When studying the aggregative stability of dispersed systems by sediment volumetry, nanobubbles are formed due to water structure imperfections in the contact area, and the coalescence of nanobubbles results in a hydrophobic attraction force. Changes in the aggregative stability of aqueous dispersions of particles can be explained as follows: water molecules with a high potential of interaction with medium molecules are difficult to flow into the interfacial gap between particle surfaces, and the outflow of water molecules with a high intensity of interaction with a solid surface is impaired. Excessive osmotic pressure between hydrophilic surfaces causes their hydrophilic repulsion, and excessive osmotic pressure of the surrounding water (reduced osmotic pressure between surfaces) causes hydrophobic attraction of the surfaces. To change the result of flotation, it is sufficient to bring the heat flow to a thin liquid layer of nanoscale thickness with the action of forces of structural origin localized inside, which determine the stability of wetting films. To increase the temperature in the interfacial gap between theparticle and the bubble due to the heat of water vapor condensation, it is proposed to use a mixture of air with hot water vapor as a gas during flotation. The developed flotation method was tested in the flotation of gold-bearing ores. The rational vapor consumption determined based on the factorial experiment results is 10.7·10^–3 kg/(s·m²) at a xanthate consumption of 1.74 g/t. The rougher flotation operation used a jet method of flotation circuit design, which provides for the combination of the initial feed and the rough concentrate. In comparison with ore flotation according to the factory scheme, the yield of concentrate sent for hydrometallurgical processing is 23.4 rel.% less while maintaining the gold recovery level achieved.

The paper considers the features of gold deportments in technogenic raw materials – aged clinker of zinc production at the Belovsky zinc plant (Belovo, Kemerovo Region). The Belovsky plant operated from 1930 to 2003 using zinc concentrates from the Salairsky ore mining and processing plant. After the plant shutdown, clinker dumps were stored at the plant’s mill site and were repeatedly washed with acidic solutions to isolate copper. This form of storage and leaching led to the transformation of precious metal deportments in clinker, which currently makes it difficult to extract gold. The gold content in clinker is at the level of 2–3 g/t, which makes gold recovery profitable. The presence of carbon in clinker complicates the use of known methods of both analytical detection of gold and its recovery. A method is proposed for determining the deportment and content of gold taking into account the fact that gold may be present in the form of free fine gold, as well as gold finely disseminated in iron and its oxides, in sulfide phases, in the quartz-silicate part of clinker and in the carbonaceous phase. It was shown that gold deportments in clinker change depending on the storage conditions and preceding acid treatment, and this affects the choice of the material processing flow chart. The share of gold available for leaching is at least 40 %. The increased associativity of gold with the coal (flotation-active) phase and the sorption activity of coal significantly interfere with the study into the properties of gold deportments in clinker, which requires preliminary carbon removal.

The lack of understanding as to the nature of interfacial interaction between reinforcing particles and the matrix alloy during repeated remelting of cast composite materials is one of the problems hindering the expansion of their industrial application. This research is aimed at establishing the effect of repeated remelting of AK12 + 10 vol.% SiC aluminum matrix composites on the retention and chemical stability of silicon carbide reinforcing particles. It is shown that an increase in the number of remelting iterations is not accompanied by any new phases appearing at the interfaces between particles and the matrix, which indicates the stability of the SiC reinforcing phase in aluminumsilicon melts under the considered temperature-time and concentration conditions. Repeated remelting of aluminum matrix composites with silicon carbide shifts the particle distribution uniformity towards a more uniform distribution degree (on average 0.81046 at the first remelting iteration, 0.6901 at the second one and 0.5609 at the third one) and slightly reduces their average sizes (from 70.74 μm at the first iteration to 65.76 μm at the second one and 61.21 μm at the third one), apparently due to particle fragmentation that leads to an increase in the quantity of finer particles. At the same time, the share of the area occupied by particles in the section regions under consideration remains practically unchanged (10.9293, 10.9607 and 11.6483 % at the first, second and third remelting iterations, respectively). In the course of repeated remelting of Al–SiC aluminum matrix composites, processes of reinforcing particle redistribution occur that lead to the destruction of agglomerates even without intensive mixing with an impeller. Due to this, the uniformity of particle distribution in the structure of secondary aluminum matrix composite ingots can be significantly improved.

The paper provides the results of studies on interaction between titanium melts and silica-containing investment molds. Pure silicon, compounds of titanium oxides and silicides were detected by X-ray diffraction analysis in the contact zone. The problem of the negative impact exerted by the mold on the casting is solved by using thermally stable and chemically resistant monocorundum molds based on an alumina sol binder. A refractory suspension was developed for investment casting containing special additives to improve wax mold wetting with the suspension, and to increase the mold shell strength. The article studies sedimentation properties of suspension. A method was developed for accelerated curing of sequentially applied refractory suspension layers by vacuum drying and subsequent chemical curing with a gaseous reagent. The formation time is reduced from 3–5 h to 20–30 min per layer. Comparative studies of kinetics of alumina sol binder convective drying and vacuum dehydration were conducted. The process of moisture removal per unit surface of the applied refractory layer in a vacuum of 5–10 kPa increases by 2–6 times. X-ray phase analysis was used to study the alumina sol conversion during high-temperature heating. The solid gel of the α-Al₂O₃ stable phase is obtained in the alumina sol mold shell when the calcination temperature rises to 1300–1350 °C with a sufficient strength of 9–12 MPa provided by sintering additives added to the suspension. Recommendations are given for additional protection of refractory ceramic layers after vacuuming and drying: treatment of the last layer with gaseous curing agents and application of a polyvinylacetal solution with a density of 1100–1200 kg/m³. The process solutions proposed will make it possible to increase both the efficiency of titanium alloy forming and casting processes and the quality of castings.

