Light scattering study of collective effects during evaporation and condensation in a disordered porous material

Bonnet, Fabien; Melich, Mathieu; Puech, L.; Wolf, P. E.

doi:10.1209/0295-5075/101/16010

Cited by 13 publications

(24 citation statements)

References 32 publications

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“…1a) [10]. This process has been observed in simulations [8,11] and has been proposed on several occasions to explain the shape of desorption isotherms in nano-scale porous media [8,12,13], or the apparent emergence of drying events far from the evaporation front [14,15]. Yet, we are unaware of direct optical observation of desorption by cavitation or of an investigation of its effect on drying dynamics.…”

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confidence: 80%

Drying by Cavitation and Poroelastic Relaxations in Porous Media with Macroscopic Pores Connected by Nanoscale Throats

et al. 2014

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We investigate the drying dynamics of porous media with two pore diameters separated by several orders of magnitude. Nanometer-sized pores at the edge of our samples prevent air entry, while drying proceeds by heterogeneous nucleation of vapor bubbles -cavitation -in the liquid in micrometer-sized voids within the sample. We show that the dynamics of cavitation and drying are set by the interplay of the deterministic poroelastic mass transport in the porous medium and the stochastic nucleation process. Spatio-temporal patterns emerge in this unusual reaction-diffusion system, with temporal oscillations in the drying rate and variable roughness of the drying front.The desorption, or drying, of liquids from porous media is important in a variety of contexts, both in nature (e.g., the movement of water in plants [1]) and in technology (e.g., the synthesis [2] and characterization [3] of advanced materials). Studies of desorption have focused on the dynamics and pattern formation associated with drying [4-6] and the thermodynamics that define the shapes of desorption isotherms [7,8]. Despite this attention, uncertainties remain regarding the physical processes that govern desorption. It has been proposed that, rather than by receding of the liquid phase from the edges of the material, drying from porous media could occur by cavitation, i.e. the spontaneous formation of vapor bubbles either when the liquid tensile strength is attained [9] or by thermally activated nucleation in the metastable pore liquid (Fig. 1a) [10]. This process has been observed in simulations [8,11] and has been proposed on several occasions to explain the shape of desorption isotherms in nano-scale porous media [8,12,13], or the apparent emergence of drying events far from the evaporation front [14,15]. Yet, we are unaware of direct optical observation of desorption by cavitation or of an investigation of its effect on drying dynamics.In this Letter, we present a tailored porous medium formed of microfabricated voids coupled to each other and the outside via a nanoporous substrate (Figs. 1b-1c). This extreme ink-bottle structure -large pore bodies connected via narrow throats [16] -has allowed us to observe the nucleation and growth of cavitation bubbles during drying (Fig. 1d) and to show that this process gives rise to interesting coupled drying dynamics that is tunable with geometry.Drying occurs when a saturated porous medium is placed in a sub-saturated atmosphere (relative humidity p v /p sat < 1, where p v and p sat are the vapor pressure and its saturation value). At high relative humidity, evaporation results in the formation of menisci in the pores at the surface of the material, until local mechanical and andarXiv:1402.6776v2 [cond-mat.soft]

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confidence: 80%

Drying by Cavitation and Poroelastic Relaxations in Porous Media with Macroscopic Pores Connected by Nanoscale Throats

et al. 2014

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“…Another classical explanation for a well-defined evaporation threshold is that it follows from a percolation phenomenon in a disordered pore network . This mechanism has been directly checked by optical measurements in Vycor. − However, this scenario requires interconnected pores. While this hypothesis seemed ruled out by measurements performed 20 years ago, a growing number of recent experiments (NMR diffusion measurements and X-ray tomography , ) suggest that there is indeed a large density of connections between neighboring pores.…”

Section: Introductionmentioning

confidence: 97%

“…Another classical explanation for a well defined evaporation threshold is that it follows from a percolation phenomenon in a disordered pore network [10]. This mechanism has been directly checked by optical measurements in Vycor [11][12][13][14]. However, this scenario requires interconnected pores.…”

Section: Introductionmentioning

confidence: 99%

Evaporation Process in Porous Silicon: Cavitation vs Pore Blocking

et al. 2021

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We have measured sorption isotherms for helium and nitrogen in wide temperature ranges and for a series of porous silicon samples, both native samples and samples with reduced pore mouth so that the pores have an ink-bottle shape. Combining volumetric measurements and sensitive optical techniques, we show that, at high temperature, homogeneous cavitation is the relevant evaporation mechanism for all samples. At low temperature, the evaporation is controlled by meniscus recession, the detailed mechanism being dependent on the pore length and on the mouth reduction. Native samples and samples with ink-bottle pores shorter than one micrometer behave as an array of independent pores. In contrast, samples with long ink-bottle pores exhibit long-range correlations between pores. In this latter case, evaporation takes place by a collective percolation process and not by heterogeneous cavitation as previously proposed. The variety of evaporation mechanisms points to porous silicon being an anisotropic three dimensional pore network rather than an array of straight independent pores.

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“…Wherefore, a number of ultrasonic studies of fluids in confinement were performed using Vycor glass as the adsorbent [90,[93][94][95][96][97][98][99][100][101][102]. Finally, Vycor glass is optically transparent, therefore suitable for the comparison of ultrasonic measurements with optical experiments [95,96,[103][104][105][106][107]. A important step was made in 1988 by Warner and Beamish, who used ultrasonic experiments to investigate fluid adsorption on nanoporous samples and their surface area [90].…”

Section: B Coupled Adsorption-ultrasonic Measurementsmentioning

confidence: 99%

Elastic properties of confined fluids from molecular modeling to ultrasonic experiments on porous solids

Dobrzanski

Gurevich

Gor

2021

Applied Physics Reviews

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Fluids confined in nanopores are ubiquitous in nature and technology. In recent years, the interest in confined fluids has grown, driven by research on unconventional hydrocarbon resources -shale gas and shale oil, much of which are confined in nanopores. When fluids are confined in nanopores, many of their properties differ from those of the same fluid in the bulk. These properties include density, freezing point, transport coefficients, thermal expansion coefficient, and elastic properties. The elastic moduli of a fluid confined in the pores contribute to the overall elasticity of the fluid-saturated porous medium and determine the speed at which elastic waves traverse through the medium. Wave propagation in fluid-saturated porous media is pivotal for geophysics, as elastic waves are used for characterization of formations and rock samples. In this paper, we present a comprehensive review of experimental works on wave propagation in fluid-saturated nanoporous media, as well as theoretical works focused on calculation of compressibility of fluids in confinement. We discuss models that bridge the gap between experiments and theory, revealing a number of open questions that are both fundamental and applied in nature. While some results were demonstrated both experimentally and theoretically (e.g. the pressure dependence of compressibility of fluids), others were theoretically predicted, but not verified in experiments (e.g. linear scaling of modulus with the pore size). Therefore, there is a demand for the combined experimental-modeling studies on porous samples with various characteristic pore sizes. The extension of molecular simulation studies from simple model fluids to the more complex molecular fluids is another open area of practical interest.

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Light scattering study of collective effects during evaporation and condensation in a disordered porous material

Cited by 13 publications

References 32 publications

Drying by Cavitation and Poroelastic Relaxations in Porous Media with Macroscopic Pores Connected by Nanoscale Throats

Drying by Cavitation and Poroelastic Relaxations in Porous Media with Macroscopic Pores Connected by Nanoscale Throats

Evaporation Process in Porous Silicon: Cavitation vs Pore Blocking

Elastic properties of confined fluids from molecular modeling to ultrasonic experiments on porous solids

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