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9 Apr 2001

Volume 78, Issue 15, pp. 2095-2255

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Hydrogen storage in aligned carbon nanotubes

Yan Chen, David T. Shaw, X. D. Bai, E. G. Wang, C. Lund, W. M. Lu, and D. D. L. Chung

Appl. Phys. Lett. 78, 2128 (2001); http://dx.doi.org/10.1063/1.1341224 (3 pages) | Cited 38 times

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Aligned carbon nanotubes (CNTs) with diameters of 50–100 nm, synthesized by plasma-assisted hot filament chemical vapor deposition, were employed for hydrogen adsorption experiments in their as-prepared and pretreated states. Quadruple mass spectroscopy and thermogravimetric analysis show a hydrogen storage capacity of 5–7 wt% was achieved reproducibly at room temperature under modest pressure (10 atm) for the as-prepared samples. Pretreatments, which include heating the samples to 300 °C and removing of the catalyst tips, can increase the hydrogen storage capacity up to 13 wt% and decrease the pressure required for storage. The weight gains were measured after the samples moved out of the hydrogen environment. The release of the adsorbed hydrogen can be achieved by heating the samples up to 300 °C. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
68.43.Mn Adsorption kinetics
84.60.-h Direct energy conversion and storage
81.07.De Nanotubes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Enhancement of the molecular nitrogen dissociation levels by argon dilution in surface-wave-sustained plasmas

M. Tabbal, M. Kazopoulo, T. Christidis, and S. Isber

Appl. Phys. Lett. 78, 2131 (2001); http://dx.doi.org/10.1063/1.1359775 (3 pages) | Cited 10 times

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In this work, the nitrogen molecular dissociation level in Ar/N2 surface-wave plasma is evaluated as a function of plasma parameters such as Ar percentage in the gas mixture, power absorbed in the plasma, and total pressure in order to design an efficient N-atom source that can be used for various applications such as thin-film deposition and materials surface modification. This plasma is operated at 40.68 MHz and the nitrogen dissociation rate is determined, in the remote plasma, by analyzing the optical emission of the first positive molecular nitrogen band. For all operating conditions, the dissociation rate ([N]/[N2]) of N2 molecules was enhanced, as the percentage of Ar in the mixture increased from 0 to ∼95%, and dissociation rates higher than 2.5% were measured. This gain in the dissociation rate became more pronounced when the plasma power and total pressure increased from 40 to 120 W and from 4 to 7.5 Torr, respectively. These results are discussed in terms of the kinetics of the electrons, nitrogen atoms, and molecules and confirm theoretical kinetic models presented in the literature. © 2001 American Institute of Physics.
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52.50.Dg Plasma sources
82.37.Np Single molecule reaction kinetics, dissociation, etc.
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
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