MEASUREMENT OF DIFFUSION IN LIQUIDS WITHIN POROUS SOLIDS BY X-RAY MICRORADIOGRAPHY - DETERMINATION OF ERRORS AND OPTIMIZATION OF EXPERIMENTAL CONDITIONS

In principle, X-ray absorption measurements provide a straightforward method for determining local concentrations and fluxes, and hence loca l diffusion coefficients, during diffusion of species with high atomic number, within liquids, gels or opaque porous solids. However the app lication of this method is limited by the errors arising from X-ray ph oton statistics, which cannot be calculated exactly by analytical meth ods. Numerical simulation has been used to investigate the influence o f experimental variables on the errors in diffusion coefficients deter mined by an application of Fick's 1st Law. From these, guidelines have been developed for optimization of experimental conditions.