查看更多>>摘要：? 2022 Elsevier B.V.V2O5 nanostructures doped with 1% Co have been successfully synthesized by simple hydrothermal method. Structural and morphological aspects, vibrational spectra and optical properties (linear and nonlinear) of pristine as well as Co-doped V2O5 (V2O5:Co) nanoparticles are investigated. X-ray diffraction patterns indicate that both V2O5 and Co doped V2O5 are stabilized in an orthorhombic structure. Energy band gaps measured using the Tauc plot give 2.24 eV for V2O5 and 2.16 eV for Co doped V2O5. When excited using 5 ns laser pulses at 532 nm in the open aperture Z-scan configuration, pristine as well as Co-doped V2O5 nanoparticles are found to show excellent nonlinear absorption, which arises from strong reverse saturable absorption occurring in the sample at this wavelength. The corresponding effective two-photon absorption coefficients are in the range of 10?11 to 10?12 m/W, and effective three-photon absorption coefficients are in the range of 10?22 to 10?23 m3/W2. When excited at the same wavelength using a continuous wave laser beam, the effective two-photon absorption coefficient gets enhanced to 10?6 m/W. These results confirm the suitability of V2O5 and Co-doped V2O5 nanoparticles for the fabrication of optical limiter devices for the protection of human eyes and sensitive optical detectors from hazardous laser radiation.
查看更多>>摘要：? 2022 Elsevier B.V.The present work investigated the correlations between heat treatment and the microstructure and magnetic properties of the in situ alloyed Fe-50%Ni samples manufactured using laser-based direct energy deposition under different production conditions. The samples with high relative density were directly synthesized from the pure Fe and Ni elemental powders. In addition, a fine FCC microstructure with relatively elongated grains in the building direction was observed in the as-print samples. After applying short-time heat treatment, the grain morphology remained unchanged, while the grain size and microhardness were slightly increased and decreased, respectively. This also caused the reduction in internal residual stresses and, subsequently, partial stress relaxation in the microstructure. According to the electron probe microanalysis results, the simultaneous Fe and Ni depletion/enrichment formed during the in-situ alloying was practically decreased after applying short time heat-treatment, resulting in the significant improvement of magnetic properties, as compared to the as-built ones. The maximum magnetization, coercivity, and curie temperature of ~170 emg/g, 1.8 Oe, and 530 °C, respectively, were obtained in the optimum processed sample, which were significantly higher than those of other soft magnetic permalloys produced by additive manufacturing methods.
查看更多>>摘要：? 2022 Elsevier B.V.Lead selenide (PbSe) is considered to be decent candidate replacing lead telluride (PbTe) as intermediate temperature (600–900 K) thermoelectric application due to its lower intrinsic lattice thermal conductivity, higher thermal stability, and larger abundance of Se than Te. To improve the thermoelectric performance of n-type PbSe, we constructed an n-type PbSe-Sb2Se3 pseudo-binary via alloying Sb2Se3 into PbSe matrix to obtain a reduced lattice thermal conductivity at a broad temperature range. Next, we introduced extra Zn into matrix to optimize the electron concentration. Last, we further added excess Ag2Se to modulate the lattice thermal conductivity at temperature< 523 K. Eventually, we obtained an ultralow lattice thermal conductivity of ~ 0.40 W m?1 K?1 and a large peak ZT of ~ 1.36 at 773 K in the composition of (PbSe)40(Sb2Se3)Zn0.1(Ag2Se)0.75; meanwhile, the average ZT between 323 and 773 K is as high as ~ 0.78, revealing a significant improvement over pristine PbSe.
