Search Results (2,539)

High-entropy alloys formed by metals are usually classified as those with magnetic elements, such as Fe, Co, and Ni, and alloys containing a significant percentage of aluminum. In the first case, the functional responses of greatest scientific and technological interest are both mechanical and magnetic. Concerning applications, the main interest focused on health and energy. Among the various techniques used to obtain high-entropy alloys in powder form, one of the most widely applied is mechanical alloying. This paper reviews recent results and prospects, including machine learning. Full article

This study explores the effects of sputtering pressure and power on FeCoNi high-entropy alloy films prepared by DC magnetron sputtering, focusing on microstructure, surface morphology, and static/high-frequency magnetic properties. In situ Lorentz TEM (LZ-TEM) was used to directly observe magnetic domain evolution. Results show that low sputtering pressure (1 mTorr) promotes strong FCC (111) crystallization, and smooth and dense surfaces. Increasing pressure leads to amorphization, higher roughness, and degraded magnetic performance. Under optimized pressure, 100 W sputtering power yields the best crystallinity, the smoothest surface, and optimal soft magnetic properties, including high remanence ratio, low coercivity, and clear ferromagnetic resonance in the 2–7.5 GHz range. The optimal parameters are confirmed as 1 mTorr and 100 W, producing uniform nanocrystalline FeCoNi films. In situ LZ-TEM reveals river-like domain walls, vortex–antivortex structures, and uniform magnetic moment precession, indicating weak domain pinning and excellent high-frequency magnetization consistency. This study provides experimental and theoretical support for the controllable fabrication of high-performance FeCoNi soft magnetic films for high-frequency devices. Full article

The use of wood chips in the heating sector leads to the generation of combustion waste with variable properties, which poses challenges for their rational management. To determine the variability of combustion waste, samples were collected over a 13-week period during the heating season, as weekly aggregate samples from a biomass bioheating plant burning wood chips. Three waste fractions were obtained for analysis: residue from the grate (B1), dust from the dust collector (B2), and boiler dust (B3). Dry matter (DM), reaction (pH_KCl), electrolytic conductivity (EC), content of total carbon (TC), total nitrogen (TN), macronutrients (P, K, Mg, Ca, Na), and heavy metals (Fe, Mn, Zn, Cu, Pb, Cd, Cr, Co, Ni) were determined in the collected samples. All waste fractions were characterized by an alkaline reaction. Regardless of the waste fraction, the macronutrient content was dominated by Ca, K, and Mg, with significantly lower levels of P and Na. Among heavy metals, Fe, Mn, and Zn had the highest recorded contents, and the lowest by far was Cd. With respect to sampling dates, the least diversified chemical composition was observed for B1 samples, more diversified for B2, and the most diversified for B3. In turn, regardless of the waste fraction, the most diversified results were observed for Cd and Pb, and the least for pH, DM, and TC. Concerning environmental management of combustion waste, fraction B1 deserves attention, as it was characterized by the richest chemical composition (TN, P, K, Mg, Ca, Na, Mn, Zn, Cu, Co, Ni). However, due to the highest content of undesirable heavy metals (Pb, Cd) and the highest salinity, it requires constant monitoring of the composition. Full article

In this work, Fe, Co, Ni, Cu, and Mo powders were used as starting materials to prepare high-entropy alloy (HEA) thin films by a coating and vacuum sintering process. Using the HEA thin film as the substrate, selenium was subsequently deposited by chemical vapor deposition (CVD) to obtain high-entropy alloy selenide thin films (HEASe). The phase structure, surface chemical states, morphology, and elemental distribution of the porous films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The electrocatalytic hydrogen evolution performance of the electrodes was evaluated using a three-electrode configuration in 0.5 M H₂SO₄, 1 M KOH, 1 M KOH + 0.5 M NaCl, and 1 M KOH + 0.5 M Na₂S solutions. The results indicate that the HEA selenide thin-film electrodes exhibit favorable electrocatalytic behavior in all four electrolytes. Among them, HEASe-450 shows the best overall performance. In 0.5 M H₂SO₄, it requires an overpotential of only 57.6 mV to reach a current density of 10 mA cm⁻², with a Tafel slope of 146.96 mV dec⁻¹. In 1 M KOH, the overpotential at 10 mA cm⁻² is 50.1 mV, and the corresponding Tafel slope is 142 mV dec⁻¹. In 1 M KOH + 0.5 M NaCl, the overpotential is 52.7 mV with a Tafel slope of 122.72 mV dec⁻¹. In 1 M KOH + 0.5 M Na₂S, an overpotential of 85 mV is required, and the Tafel slope increases to 236 mV dec⁻¹. Full article

