Vol 58, No 3 (2017)

Results of an investigation into a new method of magnetic liquid separation, which differs from known ones by the presence of a bilayer separation medium in the form of immiscible ferromagnetic liquids of different densities, are presented. During the separation in a bilayer medium, the equilibrium condition of a particle on a flat surface, which is written according to the Young law and Neumann rule, should be supplemented by the linear tension of a curve-phase interface surface. The linear tension is the force and energy barrier, which prevents fastening of small particles of precious metals at the phase interface, and the cause of their effective separation into a heavy fraction. The method of magnetic liquid separation is tested for concentrates containing platinum group metals. It is established that, during the separation in the bilayer medium, the recovery of platinum group metals into the heavy fraction is 25.89%, while that for the waterbased ferromagnetic liquid is 19.73%. The quality of the heavy fraction makes gives the opportunity to direct it to the hydrometallurgical stage bypassing the copper plant, which increases the recovery of precious metals by 5.0 abs %.

Flotation properties of dialkyl dithiophosphates of alkali metals BTF-1552, IMA-206, and IMA-I413 are investigated. Concentration characteristics using the M-TF reactant and its mixture with IMA-I413 and xanthate are evaluated. Based on these investigations, it is established that the application of the mixture of collectors IMA-I413 and butyl xanthate in the ratio 5: 1 with the consumption of 20 + 5 g/t makes it possible to increase the recovery into the copper concentrate by 0.79% for Cu, by 4.1% for Au, and by 2.4% for Ag with a twofold decrease in the yield of the sulfide concentrate. The disadvantage of this composition of reactants is an increase in the As content in the copper concentrate by 0.67%. The better characteristics by an increment of recovery of copper and precious metals among the tested samples are observed for the BTF-1552 collector. The recovery into the copper concentrate increased by 1.9% for Cu, by 3.2% for Au, and by 1.8% for Ag with a decrease in the yield of the sulfide concentrate by a factor of 1.4. An increase in the As content in the copper concentrate is 0.34%.

The process flowsheet of dusty wastes forming during metallurgical brass production with the use of two-stage leaching is proposed. The production solution, which contains the main amount of zinc ions (0.46 mol/L) and a small amount of copper ions (less than 0.02 mol/L) is formed at the first stage during the dust dissolution with the 0.5 mol/L sulfuric acid solution. Copper and zinc are sequentially electrochemically isolated from this solution at the current density of 0.1 A/dm² and 5.0 A/dm², respectively. A dry residue (cake) is subjected to copper–ammonia leaching, due to which copper completely transfers into the solution, while accompanying metals remain undissolved. To recover copper from the formed solution, liquid extraction with the solution of 0.34 mol/L DX-510A in kerosene is applied. Copper ions are recovered from the organic phase by reextraction with the 2.0 mol/L sulfuric acid solution. Cathodic copper is isolated from the sulfuric acid electrolyte at the current density of 1.5–2.0 A/dm². The advantages of the proposed flowsheet are an increase in environmental safety due to the use of recirculation of solutions at all process stages, as well as minimization of wastes of the whole process of processing of dusty metallurgical slime.

In order to ascertain the impact of titanium additives on carbon anode reactivity, different titanium content of carbon anodes were prepared with the single factor experimental method, and test its reactivity in CO₂ and air atmosphere respectively. The micro structure of carbon anodes and pitch cokes were tested by XRD. The pyrolysis process of pitch was tested with the TG-DTG method. The results show that the residual rate and chalking rate of carbon anode can also be significantly improved by increasing titanium content. Titanium additives can refine the crystallite size of carbon anode, promote the asphalt carbonization. The titanium additives can increase the apparent activation energy and pitch coke yield of the pyrolysis process, when the titanium content is 1.5%, E_a is 56.405 KJ/ mol, reaction order is 6.4, and the rate of pitch coke yield is 50.5%.

