查看更多>>摘要：? 2022 Elsevier B.V.The cathode materials are an important aspect of lithium sulfur battery research. This paper focuses on the electrochemical changes in the interface between cathode and electrolyte, via the surface modification of CNTs@S composites by different types of surfactant. And the cause of this phenomenon is speculated through some comparative experiments. We find that the surfactant adsorbed on the surface of the CNTs@S produce two effects in opposite directions on the interface between cathode and electrolyte: On the one hand, interaction between the hydrophilic group of surfactant and the electrolyte reducing the charge transfer impedance and improving the electrochemical reaction rate; On the other hand, the contact between the hydrophobic group of surfactant and CNTs@S leads a new impedance creating. If these two opposite effects are properly controlled, the battery impedance can be substantially reduced. Finally, with the CNTs@S cathode modified by APG, the charge transfer impedance decreased from 127.2 Ω to about 6.3 Ω, even with the newly generated contact impedance, the total impedance is approximately 1/9 of the original. This change increases the maximum charge and discharge current density of the CNTs@S battery from 1 C to 7 C. Even both with a high sulfur loading of 5.3 mg cm?2 and a low electrolyte/sulfur ratio of 4.1 mL g?1, the Li-S batteries with CNTs@S cathode modified by APG still deliver a high capacity of 2.38 mAh cm?2 (66% of initial capacity) after 50 cycles. Moreover, this simple modification strategy is suitable in different carbon-sulfur composites to improve the high current density charge and the discharge performance of Li-S batteries. It brings a new mentality to the industrial application of Li-S batteries.
查看更多>>摘要：? 2022 Elsevier B.V.A simple hydrothermal route is used to prepare 3D porous hydrated vanadium oxide porous microspheres with different crystal water content. It is the first report that too much water molecule can lead to poor Zn storage performance and optimal structural water content is needed to improve electrochemical performance. By tuning the ratio of Zn to V during the synthesized process, Zn0.146V2O5?0.579 H2O porous microspheres with optimal structural water content exhibit superior electrochemical performance for a promising aqueous rechargeable Zn-ion batteries. At the current density of 0.1 A g?1, it can register a high reversible discharge capacity of 416 mAh g?1. An initial discharge capacity can reach 192 mAh g?1 at the current density of 10.0 A g?1, the specific capacity remains at 202 mAh g?1 and the capacity retention is 105% after 10,000 cycles. Optimal structural water content as well as synergistic effect of pre-intercalated Zn2+ ions should be responsible for excellent electrochemical performance of cathode materials.
查看更多>>摘要：? 2022 Elsevier B.V.Face-centered-cubic (FCC) high-entropy alloys (HEAs) can be strengthened through boron doping. However, the existing form of boron and its effect on the deformation mechanism of FCC HEAs have been rarely reported. The present work demonstrates for the first time the effect of the interstitial boron and boron-rich precipitate on the deformation mechanisms of the FCC (CoCrFeNi) HEAs. The dominant deformation mechanism of CoCrFeNi HEAs is dislocation slip, whereas the interstitial boron atoms dissolved in the matrix, thereby reducing the stacking fault energy (SFE) and transforming the dominant deformation mechanism to deformation twins. The loss of Cr from the matrix after boride formation increased the SFE, which led to transforming the dominant deformation mechanism from deformation twins to dislocation slip. Based on the results, we firstly propose to tune the deformation mechanism of FCC HEAs via boron doping, which provide a new strategy for designing and optimizing the HEAs.
查看更多>>摘要：? 2022 Elsevier B.V.The phase transitions of unpoled and poled Na0.5Bi0.5TiO3 (NBT) single crystals were studied using structural, hysteresis loops, polarizing-microscope, dielectric, mechanical (the first measurement), thermal expansion strain and calorimetric measurements. It was found that phase transitions in NBT are first-order and clearly demonstrate ferroelastic aspects. Both rhombohedral-tetragonal and tetragonal-cubic transformations are accompanied by a softening of mechanical properties like in improper ferroelastic transitions. It was concluded that the difference in the internal friction between unpoled/poled states and between [001]c/[111]c poled states can be associated with a difference in the density of mobile ferroelastic twin walls in these states.
