Two Confined Phases of Argon Adsorbed Inside Open Single Walled Carbon Nanotubes
Isothermal adsorption of Ar on single walled carbon nanotubes (SWNTs) has been studied at 77 and 87 K. The SWNTs have been grown by laser vaporization of a graphite pellet containing 0.6% (atomic) Ni/Co catalyst. The nanotubes have been prepared for argon adsorption measurements by prolonged outgass...
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Published in | Langmuir Vol. 20; no. 14; pp. 5940 - 5945 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
06.07.2004
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Subjects | |
Online Access | Get full text |
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Summary: | Isothermal adsorption of Ar on single walled carbon nanotubes (SWNTs) has been studied at 77 and 87 K. The SWNTs have been grown by laser vaporization of a graphite pellet containing 0.6% (atomic) Ni/Co catalyst. The nanotubes have been prepared for argon adsorption measurements by prolonged outgassing of as-grown material in a vacuum at room temperature (295 K), at elevated temperatures of up to 475 K, and by oxidization for 2 h in dry air at 470 K. Formation of two condensed phases of Ar in the interior of SWNTs has been observed at 77 K. The low-density phase is formed at 155(5) μTorr, while the high-density phase, at 120(5) μTorr. At 87 K, only a single phase has been observed at 185(5) μTorr. Condensation at both 77 and 87 K appears to be the first-order phase transition. Onset of the quasi-one-dimensional linear (one-channel) phase and the quasi-two-dimensional monolayer (six-channel) phase formation on the external surface of bundles has been observed at 77 K near 0.0017 and 0.8 Torr, respectively, and at 87 K near 0.018 and 5 Torr, respectively. Isosteric heats of adsorption for the one-channel phase, the first external layer, and the second external layer have been determined to be equal to 137, 107, and 70 meV, respectively. |
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Bibliography: | ark:/67375/TPS-3Z8ZP1D2-R istex:B5056BB876D86DAEE6632F62533630F4DA44B492 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0743-7463 1520-5827 |
DOI: | 10.1021/la0358872 |