Cherednychenko S. Synthesis and features of carbon nanostructures and composites

The dissertation is devoted to the study of the features of new carbon nanostructures and composites, in particular, thermally reduced multi-layer graphene oxide (MTGO) modified by a high-frequency discharge in a hydrogen atmosphere, polymer composites based on modified graphene and obtained by the method of thermos-vacuum cryogenic sublimation of hydrated C60 fullerene. Іt was found that i) treatment with a high-frequency discharge in a hydrogen atmosphere of MTRGO significantly changes its adsorption characteristics; ii) composite structures based on epoxy compound and polyester resin with certain methods of adding graphene oxide, thermally reduced graphene oxide (TRGO) and MTRGO acquire a number of significantly increased mechanical characteristics; iii) the possibility of obtaining a stable solution of C60 fullerene in water by the vacuum-cryogenic-sublimation method without the use of organic solvents was qualitatively confirmed. In the 1th chapter a literature review of the influence of the energy-geometric state of condensed carbon on the morphology and sorption properties of graphene and the differences in the energy structure of graphene and fullerene are considered. Particular attention is paid to the physical and chemical modification and methods of synthesis of the specified nanostructures. The 2nd chapter describes the method of obtaining and subsequent characterization of TRGO. Also, a description of the original method of modification of TRGO by high-frequency pulsed discharge treatment in a hydrogen atmosphere, than was developed in the work, is described. In the 3rd chapter the morphology of a modified TRGO sample was investigated by scanning electron microscopy, it was shown that treatment with a high-frequency discharge in a hydrogen environment leads to delamination, i.e., deformation of carbon planes, an increase in the "pores" of MTRGO. It was revealed: an increase in interlayer distances, partial destruction of carbon layers, and the presence of chemical modification of graphene planes with hydrogen in the process of hydrogen plasma treatment and the physical interaction of molecular hydrogen with hydrogen atoms chemically sorbed by MTRGO layers. The total concentration of atomic hydrogen chemically sorbed by the MTRGO sample was 15.4 atoms. % (or 1.3% by mass). It was found that the treatment of TRGO with a pulsed gas discharge increased the physical sorption of hydrogen by 1.5 times. The 4th chapter is devoted to the creation and mechanical testing of polymer composites: - adhesive composite epoxy resin - graphene oxide: the strength of the adhesive joint increased more than 3 times (TRGO concentration 1%/epoxy resin without hardener) compared to an adhesive joint with a pure epoxy matrix; - in the case of the polyester resin – glass fiber – TRGO structural composite (TRGO concentration 1 wt. %/polyester resin without hardener), microhardness increased to 80%, impact strength to 37%, static bending strength increased by 52% compared to the control sample without TRGO. When MTRGO was added to the polyester matrix in the same concentration, the microhardness increased to 100%, the impact toughness to 43%, and the static bending strength to 54% compared to the control sample. In the 5th chapter, the application of the original method of vacuum-sublimation cryogenic deposition (VS-CD) for the preparation of water-colloidal solution of fullerene (FWCS) is considered. It is shown that the solid phase obtained by condensation of a mixture of C60 fullerene vapor and water vapor on a metal surface cooled by liquid nitrogen, after melting, is a stable aqueous colloidal solution of C60 fullerene without the use of any dispersing treatment, such as ultrasound irradiation. The results of the FWCS characterization using UV-Vis absorption spectroscopy and their comparison with known literature data on hydrated fullerenes made it possible to conclude that the C60@{H2O}n hydrated fullerene C60 complexes are present in the FWCS. The results obtained in the dissertation work not only deepen fundamental knowledge about the properties of carbon structures, but also have purely practical significance. Thermally reduced graphene oxide modified by a high-frequency pulsed discharge is a new material that has improved characteristics of hydrogen sorption and storage and it can be used for polymer-based nanocomposites with improved mechanical properties. Such materials are very promising as structural elements of unmanned aerial vehicles, in aircraft construction and aerospace engineering, as they have low weight and enhanced operational properties. The proposed cryogenic vacuum-sublimation method of obtaining colloidal solutions of fullerenes in water can be used to create stable aqueous complexes of organic and inorganic compounds as for as in biophysical research.