The influence of solutes on kinetics and thermodynamics of liquid indium-oxygen systems
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I.
INTRODUCTION
COEXISTENCE of gases with liquid metals is very common in pyrometallurgical processes and in ingot production. In the practical realms, there is interest in gas- liquid metal interactions because of the influence of dissolved gases on the mechanical, electrical, and chemical properties of solid and liquid metal systems. In the case of solid metals, it is the interaction of gases with the liquid metal prior to and during solidification that determines the concentration and state of gases dissolved in the solid. As a consequence, interest focuses ultimately on the g a s - liquid metal interaction, even when the solid state is of interest. Fundamental knowledge in this area also contributes to improved understanding of the structure and properties of liquid metals. Recent advances in the theory and technology of solid state electrochemistry have provided a valuable tool for material research. Galvanic cells using solid oxide electrolytes may be used in a wide range of scientific and technological applications. ~.2Solid oxide electrolytes have been widely used to measure the Gibbs free energy of formation of different oxides 3'4'5 and the solubility and diffusivity of oxygen in liquid and solid metals. 6-t3 There have been a few studies of the oxygen diffusivities and solubilities in binary alloys, t~-18 Studies of oxygen diffusion and solubilities in In-Ga systems have shown a remarkable decrease in the diffusivity of oxygen near pure Ga and a large increase in oxygen diffusivity near pure In. ~3Investigation of diffusivity and solubility of oxygen in liquid In-Sn, ln-Pb, In-Cu, InAg, and In-Ti is expected to provide further information, which related to these unexpected results. II.
such a cell may be directly related to the diffusion coefficient of oxygen, without requiring knowledge of the initial oxygen concentration in the liquid metal. The electrolyte yttria-stabilized zirconia, YSZ (eight mol pct Y203), was used in most experiments because its electrolytic domain extends to the required low ranges of oxygen chemical potential; however, when appropriate, calcia-stabilized zirconia, CSZ (15 mol pct CaO), has been used. The heart of the apparatus is an electrochemical cell consisting of a YSZ electrolyte and two electrode compartments. The cell may be represented as Pt, Air (Po2 = 0.21 atm) [ YSZ [ liquid metal-oxygen, W/Pt. A schematic drawing of the electrochemical cell is shown in Figure 1. The experimental method assumes a transference number of unity for oxygen ions in the electrolyte. Under these conditions, Faraday's law relates the current through the cell and the number of equivalents of oxygen transported from one electrode to the other:
1/ZF = dn(O)/dt,
where I is the cell current in amperes, Z is the number of electrons involved in the corresponding half reaction, F is the Faraday (96487 coulombs/equivalent), n (0) is the number of mols (or gram atoms) of oxygen transported, and t is the time in seconds. The Nernst equation expresses the relation between the EMF applied to the elec
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