Relation between the Transport or Friction Coefficients of Elementary Ions and the Interdiffusion Coefficients of Neutral Oxide Components in Multicomponent Slags

Abstract

Molten slag oxides are considered to be dissociated into single ions and/or ionic polymers. In multicomponent systems, linear relations between the fluxes of the ionic species and their electrochemical potential gradients have been introduced for isothermic and isobaric conditions. Relations among transport (and friction) coefficients of ions and the diffusion coefficient matrix of neutral component oxides have been obtained by using the conditions of the electroneutrality and local thermodynamic equilibrium in the slag. All transport (or friction) coefficients can in principle be experimentally determined regardless of the number of components in the slag. The practical aspects of the derived equations have been discussed with respect to 1) transport coefficients and their relation to tracer diffusion coefficients, 2) the interdiffusion coefficient and its relation to tracer diffusion coefficients in quasibinary slags, with some numerical examples, and 3) an approximate treatment given for the rate of diffusional relaxation processes in multicomponent systems for very short and for very long times. Also, rate equations have been derived for the oxidation of a metal by an oxidizing gas, when the metal is contained in a metal bath covered with a multicomponent slag layer. This equation can be compared with Wagner's equation for the oxidation of pure metals.