查看更多>>摘要：? 2022As we all known, the most promising alternative anode for the next-generation energy storage devices is the lithium metal anode. But the unpredictable dendrite growth and volume expansion during the cycles impedes its applications and commercialization. The Li-Cu-Zn three-phases alloy materials (including Li2Cu3Zn, Li-Zn and Li) have been synthesized to solve these problems. According to the density functional theory (DFT) analysis, all results indicate that the Li2Cu3Zn ternary alloy has the higher absorption energy of Li than bare Li, suggesting the superior lithiophilic. Meanwhile, the construction of Li2Cu3Zn alloy 3D skeleton is beneficial to uniform the Li+ flux and reducing the local current density. Furthermore, based on the analysis of in-situ X-ray diffraction, Li2Cu3Zn skeleton can keep stable during the cycles. The Li-Cu-Zn electrodes exhibit the stable cycling performance about more than 1200 h and pure lithium only for about 120 h (at 1 mA cm?2 and 1 mAh cm?2). And at 0.5 C, after 100 cycles, the NCM811 (LiNi0.8Co0.1Mn0.1O2) ||Li-Cu-Zn cell delivers an excellent cycling stability for 92.3% capacity retention. In this work, uniform deintercalation of lithium ions through three-dimensional alloy framework structure provides a research basis for lithium-free anodes.
查看更多>>摘要：? 2022 Elsevier B.V.Due to the increasing demand of new energy vehicles and large-scale power grids for high energy density devices, lithium-sulfur batteries (LSBs) have attracted more and more researchers' attention stemming from their advantages of high theoretical specific capacity, low cost of active substances and environmental friendliness. However, there are still some intractable problems hindering the commercialization of LSBs, among which the most serious problem is “shuttle effect” of polysulfides. For the purpose of solving this problem, this paper prepared hollow structure molybdenum sulfide/cobalt sulfide mixed with amorphous carbon (MoS2/Co9S8/C) (HMCC) nanoparticles using ZIF-67 as the precursor and coated on the side of ordinary PE separator facing the positive electrode by a simple scraper coating process. The combination of MoS2 and Co9S8 bimetallic sulfides can not only adsorb and catalyze the rapid transformation of intermediates, but also effectively conduct lithium ions mainly because of the exposure of many active sites of layered MoS2 in the outermost layer. In addition, a small amount of carbon inside can enhance electrical conductivity of the coating, increasing the utilization of active substances, and the stable hollow structure can act as a "transfer station", greatly inhibiting the large amount of polysulfides to run off. The dual advantages of structure and composition make the modified separator have excellent performance in different current densities. Reversible specific capacities of 930.4 mAh g?1 and 690.7 mAh g?1 are released at 0.5 C and 1 C, and capacity retention of 72 % and 64 % after 500 and 600 cycles, respectively. In addition, due to the rapid conduction of lithium ions, the growth of lithium dendrites is greatly inhibited, which maintains the high safety of the battery. This provides a new research direction for the application of other new bimetallic sulfides in the separator modification of LSBs.
查看更多>>摘要：? 2022Visible light-driven photocatalytic technology has become an effective method to remove U(VI) from wastewater. Herein, MoO3 quantum dots (MQDs) were prepared by a one-step oxidation method using molybdenum disulfide as the precursor. The MQDs were used to modify g-C3N4 nanosheet photocatalysts (MQDn-C3N4, where n represents the mass percentage of MQDs) to enhance the photocatalytic performance of g-C3N4 nanosheets. The morphology, chemical composition and optical properties of the MQDn-C3N4 composites were investigated by a series of characterization methods. The MQD3-C3N4 could remove 96.4% of U(VI) after 150 min of illumination, which was about 1.9 times that of g-C3N4. The MQD3-C3N4 samples had excellent stability and recyclability after five cycles. The possible mechanism of the photocatalytic process was proposed through radical trapping experiments and electron spin-resonance, in which the reduction of U(VI) is facilitated by photogenerated e– and ?O2– radicals. The MQDn-C3N4 photocatalyst is expected to provide new concepts for the treatment of wastewater containing radionuclides.
