Browsing by Author "Klages, Claus‐Peter"

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    A chemical-kinetic model of DBDs in Ar-H2O mixtures
    (Weinheim : Wiley-VCH, 2020) Klages, Claus‐Peter
    A simplified chemical-kinetic model was applied to Ar-H2O dielectric-barrier discharges (DBDs), presuming that dissociation processes are only due to energy transfer from excited Ar species. Good agreement was obtained between the densities of HO, H2, and O2 and experimental data from the literature, whereas a discrepancy for H2O2 could not be explained. The model is useful for designing DBD reactors and process development. Steady-state densities of H atoms increase with decreasing fractions of (Formula presented.) which should be kept below 0.1% to obtain a large zone of virtually constant and large H-atom density in the DBD reactor, whereas the HO density is hardly affected by (Formula presented.). O2 contaminations must be kept well below 100 ppm in to attain maximum H-atom densities.
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    Does the energy transfer from Ar(1s) atoms to N2 lead to dissociation?
    (Hoboken, NJ : Wiley Interscience, 2020) Klages, Claus‐Peter; Martinovs, Andris; Bröcker, Lars; Loffhagen, Detlef
    Dielectric-barrier discharges (DBDs) in Ar–N2 mixtures, with N2 fractions in 0.1–1% range, would be attractive alternatives to DBDs in pure N2 if energy-transfer reactions between Ar(1s) atoms and N2 molecules were an efficient source of N atoms. Attempts to functionalize polyolefins in flowing postdischarges fed by such DBDs, as well as the search for the First Positive System in the emission spectrum, however, failed. Evidently, the energy-transfer reactions do not produce N atoms. For Ar(1s3) and Ar(1s5) metastable states, this fact has already been reported in the literature. For Ar(1s2) and Ar(1s4) resonant states, a quantitative argument is derived in this paper: energy transfer from Ar(1s) atoms to N2 molecules is not an efficient source of N atoms.
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    Evidence of ionic film deposition from single-filament dielectric barrier discharges in Ar–HMDSO mixtures
    (Weinheim : Wiley-VCH, 2020) Bröcker, Lars; Perlick, Gesa S.; Klages, Claus‐Peter
    The short residence time of Ar–HMDSO (Ar–hexamethyldisiloxane) gas mixtures rapidly flowing across atmospheric-pressure, glow-type, single-filament dielectric barrier discharges is utilized to accomplish thin-film deposition via a purely ionic route. A comparison of thin-film volumes obtained from profilometry, on the one hand, and from the transferred charge, on the other hand, enables to evaluate the mass of the ions contributing to the film growth. For HMDSO fractions at the lower end of the studied range of molar fractions, 50 ppm, pentamethyldisiloxanyl cations (Me3SiOSiMe2+, PMDS+), generated from the monomer via Penning ionization by Ar(1s) species, are mainly responsible for film formation. For HMDSO fractions growing beyond 1,000 ppm, ionic oligomerization processes by reactions of PMDS+ with HMDSO molecules result in a 2.5-fold increase of the average deposited ion mass.