Powder Metallurgy and Metal Ceramics最新文献

The development and detailed characterization of mesoporous ternary nanocomposite Ag/Ce/N/ZnO were meticulously undertaken using a hydrothermal technique. The elemental composition was authenticated through energy-dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS), confirming the constituents of the developed samples. Surface and pore structure analyses, conducted via the Brunauer–Emmett–Teller (BET) method, revealed the mesoporous characteristics of the materials, evidenced by class IV hysteresis loops, highlighting an enhanced surface area to 59.01 m²/g due to mesoporosity. Ultraviolet-visible (UV-Vis) spectroscopy results indicated a reduction in the optical band gap from 3.094 to 2.501 eV, associated with increased Ag-dopant concentration to 6%. The structural integrity, maintained as a hexagonal wurzite configuration, was verified by X-ray diffraction (XRD), which also showed a slight increase in crystallite dimensions from 21 to 23 nm with higher doping levels. Scanning electron microscopy (SEM) analyses depicted the synthesized entities' agglomeration tendencies and distinct morphological features. Photoluminescence (PL) studies suggested decreased electron-hole recombination rates for samples with elevated doping ratios. Moreover, these enhanced materials showcased augmented photocatalytic performance in the degradation of methylene blue and Congo red dyes after 90 min of contact, indicating their promising applications for water purification.

The electromagnetic characteristics, particularly the real ε_r′ and imaginary ε_r″ parts of the dielectric constant, of new AlN-based composites with additions of powdered diamond, soot, and diamond with 3–5 wt.% molybdenum, synthesized by hot pressing, were studied at frequencies ranging from 12.4 to 18 GHz. Structural features and key phases of the composites—AlN, C (graphite), Al₃(O, N)₄, Al, and Mo₂C (in the AlN–Y₂O₃–C (diamond)–Mo system)—were determined by X-ray diffraction. Scanning electron microscopy with energy-dispersive X-ray analysis for determining the quantitative elemental composition of the key phases revealed a low oxygen content in the AlN lattice. Measurements of the electromagnetic characteristics showed that the new composites with graphite phase inclusions had stable dielectric characteristics over the entire frequency range (ε_r′ = 12.38–33.03 and tgδ = 0.009–0.214). The introduction of 3% diamond powder to the AlN-based charge hardly increased the ε_r′ and tgδ values (12.3 and 0.009, respectively). When a 5% : 5% mixture of diamond and molybdenum powders was added, the dielectric constant ε_r′ reached 17.04 and tgδ was 0.067. Composites with 5% soot demonstrated the highest dielectric constant (33.03) and dielectric losses (0.214). Thus, the dielectric constant was found to be increased through specific phase composition of the materials and dispersed distribution of conductive phases (C, Mo₂C) within the composites with minimal contacts between them.

Solid oxide fuel cells (SOFCs) are among the most promising energy-generating devices, offering high efficiency, environmental friendliness, and flexibility to use a wide range of fuels. The main components of an SOFC are an electrolyte, an anode, a cathode, and a connector (interconnect). The operating principle of SOFCs is as follows. Oxygen is supplied to the cathode, where it is reduced. Oxygen ions move through a dense ceramic electrolyte (ionic conductor) from the cathode to the anode. Meanwhile, hydrogen is supplied to the anode, where a catalyst (metallic nickel) promotes its dissociation into atoms. When hydrogen is oxidized, it releases electrons into the external electric circuit, forming water in the process. The water formation reaction is exothermic. As a result, a constant electric current flows through the external electric circuit, enabling the direct conversion of chemical energy into electrical energy. The interconnect is a component that connects individual fuel cells into a power system — an SOFC stack. A brief overview of materials for ceramic fuel cell connectors (interconnects) and areas for improving their properties are provided. The classification of ceramic (lanthanum chromite LaCrO₃) and metallic (chromium-based alloys, nickel–chromium alloys, and ferritic stainless steels) interconnect materials is presented. Ceramic interconnects are commonly used for high-temperature SOFCs (~1000°C). The disadvantages of these materials include the difficulty of manufacturing interconnects with complex shapes and their high cost, resulting from the use of rare-earth elements. Among metallic materials, ferritic stainless steels with high chromium content (Crofer 22 APU and Crofer 22) are the most promising in terms of key performance indicators. The main shortcomings of modern chromium-based steel materials for interconnects in SOFC energy systems and the principles for changing the development paradigm for advanced lightweight materials with improved properties are outlined. The replacement of chromium steels with promising titanium-based composites is proposed.

