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Mixtures of carbon nanotubes (CNTs) and graphene oxide (GO) in composite materials often exhibit synergistic effects with respect to mechanical and electrophysical properties. In this paper, the mechanisms of interaction between CNTs, GO and epoxydian resin macromolecules were discussed based on the results of molecular dynamics simulations. Calculations were performed in the MM3 force field at exposure times up to 100 ps. The influence of the CNT’s graphene layers shape and the presence of oxygen-containing functional groups on the self-assembly process during the epoxy composite formation has been demonstrated. It is shown that graphene oxide sheets are arranged around cylindrical nanotubes and envelop them, while when using tapered nanotubes, the formation of alternating layers of CNTs and GO should be expected. The presence of oxygen-containing groups on the surface of cylindrical nanotubes promotes the penetration of epoxydian resin macromolecules into the space between CNTs and GO. The simulation results of the "cylindrical CNTs - GO" and the "conical CNTs - GO" hybrid particles were confirmed by scanning electron microscopy data.

Different carbon nanomaterials are considered as promising supports for Fischer-Tropsch synthesis (FTS) catalysts of syngas transformation into hydrocarbons. At the same time, consolidation of carbon nanoparticles into a dense bulk material is one of the most important challenges faced by the catalytic industry. In this work consolidated Co and Fe catalysts supported on graphene nanoflakes (GNFs) were for the first time synthesized by spark plasma sintering (SPS). The synthesized catalysts contained reduced carbon-encapsulated metal nanoparticles embedded into the GNF framework, which ensured their activity in FTS without pre-activation. SPS significantly increased both the activity (from 77 to 91 µmolCO×gCo−1 ×s−1) and TOF (from 0.024 to 0.073 s−1) of the Co/GNF catalyst compared to the unsintered sample. In contrast, the activity of the Fe catalysts decreased after SPS, but their C5+ selectivity and olefins to paraffins ratio increased. These enhancements were attributed to the unique core-shell structure of the nanoparticles, highly active surface cobalt atoms, and close contact between carbon support and iron particles. SPS was proved to be a powerful approach to activate carbon-supported FTS catalysts, increase their density and modify their catalytic performance.

The tribological and rheological characteristics of three industrially produced greases and a model lubricant (medical vaseline) doped with new carbon nanoflakes additives (few layer graphite nanof...

Jellyfish-like graphene nanoflakes (GNF), prepared by hydrocarbon pyrolysis, are studied with electron paramagnetic resonance (EPR) method. The results are supported by X-ray photoelectron spectroscopy (XPS) data. Oxidized (GNFox) and N-doped oxidized (N-GNFox) flakes exhibit an extremely high EPR response associated with a large interlayer interaction which is caused by the structure of nanoflakes and layer edges reached by oxygen. The GNFox and N-GNFox provide the localized and mobile paramagnetic centers which are silent in the pristine (GNF p ) and N-doped (N-GNF) samples. The change in the relative intensity of the line corresponding to delocalized electrons is parallel with the number of radicals in the quaternary N-group. The environment of localized and mobile electrons is different. The results can be important in GNF synthesis and for explanation of their features in applications, especially, in devices with high sensitivity to weak electromagnetic field.

The effect of synthesis conditions and incorporation of heteroatoms on the structure and morphology of few-layer graphene nanoflakes is investigated using Raman spectroscopy, X-ray photoelectron spectroscopy, and electron microscopy. It is found that doping with nitrogen forms defects inside graphene layers, while incorporation of silicon in contrast results in their bending and the formation of interlayer defects. Increasing the synthesis temperature reduces the number of defects in the material via graphitization and increase in the number of layers.

