Controlled evolution of carbon nanotubes coated by nanodiamond: the realization of a new class of hybrid nanomaterials

We report a new class of nanostructured carbon materials, which couple nanosized diamond with singlewalled carbon nanotubes. This exciting material is being produced in our laboratories in a modified CVD reactor by means of reactions between carbon nanopowders and atomic H. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, and reflection high-energy electron diffraction (RHEED) have been used to study samples grown for various deposition times. The information achieved by combined use of these characterization techniques has enabled the construction of a time-growth sequence for the two carbon nanophases and has enlightened the peculiar growth of such hybrid carbon systems. The tubular inner structures are found to be bundles of single-walled carbon nanotubes (SWNT) up to 15 ím long, and the outer deposits consist of wellshaped diamond crystallites with diameters in the 20-100 nm range. The one-step synthesis approach described here provides an experimental route to the production of ordered arrays of rigid nanotubes coated by diamond nanocrystallites.