Cu–Ti composite particles were obtained using the method of copper deposition from its sulfate solution onto titanium powder particles with simultaneous mechanical activation (MA) of the mixture in an AGO-2 planetary ball mill for 5 min. CuSO₄ ·5H₂O concentration in the solutions was 10 and 16 % providing a molar ratio of Cu/Ti = 0.85 and 1.36, respectively, in case of complete copper reduction. When mechanically activated, copper is rapidly reduced to a highly dispersed partially amorphous powder and composite particles with a fine laminate structure and high reactivity are formed. The composite powders obtained were washed and stored in argon atmosphere, since reduced copper is highly active and rapidly oxidizes in air to Cu₂O. After drying, the mixture was additionally mechanically activated during 5 min. Billets 3 mm in diameter and 1.5 mm in height were pressed from the obtained powders and heated in atmosphere to 700–1200 °C. When the samples were heated, an intense reaction began with heat release (thermal explosion) and formation of intermetallic compounds of TiCu, Ti₂Cu₃ and Ti₂Cu. The critical ignition temperature for the composite powders obtained by MA with simultaneous copper deposition from its solution is 480 °С, which is 400 °С lower than the ignition temperature of a conventional mixture of titanium and copper powders. The alloy has a dendritic structure at heating temperatures close to the melting point. When the melting point is exceeded by more than 100 °C, phase distribution in the alloy becomes more uniform, and their size decreases.

The peculiarity of obtaining metal powders by direct current electrolysis is changes in the morphology of particles over the loose deposit layer thickness up to the formation of large spherulites. Deposit should be periodically removed from the cathode in order to obtain a powder with homogeneous composition. This paper justifies the choice of the parameter describing the change in loose deposit properties, and proposes a method for determining the periodicity of its removal from the cathode. Loose zinc deposits were obtained at 25 °C from zincate electrolyte containing 0.3 mol·l^–1 of ZnO and 4 mol·l^–1 of NaOH at a current setpoint exceeding 6 times the limiting diffusion current calculated using the smooth electrode. Electrode potential, deposit thickness and evolved hydrogen volume were measured directly in the process of electrolysis. Current redistribution between the metal reduction and hydrogen evolution leads to a change in the structure of loose deposit particles. It is shown that the differential current efficiency of zinc is the parameter describing the change in the loose zinc deposit density. Its value should not exceed 0.96 to ensure deposition of loose deposit with homogeneous properties. A further increase in current efficiency will lead to the formation of aggregates at the deposit growth front. It is proposed to determine the periodicity of loose deposit removal from the cathode using the empirical equation for the time dependency of differential current efficiency of zinc. The mathematical and statistical analysis of the data obtained in six replicates was carried out. The interval approach made it possible to significantly narrow the range of permissible differential current efficiency values and, as a consequence, to determine empirical equation coefficients with acceptable accuracy and calculate the growth time period of a deposit with homogeneous structure. The obtained approach can be used to estimate the time period of loose metal deposition accompanied by hydrogen evolution.

This paper studies the effect of surfactants on the particle size of metal nanopowders (NPs): iron, cobalt and nickel synthesized using chemical-metallurgy method – hydrogen reduction of hydroxide compounds FeOOH, Co(OH)₂ and Ni(OH)₂ at 400, 285, and 280 °С, respectively. These hydroxides were pre-synthesized via chemical deposition from the corresponding nitrate solutions with NaOH alkali solution (10 wt.%) using sodium dodecyl sulfate (SDS) (0.1 %) and ethylenediaminetetraacetic acid disodium salt (EDTA) (0.3 %). The obtained NPs were studied using such methods as X-ray diffractometry (XRD), scanning electron microscopy (SEM), and measurements of the specific surface area by low-temperature nitrogen adsorption. According to XRD shows that all the obtained samples of NPs Fe, Co and Ni contain pure metallic phases. The results of electron microscopic analysis and measurement of the specific surface area of powder samples show that the addition of various surfactants to the initial synthesis medium of hydroxide compounds has a significant effect on the size and morphology of the obtained NPs. It was found that the addition of 0.1 % SDS leads to a decrease in the average size of the obtained particles, and the presence of 0.3 % EDTA contributes to the formation of larger metal particles. It was shown that the use of 0.3 % EDTA in deposition of initial hydroxide precursors makes it possible to obtain metal NPs with the narrowest crystallite size distributions.

