Search Results (7,153)

Plasma nitriding is an advanced method to increase the hardness and wear resistance of different metal parts with complex shapes and geometries. The modelling is an appropriate approach for better understanding and improving such technologies based on multi-physical processes. Mathematical models of the coupled electromagnetic, fluid flow, and thermal processes in vacuum chambers for the low-temperature plasma treatment of metal parts have been developed. They were solved numerically via ANSYS/CFX software for a discretized solid and gas space of a plasma nitriding chamber. The specific electrical conductivity of the gas mixture, containing plasma, has been calibrated on the basis of an electrical model of the chamber and in situ measurements. The three-dimensional fields of pressure, temperature, velocity, turbulent characteristics, electric current density, and voltage in the chamber have been simulated and analysed. Methods for further development and application of the models and for technological and constructive enhancement of the plasma treatment technologies are discussed. Full article

It has been demonstrated that a monomolecular surface film with semiconducting characteristics forms on an austenitic, corrosion- and heat-resistant chromium–nickel steel with 0.10 wt.% C, 20 wt.% Cr, 9 wt.% Ni, and 6 wt.% Mn (10Kh20N9G6), microalloyed with yttrium, in aqueous 1 M H₂SO₄. This passive layer exhibits semiconducting behavior, as confirmed by electrochemical impedance and capacitance measurements. For the first time, key electronic parameters, including the flat-band potential, the thickness of the semiconductor layer, and the Fermi energy, have been determined from experimental Mott–Schottky plots obtained for the interphase boundary between the yttrium-microalloyed austenitic Cr–Ni steel (10Kh20N9G6) and aqueous 1 M H₂SO₄. The results reveal a systematic shift in the flat-band potential toward more negative values with increasing yttrium content in the alloy, indicating a modification of the electronic structure of the passive film. Simultaneously, a decrease in the Fermi energy is observed, suggesting an increase in the work function of the metal surface due to the presence of yttrium. These findings contribute to a deeper understanding of passivation mechanisms in yttrium-containing stainless steels. The formation of a semiconducting passive film is essential for enhancing the electrochemical stability of stainless steels, and the role of rare-earth microalloying elements, such as yttrium, in this process is of both fundamental and practical interest. Full article

This study aimed to experimentally investigate the differences in metallic structures owing to the gas nitriding and quenching process (GNQP) temperature of the Ti-15mass%Nb alloy and differences in the tribological properties of the surface layer. The GNQP heating temperature was 1023 K or 1223 K, and the holding time was set to 1 h. In the X-ray diffraction profiles, the diffraction peak of the (10$\overline{1}$1) plane of the hexagonal close-packed phase exhibited a shift toward lower angles, following the sequence AN:α, AQ:α′, and GNQP:α-TiN_0.3. In both the 1023 K and 1223 K GNQP specimens, the α″ phase exhibited lower values than the α′ phase; nonetheless, it still exhibited larger values than the annealed α phase. Based on transmission electron microscopy observations, the high core hardness of the 1223 K GNQP specimen was attributed to solid-solution strengthening caused by nitrogen diffusion or to strain hardening associated with the diffusion and was not attributed to the influence of precipitation phases, such as the ω phase. In the friction and wear tests, both the 1023 K and 1223 K GNQP specimens exhibited narrower wear track widths, clearly demonstrating that the GNQP enhanced the wear resistance. Moreover, the TiO₂ layer was effective in maintaining a low coefficient of friction. Full article

Zinc (Zn), a ubiquitous environmental transition metal primarily existing as Zinc ions (Zn²⁺), plays a critical role in various biological processes. Its extensive application in agriculture, industry, and healthcare has led to significant environmental contamination. However, the mechanistic contribution of Zn²⁺ to bacterial antibiotic resistance and virulence remains insufficiently understood. This review explores the sources, cycling, and environmental accumulation of Zn²⁺ in a One Health context, emphasizing their impact on bacterial antibiotic resistance and virulence. Zn²⁺ promote bacterial antibiotic resistance by regulating efflux pumps, biofilm formation, expression and transfer of antibiotic resistance genes, as well as synergistic effects with other heavy metals and antibiotics. Meanwhile, Zn²⁺ promote bacterial virulence by regulating quorum sensing, secretion and metal homeostasis systems, as well as oxidative stress response and virulence factor expression. Additionally, it highlights the potential of targeting Zn homeostasis as a strategy to combat environmental antibiotic resistance. Collectively, these findings provide key insights into the mechanisms by which Zn²⁺ regulate bacterial antibiotic resistance and pathogenicity, offering valuable guidance for developing strategies to mitigate the global threat of antibiotic resistance. Full article

