Breaking Cassie’s Law for Condensation in a Nanopatterned Slit.

0541155 - ÚCHP 2022 RIV US eng J - Journal Article
Láska, Martin - Parry, A.O. - Malijevský, Alexandr
Breaking Cassie’s Law for Condensation in a Nanopatterned Slit.
Physical Review Letters. Roč. 126, č. 12 (2021), č. článku 125701. ISSN 0031-9007. E-ISSN 1079-7114
R&D Projects: GA ČR(CZ) GA20-14547S
Institutional support: RVO:67985858
Keywords : capilary condensation * phase-equilibria * nerrow pores
OECD category: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect)
Impact factor: 9.185, year: 2021
Method of publishing: Open access
https://spiral.imperial.ac.uk:8443/bitstream/10044/1/88421/2/slit_periodic_letter2.pdf

We study the phase transitions of a fluid confined in a capillary slit made from two adjacent walls, each of which are a periodic composite of stripes of two different materials. For wide slits the capillary condensation occurs at a pressure which is described accurately by a combination of the Kelvin equation and the Cassie law for an averaged contact angle. However, for narrow slits the condensation occurs in two steps involving an intermediate bridging phase, with the corresponding pressures described by two new Kelvin equations. These are characterised by different contact angles due to interfacial pinning, with one larger and one smaller than the Cassie angle. We determine the triple point and predict two types of dispersion force induced Derjaguin-like corrections due to mesoscopic volume reduction and the singular free-energy contribution from nanodroplets and bubbles. We test these predictions using a fully microscopic density functional model which confirms their validity even for molecularly narrow slits. Analogous mesoscopic corrections are also predicted for two-dimensional systems arising from thermally induced interfacial wandering.
Permanent Link: http://hdl.handle.net/11104/0319406