Experiments were conducted on high-energy surface treatment of a structural steel substrate with a flow of tungsten, nickel, and titanium nitride powder particles. The impact pressure of the steel target and particles accelerated by explosion energy was estimated using the momentum conservation equation and the linear equation of the particle material shock adiabat. It was found that the impact pressure of the target and particles is 62 GPa for a tungsten particle, 48 GPa for a nickel particle, and 41 GPa for a titanium nitride particle. The heating temperature of particles during their collision with the steel target surface was calculated taking into account the conditions of mass and momentum conservation at the shock wave front. The maximum heating temperature of particles at the point of their collision with the substrate surface (at a particle velocity of 2000 m/s) is 1103 K for tungsten particles, 755 K for nickel particles, and 589 K for titanium nitride particles. It was shown that the steel target strength increases when it is subjected to high-energy treatment with a flow of particles. The maximum hardening of the steel target surface layer increases by 32–55 % compared to initial microhardness and is observed at a depth of 2–4 mm from the treatment surface. Then it decreases to the value of starting material microhardness (170 HV) at a distance of 15–20 mm from the treated surface.

The paper focuses on obtaining Ti₂AlC and Ti₃AlC₂ MAX phase powders by self-propagating high-temperature synthesis (SHS) from oxide raw materials using magnesium-thermal reduction. The source of titanium was its oxide TiO₂ with magnesium used as a reducing agent. Cleaning from magnesium oxide was conducted in hydrochloric acid solution with a concentration of 1:3 at t = 70 °C. The yield of the target product in magnesium thermal reduction is 35–40 %. It was found that the synthesis product consisted of Ti₂AlC, MgAl₂O₄ and TiC after chemical leaching in hydrochloric acid at the stoichiometric ratio of components. MgAl₂O₄ spinel was formed due to the lack of magnesium reducing agent in the green mixture, while some part of aluminum reacted with titanium oxide reducing it and forming Al₂O₃ . It led to MgO·Al₂O₃ formation. An increase in the excess magnesium content in the green mixture from 20 wt.% to 30 wt.% leads to the complete reduction of titanium from its oxide by magnesium with the formation of Ti₂AlC MAX phase and titanium carbide. A decrease in carbon content by 10 wt.% in the green mixture leads to a decrease in titanium carbide content to 4 %. With an excess content of soot from 20 % to 35 %, a product containing Ti₃AlC₂ , Ti₂AlC and TiC MAX phases is formed, and the mass fraction of Ti₃AlC₂ increases from 86 % to 89 %, respectively. The resulting powders are agglomerates consisting of thin plates of 70–100 nm thick MAX phases. 87 % of such agglomerates are less than 65 μm in size.

A new method is proposed for the engineering of SiC-based ceramic-matrix composite materials strengthened by discrete carbon fibers and single-crystal silicon carbide nanowires. Depending on the macrokinetic characteristics of the combustion process, either diffusion layers, particles of silicon carbide or silicon csrbide nanowires with a diameter of 10–50 nm and a length of 15–20 μm can be formed on the surface of carbon fibers. The sequence of chemical transformations and structure formation in the combustion wave of Si–C–C₂F₄ and Si–C–C₂F₄–Ta mixtures was studied. Silicon carbide nanowires formed in the combustion wave had high crystallinity and a defect-free TaSi₂/SiC interface. The misorientation of the lattices at the interface is about 6 %. Nanowires are able to relax the mechanical stresses during growth via the rotation along the growth direction. The optimal combustion temperature for the growth of silicon carbide nanofibers is 1700 K at a ratio of C₂F₄ : C = 2. The lower temperature threshold for the growth of silicon carbide nanowires is caused by a decrease in the yield of reactive fluorides, while the upper temperature threshold is caused by a failure of the adsorption blocking mechanism on the surface of the nanofibers and the destabilization of the TaSi₂ + Si eutectic droplet. Composites with a SiC–TaSi₂ ceramic matrix and a relative density of 98 %, a hardness of 19 GPa, a flexural strength of 420 MPa, and a fracture toughness of 12.5 MPa·m^1/2 were obtained by hot pressing An increase in the strength of the carbon fiber-matrix interface has manifested in the suppression of carbon fiber pull-out from the matrix.

