Continuous Freezing of Argon in Completely Filled Mesopores

Abstract

We have studied the phase transition of argon in completely filled mesopores. Our effective medium analysis of ultrasonic measurements clearly indicates a continuous phase transition of argon in completely filled pores over a broad temperature range of about 45 K. With decreasing temperature, the amount of frozen argon increases and below about 30 K all adsorbed argon (including the first few layers near the pore wall) is frozen with a shear modulus about equal to the bulk shear modulus. It is remarkable, that in a system showing such a pronounced confinement effect--a continuous phase transition over 45 K--the bulk properties are preserved. A comparison with temperature cycles with one and two adsorbed layers shows, that due to the presence of solid argon in the center of the pores the first few layers are already frozen at a higher temperature (30 K) compared to single layers (20 K). The transfer of our technique from the simple model system that we present in this Letter to other more complex adsorbates and different porous samples should help to enlighten the phase behavior under confinement in further studies.

Quantized Self-Assembly of Discotic Rings in a Liquid Crystal Confined in Nanopores

“…The phase transition quantization exemplifies in a remarkable manner how confinement can alter the physics of liquid crystals [14,18,25,31,32,[52][53][54][55][56][57][58][59][60][61][62][63] and allows us to determine the otherwise hard to access bend elastic constant [64]. More generally, it highlights how curved geometries can alter self-assembly and crystallization [14,23,24,65,66] and how versatile soft matter can adapt to extreme spatial constraints with new architectural principles dynamics, as has been similarly discussed for simple molecular [38,[67][68][69] and polymeric systems [70][71][72][73][74][75]. Finally, we envision that the spontaneous, temperature-tunable nanoscale ring formation demonstrated here along with the one-dimensional charge carrier pathways and mechanical stability of the membranes may provide a versatile playground for the study of electronic and magnetic confinement effects [76] or even of the fluid-wall-interaction-induced deformations of nanopores [77].…”

Effect of Surface Texture on Freezing in Nanopores: Surface-Induced versus Homogeneous Crystallization

“…[1][2][3][4][5] Freezing of liquids confined at the nanoscale is also relevant to applications involving lubrication, nanotribology, and fabrication of nanomaterials. 6,7 Some experimental and theoretical works on simple liquids have proposed that the in-pore freezing point T f is shifted to lower (higher) temperature with respect to the bulk freezing temperature showing that the freezing point for cyclohexane between parallel mica surfaces in a surface force apparatus is not elevated but decreased with respect to the bulk.…”

Modulus–pressure equation for confined fluids

“…Beamish and co-workers used it to study the properties of liquid helium [11][12][13] and also proposed ultrasonic experiments for probing the surface area of nanoporous materials [14]. Later ultrasonic experiments became widely used for studying phase transitions in confinement, both liquid-vapor [15][16][17][18] and solid-liquid [19][20][21][22][23][24][25][26][27][28]. Among these works, it is worth pointing out the paper of Page et al [16], which first showed that when the pores are completely filled with a liquid-like capillary condensate, the modulus of the fluid (n-hexane) was not constant, * Corresponding author, e-mail: gennady.y.gor@gmail.com but a monotonic function of the gas pressure p (lower pressure corresponds to lower modulus).…”