Influence of oxygen gas on characteristics of self-organized luminous pattern formation observed in an atmospheric dc glow discharge using a liquid electrode

Abstract

Self-organized luminous pattern formation is observed in the liquid surface of an atmospheric dc glow discharge using a liquid electrode with a miniature helium flow. The factors affecting pattern formation are the gap length, discharge current, helium mass flow rate and polarity. The pattern shape depends on the conductivity and temperature of the liquid electrode. A variety of patterns were observed by changing the conductivity and temperature of the liquid. We clarified that the self-organized pattern formation depends on the amount of electronegative gas, such as oxygen, in the gas in the electrode gap. When an oxygen gas flow was fed to the liquid surface from the outside in an obliquely downward direction, namely, the amount of oxygen gas on the liquid surface was increased locally, self-organized pattern formation was observed in the region with the increased amount of oxygen gas. When the amount of oxygen in the gas in the gap was changed by using a sheath flow system, the appearance of the pattern changed. The presence of oxygen gas strongly affected the self-organized pattern formation of the atmospheric dc discharge using a liquid anode.

Pattern formation and self-organization in plasmas interacting with surfaces

“…As for figure 18, a DC glow discharge of He over a liquid anode is used. For both, a 1% NaCl solution or tap water anode, the self-organization of patterns tends to appear for larger inter-electrode spacing and high currents [167,169]. The emergence of patterns was also found to be dependent on the axial flow rate, with lower flow rates favoring the formation of patterns; as well as on the liquid temperature, par ticularly on the vapor pressure [167].…”

“…Such response is qualitatively maintained for higher flow rates of incident gas. Moreover, further investigations show the emergence of anode patterns due to the diffusion of air on a He discharge, whereas no patterns are observed when a sheath flow of N 2 (which limits the entrainment of O 2 into the discharge) is used [167].…”

“…(a) The obtained patterns transition from a single constricted diffuse spot, to set of concentric annular patterns, and then to an array of spot patterns for increasing values of current in an atmospheric-pressure DC glow discharge on a liquid water anode; and (b) the imposition of an incident lateral flow of gas causes only the deflection of the plasma column when N 2 is used, whereas a complex pattern emerges when O 2 is used. (Adapted from [167] with permission, copyright 2014 IOP Publishing Ltd.) constricted diffuse spot, to a set of concentric annular patterns, and then to an array of spot patterns for increasing values of current. Figure 18(b) depicts the effect of the imposition of an incident lateral flow of molecular gas on the obtained patterns.…”

“…A different line is used for a given electrode spacing, whereas a shaded area indicates a specific type of pattern. (Adapted from [167] with permission, copyright 2014 IOP Publishing Ltd.) study of pattern formation and self-organization phenomena in plasmas interacting with surfaces is important not only for a deeper understanding of nature, but also for their relevance to technological applications that exploit or mitigate selforganization, e.g. from surface activation and texturization, to electrode erosion and process nonuniformity.…”

Comparison between the water activation effects by pulsed and sinusoidal helium plasma jets

“…Plasma jets are normally excited by pulsed voltages with kilohertz repetition frequencies as well as sinusoidal voltages in the kilohertz-to-megahertz range. [15][16][17][18][19][20] Besides, related studies have been reported with concern of the discharge characteristics, 21 the discharge mechanism, 22,23 and the analysis of plasma products, 24 etc. Recently, the comparisons of pulsed and sinusoidal plasma jets in the gas phase have been reported, 15,25 and the results show that pulsed excitation is more efficient to produce energetic electrons rather than heat the gas, 25 and hence more reactive species can be generated in pulsed plasmas.…”