查看更多>>摘要：? 2022 Elsevier B.V.The long period stacking ordered (LPSO) structure in Mg-based alloy presents a high content of Mg and evenly-dispersed transition metal (TM) and rare earth (RE) elements, which shows great potential in hydrogen storage. In this work, Mg96Y2Zn2 alloy with high proportion of LPSO structure was prepared, forming fine α-Mg dendrite and the interdendrite region with homogeneous Zn and Y distributions. Results indicate that Mg96Y2Zn2 alloy decomposes into YH2 + Mg(Zn) composite after hydrogen ab/desorption, of which nanosized YH2 is in-situ formed from the irreversible decomposition of LPSO and eutectic phase and Mg(Zn) is generated from the dissolution of Zn atoms in Mg lattice. This composite can absorb 5.36–5.79 wt% hydrogen and desorb hydrogen at a lower temperature than pure MgH2, which ascribes to the “hydrogen pump” effect of YH3 and the catalyst of MgZn2. The hydrogenation process of Mg96Y2Zn2 alloy is dominated by one-dimension diffusion rate of hydrogen atoms, while the dehydrogenation process is dominated by two-dimension interface movement of the metal/hydride phases. The in-situ formed YH2 nanophase and Mg(Zn) originated from LPSO structure are stable and evenly dispersed, thus the Mg96Y2Zn2 alloy shows enhanced hydrogenation capacity and kinetics.
查看更多>>摘要：? 2022 Elsevier B.V.Nowadays, transition metal oxides (TMOs) have gained much attention as potential candidates for supercapacitors owing to their remarkable properties for instance vast abundance, a high value of theoretical capacitance, easy accessibility, and eco-friendly nature. But low electric conductivity of TMOs restrains them from reaching their theoretically predicted value for capacitance. Activated carbon with enormous surface area and excellent conductivity has been chosen to augment the conductivity of TMO-based electrodes. Here in this paper, we have synthesized MnO2 nanorods via a facile hydrothermal process. These nanorods have been loaded onto activated carbon via a straight-forward sol-gel approach at room temperature. The obtained nano-composite exhibited superior capacitance of 398.5 F g?1 at 1 A g?1 than MnO2 (161.8 F g?1). The composite attained excellent energy of 105.2 Wh kg?1 (at 2 kW kg?1). Further, the composite was tested for device application. Three symmetric supercapacitor cells joined in series were proficient to glow a blue LED for about one minute while the red LED was illuminated for about 12 min. This suggested that the composite material has broad potential applicability as supercapacitor electrode material.
查看更多>>摘要：? 2022 Elsevier B.V.Stimulation-responsive luminescent materials have attractd intense attention due to their excellent optical properties in the anticounterfeiting application. At present, most the anticounterfeiting materials are based on single luminescence and fixed excitation patterns, resulting in a poor anticounterfeiting effect. Therefore, developing multimodal anticounterfeiting materials that change their luminous color under different wavelength stimuli has become a significant challenge. In this work, we reported a multimodal luminescent La4GeO8: Bi3+, Er3+ phosphor, which could emit white, blue-green, baby blue and orange-yellow light at the excitation wavelength of 250–430 nm. Moreover, it also showed green upconversion (UC) luminescence when irradiated with near-infrared (NIR, 980 nm and 808 nm) lasers. Notably, the material exhibited good humidity resistance and stability. Based on these integrated features, we designed an anticounterfeiting device. The results suggested that the anticounterfeiting device could quickly realize multimodal anticounterfeiting using common light source {NIR (808 nm or 980 nm) laser and ultraviolet (UV) lamp}. These combined characteristics will be difficulty to forge and show high security in anticounterfeiting applications.
