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Plasmachemical reactors for special syntheses and decomposition
Brožek, Vlastimil ; Janča, J. ; Mastný, L.
In the contribution the design of laboratory plasmachemical reactors for performing chemical reactions with high activation energy is described. It concerns RF-reactors with the capacity or induction excitation of the plasma, plasmachemical reactor with the unipolar microwave discharge, low-frequency gliding plasma reactor (Glid-Arc), and particularly the high-performance generator with water stabilized plasma of Czech provenience WSP®. Operation, effectiveness and output of these reactors are demonstrated on the syntheses of boron carbide and boron nitride of both solid and gaseous precursors, on the syntheses of inorganic pigments on the basis of zirconia, fluorite or condensed polyphosphates and also on tungsten carbide. All of them can be prepared in nanometric particle size with high specific surface area (tens of m2/g).
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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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