Hydrogen-mediated transformation of fullerene at high pressures and temperatures

The hydrogenation of fullerenes was used to chemically activate the polymerization of molecules with the formation of superhard phase at a pressure of 8 GPa and temperatures up to 1170 K. The preparation of samples in one experiment from slightly hydrogenated and non-hydrogenated fullerenes separated by a molybdenum plate in a high-pressure cell and the study of the properties of the samples at the conjugated surfaces revealed the chemical activation effect free from the effects of temperature and pressure gradients. The 3D polymerization and inhibition of the graphitization of hydrogenated fullerene in a range of 970–1170 K are proposed to be responsible for spectacular increase in the sample hardness, which is twice as high as that of the reference sample. Metal-matrix composites with use of hydrogenated or non-hydrogenated fullerenes were synthesized under pressure to overcome the problem of the brittleness of bulk samples obtained from fullerenes. The excellent tribological properties of the cobalt-matrix composite reinforced with the particles of 3D-polymerized hydrogenated fullerene were revealed, opening up the possibility of using the new material as miniature friction bearings. [Display omitted] •“Slight” hydrogenation of fullerenes chemically activates 3D polymerization.•At 8 GPa and 1020 K, C60 undergoes graphitization, while C60H3.5 turns into a superhard 3D polymer.•The 3D polymer is characterized by a hardness of up to 49 GPa and a friction coefficient of 0.02.•Co-matrix composite reinforced with 3D-polymerized C60H3.5 particles demonstrates excellent tribological properties.