SU1193564A1 - Method of determining oxygen diffusion coefficient in metals and oxides - Google Patents

Abstract

METHOD FOR DETERMINING THE DIFFUSION OF OXYGEN, CA IN METALS AND OXIDES By applying external voltage to the electrodes of the electrochemical cell, measuring the ion current in time, and calculations from the data obtained from the diffusion coefficient. characterized in that in order to increase the accuracy of determining the diffusion coefficient while simultaneously expanding the circle of objects, the dependence of the electromotive force of the element on the time of removal is determined. external voltage and calculate the diffusion coefficient L by the formula M D where M is the amount of oxygen transferred through the electrolyte; § C the value of the excess oxygen concentration on the (L surface at the time t that has passed since the moment of switching on the external voltage.

Description

i / | aa / 1.460 1.390 1.352 1.312 1.302 1.289 1.280 1.274 1.268 1.264 t / c / 5 10 15 20 25 30 35 40 45 50

Then the cell is opened and the EMF is measured over time. . 1E / mV / 45.30 47..40 49.20 49.71 50.07 50.58 50.76 50.89 51.12 51.30 t / c / 70 80 100 110 120 140 150 160 160 180 200 E / mV / 51.42 5U52 51.62 51.72 52.11 - the equilibrium value of t / c / 200 240 270 270 300 600

The EMF values are recalculated to the value of the excess oxygen concentration on the surface according to the formulas which are obtained under the assumption that the oxygen activity coefficient is independent of the oxygen concentration.

f

2F

 expr (

R

C C

RT

Where

the equilibrium concentration of oxygen at the electrolyte / electrode interface, expressed in g-at / m;

T is the temperature; Ep, E is the equilibrium and current value of the emf.

A graph of the dependence l (i С f (1 (1 t)) is plotted.

linear dependence domain :: - J 01 t

0.5 At small times (up to 10 s) after the element has been opened (the elec- tine has not yet come down) of the olite and the reference electrode, at large (over 200) the difference between the equilibrium and current EMF values approaches the value of the fluctuation of the equilibrium EMF value (50 / Iv), due to the temperature drift. Ten points that fall into the area of direct proportionality are processed by the least squares method with a confidence interval of 95%. According to the obtained linear dependence, the Irt C value is calculated in the center of the interval (at the minimum point of dispersion). For .0, 111 С 8.69jf0.01 . From the data on the dependence of the ion current on time, calculate the amount of oxygen transferred by the formula p

Z

one"

- (PM

one

de i, i k K + i is the previous and subsequent values of current and time.

M - the amount of transferred

oxygen in g-at; n is the number of measurements. The calculated values of the substitute M

5 are in formula D

 t.

,

D (1.28 ± 0.04) is thus obtained. The error is 3%.

In this way, the proposed method allows determining B with an error of two to three times lower than the basic method and one and a half to two times lower than the error of the known method (8%).

Claims (1)

METHOD FOR DETERMINING THE DIFFUSION COEFFICIENT OF KIS LOR 0, CA IN METALS AND OXIDES by applying external voltage to the electrodes of the electrochemical cell, measuring the ion current in time and calculating the obtained diffusion coefficient, characterized in that, in order to increase the accuracy of determining the diffusion coefficient while expanding the circle objects, determine the dependence of the electromotive force of the element on the time of removal. external voltage and calculate the diffusion coefficient B by the formula where M is the amount of oxygen transferred through the electrolyte; C is the magnitude of the excess oxygen concentration on the surface at the time £ elapsed from the moment the external voltage was turned on. >