Two types of interstitial channels were distinguished: non-defect, defined as interstitial channels in perfectly packed arrays of nanotubes all having the same diameter (homogeneous) defined where three tubes met, and defect interstitial channels, present in bundles composed of nanotubes having different diameters (heterogeneous) where four or more tubes met. Grand canonical Monte Carlo simulations were made of Ne on various model carbon nanotube bundles in order to explore the role of non-defect and defect interstitial channels in adsorption. Simulations were performed for closed and partially open homogeneous and heterogeneous bundles. The specific surface area, the isosteric heats of adsorption and adsorption isotherms were computed on the basis of the simulations, and these values were compared with experimentally measured quantities for Ne adsorption on carbon nanotubes produced by the HiPco process. Analysis of the results indicated that gases did not adsorb in non-defect interstitial channels. When considering Ne adsorption alone, there was an ambiguity concerning whether homogeneous or heterogeneous bundles were better models. However, taken together with previous work on Ar, CH4, and Xe, it was concluded that a model consisting of heterogeneous bundles with ∼11% open nanotubes, having non-defect blocked interstitial channels, but allowing adsorption in the defect interstitials, best described the reported experimental data for these gases on HiPco nanotubes. It was found thatquantum mechanical diffraction effects had to be taken into account when modeling Ne adsorption under experimental conditions.

Defect and Nondefect Interstitial Channel Availability in Carbon Nanotube Bundles: Comparison of Modeling with Experiments. M.R.Labrosse, J.K.Johnson: Journal of Physical Chemistry C, 2010, 114[17], 7602-10