The aim of this work was to determine the anisotropy of the electrophysical and mechanical properties of rubber reinforced with a hybrid filler CNTs&CB (carbon nanotubes and carbon black) as a function of CNT content and the technological parameters of the production process. A significant difference in electrical conductivity (σ) and dielectric permittivity (ε) in three perpendicular directions was found for CNT concentrations ranging from 0 to 0.007 in volume fraction. The highest values of σ and ε were observed in the calendering direction, with slightly lower values in the perpendicular direction. This effect was attributed to the orientation of polymer molecules and CNTs along the direction of movement during calendering, as well as the disruption of the cluster structure in the transverse direction. Although the calculated percolation threshold values of the investigated system differed slightly, a correlation was observed between the mechanical and electrophysical properties of CNTs&CB rubber. This correlation enables rubber products to be designed with optimal properties tailored to the desired direction.

This study demonstrates two novel surfactant-free methods for preparing stable hybrid dispersions: (i) oxidized graphene nanoparticles (GNPs) combined with carbon nanotubes (CNTs), and (ii) oxidized CNTs combined with GNPs. The GNP exfoliation process achieves a primary fraction (99.9% by count, ≥26% by mass) with tunable sizes (10–150 nm to 30–800 nm), controlled by exfoliation process (current density, electrolyte concentration, and suspension optical density). In Method 1, GNPs (70–150 nm) were oxidized in H2SO4 (96–98 wt%)/K2Cr2O7 (0.7 g per 2 g acid), diluted to 15% H2SO4, washed to pH 5.5, ultrasonicated (1 min), then combined with CNTs pre-dispersed in ethanol (0.5 mL). In Method 2, CNTs were anodically oxidized in 55% H2SO4 (5–30 mA/cm2, 200 A•h/kg), washed to pH 6.5–7, and dried (800°C, 20 s) before GNP incorporation. Both methods produced dispersions stable ≥3 days. The hybrid CNT@GNP dispersions were deposited onto AlSi10Mg alloy powders and polychlorotrifluoroethylene (PCTFE) via rotary evaporation. This approach facilitated uniform nanocarbon distribution, resulting in: (a) reduced electrical percolation thresholds, (b) enhanced mechanical strength at lower CNT@GNP loadings in PCTFE composites, and (c) improved processability of modified AlSi10Mg powders for 3D printing applications.

It has been experimentally shown that thermomechanical processing of polyamides in an oxidizing environment (in air) leads to structural degradation and loss of mechanical characteristics of the polymer. Reinforcement of polyamides PA6, PA6.6, PA12 with a nanosized carbon filler (carbon nanotubes (CNTs) and graphene nanoparticles) in small quantities (up to 0.5

Here we disclose a method for obtaining highpurity expanded graphite (EG) with a carbon content of > 99.5% wt. from flotation-enriched graphite with a carbon content of 94-97% wt. It has been experimentally shown that this effect is produced by a combination of the synthesis process of oxidized graphite (intercalation of graphite by anodic treatment in concentrated sulfuric acid followed by hydrolysis) and chemical cleaning using solutions of ammonium bifluoride in sulfuric acid and Trilon B in an alkaline buffer as cleaning reagents. The methods of X-ray phase analysis and thermogravimetry show that the interaction of oxidized graphite with cleaning reagents does not reduce the ability to expand. The magnitude of the mass loss of oxidized graphite and the temperature range of such losses practically do not change. The main mineral impurities of graphite ore are aluminosilicates up to 60-80% wt., effectively interact with hydrofluoric acid. Iron, calcium and magnesium oxides are converted into a soluble state when interacting with Trilon B. Quantum-chemical calculations show that the Trilon B molecule is better physically sorbed on an oxidized graphenelike plane than on its native form, interaction energy (- 412 kJ/mol), (-188 kJ/mol), respectively. The interaction of Trilon B with Ca2+ and Mg2+ cations, regardless of the nature of the cation, is thermodynamically more likely in an aqueous solution than in the adsorbed state on the surface of the oxidized graphene plane. The proposed method ensures high purity of.G, which significantly reduces the cost of the technology and reduces environmental pollution.

Polymers reinforced with carbon fillers are used in load-bearing structures, racing cars, sports equipment, aircraft and drones due to their special stiffness and strength, as well as their electromagnetic shielding or absorption properties. The search for new materials, composites and quick prediction of their properties is an urgent task of polymer materials science. The paper shows that predicting the mechanical strength of the composites is possible by measuring electrical conductivity at low frequencies and extrapolating these values using the obtained expressions. The relative mechanical bending strength has a quadratic dependence on the filler content and can be represented with satisfactory accuracy by the low-frequency electrical conductivity for the composite system.

