查看更多>>摘要：Silicon suboxide (SiOx, 0 < x < 2) is recognized as one of the next-generation anode materials for high-energy-density lithium ion batteries (LIBs) due to its high theoretical specific capacity and abundant resource. However, the severe mechanical instability arising from large volume variation upon charge/discharge cycles frustrates its electrochemical performance. Here we propose a well-designed sandwich-like structure with sandwiched SiOx nanoparticles between graphene sheets and amorphous carbon-coating layer so as to improve the structural stability of SiOx anode materials during cycling. Graphene sheets and carbon layer together construct a three-dimensional conductive network around SiOx particles, which not only improves the electrode reactions kinetics, but also homogenizes local current density and thus volume variation on SiOx surface. Moreover, Si-O-C bonds between SiOx and graphene endow the strong particle adhesion on graphene sheets, which prevents SiOx peeling from graphene sheets. Owing to the synergetic effects of the structural advantages, the C/SiOx@graphene material exhibits an excellent cyclic performance such as 890 mAh/g at 0.1 C rate and 73.7% capacity retention after 100 cycles. In addition, it also delivers superior rate capability with a capacity recovery of 886 mAh/g (93.7% recovery rate) after 35 cycles of ascending steps at current range of 0.1-5 C and finally back to 0.1 C. This study provides a novel strategy to improve the structural stability of high-capacity anode materials for lithium/sodium ion batteries.
查看更多>>摘要：Rechargeable aqueous magnesium-ion batteries (MIBs) show great promise for low-cost, high-safety, and high-performance energy storage applications. Although manganese dioxide (MnO2) is considered as a potential electrode material for aqueous MIBs, the low electrical conductivity and unsatisfactory cycling performance greatly hinder the practical application of MnO2 electrode. To overcome these problems, herein, a novel Mg-intercalation engineering approach for MnO2 electrode to be used in aqueous MIBs is presented, wherein the structural regulation and electrochemical performance of the Mg-intercalation MnO2 (denoted as MMO) electrode were thoroughly investigated by density functional theory (DFT) calculations and in-situ Raman investigation. The results demonstrate that the Mg intercalation is essential to adjusting the charge/ion state and electronic band gap of MMO electrode, as well as the highly reversible phase transition of the MMO electrode during the charging-discharging process. Because of these remarkable characteristics, the MMO electrode can be capable of delivering a significant specific capacity of similar to 419.8 mAh center dot g(-1), while exhibiting a good cycling capability over 1000 cycles in 1 M aqueous MgCl2 electrolyte. On the basis of such MMO electrode, we have successfully developed a soft-packaging aqueous MIB with excellent electrochemical properties, revealing its huge application potential as the efficient energy storage devices.
查看更多>>摘要：Efficiency enhancement of Cs-0.1(CH3NH3)(0.9)PbI3 solar cell devices was performed by using iso-butyl ammonium iodide (IBA) passivated on Cs-0.1(CH3NH3)(0.9)PbI3 films. The n-i-p structure of perovskite solar cell devices was fabricated with the structure of FTO/SnO2/Cs-0.1(CH3NH3)(0.9)PbI3 (FTO, i.e. fluorine doped tin oxide) and IBA/Spiro-OMeTAD/Ag. The effect of different weights of IBA passivated on Cs-doped perovskite solar cells (PSCs) was systematically investigated and compared with non-passivated devices. It was found that the 5-mg IBA-passivated devices exhibited a high power conversion efficiency (PCE) of 15.49% higher than 12.64% of non-IBA-passivated devices. The improvement of photovoltaic parameters of the 5-mg IBA-passivated device can be clearly observed compared to the Cs-doped device. The better performance of the IBA-passivated device can be confirmed by the reduction of PbI2 phase in the crystal structure, lower charge recombination rate, lower charge transfer resistance, and improved contact angle of perovskite films. Therefore, IBA passivation on Cs-0.1(CH3NH)(0.9)PbI3 is a promising technique to improve the efficiency of Cs-doped perovskite solar cells.
