Search Results (74)

To enhance the high-temperature oxidation resistance of chromium carbide metal ceramic coatings, micro/nanoparticle modification was applied to the alloy binder phase of the typical Cr₃C₂-NiCr coating. This led to the development of Cr₃C₂-NiCrCoMo and Cr₃C₂-NiCrCoMo/nano-CeO₂ coatings with superior high-temperature oxidation performance. This study compares the high-temperature oxidation behavior of these coating samples and explores their respective oxidation mechanisms. The results indicate that the addition of CoCrMo improves the compatibility between the oxide film and the coating, enhancing the microstructure and integrity of the oxide film. Compared to Cr₃C₂-NiCrCoMo coatings, the incorporation of nano-CeO₂ promotes the reaction between oxides in the Cr₃C₂-NiCrCoMo/nano-CeO₂ coating, increasing the content of binary spinel phases, reducing thermal stress at the oxide–coating interface, and improving the adhesion strength of the oxide film. As a result, the oxidation rate of the coating is reduced, and its oxidation resistance is improved. Full article

This study evaluates the wear and corrosion resistance of the Cu-50Ni-5Al alloy reinforced with CeO₂ nanoparticles for potential use as anodes in molten carbonate fuel cells (MCFCs). Cu–50Ni–5Al alloys were synthesized, with and without the incorporation of 1% CeO₂ nanoparticles, by the mechanical alloying method and spark plasma sintering (SPS). The samples were evaluated using a single scratch test with a cone-spherical diamond indenter under progressive normal loading conditions. A non-contact 3D surface profiler characterized the scratched surfaces to support the analysis. Progressive loading tests indicated a reduction of up to 50% in COF with 1% NPs, with specific values drop-ping from 0.48 in the unreinforced alloy to 0.25 in the CeO₂-doped composite at 15 N of applied load. Furthermore, the introduction of CeO₂ decreased scratch depths by 25%, indicating enhanced wear resistance. The electrochemical behavior of the samples was evaluated by electrochemical impedance spectroscopy (EIS) in a molten carbonate medium under a H₂/N₂ atmosphere at 550 °C for 120 h. Subsequently, the corrosion products were characterized using X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the CeO₂-reinforced alloy exhibits superior electro-chemical stability in molten carbonate environments (Li₂CO₃-K₂CO₃) under an H₂/N₂ atmosphere at 550 °C for 120 h. A marked reduction in polarization resistance and a pronounced re-passivation effect were observed, suggesting enhanced anodic protection. This effect is attributed to the formation of aluminum and copper oxides in both compositions, together with the appearance of NiO as the predominant phase in the materials reinforced with nanoparticles in a hydrogen-reducing atmosphere. The addition of CeO₂ nanoparticles significantly improves wear resistance and corrosion performance. Recognizing this effect is vital for creating strategies to enhance the material’s durability in challenging environments like MCFC. Full article

The mechanical response of high-entropy alloys (HEAs), specifically the FeNiCrCoAl HEA, was studied at both bulk and nanoparticle scales using molecular dynamics simulations. These simulations were performed using the LAMMPS software with an Embedded Atom Method (EAM) potential. The results show that Bulk HEAs exhibited enhanced hardening and plasticity, while in nanoparticles, distinct deformation patterns were observed, including nanotwin formation, V-shaped stacking fault planes, and intermittent dislocation activity due to free surface effects. The crystallographic orientation with respect to the compression significantly affected the deformation mechanisms, with the [100] direction favoring progressive hardening, while the [110] and [111] directions exhibited different stacking fault and dislocation dynamics. A detailed analysis using von Mises stress and dislocation analysis provided insights into the effects of scale on mechanical properties. Full article

Research into the introduction of alloying and reinforcing nanocomposites into nickel (Ni) coatings has been motivated by the need for tribologically superior coatings that will improve energy efficiency. Using pulse electrodeposition, this work investigates the effects of adding cobalt (Co) as the alloying nanoparticle and silicon carbide (SiC), zirconium oxide (ZrO₂), and aluminium oxide (Al₂O₃) as reinforcing nanocomposites to Ni coatings. The surface properties, mechanical strength, nanotribological behaviour, and wettability of these coatings were analysed. Surface characteristics were evaluated by the use of a Scanning Electron Microscope, revealing a grain dimension reduction of approximately ~7–43% compared to pristine Ni coatings. When alloying and reinforcing nanocomposites were added to Ni coatings, nanoindentation research showed that there was an increase in nanohardness of ~12% to ~69%. This resulted in an improvement in the tribological performance from approximately 2% to 65%.The hydrophilic nature of Ni coatings was observed with wettability analysis. This study demonstrates that nanocomposite reinforcement can be used to customise Ni coatings for applications that require exceptional tribological performance. The results point to the use of Ni-Co coatings for electronics and aerospace sectors, with more improvements possible with the addition of reinforcing nanoparticles. Full article

