Modulus–pressure equation for confined fluids

Gor, Gennady Y.; Siderius, Daniel W.; Shen, Vincent K.; Bernstein, Noam

doi:10.1063/1.4965916

Cited by 27 publications

(84 citation statements)

References 67 publications

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“…where, in our case, P is the solvation pressure in the fluid phase, P 0 is some reference pressure, and K T = dK T /dP , which is constant in the first approximation. This dependence holds for confined fluids as well [22,33], moreover with the same slope K T [24]. The solvation pressure P in the confined fluid (not to be confused with vapor pressure p) consists of two terms [52]: the solidfluid interaction term and Laplace pressure…”

Section: Discussionmentioning

confidence: 86%

Effect of pore geometry on the compressibility of a confined simple fluid

Dobrzanski

Maximov

Gor

2018

The Journal of Chemical Physics

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Fluids confined in nanopores exhibit properties different from the properties of the same fluids in bulk; among these properties is the isothermal compressibility or elastic modulus. The modulus of a fluid in nanopores can be extracted from ultrasonic experiments or calculated from molecular simulations. Using Monte Carlo simulations in the grand canonical ensemble, we calculated the modulus for liquid argon at its normal boiling point (87.3 K) adsorbed in model silica pores of two different morphologies and various sizes. For spherical pores, for all the pore sizes (diameters) exceeding 2 nm, we obtained a logarithmic dependence of fluid modulus on the vapor pressure. Calculation of the modulus at saturation showed that the modulus of the fluid in spherical pores is a linear function of the reciprocal pore size. The calculation of the modulus of the fluid in cylindrical pores appeared too scattered to make quantitative conclusions. We performed additional simulations at higher temperature (119.6 K), at which Monte Carlo insertions and removals become more efficient. The results of the simulations at higher temperature confirmed both regularities for cylindrical pores and showed quantitative difference between the fluid moduli in pores of different geometries. Both of the observed regularities for the modulus stem from the Tait-Murnaghan equation applied to the confined fluid. Our results, along with the development of the effective medium theories for nanoporous media, set the groundwork for analysis of the experimentally measured elastic properties of fluid-saturated nanoporous materials.

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Section: Discussionmentioning

confidence: 86%

Effect of pore geometry on the compressibility of a confined simple fluid

Dobrzanski

Maximov

Gor

2018

The Journal of Chemical Physics

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“…133,134 In particular, it was shown that the change in the elastic modulus of the adsorbed fluid is linearly related to the adsorption stress in the pores. 135,136 E. Surface stress approach…”

Section: Coupling Between Thermodynamic and Elastic Aspects Of Adsmentioning

confidence: 99%

Adsorption-induced deformation of nanoporous materials—A review

Gor

Huber

Bernstein

2017

Applied Physics Reviews

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222

214

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When a solid surface accommodates guest molecules, they induce noticeable stresses to the surface and cause its strain. Nanoporous materials have high surface area and, therefore, are very sensitive to this effect called adsorption-induced deformation. In recent years, there has been significant progress in both experimental and theoretical studies of this phenomenon, driven by the development of new materials as well as advanced experimental and modeling techniques. Also, adsorption-induced deformation has been found to manifest in numerous natural and engineering processes, e.g., drying of concrete, water-actuated movement of non-living plant tissues, change of permeation of zeolite membranes, swelling of coal and shale, etc. In this review, we summarize the most recent experimental and theoretical findings on adsorption-induced deformation and present the state-of-the-art picture of thermodynamic and mechanical aspects of this phenomenon. We also reflect on the existing challenges related both to the fundamental understanding of this phenomenon and to selected applications, e.g., in sensing and actuation, and in natural gas recovery and geological CO2 sequestration.

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“…An additional challenge is that the measurement of the PSD ℱ ( w , μ 1 , p , T ) would necessitate measurements of the PSD at single pressures, which is not possible with existing adsorbent characterization techniques. Recent work by Gor et al [14–16] discusses relationships between pore size and the compressibility of a liquid-like confined fluid, measured at a single pressure, which might be further developed to compute the PSD of a material using single-pressure measurements. Such a method could provide the single-pressure measurements essential to application of the statistical mechanics presented here.…”

Section: Discussionmentioning

confidence: 99%

Relationship between pore-size distribution and flexibility of adsorbent materials: statistical mechanics and future material characterization techniques

2017

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Measurement of the pore-size distribution (PSD) via gas adsorption and the so-called “kernel method” is a widely used characterization technique for rigid adsorbents. Yet, standard techniques and analytical equipment are not appropriate to characterize the emerging class of flexible adsorbents that deform in response to the stress imparted by an adsorbate gas, as the PSD is a characteristic of the material that varies with the gas pressure and any other external stresses. Here, we derive the PSD for a flexible adsorbent using statistical mechanics in the osmotic ensemble to draw analogy to the kernel method for rigid materials. The resultant PSD is a function of the ensemble constraints including all imposed stresses and, most importantly, the deformation free energy of the adsorbent material. Consequently, a pressure-dependent PSD is a descriptor of the deformation characteristics of an adsorbent and may be the basis of future material characterization techniques. We discuss how, given a technique for resolving pressure-dependent PSDs, the present statistical mechanical theory could enable a new generation of analytical tools that measure and characterize certain intrinsic material properties of flexible adsorbents via otherwise simple adsorption experiments.

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Modulus–pressure equation for confined fluids

Cited by 27 publications

References 67 publications

Effect of pore geometry on the compressibility of a confined simple fluid

Effect of pore geometry on the compressibility of a confined simple fluid

Adsorption-induced deformation of nanoporous materials—A review

Relationship between pore-size distribution and flexibility of adsorbent materials: statistical mechanics and future material characterization techniques

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