This article presents experimental data on the flotation behavior of two samples of copper–nickel sulfide ore. The AM-1 ore contained chalcophyllite and sulfide minerals, including pentlandite, violarite, and nickel-bearing pyrrhotite. Its gangue minerals comprised antigorite, amphibole, olivine, spinel-group minerals, and cordierite. The AM-2 ore contained chalcopyrite, pentlandite, and predominantly phyllosilicate gangue minerals, including wonesite and chamosite. The modifiers tested comprised the aromatic reagents R1–R5. R1 and R2 are nitrogen-containing aromatic heterocycles, whereas R3–R5 are azo compounds bearing a hydroxyl substituent ortho to the azo group. When added at a dosage of 1.0 g/t before the collector, potassium butyl xanthate, the modifiers enhanced both copper and nickel recovery. The greatest improvements were obtained with R1 and R3. For the AM-1 ore, these reagents increased copper recovery by 1.0 and 1.8 %, respectively, and nickel recovery by 2.0 and 1.8 %, while the concentrate yield remained unchanged at 24.5 %. The Hancock–Luyken and Cohen efficiency indices and the Trushlevich selectivity index increased by 3–5 % relative to the baseline values. For the AM-2 ore, R1 and R3 produced smaller increases in recovery: 0.25 and 0.15 % for copper and 0.45 and 0.10 % for nickel, respectively. The concentrate yield remained unchanged at 46.0 %, while the efficiency and selectivity indices were virtually unaffected. Unlike R3 and R4, R5 contains two azo groups rather than one. It increased copper and nickel recovery by an average of approximately 1.0 % but also increased the concentrate yield by approximately 3–4 %. For both ore samples, R5 reduced the Hancock–Luyken and Cohen efficiency indices and the Trushlevich selectivity index. The lower selectivity of R5 may result from its interaction with magnesium sites on the surfaces of magnesium-bearing silicate minerals in addition to copper and nickel ions. Overall, the results indicate that R1 and R3 are the most promising modifiers for copper–nickel ore flotation.

This study investigates high-temperature plasma-chemical synthesis (PCS) and plasma-chemical reduction (PCSR) for the production of metallic tungsten (W) from a multicomponent scheelite concentrate using B₄C as the reducing agent. A method was developed that combines the decomposition of the mineral matrix with the subsequent synthesis of tungsten-containing phases under high-frequency arc plasma conditions. Particular attention was paid to mathematical modeling of the process; a polynomial neural network model (PNNM) was proposed to parameterize the system of differential equations of the process and to account for nonlinear and synergistic relationships between key factors – temperature, current, plasma-forming gas flow rate, feedstock particle size, and B₄C content. The model enabled prediction of target product yields and identification of optimal combinations of process parameters. The influence of boron carbide content (20–60 wt. %) on the phase composition of the synthesis products was experimentally investigated. Dendritic structures consisting of metallic tungsten, tungsten carbides (WC and W₂C), and tungsten borides (WB and W₂B) were found to form at B₄C contents ranging from 35 to 50 wt. %. Sub­sequent ultrasonic cleaning efficiently separated tungsten dendrites from phases containing accompanying compounds, yielding a tungsten concentrate containing >95 wt. % W. The results demonstrate that a combined approach integrating plasma-chemical technology and mathematical modeling is promising for the energy-efficient processing of refractory ores that are difficul­t to beneficiate, particularly scheelite concentrate from the Russian Far East.

The functions derived within the two-phase local-equilibrium region model were used for self-consistent calculation of the thermophysical properties of vanadium, nickel, and chromium in the condensed state. Unlike piecewise-continuous approximation and smoothing of measured values over individual temperature intervals using power polynomials, as commonly employed by experimentalists, the proposed formulas describe the experimental data over the temperature range from absolute zero to the evaporation temperature. The modeled materials may differ in chemical nature, belong to different groups of the Periodic Table, and have substantially different thermophysical properties. In particular, vanadium belongs to Group V and is paramagnetic; nickel belongs to Group VIII and exhibits ferromagnetic properties below the Curie point; chromium belongs to Group VI and changes from the paramagnetic to the antiferromagnetic state below the Néel point. Despite these differences, the proposed formulas adequately describe the heat capacity, coefficient of linear thermal expansion, density, thermal conductivity, and thermal diffusivity of these metals. The results showed, for example, that at 300 K the heat capacity increases in the order chromium–vanadium–nickel, whereas at 2400 K it increases in the order nickel–vanadium–chromium. This indicates increased mobility of chromium atoms during the crystal–liquid phase transition, whereas the heat absorbed by nickel is expended on its expansion, which is substantially greater than that of the other two metals. Between 300 and 2400 K, the density of vanadium decreases from 6103 to 5442 kg/m³, that of nickel from 8906 to 7283 kg/m³, and that of chromium from 7179 to 6114 kg/m³. This indicates an increase in the particle-free volume, i.e., the volume fraction of the “void phase.” Thus, comparing the thermal properties of metals with different physical characteristics provides insight into the transformation of matter during a phase transition.

