2-dimensional micro discharge array sources that comprise of hundreds or thousands of geometrically identical micro cavities have been discussed for homogeneous large area treatment: In each individual cavity a Micro discharge is operated at or close to atmospheric pressure. The devices are primarily built from silicon Wafers modified by micro-structure techniques. They can be produced up to dimensions of several square decimetres. A simplified metal-grid micro plasma array has been developed in the DFG research Group FOR 1123 as an alternative to silicon based micro discharge arrays which often suffer from limited lifetimes. It consists of a stack formed by a stainless steel grid, a dielectric sheath, and a counter electrode. It Shows excellent stability and physical comparability to silicon-based devices. In contrast to the silicon based devices the metal grid arrays can be scaled up - in principle - to very large dimensions. Recently, it was shown that the behaviour of micro discharge arrays corresponds to that of a set of coupled individual dielectric barrier discharges. Depending on applied electrical field, polarity, and pressure the
discharges extend out of the cavities. Thus, enclosing the array structure with a second dielectric at a small gap distance forms an in-plasma-catalyst (IPC) reactor. Volatile organic compounds (VOC) in gas flown through can be reformed in this reactor. The gas flow, or throughput of the IPC, is determined by the dimension of the array and the open gap to the dielectric cover, where a larger gap may reduce the conversion efficiency. These devices also allow to integrate dielectric, catalytic surfaces as the cavity bottom. Apart from direct gas reformation, plasma is also used to ’clean’ and ’refresh’ occupied catalytic surface sites.The plasma parameters as well as the distribution of the discharges inside and above the cavities are strongly dependent on parameters such as cavity dimension, pressure, and voltage, and can thus be controlled externally. The resulting plasma determines as well the gas reformation as the direct interaction with the catalytic
surfaces. Hence, a detailed insight into the resulting plasma parameters is required.
The recently developed metal-grid micro discharge arrays ideally allow the control and investigation of the geometric influences on the micro discharges. We will investigate in detail the impact of the plasma conditions on the catalytic processes by observing the volume very close to the catalyst (MnO2, Al2O3). Following the gas flow (starting with CO2) across the device will yield an understanding of the process dynamics. Based on the understanding of the conversion processes and the discharge behaviour, changes of the cavity geometry or of the electronic excitation will allow to influence the processes. This will be forwarded by introducing an segmented IPC reactor composed of several independently driven sub-arrays. We will investigate in Detail the influence of the plasma conditions on the catalyst (’refreshing’) as well as the catalytic processes on the
plasma by observing the volume very close to the catalyst (MnO2, Al2O3) with phase- and space-resolved optical diagnostics. Ex-situ measurements of the catalytic surfaces of the disassembled configurations will then allow the investigation of the combined plasma and catalytic effects on the dielectric surfaces on the mm scale.
Powered by ChronoForms - ChronoEngine.com
copyright 2018 | SFB 1316 | Transient Atmospheric Pressure Plasmas - From Plasmas to Liquids to Solids