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This paper considers the laser additive manufacturing process using the heat conduction equation with an instantaneous point heat source. It is shown that, under certain limitations, the depth of the substrate melt pool is accurately described by a self-similar solution. Two-parameter correlations for the melt pool depth and width with the Peclet number (the ratio of the scanning speed to the thermal diffusivity) and the dimensionless enthalpy (the ratio of the specific energy absorbed by the material to the energy required for melting) are derived. Criteria for the occurrence of two melting modes - keyhole and conduction - are established. It is demonstrated that the derived analytical correlations are in good agreement with experimental data.

This paper describes the CCDS2000 detonation coating system and demonstrates its capability for depositing electrically insulating and wear-resistant aluminum oxide coatings. The dielectric strength of the coatings exceeds 25 kV/mm within a thickness range of 50-300 μm. The coatings exhibit an electrical resistivity ρ_e > 2.67 × 10¹³ Ω·cm at 20°C and a relative humidity of up to 59%. A further increase in humidity caused a sharp decrease in ρ_e by 2-3 orders of magnitude. The coatings exhibit adhesion to a steel substrate of 60-70 MPa, a microhardness value HV0.1 = 1522-1655, and a porosity of 0.35-1.00%. Evidently, the C₂H₂ + 2O₂ detonation mixture is optimal for obtaining electrically insulating coatings, whereas the 0.69C₂H₂ + 0.53C₃H₆ + 2.51O₂ mixture yields the best wear resistance. The use of the dual-fuel mixture results in a fourfold increase in abrasive wear resistance and a 34% improvement in erosive wear resistance.

This study investigates a friction stir welding process for joining high-strength aluminum alloys. By implementing an active liquid cooling system and a post-weld aging treatment, a weld strength equivalent to the base material is achieved. The effect of cooling intensity on the microstructure and mechanical properties of the welds is examined. Optimal welding parameters for producing equal-strength joints are identified.

This study investigates the contact interaction between a thin composite strip and the rolls during rolling, focusing on conditions that ensure a horizontally straight exit end. The values of friction coefficients required to maintain a straight exit end during asymmetric rolling of a multilayer metallic material are determined. A finite element modeling of asymmetric rolling of a five-layer composite is performed with varying friction coefficients on rolls. The tool-workpiece interaction is modeled using the Amontons-Coulomb friction law, with the friction coefficient ranging from 0.1 to 0.4. The results show that a friction coefficient of 0.2 on both rolls minimizes the curvature of the exit end, resulting in an almost perfectly straight strip. For this optimal case, the stress-strain state is analyzed and the linear velocity distribution across the strip in the rolling direction is investigated. The analysis suggests that, upon passing across the deformation region, all material points move at a uniform velocity, which is significantly lower than the peripheral velocity of the lower roll, indicating persistent slip of the strip at the lower surface of the roll.

The results of studies on the synthesis of anionic substances based on a mixture of higher carboxylic acids isolated from linseed oil as well as individual linolenic acid (C18:3) are presented. Potassium, sodium and calcium salts were obtained based on synthesised sulphonic acids at a ratio of 1 : 2 : 1 at room temperature. The synthesised compounds are characterised by the necessary physicochemical, surface-active and anticorrosive functional properties. It is shown that the maximum surface activity is observed in the sodium salt of sulphated linolenic acid (the surface tension at the kerosene-water interface decreases from 42.4 to 4.1 mN/m). This fact indicates the surface activity of the compound the molecules of which are diphilic and include a large hydrocarbon fragment. The maximum efficiency of the compounds in protecting against carbon dioxide corrosion is 98.7 % at a concentration of sodium salt obtained from linolenic acid 100 ppm. As a result of the conducted studies, it was established that based on polyunsaturated fatty acids contained in linseed oil as well as individual linolenic acid, the synthesised surfactants are effective inhibitors of corrosion of low-carbon steels when protecting against carbon dioxide corrosion in mineralised environments at elevated temperatures.

The effect of the concentration of lanthanum introduced into high-silica TsVN zeolite (the zeolite with HZSM-5 structure of MFI type) in methanol conversion into С₂-С₄ olefins and p-xylene has been investigated. Lanthanum-modified zeolite catalysts with La content 1.0-5.0 wt% were characterised by X-ray diffraction, low-temperature nitrogen adsorption, and temperature-programmed ammonia desorption. It has been shown that an increase in lanthanum content in the catalyst causes a decrease in specific surface area, total pore volume and mean pore diameter. As a result of La interaction with acidic OH groups of zeolite, the strength and amount of strong Brønsted acid sites decrease, while new stronger Lewis acid sites are formed. It has been determined that the yield of С₂-С₄ olefins and selectivity to p-xylene depend on the ratio of acid sites of different types, the volume and mean diameter of pores in zeolite, which are controlled by lanthanum content variation. The maximum yield of С₂-С₄ olefins (33.7 wt%) from methanol at 400 °C is achieved over the catalyst modified with 5.0 wt% lanthanum. The maximum yield of xylenes (21.7-22.6 wt%) with p-xylene selectivity equal to 71.6-79.3 % is achieved over the catalyst modified with 3.0-4.0 wt% lanthanum.

