查看更多>>摘要：Transition metal phosphides (TMPs) have attracted great interest owing to the metallic properties and high specific capacities. Here, we designed hollow NiCoP nanocubes with increased specific surface area using a Ni-Co Prussian blue analogue as a self-template and NH3 center dot H2O as an etching agent. During the synthesis, both carbonization and phosphorization are completed in one step. The obtained hollow structure alleviates the volume variation of electrode material during reversible electrochemical reaction. Meanwhile, the residual carbon distributed uniformly in NiCoP at the molecular level, resulting in a high conductivity. DFT calculations further reveal that the electrical conductivity of NiCoP is superior to those of monometallic phosphide and metal oxide. Therefore, the optimized NiCoP-4-50 0 displays a high specific capacity (1590 F g(-1) at 1 A g(-1)) and outstanding cycling stability (78.2% retention after 12,000 cycles). Moreover, a prepared hybrid supercapacitor device delivers an energy density of 38.4 W h kg(-1) with a power density of 799.9 W kg(-1) at 1 A g(-1). The results indicate that the obtained high-performance TMPs with hollow structures have an application potential for energy storage devices. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：A serious of Zr-2(WO4)(PO4)(2) (ZWP):Er3+,Yb3+ phosphors by co-doping Li+ ions were prepared by solid state reaction method. Based on the X-ray diffraction (XRD) and scanning electron microscope (SEM), the lattice structure and morphology of prepared samples were performed. Meanwhile, the up-conversion lumines-cence (UCL) spectra were measured from room temperature to 693 K under 980 nm laser excitation. With the intervention of Li+ (0.04, 0.06, 0.08, 0.10), the green UCL intensities of ZWP:0.02Er(3+), xYb(3+) (x = 0.02, 0.04, 0.06, 0.08) phosphors was remarkably strengthened by 4.2, 2.6, 3.3, 5.5 times at room temperature, respectively, and the thermal enhancement of H-2(11/2)-> I-4(15/2) transition UCL of Er3+ was observed due to the negative thermal expansion (NTE) of ZWP host. In Addition, the co-doping Li+ enhanced the absolute temperature sensitivities, and the maximum absolute sensitivity and relative sensitivity of ZWP:Er3+,Yb3+,Li+ phosphors were derived to be 0.01345 K-1 and 0.01198 K-1, respectively. The mechanism of the enhanced UCL intensity and temperature sensing by co-doping Li+ was discussed. The obtained re-sults indicate that the NTE Er3+/Yb3+/Li+ tri-doped ZWP phosphors with a high temperature sensitivity can be applied as optical thermometer. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：This work proposes a novel strengthening strategy for HCP alloy by fully utilizing the strengthening roles from texture and dual-precipitates in both basal and prismatic planes. The binary Mg-7Al (at%) alloy fabricated by such a strategy exhibits a superior combination of strength and strain hardening rate in major plastic strain ranges. Unlike conventionally fixed distribution of precipitate on given lattice plane, both basal and prismatic Mg17Al12 precipitates are firstly engineered to co-exist and reinforce Mg alloy. Additionally, this work reports the presence of a new precipitate morphology with a hammer-like geometric configuration for the first time to date. Further application and extension of this novel strengthening strategy to other HCP alloys, like Ti, Zr, are also discussed. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Recently, bismuth-based hybrid organic-inorganic halide perovskite-like materials have attracted great attention due to their friendly and safely processing, chemical stability, and photoconductive properties. Here, we report a simple method to prepare a new lead-free hybrid material of hydrazine iodobismuthate (HyBI) with semiconductor properties, adopting zero-dimensional (0D) perovskite-like structure, and its crystal, thermal, bandgap, and optoelectronic properties were explored. It is noteworthy that HyBI has a direct bandgap of 1.99 eV, carries mobility as high as 64.2 cm2V-1s-1, charge-trap density of 2.32 x 1010 cm-3. Moreover, self-powered photodetector devices were fabricated using HyBI, which showed the re-sponsivity under 470 nm was 7.63 mA/W. This work highlights the material as a promising candidate for lead-free optoelectronic applications. (c) 2021 Published by Elsevier B.V.
