Discussion on the mechanical behavior of carbon nanotube/C60 composite based on observation of interfacial structure

The effects of the interfacial fine structure (interfacial bonding interaction) on the mechanical properties of nanotube/C60 composite were examined by high resolution transmission electron microscope (HRTEM) observations of nanotube/vapor-deposited C60 crystal interfaces and pull-out tests of high modulus carbon fiber with a vapor-deposited C60 single crystal. Interfaces between nanotube and {111}-faceted C60 crystal were observed to possess a parallel orientation relationship between the tube axis and [110] of the C60 crystal. The shear strength of the carbon fiber/C60 composite was estimated to be 4.4 x 10(-2) MPa. Interfacial sliding was observed in the carbon fiber/C60 single crystal interface without deformation of the C60 matrix nor the fracture of fiber. It has been inferred that the pull-out of the carbon fiber from the C60 matrix is due to the shear sliding, which is caused by the weak bonding between graphitic basal plane and C60. The experiments have indicated that the ductility of the nanotube/C60 composite originates probably from sliding at the interface between the nanotube and the C60 matrix.