查看更多>>摘要：Fe3O4, as a typical absorber, its electromagnetic wave (EMW) absorption properties are far from meeting the requirements of practical application due to its poor impedance matching. In this study, three kinds of novel heterogeneous structured composites, dendritic Fe3O4@(HCl doped PANI), Fe3O4@(p-TSA doped PANI) and Fe3O4@(dedoped PANI), were prepared via hydrothermal method combined with thermal reduction and in-situ polymerization, and their phase composition, microscopic morphologies, static magnetic properties, EMW absorption performance and absorption mechanisms were investigated. The results showed that the introduction of different medium doped and dedoped PANI greatly enhanced the EMW absorption performance of Fe3O4. The outstanding advantages of Fe3O4@(HCl doped PANI) were that the widest effective absorption bandwidth (EAB) up to 6.08 GHz in a relatively thin thickness of 2.1 mm. And the Fe3O4@(dedoped PANI) composite achieved strong absorption ability (? 53.08 dB@3.04 GHz) at low frequency in a relatively thin thickness (4.9 mm). The remarkable improvement of EMW absorption performance of dendritic Fe3O4@PANI composites could be attributed to the introduction of dissipation mechanisms, the optimization of impedance matching characteristics and the formation of appropriate conductive network microstructure. The dendritic Fe3O4@PANI composites are promising EMW absorption materials and have great practical application value.
查看更多>>摘要：MgFe2O4 spinel with abundant oxygen vacancy was synthesized by a simple precipitation method, and tested in photocatalytic reduction of CO2 with water vapor as reductant. A series of characterization including XRD, XPS, EPR, PL spectrum, UV–vis DRS and TPD-CO2 were performed to investigate the influence of calcination temperature on morphology, optical and electronic properties of MgFe2O4 spinel. The results demonstrated that the oxygen vacancy concentration increases first and then decreases with the increase of calcination temperature. By introducing oxygen vacancies, the recombination of photogenerated electron-hole pairs was significantly suppressed, visible light absorption and chemisorption capacity of CO2 were dramatically boosted. Mg-Fe-750 with the richest oxygen vacancies exhibits the highest photocatalytic activity, for which the production rate of CO and H2 was 24.4 and 34.3 μmol/gcat/h, respectively.
查看更多>>摘要：Microstructural evolution and sagging behavior of Al-1.3Mn-1.5Zn-xZr (x = 0.03, 0.09 and 0.13) layer core sheets for brazing were systematically investigated. It was found that the 0.03 wt% zirconium addition could slightly improve the sagging resistance of the Al-1.3Mn-1.5Zn sheet. When the zirconium addition was increased to 0.09 wt%, the sagging resistance was significantly improved, which was mainly attributed to the coarse equiaxed grains with a homogeneous distribution during the sagging test. However, the 0.13 wt% zirconium addition damaged the sagging resistance of the Al-1.3Mn-1.5Zn sheet, caused by the many finer grains, despite the formation of more nano-sized α-Al(MnFeSi) phases and fewer nano-sized Al3Zr precipitates. Furthermore, the lognormal correlation between the sagging distances of the experimental sheets and their reserved tensile properties after air-cooling at the different sagging time was also explored in this study.
查看更多>>摘要：Interface passivation to construct a Z-scheme heterojunction can not only improve the separation efficiency and redox ability of photo-generated carriers, but also retain the excellent optical properties of non-metallic plasma. In this work, the optical performance and carrier dynamics of g-C3N4?x/MoO2.69(OH)0.31 heterojunction were optimized by passivating the interface oxygen vacancies. The adsorption of -OH groups on the surface oxygen vacancy sites of MoO2.69(OH)0.31 was hindered due to the formation of heterogeneous interface. This in turn significantly inhibited the charge recombination at the oxygen vacancy-induced deep trap states, while maintaining the stable and continuously enhanced visible-near infrared light absorption. The conduction band of g-C3N4?x provided the appropriate energy platform to accept the photo-generated electrons of MoO2.69(OH)0.31, resulting in the high utilization of high-energy “hot electrons”. The prepared g-C3N4?x/MoO2.69(OH)0.31 heterojunction showed the enhanced full-solar-spectrum photocatalytic performance for the degradation of the organic pollutants. Moreover, Ti3C2 nanosheet-wrapped g-C3N4?x/MoO3?x was synthesized to alleviate the photo-corrosion of g-C3N4?x/MoO3?x. The composite photocatalyst exhibited the further improved photocatalytic activity while maintaining good recyclability and structural stability. This work provided a new strategy for the preparation of defect-mediated heterojunction photocatalysts with high activity and stability.
