Capillary condensation of adsorbates in porous materials

Horikawa, Toshihide; Do, D.D.; Nicholson, D.

doi:10.1016/j.cis.2011.08.003

Cited by 383 publications

(255 citation statements)

References 189 publications

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“…These curves represent the mass of the gas, typically N 2 or Ar at liquid nitrogen temperature, adsorbed onto a substrate as a function of the equilibrium vapour pressure of the surrounding vapour. In the case of porous materials having pores ranging from 10 to 100 nm in size, they always exhibit two main features: (i) a sharp increase in the amount of adsorbed gas well below the liquidvapour coexistence pressure P 0 of the bulk adsorbate, which is explained in terms of capillary condensation in the small pores 11,12 . Below a certain pressure, a film covers uniformly the inner walls of the cavity, whereas above it the cavity fills up completely with liquid, even though that phase is not thermodynamically stable in bulk; (ii) a hysteresis loop between the adsorption (gas is added to the sample cell) and the desorption (gas is removed from the sample cell) branches.…”

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confidence: 99%

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Continuous adsorption in highly ordered porous matrices made by nanolithography

et al. 2013

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The exposed surface area of porous materials is usually determined by measuring the mass of adsorbed gas as a function of vapour pressure. Here we report a comprehensive study of adsorption in systems with closed bottom, not interconnected pores exhibiting different degrees of disorder, produced with methods encompassing nanolithography and dry and wet etching. Detailed adsorption studies of these matrices show hysteresis loops, as found always in pores having sizes of tens to hundreds of nanometres. The observed variations in the loop shape are associated with changes in the pore morphology. In regular pores formed by vertical and smooth walls, continuous adsorption is found for the first time in agreement with thermodynamic considerations valid for ideal pores. This suggests that irregularities in the walls and pore openings are the key factors behind the hysteresis phenomenon. Interestingly, pores having rough walls but a pyramidal shape also do not show any hysteresis.

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confidence: 99%

“…Despite its commonplace occurrence, the origin of the hysteresis phenomenon is still a matter of debate 12,13 . According to macroscopic thermodynamic arguments 14 , the hysteresis is usually explained in terms of the different shape of the vapour/adsorbate interface during adsorption and desorption in a cylindrical pore with open ends 1,2 .…”

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Continuous adsorption in highly ordered porous matrices made by nanolithography

et al. 2013

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“…The drive to improve our understanding of the microscopic origin of hysteresis has been greatly facilitated by the synthesis of ordered mesoporous solids and advances in computer simulation (Horikawa et al, 2011). Several attempts have been made to tailor adsorbent solids in order to study the dependence of hysteresis on pore structure, for example by synthesising pores with either open ends, or with one end closed, or pores with narrower openings to the surrounding gas (Bruschi et al, 2008;Bruschi et al, 2010;Wallacher et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Adsorption isotherms for gases in meso-porous adsorbents exhibit hysteresis at temperatures below a critical hysteresis temperature, T ch (Everett and Haynes, 1973;Horikawa et al, 2011;Thommes, 2004) which depends on the parameters characterising the adsorbent pores (cross sectional shape and width, inter-connectivity, and the form of the adsorbent-adsorbate potential) and also on the adsorbate. The drive to improve our understanding of the microscopic origin of hysteresis has been greatly facilitated by the synthesis of ordered mesoporous solids and advances in computer simulation (Horikawa et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

A molecular simulation study of adsorption and desorption in closed end slit pores: Is there a hysteresis loop?

Fan

Zeng

et al. 2015

Chemical Engineering Science

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This paper reports detailed simulations of adsorption and desorption of argon in closed end slit pores with the aim of investigating the existence of hysteresis. The classical thermodynamic approach implies that there should be no hysteresis in a closed end pore because it assumes that the condensed phase is identical to a uniform bulk liquid and that the interface between the gas-like region and the dense adsorbate region is the same when the pore fills as when it empties. Our simulations show that hysteresis is possible and we support this assertion with evidence from a critical analysis of the classical equation. Our extensive results show that hysteresis can occur in closed end pores because of the continuous structuring of the adsorbed phase induced by the combined effects of the solid-fluid interaction and the fluid-fluid interaction.

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“…The hysteresis loop in an adsorption isotherm is a valuable tool for probing the character of a porous solid, since its size, shape and position are sensitive to adsorbate, temperature and the porous structure [1][2][3] . Thus for example, for a given temperature and adsorbate, the boundary loop can be used to derive pore size distribution.…”

Section: Introductionmentioning

confidence: 99%

Hysteresis and scanning curves in linear arrays of mesopores with two cavities and three necks

Zeng

Tan

et al. 2016

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Adsorption of argon at 87K in a linear array of slit mesopores composed of two cavities and three necks has been investigated using Grand Canonical Monte Carlo simulation. Hysteresis and scanning was found to depend on the relative size of the necks and cavities and on whether the necks are wider or narrower than the critical width that demarcates cavitation from pore blocking. There are 26 possible combinations for the linear array. By considering the behaviour of hysteresis scanning curves, we are able to identify four distinct groups: (i) Group 1: The descending scanning spans the boundary curve of the hysteresis loop due to stretching of the condensate in the small cavity.(ii) Group 2: The descending curve partially spans the loop and returns to the adsorption boundary. This occurs either because the condensate stretches in the small cavity, followed by evaporation via a pore blocking mechanism; or because the condensate evaporates as the meniscus recedes in the large neck that joins the two cavities.(iii) Group 3: The descending curve spans the loop as in Group 1 but there is a small sub-loop associated with emptying and filling of the large neck connecting the large cavity to the surrounding gas.

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Capillary condensation of adsorbates in porous materials

Cited by 383 publications

References 189 publications

Continuous adsorption in highly ordered porous matrices made by nanolithography

Continuous adsorption in highly ordered porous matrices made by nanolithography

A molecular simulation study of adsorption and desorption in closed end slit pores: Is there a hysteresis loop?

Hysteresis and scanning curves in linear arrays of mesopores with two cavities and three necks

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