The paper determines the structural formula and quantum chemical characteristics of the most energetically probable, stable conformation of the bioreagent molecule formed during the oxidation of iron (II) ions by the autotrophic mesophilic iron-oxidizing bacteria Acidithiobacillus ferrooxidans in a solution of sulfuric acid consisting of iron (III) ion and three acid residues of glucuronic acid.
The bioreagent oxidant is widely used in the industry for leaching metals from non-ferrous sulfide ores and enrichment concentrates.
The quantum chemical characteristics of the bioreagent molecule are analyzed in comparison with the characteristics of anhydrous iron (III) sulphate, also used in hydrometallurgy as an oxidizer. The structure and quantum-chemical characteristics are studied using the method of molecular computer simulation, the theory of boundary molecular orbitals, and the Pearson principle. It has been established that the most energetically probable, stable conformation of the bioreagent molecule contains the acid residues of glucuronic acid of a non-cyclic structure. According to the research results, the bioreagent refers to the more rigid Lewis acid – electron acceptor – than iron (III) sulphate. The bioreagent molecule is less polarized, characterized by lower absolute electronegativity and 2 times larger volume. A theoretical substantiation of the greater persistence of primary sulphides – pyrite, pentlandite, chalcopyrite, relative to the secondary minerals – pyrrhotine, chalcocite and covellite is proposed based on the calculated values of the boundary molecular orbitals, absolute stiffness and electronegativity of iron, copper and nickel sulfides. The bioreagent characteristics that determine the interaction efficiency – volume, heat of formation, steric energy and its components, total energy, etc. are many times greater than for Fe2(SO4)3. The high oxidative activity of the bioreagent relative to Fe2(SO4)3 can be justified by the higher partial charge of the iron atom, the greater length of bonds between atoms, the lower energy of the lower free molecular orbitals and the greater degree of charge transfer during the interaction of the bioreagent with the sulfide minerals.

The article presents the results of experimental cleaning of copper manufacture solutions from arsenic with pseudobrookite (Fe2TiO5).
The stochastic-determined design of experiment at four levels was used to study the properties of pseudobrookite as an arsenic precipitator in copper sulphuric acid solutions. The following variable factors were selected: frequency rate of precipitator dispensing: 1–4; precipitator-to-arsenic ratio (Fe2TiO5 : As): (1÷2,5):1; process temperature (t, °C): 25–60; sulfuric acid concentration (H2SO4 g/l); 120–200; experiment duration (time, minutes): 15-60. The process of arsenic sedimentation from copper electrolyte was studied using the process solution of Kazakhmys Corporation LLC (Balkhash) with the following component contents, g/l: 50,7 Cu; 7,75 Ni; 9,83 As; 200,0 H2SO4, etc. X-ray and IR spectroscopy identified and confirmed the presence of arsenate ion in the solid sediment composition as a complex compound of iron hydroxysulphate arsenate and iron pyroarsenate. The plots of arsenic sedimentation rate versus studied factors were made to determine significant parameters (precipitator-to-arsenic ratio, working solution temperature and experiment duration) that determine the efficiency of arsenic extraction to a solid phase with pseudobrookite.
The generalized formula for the mathematical dependence of the degree of arsenic sedimentation with pseudobrookite on the process conditions (Protodyakonov equation) was calculated. Optimal conditions for the process of copper electrolyte purification were determined where over 60 % of arsenic is extracted to the sediment. A new method for copper electrolyte cleaning from arsenic with pseudobookite was developed.

The samples of ML19 magnesium alloy with composition, wt. %: (0,1÷0,6)Zn–(0,4÷1,0)Zr–(1,6÷2,3)Nd–(1,4÷2,2)Y was investigated.
The influence of Nd, Y, Zn and Zr on the equilibrium phase transitions temperatures and phase composition using the Thermo-Calc software is established. The Scheil–Gulliver solidification model was also used. We show the significant liquidus temperature increase if zirconium content in alloy is higher than (0,8–0,9) wt.%. Thus, the higher temperature of melting is required (more than 800 °C).
This is undesirable if melting in a steel crucibles. The change of equilibrium fractions of phases at different temperatures in ML19 magnesium alloy with a minimum and maximum amount of alloying elements are calculated. A microstructures of the alloys with different amount of the alloying elements in as-cast and heat-treated condition has been studied using scanning electron microscopy (SEM). We investigate the concentration profile of Nd, Y, Zn and Zr in the dendritic cell of as-cast alloy. An amount of neodymium and zinc on the dendritic cell boundaries is increased. High concentration of yttrium is observed both in center and on the boundaries of the dendritic cell. High zirconium concentration mainly observed in the center of the dendritic cells. A small amount of yttrium is also present in a zirconium particles. These particles acting as the nucleation sites for the magnesium solid solution (Mg) during the solidification.
The effect of aging temperature (200 and 250 °C) on the hardness of a samples after quenching was studied. Aging at 200 °C provides a higher hardness. Investigated the change of the hardness quenched samples during the aging at 200 °C. The maximum hardness is observed in samples aged for 16-20 hours. The two-stage solution heat treatment for 2 h at 400 °C and 8 h at 500 °C with water quenching and aging at 200 °C for 16 h was performed. This heat treatment enable us to get tensile strength 306 ± 8 MPa and yield strength 161 ± ± 1 MPa with elongation 8,7 ± 1,6 %.

