X-ray Raman scattering studies on C60 fullerenes and multi-walled carbon nanotubes under pressure

X-ray Raman scattering experiments were performed on C-60 fullerenes and multi-wall carbon nanotubes (MWCNT) up to 20 GPa and 25 GPa using a diamond anvil cell and synchrotron radiation at HPCAT, Advanced Photon Source. The intensity of the near edge peaks representing sp(2) hybridization (pi*) decreases with increasing pressure in both materials. Around 13 GPa the X-ray Raman spectra of C-60 completely transformed to sp(3) type bonding leading to diamond-like phase. Similar features have been observed in MWCNT at 16 GPa indicating the formation of strong interlayer covalent bonds. Our experiments are in excellent agreement with recent theoretical simulations reported on the mechanical behaviour of compressed nanotubes and provide direct experimental evidence for bond switching of these carbonaceous systems at high pressures. (c) 2006 Elsevier B.V. All rights reserved.