Issue

In this work, a series of samples of composite materials based on ultra-high molecular weight polyethylene and a hybrid filler containing graphene nanoplates and iodized multi-walled carbon nanotubes (MWCNTs) were obtained by pressing followed by sintering. The resulting nanocomposites were studied by X-ray phase analysis and Raman spectroscopy. The iodine concentration in the modified MWCNTs was determined by energy dispersive X-ray fluorescence analysis. Assessment of the structural features of nanomaterials using X-ray phase analysis indicates the absence of iodine in the interlayer space of graphene sheets, while a change in the surface is observed. Raman spectroscopy data indicate an insignificant destructive effect of iodine on the surface of the nanomaterial. The study of electrical conductivity showed that when using iodine-modified MWCNTs as a filler, the percolation threshold shifts to lower filler concentrations, in comparison with nanocomposite samples containing unmodified nanotubes. An increase in the concentration of graphene nanoplates contributes to a twofold decrease in the percolation threshold. The maximum electrical conductivity of 5.4×10–4 S⋅cm–1 was achieved in ultra-high molecular weight polyethylene nanocomposites containing 3 wt. % iodinated multi-walled carbon nanotubes and 1 wt. % graphene nanoplates.

During sintering of a nanodiamond powder with a coating based on non-diamond forms of carbon with a thickness of about 10 Å at relatively low pressures and temperatures, a nanostructured diamond material is formed by the transition of graphite-like carbon to diamond. It has been shown that nanodiamond powder modified with non-diamond forms of carbon is an “active” base on which a nanometer layer of graphite-like carbon transforms into diamond during thermobaric sintering. The influence of preliminary annealing of nanodiamonds in a disammonia atmosphere and in oxidizing and hydrocarbon-containing atmospheres on the structure and microhardness of nanodiamond polycrystals has been shown. It has been established that the atmosphere in which modifying annealing is carried out affects the content of the diamond phase and the size of nanodiamond crystallites in a polycrystalline material. The preliminary modification (functionalization) of the nanodiamond surface with carbon-containing compounds stimulates the process of diamond formation. In this case, the most significant increase in the microhardness of diamond polycrystals is observed after the modification of nanodiamonds in oxidizing and hydrocarbon atmospheres. It has also been established that the modifying treatment of nanodiamonds with hydrocarbons stimulates the processes of diamond synthesis, and an increase in pressure suppresses the graphitization of diamond and activates the transformation of graphite-like carbon into diamond, which contributes to sintering of diamond grains.

The object of this study is composite multicomponent nanostructured coatings, which are used to increase the durability of the working surfaces of valves operated at critical facilities in the petrochemical and nuclear industries. The aim of thestudy is to experimentally determine the main characteristics of coatings Ti–TiN–(Ti, Mo, Al)N, Ti–CrN–(Cr, Mo, Al)N, Ti–Zr–ZrN–(Zr, Mo, Al)N obtained by the method of substance condensation by cathodevacuum- arc deposition with filtration of the microdroplet phase, and to select the most preferable characteristics for shutoff valves. To determine the coefficient of dry friction, tribological tests were carried out, instrumental indentation was used to establish the hardness of the samples, and the roughness was determined by the profile method. It was found that the best values of the studied characteristics, namely, indentation hardness (38.9 GPa) and roughness (average profile deviation is 0.242 μm), according to the test results, are samples coated with Cr–CrN–(Cr, Mo, Al)N ; according to the results of tribological tests, the Cr–CrN–(Cr, Mo, Al)N coating also has the lowest friction coefficient (0.0806). A promising direction for further research may be the development and study of new multicomponent nanocomposite coatings based on high-entropy alloys.

The inertia of silicon carbide (SiC) when creating polymer composite materials (PCM) often does not allow creating a high-quality final product. This is due to the weak interfacial interaction between the filler and the polymer. This paper presents a method for modifying silicon carbide with a controlled content of 3-aminopropyltriethoxysilane (APTES) on its surface. The modifier will create active functional groups on the surface of silicon carbide, and they will be the first to interact. In the study, a step-by-step assessment of the change in the surface of filler particles during the formation of reactive groups by IR spectroscopy was carried out and the effect of the proposed method on the bulk density of SiC particles was determined. The presented work contains data on the study of the adsorption kinetics of the filler after its modification, and describes the conditions under which the most complete addition of functional groups occurs during treatment with silane.The factors that can be used to vary the content of functional groups on the surface of silicon carbide, thus changing its activity, have been identified. The effectiveness of the proposed modification method is shown and samples with a reactive surface of SiC particles are obtained, which are the most promising for the creation of polymer composite materials.

The authors have developed a technology for creating a nanomodified binder for construction purposes, in which a uniform distribution of carbon nanomaterials is achieved by controlled synthesis of nanomaterials in the structure of the binder. The synthesis of carbon nanomaterials (CNM) was carried out by chemical vapour deposition of hydrocarbons on metal oxide catalysts. Cement CEM I 42.5H (M500 D0) and metal-oxide catalyst Ni–MgO (92.5 %–7.5 %, obtained by thermal method) were used as a raw material. The optimum catalyst/cement ratio of 0.2 was found to yield the specified CNM quality. If the catalyst/binder ratio is increased (without changing the other parameters), the specific yield value of the nanomodifier decreases, which can be explained by “poisoning” of the catalyst and, consequently, the formation of unstructured carbon. The nanomodifier was investigated by scanning electron microscopy, Raman spectroscopy and thermal gravimetry. Using Raman spectroscopy, the shape and position of the characteristic G and D bands showed that a material containing multi-walled carbon nanotubes (MWCNTs) was synthesized on the cement binder matrix. According to thermal gravimetry data, the obtained nanomodifier is resistant to thermal decomposition up to 500 °С. Experimental studies of the influence of the obtained additive on the characteristics of the construction composite were carried out on samples of fine-grained concrete. It is established that compressive strength for nanomodified samples increases by 18–20 %.

This study aimed to find and investigate new oxide catalysts for glucose electrooxidation operating in a neutral medium. The catalysts were prepared in the form of dispersion deposited on a carbon substrate; the obtained electrodes were characterized. The following oxides were studied for the ability to enzyme-free glucose oxidation: tin(IV) oxide, tungsten(VI) oxide, titanium(IV) oxide and manganese(IV) oxide. During the tests, such analysis techniques as cyclic voltammetry and chronoamperometry were applied. A phosphate buffer solution (pH 7.40) was used as a working electrolyte (background solution). The study proves that the electrode based on manganese(IV) oxide mixed with acetylene black shows a stable current for the anodic oxidation of glucoseunder continuous polarization during at least two hours, and stable under keeping in the working electrolyte. The dependence between the current and the root of the glucose concentration was shown to have a quasilinear character, and therefore this electrocatalyst can act as a promising and inexpensive material for continuous glucose monitoring sensors.

The development of metamaterials of various types (electromagnetic, acoustic, mechanical) is characterized by a single approach – the response of the medium to external influences required for solving a specific problem is “designed” by using a system of elements organized in a certain way, made from ordinary, well-known materials. This approach is universal and allows successfully solving a wide range of problems in various fields of science and technology. It is used in wildlife to create materials that provide optimal adaptation of a living organism. Rationally designed mechanical metamaterials have a number of unusual properties. In particular, they can meet conflicting requirements by combining, for example, high rigidity with high fracture toughness and low density. This makes them extremely promising for the development of new structural materials based on them. It is concluded that additive technologies can be successfully used to create mechanical metamaterials with ultra-properties – ultralight and superrigid. The principles of creating auxetic metamaterials based on open-cell foams are described in detail.