Архив

The compression isotherm and potential jump methods were used to study Langmuir monolayers formed from individual solutions of carbon nanotubes (CNTs) and their mixtures with arachidic acid (AA) in various ratios. The optimal amount of CNT solution (200 μL) for forming a Langmuir layer was empirically found. When transferred to a solid substrate, the layer has an average conductivity of about 4.3⋅10–12 S⋅sq–1. It was also found that when applying the second and subsequent layers, the film conductivity increases by more than 6 orders of magnitude (up to 5.08⋅10–6 S⋅sq–1). In the study of mixtures of carbon nanotube solutions (without amphiphilic properties) and arachidic acid (a typical representative of a surfactant), an optimal ratio of the volumes of the prepared solutions was found (CNT : AA – 80 : 20), at which it is possible to control the degree of compression of the carbon nanotube layer on the surface of the aqueous subphase. It was shown that the introduction of AA molecules into the composition of CNTs allows an additional increase in the films conductivity by more than two orders of magnitude (up to 1.18⋅10–3 S⋅sq–1), compared to films of individual CNTs. The studied films can be used as a platform for the creation of various devices for micro- and nanoelectronics, optoelectronics, photovoltaics and flexible electronics.

In this work, the influence of graphene oxide (GO) additives on the structure and morphology of graphite filler, as well as the strength characteristics of final carbon-graphite composites, is investigated. The formulation of prototype charge samples was selected using the mathematical method of experiment planning and the Hartley plan. The granulometric composition of the initial and modified charge samples, along with their adsorption capacity with respect to pitch, was determined. Scanning electron microscopy, Raman spectroscopy, XRD analysis, vibration density measurements, and specific surface area analysis (via BET) were used to evaluate the structure and morphology of the filler particles. It was found that when 0.9 wt. % GO is added to the filler composition, a denser grain structure with fewer voids is formed. At the same time, the specific surface area decreases by a factor of 3.6, while the sorption capacity for pitch, on the contrary, increases by a factor of 2.7, indicating a change in the chemical composition of the filler particle surfaces. According to Raman spectroscopy data, the modified charge samples exhibit a higher D/G ratio, the presence of functional groups on the particle surface, and a predominance of edge defects. Physical and mechanical testing of the samples after firing revealed that the introduction of 0.9 wt. % graphene oxide increases the compressive strength from 35.5 to 97.5 MPa. These results are significant for the development of new composite materials for tribotechnical applications.

In this paper, the effect of carbon nanotubes coated with silicon dioxide, used as a filler in alkyd enamel PF-115, on the adhesion strength of the modified alkyd enamel paint to steel reinforcement and on the adhesion of reinforcement coated with modified alkyd paint to concrete was investigated. The adhesive tape method (ASTM D3359 Standard) was used to study the adhesion strength. To test the effect of the corrosion resistance of the coating on the adhesion strength between the coated reinforcement and concrete, the samples were subjected to a preliminary accelerated corrosion process in a sodium chloride solution under the influence of a direct electric current of 0.5 A, after which pullout tests were carried out. The results showed that with an increase in the nanofiller content, the adhesion strength decreases insignificantly, and the force for pulling out reinforcement from concrete increases for the coated samples with an increase in the nanofiller concentration to 0.349 wt. %, after which it begins to decrease. The improvement in the overall corrosion resistance characteristics of the coating after the application of a modified alkyd enamel used as a protective coating for steel reinforcement containing carbon nanotubes with silica with a concentration of 0.349 wt. % was established.