This study investigated the effect of adding 1 wt. % yttrium oxide (Y₂O₃) nanopowder on the density, microstructure, and mechanical properties of the VZh159 nickel-based superalloy produced by selective laser melting (SLM). Specimens were fabricated using a 3DLam MINI system equipped with an ytterbium fiber laser with a maximum power of 300 W under ten processing conditions spanning a volumetric energy density E_V range of 74–169 J/mm³. Density was determined by hydrostatic weighing, microstructure was examined by scanning electron microscopy (SEM), and Vickers microhardness and room-temperature tensile properties were measured both in the as-built condition and after heat treatment (solution heat treatment followed by aging). The results showed that the Y₂O₃ addition narrow the optimal processing window: a maximum relative density of 99.5 % was achieved at E_V ≥ 127 J/mm³, compared with 99.8 % at 83 J/mm³ for the unmodified alloy. In the as-built condition, Y₂O₃ has virtually no effect on ultimate tensile strength (Δσ_u < 1 %) but reduced elongation from 35.9 to 30.6 %. After heat treatment, the VZh159 + 1 % wt. % Y₂O₃ composite exhibited 10 % higher yield strength by (865 vs. 787 MPa), 4 % higher ultimate tensile strength by (1170 vs. 1122 MPa), and 57 % higher elongation (15.5 vs. 9.9 %) than the unmodified alloy. The following mechanisms are considered: dendrite refinement through heterogeneous nucleation, grain-boundary pinning during heat treatment via the Zener mechanism, and dispersion strengthening.

This article presents the results of producing a high-entropy alloy of the Ti–Zr–Al–V–Cr system, intended for practical use as cathode targets in NNV-6.6 vacuum arc systems, using a combined method of melting and remelting. It is shown that direct remelting of the components by vacuum arc melting (VAM) in a copper mould leads to cracking of ingots due to high thermal stresses (cooling rate of 10²–10³ °C/s), while switching off cooling causes copper contamination. To solve the problem, a combined method is proposed: preliminary melting of the components by VAM, followed by vacuum induction remelting (VIM) and casting into a mold. A special ceramic lining based on oxides containing up to 2 wt. % rare-earth metal oxides was used, ensuring minimal impurity contamination. The optimal crystallization parameters were selected: reduction of the cooling rate to 5–10 °C/s, use of a copper base plate for directional heat extraction and a feeder head to compensate for shrinkage effects. Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed the chemical homogeneity of the resulting ingots (the contents of Ti, Zr, Al, V, and Cr were 16–27 at. %). The microhardness of the alloy was 768–789 HV with high reproducibility across batches. The cathode targets were successfully tested in the NNV-6.6-I1 installation: single-layer and two types of multilayer coatings were deposited on substrates made of Ti–6Al–4V titanium alloy. The developed technology ensures the production of defect-free ingots of a specified geometry (\(\emptyset \)80–85 mm, h = 45 mm), suitable for industrial use in vacuum arc deposition processes for protective coatings.

The study investigated a promising and commercially attractive method for producing metal parts from a metal-polymer paste. The starting material used was a paste containing 79.55 wt. % filler in the form of spherical powder of 316L steel with a typical particle size distribution for selective laser melting additive manufacturing that was D50 = 39.9 μm. The work was aimed to study printing parameters and post-processing, including debinding followed by sintering, and their influence on the characteristics of the resulting metal samples. Porosity, shrinkage, relative density, microstructure, and mechanical pro­perties of the samples after sintering in the temperature range of 1285–1320 °C were examined. The content of δ-ferrite was assessed, the grain growth process was investigated, and the evolution of mechanical properties was analyzed. The applied printing and post-processing parameters enabled achieving a relative density of 89 %, which is associated with the relatively low filler content in the initial paste. However, the technology is promising for mechanical applications and for manufacturing small batches of complex-shaped parts that are unprofitable to produce using powder bed fusion and directed energy deposition techniques, as well as for obtaining porous structures used, in particular, in the production of implants.

This study examines prospects for developing new strain-gauge alloys based on the Hf–Ta–Ti system, including their synthesis, crystal and electronic structures, and electron-transport anomalies under hydrostatic compression and uniaxial strain. The developed alloys exhibited anomalously high gauge factors (GF = 4.52–5.62), 2–3 times those of the commercial strain-gauge alloys constantan and nichrome. The gauge factor varied nonadditively with elemental composition. All the alloys exhibited near-zero Seebeck coefficients relative to copper (approximately –0.5 μV/K). A satisfactory correlation was found between GF and elastic anisotropy in the studied system. The strong chemical disorder characteristic of this class of multicomponent (high-entropy) solid solutions results in high electrical resistivity with low temperature coefficients of resistance (10–300 ppm/K) and pronounced interband s–d scattering. These transport mechanisms account for the anomalously strong effect of strain (hydrostatic compression and uniaxial tension) on the electrical conductivity of the studied alloys. The anomalous strain-gauge response is shown to arise primarily from a substantial change in the Debye temperature caused by anisotropic deformation of the crystal lattice.

This study examined the temperature dependences of short-circuit currents in polar-cut α-LiIO₃ crystal samples with different combinations of of indium, silver, aluminum, and chromium conductive coatings. The coatings were applied to the opposite faces of the samples according to the sign of the piezoelectric response, which indicated the polarity of each face. Short-circuit currents were measured using the SKIP test system over the temperature range of 20–210 °C without an applied external electric field. Short-circuit currents were detected even at room temperature in the absence of prior external stimulation and could change by several orders of magnitude during heating. Both the magnitude and direction of the currents depended on the coating materials and on the polarity of the coated faces. For α-LiIO₃, the short-circuit currents were reduced to near-zero levels using two asymmetric coating configurations: Al(−)/In(+), with aluminum applied to the face exhibiting a negative piezoelectric response and indium to the face exhibiting a positive response; and Cr(−)/Al(+), with chromium applied to the negative-response face and aluminum to the positive-response face. The short-circuit currents remained within 10^–14–10^–13 A range were nearly temperature-independent up to 210 °C. These low current values indicate limited near-electrode electrochemical activity.