The paper describes the results of studying ways to improve the contrast of calcite and scheelite technological properties using water glass combined with aluminum, zinc, iron, magnesium sulphate salts, a mixture of water glass and calcium chloride, sodium carboxymethyl cellulose (CMC), combinations of sodium oleate with low-polar compounds (neonol, fatty isoalcohols), liquid phase and oleate ultrasound treatment. The monomineralic fraction of calcite floated by mechanical cell demonstrated that the minimum recovery of calcite is achieved by combining the Fe(II) salt and water glass (3(4) : 1). When f loating lean sheelite ore with a high carbonate modulus on domestic water, the combined use of water glass and CaCl2 reduces the floatability of calcium. Calcium chloride added to water glass on recycling water leads to a certain increase in the rough concentrate yield (13.8 to 14.1 %) with a significant decrease of WO3 recovery to the finished selection concentrate (72.7 to 53.3 %) and a deterioration in the concentrate quality. Replacement of water glass with CMC did not show satisfactory results. Ultrasonic treatment of pulp, liquid phase, collector leads to a certain increase in the calcite floatability, possibly due to the higher liquid phase temperature and increased proportion of the oleate ionic form. The use of neonols in the reagent scheme of flotation of scheelite-containing ore with a high carbonate modulus found no evidence of a decrease in the flotatability of calcite obtained when studying monomineralic calcite fractions unlike fatty isoalcohols that provided better concentrates in the selection cycle in comparison with a single oleate.

In the non-ferrous metal industry a unique position is given to electrolytic production as being one of the most energy-consuming and environmentally dangerous technologies. Thus, for example, obtaining aluminum by cryolite-alumina melt electrolysis is accompanied by the atmospheric emissions of fluorine-, sulphur-containing substances and hydrocarbons, and magnesium production – by the emission of chlorine and organochlorine compounds. By present time those suggestions in terms of aluminum and magnesium production are considered relevant that are aimed at improving the environmental situation in the vicinity of metallurgical plants. Despite the fact that existing aluminum and magnesium production technologies are under favorable conditions for development and can be really adopted at existing plants, there are ideas and suggestions appearing to create new technologies based on scientific advances in electrolytic light metal production. The authors used magnesium and aluminum as research objects. They considered interaction between metals and aqueous solutions of their salts – MgSO4, MgCl2, Al2(SO4)3, AlCl3 chlorides and sulfates. It is shown that such interactions always take place in a diffuse area that provide for using various design solutions when selecting the process instrumentation. Experimental data were used to determine the reaction order with respect to the solvent, speed and activation energy constants. The results prove the assumption that it is preferable to use chloride media facilitating the process course based on primary electrode reactions and excluding any auxiliary interactions. It is demonstrated that chloride solutions can serve as operating electrolytes and can carry the recovered metal ions. At the same time electrolytic saturation guarantees the impossibility of a reversible process – secondary metal melt which leads to reducing the main indicators of cryolite-alumina melt electrolysis.

A model unit simulating the actual conditions of electrolytic aluminum production was used to conduct an experimental study of ledge to determine its dynamic behavior (formation/dissolution) depending on the electrolyte overheating temperature, lining thermal resistance and cryolite-alumina electrolyte composition. A window was mounted in the front wall of the unit housing to change the lining material. Ledge is formed due to the heat flow generated by the temperature difference between the electrolyte and electrolyzer walls. The electrolyte cryolite ratio (CR) varied in the range of 2.1–2.5. The alumina concentration in the electrolyte did not exceed 4.5 wt.%. Shape change in the electrolyzer working space during electrolysis was determined by the thickness of the formed ledge on the walls and bottom. The dynamic ledge formation in the experimental cell begins at the overheating of 3–4 degrees. It was found that with a decrease in the thermal resistance of the lining material from 16 to 14 m2/W at the same overheating temperature, the side ledge with a greater thickness was formed, however, the decrease in the thermal resistance hardly affected its thickness when the ledge has been already formed. As in the industrial electrolyzer, the ledge profile formed in the experimental cell can be conditionally divided into three zones: bottom ledge, metal/electrolyte interface ledge and side ledge. The dynamic behavior of the side ledge was different from the bottom ledge: the higher the CR, the thicker the side ledge and the thinner the bottom ledge. Chemical analysis of components in the dry knockout showed that the CR and Al2O3 concentration increase throughout the cell height from top to bottom. It was concluded that the side ledge has a heterogeneous composition depending on the electrolyte composition and cooling rate.

