The research is intended to develop a technology for the production of finely dispersed (10 to 100 μm) powders of titanium and its alloys suitable for use in additive technologies after classification and spheroidization. A eutectic mixture was used as electrolyte, mole fractions: BaCl₂ – 0.16, CaCl₂ – 0.47, NaCl – 0.37, melting point of 452 °C. Electrolytes with a similar composition are used in industry for the electrolytic production of sodium with high current efficiency. No titanium salts were added to electrolyte. Sodium losses due to evaporation, corrosion, and ion recharge were replenished by a periodic increase in electrolysis current. A VT1-0 titanium plate was used as an anode. The walls of a steel crucible served as a cathode. Sodium was released on these walls and dissolved in electrolyte. Titanium ions were reduced in the bulk of electrolyte and in the anode layer. It is the first time that the results obtained were interpreted using the data on the electrode potentials of Ti³⁺/Ti, Ti²⁺/Ti, Ti³⁺/Ti²⁺ systems. It was shown that the concentration of slowly moving complex Ti3+ ions increases in the anode layer, and sodium dissolved in electrolyte reduces mainly Ti²⁺ ions in the electrolyte volume in the first 12 min of electrolysis. Starting from the 20th min, the concentration of Ti²⁺ ions in the anode layer begins to increase rapidly according to the reaction: 2Ti³⁺ + Ti = 3Ti²⁺ as titanium powder accumulates in the electrolyte volume. At the same time, the proportion of sodium consumed for the reduction of Ti³⁺ ions to Ti²⁺ decreases, which contributes to an increase in current efficiency and cathode potential stabilization for 30 minutes at –2.963 V. After the 50^th min, the reactivity of the salt melt begins to decrease, the concentration of Ti³⁺ ions increases steadily until it levels off with the concentration of Ti²⁺ ions at the 85th min. This sharply increased the current consumption for ion recharge and made it necessary to stop electrolysis after switching on a current of 12 A for a short time (for 40 s). After 10 s, judging by the change in the cathode potential, sodium dissolved in electrolyte was almost completely consumed for titanium ion reduction. After 6 min, the potentials of electrodes returned to the initial anode potential value indicating that the system returned to its original state with the near-zero content of titanium salts and dissolved sodium. 95 % of powder was obtained in the electrolyte volume. Current efficiency was 84.0 % and turned out to be close to the value calculated from the average valence of titanium ions and the loss of anode weight (87.0 %). After ultrasonic dispersion, more than 80 % of powder was in the 10–100 μm range with a maximum at 36 μm. X-ray phase analysis showed that this is practically pure α-titanium (93.06 %) and oxygenated α-titanium (5.45 %). The originality of the research consists in the use of a volumetric, intensive, electrolytic method for producing finely dispersed titanium powders with no dissolved sodium and titanium chlorides in the initial and final electrolytes, in a stepwise increase in the current and potentiometric process control. The uniqueness of the research consists in the titanium powder obtained where the major part is in the melt volume in the form of intergrowths that are easily crushed by ultrasonic dispersion into individual crystals. Over 80 % of these crystals were in the range of 10–100 μm required for additive technologies with an average size of 36 μm.

The research focuses on aluminum composite granules obtained by the mechanical alloying of VAS1 aluminum alloy and silicon carbide initial powders. It was found that the morphology and average size of composite granules change as the time of mechanical alloying increases. There are the processes of aluminum matrix plastic deformation and the introduction of silicon carbide particles into the matrix, «cold welding» of agglomerates to each other and the growth of an average granule size up to 550 μm that occur for 40 hours of processing. After longer mechanical alloying (60 h), the structure of composite granules becomes uniform, and the average particle size reaches ~150 μm remaining virtually unchanged as the process time increases. X-ray analysis showed that there is a change not only in the morphology of composite granules, but also in their internal structure: coherent scattering regions decrease, the lattice constant of the aluminum matrix alloy changes, microdeformations and stacking faults increase. Transmission electron microscopy studies were conducted in order to study the material microstructure more deeply. Their results proved that the material has a uniform ultra-fine grain structure. The solid solution of aluminum has a maximum grain size of 160 nm. Dislocation density in the composite is rather high. The structure features nanosized plate-like Si particles and silicon carbide existing in the material as distributed splintery coarse particles. No diffusion zone between SiC particles and the base material was found.

