Sandrine Villeger

Interaction of N atoms through a nylon membrane in nitrogen flowing post discharges

The results of investigations conducted with a nylon membrane exposed to a N2 flowing (1 Ln min−1, i.e. 1 normal litre per minute) microwave (100 W) post discharge, produced at low gas pressure (1–30 mbar), are presented. The N atoms transmission through the nylon membrane was measured from the intensity variation of the N2 first positive afterglow before and after the nylon membrane. The physical surface property changes were observed by SEM microscopy.It appeared that N atoms penetrate and cross the nylon (pore diameter 5 µm) with a transmission factor of about 20% at the beginning of the treatment (first few minutes of the treatment time). This coefficient increased to 50% after 30 min of exposure. The modification of the membrane holes was followed by SEM. An increase in the nylon pores with the treatment time, from 5 to 10 µm after 5 min of treatment, is shown. The CN emission observed by emission spectroscopy during treatment confirmed this finding. It is a result of N atoms reacting with CHx radicals coming from nylon etching. On the other hand, the NOβ observed are the result of recombination of N atoms with O atoms coming from gas impurities (air and water vapour). A transmission factor of about 5% of O atoms through the nylon membrane at the initial treatment time is deduced.