查看更多>>摘要：In this paper, high color performance Pr cation doped zircon (Pr-ZrSiO4) yellow pigment has been prepared by inorganic sol-gel method. Meanwhile, the detailed process parameters for preparation of Pr-ZrSiO4 pigment were systematically investigated. The research results indicate that the optimal process parameters are Pr-doping amount of 6 mol.%, calcination temperature of 900 °C, holding time of 2 h and Si/Zr ratio of 1.05. The synthesized Pr-ZrSiO4 pigment shows an intense yellow hue, which chromatic parameters are L* = 81.84, a* = 4.36, b* = 70.55 and C* = 70.68. Moreover, the pigment shows outstanding tinting performance for ceramic glaze, suggesting its attractive application in ceramic decoration. XPS analysis demonstrated that the Pr cations in the Pr-ZrSiO4 pigment consists of two valence states, namely trivalent and tetravalent. Finally, heterogeneously distributed behavior of Pr cations in the pigment was discovered.
查看更多>>摘要：Developing multi-transitional metal electrocatalysts via a facile, rapid and cost-effective approach to achieve highly catalytic activity and long-term durability remains challenging. Herein, a novel cathode plasma electrolytic deposition (CPED) technology is successfully applied to directly fabricate ternary noble metal-free FeCoNi alloys with duplex phases on 304 stainless steel substrate as self-supporting electrocatalysts for oxygen evolution reaction (OER). Effects of the CPED technical parameters on the microstructure, morphology, and electrochemical properties of ternary FeCoNi alloys are systematically investigated by a series of orthogonal experiments. The as-received FeCoNi alloy, composed of duplex phases (i.e. face-centered cubic and body-centered cubic), is found to be able to achieve a current density of 10 mA cm?2 at an overpotential of 285 mV in 1 M KOH electrolyte with a Tafel slope of 42 mV dec?1, and long-term stability. This work provides a new way to synthesize multi-component electrocatalysts for energy storage and conversion in a large scale base for practical commercialization.
查看更多>>摘要：The design of cathode material with unique structure and excellent electrochemical property is critical for the development of energy storage device. We report herein the synthesis of a nanocomposite with heterostructure of metallic nickel (Ni) and nickel sulfide (Ni3S2) through a facile solid-gas state reaction method, using Ni-ZIF MOFs and sulfur as precursors. The electrochemical energy storage capabilities of the synthesized composite as cathodes for both supercapacitor and zinc ion batteries have been investigated. Owing to the good conductivity of metallic Ni and superior pseudocapacitive behavior of the Ni3S2, the Ni/Ni3S2 nanocomposite exhibit excellent energy storage capability in both supercapacitor and zinc ion batteries. It was revealed that the Ni/Ni3S2 nanocomposite exhibit an excellent specific capacity of 2228 F g?1 at a current density of 4 A g?1. A high capacity of 1496 F g?1 is remained even at a high current density of 12 A g?1, demonstrating good rate capability of the electrode material. When the Ni/Ni3S2 was used as the cathode material for zinc ion battery, the assembled Ni/Ni3S2//Zn aqueous zinc ion battery can provide a high energy density of 379 Wh kg?1 at power density of 0.34 kW kg?1. The battery also exhibits long-term cyclic stability with capacity retention ratio of 84.1% after 1000 cycles and good rate performance. Our work proposed a facile route to produce transition metal sulfide nanocomposite with excellent capacitive properties as cathode material for the supercapacitor and aqueous zinc ion batteries in green energy storage application.