Nitrogen-doped carbon nanomaterials show unique properties in catalysis both as an active component and as a support. The oxidized and N-doped graphene nanoflakes (GNFs) of low domain size (10–30 nm) have been studied in present work as supports for cobalt-based Fischer-Tropsch catalysts. Three supports with different types of dominating nitrogen species were synthesized and the effect of both the nature and localization of nitrogen species in the support on the structure and performance of 10 wt.% Co catalysts was investigated. Varying the synthesis technique and post-synthesis treatment, the cobalt particle size and hence the activity of catalyst can be tuned. The catalysts supported on oxidized pristine and N-doped GNFs were found to be the most active. Transformations of N-groups during catalyst preparation and reduction were observed. In the case of edge localization of N-groups the cross-linking of support particles was detected that led to the diffusion hindering and low CO conversion over corresponding catalyst.

Because of its contribution to greenhouse effect, carbon dioxide conversion to valuable chemicals is one of the most challenging issues facing the modern world. A new type of iron catalysts of CO2 hydrogenation into hydrocarbons was synthesized by spark plasma sintering of carbon nanotubes decorated with iron oxide nanoparticles. This treatment produced carbon-encapsulated iron nanocrystals embedded in a dense framework of CNTs. The sintered catalysts were tested without pre-reduction in CO2 hydrogenation under supercritical conditions (350 °C, 8.5 MPa) and showed high specific activities of 5.4–12.2 molCO2gFe−1s−1 and promising C2+ selectivities of 40–50 mol.% at rather low H2:CO2 ratios of 1 and 2. The high efficiency of the catalysts was attributed to the stabilization of metal nanoparticles by carbon shells and increased density of CNT support, which led to higher degree of metal – support interaction and intensified carbidization and CO activation.

—Viscosity and the viscosity–temperature dependence are the main criteria for selecting plastic lubricant materials (PLM). The viscoelastic flow of three industrially produced PLM doped with four types of carbon nanostructure (CNS) was assessed. The effect of concentration, type of CNS, and frequency shift (shear and oscillation tests) on this indicator was analyzed. It was shown that the general trend for all the studied systems is a decrease in dynamic viscosity and viscoelastic properties upon the addition of CNS into the basic PLM in the range of shear velocities from 0 to 10 rps and the frequency range from 0.1 to 12 Hz. Shungite carbon nanoparticles have the least effect on the elastic properties of the systems. It was found that the magnitude of the decrease in viscosity of the PLM doped with CNS (additive concentration of 0.5 or 1.0 wt %) depends on the spatial structure of CNS and can be represented by the following sequence: 2D (multilayer oxidized graphene) > 1D (single-walled carbon nanotubes) > 1D (multiwalled carbon nanotubes).

Present work demonstrates the differences between the structure and surface transformations of carbon nanotubes (CNTs) and graphene nanoflakes with small particle size (GNFs) under oxidation and N-doping using Raman spectra processing. Jellyfish-like GNFs are rather new material that differs from the commonly known graphene nanoflakes by rounded edges and small size of particles (

Doping of graphene-based nanomaterials is one of the most effective approaches for the modification of their physicochemical properties [...]

The paper presents experimental data on the rheological properties of “Vaseline – Carbon Nanoparticles” systems, which were obtained through oscillation tests. The nanoparticles used are multi-layered oxidized graphene (Gr), single- (SWCNTs) and multi-walled (MWCNTs) carbon nanotubes, as well as shungite nanocarbon (Sh). It was demonstrated that when carbon nanoparticles were added to the Vaseline (VM) at concentrations from 0.5 to 1.5 wt.%, the elasticity of the systems increased as compared with the pure VM, wherein the system containing 1.0 wt. % of MWCNTs was characterized by the greatest elasticity. All the studied carbon nanoparticles proved to be rheomodifiers. However, Gr, SWCNTs and MWCNTs acted essentially depending on their concentration in the vaseline system, resulting in both shortening and lengthening of the relaxation time. The natural shungite nanocarbon always led to the decrease of the relaxation time within the studied concentration range. The obtained results form an experimental basis for the development of scientific approaches to the production of lubricants operating in various friction modes