The presence of reactive hydrogen-silyl (SiH) bonds in oligomethylhydrosiloxanes provided their widespread use in the building, paper, textile and rubber industries. Low molecular weight fractions of methylhydrosiloxanes, both cyclic and linear, negatively affect the performance of oligomer-based materials. The main goal of the present study is detection and identification of these fractions in the commercial product 136-157M, as well as in the co-oligomers synthesized from it. A method of gas chromatography-mass spectrometry was used in the study. First, we proved that an increase in the temperature of the column and evaporator from 60°C to 300°C does not change the composition of the low molecular weight fractions. Consequently, no depolymerization processes related to the formation of low-molecular-weight compounds occur during the analysis. To perform a qualitative analysis, the components of low-molecular-weight fraction were separated on a capillary column and then identified using a mass detector with an ion trap. It is shown that electron ionization triggers fragmentation of molecules and the formation of positively charged ions. As for methylhydrosiloxanes, cations with a molecular weight of [M – 15]⁺ arising from the rupture of the carbon-silyl bond are formed first. Moreover, when such a rupture occurs in cyclosiloxanes with a total number of units of more than four, further dissociation processes can occur with the detachment of the neutral fragment (methylsilane) and the formation of bicyclosiloxane cations. Since the set of positive ions is individual for each of the components and depends on [M]^+•, a component-wise description of the entire low molecular weight fraction becomes possible with a high degree of the reliability. It is sown that for the considered commercial sample it can be described by two homologous series — cyclic where m ≥ 4, and linear siloxanes where n ≥ 1

Copper and nickel-based alloys are widely used in various industrial settings. Their properties directly depend on the impurities and alloying additives present. Therefore, monitoring of their content in the composition of alloys is still an urgent task. Analytical characteristics of the methods used for determination As, Bi, Pb, Sb, and Sn in copper, nickel, and alloys on their base are studied using electrothermal atomic absorption spectrometry (ETAAS) with selective radiation sources, deuterium background correction, longitudinally heated graphite tube, and high-resolution ETAAS with a continuous source and a transversely heated atomizer. The parameters of the temperature program of the atomizer were optimized for both version of the atomic absorption spectrometry. The revealed interfering effect of the matrix (Cu and Ni) of the studied samples significantly distorts the analytical signals of the analytes and results in significant non-selective absorption. It is shown that when constructing calibration dependencies using ETAAS with selective radiation sources, it is necessary to add a matrix component to the calibration solutions, whereas for high-resolution ETAAS it is possible to avoid introduction of the matrix component without increasing the error of analysis. The developed procedures were tested in analysis of the high-purity copper and nickel samples and standard samples of the composition of the alloys based on copper VSM14-5 (rough copper), VSM14-6 (bronze), and nickel VSN2-2. The achieved detection limits for high-resolution ETAAS with a continuous source leveled at n × 10^–5 %, whereas for low-resolution ETAAS with selective radiation sources the detection limits were higher by an order of magnitude. To determine lower concentrations of the elements in such materials, separation of the sample matrix should be used.

A comparison of two standard test methods for determining the laboratory effectiveness of oil spill dispersants — ASTM F2059-17 «Standard Test Method for Laboratory Oil Spill Dispersant Effectiveness Using the Swirling Flask» and ASTM F3251-17 «Standard Test Method for Laboratory Oil Spill Dispersant Effectiveness Using the Baffled Flask» — is presented in this article. It is underlined that ASTM F2059-17 and ASTM F3251-17 are almost identical from the methodological and technical points of view. The main differences lie in specific design features of the applied test vessels and mixing energies created inside them. It is reasonably established that ASTM F2059-17 can be defined as a low-energy, but ASTM F3251-17 — as a high-energy laboratory test method. The specific examples of application of the test methods for determining the effectiveness of commercially available dispersants are given. It is also concluded that both test methods are necessary to apply for a correct understanding of the dispersant effectiveness. Herewith, the results obtained according to ASTM F2059-17 should be conditionally considered as the lower limit and those according to ASTM F3251-17 — the upper limit of effectiveness of the dispersant. Moreover, the use of gas chromatography with flame ionization detection (GC-FID) is emphasized to be sometimes impossible as a recommended in both ASTM F2059-17 and ASTM F3251-17 method for analyzing the oil extracts obtained during the test. The UV spectrophotometry is proposed instead of GC-FID as an alternative. However, its application is possible only after mandatory optimization of the measurement parameters for each specific oil.