Carbon fillers are widely used in the polymer composite materials to control electrophysical properties, which makes them promising for shielding/absorbing electromagnetic radiation in various bands, protection against radio interference and antistatic coatings, etc. The study of percolation transitions in such materials is a priority for such tasks. Epoxy resin-carbon fiber (ER-CF) and epoxy resin-carbon fiber-carbon nanotubes (ER-CF-CNT) systems with different filler contents were investigated. Electrophysical studies were carried out in the frequency range of 8–12 GHz by the non-contact method, and electrical conductivity at low frequencies of 0.1, 1 and 10 kHz was measured by the two-contact method. The bending strength was tested on a 2167 P-50 tensile tester. It was found that: the electrical conductivity at low frequencies and the complex permittivity at 9 GHz of the composites change significantly (percolation transition) in the range of 0.001–0.005 volume fraction of the combined filler; the values of the real and imaginary components of the complex dielectric constant of the composites are 50, which indicates a significant level of interaction between the components of the system and a uniform distribution of the conductive component in the composite; the maximum values of the relative flexural strength are observed at the content of CF-CNT proportional to the percolation threshold in the systems. The composites have a high level of strength at a low content of fillers, which, makes them attractive for use as protective coatings for absorbing or shielding from microwave EMFs.

The purpose of the work is to establish the possibility of obtaining expanded graphite of high purity (carbon content more than 99.5 % wt.) from flotation-enriched graphite (carbon content 94–97 % wt.) by combining into one process intercalation of graphite with a solution of potassium dichromate in concentrated sulfuric acid with subsequent hydrolysis, and chemical purification using solutions of ammonium bifluoride in sulfuric or hydrochloric acid and Trilon B in an alkaline buffer as purification reagents, and to confirm this possibility by quantum chemical calculations. It has been experimentally shown that combining oxidized graphite synthesis and its chemical purification into one process allows obtaining expanded graphite of high purity, with a carbon content of 99.75–99.85 % wt. The methods of X-ray diffraction and thermogravimetry show that the interaction of oxidized graphite (the residual compound of intercalation of graphite with sulfuric acid) with cleaning reagents does not reduce the ability to expand. The magnitude of the mass loss of oxidized graphite according to various variants of chemical post-cleaning and the temperature range of such loss remain practically unchanged. Quantum chemical calculations of the adsorption energy (∆Eads) of one molecule of Trilon B on the surface of a graphene-like plane (GLP), the complexation reaction of metal sulfates, the energy effect of the interaction of Trilon B with sulfates of alkaline earth metals in an aqueous solution, and with the participation of the surface of the graphene plane were carried out using the GAMESS (US) program by the density functional theory (DFT) method with the B3LYP functional and the 6-31G(d,p) basis set, taking into account the Grimme D3 dispersion correction within the PCM polarizable continuum. The results of the analysis of quantum chemical calculations indicate that the Trilon B molecule is better physically sorbed on the oxidized GLP (–412 kJ/mol) than on its native form (–188 kJ/mol). The values of the energy effect of the complexation of magnesium and calcium cations with Trilon B have a negative value both in an aqueous solution and in the presence of the oxidized form of GLP. This indicates the thermodynamic probability of this process, which is consistent with the experimental results. Regardless of the nature of the cation, its interaction with Trilon B is thermodynamically more likely in an aqueous solution than in the adsorbed state on the surface of oxidized GLP.

Multilayer graphene nanoparticles (GNPs) have unique properties and potential for application. They are more stable compared to single-layer graphene and are suitable for mass production by splitting precursors with a graphite-like structure. The problem is not in the production of GNPs, but in the regulation of its characteristics. The application of GNPs is hindered by their agglomeration due to van der Waals interactions. To avoid this, it is necessary to create a gap between GNPs. Carbon nanotubes (CNTs) are an ideal candidate for this. CNTs can reduce internal electrical resistance and improve overall electrical conductivity. Therefore, the production of GNPs@CNTs hybrids is of interest. In work, a simple and cheap method of GNP synthesis by anodic exfoliation of expanded graphite (EG) foil in a weak alkaline electrolyte is shown. A two-level method of regulating the structure of GNPs by adjusting the nanoscale cluster structure of EG by changing the parameters of its production process and modes of “secondary intercalation”, i.e., anodic oxidation of the EG foil, is revealed. The method of synthesis of dispersions of GNPs@CNTs and film materials from them is described. The structural characteristics of GNPs, CNTs and their composites, determined by the methods of X-ray diffraction, LCS, Raman spectroscopy, XPS, DTA, TG are presented. The energetic effects of the interaction of partially oxidized graphene-like planes with each other were elucidated by the methods of quantum chemistry. It was found that the reaction between hydroxyl and aldehyde groups of two interacting graphene-like planes is thermodynamically most probable.

