HIGH-PRESSURE SYNTHESIS OF NANOSTRUCTURED ULTRAHARD MATERIALS ON THE BASES OF FULLERENES, THEIR STRUCTURE AND PROPERTIES

摘要

Synthesis conditions, structures and physical properties of superhard and ultrahard forms of carbon obtained from C_(60) fullerene by static high-pressure-high-temperature treatment are presented. The unit-cell parameters and intermolecular bonds has been found using molecular mechanics calculations and X-ray diffraction profile analysis. The weighted pattern factor R_(wP) of 5-10 percent has been achieved when besides (2+2) intermolecular bonds a "common 4-member ring" and (3+3) type links considered. The sound velocities have been measured and a full set of elastic modules calculated. The highest value of longitudinal sound wave velocity 26 +- 2 km/s has been found which is a record value for known solids. The bulk elastic modulus and the hardness of ultrahard fullerites are higher than the values for diamond. The correct diamonds hardness at room temperature has been measured using the ultrahard fullerite indentors.