AMORPHIZATION OF FULLERITE (C-60) AT HIGH-PRESSURES

A number of carbon phases, which are metastable under normal conditions and which include amorphous ''phases,'' were synthesized from fullerite crystals (C-60) by heating to different temperatures (from 20 to 700 degrees C) under a pressure of 12.5 GPa. The structure, Raman spectra, density, and mechanical properties of the samples obtained were studied. It was found that amorphization of fullerite occurs in a wide temperature range and includes the following: 1) at the initial stages partial amorphization with preservation of C-60 molecules and formation of intermediate crystalline phases and 2) at the final stages - complete amorphization in the system of atoms with destruction of C-60 molecules and formation of a disordered network with a large fraction of sp(3) bonds. The mechanical properties of the intermediate phases are approximately half as goad as those of diamond and the mechanical properties of the amorphous ''phases'' are close to those of ''diamond.'' (C) 1995 American Institute of Physics.