查看更多>>摘要：A Z-scheme heterostructure of Mo, W co-doped BiVO4 (Mo,W:BVO/BiOCl@C) was fabricated by a simple solid solution drying and calcination (SSDC) method. The heterostructure was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), etc. Under visible light irradiation, Mo,W:BVO/BiOCl@C heterostructure exhibits excellent photoelectrochemical capability compared with other as-prepared samples. The photocurrent density and the incident photon-to-electron conversion efficiency (IPCE) are about 5.4 and 9.0 times higher than those of pure BiVO4, respectively. The enhancement of the photoelectrochemical performance can be attributed to the construct of Z-scheme system, which is deduced from the radical trapping experiments. The Mo,W:BVO/BiOCl@C Z-scheme heterojunction enhances the visible-light absorption and reduces the recombination rate of charge carriers. This work provides an effective strategy to construct Z-scheme photoelectrodes for the application of photoelectrochemical water splitting.
查看更多>>摘要：A low-alloyed Mg-2Zn-0.8Sr-0.2Ca matrix composite reinforced by TiC nano-particles was successfully prepared by semi-solid stirring under the assistance of ultrasonic, and then the as-cast composite was hot extruded. The results indicated that the volume fraction of dynamical recrystallization and the recrystallized grain size have a certain decline at lower extrusion temperature or rate. The finest grain size of similar to 0.30 mu m is obtained in the sample extruded at 200 degrees C and 0.1 mm/s. The as-extruded sample displays a strong basal texture intensity, and the basal texture intensity increases to 5.937 mud while the extrusion temperature increases from 200 to 240 degrees C. The ultra-high mechanical properties (ultimate tensile strength of 480.2 MPa, yield strength of 462 MPa) are obtained after extrusion at 200 degrees C with a rate of 0.1 mm/s. Among all strengthening mechanisms for the present composite, the grain refinement contributes the most to the increase in strength. A mixture of cleavage facets and dimples were observed in the fracture surfaces of three as-extruded nanocomposites, which explain a mix of brittle-ductile fracture way of the samples.
查看更多>>摘要：Microarc oxidation (MAO) is an effective surface treatment method for Ti alloys to allow their application in extreme environments. Here, binary electrolytes consisting of different amounts of sodium phosphate and sodium silicate were designed for MAO. The surface morphology, composition, and properties of MAO coatings on Ti-6Al-4V alloy treated in 0.10 mol/L electrolyte were investigated to reveal the effect of PO4(3-) and SiO3(2-) on the growth kinetics of the MAO coatings, using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and potentiodynamic polarization. The results showed that PO4(3-) is beneficial for generating microarcs and forming pores within the coating, resulting in a thick but porous coating. SiO3(2-) facilitates the blocking of pores in the outer deposition layer and impedes the generation of microarcs, resulting in a thin dense coating. The thickness, density, phases content, and polarization resistance of the MAO coatings are primarily affected by the intensity of microarcs for low SiO3(2-) contents, and by the number of microarcs when the SiO3(2-) content is sufficiently high. The thickness of MAO coatings obtained in P/Si electrolytes shows a piecewise linear increase with increasing process time during the three stages of microarc discharge. SiO3(2-) is beneficial to the density increase of the coating formed in the previous stage of microarcs discharge, but slows down the growth of the coating formed in the next stage.
查看更多>>摘要：Silver-based alloys are significant light-load electrical contact materials (ECMs). The trade-off between mechanical properties and electrical conductivity is always an important issue for the development of silver-based ECMs. In this paper, we proposed an idea for the regulation of the mechanical properties and the electrical conductivity of Ag-11.40Cu-0.66Ni-0.05Ce (wt%) alloy using in-situ composite fiber-reinforcement. The alloy was processed using rolling, heat treatment, and heavy drawing, the strength and electrical conductivity were tested at different deformation stages, and the microstructures during deformation were observed using field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) and electron backscatter diffraction (EBSD). The results show that the method proposed in this paper can achieve the preparation of in-situ composite fiber-reinforced Ag-Cu-Ni-Ce alloys. After the heavy deformation drawing, the room temperature Vickers hardness of the as-cast alloy increased from HV 81.6 to HV 169.3, and the electrical conductivity improved from 74.3% IACS (IACS, i.e., international annealed copper standard) to 78.6% IACS. As the deformation increases, the alloy strength displays two different strengthening mechanisms, and the electrical conductivity has three stages of change. This research provides a new idea for the comprehensive performance control of high-performance silver-based ECMs.
