Collapsing carbon nanotubes and diamond formation under shock waves

In order to investigate the mechanical properties of carbon nanotubes, dynamic shock wave pressures (less than or equal to 50 GPa) were applied on arc-discharge-generated carbon nanotubes containing polyhedral nanoparticles. High-resolution transmission electron microscopy (HRTEM) studies of the shock-recovered samples reveal that: (i) layers of the outer shells of the nanotubes break and transform into curled graphitic structures and (ii) the inner tube walls and bulk material display structural defects. Further X-ray powder diffraction and HRTEM analyses exhibit the presence of diamond nanocrystals which are produced after the shock-wave compression of polyhedral particles (present in the starting material). (C) 1998 Elsevier Science B.V. All rights reserved.