Microwave absorbers with infrared camouflage are highly desirable in military fields. Self-supporting 3D architectures with tailorable shapes, composed of FeCoNi alloy/carbon nanotubes (CNTs) @ carbon nanofibers (CNFs), were fabricated in this study. On the one hand, multiple loss mechanisms were introduced into the high-elastic sponges. Controllable space conductive networks caused by the in situ growth of CNTs on the CNFs contributed to the effective dielectric and resistance loss. Moreover, the uniformly distributed magnetic alloy nanoparticles (NPs) with dense magnetic coupling resulted in magnetic loss. On the other hand, heterogeneous interfaces were constructed by multicomponent engineering, causing interfacial polarization and polarization loss. Furthermore, the internal structures of sponges were optimized by regulating the alloy NPs sizes and the growth state of CNTs, then tuning the impedance matching and microwave absorption. Therefore, the high-elastic sponges with ultra-low density (7.6 mg·cm⁻³) were found to have excellent radar and infrared-compatible stealth properties, displaying a minimum refection loss (RL_min) of −50.5 dB and a maximum effective absorption bandwidth (EAB_max) of 5.36 GHz. Moreover, the radar stealth effect of the sponges was evaluated by radar cross-section (RCS) simulation, revealing that the multifunctional sponges have a promising prospect in military applications. Full article

This study focused on synthesizing AlNiCo and CoNi materials using a low-energy milling process. The aim was to explore the formation of low-energy phases in both systems, contrasting with the typical research on phases formed under high-energy conditions. In the Co-20 wt% Ni system, the phases ${\mathrm{Co}}_{0.75}{\mathrm{Ni}}_{0.25}$ and Ni were identified, as well as the FCC cubic phase of CoNi, using X-ray diffraction (XRD) with a molybdenum radiation source. The observed behavior aligned closely with the miscibility curve in the equilibrium phase diagram, which included a region of alloys with varying structures and similar compositions. A notable feature was the presence of a predominantly dispersed hexagonal Ni zone, consisting of nanoparticles. Transmission electron microscopy (TEM) was employed to observe the FCC CoNi phase, which displayed a specific arrangement. AlNiCo and CoNi alloys were successfully synthesized through mechanical alloying, incorporating equilibrium and non-equilibrium phases. Full article

Because of their high mixing entropies, multi-component alloys can exhibit enhanced catalytic activity compared to traditional catalysts in various chemical reactions, including hydrogenation, oxidation, and reduction processes. In this work, new AgCoCuFeNi high entropy alloy nanoparticles were synthesized by the hydrogen reduction-assisted ultrasonic spray pyrolysis method. The aim was to investigate the effects of processing parameters (reaction temperature, precursor solution concentration, and residence time) on the microstructure, composition, and crystallinity of the high entropy alloy nanoparticles. The characterization was performed with scanning electron microscope, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The syntheses performed at 600, 700, 800, and 900 °C, resulted in smaller and smoother spherical particles with a near-equiatomic elemental composition as the temperature increased to 900 °C. With 0.25, 0.1, and 0.05 M precursor solutions, narrower size distribution and uniform AgCoCuFeNi nanoparticles were produced by reducing the solution concentration to 0.05 M. A near-equiatomic elemental composition was only obtained at 0.25 and 0.05 M. Increasing the residence time from 5.3 to 23.8 s resulted in an unclear particle microstructure. None of the five metal elements were formed in the large tubular reactor. X-ray diffraction revealed that various crystal phase structures were obtained in the synthesized AgCoCuFeNi particles. Full article

In this study, the surface and textural properties as well as the catalytic performance of Ni/CeO₂ and NiIn/CeO₂ catalysts prepared by wet impregnation (WI) and deposition–precipitation (DP) are investigated. The addition of Ni (3.0 wt.%) resulted in a decrease in the specific surface area and pore volume in the case of the WI method, possibly due to a blockage of mesopores. A minimal addition of In (0.25 wt.%) caused a further decrease in the surface area in both cases. XRD analysis showed that Ni deposited on CeO₂ by DP resulted in some lattice incorporation, affecting the crystallinity of the support. The H₂-TPR profiles altered depending on the different ways of Ni and In introduction. STEM-EDS-derived elemental maps indicated that the Ni and NiIn particles deposited on CeO₂ using the DP method were somewhat smaller than in the WI synthesis. A comprehensive CO-DRIFTS analysis proved a direct Ni-In interaction in bimetallic samples, leading to the formation of a surface NiIn alloy. Ni/CeO₂ catalysts showed a higher activity in the process of dry reforming of methane (DRM) than the bimetallic counterparts at 650 °C, with the Ni_DP sample performing slightly better. However, the Ni_DP catalyst showed significant coking, which was drastically reduced by the addition of In. The agglomeration of Ni and/or NiIn particles during the 6 h DRM reaction somewhat impaired the catalyst performance. Overall, this study highlights the intricate relationship between the catalyst preparation, surface properties and catalytic performance in the DRM reaction and emphasizes the beneficial role of In addition in reducing the coking of the monometallic catalyst and the critical location and surface morphology of nickel nanoparticles decorated with indium and in contact with ceria. Full article

