Capillary Condensation in the Void Space between Carbon Nanorods

Morishige, Kunimitsu; Nakahara, Ryo

doi:10.1021/jp8027403

Cited by 8 publications

(12 citation statements)

References 29 publications

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“…Attempts to describe the adsorption and capillary condensation for geometries other than simple slit-or cylindrical pores were carried out by Philip (1977b) already in the 1970s for two parallel cylinders. This idea was further developed by Morishige and Nakahara (2008) into a comprehensive theoretical framework for the transition from a liquid film phase to a "bridged" phase, effectively spanning the void space between the two adjacent cylinders. Dobbs and Yeomans (1993) extended the approach of Philip by numerically minimizing the grand potential of different configurations of liquid in the open pore space between cylindrical rods located on a square lattice.…”

Section: Introductionmentioning

confidence: 99%

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Capillary bridge formation between hexagonally ordered carbon nanorods

et al. 2020

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Capillary condensation within the pore space formed by a hexagonal arrangement of carbon nanorods is investigated using a thermodynamic model. Numerical solution of the corresponding non-linear differential equations predicts two characteristic equilibrium phase transitions corresponding to liquid-bridge formation between adjacent rods, and the subsequent filling of the entire pore space with liquid adsorbate at higher relative pressure, respectively. These separate transitions are predicted for a wide range of porosities, as demonstrated for two non-polar fluids, nitrogen and n-pentane, employing experimentally determined reference isotherms to model the fluid-solid interactions. The theoretical predictions are compared to experimental data for nitrogen and n-pentane adsorption in an ordered mesoporous CMK-3 type material, with the necessary structural parameters obtained from small-angle X-ray scattering. Although the experimental adsorption isotherms do not unambiguously show two separate transitions due to a high degree of structural disorder of the mesopore space, their general trends are consistent with the theoretical predictions for both adsorbates.

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Section: Introductionmentioning

confidence: 99%

“…for nitrogen on annealed activated carbon at 77 K, and from measurement for n-pentane on an annealed carbon xerogel at 273 K Fluid surface tension values for n-pentane and nitrogen were taken from Refs (Gor et al 2013). and(Morishige and Nakahara 2008), respectively…”

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confidence: 99%

Capillary bridge formation between hexagonally ordered carbon nanorods

et al. 2020

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“…In a previous study, we concluded that ices confined in ordered mesoporous carbons CMK-3, CMK-8, and CFA2 exhibit similar depressions in the melting point as compared to the bare silica pores of similar pore sizes, although the pore size of these carbons is difficult to be defined. The structures of these ordered mesoporous carbons are exactly the inverse replicas of the ordered mesoporous silicas, and thus the pores consist of the void space between regularly arranged carbon nanorods . In addition, the carbon walls possess micropores that result in micropore filling of water vapor and thus make the pore walls less hydrophobic.…”

Section: Introductionmentioning

confidence: 99%

“…The structures of these ordered mesoporous carbons are exactly the inverse replicas of the ordered mesoporous silicas, and thus the pores consist of the void space between regularly arranged carbon nanorods. 28 In addition, the carbon walls possess micropores that result in micropore filling of water vapor and thus make the pore walls less hydrophobic. All these experimental studies suggest that the influence of hydrophobicity on the freezing and melting of the confined water still remains to be unsettled.…”

Section: ■ Introductionmentioning

confidence: 99%

Influence of Pore Wall Hydrophobicity on Freezing and Melting of Confined Water

Morishige

2018

J. Phys. Chem. C

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To examine the influence of pore wall hydrophobicity on freezing and melting behavior of a confined water, we measured the X-ray diffraction pattern of water in the nearly cylindrical pores of ordered mesoporous carbons during cooling and heating processes. The pore walls of the ordered mesoporous carbons are crystalline and cannot form hydrogen bonds with water molecules. Capillary condensation of water in the hydrophobic mesopores takes place very slowly only close to the saturation pressure of a bulk water. Nevertheless, freezing and melting of water confined in the hydrophobic mesopores occurred almost in the same way as those in mesoporous silicas with similar pore sizes, the pore walls of which are amorphous and can form hydrogen bonds with water molecules. This clearly indicates that the pore wall hydrophobicity does not affect appreciably the freezing and melting behavior of the confined water. The existence of a thin water layer between core ice and the pore walls is responsible for it.

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“…The observed mesopores indicate that the mesospace is enclosed by four silica nanowires. [16] The obtained silica replicas were used as the second template for the preparation of mesoporous precious metals (Ru, Pd, and Pt; Figure 1). As one example, herein we demonstrate the details of mesoporous ruthenium synthesis.…”

Section: Resultsmentioning

confidence: 99%

A Rational Repeating Template Method for Synthesis of 2 D Hexagonally Ordered Mesoporous Precious Metals

Takai

Doi

Yamauchi

et al. 2010

Chemistry An Asian Journal

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A repeating template method is presented for the synthesis of mesoporous metals with 2D hexagonal mesostructures. First, a silica replica (i.e., silica nanorods arranged periodically) is prepared by using 2D hexagonally ordered mesoporous carbon as the template. After that, the obtained silica replica is used as the second template for the preparation of mesoporous ruthenium. After the ruthenium species are introduced into the silica replica, the ruthenium species are then reduced by a vapor-infiltration method by using the reducing agent dimethylamine borane. After the ruthenium deposition, the silica is chemically removed. Analysis by transmission and scanning electron microscopies, a nitrogen-adsorption-desorption isotherm, and small-angle X-ray scattering revealed that the mesoporous ruthenium had a 2D hexagonal mesostructure, although the mesostructural ordering is decreased compared to that of the original mesoporous carbon template. This method is widely applicable to other metal systems. By changing the metal species introduced into the silica replica, several mesoporous metals (palladium and platinum) can be synthesized. Ordered mesoporous ruthenium and palladium, which are not easily attainable by the soft-templating methods, can be prepared. This study has overcome the composition variation limitations of the soft-templating method.

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Capillary Condensation in the Void Space between Carbon Nanorods

Cited by 8 publications

References 29 publications

Capillary bridge formation between hexagonally ordered carbon nanorods

Capillary bridge formation between hexagonally ordered carbon nanorods

Influence of Pore Wall Hydrophobicity on Freezing and Melting of Confined Water

A Rational Repeating Template Method for Synthesis of 2 D Hexagonally Ordered Mesoporous Precious Metals

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