Aluminum oxide is widely used as a catalyst carrier, including in internal combustion engine systems, where operating temperatures exceed 1000 °C. As such, aluminum oxide must exhibit enhanced thermal stability. This property is linked to the presence of pentacoordinated centers on the surface of the γ-phase of Al₂O₃. This paper examines the effect of the pH during aluminum hydroxide precipitation on the formation of pentacoordinated centers on the surface of aluminum oxide. The samples of aluminum hydroxide were synthesized via controlled double-jet precipitation, followed by thermal decomposition into oxides. Precipitation was carried out at constant pH levels, and for comparison, parallel samples were synthesized at pH values of 5, 6, 7, 8, and 9. The precursors for precipitation were a 1 M aluminum nitrate solution (Al³⁺) and a 10 wt. % ammonia solution (NH₄OH). The solutions were introduced into the reactor in a dropwise mode with continuous stirring. The resulting aluminum oxide samples were analyzed using X-ray diffraction and nuclear magnetic resonance techniques. The data show a direct correlation between the pH of aluminum hydroxide precipitation and the presence of pentacoordinated centers on the aluminum oxide surface: the higher the pH, the lower the content of pentacoordinated atoms. Additionally, a relationship was observed between the pH value and the size of the coherent scattering region, with an increase in coherent scattering observed at higher pH levels.

The article focuses on researching the technology of cementation purification of zinc sulfate solutions from impurities that adversely affect the electrolysis of zinc. The purpose of this work is to explore new approaches for deep cementation purification of solutions, aimed at reducing the consumption of zinc dust and activating additives (antimony and copper compounds) in the technological process, while improving the quality of the purified solution by decreasing the content of cobalt, nickel, and cadmium in the solution supplied for zinc electrolysis. In this study, a new technology for the cementation purification of industrial solutions was developed, which includes the following stages of impurity removal using zinc dust: preliminary purification stage to remove copper to a concentration of 90–110 mg/L; co-precipitation of copper, cadmium, cobalt, and nickel with the addition of antimony trioxide; deep purification of the solutions from all impurities remaining after the first stage. The purification process was conducted under the following conditions: the preliminary deposition took place at a temperature of 50 °C, with a duration of 30 min and a zinc dust consumption of 0.2–0.4 g/L; the first purification stage occurred at a temperature of 80 °C, for a duration of 1 h, with a zinc dust consumption of 2–3 g/L, and an antimony dosage of 3–6 mg/L; the second purification stage was carried out at a temperature of 75–80 °C, for a duration of 1 h, with a zinc dust consumption of 2–3 g/L, and dosages of copper sulfate and antimony at 50 mg/L and 2–3 mg/L, respectively.

The study investigates the physicochemical patterns of tin leaching from the surface of glass substrates from decommissioned displays in hydrochloric, sulphuric, and methanesulphonic acids. The effects of acid concentration (0.1–1.0 N), duration (10–60 min), temperature (298–353 K), and ultrasonic treatment intensity (UST) (120–300 W/cm²) on leaching performance were evaluated. It was demonstrated that ultrasonic treatment positively impacts sulphuric acid leaching of tin, increasing its recovery by 14–16 %. However, during leaching in hydrochloric and methanesulphonic acid solutions, UST led to a reduction in tin recovery to 28 % and 1.7 %, respectively, due to acid decomposition under ultrasound. The partial reaction orders for tin leaching in HCl, H₂SO₄, and CH₃SO₃H were determined to be 0.8, 1.4, and 1.1, respectively, and changed to 1.5, 1.1, and 0.3 under ultrasound for the corresponding acids. An increase in temperature from 298 K to 333 K significantly improved tin recovery in sulphuric and hydrochloric acids. However, raising the temperature to 353 K led to a decrease in tin ion concentration after 10–20 min, likely due to tin hydrolysis and precipitation. The calculated apparent activation energies of tin oxide dissolution in HCl solutions were 40.4 kJ/mol without UST and 22.9 kJ/mol with UST. For H₂SO₄, the apparent activation energy was 4.0 kJ/mol, increasing to 29.0 kJ/mol under ultrasonic treatment. Therefore, the study showed that tin leaching from glass substrates of decommissioned displays proceeds in a kinetic regime when HCl is used and in a diffusion regime in H₂SO₄ solutions, with ultrasonic treatment facilitating the transition to a mixed regime.

Chalcopyrite (CuFeS₂) is one of the primary minerals processed on an industrial scale for copper production and often dominates copper concentrates sent for pyrometallurgical processing. This study demonstrates the efficient and selective extraction of copper from chalcopyrite concentrate through sulfating roasting, sulfuric acid leaching, and solvent extraction. At a roasting temperature of 700 °C for 1.5 h, chalcopyrite fully decomposes into hematite (Fe₂O₃) and chalcanthite (CuSO₄). Leaching the calcine with a 0.02 M sulfuric acid solution transfers most of the copper to the aqueous phase, while iron concentrates in the solid residue. Additionally, precious metals concentrate in the residue after leaching of the calcine, with the following content in g/t: Pd – 41.61, Pt – 5.65, Ag – 96.22, Au – 4.81. The removal of iron from the leach solution using solvent extraction with di-2-ethylhexyl phosphoric acid was highly effective: with a 25 % extractant solution and an organicto-aqueous ratio of 1:1 over two stages, the iron concentration in the aqueous phase dropped from 3.05 to 0.01 g/dm³, and with an organic-toaqueous ratio of 1:2 over four stages, it decreased to 0.006 g/dm3. After iron purification and solution evaporation, copper sulfate was obtained with the following composition (%): CuSO₄·5H₂O – 99.84 (equivalent to 25.42 % copper), Ni – 0.014, Al – 0.007, Fe – 0.0003, As – 0.0002.