Niobium-based composites doped with functional and alloying additives (Si, Hf, Ti, Al, etc.) have prospects for industrial applications such as aircraft engine building. Previously the authors demonstrated that such composites can be synthesized in autowave mode (combustion mode) using highly exothermic Nb2O5 mixtures with Al, Si, Hf and Ti. It was shown that hafnium actively participates in Nb2O5 reduction, and this makes it difficult to introduce it into the composite. This paper focuses on the possibility to synthesize Nb composites doped with a high amount of Hf using centrifugal SHS metallurgy. Experiments on a centrifugal unit under 40 g force demonstrated that reactive Hf replaced by its less reactive compounds Hf–Al or Hf–Ti–Si–Al in Nb2O5/Al mixtures enabled combustion in a steady frontal mode rather than in an explosive one. With the increasing size of Hf–Al granules (from 0–40 to 160–300 μm), the Hf content of resultant composites was found to grow from 1,3 to 3,8 wt.%. In case of Hf–Ti–Si–Al granules 1–3 mm in size introduced to the charge, the Hf content of synthesized composites based on niobium silicides attained a value of up to 8,1 wt.%.
Electron microscopy and X-ray diffraction analysis were used to determine the integral composition and distribution of basic and doping elements in the structural components of synthesized composites as well as their phase composition. Composites with a maximum content of Hf (8,1 wt.%) contain three structural constituents: (1) a metal Nb–Si–Ti matrix; (2) intergrain boundaries containing Nb, Ti, and Al; and (3) hafnia-based inclusions. The XRD pattern showed the presence of three phases in the composite: Nb and Nb5Si3 solid solutions as well as minor amounts of Nb3Si.

One of the main widespread methods of metal forming is pressing characterized by a favorable plastic deformation pattern with the predominant effect of all-round compressive stresses. This allows deforming low-ductile materials and alloys with sufficiently high degrees of deformation. This paper studies plastic deformation conditions at hydro-mechanical pressing as one of pressing types. A distinctive feature of hydro-mechanical pressing as compared to other pressing types is the ability to control the movement of the billet and prevent its ejection at the final process stage. The study covers the conditions of hydro-mechanical pressing which combines the use of high-pressure working fluid and the mechanical impact of the tooling on the pressing die. Formulas for the components of the total hydro-mechanical pressing stress are derived to serve the basis for determination of the optimal process tool geometry. Taper angles of the hydro-mechanical pressing die are optimized depending on the main pressing process parameters. The dependency graphs are plotted for the ratio of pressing stress to the resistance of pressed material deformation as a result of drawing that confirmed the presence of optimum taper angles of pressing dies.

The article shows the evolution of the crystallographic texture and anisotropy of properties during the cold rolling of Al–Mg–Li aluminum-lithium alloy 1420 sheets. Hot-rolled 1420 alloy billets were rolled in a cold condition with intermediate quenching under the following schedule: 7,3 mm → 4,8 mm → 3,0 mm → 1,8 mm. After each pass samples are taken for mechanical testing and structure analysis using optical microscopy and diffractometry. Sheets in all the analyzed conditions characterize by a deformed fiber structure and a considerable anisotropy of mechanical properties. Maximum ductility is observed at 45° to the rolling direction. The nature of anisotropy formed during hot rolling does not change during the cold rolling process. Sheets made of 1420 alloy maintain non-recrystallized structures and have a sharp deformation texture at all stages of rolling. Thus, pole figure and preferred orientation analysis revealed an increase in the volume ratio of rolling textures (slow for brass type and fast for S type) with the growing total cold rolling deformation. Recrystallization textures (R type) are present in small quantities only after hot rolling. The volume fraction of a textureless component decreases with the growth of deformation. The results obtained in the studies allow for the conclusion that first of all it is necessary to provide recrystallization in 1420 alloy sheets at the stage of hot rolling and obtain a recrystallized hot rolled billet for subsequent cold rolling in order to reduce the volume fraction of deformation texture and anisotropy of properties.

