Anomalously slow relaxation of a nonwetting liquid in the disordered confinement of a nanoporous medium
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DISORDER, AND PHASE TRANSITION IN CONDENSED SYSTEM
Anomalously Slow Relaxation of a Nonwetting Liquid in the Disordered Confinement of a Nanoporous Medium V. D. Borman, A. A. Belogorlov, V. M. Zhuromskii, and V. N. Tronin* National Research Nuclear University MEPhI, Kashirskoe sh. 31, Moscow, 115409 Russia *e-mail: [email protected] Received May 1, 2015
Abstract—The time evolution of the water–disordered nanoporous medium Libersorb 23 (L23) system has been studied after complete filling at elevated pressure followed by full release of overpressure. It is established that relaxation of the L23 rapidly flows out during the overpressure relief time, following the variation in pressure. At a temperature below that of the dispersion transition (T < Td = 284 K), e.g., at T = 277 K, the degree of filling θ decreases from 1 to 0.8 within 10 s. The degree of filling varies with time according to the power law θ ~ t–α with the exponent α < 0.1 over a period of t ~ 105 s. This process corresponds to slow relaxation of a metastable state of a nonwetting liquid in a porous medium. At times t > 105 s, the metastable state exhibits decay, manifested as the transition to a power dependence of θ(t) with a larger exponent. The relaxation of the metastable state of nonwetting liquid in a disordered porous medium is described in the mean field approximation as a continuous sequence of metastable states with a barrier decreasing upon a decrease in the degree of filling. Using this approach, it is possible to qualitatively explain the observed relaxation process and crossover transition to the stage described by θ(t) with a larger exponent. DOI: 10.1134/S1063776115120043
1. INTRODUCTION In recent years, much attention is devoted to researching the state and properties of disordered media such as glasses, colloids, polymers, loose materials, etc. [1–12]. Numerical simulations have been carried out [6, 7, 16, 18] and phenomenological models have been formulated, including dynamic heterogeneity (DH) [2, 5, 21], random first-order transition (RFOT) theory, topological bond-oriented local configurations [1, 6, 7, 16, 18, 27, 28], shear transformation zone (STZ) [1, 4, 9, 13, 19], etc. (see, e.g., [1–3, 10, 14, 20]), which employ the concept of local structures (configurations) that determine the properties of disordered media. These models have been used to describe the states and properties of glasses, colloids, polymers, and loose media, as well as liquid–glass transitions and sol–gel processes that lead to the appearance of random order. According to [1, 22, 23], these media are nonergodic and are characterized by anomalously slow relaxation of local nonequilibrium states, which is phenomenologically described by the law of stretched exponential relaxation [1, 8, 12, 27]. This anomalously slow relaxation implies that, for an arbitrarily long observation time (shorter than the lifetime of states), the system cannot reach any point in the phase space [1]. In phenomenological models of disordered media, the anomalously slow (power-law) rel
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