查看更多>>摘要：Designing semiconductor photocatalyst with high visible-light sensitivity and good photocatalytic performance is still a key issue for pollutant remediation and energy storage. In this work, a series of (BiO)2OHCl@Bi24O31Cl10 composite photocatalysts were synthesized through an ammonia-dependent aqueous strategy with (BiO)2OHCl as the in-situ formed precursor. More ammonia introduction in the synthetic system led to faster transformation of (BiO)2OHCl to Bi24O31Cl10 component and resulted in composites with controllable compositions. The Bi-based heterostructures extended good visible-light absorption ability and strengthened internal electric field (IEF) to induce the generation of charge carriers and promote bulk-charge separation (BCS) efficiency for antibiotic removal. (BiO)2OHCl@Bi24O31Cl10 composites with optimum compositions exhibited superior photocatalytic activities on levofloxacin (LEV) degradation under visible-light irradiation, roughly two times higher than that of individual (BiO)2OHCl or Bi24O31Cl10 powders. The high degradation efficiency and rapid reaction kinetics would be ascribed to the valid charge transfer from the bulk interior to the surface of composite catalysts. The sheet-like Bi24O31Cl10 at catalyst surface and matched band structures of two components in (BiO)2OHCl@Bi24O31Cl10 heterostructures are also proposed as vital factors to influence the photocatalytic performances. This study hopes to provide new insights for the design of visible-light induced bismuth-based photocatalysts for practical applications.
查看更多>>摘要：The hot deformation behavior of a Ti-47.5Al-2.5V-1.0Cr-0.2Zr alloy was investigated through thermal simulation experiments. The thermal deformation temperature range was 1050–1200 °C with a strain rate of 0.001–1 s?1. The connections between the stress, strain rate, and temperature were established using a constitutive equation, which included the influence of strain. The correlation coefficient between the calculated stress and the experimental data was 0.991, which indicated that the predicted stress curve was consistent with the experimental results and that the constitutive relationship could accurately predict the deformation behavior. The processing map indicated the optimum hot deformation ranges of temperatures and strain rates were determined to be 1140–1180 °C and 0.001–0.006 s?1, respectively. The proportion of dynamic recrystallization(DRX) and low dislocation density regions was higher in the optimum hot deformation region than in the instability region, and no instability phenomena, such as cracking, were found; hence, the thermal processing map predictions agreed well with the microstructure. The dominated deformation mechanism of the TiAl alloy mainly depended on DRX, and the movement of dislocations and twins were the typical deformation mechanisms.
查看更多>>摘要：Lithium-sulfur (Li-S) batteries are a promising next-generation energy storage technology due to high theoretical energy density, low cost and abundant reserves. However, the poor electronic conductivity of sulfur and huge volume change hindered their commercial applications. In this paper, selected as a cathode host of Li-S batteries from two Ce-MOFs with dissimilar open metal sites for the first time, Ce-MOF-808 was synthesized and then coated with a Polypyrrole (PPy) layer (Ce-MOF-808@S/PPy). Material characterization and electrochemical performance tests were conducted. Results show that Ce-MOF-808@S/PPy has a high specific surface area of 437.491 m2 g?1, with special micro-mesoporous structures. Ce-MOF-808@S/PPy composite possesses the initial discharge specific capacity of 1612.5 mA h g?1 and discharge specific capacity of 771.9 mA h g?1 at 0.1 C after 100 cycles. Additionally, the battery still maintains a reversible specific capacity above 470 mAh g?1 with 40% capacity retention rate at a rate of 2 C after 200 cycles of charge and discharge. Improved electrochemical performances are mainly attributed to the Ce-MOFs with special micro-mesoporous structures and high specific surface area conducive to inhibiting the shuttle effect and volume expansion through physical adsorption and stable channel structures, the Ce sites with unique adsorption and catalytic effect, and the PPy coating layer adsorbing the polysulfide and acting as charge collectors to enhance conductivity.
