The effect of the concentration of V₂O₅ vanadium pentoxide hydrogel applied in concentrations 5 and 10 % on ASD-4 grade aluminum, on its structural and adsorption properties was studied by the low-temperature nitrogen adsorption method. High-purity nitrogen was used as an adsorbate. Adsorption isotherms were measured with the specific surface area and porosity of powders calculated and results of morphology studies presented. Since BET diagrams are linear in the interval of relative pressures from 0.05 to 0.35 Р/Р₀ , the BET model is well applicable for the calculation of the specific surface area of samples. According to our calculations, the specific surface area was 0.65 m²/g for ASD-4 sample, 6 m²/g for ASD-4 + 5 % V₂O₅ composition, and 16 m²/g for ASD-4 + 10 % V₂O₅. Therefore, hydrogel application increases the specific surface area of initial ASD-4 tenfold and more. Grain size analysis showed that both samples have a rather narrow particle size distribution after hydrogel application, which indicates the monodispesity of the system. The average particle size was ~5÷7 μm for ASD-4, ~9 μm for ASD-4 + 5 % V₂O₅ , and ~11 μm for ASD-4 + 10 % V₂O₅. It was established that mesopores 35 to 40 Å in radius appeared in the modified sample due to the layered structure of xerogel applied. It was shown that the ASD-4 + 10 % V₂O₅ sample exhibits the greatest adsorption activity.

The microstructures of alloys formed during the sintering of tungsten powder mixtures (PV2, 3.8–6.0 μm average particle size) and copper (PMS-11, 45–60 μm fraction) prepared by various methods were compared. The methods included simple metal powder mixing, mechanical activation (MA) of metal powders, copper precipitation from the solution of its sulfate (CuSO₄·5H₂O) on tungsten powder with simultaneous mechanical activation. The molar ratio of metals in mixtures Cu/W = 1. An aqueous solution for copper deposition included diethylene glycol (up to 30 %), glycerin (up to 8 %), hydrofluoric acid (up to 0.1 %), wetting agent OP-10 (up to 0.8 %). Mechanical activation was carried out in an AGO-2 planetary mill with 200 g of steel balls charged into the drums rotating at 2220 rpm for 5 min. Reduced copper in the solution and in the air rapidly oxidizes to the Cu₂O oxide, so the composite powders obtained were washed, dried, and stored in an argon atmosphere. Samples pressed from the powders obtained (tablets 3 mm in diameter, 1.5–2.0 mm in height with a density of 7.7–8.0 g/cm³) were sintered in argon at atmospheric pressure and temperatures from 1000 to 1500 °C. During the sintering of Cu–W composite particles, several areas of the process can be distinguished. «Solid phase» sintering occurs at the contact points of composite particles at temperatures lower than the copper melting point. When samples are heated from the melting point to 1200 °C, samples are sintered by the liquid-phase mechanism from the conventional mixture of metal powders to form a low-porous cake. When composite powders obtained by MA during the copper deposition and MA of metal powder mixtures are sintered, samples are delaminated with the formation of large pores elongated perpendicular to the pressing axis and partially filled with copper melt. When samples obtained by powder MA are heated above 1400 °C, phase separation occurs and almost all copper is displaced from the sample to the surface.

The paper describes main methods for assessing the deformed state of porous body metal frames developed by different authors based on the analysis of yield conditions and governing equations, using the principle of equivalent strains and stresses, and studying the kinetics of metal strain during pressing. Formulas were derived to determine the components of the powder particle material strain tensor through dyads, as scalar products of the basis vectors of the convected coordinate system at each moment of porous molding strain. The expediency of using the analytical expressions developed to determine the deformed state of the particle material was experimentally substantiated subject to the known displacement vector parameters of representative elements (macrostrains) of porous billets. The applications of well-known analytical expressions were established, and the proposed formulas proved applicable for the deformed state assessment of particle metal during the pressure processing of powder products of different configurations and designing billets with a defined porosity and geometric parameters as a basis for compiling software algorithms for the computer simulation of porous molding hot stamping.

