查看更多>>摘要：Enthalpic interaction between the elements determines the stability of the local structures in the alloy system. Multicomponent synergistic effect is expected to improve the thermal stability and the relevant properties, by regulating the enthalpic interaction. In this work, the composition of Cu-Ni-Sn alloys is explained by introducing the cluster-plus-glue-atom mode, and the strong and weak enthalpic interaction elements Si and Zn, respectively, are chosen for multi-componentization of Cu-Ni-Sn alloys. The results demonstrate that the synergistic effect of Zn and Si improves the stability of both the Cu matrix and D0_(22) or L1_2-γ' phase, inhibits the discontinuous precipitation effectively and gains a notable higher strength-over-resistivity ratio (H_(R/ρR)) than the Cu-15Ni-8Sn (wt. %) (C72900) alloy. After adding Si and Zn, the reinforcing enthalpic interaction between the elements is the crucial factor for the stability enhancement of the alloys, and it is embodied by two aspects: (a) the reducing elastic strain energy in the solution treated alloys; (b) the more homogeneous surface potential and the higher work function in the age treated alloys. Additionally, Compared with the Cu_(80)Ni_(15)Sn_5 alloy that based on the ideal cluster formula, the Cu_(79.68)Ni_(15.63)Sn_(4.69) alloy, based on the modified cluster formula: {[Cu-Cu_xNi_(12-x)]Cu_3}_a{[Sn-Ni_yCu_(12-y)]Sn_3}_(16-a), possesses a preferable thermal stability whatever solution treated or age treated state, and exhibits a decreasing amount of discontinuous precipitation although has a slightly lower H_(R/ρR), which is beneficial to the improvement of the workability of the alloys. The modified cluster formula is more suitable for the compositional design of Cu-Ni-Sn alloys. The work provides an effective theoretical and experimental basis for the composition design of high stability Cu-Ni-Sn alloys.
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：In this work, a novel Cu decorated Fe_3O_4@ CeOHCO_3 nanocomposite (Cu-Fe_3O_4@CeOHCO_3) has been prepared by a one-step hydrothermal method. Fabricating into the electrode, the electrochemical properties of the prepared materials were characterized by cyclic voltammetry (CV), galvano-static charge-discharge (GCD) test and electrochemical impedance spectroscopy (EIS). The specific capacitance of the Cu-Fe_3O_4@ CeOHCO_3 electrode was 324.7 F g~(-1) at a current density of 1.0 A g~(-1) with a capacitive retention of 88.3% after 1000 charge-discharge cycles. The assembled asymmetric supercapacitor(ASC) device can provide an energy density of 35.4 W h kg~(-1) with a high power density of 781.9 W kg~(-1). DFT calculations prove that the surface modification of Cu functions significantly in modulating the electronic structure and super-capacitive properties of CeOHCO_3. Our self-assembled Cerium-based composite may initiate the suitability for energy storage devices and provides a valuable reference for the fabrication in sodium Ion supercapacitors.
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.
查看更多>>摘要：The liquid-solid phase transitions and solidified microstructures of highly undercooled Fe-Zr eutectic melts were investigated by the drop tube technique. The quantitative relationships among droplet diameter (D), undercooling (ΔT) and cooling rate (R_c) were calculated for three types of eutectic alloys (Fe-9.8 at. % Zr, Fe-6 at. % Zr and Fe-16 at. % Zr alloys). Furthermore, the evolutions of solidified microstructure with droplet diameter were studied. The results show that the eutectic microstructure for Fe-9.8 at. % Zr droplet transforms from regularly lamellar shape to anomalous shape as the diameter reduces. The α-Fe dendrite in Fe-6 at. % Zr droplet transforms from coarse dendrite to refined dendrite with the decrease of droplet diameter, while the Fe_2Zr dendrite in Fe-16 at. % Zr droplet transforms from faceted dendrite to non-faceted grain. Besides, a remarkable solid solubility extension was found in both the α-Fe dendrites of Fe-6 at. % Zr alloy and the Fe_2Zr dendrites of Fe-16 at. % Zr alloy. The solid solubility of the a-Fe dendrite increases from 3 at. % to 5.6 at. % when the droplet diameter reduces from 1069 to 212 um, while it decreases from 31 to 22 at. % in the Fe_2Zr dendrite as the diameter reduces from 991 to 228 um. The microstructural morphology and solid solubility are directly related to the nano-hardness and Young's elastic modulus of alloys. The nano-mechanical properties of the eutectic gradually increase with the refinement of the layers, and gradually decrease as the irregularity of the anomalous eutectic increases. With the reduction of droplet diameter, the nano-hardness rises and Young's elastic modulus continuously diminishes for the a-Fe dendrite due to the increase in the solute content of Zr, while these two mechanical properties gradually decrease for the Fe_2Zr dendrite because of the reduction in the solute content of Zr.
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Elsevier