Active species in N₂and N₂-O₂afterglows for surface treatments

Abstract

Production of active species is studied in N 2 and in N 2 -O 2 afterglows of electrical discharges at low and atmospheric gas pressures. They are produced in microwave discharges in a large range of gas pressures from a few Torr to 100 Torr and in corona discharges at atmospheric gas pressure. The active species in N 2 afterglows are the N-atoms which are in the range of a few percents in the afterglows. The effect of O 2 molecules in low percentages in low pressure N 2 microwave plasmas and as impurity in corona N 2 discharges is specially analysed. The interaction of N and O-atoms with surfaces is studied for bacteria decontamination and for transmission of Natoms though porous membranes. The processes of bacteria decontamination in N 2 -O 2 afterglows are described for low pressure microwave and atmospheric pressure corona discharges. Transmission of N-atoms through porous membranes is studied at medium pressure (10100 Torr) microwave afterglows.

Experimental characterization of TIAGO torch discharges: surface wave discharge behavior and (post-)discharge kinetics

“…) are detected in the plume region (mainly in Zone III) (figure 5(c)) together with the emission of the NO γ band (figures 5(c) and (d)) with the reduced presence of charged particles suggests that the plume could behave as an afterglow (post-discharge) observed after N 2 -O 2 -based discharges, as has been extensively reported [59][60][61][62][63][64][65], although the non-negligible concentration of charged particles needs to be discussed.…”

“…This behavior can be explained by the destruction of nitrogen ions detailed previously through reaction (9), providing this region with a higher density of nitrogen -atoms. Indeed, the emission of the FPS, N 2 (B 3 Π g → A 3 Σ + u ) started being detectable in positions where the FNS reaches its maximum, tending to be more noticeable as FNS intensity decreases, supporting the idea of the destruction of N + 2 in the latter positions of Zone II by (9) since nitrogen atoms are required for the emission of the FPS [59,60].…”

“…through the emission of the first positive system (FPS; B 3 Π g → A 3 Σ + u ) (figure 6). Nonetheless, according to [59,60] the upper level N 2 ( B 3 Π g ) can be reached by the recombination of nitrogen atoms in the gas volume of an Ar − N 2 afterglow by reaction (6) producing to the emission of the FPS. Actually, the emission of the FPS has been noted as a fingerprint of nitrogen atoms in the plasma afterglow [60] N…”

“…According to [60][61][62][63], at microwave discharges operated at atmospheric pressure, high dissociation rates of N 2 into atomic nitrogen (7) and O 2 into atomic oxygen (8) by electron collisions can be obtained even with low percentage concentrations of these gases. Besides, according to [56] nitrogen atoms with high kinetic energy can also be formed by dissociative recombination of N + 2 ions (9) [63,64].…”

Time-resolved study of pulsed Ar–N2and Ar–N2–H2microwave surfaguide discharges using optical emission spectroscopy

“…Several important theoretical predictions were supported experimentally by the same authors [13,14]. In general, a considerable amount of research has focused on the basic applications of microwave discharges [4,5,16,17], gas temperature measurements [5,9,18], and the evaluation of atomic species production [3,19,20] is related mainly to the non-pulsed MSGDs. As a result, pulsed MSGDs remain rather unexplored, even though the study of molecular gas dissociation and time evolution of the plasma characteristic temperatures (T gas , T rot , T vibr , T e ) is of particular interest in this case.…”