Microwave Plasmas at Atmospheric Pressure

Abstract

Microwave plasmas at atmospheric pressure are used for surface treatments like for example cleaning, sterilization or decontamination purposes, for a pre-treatment to increase the adhesion of lacquer, paint, or glue, and for the deposition of different kind of layers and coatings. Micro plasma jets can also be applied for biomedical applications and for treatment of small and complex geometries like for example the inside of capillaries. Larger plasma torches which exhibit higher gas temperatures can also be used for chemical syntheses like waste gas decomposition, methane pyrolysis, or carbon dioxide dissociation and for plasma spraying purposes. In the present publication an overview on the development and the investigation of the operating principle of two atmospheric pressure microwave plasma torches at frequencies of 2.45 GHz and 915 MHz will be presented. The plasma sources are based on a cylindrical resonator combined with coaxial structures. To explain how these plasma sources work, simulations of the electric field distribution will be discussed. Furthermore, some physical characteristics of an air and an Ar/H2 atmospheric plasma like gas temperatures, excitation temperatures and densities as well as the heating of the plasma by the microwave will be investigated.

Design and optical study of a microwave plasma torch in nitrogen used for the evaporation of aluminium wires

“…The torch is similar to the torches operated in Ar, Ar–N 2 gas mixtures, or in ambient air . The torch in Ref.…”

“…This type of plasma has been an object of continuous attention and development. In general, microwave discharges (MWDs) are characterized by high flexibility of design and adaptability to particular applications. The design of MWDs has considerable influence on its operation range, for example, available pressure ranges, types of useable feed gases, power dissipation processes, excited discharge volumes, and also vacuum compatibility, and might strongly influence the discharge parameters, including the plasma composition, gas temperature, and electron energy distribution function.…”

“…During the last decade, much progress has been achieved, in particular, in the generation and sustenance of atmospheric‐pressure MWDs. The flexibility of the design of MWDs provides opportunities for new applications of microwave plasmas. This work concerns the development of an MWD for aluminium nitride (AlN) synthesis.…”

Atmospheric Pressure 2.45-GHz Microwave Helium Plasma

“…The motivation was the observation of time evolution of a mw helium discharge. The mw discharge imaging was used for argon and helium discharges and observed plasma structure changes [12] and different plasma regimes and modes [7], [13]. This paper concerns temporal evolution of an atmospheric-pressure mw helium plasma and its parameters.…”

“…On the other hand, the atmospheric-pressure mw plasma parameters were determined by optical emission spectrum (OES) method in several works. The Boltzmann plot method was used to calculate excitation temperature of argon [6], [7] and helium [8] mw discharges. A 13-mm-diameter helium plasma has been generated by atmospheric-pressure plasma torch that consists of a copper antenna in a quartz tube [9].…”