Hydrogen in an oscillating porous Vycor glass

Kondo, Yasushi; Schindler, M.; Pobell, F.

doi:10.1007/bf00754576

Cited by 13 publications

(6 citation statements)

References 13 publications

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“…In an investigation of hydrogen in Vycor with 6 nm diameter pores, using a torsional oscillator, vapour pressure data and capacitance measurements, it was found that an amorphous component adsorbed strongly to the pore walls. Excess hydrogen would leave the pores as the temperature was lowered [74,75], in contrast to the results of a related study [73].…”

Section: Hydrogen and Heliumcontrasting

confidence: 74%

Confinement effects on freezing and melting

Christenson¹

2001

J. Phys.: Condens. Matter

574

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: Hydrogen and Heliumcontrasting

confidence: 74%

Confinement effects on freezing and melting

Christenson¹

2001

J. Phys.: Condens. Matter

574

594

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“…[1][2][3][4][5][6] The superfluid transition temperature of H 2 should be of the order of 1 or a few kelvin considering the analogy of H 2 to 4 He. 2 The superfluid transition temperature ͑2.18 K͒ of 4 He is comparable to T BC ϭ3.13 K ͑Bose-Einstein condensation temperature͒.…”

Section: Introductionmentioning

confidence: 99%

“…1 However, bulk p-H 2 freezes at 13.8 K; therefore one must achieve a substantial depression of the freezing temperature to obtain a superfluid transition. The most widely employed technique to realize H 2 in the liquid state at TϽT 3 is confining it into a small space, such as micropores of porous glasses [3][4][5][6][7] or zeolites. 8 Although this technique is very common, the mechanism of the freezing temperature depression is not yet clear.…”

Section: Introductionmentioning

confidence: 99%

“…Brewer et al 5 have measured the heat capacity of H 2 in porous Vycor glass ͑typical R p Ϸ3 nm͒ at 4 K ϽTϽ15 K. They observed an anomalous behavior and interpreted it as a possible indication of a superfluid transition of H 2 at around 9.6 K. We have already presented some of the results discussed in this paper in a short communication: It focused on the search for a possible superfluid transition of H 2 in Vycor glass. 6 Here we concentrate on the free energies of solid and liquid H 2 in porous Vycor glass.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen in porous Vycor glass

et al. 1996

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Hydrogen in porous Vycor glass ͑pore radius R p ϭ3.0 nm͒ has been investigated with a torsional oscillator technique at 7.5 K рTр 22 K. H 2 molecules which are adsorbed in Vycor at TϾT 3 (T 3 , triple point of bulk H 2 ) leave the Vycor when decreasing the temperature to below a characteristic value T c рT 3 ; T c depends on the amount of H 2 in the Vycor. This interpretation of the data is supported by simultaneous measurements of the H 2 vapor pressure. A similar phenomenon is observed with a capacitor filled with Vycor into which H 2 is condensed. We conclude that the free energy of solid H 2 in the Vycor is larger than that of bulk solid H 2 . Information on the free energy of H 2 confined in the Vycor is important to understand the depression of its freezing temperature in restricted geometries. We also discuss the properties of solids and the depression of their freezing temperature in restricted geometries.

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“…Filled pores prevent free exchange of matter between vapor and condensed phases. Some exceptions have been noted, particularly with hydrogen and helium, which are in some cases able to diffuse effectively through the solid matrix. − By contrast, capillary condensation in the SFA is studied under conditions of true equilibrium with the vapor phase. In experiments carried out below T m , it has been shown that liquid condensates form between mica surfaces for moderate temperature depressions Δ T = T m − T , , but that these are limited in size at coexistence, when the vapor is in equilibrium with bulk solid.…”

Section: Introductionmentioning

confidence: 99%

What Determines the Size of Liquid Capillary Condensates Below the Bulk Melting Point?

2007

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Capillary condensation from vapor has been studied at temperatures below the bulk melting point T m of the condensing substance using a surface force apparatus. Both mica and mica modified by self-assembly of a fluorinated surfactant (perfluoro-1H,1H,2H,2H-decylpyridinium chloride) have been used as substrate surfaces. The condensing liquids, cyclooctane and menthol, nearly wet (contact angle <15°) mica but show a high (∼60°) contact angle on the fluorinated surface. As in previous studies with unmodified mica, we find that both cyclooctane and menthol condense as liquids below T m, and that the size of the condensates at solid−vapor coexistence is limited and inversely proportional to the temperature depression below T m, or ΔT. A comparison of the size of the condensates between the fluorocarbon surfaces and the mica surfaces and the quantitative dependence of the size of the condensate on ΔT for cyclooctane lead us to conclude that the maximum condensate size is determined by the equilibrium between condensed, “supercooled” liquid and vapor, and is hence proportional to the surface tension of the liquid−vapor interface. From a consideration of the equilibrium between a liquid and a hypothetical solid condensate, it is concluded that a solid condensate does not usually form for kinetic reasons although two exceptions were found in earlier work.

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Hydrogen in an oscillating porous Vycor glass

Cited by 13 publications

References 13 publications

Confinement effects on freezing and melting

Confinement effects on freezing and melting

Hydrogen in porous Vycor glass

What Determines the Size of Liquid Capillary Condensates Below the Bulk Melting Point?

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