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Thermal Coatings for Glass Industry
Chráska, Pavel ; Neufuss, Karel
A new type of plasma torch with combined stabilization of electric arc by water vortex and gas flow is presented. This hybrid water/gas stabilization offers the possibility of adjusting plasma jet parameters within a wide range from high-enthalpy low-density plasmas typical for liquid stabilized torches to lower enthalpy higher density plasmas generated in gas stabilized torches. Moreover, gas flow in the cathode part protects a cathode tip and thus a consumable graphite cathode used in water-only stabilized plasma torches could be replaced by a fixed tungsten cathode. Examples of hybrid WSP torch utilization for high temperature application are given.
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Production of nanoparticles utilizing water stabilized plasma
Bertolissi, Gabriele ; Brožek, Vlastimil ; Chráska, Tomáš ; Mušálek, Radek ; Neufuss, Karel ; Mastný, L. ; Sofer, Z.
Water stabilized plasma torch (WSP®) generates plasma jet with max. plasma velocity in the nozzle exit 7000m/s and temperature of 25000-30000 K. Reactants injected into the plasma jet undergo complicated radical reactions. Interaction of plasma with injected reactants depends on energy settings of the WSP plasma torch and lasts from 5 to 10 ms. Droplets of inorganic compound solution are fed to the plasma jet by pressurized spray nozzle device. Compounds of AgI,AlIII,TiIV,PtIV,VV, and CrVI undergo decomposition in the extremely high plasma temperature and the decomposed products are collected in liquid separators. Size of the produced nanoparticles in unsettled fraction is from 10 to 200 nm and depends primarily on concentration of inputting aerosol particles. In the case of 15 seconds reaction time and use of saturated solutions at 20°C, one can obtain colloidal solutions with silver, platinum, alumina, titania, vanadia, and chromia nanoparticles in concentrations of 3 to 180mg
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Processes of Nanoparticle Formation in Low Temperature Plasma
Brožek, V. ; Mastný, L. ; Moravec, Pavel ; Neufuss, Karel ; Ondráček, Jakub ; Ždímal, Vladimír
This work describes the synthesis of nanoparticles during interaction of several different metals (Ag) or their respective oxides (TiO2, Cr2O3) with oxygen-hydrogen plasma having temperatures above 25000 K. Resulting nanoparticles and/or their aggregates in the size range of 25-300 nm were deposited on metallic targets and/or trapped in the water filters and separated using ultra-centrifugal apparatus. The aerosol spectrometer SMPS 3936 (scanning mobility particle sizer) was used to study the particle size distribution of generated nanoparticles in the size range 14 – 700 nm. In order to extend the measured particle size range towards larger sizes, the APS 3321 spectrometer (aerodynamic particle sizer) with the size range 500-20000 nm was used simultaneously. Both spectrometers were set-up to sample with three minute time resolution. Process conditions and production of inorganic nanoparticles of defined composition are discussed in this work.
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Chemical aspects of the anti-ballistic armors preparation by plasma deposition
Brožek, V. ; Chráska, T. ; Mušálek, R. ; Neufuss, Karel
This paper informs about possibility to deposit ceramic-metallic composites on different types of metallic and ceramic substrates by thermal spraying, namely plasma spraying. Preparation of free-standing deposits as well as metal-reinforced composites is described. Results of plasma deposition of two ultra-hard ceramic materials (titanium boride and nitride) are presented in more details. Plasma deposition of materials carried out in specific technological conditions preventing undesirable high-temperature oxidation of ultra-hard ceramics is costly. Therefore, deposition conditions which should lead to improvement of surface properties of currently used antiballistic ceramics were studied and described.
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Aerosol Nanoparticles Formed during Plasma Deposition
Ždímal, Vladimír ; Moravec, Pavel ; Doležal, B. ; Brožek, Vlastimil ; Neufuss, Karel
Results of pilot-plant experiments on a plasmatron WSPR constructed at the Institute of IPP AS CR are shown in this paper, dealing with plasma deposition of the ultrafine and fine aerosol fractions of some metallic materials. In this work we concentrated on its side-product investigating the ultrafine particles released during the process into the aerosol phase. The aerosol particle size distribution was studied in a near real time using the state-of-the-art aerosol spectrometers operated by the ICPF AS CR. It was verified that these instruments are able to take aerosol samples in the close vicinity of a high-temperature plasma and still provide sensible results. In the present work we discussed the possibility to produce aerosol nanoparticles of a defined composition and properties by the plasmatron technique.
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Tungsten filters
Brožek, Vlastimil ; Matějíček, Jiří ; Neufuss, Karel
Spheroidized tungsten powder was sintered by HIP and BELT methods at 1750°-1950°C. Sintering temperature and sintering pressure, which controls the pore distribution in final products, was optimized by increased hardness of tungsten particles through the formation of unreacted WC ore W2C core. Porosity and permeability of tungsten filters, which application is foreseen in high temperature filtration of metals and melts inorganic substances were measured.
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Metallic and ceramic filters for high temperature applications
Brožek, Vlastimil ; Neufuss, Karel
Tungsten, tungsten carbide, aluminium oxide, titanium oxide, zirconium silicate and tungsten silicide powders were spheroidized in water stabilized plasma. After shape-classification the microfilters were sintered by HIP and HP methods at 1800-2000°C and 150-270 MPa. The permeability, porozity, corrosive and temperature resistence and mechanical properties were tested.
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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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Plasma spray deposition of tungsten matrix cermets
Brožek, Vlastimil ; Matějíček, Jiří ; Neufuss, Karel
This article describes experimental results of plasma spray deposition of tungsten carbide molten by a water stabilized plasma in a WSP® generator. During the deposition on ceramic or metallic substrates, chemical changes take place: decrease of bonded carbon content and formation of metallic tungsten. In the deposit, tungsten forms a matrix that fixates the unreacted monocarbide WC from the starting powder and hemicarbide W2C formed by the thermal decomposition. the ration of these carbides and the tungsten matrix can be controlled by a complex array of spraying parameters. These parameters, such as starting powder size, injection velocity, feeding distance, spraying distance and cooling mode, are confronted with the final product properties – structure, composition and mechanical properties (hardness and Young’s modulus). The materials presented here reached Young’s moduli between 135 and 250 MPa and microhardness of the matrix around 9.23 GPa.
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