Asymmetric rolling of aluminum alloys is one of the methods for improving their mechanical and performance characteristics. Kinematic asymmetry during rolling is achieved by varying the roll speed ratios (V₁ /V₂). It is believed that when V₁ /V₂ > 3, the process of asymmetric rolling, by combining significant compression and shear deformations, approximates the processes of severe plastic deformation. It has been found that the majority of studies are based on data obtained within a limited roll speed ratio range, V₁ /V₂ < 2, in asymmetric rolling. This article examines the effects observed at V₁ /V₂ = 1÷7.7. The implementation of this condition became possible thanks to a unique scientific facility – the 400 laboratory-industrial asymmetric rolling mill at the Zhilyaev laboratory “Mechanics of Gradient Nanomaterials” at Nosov Magnitogorsk State Technical University Experiments were conducted on asymmetric thin-sheet rolling of aluminum alloys 2024, 5083, and 6061, as well as accumulative roll bonding to produce laminated sheet aluminum composites 5083/2024, 5083/1070, and 6061/5083. The disadvantages of asymmetric rolling compared to symmetric rolling were identified: sample failure was observed at single relative reductions of 37 % for layered sheet aluminum composites (5083/2024) and 40 % for thin-sheet aluminum alloys (6061). The nuances of material preparation for processing were described, including the necessity of cleaning and degreasing the alloy surfaces before bonding into a composite. The rolling temperature regimes were selected, determining cold asymmetric thin-sheet rolling (room temperature processing) and warm asymmetric accumulative roll bonding (heating of the workpieces in the furnace before rolling at 320–350 °C). A reduction in rolling force (by a minimum of 1.3 times), the ability to vary hardness (including an increase by a minimum of 30 %), and technological plasticity with changes in the roll speed ratios within the range of 2 to 7.7 were demonstrated. Options were proposed for reducing the processing cycles of aluminum alloys without compromising the quality of the finished product by reducing the number of rolling passes and annealing steps in the standard process scheme.

Currently, siliconized carbon-carbon composites (C/C composites) hold a significant position among materials used in nonferrous metallurgy. The process of Liquid Silicon Infiltration (LSI) for porous C/C composites is strongly inf luenced by their microstructural characteristics. Studying the effect of the porous structure of various C/C composites on the completeness of silicon infiltration can enable the regulation of the phase composition of siliconized materials over a wide range, as well as the physical, mechanical, and thermophysical properties of C/C–SiC composites. This paper presents the results of analyzing the porous structure and strength characteristics of C/C composites based on needle-punched preforms with different types of carbon matrices (pyrocarbon, natural and synthetic pitch coke, and phenol-formaldehyde resin coke) and the C/C–SiC composites derived from them. Due to the specific features of carbon matrix formation from liquid or gas phases, differences in pore size distribution were observed. A carbon matrix formed by the gas-phase method exhibits fewer nanoscale pores compared to one formed by the liquid-phase method. The inf luence of the pore structure and the nature of the matrix carbon in various needle-punched preforms on the degree of saturation during LSI, infiltration depth, and mechanical properties was determined.

A copper alloy with small additions of palladium and silver (Cu–1.5Pd–3Ag (at. %))—which has potential applications as a corrosionresistant conductor of weak electrical signals—was studied using X-ray diffraction analysis, microhardness measurements, specific electrical resistivity, and tensile mechanical properties tests. Samples were examined in several initial states: quenched (from 700 °C) and deformed at room and cryogenic temperatures (with a 90 % reduction in cross-sectional area in both cases). To study the processes of structural reorganization and property evolution, the initial samples were annealed in the temperature range from 150 to 450 °C (in 50 °C increments), followed by cooling in water or air. The duration of the heat treatments ranged from 1 to 48 hours. It was established that annealing the Cu–1.5Pd–3Ag alloy at temperatures below 450 °C leads to the precipitation of silver-based phase particles in the Cu matrix. Annealing of the initially quenched alloy was found to slightly increase its specific electrical resistivity (ρ) from 3.55·10–8 to 3.8·10–8 Ohm·m (after 48 h at 250 °C). It was revealed that alloying copper with 1.5 at. % palladium and 3 at. % silver enhances the strength properties (the yield strength of the alloy reaches 500 MPa) and raises the recrystallization temperature, while the electrical conductivity of the alloy remains around 50 % IACS. The optimal combination of properties (strength, ductility, and electrical conductivity) is observed after annealing the pre-cryodeformed alloy at 250 °C for less than 18 h. Extending the annealing time causes overaging, resulting in softening. The results of this study can be applied in the development of a new high-strength material with reduced electrical resistivity.