Water diffusion in nanoporous glass: an NMR study at different hydration levels |
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Authors: | Majolino Domenico Corsaro Carmelo Crupi Vincenza Venuti Valentina Wanderlingh Ulderico |
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Institution: | Department of Physics, University of Messina, C.da Papardo, S.ta Sperone 31, P.O. Box 55, 98166 S. Agata, Messina, Italy. majolino@unime.it |
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Abstract: | By pulsed field gradient nuclear magnetic resonance measurements, we investigated the translational diffusion of water confined in the 200 A diameter pores of a sol-gel silica glass. The experiments, performed as a function of the hydration level, showed an enhancement of the self-diffusion coefficient when the water content corresponds to one or fewer monolayers. An explanation for this occurrence has been given in terms of a two-phase process involving a fast molecular exchange between the liquid and the vapor phase. Moreover, in partially filled pores, the surface water diffusion coefficient was measured, and was 4 times lower than the diffusion of liquid confined water in saturated spaces. |
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