V. E. Muradyan

Photoreduction of graphite oxide

The photoreduction of graphite oxide (GO) films and solutions by UV light was studied. The electrical resistance of a GO film decreases upon irradiation by more than an order of magnitude. The threshold of photoreduction was determined to be 3.2 eV. The photoreduction is accompanied by an increase in absorption in the visible spectral region, and the CO, CO2, O2, and H2O molecules were found in the gas phase above the irradiated GO film.

Photoreduction of graphite oxide nanosheets with vacuum ultraviolet radiation

Films of graphite oxide nanosheets have been prepared by deposition from an aqueous alcohol emulsion onto a Teflon FEP substrate. The behavior of the films exposed to monochromatic vacuum UV radiation at a wavelength of 123.6 nm has been studied. It has been found that irradiation decreases the water content and the amount of hydroxyl (OH) groups and increases the concentration of double bonds in the film. At the same time, irradiation does not decrease the amount of C=O groups in the carboxyl and ketone moieties.

Characterization of fluorinated multiwalled carbon nanotubes by x-ray absorption spectroscopy

The C 1s and F 1s x-ray absorption spectra of fluorinated multiwalled carbon nanotubes with different fluorine contents and reference compounds (highly oriented pyrolytic graphite crystals and “white” graphite fluoride) were measured using the equipment of the Russian-German beamline at the BESSY II storage ring with a high energy resolution. The spectra obtained were analyzed with the aim of characterizing multiwalled carbon nanotubes and their products formed upon treatment of the nanotubes with fluorine at a temperature of 420°C. It was established that, within the probing depth (∼15 nm) of carbon nanotubes, the process of fluorination occurs uniformly and does not depend on the fluorine concentration. The interaction of fluorine atoms with multiwalled carbon nanotubes in this case proceeds through the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton and is accompanied by a change in the hybridization of the 2s and 2p valence electron states of the carbon atom from the trigonal (sp2) to tetrahedral (sp3) hybridization.

Composite materials based on graphene nanoplatelets and polypropylene derived via in situ polymerization

In recent years researchers have paid considerable attention to the creation of multifunctional polymer composite materials bearing nanoscale fillers. The introduction of nanoparticles into polymer matrices in relatively small concentrations (reaching 2.5 vol %) makes it possible to produce materials possessing better properties than the initial matrix polymers and conventional dispersion-filled composites. Carbon nanostructures are promising fillers for polymer nanocomposite materials: fullerenes, carbon nanotubes, nanofibers, and graphene nanoplatelets. A combination of structural, physicomechanical, and electrophysical properties of these fillers upon their introduction into polymer matrices affords the creation of composite materials possessing improved stress-strain, electro- and thermophysical characteristics, and noncombustibility.

Structural and Morphological Changes Induced by Intense Shock Waves in Carbon Nanotubes

The morphological and structural characteristics of multiwalled carbon nanotubes subjected to multi shock-wave compression to pressures of about 120 GPa and temperatures of 2000 K are comprehensively analyzed experimentally and theoretically. The calculations relevant to the thermal history of shock compression followed by unloading of the multiwalled carbon nanotubes are performed. Diffractometer structural studies of the samples before and after shock loading are carried out. The morphological properties of the multiwalled carbon nanotubes are studied by scanning electron microscopy and transmission electron microscopy of the pristine and explosion-treated samples. It is shown that multiwalled carbon nanotubes subjected to a strong shock compression undergo the following changes: (a) most nanotubes transform into graphite structures with an increased spacing between graphene planes and (b) some nonvolatile nanotubes exhibit irreversible distortions in shape.

Specific features of the electronic structure of fluorinated multiwalled carbon nanotubes in the near-surface region

The C 1s and F 1s X-ray photoelectron spectra of fluorinated multiwalled carbon nanotubes with different fluorine contents have been measured using the equipment of the Russian-German beamline at the BESSY storage ring by varying the energy of exciting photons. It has been established that two fluorocarbon phases in which the chemical bonding is characterized by a different electron transfer from carbon atoms to fluorine atoms are formed in the near-surface region of nanotubes with fluorine concentrations of 10–39 wt %. The content of the dominant first phase with a large electron transfer in nanotubes remains unchanged with an increase in the probing depth. This phase is identified as a bulk phase formed as a result of the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton without its destruction. The second phase with a small electron transfer is a near-surface phase, because it is predominantly located within two or three upper graphene monolayers and its contribution considerably decreases with an increase in the probing depth of fluorinated multiwalled carbon nanotubes.

Mechanochemical synthesis and properties of fullerene derivatives

A technique was developed of mechanochemical synthesis of the fullerene C60 water-soluble derivatives. The derivatives obtained were characterized by elemental analysis, IR spectroscopy, and thermogravimetric analysis. The effect the substances obtained on the mechanical properties of the polyvinyl alcohol films was studied. A strengthening effect of fullerene derivatives on the elastic modulus, tensile strength, and tensile deformation of the polyvinyl alcohol films were found to become apparent already at the concentrations of 0.1–0.2 wt %.

Polymeric Dressing Formulations Containing Water-Soluble Fullerene Derivatives

The effect of small additions of water-soluble fullerene C60 derivatives on the strength properties of polyvinyl alcohol films was examined. Solutions of polyvinyl alcohol and fullerenol were tested as polymeric dressing formulations for glass-reinforced plastics based on a thermoplastic polyethylene or polyamide matrix.

Elastification of heat-resistant epoxy polymer matrices

The behavior of fracture toughness parameters in comparison with other physicomechanical parameters of failure was examined with the aim to evaluate the efficiency of modification (elastification) of heat-resistant binders, with four epoxy-amine compounds taken as examples.

Adhesive strength of fullerene-doped epoxyamine compositions

Dependence of adhesive strength of model gluing epoxide compositions glass-binder-glass hardened with aliphatic and aromatic amine hardeners on the fullerene additive content is studied. When aromatic amine is used as a hardener of epoxy-diane resin, addition of fullerenes does not affect the adhesive strength. On the contrary, when aliphatic amine hardener is used, the increase of adhesive strength as compared to nondoped composition was 400%. Use of a mixture of aliphatic and aromatic hardener leads to substantial synergism of their effect on strength properties of the fullerene-doped compositions.