The development of low-cost, high-performance oxygen electrocatalysts is of great significance for energy conversion and storage. As a potential substitute for precious metal electrocatalysts, the construction of efficient and cost-effective oxygen electrocatalysts is conducive to promoting the widespread application of zinc–air batteries. Herein, Co_xNi_yMOF nanoparticles encapsulated within a carbon matrix were synthesized and employed as cathode catalysts in zinc–air batteries. Co_0.5Ni_0.5MOF exhibits superior oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance and durability. The zinc–air battery assembled with Co_0.5Ni_0.5MOF as the air cathode exhibits a maximum power density of 138.6 mW·cm⁻². These improvements are mainly attributed to the optimized metal composition of the cobalt–nickel alloy, which increases the specific surface area of the material and optimizes its pore structure. Significantly, the optimization of the electronic structure and active sites within the material has led to amplified ORR/OER activity and better zinc–air battery performance. This study underscores the immense promise of Co_0.5Ni_0.5MOF catalysts as feasible substitutes for commercial Pt/C catalysts in zinc–air batteries. Full article

Dense multi-cationic Sm-Co-O, Sm-Ni-O, Al-Co-O, Al-Ni-O, and Al-Ni-Co-O oxide aerogels were prepared by epoxide-driven sol–gel synthesis. Catalysts for dry reformation of methane, Sm₂O₃/Co, Sm₂O₃/Ni, Al₂O₃/Co, Al₂O₃/Ni, Al₂O₃/Co, and Ni were prepared by reduction of aerogels with hydrogen and their catalytic activities and C-deposition during dry reformation of methane were tested. Catalytic tests showed high methane conversion (93–98%) and C-deposition (0.01–4.35 mg C/g_cat^.h). The highest content of C-deposits after catalytic tests was determined for Al₂O₃/Co and Al₂O₃/Ni catalysts, which was related to the formation of Al alloys with Co and Ni. A uniform distribution of Co⁰ and Ni⁰ nanoparticles (in the form of a CoNi alloy) was found only for the Al₂O₃/Co and Ni catalysts, which showed the highest activity as well as low C deposition. Full article

High-entropy alloys (HEAs) have attracted a great deal of research interest these days because of their attractive properties. Low-temperature chemical synthesis methods are being developed to obtain nanoscale HEAs with low energy consumption. In this study, we prepared HEA Al_0.2Co_1.5CrFeNi_1.5Ti_0.5 nanoparticles from high-entropy oxide (HEO) (Al_0.2Co_1.5CrFeNi_1.5Ti_0.5)₃O₄ by a deoxidation process via a CaH₂-assisted molten salt method at 600 °C. X-ray diffraction measurements demonstrated that the oxide precursor and the reduced product have single-phases of spinel structure and face-centered cubic structures, indicating the formation of HEO and HEA, respectively. The HEA nanoparticles exhibited superior catalytic performance in the liquid-phase hydrogenation of p-nitrophenol at room temperature with little leaching of the component elements. Scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometry (EDX) exhibited a good distribution of constituent elements over the HEA nanoparticles in a micro-sized range. However, transmission electron microscopy (TEM) with EDX revealed a slight deviation of elemental distributions of Al and Ti from those of Co, Cr, Fe, and Ni in a nano-sized range, probably due to the incomplete reduction of aluminum and titanium oxides. The elemental homogeneity in the HEA nanoparticles could be improved by taking advantage of the HEO precursor with homogeneous elemental distributions, but the experimental results suggested the importance of the total reduction of oxide precursors to prepare homogeneous HEAs from HEOs. Full article

