A rapid and easy to use method for monitoring transformations of heavy oil fractions during secondary processes of oil refining is proposed. The method is based on the study of changes in the molecular weight characteristics by gel-permeation chromatography (GPC) using a refractometric detector. Optimal conditions for registration of the chromatograms (temperature, eluent consumption and its composition) were specified. Heptane, toluene, and toluene added with 1% and 5% of methanol were studied as eluents, the polarity indices being arranged in a series 0.2; 2.4; 2.43; 2.54. The effect of the nature of the solvent on the type of the product chromatogram is determined. It is shown that addition of a polar solvent to a nonpolar one increases the polarity index, reduces both the degree of association of petroleum molecules and adsorption on the gel. The most available toluene which meets the GPC requirements is chosen as an eluent. Addition of 1% CH₃OH to the eluent promotes suppression of polyelectrolyte effects and adsorption. The revealed absence of the dependence of the retained volume and the type of chromatograms on the eluent flow rate and temperature indicates that separation is carried out under conditions of exclusion and completely obeys the theory of exclusive liquid chromatography. The transformation of raw materials during a technological process of oil production at the JSC «ANKhK» was studied using the GPC method under above-mentioned chromatographic conditions. We have studied vacuum distillate of the primary oil refining unit ELOU+AVT-6 (VD) and the product of hydrocracking of the vacuum distillate of the 123PM unit (HVD). It is shown that determination of the molecular weight characteristics provides an important information about the behavior of technological processes. The HVD meets the requirements for hydrocracking products. A decrease in the content of aromatic hydrocarbons in comparison with the raw feedstock is proved by the data of thin layer chromatography (TLC).

Synthesizing and studying the properties of nanomaterials based on layered molybdenum disulfide, often face a need for rapid elemental analysis and prompt return of the material to the customer. Sometimes, nanoparticles of molybdenum disulfide are to be modified with metal compounds to improve the catalytic or magnetic properties of the material. We propose a method for rapid X-ray fluorescence determination of molybdenum and cobalt in the range of 10 – 50% in such compounds using a bulk method without dilution. Analytical signals were measured at the wavelengths of MoKα and CoKα lines using a VRA-30 spectrometer (Carl Zeiss, Germany; X-ray tube with Rh anode). The metal content was calculated using the derived coupling equations. The determination error ranges within ±2.7% (abs.) and 1.4% (abs.) for Mo and Co, respectively. Correctness of the method was confirmed for a batch of synthesized compounds by comparison of the results obtained with the data of XRF analysis using the dilution method traditionally used in the laboratory. The proposed rapid method provides simplification of the procedure and more than 4-fold shortening of analysis in time, the sample being preserved and can be used for further research.

An approach to the simultaneous isolation of As (III) and Se (IV) from solutions on a new S,N-containing sorbent followed by determination of the analyte in the sorbent phase using total reflection X-ray fluorescence (TXRF) has been proposed. To match the goal, a sorbent with a branched structure was synthesized on the base of polyacrylamide modified with formaldehyde and hydrogen sulfide. This is a heteroatomic copolymer containing sulfide bridges in the chain and crosslinking by a tertiary amine. Conditions for the quantitative co-extraction of As (III) and Se (IV), i.e., sorption in solutions of 1 M HNO₃ with calcium ions present, heating to 60°C and phase contact time of 1 h were determined. The mechanism of sorption interaction of the analytes under specified conditions is discussed. It is shown that a 100-fold excess of iron, zinc and copper does not interfere with the extraction of analytes, thus providing the possibility of As (III) and Se (IV) isolation from different types of raw materials and processed products using the synthesized sorbent. A method for the direct XRF quantification of arsenic and selenium with sr 0.09 and 0.08, respectively, in the sorbent phase has been developed. The correctness of the results was confirmed by the ICP-MS method in analysis of aqueous reference solution after dissolution of the sorbate in HNO₃ (1:1).

