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 diamond anvil cell to 46 GPa at room temperature. Synchrotron energy dispersive x-ray diffraction studies were carried out to monitor the irreversible amorphization transformation followed by nanoindentation studies of the pressure-quenched samples. Micro-Raman studies indicate broad bands at 1570 and 1422 cm⁻¹ indicative of an amorphous phase with a mixture of ${\mathrm{sp}}^2$ - and ${\mathrm{sp}}^3$ -bonded carbon. Nanoindentation studies on the quenched amorphous phase 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 establish that the hard carbon phases can be produced from C-70 fullerene by application of pressure at room temperature.