Berlin 2005 – wissenschaftliches Programm
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DF: Dielektrische Festkörper
DF 4: Poster
DF 4.19: Poster
Samstag, 5. März 2005, 08:30–16:30, Poster TU C
Broadband Dielectric Spectroscopy of Water confined in MCM-41 Molecular Sieve Materials — •Banys Juras1, Kinka Martynas1, Meskauskas Agnius1, Poeppl Andreas2, Voelkel Georg2, Boehlmann Winfried 2, Umamaheswari Venkatesan 2, and Hartmann Martin3 — 1Faculty of Physics, Vilnius University, Sauletekio 9, 2040 Vilnius, Lithuania — 2University of Leipzig, Faculty of Physics and Geoscience, Linnéstr. 5, D-04103 Leipzig, Germany — 3Department of Chemistry, Chemical Technology, University of Kaiserslautern, Erwin-Schrödinger-Str. 54, D-67663 Kaiserslautern, Germany
Dielectric properties of water adsorbed in pure siliceous and aluminum containing mesoporous MCM - 41 materials have been investigated in the frequency range 20 Hz to 1 MHz. The dielectric spectra revealed three dispersion regions, liquid like free water in the center of the mesopores, an intermediate water layer with reduced mobility, and an interfacial water layer at the inner surface of the mesopores. The latter displays features of the glassy state of a hydrogen-bonded system although the temperature dependence of the mean relaxation time follows the Arrhenius law. The analysis of the relaxation time distribution by means of a double well potential indicates a strong dependence of the water hydrogen bond strength in the interfacial layer on the framework aluminum concentration. Typical saddle point have been obtained for the relaxation time at higher temperatures.