查看更多>>摘要：Interface engineering is an effective strategy to optimize the electronic properties of MoS2, yielding significantly improved electrochemical performance of lithium-ion batteries. We have designed carbon cloth (CC) decorated by a MoS2/ZnS-NC heterostructure, where ZnS with N-doped carbon (ZnS-NC) is derived from zeolitic imidazolate framework‐8 (ZIF-8) carbonation. A MoS2/ZnS-NC@CC heterostructure with abundant heterointerfaces, high conductivity, and N heteroatom doping greatly enhances electron/ion diffusion kinetics, thereby improving electrochemical performance. The MoS2/ZnS-NC@CC anode exhibits improved lithium storage capacity due to its structural advantage. Electrochemical measurements reveal that the MoS2/ZnS-NC@CC binder-free electrode delivers an initial discharge capacity of 1427.2 mAh g?1 at a current density of 100 mA g?1 and good cycling stability after 200 cycles.
查看更多>>摘要：The development of electromagnetic wave absorbers, which have widespread application prospects, requires new lightweight, multifunctional materials that can be used in harsh environments. Herein, ultralight SiC/Si3N4 aerogels are prepared by freeze-drying and carbothermal reduction reaction, and their microstructures were investigated by transmission electron microscopy, Raman spectroscopy, and X-ray absorption near-edge structure at the N K-edge. The result of morphology analysis indicates that the porous structure of SiC/Si3N4 aerogels are composed of SiC and Si3N4 nanowires. The optimal prepared SiC/Si3N4 aerogel possesses high absorption performance with a minimum reflection loss of ? 25 dB and a wide effective absorbing bandwidth of 4.3 GHz (6.1–10.4 GHz) at a thickness of 3.97 mm. Such superior absorption performance is due to excellent impedance matching and enhanced polarization loss. Moreover, the SiC/Si3N4 aerogel is thermostable under air atmosphere below 1100 °C, which can be attributed to the presence of Si3N4. These achievements suggest that SiC/Si3N4 aerogel is promising candidate for electromagnetic wave absorption in harsh environment.
查看更多>>摘要：BiSe has recently emerged as a new promising Te-free thermoelectric material due to its superlattice structure and intrinsic low thermal conductivity. However, the inherent high carrier concentration of BiSe limits its thermoelectric performance. In this paper, Ag and Na were doped in polycrystalline BiSe to tune its thermoelectric transport properties. A series of Ag-doped and (Ag, Na) co-doped samples were synthesized via solid-phase sintering method and spark plasma sintering (SPS). It is found that Ag doping can effectively reduce the lattice thermal conductivity of BiSe, thereby reducing the total thermal conductivity, which increases the ZT value of Bi0.97Ag0.03Se from 0.24 to 0.28. Along with the co-doping of 1% Na, the carrier concentration of the (Ag, Na) co-doped sample effectively reduces from 32 × 1019 cm?3 to 6 × 1019 cm?3, while the mobility greatly increases, so that the electrical conductivities are maintained in a high range, and the Seebeck coefficients are slightly increased. A maximum ZT value of 0.31 at 523 K is achieved in Bi0.96Ag0.03Na0.01Se along the SPS pressing direction as a result of the higher power factor and lower total thermal conductivity, which is about 30% higher than that of undoped BiSe.
查看更多>>摘要：? 2022 Elsevier B.V.In 4Se3, a member of the lead free chalcogenide family, is a promising thermoelectric material with layered structure. In this work, we explored the structural and thermoelectric transport properties of In4Se3 and In4Se3-x (0.25 ≤ x ≤ 0.55) with an aim to investigate the presence of Se-vacancy in In4Se3-x material system and its effect in the thermoelectric properties. A collective process of solid state reaction, ball milling and spark plasma sintering was used to prepare the compounds. Se-vacancy along with the presence of indium nanoparticles of 20–50 nm with the main orthorhombic In4Se3 phase was established. The Se-vacancy in In4Se3-x enhanced the power factor by increasing the carrier concentration. A significant reduction in the lattice thermal conductivity in In4Se3-x enhanced the thermoelectric figure of merit with maximum ZT of 1.03 achieved at 699 K for In4Se2.6 among the series of samples. It is found that the position of the Fermi level as a result of the carrier concentration together with a smaller band gap is responsible for a significant increase in power factor.
