Kompleksnoe Ispolzovanie Mineralnogo Syra = Complex use of mineral resources

Investigation of the Structure and Composition of TiN and CrN Coatings as a Function of Deposition Parameters

Wed, 29 Apr 2026 00:00:00 +0000

Addressing corrosion and wear in assemblies, components, machine parts, and equipment operating in aggressive environments under severe wear conditions remains a pressing challenge and continues to draw focused scientific attention. This work aimed to investigate how the key magnetron sputtering parameters (working pressure, plasma current, and process-gas flow rates) affect the surface morphology, microstructure, and composition of TiN and CrN films deposited under different conditions. Microstructural analysis revealed that, across the investigated parameter window, the films exhibit a columnar cross-sectional architecture and a smooth surface morphology with no visible defects, showing no pronounced differences between the deposition regimes. After 30 min of deposition, the film thickness ranged from 0.17 to 0.46 μm for TiN and from 0.59 to 3.46 μm for CrN, depending on the sputtering conditions. The results demonstrate that plasma current and working pressure have a strong effect on film thickness and chemical composition, whereas variations in the working-gas flow rate exert a coupled influence on thickness, microstructure, and the stoichiometry of TiN and CrN layers. Elemental analysis further indicates that increasing the pressure to 0.65 Pa increases oxygen incorporation in the films. During chromium sputtering, raising the plasma current to 1.5 A leads to film delamination. For TiN, a balanced regime with a moderate N2 flow is preferable, providing a reasonable growth rate and a composition close to stoichiometric. For CrN, the range of stable operating conditions is substantially broader, and the process parameters have a more pronounced impact on its structure and composition. These findings can support the design of TiN/CrN wear-resistant multilayer coatings produced by magnetron sputtering for protecting machine parts and equipment against wear and corrosion.

Acid and Thermal Activation of Clay Separated from Kaoline for Uranium Purification

Thu, 02 Apr 2026 00:00:00 +0000

Clay minerals are commonly used as adsorbents due to their wide availability, large specific surface area, and cation exchange capabilities, making them suitable for removing heavy metal ions from wastewater. This study investigated the activation of clay by acid and thermal treatment to obtain an adsorbent for the purification of uranium from impurities such as iron and magnesium. Acid modification of clay samples was carried out with sulfuric acid (15%) at a temperature of 80–90 °C for 3 hours. While the activation of the clay using the thermal process was performed at 600–650 °C for 12–24 hours. X-Ray Diffraction, Electron Paramagnetic Resonance (EPR), and Fourier Transform Infrared Spectroscopy (FTIR) were used to analyse the clay's chemical composition and structural changes before and after activation. FTIR identified free OH groups and hydrated SiO2. EPR showed a high level of paramagnetic centers linked to structural defects and oxygen vacancies, which contribute to the material's strong adsorption and catalytic activity. After acid treatment, the clay particles exhibited a notable rise in specific surface area, expanding from 35.2 m²/g to 342.5 m²/g. Additionally, the specific pore volume grew substantially, increasing from 0.024 cm³/g to 0.30 cm³/g.

Purification of metallic ions from technological solutions before sorption recovery of rhenium under JSC Almalyk MMC

Wed, 08 Apr 2026 00:00:00 +0000

In this article, rhenium’s distinct physicochemical characteristics, which make it essential for petrochemistry, electrical technology, rocket and aviation engineering, and the manufacturing of catalysts and high-precision tools, account for the metal's rising demand. The main source of rhenium at JSC "Almalyk MMC" is the off-gases produced when molybdenum concentrates are roasted, where rhenium is mostly found as Re2O7. High selectivity and overall efficiency are ensured by optimizing the process parameters at each of the multiple subsequent technical phases involved in rhenium recovery. Perrhenate sorption is less efficient when organic molecules and Mn²⁺ and Cu²⁺ ions are present in the process fluids. Oxidative-precipitation techniques were used for the first purification: Mn ions were oxidized and precipitated using potassium permanganate, and Cu2+ ions were selectively precipitated using an ammonium sulfide solution (NH4)2S. ICP-OES was used to assess the composition of the solutions, while SEM and EDS were used to examine the roasting gas-dust products. Using contemporary analytical methods, a thorough investigation of the applicable phases of selective purification was conducted for the first time under the circumstances of JSC "Almalyk MMC." It was shown that treating the solutions with KMnO4 and (NH4)2S efficiently eliminates interfering elements without causing rhenium and molybdenum losses, resulting in ideal circumstances for the sorption of perrhenate ions later on. Manganese and copper concentrations dropped from 1.44 to 0.0039 and 2.68 to 0.0036 g/l, respectively, demonstrating the great purification process efficiency. Rhenium and molybdenum concentrations did not alter during these phases, suggesting that they were fully preserved.

