Condensation and evaporation transitions in deep capillary grooves

Malijevský, Alexandr; Parry, A. O.

doi:10.1088/0953-8984/26/35/355003

Cited by 21 publications

(35 citation statements)

References 35 publications

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“…These and related studies are also of practical relevance to nanotechnologies involving the fabrication of functional surfaces which control the adsorption of microscopically small amounts of liquid [11]. For geometrically sculpted substrates, theoretical studies of wedges [12][13][14], grooves [15][16][17] and cones [18] have shown that the wall geometry can dramatically alter the adsorption properties and accompanying interfacial fluctuation effects. New transitions also arise for planar but chemically heterogeneous substrates in which the wall is a composite formed by materials with different wetting properties.…”

Section: Introductionmentioning

confidence: 96%

Scaling behavior of thin films on chemically heterogeneous walls

2017

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We study the adsorption of a fluid in the grand canonical ensemble occurring at a planar heterogeneous wall which is decorated with a chemical stripe of width L. We suppose that the material of the stripe strongly preferentially adsorbs the liquid in contrast to the outer material which is only partially wet. This competition leads to the nucleation of a droplet of liquid on the stripe, the height h m and shape of which (at bulk two-phase coexistence) has been predicted previously using mesoscopic interfacial Hamiltonian theory. We test these predictions using a microscopic Fundamental Measure Density Functional Theory which incorporates shortranged fluid-fluid and fully long-ranged wall-fluid interactions. Our model functional accurately describes packing effects not captured by the interfacial Hamiltonian but still we show that there is excellent agreement with the predictions h m ≈ L 1/2 and for the scaled circular shape of the drop even for L as small as 50 molecular diameters. For smaller stripes the droplet height is considerably lower than that predicted by the mesoscopic interfacial theory. Phase transitions for droplet configurations occurring on substrates with multiple stripes are also discussed.

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Section: Introductionmentioning

confidence: 96%

Scaling behavior of thin films on chemically heterogeneous walls

2017

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“…In this section we present the DFT results of the condensation in grooves of finite depth D and width L formed of completely wet walls and compare with predictions based on a slab model [24]. The slab model has been used previously [13,18] to analyze the critical behaviour of condensation and evaporation in infinitely deep grooves and it is straightforward to extend the analysis for grooves of finite depths. Within the model one assumes that the one-body fluid density ρ(r) = ρ(x, z) adopts only three values: i) ρ(r) = ρ l , the liquid density at bulk two-phase coexistence, if the fluid occupies the volume near the side and bottom walls as described in Fig.…”

Section: Resultsmentioning

confidence: 99%

Continuous condensation in nanogrooves

Malijevský

2018

Phys. Rev. E

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We consider condensation in a capillary groove of width L and depth D, formed by walls that are completely wet (contact angle θ=0), which is in a contact with a gas reservoir of the chemical potential μ. On a mesoscopic level, the condensation process can be described in terms of the midpoint height ℓ of a meniscus formed at the liquid-gas interface. For macroscopically deep grooves (D→∞), and in the presence of long-range (dispersion) forces, the condensation corresponds to a second-order phase transition, such that ℓ∼(μ_{cc}-μ)^{-1/4} as μ→μ_{cc}^{-} where μ_{cc} is the chemical potential pertinent to capillary condensation in a slit pore of width L. For finite values of D, the transition becomes rounded and the groove becomes filled with liquid at a chemical potential higher than μ_{cc} with a difference of the order of D^{-3}. For sufficiently deep grooves, the meniscus growth initially follows the power law ℓ∼(μ_{cc}-μ)^{-1/4}, but this behavior eventually crosses over to ℓ∼D-(μ-μ_{cc})^{-1/3} above μ_{cc}, with a gap between the two regimes shown to be δ[over ¯]μ∼D^{-3}. Right at μ=μ_{cc}, when the groove is only partially filled with liquid, the height of the meniscus scales as ℓ^{*}∼(D^{3}L)^{1/4}. Moreover, the chemical potential (or pressure) at which the groove is half-filled with liquid exhibits a nonmonotonic dependence on D with a maximum at D≈3L/2 and coincides with μ_{cc} when L≈D. Finally, we show that condensation in finite grooves can be mapped on the condensation in capillary slits formed by two asymmetric (competing) walls a distance D apart with potential strengths depending on L. All these predictions, based on mesoscopic arguments, are confirmed by fully microscopic Rosenfeld's density functional theory with a reasonable agreement down to surprisingly small values of both L and D.

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“…coexistence between thin and thick liquid films adsorbed on the side walls. These transitions in slit pores are first-order, but in grooves they are continuous, due to the attractive effect of the capping wall, which can nucleate films and capillary liquid metastable in the slit pore [15,16,[18][19][20]38]. Consider approaching the condensation line 1 in Figure 2 at the constant temperature T = 0.87, by thermodynamically quasi-statically advancing from a low value of ∆µ towards the condensation value ∆µ 1 , across the transition lines 6 and 7.…”

Section: Wetting Phenomenologymentioning

confidence: 96%

“…Subsequent studies by Yatsyshin et al [15] and Rascón et al [19] demonstrated the possible existence of a capillary wetting temperature, T cw , which separates firstorder and continuous condensation regimes in the groove. In particular, for systems with dispersive intermolecular fluid-fluid and fluid-substrate interactions, it was shown that above T cw , the height of the meniscus from the capped end diverges on approaching the chemical potential of condensation, µ c , as (µ c − µ) −1/4 [15][16][17][18]20].…”

Section: Introductionmentioning

confidence: 99%

Mean-field phenomenology of wetting in nanogrooves

Yatsyshin

Kalliadasis

2016

Molecular Physics

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In this special issue article we bring together our recent research on wetting in confinement, in particular planar walls, wedges, capillary grooves and slit pores, with emphasis on phase transitions and competition between wetting, filling and condensation, and highlight their similarities and disparities. The results presented are obtained with the classical density functional theory (DFT) for fluids, which is a mean-field statistical mechanical framework for including the spatial variations of the fluid density into the thermodynamic equation of state.For wetting in sculpted substrates, we solve numerically the DFT equations to obtain the fluid density profiles, wetting isotherms and phase diagrams. This allows us to contrast the wetting phenomenology of grooves, planar walls, slit and wedge-shaped pores. Of particular interest are the transitions associated with capillary condensation, planar pre-wetting and mean-field wedge pre-filling lines.

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Condensation and evaporation transitions in deep capillary grooves

Cited by 21 publications

References 35 publications

Scaling behavior of thin films on chemically heterogeneous walls

Scaling behavior of thin films on chemically heterogeneous walls

Continuous condensation in nanogrooves

Mean-field phenomenology of wetting in nanogrooves

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