The purpose of this work was to investigate the interaction of graphene-like nanoclusters with fragments of polymers of the same nature, but of a slightly different structure, for example, polyethylene (PE) and polypropylene (PP), experimentally and using quantum chemistry methods. It is experimentally shown that the reinforcement of PE and PP with carbon nanotubes (CNTs) by mixing in the melt, previously distributed from a stable aqueous dispersion on the surface of the polymer powder, leads to a change in structural, mechanical and thermodynamic characteristics.The degree of crystallinity changes, and the coherent scattering domain (CSD) size, the fracture stress increases, the fracture deformation, thermodynamic characteristics change, and such changes in characteristics for the PP-СNTs system prevail in comparison with the PE-CNTs system. The interaction energy of graphene-like fragments with PE and PP oligomers was calculated. It was established that the energy of interaction of a graphene-like nanocluster with a PP oligomer is greater, compared to PE, which is consistent with experimental data on the melting temperatures of pure polymers and polymer composites with nanotubes. The polymer with the surface of the nanocarbon fragment forms an intermolecular complex that is not covalently bound but is held by intermolecular dispersion forces.

The strength characteristics of model samples of fiberglass with epoxy binder RH 285 and hardener LH 286 reinforced carbon nanotubes (CNTs) anodically oxidized and the initial, respectively, were studied. CNTs are characterized by Raman and X-ray photoelectron spectroscopy. It is shown that the oxygen content and the specific surface area of CNTs change in the opposite to the amount of transmitted electricity in the range of 30–20 A h/kg. It was found that the synergistic effect of increasing the strength occurs when the initial CNTs are added into the amine hardener by ultrasonic treatment and anodically oxidized CNTs into epoxy resin (mixing on a three-roll mixer). This effect is because the amine hardener plays the role of surfactant in relation to CNTs, orienting the carbon part to CNTs, amine outward, i.e., preventing agglomeration of CNTs. The same effect is observed for oxidized CNTs in epoxy resin (charged CNTs are repelled), and oxygen-containing groups catalyze the polymerization of epoxy resin.

Here, we explain the method of obtaining the expanded graphite-multiwall carbon nanotubes nanocomposite, give its structural and mechanical characteristics important for application, and, based on quantum chemical calculations, propose a mechanism for the formation of a chemical bond between oxidized graphene-like planes. Synthesis of expanded graphite-carbon nanotubes without binders consists in simultaneous deagglomeration of carbon nanotubes and intercalation of natural graphite. This procedure was carried out in two variants: electrochemical (anodic) oxidation and chemical oxidation. Graphite oxidized to the first stage (blue) was hydrolyzed, washed to neutral pH, dried, and heat-treated at a temperature of ~1000°C in a gas horizontal industrial furnace. The resulting expanded graphite powder was rolled on horizontal rolls. X-ray photoelectron spectroscopy was used to determine the amount of oxygen and the type of oxygen-containing groups on the surface of expanded graphite and carbon nanotubes and the dependence on the amount of electricity passed during anodic oxidation. Features of the structure of expanded graphite obtained by various methods and composite expanded graphite-multi-walled carbon nanotubes were investigated by Raman spectroscopy. The energy effects of the interaction of partially oxidized graphene-like planes with each other and their dependence on the nature of the oxygen-containing functional groups present in them and on the dimensions of the graphene-like planes themselves were clarified by quantum chemistry methods. It was established that the most thermodynamically probable is the reaction between the hydroxyl and aldehyde groups of two interacting graphene-like planes, regardless of their sizes.

One of the decisive factors that determines the effectiveness of using carbon nanotubes (CNTs) for reinforcing polymer matrices is their uniform distribution in the matrix. It is shown that the percolation threshold in the polychlorotrifluoroethylene (PCTFE)–CNTs system, determined by electrical conductivity data, shifts to lower values with a more uniform distribution of CNTs, while the electrical conductivity increases and correlates with the structure and strength characteristics. Preliminary deagglomeration of CNTs was carried out using ultrasonic treatment in a dispersion of graphene nanoplatelets (GNPs). Three water systems with a CNTs content of 0.5, 0.25, and 0.125 wt.

