Abstract
Chemical stresses induced during a diffusion process have a great influence on the diffusion process by enhancing the diffusion coefficient. The effective diffusion coefficient is a function of the concentration when chemical stresses are taken into account. The diffusion equation with the effective diffusion coefficient is numerically solved for the three cases, namely, permeation through a membrane, one-side charging and two-side charging of membranes, with the flux continuity boundary conditions, which include the surface effect, i.e., the adsorption, absorption and desorption reactions. The results indicate that chemical stresses enhance the diffusion process. If chemical stresses are neglected, both two-side charging and one-side charging have the same concentration profiles. However, when the chemical stresses are fed back to the diffusion, the concentration level for the two-side charging is higher than that for the one-side charging. The surface effect is also investigated by changing the ratio of the drift velocity in surface to the drift velocity in bulk, showing that the diffusion process is promoted by the increase of the drift velocity ratio. © 2007 American Institute of Physics.