查看更多>>摘要：? 2022 Elsevier B.V.The effect of reduction on microstructure evolution and mechanical properties in a near α-Zr alloy (Zr0.5Be, wt%) has been studied in detail during cold rolling. The results indicate that the strength of (002)α texture increases gradually with the increase of reduction, which can be attributed to the activation of base slip of α phase under high stress concentration. In the process of cold rolling reduction from 0% to 70%, deformation mode of the α-laths changes from rigid rotation along the RD direction to plastic strain gradually. Microscopic analysis results show that the dislocation slip dominates the plastic behavior of the alloy and the evolution path of the microstructure can be described as: (I) the stage of increasing dislocation density, (II) the stage of dislocation wall and dislocation cell formation, (III) the stage of subgrain formation, and (IV) the stage of nanocrystalline formation. Also, as the reduction increases from 0% to 70%, the tensile strength increases while the fracture elongation decreases. The sample subjected to 70% reduction can display the highest ultimate tensile strength (~ 930 MPa) and retain a fracture elongation of 8.6%. The combined effects of fine grain strengthening, dislocation strengthening and strain hardening play a leading role in the increase of strength and decrease of fracture elongation.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, a kind of novel Al matrix composite reinforced by CoCrFeNi HEA particles was fabricated by cold spray (CS) and subsequent friction stir processing (FSP) for the first time. The microstructure and mechanical properties of cold-sprayed (CSed) and friction stir processed (FSPed) CoCrFeNip/6061Al composites were examined using scanning electron microscopy, energy dispersive spectroscopy, electron backscattering diffraction, X-ray diffraction, and hardness and tensile tests. The results demonstrated that CSed samples exhibited a number of micro-pores in the Al matrix with homogeneous distribution of HEA particles, but heterogeneously distributed grain size. Continuous dynamic recrystallization and geometric dynamic recrystallization occurred at the interface between the HEA particles and Al matrix. Following FSP, the micro-pores were eliminated, and a small amount of HEA particles was fragmented and uniformly dispersed in the Al matrix. Moreover, the average size of HEA particles was refined from ~21–14 μm. The Al matrix exhibited dynamic recrystallization and particle-stimulated nucleation recrystallization, thus resulting in an average grain size of ~1.9 μm. Obvious diffusion layers of 0.5 μm and 1 μm in thickness occurred at the interface between the HEA particles and Al matrix in CSed and FSPed samples, respectively. A new phase with a body-centered cubic structure was confirmed to be an HEA in diffusion layers. Compared with CSed samples, the microhardness, ultimate tensile strength, and elongation of the FSPed samples increased by 91%, 60%, and 130%, respectively. The improved mechanical properties are attributed to the high density and enhanced interfacial bonding. Thus, this study provided a novel method for preparing high-performance Al matrix composites reinforced by HEA particles.
查看更多>>摘要：? 2022 Elsevier B.V.The present work is an effort to develop a set of newer aluminum alloys with a minor amount of alloying additions such as Co, Sc and Zr to pure Al in order to achieve higher strength along with a reasonable tensile ductility and improved microstructural stability at elevated temperatures. The alloys were melted using vacuum arc melting and were produced in rectangular slabs by suction casting. The slabs were cold rolled at room temperature up to ~80% reduction followed by direct aging at two different temperatures of 375 °C and 450 °C for 24 h. The effects of alloying additions, cold rolling and subsequent thermal aging were investigated by detailed microstructural examination and tensile testing at room temperature. Microstructural analysis revealed that the alloy contained significant volume fraction of second phase particles such as Al9Co2, Al3Sc and Al3(Sc1?xZrx) and were preferentially distributed in supersaturated equiaxed cells of Al matrix. The existence of Al3(Sc1?xZrx) precipitates together with large fraction of Al9Co2 phase led to higher yield strengths of ~180–250 MPa and 17–20% tensile elongation. Electron backscattered diffraction observations showed equiaxed cells extensively deformed columnar grains and subgrain formation within the elongated grains in the rolling direction. The cold rolled plus aged samples exhibited a major fraction of rotated cube texture along with improved microstructural stability after high-temperature aging. This could be related to the existence of fine and stable Al9Co2 phase and Al3(Sc1?xZrx) precipitates, which control grain growth and thereby these alloys thermally stable at high temperatures.
查看更多>>摘要：? 2022 Elsevier B.V.Commercial graphite anodes show limited capacity in lithium-ion batteries, which inhibits the development of high-energy and high-power devices. Although the theoretical capacity of SnO2 based anodes is three times higher than that of graphite, their practical application is hindered by the poor cycling stability. In this study, we report a ball-milling assisted exfoliation method for the scalable production of delaminated MXene nanosheets, followed by the preparation of 5 nm SnO2 nanocrystals anchored on MXene nanosheets through a hydrothermal reaction. SnO2/MXenes nanocomposites exhibit long cycling life up to 1000 cycles with a high capacity of 904 mA h g?1, which can be ascribed to the high conductivity of the MXene substrates, and the anchoring effect between SnO2 nanoparticles and MXene sheets that can prevent crystal aggregation or collapse during cycling.
