Planar screen-printed potentiometric sensors sensitive to cephalosporin antibiotics cefuroxime (Cefur) and cefotaxime (Ceftx) has been developed. Cefotaxime is an amphoteric antibiotic with carboxyl and aminothiazole groups (third generation), cefuroxime is an acidic antibiotic of the second generation. Tetradecylammonium associates with complex compounds silver (I)-cefuroxime (cefotaxime) were used as electrode-active components (EAC). The linearity intervals of the electrode functions for unmodified sensors are 1 × 10^–5 (1 × 10^–4) – 1 × 10^–2 M, angular coefficients 46 ± 6 mV/pC, response time 40 sec. The role of magnetic nanoparticles Fe₃O₄ and cetylpyridinium chloride (CPCh) in improving the electroanalytical properties of sensors in aqueous of cefuroxime and cefotaxime is shown. Optimal ratios of modifiers in carbon-containing inks (Fe₃O₄:CPCh = 1:2.5) were found. The main electroanalytical characteristics of the sensors are determined. The introduction of a binary mixture of magnetic nanoparticles and cetylpyridinium chloride into carbon-containing inks leads to an improvement in the electroanalytical properties of planar sensors sensitive to cefuroxime and cefotaxime: at the same time, the detection limit of 1 × 10^–6 (1 × 10^–7 M) decreases, angular coefficients (55 ± 3 mV/pC) and linearity intervals of the electrode functions (1 × 10^–6 – 1 × 10^–2 M), response time 26 – 30 sec. The adsorption of surfactants at the interface ensures the stability of the suspension of nanoparticles and allows the concentration of analyte molecules. Electrostatic and hydrophobic interactions of surfactants increase the solubility of organic compounds. The use of modified screen-printed sensors for the determination of cefuroxime and cefotaxime in medicinal preparations and model aqueous with added antibiotics is shown.

The possibility of getting block-porous systems modified with sorption-active materials for the determination of volatile organic compounds was considered. The prepared samples of the block-porous systems differ in the base material (AD1 aluminum and X20N80 steel) and porosity (0.6 and 0.75). Before applying a layer of sorption-active material on the surface of the block sample, an adsorption layer was formed by chemical (for aluminum) oxidation and thermal (for steel) oxidation. Activated carbon BAU, Polysorb-1 and polymethylsiloxane as a binding agent were used as modifiers. When studying the surface morphology, it was found that the most uniform distribution of particles of the sorption-active material is observed for Polysorb-1 on the steel surface. To compare the sorption characteristics of the resulting sorption systems, the degree of recovery during concentration and desorption using a standard gas mixture of hexane with a concentration of 0.7 mg/liter was assessed. The values of the recovery degree for the studied samples are comparable to those of powdered sorbents and differ depending on the amount of the applied active layer. It is shown that the highest recovery degree (61%) is achieved for samples of sorption systems with Polysorb-1 and polymethylsiloxane applied to the surface, since both substances exhibit sorption activity towards volatile organic compounds. Moreover, it is shown that when samples of sorption systems were used even five times, there was no decrease in the degree of extraction during sorption and desorption, which indicates the effectiveness of their repeated use.

The content of a number of strategic metals (Au, Sc, La, Sm, Eu, Dy) at the level comparable to their average contents in graphite-bearing rocks of the south of the Russian Far East was determined by the method of instrumental neutron activation analysis (INAA) on an original device with a radionuclide neutron source based on ²⁵²Cf. A key advantage of INAA in analysis of difficult-to-dissolve carbon-containing materials is a non-destructive character of the method. The proposed methodological approach avoids the complex procedure of sample decomposition, analyte separation and associated problems (dissolution, contamination and losses). It is shown that there is no significant influence of carbon contained in the sample on the INAA results when up to 300 cm³ of sample containing at least 87 %wt. of carbon are introduced into the activation zone. The detection limit of the method was calculated for a number of the determined elements. The possibility of determining the content of Sc, La, Sm, Eu, and Dy in natural high-carbon objects below the clarke level was confirmed. The absence of any significant dependence of the INAA results on the density and coarseness of the studied samples was revealed. The results of determining strategic metals in graphite-bearing metamorphic rocks of the south of the Russian Far East were compared for two different INAA options (reactor and with ²⁵²Cf radionuclide source). The comparison showed that data obtained at the device with the radionuclide source ²⁵²Cf for most of the elements under study match the results obtained earlier on a WWR-M reactor at the St. Petersburg Institute of Nuclear Physics named after B. P. Konstantinov. At the same time, the possibility to irradiate samples of 50 – 100 cm³ ensures high representativeness of the sample when activated with the ²⁵²Cf isotope. The INAA method with radionuclide source ²⁵²Cf is suitable for the analysis of carbon-containing materials for trace elements, the determination of which is difficult due to complex sample preparation, analyte separation and other related problems.