查看更多>>摘要：? 2022Carbon materials are considered as prospective candidates for Na-ion batteries (SIBs) anodes, which have attracted significant attention. It is critical to develop a novel carbon anode with high specific capacity and excellent coulombic efficiency for practical application of SIBs. Herein, N/S-codoped hollow carbon spheres with rich carbon nanotubes is developed to work as sodium ion batteries anode. Owing to the unique structure, the material exhibits excellent performance and cycling stability at ultrahigh rate. In addition, the capacity maintains at 130 mA h g-1 under a current density of 10 A g-1 after 5600 cycles. The mechanisms of surface-dominated storage are elaborated by electrochemical test, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, Raman analysis, ex situ X-ray diffraction. Furthermore, we quantitatively calculate the relationship between the extra specific capacity and the introduced defect, which can give the inspiration of improving the performance of sodium ion batteries. These results benefit the development of novel excellent sodium storage materials.
查看更多>>摘要：? 2022 Elsevier B.V.As a result of their excellent creep strength at high temperatures, oxide dispersion strengthened alloys are attractive candidates as structural materials for high temperature applications. However, traditional production processes encounter several challenges when producing complex shape. This study employed a single/multi-track process optimization approach for the preparation of oxide dispersion strengthened nickel-based superalloy by laser metal deposition. A multi-objective optimization method (power, scanning speed, powder feed rate) was adopted in the preparation process to improve the dilution, wetting angle, powder capture efficiency and hardness of the single-track. The Taguchi method-Principal component analysis-Gray relational analysis-Response surface methodology was used to optimize the characteristics of single-track. Thermocapillary convection drives the motion of gas bubbles in single-track depositions, while surface pores typically cluster along the track edge. The microstructure and crack of multi-track are optimized by overlapping ratio. In order to investigate the effect of the transition from columnar to equiaxed, the microstructure of the laser-deposited bulk specimen was studied. The results verify the feasibility of multi-objective process optimization in track and present experience for the application of microstructure and mechanical properties of track process optimization laser-deposited sample.
查看更多>>摘要：? 2022 Elsevier B.V.We report on the effects of Fe substitution on the structural and magnetic properties of the YCo12-xFexB6 series of compounds by combining scanning electron microscopy, energy dispersive X-ray microanalysis, X-ray powder diffraction and magnetic measurements. The rhombohedral R3?m structure of the YCo12-xFexB6 is retained up to about x = 4.5 Fe atom per formula unit, a value that we assign to the estimated solubility limit for polycrystalline samples. The unit cell is found to expand regularly upon increasing the iron content with a rate of 1.55 ?3 per Fe atom, the expansion being larger along the basal plane. Clues for the preferential substitution scheme of Fe for Co are discussed. It is also shown that Fe for Co substitution induces dramatic changes on the magnetic properties such as a strong decrease of the ordering temperature and a significant reduction of the spontaneous magnetization.
查看更多>>摘要：? 2022 Elsevier B.V.The development of rare-earth zirconates with tunable thermal expansion coefficient (TEC) and thermal conductivity is of great importance in the area of thermal barrier coatings. In general, TEC can be tailored by the average electronegativity difference, and the thermal conductivity can be customized by the atomic mass difference and/or ionic radius. Based on this thermophysical properties design principle, a series of high-entropy rare-earth zirconate ceramics were synthesized and characterized, and the obtained results indicate that: (1) the TEC is negatively correlated with the average electronegativity difference of cation and anion concerning its corresponding compound; (2) the thermal conductivity is negatively correlated with the atomic mass difference and ionic radius difference concerning its corresponding compound; (3) the synthesized ceramics have excellent high-temperature long-term thermal phase stability, larger TEC (RT-1500 °C, 10.20 ~ 10.39 × 10-6 K-1), lower thermal conductivity (1500 °C, 1.17 ~ 1.37 W·m-1·K-1), and higher fracture toughness (1.61 ~ 1.69 MPa·m1/2) compared with lanthanum zirconate. The tailorable design principle involved in this work sheds new insights for designing alternative ceramics with pre-assigned thermophysical properties for the next-generation thermal barrier coatings.