查看更多>>摘要：The oxide dispersion strengthened Mo alloys (ODS-Mo) prepared by traditional ball milling and subsequent sintering technique generally possess comparatively coarse Mo grains and large oxide particles at Mo grain boundaries (GBs), which obviously suppress the corresponding strengthening effect of oxide addition. In this work, the Y2O3 and TiC particles were simultaneously doped into Mo alloys using ball-milling and subsequent low temperature sintering. Accompanied by TiC addition, the Mo-Y2O3 grains are sharply refined from 3.12 to 1.36 mu m. In particular, Y2O3 and TiC can form smaller Y-Ti-O-C quaternary phase particles (similar to 230 nm) at Mo GBs compared to single Y2O3 particles (similar to 120 nm), so as to these new formed Y-Ti-O-C particles can more effectively pin and hinder GBs movement. In addition to Y-Ti-O-C particles at GBs, Y2O3, TiOx, and TiCx nanoparticles (<100 nm) also exist within Mo grains, which is significantly different from traditional ODS-Mo. The appearance of TiOx phase indicates that some active Ti within TiC can adsorb oxygen impurities of Mo matrix to form a new strengthening phase, thus strengthening and purifying Mo matrix. Furthermore, the pure Mo, Mo-Y2O3, and Mo-Y2O3-TiC alloys have similar relative densities (97.4%-98.0%). More importantly, the Mo-Y2O3-TiC alloys exhibit higher hardness (HV0.2 (425 +/- 25)) compared to Mo-Y2O3 alloys (HV0.2 (370 +/- 25)). This work could provide a relevant strategy for the preparation of ultrafine Mo alloys by facile ball-milling.
查看更多>>摘要：The thermal conductivity of diamond particles reinforced copper matrix composite as an attractive thermal management material is significantly lowered by the non-wetting heterointerface. The paper investigates the heat transport behavior between a 200-nm Cu layer and a single-crystalline diamond substrate inserted by a chromium (Cr) interlayer having a series of thicknesses from 150 nm down to 5 nm. The purpose is to detect the impact of the modifying interlayer thickness on the interfacial thermal conductance (h) between Cu and diamond. The time-domain thermoreflectance measurements suggest that the introduction of Cr interlayer dramatically improves the h between Cu and diamond owing to the enhanced interfacial adhesion and bridged dissimilar phonon states between Cu and diamond. The h value exhibits a decreasing trend as the Cr interlayer becomes thicker because of the increase in thermal resistance of Cr interlayer. The high h values are observed for the Cr interlayer thicknesses below 21 nm since phononic transport channel dominates the thermal conduction in the ultrathin Cr layer. The findings provide a way to tune the thermal conduction across the metal/nonmetal heterogeneous interface, which plays a pivotal role in designing materials and devices for thermal management applications.
查看更多>>摘要：The Fe49.7Cr18Mn1.9Mo7.4W1.6B15.2C3.8Si2 amorphous coating was deposited on T91 steel substrate by using the high-velocity oxygen fuel (HVOF) spray technique to enhance the corrosion resistance of T91 stainless steel in liquid lead-bismuth eutectic (LBE). The corrosion behavior of the T91 steel and coating exposed to oxygen-saturated LBE at 400 degrees C for 500 h was investigated. Results showed that the T91 substrate was severely corroded and covered by a homogeneously distributed dual-layer oxide on the interface contacted to LBE, consisting of an outer magnetite layer and an inner Fe-Cr spinel layer. Meanwhile, the amorphous coating with a high glass transition temperature (T-g = 550 degrees C) and crystallization temperature (T-x = 600 degrees C) exhibited dramatically enhanced thermal stability and corrosion resistance. No visible LBE penetration was observed, although small amounts of Fe3O4, Cr2O3, and PbO were found on the coating surface. In addition, the amorphicity and interface bonding of the coating layer remained unchanged after the LBE corrosion. The Fe-based amorphous coating can act as a stable barrier layer in liquid LBE and have great application potential for long-term service in LBE-cooled fast reactors.
NSTL
Springer Nature