Various methods of corrosion monitoring are used to control the aggressiveness of the operating conditions of oil and gas facilities and ensure their safe and reliable operation. One of them is the analysis of the resulting corrosion products and other sediments and deposits to obtain data on their composition. We present the results of studying sediments when determining the mechanisms and causes of corrosion processes followed by the development of measures aimed at the elimination of the factors promoting the corrosion development. The composition of sediments formed at the facilities of a gas complex was studied. Inorganic compounds and elemental composition were analyzed by X-ray diffraction and scanning electron microscopy. It is revealed that elemental sulfur is present in the composition of sediments, indicating the presence of dangerous sulfur-containing compounds in the system (for example, H₂S). Using IR spectroscopy and chromate-mass spectrometry, the organic components of sediments formed during preparation of the methanol solution of a corrosion inhibitor were determined. It is shown that the reason for their formation is the presence of oil hydrocarbons in the solution. When analyzing the sediments formed inside the water transport pipe, it was shown that they include iron oxides and hydroxyoxides. At the same time, in places of a through defect on the outer surface of the pipe, corrosion products consisting of Fe(II) or Fe(III) hydroxides with layers of anions and water molecules, the so-called «green rust», are formed. Unstable under operating conditions, such a sediment is unable to protect the steel surface from corrosion. The results obtained can be used in conducting corrosion monitoring at gas facilities to identify corrosion factors affecting the formation of sediments and deposits.

Steel S690QL is designed for welded heavy-loaded structures: lifting booms, traverses, trailers of heavy trucks, etc. We present the results of studying the mechanical properties and the microstructure of S690QL steel manufactured both in Russia and abroad, as well as the viscous properties of welded samples at different temperatures. The methods of atomic emission spectroscopy, tensile and impact strength tests, and microstructural analysis were used. Hardness was determined by the Vickers method. It is shown that the chemical composition of both grades of steel is almost identical. The values of the impact strength of samples made of domestic S690QL exceed those of foreign ones. This is especially true for metal that has not been subjected to welding processes (the impact strength for Russian steel S690QL in this zone was 200 J/cm² at –40°C, which exceeds the impact strength for foreign analogs in the same zone by almost 80%). The temperatures of brittle-viscous transition (BVT) for zones of welded joints made of Russian steel S690QL were determined. In the areas of welded metal deposit and heat affected zones the BVT temperature was –40°C. The microstructures of both steels are similar in all areas of the weld seam of control welded joints. The hardness in the studied samples of welded joints has similar values and similar changes in the zones of welded joints. The results obtained can be used in mechanical engineering for certification and design of welded structures, primarily for the Arctic zone.

A high-voltage power supply, as an X-ray tube, is one of the main components of X-ray machines widely used in studying the structure of materials, assessing the internal structure of components and mechanisms, and non-destructive testing of technological processes. In monoblock-type devices, the X-ray tube and power supply are located in a common enclosure, while in cable-type setups, the X-ray emitter with the tube and the power supply are connected by a high-voltage cable. We present the results of research in creating a high-voltage stabilized power supply for X-ray tubes as a part of a cable-type apparatus. Electrical circuits and the design of the power supply based on a full bridge voltage inverter built on power bipolar transistors are developed. Adjustment of the output voltage and power of the source is carried out through PWM modulation of the rectified mains voltage applied to the primary winding of the high-voltage transformer. The use of a solid-state compound with increased thermal conductivity allowed us to use forced air cooling of the source and place it within the dimensions of the Rack Mount standard (4U form factor). The experience of the power supply operation in conditions of a large industrial enterprise has shown that its electrical and dimensional parameters provide the possibility of successful use in X-ray installations intended for the structure control of materials.

