Extraction of sulfur compounds from oil and petroleum products is a high priority task associated with tightening of the criteria of fuel quality control, negative impact of sulfur on the processing and storage of crude oil, environmental safety, as well as widespread use of organosulfur substances in different industries. The selectivity of several organic and inorganic extractants (methanol, N,N-dimethylformamide, acetonitrile, 15% NaOH, PEG 4000, PEG 200, diethylene glycol, monoethanolamine, dimethylacetamide, n-methylpyrrolidone) in relation to thiophene, dibenzothiophene, thiophenol, dodecanethiol and metilsulfide was studied for model solutions of organic sulfur compounds in n-heptane and n-octane. Extraction was carried out under static conditions. Sulfur content in the initial sample and in the sample after extraction was determined using an x-ray fluorescence analyzer SPECTROSCAN S. Chromatographic analysis of the samples was performed on an Agilent gas chromatograph with a mass-selective quadrupole detector. The selectivity of the studied extractants in relation to the studied groups of sulfur compounds was assessed through recovering (%) of a particular sulfur compound. It is shown that acetonitrile, N,N-dimethylformamide, dimethylacetamide and n-methylpyrrolidone are the most effective extractants for thiophene extraction. Methanol, N,N-dimethylformamide, acetonitrile, PEG200, diethylene glycol, monoethanolamine, dimethylacetamide and n-methylpyrrolidone are capable of extracting a wide range of organosulfur compounds from model solutions. Aqueous solutions of PEG 200 and PEG 4000 provide extraction less than 11% of organosulfur compounds, whereas 15% NaOH solution and a mixture of 50% NaOH:ethanol (1:2) are selective extractants for aliphatic mercaptans and provide up to 99% extraction of thiophenol and dodecanthiol, respectively. It was found that n-methylpyrrolidone, dimethylacetamide and N,N-dimethylformamide have the highest extraction capacity among the studied extractants. A series of studies gives ground to propose a possible extraction scheme for recovery of mercaptans from a mixture of organosulfur compounds.

A procedure for determination of Ag, As, Bi, Fe, Ni, Pb, Sb, Sn, Zn, and Cu in copper alloys using ICP AES with spark sampling has been developed. Spark sampling conditions were specified when studying the effect of discharge parameters on the line intensity and relative standard deviation (sr) (the discharge power level changed from 1 to 9 units on the SSEA scale (from 2.10 to 3.30 kW), discharge frequencies and pre-firing time ranged within 100 to 800 Hz and 30 to 70 sec, respectively). The conditions of atomic emission determination of normalized elements were studied. Analytical lines were selected taking into account the maximum intensity in the absence of spectral overlaps. The advantage of using the method of internal standard and the method of multidimensional calibration of the spectrometer is shown. Calibration of the spectrometer was carried out using monolithic standard samples of copper alloys. The accuracy of determination of the elements in copper alloys was proved in analysis of standard samples and comparative analysis of the obtained results and data obtained by recommended GOST methods. Statistical processing of the measurement results by the Student criterion did not reveal systematic errors. The results of the determinations obtained by the developed method show that rational combination of spark sampling and ICP-AES analysis provided high precision of rapid (duration of analysis is reduced to 30 minutes) and cost-effective determination without a necessity of using chemical reagents.

A possibility of using tetracyanoethylene (TCNE) as a photometric reagent for determination of the dipyrone content in pharmaceuticals is considered. A photometric form was obtained in the aqueous phase in an acetate buffer medium (pH 3.13). The resulting π-complex revealed two absorption bands at (400 and 420) nm with molar absorption coefficients of 1.56 Ч 10⁴ and 1.62 Ч 10⁴, respectively. Due to a high lability of the photometric reagent, the optical density of the complex thus formed must be measured immediately after preparation. The composition and possible mechanism of π-complex formation were determined using the methods of molar ratios and isomolar series: the active substance interacts with the reagent in a molar ratio 1:1. The calculated value of the stability constant of the formed π-complex was 1.42 Ч 10⁶. Proceeding from the obtained data, a spectrophotometric method of dipyrone determination in drugs is developed with a detection limit of 42.63 μg/ml (the error of determination being below 3.0%). The linear dependence of the analytical signal on the concentration of the active substance is observed in the range of 20 – 100 μg/ml. Testing of the spectrophotometric method for dipyrone determination was carried out on tablets and injection solutions manufactured in Russia. There is a good convergence between the results of dipyrone determination by the developed and arbitration methods (pharmacopoeia monograph 2.1.0003.15). The analysis revealed that the content of dipyrone in the dosage form corresponds to the declared. The developed technique is easy to use accessible in equipment and can be recommended for determination of dipyrone in conditions of a conventional analytical laboratory.