查看更多>>摘要：? 2022In this work, a novel set of methods is prοposed for tuning the oxygen vacancy distribution through the combination of several effects. More specifically, the incorporation of a Ti nano-island (NI), as well as the insertion of a thin layer of HfO2 with 10 nm thickness and the subsequent enforcement of an annealing step at 400 ℃ are employed to improve the performance of the resistive switching memory devices. The acquired results indicate that the embedded Ti NI array can significantly reduce the switching voltage and the statistical dispersion of the switching characteristics, whereas the increase of both the high resistance state (HRS) and low resistance state (LRS) resistance levels and the reduction of the operating current values are attributed to the existence of the HfO2 layer. Subsequently, the annealing process under air conditions can effectively reduce the oxygen vacancy content within the device and further improve the RHRS and on/off ratio. The reduction of the oxygen vacancy concentration is caused by the diffusion of oxygen ions in the air to the dielectric layer during annealing. Hence, it is concluded that the simultaneous incorporation of a Ti NI, a functional layer and a rapid thermal annealing step are regarded as a novel promising and practical technology for significantly improving the whole performance of the memristive elements.
查看更多>>摘要：? 2022 Elsevier B.V.Designing novel and highly efficient photodetectors is a significant work as well as full of challenges. Herein, 2D SnSSe (SSS) porous nanoplates (Sn: S: Se=1: 1: 0.5) with atom-level heterojunctions were obtained from optimized hydrothermal synthesis, and a novel SSS-based photoelectrochemical detector was constructed accordingly. The morphology, microstructure, chemical states and light absorption performance of the SSS sample were clearly revealed by various characterization methods. Further analysis showed that there was an internal electric field in the SSS sample, which resulted from no coincide centers of the positive and negative charge. Due to the internal electric field and porous structure, the SSS sample had lower internal resistance (0.3 KΩ), which was conducive to the transmission of internal carriers, and could enhance the photoelectrochemical (PEC) activity eventually. In addition, a possible schematic illustration of the SnSSe-based photodetector was accordingly proposed. This SnSSe-based photodetector exhibited a higher photocurrent density (262.8 μA/cm2) that was 28.9 and 4.8 times of the SnS2 and SnSe2 and showed a higher photo-responsivity (0.24 mA/W) with a higher response speed. Moreover, the conduction band position of the SSS sample was higher than the O2/?O2? and H+/H2 from band structure analysis, revealing it could also be used as a photocatalyst in photocatalytic degradation and photocatalytic hydrogen production. This pioneering work put forward a new scheme for the preparation of ternary SnSSe and revealed its potential application in the field of photodetection.
查看更多>>摘要：? 2022 Elsevier B.V.The effects of carbon and molybdenum on the strain-induced nanostructural evolution and strength-ductility trade-off in Fe40Mn40Co10Cr10, Fe39.5Mn40Co10Cr10C0.5, and Fe38.3Mn40Co10Cr10Mo1.7 high-entropy alloys (HEAs) were investigated at room temperature (RT) and cryogenic temperature (CT). Deformation twinning was the dominant deformation mechanism for all the three HEAs at RT. The addition of Mo enhanced the metastability and thus increase the volume fraction of ε-martensite with strain in Fe38.3Mn40Co10Cr10Mo1.7 at 77 K. The fractions of annealing twins played important roles in the nanostructural evolution and grain refinement of the Fe38.3Mn40Co10Cr10Mo1.7 at CT. The nanostructural evolution was found to be controlled by modifying SFE, the friction stress for cross slip and Gibbs free energy for phase transformation (ΔGfcc?hcp) via alloying with Mo or C. The nucleation of mechanical twinning at RT and the preferential occurrence of strain-induced martensitic transformation at CT was found to induce the grain partitioning through the hierarchical structure formation and enhanced work hardening rate. The simultaneous occurrence and synergistic effect of twinning-induced plasticity/transformation-induced plasticity in Fe39.5Mn40Co10Cr10C0.5 exhibited an excellent strength/ductility combination (1022 MPa/~ 110%) at 77 K.