The paper considers a method used to determine Faraday current efficiency (CeF) based on the ratio of partial currents of metal and hydrogen reduction. To calculate the Faraday current efficiency based on polarization measurements, it is necessary to know the working current density and potential (Ei) at which the metal is deposited in the corresponding solution, as well as kinetic parameters of hydrogen evolution for determining the partial current density of hydrogen (iН2 ) at this potential. The proposed method was used to calculate current efficiency for the processes of nickel extraction and nickel coating application from solutions containing nickel sulfate at current density of 300 A/m2. The study allowed to determine kinetic parameters of hydrogen evolution by the polarization curve obtained in the background electrolyte solution containing 120 g/l of magnesium sulfate and 18 g/l of boric acid at pH = 3.9. An equation was obtained to calculate the partial current density of hydrogen evolution at any potential by kinetic parameters. The use of kinetic regularities made it possible to calculate nickel CeF in sulphate solutions of different composition and with different pH values (3.0 and 4.1). The calculated CeF values within the margin of error coincide with the current efficiency value determined by the gravimetric method using a copper coulometer. It is shown that the division of the «total current efficiency» (CeΣ), which is a commercial indicator, into Faraday (CeF) and apparatus (Ceap) indicators in combination with the method using partial polarization provide additional information about the degree of process perfection.

Binary niobium alloys with tin, lead and cadmium were obtained by precipitation of nanosized metal particles dispersed in lowpressure plasma using the thermal fluctuation melting effect. The thermal fluctuation melting effect implies that a small particle is in the quasi-liquid state up to a certain critical size which, if exceeded due to steam condensation or fusion (coalescence) of other quasiliquid particles, results in the drop crystallization. The critical sizes of particles being in the quasi-liquid state and capable of coalescing and forming an alloy – solid solution – were found: Nb – 2.1÷2.2 nm, Sn – 0.4 nm, Pb – 0.6 nm, Cd – 3.2 nm. The following concentrations were determined as the boundary of a range where solid metal solutions exist in niobium, at%: Sn – 25.5, Pb – 23.0, Cd – 64.5. The solid solution is a crystal lattice of the niobium as a matrix metal comprising lead, cadmium and tin atoms. The Nb matrix lattice parameters change with additional stresses arising in it up to its destruction due to the fact that the atom sizes of embedded metals differ from those of matrix niobium. The body-centered cubic lattice parameters of solid solutions increase with the rising Pb, Cd и Sn concentrations since they have larger atomic sizes as compared to niobium. A change in the crystal lattice growth rate was observed for lead and cadmium alloys due to a change in the impurity atom arrangement in the niobium matrix lattice. The critical sizes of metal particles obtained were used to estimate surface tension parameters at the crystal/melt interface as follows: 1.17–1.22 J/m2 for Nb, 1.15·10–2 – for Sn; 1.48·10–2 – for Pb; 0.142 – for Cd. Refractory niobium alloying with tin, lead and cadmium is an example of using the size effect to produce new materials.

