A kinetic study on oxygen transfer between solid oxide phase of ZrO2·CaO and liquid metal phase of silver with the aid of electromotive force decay curves

Abstract

An experimental method was developed to compare the rate of the metal-oxide interface reaction, O2−=O+2e, with the rate of oxygen transfer in liquid metal. A direct current was supplied to cause the polarization of the galvanic cell, Air: Liquid Ag−O÷ZrO2·CaO÷Liquid Ag−O: Air. The electromotive force decay curves were obtained at 1100°C immediately after the supply of the current was cut off. The degree of the polarization was increased by increasing the current and its duration time and by decreasing the area of metal-oxide interface. The absolute value of the electromotive forces was affected by the direction of oxygen transfer. The depolarization was accelerated by stirring the liquid silver. The shapes of decay curves were estimated with the rate controlling step at the first order interface reaction and at the nonsteady state diffusion of oxygen in liquid metal. From the shape of the measured decay curves and the stirring effect, it was concluded that the rate of the interface reaction is much more rapid than the rate of oxygen transfer in the liquid metal under the present experimental condition.