Sorption of indium ions from polycomponent solutions with preliminarily reduced iron(III), which contain, g/dm³, 0.084 In³⁺, 6.2 Fe²⁺, 67.0 Zn²⁺, and 19.6 H₂SO₄, on the Metosol reagent, is investigated in the dynamic mode. The Metosol reagent represents montmorillonite of composition (Na,Ca)_0.3(Al,Mg)₂Si₄O₁₀(OH)₂(H₂O)_n, modified with di(2-ethylhexyl)phosphoric acid. The absorption dynamics of ions by it is investigated by frontal chromatography. The values of working (DEC) and total (CDEC) dynamic exchange capacities of the mineral sorbent are determined depending on the eluent specific passing rate and temperature. The main parameters of the sorption technology of the selective recovery of indium from process solutions of the zinc production on the Metosol reagent in columns followed by the desorption of metal with the hydrochloric acid solution (1: 1) are substantiated and calculated.

Pilot smeltings of the intermetallic titanium alloy are performed during the work in the vacuum induction smelting installation with a “cold crucible” and the blades of a gas-turbine engine are fabricated by the casting method according to investment models in the centrifugal field. The structure of the initial charge billet for casting the intermetallic titanium alloy is investigated and its chemical composition is analyzed. The process parameters of casting and results of metallographic analysis of fabricated blades are presented. It is established that the cast blade structure has a lamellar structure and consists of phases γ and α₂. The results of testing mechanical properties are presented. It is established that ultimate tensile strength σ_B = 765 MPa, yield point σ_y = 726.5 MPa, and relative elongation δ = 1.6%. The stress distribution on the blade pen is investigated and its distribution diagrams are constructed. Blade samples are tested for long-term strength (t = 650°C, τ = 500 h), fatigue strength, and impact toughness.

The possibility of application of boriding media based on boron carbide—which additionally contain chromium, titanium, and silicon—for the diffusion hardening of titanium alloys is considered. Boriding in amorphous boron is performed for comparison. The microstructure, elemental composition, and phase composition of diffusion coatings on the OT4 titanium alloy formed by saturation in powder media are investigated. Hardening boride layers are formed on the titanium alloy form saturating media based on amorphous boron and multicomponent mixtures based on boron carbide. In all cases, the phase composition of the coating corresponds to phases TiB, Ti₂B₅, and Fe₂Ti. It is revealed that coatings from 30 to 150 μm thick are formed in conditions of the solid-phase saturation of titanium from powder mixtures due to the diffusion. Temperature-temporal conditions of formation of boride layers on OT4 titanium from powder saturating media are investigated and optimal modes for the formation of operable boride coatings are established. The optimal temperature range for processes of chemical-thermal boriding of titanium (900–1150°C) and saturation time (from 2.5 to 5 h) are determined. The maximal thickness of the operable boride coating on the OT4 titanium alloy is established, being from 180 μm in the case of saturation from B_amorph and up to 240 μm for the 50% B₄C + 20% SiC + 25% CrB₂ + 5% NaCl mixture at 950°C and saturation time of 4 h. Herewith, it should be noted that it was considered that the largest coating thickness is that retaining on the hardened sample surface.

The methods for calculating the duration of the superplastic forming of a circular membrane are considered. The results of calculations by analytical formulas are compared with the solution of boundary-value problems of the theory of creep and viscoplasticity found in the medium of the ANSYS software complex. The values of material constants were determined by the data of uniaxial tests and testing formings of the VT6 titanium alloy (Ti–6Al–4V).

The feasibility of developing a waste heat recovery system from waste hot air generated by the reduction system in Kroll process to pre-heat water is studied in this paper, in order to reduce energy loss. In the proposed system, the hot air from reduction reactor was first collected by pipelines with insulating material, and then supplies to a shell-and-tube heat exchanger to heat up water. And the energy, exergy analysis of the whole waste heat recovery system have been carried out firstly on the basis of material, energy and exergy balance. Then, the thermo-economic analysis and economic analysis of the waste heat recovery system are also discussed. The results show that the waste heat recovery system presented in this paper could be applied not only for restricted category of reduction system in Kroll process, although the energy efficiency and exergy efficiency of the waste heat recovery system are as low as 26.84% and 11.09%, respectively. And more than two times equivalent energy could be obtained from the waste heat recovery system. The payback period of a waste heat recovery system is about 4.39 years.

