The aim of the research is to obtain wear-resistant products from composite materials of a new type using the SHS technology. The Ti–Cu–C system was selected taking into account the data available in the scientific and technical literature. Various SHS charge compositions consisting of titanium powder, copper powder, and carbon black were experimentally burned to determine compositions that can burn during the SHS process and provide a melt containing titanium carbide and titanium cuprides as a binder featuring higher mechanical properties and lower melting points than pure copper. Model samples of products in the form of bushings with an outer diameter of 70 and 110 mm were produced by burning the SHS charge with selected compositions in a reactor followed by the compaction of the resulting melt with a force of 50–60 t. After the rough workpiece electrical discharge machining, samples were cut out for phase analysis, X-ray spectral analysis, and wear tests. With an optimal ratio of SHS charge components, titanium carbide and a binder in the form of titanium cuprides of different compositions were revealed in the model sample material. Using the method of testing for wear when sliding on a fixed abrasive under a specific pressure of 1 MPa, it was determined that the relative abrasive resistance of the new material at a hardness of 50–52 HRC is 1.8–2.0 units in comparison with the hardened tool and die steel Kh12MFL. In order to implement the technology in practice, an algorithm was developed for calculating the compositions of the newly formulated SHS charge, while its principle is such a ratio of components where the introduced carbon forms titanium carbide with titanium, and the added excess titanium forms titanium cuprides with copper. The developed material can be considered as promising for use as elements of equipment operating under abrasive wear conditions. This development is patented, Patent No. 2691656 (Russian Federation).

This paper focuses on obtaining cermet composite materials by SHS compaction. The study covers the effect of mechanical activation of metal components contained in reaction mixtures based on the Ti + C + Cr + Ni system when treated with grinding media in a ball mill. Two mechanical activation methods were used for Ti, Cr and Ni metal powders. In the first method, Cr and Ni powders were activated with grinding media separately from other reaction mixture components, and then mixed with titanium and carbon black powders. It is shown that the preliminary mechanical activation of inert components reduces the temperature and rate of combustion and increases the average size of carbide grains. In the second method, Ti + + Cr, Ti + Ni, and Ti + Cr + Ni powder mixtures were jointly processed in a ball mill, and then mixed with carbon black. This method provided mechanical activation of titanium particles with a minimum effect of grinding media on Cr and Ni powders. This led to an increase in the combustion rate and temperature, a decrease in the average size of carbide grains, and an increase in the composite structure homogeneity. A mechanism is proposed for the interaction of reagents (Ti + C) with the participation of activated Cr and Ni particles in combustion and structure formation zones, according to which the mechanical activation of inert components leads to their direct participation in the reaction interaction of titanium with carbon, which determines a decrease in the combustion rate and temperature and affects the fineness and structural homogeneity of compact composites. The results obtained were used to increase the structural homogeneity and fineness of the STIM-3B composite (Grade 3B synthetic hard tool material).

The paper focuses on the theoretical and experimental study of the mechanisms of reaction mixture combustion in the ≪chemical oven≫ mode in a three-layer Ni–Al/Ti–Co/Ni–Al sample. Experimental studies were carried out in a reactor in an argon atmosphere at atmospheric pressure and an ambient temperature of 298 K on rectangular samples pressed from Ni–Al and Ti–Co powder mixtures in the form of a three-layer package. The Ti–Co acceptor layer was in the middle of the sample, and the Ni–Al donor layer was outside. The acceptor layer thickness was varied from 4.3 to 13 mm, while the donor layer thickness (4.7 mm) remained constant. It was found that as the acceptor layer thickness increases, the combustion wave front propagation velocity and reaction initiation temperature decrease, and the maximum temperature in the front remains constant and equal to the melting point of the final product. The time of acceptor layer heating before the reaction increases. The acceptor mixture reaction proceeds in the thermal explosion mode when the thickness of the acceptor layer exceeds that of the donor one. Maximum temperature in this case is higher than the melting point of the final product. The inner layer synthesis modes change with an increase in the acceptor layer thickness: stationary – pulsating – extinction. The mathematical model of the three-layer sample high-temperature synthesis in dimensional variables is constructed taking into account heat transfer with the environment. As a result of experimental studies and numerical calculations, the critical thickness of the inner layer was found to be 15 mm, at which the inner layer combustion becomes impossible at fixed sizes of donor layers. Critical conditions for the combustion wave propagation along the acceptor layer are weakly dependent on the external heating source. The experimental technique and mathematical model of the layered system combustion can be used to assess the critical conditions for the metal composite synthesis in the frontal combustion mode.

