Instability of homogeneous barrier discharge in humid air, N2 and O2 at atmospheric pressure

Summary form only given. Dielectric Barrier Discharges (DBDs) can be applied to surface treatment, ozone generation, removal of NOx in diesel exhaust gas and so on. However in case of surface treatment of thin polymer film by DBD, pinholes or nonuniform surface modification may sometimes appear because the DBD is composed of many filamentary micro discharges. Therefore, many researchers have investigated various methods to generate the stable homogeneous barrier discharge at atmospheric pressure. In 2009, we succeeded in generating homogeneous discharge in air, nitrogen and oxygen by using barriers made of alumina A473 (Supplier: Kyocera Corporation). This discharge is recognized as an Atmospheric Pressure Townsend Discharge (APTD). Recently, we found interesting phenomena that although the APTD can be generated in humid oxygen, it cannot be generated in humid air and humid nitrogen (RH: 80%). In this study, in order to clarify why discharge mode in humid air or nitrogen gas transferred from homogeneous mode to filamentary mode, we analyzed gas components after discharge using an FTIR analyzer with a long path gas cell (1 m).The results showed that in case of dry air, O₃, N₂O₅ and N₂O were detected in exhaust gas, however, in case of humid air, O₃, N₂O₅, N₂O, NO₂ and HNO₃ were detected. In case of humid nitrogen gas, N₂O₅, N₂O and NO₂ were detected. However in case of humid or dry oxygen gas, O₃ was only detected. Therefore, our conclusion is that the generation of NO₂ and/or N₂O₅ seems to be a cause of transition phenomena from homogeneous mode to filamentary mode.