Radial deformation of carbon nanotubes in supersonic collisions with a silicon surface

Using molecular dynamics simulations, we studied the radial deformation of a carbon nanotube (CNT) in supersonic collisions with a silicon surface. High speed (5 km/s) impact on its sidewall causes an abrupt and partially irreversible deformation of the 0.81 nm diameter CNT. The diameter of the CNT is decreased by more than 50% within 0.3 ps after the onset of the collision. This deformation relaxes on a half picosecond time scale, but vibrational energy in the tube relaxes much more slowly. Upon completion of the relaxation, the CNT shows an irreversible radial compression ranging from 7% to 35% of its original diameter. Also, the CNT penetrates below the surface to a distance of up to 13% of its diameter. In the case of near glancing incidence, the CNT scratches and rolls along the surface. At a speed of 700 m/s, the CNT is either scattered from or bound to the surface without any irreversible deformation. At a speed of 15 km/s, the CNT loses its radial elasticity and is completely fragmented. These results are interpreted by examining the effective temperature of the nanotube that is produced during the collision, and it is found that collisions that produce a local temperature near 2000 °C lead to irreversible damage. This concept is used to interpret recent CNT spraying measurements involving larger multiwalled CNTs.