Formation of s p³ bonding in nanoindented carbon nanotubes and graphite

The formation of sp³ bonding structures was investigated using molecular dynamics simulation technique in nanoindented carbon nanotubes (CNT) and graphite. Both graphite and CNTs were found to experienced a soft-to-hard phase transformation at room temperature at compressive stresses of 12 and 16 GPa, respectively. In graphite, deeper penetration was found to lead to the formation of interlayer sp³ bonding, resulting in a nanohardness that increases linearly with the penetration depth. The results show that during nanoindentation, the maximum nanohardness of graphite reaches 109 GPa, and CNTs 120 GPa.