查看更多>>摘要：? 2022 Elsevier B.V.The intrinsic mechanical properties of NbTaTiZr and NbTaTiZrX (X[dbnd]Mo, W) are studied by using a first-principles calculation in combination with special quasi-random structure. For NbTaTiZr RHEA, the ideal tensile strength (ITS) and compressive strength (ICS) along [001] direction is respectively calculated to be 5.64 GPa and ?18.4Gpa at the strain 11% and ?20%. For shear loading along (211)[111] slip system, the ideal shear strength (ISS) is 3.03 GPa as the strain is about 20%. With addition of Mo into NbTaTiZr, the ITS, ICS and ISS respectively increase up to 9.7, ?19.3 and 4.73 GPa, and the addition of W enhances the ITS, ICS and ISS up to 10.5, ?21.1 and 5.12 GPa, respectively. Hence addition of Mo or W can significantly improve the ideal strength, especially stronger impact of W element. The calculated elastic moduli E[001] and G[111] are in reasonable agreement with the initial slope of the stress-strain relationship. The derived dimensionless ITS and ISS from first-principle calculations is underestimated the ideal strength in comparison with the prediction by the universal empirical model. Then the microcosmic mechanism is further studied by examination of the detailed bond length variation of three HEAs during the corresponding deformation. Near the critical strain under of tension and shear, the slower descend of stress originates from the gradual breakage of atomic bonds, while the compressive stress decreases rapidly owing to all bond fracturing almost simultaneously. Finally, the ideal strength of three HEAs is further analyzed from electronic structure.
查看更多>>摘要：? 2022 Elsevier B.V.TiO2 is a potential candidate for thin film electrode in Li ion batteries since it is abundant, cheap, has high theoretical specific capacity and can be produced in thin film form of desired crystallographic phase relatively easily by various physical vapor deposition techniques. Rutile phase TiO2 thin films have been prepared by radio frequency magnetron sputtering technique on stainless steel substrates at 450 °C substrate temperature, followed by post deposition annealing in air at 600 °C. These samples have been used as anode in Li ion batteries which are subjected to discharge/charge cycles. The electrodes have been extracted by de-crimping the batteries at various stages during the 1st discharge and 1st charge cycles and structural characterizations of these samples have been carried out by Grazing Incidence X-ray diffraction measurements with a laboratory X-ray source and Extended X-ray absorption fine structure measurements using synchrotron radiation. A clear signature of rutile to anatase phase transition has been observed in the samples during 1st discharge or Li ion insertion process, which is subsequently retained during the 1st charging cycle also. This is also verified by Raman spectroscopy measurements on few samples and is further corroborated by the constant voltage plateau observed in the galvanostatic cycle (potential versus capacitance plot) of the Li ion battery also during the 1st discharge cycle.
查看更多>>摘要：? 2022 Elsevier B.V.The rational design of hierarchical nanostructure consisting of multiple components with remarkable electrochemical performance is regarded as a significant technique for fabricating high-performance energy storage devices. Herein, self-supported tree-like (Ni,Co)Se2/Ni(OH)2 heterogeneous nanoarrays on carbon cloth (CC) used as electrode materials of supercapacitors (SCs) are designed and synthesized by a multi-step approach. The (Ni,Co)Se2 core can boost electron transport due to excellent conductivity, and the shell layer of Ni(OH)2 nanoflakes improves the surface area. Profiting from the cooperative effects of two active materials and core-shell architecture, the tree-like (Ni,Co)Se2/Ni(OH)2 composite delivers a superior capacity, outstanding rate capability and still retain 151.3 mAh g?1 after 3000 charge/discharge cycles. Meanwhile, the flexible hybrid supercapacitor (HSC) fabricated by the (Ni,Co)Se2/Ni(OH)2 and activated carbon (AC) also manifests a satisfied energy density of 0.79 mWh cm?2 under 1.35 mW cm?2. Therefore, it can be considered that the as-prepared hierarchical (Ni,Co)Se2/Ni(OH)2 nanoarrays are promising candidate for HSC devices in energy storage and conversion.
NSTL
Elsevier