Search Results (788)

Copper-deficient copper selenide (Cu_2−xSe) nanocrystals possess strong near-infrared (NIR) absorption and efficient photothermal conversion, making them attractive candidates for photoacoustic imaging. In this study, Cu_2−xSe nanocrystals with distinct morphologies were synthesized using different selenium precursors and evaluated as photoacoustic contrast agents. Se–oleylamine precursors produced predominantly disk-shaped nanocrystals with average dimensions of approximately 20 nm in diameter and 5 nm in thickness, while Se–TOP/TOPO precursors yielded smaller spherical nanocrystals. Structural characterization by transmission electron microscopy, high-resolution TEM, and selected-area electron diffraction confirmed the formation of highly crystalline copper-deficient Cu_2−xSe nanocrystals with a face-centered cubic crystal structure. UV–Vis–NIR spectroscopy revealed broad optical absorption extending into the NIR region, with morphology-dependent spectral characteristics. Multispectral optoacoustic tomography demonstrated strong photoacoustic signal generation from both nanodisks and nanospheres over a broad wavelength range. In vivo studies using PEGylated Cu_2−xSe nanospheres showed successful lymphatic uptake following hind paw injection and enabled visualization of the draining popliteal lymph node through spectral unmixing of nanoparticle and hemoglobin signals. These results demonstrate that Cu_2−xSe nanocrystals are promising photoacoustic contrast agents for lymphatic imaging and other biomedical imaging applications. Full article

In this study, green-synthesized silver nanoparticles derived from Zingiber officinale (G-AgNPs) were investigated as potential modulators of transmembrane serine protease 2 (TMPRSS2), a host-associated protease involved in viral entry mechanisms. Before nanoparticle synthesis, the phytochemical composition of ginger extract was analyzed using high-performance liquid chromatography (HPLC) with photodiode array detection. Silver nanoparticles were synthesized using aqueous ginger extract as a reducing and stabilizing agent. The nanoparticles were characterized by ultraviolet–visible spectroscopy (UV–Vis.), Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), zeta potential analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The synthesized silver nanoparticles exhibited a face-centered cubic (fcc) crystalline structure, nanoscale particle size distribution, and moderate colloidal stability. Transmission electron microscopy revealed predominantly quasi-spherical nanoparticles with an average diameter of 10.61 ± 1.31 nm, while X-ray diffraction indicated an average crystallite size of 15.28 ± 5.48 nm. Biological evaluation demonstrated robust, broad-spectrum antibacterial activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, with distinct susceptibility profiles. Minimum Inhibitory Concentration (MIC) values were 3.125 µg/mL and 12.5 µg/mL, and Minimum Bactericidal Concentration (MBC) values were 6.25 µg/mL and 25.0 µg/mL, respectively. Cell culture assays confirmed high cytocompatibility with L929 fibroblasts at all tested concentrations. In a fluorometric enzyme assay, the silver nanoparticles inhibited TMPRSS2 activity in a concentration-dependent manner, achieving 51.24% inhibition at 100 µg/mL and an estimated IC50 of 40.06 µg/mL. Although the inhibitory activity was lower than that of Camostat, the findings suggest that ginger-mediated silver nanoparticles represent promising plant-based nano-bioactive systems for further investigation of TMPRSS2 modulation. Full article