Creeping ultrasonic waves are used in echo flaw detection of near-surface and near-bottom zones of metal products of plane-parallel or cylindrical shape. The creeping (lateral) waves are also used in testing products by the time-of-flight diffraction method as the earliest (reference) signal, followed by the useful signals of waves diffracted on metal discontinuities. The purpose of this study is to evaluate the ability of the creeping wave to propagate over a concave metal surface. We have studied experimentally the attenuation of the amplitude of a creeping wave with the distance upon wave propagation over concave metal surfaces of different radii. The velocity of propagation of the creeping wave does not depend on the radius of curvature and equals to the velocity of the bulk longitudinal wave. The results obtained provide the possibility of using the time-of-flight diffraction method in control of the objects with concave surfaces, in particular, for in-tube testing.

The composition of sludges (wastes of bearing industry enterprises) is determined by the characteristics of the abrasive tool used upon manufacturing, grade of the processed material, cutting-tool lubricant (CTL) and modes of treatment. We present the results of studying the mineralogical and grain size composition of the regenerated grain from bearing sludges. The material under study is shown to have the following composition, %: abrasive particles — 5 – 8, metal particles — 50 – 90, binder — 2 – 5, balance — SOG, oil and various pollutants. The dispersion of solid particles ranges within 0.1 – 0.3 mm. The abrasive grains have a predominantly splintery shape, the individual binder particles being observed on their surface. The interlayer-cemented aggregates of two — three crystals and a large number of small splintery particles are also present. It is shown that the samples with a regenerated material containing fine abrasive grain and metal particles as a filler exhibit the highest mechanical strength and thermal conductivity. The results obtained can be used when using regenerated abrasive grain from sludge for manufacturing, e.g., grinding wheels, preparation of a molding abrasive mixture, etc.

The goal of the study is to compare the properties of epoxy composites with initial and water-treated (hydrated) water-hardening binders (gypsum and cement). The effect of 50% filling of ED20 epoxy resin with initial and water-treated binders (cement and gypsum) on the strength of composites, their structure and physicomechanical properties is considered. An increase in such indicators as the elastic modulus value, fire- and heat resistance, as well as the resistance to organic solvents was observed. Optical and SEM microscopy revealed a difference in their structure compared to the original composites. However, there was no noticeable effect on the strength characteristics of conventional heat treatment (50 – 60°C). After heating at 250°C, the effect of thermal hardening (and thermoplasticization) was observed for filled composites: a significant increase in the compressive strength (and plasticity), microhardness, and abrasion resistance, compared to an unfilled polymer. The results obtained can be used to develop polyepoxide materials with new properties necessary for solving important production applications.

Modification of polymers with fillers provides the possibility of changing their physical and mechanical properties. The goal of the study is a comprehensive analysis of the effect of nanodispersed additives and other powdery substances on the strength of multilayer composite materials (CM). A series of multilayer composite specimens based on fiberglass and carbon fabric was made with the addition of fillers in a concentration of 1 and 3 wt.% to an epoxy polymer matrix. Nanopowders of silicon dioxide Tarkosil (T20, T50, T80, T110), fine powders of copper, collagen and cellulose fibers were used as fillers. Two types of tests, i.e., for compression and for impact were carried out. The introduction of nanopowders into CM changes their strength properties: the samples added with T110 nanomaterial withstand the maximum compressive load at a concentration of 1 and 3 wt.%. The results of impact tests of the samples with fillers and computer simulation of the impact and punching of the samples using the ANSYS/LS-DYNA software product, are presented. A method for numerical simulation of the impact process has been developed, which provides studying the dynamics of deformation and fracture of multilayer samples. Impact tests of the samples carried out at different values of the impact velocity (from 380 to 450 m/sec) revealed either puncture of the CM plates or damage such as delamination and splitting. In the impact test of multilayer specimens of composite materials with fillers added to the epoxy polymer matrix, the interlayer defects appeared in the form of delamination; samples without additives were pierced through under the impact. The experimental data on the degree of damage to multilayer plates after the impact matched the results of computer simulation.