查看更多>>摘要：? 2022 Elsevier B.V.Hole transport materials play an essential role in the performance of perovskite detectors (PDs). Therefore, hole transport materials with excellent performance can significantly promote photoinduced holes' extraction rate and mobility. Spiro-OMeTAD, a small organic molecular material, has high solubility and excellent film-forming properties and is ideal for the hole transport layer (HTL) of photodetectors. In this work, a small amount of CsI is introduced into Spiro-OMeTAD together with Li-TFSI and TBP as additives. It is found that CsI and TBP formed a complex, which inhibited the agglomeration of Li-TFSI in Spiro-OMeTAD, thus preventing the rapid evaporation of TBP from leaving some cracks Spiro-OMeTAD. The photodetectors exhibit broadband response from near-ultraviolet to near-infrared (300–800 nm), achieving fast response (rise/fall time is 54.1/10.7 μs) and low dark current density (9.72 ×10?10 A cm?2). The detector can be self-powered at zero bias voltage, the external quantum efficiency (EQE) is 88%, the Responsivity (R) is 0.48 A W?1, and the detectivity (D*) is close to 2.7 × 1013 Jones. When the photovoltaic detector is placed in a nitrogen-filled glove box without special packaging for more than two months, the EQE remains 98.1% of the original. This study provides a simple method for fabricating a large area of high-performance planar PDs.
查看更多>>摘要：? 2022 Elsevier B.V.The effect of magnesium introduction on the structural, thermal, and luminescent characteristics of Zn2SiO4:Mn at the fixed magnesium concentration of 6 at% has been studied. Zn1.88–2xMn2xMg0.12SiO4 phosphors were synthesized by the solid phase method. The structural properties were studied using X-ray diffraction. The luminescent properties were characterized by the PLE and PL spectra. The charge state of manganese ions was determined by the XPS method. It was found that the Zn1.88–2xMn2xMg0.12SiO4 samples at x ≤ 0.14 were single-phase. The unit cell parameters of the solid solutions changed nonmonotonically with increasing x. The change in the linear trend of the parameters occurred at x = 0.06, and was caused by the oxidation of a part of the Mn2+ ions to Mn3+. The introduction of 6 at% magnesium into the Zn2–2xMn2xSiO4 structure caused an inversion of the crystallographic positions in which manganese was predominantly oxidized. It was shown that the melting temperatures of the Zn2–2xMn2xSiO4 and Zn1.88–2xMn2xMg0.12SiO4 solid solutions decreased with increasing manganese concentration, but were practically independent of the presence of magnesium. The structural phase transition α→β was recorded in the premelting region for all Zn2–2xMn2xSiO4 compositions. For the Zn1.88–2xMn2xMg0.12SiO4 solid solutions, the α→β transition was registered only for x?0.06. The optimal photoluminescence intensity of Zn2–2xMn2xSiO4 shifted to the region of lower values of x with the introduction of magnesium and turned out to be maximum for Zn1.76Mn0.12Mg0.12SiO4. The introduction of 6 at% magnesium reduced the decay time by almost a factor of two; for the sample with x = 0.06 the decay time was 0.654 ms.
查看更多>>摘要：? 2022 Elsevier B.V.Aqueous zinc-ion batteries (ZIBs) have been noted as promising large-scale energy storage systems owing to their cost-effective and environmentally friendly merits. However, the further development of ZIBs is limited by suitable cathodes, which normally suffer from the challengers of cathode dissolution, poor electronic conductivity, and low ion diffusion coefficient. Herein, we adopted a simpler, prone largescale preparation strategy of in situ polymerization at room temperature to prepare V2O5-polypyrrole (V2O5-PPy) nanobelt composite that the V2O5 act as an oxidant for pyrrole (Py) polymerization, and Py in situ polymerized on the V2O5. The V2O5-PPy nanobelt composite contributes to preventing the dissolution of vanadium elements, improving electronic conductivity, and forming oxygen vacancies (V?). As a result, an excellent initial discharge capacity of 441 mAh g?1 at 0.1 A g?1 and 291 mAh g?1 at a high current density of 5 A g?1 was realized. More importantly, a capacity retention rate of 95.92% after the long-term 2000 cycles at a high current density of 5 A g?1 was achieved. The capacitance control is dominant and accounts for 80.76% at 0.5 mV s?1, and the zinc ion diffusion coefficient during the cycle is 4.4 × 10?8-1.62 × 10?9 cm2 S?1, indicating good kinetics. Our work provides a feasible strategy for the large-scale fabrication of V2O5-PPy for ZIBs.
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