Freezing and melting of methanol in a single cylindrical pore : Vitrification of methanol

Morishige, Kunimitsu; Kawano, Keizi

doi:10.1051/jp4:2000717

Cited by 3 publications

(1 citation statement)

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“…A subsequent study with Kr considered in more detail factors such as pore blockage, the capillary triple point and hysteresis [142]. Similar studies of methanol in MCM-41 (d from 2.4 to 5 nm) and SBA-15 (7.8-14 nm) showed a progression from vitrification in the smaller pores (7.8 nm and smaller) to crystallization [143,144]. A very large hysteresis between freezing and melting was observed in the larger pores, and depression of both transitions was large compared to that of water.…”

Section: Cylindrical Pores-mcm-41 Etcmentioning

confidence: 83%

Confinement effects on freezing and melting

Christenson¹

2001

J. Phys.: Condens. Matter

581

594

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A review of experimental work on freezing and melting in confinement is presented. A range of systems, from metal oxide gels to porous glasses to novel nanoporous materials, is discussed. Features such as melting-point depression, hysteresis between freezing and melting, modifications to bulk solid structure and solid-solid transitions are reviewed for substances such as helium, organic fluids, water and metals. Recent work with well characterized assemblies of cylindrical pores like MCM-41 and graphitic microfibres with slit pores has suggested that the macroscopic picture of melting and freezing breaks down in pores of molecular dimensions. Applications of the surface force apparatus to the study of freezing and melting phenomena in confinement are discussed in some detail. This instrument is unique in allowing the study of conditions in a single pore, without the complications of pore blockage and connectivity effects. The results have confirmed the classical picture of melting-point depression in larger pores, and allowed the direct observation of capillary condensation of solid from vapour. Other results include the measurement of solvation forces across apparently fluid films below the bulk melting point and a solid-like response to shear of films above the bulk melting point. These somewhat contradictory findings highlight the difficulty of using bulk concepts to define the phase state of a substance confined to nanoscale pores.

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Section: Cylindrical Pores-mcm-41 Etcmentioning

confidence: 83%

Confinement effects on freezing and melting

Christenson¹

2001

J. Phys.: Condens. Matter

581

594

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Confinement of nematic liquid crystals in SBA mesoporous materials

Frunză

Frunzǎ

Schönhals

et al. 2002

Studies in Surface Science and Catalysis

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Melting/freezing behavior of a fluid confined in porous glasses and MCM-41: Dielectric spectroscopy and molecular simulation

Śliwińska-Bartkowiak

Dudziak

Sikorski

et al. 2001

The Journal of Chemical Physics

125

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We report both experimental measurements and molecular simulations of the melting and freezing behavior of fluids in nanoporous media. The experimental studies are for nitrobenzene in the silica-based pores of controlled pore glass, Vycor, and MCM-41. Dielectric relaxation spectroscopy is used to determine melting points and the orientational relaxation times of the nitrobenzene molecules in the bulk and the confined phase. Monte Carlo simulations, together with a bond orientational order parameter method, are used to determine the melting point and fluid structure inside cylindrical pores modeled on silica. Qualitative comparison between experiment and simulation are made for the shift in the freezing temperatures and the structure of confined phases. From both the experiments and the simulations, it is found that the confined fluid freezes into a single crystalline structure for average pore diameters greater than 20, where is the diameter of the fluid molecule. For average pore sizes between 20 and 15, part of the confined fluid freezes into a frustrated crystal structure with the rest forming an amorphous region. For pore sizes smaller than 15, even the partial crystallization did not occur. Our measurements and calculations show clear evidence of a novel intermediate ''contact layer'' phase lying between liquid and crystal; the contact layer is the confined molecular layer adjacent to the pore wall and experiences a deeper fluid-wall potential energy compared to the inner layers. We also find evidence of a liquid to ''hexatic'' transition in the quasi-two-dimensional contact layer at high temperatures.

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Freezing and melting of methanol in a single cylindrical pore : Vitrification of methanol

Cited by 3 publications

References 0 publications

Confinement effects on freezing and melting

Confinement effects on freezing and melting

Confinement of nematic liquid crystals in SBA mesoporous materials

Melting/freezing behavior of a fluid confined in porous glasses and MCM-41: Dielectric spectroscopy and molecular simulation

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