Structure and deformation behavior of carbon nanotubes reinforced nanocrystalline C60 composite

Carbon nanotube reinforced nanocrystalline C60 was prepared at room temperature by drawing the composite sheathed in silver tube. Fine structures of the composite were examined by high resolution electron microscopy (HREM) and the mechanical properties by conventional tensile tests. HREM observation shows that carbon nanotubes in the composite are defect free and aligned well in the direction of the wire. The stress-strain curve of the composite wire de-sheathed by evaporation of silver through heat treatment gives approximately 20 times increase in the fracture stress over that of polycrystalline C60 with higher fracture strain (over 10%). The fracture surface of the wire shows that nanotubes were pulled out but not fractured. TEM observation of interface structure of C60 vapor deposited nanotubes as well as pull-out tests were performed of C60 single crystals vapor-deposited on single high elasticity carbon fibers which have similar surface structure as nanotube to examine the origin of the large elongation of the composite. It has been inferred that shear deformation takes place in the carbon fiber/C60 single crystal interface with little deformation of matrix but without fracture of the fiber and that the pull out was mainly caused by the shear deformation, which was probably made possible by a weak interaction between graphitic basal plane and C60. The experiments lead us to a new concept of a ductile C/C composite.