Characterisation of diffusion/permeation properties of materials by tracer methods

The present paper is a brief presentation of the phenomenon of mass transport through solids by diffusion, and of associated characterisation techniques. Starting from a common approach, the cases of porous and non-porous solids are examined. In each case, one measurement technique, preferably involving the use of tracers, is described and the methods and main findings of a case study are discussed to exemplify the potential but also the intricacies of diffusion in solids.