The paper presents the results of studies of the fine structure, chemical and phase composition of boundaries between the components of the Cr₃C₂-Ti hard alloy containing 40 wt.% of titanium bond in the state after explosive pressing, as well as after heat treatment. The powder mixture was subjected to shock-wave loading at a heating temperature of 730 °C and pressure of 14 GPa to ensure the maximum compaction and consolidation of the powder mixture without sintering. Compact specimens were heat-treated by heating from 400 to 700 °С and holding in the oven for 1 hour followed by still air cooling. The equilibrium phase composition was calculated by numerical thermodynamic modeling using Thermo-Calc software. The structure and elemental composition were studied using FEI Quanta 3D and Versa 3D electron microscopes with an integrated focused ion beam system for foil fabrication, as well as FEI Tecnai G2 20F and Titan 80-300 transmission electron microscopes with foil transmission scanning mode. The Bruker D8 Advance diffractometer was used for X-ray phase analysis. It was shown that the formation of strong interfacial boundaries under explosive pressing of titanium and chromium carbide powder mixtures is accompanied by chemical interaction between the components with the formation of boundary layers having a total thickness of about 90 nm. There is a continuous monotonic change in the Cr and Ti content within the transition layer at the almost constant carbon content. The phase composition of layers corresponds to the equilibrium one calculated at the shock-wave compression pressure but it is thermodynamically nonequilibrium under normal conditions. When heated to 400 °C, boundary layers dissolve with the transition of Cr₃C₂-Ti hard alloys into a two-phase state. When heated to 700 °C, alternating layers of carbon-depleted chromium carbides (Cr₇C₃, Cr₂₃C₆) and titanium carbide (TiC) form along the interfacial boundaries by carbon diffusion from the original chromium carbide (Cr₃C₂) to titanium.

The article presents the results of studies into the gas-phase synthesis of silicon carbide fibers using silicon powder, polytetrafluoroethylene (PTFE) energy additive and polyethylene (PE) powder by self-propagating high-temperature synthesis (SHS). Stoichiometric mixtures were used for experiments. Green mixture components were mixed in a 3 liter drum with tungsten carbide balls for 30 min. The green mixture weight was 500 g. Experiments were conducted in the SHS-30 industrial reactor. Silicon + PTFE mixture combustion was accompanied by a rapid increase in pressure from 0.5 to 4.0 MPa in less than 1 s, and a relatively rapid pressure drop to 1.5 MPa in 1.5 min. The combustion rate was more than 50 cm/s. It was established that there was a spread of the mixture components during the combustion due to the high combustion rate and intense gas emission. A cottonlike material of light blue color was obtained; it consisted of 100-500 nm thick silicon carbide fibers. The maximum pressure in the reactor reached 3.1 MPa in 1 s during the silicon + PTFE + PE combustion and then decreased to 1.5 MPa in 3 min. The combustion rate was about 40 cm/s. The entire volume of the reactor was filled with blue-grey cotton-like silicon carbide and SiC powder with equiaxed 0.5-3,0 μm particles merged into conglomerates. Needle-like silicon crystals were formed in the transition layer between the powder and silicon carbide fibers. The results of experiments proved the possibility of obtaining silicon carbide nanofibers in relatively large quantities during the combustion of exothermic mixtures.