The article considers the possibility of binding free carbon existing in the VC_0.40O_0.53–C_free nanocrystalline composition to the carbide phase. This composition is obtained by plasma-chemical synthesis in a low-temperature nitrogen plasma. As a carbide former, titanium was used in the form of its nickelide TiNi, which has a melting point of 1310 °С. Experiments were carried out under vacuum sintering conditions involving the liquid phase at 1500 °C for 40 min. The data obtained in X-ray diffraction, scanning electron microscopy and energy-dispersive analysis were used to determine the phase composition and microstructural features of sintered samples. Liquid-phase interaction between the VC_0.40O_0.53–Cfree nanocrystalline composition and titanium nickelide, the content of which varied from 10 to 99 wt.%, was studied based on the results of experiments. It was shown that the content of C_free and VC vanadium carbide increases with the simultaneously increasing TiC content as the TiNi mass content increases in the range of 10–90 wt.%. With a further increase in the titanium nickelide content to 99 wt.%, Ti₃Ni₄ and Ni₃Ti nickelides are present after sintering. The content of free carbon increases to 88 wt.%, and the amount of TiC decreases to 5 wt.%. The data obtained in the course of the study were used to propose various schemes of processes occurring during the (VC_0.40O_0.53–C_free)–TiNi liquid phase sintering. In particular, sintering involving the liquid phase proceeds in three stages including TiNi melting, refractory base dissolution, its reprecipitation in the form of TiC_x and VC_x carbides, and cooling of the resulting composition. It should be noted that the mechanism of liquid-phase interaction during vacuum sintering involving the liquid phase was developed on the basis of the laws presented in the paper by M. Gumenik.

A new high-temperature antifriction composite material 90 % MoSi₂ + 10 % MoS₂ was developed with a static friction coefficient of less than 0.3. The material is functional at temperatures up 1500 °C under neutron irradiation in an inert gas environment. Modes of initial MoSi₂ and MoS₂ powder mixture preparation and hot pressing of the resulting charge in a vacuum induction unit in graphite molds were worked out at a temperature of 1600–1650 °C, specific hot pressing pressure of 25 MPa, and holding for 1 h at these values of temperature and pressure. Tribotechnical properties of the material depending on the compression force in the friction pair and on the counterbody material hardness were investigated. It was shown that the higher the compression force and the harder the counterbody material in the friction pair, the lower the coefficient of friction. The effect of temperature on the physical, mechanical and heat-transfer properties of the material was established. As the temperature increases from 20 to 1000 °C, the material compressive strength decreases from 1388 to 739 MPa. An increase in the temperature from 25 to 400 °C leads to an increase in the specific heat capacity from 427 to 596 J/(kg·K) and the coefficient of heat conductivity from 2.35 to 3.41 W/(m·K). Plain bearings made of this material successfully passed durability and reactor tests.

The study covers the effect of chromium on the structure, mechanical properties, and adhesion of alloys used as a binder for metal-diamond composites. Cu–Cr powder mixtures were obtained by high-energy ball milling in a planetary centrifugal mill. This process was used to obtain two-phase Cu–Cr powders with uniformly distributed submicron Cr particles. Cu–Х%Cr compact samples (where Х = 10, 30 and 50 %) were obtained by hot pressing. It was found that Cu–30%Cr compact samples showed the best mechanical properties (9 times higher as compared to pure copper). These alloys feature a hardening mechanism based on the Hall–Petch law. The resulting alloys have a homogenous ultrafine structure, which results in high ultimate bending strength (2330 MPa). Chromium addition to the copper binder considerably increases its adhesion to diamond in metal-diamond composites due to chemical interaction between chromium included into the binder and diamond carbon with Cr₃C₂ carbide formation.

The article provides a general overview of the production methods and applications of carbon materials with a large specific surface area. The following materials were taken as objects for the study: SK-AG-3 granular activated carbon produced by OJSC «Sorbents of Kuzbass», Kemerovo, activated cellulose fiber produced by the Krasnoyarsk Chemical Fiber Plant after carbonation, graphitization, and gas-phase activation at 900 °C in carbon dioxide current, Busofit-T carbon fabric produced by OJSC «SvetlogorskKhimvolokno», thermally expanded fluorinated graphite produced by OJSC «Siberian Chemical Combine». The porous structure of these materials was investigated by low-temperature volumetric nitrogen adsorption at the ASAP 2020 unit. Nitrogen adsorption-desorption isotherms were recorded in a relative pressure range of p/p₀ = 0.05÷1.0 at 77 K. The specific surface area was estimated by the BET method based on the adsorption isotherm at p/p₀ = 0.05÷0.30. The specific surface area was 485, 1241, 1156 and 290.5 m²/g for activated carbon, activated carbon fibers, Busofit-T fabric and thermally expanded graphite, respectively. The volume of mesopores and their size distribution were calculated by the Barrett-Joyner-Нalenda (BJH) method in a pressure range of p/p₀ = 0.35÷0.95. The volume of micropores and their size distribution were calculated by the Horvath-Kawazoe method using the nitrogen adsorption-desorption isotherm in a relative pressure range of p/p₀ = 0.00÷0.01. These methods were also used to determine the average diameter of mesopores and micropores. A comparative analysis of the results obtained was carried out. A relationship between the internal structure of the investigated materials and the porous structure properties was traced. It was shown that activated carbon, fibers, and carbon fabrics are microporous materials, and thermally expanded graphite has a mesoporous structure.

