Yutaka Takahashi1, Yoshiaki Takada2, Shigeo Kotake1,Akihito Matsumuro2 and Masafumi Senoo1
1Department of Mechanical Engineering, Faculty of Engineering, Mie University, Tsu
Carbon 60 was pressure-treated at 3 and 5.4 GPa at 291-1073 K. No change was noticed at 291 K. It collapsed into graphite at 1073 K. Polymerized fcc-phase reported by Iwasa et al. was obtained at 373-873 K. The lattice parameter of the phase was measured at the atmospheric pressure to clarify the sintering temperature and pressure dependences. It decreased continuously from a=1.417 nm down to 1.32 nm as the sintering temperature increased, which indicates that the polymerization is thermally activated. The applied pressure was, however, hardly affected.
The polymerized phase was metastable at the ambient pressure but converted to a pristine phase (a=1.417 nm) by heat treatment. The endothermic reaction and the recovery of lattice parameter were observed at 500-550 K. After the transition, the structure modification still continued during prolonged heating, which suggests that the recovery was incomplete.
From the geometrical requirement of a truncated icosahedron molecule, we proposed the structure model of the polymerized fcc-phase based on the ring-opening reaction. Some considerations were also made for the T-P phase diagram proposed by Sundqvist et al.
(Received March 29, 1996)
fullerene, high pressure, polymerization, truncated icosahedron, ring-opening reaction, phase transition
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