In powder-blown additive manufacturing, the microstructure and mechanical characteristics of the deposited layers are influenced greatly by the process parameters used. The microstructures and mechanical properties of the 1718 nickel alloy processed by additive manufacturing were investigated in this research. The samples were subsequently used to prepare metallographic specimens for observations by optical microscopy and scanning electron microscopy, and hardness test. It was found that the fine equiaxed grains are presented in the build and side surface. There is no difference of the microstructure along the build direction. Subsequently, the hardness is uniform along the thickness and the value is around 260 HV. The potential application includes imitation jewelry and holloware.

The results of high-temperature electrochemical synthesis of powders of holmium and nickel intermetallic compounds are presented. Optimal synthesis conditions of these compounds are as follows: the electrolysis temperature (923–1073 K), cathodic current density (0.5–1.9 A/cm²), and composition of the electrolysis bath (mol %): KCl(48.25–49.5)–NaCl(48.25–49.5)–HoCl₃(0.5–3.0)–NiCl₂(0.5–2.5). The composition of formed powders is investigated by X-ray phase analysis and scanning electron microscopy.

A computer modeling procedure of densification of the noncompact titanium feedstock is considered. The modified Drucker–Prager cap model is used to describe the rheological flow of the deformed mass. It is shown that, when identifying the accepted model with the accuracy acceptable for engineering calculations, it is reasonable to use the auxiliary curve based on the Bernoulli lemniscate, which makes it possible to reduce the number of experiments necessary to construct the piecewise-smooth Drucker–Prager yield curve. The plastic deformation of the representative volume cell of sieving the titanium sponge in various deformation modes is investigated. To improve the formability of the noncompact titanium-containing feedstock, the plasticizing effect associated with an increase in the amount of the plastic β-phase upon hydrogen alloying is used. It is revealed based on theoretical and experimental investigations that hydrogen alloying makes it possible to form a denser billet at invariable temperature and compaction force compared with the traditional densification technology of titanium sponge. It is established that the distribution uniformity of relative density over the axial billet section increases with the additional hydrogen alloying. The satisfactory convergence of results of computer modeling and an experimental investigation into the compaction of the titanium sponge in a closed die is shown.

The Ti₂AlN MAX-phase is synthesized by reaction sintering from Ti–AlN powder mixtures. The optimal synthesis mode of the compound containing less than 1% of the TiN impurity phase is established. It includes isothermal annealing at 1300°C for 2 h in argon at a pressure of 3 atm. The influence of the preliminary mechanical activation of the powder mixture and the reaction synthesis medium on the yield of the Ti₂AlN phase are investigated. It is shown that the activation leads to an increase in the content of the secondary TiN phase. It is revealed that the vacuum synthesis also does not make it possible to form the singlephase Ti₂AlN material.

The heat capacity of mechanically activated nanocrystalline carbonyl iron and the sample of iron nanocomposite with the addition of isoelectronic sp-elements (C, Ge, Sn) with a grain size of the order of 2‒5 nm is determined in a temperature range of 300–450 K using an IT-s-400 calorimetric device. Thermalphysical studies of the temperature dependence of the heat capacity are performed for mixtures of nanocomposites differing by the composition 68 at % Fe–32 at % M (M—Ge, Sn) and 95 at % Fe–5 at % C. It is shown that the introduction of sp-elements into nanocrystalline iron leads to substantial variations in the heat capacity over the whole temperature range under study. The heat capacity strongly depends on the introduced sp-element and degree of disorder of the formed material.