Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: Poster: Interfaces and Thin Films

CPP 19.21: Poster

Dienstag, 15. März 2011, 18:00–20:00, P2

The structure of the interface between a solid substrate and a supercritical gas — •Sebastian Holz, Julia Nase, Michael Paulus, and Metin Tolan — Fakultät Physik/DELTA, TU Dortmund, 44221 Dortmund

Adsorption at interfaces is critical for many processes in nature, e. g. formation of gas hydrates, catalysis, or industrial applications like water purification. The formation of an adsorption layer enhances the gas offer significantly and is thus of importance for transport and exchange processes at membranes and interfaces in nature. More than 100 models have been established to describe the various types of adsorption isotherms. Supercritical adsorption, however, is far less understood, though this phenomenon has been known for some time now. It has tremendous importance in industrial applications like high pressure gas storage systems, Supercritical Fluid Chromatography (SFC), and polymer processing. However, the interface with a possible restructuration of the supercritical molecules has never been directly measured. In particular, the exact density profile along the surface normal can be determined by x-ray reflectometry, a reliable and well adapted technique to determine the thickness and roughness of interfaces.

We report on preliminary results concerning the adsorption of supercritical carbon dioxide and methane on a silicium wafer. The critical point of carbon dioxide is at T = 304,1 K and p = 73,8 bar and of methane at T = 190,6 K and p = 46,1 bar. We present a new measurement environment meeting the demands of this experimentally difficult study.