查看更多>>摘要：? 2022 Elsevier B.V.Designing components and optimizing structure is considered an effective strategy to enhance the electromagnetic wave absorption of materials. In this study, a two-step method was successfully used to fabricate Fe-metal-organic framework derived iron nitride and carbon-based composites, which combined the porous structure of metal-organic frameworks with the excellent electromagnetic properties of Fe4N. By comparing the composite samples' morphology, structure, composition characteristics, and electromagnetic properties before and after nitriding, reasons for improving electromagnetic wave absorption performance are revealed. The formation of the Fe4N phase and the porous structure optimize impedance matching, which significantly enhances the electromagnetic wave absorption capacity of the composite. When the Fe4N @ carbon composite has a matching thickness of 2 mm, the minimum reflection loss reaches ? 56 dB, and when the matching thickness is 2.5 mm, the reflection loss reaches ? 42 dB at 13.4 GHz. The effective absorption bandwidth reaches 6.7 GHz. This research brings a new design scheme for improving electromagnetic wave absorption materials.
查看更多>>摘要：? 2022 Elsevier B.V.Transition metal carbide is being used as an emerging high-capacity anode material for the next-generation potassium ion batteries (PIBs). Herein, a general method was introduced for the preparation of nanocomposites from metal–organic frameworks (MOFs) coated with ammonium ferric citrate. A novel composite material of Fe3C nanoparticles was designed and prepared by pyrolysis of MOF, and embedded in graphitic carbon as a PIB anode (Fe3C@MOF–C/N). The Fe3C particles were encapsulated in an N-doped carbon shell with a hierarchical porous carbon network. N-doped porous carbon exhibited a large specific surface area and abundant carbon edge defects, which led to the increase in the number of exposed active sites, facilitating the adsorption of potassium ions. As a result, the prepared carbon material shows high structural stability, electrical conductivity, and proton conductivity. As a PIB anode, Fe3C@MOF–C/N-1 shows a high capacity of 294 mAh g?1 over 1000 cycles at 200 mA g?1, revealing its potential application as carbon material in PIB anodes.
查看更多>>摘要：? 2022 Elsevier B.V.Magnetic assisted jet electrodeposition was used to prepare NiCoP alloy thin films efficiently and rapidly, in comparison with the films prepared using traditional jet electrodeposition. The surface morphology, crystal structure, magnetic properties, film adhesion, and corrosion resistance of the NiCoP alloy films were studied. The experimental results show that the magnetic assisted jet electrodeposition effectively changed the microstructure and properties of NiCoP alloy films. Magnetic assisted jet electrodeposition inhibited the growth of pores and nodules on the surface of the film, and the adhesion between the film and the substrate was enhanced. Furthermore, magnetic assisted jet electrodeposition accelerated the refinement of nanocrystallines embedded in amorphous phase of the films, which results in an obvious increase of the saturation magnetization to 201.43 emu/g. Magnetic assisted jet electrodeposition can improve the comprehensive performance of NiCoP alloy thin films, which is expected to be used in modern magnetic materials development.
查看更多>>摘要：? 2022 Elsevier B.V.Concerning the practical applications, dielectric capacitors with simultaneously high recoverable energy density (Wrec) and large energy storage efficiency (η) under a low electric field is imperative and challenging. Herein, a strategy of complex ions substitution is proposed to achieve the goal. The (1-x)(0.75Na0.5Bi0.5TiO3-0.25SrTiO3)-xLa(Mg2/3Ta1/3)O3 (NBST-xLMT) ceramics were fabricated through a solid-state reaction method. A significantly enhanced breakdown electric field (Eb) of 246.03 kV/cm is obtained in NBST-0.06LMT ceramics due to the refined average grain size (AGS), the enhanced band gap width and the inhibited oxygen vacancies by LMT doping. Furthermore, a high Wrec of 3.18 J/cm3and large η of 86% are concurrently achieved in NBST-0.06LMT ceramics under a relatively low electric field of 246 kV/cm. Meanwhile, the variations of (Wrec, η) under 170 kV/cm are less than 10% from 30 ℃ to 200 ℃, indicating an excellent thermal stability. Besides, the ceramics show a fast discharge rate of 155 ns by a charge-discharge measuring. In general, our results demonstrate the strategy of complex ions substitution is an effective way to achieve high energy storage performance under a relatively low electric field in NBT-based ceramics.