The book considers the patterns of formation of the structure and properties of sp2-hybridized carbon nanoformations: nanotubes (CNTs), expanded graphite (EG), graphene nanoparticles and composite materials (CM) with their participation with carbon, polymer and ceramic matrices, including EG-CNTs composite, as well as the mechanism of influence of low content of nanosized fillers on the functional and operational characteristics of the created nano-CM. It is experimentally confirmed that the mechanism of strengthening of low-filled matrices consists in creation by a grid of CNTs of layers of the matrix in a nanosized state with improved characteristics. The monograph is intended for specialists in the field of physical and chemical material science.

The aim of the current study was to find changes in the structure and state of the surface of graphene oxide (GO) under the conditions of its reduction and modification by hetero atoms of nitrogen and amino acids. Reduction of GO was performed with hydrazine hydrate (R-GO), doping with nitrogen atoms - urea impregnation and subsequent heat treatment (N-GO), and the surface of GO was modified with sulfur-containing amino acid – L-cysteine by nucleophilic addition (L-GO). The samples obtained were characterized by analytical methods, such as Raman scattering, IR spectroscopy, TPD-mass-spectrometry, dynamic light scattering spectroscopy. The available Raman spectra indicate a defective structure of GO, reduction of GO leads to greater ordering of the structure in relation to GO, nitrating and modification by amino acid - to the opposite effect, a slight deterioration of the structural state. According to the results of IR spectroscopy, also confirmed by TPD-MS, GO has a large number of functional surface groups: (OH), (C=O), (C=C), (C-O-C), (CO-O-CO), (CH). Hydrazine reduction completely hydrophobizes the surface, in the IR spectra there is only a peak at ~ 1040 cm–1, which corresponds to CO-O-CO vibrations, with significantly reduced intensity, as well as bands at 2120 and 2300 cm–1, which indicate the aromatic nature of the samples and exist in all GO derivatives. In nitrogen and sulfur-containing samples (L-GO) a new peak of ~ 1520 cm–1appears, which corresponds to N-H vibrations in amines. Sulfur-containing derivatives have valence vibrations at 600 cm–1, which most likely corresponds to S-H bonds. Thus, modification of GO leads to a significant change in its structure and surface chemistry, which in turn affects the capability of the obtained samples to capture free radicals. Previous empirical studies have shown that this property increases in the series L-GO > GO > N-GO > R-GO.

In the present work, a comprehensive study of mechanical alloying of Ni-carbon nanotubes (CNT) and Ni-Graphite equiatomic powder mixtures under the same technological modes has provided to reveal the features of using different types of carbon (CNT or graphite) as a charge component. The as-milled powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and magnetometric study. A novel nanoscale fcc NiC monocarbide was synthesized regardless the type of the charge used. According to the XRD study the formation of this phase takes place in two stages. A two-step carbide formation mechanism has been proposed. The associated changes in the nickel lattice, such as changes in the lattice parameter, lattice strain and residual stresses, which led to the formation of NiC monocarbide were also evaluated and discussed. Parameters of the electronic structure of NiC were calculated using the MStudio MindLab 7.0 software package with the experimental data on the crystal structure of the NiC phase obtained as input. Temperature dependencies of magnetic susceptibility of NiC synthesized have been studied up to 950 K. Carbides synthesized were found to be weak ferromagnets at the room temperature and their Curie temperature T-C ranges within 670 - 725 K. The calculated value of the magnetic moment per nickel atom (2.83 mu(B)) is higher than that of a bulk Ni (1.3 mu(B)). Likely, the observed increase of mu is caused by the presence of a certain amount of residual single-domain ferromagnetic Ni nanoparticles in the samples synthesized. (C) 2021 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights reserved.

Mechanical alloying of the elemental powder mixture of nickel-multiwalled carbon nanotubes (Ni-CNT) and nickel-spectroscopic grade graphite (Ni-SGG) is performed in a high energy planetary ball mill under the same technological modes.Nanocrystalline NiC x carbide (x = 0.3-0.4)synthesized is examined by X-ray diffraction methods (phase and structural analysis, determination of the real structure parameters, etc.).The carbides synthesized are ferromagnets, the coercive force of which (H c = 6-12 kA/m) depends on the amount of interstitial carbon atoms in octahedral voids of Ni crystal lattice.It is shown that an allotropic form of carbon (SGG or CNT) used at mechanical alloying effects the charge components interaction as well as the crystal structure and properties of final synthesis products.