Corrosion of carbon steel components represents a major economic and safety challenge in industrial applications, motivating the development of protective thin film coatings with optimized deposition parameters. This study investigates the deposition of nickel nitride (Ni-N) thin films on AISI 1016 carbon steel and silicon (111) wafers by reactive radio-frequency (r.f.) magnetron sputtering at three power levels: 150, 175, and 200 W. Surface color, film thickness, roughness, crystal structure, mechanical properties, and electrochemical behavior were evaluated using optical microscopy, stylus profilometry, atomic force microscopy (AFM), X-ray diffraction (XRD), nanoindentation, and potentiodynamic polarization combined with electrochemical impedance spectroscopy (EIS). Increasing r.f.-power produced systematic surface color changes consistent with variations in film thickness, which ranged from approximately 25.0 to 50.7 nm. Higher deposition power promoted smoother surfaces, with average roughness (Ra) decreasing from 64.28 nm at 150 W to 20.62 nm at 200 W. XRD analysis revealed a monocrystalline Ni₃N hexagonal close-packed (HCP) phase at 150 W, transitioning to a dual-phase Ni₃N (HCP) and Ni₄N face-centered cubic (FCC) microstructure at 175 and 200 W. The highest hardness (11.80 ± 3.34 GPa) was recorded at 150 W, accompanied by pop-in events attributed to dislocation nucleation in the HCP lattice. Electrochemical evaluation in 3.5 wt.% NaCl solution demonstrated that films deposited at 150 and 175 W exhibited corrosion current densities and rates exceeding those of bare steel, confirming that these conditions accelerate rather than inhibit corrosion. Only the film deposited at 200 W achieved superior corrosion protection, with a corrosion current density and rate approximately 50% lower than bare steel, attributed to its denser microstructure and smoother surface morphology. These findings demonstrate that r.f. power is a critical parameter governing the properties of Ni-N thin films, and that careful optimization of deposition conditions is essential before recommending such coatings for industrial corrosion-protective applications. Full article

To overcome the insufficient hardness and wear resistance of CoCrFeNi alloy coatings under heavy-load conditions, CoCrFeNi-TiC composite coatings with varying TiC mass fractions were fabricated on a 42CrMo substrate using laser cladding. The present study systematically investigates the effects of TiC content on phase composition, microstructural evolution, microhardness, and tribological behavior. The results show that TiC addition does not change the primary phase constitution of the face-centered cubic (FCC) matrix, but induces lattice distortion and grain refinement, resulting in a pronounced enhancement of coating hardness. As the TiC content increased, the average microhardness rose from 222.9 HV_0.2 to 380.9 HV_0.2, which was 1.7 times that of the coating without TiC. The enhanced hardness is mainly attributed to grain refinement, solid-solution strengthening, and the dispersion effects of TiC particles. The tribological performance showed a non-monotonic dependence on TiC content. Among the tested samples, the coating with 10 wt.%TiC showed the best wear resistance, with an average friction coefficient of 0.56 and a wear rate of 1.15 × 10⁻⁴ mm³/(N·m). However, further increasing the TiC content to 15 wt.% slightly reduced wear resistance because particle spalling promoted three-body abrasive wear. These results indicate that an appropriate TiC content can improve the balance between hard-phase strengthening and wear stability of CoCrFeNi-based composite coatings. This work clarifies the microstructure regulation and wear failure mechanism of TiC-reinforced coatings, providing experimental guidance for heavy-load service coating design. Full article

CoCrFeMnNi high-entropy alloy (HEA) coatings were fabricated on an S41500 stainless steel substrate by laser cladding and subsequently strengthened using machine hammer peening (MHP) at three hammering energies of 1.7 J, 3.5 J, and 5.0 J. The effects of MHP treatment on the phase structure, surface morphology, microhardness, and tribological properties of the coatings were systematically investigated. The results showed that all coatings retained a single-phase face-centered cubic (FCC) structure after MHP treatment, indicating excellent microstructural stability during impact-induced strengthening. With increasing hammering energy, the surface morphology gradually evolved from discrete hammering indentations to a more continuous orange-peel-like texture, while the surface roughness initially increased and then decreased. MHP significantly enhanced the surface hardness of the coatings. In particular, the MHP3.5 sample exhibited the highest surface hardness of approximately 420 HV, representing an increase of about 120% compared with the untreated coating. Under dry sliding conditions at a load of 30 N, the MHP3.5 sample exhibited the lowest and most stable friction coefficient, maintaining a steady-state value of approximately 0.40–0.45. Its specific wear rate decreased by nearly 45% compared with that of the untreated coating. The improved wear resistance was mainly attributed to the combined effects of strain hardening, grain refinement, and dislocation strengthening induced by machine hammer peening. Considering the hardness, friction coefficient, and specific wear rate results together, a hammering energy of 3.5 J was identified as the most suitable MHP parameter under the low-load wear conditions investigated in this study. Full article

