Mechanical properties of the 3D polymerized, sp2-sp3 amorphous, and diamond-plus-graphite nanocomposite carbon phases prepared from C60 under high pressure

Mechanical properties (Vicker's hardness, Young's modulus, and fracture toughness coefficient) have been studied for the three-dimensionally polymerized, amorphous, and nanocrystalline diamond-plus-graphite composite carbon phases prepared from fullerite C-60 by temperature treatment under pressure. The hardness was found to increase gradually with the synthesis temperature. The experimental values of hardness are well correlated with the density of samples regardless of the phase structural nature, displaying the same dependence as amorphous carbon films. It has been shown that the hardness and Young's modulus of both polymerized crystalline and disordered phases, though not as high as those of diamond, are comparable to the properties of cubic BN, while fracture toughness coefficient can be higher than that for diamond. An unusual combination of high hardness and high plasticity has been established for strongly polymerized C-60. (C) 1998 American Institute of Physics.