The paper presents the results of an experimental study into the possibility of producing ultra-high temperature ceramics  constituting solid solutions of HfC and ZrC carbides by the single-stage electro-thermal explosion (ETE) method under pressure.  Adiabatic flame temperature and phase composition of the equilibrium final product were calculated based on thermodynamic  data. It was shown that when the ZrC content in the final product is less than 20 wt.%, adiabatic flame temperature reaches 3800– 3900 K, and the combustion product contains hafnium and zirconium carbides. The effect of mechanical activation modes in an  AGO-2 planetary centrifugal mill used for a reaction mixture containing Hf, Zr and C powders on its properties, phase composition  formation and the microstructure of carbide solid solutions was studied. It was shown that high-energy mixing in hexane leads to  the destruction of the crystal structure of Hf and Zr particles and the formation of amorphous composite particles. The synthesized  samples of ultra-high temperature ceramics were studied by X-ray phase and microstructure analyzes. It was shown that exothermic  synthesis leads to the formation of single-phase solid solutions of HfC and ZrC carbides with the average particle size of 0.2–1.5 μm.  The residual porosity of the binary carbides obtained is 10–12 %. It was found that, despite the high temperature of sample heating  during ETE under pressure, the particle size of the resulting solid solutions is significantly (by an order of magnitude) smaller than  the particle size of similar complex carbides (20–50 μm) obtained by other methods (SPS and hot pressing). This is associated with  the rapidity of the exothermic interaction of the reagents (10–50 ms) during ETE.

Refractory composite ceramic material in the LaB₆–W₂B₅ system with a component ratio of 50 : 50 vol.% was obtained  by reactive hot pressing in a graphite mold. A heterophase powder containing lanthanum hexaboride, metallic tungsten, and  amorphous boron preliminarily ball-milled for 20 h with tungsten balls was used as the initial reaction mixture. The average particle size of the milled mixture was 2.9 μm. A relative density of 92 % was achieved at a temperature of 1800 °C with isothermal holding  for 15 min at 30 MPa in an argon atmosphere. The structure and composition of the LaB₆–W₂B₅ material were studied by X-ray  diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The composition of the ceramics contained  two phases – cubic LaB₆ lanthanum hexaboride and hexagonal W₂B₅ tungsten pentaboride. The ceramic structure featured by  ordered lamellar W₂B₅ particles in a LaB₆ polycrystalline matrix. During the reactive hot pressing of the LaB₆–W–B mixture, the  predominant growth of W₂B₅ crystals along (101) atomic planes was observed. Resulting lamellar W₂B₅ particles were oriented in  the LaB₆ matrix perpendicular to the pressing load. Images obtained with electron microscopy were used for the three-dimensional  visualization of the LaB₆–W₂B₅ structure. Three-point bending tests were conducted on 3×3×30 mm samples. The dependence  of bending strength on the direction of applied breaking load was established. When a breaking load was applied perpendicular to  the surface of the lamellar W₂B₅ particles, the ultimate strength was 420 MPa, while when loaded along the plane of the particles,  bending strength increases to 540 MPa. The anisotropy coefficient of ultimate strength was 0.78.