The paper focuses on the development of a cermet coating production technology using the method of self-propagating high-temperature synthesis (SHS). The relevance of this study is associated with the widespread use of flat electric heaters and protective coatings for various purposes. A method for producing electrically conductive coatings using SHS in Ni + Al and Ti + + Al + C powder mixtures was proposed. The features of the autowave SHS process in Ni + Al and Ti + Al + C powder mixtures were investigated. The mixture was applied to a ceramic substrate in the form of a layer (0.2÷2.0)·10^–3 m in thickness through a stencil in the form of a suspension in isopropyl alcohol. The effect of the mixture powder layer thickness on the front propagation velocity and maximum temperature was studied. It was shown that these parameters naturally increase with an increase in the thickness. It was found that the coating based on the Ni + Al mixture consists of NiAl, Ni₃Al intermetallic compounds, and the coating based on Ti + Al + C consists of TiC and MAX phases of Ti₂AlC, Ti₃AlC₂. The coating based on intermetallic compounds consists of rounded particles fused together and containing NiAl, Ni₃Al phases. Coatings obtained from the Ti + Al + C mixture contain needle crystals of MAX phases and interspersed rounded particles of titanium carbide. The content of the NiAl and Ti₂AlC target phases increases with the increasing layer thickness. Coatings based on NiAl, Ni₃Al and Ti₂AlC, Ti₃AlC₂ heat-resistant phases (0.2÷1.2)·10^–3 m in thickness with a specific electrical resistance of 0.1–0.6 μΩ·m were obtained.

The paper studies the effect of mechanical activation (MA) modes when stirring a stoichiometric mixture of titanium and soot powders in a ball mill on the properties of mixtures, combustion parameters, relative density, and the microstructure of consolidated titanium carbide samples obtained by SHS. MA conditions for Ti + C reaction mixtures in a ball mill were determined. An increase in the mass of grinding bodies activates the MA mechanism. It was shown that the greatest effect from MA was obtained with a two-stage preparation of mixtures: firstly, the titanium powder was activated separately, then the components were mixed together, and this process included not only their mixing, but also soot powder activation. It was found that combustion behavior is affected by the activation of not only titanium, but also soot. After MA of both components, an anomalous increase in the burning rate (more than 100 cm/s) was found on pressed samples. At the bulk density, there was no effect of MA on the mixture combustion process, since in this case the burning rate of all mixtures was in the range of 1.5–2.5 cm/s. It was revealed that MA of reagents for pressed samples leads to an increase in the combustion temperature, an increase in the relative density of the consolidated refractory product to 93–95 %, and a decrease in the average size of TiC grains. A decrease in the residual porosity of consolidated TiC is due to an increase in the hot pressing temperature and plasticity of the product synthesized during the reaction mixture combustion after MA. The main reason is an increase in the exothermic interaction rate. It was shown that MA when mixing reagents makes it possible to control combustion parameters, the microstructure of consolidated products and opens up new opportunities for obtaining refractory materials featuring a unique structure and properties by SHS pressing.

The study covers the structure, elemental and phase composition of products formed in the contact interaction between diamond and low-carbon steel in vacuum at the Fe–C eutectic melting temperature. Cylindrical tablets made of low carbon steel with a maximum carbon content of 0.1 wt.% and natural diamond crystals in the form of a pyramid (or truncated pyramid) were used as contact pairs. The flat bases of diamond crystals were mounted on the horizontal surface of steel tablets with the load applied to the top of diamond crystals. Contact samples were sintered in a vacuum furnace at a maximum heating temperature of ~1165 °C. After holding at this temperature for 5 minutes, the furnace was turned off and the temperature in its chamber decreased in free cooling mode. Sintered diamond/steel tablet samples were studied by optical and scanning electron microscopy, X-ray diffraction analysis and Raman spectroscopy. It was found that the Fe–C eutectic melt forms in the diamond/steel tablet contact zone, a thin layer of which, when solidified, welds a diamond crystal to the steel tablet under the temperature-time heating mode specified in the experiment. Their bonding strength is such that welded samples without separation can withstand intense cyclic loads during grinding and polishing when making longitudinal sections of samples necessary for metallographic studies. It was shown that the Fe–C eutectic alloy is a gray cast iron with a ferrite-perlite metal base and lamellar graphite inclusions. The microhardness of the solidified Fe–C eutectic was ~1714 MPa. The initial steel tablet with a ferrite-perlite structure was subjected to cementation during sintering in contact with diamond. The most intensive cementation occurred in the ~110 μm thick unmelted upper layer of the steel tablet, which adjoined the Fe–C eutectic during sintering. The microhardness of this layer was ~4945 MPa. As it deepens into the steel tablet there is a gradual transition of the perlite-cementite structure to a perlite one and further to the initial ferrite-perlite microstructure inwards the steel tablet. At the same time, the microhardness changes from ~ 4945 to 1570 MPa.

