Kinetics of oxide formation in liquid copper and silver |
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Authors: | Antonio Luraschi John F Elliott |
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Affiliation: | (1) Department of Metallurgy and Materials Science, Massachusetts Institute of Technology, 02139 Cambridge, Mass |
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Abstract: | The process of formation of oxide phases in liquid copper and liquid silver has been studied by pumping oxygen into the liquid
alloy with the use of a solid-electrolyte electrochemical cell. The oxygen potential at the electrolyte-metal interface is
monitored simultaneously by the electrochemical cell. A wide range of effects were observed ranging from the very rapid formation
of a layer of oxide at the electrolyte-metal interface to what appears to be homogeneous nucleation of the oxide in the metal.
The results may help to explain some of the difficulties that sometimes have been observed in using this type of cell to measure
the oxygen potential of a liquid metal. The results indicate that a supersaturation ratio of about 9 is necessary for homogeneous
nucleation of iron oxide (most probably Fe3O4(s)) in liquid copper containing 0.01 to 0.07 pct iron. The interfacial tensionσ
Cu-Fe
3O4 is calculated to be 0.74 J/m2. In experiments with higher concentrations of deoxidant (0.2 pct Fe in Cu and 0.2 to 0.4 pct Ni in Ag) equilibrium precipitation
of oxides apparently predominates over homogeneous nucleation for the experimental conditions employed. A mathematical model
which partly explains the different effects observed is presented. |
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