Powder Metallurgy and Metal Ceramics最新文献

Basalt stone is widely used as a filler in composite materials. The heat-resistant and hard nature of basalt stone, which is formed from volcanoes, makes it essential for the thermal and mechanical properties of composite materials to be improved. The improvement of these properties is affected by the size of the material used. The smaller the filler particles, the greater the contact between the matrix and the filler particles in the composite material. This automatically increases the bond between them and improves the material's properties. Basalt, originally large in size, is processed into nano-sized to maximize its function. To reduce the size of basalt to the nanoscale, a planetary ball mill was used, in which stainless steel and zirconium balls rotate at a certain speed for varying periods of time. The effect of changes in rotation speed, grinding time, and the type of balls used in the planetary ball mill on the dispersibility and morphology of the ground material was studied. Both the rotating speed and milling time impact the size obtained. Significant size reductions occur when the rotation is faster and the milling time is longer. However, the change becomes less significant after a specific period. The smallest size obtained is 199.9 nm, which is 14% of the initial size before milling, which was 1421.9 nm. This smallest size is achieved through three stages of the process, using different balls at each stage.

Boehmite (AlOOH), due to its porous structure, excellent adsorption properties and high thermal stability, is widely used in various areas, including petrochemistry, biology and medicine (catalysts, flame retardants, functional ceramics, etc.). We propose replacing traditional Al salts (or Al alkoxides) with industrial-grade aluminium hydroxide Al(OH)₃ as the precursor and using a hydrothermal method to synthesise phase-pure boehmite powder. The phase transition from gibbsite to boehmite can be achieved by adjusting the hydrothermal temperature using industrial-grade aluminum hydroxide (Al(OH)₃) as the starting material. Based on this, the study investigated the influence of hydrothermal reaction temperature on the crystal structure and microscopic morphology of boehmite. The samples were characterized using a variety of analytical methods, including XRD, SEM, TEM, HRTEM, particle size distribution, and TG–DSC, to comprehensively analyze the phase, microscopic morphology, and phase transition process. Results demonstrate that pure-phase boehmite powder with a square plate-like morphology can be obtained at hydrothermal temperatures above 180°C. The square plates exhibit smooth surfaces, clear boundaries, and an average particle size of approximately 0.88 μm. Dehydration kinetics analysis using the Popescu method confirms that the synthesized boehmite has a thermal decomposition temperature above 700K and a dehydration weight loss of 17%. The dehydration process follows a model mechanism function of f(α) = 2(1 – α)^1/2, indicating a two-dimensional phase boundary reaction of shrinking cylindrical bodies. The average activation energy (E_a) for the dehydration process is determined to be 211.40 kJ/mol, the average pre-exponential factor (A) is 5.05 · 10¹³ min^–1, and the average correlation coefficient (R²) is 0.9939.

Biological methods (green synthesis) involving natural sources (bacteria, fungi, algae, plants, etc.) were developed in the 21st century in South and East Asia, South America, and Middle East countries. The mechanism of ZrO₂ nanoparticle formation using microbial systems (bacteria and fungi) includes biosorption and bioreduction. Rounded and rod-shaped primary particles, comprising a mixture of m-ZrO₂ and t-ZrO₂ phases, were synthesized. These powders exhibit effective antimicrobial and antibiofilm activity and are promising for the delivery of pH-sensitive drugs and the development of biosensors. The use of various plant extracts in thermal decomposition, coprecipitation, sol–gel processes, solution combustion, and hydrothermal synthesis was explored. The growth of ZrO₂ nanoparticles during green synthesis proceeds through three stages: activation, growth, and termination. The resulting ZrO₂ powders hold promise for applications in novel antimicrobial agents, anticancer drugs, photocatalysts for wastewater treatment, fillers in polymer nanocomposites, and nanoadditives to enhance the efficiency of diesel engines. Composite powders such as ZrO₂/RGO with improved anticancer properties, ZrO₂/PdO and ZrO₂ : Sm³⁺ (11 mol.%) for photocatalysts, and ZrO₂ : Mg (0.1–5 mol.%) for nanophosphors in display devices were developed. The choice of the synthesis route for the starting powders is based on the intended application of the final material. The synergistic effect of physicochemical and biological approaches in green synthesis expands the potential for microstructural design of functional ZrO₂-based materials for diverse applications.

