| AVS 61st International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS+SE-ThA |
| Session: | Atmospheric Pressure Plasma Processing; Fundamental and Applications |
| Presenter: | François Reniers, Université Libre de Bruxelles, Belgium |
| Authors: | D. Merche, Université Libre de Bruxelles, Belgium N. Vandencasteele, Université Libre de Bruxelles, Belgium A. Ozkan, Université Libre de Bruxelles, Belgium J. Hubert, Université Libre de Bruxelles, Belgium F.A.B. Reniers, Université Libre de Bruxelles, Belgium |
| Correspondent: | Click to Email |
In atmospheric plasma processes, the use of a main gas, usually considered as inert, to sustain the plasma is common. Nitrogen, argon and helium are the most regularly used gases. If the nature of the gas has a strong influence in the breakdown discharge voltage (due to Paschen Law), it also leads to plasmas which are optically and electrically different. This has drastic consequences on the chemistry and structure of plasma deposited coatings and on the chemistry of plasma treated gases. In this study, we compare, and try to explain, the results obtained on different topics using either argon or helium as main plasma gas.
All experiments have been conducted in dielectric barrier discharge reactors, powered with sinusoidal AFS generators, operating at frequencies lower than 40 kHz. For all the studies the reactors have been pumped down to evacuate contaminations and then backfilled with the plasma gas (Ar or He). The precursor is then injected in the DBD through the appropriate flow of the carrier gas.
Internal chemistry of coatings :
Through a combined XPS, FTIR and SIMS study, it is shown that the degree of cross-linking, the branching and the number of insaturations of plasma-polymerized polystyrene or sulfonated polystyrene (for fuel cell applications) is higher with argon than with helium, whereas the density of aromatics exhibits the opposite behavior.
Surface roughness of coatings
Similarly, for all the organic coatings synthesized by a dielectric barrier discharge (PS, CFx from C6F12, PA), the roughness, determined by AFM is always higher with argon than with helium.
Conversion of CO2 by DBD
Finally, the conversion rate of CO2 into CO in atmospheric plasma conditions (DBD), is higher when argon is the main plasma gas than with helium.
It is suggested that all these effects are strongly related to the plasma operating mode and to the energy distribution inside the plasma.
This work is supported by PSI-IAP 7 (plasma surface interactions) from the Belgian Federal Government BELSPO agency