Restricted diffusion in silica particles measured by pulsed field gradient NMR.
The restricted diffusion coefficient of water through porous silica is measured by pulsed field gradient (PFG) NMR as a function of loading in order to develop a model for self-diffusion at full pore filling in sol-gel-made porous silica particles. This model describes the pore or intraparticle diffusion coefficient as a function of particle porosity, tortuosity, and the steric hindrance applied on the molecules by the pore space. The particle morphology is characterized by nitrogen adsorption and an appropriate tortuosity model is chosen in comparison with literature data. To characterize the material, NMR relaxation and diffusion studies at different degrees of pore filling were carried out in relation to the silica/water adsorption isotherm.
Veith
Susanne R
SR
Particle Technology Laboratory, Department of Mechanical and Process Engineering, Sonneggstr. 3, ML F25, Eidgenössische Technische Hochschule Zürich, 8092 Zürich, Switzerland.
Hughes
Eric
E
Vuataz
Gilles
G
Pratsinis
Sotiris E
SE