Metallized coatings can significantly improve the operational properties of quartz fibers. The research was conducted to determine the crack resistance, strength and dynamic fatigue of optical fibers without any coating and with copper coatings. The microhardness of quartz fibers was measured by the diamond indentation of end surfaces. The stress intensity parameter K1c was found from the A. Niihara semi-empirical dependence. The geometry of indentation and radial cracks was studied using a scanning electron microscope. The crack resistance of uncoated quartz turned out to be almost 3 times less as compared to the copper coating fiber, which is presumably due to the additive contribution of compressive stresses on fiber surfaces and quartz wetting with copper. Copper-coated optical fiber drawing increases the tensile strength, crack resistance and dynamic fatigue parameter, and it is the main resource for maintaining operation in the conditions of a statistical approach to structural strength. Comparative tests were conducted to check the optical fiber strength by two-point bending and axial tension methods. Experimental tests conducted to check the ultimate mechanical strength of quartz optical fibers showed a significant spread of data, which indicates the presence of cracks of various sizes in a brittle solid and is a characteristic feature of brittle fracture as suggested by the A. Griffiths theory. In addition, it was assumed that the chaotic distribution of defects and microcracks extends along the entire length of a brittle solid, a quartz optical fiber in this case. A statistical model based on the Weibull distribution was used to describe surface microcracks depending on the fiber length. As a result, Weibull graphs were plotted in coordinates connecting the probability of failure with the strength, fiber length and parameter describing the ultimate strength.

This paper focuses on the development of composite materials based on the Fe–Ni–Cu alloy with hollow corundum microspheres (HCM). The composites were produced by means of powder metallurgy: by mixing initial metallic powders in various types of mixers followed by hot pressing. Compact samples of Fe–Ni–Cu + HCM composites featured high relative density and microstructure homogeneity. The introduction of HCM leads to a decrease in strength to 30 % (from 1125 MPa to 800 MPa at a HCM concentration of 15 vol.%). However, resulting composite materials retained high plasticity. It was established by the micromechanical modeling method that such composites have stress concentration regions not at the interface between HCM and the matrix, but on the inner surface of microspheres. On the contrary, the adjacent matrix volume around HCM features stress relaxation and «unloaded» regions formed. HCM introduction into the matrix based on the Fe–Ni–Cu alloy increases wear resulting from friction on M300 concrete by 50–170 % with a grain size of 70–100 μm and by 160–325 % with a grain size of 100–140 μm. During friction, HCMs act as a reservoir for debris (concrete particles), so the matrix surface remains free of wear products and directly contacts the material processed. The heavy wear of composites with HCM makes them promising for use as a binder in diamond tools designed for the dry cutting of concrete and reinforced concrete.

Machines and mechanisms contain units responsible for their movement and stopping, and such units use friction materials. These units include oil-cooled brakes, hydromechanical transmissions, and clutches. They use mainly copper-based friction materials providing the high coefficient of friction and wear resistance. These materials feature by effective heat dissipation since a large amount of heat is released in these areas for a short period of time. The paper presents the results of studies into the effect of iron addition into a frictional powder material based on BrO6 and BrO12 bronze on its structure, mechanical and tribotechnical properties. It was shown that the introduction of iron contributes to an increase in the coefficient of friction from 0.034 to 0.055 for the BrO6-based friction material and from 0.042 to 0.073 for the BrO12-based friction material. It was determined that the ultimate compression strength of the BrO12-based friction material is 340 MPa without iron addition, 310 MPa at 10 vol.% of iron, and 180 MPa at 50 vol.% of iron. This is due to the fact that the iron content of more than 30 vol.% results in the change of the frame structure of the material to the matrix one having a sintering temperature higher than the temperature used in the paper for friction material sintering. It was found that for the BrO6-based friction material there are both rounded and elongated inclusions in the copper phase up to 2.5 μm in size with the iron content of 30–50 %. In the BrO12-based material there are more iron inclusions in the copper phase and their size are much larger, the length of inclusions reaches 20 μm, and the iron content in them is 49–73 %.