This review extensively discusses current developments in bimetallic nanoparticle–GO and bimetallic nanoparticle–MOF nanocomposites as potential catalysts for HER, along with their different synthesis methodologies, structural characteristics, and catalytic mechanisms. The photoelectrocatalytic performance of these catalysts was also compared based on parameters such as Tafel slope, current density, onset potential, turnover frequency, hydrogen yield, activation energy, stability, and durability. The review shows that the commonly used metal alloys in the bimetallic nanoparticle–GO-based catalysts for HERs include Pt-based alloys (e.g., PtNi, PtCo, PtCu, PtAu, PtSn), Pd-based alloys (e.g., PdAu, PdAg, PdPt) or other combinations, such as AuNi, AuRu, etc., while the most used electrolyte sources are H₂SO₄ and KOH. For the bimetallic nanoparticle MOF-based catalysts, Pt-based alloys (e.g., PtNi, PtCu), Pd-based alloys (e.g., PdAg, PdCu, PdCr), and Ni-based alloys (e.g., NiMo, NiTi, NiAg, NiCo) took the lead, with KOH being the most frequently used electrolyte source. Lastly, the review addresses challenges and prospects, highlighting opportunities for further optimization and technological integration of the catalysts as promising alternative photo/electrocatalysts for future hydrogen production and storage. Full article

High-entropy alloys (HEAs) are a class of metal alloys consisting of four or more molar equal or near-equal elements. HEA nanomaterials have garnered significant interest due to their wide range of applications, such as electrocatalysis, welding, and brazing. Their unique multi-principle high-entropy effect allows for the tailoring of the alloy composition to facilitate specific electrochemical reactions. This study focuses on the synthesis of high-purity HEA nanoparticles using the method of femtosecond laser ablation synthesis in liquid. The use of ultrashort energy pulses in femtosecond lasers enables uniform ablation of materials at significantly lower power levels compared to longer pulse or continuous pulse lasers. We investigate how various femtosecond laser parameters affect the morphology, phase, and other characteristics of the synthesized nanoparticles. An innovative aspect of our solution is its ability to rapidly generate multi-component nanoparticles with a high fidelity as the input multi-component target material at a significant yielding rate. Our research thus focuses on a novel synthesis of high-entropy alloying CuCoMn_1.75NiFe_0.25 nanoparticles. We explore the characterization and unique properties of the nanoparticles and consider their electrocatalytic applications, including high power density aluminum air batteries, as well as their efficacy in the oxygen reduction reaction (ORR). Additionally, we report a unique nanowire fabrication phenomenon achieved through nanojoining. The findings from this study shed light on the potential of femtosecond laser ablation synthesis in liquid (FLASiL) as a promising technique for producing high-purity HEA nanoparticles. Full article

Transition metallic binary alloys have attracted enormous attention in regard to the non-enzymatic detection of glucose due to their high electrocatalytic activities induced by the synergistic effect between the individual metallic species. However, the easy aggregation of the bimetallic particles has limited their performance. Herein, a facile metal–organic framework (MOF)-derived strategy is developed to synthesize a hybrid containing binary Co–Ni nanoparticles decorated on an N-doped porous carbon matrix (Co_xNi_y/N-C) for the non-enzymatic detection of glucose. The Co/Ni ratio in the hybrid is investigated to regulate its electrocatalytic behaviors for glucose sensing. A hybrid with the optimal Co/Ni ratio of 1:1 displays two linear detection ranges (0.5 µM to 1 mM and 1 mM to 10 mM) with a detection limit of 0.11 µM for glucose. The feasibility of using this hybrid-modified SPE for glucose detection in real serum samples has also been validated. Full article

Pulsed laser ablation in liquids (PLAL) is a versatile technique to produce high-purity colloidal nanoparticles. Despite considerable recent progress in increasing the productivity of the technique, there is still significant demand for a practical, cost-effective method for upscaling PLAL synthesis. Here we employ and unveil the fundamentals of multi-beam (MB) PLAL. The MB-PLAL upscaling approach can bypass the cavitation bubble, the main limiting factor of PLAL efficiency, by splitting the laser beam into several beams using static diffractive optical elements (DOEs). A multimetallic high-entropy alloy CrFeCoNiMn was used as a model material and the productivity of its nanoparticles in the MB-PLAL setup was investigated and compared with that in the standard single-beam PLAL. We demonstrate that the proposed multi-beam method helps to bypass the cavitation bubble both temporally (lower pulse repetition rates can be used while keeping the optimum processing fluence) and spatially (lower beam scanning speeds are needed) and thus dramatically increases the nanoparticle yield. Time-resolved imaging of the cavitation bubble was performed to correlate the observed production efficiencies with the bubble bypassing. The results suggest that nanoparticle PLAL productivity at the level of g/h can be achieved by the proposed multi-beam strategy using compact kW-class lasers and simple inexpensive scanning systems. Full article