Rare Metals最新文献

This study comprehensively investigates the effects of annealing on the structural, electrochemical properties and passivation film characteristics of Ti₂₀Zr₂₀Hf₂₀Be₂₀Ni₂₀ (at%) high-entropy metallic glass (HE-MG). Subjected to various annealing temperatures, the samples were analyzed in a 3.5 wt% NaCl solution to evaluate changes in their microstructure and assess their corrosion resistance. Findings reveal that the HE-MG undergoes multistage crystallization, displaying an amorphous matrix integrated with face centered cubic (FCC) and Ni₇Zr₂ phases between 420 and 500 °C, indicating robust thermal stability. Electrochemical assessments identify a critical temperature threshold: Below the glass transition temperature (T_g), the HE-MG maintains excellent corrosion resistance, promoting stable passivation layers. Above T_g, enhanced long-range atomic rearrangement during relaxation increases passivation layer defects and significantly diminishes corrosion resistance. X-ray photoelectron spectroscopy (XPS) analyses show that the primary components of the passivation layer are TiO₂, ZrO₂, HfO₂ and BeO. Increased annealing temperatures lead to enhanced Be and Ni content and decreased Ti, Zr and Hf. Additionally, high mixing entropy and significant atomic size mismatch suppress long-range atomic rearrangement and crystallization. The crystallization begins above T_g by 20 °C, with crystalline phases evenly distributed within the matrix without drastically affecting corrosion resistance. This investigation highlights the impact of thermal treatment on the properties of HE-MG, contributing valuable insights into optimizing their performance and applications.

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Abstract

Inverted perovskite solar cells (PSCs) have stood out in recent years for their great potential in offering low-temperature compatibility, long-term stability and tandem cell suitability. However, challenges persist, particularly concerning the use of nickel oxide nanoparticles (NiO_x NPs) as the hole transport material, where issues such as low conductivity, impurity-induced aggregation and interface redox reactions significantly hinder device performance. In response, this study presents a novel synthesis method for NiO_x NPs, leveraging the introduction of ammonium salt dopants (NH₄Cl and NH₄SCN), and the solar cell utilizing the doped NiO_x substrate exhibits much enhanced device performance. Furthermore, doped solar cells reach 23.27% power conversion efficiency (PCE) when a self-assembled monolayer (SAM) is further employed. This study provides critical insights into the synthesis and growth pathways of NiO_x NPs, propelling the development of efficient hole transport materials for high-performance PSCs.

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Zinc (Zn)-based alloys have emerged as promising bioresorbable metals for orthopedic implants because of their favorable combination of moderate degradation rates, good mechanical properties, and biocompatibility. In addition, the performance of bone implants relies heavily on their osteointegration ability, which is closely related to the immune responses triggered after implantation. In this study, two Zn-based alloys, Zn–2Cu and Zn–2Cu–0.8Li were developed, to improve the comprehensive properties of Zn implants. The introduction of copper (Cu) and lithium (Li) via alloying improved the hardness and localized corrosion resistance of Zn-based specimens. Both the Zn alloys exhibited enhanced adhesion, proliferation, and osteogenic differentiation behaviors when tested with MC3T3-E1 cells. Importantly, the immune response of RAW264.7, mediated by the two Zn alloys, with pure Zn as a control was systematically investigated. The results demonstrated that the synergistic release of Cu²⁺ and Li⁺ played a pivotal role in promoting the anti-inflammatory and osteoimmunomodulatory properties of degradable Zn. By alloying with Cu and Li, we achieved sequential and sustained ion release, resulting in the synergistic enhancement of osteoimmunomodulation through the modulation of the JAK-STAT signaling pathway. Finally, the Zn-based specimens were evaluated in vivo using rat mandibular defect models. After 8 weeks, the Zn–2Cu–0.8Li group exhibited significantly higher bone regeneration than the Zn–2Cu and pure Zn groups. These findings highlight the beneficial immune response and potential of Zn–Cu–Li alloys as novel biodegradable materials for orthopedic implants.

Grapical abstract

Based on the unique catalytic properties of precious metals, the introduction of precious metals into metal oxide semiconductors will greatly improve the gas-sensitive properties of materials. As a new type of porous material, metal–organic frameworks (MOF) can be used for gas separation and adsorption due to their adjustable pore size and acceptable thermal stability. In this work, the ZIF-71 MOF was synthesized on CuO nanofibers doped with different concentrations of Ru to form a Ru–CuO@ZIF-71 nanocomposite sensor, which was then used for H₂S detection. The sensor shows sensitivity to trace amounts of H₂S gas (100 ppb), and the response is greatly enhanced at the optimal Ru doping ratio and operating temperature. The introduction of the ZIF-71 membrane can significantly increase the selectivity of the sensor while further improving the sensitivity. Finally, the possible sensing mechanism of the Ru–CuO@ZIF-71 sensor was explored. The enhancement of the H₂S gas sensing properties may be attributed to the catalysis of Ru and the formation of the Schottky junction at the Ru–CuO interface. Besides, the calculation based on density functional theory reveals enhanced adsorption capacities of CuO for H₂S after Ru doping. Therefore, the Ru–CuO@ZIF-71 sensor has strong application potential in exhaled gas detection and portable detection of H₂S gas in industrial environments.

