Capillary Condensation in Linear Mesopores of Different Shape

Wallacher, Dirk; Künzner, N.; Kovalev, D.; Knorr, Nikolaus; Knorr, K.

doi:10.1103/physrevlett.92.195704

Cited by 163 publications

(245 citation statements)

References 24 publications

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“…Mean density functional theory 15 , molecular dynamics simulations of adsorption and desorption by diffusive mass transfer into model pores 16 and grand canonical Monte Carlo simulations 17 confirm this classical picture of adsorption in a single pore. In contrast to theoretical predictions, experiments with mesoporous matrices characterized by a trivial porous network topology consisting of straight and not interconnected pores show that adsorption is always characterized by pronounced hysteresis loops independent of whether the pores are open at one or at both ends 7,12,[18][19][20][21] . In other words, in these materials the pores appear not to be independent during an adsorption isotherm.…”

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confidence: 61%

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: 61%

Continuous adsorption in highly ordered porous matrices made by nanolithography

et al. 2013

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“…On the one hand, this matrix allows one to study the influence of spatial confinement on the physics and chemistry of liquids [9][10][11][12][13][14][15]. On the other hand, it is possible to synthesize composite materials with finely tuned optical and electrical properties by liquid adsorption or infiltration [4,16].…”

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confidence: 99%

Elastic response of mesoporous silicon to capillary pressures in the pores

Gor

Bertinetti

Bernstein

et al. 2015

Applied Physics Letters

112

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We study water adsorption-induced deformation of a monolithic, mesoporous silicon membrane traversed by independent channels of ∼8 nm diameter. We focus on the elastic constant associated with the Laplace pressure-induced deformation of the membrane upon capillary condensation, i.e. the pore-load modulus. We perform finite-element method (FEM) simulations of the adsorption-induced deformation of hexagonal and square lattices of cylindrical pores representing the membrane. We find that the pore-load modulus weakly depends on the geometrical arrangement of pores, and can be expressed as a function of porosity. We propose an analytical model which relates the pore-load modulus to the porosity and to the elastic properties of bulk silicon (Young's modulus and Poisson's ratio), and provides an excellent agreement with FEM results. We find good agreement between our experimental data and the predictions of the analytical model, with the Young's modulus of the pore walls slightly lower than the bulk value. This model is applicable to a large class of materials with morphologies similar to mesoporous silicon. Moreover, our findings suggest that liquid condensation experiments allow one to elegantly access the elastic constants of a mesoporous medium.Mesoporous silicon (pSi) prepared by electrochemical etching of bulk silicon has been attracting much attention from both fundamental and applied sciences owing to its unique optical, electrical and thermal properties [1][2][3][4][5][6]. While control over mechanical properties of pSi is necessary for its applications, the understanding of its response to mechanical loads is mainly limited to measuring Young's modulus of porous samples [7,8].Since pSi can be prepared as a bulk (monolithic) mesoporous system with parallel, channel-like independent pores, it has been of a particular interest for studies of fluid adsorption [4]. On the one hand, this matrix allows one to study the influence of spatial confinement on the physics and chemistry of liquids [9][10][11][12][13][14][15]. On the other hand, it is possible to synthesize composite materials with finely tuned optical and electrical properties by liquid adsorption or infiltration [4,16]. Therefore, exploration of the mechanical properties of silicon relevant to interactions with liquids, the topic of this Letter, is also of high importance.When a fluid is adsorbed in a mesopore, it exerts a pressure on the pore walls, which is typically of the order of 10 7 Pa [17]. This pressure causes deformation of the pore, and as a result deformation of the porous material as a whole. This effect, known as adsorption-induced deformation has been experimentally observed for various mesoporous materials: Vycor glass [18,19], templated silica [20][21][22], low-k films [23,24], aerogels [25,26], porous gold [27] and pSi [28]. There are two ways to * ggor@princeton.edu measure the adsorption strains experimentally: for materials which can be prepared as macroscopic samples, the dilatometric technique can be used, and the reported strain is...

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“…Experimental studies have shown conflicting results: for example isotherms in aluminium and silicon adsorbents with closed end pores exhibit hysteresis loops (Bruschi et al, 2008;Coasne et al, 2002;Wallacher et al, 2004). However, these real materials may have irregularities on the surface that could be responsible for the hysteresis (Bruschi et al, 2008;Puibasset, 2009).…”

Section: Introductionmentioning

confidence: 95%

“…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). In particular, the possible existence of hysteresis in closed end pores has been a controversial topic that has important consequences for more complex materials where pore cross sections may vary from place to place.…”

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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Capillary Condensation in Linear Mesopores of Different Shape

Cited by 163 publications

References 24 publications

Continuous adsorption in highly ordered porous matrices made by nanolithography

Continuous adsorption in highly ordered porous matrices made by nanolithography

Elastic response of mesoporous silicon to capillary pressures in the pores

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

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