Friction Stir Processing (FSP) has emerged as an advanced solid-state surface engineering technique for tailoring high-performance surface architectures in metal matrix composites (MMCs). By combining localized thermo-mechanical deformation with controlled material flow, FSP enables grain refinement, homogeneous dispersion of reinforcement, and strong interfacial bonding without melting or altering bulk properties. This review critically examines the role of FSP in enhancing the mechanical, tribological, and corrosion performance of composites, with emphasis on process–structure–property relationships. Key strengthening mechanisms, including grain boundary strengthening, load transfer, particle pinning, and defect elimination, are systematically discussed, along with their implications for wear resistance, fatigue life, and durability. Special attention is given to corrosion and tribo-corrosion behavior, highlighting electrochemical mechanisms such as micro-galvanic interactions, passive film stability, and interfacial chemistry. Furthermore, the eco-efficiency, industrial viability, and sustainability advantages of FSP are evaluated in comparison with conventional surface modification techniques. The review concludes by identifying critical challenges and outlining future research directions for the scalable, multifunctional, and sustainable design of composite surfaces. Full article

Metal–organic frameworks (MOFs) and porous organic frameworks (POFs) have been extensively explored in recent years as lubricant additives for various systems due to their structural designability, pore storage capacity, and tunable surface chemistry. These materials are utilized to construct low-friction, low-wear interfaces and investigate the potential for superlubricity. This paper systematically reviews the tribological behavior and key mechanisms of MOFs/POFs in oil-based, water-based, and solid coating systems. In oil-based systems, MOFs/POFs primarily achieve friction reduction and wear resistance through third-body particles, layer slip, and synergistic friction-induced chemical/physical transfer films. However, limitations in achieving superlubricity stem from the multi-component heterogeneity of boundary films and the dynamic evolution of shear planes. In water-based systems, MOFs/POFs leverage hydrophilic functional groups to induce hydration layers, promote polymer thickening, and soften gels through interfacial anchoring. Under specific conditions, a few cases exhibit superlubricity with coefficients of friction entering the 10⁻³ range. In solid coating systems, two-dimensional MOFs/COFs with controllable orientation leverage interlayer weak interactions and incommensurate interfaces to reduce potential barriers, achieving structural superlubricity at the 10⁻³–10⁻⁴ level on the micro- and nano-scales. However, at the engineering scale, factors such as roughness, contamination, and discontinuities in the lubricating film still constrain performance, leading to amplified energy dissipation and degradation. Finally, this paper discusses key challenges in achieving superlubricity with MOFs/POFs and proposes future research directions, including the design of shear-plane structures. Full article

Lost circulation in oil-based drilling fluids (OBDFs) remains difficult to mitigate because particulate lost circulation materials depend on bridging/packing and gel systems for aqueous media often lack OBDF compatibility and controllable in situ sealing. A dual-precursor oil–water biphasic metal–organic supramolecular gel enables rapid in situ sealing in OBDF loss zones. The optimized formulation uses an oil-phase to aqueous gelling-solution volume ratio of 10:3, with 2.0 wt% Span 85, 12.5 wt% TXP-4, and 5.0 wt% NaAlO₂. Apparent-viscosity measurements and ATR–FTIR analysis were used to evaluate the effects of temperature, time, pH, and shear on MOSG gelation. Furthermore, the structural characteristics and performances of MOSGs were systematically investigated by combining microstructural characterization, thermogravimetric analysis, rheological tests, simulated fracture-plugging experiments, and anti-shear evaluations. The results indicate that elevated temperatures (30–70 °C) and mildly alkaline conditions in the aqueous gelling solution (pH ≈ 8.10–8.30) promote P–O–Al coordination and strengthen hydrogen bonding, thereby facilitating the formation of a three-dimensional network. In contrast, strong shear disrupts the nascent network and delays gelation. The optimized MOSGs rapidly exhibit pronounced viscoelasticity and thermal resistance (~193 °C); under high shear (380 rpm), the viscosity retention exceeds 60% and the viscosity recovery exceeds 70%. In plugging tests, MOSG forms a dense sealing layer, achieving a pressure-bearing gradient of 2.27 MPa/m in simulated permeable formations and markedly improving the fracture pressure-bearing capacity in simulated fractured formations. Full article

Heavy metal pollution poses a serious threat to soil ecosystems worldwide, as long-term exposure can alter microbial community functioning and reduce overall ecosystem resilience. This study investigated the impact of heavy metal contamination in technogenic industrial areas of the East Kazakhstan Region on soil microbial communities. Soil samples were collected for chemical and metagenomic analyses. Concentrations of Zn, Pb, Cu, and Cd were quantified by flame atomic absorption spectrometry (FAAS). Using long-read whole-metagenome nanopore sequencing, we conducted strain-level profiling of soils with different levels of metal contamination. This approach provided high-resolution taxonomic data, enabling detailed characterization of microbial community structure. Heavy metal exposure did not significantly reduce microbial diversity or richness but influences the quality of community composition. Metal-resistant taxa dominated contaminated soils. Overall, the results highlight the value of long-read sequencing for resolving strain-level responses to environmental contamination. Full article