In this study, hydroxyapatite (HA) was used as a bioceramic on a TiNi shape memory alloy. Butanol and tri-ethanolamine were used as suspensions with HA particles. The electrophoretic deposition (EPD) process was performed at 20, 30, and 40 V for 1–5 min on the cathode. Samples were left at room temperature for 24 hours to obtain slow drying after deposition. Weight and layer thickness were then measured. Sintering was conducted in an Ar atmosphere at 800°C for 2 h. The phases and surface morphologies were examined using XRD and SEM. The results showed that a uniform, homogeneous, crack-free coating layer can be achieved at a voltage of 30 V and low sintering temperatures. Also, longer deposition times increased the coatings' weight and thickness. Compared to other deposition methods, such as sol-gel and plasma coating, the method presented in this research can be used as an alternative method for bioactive coatings. The hardness of the undecorated HA coatings obtained at 15 and 30 V EPD voltage reached 0.2245 ± 0.036 GPa and 0.0661 ± 0.008 GPa, respectively.

Three layered materials from technically pure iron sheets with varying degrees of interlayer bonding were produced by hot and cold pseudovacuum rolling methods. The elastic, damping, and high-cycle fatigue characteristics of the materials were determined through resonant vibration testing of flat samples under bending conditions. Known fatigue damage dependences based on the cyclic strength energy density model for structural materials under low-cycle fatigue were considered. Using the studied materials as an example, the feasibility of extending this energy-based approach to the high-cycle fatigue and nondestructive loading regions was demonstrated. The elastic and inelastic components of the strain energy density were calculated from experimental fatigue curves for rolled layered materials over a range of 105 to 107 load cycles and from dependences of the vibration decrement on the cyclic loading amplitude varying from low to destructive strains. Thus, the strain energy density model was extended to the nondestructive cyclic (operational) loading region. In this case, the density of the elastic component of cyclic strain energy was found to be 1.92 times more sensitive to load amplitude than the destructive fatigue curve stresses, while the reliability coefficient for the total cyclic strain energy density was significantly higher than that for the inelastic strain energy density. The decrement of vibrations as a function of cyclic load amplitude and, accordingly, the inelastic component of the strain energy density were shown to be sensitive to the interlayer bonding strength, while the fatigue resistance (endurance limit) was sensitive to the degree of cold rolling applied to the layered materials.

Establishing the relationship between atomized particle sizes and atomization process parameters is important both theoretically and technologically. However, the large number of process parameters complicates this task. A potential solution is to establish simple dependences on the main (defining) parameters (or functional dependences). Determining the mass median particle diameter of a powder batch is particularly difficult, so this study incorporates data from other authors in addition to personal research findings. This study used personal research findings and calculations of the mass median particle diameter of the powders produced at the pilot plant of the Frantsevich Institute for Problems of Materials Science by high-pressure (0.05 to 200 MPa) water atomization of the Al-40.1 Cu-16.9 Fe melt. A series of experiments were performed on the Al-40.1 Cu-16.9 Fe alloy to produce powders by varying the atomization pressure and melt temperature. The dataset included the size distributions of water-atomized powders of pure metals: lead, zinc, copper, stainless and high-speed steels, and copper-phosphorus and ferrosilicon alloys. For comparison, mass median diameters of lead, aluminum, and copper powder particles produced by compressed air atomization at 0.4 to 2.8 MPa were also used. Based on these data, the relationship between the ratio of the mass median particle diameter to the gravitational melt jet diameter, d₅₀/D (inverse degree of atomization), and the Weber number (We) was plotted in logarithmic coordinates. The correlation between the inverse degree of water and gas atomization for liquid metals and alloys and the Weber number followed a linear dependence: (text{lg}left({d}_{50}/Dright)=2.0-0.5times text{lg}left(text{We}right)).

