The article covers a specific property of nanobubbles – spontaneous spreading over a solid hydrophobic substrate-particle adhered to them due to high capillary gas pressure in nanobubbles (Pk > 106 N/m2 ). The calculation principle of bubble spreading curves was considered and the parameter X responsible for intensity was introduced. The relation X(а) (а – bubble base diameter) was represented by a bimodal curve confirming that the process of nanobubble spreading was energetically supported by two independent sources acting sequentially. The first source was conditioned by reduction (approximately by 11 %) of nanobubble curvilinear surface area at the initial stage of spreading, and the second one was conditioned by the work of gas expansion due to a drop in Pk during the bubble spreading. The parameter X value was characterized by a significantly larger slope of the relation X(а) at the initial stage of spreading as compared to the second stage. As it turned out, the property which was found to determine the efficiency of industrial flotation processes in the past, now regains its application perspective. Due to the fact that this property becomes apparent in a limited range of bubble sizes, it was suggested to be labeled as a physical (or natural) fractal by analogy with Brownian motion which becomes apparent in a certain range of particle sizes. The influence of flotation agent surface activity on the shape of bubble spreading curves was demonstrated.

Various stages of copper charcoal deoxidation kinetics were mathematically described with regard to the reduction stage of blister copper fire refining. It was demonstrated that the process rate was controlled by carbon mass transfer in the melt volume with metal oxygen recovery occurring to a 2-stage scheme. In order to intensify copper deoxidation it was considered reasonable to blow-in fine coal directly into the molten metal volume with inert or natural gas.

The developed laboratory technology of compounding coal tar and petrochemical products followed by distillation was tested under industrial conditions. The produced pilot batch of the pitch compound had a lower content of benzo(a)pyrene compared to traditional coal-tar pitch that should reduce harmful emissions in the aluminum industry. An experimental batch of the compound pitch was used in the production of under-pin anode paste. It was noted that changing current-carrying pins on the Soderberg anodes installed on the experimental under-pin anode paste was performed in the normal mode, electrolytic cell operation was normal, and no anode failures were recorded.

In order to simulate tungsten powder fluorination with fluorine and condensation of WF6 produced, computational methods based on the physical and chemical process principles were developed which satisfactorily describe experimental data available. They were used to optimize the equipment size and parameters of two-stage tungsten powder fluorination process with the condensation of liquid WF6 after each stage at 2,5–3,0 °C. The possibility of WF6 production at an output rate of 5,23, 6,53 and 7,83 kg/h in reactors with a diameter of 200, 300 and 360 mm respectively, at a temperature of 300–350 °C without forced cooling of the most heat-stressed first fluorinator was demonstrated. Besides, the total fluorine utilization over 99,99 % was achieved with the amount of hazardous gases escaping the process (F2, WF6) below their maximum permissible concentrations even in the ventilation gas volume. Some recommendations were given on the organization of tungsten powder fluorination flow process.

In order to extract cerium from rare-earth metals (REM) recovered from Russian raw materials, the following modern domestic equipment was selected: OXITRON-58L-O2 diaphragm electrolyzer manufactured by LLC «Delfin Aqua» with the purpose of Ce(III) to Ce(IV) oxidation; EC-10FA centrifugal extractor manufactured by LLC «LIT» with the purpose of Ce(IV) extraction from the sum of REM. These units were used in the studies performed to identify conditions that would lead to cerium oxidation to a 4-valent state with the electrochemical method as well as to recover and clean Ce(IV) from rare-earth metals with the solvent extraction method. The experiments were performed with standardized test solutions of cerium nitrate and process solutions obtained using loparite concentrate from the Solikamsk Magnesium Plant. The conditions were identified and equipment operation modes were designed in order to enable the chosen electrolyzer model to achieve a degree of cerium oxidation in REM process solutions over 99 % at power consumption below 0,8 kW/h per 1 kg of CeO2, and extract cerium from REM concentrate solution using the laboratory cascade of 20 centrifugal extractors with further production of 99,6 % pure CeO2.

The paper examines the features of silicon behavior (neat – Kr0 grade, alloy – Cu–50 % Si) when introduced into oxidized copper melt. The minimum value of oxygen content in copper was found. With this value silicon introduction leads not to deoxidation of the entire volume with silicon oxide formation, but only to surface deoxidation at the «silicon/oxidized molten copper» interface with the formation of liquid Cu–Si alloy immiscible with the main melt and shaped as a ball with a total weight of 5–10 % of the whole melt. The mechanism of such ball appearance was described. It was found that the ball formation rate is affected by the amount of oxygen in molten copper. The results obtained are valuable from a practical perspective and may be used in copper alloy production.

The ABAQUS engineering analysis package was used for mathematical modeling of the drawing process for a billet obtained by compressing titanium sponge taking into account potential cavitation during forming. It was shown that for a low drawing ratio the maximum porosity is formed equally both due to changes in existing pores and appearance of new defects whereas when the drawing ratio increases, it is caused mainly by the growth of newly formed discontinuities with the area of origin corresponding to the area of tensile stress. For the larger drawing ratio and cone angle, the volume fraction of newly formed defects significantly affects the overall porosity. This increases the damage and may lead to bar breakage.

The energy method used for solving metal forming process problems was further developed. The algorithm was designed and formulas for calculating power parameters of one-piece die strip drawing were given. Calculation results satisfactorily correspond with the data obtained in experimental studies and allow for deeper understanding of the nature of specific friction force distribution in the deformation area based on the power balance of these forces and resultant friction force on a workpiece surface. The method is effective for the design of rational one-piece die strip drawing sequences.

The article reviews the properties of nanostructured multilayer coatings (Ti, Al)N–Mo2N obtained by plasma-ion vacuum arc deposition method (arc-PVD). The thickness of coating layers was comparable to the size of a grain, which was about 30–50 nm. Coating hardness reached 40 GPa with relative plastic work of deformation of about 60 %. It was found by the measuring scratching method that cohesive nature of coating destruction takes place entirely by a plastic strain mechanism, which was the evidence of its high viscosity. Local coating abrasion to a substrate level occurred at a load in the order of 75 N. Under test conditions as per «pin-on-disk» scheme using the opposing Al2O3 element at a load of 5 N, coating friction factor was equal to 0,35 and 0,50 at 20 °C and 500 °C respectively. Besides, it was practically not worn due to formation of MoO3 oxide in the friction zone (Magneli phase) which served as a solid lubricant. The increase in friction factor and appearance of significant wear were observed with further rising of test temperature. Such effect was due to intensified sublimation of MoO3 from friction surfaces with subsequent reduction of its lubricating efficiency.

The study covers the microstructure of Cu–Pb alloys containing 7, 32, 50, 55 and 73 at.% Pb preliminary superheated in their liquid state to 1300 °C and crystallized at a cooling rate of 10 °C/sec. It was demonstrated that melt overheating resulted in complete or partial suppression of metal separation and formation of its more uniform structure that serve as an indirect evidence of changes in the structural state of metallic liquid. The application of homogenizing heat treatment of Cu–Pb melts by superheating to a temperature specific for each compound as a method to obtain massive ingots with a homogeneous structure was justified. It was demonstrated that Cu–50 at.% Pb alloy characterized by the highest value of mixing entropy is the most promising composition for massive ingot production by homogenizing heat treatment of a melt. The minimum micro-hardness difference of phases based on copper and lead for Cu–50 at.% Pb alloy determined material ability to withstand mechanical loads without residual deformation and failure, as well as its resistance to various types of wear.