Synthesis of superhard and ultrahard materials by 3d-polymerization of C60, C70 fullerenes under high pressure (15 GPa) and temperatures up to 1820 K

Solid fullerenes C 60 and C 70 have been treated at high pressure of 15 GPa and high temperatures of 520-1820 K for a time of exposure of 60 s and a quenching rate of 300 K s -1 using a toroid-type apparatus. X-ray diffraction and Raman spectra confirm the realization of 3D-polymerized phases in these solids at 15 GPa. The pressure/temperature maps of synthesis of metastable carbon phases on the basis of C 60 and C 70 have thus been extended to 15 GPa. The longitudinal and shear sound wave velocities were measured by acoustic microscopy techniques. A maximum sound wave velocity of (21 ± 1) x 10 5 m s -1 was observed in the sample synthesized from C 60 at T = 1170 K. The elastic constants were calculated using experimental data. The acoustic microscopy images of experimental samples have been investigated.