Karl Franzens University Graz
Graz University of Technology
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Karl Franzens University Graz | Graz University of Technology | |
Phase transitions in confined geometry Nanoporous materials with cylindrical pores of some nanometers in diameter on a highly ordered pore lattice are ideal model systems to study the behaviour of fluids and solids in confinement. We report on the liquid film formation and on the gas-liquid phase transition (capillary condensation) of simple fluids by applying in-situ small-angle X-ray (SAXS) and neutron scattering (SANS). Moreover, we study the self assembly of amphiphilic molecules as well as the freezing and melting of water in confinement with these methods. In particular, we address the interaction of the guest molecules with the solid pore walls. This interaction leads to a pressure dependent (or temperature dependent) deformation of the solid material, which is monitored by following the shift of the Bragg reflections from the pore lattice. In the case of capillary condensation of simple fluids, this effect allows extracting nanoelastic properties of the material. Upon freezing and melting of water in confinement, the elastic response of the pore lattice is used as a nanoprobe to draw conclusions about the phase state of water as a function of temperature. |