Influence of ambient air on the flowing afterglow of an atmospheric pressure Ar/O2 radiofrequency plasma

Abstract

International audienceThe influence of ambient air on the flowing afterglow of an atmospheric pressure Ar/O2 radiofrequency plasma has been investigated experimentally. Spatially resolved mass spectrometry and laser induced fluorescence on OH radicals were used to estimate the intrusion of air in between the plasma torch and the substrate as a function of the torch-to-substrate separation distance. No air is detected, within the limits of measurement uncertainties, for separation distances smaller than 5 mm. For larger distances, the effect of ambient air can no longer be neglected, and radial gradients in the concentrations of species appear. The Ar 4p population, determined through absolute optical emission spectroscopy, is seen to decrease with separation distance, whereas a rise in emission from the N2(C–B) system is measured. The observed decay in Ar 4p and N2(C) populations for separation distances greater than 9mm is partly assigned to the increasing collisional quenching rate by N2 and O2 molecules from the entrained air. Absorption measurements also point to the formation of ozone at concentrations from 10^14 to 10^15 cm-3, depending both on the injected O2 flow rate and the torch-to-substrate separation distance

LDPE Surface Modifications Induced by Atmospheric Plasma Torches with Linear and Showerhead Configurations

“…Although some VUV are known to be emitted by plasma, the effect of these radiations can be considered as negligible for the treatment of polymers due to the ambient air oxygen absorption . In the pure Ar post‐discharge, the main species are highly‐excited states of Ar but also OH and O radicals . Also, simulations performed by Atanasova et al on the showerhead plasma torch show the presence of Ar 2 + ions in the post‐discharge few millimeters away from the grounded electrode .…”

“…This current being positive, it represents a flow of positively charged gaseous species that could result from Ar 2 + ions. O + , N + , O 2 + , N 2 + , or even Ar + ions might participate to this positive current but as no emission from them could be detected by optical emission spectroscopy, they might be involved in non‐radiative processes …”

The effect of collisional quenching of the O 3p3PJstate on the determination of the spatial distribution of the atomic oxygen density in an APPJ operating in ambient air by TALIF

“…Duluard et al used mass spectrometry and LIF on OH radicals to estimate the intrusion of air in an Ar/O 2 RF atmospheric pressure plasma [15]. Yonemori et al obtained the 2D distribution of air-helium mixture ratio in a helium atmospheric plasma jet by LIF on OH radical which has a longer effective lifetime compared with the O 3p 3 P J state [16].…”

Molecular Surface Analysis and Depth-Profiling of Polyethylene Modified by an Atmospheric Ar-D2O Post-Discharge

“…However, water vapor can be deliberately introduced into an atmospheric post‐discharge to generate large densities of OH and O radicals, that could be homogeneously grafted onto polymer surfaces. In this branch of research, recent and complementary studies, such as the simulations conducted by Atanasova et al, the experimental contributions of Duluard et al and the plasma diagnostics of Collette et al, all based on the same plasma device as the one used in this work, elucidate the chemical mechanisms occurring in presence of water. Specifically, the production of O, H, and OH radicals as well as H 2 O 2 has been evidenced as responsible of the LDPE surface modifications induced by an Ar/H 2 O post‐discharge.…”