Study of surface dielectric barrier discharge generated using liquid electrodes in different gases

Design and evaluation of plasma polymer deposition on hollow objects by electrical plasma generated from the liquid surface

“…grade) in distilled water with total conductivity of 30 mS · cm −1 was used as liquid electrodes. The choice of oxalic acid instead of some commonly known inorganic electrolytes (e.g., NaCl) was made to prevent the formation of salt crystals in the discharge zone, as it was found that formed crystals markedly deteriorate discharge uniformity and may affect the coating process . A PTFE tube with an outer diameter of 8 mm and inner diameter of 7 mm was inserted vertically into an oxalic acid solution and filled by the identical solution.…”

“…Electrical characteristics of the discharge were monitored by a digital oscilloscope Keysight DSOS204A oscilloscope connected to a voltage and current probes. The electrical discharge contains a large number of small current pulses predominantly in positive half‐cycle, which is in a good correlation with our previous measurements or according to Akishev et al that practically no streamers are visible during the negative polarity . Resonant frequencies and applied voltages ranged from 27 to 29 kHz and 13–17 kV, depending on the side and the mode of treatment.…”

“…The atmospheric pressure DBD discharges in its various forms, among which we can include our discharge, consist from filamentary microdischarges and, consequently, are usually highly non‐uniform. Our electrical discharge where the plasma ring is developed from liquid electrode, results in visually almost uniform diffuse plasma up to several centimeters in height.…”

“…In principle, the SDBD is generated due to high electric field generated in our case by the triple point effect at the common line between air, liquid electrode surface, and tube wall surface . Detailed description and some characteristics of this type of electric discharge can be found in the work of Galmiz et al Technically, any electrically conductive liquid can be used as the liquid electrode, but from the practical standpoint, low conductivity of solution leads to heating of the liquid electrode. In order to increase the conductivity of water based electrode and prevent the overheating, the 5 wt% solution of oxalic acid (Sigma–Aldrich, p.a.…”

“…Combining the basic features of discharges generated in contact with water with SDBDs by using water‐solutions as the discharge electrodes, we have designed a new type of SDBD generating thin layers of plasma which propagate along the treated polymer surfaces. The technique was aimed to achieve uniform atmospheric pressure plasma treatment of inner and/or outer surfaces of polymeric tubes and other hollow dielectric bodies .…”