By thermal desorption spectroscopy (TDS), we evaluated the hydrogen storage properties of carbonˆne particles including singlewall carbon nanotubes (SWNTs) synthesized by plasma-assisted hotˆlament chemical vapor deposition, along with commercialized single-wall carbon nanotubes. Two hydrogen desorption peaks, one between 100 and 200°C and the other between 500 and 600°C, were observed for the carbonˆne particles as well as for SWNTs in the spectra of TDS. Activation energy determined by varying raising temperature revealed that the lower-temperature peak is derived from physisorbed hydrogen. Peaks of CO desorption from the carbon ne particles, which appeared by the oxidation of carbon, were also observed around the higher-peak temperature. The result suggests that synthesized carbonˆne particles contain a lot of defects and bents with large speciˆc surface areas, which have the potential of larger amount of hydrogen adsorption.
We present a numerical method of determining the wavelength of dendritic sidebranches accompanying the needle crystal. Our method uses a linearization of the equations of interface evolution about the exact steady-state solution. We show that although the steady state is linearly stable, small perturbations will be selectively amplified, giving rise to observable branching. The sidebranches are stationary in the laboratory frame of reference and their wavelength scales as the tip radius for physical values of the dimensionless undercooling.
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