The Jiaodong gold-mineralized area is one of the most significant gold districts in China. The newly discovered Moshan gold deposit is hosted in the Late Jurassic Queshan granite, previously considered a prospecting blind zone. In this study, pyrite from the Moshan gold deposit is examined as the primary research subject. To elucidate the ore-forming processes and genetic mechanisms of this deposit, we conducted a comprehensive mineralogical and geochemical study on pyrite, the principal gold-bearing mineral. EPMA and LA-MC-ICP-MS analyses reveal that the pyrite is slightly sulfur-deficient (average S/Fe ratio of 1.976) and exhibits trace element variations (As, Co, and Ni) strongly correlated with distinct metallogenic stages. Gold occurs in various forms, including visible inclusion gold, fracture gold, and invisible nano-particulate gold (Au⁰). The in situ sulfur isotope δ³⁴S values range from 7.11‰ to 9.40‰ (average 8.00‰), displaying high homogeneity and a positive deviation from the troilite in the Canyon Diablo iron meteorite. By integrating pyrite S-Fe relationships, Co-Ni-As systematics, and sulfur isotope characteristics, the study indicates that the Moshan gold deposit originates from a magmatic-hydrothermal source. The ore-forming materials predominantly derive from Mesozoic granite-derived magmatic-hydrothermal fluids, with a minor contribution from crustal basement materials. The depth of mineralization is interpreted as mid-shallow. These findings not only highlight the metallogenic potential of the Queshan granite and clarify the genetic relationship between the Moshan gold deposit and other regional gold deposits but also provide a novel theoretical foundation and technical support for deep gold exploration in the Jiaodong region. Full article

In this work, a comprehensive first-principles investigation of the electronic, magnetic, and optical properties of pristine and Fe-, Co-, and Ni-doped MoS₂ monolayers is presented within the framework of density functional theory. Substitutional transition-metal doping at the Mo site is shown to induce spin-polarized impurity states within the pristine band gap, leading to significant modifications of the electronic structure, including metallic, semimetallic, or half-metallic behavior depending on the dopant species. The calculated spin-resolved band structures and projected density of states reveal a strong hybridization between the dopant $3d$ orbitals and the Mo-$4d$/S-$3p$ states, giving rise to sizable magnetic moments and dopant-dependent exchange splitting. When spin–orbit coupling is included, the combined effect of exchange interactions and relativistic effects leads to an effective valley splitting at the K and $K^{\prime }$ points, whose magnitude and sign depend sensitively on the chemical nature of the dopant. Optical properties are analyzed within a linear-response framework, showing pronounced dopant-induced modifications of the optical spectra. While the pristine monolayer exhibits well-defined excitonic features, transition-metal substitution introduces low-energy optical transitions associated with impurity-related states. Consequently, the exciton binding energies estimated from the difference between the electronic and optical gaps are interpreted as effective measures of dopant-induced perturbations to optical transitions, rather than as quantitative many-body excitonic binding energies in the strict sense. These results provide microscopic insight into the interplay between magnetism, spin–orbit coupling, and optical response in doped MoS₂ monolayers, highlighting the potential of transition-metal substitution as a route to engineer spin- and valley-dependent phenomena in two-dimensional materials. Full article

Catalytic materials are central to the advancement of hydrogen generation technologies, playing a pivotal role in enabling sustainable, carbon-neutral energy systems. Hydrogen can be produced via electrochemical water splitting, thermochemical reforming, or photocatalysis—each imposing unique performance requirements on catalysts in terms of activity, selectivity, stability, and efficiency. While traditional noble metals (e.g., platinum, ruthenium, iridium) provide benchmark catalytic activity, their widespread use is hindered by scarcity, high cost, and limited long-term durability. Consequently, researchers have increasingly focused on earth-abundant alternatives such as transition metals (Ni, Co, Fe, Mo), alloys, metal oxides, carbides, sulfides, nitrides, and carbon-based systems. Among these, two-dimensional materials, particularly the MXene family, have attracted significant attention due to their metallic conductivity, layered structure, and tunable surface chemistry. These features enable rapid charge transfer and abundant active sites, making MXenes and related nanostructured catalysts promising for both the Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) across a wide range of electrochemical conditions. Parallel efforts have integrated novel semiconductors, plasmonic nanomaterials, and hybrid heterostructures to improve the efficiency of solar-to-hydrogen energy conversion. This paper reviews the main types of catalytic materials used in hydrogen production, explains their design strategies and structure–performance relationships, and discusses key engineering challenges such as integrating renewable energy sources, scaling up manufacturing, and ensuring long-term durability in real-world systems. Future research goals are also highlighted, including the development of affordable non-noble catalysts, enhancing catalyst stability through surface and defect engineering, and coupling hydrogen production with circular economy principles, all of which are essential to making hydrogen generation more efficient, scalable, and cost-effective as the world transitions to clean and sustainable energy. Full article

