Low-Temperature Dynamics of Water Confined in Unidirectional Hydrophilic Zeolite Nanopores
Résumé
The dynamical properties of water molecules confined in the hydrophilic nanopores of AlPO4-54 zeolite investigated with Quasi-Elastic Neutron scattering as a function of temperature down to 2 K. Water molecular diffusion into the pore is measured down to 258 K. Diffusion follows a jump mechanism with a jump distance increasing with temperature and an activation energy of Ea = (20.8 ± 2.8) kJ/mol, in agreement with previous studies on similar confining media. Water rotational diffusion is instead measured down to temperatures (118 K) well below the water glass transition. The rotational time scale shows a non-Arrhenius behavior down to the freezing of water diffusion, while it has a feeble temperature dependence below. This fast molecular reorientation (fractions of nanoseconds) is believed to take place in the dense, highly disordered amorphous water present in the pore center, therefore indicating its plastic amorphous nature.
Domaines
Physique [physics]Origine | Fichiers produits par l'(les) auteur(s) |
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