A new model on hydrogen permeation is proposed, considering absorption and desorption processes on th sample surfaces. Analytical solution, satisfying the flux continuity rather than the concentration boudnary conditions, is derived from the model. Drift velocity through surface and drift velocity in bulk are introduced and their ratio determines the validity of the time-lag model. When the ratio of drift velocity through surface over that in bulk aproaches infinity, the proposed model is reduced to the time-lag one. The diffusivity and the drift velocity through surface can be evaluated by fitting the entire normalized permeation curve. The obtained results can perdict the effects of temperature, sample thickness and energy barriers of absorption and desorption on the permeation process. The thickness effect occurred is using the time-lag model is well explained by the effects of absorption and desorption on the permeation process.
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