The surface tension and the contact angle of liquid iron on the alumina substrate were measured at 1823 K over a wide range of oxygen concentration in the iron by the sessile drop method under the condition of oxygen transfer from the gas phase to liquid iron (3.8×10⁻⁶ mol/m²s).
It was presumed from the considerations of time-dependence of surface tension and the increasing rate of oxygen in liquid iron that the adsorption reaction at the liquid iron surface should be nearly in equilibrium with oxygen in liquid iron under the rate of oxygen transfer in the present study.
From the Gibbs adsorption isotherm, the excess quantities for oxygen at the liquid iron surface and the interface between liquid iron and alumina substrate were calculated as 2.1×10⁻⁵ mol/m² and 2.4×10⁻⁵ mol/m², respectively. The excess quantity for oxygen at the liquid iron surface is in good agreement with those obtained by previous investigators under the assumption of adsorption equilibrium of oxygen at the surface.
The relation between the surface tension, γ_lg (N/m), and the oxygen activity in the liquid iron is given by the following equation:
(This article is not displayable. Please see full text pdf.)
\ oindentThe contact angle of liquid iron on the alumina substrates decreases with increasing oxygen content in the iron. The work of adhesion increases with increasing oxygen content up to 0.03 mass%, while above 0.03 mass%, it increases very gradually with increasing oxygen content. FeO·Al₂O₃ was detected at the interface for the high oxygen level.