Search Results (5,315)

Al-based composites have attracted significant attention in the aerospace, automotive, and electronic industries due to their lightweight characteristics, high specific strength, and superior thermal conductivity. Although Al–cBN composites exhibit enhanced mechanical and wear properties, galvanic interactions between the Al matrix and carbon-based reinforcements can accelerate localized corrosion and reduce electrochemical stability in chloride-containing environments. To improve these limitations, Ni coating has been considered an effective surface modification method because of its high corrosion resistance and electrochemical stability. However, investigations on the surface and electrochemical behavior of Ni-coated Al–cBN composites remain limited. In this study, the surface characteristics and electrochemical behavior of Ni-plated Al–cBN composites were systematically investigated. Surface morphology and microstructural evolution were analyzed using FE-SEM, while crystallographic characteristics and phase evolution were examined through XRD analysis. In addition, electrochemical properties were evaluated using OCP and potentiodynamic polarization measurements. The results revealed that the specimen plated for 600 s exhibited a corrosion potential shift from −0.92 V to −0.38 V, together with a significant reduction in corrosion current density, indicating improved electrochemical stability and corrosion resistance due to the formation of a dense Ni coating layer. These results demonstrate that electroless Ni plating is an effective surface modification technique for enhancing the corrosion resistance and electrochemical stability of Al–cBN composites. Full article

The demand for large-scale high-performance components with tailored properties in the aerospace and automotive industries has increased interest in multi-material additive manufacturing (AM). Among AM techniques, the Wire Arc Additive Manufacturing (WAAM) process is preferred for bimetallic fabrication due to high deposition rates, low equipment costs, and efficient material utilization. However, differences in metallurgical and thermal properties between dissimilar alloys can cause heat accumulation, leading to thermal stresses, cracking, and weak interfacial bonds. To the best of the authors’ knowledge, no study has reported the fabrication and characterization of a 17-4PH SS/Inconel 625 joint using the large-scale CMT-WAAM Process. To fill this gap, this study characterizes the microstructure and elemental distribution of the joint using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray Microscopy (XRM) and energy dispersive spectroscopy (EDS). Microstructural analysis revealed a martensitic matrix with retained δ-ferrite in the 17-4PH region, a fully austenitic γ-phase in the Inconel 625 region, and a mixed BCC–FCC transition zone at the interface. EDS results demonstrated a Fe–Ni compositional gradient across the interface. Radiographic inspection confirmed a defect-free build, and XRM results showed a porosity of less than 0.003% only in the 17-4PH region. Tensile testing confirmed joint integrity, with fracture occurring in the Inconel 625 region, and average yield and ultimate tensile strengths of 391 ± 7 MPa and 676 ± 9 MPa, respectively. The simplified Johnson-Cook constitutive model successfully predicted the ultimate tensile strength (UTS), with a prediction error of 9.3% compared to the experimental result. Furthermore, a novel 3D-structured light scanner technique was developed and validated with an extensometer to provide insight into localized strain behavior. Full article

Composite hydrogel based on acrylic acid and acrylamide, modified with metal ions (Ni²⁺, Al³⁺, Fe²⁺, Fe³⁺) with concentration 0.3 wt%, were synthesized in water or polyethylene glycol (with a molecular weight of 400 Da) at three monomer ratios (7/3, 1/1, 3/7). Dynamic mechanical analysis shows that the equilibrium modulus of elasticity (<!-- MathType@Translator@5@5@MathML2 (no namespace).tdl@MathML 2.0 (no namespace)@ --> Full article

Carbon dioxide (CO₂) conversion in non-thermal plasma is a promising route for carbon utilisation under mild conditions. This study investigates the performance and dynamic behaviour of kaolin-based catalysts modified with Ni (nickel), Ni–Ce (nickel-cerium), and Fe–Cu (iron-copper) oxides in a Dielectric Barrier Discharge (DBD) reactor. Materials were characterised using X-ray diffraction, energy-dispersive X-ray fluorescence, and scanning electron microscopy with energy-dispersive X-ray spectroscopy. CO₂ conversion was evaluated at varying Plasma Energy Numbers (PEN = 1.65–20) with time-resolved gas analysis over a 10 min period. Results demonstrate that the kaolin support is not inert; its dielectric properties actively influence discharge characteristics. Ni-based catalysts exhibited the highest stable activity, reaching ~53% conversion for samples calcined at 500 °C. Conversely, adding cerium oxide significantly decreased conversion and induced temporal instabilities, contrasting with its typical role in thermal catalysis. Time-resolved measurements revealed that Ni–Ce and Fe–Cu systems exhibit initial activity followed by gradual deactivation, suggesting plasma-induced surface restructuring. These findings highlight that catalyst performance in DBD is governed by a complex interplay of chemical activity and plasma–material interactions. The generated time-series data provide a robust foundation for machine learning applications in predictive modelling and stability classification of plasma-catalytic systems. Full article