The problem of increasing the fire resistance of buildings and structures is still relevant. Nowadays, fireproof intumescent and other materials with a limited service life are used to ensure fire safety of infrastructure and social facilities. Among these, fire-proofing of metal structures is one of the vital problems. The results of studying samples of fire-retardant intumescent coatings based on ammonium polyphosphate-melamine-pentaerythritol and subjected to artificial climatic aging (3, 6, and 9 years) and thermal exposure (heating to 300 and 500°C) are presented. The methods of X-ray diffraction and thermal analyzes, optical and IR spectroscopy are used to study the phase and structural composition of materials. It was found that the intumescence of the samples significantly decreases during service life of the coating. This leads to a decrease in the fire resistance of the protected object. Moreover, a sharp change in the phase composition of materials occurs as a result of aging and heating, accompanied by a decrease in the degree of crystallinity. Since the composition of fire-retardant coatings plays a key role in ensuring the fire safety of buildings and structures, the results of the study can be used for timely detection of violations in the quality of coatings and forecasting their service life.

Modern methods for classifying motor oils by viscosity classes and groups of the performance properties are characterized by the lack of information about the temperature range of the oil working capacity and tendency to aging due to the design features of internal combustion engines, operating modes and conditions, the degree of forcing and technical condition. One of the main goals of improving the technical and operational indicators of the designed and operated equipment is the selection of appropriate lubricants, the proper choice of optimal modes of operation and lubrication. We present the results of studying the effect of temperature on the performance of lubricants, review and analyze methods for their control. The temperature parameters of the working capacity of lubricants are determined by the method of thermostating. A photometric device for direct photometry of oxidized oils and electronic weighing machine were used as measuring instruments. The optical density and evaporation coefficient of the lubricant were estimated proceeding from the results of testing a sample of partially synthetic motor oil. The temperature and time dependences of the optical density, oxidation resistance coefficient, volatility, thermal oxidation stability coefficient, and temperature limits for the test specimen were determined, including the temperatures of the onset of oxidation, evaporation and temperature transformations, critical temperatures of the processes considered and potential in-service life. The proposed method provides the ability to compare various lubricants of the same duty by the temperature parameters and determine the temperature range of their efficient use in mechanical systems.

Traditional methods used for assessing the properties of polymer composite materials (PCM) in most cases present a generalized picture and only few of them provide more detailed information. We present the results of studying carbon fiber samples molded using the infusion method with a thickness of about 8 mm. The microhardness of the PCM matrix was measured on transverse sections in two mutually perpendicular planes, named side and end surfaces, load of a microhardness indenter being 10 g (0.1 N). The studies revealed that the microhardness of the carbon fiber matrix in depth from the front surface of the sample to opposite one varies according to a parabolic law with maximum values in the core and minimum values in the subsurface zones. Moreover, statistical calculations showed the significance of differences in the microhardness values measured in two mutually perpendicular planes. The obtained graphical dependences of the microhardness variation measured over the thickness of the samples in two mutually perpendicular planes are similar in shape, whereas the volume anisotropy coefficients are almost equal. Microscopic studies of transverse sections of the samples revealed the structure of the studied carbon fiber reinforced plastic, provided determination of the thickness of the matrix and layers of the carbon filler, as well as the layout and orientation of the carbon filler tapes. The results of microscopic studies of zones in which the matrix microhardness was measured directly are also presented along with the obtained images of thin sections with indenter prints of the microhardness tester which indicate that the measurements were carried out directly on the matrix in areas free of the filler. The use of microhardness as a differential characteristic made it possible to evaluate the properties of the matrix in each specific structural component. The results can be used in assessing the properties of molded PCM structures.

Features of the creep process in single-crystal nickel-based superalloys are studied in a wide range of temperatures and holding time for different crystallographic orientations. The results of experimental study of high-temperature creep obtained for different single-crystal superalloys are presented. The dominance of stage III of creep is observed for considered temperature range and loads. Uniform creep models describing I, II, and III stages, are proposed taking into account damage accumulation based on the Norton – Bailey relations and power law of evolution for the scalar damage measure of Kachanov – Rabotnov. A hierarchical sequence of creep models of various degrees of complexity is suggested depending on the necessity of taking into account stage I. A material model including six constants is sufficient to describe stages II and III. Simultaneous accounting of all three stages of creep can be carried out using model with nine constants. The assumption on the absence of damage at the first stage leads to a material model with ten constants. The entered additional tenth parameter characterizes the duration of the first stage. Identification methods for the parameters of the introduced models based on using the least-squares method and Nedeler – Mead method for solving the problem of minimizing the error functional are proposed. The results of verification of the proposed inelastic deformation models are presented for various nickel-based single-crystal superalloys. The standard deviation between the experimental and computation results for all the proposed creep models does not exceed 10%. This allows us to recommend the developed approach for estimating the level of irreversible accumulated strains and durability of the structural elements made of single-crystal superalloys.

