The effect of C60 fullerene polymerization processes on the mechanical properties of clusters forming ultrahard structures of 3D C60 polymers

We observed the effect of high (up to 80 GPa) pressure, catalyst (CS2) and laser irradiation on the process of three-dimensional (3D) polymerization of fullerene C60 and the mechanical properties of the 3D C60 samples. The studies were carried out using resonant Raman spectroscopy and piezospectroscopy, high resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy. We have revealed that the 3D C60 structure consists of at least two types of clusters formed by covalent bonds with a different set of force constants, while C60 molecules, as one of the elements of the 3D C60 structure (clusters), are preserved at least up to a pressure of 80 GPa. The intensity of Raman scattering depends on the wavelength of the exciting radiation (resonance effect) and a set of force constants: the higher their values, the shorter-wavelength exiting radiation is required for Raman scattering observation by such clusters. Clusters with bulk moduli from 454 GPa to 644 GPa are formed depending on methods of C60 polymerization. According to the set of clusters, 3D C60 samples with bulk moduli from 506 GPa to 608 GPa were obtained.