Seminars

Non-equilibrium (cold) plasmas are increasingly used in the chemical processing of gases for fuel synthesis, exhaust treatment, plasma assisted combustion, bio-fuels, plasma medicine, sterilization, plasma deposition, and etching. Typically, these discharges are operated at low pressure (~100 mTorr) constituting a uniform diffuse glow discharge. In recent years interest has increased in understanding and developing of cold high pressure (atmospheric) discharges. Here the focus is on the high-pressure streamer discharge. The main benefits of plasma streamers are their ability to operate outside vacuum conditions, plasma chemistry (especially production of radical species), low cost, and controllability.

In the presented thesis, streamer discharges in molecular gases have been investigated for two applications: (1) CO₂ reforming, and (2) ignition of thermal discharge. It was found that the streamers low energy tail primarily excites vibrational modes of molecular gases, while the streamer head is responsible for ionization and dissociation reactions. In (1), the excitation of the vibrational modes resulted in a secondary dissociation mechanism which was utilized to increase the conversion of CO₂. In this work pulsing of the streamer discharges populated the low lying vibrational modes which lead to vibrational exchange, and excitation of high vibrational modes. These high vibrational modes then dissociate, increasing the conversion of CO₂. In (2), excitation of the vibrational modes prevented the surface streamer discharge from bridging the inter-electrode gap. The decrease in conductivity due to vibrational losses prevented the ignition of a thermal discharges in argon-methane mixtures.