The selective electrocatalytic conversion of glycerol into value-added products provides a sustainable and efficient strategy for addressing the surplus of biomass-derived waste generated from the biodiesel production. In this paper, a series of carbon-supported PtPdRhRu quaternary alloy nanocatalysts (PtPdRhRu/C) with different atomic ratios (Equi, Pt-rich, Pd-rich, Rh-rich and Ru-rich) were prepared via a one-pot polyol method. The effects of these atomic ratios on the catalytic performance and the selectivity of the glycerol conversion to high-value products were investigated. The as-prepared PtPdRhRu/C nanocatalysts all possess a single-phase face-centered cubic (fcc) structure. Specifically, their mass activities are 10.5, 9.4, 8.1, 1.9 and 6.4 times higher than that of commercial Pt/C (20 wt%) for the Pt-rich, equimolar, Pd-rich, Rh-rich, and Ru-rich catalysts, respectively. This enhancement is suggested to be associated with the unique electronic modulation and synergistic effects inherent in the multicomponent surface. The Pd-rich catalyst exhibits a selectivity of 72% for glyceraldehyde, while the Rh-rich catalyst shows 53% selectivity for oxalic acid. The C2/C3 product ratio for the Rh-rich catalyst reaches 1.13, compared to 0.82 for the Ru-rich catalyst, suggesting that the presence of Rh and Ru atoms promotes C-C bond cleavage. In contrast, the C2/C3 ratios of the Pt-rich and Pd-rich catalysts are relatively low; notably, the C2/C3 ratio of the Pd-rich catalyst is only 0.20. This implies that the inclusion of Pt and Pd elements in the quaternary alloy is more conductive to the retention of C3 frameworks. These findings highlight the PtPdRhRu platform as a versatile framework for tuning the geometric and electronic environment of catalysts, providing a strategic approach for the selective electro-conversion of complex polyols. Full article

TiN/TiAlN coatings were deposited on 40Cr steel substrates by DC magnetron sputtering to improve the surface tribological performance of the steel. The influence of sputtering power (80, 100, 120, 140, 160 and 180 W) on coating morphology, phase structure, adhesion strength and wear behavior was evaluated using SEM, EDS, XRD, Vickers microhardness testing, scratch testing and ball-on-disk tribological testing. The coatings were dense and relatively smooth, with only a small number of submicron particles. Increasing sputtering power increased the coating thickness, and the EDS results suggested an increase in Al content of up to 160 W, whereas the crystallite size of the TiAlN (200) phase first decreased and then increased. XRD analysis showed that the coatings were dominated by face-centered cubic TiAlN, accompanied by weak TiN and AlN diffraction peaks. Among the tested samples, the coating deposited at 140 W showed the most favorable measured combination of adhesion and tribological properties within the tested series, with a thickness of 1.76 μm, a Vickers microhardness of 906.35 HV0.25, an adhesion strength of 45.6 N, an average friction coefficient of 0.322 and a specific wear rate of 28.37 × 10⁻⁷ mm³ N⁻¹ m⁻¹. These measured trends are consistent with the dense morphology, refined crystallites, high microhardness and higher measured adhesion observed at moderate sputtering power. In contrast, excessive sputtering power was associated with particle coarsening and coating defects, accompanied by higher measured friction and wear. 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

