Critical depletion of pure fluids in colloidal solids: Results of experiments on EURECA and grand canonical Monte Carlo simulations.

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Details zur Publikation

Autorinnen und Autoren: Thommes M
Zeitschrift: Lecture Notes in Physics
Verlag: Springer
Jahr der Veröffentlichung: 1996
Band: 464
Heftnummer: Materials and Fluids under Low Gravity
Seitenbereich: 51-9-9
ISSN: 0075-8450


A microgravity expt. on the EURECA-1 mission of ESA was performed to study the adsorption of a near-crit. fluid (SF6) on a finely dispersed graphitic adsorbent (Vulcan 3-G graphitized carbon). The exptl. set-up was housed in a 3-stage high-precision thermostat (HPT) which allows for a temp. control within 1 mK over periods of days. The adsorption (surface excess amt.) Γ was measured as a function of temp. (T) along near-crit. isochores by using a volumetric technique. Five independent runs (either at the crit. d. (ρ/ρc = 1.01) or a slightly higher d. (ρ/ρc = 1.04)) were performed. The EURECA expt. confirmed a novel crit. sorption phenomenon, which is due to the colloidal state of the adsorbent. At temps. well above the crit. temp. (Tc), the adsorption excess amt. (Γ) increases with decreasing temp., but closer to Tc, exhibits a max. and then decreases sharply for T → Tc. The phenomenon was also obsd. for near-crit. isochores of SF6 in a mesoporous glass material. Grand canonical Monte Carlo simulations for a fluid in a slit-pore suggest that the neg. crit. adsorption effect is caused by depletion in the core region of the pore as T approaches Tc. This effect, (which the authors call crit. depletion), is believed to be driven by the proximity of the bulk fluid to its crit. point. It may be of significance whenever fluids in contact with mesoporous or colloidal materials approach their crit. point. [on SciFinder(R)]

FAU-Autorinnen und Autoren / FAU-Herausgeberinnen und Herausgeber

Thommes, Matthias Prof. Dr.
Lehrstuhl für Thermische Verfahrenstechnik

Zuletzt aktualisiert 2019-05-03 um 20:53