Sergiy Revo

Structure and Strength of Iron-Copper-Carbon Nanotube Nanocomposites

Nanocomposite materials of the Fe-Cu system with/without small addition of carbon nanotubes have been synthesized by mechanochemical activation of elemental Fe and Cu powders in a high-energy planetary ball mill and have been examined by the X-ray diffraction method, SEM and the thermopower methods; the tensile strength of the materials obtained has been estimated. The metastable (Fe, Cu) supersaturated solid solution is formed in the Fe-Cu nanocomposites during milling process. The coherent scattering block size of the materials obtained is decreased with increase of milling time. The duration of mechanochemical activation affects the physical properties of nanocomposites studied. Addition of a small amount of nanotubes into Fe-Cu charge results in a significant increase of strength of the Fe-Cu (4:1) + CNT nanocomposite materials (NCMs) obtained.

Thermal analysis of polyethylene + X% carbon nanotubes

The aim of this research is to study the influence of the multi-walled carbon nanotubes (MWCNTs) on the thermomechanical and structural properties of high-density polyethylene. Several, complementary experimental techniques were used, namely, dilatometry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Raman spectroscopy, and infrared (IR) spectroscopy. Dilatometry data showed that nanocomposites exhibit anisotropic behavior, and intensity of the anisotropy depends on the MWCNT concentration. The shapes of the dilatometric curves of the nanocomposites under study differ significantly for the radial and longitudinal directions of the samples. DSC results show that MWCNTs weekly influence calorimetry data, while Raman spectra show that the ID/IG ratio decreases when MWCNT concentration increases. The IR spectra demonstrate improvement of the crystallinity of the samples as the content in MWCNTs rises.

Effect of structural and morphological features of a nanocarbon component on electrophysical properties of fluoroplastic composite materials

This work studies placement and contact features of thermally exfoliated graphite (TEG) particles with different dispersion levels under compression and analyzes the effect of the carbon filler’s morphology on the electrophysical properties of nanocomposite materials (NCMs) with fluoroplastic. The electric resistance and dielectric permittivity of NCMs were studied using four-, threeand two-electrode circuits. It has been found experimentally that the percolation threshold calculated by the concentration dependences of the electric resistance values is shifted towards the region of lower filler concentrations from 12.5 to 5.2 vol % with an increase in the mean value of the cross sections of TEG particles from 40 to 500 μm. These data were used to find the critical t indices for nanocomposites and to establish the laws of formation of a current-conducting cluster in a polymer matrix. It has also been shown that a decrease in the dispersion level of the carbon component in NCMs affects the polarization processes of its particles and leads to higher dielectric permittivity.

Luminescence of the Alkali-Metals Nitrites Incorporated into Cellulose Matrix

Surface morphology and photoluminescence (PL) properties of both microcrystalline cellulose (MCC), microcrystalline powders of the alkali metals nitrites MNO2 (M = Na. K, Cs) (MCN) and two-component composite materials based on the MCC and MCN have been studied and characterized by means of optical microscopy and luminescence spectroscopy.

Structure and sorption characteristics of nanoporous carbon materials

Results of a study of the structure of porous carbon materials (PCMs) prepared by the carbonization of plant raw materials and the modification of oxidized or thermally expanded graphite have been described. It has been experimentally found that the studied materials have a porous fractal structure with an average micropore radius of 17–37 Ǻ. Based on this finding and results of previous studies, it is reasonable to state that the studied materials can be effectively used as supercapacitor electrodes. Adsorption/desorption of vapors and an aqueous solution of ethyl alcohol has revealed that the resulting materials are not inferior to pharmaceutical activated carbon with respect to the studied parameter. At a temperature of 37°C, carbonized sunflower seed shells retain the adsorbate three times longer than activated carbon does; this feature makes it suitable for use in medical applications.

Surface modification and creation of nano-objects for nanoelectronics

The practical use of a scanning tunneling microscope for modifying the sample surface and for creation of nano-objects on the sample surface is shown. The possibility of modification of the sample surface by tunneling current was shown. Nano-objects on the surface of the experimental samples were created using contact and non-contact modification of surface. This may also enable preparation of the surface for subsequent applications in which it is necessary to reduce the average irregularities of the surface.

Structure Features, Strength, and Microhardness of Nanocomposites Obtained from Fe, Cu, and Carbon Nanotubes

The effect of the treatment mode on the structure and mechanical properties such as strength and hardness of the nanocomposite materials (NCMs) synthesized from Fe, Cu, and carbon nanotubes (CNTs) has been studied. A comparison of the characteristics of nanocomposites obtained by two different methods, namely, by mechanochemical activation in a planetary ball mill and without milling, has been provided. It has been shown that materials obtained without pretreatment of their components in a ball mill do not demonstrate any advanced mechanical properties and their components are not dissolved. But a number of metastable solid solutions are formed in NCMs after mechanochemical treatment of Fe, Cu, and CNT powder mixture in a ball mill. Moreover, it is shown that several phases were forming at the different stages of the milling process of Fe and CNT powders, namely, α-(Fe,C) and γ-(Fe,C) supersaturated solid solutions along with the Fe3-x C and the Fe7C3 carbide phases. These phases mainly determine the properties of material. Thus, it was found that mechanical milling allows to obtain NCMs with higher characteristics than without such processing. So, the tensile strength σB of NCMs obtained from Fe and Cu powders reaches 1800 MPa, whereas this value in a case of NCMs obtained without milling of components is 1200 MPa. The microhardness of Fe-CNT nanocomposites reaches 10 GPa compared to 5 GPa for Fe-C NCMs. The criteria of the powder mixture treatment for nanocomposites synthesized to ensure uniform distribution of the components, CNT agglomerate dispersing, predicted changes in morphology, phase composition of the powders, and characteristics of the NCMs obtained have been optimized.

A composite of nanoporous carbon and thermally exfoliated graphite as an effective electrode material for supercapacitors

Results are presented of studies on the structure and properties of nanocomposite materials (NCM) based on nanoporous carbon (NPC) and thermally exfoliated graphite (TEG). NCM is promising as electrode material for supercapacitors (SC) with a double electric layer. NPC was obtained from a phytogenic raw material using hydrothermal carbonization. TEG was produced from oxidized natural graphite by thermal exfoliation. A JSM-6490LV (JEOL Ltd., Japan) electron microscope was used to study the samples’ microstructure. A Quantachrome Autosorb instrument was used to study nitrogen adsorption/desorption isotherms and analyse porous structure. The multipoint Brunauer–Emmett–Teller (BET) method was used to determine the specific surface area of electrodes. The electrochemical properties of the samples were analyzed using the methods of galvanostatic cycling and electrochemical impedance spectroscopy employing an AUTOLAB PGSTAT12 (ECO CHEMIE, the Netherlands) measuring instrument. Our study shows that the employment of TEG in this NCM reduces the internal resistance of supercapacitors (SC), and this increases their specific capacitance. The results of electrochemical studies show that the capacitance of SCs based on the noted NCMs amounts to 155–160 F/g. An equivalent circuit is proposed, allowing the simulation of impedance spectra in the frequency range of 10−3–105 Hz. A physical interpretation of each element of the electric circuit is presented.

Spectroscopy of the alkali-metal nitrite and nitrate incorporated into cellulose host matrix

Morphology and photoluminescence (PL) properties for microcrystalline cellulose (MCC), microcrystalline nitrite, MNO₂, or nitrate, MNO₃, (MCN) powders of common formulae MNO_n (n = 2, 3) (M = Na. K, Cs) and two-component materials composed of MCC and MCN have been studied and characterized.