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Aqueous zinc-ion batteries (AZIBs) have developed rapidly in recent years but still face several challenges, including zinc dendrites growth, hydrogen evolution reaction, passivation and corrosion. The pH of the electrolyte plays a crucial role in these processes, significantly impacting the stability and reversibility of Zn²⁺ deposition. Therefore, pH-buffer tris (hydroxymethyl) amino methane (tris) is chosen as a versatile electrolyte additive to address these issues. Tris can buffer electrolyte pH at Zn/electrolyte interface by protonated/deprotonated nature of amino group, optimize the coordination environment of zinc solvate ions by its strong interaction with zinc ions, and simultaneously create an in-situ stable solid electrolyte interface membrane on the zinc anode surface. These synergistic effects effectively restrain dendrite formation and side reactions, resulting in a highly stable and reversible Zn anode, thereby enhancing the electrochemical performance of AZIBs. The Zn||Zn battery with 0.15 wt% tris additives maintains stable cycling for 1500 h at 4 mA·cm⁻² and 1120 h at 10 mA·cm⁻². Furthermore, the Coulombic efficiency reaches ~ 99.2% at 4 mA·cm⁻²@1 mAh·cm⁻². The Zn||NVO full batteries also demonstrated a stable specific capacity and exceptional capacity retention.

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A new Cu-Cr-Sc alloy was designed, prepared and subjected to deformation heat treatment. Transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) were employed to investigate the effects of Sc on the microstructural changes in the Cu-Cr alloy in different states, examine the changes in the precipitates during aging, reveal the intrinsic correlation between the structure and property in the peak aging state, and evaluate the Sc distribution in the Cu-Cr alloy. The addition of Sc significantly increased the yield strength of the Cu-Cr alloy by ~ 24.6% after aging at 480 °C for 1 h, while it had a high electrical conductivity of 81.5% international annealed copper standard (IACS). This enhancement was attributed to the effective inhibition of Cr phase coarsening and recrystallization through the addition of Sc, which strengthened the alloy. Furthermore, in the Cu-Cr-Sc alloy, most of the Sc atoms precipitated as the Cu₄Sc phase, with a small amount of Sc segregating at the grain boundaries to pin them. This grain boundary pinning helped to inhibit grain growth and further improve the strength. The main strengthening mechanisms identified in Cu-Cr-Sc alloys were dislocation strengthening and precipitation strengthening.

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Recently, high-entropy materials are attracting enormous attention in battery applications, encompassing both electrode materials and solid electrolytes, due to the pliability and diversification in material composition and electronic structure. Theoretically, the rapid ion transport and the abundance of surface defects in high-entropy materials suggest a potential for enhancing the performance of composite solid-state electrolytes (CPEs). Herein, using a high-entropy oxide (HEO) filler to assess its potential contributions to CPEs is proposed. The distinctive structural distortions in HEO significantly improve the ionic conductivity (5 × 10⁻⁴ S·cm⁻¹ at 60 °C) and Li-ion transference number (0.57) of CPEs. Furthermore, the enhanced Li-ion transport capability extends the critical current density from 0.6 to 1.5 mA·cm⁻² in Li/Li symmetric cells. In addition, all-solid-state batteries incorporating the HEO-modified CPEs exhibit superior rate performance and cycling stability. The work will enrich the application of HEOs in CPEs and provide fundamental understanding.

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Abstract

Designing rational transition-metal/carbon composites with highly dispersed and firmly anchored nanoparticles (NPs) to prevent agglomeration and shedding is crucial for realizing excellent electrocatalytic performances. Herein, a biomass pore-confined strategy based on mesoporous willow catkin is explored to obtain uniformly dispersed CoFe NPs in N-doped carbon nanotubes and hollow carbon fibers (CoFe@N-CNTs/HCFs). The resultant catalyst exhibits enhanced electrocatalytic performance, which affords a half-wave potential of 0.86 V (vs. RHE) with a limited current density of 6.0 mA·cm⁻² for oxygen reduction reaction and potential of 1.67 V (vs. RHE) at 10 mA·cm⁻² in 0.1 M KOH for oxygen evolution reaction. When applied to rechargeable zinc–air batteries, a maximum power density of 340 mW·cm⁻² and long-term cyclic durability over 800 h are achieved. Such superior bifunctional electrocatalytic activities are ascribed to the biocarbon matrix with abundant mesopores and unobstructed hollow channels, CoFe NPs with high dispersion and controllable nanoscale and the hybrid composite with optimized electronic structure. This work presents an effective approach for constraining the size and dispersion of NPs in a low-cost biocarbon substrate, offering valuable insights for designing advanced oxygen electrocatalysts.

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The zinc indium sulfide (ZnIn₂S₄) semiconductors have garnered significant interest in photocatalysis due to their environmentally friendly characteristics, appropriate bandgap, and high absorption coefficient. However, the exploration of advanced strategies to realize the effective and tailored doping still poses significant challenges in enhancing hydrogen evolution performance. In this work, a mild cation exchange strategy is reported to incorporate Ag cations into flower-like ZnIn₂S₄ microspheres, enabling the selective replacement of Zn atoms by Ag. Remarkably, the as-fabricated Ag-ZnIn₂S₄ exhibited exceptional photocatalytic hydrogen production performance, achieving a rate of 8098 μmol·g⁻¹· h⁻¹ under visible light irradiation. This is 4 times than that of pristine ZnIn₂S₄ (2002 μmol·g⁻¹· h⁻¹), and stands as the highest one among metal-doped-ZnIn₂S₄ photocatalysts ever reported. Along with the theoretical calculations, it has been confirmed that the enhanced photocatalytic hydrogen generation behavior can primarily be attributed to the synergistic effect with improved light absorption, reduced adsorption energy, increased active sites and optimized charge carrier transfer, induced by the cation exchange with Ag in ZnIn₂S₄. This work might provide some valuable insights on the design and development of highly efficient visible light driven photocatalysts for water splitting applications.

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