Phase transformations in the Al–Ca–Mg–Si system in the area of aluminum-magnesium alloys were studied using the Thermo-Calc program. The liquidus projection was constructed for this quaternary system at 10 % Mg. It was shown that the following phases can crystallize primarily at 10 % Mg depending on calcium and silicon concentrations (except for the aluminum solid solution (Al)): Al4Ca, Mg2Si and Al2CaSi2. The pattern of quaternary alloy crystallization was studied using a polythermal cross section calculated at 10 % Mg and 84 % Al. It was assumed based on the analysis of phase transformations taking place in the alloys of this section that the Al–Al2CaSi2–Mg2Si quasiternary cross section is present in the Al–Ca–Mg–Si system. 3 experimental alloys were considered for the quantitative analysis of phase composition, namely Al–10%Ca–10%Mg–2%Si, Al–4%Ca–10%Mg–2%Si and Al–3%Ca–10%Mg–1%Si. Metallographic studies and electron probe microanalysis (EPMA) were carried out using the TESCAN VEGA 3 scanning electron microscope. Critical temperatures were determined using the DSC Setaram Setsys Evolution differential calorimeter. The results of the experiments are in good agreement with the calculated data. In particular, a peak at t ~ 450 °C is detected in all alloys, which corresponds to the temperature of the nonequilibrium solidus and the invariant eutectic reaction L → (Al) + Al4Ca + Mg2Si + Al3Mg2.
It is found that the structure of the Al–3%Ca–10%Mg–1%Si alloy is closest to that of the eutectic alloy. In terms of density and corrosion resistance, it is not inferior to the AMg10 alloy and even superior in hardness. Therefore, this alloy can be considered as a basis for creating new «natural composite» cast materials.

The paper focuses on the production of compact ceramics ZrB2–SiC–(MoSi2) using the hybrid SHS + HP technology, as well as on its phase composition, structure and high-temperature oxidation kinetics. Reaction mixtures were obtained according to the following scheme: mechanical activation of Si + C powders; wet admixing of Zr, B and MA powders of Si + C mixture; drying of mixtures in a drying cabinet. The composite SHS powder ZrB2–SiC was obtained in the SHS-reactor in combustion mode by element synthesis.
Compact samples were produced using the hot pressing method by SHS powder consolidation. Resulting samples characterized by a homogeneous structure and low residual porosity not exceeding 1,3 %. In total, two compositions were chosen for tests: the first one rated for ZrB2 + 25 % SiC formation, the second one similar to the first one, but with the addition of 5 % commercial MoSi2 powder. The microstructure of samples is represented by dispersed dark gray rounded SiC grains distributed among the light faceted ZrB2 grains.
The sample with the MoSi2 additive has a more finely dispersed structure. High-temperature oxidation of samples at 1200 °С forms complex oxide films SiO2–ZrO2–(B2O3) about 20–30 μm in thickness on their surface, which serve as an effective diffusion barrier and reduce oxidation rate. The complex ZrSiO4 oxide is also present in the oxide film structure after long holding times (more than 10 hours). In addition, after 10 hours of testing, a slight decrease in the mass of the samples is observed, which is due to the volatilization of B2O2, CO/CO2, MoO3 gaseous oxidation products. The sample with MoSi2 added demonstrates better resistance to oxidation.

A novel method was developed to form a protective layer on 08KhG17T stainless steel used to make interconnectors for solid oxide fuel cells. The method was based on the electrocrystallization of metals from non-aqueous electrolyte solutions on the stainless-steel interconnector surface with subsequent thermal treatment. Chemical composition of electrolyte was selected so that the surface is coated with an oxide protective layer of the following composition: LaMn0,9Cu0,1O3. As a result, a uniform oxide layer was formed on the stainless steel interconnector surface to protect stainless steel against high-temperature oxidation resulting in degraded functional properties of the interconnector. The coatings formed were characterized by means of grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy from the surface and in the cross section. Elemental and phase composition analyses have shown that the main components of the protective coatings are compounds with perovskite and spinel structures. The protective coating in contact with cathode material based on lanthanum strontium manganite have shown significantly lowered chromium penetration from steel as a result of diffusion annealing in comparison with the sample without the protective coating. Interconnector bonding to the protective coating has shown no noticeable degradation during at least 500 h at 850 °C in ambient air.