Phase Transformations in Carbon Fullerenes at High Shock Pressures

Abstract

C 60 powders were shock-compressed quasi-isentropically and quenched from pressures in the range 10 to 110 GPa (0.1 to 1.1 Mbar). Recovered specimens were analyzed by Raman spectroscopy and optical microscopy. C 60 fullerenes are stable into the 13- to 17-GPa pressure range. The onset of a fast (∼0.5 μs) reconstructive transformation to graphite occurs near 17 GPa. The graphite recovered from 27 GPa and about 600°C is relatively well ordered with crystal planar domain size of about 100 Å. Above 50 GPa a continuous transformation to an amorphous state is observed in recovered specimens. The fast transformation to graphite is proposed to occur by π-electron rehybridization which initiates breakup of the ball structure and formation of the graphite structure at high density.