查看更多>>摘要：The potential advantages of nano-alloys and particularly, nano-porous alloys, place them at the “spotlight” of heterogeneous catalysis. Nevertheless, controlling the precise compositions of these materials is still a synthetic challenge. Previous research introduced the fabrication of metals and alloys with a high nano-scale porosity and controllable compositions, via a hydrogen-mediated chemical reduction process of metal complex salts. We have used this procedure to obtain two magnetic nano-porous Co-Pd alloys, pure porous palladium and pure porous cobalt. Single crystal X-ray diffraction studies enabled structural determination of the two Co-Pd bi-complex salts that were used as precursors for these alloys. Powder X-ray diffraction studies determined the crystalline phases of the alloys and indicated the nanometric size of their crystallites. High-resolution scanning electron microscopy indicated that these alloys assemble as highly porous clusters of interconnected nano-crystallites. It also indicated that each alloy cluster preserves the micrometric morphologies of its salt precursor. Energy dispersive X-ray spectroscopy showed that the alloys exhibit uniform composition down to the micro-level, which preserved the Co/Pd ratio within the salts. Focused ion beam tomography enabled 3D structural representation of the alloys and metals. Geometrical analysis of the 3D reconstructed data determined 90% porosity and a specific surface area of ~100 m2/g for the alloys. In addition, the alloys showed improved catalytic activity in the semi-hydrogenation of phenylacetylene, compared to the pure metals and commercial Pd/C. Moreover, their magnetic properties enabled facile recovery at the end of the reaction. The yield for styrene in this reaction was increased using “design of experiments” (DOE), a method for optimization of reaction conditions. Furthermore, our experiments implied that a highly porous structure significantly improves the selectivity of styrene in the reaction. These results demonstrated the advantage of fabricating nano-porous alloys with uniform compositions that may exhibit special properties and serve as new and efficient catalysts.
查看更多>>摘要：The experimentally determined integral enthalpy of mixing of liquid Ag-Mg alloys has been presented. Three separate measurements have been made at 991, 1141, and 1272 K with the use of an MHTC 96 Line Evo line drop calorimeter. The values of integral molar mixing enthalpy are characterized by negative deviations from the ideal solutions in the entire concentration range. Based on the obtained calorimetric results and other thermodynamic data available in the literature, the Ag-Mg system has been re-optimized. Additionally, the mechanical properties of the Ag-Mg intermetallic phases have been calculated based on the ab initio calculations.
查看更多>>摘要：The evolution of the structure, electrical resistivity and microhardness of the non-stoichiometric Cu-56Au (at%) alloy during the disorder?order phase transitions of samples with different thermo-mechanical histories has been studied. It was found that the rate of atomic ordering of the Cu-56Au alloy was much lower compared to the equiatomic Cu-50Au alloy that had been well studied earlier. It was shown that the deformation of the quenched alloy slowed down the rate of atomic ordering. It was established that annealing of the quenched alloy for 1 week at 250 °C led to the formation of the CuAuI phase with a degree of long-range atomic order S ≈ 0.8. The electrical resistivity of the alloy in this state is ρ = (7.75 ± 0.04) × 10 = (7.75 ± 0.04) × 10–8 Ωm, which is the lowest value known for this alloy. It was revealed that the ordered CuAuII phase forms as a result of annealing of the Cu-56Au alloy at high temperature followed by slow cooling to room temperature. During the experiments, we did not receive any data confirming the CuAuII→CuAuI transition both at heating and at cooling of the alloy. There was made a conclusion of a high thermal stability of the ordered orthorhombic CuAuII phase in the alloy under investigation.
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Elsevier