查看更多>>摘要：Because of their multiple chemical valence states, multi-element transition metal oxides can undergo reversible redox reactions between the different valence states during charging and discharging. However, the low electrical conductivity of transition metal oxides limits the rate of electron transfer. The combination of transition metal oxides with three-dimensional carbon substrate is a promising but extremely challenging strategy to prepare high specific capacitance, stable and environmentally friendly supercapacitor electrode materials. Here we report a facile one-step vapor deposition synthesis of network-like FeNb_2O_6 nanostructures directly growing on flexible carbon cloth (CC). The as-prepared FeNb_2O_6/CC composite has good electrical conductivity, and the network-like structure also makes it have large specific surface area. Resultantly, the composite exhibits an high specific capacity of 365.9 mAh g~(-1) at a current density of 2.5 A g~(-1). And at the current density of 25 A g~(-1) a specific capacity of 75.9 mAh g~(-1) can still be maintained.
查看更多>>摘要：Na_(0.44)MnO_2 microrods with high crystallinity have been prepared by a simple solid-phase method and then coated with ln_2O_3 by precipitation method. 1 wt% ln_2O_3 coating could improve the sodium-storage capability of Na_(0.44)MnO_2 microrods significantly. The original Na_(0.44)MnO_2 microrods could provide the maximum discharge capacity of 100.3 mAh g~(-1) under a wide voltage of 2.0-4.5 V at 1 C, but the discharge capacity rapidly decreases to 70.4 mAh g~(-1) after 400 cycles, which was only 70.3% of the maximum capacity. However, the Na_(0.44)MnO_2 coated with 1 wt% In_2O_3 exhibited a high discharge capacity of 90.9 mAh g~(-1) after 400 cycles, with high-capacity retention of 86.7% in the same case. Moreover, compared with Na_(0.44)MnO_2, 1 wt% In_2O_3 coated Na_(0.44)MnO_2 shows better rate capability. Even at a high current density of 10 C, the discharge capacity is 63.6 mAh g~(-1), much larger than the 32.9 mAh g~(-1) of the pristine Na_(0.44)MnO_2. The mechanism of In_2O_3 coating improving the electrochemical performance of Na_(0.44)MnO_2 microrods was studied in detail.
查看更多>>摘要：In this paper, the mechanism on the nucleation of orientation-preferred Cu_6Sn_5 at different temperatures and solder compositions was investigated. Results suggest that affected by temperature and solder composition, the distribution of clusters in solder plays an important role in the formation of preferred orientation. Higher temperature, Ag element and an appropriate amount of Cu element are favorable for the nucleation of orientation-preferred Cu_6Sn_5. However, the increase of Cu-Sn clusters size with the increase of Cu addition will lead to the nucleation of Cu_6Sn_5 in liquid solder, which does not need to follow the rule of the minimal lattice mismatch between Cu_6Sn_5 and Cu substrate. Meanwhile, the addition of Cu and Ag is conducive to the increase of grain size. Besides, the difference in solder volume between the central and edge region results in the difference in grain orientation. Furthermore, a model is established to illustrate that how the reflow temperature, Cu and Ag content affect the nucleation of orientation-preferred Cu_6Sn_5 through affecting the cluster evolution. The results have significant meaning in understanding and controlling the formation of Cu_6Sn_5 preferred orientation and improving the reliability of solder joints.
查看更多>>摘要：The lack of selectivity of Zinc oxide nanoparticles (ZnO NPs) in the wastewater purification process is considered a severe limitation. This research aims to use surface-modified ZnO NPs with different surface charges for selective removal of methyl orange (MO) and methylene blue (MB) dyes from an aqueous mixture solution. The sonophotocatalyst process was investigated to improve the selective oxidation of the aqueous mixture. The surface of the ZnO NPs has been modified with a silane coupling agent (APTES and MPTMS) to get active surface functional groups. The synthesized modified ZnO NPs were characterized by XRD, FE-SEM, TEM and FTIR analysis. The surface charge and absorption spectrum were investigated using Zeta potential and UV-Vis spectrophotometer approaches, respectively. The selective sonophotocatalytic of anionic MO and cationic MB dyes was performed via APTES-ZnO and MPTMS-ZnO NPs, respectively. The selective removal was optimized using Response Surface Methodology (RSM) based on the Box-Behnken Design (BBD). To this end, the effects of catalyst dosage, dye concentration, and reaction time on selective removal were investigated under various experimental conditions. The results revealed that unmodified ZnO NPs have no selectivity in the decomposition of an MO and MB mixed, whiles the change in surface charges of ZnO NPs has been shown to change significantly the selectivity efficiency of ZnO NPs.
查看更多>>摘要：A series of Dy~(3+)-doped sodium lanthanum orthosilicate oxyapatites, NaLa_(9-x)Dy_x(SiO_4)_6O_2 (NLSO:xDy, x = 0-0.3), were synthesized by the solid-state reaction method at 1100 °C, with the aim of developing yellow emitting phosphors for applications in w-LEDs. Their crystal structure, morphology and particle size distribution, electronic structure, Raman spectra, concentration- and temperature-dependent luminescent properties were investigated for the first time. The crystal structure was refined by the Rietveld method. Undoped NLSO is hexagonal (space group P6_3/m - C_(6h)~2) with lattice constants a = b = 9.6917(3) A and c = 7.1836(4) A. It is shown that Dy~(3+) ions substitute for the La~(3+) ones in two types of sites with C_3 and C_s point symmetries. The first-principle calculations for undoped NLSO revealed an indirect bandgap of 5.06 eV. The NLSO:0.2Dy phosphor exhibited intense yellow emission with CIE 1931 chromaticity coordinates of (0.469, 0.495) and a correlated color temperature of 3150 K owing to the hypersensitive electric-dipole transition ~4F_(9/2)→~6H_(13/2) (571 nm) dominating in the luminescence spectrum. Excellent thermal stability was found for this apatite phosphor (the activation energy is 0.23 ± 0.02 eV).