In this work, the elastic and strength properties of polymer composites with a polytrifluorochlorethylene matrix and a thermally expanded graphite filler were evaluated by the nanoindentation method, and the effect of the dispersion and concentration of the filler on the mechanical characteristics of nanocomposite materials was considered. It is shown that the microhardness of nanocomposite materials decreases with increasing filler concentration. An increase in the microhardness and Young's modulus with the growth of filler particles was observed for nanocomposite materials with a filler concentration of 3 vol.%. As for nanocomposite materials with a filler volume fraction of 10 vol.%, similar behavior of the mechanical characteristics was observed with an increase in the dispersion of thermally expanded graphite particles to 180 μm. A subsequent increase in the average particle size of thermally expanded graphite leads to a decrease in Young's modulus and microhardness of composites, which may be associated with different degrees of polymer structuring and the formation of different orientational orders from the filler. The observed changes in Young's modulus and H/E ratio indicate a change in the amorphous crystalline behavior of the composite to that characteristic of fine-crystalline materials and depends on the dispersion of thermally expanded graphite.

Experimentally, by methods of X-ray phase analysis, temperature-programmable desorption mass spectrometry, electrical resistance, tension and compression, it was found that nanoscale fillers (carbon nanotubes, pyrogenic oxides of silicon, titanium and titanium-silicon, and polymers with structure, mechanical (stress and strain deformation) and thermodynamic (melting and thermodestruction temperatures) properties. According to the results of quantum chemical calculations, such effects can be explained by the interaction of the polymer with the nanofiller and the formation of intermolecular complexes due to intermolecular dispersion forces. Експериментально, методами рентгенофазового аналізу, температурно-програмованої десорбційної мас-спектрометрії, електроопору, розтягу та стискання, встановлено, що нанорозмірні наповнювачі (вуглецеві нанотрубки, пірогенні оксиди кремнію, титану та титанокремнезему) при взаємодії з деякими біо-, сітчастими та лінійними полімерами змінюють їхню структуру, механічні (напругу та деформацію руйнування) і термодинамічні (температури плавлення та термодеструкції) властивості. За результатами квантово-хімічних розрахунків такі ефекти можуть бути пояснені взаємодією полімеру з нанонаповнювачем і утворенням міжмолекулярних комплексів за рахунок міжмолекулярних дисперсійних сил.

This article is a review of the Mn+1AXn phases (“MAX phases”, where n = 1, 2 or 3), their MXene derivatives and the reinforcement of polymers with these materials. The MAX phases are a class of hexagonal-structure ternary carbides and nitrides ("X") of the transition metal ("M") and the A-group element. The unique combination of chemical, physical, electrical and mechanical properties that combine the characteristics of metals and ceramics is of interest to researchers in the MAX phases. For example, MAX phases are typically resistant to oxidation and corrosion, elastic, but at the same time, they have high thermal and electrical conductivity and are machinable. These properties stem from an inherently nanolaminated crystal structure, with Mn+1Xn slabs intercalated with pure A-element layers. To date, more than 150 MAX phases have been synthesized. In 2011, a new family of 2D materials, called MXene, was synthesized, emphasizing the connection with the MAX phases and their dimension. Several approaches to the synthesis of MXene have been developed, including selective etching in a mixture of fluoride salts and various acids, non-aqueous etching solutions, halogens and molten salts, which allows the synthesis of new materials with better control over the chemical composition of their surface. The use of MAX phases and MXene for polymer reinforcement increases their thermal, electrical and mechanical properties. Thus, the addition of fillers increases the glass transition temperature by an average of 10%, bending strength by 30%, compressive strength by 70%, tensile strength up to 200%, microhardness by 40%, reduces friction coefficient and makes the composite material self-lubricating, and 1 % wt. MAX phases increases thermal conductivity by 23%, Young’s modulus increases. The use of composites as components of sensors, electromagnetic protection, wearable technologies, in current sources, in aerospace and military applications, etc. are proposed.

The cubic Ni3.3C carbide has been fabricated by mechanical alloying of elemental Ni powder and the multiwalled carbon nanotubes in a high energy planetary ball mill. Crystal structure of carbide obtained belongs to the defective structure of ZnS sphalerite type according to x-ray diffraction data. Parameters of the electronic structure of Ni3.3C were calculated by linearized muffin-tin orbitals method within the plane-wave approximation using as an input the defined parameters of crystal structure. Magnetic properties, such as temperature and field dependences of the magnetic susceptibility of Ni3.3C have been studied. Based on experimental data obtained by studying the crystal structure and magnetic properties of Ni3.3C, as well as on the basis of calculations of electronic structure parameters, a preferred displacement of the carbon atoms in tetrahedral voids of Ni crystal lattice has revealed.