Intercalation of heavy alkali metals (K, Rb and Cs) in the bundles of single wall nanotubes

The electric-are discharge carbon deposits (collaret) containing Single Wall Carbon Nanotubes (SWNTs) were heat treated at 1600 degreesC during 2 days under N-2 flow in order to eliminate the Ni catalyst by sublimation, without modifications of the SWNTs ropes. Sorting this deposit by gravity enabled to obtain in the coarsest particles higher amount of SWNTs ropes than in other particle sizes. The coarser particles of the carbon deposits were reacted with the alkali metals vapour giving intercalated samples with a MC8 composition. The intercalation led to an expansion of the 2D lattice of the SWNTs so that the alkali metals were intercalated in between the tubes within the bundles. Disordered lattices were observed after intercalation of Rb and Cs. The simulations of the X-ray diffractograms of SWNTs reacted with K, gave the best fit for three K ions occupying the inter-tubes triangular cavities. The investigations by EPR, and C-13 NMR, showed that doped carbon deposits are metallic.