title: NMR study of the vapor phase contribution to diffusion in partially filled silica glasses with nanometer and micrometer pores.
abstract: The contribution of the vapor phase to molecular diffusion in porous silica glasses with nanometer (Vycor) and micrometer (VitraPor#5) pores partially filled with water (polar) or cyclohexane (nonpolar) was investigated with the aid of field-gradient NMR diffusometry. Due to the vapor phase, the effective diffusion coefficient of cyclohexane filling micrometer pores (VitraPor#5) increased up to 10 times relative to the value in bulk liquid upon reduction of the pore space filling factor. On the other hand, the effective diffusion coefficient of water first decreases and then increases when the liquid content is reduced. The dependence of the effective diffusion coefficient on the pore filling factor is strongly related to the pore dimension. A general two-phase exchange model is presented that is well accounting for all experimental diffusion features.
authors.affiliation: Physics Department, Technical University, 400020 Cluj-Napoca, Romania. ioan.ardelean@phys.utcluj.ro
authors.forename: Ioan
authors.initials: I
authors.lastname: Ardelean
authors.forename: German
authors.initials: G
authors.lastname: Farrher
authors.forename: Carlos
authors.initials: C
authors.lastname: Mattea
authors.forename: Rainer
authors.initials: R
authors.lastname: Kimmich
mesh_terms: D003510:Cyclohexanes; D004058:Diffusion; D005898:Glass / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D016062:Porosity; D014835:Volatilization; D014867:Water
chemical_list: D003510:Cyclohexanes; D014867:Water