Phase behaviour of argon and krypton adsorbed in mesoporous Vycor glass

Abstract

The phase behaviour of Ar and Kr adsorbed in Vycor glass at pressures and temperatures above the bulk triple point and below the bulk critical point has been investigated. Ar is found to condense in the pores ∼2 K above the bulk transition and freeze ∼10 K below the bulk transition. In contrast the condensation transition for Kr is shifted up by 4 K and freezing shifted down by 15 K. There is a pronounced hysteresis (4–6 K) at the liquid/solid phase boundary and a lesser amount (∼2 K) at the gas/liquid boundary. We find clear differences between the pore filling and emptying processes at the gas/liquid phase boundary and evidence of pore blocking on desorption. In addition microbubbles or large gas–liquid interfaces are thought to occur when Kr condenses in the pores but this effect is absent in Ar. Finally, solid Ar in the pores melts in a more continuous way than Kr.

Capillary Condensation of Binary and Ternary Mixtures of n-Pentane–Isopentane–CO2 in Nanopores: An Experimental Study on the Effects of Composition and Equilibrium

“…Studies on the confined bubble point include the work of Cho et al., Luo et al, Jones and Fretwell, , and Yun et al While all the studies, except for that of Luo et al, witnessed depression of the confined bubble point with respect to that of the bulk, the results must be viewed in the context of the experimental path. The two paths available for studies of confined phase phenomena are adsorption and desorption.…”

“…In adsorption, the initial phase of the bulk fluid is gaseous. Adsorption experiments are exemplified in the literature by the works of Jones and Fretwell 7 and Yun et al, 8 who used positron annihilation spectroscopy and a volumetric flow-through approach, respectively. In desorption, the initial phase of the bulk fluid is liquid.…”

Molecular dynamics simulation of effective thermal conductivity of vapor-filled nanogap and nanocavity

“…The cold surface is below the triple-point temperature ͓T tp =85 K ͑Ref. 21͔͒, T c = 80 K, whereas the hot surface is above it, T h = 90 K. Noting that the triple-point temperature of Ar confined in Vycor glass nanopore is only 2 K larger than that for the bulk Ar, 21 thus we expect the equilibrium phase diagram of the confined Ar to be different. Here we only use the bulk triple-point temperature as a reference when addressing phase change in the Ar-Pt nanogap.…”

Condensation and Freezing of a Binary Gas Mixture Adsorbed in Mesoporous Vycor Glass

“…These gases were chosen for the comparatively simple nature of their interatomic forces and easy accessibility of the relevant phase boundaries. We and others have already experimentally investigated the behavior of pure Ar and Kr gases in Vycor and other porous media. Interestingly, there is evidence of a low-temperature transition near T melt /2 of Ar in crushed Vycor where the mobility of the solid Ar increases by several orders of magnitude and solid Ar migrates out of the sample .…”