The study covers the effect of nickel boride (Ni₃B) additives on phase-structure formation, physical and mechanical properties and resistance of iron – high-carbon ferrochrome powder (35 wt.%) to abrasive wear. It was found that Ni₃B additives provide the formation of a multiphase, microheterogeneous structure of a matrix-filled material consisting of chromium steel and solid inclusions of complex chromium-iron carbides such as Ме₃С, Me₇C₃ and Me₂₃C₆ and borides FeB, Fe₂B that significantly increase the microhardness of solid phases from 8.34 to 11.65 GPa. It was also revealed that the increase in the content of a doping additive from 3.5 to 8.7 wt.% increases base material resistance to abrasion wear from 6.9 to 12.2 km/mm and decreases hardness from 75 to 68 HRA and bending strength from 1560 to 844 MPa. The method of optical profilometry was used to study the topographical features of worn surface morphology to estimate the depth and local development of wear on sample surfaces with standardized roughness parameters calculated based on 2D or 3D profiles. Average roughness parameters for each composition were found to be R_a = 0.44÷0.6, R_z = 0.49÷1.2 μm, and R_p = 0.26÷0.56 μm for materials doped with Ni₃B, and R_a = 1.860 μm, R_z = 0.813 μm, R_p = 3.356 μm for the base material. It was shown that the promising compositions that combine acceptable physical and mechanical properties and improved abrasive wear resistance are materials based on the Fe–35%FeН800 system containing 5.2–6.9 wt.% of Ni₃B.

The study covers physicochemical characteristics and gas sensitivity mechanisms of nickel oxide (NiO) and nickel ferrite (NiFe₂O₄) obtained by levitation-jet synthesis. The properties of synthesized materials were studied using various spectroscopic methods. XPS showed that the presence of Ni³⁺ ions in samples decreased significantly with an increase in the specific surface area of the powders and decrease in the average diameter of their particles. In this regard, it can be concluded that the number of uncompensated Ni²⁺ vacancies in such samples also decreases, and concentration of O^2– vacancies, on the contrary, increases significantly. The Raman spectra of nanoscale NiO lacked the magnon band, which is usually observed at ν = 1500 cm^–1 , whereas the spectrum of nanoferrite sample had a pronounced 2M band, which indicates an increase in spin correlation. According to the analysis of UV spectra of the samples obtained, there is an increase in reflectivity values with an increase in wavelength for large nanoparticles compared to the corresponding values for small particles. In this regard, we assumed that Ni-based oxide nanoparticles are semiconductors with an indirect transition to band gap energy, and this is in sharp contrast to the data obtained earlier by other researchers. Gas sensitivity of nanoscale powders was investigated in relation to carbon monoxide and nitrogen dioxide at operating temperatures of 350–500 °C. Evaluation of the obtained results allowed us to conclude that the operating characteristics of sensors proposed by us are superior in a number of parameters to the similar characteristics of sensors made of commercial powders, as well as of powders obtained by other synthetic methods.

The paper provides a review of results obtained when using metallization coatings to protect the outer surface of electric centrifugal pump (ECP) equipment against the complicating factors in oil wells. Metallization coating is applied by thermal spraying using the method selected based on the chemical composition, materials used and properties of the finished coating. The most common coatings on the Russian market are Monel and alloys based on austenitic stainless steel applied by methods of electric arc metallization or high-speed spraying. Traditional coatings obtained by thermal spraying feature by insufficiently high level of physical, mechanical and chemical properties. The studies of failed cases of submersible motors show that most critical shortcomings of the coatings used include insufficient resistance to mechanical impact and abrasive wear, higher electrochemical potential in relation to the base metal, application technology violations, and significant coating porosity. One of the main reasons for the observed shortcomings is the limited number of traditionally used methods and materials. In order to solve the problem of using protective coatings for submersible motors, significantly improve their properties, service life and economic efficiency, it is necessary to use modern achievements of science in the development of coatings to protect metal surfaces from wear and corrosion, namely: to expand the number of methods and materials for coating application; to develop a methodology for coating quality assessment; to develop a methodology for assessing the economic efficiency of protective coatings. Solving these tasks will enable a reasonable technical and economic choice of a specific submersible motor coating for specific operating conditions.