Purification of lanthanum chloride solution through tertiary amine extraction: thermodynamic and graded assessment

N. Zulkifli, N. Shoparwe, A.H. Yusoff, A.Z. Abdullah, M.N. Ahmad — Wed, 22 Apr 2026 00:00:00 +0000

Purification of lanthanum chloride from high-load zinc contaminants remains a major challenge in producing grade 5N lanthanum oxides. This study investigates the process of matrix-driven solvent extraction using tertiary amine N235 to treat a 1.41 M rare earth oxides (REO) industrial lanthanum chloride feed containing 3000 mg/L zinc. Thermodynamic modelling with Medusa Hydra and Langmuir isotherms revealed that the high chloride activity (> 4 M) of the matrix induced significant changes in coordination towards the extractable [ZnCl₄]^2- complex. This transition has a spontaneous Gibbs free energy of -14.68 kJ/mol. While the two-stage counter-current flow sheet meets the industry target of less than 50 mg/L zinc, the five-stage configuration achieves a four-log reduction to 0.23 mg/L, effectively achieving 99.999% purity. This reagent's lean approach, using water-induced stripping, offers a sustainable and mathematically validated framework for ultra-high purity rare earth finishes.

Qualitative Analysis of the Circuits of Au-Tonomous Inverters with Shut-off Valves

Fri, 24 Apr 2026 00:00:00 +0000

The article presents the results of a qualitative analysis of circuits of autonomous current and voltage inverters with cut-off valves. The influence of the charge on the switching capacitor in parallel and series equivalent circuits on the restoration of the switching properties of the thyristors in the inverter power circuit is studied. It is shown that, due to the energy periodically accumulated in the inductive elements of the load, the voltage across the switching capacitor in the cut-off state is higher than in a conventional parallel autonomous current inverter. This ensures increased switching stability of the inverter. Consequently, the circuit of an autonomous current inverter with cut-off valves remains operational in valve converters for variable-frequency electric drives and maintains performance during sudden load surges and short circuits, since the voltage on the switching capacitor does not depend on the load voltage. Thus, the charge on the switching capacitor is preserved even when the load voltage drops sharply between thyristor commutations.

Biogenic Amine Determination by High-Performance Liquid Chromatography Using a Sol Gel Immobilized 2 Hydroxy 5 nitrobenzaldehyde 2,4 dinitro phenyl hydrazone Solid Phase Extractant

Abdassalam Abdelhafiz Tameem, Salam Salhin Mohamed, Afiyah Alnaas, Eny Kusrini — Wed, 29 Apr 2026 00:00:00 +0000

This study focuses on the solid phase extraction of biogenic amines (BAs) using a sol-gel adsorbent immobilized with a hydrazone ligand, named 2-hydroxy-5-nitrobenzaldehyde-2,4-dinitrophenylhydrazone. The hydrazone compound was synthesized and characterized through Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR) spectroscopy. The efficiency of the sorbent material for extracting BAs was evaluated using the solid phase extraction (SPE) method. Key experimental parameters affecting BA extraction, including pH, equilibrium time, ligand concentration, and biogenic amine (BA) concentration, were systematically investigated. The results indicated a strong recovery of BAs from aqueous samples, demonstrating a significant affinity between the sol-gel matrix containing the hydrazone ligand and the target analytes. The findings demonstrate that incorporating the hydrazone ligand resulted in a marked enhancement of extraction efficiency at a concentation of 17 × 10^-3 M. Notably, the method exhibited high selectivity for aliphatic biogenic amines such as putrescine (PUT), cadaverine (CAD), and spermidine (SPD). This extraction method was successfully applied to food samples, yielding good recovery rates.