In permanently submerged coastal wetlands, interactions between biogeochemical processes and microbial communities strongly influence greenhouse gas (GHG) fluxes. To improve our understanding of how redox-driven processes shape GHG dynamics in these ecosystems, we investigated the relationships among iron (Fe) pools, microbial dynamics, and the potential GHG production in subaqueous soils from an interdunal wetland in San Vitale Park (Italy), permanently submerged and affected by seasonal oscillations of the saline water table. Two subaqueous soil columns (WAS-2 and WAS-4), collected from similar settings, were analyzed. Surface layers of WAS-4 showed higher salinity and carbonate content, whereas WAS-2 was characterized by overall higher Fe concentrations. Distinct vertical distributions of organic matter and sulfur (S) were shown along depth. Laboratory incubations revealed that nitrous oxide (N₂O) production was up to ten times higher in WAS-2 than in WAS-4, with peaks in the top 13–14 cm, consistent with more active nitrification-denitrification in surface layers. Methane (CH₄) and carbon dioxide (CO₂) fluxes decreased with depth, reflecting reduced availability of labile carbon. Methanomicrobiales dominated CH₄-producing layers, indicating hydrogenotrophic methanogenesis, while amoA-carrying Nitrosomonadales and Thaumarchaeota, occurred in shallow, organic-rich layers where ammonia supported nitrification and denitrification. Denitrifiers mainly belonged to α- and β-Proteobacteria, consistent with their direct contribution to N₂O peaks. Spearman’s correlations showed N₂O positively correlated to sulfur and labile carbon (C), supporting denitrification under moderately reducing conditions. CH₄ and CO₂ positively correlated with organic C (Corg), total nitrogen (TN), and reactive Fe forms, reflecting redox-mediated microbial respiration and methanogenesis. Trace elements (B, Cr, Cu, Ni) acted as micronutrients or inhibitors depending on concentration. Canonical correspondence analysis indicated depth-structured links among gas fluxes, soil chemistry (Corg, TN, S/C, CaCO₃, P), and microbial distributions: surface layers, rich in labile C and nutrients, supported active bacteria and archaea involved in decomposition, nitrification, and denitrification, whereas deeper layers hosted oligotrophic archaea adapted to inorganic substrates. Overall, Fe pools appeared to be associated with soil processes relevant to GHG dynamics, although the extent of their regulatory role remains uncertain due to potential alterations of redox-sensitive Fe fractions during sample handling. These results contribute to broader efforts to predict GHG emissions in submerged wetland soils by linking redox stratification, inorganic chemistry, and microbial functional groups. Full article

This study investigated the properties of a composite NiCrFeSiB coating with fine-dispersed WC additives, deposited by the HVOF method. The NiCrFeSiB powder alloy with WC additives was applied to a steel substrate. The WC content in the coating was 10, 15, and 20% by weight. The particle size distribution of the mixture ranged from 3 to 10 µm. The WC used was the WC8 alloy (92% WC, 8% Co). The levels of stress, phase composition, hardness, wear resistance, and coating structure were investigated. The studies revealed that the structure was primarily composed of the γ-Ni-Fe solid solution phase, with secondary phases including Ni₃B, Fe₃B, (Cr,)₂B, and carbides of the W₂C, WC, M₇C₃ type. A small amount of the initial WC particles was also present. The use of a fine-dispersed NiCrFeSiB powder mixture with WC particles resulted in a nearly twofold increase in hardness and wear resistance compared to the same parameters of the coating without WC. The coating with 20% WC exhibited the highest hardness. However, its wear resistance was lower than that of the coating with 15% WC. This fact could be explained by a slight difference in the phase composition and an increase in the proportion of the unsolidified WC phase in the structure. This led to the spalling of fine particles and a reduction in wear resistance. The study demonstrated the feasibility of using a fine-dispersed NiCrFeSiB coating with WC additives without additional remelting. Similar hardness and wear resistance results were achieved immediately after HVOF spraying when using a fine-dispersed NiCrFeSiB + 15% WC/Co mixture with a 92/8 composition. This simplification of the technology reduced the coating application process time. It also lowered production costs by eliminating the remelting stage. Full article

