Modified Kelvin equations for capillary condensation in narrow and wide grooves

Abstract

We consider the location and order of capillary condensation transitions occurring in deep grooves of width $L$ and depth $D$. For walls that are completely wet by liquid (contact angle $\theta =0$) the transition is continuous and its location is not sensitive to the depth of the groove. However for walls which are partially wet by liquid, where the transition is first-order, we show that the pressure at which it occurs is determined by a modified Kelvin equation characterized by an edge contact angle ${\theta }_E$ describing the shape of the meniscus formed at the top of the groove. The dependence of ${\theta }_E$ on the groove depth $D$ relies, in turn, on whether corner menisci are formed at the bottom of the groove in the low density gas-like phase. While for macroscopically wide grooves these are always present when $\theta <45°$ we argue that their formation is inhibited in narrow grooves. This has a number of implications including that the local pining of the meniscus and location of the condensation transition is different depending on whether the contact angle is greater or less than a universal value ${\theta }^{\ast }\approx 31°$. Our arguments are supported by detailed microscopic density functional theory calculations which show that the modified Kelvin equation remains highly accurate even when $L$ and $D$ are of the order of tens of molecular diameters.

References in corpus (6)

• Critical Point Wedge Filling
• Complete Wetting of Pits and Grooves
• Does adsorption in a single nanogroove exhibit hysteresis?
• Capillary Contact Angle in a Completely Wet Groove
• Condensation and evaporation transitions in deep capillary grooves
• Edge contact angle and modified Kelvin equation for condensation in open pores

Cited by in corpus (8)

• Capillary condensation under atomic-scale confinement
• Phase Field Simulation of Liquid Filling on Grooved Surfaces for Complete, Partial and Pseudo-partial Wetting Cases
• Phase behaviour of fluids in undulated nanopores
• Capillary Condensation and Depinning Transitions in Open Slits
• Filling, depinning, unbinding: Three adsorption regimes for nanocorrugated substrates
• Continuous condensation in nanogrooves
• Critical effects and scaling at meniscus osculation transitions
• Effect of line tension on axisymmetric nanoscale capillary bridges at the liquid-vapor equilibrium