查看更多>>摘要：In this article, the sol-gel synthesized beta-Li2TiO3, referred to as sg-beta-Li2TiO3, exhibits superior electro-chemical performance, compared with the theoretical specific capacities of frequently investigated Titanium based oxides, for example, LiTiO2 (143 mAh g(-1)), Li4Ti5O12 (175 mAh g(-1)) and Li2Ti3O7 (198 mAh g(-1)). It delivers a considerable specific capacity of more than 200 mAh g(-1) within 100 cycles and close to 200 mAh g(-1) after 200 cycles and preserves coulombic efficiency above 97% for all the cycles. After more than 500 cycles, the reversible specific capacity of sg-beta-Li2TiO3 is more than 170 mAh g(-1) and a less than 2% capacity degeneration is observed for the followed several hundreds of cycles. DFT calculations and MD simulations show 8 f void mediated diffusion comprise the two dimensional diffusion layer on a-b plane and the neighboring diffusion layers are interconnected by two 8 f voids via a Li2 atom. Low energy barriers and high Li+ activities are observed. Three intermediate phases, corresponding to intercalation level x = 0.5, 0.75 and 0.875 in beta-Li2+xTiO3, are identified for the intercalation process with the maximal intercalation level 0.875. Both ex-situ XRD and theoretical calculations reveal low volume change or strain less than 5% in the intercalation process. Also, an insulator-metal transition upon lithiation is observed by the electronic structure analysis. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Developing high-performance and low-cost catalysts for replacing Pt-based catalysts is a significant challenge for solar cells and water splitting applications. In this work, a bifunctional hybrid catalyst of MnTa2O6@MPC (MPC: mesh-like bio-based porous carbon) was synthesized, using a co-precipitation approach. Benefiting from the high specific surface area (332.743 m(2) g(-1)), integrating the merits of the electrical conductivity of MPC, the outstanding electrocatalytic ability of MnTa2O6, and the synergistic effect between MnTa2O6 and MPC, the catalytic activity of MnTa2O6@MPC was significantly enhanced. To boost the photovoltaic performance of dye-sensitized solar cells, a novel Cu2+/Cu+ redox mediator and dye (Y123, D35) were adopted for replacing the traditional I-3(-)/I- redox mediator and N719 dye, respectively. The resulting advanced solar cell with the Cu2+/Cu+ redox mediator based on the MnTa2O6@MPC counter electrode catalyst exhibited a photovoltage of similar to 0.88 V, and cell efficiencies of 3.41% and 1.92% for the D35 and Y123 dye systems, respectively, which are respectively 16% and 8% higher than that of Pt. MnTa2O6@MPC also exhibited significant catalytic ability for hydrogen production, yielding a small overpotential of 141.9 mV at a current density of 10 mA cm(-2) and a small Tafel slope of 105.0 mV dec(-1) in an alkaline medium. This work provides promising guidance for designing bifunctional hybrid electrocatalysts for high-performance new energy devices. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The transformation and superelasticity characteristics of solution-treated Ti50Ni48Fe2 and aged-hardened Ti49.2Ni49.3Fe1.5 shape memory alloys during cyclic compressive deformation were investigated. The Ti50Ni48Fe2 alloy could not be precipitation hardened, while the Ti49.2Ni49.3Fe1.5 alloy, aged at 400 degrees C, was hardened by Ti3Ni4 precipitates. During the cyclic deformation, the B2 reversible arrow R reversible arrow B19' transformation peaks broadened and spread to a large temperature span. At the same time, the superelasticity behavior became linear, and the associated elastocaloric cooling capacity decreased to a stable value. Among these samples, Ti49.2Ni49.3Fe1.5 alloy aged at 400 degrees C for 150 h exhibited the largest recoverable strain in superelasticity and retained the largest cooling effect after 1000 deformation cycles. Furthermore, it showed elastocaloric cooling of -4.1 degrees C to -7.0 degrees C at operating temperatures of -40-80 degrees C. Experimental results revealed that B19' transformation was suppressed significantly by cyclic deformation, and thus the transformation occurred in a wide temperature range of -160 to -50 degrees C. Additionally, the linear superelasticity exhibited a low slope of the Clausius-Clapeyron relation of about 0.5 MPa/degrees C. These features allow the alloys to exhibit super-elasticiy and the elastocaloric effect over a wider temperature range. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The photoemission and electron collection properties of nanostructure photoemitter based on parallel aligned (Al)GaN nanowall arrays are investigated. In general, the photoelectric conversion efficiency of intrinsic GaN NWAs exhibit a significant improvement compared with planar photoemitter. Assisted by the built-in field induced by gradient decreasing Al component along axial direction of the nanowall, the proportion of emitting photoelectrons on each surface of a nanowall is redistributed and the collected photocurrent is obviously enhanced yet with a negative effect against quantum efficiency and emitted photocurrent. External field incorporation can tune the electron emitting path and improve the collection efficiency, but accompanied with a further decline in emitting photocurrent and quantum efficiency. For a certain configuration with nanowall height of 1 }tm and spacing length of 1 }tm, the optimum field intensity for emitting and collected photocurrent are respectively 0.3 and 0.5 V/}tm. The alteration of photocurrent varied with field intensity dominated by the photoelectrons from the top surface and irradiated side face of the nanowall. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Large-scale production of high-quality molybdenum disulfide (MoS2) nanotubes is important due to their special structure and inherent properties. In this paper, we reported a low-cost approach to synthesize ultra-long Na doped MoS2 nanotubes on a large-scale by sulfurizing the precursors which produced by a hydrothermal method. Sodium chloride (NaCl) and ammonium molybdate solution are stirring in a heated water bath to prepare these precursors. Then Na doped MoS2 nanotubes are obtained by vapor-phase sulfurization using sulfur powder as S source. Transmission electron microscopy (TEM) images, X-ray dif-fraction (XRD) pattern, Raman spectra and X-ray photoelectron spectroscopy (XPS) prove the crystal structure of Na doped MoS2 with elemental composition of NaxMoS(2) (x = 0.38-0.4 4). The morphology of the samples shows pure high-quality Na doped MoS2 nanotubes with length ranging from 100 to 300 mu m. When used as the counter electrode (CE) of dye-sensitized solar cells (DSSCs), these nanotubes have excellent electrocatalytic activity. A power conversion efficiency of 5.85% is recorded in these solar cells, which is near that of the referenced Pt counter electrodes. This makes these nanotubes are ideal CEs of DSSCs. So this method is a simple and convenient approach to synthesize transition metal dichalcogenides (TMDs) nanotubes on a large scale. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Phase transformation and microstructure evolution of a Ti2AlNb alloy upon cooling from B2/beta phase at rates of 0.02-100 degrees C/s were investigated by using X-ray diffractometer, scanning electron microscope, and thermal dilatometer. At the lowest cooling rate of 0.02 degrees C/s, both alpha(2) and O phases precipitate from the B2/beta phase. The precipitation is prior to occur at the grain boundary of the parent phase, which even makes alpha(2) phase almost disappear from the interior of the grain. Cooling the alloy at a higher rate results in a decreasing amount of the precipitates. The critical rate for the complete depression of alpha(2) and O phase precipitation is 0.5 degrees C/s and 4 degrees C/s, respectively. According to the established continuous cooling transformation (CCT) diagram, the temperature interval for B2/beta -> O phase transformation decreases with increasing cooling rate. The alloy cooled at the rate of 0.1 degrees C/s has the highest microhardness for the appropriate size and amount of the precipitated phases. (C) 2021 Elsevier B.V. All rights reserved.
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