Fig. 1
Criticality in confined fluids. Shift in the gas/liquid transition for a fluid having a molecular size σ confined in a nanopore of a diameter D. On the one hand, in mesopores, typically for D ≳ 10σ, the fluid can be treated using a continuum model which rests on capillarity ingredients such as the surface tension, radius of curvature of the gas/liquid interface, etc. (right). On the other hand, in micropores, typically for D ≲ 10σ, the molecular granularity of the fluid has to be taken into account and continuum models no longer apply (left). For a given pore size D, the bulk gas/liquid coexistence (dashed line) and the bulk critical point pc, Tc (black sphere) are shifted to lower pressure and temperature with a scaling that depends on D. In particular, upon confinement in a pore of a size D, the critical point Tc is shifted to a lower value Tcc such that ΔTc = Tc − Tcc ∼ Tcσ/D