Ascaris lumbricoides is one of the most epidemiologically significant soil-transmitted helminths, and the environmental persistence of its eggs is largely attributed to their robust structural architecture. The search for ovicidal alternatives capable of overcoming this barrier has increasingly focused on metallic nanoparticles obtained through biological synthesis. Scanning electron microscopy (SEM) was employed to evaluate the ultrastructural effects of silver nanoparticles (AgNPs) biosynthesised by the nematophagous fungus Duddingtonia flagrans on A. lumbricoides eggs. Ultraviolet-visible spectroscopy and transmission electron microscopy confirmed the synthesis of AgNPs, revealing predominantly spherical, well-dispersed particles with an average diameter of 9.22 ± 4.9 nm. Cytotoxicity assays indicated an IC₅₀ of 7.7 µg/mL. SEM analyses showed that eggs in the control group maintained intact morphology, with no apparent deformities. In contrast, exposure to AgNPs induced pronounced structural alterations, including marked wrinkling, surface erosion and shell collapse, suggesting disruption of multiple layers. Albendazole alone produced deep linear fissures consistent with internal metabolic failure, though with minimal external erosion. The combined treatment with AgNPs and albendazole resulted in severe degradation. These findings demonstrate that AgNPs exhibit significant ovicidal activity and may serve as effective adjuvants to enhance the action of conventional anthelmintics against highly resistant helminth eggs. Full article

Energy conservation and efficiency enhancement necessitate continuous advancement in the development and preparation of multifunctional, high-performance lubricant additives. This paper reports three novel ashless, phosphorus-free, multifunctional nitrogen-containing heterocyclic dialkyl dithiocarbamate derivative additives (Py-2-DBDTC, PDM-DBDTC, and BZT-DBDTC). Thermal stability, oxidation resistance, and tribological properties were investigated for the synthesized additives. All three additives demonstrated excellent thermal stability and oxidation resistance. Furthermore, their extreme-pressure properties improved by 116.33% or more compared to the base oil, while wear reduction rates also exceeded 58.32%. Under both point-to-point and point-on-flat friction conditions, the friction-reducing performance of all three additives was equally outstanding. Across a broad temperature range (25 °C–150 °C), all additives maintained their friction-reducing properties. Analysis of the worn surface morphology reveals that all three additives undergo tribochemical reactions during the friction process, forming tribofilms containing sulfur elements. Research indicates that introducing different nitrogen-containing heterocyclic structures into dialkyl dithiocarbamates can effectively enhance the adsorption capacity of the additives on metal surfaces and promote the formation of tribofilms at the friction interface, thereby significantly improving tribological performance. These systematic investigations not only provide important guidance for the molecular design and industrial application of multifunctional lubricant additives but also further advance the development of sustainable lubrication technologies. Full article

In the present contribution, Hot-rolled and annealed ferritic stainless steel T4003 with three distinct Mo contents (0%, 0.1%, and 0.2%) served as the research subject. Weldability tests were implemented by means of gas metal arc welding. Coupled with microstructural characterization, mechanical property assessments, and electrochemical corrosion tests, the regulatory mechanism of Mo on the microstructure and properties of the HAZ was systematically elucidated. Results demonstrate that the influence of Mo content on the evolution of the coarse-grained region structure of heat affected zone becomes significant. The addition of 0.1% Mo refines the grains, increasing the fraction of lath martensite to 70–75% while limiting the maximum width of the coarse-grained zone to 0.64 mm. Meantime, the addition promotes the precipitation of (Nb, Ti, Mo) (C, N) composite carbonitrides, enhancing overall performance through synergistic grain refinement and second-phase strengthening. The sample with 0.1% Mo exhibits an average low-temperature impact energy of 16.3 J at −40 °C, with the highest Vickers hardness in the HAZ, favorable strength–plasticity synergy of the welded joint, and optimal corrosion resistance. The coarse-grained zone of the 0.2% Mo sample is dominated by coarse δ-ferrite and features a larger width, and the HAZ shows inferior mechanical properties and corrosion resistance. The precipitated phases in the 0.2% Mo segregate along the grain boundaries and distribute in a chain-like distribution, exacerbating the deterioration of material properties. These findings provide a technical reference for optimizing the composition design of T4003 ferritic stainless steel and ensuring its safe application in railway freight vehicles. Full article