Solid-state heat pumps based on caloric effects are emerging as a promising alternative to conventional vapor. compression systems owing to their use of solid refrigerants with zero global warming potential. However, single-effect caloric technologies are intrinsically limited by the temperature-dependent nature of the caloric response, which typically exhibits a peak adiabatic temperature change within a narrow temperature range. In this context, multicaloric approaches offer a promising pathway to enhance thermal performance by combining multiple external fields. This work focuses on the comparison between simultaneous and sequential (cascade) multicaloric operation, with particular attention to the interaction between field application and the temperature-dependent caloric behavior of the material. A finite element model is developed to investigate a multicaloric solid-state heat pump operating in the air conditioning temperature range. A representative material is considered: Mn_0.6Ni_0.6Fe_0.4Co_0.4Si_0.95Ga_0.05, characterized by distinct magnetocaloric and barocaloric responses occurring at different temperature ranges. The analysis explores different field application strategies, including both simultaneous and sequential configurations. The preliminary results suggest that simultaneous multicaloric operation enables a more effective exploitation of the caloric response by aligning the field activation with temperature regions closer to the corresponding peaks. In this framework, cascade strategies appear to offer additional flexibility in tuning system performance under realistic operating conditions. The proposed approach provides a new perspective for the design of multicaloric heat pumps, highlighting the potential role of thermodynamic matching between field activation and material response. Ongoing work is focused on further quantifying these effects and identifying optimal operating conditions. Full article

To clarify the anomalous corrosion behavior in Cu-containing CoCrNi-based medium-entropy alloys, in which an enhanced corrosion driving force is accompanied by a reduced overall corrosion rate, the phase constitution, microstructure, electrochemical behavior, post-corrosion morphology, and surface chemical states of CoCrNi, CoCrNiCu, and CoCrNiCuFe alloys were systematically compared. The results show that Cu addition induces pronounced phase separation in the CoCrNi matrix, leading to the formation of a Cu-depleted FCC1 phase, a continuous Cu-rich FCC2 intergranular network, and dispersed nanoscale Cu-rich precipitates, with an FCC2 area fraction of about 0.145. In 3.5 wt.% NaCl solution, CoCrNiCu exhibits a stronger thermodynamic tendency for corrosion, whereas its overall corrosion rate does not increase, but instead shows the lowest corrosion current density and higher impedance, indicating an anomalous electrochemical response. Post-corrosion SEM morphology, EDS elemental mapping, and XPS valence-state analyses further reveal that corrosion is mainly concentrated in the Cu-rich phases and their adjacent narrow regions, while the Cu-rich phases themselves remain relatively stable as non-sacrificial cathodes. Semi-quantitative thermodynamic and mass-transport calculations indicate that although Cu-induced phase separation enhances the micro-galvanic corrosion driving force, with an estimated interphase potential difference of about 0.337 V, the overall corrosion rate remains constrained by the oxygen diffusion supply during cathodic oxygen reduction on the Cu-rich regions. Therefore, the anomalous corrosion response of CoCrNiCu can be attributed to the synergistic effect of the enhanced micro-galvanic corrosion driving force caused by Cu-induced phase separation and the restricted cathodic oxygen supply. Full article