The article presents engineering solutions developed to create deforming devices with a power drive made of a shape memory material. As an example, the paper considers designs of a press, a stamp press made using new designs of multi-link power drives. A method is proposed for engineering a universal multi-link power drive with power elements made of a thermally thin shape memory material. The paper provides the analysis of thermal processes in power elements of various shapes, geometric dimensions and using different methods of their heating (current transmission heating, convective and radiant heat exchange) to determine the efficiency of the engineered devices. Processing and operational properties of thermally thin power elements of a multi-link power drive are investigated. To determine their qualitative and quantitative indicators, a measuring bench was created with such functions as recording the amperage, temperature change, displacement, and developed forces on a single time scale. A relationship between the heating rate, rate of operating force development and return deformation force was found. A line of universal power drives with a developed deformation force of 500–10000 N and a displacement of 1.0–8.0 mm was created based on the calculations performed with the results of their testing and use in existing models of deforming devices presented.

An effective approach to increasing the fatigue resistance of metal products is to create compressive residual stresses on the surface of the product using surface plastic deformation (SPD) processing. One of the effective SPD methods is the process of abrasive-free ultrasonic finishing (AFUF). Another well-known approach to improving mechanical properties including fatigue resistance is to create an ultrafinegrained (UFG) structural state in the product. This research focuses on the finite-element study of the stress-strain state of a UFG workpiece subjected to SPD by the AFUF method. Commercially pure Grade 4 titanium in the UFG state obtained by the ECAP-Conform method was chosen as a workpiece material. In the course of the study, the stress-strain state of the deformation zone was analyzed after a single indentation with subsequent unloading under the elastic-plastic scenario. The effect of the indenter oscillation amplitude and its geometry on radial residual stresses including their depth of occurrence, average normal stress and strain intensity was analyzed. It was found that as the indenter radius increases, the strain intensity (e) value decreases. The e parameter distribution has a gradient nature with a decrease in values from the surface to the center of the workpiece. An analysis of simulation results shows that radial residual stresses in the deformation zone are predominantly compressive, and, accordingly, they will increase the fatigue resistance of the finished product. It was established that as the indenter oscillation amplitude increases, the values of compressive radial residual stresses also increase. Their maximum values reach 540 MPa at an amplitude of 75 μm with the depth of these stresses up to 0.3 mm. An increase in the indenter radius, i.e. in fact the contact area, leads to an increase in the magnitude of compressive radial residual stresses with an almost linear behavior.

The paper focuses on the study of the combustion kinetics and mechanisms of elemental mixtures in the Zr–Mo–Si–B system, as well as the analysis of phase and structural transformation stages in the combustion wave. A thermodynamic analysis of potential chemical reactions occurring in the combustion wave was carried out. The reaction of ZrB₂ formation is preferred in the range of 298–2500 K. Above 2200 K, the formation of MoB becomes more thermodynamically advantageous as compared to MoSi₂. Phase stability estimates of combustion products showed that ZrB₂, MoSi₂ and MoB phases are in equilibrium. Experimental dependences Т_c(Т₀) and U_c(Т₀) are linear, which implies an unchanged combustion mechanism at T₀ = 298÷800 K. Preheating leads to an increase in U_c. Similarly, an increase in the proportion of Zr and B in the mixture has a similar effect, i.e. an increase in heat emission and T_c. With a minimum content of Zr and B, the interaction between Mo and Si with the formation of MoSi₂ by the reaction diffusion mechanism is decisive. As the proportion of Zr and B increases, the rise of T₀ to 750 K does not affect the T_c. E_eff values (50–196 kJ/mol) confirm the significant influence of liquid-phase processes on the combustion kinetics. The mechanism of structure formation was studied. A Si–Zr–Mo melt is formed in the combustion front. The primary grains of ZrB₂ and MoB crystallize from this melt as it is saturated with boron. At the same time, the melt spreads over the surface of Zr and Mo particles. This leads to the formation of ZrSi_x, MoSi_x films. Core-shell structures are formed behind the combustion front, which disappear as they move towards the post-combustion zone. The phase composition of products is formed in the combustion front in less than 0.25 s.

The influence of heating and cooling routes prior to the Ti–22Nb–6Zr (at.%) shape memory alloy ageing on the intensity of the isothermal ω_iso phase formation in the temperature range from 250 to 350 °C for 1 and 3 h was studied by X-ray diffraction. It was shown that for intensive ω_iso phase formation, the most efficient scheme for entering the ageing interval includes rapid water cooling to the room temperature from the annealing temperature of 600 °C and subsequent rapid heating to the ageing temperature of 300 °C. All other schemes used for entering the aging interval including slow cooling and/or heating do not lead to the formation of any X-ray identifiable ω_iso phase amount. Whereas, the β → ω_iso transition in the temperature range from 250 to 350 °C has a pronounced C-shaped kinetics with a maximum at 300 °C. When aged in the entire range of t = 250÷350 °С, the alloy features higher durability and hardness compared to the initial state. Moreover, the hardness gradually increases with an increase in the ageing temperature from 250 to 300 °C and remains constant in the temperature range of t = 300÷350 °С. The β phase lattice parameter of the Ti–22Nb–6Zr alloy remains unchanged over the entire aging temperature range of 250–350 °C, which indicates the absence of noticeable diffusion element redistribution in the solid solution during the ω_iso phase formation. The ω_iso phase formed during the Ti–22Nb–6Zr alloy ageing over the entire temperature range of t = 250÷350 °С has the ratio с_ω /а_ω = 0.613 ± 0.002, which is similar to the с_ω /а_ω ratio for the shear-type athermal ω_ath phase, which in turn further emphasizes the identity of these two phase varieties.