corrosion rates have been measured
Preparation of spheroidized and nano-structural spinels by the SPPS method
Brožek, Vlastimil ; Lukáč, František ; Medřický, Jan ; Mušálek, Radek ; Mašláni, Alan ; Mastný, L. ; Brodil, R.
Solution Precursor Plasma Spraying (SPPS) method, using hybrid water-stabilised plasma torch (WSP®-H), is presented in this study. Precursor, in a form of a solution of inorganic salts, is injected into the plasma jet, where the temperature can reach up to 25 000 K and a series of reactions lead to the formation of spherical sub-micrometric sized particles. The complete process of evaporating the liquid, crystallization, thermic decomposition, melting and recrystallization takes place in few milliseconds before the particles solidify. Melted nanoparticles can be either directly collected in order to obtain ultrafine powders or deposited onto a substrate to form micro-splats and continuous polycrystalline, and often partially amorphous, coatings. The possibility of continuous and discontinuous changes of stoichiometric composition in tetrahedral and octahedral configurations were analysed for the deposits of MgAl2O4, CoAl2O4 and CoFe2O4 spinels. Furthermore, thin colourful coatings of ruby and modified cobalt oxides were deposited onto ceramic and metallic substrates.
Photocatalytic Decomposition of Wastewater from the Production of Explosives
Brom, Petr ; Brožek, Vlastimil ; Březina, Václav ; Hlína, Michal ; Mastný, L. ; Novák, M.
Water stabilized plasma generator WSP® H-500, operating on the principle of Gerdien arc was used for the photocatalytic decomposition of furazan- and picraminate-based explosives. The generator emits intensive radiation in the range of 300-660 nm, which allows not only to activate photocatalysts based on TiO2, but also other semiconductor oxides with a narrower band gap, such as tungsten oxide. The photocatalytic decomposition of sewage and slurries containing the potassium salt of 4-hydroxy-4,6-dihydro-5,7- dinitrobenzofurazane-3-oxide (KDNBF) or sodium picraminate (NaC6H4N3O5) was performed using the anatase paste and newly developed photocatalyst produced by the company Precheza a.s. The photocatalytic reactor was built using a quartz tube coil with an internal volume of 650 ml, with a nominal size of the irradiated area of 7.5 dm2 (value reduced by the area of the gaps between coil turns) to enable the flow the processing solution or suspension of up to 10 l / min. The centre of the coil is exposed to the plasma jet with the intensity\nof 80 kW; of which 15 kW is transformed into the light radiation. 11% of the radiation output was used for the presented experiments. The time of exposition was 45 mins and 20 l of solution were treated. In the case of KDNBF, 90% of the compound was decomposed. Moreover, 100% of sodium picraminate were decomposed after 15 minutes into low-molecular inorganic compounds. Advantage of the assembly is the ability to treat highly dangerous chemical compounds in a closed cycle and test selective catalyst
Black Chromia Plating for the Solar Radiation Absorbers
Brožek, Vlastimil ; Březina, Václav ; Brom, Petr ; Kubatík, Tomáš František ; Vilémová, Monika ; Mastný, L. ; Novák, M.
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
Boronized stainless steel with zirconia coatings
Brožek, Vlastimil ; Kolísko, J. ; Kubatík, Tomáš František ; Mastný, L. ; Pokorný, P. ; Tej, P.
Conditions of boronizing are described using a reactive diffusion method of boron from boron carbide and lanthanum hexaboride so that the formation of Fe2B is preferred to FeB which is more brittle and whose structure does not satisfy the conditions for perfect adhesion of modified zirconia ceramics. Perfectly rigid adhesive connection of needle-like embedded interlayers Fe2B in steel AISI 303 prepared by reactive diffusion of a boronizing medium without activators at 1000 ° C and exposure of 2-4 hours has the value of 20 - 24 MPa at the Pinn-off test.Ceramic coatings from Al2O3-ZrO2 ceramics formed on those interlayers have the value of bond strength up to 14 - 20 MPa.Thermal cycling between 100°C - 600 °C confirmed good adhesion of coatings with the underlying steel.During thermal cycling at elevated temperatures (600-1000 °C) there occurs a statistically significant number of faults in cohesion and mechanical destruction of the coatings. One of the reasons are secondary changes

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