The electrochemical properties of composite electrodes produced from ZrNi_1.2Mn_0.5Cr_0.2V_0.1 and ZrNi_1.2Mn_0.45Cr_0.2V_0.15 alloys with and without copper powder additions, pressed with alloy-to-copper weight ratios of 1 : 0.5 and 1 : 1, were studied under two discharge modes: discharge to a voltage of 0.85 and 0.7 V between the test electrode and the counter electrode. X-ray diffraction was employed to determine the phase composition of the alloys. An increase in vanadium content by ~1.3 wt.% led to a significant decrease in the amount of the Zr₇Ni₁₀ phase in the ZrNi_1.2Mn_0.5Cr_0.2V_0.1 and ZrNi_1.2Mn_0.45Cr_0.2V_0.15 alloys (~17 and ~8 vol.%, respectively). The activation of the starting electrodes (without copper additions) depends on the amount of this phase with discharge to 0.85 V: the ZrNi_1.2Mn_0.5Cr_0.2V_0.1 alloy electrode, with a higher Zr₇Ni₁₀ content, activated faster. Composite electrodes from both alloys with 1 : 1 copper additions discharged to 0.7 V activated at the same rate within eight cycles, indicating that activation in these conditions does not depend on the Zr₇Ni₁₀ content. The substitution of manganese with vanadium slightly decreased the maximum discharge capacity of the electrodes (with and without copper powder additions) under both discharge modes. When discharged to 0.7 V relative to the Ni(OH)₂ electrode (or ~0.4 V relative to the Hg/HgO electrode), both alloy electrodes, with and without copper powder additions, preserved their cyclic stability and showed accelerated activation compared to discharge at 0.85 V. The maximum discharge capacity was achieved with 1 : 1 copper additions and discharge to 0.7 V: 385 mA · h/g for the ZrNi_1.2Mn_0.5Cr_0.2V_0.1 alloy and 400 mA · h/g for the ZrNi_1.2Mn_0.45Cr_0.2V_0.15 alloy (versus ~280 mA · h/g at 0.85 V). Thus, a lower manganese content, along with an accordingly higher vanadium content (~1.3 wt.%), only slightly reduced the maximum discharge capacity of the electrodes and slowed their activation in the absence of catalytic additions. The activation of the starting electrodes produced from both alloys depends on the Zr7Ni₁₀ content but does not depend on this phase in the case of 1 : 1 copper additions and discharge to 0.7 V.

This study focuses on synthesizing and characterizing CaSnO₃:Bi²⁺ near-infrared (NIR) long persistent luminescent materials. NIR persistent luminescent materials enable safe and efficient imaging due to their deep tissue penetration and reduced phototoxicity compared to ultraviolet (UV) excited materials. The CaSnO₃:Bi²⁺ materials were synthesized using a high-temperature solid-state method. The effects of varying Bi²⁺ doping concentrations (1, 2, 5, 7, and 10%) on the material’s properties were systematically investigated. The synthesis process was confirmed by X-ray diffraction (XRD) analysis, revealing a perovskite structure for all samples. Scanning electron microscopy (SEM) analysis indicated uniform particle sizes of approximately 1 μm, successfully incorporating Bi²⁺ ions confirmed by energy-dispersive X-ray spectroscopy (EDS). The luminescent properties of the CaSnO₃:Bi²⁺ materials were characterized using fluorescence spectroscopy and thermoluminescence spectroscopy. The excitation and emission spectra showed peaks at 260, 620, and 680 nm, corresponding to the transitions of Bi²⁺ ions. The samples exhibited NIR persistent luminescence under 260 nm excitation, with the CaSnO₃:5% Bi²⁺ sample demonstrating the highest phosphorescence intensity and longest decay time. This optimal performance was attributed to the highest trap concentration, confirmed by thermoluminescence spectroscopy. The persistent NIR luminescence of the CaSnO₃:Bi²⁺ materials was attributed to trap level up-conversion, a phenomenon where NIR excitation leads to NIR emission without the involvement of up-conversion materials. This mechanism arises from the reverse carrier transition from deep traps (DTs) to shallow traps (STs). Thermoluminescence spectroscopy further confirmed the occurrence of trap level up-conversion in the CaSnO₃:5% Bi²⁺ sample. The successful synthesis and characterization of CaSnO₃:Bi²⁺NIR long persistent luminescent materials with trap level up-conversion mechanisms opens up new avenues for their application in various fields.

