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Kvantifikace struktury žárovových nástřiků s pomocí objemové rekonstrukce
Ctibor, Pavel ; Lechnerová, R. ; Hofmann, P.
The paper introduces a way to study structure of thermally sprayed coatings in detail. Two microstructures are compared, which originate from two different spraying techniques used for the same material. The material selected is stainless steel AISI 316L and the techniques are plasma spraying using water-stabilized plasma gun and wire arc spraying. A sophisticated analytical technique is applied which was developed for a 3D reconstruction of the architecture of thermally sprayed coatings, revealing their main characteristic structural features such as porosity and oxide phase. The technique is called 3D mapping and describes the shape of pores, their interactions, etc. It is based on optical microscopy and software treatment of microstructural images. Also it is possible to detect pores or the structural phases, provided that they can be separated by proper threshold. This method is here applied first time on wire arc sprayed coating and also on metallic coating containing oxides.
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Elektrická rezistivita podstechiometrického TiO2 vyrobeného plazmovým nástřikem
Ctibor, Pavel ; Sedláček, J. ; Neufuss, Karel
The work is concentrated on electric resistivity of plasma sprayed titania TiO2. Synthetic conventional TiO2 powder and powder prepared by agglomeration of nanopowder particles were sprayed and measured. Spraying was carried out using the water-stabilized plasma system (WSP®) and resistivity measurement was applied on TiO2 layers detached from the substrate. Variations in basic spray conditions – spray distance, feedindg distance and substrate preheating temperature were commented from the point of view of their influence on electric resistivity.
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Fotokatalytické technologie a nové nanopovrchové materiály v roce 2005
Peterka, F. ; Jirkovský, Jaromír ; Šubrt, Jan ; Špatenka, P. ; Krýsa, J. ; Lukeš, Petr ; Kavan, Ladislav ; Štengl, Václav ; Kolouch, A. ; Klusoň, P.
Current state of art in the research and development of photocatalytic titanium oxide nanosurface materials and their practical applications is discussed. The main objectives of new European COST Action “PHONASUM” (COST 540), which is understand as European platform to group the existing European collaborations and to allow for a large exchange between the different European groups focussing on the development of photocatalytical nanomaterials and standard photoactivity testing methods are presented. Specific aims and scientific results of the Research Centre for Nanosurface Engineering "NANOPIN" established in 2005 under the Research and Development Program of the Ministry of Education, Youth and Sports of the Czech Republic are shown in more detail.
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Plasma and plasma sphere
Weinzettl, Vladimír
The article introduces the term "plasma" and a history and present status of a research of plasma. In the second part of the article, the "plasma sphere" experiment is described, i.e. the experiment of a high frequency discharge in a gas.
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Složení a struktura plazmově stříkaných prášků chromové ocele
Schneeweiss, O. ; Voleník, Karel ; Kolman, Blahoslav Jan
Chromium steel powder (13% Cr) was sprayed by a water stabilized plasma gun. The changes of composition and structure occurring during two plasma spraying stages were studied. To characterize the main features of the first (in-flight) stage product, the molten powder particles flying in the plasma stream were trapped and quenched in liquid nitrogen. At the second stage, the particles were allowed to hit a solid substrate and to form a coating. The composition of the feedstock powder and the samples resulting from both plasma spraying stages were determined by chemical methods and X-ray microanalysis. Significant Cr-depletion was due mainly to selective oxidation of chromium at the in-flight stage. At the second stage, the composition changes were less important. Some details of the structure, in particular the distribution of Cr-atoms in the nearest neighbourhood of a Fe-atom, were assessed employing the results of Mössbauer spectroscopy.
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Adhesion improvement of plasma sprayed coatings ceramics-metal
Brožek, Vlastimil ; Neufuss, Karel
The paper summarizes knowledge dealing with shape similarity of the profile of surfacial anchoring of iron borides onto steel substrates, devoted to covering by ceramic coating using thermal or plasma spraying. Boride interlayer improves the conditions for deposition of ceramic materials having different dilatation characteristics. By this way cermet coatings on steels designed for cyclic thermal load up to 1000°C could be carried out.
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Photocatalytic activity of titanium precursors treated in low temperature plasma
Brožek, Vlastimil ; Matějíček, Jiří ; Šrank, Z. ; Mastný, L. ; Janča, J.
In order to obtain compact photocatalytically active materials, the possibility of preparation of new titania forms by oxidation of titanium compounds, having different crystal structures and oxidation degree, was verified. Four model substances were chosen: titanium carbide, nitride, diboride and Ti2O3. These compounds were prepared in the form of high-specific-surface powder, as well as large-area compact free-standing parts by CVD, PVD and especially plasma spraying. After high temperature treatment in a water stabilized plasma, generated by the WSP torch, a measurable photoactivity was observed; this could be further improved by controlled oxidation below 450°C. Oxidation in an RF-generated oxygen plasma appeared more efficient, especially in shorter reaction times. However, the experiments have shown that even keeping the reactor walls at 450°C did not prevent the uncontrolled temperature rise inside, during the reaction of the oxygen plasma with titanium compounds.
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