E. Ricci et al., CHARACTERISTIC TIMES OF OXYGEN MASS-TRANSFER AT THE LIQUID-METAL VAPOR INTERFACE, Journal of Materials Science, 33(2), 1998, pp. 305-312
The interactions of liquid metals and alloys with the environment most
ly depends on the thermodynamic properties of the liquid surface. In f
act, the surface tension is strongly influenced by the presence in the
surrounding atmosphere of reactive gases through solution, adsorption
mechanisms and/or surface reactions. In particular, oxygen, which sho
ws a high surface activity towards a large number of metallic systems,
is the most important contaminant of liquid metals and alloys. Theore
tical approaches for estimating the oxygen mass transfer at the liquid
-vapour interface under inert atmosphere and vacuum have been develope
d already in order to relate the observed physical properties to the r
eal surface composition data. In the present work a model of the inter
facial transport of a liquid metal-oxygen system under Knudsen conditi
ons that foresees the temporal evolution of the interfacial compositio
n is presented. The diffusion characteristic times for reaching steady
-state conditions are evaluated in order to define two system ''sizes'
' depending on the different oxygen transport mechanisms in the liquid
phase. An experimental study of the interface evolution is at present
under way and preliminary results show a satisfactory agreement with
theoretical studies.