Berlin 2005 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 28: Nano structures
CPP 28.3: Talk
Tuesday, March 8, 2005, 15:45–16:00, TU C243
Structural characterization of physisorbed nitrogen films in periodic mesoporous silica by small-angle diffraction — •Andreas Schreiber1,2, Ingke Ketelsen1, Sebastian Schemmel1, Ernst Hoinkis3, and Gerhard H. Findenegg1 — 1Stranski Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Sekr. ER1 — 2POROTEC GmbH, Hofheim/Ts. — 3Hahn-Meitner Institut Berlin
Periodic mesoporous oxides such as MCM-41 represent nanostructured host materials exhibiting quasi-periodic order on a mesoscopic scale while being amorphous on the atomic scale. Due to their well-defined pore geometry they are useful for fundamental studies in fluid physics, such as the effect of pore size on physisorption and pore condensation. We have studied nitrogen adsorbed films in MCM-41 and SBA-15 using small-angle neutron diffraction by analysing the intensities of the leading Bragg peaks resulting from the 2D hexagonal packing of the cylindrical pores. The dependence of the peak intensities on the amount of adsorbed gas can be reproduced by a crystallographic model [1] with the form factor F(R1,R2) of a core-shell cylinder, where R2 represents the pore radius and t = R2-R1 the film thickness. This analysis was used to discriminate between semi-empirical expressions for t as a function of the relative pressure p/p0.
[1] M. Impéror-Clerc et al., J. Amer. Chem. Soc. 122 (2000) 11925