Six diamond tube drills were fabricated by vacuum impregnation using cutting grains of natural diamonds of grade A1 with grain sizes of 250/200, 315/250, 500/400, 800/600, 1000/800, and 1200/1000 μm. For comparative analysis, three drills were produced with synthetic diamonds of grades AS32 500/400, AS400 315/250, and AS400 500/400 (DSTU 3292–95). To ensure reliable fixation in the tool body, diamond grains coated with molybdenum and copper were embedded in a Cu–15 wt.% Sn matrix with added fillers (5 wt.% ultrafine diamond powder of grade ASM 1/0 and molybdenum). The compressive strength of the diamond grains was evaluated. The paper presents results from comparative laboratory tests of the diamond drills in marble, granite, and silicon carbide-based abrasive stone. Performance characteristics—drilling speed and drill wear—were studied as functions of the natural diamond grade used. The drilling speed depended on the size of the diamond grains. The lowest drilling speeds (3.52, 6.83, and 23.1 mm/min for granite, marble, and abrasive stone) were observed in drills equipped with small (A1 250/200 μm) and weak (50 N) diamond grains. When larger (A1 1200/1000 μm) and stronger (350 N) diamond grains were used, the drilling speed increased significantly (by approximately 4, 3.2, and 3.8 times) to 14.07, 22.1, and 87.99 mm/min for granite, marble, and abrasive stone, respectively. The lowest drilling speed observed in granite with all tested drills was due to its high hardness, being approximately twice that of marble. However, despite even greater hardness of silicon carbide, forming the base of the abrasive stone, the drilling speed remained high. When marble was drilled with tools containing the smallest diamond grains (A1 250/200 μm), their wear amounted to 0.0139 g. For harder materials (granite and abrasive stone), tool wear increased significantly (by factors of 41 and 48), reaching 0.5701 and 0.6665 g. With increasing grain size and compressive strength of the natural diamond grains, drill wear decreased, by factors of approximately 8, 317, and 14 for marble, granite, and abrasive stone. The greatest reduction in wear was recorded for granite. As a result, drills equipped with large and strong diamond grains (A1 1000/800 and A1 1200/1000) exhibited similarly minimal wear in the drilling of marble and granite: 0.0036 and 0.0018 g for granite and 0.0035 and 0.0017 g for marble.

Composite materials reinforced with titanium nitride particles, which serve as the basis for manufacturing 3D-printed components that are promising for use in extreme environments, such as cutting tools, wear-resistant and protective coatings, biomedical products, and electrochemical energy capacitors, were studied. Linear and nonlinear acoustic methods were employed to evaluate the elastic and damping properties of polypropylene-based composites reinforced with up to 46 vol.% titanium nitride particles. When the volume content of titanium nitride particles raised from 20% to 46%, Young’s modulus of the composites was found to increase from 4.91 to 9.77 GPa and their shear modulus from 1.85 to 3.55 GPa. The dependence of both elastic moduli on the ceramic volume content over the studied range can be described with satisfactory accuracy by the Halpin–Tsai equation, using an empirical reinforcement particle shape factor of 4.2, which closely matches the experimentally determined value. The damping capacity of the studied composites ranged from 0.06 to 0.12 and was slightly lower in the composite with the higher titanium nitride content. The damping behavior of the composites as a function of the maximum cyclic strain amplitude exhibited a minimum at stress levels around 2.5 MPa. At the same stress levels, a discontinuity in the amplitude dependence of the relative resonance frequency shift was observed. The authors attribute both phenomena to structural transformations within the composite that occur during cyclic deformation under the specified amplitudes and oscillation frequencies. The results demonstrate the potential of acoustic nondestructive methods to monitor the quality of filaments for 3D printing and finished composite products.

Innovative applications such as lightweight structural and energy-absorbing uses have been found for magnesium-based foams due to their exceptional properties, such as low density, high specific strength, and excellent energy absorption. This review explores the influence of various space holder materials and manufacturing methods on the structural, mechanical, and thermal properties of magnesium-based foams. Key observations indicate that specific energy absorption is improved with certain space holders and manufacturing techniques, while corrosion resistance is significantly enhanced with higher space holder fractions. However, increasing porosity reduces thermal conductivity and peak compressive strength, highlighting the trade-offs in foam design. Comparisons among stir casting, powder metallurgy, and melt foaming methods reveal notable differences in density, mechanical strength, and corrosion resistance. Stir casting produces Mg foams with a density of 1.57 g/cc and a porosity of 16.5%, offering moderate mechanical strength (peak compressive stress ~208 MPa) and corrosion resistance. Powder metallurgy yields highly porous foams (up to 84.5%) with lower density (0.28 g/cc) but reduced strength (~30 MPa) and corrosion resistance. Melt foaming balances porosity (44.6%) and strength (56.97 MPa), making it suitable for energy absorption, though corrosion resistance varies with processing conditions. Furthermore, thermal conductivity studies suggest that magnesium foams can be tailored for applications requiring thermal insulation. The results underscore the need for optimized manufacturing techniques and tailored space holder materials to achieve the desired balance of properties. Optimization can be achieved by carefully controlling porosity levels, selecting suitable space holder materials, and fine-tuning processing parameters, such as sintering temperature and infiltration conditions, to balance mechanical strength and thermal insulation. This review provides a comprehensive understanding of the current advancements in magnesium foam research and outlines the pathways for developing next-generation magnesium foams for diverse industrial and biomedical applications.

