The chemical diffusion of O in the liquid oxide was studied via the oxidation of the melt in a long capillary at 1615C. It was found that, when pure O was used as the oxidizing agent, the surface composition of the slag was in close agreement with the expected gas-slag equilibrium. This suggested that diffusion was the controlling step. This was not so when air, 5%O in Ar or pure CO2 was used to oxidize the slag. The deviation of the surface composition from the expected equilibrium value was then in accord with a mechanism of mixed control by gas-slag reaction and bulk diffusion. The average value of the chemical diffusivity of O (or Fe), in liquid oxide with an Fe2+/Fe of between 0.25 and 0.77, was found to be 3 x 10-7m2/s. This value was 1 to 2 orders of magnitude higher than those deduced from earlier studies. There appeared to be some correlation, between the chemical and ionic self-diffusivities, via the Darken equation.

Y.Sayadyaghoubi, S.Sun, S.Jahanshahi: Metallurgical and Materials Transactions B, 1995, 26[8], 795-80