Generators of Atmospheric Pressure Diffuse Discharge Plasma and Their Use for Surface Modification

Abstract

Studies of the properties of runaway electron preionized diffuse discharges (REP DDs) and their possible use have been carried out for more than 15 years. Three experimental setups generating a low-temperature atmospheric-pressure plasma and differing in the geometry of a discharge gap were developed. They allow the treatment of surfaces of different materials with an area of several tens of square centimeters. A diffuse discharge plasma was formed in the pulse–periodic mode by applying negative voltage pulses with an amplitude of several tens of kilovolts and a duration of 4 ns to a discharge gap with sharply non-uniform electric field strength distribution. This paper presents experimental results of the study of the surface layer microstructure of copper and steel specimens of different sizes after treatment with the REP DD plasma in nitrogen flow mode and nitrogen circulation mode in the discharge chamber. It was shown that after 105 discharge pulses, the carbon concentration decreases and a disoriented surface layer with a depth of up to 200 nm is formed. Moreover, the results of X-ray phase analysis did not reveal changes in the phase composition of the surface of copper specimens. However, as a result of surface treatment with the REP DD plasma, the copper lattice becomes larger and the microstress increases.

Ignition of Carbon Black during Nanosecond Diffuse and Spark Discharges in Air at Atmospheric Pressure

“…The flat electrode (anode) is exposed to reactive species and optical radiation resulting from ionization and excitation in plasma, as well as high-energy electrons and X-rays caused by their deceleration. Some results from modifying the surfaces of various materials with this kind of plasma are presented in [15].…”

“…We believe that the damage to the anode surface mentioned in papers [16,[19][20][21][22] is due to the relatively long duration of both the voltage pulse itself and its rise time, which leads to discharge constriction. Our previous studies [15,24] have shown that local damage to the surface of a flat electrode is only observed when anode spots are formed, which occur when the interelectrode distance decreases or the energy input increases. A discharge mode in which uniformity is improved and there is no local damage to the anode is implemented with an increase in the gap width as well as a decrease in the amplitude or duration of the applied voltage pulse.…”

Thin Luminous Tracks of Particles Released from Electrodes with A Small Radius of Curvature in Pulsed Nanosecond Discharges in Air and Argon

“…The formation of such discharges is accompanied by the generation of runaway electrons and X-rays [1,3,6], and the discharges themselves find practical applications in various scientific and technical fields. Thus, the diffuse discharge formed in the gap with a cathode with a small radius of curvature is used to clean surfaces from carbon, as well as to improve adhesion, to oxidize, and to harden a surface of various metals [7]. The use of pointed cathodes makes it possible to form diffuse discharges in pressured gases in a wide range of experimental conditions [1][2][3][4][5][6].…”

Thin Luminous Tracks of Particles from Electrodes with a Small Radius of Curvature in Pulsed Nanosecond Discharges in Air and Argon

“…[1,3,6], and the discharges themselves find practical applications in various scientific and technical fields. Thus, the diffuse discharge formed in the gap with a cathode, which had a small radius of curvature, was used to clean surfaces from carbon, improve adhesion, oxidize and harden the surface of various metals [7]. The use of point cathodes makes it possible to form diffuse discharges in pressured gases in a wide range of experimental conditions [1][2][3][4][5][6].…”