Berlin 2008 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 45: Nanostructured Materials VI
MM 45.2: Vortrag
Donnerstag, 28. Februar 2008, 15:15–15:30, H 0111
Modeling experimental SAXS data from fluid sorption in ordered mesoporous silica — •Dirk Müter1, Susanne Jähnert2, Gerhard Findenegg2, and Oskar Paris1 — 1Department of Biomaterials, MPI of Colloids and Interfaces, Potsdam — 2Stranski Laboratory of Physical and Theoretical Chemistry, TU Berlin
Experimental small angle x-ray scattering (SAXS) data from an in-situ sorption experiment of dibromomethane (CH2Br2) in 2D hexagonally ordered mesoporous silica (SBA-15) are evaluated using two complementing modeling approaches. The SAXS data were measured as a function of relative vapor pressure of dibromomethane at room temperature. The integrated intensities of up to 10 measured Bragg reflections were simultaneously fitted with a superposition of analytical functions derived from an improved model for the formfactor of the pore/liquid system [1]. By this the pore morphology can be described, and the sorption process can be followed quantitatively in terms of liquid film formation and capillary condensation. However, a discrepancy of the total amount adsorbed is noticed in comparison to the sorption isotherm measured by a microbalance. To account for this difference we have studied a model in which additional micropores are randomly inserted in the mesopore walls of the silica matrix. Numerical Fourier transformation of this model system shows that the micropores contribute mainly to diffuse scattering while adsorption into these additional pores improves the agreement with the microbalance measurements.
[1] G. Zickler et al., Phys. Rev. B 73 (2006) 184109.