Dynamics of capillary condensation in aerogels

Abstract

Dynamics of capillary condensation of liquid 4He in various density silica aerogels was investigated systematically. Interfaces were clearly visible when bulk liquid was rapidly sucked into the aerogel. Time evolution of the interface positions was consistent with the Washburn model and their effective pore radii were obtained. Condensation was a single step in a dense aerogel and two steps in a low density aerogel. Crossover between the two types of condensation was observed in an intermediate density aerogel. Variety of the dynamics may be the manifestation of the fractal nature of aerogels which had a wide range of distribution of pore radii.

Absolute limit for the capillary rise of a fluid

“…where η is the shear viscosity of the liquid. Both simulations [27,28] and experiments [29,30] have been used recently to investigate fluid uptake dynamics at the nanoscale. The qualitative predictions of the L-W equation have been borne out, even for R ≃ 1 nm capillaries.…”

Spontaneous imbibition in a slit pore: a lattice–gas dynamic mean field study

“…Although we shall mainly consider the case of primary imbibition, when a liquid invades a dry capillary and precursor films appear in the complete wetting regime (which is the situation considered in the recent simulation studies [4,6]), we shall also briefly investigate the case where the liquid advances over pre-existing thin films (prewetted capillary) which is encountered in many actual situations, in particular in experiments with nanoporous solids [3,19]. We consider the case of a slit pore schematically represented in Fig.…”

Formation of superfluid liquid pocket in aerogel and its solidification by cooling

“…It has been used to investigate the disorder effects on condensed phases of He [3,9,11,13,14,[22][23][24][25][26]. A silica-aerogel sample of 96% porosity was grown in situ in a flat glass tube by Panasonic Corporation.…”

“…Silica-aerogels are highly porous materials whose pore size is on a nanometer scale while at the same time being very transparent; we can thus investigate the dynamics inside the material by visual observation. There have been several reports on the imbibition process of normal fluid and superfluid 4 He in aerogel by visualization [10][11][12]; superfluid 4 He is imbibed in aerogel at a constant rate while normal fluid 4 He is imbibed following the classical Washburn law. Anomalous two-step imbibition was also found in highly porous aerogels [11].…”