Figure 3. Diffusion resistances for water at the nanoscale.

(a) Scanning electron microscopy of the considered MFI zeolites (scale bar, 3 μm). (b) Representation of a zeolite specimen: water molecules can intrude the nanopores through the surface S_p, whereas V=S_pL is the volume of the specimen. (c) Water transport through microporous materials is influenced by a series of nanoscale mass transport phenomena, namely: (1) bulk diffusion; (2) sticking probability to the solid surface; (3) resistance to micropore intrusion due to surface barriers (1/α); (4) diffusion resistance in the micropore network (L/(ΓD)).