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Wilson, T.; Tyburski, A.; DePies, M.; Vilches, O. E.; Becquet, Denis; Bienfait, M.

doi:10.1023/a:1013769823838

Cited by 93 publications

(87 citation statements)

References 18 publications

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“…In the form of bundles or ropes, they have a rather large surface area per gram of material which makes them suitable for physisorption studies using somewhat conventional techniques. Although many types of carbon nanotubes exist, considerable theoretical [16][17][18][19][20][21][22][23][24][25][26][27] and some experimental [28][29][30][31][32][33][34][35][36] work has been done on the adsorption of many rare gas atoms and simple molecules deposited on closed-end single-wall carbon nanotube (SWNT) bundles. The attraction of the SWNT bundles is that on the interstitial channels between three nanotubes and on the grooves between two nanotubes on the outside surface of a bundle, one-dimensional (1D) chains of atoms/molecules can be adsorbed.…”

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confidence: 99%

Helium adsorbed on carbon nanotube bundles: one-dimensional and/or two-dimensional solids?

Wilson

Vilches

2003

Low Temperature Physics

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Heat capacity measurements of 4 He adsorbed on closed-end single-wall carbon nanotube bundles in the temperature range 1.5 K < T < 6 K are reported. Heats of adsorption Q st calculated from isotherms measured on the same calorimeter cell are included. We correlate Q st features with features of the helium heat capacity. We discuss possible interpretations of the current data. Single layer helium films physisorbed on exfoliated graphite have been studied in great detail, both experimentally and theoretically, for a long time [1][2][3][4][5]. These films provided, for the first time, realizations of several phases of matter in reduced dimensionality: two-dimensional (2D) gases and fluids [6][7][8], commensurate (CS) [9,10] and incommensurate (ICS) solids [11][12][13], as well as the phase transitions between them as a function of temperature and coverage.A new carbon material discovered in the last decade is carbon nanotubes [14,15]. In the form of bundles or ropes, they have a rather large surface area per gram of material which makes them suitable for physisorption studies using somewhat conventional techniques. Although many types of carbon nanotubes exist, considerable theoretical [16][17][18][19][20][21][22][23][24][25][26][27] and some experimental [28][29][30][31][32][33][34][35][36] work has been done on the adsorption of many rare gas atoms and simple molecules deposited on closed-end single-wall carbon nanotube (SWNT) bundles. The attraction of the SWNT bundles is that on the interstitial channels between three nanotubes and on the grooves between two nanotubes on the outside surface of a bundle, one-dimensional (1D) chains of atoms/molecules can be adsorbed. These chains may be in the form of 1D gases and fluids if mobile [17,21,26,27] and perhaps commensurate and/or incommensurate solids [37]. Further adsorption on the outside surface of the bundles should lead to their coating with a monolayer that physically resembles adsorption on graphite, perhaps with different properties due to the curvature of the graphene surfaces, finite size, and confinement between grooves of the bundle [37]. A crossover from 1D to 2D or 3D properties is then possible, given that one can start with 1D chains that eventually, as a function of coverage and/or temperature, interact with each other in 2D and 3D space.In this article we report on initial studies of the heat capacity of 4 He on SWNT bundles as a function of temperature and volume of gas adsorbed (coverage); these measurements are complemented by a few volumetric adsorption isotherms on the same bundles. Two previous somewhat indirect measurements of the heat capacity of 4 He on SWNT bundles have appeared [38,39]. In both cases, the prime intent of the measurement was to obtain the heat capacity of the nanotubes; 4 He was used as exchange gas to cool the bundles and/or the calorimeter and inner parts of the cryostat.

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Helium adsorbed on carbon nanotube bundles: one-dimensional and/or two-dimensional solids?

Wilson

Vilches

2003

Low Temperature Physics

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“…Additionally, the very small pore volume associated with these sites would give a very small contribution to the hydrogen storage, even if these were accessible [57,58]. At least two different adsorption sites for hydrogen in single-walled carbon nanotubes could be identified by inelastic neutron scattering (INS) [59], by low-temperature hydrogen adsorption [60], by thermal desorption spectroscopy [61], and by Raman spectroscopy [62,63]. As an example, using INS Georgiev et al determined two energetically different adsorption sites for hydrogen in closed SWCNTs [59].…”

Section: Carbon Materialsmentioning

confidence: 99%

Physisorption in Porous Materials

Hirscher¹,

Panella²

2010

Handbook of Hydrogen Storage

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Physisorption or physical adsorption is the mechanism by which hydrogen is stored in the molecular form, that is, without dissociating, on the surface of a solid material. Responsible for the molecular adsorption of H 2 are weak dispersive forces, called van der Waals forces, between the gas molecules and the atoms on the surface of the solid. These intermolecular forces derive from the interaction between temporary dipoles which are formed due to the fluctuations in the charge distribution in molecules and atoms. The combination of attractive van der Waals forces and short range repulsive interactions between a gas molecule and an atom on the surface of the adsorbent results in a potential energy curve which can be well described by the Lennard-Jones Eq. (2.1).where e is the depth of the energy well, r i the distance between an H 2 molecule and a generic atom i on the surface and s the value of r i for which the potential is zero [1]. The minimum of the potential curve occurs at a distance from the surface which is approximately the sum of the van der Waals radii of the adsorbent atom and the adsorbate molecule. For microporous materials (r pore < 1 nm) [2] where the pore dimensions are comparable to the diameter of the adsorbate molecules this interaction potential is also influenced by the pore shape and the pore dimensions. Adsorption is an exothermic process, that is, heat is released during the adsorption of gas molecules on a surface. Owing to the low polarizability of the H 2 molecule this type of interaction is very weak and leads to low values of the heat of adsorption, typically in the range of 1-10 kJ mol À1 [3]. Compared to chemisorption which involves a change in the chemical nature of the H 2 molecule by, for example, dissociation, physisorption has approximately a ten times smaller heat of adsorption. Chemical hydrides and complex hydrides, which store hydrogen chemically, both have the disadvantage of producing an excessive amount of heat during fast Handbook of Hydrogen Storage. Edited by Michael Hirscher

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“…[1][2][3][4][5][6][7] In these structures, the only places available for adsorption are their outer surfaces, in particular the grooves between two adjacent tubes. 8 Other possible locations are the triangular interstices among three neighboring tubes in the bulk part of the bundle.…”

Section: Introductionmentioning

confidence: 99%

“…These correspond to armchair nanotubes between (5,5) and (16,16) in the standard nomenclature. Our main aim is to compare our results with both the ones for H 2 on the same surface 16 and those for 4 He on graphene, 21 a flat surface that can be considered a tube of infinite radius.…”

Section: Introductionmentioning

confidence: 99%

4He adsorbed outside a single carbon nanotube

Gordillo

Boronat

2012

Phys. Rev. B

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The phase diagrams of 4 He adsorbed on the external surfaces of single armchair carbon nanotubes with radii in the range 3.42-10.85Å are calculated using the diffusion Monte Carlo method. For nanotubes narrower than a (10,10) one, the ground state is an incommensurate solid similar to the one found for H 2 on the same substrates. For wider nanotubes, the phase with the minimum energy per particle is a liquid layer. Curved √ 3 × √ 3 registered solids similar to the ones found on graphene and graphite were unstable for all the tubes considered.

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Cited by 93 publications

References 18 publications

Helium adsorbed on carbon nanotube bundles: one-dimensional and/or two-dimensional solids?

Helium adsorbed on carbon nanotube bundles: one-dimensional and/or two-dimensional solids?

Physisorption in Porous Materials

4He adsorbed outside a single carbon nanotube

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