Nanoindentation and x-ray diffraction studies of pressure-induced amorphization in C-70 fullerene

We have carried out high-pressure studies on a C-70 fullerene sample in a d iamond anvil cell to 46 GPa at room temperature. Synchrotron energy dispers ive x-ray diffraction studies were carried out to monitor the irreversible amorphization transformation followed by nanoindentation studies of the pre ssure-quenched samples. Micro-Raman studies indicate broad bands at 1570 an d 1422 cm(-1) indicative of an amorphous phase with a mixture of sp(2)- and sp(3)-bonded carbon. Nanoindentation studies on the quenched amorphous pha se shows an elastic loading behavior with a hardness of 18 GPa, which is 2- 3 times that of the surrounding steel gasket. Our results conclusively esta blish that the hard carbon phases can be produced from C-70 fullerene by ap plication of pressure at room temperature. (C) 2000 American Institute of P hysics. [S0003-6951(00)03832-8].