The creep-resistant γ-TiAl-based Ti₄₆Al₄₉Nb₄Mo₁ alloy, with a composition close to that of the third- generation TNM alloy, was developed with the powder metallurgy method using titanium hydride and intermetallics as starting materials. The alloy had a duplex structure, with 20–25 μm grains, consisting of 22% α₂ phase and 78% γ phase. No additional phases were detected. Mechanical properties of the powder material at temperatures up to 850°C were studied by compression and bending tests. At a temperature of 20°C, the Ti₄₆Al₄₉Nb₄Mo₁ alloy exhibited a bending strength of 800 MPa and significant high-temperature strength, remaining at a level of 670 MPa at 850°C. The alloy also showed enhanced creep resistance in compression tests, attributed to its fine-grained duplex structure. At temperatures up to 800°C, the alloy demonstrated considerably higher yield stress and strengthened more rapidly than the three-component material. Creep testing of the Ti₄₆Al₄₉Nb₄Mo₁ alloy between 750 and 800°C indicated increased high-temperature creep resistance. The strain rate sensitivity remained unchanged at both 750°C and at 800°C under all applied loads, suggesting an invariant deformation mechanism. The calculated thermal activation parameters for creep were in good agreement with data for cast alloys of this class. The mechanical properties of the Ti₄₆Al₄₉Nb₄Mo₁ alloy indicate its potential for use at temperatures up to 800°C.

This paper examines the relative merits of integral and traditional segmented compaction concerning three key aspects: uniformity of relative density, distribution of low-density areas, and the influence of loading mode on relative density. Under the actual operational conditions and anticipated dimensions of the final product, the initial dimensions of the material and the surface pressure applied before compaction are calculated. The average relative density and relative density distribution of circular titanium electrode blocks with different diameters (450, 500, and 550 mm) and different compaction processes were analyzed in the densification process. The impact of lubrication on the relative density distribution was investigated by modifying the coefficient of friction from 0.7 to 0.5, 0.3, and 0.1. The findings indicate that the electrode block's diameter significantly influences the relative density distribution. When the diameter exceeds 500 mm, it is imperative to pay particular attention to the low-density area (less than 0.7), which exhibits a notable increase from 0.42 to 1.71% in unidirectional compaction and from 0.02 to 0.18% in bidirectional compaction when the integral method is employed. Accordingly, the reduction in slag volume resulting from this factor should be considered when using the integral compaction method. In the case of electrode blocks with a diameter of 800 mm, the percentage of relative density between 0.7 and 0.8 under bidirectional compaction is higher than that under unidirectional one. However, the results were contrary in the range of 0.8 to 0.9. Compared to the integral method, the segmented method exhibited a comparable trend, with a percentage of relative density between 0.7 and 0.8, reaching 86.03% and a percentage of less than 0.7, equaling 0%. Furthermore, the core density of the segmented method is also higher than that of the integral one and has a standard deviation of approximately half that of the integral method. It indicates that in the case of uniform mixing, the uniformity of the segmented compaction is superior, and segregation is not readily produced. The standard deviation of the relative density distribution decreased with a reduction in the coefficient of friction, suggesting that the lubricant addition is beneficial in enhancing the uniformity of the density.