Evaluation of experimental data of diffusion in semiinfinite two-phase systems with nonstationary interphase boundary by means of thermal potentials I. Theory

Abstract

The present work proceeds from the diffusion equation solution for the nonstationary interphase boundary by means of the thermal potentials. The relations for the amount of material determination in the sample after diffusion and the Matano plane position are derived as well as the original balance equations of the first type from these relations. Furthermore, the balance equations of the second type characterizing the relations between the immediate diffusion flows densities on the interphase boundary are presented. It was possible to make the analytical expression of the concentration gradients on the interphase boundary movement velocity calculation from the experimentally determined concentration profiles. These methods proceed from the knowledge of the areas below these curves, from the concentration gradients on the interphase boundary, from the product of both the quantities and from the knowledge of the area, gradient and interphase movement distance.

Twelve equations including the balance equations are derived for three diffusion characteristics calculation. Three equations in which the experimentally determined quantities are burdened by the least experimental error are used for the diffusion characteristics calculation and the remaining ones are used for checking.