Oxygen transport and dynamic surface tension of liquid metals.

Theoretical models have been developed to study the behaviour of liquid metal surfaces in the presence of gaseous surface active elements, relating the mass exchange between the liquid metal and the surrounding atmosphere under the Knudsen regime. Steady-state conditions can be defined for which an 'effective oxidation pressure' is formulated, providing a useful means for a sound choice of the most convenient conditions for oxygen-free high-temperature surface tension measurements. The experimental results presented here concern dynamic surface tension measurements in a time window ranging from half a second to hours. They confirm the theoretical predictions of the model and reveal unexpected behaviours of the liquid surface when subjected to different temperature profiles