The study covers the phase composition, morphology and properties of coatings deposited on steel by means of short pulse selective laser alloying of titanium carbohydride-based mechanocomposites. Mechanocomposites were fabricated by milling of Ti and Ti–Cu powders in a liquid hydrocarbon environment. The synthesized mechanocomposites and fabricated coatings are investigated by X-ray diffraction, scanning electron microscopy and optical microscopy. The phase composition of mechanocomposites is represented by titanium carbohydride phase with a size of powder particles ranging from 2 to 30 μm for powders without copper, and from 1 to 10 μm for copper-containing powders. Coatings fabricated from powder mechanocomposites have a gradient structure. The Ti(C,H) powder coating contains 48 vol.% of the titanium carbide phase in a shell of Fe–Ti intermetallic compounds. The Ti(C,H)–Cu powder coating contains 85 vol.% of titanium carbide inclusions surrounded by Ti(Fe,Cu) and CuTi₂ phases. Round-shaped carbide inclusions formed have a size of 50 to 200 nm, and dendritic ones are up to 5 μm. Coatings have a microhardness of 10 GPa and 8 GPa for compositions without and with copper, respectively. Coatings were tested for wear resistance under the conditions of dry friction in pairs with the balls made of steel and VK6 tungsten carbide alloy. Coefficients of friction for both coating types are 0.16–0.3 with the ball made of VK6 tungsten carbide alloy and 0.2–0.4 with the ball made of hardened steel. Coatings almost do not wear out under the counterbody load of 10 N and testing time of 20 min.

Porous nickel and nickel-cobalt alloy deposits were obtained by electrodeposition on a dynamic hydrogen bubble template. Deposition was carried out from chloride electrolytes in a galvanostatic mode at a current density of 0.3 A/cm². The porosity of the obtained deposits is associated with the macro- and micropores. It was found that the nickel and nickel-cobalt alloy deposits feature by different porous layer structures. In case of nickel, a typical foam structure is formed, while the Ni–Co alloy deposit morphology is more like loose (powder) metals. The total porosity of the obtained structures calculated based on experimental data decreased with the deposit thickness: from 0.4 to 0.1 for nickel foams, and from 0.9 to 0.8 for the Ni–Co deposit. It was shown that the dependences of the macropore number and the fraction of the surface occupied by them can be approximated by lognormal distribution. The agreement between the experimental values and values calculated by approximating equations indicates the stochastic nature of the macropore system formation. The catalytic properties of the obtained porous deposits toward the hydrogen evolution reaction in alkali were investigated. It was found that the decrease in the hydrogen evolution potential in comparison with a smooth electrode reaches 370 mV for nickel foams, and 440 mV for porous Ni–Co alloy deposits. However, the high porosity of the Ni–Co alloy caused poor adhesion of the deposit to the substrate; therefore, the porous Ni–Co deposit cannot be used without further strengthening. The dependences of the depolarization value during hydrogen evolution on the average diameter of pores, their number, and the macropore fraction were analyzed. Optimal properties of foams that reduce the potential of hydrogen evolution in alkali are as follows: pore diameters from 30 to 50 μm and their quantity from 50 to 100 pcs/mm².

The paper presents the results of experiments on the production of composite fibers based on polyacrylonitrile (PAN) and magnetite. For this, magnetite nanoparticles were synthesized by the method of chemical condensation from iron (III) chloride solutions with a concentration of 0.32 mol/l and iron sulfate with a concentration of 0.2 mol/l by gradually adding a 25 % aqueous ammonia solution. It was shown that a simple deposition method can be used to synthesize homogeneous nanoparticles of Fe₃O₄ magnetite with a particle size of 8–25 nm. This is confirmed by the results of X-ray phase analysis and transmission electron microscopy. Magnetite nanoparticles were then used to obtain PAN/Fe₃O₄ composite fibers by adding magnetite in a 7 wt.% PAN solution in dimethylformamide. Fibers were obtained from the PAN/Fe₃O₄ suspension in dimethylformamide by electrospinning. Scanning electron microscopy showed that magnetite nanoparticles are uniformly distributed throughout the fiber surface, and the fiber size is 288–658 nm. The comparison of PAN fibers without the magnetite additive and PAN/Fe₃O₄ fibers showed that the addition of magnetite leads to a decrease in the fiber diameter at the same polymer concentrations and electrospinning conditions. XRD and elemental analysis of PAN/Fe₃O₄ fibers showed that magnetite particles in the fibers did not change their chemical composition and represent single-phase magnetite in a polymer matrix. The results obtained in the studies showed the possibility of obtaining composite fibers based on magnetite by the electrospinning method. Resulting composite fibers may be useful in practical scientific and engineering applications.