An increase the operating temperature range of structural elements and aircraft assemblies is one of the main goals in developing advanced and new models of aerospace equipment to improve their technical characteristics. The most heat-loaded aircraft structures, such as a combustion chamber, high-pressure turbine segments, nozzle flaps with a controlled thrust vector, must have a long service life under conditions of high temperatures, an oxidizing environment, fuel combustion products, and variable mechanical and thermal loads. At the same time, modern Ti and Ni-based superalloys have reached the limits of their operating temperatures. The leading world aircraft manufacturers — General Electric (USA), Rolls-Royce High Temperature Composite Inc. (USA), Snecma Propulsion Solide (France) — actively conduct fundamental research in developing ceramic materials with high (1300 – 1600°C) and ultrahigh (2000 – 2500°C) operating temperatures. However, ceramic materials have a number of shortcomings attributed to the high brittleness and low crack resistance of monolithic ceramics. Moreover, manufacturing of complex configuration and large-sized ceramic parts faces serious difficulties. Nowadays, ceramic composite materials with a high-temperature matrix (e.g., based on ZrC-SiC) and reinforcing filler, an inorganic fiber, (e.g., silicon carbide) appeared most promising for operating temperatures above 1200°C and exhibited enhanced energy efficiency. Ceramic fibers based on silicon compounds possess excellent mechanical properties: the tensile strength more than 2 GPa, modulus of elasticity more than 200 GPa, and thermal resistance at a temperature above 800°C, thus making them an essential reinforcing component in metal and ceramic composites. This review is devoted to silicon carbide core fibers obtained by chemical vapor deposition of silicon carbide onto a tungsten or carbon core, which makes it possible to obtain fibers a 100 – 150 μm in diameter to be used in composites with a metal matrix. The coreless SiC-fibers with a diameter of 10 – 20 μm obtained by molding a polymer precursor from a melt and used mainly in ceramic composites are also considered. A comparative analysis of the phase composition, physical and mechanical properties and thermal-oxidative resistance of fibers obtained by different methods is presented. Whiskers (filamentary crystals) are also considered as reinforcing fillers for composite materials along with their properties and methods of production. The prospects of using different fibers and whiskers as reinforcing fillers for composites are discussed.

Methods for evaluation of Young’s modulus (E_m) of structural materials by instrumented indentation using ball indenter have been considered. All these techniques are based on the solution of elastic contact problems performed by H. Hertz. It has been shown that registration of the initial elastic region in the «load – displacement» indentation diagram provides the E_m determination for metals and alloys. However, it is necessary to evaluate accurately the elastic compliance of a device, to use an indenter with a large radius R, and ensure a high surface quality of the test material in advance. Methods for E_m determation, when indentation diagrams are recorded in the elastoplastic indentation region, should include the effect of plastic deformation on the elastic displacement calculated by H. Hertz expression. However, it appeared essential to determine the relation between the elastic α_el and plastic h components of the total elastoplastic displacement α and the elastic displacement α₀ estimated by H. Hertz expression for a definite indentation load. A close correlation between α₀ and α_el is revealed for steels, aluminum, magnesium, and titanium alloys when using indenters with a radius of R = 0.2 – 5 mm (diameter D = 0.4 – 10 mm) and maximum indentation load F_max = 47 – 29430 N (4.8 – 3000 kgf). It is also shown that a gradual decrease in E_m is observed with an increase in R(D) at the same degree of loading F/D² for the same material. This fact was explained by the scale factor effect.

An analytical scheme for the analysis of silicified graphite SG-P, a four-phase composite material consisting of silicon, carbon, silicon carbide and silicon dioxide, has been developed. The procedure can be successfully used in the quality control of raw materials and in the study of the phase composition of finished products The porosity and density of the graphite base, as well as the impurities contained in the base and silicon change the course of silicification and the properties of the finished product as well. The impurities are the main reason for the formation of delamination, swelling, cracking and light spots on the treated surfaces. It should be noted that the iron content 0.023 – 0.17 wt.% in the carbon material intended for silicification, leads to catalytic graphitization of the artificial graphite and dispersion in the silicon melt. Methods of rapid assessment of the quality of raw materials are to be used to provide quick understanding of their suitability for manufacturing final products on their base. Quality control of the silicified graphite produced at the JSC «Research Institute Graphite» is carried out by determination of the phase composition of the finished product by chemical and X-ray diffraction methods of analysis. The content of silicon carbide (not less than 45%), unbound silicon and carbon (not more than 20 and 35%, respectively) affects the corrosion resistance and thermal expansion of silicified graphite.