Investigation of the dynamics of a percolation transition under rapid compression of a nanoporous body-nonwetting liquid
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SORDER, AND PHASE TRANSITION IN CONDENSED SYSTEMS
Investigation of the Dynamics of a Percolation Transition under Rapid Compression of a Nanoporous Body–Nonwetting Liquid System V. D. Bormana, A. A. Belogorlova, G. V. Lisichkinb, V. N. Tronina, and V. I. Troyana a
Moscow Institute of Engineering Physics, Moscow, 115409 Russia b Moscow State University, Moscow, 119992 Russia e-mail: [email protected] Received July 20, 2007; in final form, October 1, 2008
Abstract—The dynamics of infiltration of a nanoporous body with a nonwetting liquid under rapid compression is studied experimentally and theoretically. Experiments are carried out on systems formed by a hydrophobic nanoporous body Libersorb 23, water, and an aqueous solution of CaCl2 at a compression rate of p˙ ≥ 104 atm/s. It is found that the infiltration begins and occurs at a new constant pressure independent of the compression energy and viscosity of the liquid. The time of infiltration and the filled volume increase with the compression energy. A model of infiltration of a nanoporous body with a nonwetting liquid is constructed; using this model, infiltration is described as a spatially nonuniform process with the help of distribution functions for clusters formed by pores accessible to infiltration and filled ones. On the basis of the proposed system of kinetic equations for these distribution functions, it is shown that under rapid compression, the infiltration process must occur at a constant pressure pc whose value is controlled by a new infiltration threshold θc = 0.28 for the fraction of accessible pores, which is higher than percolation threshold θc0 = 0.18. Quantity θc is a universal characteristic of porous bodies. In the range θc0 < θ < θc, infiltration of the porous body should not be observed. It is shown that the solution to the system of kinetic equations leads to a nonlinear response by the medium to an external action (rapid compression), which means the compensation of this action by percolation of the liquid from clusters of filled pores of finite size to an infinitely large cluster of accessible but unfilled pores. As a result of such compensation, infiltration is independent of the viscosity of the liquid. It is found that all experimental results can be described quantitatively in the proposed model. PACS numbers: 05.40.-a, 47.53.+n DOI: 10.1134/S1063776109030042
1. INTRODUCTION After compression of a system formed by a nanoporous body and a nonwetting liquid to the threshold pressure value pc0, the liquid fills the pores of a porous body. In accordance with prevailing concepts, passage of the liquid from the bulk to the dispersed state can be described as a percolation-type transition [1]. The percolation-type spatial distribution of clusters formed by pores filled with the liquid is confirmed by the “devil’s staircase” effect involving the change in the resistance of a porous body (porous glass) upon its infiltration with mercury in the vicinity of the threshold infiltration pressure [2]. The percolation type of infiltration of porous
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