This study experimentally investigates the formation dynamics of a Ni–Cu solid solution during high-energy ball milling (HEBM) of a Ni and Cu powder mixture in planetary mills. The influence of processing conditions and gas atmosphere composition is examined. It is shown that the formation of a solid solution critically depends on the milling speed: at 300 rpm, no mutual dissolution of metals was observed, whereas at 694 rpm, a solid solution was formed within a relatively short time – no more than 30 minutes. In an oxygen-free atmosphere, intense cold welding of particles occurred, forming large (up to 2–3 mm) disk-shaped and oval flakes, which later became rounded and acquired a spherical shape. In an air atmosphere, cold welding was slowed down, and the metals became less ductile due to oxygen absorption. HEBM in airresulted in the powder consisting of smaller particles with rounded and flake-like shapes (300–400 μm along the surface of flakes, less than 100 μm across). The most homogeneous solid solution structure was formed in an air atmosphere. Thus, the optimal conditions for the mechanosynthesis of metallic solid solutions are processing in a planetary mill at 500–700 rpm in an air atmosphere. The findings of this study can be used to optimize the mechanical synthesis of metallic solid solutions, including Cantor high-entropy alloys with a face-centered cubic structure.

The problem of reinforcing wood-polymer composites (WPC) is currently being solved by the introduction of bonding agents that improve adhesion between wood filler and polymer. However, the introduction of such additives does not strengthen these composites to the extent that they can be used in new areas of construction. Filling of composites with fiber modifiers shows its high efficiency. In this paper, the effect of chrysotile-asbestos fibers of different lengths on physical and mechanical characteristics of polyvinyl chloride (PVC)-based wood-polymer composites was studied. The study showed that the most effective fibers for reinforcing WPC were 2 mm long, with a 25 % increase in tensile strength and a 38 % increase in flexural strength. The optimum asbestos content was 7.5 pbw for all fiber lengths. The proposed compositions of PVC-based WPCs will make it possible to expand the range of products based on them, including in the field of structural plastics.

This article deals with a problem relevant for modern industry – the development of new composite materials based on oxide ceramics used in application of protective coatings to parts and cutting tools. The authors proposed the free SHS compression method as a technology for producing such materials; it combines the process of self-propagating hightemperature synthesis of materials and their subsequent high-temperature shear deformation of the resulting products. The influence of free SHS compression process parameters on the process of manufacturing products from the selected research objects has been studied. It has been found that for the tested materials there is an optimal temperature-time treatment interval that allows manufacturing high-quality products. A study of the phase composition and microstructure of the obtained products has been conducted. The paper also studies the physical and mechanical properties of the obtained products, and conducts heat resistance tests in the temperature range of 1000–1300 °С for 10 hours.

The paper presents mainly new or previously unanalysed data from the most important published papers of the last five years. Several possible mechanisms for the synthesis of detonation nanodiamonds (DND) are considered. A simple predictive estimate of the DND yield based on the content of elements in the explosive molecule is proposed. It is shown that nitrogen is not an inert element in the nanodiamond synthesis process. It is possible to form a fractal carbon lattice with simultaneous fluctuations of carbon density in the chemical reaction zone (CRZ) with the formation of a three-dimensional ordered core in the nodes of the lattice. The time of formation of such a carbon structure is close to 50 ns. For DND formation, the time of chemical reactions is 0.1–0.3 μs, and the width of the CRZ is 0.4 to 1.4 mm. The electrical conductivity of the 'plasma' in the CRZ is determined by the carbon content of the explosives, which forms extended conducting structures. It is shown that the region with the highest DND yield (up to 8.5 wt. %) is limited by the pressure in the Chapman-Jouguet plane of 23–29 GPa and the temperature of 3850–4350 K, the optimum oxygen balance of the explosive is in the range of –42÷–53 %, and the detonation velocity is in the range of 7250–8000 m⋅s–1. In general, DNDs from different explosives have close crystallographic parameters (except for nanodiamonds from benzotrifuroxane). To increase the yield of DNDs, it is necessary to use an aqueous charge shell, which is a solution of urotropine, urea or hydrazine. For the first time, the process of DND production from Tetryl and its binary and ternary charges was developed and recommended for industry, with a DND yield of ~7 wt. %. Experience with the industrial production of DND has shown that it is realistic to obtain nanodiamonds with a yield of 8.5 wt. % at their content in the diamond containing blend of 72 % and non-combustible impurities of 1.6 wt. %.