The study covers scandium adsorption in batch conditions by VSK, DAS and PFT activated carbon grades (Russia) of different origin (сoconut shell, аnthracite, thermoset waste, respectively) from sulfuric acid-chloride solutions (pH = 2) simulating the composition of the underground leaching solutions of polymetallic ores. It was found that scandium adsorption by DAS and VSK carbons proceeds with the highest distribution coefficients (133 and 45.8 cm3/g, respectively). Isotherms of scandium adsorption with these carbons are linear and described by the Henry equation with constants 133 ± 21 and 46 ± 7 cm3/g, respectively. A limited solution volume method was used to obtain the integral kinetic curves of scandium adsorption. Their linearization according to the kinetic models of the pseudo-first, pseudo-second order, the Elovich model and the Weber–Morris intra-particle diffusion model indicates that the kinetics of scandium adsorption with VSK carbon having a higher correlation coefficient (0.999) is described using the pseudo-second order model. Description of the kinetic data obtained during the adsorption of scandium with DAS carbon showed that for all the models used the correlation coefficient is low (<0.939), while the highest value is observed when using the intra-particle diffusion model. It was suggested that the scandium adsorption process occurs in the mixed diffusion region. The possibility of scandium elution from VSK and DAS carbons with sodium carbonate solution (10 %) was studied in batch conditions, where the degree of scandium desorption in two stages of elution was 84.0 and 90.4 %, respectively.

Currently the most common method of the magnesium alloys flux free melting is the melting under the gas protective atmosphere. This atmosphere consists of inert carrier gas with low addition of active gas. The ML19 casting magnesium alloy contains Y and Nd that enough active. The interaction of such alloys with gas protective atmospheres is poorly studied and has serious practical importance. Sulfur hexafluoride (SF6) has a great influence on the global warming and because of that its application is limited. As a result, the number of countries cross over to HFC-R134a as the active gas. This paper presents the investigation of the effect of gas protective mixtures consisting of carrier gas (argon of nitrogen) and active gas (SF6 or HFC-134a) on the composition of protective layer formed on the surface of ML19 magnesium alloy melt. It was developed a special laboratory setup providing the contact of the protective gas mixture with the alloy during heating, melting and solidification of the samples and preventing the influence of the surrounding atmosphere. The loss of the alloying elements was negligible but in the case of using nitrogen as a carrier gas the Y and Nd content in alloy was lower than if the argon is used. If SF6 is used as an active gas, the Zr content in alloys was lower. Composition and thickness of oxide film that formed in both SF6 and HFC-R134a protective atmospheres are mostly the same. The surface film is consist of magnesium fluoride (MgF2) with admixtures of oxides, fluorides and nitrides of zirconium, yttrium and magnesium. The key difference of protective layer phase composition if HFC-R134a used as an active gas is presence of the large amount carbon in the form of compounds and in a free state. Additionally, it was established that using of HFC-134a in protective atmosphere requires more careful dosage given the fact of its percentage in the gas mixture of more than 1 vol.% leads to severe corrosion of the crucible inner surface during the melting.

The study covers coatings obtained on 40Kh steel substrates by electro-spark deposition (ESD) using TiC–NiCr and TiC–NiCr– Eu2O3 electrodes. Coatings were deposited by the Alier-Metal 303 unit in argon environment under the normal pressure using direct and opposite polarity. The structure, elemental and phase composition of electrodes and coatings were studied using X-ray phase analysis, scanning electron microscopy, energy dispersive spectroscopy, glow discharge optical emission spectroscopy, and optical profilometry. Mechanical and tribological properties of coatings were determined by nanoindentation and testing according to the «pin-disk» scheme including high-temperature conditions in the range of 20–500 °C. The tests conducted include abrasive wear tests using the Calowear tester, impact resistance tests using the CemeCon impact tester, and tests for gas and electrochemical corrosion resistance. Test results showed that electrodes contain titanium carbide, nickel-chromium solid solution, and europium oxide in case of a doped sample. Coatings exhibit the same phase composition but solid solution is formed on the iron base. Coatings with the Eu2O3 additive do not differ significantly in structural characteristics, hardness, friction coefficient, and exceed the base coatings in terms of their abrasive resistance, repeated impact resistance, heat and corrosion resistance. There was an increase in impact resistance by 1.2–2.0 times, a decrease in corrosion current by more than 20 times, and an oxidation index by almost 2 times during the transition to doped coatings.