查看更多>>摘要：? 2022 Elsevier B.V.Industrial application of water electrolysis has called for the development of oxygen evolution electrocatalysts that are low-cost, stable and have low overpotential. Substituting the precious metal catalysts with more accessible transition metal oxide such as Fe2O3 is a key solution for applications in water electrolysis. Here, we show an efficient modified electrode for oxygen evolution, which be developed by co-electrodeposition of graphene oxide and Fe2O3 nanoparticles directly onto macroporous nickel foam substrate. Then, using an electrochemical procedure, in-situ electro-polymerization of pyrrole and graphene oxide reduction are performed on the electrode surface. The sugar-cubic Fe2O3 nanoparticles are also prepared by the hydrothermal method. The morphology and structure of the Fe2O3 nanoparticles and Fe2O3/ graphene nanocomposites are characterized by Field-Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray spectroscopy (EDX), Fourier Transform Infra-Red spectroscopy (FT-IR), X-Ray Diffraction (XRD), Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS) methods. Moreover, the OER activities of the synthesized catalysts are investigated by using Linear Sweep Voltammetry (LSV), Chronopotentiometry (CP) and Electrochemical Impedance Spectroscopy (EIS) methods. The electrocatalytic activity of the sugar-cubic Fe2O3/nitrogen-doped graphene nanocomposite prepared by hydrothermal method in alkaline media shows outstanding advantages, so that its over potential was 313 mV and its Tafel slope was 81 mV/dec.
查看更多>>摘要：? 2022 Elsevier B.V.An appropriate amount of (Li,Ce) ions are incorporated into bismuth layer-structured piezoelectric ceramics to reduce the oxygen vacancy concentration, limit the grain growth, and enhance the electrical properties and hardness of the ceramics. The existence of a pseudo-tetragonal phase region, the change in the domain structure, and the increase in the spontaneous polarization promote the enhancement of the piezoelectric properties. Additionally, the conductive mechanism in the high-temperature regions is discussed in terms of the direct-current resistivity. A moderate amount of the (Li,Ce) dopant ions can effectively improve the thermal depoling behavior of CaBi2Nb2O9 (CBN)-based ceramics. Consequently, the Ca0.88(LiCe)0.06Bi2Nb2O9 ceramic exhibits an optimal d33 piezoelectric coefficient of 18.5 pC/N and an excellent thermal depoling behavior. Furthermore, the results of the Vickers indentation hardness test reveal that the hardness of CBN-based ceramics is improved to 3.78 GPa.
查看更多>>摘要：? 2022 Elsevier B.V.Eighteen isotypic, lithium-containing rare-earth sulfides, crystallizing in the chiral, polar, and noncentrosymmetric space group P63 with the La3CuSiS7-structure type have been prepared via direct combination of the elements or binary sulfides; nine of these compounds are reported for the first time. The structures of these compounds, with the formulae Ln3LiTS7 (Ln = La, Ce, Pr, Nd, Sm, Gd, and Dy for T = Si or Ge; Ln = La, Ce, Pr, and Nd for T = Sn), were determined by single crystal X-ray diffraction. According to X-ray powder diffraction data, the Ln3LiTS7 compounds are the major phase of the reaction products. All of the compounds are semiconductors with optical bandgaps spanning nearly the entire visible region. The Si- and Ge-containing analogs show high thermal stability,> 1000 °C, while the Sn-containing compounds melt in the vicinity of ~740 °C. The compounds show potentially broad regions of optical transparency in the infrared regime. Calculated bond valence sums (BVSs) and global instability index (G) values confirm the Ln3+ oxidation state and stable crystal structures with reasonable strain, respectively. Ce3LiGeS7 and Ce3LiSnS7 display non-phase-matching but significant second-harmonic generation responses with χ2 values of 21 ± 1 and 28 ± 1 pm/V, respectively at λ = 1.8 μm. The laser-induced damage threshold values for Ce3LiGeS7 and Ce3LiSnS7 are> 3 × commercial AgGaSe2, for picosecond pulses at λ = 1.064 μm. These two compounds also exhibit moderate third-harmonic generation responses. Additionally, crystal-chemical correlations are discussed.
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