查看更多>>摘要：Gd0.2Ce0.8O3-δ (GDC) and Er0.2Bi0.8O1.5 (ESB) materials were prepared by sol-gel and co-precipitation methods. xESB (x = 1–5 wt%) was added into GDC electrolyte to investigate the effect of ESB adding on the microstructure and electrochemical properties. The results indicated that the adding of ESB improved the densification of electrolyte and generated more oxygen vacancies. The adding of ESB reduced the grain/grain boundary resistance and total resistance. 4 wt% ESB adding resulted in the highest grain boundary conductivity σgb and total conductivity σt. At 450 °C, the σgb and σt of the 4ESB-GDC were 9.23 and 3.12 times higher than GDC, respectively. At 700 °C, the SOFC (solid oxide fuel cell) supported by 4ESB-GDC electrolyte acquired a power density of 0.60 W cm?2, which was 55% higher than the SOFC supported by GDC electrolyte. During 70 h of high temperature operation, the output performance remained stable. Therefore, 4ESB-GDC should be a promising composite electrolyte candidate for IT-SOFCs (Intermediate temperature solid oxide fuel cells).
查看更多>>摘要：In this work, the three-dimensional tensile creep anisotropy of a hot-rolled Mg-0.9Mn-1.5Ce (wt%) alloy sheet was investigated. Creep tests were carried out at 453 K, 473 K and 493 K under various applied stresses. The loading directions were parallel to the transverse direction (TD), rolling direction (RD), and normal direction (ND). Experimental results showed that creep behavior had a strong dependence on the loading direction under the given ranges of stress and temperature, in which the creep resistance was ranked in the order of TD ≈ RD> ND. Thermodynamic calculations and microstructure characterization illustrated that the creep mechanism displayed an intense dependence on stress and temperature in the TD and RD samples, which exhibited similar creep behaviors. Specifically, the viscous gliding of dislocations dominated the creep at 453 K. Pyramidal< c + a> slip started to activate and gradually controlled the creep because of the thermal activation at 473 K. As the temperature increased to 493 K, dislocation climb and pyramidal< c + a> slip together controlled the creep. Conversely, the creep mechanism barely changed in the ND sample, which included {101?2} twinning and cross-slip. The dense twins developed in the ND sample directly caused early creep fracture, and< a> dislocation cross-slipping between the basal plane and prismatic plane supplied a large creep strain and accelerated creep rate. Unexpectedly, the heavy interactions between pyramidal dislocations and dynamic precipitates offered an extra strengthening factor for creep resistance in the TD and RD samples. Consequently, the poorest creep resistance was obtained in the ND sample. In addition, the breakaway of dislocations from the solute atmosphere or precipitates by climbing was the main reason for the power-law breakdown at 493 K in the TD and RD samples.
查看更多>>摘要：Developing high performance porous carbon is a significant issue for the anode materials of lithium-ion batteries. Here, fluorine-rich tubular porous carbon (FTPC) was prepared by low temperature pyrolysis of fluorine-rich conjugated microporous polymer. Tubular porous carbon (TPC) was also prepared from conjugated microporous polymer and used as a control. The structure and lithium storage properties of the FTPC and TPC were compared and investigated. Compared with TPC, FTPC possesses large mesoporous and macroporous specific surface area as well as rich fluorine (up to 16.10 wt%), which make FTPC show superb specific capacity and rate performance. The initial charge capacity of FTPC is as high as 786 mAh g?1, much higher than that of TPC (151 mAh g?1). In addition, quantitative kinetic analysis discloses the dominated pseudocapacitive contribution of lithium storage in FTPC, attributed to the one-dimensional hollow structure, developed porous structure and high fluorination. Our work provides a new way to design and improve the lithium storage properties of porous carbon.
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