Cobalt-containing spinel-type ultramarine pigments were obtained by self-propagating high-temperature synthesis (SHS) in the ZnO-MgO-CoO-Al(OH)₃-Al system. Starting components were oxides of cobalt (Co3O4) and zinc (ZnO), aluminum hydroxide (Al(OH)₃), and 6-water magnesium nitrate (Mg(NO₃)₂•6H₂O). ASD-4 grade aluminum powder was used as a reducing metal. The samples with a diameter of 40 mm were synthesized. The combustion wave velocity was 1-2 mm/s, and the maximum synthesis temperature was 1180 °С. Parallel aluminum oxidation and aluminothermic reactions were the leading reactions providing the synthesis of spinel-based ceramic pigments in the layer-by-layer combustion mode. They result in charge self-heating up to the synthesis temperatures of spinels that are also formed with the release of heat. The fast destruction of Al(OH)₃ upon heating leads to the formation of active submicron y-A1₂O₃, which is involved in the further synthesis of finely dispersed spinel. Endothermic effects associated with Al(OH)₃ decomposition lead to burning sample cooling. This complicates the SHS implementation and requires additional heat supply. Gases emitted during thermal decomposition loosen the charge in the heating zone and reduce the maximum combustion temperature that allows solid-phase synthesis without any melting of the product to obtain it in a finely dispersed state. The microstructural analysis of samples by scanning electron microscopy confirmed the finely dispersed structure of pigments. IR spectroscopy and X-ray diffraction analysis revealed spinel structures. The paper presents the particle size distribution histograms for starting Al(OH)₃, Al(OH)₃ after heating, and synthesized spinels. It was shown that the pigment contains the maximum number of 903 nm particles. Therefore, obtaining finely dispersed spinel-type pigments by solid-phase synthesis directly in the combustion wave greatly simplifies their production process due to the absence of a grinding stage.

The study covers the elemental synthesis features of Hf-Ta-B-Ti-Si ceramic materials used to obtain promising high-temperature ceramics and analyze its structure and properties. The macrokinetics of self-propagating high-temperature synthesis (SHS) were studied. Combustion temperature and velocity as a function of initial temperature were plotted. It was established that chemical interactions occurring in the liquid phase play a pivotal role in the combustion process. Structure and phase formation processes were studied using the stopped combustion front technique. The mechanism of phase formation in the combustion wave was determined. The primary crystals of hafnium, titanium and tantalum diborides are precipitated from the super-saturated melt after the Si and Ti contact melting and B, Hf and Ta dissolution in the melt through the reactive diffusion process. A two-phase structure consisting of complex solid solutions based on diboride and borosilicide is formed due to the similarity of the crystal lattices. Porous synthesis products of the specified composition were milled into powders with the required particle size distribution for subsequent hot pressing (HP) or spark plasma sintering (SPS). It was found that specimens produced by HP, SPS, and SHS pressing feature a similar phase composition containing solid solutions based on diboride (Hf,Ti,Ta)B₂ and borosilicide (Hf,Ti,Ta)₅Si₃B. Specimens were made of ceramics produced using the above technologies for physical-mechanical testing. It was found that the hardness and elastic modulus of (Hf,Ti,Ta)B₂ solid solution are 2-3 times higher than that of (Hf,Ti,Ta)₅Si₃B borosilicide. Depending on composition, the density of ceramics produced varied from 8 to 6.5 g/cm³, which corresponds to a porosity of less than 5 %. Temperature dependences of heat capacity and diffusivity were determined. The heat conductivity of ceramics produced by HP and SPS was 24.05 and 23.1 W/(m•K), respectively.

Self-propagating high-temperature synthesis (SHS) was carried out in the Ni-Al-Ti-B system. The aim of the study was to obtain a composite material with ceramic and intermetallic frameworks and with a developed porous structure in the combustion mode in one process step from the «boron-titanium-large nickel-clad aluminum granules» powder system pressed by sequential batch compaction. The synthesis process featured by a stage nature where a highly exothermic reaction between titanium and boron formed a boride matrix with developed open porosity and acted as a «chemical furnace» to maintain the reaction in clad granules resulting in nickel aluminides. The aluminide melt impregnated the porous diboride matrix. The synthesis stages are reflected in the process thermograms. The final structure of the product features multi-scale porosity characterized by large round pores (~100÷160 μm in diameter) with the location corresponding to the position of clad granules in the original powder system. Small (0.1-5.0 μm) and some average-sized (up to 15 μm) diboride matrix pores are filled with nickel aluminides. The resulting material has a composite structure in analogy with interpenetrating frameworks - ceramic (TiB₂) and aluminide (NiAl, Ni₃Al). The diboride matrix is formed by randomly oriented small hexagonal crystals with a size of mainly ~0.2÷1.0 μm across. Diboride crystalline grains increase in size to 2-6 um in diameter and 0.5-2.0 μm in thickness near the macropores becoming strongly plate-shaped. The main size of intermetallic layers filling the pores between the diboride crystalline grains is ~0.2÷1.0 μm.