The study covers the effect of thermal diffusion saturation (TDS) of VK6 and VK15 hard alloys. A charge of 48.5 % K₄(Fe(CN)₆), 50 % Al₂O₃ (buffer substance), and 1.5 % NH₄Cl (activator) was used for TDS of the surface of samples (billets). K₄(Fe(CN)₆) yellow blood salt, B₄C borax, CuO copper oxide were used as a saturating element. Each container was loaded with 5 billets (each brand – VK6, VK15 – separately) and charge. Containers were sealed and subjected to heating up to 900 °C and exposure at a given temperature for 2 hours and up to 1100 °C with exposure for 4 hours. Then they were cooled together with the oven for 6 hours. After the TDS of VK6 and VK15 hard alloys, hardness was increased insignificantly with an increase in bending strength from 13.6 to 57 % in comparison with the initial state. The relationship between stress and relative longitudinal strain for VK6 and VK15 before and after TDS indicates an increase in the Young’s modulus after TDS. The resistance of samples during the cutting test increased up to 2 times. It is impossible to make a clear conclusion on wear resistance tests by turning, since there is a large variation in the amount of wear even on equally processed samples. It is also recommended to increase the number of passes in further wear resistance tests, since wear after the 1st pass is often not evident and associated with a defective surface layer. An increase in temperature from 900 to 1100 °C during thermal diffusion saturation increases the diffusion layer depth for the VK6 hard alloy, improves its performance due to fewer pores, inclusions and breaks in the surface layer, which can be explained by an increased diffusion intensity of various compounds (sodium tetraborate, potassium hexacyanoferrate, copper oxide) with and without activators, as well as impurity redistribution in the process of polymorphic transformation. The microhardness values of VK6 and VK15 samples after TDS as compared to initial samples. The best thermodiffusion saturation medium for VK6 and VK15 hard alloys, which increases their performance by 2 times: Al₂O₃ + NH₄Cl + K₄(Fe(CN)₆) at 900 °C. The fractographic analysis of sample fractures before and after treatment was performed to identify a general trend and make a reasonable choice of an optimal thermodiffusion saturation mode. It was found that the nature of fracture remains virtually the same (brittle fracture runs along grain boundaries) with an increase in the temperature of thermal diffusion saturation, but intergranular facets become smaller due to the brittle precipitates of tungsten carbide particles.

The paper focuses on the process of microspherical Fe₃O₄ particle cladding into a dense shell of Al nanoparticles using a rotating magnetic field (RMF) of uniformly oriented permanent magnets (NN, SS). The author’s unit for generating a rotating magnetic field is presented. Coated magnetite particles were used to form a composite material with a close-packed structure. The transition of an array of Fe₃O₄ particles from a fibrous dispersed structure to a dense packing upon applying a rotating magnetic field is described according to obtained photo materials. The spectra of reflection, absorption and attenuation of electromagnetic radiation of composite materials with «core–shell» particles are obtained for various material thicknesses. The minimum reflection coefficient is set at –4.5 dB. According to the comparative analysis of attenuation spectra, this indicator decreases in the presence of an Al nanoparticle shell on microspherical Fe₃O₄ particles in the composite material in contrast to particles without a shell. To explain the reflection and absorption spectra, we develop a hypothesis about the effect of the surface charge density in the layered shell on the change in the of Fe₃O₄ particle magnetization. The presented method of cladding Fe₃O₄ microparticles with Al nanoparticles using a rotating magnetic field makes it possible to create composite materials of a large size range for a wide range of applications. The possibility of forming a structure of magnetically controlled particle arrangement based on the developed unit opens up new prospects in various fields of science – from microelectronic technology to the creation of controlled filtration using a rotating magnetic field.