Studies of CO₂ sorption by composite sorbents based on the active component (branched polyethylenimine) dispersed using a porous support have been carried out. Composite materials with a branched polyethylenimine content of 40 wt% were synthesised on the basis of four porous supports of different chemical nature, including two polymer materials, silica gel and aluminium oxide. The sorption properties of the obtained composite sorbents were studied in the process simulating the removal of CO₂ from biogas (CO₂ concentration in the gas mixture was in the range from 15 to 50 vol%). Based on the results of the sorption experiments, the values of the dynamic sorption capacity and enthalpy of CO₂ sorption were determined for the materials. It is shown that the sorption properties of composite sorbents are mainly determined by the choice of a porous support. The analysis of thermal energy consumption for the regeneration of composite sorbents within the adsorption cycle was carried out, on the basis of which the promising materials for the extraction of CO₂ from biogas were selected.

Results of the studies on surface cleaning of the end-of-life R-Fe-B (R = Nd, Pr, Tb, Dy) system magnets by chemical etching to involve them in recycling are presented. The material for experiments included magnets that were disassembled from the end-of-life hard disk drives for personal computers. The choice of these parts was conditioned by their low cost, easy disassembling, and small size. Disassembled magnets were demagnetized at 623 K and medium vacuum through 4 h. Sandblasting with slag abrasives supplied at a pressure of 300 kPa was carried out to remove the electrodeposit coating from their surface. A specimen was prepared on the cleaned surface, which was subjected to oxidation under natural conditions. The effect of acid type (nitric, hydrochloric, sulphuric) and acid solution concentration on the efficiency of etching the oxidised surface and on the behaviour of rare-earth and doping elements during chemical etching was investigated. The morphology of specimen surface and oxygen content were analysed by scanning electron microscopy. It has been found that chemical etching with 0.5-1.0 wt% sulphuric acid solution for 1 min leads to a decrease in oxygen content from 3.1±0.2 to (2.2±0.2)-(2.4±0.1) wt% on the surface of the major stoichiometric phase of the alloy, as well as to etching the phases enriched with rare-earth metals off the surface and to the formation of pores on their place.

The influence of phthalic anhydride concentration in the reaction mixture on the composition and colloidal stability of the products of catalytic acylation of petroleum tar in the presence of AlCl₃ has been assessed. Tar from the West Siberian oil and the products of its interaction with phthalic anhydride were used as the objects of investigation. The analysis of changes in the composition, structure and aggregation stability of tar and its components was carried out using liquid adsorption chromatography, IR spectroscopy, and visible spectrophotometry. The dynamics of asphaltene aggregate growth was estimated by the dynamic light scattering method. It has been found that at phthalic anhydride concentration of 25 % per tar mass, about 7 wt% of resins lose the ability to dissolve in n-alkanes and are converted into asphaltenes due to the incorporation of carboxybenzoyl radical into their molecular structure, which is confirmed by the results of IR spectroscopy. The process of tar acylation increases its colloidal stability by 20-30 %, depending on the ratio of reagents.

A highly dispersed palladium catalyst supported on nitrogen-doped carbon nanotubes was studied in CO₂ hydrogenation to formic acid in the liquid phase at temperatures of 100-150 °C and high pressure. It has been shown that an increase in the catalyst loading (from 1.6 to 4.0 g/L), total pressure (from 20 to 40 atm) and P_H2/P_CO2 ratio (from 1 : 1 to 2 : 1) in the reactor allows increasing the yield of formic acid by over 5 times. At 150 °C, the maximum formic acid yield (27.6 g/g_Pd) with a selectivity of 98 % was obtained. The presence of a lot of single palladium atoms in the catalyst, in addition to its nanoparticles 1.5 nm in size, was determined to have a positive effect on the course of CO₂ hydrogenation, as in the case of formic acid decomposition. On the basis of the high efficiency of this catalytic system in the reaction of formic acid decomposition to produce pure hydrogen, a conclusion was made about its potential for use in the cycle of chemical storage of hydrogen based on CO₂.