SU1293568A1 - Method of determining self-diffusion factor - Google Patents

Abstract

The invention relates to the field of metrology of diffusion processes in non-stoichiometric compounds. The purpose of the invention is to increase the expressiveness, accuracy and accuracy of determining the coefficient of self diffusion. At the same time, the scaling kinetics and the dynamics of the change in the degree of deviation from thermodynamic equilibrium at the metal-scale interface are measured at the initial stage of the process until a steady-state scaling regime is established. The correlation between the parabolic oxidation constant Kp and the degree of deviation from equilibrium at the metal – scale interface U – scale allows one to calculate the self-diffusion coefficient D; according to the formula D- -RTdKp / 2FdU, where R is universal on the gas constant, T is the temperature, and F is the Farade number. 2 Il. (L

Description

1129

The invention relates to the metrology of diffusion transfer processes in non-stoichiometric compounds and can be used to determine the self-diffusion coefficient in non-stoichiometric compounds (for example, in chalcogenides and oxides).

The aim of the invention is to increase the rapidity and accuracy of wear, reduce the time and degree of destruction of the scale.

On phi d.1 is a diagram of the device for implementing the method; Fig. 2 shows the dependence of the parabolic scale constant on the potential difference,

The method is carried out as follows.

The studies were carried out on a copper sulfide sample at 300, 350 and 400 ° C. A diagram of the experimental setup for carrying out the proposed method is presented in Fig. 1. Sample I under test is a tablet with a diameter of 15 mm, to which a quartz tube 2 with a diameter of 10 mm and a copper tablet 3 with a diameter of 10 mm are ground on top. Inside the quartz tube there is sulfur 4. The potential difference U at the metal-scale interface is measured using a complex potential probe 5,

The method of determining the coefficient of self-diffusion, -concluded in the forms

40

consisting of copper and ion filter,.

having unipolar conductivity 35 of the contact between the sample and the copper cations in the temperature range under study. As an ion filter, monovalent copper grade bhroma is used as the ion filter. The scaling kinetics is determined by the displacement rate of the CUjS / S interface. The displacement of the interface is determined visually using a cathetometer (KM-4) 6 with an accuracy of ± 0.01 mm. The entire device is located inside a quartz tube through which a stream of purified argon is passed.

using a diffuser plate, measuring the time dependence of the thickness of the oklin layer in the contact area, determining the parabolic calcification constant, and calculating the self-diffusion coefficient, which, in order to increase the efficiency and accuracy of determination, synchronously with the thickness of the scale, measure the potential difference between a layer of scale and diffuse constants define a functional dependent parabolic scale plate on the potential difference, and

After the sample is brought into contact with the metal at a given temperature, the changes in potential difference at the interface of Cu / Cu2S and the square of the thickness of the scale (s) over time are recorded. The parabolic scaling constant Kp is determined from the slope of the curve (i) f (t). The time to establish the stationary values of the potential differences is 60-80 minutes.

Fig 2 shows the dependence

Sy ;;; at 400 ° C

Cr f (u) for system By

the slope of the linear region of the dependence of Kp (i). in the initial stage by the formula

0

15

five

0

25

2F dU

universal gas constant, J / (mol K); temperature. TO; Farade number, CL g / eq; parabolic scaling constant, potential difference at the metal-scale interface, V ;;

the slope of the linear section in the initial stage of the dependence Kp (u), the coefficients D ,,, the self-diffusion of copper, the values of which are given below T ° C 300

350

D where P T - F dKp

ai

D

400

formula from

and

The method for determining the coefficient of self-diffusion, -concluded in the

 contact between sample and

plate diffusant, measuring the time dependence of the thickness of the scale of the scale in the contact area, determining the parabolic constant of the scale formation and calculating the self-diffusion coefficient, characterized in that, to increase expressivity and accuracy of determination, the potential difference between the layer of scale and constants is measured simultaneously with the thickness of the scale diffusant, determine the functional dependence of the parabolic scale plate on the potential difference, a.

self-diffusion coefficient D; calculated by the expression

RT, aCr 2p ai

D; -

- universal gas constant, J / (mol K); - temperature. TO; - Farade number, CL g / eq; - parabolic scaling constant, cm / s;

and - potential difference at the metal-dross interface, B;

the slope of the linear section in the initial stage of the dependence Kp (U).

/ (

ga-

550

N.Slobod iik

35O ig.g.

Compiled by A, Koshcheev Tehred I.Popovich

376/45

Circulation 777, Subscription VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab ,, d.4 / 5

Production and printing company, Uzhgorod, ul, Proektna, 4

d7O

Proofreader G. Reshetnik

Claims (1)

Claim The method for determining the coefficient of self-diffusion, which consists in forming contact between the sample and the diffuser plate, measuring the time dependence of the thickness of the scale in the contact area, determining the parabolic constant of scale formation and calculating the coefficient of self-diffusion, characterized in that, in order to increase expressivity and accuracy of determination, synchronously with the thickness of the scale layer, measure the potential difference between the scale layer and the diffusant constant, determine the functional dependence of the parabolic astin scale formation from a potential difference as well. self diffusion coefficient D; calculated using the expression, ₌ rt, acre 2F'dU 'where R is the universal gas constant, J / (mol "K); T is the temperature, K; F is the Faraday number, C "g / equiv; K is the parabolic constant of scale formation, cm ² / s; potential difference at the metal - scale interface, V; ac _r dU ~ ~ ^slope of a linear portion in an initial stage depending K _p (u). Proofreader G. Reshetnik