查看更多>>摘要：Rational design of metal oxide heterostructures is of great importance for gas sensors to be applicable in the detection of inflammable, explosive and toxic gases. Herein, we designed CuO/In_2O_3 heterostructures with flower-like structures via a highly efficient one-step hydrothermal technique and constructed optimal structures to improve formaldehyde sensing properties. Consequently, the obtained 7-CuO/In_2O_3 flowerlike structures with uniform p-n heterostructure and a large quantity of oxygen vacancies exhibits the best sensing properties for detecting formaldehyde. The corresponding response value is 11.67-10 ppm formaldehyde at a low operating temperature of 100 °C, which is approximately 2.97 times higher than that of pure ln_2O_3 sensor (3.93 at 200 °C). Besides, the 7-CuO/In_2O_3 sensor also exhibits good reproducibility and stability, sub-ppm-level detection limit (1.38-0.5 ppm), high selectivity, and outstanding long-term stability, which benefits from the synergistic effect of strong oxygen adsorption capacity, p-n heterojunction between CuO and ln_2O_3, catalytic effect of CuO, and the unique flower-like structures, showing the great potential for practical formaldehyde detection.
查看更多>>摘要：Lead selenide (PbSe) is one of the most promising materials for the uncooled mid-IR detectors. Sensitization of PbSe consists of thermal treatment in the oxygen/iodine atmosphere, and was experimentally examined before. However, there were no computational studies supporting the experiments. Density functional theory (DFT) calculations have been applied for better understanding of the influence of iodine and oxygen dopants have on PbSe crystal lattice, band structure, conductance. Calculations proved that oxygen induces a more robust effect on band structure, while iodine reduces work function, increasing surface reactivity. Structural characterizations confirmed the crystallization of the lead selenite phase, during sensitization in oxygen, while the new Pb_3Se_2(IO_3)_2 phase crystallized during sensitization in iodine/oxygen rich atmosphere. U/I characterization confirmed IR sensitivity of the samples treated at 400 °C in oxygen rich atmosphere for 3 h, and for the samples treated in the iodine/oxygen rich atmosphere at 375 °C for just twenty minutes.
查看更多>>摘要：Transition metal oxides as the most promising electrode materials for supercapacitors has attracted widespread attention. However, their applications are limited by their sluggish charge transfer kinetics and insufficient active sites. Herein, we report the preparation of sulfur-doped zinc-nickel-cobalt oxides (S-ZNCO) using the synergistic effect of heteroatom doping and defect engineering by hydrothermal treatment and sulfurization method. The morphology and microstructure are characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), energy dispersive spectrometry (EDS) mapping, X-ray photoelectron spectroscopy (XPS) and Raman spectra. The results demonstrate the successful doping of sulfur atoms and introduction of oxygen vacancies, which increases the redox reaction active sites and further improves the electrochemical kinetics of the electrode material, giving rise to a high specific capacitance (2919.60 Fg~(-1) at 1 Ag~(-1)) and better electrical conductivity of the S-ZNCO electrode. Furthermore, the assembled S-ZNCO-NF//AC device achieves a high energy density of 72.97 W h kg~(-1) at a power density of 825 W kg~(-1). This work opens up new opportunities to design of advanced transition metal compounds for supercapacitors.
查看更多>>摘要：A multiphase AlMo_(0.8)NbTiW_(0.2)Zr refractory multi-principal element alloy (RMPEA) with superior elevated-temperature strength was prepared by the powder metallurgy (PM). The as-sintered RMPEA was composed of BCC matrix, lath-like B2 phase, and two Al-Zr hexagonal structure phases. The alloy (p = 7.07 g/cm3) exhibited a superior specific compressive yield strength of 153.3,107.8 and 54.7 MPa cm~3/g at the temperature of 1423,1523 and 1623 K, respectively, which were remarkable in the current designed refractory alloys. After compressing at 1423 K, the AlMo_(0.8)NbTiW_(0.2)Zr consisted of a band-like or blocky Zr_5Al_4-type phase and the BCC matrix, in which embedded amounts of spherical B2 nanoparticles with a size of 5-10 nm. The superior elevated-temperature compressive yield strength of the RMPEA at 1423 K is primarily ascribed to both the stabilization of the martensitic-transformation Zr_5Al_4-type submicron-sized phase and the precipitation of the B2 nanoparticles, afterwards impede the deformation flow.
查看更多>>摘要：High-entropy alloys (HEAs) are equimolar solid solution alloys composed of more than five elements, and their atomic arrangement is chemically disordered. Some ordering in HEAs, however, is suspected from the characteristic properties, such as high strength with good ductility at low temperatures or sluggish diffusion. Herein, we report that quasi-stable states inherent in nonequilibrium systems can be extracted by applying an electric pulse current to the system (electropulsing). In this study, changes in the electrical resistivity of the rapid-quenched CrMnFeCoNi HEA were investigated after electropulsing. No step-like large decreases reflecting nanocrystallization in amorphous alloys were observed for rapid-quenched CrMnFeCoNi by electropulsing. This indicates that quasi-stable ordered atom clusters do not exist in the CrMnFeCoNi HEA. However, the resistivity showed a slight decrease and increased with increasing electropulsing current density. A tendency to form short-range order, as Cr is preferentially surrounded by Ni, is suggested by comparison with the results of NiCr alloys.
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Elsevier