Pentlandite bioleaching offers a potentially low-energy route for nickel recovery from low-grade sulfide resources, but increasing pulp density may constrain acidophilic microorganisms through metal accumulation, mineral buffering, mass-transfer limitation, and surface-product deposition. This study evaluated pentlandite bioleaching by the nickel-resistant Acidithiobacillus ferriphilus WGS1 at pulp densities of 1%, 5%, and 10% (w/v). Leaching performance and associated interfacial and cellular responses were examined using solution chemistry, mineral and surface characterization, electrochemical measurements under 40 g/L Ni²⁺, and genome-guided transcriptomics. After 30 days at 35 °C, Ni leaching efficiencies reached 99.2%, 97.1%, and 95.7% at 1%, 5%, and 10% pulp densities, respectively, compared with 27.2%, 14.2%, and 0.76% in the corresponding sterile controls. The inoculated systems maintained lower pH and higher ORP than the sterile controls, while the residues showed pentlandite alteration, Ni depletion, secondary Fe-bearing phase formation, and changes in surface sulfur speciation. Under 40 g/L Ni²⁺, the WGS1-containing system showed a lower charge-transfer resistance and a higher corrosion current density than the abiotic system. Transcriptomic comparison between the 10% and 1% pulp-density groups identified 640 differentially expressed genes and highlighted candidate responses associated with Ni homeostasis, Fe/S oxidation, respiratory electron transfer, and energy conservation. Integration of the physicochemical, mineralogical, electrochemical, and transcriptomic results supports a literature-informed working model for WGS1-associated pentlandite bioleaching under high-pulp-density conditions. Full article

Shallow groundwater systems of rural municipalities are highly vulnerable to long-term contamination from former on-site sanitation systems, while the hydrochemical response of the aquifer after sewerage network development may be delayed by several factors. In the present study, a total of 147 shallow groundwater samples collected during the summer sampling campaigns of 2018, 2019, 2023, and 2024 were analyzed for general water-quality parameters including pH, EC, NH₄⁺, NO₂⁻, NO₃⁻, PO₄⁻, Cl⁻, SO₄²⁻, microelements, and potentially toxic elements, including As, Pb, Cd, Ni, Cu, Zn, Fe, and Mn. The dataset was evaluated using descriptive statistics, Piper, Wilcox, and Gibbs diagrams, hierarchical cluster analysis, principal component analysis, and GIS-based spatial interpolation. The results indicate that, more than ten years after sewerage network development (2014), shallow groundwater in the study area still shows considerable contamination, primarily characterized by elevated mean concentrations of ammonium (0.836 mg/L), nitrate (177.43 mg/L), and chloride (313.26 mg/L), accompanied by high electrical conductivity (3115 µS/cm) and sodium enrichment (378.12 mg/L). Spatial and boxplot analyses of SAR further indicated increasing sodium-related heterogeneity after 2018, with higher local SAR values in 2023–2024. Hydrochemical diagrams revealed a shift towards Ca-Cl type to Na–Cl types, while multivariate analyses confirmed that salinity enrichment, nitrate contamination, water–rock interaction and redox-sensitive trace element mobilization act as overlapping but partly separable controls. The nitrate–chloride source plot indicated mixed contamination origins, dominated by residual sewage influence and manure-related inputs, with diffuse agricultural nitrogen leaching. Arsenic was used as a supporting indicator of mixing with wastewater; however, As was no longer detectable in most of the investigated wells, suggesting a marked reduction in the former wastewater leakage. These results support the slow attenuation of contamination in the shallow groundwater system affected by former wastewater infiltration and highlight the need for continuous monitoring. Full article

This study evaluated trace element bioaccumulation in Nile tilapia (Oreochromis niloticus) marketed in Brazil and assessed potential implications for food safety and human health. A total of 120 farmed fish samples, including whole fish and tissues (gills, kidneys, liver, and muscle), were analyzed. Concentrations of Al, As, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) and compared with ANVISA and FAO/WHO guideline values. Arsenic concentrations complied with ANVISA limits, whereas Pb in whole Nile tilapia exceeded the permissible threshold. Nickel and Se concentrations in muscle and whole fish also surpassed FAO/WHO guidelines. Estimated Se intake from consumption of whole tilapia and muscle (fillet) reached 188.01% of the Recommended Dietary Allowance (RDA) for children aged 8 years. Contamination index values (CI) indicated bioaccumulation of Ni in multiple tissues and Se in edible portions. Human health risk assessment identified carcinogenic risks associated with As, Cr, Ni, and Pb, while non-carcinogenic risk (HI > 1) was primarily driven by As exposure. These findings highlight the need for continuous monitoring of trace elements in aquaculture products. Full article

