Dresden 2003 – wissenschaftliches Programm

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DF: Dielektrische Festkörper

DF 7: Poster

DF 7.23: Poster

Mittwoch, 26. März 2003, 14:30–18:00, P2a

Dielectric spectroscopy of SBA-15 and MCM-41 mesoporous molecular sieve materials — •Juras Banys¹, Jan Macutkevic¹, Andreas Poeppl², W Boehlmann², Georg Voelkel², and M Hartmann³ — ¹Faculty of Physics, Vilnius University, Sauletekio 9, 2040 Vilnius, Lithuania — ²Faculty of Physics and Earth Sciences, University of Leipzig, Linnestrasse 5, D-04103 Leipzig, Germany — ³Department of Chemistry, Chemical Technology, University of Kaiserslautern, P. O. Box 3049, D-67653 Kaiserslautern, Germany

Dielectric properties of MCM-41 and SBA-15 mesoporous moelcular sieve materials have been investigated in the frequency range 20Hz to 1 MHz. Dielectric spectra revealed two dispersion regions. The higher temperature dispersion at 300 - 230 K most probably is related with relatively free water freezing phenomenon in the mesopores. The low temperature (190 - 110 K) freezing is related with water molecular motion freezing on the inner surface of the materials. Obtained results support the idea that MCM-41 with framework Al stronger adsorb water compared with pure siliceous MCM-41, because both dispersion regions are much more clearly expressed in MCM-41 with Al. Also we must mark two interesting features: 1. the distribution of the relaxation times is shaped not symmetrically, probably due to the surface influence; 2. the mean relaxation time temperature dependence follows Arrhenius law in all investigated samples. The activation energy has been obtained.