Yu. M. Shul’ga

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.

Deuterofullerene C60D24 studied by XRD, IR and XPS

Abstract The deuterofullerene C60D24 was prepared from the solid C60 and was characterised by means of XRD, IR and XPS. The C60D24 was found to be a polycrystalline powder with a FCC lattice and a=14.55 A. Deuterium thermal desorption from C60D24 leads to a reversible formation of fullerene. However, the distances between the C60 molecules become significantly longer compared to the initial fullerite.

Thermally stable hydrogen compounds obtained under high pressure on the basis of carbon nanotubes and nanofibers

Compounds containing 6.3–6.5 wt % H and thermally stable in vacuum up to 500°C were obtained by annealing graphite nanofibers and single-walled carbon nanotubes in hydrogen atmosphere under a pressure of 9 GPa at temperatures up to 45°C. A change in the X-ray diffraction patterns indicates that the crystal lattice of graphite nanofibers swells upon hydrogenation and that the structure is recovered after the removal of hydrogen. It was established by IR spectroscopy that hydrogenation enhances light transmission by nanomaterials in the energy range studied (400–5000 cm−1) and results in the appearance of absorption bands at 2860–2920 cm−1 that are characteristic of the C–H stretching vibrations. The removal of about 40% of hydrogen absorbed under pressure fully suppresses the C–H vibrational peaks. The experimental results are evidence of two hydrogen states in the materials at room temperature; a noticeable portion of hydrogen forms C–H bonds, but the most of the hydrogen is situated between the graphene layers or inside the nanotubes.

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.

Fabrication and characterization of fluorinated single-walled carbon nanotubes

The optimum conditions for the fluorination of single-walled carbon nanotubes (SWCNT) in the atmosphere of gaseous fluorine with the nanotube structure remaining intact up to a stoichiometry of CFx, x ∼ 0.5 were determined. The kinetics of fluorination was examined. The fluorinated SWCNTs were characterized by various methods, including transmission electron microscopy, measurements of specific surface area and accessible internal volume, NMR spectroscopy, IR spectroscopy, X-ray absorption and photoelectron spectroscopies, thermal stability, and analysis of gaseous products by mass-spectrometry. The structure of fluorinated SWCNT was preserved up to brutto-composition CF0.5 but degree of fluorination of SWCNT bundles was decreased with distance from the SWCNT surface to its core. Such a decrease becomes evident at ∼1.5 nm distance. It means that the degree of fluorination depends on the degree of its dispersion.

Photoreduction of graphite oxide at different temperatures

The photoreduction of graphite oxide in a film exposed to UV light is investigated at 77 K and at room temperature. At a temperature of 77 K, the photodissociation of oxygen-containing groups and graphite oxide (GO) reduction occurs that is observed in the UV-vis and Raman absorption spectra. The mechanism of photoreduction is proposed, and a comparison of the photoreduction and the thermal process is carried out.

Radiation telomerization of tetrafluoroethylene in tetrahydrofuran

According to DSC, DTG, and GPC data, H(CF2CF2)nC4H7O telomers with a chain length of n = 1−4 and Tb ≈ 170−200°C were formed during the radiolysis of a binary mixture of tetrafluoroethylene + tetrahydrofuran in a molar ratio of (0.37–2)/1 between the reactants at room temperature. IR spectroscopy and quantum-chemical calculations demonstrated that telomerization occurred with chain transfer through the α-hydrogen of the furan ring.

Polymorphic transformations in nanostructured anatase (TiO2) under high-pressure shock compression

The action of dynamic pressure and temperature on polymorphic transformations in nanostructured (grain size of 8–20 nm) anatase (TiO2) is studied. The dynamic pressure of a loading pulse (10–45 GPa) is measured with a manganin gauge. The temperature of shock-compressed specimens, which is varied by varying the initial temperature and initial porosity, is found to fall into the range 500–2500 K. It is shown that as the temperature and shock compression pressure rise, the nanostructured anatase turns into a nanoanatase-nanocolumbite or columbite-rutile mixture or into almost impurity-free (pure) nanocolumbite or impurity-free microcrystalline rutile.

Phase transformations in nanostructural anatase TiO2 under shock compression conditions studied by Raman spectroscopy

Shock-wave-induced phase transformations in nanostructural titanium dioxide TiO2 (anatase) powders of two types have been studied by Raman spectroscopy. It is established that, at a shock-wave compression to 42 GPa, anatase particles can either transform into a columbite phase or exhibit amorphization.

The composites of polyaniline with multiwall carbon nanotubes: Preparation, electrochemical properties, and conductivity

Composite materials based on the multiwall nanotubes (content in the material from 1 to 65 wt %) and polyaniline are prepared and characterized. The composite materials are prepared by four methods: chemical synthesis, electrochemical synthesis, mixing of dry components, and mixing of solutions with subsequent removal of solvent. The results of calculations of the specific capacity of the composite materials, as well as their conductivity, stability, and behavior under the conditions of charging-discharging point out to their applicability in devices for the energy storage. The range of critical changes in the values of specific capacity and conductivity falls into the interval of the multiwall nanotubes content in the composite from 5 to 25 wt %. The composite materials preparation methods used in this work enable one to choose an appropriate composite preparation method reasoning from the final purpose of its application (obtaining of high capacity or conductivity). The carbon nanotubes, the body of the composite, with their stable electronic conduction, can sustain the composite’s electrical conductivity at reasonable level irrespective of the properties of the second component (polyaniline) in the case in question.