Coatings made of the materials that effectively absorb radiation, e.g., ferrite materials, are used to reduce the level of electromagnetic radiation in rooms containing household or industrial equipment. It is known that significant dissipation of the radiation energy is provided by the thickness of the shielding coating which should be comparable to the length of the electromagnetic wave in the material which, in turn, significantly decreases at high values of the magnetic permeability and permittivity of the radio-absorbing material. Ferrite radio-absorbing coatings are characterized by the high heat resistance, low flammability and small (10 – 20 mm) thickness. However, at frequencies less than 40 MHz, plates with a thickness of more than 30 mm are to be used to provide the effective absorption, and the weight and cost of the coatings increase significantly. The results of studying the effect of the sintering temperature and micro-additives of titanium, calcium and bismuth oxides on the dielectric constant of Ni- and Mn-Zn radio-absorbing ferrites are presented. Reactively pure starting oxide components with a basic substance content of more than 99.6 % wt. were used to synthesize samples using traditional oxide technology. It is shown that alloying with bismuth and titanium oxides is rather effective for obtaining radio-absorbing ferrites with a combination of high values of the magnetic permeability and dielectric permittivity. The obtained results can be used in production of ferrite radio- absorbing materials operating in the megahertz range.

The properties of interfaces in the heterostructures which frequently govern their operation are of particular importance for the devices containing heterostructures as active elements. Any further improving of the characteristics of semiconductor devices is impossible without a detail analysis of the processes occurring at the interfaces of heterojunctions. At the same time, the results largely depend on the purity of the starting materials and the technology of layer manufacturing. Moreover, the requirements to the composition and distribution of the impurity steadily get stringent. Therefore, the requirements regarding the methods of the impurity control and carrier distribution also become tougher both in the stage of laboratory development of the structure and in various stages of manufacturing of semiconductor devices. Electrochemical capacitance-voltage profiling is distinguished among the methods of electrical diagnostics of semiconductors by the absence of special preparation of the structures and deposition of the contacts to perform measurements, thus providing for gaining information not only about the impurity distribution but also about the distribution of free carriers. The goal of this work is to perform precise measurements of the profiles of free carrier distribution in semiconductor structures of different types, and demonstrate the measuring capabilities of a modern technique for concentration distribution diagnostics, i.e., electrochemical capacitance-voltage profiling. The method allows verification of the layer thickness in semiconductor heterostructures and provide a useful and informative feedback to technologists. To increase the resolution of the method and broad up the range of available test frequencies, a standard electrochemical profiler has been modified. Mapping data for GaAs substrate structure, the profiles of the concentration distribution of the majority charge carriers in SiC structures, GaAs structure with a p – n junction, pHEMT heterostructure, GaN heterostructure with multiple quantum wells, and in a silicon-based solar cell heterostructure are presented. The obtained results can be used to analyze the physical properties and phenomena in semiconductor devices with quantum-sized layers, as well as to improve and refine the parameters of existing electronic devices.

The goal of the study is to reveal the impact of change in the structural state of steel 07Kh3GNMYuA after heat treatment on the values of the critical stress intensity coefficient (K_1c) obtained at a temperature of 50°C and on the velocity of ultrasound wave propagation, as well as to determine a correlation between them for rapid assessment of the crack resistance using acoustic characteristics. The mechanical characteristics of the material and the critical stress intensity coefficient K_1c were obtained on the test machine «Inspekt 100 Table». The tangent method is used for determination of K_1c. Three samples per K_1c value were used in the experiment for a three-point bending scheme at the operating temperature T = –50°C. Acoustic parameters were measured using the echo-pulse method. The results of ultrasonic scanning of heat-strengthened samples made of steel 07Kh3GNMYuA demonstrated the possibility of non-destructive quantitative evaluation of the critical stress intensity coefficient. New data on the mechanical properties of steel 07Kh3GNMYuA and on the correlation between the velocity of longitudinal elastic waves and the values of the critical stress intensity coefficient of structures were obtained. Deviation of the calculated values of K_1c obtained using acoustic measurements from the experimental values does not exceed 10%. The proposed model, which explains change in the acoustic characteristics of steel 07Kh3GNMYuA on the basis of phase changes occurring in the steel structure upon tempering, provides conducting of similar studies for other modes of heat treatment and other steel grades. The method is a low labor- and time-consuming procedure for determination of the mechanical characteristics of the products made of steel 07Kh3GNMYuA, since it does not require the manufacturing of samples and their testing. The developed procedure can be proposed for manufacturing application, as the main or additional method for evaluation of the mechanical parameters of materials after various modes of heat treatment.

