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Progress in Plasma Processing of Materials, 1999

ISBN:
1-56700-126-2 (Print)

INFLUENCE OF COPPER VAPOR ON TRANSPORT PROPERTIES OF AIR PLASMA AT EQUILIBRIUM AND IN A MULTITEMPERATURE MODEL

S. Combadiere
L.M.C.T.S.-ESA 6015 - U.E.R. des Sciences, University of Limoges 123, Avenue Albert Thomas - 87060 Limoges Cedex - France

Jacque Aubreton
SPCTS University of Limoges, 123 av. A. Thomas, 87060 Limoges cedex, France

M. F. Elchinger
SPCTS University of Limoges, 123 av. A. Thomas, 87060 Limoges cedex, France

Pierre Fauchais
Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface UMR CNRS 6638 University of Limoges 123 avenue Albert Thomas, 87060 LIMOGES - France

Abstract

The calculations of thermodynamic and transport properties of a mixture of air and copper vapor involve 17 different chemical species and 153 weighted collision integrals. Copper vapor influences plasma properties by its lower ionization potential compared to that of N and O. At equilibrium this effect is the most important for electrical conductivity a due to the drastic increase of electron density at temperatures lower than 9,000 K. With high Cu percentage ( > 10 vol%) σ increases drastically compared to that of air for T < 9,000 K. The viscosity is slightly increased below 8,000 K compared to that of air (higher mass of the mixture) and a plateau shows-up between 7,000 and 12,000 K. The thermal conductivity K is reduced below 8,000 K and this is due to the decrease in air percentage and for 30 vol% of Cu over 8,000 K. K is increased below 12,000 K (copper ionization) while over 12,000 K it is reduced.
A new method was developed to calculate the composition of a multitemperature plasma. In this method, partition functions were expressed as a product of series expansion and plasma properties were determined at three temperatures: those of the heavy species Th, electrons Te and vibrational states Tv. When electron temperature Te is twice that of heavy species Th (at 6,000 K for example) the drastic increase of N2+, O2+ and NO+ competes with Cu++ for low Cu percentages. The plasma is electrically conductive for T > 3,000 K. For K the ionization peaks of N and O occur at 7,000 K while the ionization peak of Cu overlapps with N2 dissociation shifted to 5,200 K. The increase of Tv shifts the dissociation peaks towards higher temperatures. The viscosity peak is reduced and the curve exhibits two peaks corresponding to ionization on the one hand of Cu and the other of N and O.