查看更多>>摘要：? 2022 Elsevier B.V.Lithium-sulfur (Li-S) batteries appear to be one of the most promising energy-storage devices owing to the unparalleled theoretical specific energy, relatively inexpensive price and abundant resources. Despite these attractive features, the practical performances of sulfur cathode still remain a lot of challenges, such as the electrical insulating nature of S and Li2S, huge volume change during cycling, notorious shuttle effect of lithium polysulfide intermediates (LiPSs), sluggish redox kinetics and construction of thick electrodes with high sulfur loading. Here, CoFe2O4 nanoparticles anchored on the carbon nanotube (CNT) paper is proposed as free-standing sulfur host to address the issues. The cross-linking CNT network can serve as conductive matrix and accommodate volume change upon cycling simultaneously. Meanwhile, the CoFe2O4 nanoparticles are capable of effectively anchoring LiPSs to suppress the shuttle effect and accelerating LiPSs conversion to boost redox kinetics. Moreover, the free-standing paper electrode without any binder is conducive to constructing stable cathode with high sulfur loading. In consequence, the well-designed S/CoFe2O4/CNT paper cathodes deliver impressive electrochemical performance, demonstrating an initial discharge capacity of 755.3 mAh g?1 and remaining a high reversible capacity of 642.6 mAh g?1 after 400 cycles at 2 C with an inconspicuous decay of 0.04% per cycle.
查看更多>>摘要：? 2022 Elsevier B.V.Nickel-phosphorus amorphous plating can not only enhance the wearability and corrosion resistance of the substrate but also improve the optical performance. The preparation technology, structure and properties of thick nickel-phosphorus amorphous plating on SiCp/Al composite were studied in the work by using SEM, EDS, XRD, HRTEM, XPS, FT-IR, DSC, TMA and princeton electrochemical workstation. It is found that the Ni-P amorphous plating with thickness of 178 μm can be obtained by double zincate pretreatment method. The amorphous coating surface presents a typical cauliflower-like nodular structure, and the weight percentage concentration of P in the coating surface is about 12.36 wt%, which belong to the high phosphorus coating. The initial crystallize temperature of the Ni-P coating is about 322.5 ℃ at the heating rate of 5 ℃·min?1, the Vickers microhardness is about 554–570HV and has excellent corrosion resistance compared with the substrate. The average thermal expansion coefficient of the coating is about 14.8–15.4 × 10?6 m·℃?1, which follows a linear law at the crystallization temperature, and has a little difference at the same temperature in different directions. Apart from that, factors to affect the adhesion and thickness of the Ni-P amorphous plating were also analyzed.
查看更多>>摘要：? 2022 Elsevier B.V.Developing highly efficient electromagnetic (EM) absorbers with a broad bandwidth remains a major challenge for reducing EM pollution originating from the ever-rising electronic and telecommunication devices. Designing core-shell structures containing a magnetic core and dielectric shell could be an effective strategy to tackle this problem. Herein, we report a surface modification strategy to synthesize the FeSiAl/phosphate core-shell materials with unique rodlike structure through a facile surface passivation process. Multilevel phosphate shells are in situ introduced for significantly facilitating the EM absorbing performance by inducing multiple interfacial polarizations and obtain ideal impedance matching. Direct evidence of the morphology and microstructure evolution of resultant FeSiAl/phosphate composites correlated to the EM properties has been systematically investigated. Due to intense synergistic effects between magnetic and dielectric loss, exceptional microwave dissipation capacity can be achieved over an ultra-wide absorption bandwidth of 9.8 GHz at 2.5 mm.
查看更多>>摘要：? 2022 Elsevier B.V.The superelasticity of shape memory alloys is associated with the martensitic transformation which has been widely used in engineering applications. Here, we clarify quasi-linear superelasticity in Ni-Fe-Ga-Co shape memory alloy exhibiting a recovery strain of 3.58% at 573 K, which is far above the martensitic transformation temperature. Real-time in-situ neutron diffraction measurement was used to explore the underlying quasi-linear superelasticity mechanism via tracing the structural evolution during cyclic compression loading. Neutron diffraction observation showed that the superelasticity is correlated with stress-induced continuous variation of lattice parameter. The in-situ neutron diffraction provides the direct evidence on the anomalous diffraction peak width broadening, which mainly stems from the spatial heterogeneity in strain. The excessive Co doping is responsible for the decrease in stacking-fault energy leading to an increase in stacking faults, which suppresses the martensitic transformation and triggers the nucleation of the weak first-order phase under the external stress. The study provides insights into the interplay between superelasticity and structural transformation in shape memory alloys, and it is also instructive for understanding the anomalous high-temperature quasi-linear superelasticity in functional materials.
查看更多>>摘要：? 2022 Elsevier B.V.Medium entropy alloys (MEAs) strengthened by L12 ordered intermetallics have attracted extensive attention because of their unique mechanical properties that critically depend on the constituent elements. In this work, we design a CoCrNiAl3Ti3Cu6Nb0.8 MEA possessing bimodal L12 nano-precipitates to achieve improved synergy of strength and ductility. The as-prepared MEA exhibit a yield strength of 1.16 GPa, a tensile strength of 1.55 GPa, and a uniform elongation of 28%. The improved mechanical responses are attributed to the simultaneously operated strong- and weak-pair coupling effects and the hetero-deformation induced strengthening that derived from the bimodal distributed L12 nano-precipitates. The results presented herein demonstrate that bimodal distributed nano-precipitates might be a new strategy toward synergy of strength and ductility in MEAs.
