Effect of Pore Shape on Freezing and Melting Temperatures of Water

Abstract

To examine the effect of pore shape on freezing and melting temperatures of water, we measured X-ray diffraction patterns from water confined in four kinds of ordered mesoporous silicas with thin carbon films on the pore wall and three kinds of the inverse carbon replicas during freezing and melting processes. The melting temperature of the pore ice revealed a good correlation with the capillary condensation pressure of nitrogen at 77 K, whereas the freezing temperature of the pore water did not. This indicates that the experimental melting point represents an equilibrium solid-liquid phase transition temperature, whereas the experimental freezing point is controlled by a kinetic factor. The curvature effect of the solid-liquid interface adjacent to the pore wall did not appreciably affect the melting behavior of the pore ice. The melting point depression of the pore ice revealed an almost linear relationship with ln(p 0 /p) of the capillary condensation pressure of nitrogen at 77 K for various pores of different sizes and shapes. This strongly suggests that the reciprocal of ln(p 0 /p) for capillary condensation of nitrogen at 77 K gives a good measure of pore size, irrespective of the pore shapes, and the melting-point depression of the pore ice is almost proportional to the surface-to-volume ratio (S/V) of the pores confining it.

Wettability and Applications of Nanochannels

“…The result indicated that Ag clusters were uniformly confined in the nanochannels of mesoporous TiO 2 with an obvious confinement effect, and showed excellent solar‐light‐driven photocatalytic performance. Confinement of water in ordered mesoporous silica containing thin carbon films coated on the channel wall was carried on by Morishige et al, to study the channel shape effect on melting and freezing temperatures of water by X‐ray diffraction . It was indicated the melting temperature of ice in the nanochannel was well correlated in with the nitrogen condensation pressure at 77 K, but the freezing temperature of water in the nanochannel was not.…”

“…2D nanochannels comprised of graphene, mica, gold, reduced graphene oxide (rGO), and graphene oxide are studied to understand the confined 2D nanochannels wettability. The utilization of 3D nanochannels for wettability research contains porous carbon, porous metal, mesoporous silica, porous titanium dioxide, shale nanopores, and metal‐organic frameworks (MOFs) . The central schematic diagram of Figure shows wettability and nonwettability in 1D nanochannels, 2D nanochannels, and 3D nanochannels.…”

Proton Conductivity versus Acidic Strength of One‐Pot Synthesized Acid‐Functionalized SBA‐15 Mesoporous Silica

“…The melting occurred in a temperature range that is lower than that of bulk water, whatever the surface decoration, which is in agreement with that reported for functionalized SBA-15 or MCM-41. [43][44][45][46][47][48][49] Table 1 lists the melting temperature shifts ΔT m , with ΔT m = T m -273 K where T m is the temperature at the peak extremum. One may wonder if ΔT m is influenced by either the chemical nature of the functionalized surface or the pore diameter since it differs from one sample to another.…”

Solid phases of spatially nanoconfined oxygen: A neutron scattering study

“…Condensates embedded in nanometer wide vacancies of mesoporous substrates were exploited intensely to study the influence of these effects on known bulk properties of matter. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Simple van der Waals systems as rare gases in confinement were in the focus of interest as well as more elaborate quantum liquids and solids like helium or hydrogen isotopes. [9][10][11][12] Dioxygen O 2 was also among the extensively studied pore condensates.…”