Listeria monocytogenes (LM) contamination constitutes a paramount global threat to food safety, necessitating the urgent development of advanced, rapid, and non-destructive detection methodologies to ensure food security. This study successfully synthesized Bi₂WO₆ nanoflowers through optimized feed ratios of raw materials and further functionalized them with noble metal Au to construct a high-performance Au-Bi₂WO₆ composite nanomaterial. The composite exhibited high sensing performance toward acetoin, including high sensitivity (R_a/R_g = 36.9@50 ppm), rapid response–recovery kinetics (13/12 s), and excellent selectivity. Through UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and X-ray photoelectron spectroscopy (XPS) characterizations, efficient electron exchange between Au and Bi₂WO₆ was confirmed. This electron exchange increased the initial resistance of the material, effectively enhancing the response value toward the target gas. Furthermore, the chemical sensitization effect of Au significantly increased the surface-active oxygen content, promoted gas–solid interfacial reactions, and improved the adsorption capacity for target gases. Compared to conventional turbidimetry, the Au-Bi₂WO₆ nanoflower-based gas sensor demonstrates superior practical potential, offering a novel technological approach for non-destructive and rapid detection of foodborne pathogens. Full article

The tokamak is a toroidal device that utilizes magnetic confinement to achieve controlled nuclear fusion. One of the major technical challenges hindering the development of this technology lies in effectively dissipating the generated heat. In this study, the inner blanket structure of a tokamak is selected as the research object, and a multi–physics numerical model coupling magnetic field, temperature field, and flow field is established. The effects of background magnetic field strength, blanket channel width, and inlet velocity of the liquid metal coolant on the thermal–flow characteristics of the blanket were systematically investigated. The results indicate that compared with the L-shaped channel, the U-shaped channel reduces flow resistance in the turning region by 6%, exhibits a more uniform temperature distribution, and decreases the outlet–inlet temperature difference by 4%, thereby significantly enhancing the heat transfer efficiency. An increase in background magnetic field strength suppresses coolant flow but has only a limited impact on the temperature field. When the background magnetic field reaches a certain strength, the magnetic field has a certain hindering effect on the flow of the working fluid. Increasing the thickness of the blankets appropriately can alleviate the hindering effect of the magnetic field on the flow and improve the velocity distribution in the outlet area. Full article

Layered compounds containing the T₂O plane (T = transition metal), which is the anti-type of the CuO₂ plane in cuprate superconductors, have been explored widely because of their diverse physical properties. Among them, KV₂Se₂O has attracted much attention due to its interesting physical properties, especially the magnetic order. In this work, we report a new isostructural chromium oxyselenide, RbCr₂Se₂O. It was synthesized using a solid-state method using Rb₂CO₃ as the source of Rb and O for the title compound, with the assistance of Ba. The compound crystallizes in the space group P4/mmm with lattice parameters a = 4.01123(8) Å and c = 7.49357(18) Å. Magnetic susceptibility measurements indicate an antiferromagnetic transition at 345 K for RbCr₂Se₂O and also above room temperature, as the Néel temperature is T_N ≈ 400 K for KV₂Se₂O. The analysis of variable temperature XRD data reveals the anisotropic thermal expansion of the RbCr₂Se₂O lattice. The almost unchanged lattice parameter a near the transition temperature and the broad peak with an onset temperature of ~360 K in the differential scanning calorimetry data may have a relationship with the magnetic ordering. The measurement of electrical resistivity demonstrates the semiconducting behavior of RbCr₂Se₂O. The thermal activation model and variable-range hopping model are proposed to describe the conduction mechanism in the high- and low-temperature ranges, respectively. Full article

This study evaluated the ballistic performance and failure mechanisms of epoxy-based hybrid laminates reinforced with abaca/UHMWPE and pineapple leaf fiber (PALF)/UHMWPE fabrics fabricated by using vacuum-assisted hand lay-up. Ballistic tests utilized 9 mm full metal jacket (FMJ) rounds (~426 m/s impact velocity) under NIJ Standard Level IIIA conditions (44 mm maximum allowable BFS). This experimental test was complemented by finite element analysis (FEA) incorporating an energy-based bilinear fracture criterion to simulate matrix cracking and fiber pull-out. The results showed that abaca/UHMWPE composites exhibited lower backface signature (BFS) and depth of penetration (DOP) values (~23 mm vs. ~42 mm BFS; ~7 mm vs. ~9 mm DOP) than PALF/UHMWPE counterparts, reflecting superior interfacial adhesion and more ductile failure modes. Accelerated weathering produced matrix microcracking and delamination in both systems, reducing overall ballistic resistance. Scanning electron microscopy confirmed improved fiber–matrix bonding in abaca composites and interfacial voids in PALF laminates. The FEA results reproduced major failure modes, such as delamination, fiber–matrix debonding, and petaling, and identified stress concentration zones that agreed with experimental observations, though the extent of delamination was slightly underpredicted. Overall, the study demonstrated that abaca/UHMWPE hybridcomposites offer enhanced ballistic performance and durability compared with PALF/UHMWPE laminates, supporting their potential as sustainable alternatives for lightweight protective applications. Full article