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

A number of carbon phases, which are metastable under normal condition s and which include amorphous ''phases,'' were synthesized from fuller ite crystals (C-60) by heating to different temperatures (from 20 to 7 00 degrees C) under a pressure of 12.5 GPa. The structure, Raman spect ra, density, and mechanical properties of the samples obtained were st udied. It was found that amorphization of fullerite occurs in a wide t emperature range and includes the following: 1) at the initial stages partial amorphization with preservation of C-60 molecules and formatio n of intermediate crystalline phases and 2) at the final stages - comp lete amorphization in the system of atoms with destruction of C-60 mol ecules 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 prop erties of the amorphous ''phases'' are close to those of ''diamond.'' (C) 1995 American Institute of Physics.