查看更多>>摘要：? 2022 Elsevier B.V.γ-TiAl alloys, as the high temperature and lightweight structural material, have been applied in aerospace and automotive industry, and will remain the focus of research worldwide. After more than 40 years of development, γ-TiAl alloys not only completed the entire process from theoretical research to industrial application, but also accumulated a large amount of data. In this review, a new perspective, Al-equivalent, is selected to summarize the development trend of γ-TiAl alloys, and then the intrinsic nature of this trend is discussed in detail from the aspects of two fundamental phase transformations and solidification microstructures. Furthermore, the role of common alloying elements in γ-TiAl alloys has also been summarized from the perspective of phase transformations. There are two main purposes of this work, one is to introduce Al-equivalent based on the summary of the development process of TiAl alloys in order to reveal the inherent laws of alloy development; the other is to combine phase diagrams to investigate the effects of alloying elements on the phase transformation of TiAl alloys.
查看更多>>摘要：? 2022 Elsevier B.V.Nanotubes of Ir-Cu binary metal oxide with various composition ratios (IrxCu1?xOy with x = 0.64, 0.48 and 0.33) were prepared using electrospinning followed by thermal annealing. IrxCu1?xOy nanotubes were investigated to be composed of rutile IrO2 phase where Cu substituted Ir sites. This elemental subsititution induced the amorphization and generation of oxygen vacancy defects in the rutile phase of IrxCu1?xOy nanotubes. Among IrxCu1?xOy series, Ir0.48Cu0.52Oy nanotubes, having a reduced noble Ir content by more than a half, showed the best activity for oxygen evolution reaction (OER) in pH-universal condition, and even outperformed the material containing only Ir, commercial Ir/C and the other Ir-based binary metal oxide catalysts found in the literature. Of importance, Ir0.48Cu0.52Oy presented an excellent stability during continuous OER for 20,000 s in all the acidic, neutral and alkaline media despite their amorphousness. The introduction of Cu into IrO2 was beneficial for improving not only the OER catalytic activity but the durability along with cost-effectiveness.
查看更多>>摘要：? 2022Nanocomposites Ag-TiO2?x have been fabricated simply by Ag+ ion exchange of H2Ti3O7 nanowires. Ag NPs, appearing on the catalyst surface, exhibit strong visible-light absorption and generate hot electrons due to their localized surface plasmon resonance. Moreover, Ag introduction leads to the generation of anatase-rutile biphase heterojunction with Ti3+ defect energy level, narrowing the bandgap to 2.85 eV and inhibiting the recombination of electron-hole pairs, thus facilitating photocatalytic reduction of Cr (VI) under visible light. A possible photocatalytic reduction mechanism, i. e., the synergistic effect of the Ti3+ defect energy level, anatase-rutile heterojunction and SPR effect of Ag nanoparticles, has also been proposed.
查看更多>>摘要：? 2022 Elsevier B.V.Deep ultraviolet photodetectors (deep-UV PDs) are promising for multiple applications due to their high detecting accuracy and sensitivity in the absence of background sunlight disturbance. By alloying, the bandgap of ZnO can be extended for deep-UV optoelectronics. However, it is limited by the solubility and the crystal quality degradation for a high-component alloy, which hinders the practical applications. In this work, we simply use the 2D Ti3C2 nanoflakes to anchor on ZnO surface to enhance the deep-UV band absorption. Moreover, van der Waals heterojunctions formed at the dispersed Ti3C2/ZnO interfaces create surface depletion and passivation, which suppresses the dark current and enhances the photocurrent simultaneously. As a result, the Ti3C2 nanoflakes anchored ZnO PD shows enhanced photoresponse in the entire UV region. Particularly, in the deep-UV range this enhancement is much more significant, with a peak light to dark ratio, EQE, responsivity and detectivity of 1.64 × 104, 128.3 mA/W, 66.3% and 5.7 × 1011 Jones respectively achieved at 240 nm light illumination, which is enhanced by 284, 72, 74 and 55 times respectively compared to the pristine ZnO PD. This work provides a newly non-alloyed strategy to broaden ZnO-based deep-UV, high-performance photodetection applications.
查看更多>>摘要：? 2022In recent years, the market has pushed for higher energy density requirements for secondary rechargeable batteries. Bimetallic oxides are promising candidates for replacing graphite anode materials in lithium-ion batteries with high energy density. To improve the electrochemical performance of NiFe2O4 nanoparticles, a carbon coating layer and single-walled carbon nanotubes (SWCNTs) conductive network were in situ co-constructed simultaneously using a solvothermal method, taking into account the poor inherent conductivity and volume change upon cycling of bimetallic oxides. The cycle stability and rate capability of the obtained NiFe2O4 @C/CNTs composites with varying CNTs amounts were investigated. After 100 cycles at a current density of 200 mA g?1, the reversible capacity of NiFe2O4 @C/CNTs is 1111.8 mAh g?1. The specific capacity can still reach 631.6 mAh g?1, even at 800 mA g?1. NiFe2O4 @C/CNTs exhibits significantly improved cycle stability and rate capability in addition to high capacity. The remarkable electrochemical performance is due to the surface protective effect of the carbon coating layer as well as the conductive effect of the SWCNTs network. By firmly attaching the NiFe2O4 active nanoparticles to the electrode, unhindered electron transport and rapid diffusion of lithium ions can be realized, and volume change during cycling can be inhibited. This research paves the way for the general modification of electrode materials with low conductivity.
NSTL
Elsevier