查看更多>>摘要：? 2022There are two types of magnetocaloric effects that are the so-called direct and inverse effects originating from ferromagnetic–paramagnetic (FM–PM) and antiferromagnetic–ferromagnetic (AFM–FM) phase transitions, respectively. Here, the magnetocaloric effects of FeRh alloy, which exhibit both the direct and inverse effects, have been studied by combining first-principles calculations and Monte Carlo simulations. The magnetic exchange coupling constants in the AFM and FM phases are evaluated by first-principles calculations based on the Liechtenstein formula. The Monte Carlo calculations considering the two-phase mixtures of AFM and FM well reproduce the experimental magnetization curves at zero external magnetic field. It is also shown that the isothermal magnetic entropy changes near the AFM–FM transition temperature under magnetic fields are successfully reproduced based on the Maxwell relation. The entropy changes in a wide range of the magnetic fields near the AFM–FM and FM–PM transition temperatures are investigated and the direct and inverse magnetocaloric effects of FeRh are discussed. The giant relative cooling power of FeRh alloy is achieved due to the large saturation magnetizations and the first-order AFM–FM phase transition.
查看更多>>摘要：? 2022 Elsevier B.V.Herein, we report a facile, economic, efficient and binder-free strategy to synthesize a flower-like Bi2O3 thin films on flexible stainless steel mesh (FSSM) substrates by rotational chemical bath deposition (R-CBD) approach. The flower-like Bi2O3/FSSM exhibits a monoclinic α-Bi2O3 phase demonstrating the mesoporous nature with a 58.69 m2 g?1 specific surface area. The Bi2O3/FSSM electrode exhibits specific capacitance of 421.76 F g?1 and specific capacity of 674.8 C g?1 at 10 mA cm?2 current density, remarkable cycle stability (60% up to 1000 cycles), and high energy density (149.95 Wh kg?1) with power density (963.85 W kg?1) in 6 M KOH electrolyte. The results indicate that the 6 M KOH is optimized concentration for Bi2O3/FSSM electrodes. An aqueous asymmetric supercapacitor (ASC) device is fabricated by activated carbon (AC) as cathode and Bi2O3/FSSM as an anode. The assembled Bi2O3||AC ASC device exhibits a specific capacitance of 36.37 F g?1 at a current density of 1 mA cm?2 with the energy density (ED) of 18.24 Wh kg?1 at a power density (PD) of 1008.67 W kg?1 and 83.67% capacitance retention after 1000 cycles at the current density of 2 mA cm?2. The derived Bi2O3/FSSM served as a binder-free electrode that provides potential application for electrochemical energy storage devices.
查看更多>>摘要：? 2022 Elsevier B.V.The grain boundary diffusion process of Pr-Al-Cu at various temperatures has been applied in the sintered Nd-Fe-B magnets. Detailed evolution of the grain boundary phases and its influence on the magnetic properties were investigated. Microstructure analysis showed that the shell morphology rich in Pr and Al was significantly formed in the diffusion process at 700 °C, which was determined as (Pr,Nd)2(Fe,Al)14B phase, while Al is homogeneous in the 900 °C diffused magnets. After the annealing treatment, continuous grain boundary phases were generated in the 700 °C diffused magnet to isolate the neighbouring grains even at the depth of 1000 μm, whereas that in the 900 °C diffused magnet were scarce. Thus a pronounced enhancement of coercivity from 16.21 kOe to 21.36 kOe was yielded in the annealed 700 °C diffused magnet. Transmission electron microscopy showed that the thickness of the Pr and Al rich shell in the matrix phase grains was dramatically decreased during the annealing process. The absent shell layers facilitate the formation of (Pr,Nd)6(Fe,Al,Cu)14 phase in the intergranular regions. Also the residual diffusion source on the surface of the diffused magnets was supposed to promote the development of continuous grain boundary phases during the annealed process. Based on these results, the temperature-dependent microstructure and magnetic properties evolution was detailedly discussed.
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