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Dresden 2009 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 13: Topical Session Nanoanalytics using Small-Angle Scattering I

MM 13.2: Vortrag

Dienstag, 24. März 2009, 10:45–11:00, IFW A

In-situ SANS study of domain formation during condensation and evaporation of fluids in SBA-15 — •Maxim Erko1, Johannes Prass1, Dirk Wallacher2, Astrid Brandt2, and Oskar Paris11Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, D-14424 Potsdam, Germany — 2Helmholtz Centre Berlin, Glienicker Straße 100, D-14109 Berlin, Germany

Ordered mesoporous materials such as SBA-15 are ideal model systems to study the sorption and condensation behaviour of fluids in confined geometry. A particularly interesting question relates to collective phenomena such as the formation of domains of unfilled and filled regions that extend over much larger spatial distances than the typical pore size. We have studied the formation and dissolution of such domains upon condensation and evaporation of contrast matching H2O/D2O and Perfluoropentane (C5F12) in SBA-15 silica with in-situ small angle neutron scattering (SANS), using the DEGAS sorption system at the BENSC neutron facility at Helmholtz Centre Berlin. The SANS data can be modelled by randomly distributed domains of filled and unfilled mesopores on a lattice as described by the classical Laue-scattering. Thus, the SANS data in the capillary condensation / evaporation regime can be fitted by an analytical model with only one free parameter, i.e., the filling fraction of mesopores. The quantitative values of this parameter are compared with the results from the independent volumetric sorption experiment, and the differences are discussed with respect to the metastability of the fluid in the adsorption regime.

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