The structure and mechanical properties of 350 steel (GOST R 52246) are studied under tensile and impact bending in the zones of bend of galvanized light-gage steel structure elements. Batch sheet samples consisting of two and three samples with a V-shaped notch were used for profiles 1.5 and 2.0 mm thick, respectively. It is shown that a visco-brittle transition occurs in the temperature range of 20 – 90°C in galvanized samples subjected to plastic deformation. The critical temperature of brittleness T₃₄ of steel 350 decreases with a decrease in the thickness of rolled products from 3.0 to 1.5 mm due to a decrease in the rigidity of the stress-strain state under tension. At the same time, the size of ferrite grains in the studied ferrite-pearlite steels (1.17 – 0.22 C; 0.11 – 0.14 Si; 0.49 – 0.54 wt.% Mn) changes slightly and amounts to 8.0 – 8.9 μm. A crystalline fracture surface oriented perpendicular to the axis of the sample is formed in the zones of bending of 3-mm light-gage steel structure elements in the region of the critical temperature of brittleness in the central zones of the fracture. In the samples 2 and 1.5 mm thick, the fracture surface is formed by two shear planes oriented at an angle of 45° to the sample axis at the base of which the colonies of facets of trans-crystallite cleavage are located. Galvanized steel 350 profiles (GOST R 52246) with a ferrite grain size 8.8 – 8.9 μm can be used in light steel thin-walled (1.5 – 3.0 mm) structures in the operation temperature range of up to – 65°C.

Shape memory alloys such as titanium nickelide are currently used in different fields of engineering, construction, and medicine, due to their unique ability to recover significant inelastic deformations upon heating. Titanium nickelide plates as structural elements or medical devices are exposed to complex temperature and force impacts during operation, which leads to a change in the stress-strain state of the material. For example, a plate rigidly clamped on one side significantly changes the surface curvature during thermal cycling under load or as a result of heating after preliminary plastic deformation. Similar exposures are implemented in the devices in which the plate is used as a sensitive element, for example, temperature sensors, electrical contacts, smart ailerons, etc. When designing these elements, it is important to take into account changes in such deformation parameters as curvature, deformation, and shape recovery coefficient. The lack of information on those parameters is observed for titanium nickelide plates. We present the results of the experimental study of the shape reduction of a titanium nickelide plate both during isothermal unloading after plastic deformation and during thermal cycling under the impact of a constant bending force. It is shown that plastic deformation of the plate under isothermal conditions with an increase in the initial radius of the curvature by 3.35 times leads to an increase in the curvature by 4.83 times after pseudoelastic unloading. It is shown that the shape memory effect after isothermal bending of a rectangular titanium nickelide plate increases as the prescribed radius of the curvature decreases. Moreover, the curvature under constant load changes during thermal cycling in a complex way. The results of the study can be used in designing devices based on titanium nickelide plates.

Methods for testing the homogeneity of two independent samples refer to a classic area of mathematical statistics. Various criteria for testing the statistical hypothesis of homogeneity in different statements have been developed and their properties have been studied for more than 110 years since publication of the fundamental Student’s article. Nowadays, the streamlining of the totality of gained scientific results has become an urgent problem. It is necessary to analyze the whole variety of problem statements for testing the statistical hypotheses of the homogeneity of two independent samples, as well as the corresponding statistical criteria. Such an analysis is the goal of the article. We summarize the main results regarding the methods for testing the homogeneity of two independent samples and their comparative study which allows system analysis of the diversity of such methods in order to select the most appropriate for processing specific data. The main statements of the problem of testing the homogeneity of two independent samples are formulated using the basic probabilistic-statistical model. A comparative analysis of the Student and Cramer — Welch criteria designed to test the homogeneity of mathematical expectations is presented along with substantiation of the recommendation on the widespread use of the Cramer – Welch criterion. The criteria of Wilcoxon, Smirnov, Lehmann – Rosenblatt are considered among nonparametric methods for testing homogeneity. Two myths about the Wilcoxon criteria are dismantled. Analysis of the publications of the founders revealed the incorrectness of the term «Kolmogorov – Smirnov criterion». To verify the absolute homogeneity, i.e. coincidence of the distribution functions of samples, it is recommended to use the Lehmann – Rosenblatt criterion. The current problems of the development and application of nonparametric criteria are discussed, including the difference between nominal and real significance levels, which complicates comparison of the criteria in power. The necessity of taking into account the coincidence of the sample values (from the view point of the classical theory of mathematical statistics, the probability of coincidences is 0) is marked.