In 2024, the Ukrainian Commission on Phase Diagrams and Thermodynamics, an integral component of the Alloy Phase Diagram International Commission (APDIC), comprising 18 representatives from 26 countries, commemorated its thirtieth anniversary. The exchange of scientific information and coordination of activities of the international scientific community, mainly in the field of phase diagrams and thermodynamics, promoting the application of phase diagrams in industry and fundamental science, and dissemination of the methodology of critical evaluation of scientific information in world science are among the priority tasks of the APDIC's activity.— As part of the annual report of the Ukrainian Commission, at the APDIC meeting on May 31, 2024, information was presented on the results of Ukrainian scientists' activities in this field for 2023. It is presented in the form of a table with data on the studied systems and obtained results, and a list of references to published papers. Scientists from the Frantsevich Institute for Problems of Materials (National Academy of Sciences of Ukraine, Kyiv), Taras Shevchenko National University of Kyiv (Ministry of Education and Science of Ukraine, Kyiv), and Donbas State Engineering Academy (Ministry of Education and Science of Ukraine, Kramatorsk) provided relevant information to the Ukrainian Commission.

Solid oxide fuel cells (SOFCs) are considered a high-efficiency technology for energy conversion. Ferritic stainless steel has become the preferred material for interconnects due to its proper coefficient of thermal expansion, ease of processing, and economy. This study aims to investigate the effects of density, La, and Si content on the mechanical, high-temperature oxidation, and electrical properties of powder metallurgy ferritic stainless steel used for SOFCs interconnects. Ferritic stainless steel water atomized powders with varying contents of La and Si were pressed at 600 and 700 MPa, and then sintered at 1380°C for 3 h in a hydrogen atmosphere. The properties were evaluated in this study through metallographic observations, tensile tests, high-temperature oxidation tests, and area-specific resistance (ASR) measurements. The phases and microstructures were characterized using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results indicate that high density leads to improved oxidation resistance and electrical performance, with higher-density specimens exhibiting better oxidation mass gain and ASR values than lower-density specimens. The addition of La element improves the mechanical properties, antioxidant properties, and electrical properties of the material, and the addition of La element reduces the ASR of the specimen from 44.16 to 31.18 mΩ ∙ cm². The mechanical properties and oxidative mass gain of the specimen with low Si content are better than those of the specimen with high Si content. When the Si content is reduced from 0.7 to 0.1%, the ASR of the specimen decreases from 57.471 to 44.161 mΩ ∙ cm².

Technology for in situ synthesis of superfine Si₃N₄–NbN composite powders without the need for subsequent milling via solid-state interaction in the Si₃N₄–Nb reaction mixture was developed for the production of nitride ceramics by spark plasma sintering and hot pressing. The regularities of solid-state interaction during vacuum heat treatment of the β-Si₃N₄–27.4 wt.% Nb reaction powder mixture, calculated for the synthesis of higher niobium nitride by the 4Nb + Si₃N₄ = 4NbN + 3Si reaction, were analyzed. The interaction of the mixture components was studied under isothermal holding for 1 h at 1000, 1100, 1200, 1300, and 1400°C. Solid-state interaction with Si₃N₄ was found to occur at 1000°C, resulting in the formation of a nitrogen solid solution in niobium (α-Nb). At 1100°C, the formation of lower nitride Nb₂N and lower silicide Nb₅Si₃ was observed. An increase in the temperature to 1200 and 1300°C led to a greater amount of Nb₅Si₃, whereas the amount of Nb₂N hardly changed. At 1400°C, the product contained a mixture of γ-Nb₅Si₃ and NbSi₂ silicides, while the lower nitride was absent. Thermodynamic calculations confirmed that the formation of higher niobium nitrides under these vacuum heat treatment conditions was thermodynamically unfavorable. Based on the established structural and phase regularities of solid-state interaction in the Si₃N₄–Nb mixture, a two-stage synthesis process was developed. This process was implemented in a single cycle consisting of vacuum heat treatment at 1000°C, followed by nitriding at 1200 and 1300°C. Nitriding at 1300°C yielded a powder composed of Si3N4 and a mixture likely containing three higher niobium nitrides of different polymorphic modifications. Using the developed synthesis process, experimental batches of Si₃N₄–20 vol.% NbN and Si₃N₄–10 vol.% NbN composite powders were produced. Analysis of the experimental batches showed that all synthesized powders possessed the required phase composition and were superfine. The particle size of the Si₃N₄–20 vol.% NbN powder ranged from 400 nm to 9 μm and that of the Si₃N₄–10 vol.% NbN powder ranged from 1.5 to 5 μm.