We present a systematic study of thermal oxidation resistance of transition metal borides and carbides up to 1300 °C in a dry air environment. A High-Entropy Metal Boride (HEMB), of composition (Hf_0.2, Mo_0.2, Nb_0.2, Ta_0.2, Zr_0.2)B₂, and a similar High-Entropy Metal Carbide (HEMC) (Hf, Mo, Nb, Ta, Zr)C₅ were synthesized from precursor mixtures, under 30 MPa of pressure at a temperature of 1800 °C using a Spark Plasma Sintering Device. The synthesized phases were confirmed via X-ray Diffraction analysis, which showed a pure hexagonal AlB₂-type structure for HEMB and a face-centered cubic (FCC) structure for HEMC, with lattice parameters, a = 3.10 Å and c = 3.37 Å for HEMB and a = 4.524 Å for HEMC. Oxidation resistance was evaluated using a simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC) stage in which HEMB and HEMC were heated up to 1300 °C at a rate of 2 °C/min in a dry air environment. Scanning electron microscopy (SEM) was used to analyze the resulting oxidized material. Our study demonstrates that HEMB shows better thermal oxidation resistance as compared to a similar metal composition HEMC at high temperatures. 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

Rapid detection of heavy metals is vital for monitoring surface water contamination and preventing environmental and health risks. Traditional detection methods for metals such as lead and copper often require sophisticated, costly instrumentation, limiting their use in routine analyses. To address this challenge, we developed a cost-effective fluorescence-based approach using semiconductor quantum dots (QDs) as nanosensors for metal ion detection. The QDs were synthesized directly in aqueous medium through a reflux-assisted process employing cadmium precursors, selenium, thioglycolic acid (TGA), and branched polyethyleneimine (PEI, Mw ~25,000) as stabilizing agents. Structural analysis revealed nanoparticles with diameters below 5 nm, spherical morphology, and a zinc blende (face-centered cubic) crystalline structure. Optical characterization by UV–Vis, photoluminescence (PL), and FTIR spectroscopy confirmed effective surface functionalization and strong quantum confinement. PEI-capped QDs exhibited enhanced colloidal stability and showed pronounced fluorescence quenching in the presence of Pb²⁺ ions, indicating high sensitivity and selectivity toward lead. Both TGA- and PEI-capped QDs also demonstrated moderate responses to Co²⁺ but negligible interaction with Sn²⁺, confirming ion-specific detection. Overall, this study demonstrates that surface-engineered QDs constitute a simple, accessible platform for selective detection of toxic metals, with promising applications in environmental monitoring and water quality assessment. Full article

This study presents a novel in situ reinforcement strategy for 17-4PH stainless steel by using Nb and Cr₃C₂ powders as precursors, addressing the challenge of poor particle dispersion and interfacial bonding in conventional ex situ ceramic additions. The coatings were systematically compared with 17-4PH coatings without the addition of a reinforcing phase. The results show that the coating without Nb addition is dominated by α-Fe martensite, exhibiting a coarse columnar/dendritic microstructure. After adding Nb and Cr₃C₂, the coating successfully forms in situ face-centered cubic NbC, with a significantly refined and uniformly distributed microstructure. The 10 wt.% Nb+Cr₃C₂ coating exhibits a refined microstructure with an average grain size reduced from 1.12 μm to 0.85 μm and a microhardness of 495.5 HV, representing an 86% increase over the substrate and a 34% improvement compared to the unreinforced coating. Friction–wear tests demonstrate that the composite coating reduces wear track width and depth by approximately 50% and 45%, respectively, compared to the substrate, with the wear mechanism transitioning from severe adhesive and fatigue wear to mild abrasive wear and localized micro-delamination. In situ synthesized NbC effectively optimizes the coating microstructure, enhances interfacial bonding, and markedly improves the hardness and wear resistance of 17-4PH coatings, providing theoretical and technical support for their engineering application under severe service conditions. Full article