Experimental and analytical studies on the synthesis of a Ti-Al-based ceramic material with a nanoscale porous structure were conducted. The results of previous studies conducted by the authors showed that it is reasonable to obtain porous ceramic materials designed for filtration of liquids and gases by thermal explosion (throughout the sample) rather than by layer-by-layer combustion. Self-propagating high-temperature synthesis (SHS) was used to obtain nanoporous ceramic membranes from a mixture of powders, wt.%: 40Ti + 60Al in one stage with the TiAl3 formation. It was found that the synthesized material consists of the main phase TiAl3 with a small amount of aluminum oxidized into Al₂O₃ and unreacted. The microstructural analysis of the sample fracture showed that the resulting material has a developed surface and high open porosity. Empirically investigated open porosity is up to 48%, and the pore size ranges from 0.1 to 0.2 цт. The efficiency of the porous material obtained for the Ti-Al-based ceramic SHS filter reaches 99.999 %, gas flow resistance is 100 mmHg, filtration index is 0.062. Gas ultrafiltration capacity is up to 40 l/(cm²•h) at a pressure drop on the filter of 2 kPa, and water ultrafiltration capacity ranges from 2 to 10 l/(cm²•h) at a pressure drop on the filter of 0.1 MPa. Membranes made of ceramic materials with a gradient nanoporous structure by this method can be used as filter elements for small units providing fine water cleaning from bacteria, viruses, dissolved organic carbon, as well as for fine cleaning of air, process gases from dispersed micro-impurities and radioactive aerosols. The membrane SHS filters developed can also be used in units operating in aggressive environments and/or at high temperatures (up to 1000 °C).

The method of magnetron sputtering in an argon, nitrogen, and ethylene atmosphere was used to obtain Ta-Zr-Si-B-C-N coatings. The coating structure was studied using scanning electron microscopy, energy dispersive and X-ray phase analysis. Mechanical properties of the coatings were determined using the nanoindentation method. Tribological tests were conducted using a Tribometer automated friction machine at a load of 1 N. Wear tracks were examined on an optical profilometer. The coating oxidation resistance was studied at a temperature of 1000 °C. It was found that coatings deposited in an argon atmosphere feature the highest hardness (30 GPa) and elastic recovery (79%). In addition, they can resist to oxidation up to 1000 °C inclusive due to a protective film consisting of silicon and tantalum oxides formed on their surfaces. Reactive coatings deposited in N₂ were inferior to non-reactive coatings in terms of oxidation resistance as they completely oxidized already at 1000 °C. However, they had a low coefficient of friction that was below 0.15.

The paper presents the results of domestic and foreign studies on laser deposition of coatings using hardening carbide phases, as well as metallographic and tribological studies of coatings with Ni-Cr-B-Si alloy powders and with the addition of nanodispersed particles of titanium and tungsten carbides. Wear resistance coefficients of coatings (K_w) were determined in Brinell-Haworth abrasive wear tests. The K_w value was used in coating scratch tests to determine the coefficient С that depends on the coating hardness, treatment modes and addition of solid particles. It was found that the С value is influenced by a number of factors: processing speed, input laser power density, base penetration depth, carbide phase presence and content. The higher the penetration depth, the lower the coating wear resistance due to the mixing of the base material and the deposited coating. The introduction of tungsten carbide nanoparticles in the amount from 3 to 7 % increased the coating wear resistance by 1.5-2.0 times compared to the deposited PR-NiCr15BSi2 coating powder and by 4.6-7.1 times in relation to the base material - 40Cr steel. The microhardness of the initial powder coating was 6400-6600 MPa, and it increases with the introduction of carbides. For example, microhardness reaches 7620-9160 MPa at a WC content of 7 % in the coating. Positive deposition results were obtained at radiation energy density up to 50 W•s/mm², but its further increase leads to the burnout of alloying elements and dissociation of carbides.