Diffusion in multiphase systems with nonstationary boundaries I. Solution of diffusion in the region with boundaries movig in one direction

Abstract

In this work the problem of diffusion in a multiphase system whose both boundaries move in one direction according to the parabolic law with different velocities is analysed. The mathematical problem is solved exactly by means of thermal potentials of a double layer. The solution of the diffusion equation in the proximity to the boundary was derived and the concentration gradients on these boundaries were calculated. The numerical procedure of determining the diffusion characteristics from experimental concentration gradients on the phase boundaries was presented. As the zero approximation the result of calculations according to Vasileff and Smoluchowski, that can lead to considerable differences in the determined diffusion coefficients, was used.