Poor consolidations and the strength–conductivity trade-off limit the performance of copper alloys fabricated by laser powder bed fusion (LPBF). To address this, this study developed a strategy combining the response surface methodology (RSM) with direct ageing treatment (DAT) to achieve a favorable strength–conductivity synergy. The results showed that under the optimal process parameters, a high relative density of 99.25% (8.95 g/cm³ for theoretical density) was obtained. After direct ageing treatment at 490 °C for 60 min, the CuCrZr exhibited an ultimate tensile strength of 399.31 MPa and a thermal conductivity of 326.53 W/(m·K). To reveal the underlying mechanisms, this study employed a combination of systematic characterization via high-resolution transmission electron microscopy (HRTEM) and quantitative modeling. HRTEM characterized the uniformly dispersed nanoscale body-centered cubic (BCC) Cr precipitates that form semi-coherent interfaces with the face-centered cubic (FCC) Cu matrix, showing a crystallographic misorientation of approximately 10.5° intermediate between the classic Nishiyama–Wassermann and Kurdjumov–Sachs orientation relationships. Quantitative modeling indicates that the high strength arises from a synergistic effect: coherent strain fields exerted by the precipitates effectively pin retained dislocations, coupling Orowan and dislocation strengthening. Meanwhile, solute precipitation reduces lattice distortion, restoring notable thermal conductivity. Full article

In this work, to address the limitation of low strength and hardness of single-phase CoCrFeNi high-entropy alloy, SiC particles were introduced as a reinforcing phase to prepare CoCrFeNi matrix composites with SiC contents of 0 wt%, 1 wt%, 2.5 wt% and 5 wt% via spark plasma sintering (SPS). It was preliminarily predicted that SiC particles would be uniformly distributed along grain boundaries of the CoCrFeNi matrix. During sintering, partial SiC decomposes at high-temperature, high-activity interfaces, regulating carbide precipitation and phase structural evolution, while residual undecomposed SiC remains at grain boundaries to pin boundaries and refine grains, thereby synergistically enhancing mechanical properties and wear resistance. Microstructural characterization reveals that all samples maintain a face-centered cubic (FCC) solid-solution matrix, and samples with non-zero SiC addition contain Cr₇C₃ carbides, which are mostly distributed at grain boundaries. With the increase in SiC content, mechanical performance is remarkably improved compared with the unreinforced CoCrFeNi matrix: the hardness rises from 198.8 HV to 321.7 HV, the yield strength is greatly enhanced from 242.5 MPa to 673.4 MPa, and the tensile strength increases from 557.9 MPa to 755.7 MPa. The improved yield strength originates synergistically from grain refinement, solid-solution strengthening, grain-boundary strengthening and dislocation strengthening. By clarifying the influence of microstructural defects on critical shear stress (τ₀) and normal fracture stress (σ₀), the intrinsic mechanism governing tensile mechanical performance and ductile–brittle fracture transition was revealed. This optimized CoCrFeNi/SiC composite exhibits excellent strength–hardness comprehensive performance, showing promising application potential for high-load, wear-resistant and structural service components under severe tribological and pressure conditions. Full article

High-entropy alloys exhibit a broad light-responsive spectrum, spanning the ultraviolet to visible range, and their light absorption coefficient is significantly higher than that of traditional binary oxides. Cr/AlCrNbSiTiN/AlCrNbSiTiO gradient nano-multilayer coatings with excellent solar selective absorption properties are prepared using ion source enhanced magnetron sputtering. The effects of thickness of the absorption layer of AlCrNbSiTiN (3/4/5 min, denoted as S-3/4/5) are systematically investigated. It is worth noting that nano-multilayer coatings of S-3, S-4, and S-5 exhibit nearly perfect absorption rates of 0.9847, 0.9888, and 0.9879, respectively. The TEM images shows clear interfaces between the various coating layers, exhibiting a gradient structure that combines nanocrystalline and amorphous characteristics. From the substrate to the surface, there is an increase in the content of nanocrystalline phases, coarsening of grain sizes, and a decrease in the amount of amorphous phases. The primary absorption layer of AlCrNbSiTiN displays a typical face-centered cubic nitride structure. The XPS analysis reveals that the high-valent oxides (Nb⁵⁺, Cr⁶⁺) ensure thermal stability, whereas mixed valence states of Cr³⁺/Cr⁶⁺ may enhance visible light absorption through multi-electron transitions. This study analyzes how both the thickness of absorbing layers and high-temperature annealing affect the optical properties and photothermal conversion performance of AlCrNbSiTiN-based high-entropy coatings, which provides valuable insights for developing high-performance selective absorbers. Full article