Urban rail wheels endure prolonged exposure to frequent starts and stops, heavy cyclic loads, and complex track conditions, which often lead to premature failure modes such as wear, fatigue cracking, and corrosion in conventional wheel materials. These limitations restrict their ability to meet the evolving demands of modern rail systems for enhanced durability and performance. To address this, the present study uses laser cladding to deposit high-entropy alloy coatings with systematically varied aluminium content onto wheel substrates. The study compares phase composition, microstructure, and mechanical properties across the different coatings. Results show that increasing Al content transforms the coating microstructure from a single face-centred cubic (FCC) phase to a dual-phase structure of FCC and body-centred cubic (BCC) phases, accompanied by notable grain refinement. Among the variants, the CrMnFeCoNi(Al)₈ coating has the densest microstructure and the most favourable mechanical performance. It achieves a microhardness of 399.62 HV_0.5 in the as-clad state and 450 ± 5 HV_0.5 after heat treatment, representing an increase of approximately 12.6%. This coating also demonstrates improved corrosion resistance, with an open-circuit potential 0.07 V higher than the CL60 substrate. Multi-body dynamics simulations confirm that the clad wheels maintain excellent operational stability and safety under service conditions. Full article

Human activities inevitably affect natural ecosystems, the impact of which most often refers to negative factors resulting in the accumulation of toxic elements in environmental components. This study quantified the presence of 12 toxic elements (Cd, Co, Cr, Cu, Hg, Fe, Mn, Ni, Pb, Zn, As, and Se) in water, soil, and six melliferous plant species across the Republic of Croatia. Sampling sites were classified into four groups according to the dominant anthropogenic impact: agricultural areas, urban and traffic-affected zones, industrial vicinities, and forested hill regions. The results demonstrate the transfer of toxic elements from abiotic matrices into plants, indicating their potential as bioaccumulators. Soil contamination with toxic metals was identified as a relevant ecological risk factor, while contamination of melliferous plants highlights potential implications for human health through the production of honeybee-derived products. Element concentrations in water and soil were determined using three atomic absorption spectrometry techniques (FAAS, GFAAS, and CVAAS), whereas concentrations in floral samples of melliferous plants were measured using inductively coupled plasma mass spectrometry (ICP MS). The obtained results were interpreted in relation to natural background levels and the current national legislation. Anthropogenic impacts were further evaluated using environmental quality indices and bioaccumulation factors, revealing site-specific contamination patterns of both natural and anthropogenic origin. Full article

This work aims to develop a controlled ball milling strategy for preparing FeCoCrNiCu high-entropy alloy (HEA) powders with improved compositional homogeneity while maintaining limited oxygen uptake. Specifically, a novel two-step combined ball milling strategy integrating gradient ball-size configurations with a sequential milling procedure is proposed and systematically evaluated. Compared with conventional single-step milling, the mixed-ball and two-step configurations enhance mechanical alloying (MA) efficiency and promote the formation of more stable FCC and BCC dual-phase structures, as confirmed by X-ray diffraction (XRD) analysis. Compositional standard deviation derived from energy-dispersive X-ray spectroscopy (EDS) measurements indicates improved macroscopic uniformity, while oxygen/nitrogen/hydrogen (ONH) analysis verifies that oxygen incorporation remains limited within the tested processing window. Systematic comparison of jar filling degrees and sampling interruptions further reveals the coupled influence of collision energy distribution and exposure frequency on oxidation behavior. The results demonstrate that controlled energy distribution and minimized atmospheric disturbance are critical for balancing alloying efficiency and oxygen control in FeCoCrNiCu powders. Full article

