Balance of graphite deposition and multishell carbon nanotube growth in the carbon arc discharge

Except for atomistic models of individual carbon nanotube growth, there is still no precise understanding of the large scale deposition of carbon during the are discharge. We study the microstructure of cathode deposits in detail using scanning electron microscopy, focusing on two distinct regimes found in the deposits having different large scale morphology. The shell grown circumferentially consists of extended graphite layers with preferred orientation, and the structure reveals close similarity to pyrolitic graphite. The core region is a porous assembly of nanotubes and nanoparticles. We conclude that closed nanostructures self-assemble from a dense carbon vapor, whereas pyrographitic shell grows by continuous deposition on exposed substrates.