Novel wear-resistant materials used in friction pairs are being developed to increase their reliability and failure-free performance in operation, reduce the environmental load and energy consumption in manufacturing processes. One of the promising functional materials for manufacturing durable and wear-resistant parts and products that undergo intensive wear in operation is a powder material of the TiC – SiC system obtained by spark plasma sintering (SPS). SPS is an energy-efficient alternative to hot pressing and environmentally-friendly procedure compared to that used in manufacturing serial friction pairs from the lead-graphite composition NAMI GS-TAF-40 for tractor industry. Prototype friction pairs made of the powder material of the TiC – SiC system have been manufactured by SPS technology using sketches of a serial friction pair of the mechanical seal of a centrifugal pump 16-08-140SP of the cooling system of D-180 diesel engine developed for a T10 tractor. The goal of the study is accelerated bench testing of the obtained experimental friction pairs. The tests were carried out on the equipment of a modular block for testing mechanical seals designed for the USI «Climate». The method of accelerated testing provided simulation of the operational tests of experimental friction pairs of mechanical seals of centrifugal pumps of the cooling system of an internal combustion engine with a 2.0 – 2.5-fold acceleration. The criterion for the applicability and evaluation of the results of accelerated tests of experimental friction pairs was the similarity of temperature conditions of the water pump seal and the compression forces of the rings in the friction pair under real diesel operation and the accelerated test modes for the increased rotational speed of the centrifugal water pump shaft. A path traveled by the point of the average radius of the «contact line of touch» of the working surfaces of the rings with allowance for test acceleration coefficient (2.0 – 2.5) was taken as a basis for assessing the reliability and durability of test objects. During accelerated testing, all the test parameters were taken into account in addition to visual inspection of the test equipment and the mechanical seal. The wear resistance of the experimental friction pairs was determined by change in the mass through intermediate measurements of the ring wear after 100 and 200 hours of testing. Accelerated bench tests revealed that a friction pair with parts made of a TiC – SiC-based composite material will provide at least 1.5- fold increase in the service life of the mechanical seal of the centrifugal pump of a D180 diesel cooling system.

The goal of the study is determination of the optimal geometric dimensions of rectangular anisotropic specimens with a transverse groove when tested for uniaxial tension under conditions close to plane deformation. A test scheme in which the shear fracture mechanism is implemented in the center of the groove under conditions of plane deformation is presented. The optimal geometric dimensions of the specimen (namely, the depth, width and length of the transversal groove) were determined proceeding from numerical simulation of the experiment in the ABAQUS software package in the Explicit mode. It is shown that the initial anisotropy of the material significantly affects the deformed state in the groove. The larger the ratio of the Lankford coefficients along the rolling direction and across this direction, the closer the deformed state in the groove to the plane deformation. It is also shown that change in the geometry of the specimen with a transverse groove can provide better results in implementation of the plane deformation in the region of specimen fracture. The value of the parameter of the deformed state approaches zero when the thickness and width of the groove decrease, as well as when the width of the specimen increases. It is shown that the possibility of forming plane deformation in the groove due to the choice of specimen geometry is limited from above for any initial anisotropy. A moment of «saturation» is observed, at which the ratio of principal strains in the center of the groove does not go any further to zero despite further change in the geometry. A table of geometric dimensions of rectangular specimens with a transverse groove recommended for tensile testing under conditions of plane deformation for all types of anisotropic and isotropic sheet materials is presented.

An approach to constructing direct and inverse static characteristics of the system is considered proceeding from the experimental data obtained using a traditional «black box» concept, whereby the results of the experiment containing measured input and output values are used which, in practice, are determined with errors. The presence of various sources and trigger interference factors leads to a significant distortion of the error estimates and the formation of an inadequate conversion response. A crucially different character of the impact on the measurement results can be observed taking into account the type and sources of errors upon formation of the static characteristics and developing a model of noise arising upon measurements in actual operation conditions and during the experiment. However, analysis of the existing method based on a statistical approach and used for determining the error of the object model revealed a number of shortcomings: focusing mainly on the random components of errors and complexity of taking into account non-statistical information, including a priori information about the systematic errors, round-off and sampling errors, and the errors of the measurement system used in upon developing a model of the system. The statistical approach does not provide theoretical substantiation of the solution of the problem of the inverse static characteristic of the system which is relevant for many applications. Moreover, the fact that the interference models under experimental and real operation conditions have different sources and are generated by different factors is ignored in the framework of the statistical approach, which can lead to a significant distortion of the error estimates of the system model and to the formation of an inadequate direct and inverse transformation characteristics. We propose to eliminate the aforementioned shortcomings using the interval approach. The problem of developing a new method for constructing the passport characteristic of the inverse static function of a system is solved on the basis of a two-stage procedure of the experimental design. A new method based on the interval approach has been developed in which the problem of constructing the inverse static characteristic of the system and the problem of determining the error of the measurement system are solved separately using different types of active experiment. The boundaries of the uncertainty interval of the measurement system are defined in the general case by spline-functions. A concept of the operating range of the system, which does not coincide with the range of changes of the measured value in an active experiment, is introduced. It is shown that outside the operating range the system error sharply increases and becomes asymmetric with respect to the inverse static characteristic.