This study investigates the mechanical properties and corrosion behavior of a Co-free Fe₄₀Ni₃₀Cr₂₀V₈Mo₂ (at.%) multi-principal elements alloy (MPEA) designed for potential applications in aggressive environments. The alloy exhibits a balanced combination of strength and ductility, with a yield strength of approximately 258 MPa, an ultimate tensile strength of about 647 MPa, and a fracture elongation of around 52%, of which deformation is primarily governed by dislocation-mediated plasticity. In terms of corrosion performance, the alloy demonstrates excellent resistance in chloride-containing environments. Potentiodynamic polarization tests reveal a wide and stable passive region of approximately 1.28 V_SCE and a high pitting potential of about 0.975 V_SCE, indicating exceptional stability of the passive film. Electrochemical impedance spectroscopy (EIS) further confirms the high impedance and protective nature of the surface layer. X-ray photoelectron spectroscopy (XPS) analysis reveals that the superior anti-corrosion property is attributed to the formation of a passive film enriched with protective Cr₂O₃ and V, Mo oxides, which collectively construct an effective barrier against chloride-induced attack by reducing donor density. This work provides valuable insights for the development of alternative alloys to replace Co-containing systems in demanding corrosive applications. Full article

In this study, CoCrFeNiMn high-entropy alloys (HEAs) with different aluminum (Al) contents were fabricated, and the effects of Al content on the microstructure evolution and mechanical properties were systematically explored. The microstructural characterization results indicated that the Al content exerted a crucial regulatory effect on the crystal structure of the alloy. With increasing Al content, shifts in the characteristic XRD peaks indicate lattice expansion of the alloy. Meanwhile, the phase structure continuously evolved from a single face-centered cubic (FCC) structure to an FCC/body-centered cubic (BCC) dual-phase structure, and then finally transformed into a BCC-dominated structure. Appropriate Al element addition could produce localized stress fields near dislocations and achieve prominent solid-solution strengthening, which effectively inhibited dislocation movement and further improved the yield strength, tensile strength, and hardness of the alloy. In contrast, excessive Al addition would break through the solid solubility limit of the alloy matrix, causing obvious phase separation and the precipitation of brittle B2-ordered NiAl-type intermetallic secondary phases. These brittle secondary phases easily induced crack initiation in the plastic deformation process, which significantly deteriorated the ductility, work-hardening ability, and impact toughness of the alloys. Full article

The thermomechanical deformation behavior of high-entropy alloys (HEAs) is governed by complex interactions among strain, strain rate, and deformation temperature, necessitating robust constitutive models for accurate flow stress prediction and process optimization. In this study, a novel Zerilli–Armstrong (NZA) constitutive model was developed to characterize the hot deformation behavior of FeCoCrNi HEA. The proposed NZA model incorporates enhanced descriptions of strain hardening and deformation-temperature coupling to improve prediction accuracy. The predictability of the proposed NZA model was systematically evaluated and compared with that of the original Zerilli–Armstrong (ZA) and modified Zerilli–Armstrong (MZA) models using key statistical indicators, including the correlation coefficient (R), average absolute relative error (AARE), and root mean square error (RMSE). The findings demonstrate that the NZA model exhibits superior predictive performance, achieving an excellent correlation coefficient (R) of 0.997, a low AARE of 4.22%, and an RMSE of 5.82 MPa. These results confirm the reliability and effectiveness of the proposed constitutive framework in accurately describing the thermomechanical flow behavior of FeCoCrNi HEA over a wide range of deformation conditions. The proposed NZA model provides a robust framework for optimizing hot-forming processes and improving the manufacturing performance of HEA-based components while promoting sustainable manufacturing through reduced material consumption, enhanced energy efficiency, and support for SDGs 9 and 12. Full article