Research into the causes of failure of power equipment is necessary to eliminate or restrict their impact, as well as to develop and improve technical diagnostic methods. The last reason is especially important, since accidents or unscheduled shutdowns of power equipment result in serious damage to the economy. Standard methods of technical diagnostics used to assess the residual life of the equipment include mechanical tests of the samples cut from parts of the equipment, determination of their chemical composition, structural studies and fractography of metal fractures. The danger of hydrogen embrittlement in metals is well known. Presence of the areas of brittle fracture or facets is usually associated with hydrogen-induced fracture or hydrogen embrittlement. Direct measurements of the concentration of hydrogen dissolved in metal samples are beyond the scope of regulatory requirements, thus making quantification of the development of hydrogen embrittlement rather difficult. We have shown that technical diagnostics of the pipes of heating surfaces of boiler equipment necessitates additional approaches to the evaluation of hydrogen embrittlement. Hydrogen accumulation during operation may not show visible signs of corrosion or structural changes. It is shown that hydrogen and external thermomechanical load induce the anisotropy in the mechanical and structural properties of the pipe steels. As a result, the nature of the destruction of samples cut from pipe walls depends on the orientation of the test loads relative to the main axes of the stress tensor of operational (working) loads. Experimental data obtained indicate that when determining the causes of accidents and examining heat exchangers to assess their residual life, it is necessary to measure the distribution of the concentration of dissolved hydrogen in the metal and to carry out mechanical tests of ring samples.

Additive technologies (AT) used for the manufacture of materials and products are being introduced precipitately in modern industry. The technology of electric arc cultivation (Wire Arc Additive Manufacturing (WAAM)) is of considerable interest due to a relatively low cost of the equipment and surfaced materials, as well as due to an essential level of understanding welding processes. The cultivation of metal layers and the manufacture of volumetric parts of various geometric shapes in this case is carried out by welding wire. Chromium-nickel steels are widely used as surfaced materials for three-dimensional printing with metals. However, given the specifics of complex structural and formative processes in the implementation of WAAM, there is a need for additional studies of the structure and properties of the materials obtained. The goal of this study is to apply modern non-destructive methods of structural degradation control in the process of uniaxial stretching of ER308LSI steel obtained by the WAAM electric arc additive cultivation method. At the same time, metallographic and magnetic studies were carried out, along with the analysis of changes in microhardness during deformation of samples cut along and across the printed layers. The features of the stages of structure degradation upon uniaxial stretching and the behavior of magnetic parameters of the material were analyzed. It is shown that uniaxial stretching of WAAM-made samples leads to the formation of a large number of structural defects in the form of deformation bands, discontinuities and microcracks, the appearance of which is accompanied by a significant change in the yield strength, microhardness and in the values of coercive force H_c. Based on the obtained Hc values, a parameter of the magnetic anisotropy (A_magn), which reflects the nature of the change in the coercive force in samples cut both along and across the direction of surfacing was introduced. However, the character of these changes for longitudinally and transversely (relative to the deposited layers) cut samples is different. The results obtained can be used in diagnosing the deformed state of WAAM products.

When determining the service life of modern aircraft, it is necessary to take into account the impact of intense pulsations of sound pressure (the noise created by the operation of engines, air turbulence, changes in flight regimes), etc. on the aircraft structure. Therefore, in ground conditions, acoustic strength and fatigue tests are carried out in special reverberation chambers. During these tests it is necessary to provide a certain spectral density of the sound pressure affecting the structure under study according to the approved standards. Three types of sound generators are used to obtain the desired force impact on the structure: low-frequency, medium-frequency and high-frequency, which must create signals with the required spectral density and constant amplitude of the noise impact each in its frequency range. Nowadays, a high-frequency sound generator operating in the frequency range of 600 – 2000 Hz is being developed. The goal of the study is to modify and improve the moving element of the valve assembly to increase the electromagnetic force driving the valve gate of the valve assembly of a gas flow modulator; minimize the electromagnetic forces hindering movement, and to reduce the mass of the moving element. An increase in electromagnetic driving force is achieved using two electromagnetic thrusters. The proposed modifications reduce hindering electromagnetic forces (Lawrence forces, Foucault forces), and decrease the mass of a movable part of the valve assembly (gate). The goal is achieved by perforating the gate in those parts that are located in magnetic gaps of electromagnetic propulsion.