The importance of correct boundary conditions in the estimation of diffusion coefficients from mass sorption experiments

Abstract It is shown in this paper that the wrong choice of boundary conditions in the evaluation of diffusion coefficients in solids can lead to quite unreliable estimates. In particular the two frequent assumptions of immediate reequilibration at the interface or of a radiation--like boundary condition are shown to be completely inadequate if the process kinetics is different. To overcome these difficulties we describe a new method that estimates the unknown boundary conditions along with the diffusion coefficient. A numerical example is examined for comparison.