The magmatic Ni-Co-Cu mineralization in the Iken deposit in the central part of the Kun-Manie complex, Amur Oblast, Russia, hosted by an olivine-bearing websterite, is of a low-sulfide type. The fine-grained disseminations of base metal sulfides (BMS), dominantly pyrrhotite, pentlandite (a major source of Ni of industrial importance), and chalcopyrite, are followed by a scarce Pd-Pt-Ag mineralization. Elevated contents of Al in orthopyroxene (mean 2.78 wt.% Al₂O₃) along with Al–Na enrichment in clinopyroxene (diopside; mean 5.10 wt.% Al₂O₃) are associated with highly aluminous compositions of low-chromium members of the spinel–hercynite series. High levels of TiO₂ in kaersutite and titanian phlogopite also reflect a pronounced degree of fractionation of the ore-forming melt. Minor portions of sulfide melt are distributed evenly as a result of immiscibility at advanced stages of orthopyroxene crystallization, after the formation of olivine. Differentiated grains of droplet-like BMS largely settled in situ close to grain boundaries of orthopyroxene or occupied interstitial spaces of pyroxenes and olivine in association with spinel–hercynite and fluorapatite. A combination of late saturation in S with relatively quick cooling rates of the hypabyssal body prevented the effective settlement and accumulation of sulfide droplets in the ore zone. The well-developed lamellae of troilite (Fe₅₀S₅₀) exsolved from the host pyrrhotite Fe₄₈S₅₂ during subsolidus cooling, as a consequence of a low-temperature reaction triggered by a sudden drop in fO₂. An influx of mantle-derived fluid bearing CO₂, CO, and CH₄ with the rising magma could be the primary cause of the fO₂ reduction. Also, graphite-bearing metasedimentary rocks could have been assimilated. Tiny grains of minerals of noble metals (moncheite and merenskyite with essential amounts of melonite component, sperrylite, hessite, alloy Au_63.2Ag_36.8, and argentopentlandite) deposited late in a fluid-enriched medium under submagmatic conditions. Full article

High-entropy alloys (HEAs) are a transformative class of materials with remarkable structural and functional properties. Solid-state processing techniques, such as high-energy ball milling, are being increasingly used for their production. In these processes, the use of a process control agent (PCA) seems to be essential to prevent excessive cold welding and agglomeration; however, the influence of different PCAs on alloy formation remains insufficiently understood. This study systematically examined the effects of the PCA type, milling configuration, and elemental substitution on HEAs mechanosynthesis. A non-equiatomic alloy, Al₁₀Cr₁₂Fe₃₅Mn₂₃Ni₂₀ (selected for its known single-phase Face Center Cubic (FCC) behavior), was used to explore the PCA and mill-type effects. The alloy was synthesized in a planetary mill (Fritsch Pulverisette 7) and a vibratory mill (SPEX 8000M) using diverse PCAs, including liquid (methanol, ethanol, isopropyl, and n-heptane) and solid (stearic acid and sodium chloride) agents. In addition, lightweight equiatomic alloys MgAlTiNi(Co,Cr,Fe) were used to explore the influence of different PCAs and the effect of elemental substitution under similar PCA conditions as those used with the equiatomic alloy. The products were characterized using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and differential thermal analysis techniques. The results highlighted that the PCA selection, milling configuration, and alloy chemistry influenced the phase evolution, particle size distribution, and thermal behavior. The results provide insights into the mechanosynthesis of selected high-entropy alloys produced under different PCA and milling conditions. Full article

Sedimentary manganese deposits are an important mineral resource and also play a significant role in restoring the ancient marine environment. The redox environment of the ocean during the Mesoproterozoic era has long been a subject of controversy. This paper takes a large-scale sedimentary manganese deposit in northwest China as the research object, attempting to analyze the changes in the marine environment during the Mesoproterozoic era and their impact on the Mn mineralization processes. In recent years, an exploration breakthrough has been made in the manganese deposits in the Annanba region on the southern margin of the Dunhuang block, NW China. The Qingshagou Mn deposit is the largest and most representative in the region. Geochemical characteristics show that the ores have low average ratios of Fe/Mn (<0.19), V/Cr (<1.20), V/(V+Ni) (<0.54), and Al/(Al+Fe+Mn) (<0.30) but high average ratios of U/Th (~0.95), and Y/Ho (~28). The Post-Archean Australian Shale (PAAS)-normalized rare earth element (REE) patterns exhibit that middle rare earth elements are slightly enriched with weak positive anomalies for both Y (0.93~1.01) and Ce (0.97~1.15) and weak negative anomalies for Eu (0.87~0.99). The δ¹³C_PDB value of the ore ranges from −13.4‰ to −23.3‰, which is consistent with the δ¹³C_PDB value range of organic matter. Synthesizing these findings, it is concluded that the Qingshagou Mn deposit formed in a suboxic to oxic environment, the ore-forming materials were primarily derived from a submarine hydrothermal system, and the changes in redox conditions promoted the Mn precipitation. Full article