Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Confined Fluids

CPP 17.10: Talk

Tuesday, March 24, 2009, 12:00–12:15, ZEU 160

Analysis of sorption strains in ordered mesoporous materials by in-situ x-ray diffraction — •Johannes Prass, Dirk Müter, and Oskar Paris — Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, D - 14424 Potsdam, Germany

Sorption and condensation of fluids create stresses in nanoporous materials. These induce strains in the porous matrix. The details of the solid matrix deformation, and how far in turn a strained matrix affects the sorption process are not well understood. In order to elucidate the extend of these interactions, we apply in-situ x-ray diffraction in ordered mesoporous materials during fluid sorption and condensation. Diffraction data provide not only valuable information on the pore structure and the fluid sorption behaviour [1]. Also "strain isotherms" - i.e. the strain of the pore lattice as a function of the fluid vapour pressure - are extractable from these experiments [2]. We investigated several different materials with 2D hexagonal pore ordering, and thereby varied the material, the porosity and the pore size. In addition we varied the fluid-solid interactions by using different fluids. We demonstrate that an "elastic modulus" can be extracted from the strain isotherms. This modulus cannot be directly related to the Young's modulus or the Bulk modulus due to the peculiar loading conditions which act within the porous body. We use simple analytical considerations and finite element analysis to better understand the relationship between measured strains and elastic properties of the porous solid.

[1] G. A. Zickler et al. (2006). Phys. Rev. B 73, 184109

[2] G. Günther et al. (2008). Phys. Rev. Lett. 101, 086104