Collapsing carbon nanotubes and diamond formation under shock waves

In order to investigate the mechanical properties of carbon nanotubes, dynamic shock wave pressures (⩽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).