SKM 2021 – scientific programme

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DS: Fachverband Dünne Schichten

DS 4: Poster

DS 4.11: Poster

Tuesday, September 28, 2021, 10:00–13:00, P

Adsorption of fluids on hydrophobic surfaces under sub- and supercritical conditions — •Mike Moron, Göran Surmeier, Marc Moron, Jennifer Bolle, Susanne Dogan, Julia Nase, Michael Paulus, and Metin Tolan — Fakultät Physik/DELTA, TU Dortmund, 44221 Dortmund, Germany

Adsorption at interfaces is crucial for many industrial applications, e. g. adsorption-based separation, regeneration of adsorbents in purification processes as well as for natural gas storage. In subcritical systems the adsorption layers of different fluids had been successfully described as molecular thin layers. The layer thickness diverges when the pressure reaches the condensation pressure of the corresponding fluid, meaning that the adsorption layer transforms into a macroscopic condensate. Supercritical adsorption, however, is far less understood on a molecular scale because of the complex requirements to the experimental environment, although the phenomenon is of outstanding importance for many applications. For example, the use of supercritical CO₂ is a gentle method to dry porous materials without damaging the frameworks. We investigated the pressure dependent adsorption of the fluids argon, carbon dioxide, hexafluoroethane, octafluoropropane, and decafluoropropane on a hydrophobic silicon wafer coated with octadecyltrichlorsilane by means of X-ray reflectivity (XRR), where we could access the supercritical regime for hexafluoroethane and argon. The XRR studies were carried out at PETRA III Beamline P08 (DESY, Hamburg) at a photon energy of 25 keV and Beamline BL9 (DELTA, Dortmund) at 27 keV, repsectively.