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Microstructure and performance of titanium oxide coatings sprayed by oxygen-acetylene flame
Ctibor, Pavel ; Štengl, Václav ; Zahálka, F. ; Murafa, Nataliya
TiO2 nano-powders were agglomerated by a spray drying process for applying to thermal spraying. A conventional oxygen-acetylene flame torch was used to deposit porous partially nanostructured TiO2 coatings. Steel substrates were used as a support for tested samples. Scanning Electron Microscopy, X-ray microanalysis and X-ray diffraction were performed to study the morphology and the crystalline phases of the titania coatings. Optical bandgap and kinetics of the acetone decomposition was studied too. The best results were obtained for the powder which is available as a commercial spray feedstock. This powder seems to be most resistant against the reducing atmosphere in the jet of combustive gasses.
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Interaction of the water stabilized plasma radiation with photocatalytic suspensions
Mastný, L. ; Šaněk, F. ; Brožek, Vlastimil
The design of WSP® plasma torch with liquid used as stabilization agent, enables three different process zones for the decomposition of toxic chemicals. The first zone is inside the plasma stabilization chamber, where the liquid is in direkt contact with electric arc in the cathode zone. Second zone is at the exit notule in the outer space of the torch body. Here the nontransfered stream of the thermal plasma can act as heat source for thermal decomposition of chemical substances. The third zone was arranged in this work as a spiral from silica glass which acts as a tube flowed by the toxic liquid through and exposed to ultraviolet rays produced by the plasma. Inside such a tube the interaction of the water stabilized plasma radiation with photocatalytic suspensions was studied. As a model substances Orange II, nicotine and 2-nitroso-1-naphtol were used. The flow rate in frames 12 - 30 l/min was evaluated from the viewpoint of the effectivness of chemical decomposition.
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Fotokatalytické vlastnosti plazmově zpracovaného oxidu wolframového
Brožek, Vlastimil ; Domlátil, J. ; Mastný, L. ; Šrank, Z. ; Janča, J. ; Eliáš, M.
Tungsten trioxide with the band gap about 2.58 eV is known as a material, which a photocatalytic effect after UV-radiation exposure can be observed. However, in some cases more detailed material specification and the consideration of its complex structural and stoichiometric uniqueness are lacked in its photoactivity data. The presented work is focused on the study of tungsten trioxide samples photoactivity using the unified method that determines the reference substances colour changes after 360 nm UV-radiation exposure. The samples were prepared by from ammonium paratungstate treated in oxygen or argon plasma, which was generated by capacitive coupled RF generator operated at low partial pressures. The differences in oxygen stoichiometry which depends on total temperature plasma, because especially the presence of hydrogen coming from the ammonium cation disintegration causes a partial reduction partly to the WO2.7 oxide.
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