Laser powder bed fusion (LPBF) of AA7075 is severely constrained by a narrow process window and susceptibility to defect formation (hot cracking and porosity), which often dominates performance. In this study, 5 wt.% AlCoCrFeNi_2.1 high-entropy alloy (HEA) particles, volumetric energy density (VED = 74–222 J·mm⁻³), and subsequent T6 heat treatment were systematically investigated to reveal their combined effects on defect structure, crystallographic texture/substructure, and tensile behaviour. Quantitative EBSD shows a measurable grain refinement in the as-built state (average grain size 13.44 → 11.80 µm, ~12%) accompanied by a pronounced weakening of the <001> fibre texture (maximum MRD 4.94 → 2.38), indicating disrupted epitaxial growth and a more dispersed orientation distribution. After T6, the reinforced alloy retains a higher low-angle boundary fraction (31.62% vs. 24.17% in unreinforced AA7075) and a higher kernel average misorientation (0.80° vs. 0.60°), consistent with particle-stabilised substructure retention and retarded recovery. Across all VEDs, AA7075-HEA exhibits higher microhardness (compared with AA7075, the addition of HEA increases the hardness by roughly 20–50 HV) and tensile strength, with the intermediate VED (140.74 J·mm⁻³, T6 states) yielding the best performance. While macroscopic cracking is not fully eliminated, the results clarify that HEA-enabled texture/substructure modifications can contribute to enhanced defect tolerance and are more effectively translated into tensile performance when the as-built defect severity is controlled. These findings provide quantitative insights into defect–microstructure–property coupling in LPBF AA7075-HEA composites from as-built to T6 states. Full article

The influence of Ni and Co additions on microstructure and mechanical properties of (CoCrCuTi)_100−xFe_x high-entropy alloys (HEAs) containing 10 or 15 at. % Fe was investigated. The base HEA consisted of dendritic C14 Laves phases with interdendritic Cu-rich FCC regions. When Ni in the range of 2.5 to 10 at. % was added, a reduction in the Cu-rich phase was observed. Conversely, Co additions in the same range initially increased the Cu-rich phase but eventually led to liquid-phase separation (LPS), forming distinct Cu-lean L1 liquid and Cu-rich L2 globular regions. The average Vickers hardness values of (CoCrCuTi)₉₀Fe₁₀ and (CoCrCuTi)₈₅Fe₁₅ HEAs were measured at 790 ± 33 HV and 760 ± 20 HV, respectively. The additions of Ni and Co decreased overall hardness values. However, while Ni additions caused greater microstructural refinement, Co additions eventually led to heterogeneity due to LPS. For instance, the Vickers hardness of (CoCrCuTi)₉₀Fe₁₀ with 2.5 at. % Ni reached a maximum of 706 ± 95 HV, decreasing in hardness and scatter to 646 ± 19 HV when Ni increased to 10 at. %. In contrast, Co additions led to a marked reduction in hardness, from 574 ± 114 HV at 2.5 at. % Co to 442 ± 246 HV at 10 at. % Co. The fracture toughness (KIC), determined using Vickers indentation testing, indicated that Ni additions reduce fracture toughness, while Co additions increase it. Full article

The 316L stainless steel (316L SS) and high-entropy alloys (HEAs) are leading candidates for radiation-tolerant structural materials in nuclear environments. Additive manufacturing (AM) enables tailored microstructures through unique thermal histories, producing high dislocation densities and sub-grain features that act as effective sinks for irradiation-induced defects. In this work, a direct quantitative comparison of helium (He) irradiation response, particularly bubble formation, is conducted between 316L SS fabricated using laser powder bed fusion (LPBF) and CoCrFeNi HEAs fabricated by laser-directed energy deposition (LDED), both possessing a face-centered cubic (FCC) crystal structure and comparable principal elemental constituents. The samples were subjected to ex situ He ion irradiation using 200 keV He⁺ ions to a peak damage dose of 10 dpa at 25 °C, 400 °C, and 600 °C at the CINT User Facility at Los Alamos National Laboratory. Post-irradiation microstructural characterization was performed using transmission electron microscopy at the IVEM-Tandem Facility at Argonne National Laboratory. For LPBF 316L SS, the areal bubble density decreases from approximately 5.1 × 10⁴ µm⁻² at 25 °C to 2.1 × 10³ µm⁻² at 600 °C, while the mean bubble diameter increases from 2.9 nm to 37.4 nm. The CoCrFeNi HEA exhibits a similar trend but retains a higher areal bubble density at elevated temperatures, with values of 2.1 × 10⁴ µm⁻² at 400 °C and 3.7 × 10³ µm⁻² at 600 °C, along with a larger mean bubble size at 400 °C compared to 316L SS. These results highlight the combined roles of AM-induced microstructures, alloy compositions, and irradiation temperatures in governing He damage evolution in FCC alloys, providing guidance for the development of radiation-tolerant materials for advanced nuclear energy applications. Full article