查看更多>>摘要：? 2022 Elsevier B.V.Additive manufacturing (AM) by electron beam melting (EBM) has many advantages over the laser-based AM techniques, but is subjected to a lower cooling rate and a long time thermal exposure with a much higher temperature. Therefore, the EBMed aluminum alloys commonly have coarser solidification structures such that lower mechanical properties compared to their SLMed counterparts. In this work, we proposed a strategy of introducing TiB2 particles into heat-resistant Al-Cu-Mg-Fe-Ni alloy to enhance the grain refinement and heat resistance for EBM fabrication. Applying a “presintering-densification” scanning strategy, near fully dense samples were build up with precise contours and good surface quality. The as-built EBMed TiB2/Al-Cu-Mg-Fe-Ni composite possessed a highly homogeneous microstructure with uniformly distributed TiB2 and Fe/Ni rich intermetallic particles. A fully equiaxed grain structure was achieved in the composite with a profoundly refined grain size of ~9 μm. The improved grain refinement effect was attributed to the sufficient activation of TiB2 particles as heterogeneous nuclei under a high cooling rate. Additionally, the solidified microstructure has shown an excellent thermal stability under ~500 °C during EBM process. The coexistence of thermal stable TiB2 and Fe, Ni-rich intermetallics at grain boundaries restricted the grain growth effectively. The as-built composite exhibited a high tensile strength of 253.4 MPa with an outstanding elongation of 13.5 %. After a T6-like heat treatment, the tensile strength was increased to 322 MPa with an elongation of 9.8 %. This study might shed a new light on designing high performance aluminum alloys/composites suitable for EBM technique.
查看更多>>摘要：? 2022 Elsevier B.V.Nanocrystalline Ni-Mo alloy coatings with excellent brightness, high hardness, and corrosion resistance were prepared. Nanocrystalline Ni-Mo alloy coating with a Mo content of 14.94 at% was electrodeposited on the copper foil substrate under the optimized conditions with the current efficiency of 51.64%. The electrodeposition behavior of Ni-Mo alloy coatings was studied by cathodic polarization curve and chronopotentiometry. Chronopotentiometry showed that the nucleation rate of Ni-Mo alloys can be accelerated with the increase of current density. Meanwhile, the cathodic polarization curves show that the additives can effectively inhibit the electrodeposition of Ni-Mo alloys. The (2 0 0) and (2 2 0) diffraction peaks of Ni gradually disappeared and the grain size gradually decreased with the increase of Mo content in the alloy coating according to XRD and TEM analysis. Scanning electron microscope (SEM) and confocal microscope observation results show that the coating becomes smoother and denser with the increase of Mo content when Mo content was lower than 14.94 at%, after which the density of the coating saw a decline due to the intensified hydrogen evolution reaction. The microhardness results of the alloy coating show that the microhardness of the alloy coating is related to the solid solution strengthening, texture evolution, and plastic deformation of the alloy. Meanwhile, the alloy coating has a Hall-Petch relationship and inverse Hall-Petch relationship, and the critical grain size is 5.5 nm. The corrosion resistance of Ni-Mo alloy coating is better than that of pure Ni coating, and the corrosion resistance is optimal when the Mo content is about 15 at%. In addition, in the plating solution containing additives, the deposited Ni-Mo alloy coating is smoother and denser, and the hardness and corrosion resistance of the alloy coating is also greatly improved.
查看更多>>摘要：? 2022 Elsevier B.V.The influence of Ca element on the primary θ-Al2Cu and eutectic (θ-Al2Cu+α-Al) microstructure in Al-40wt% Cu hypereutectic alloy was investigated. The results showed that the Ca can significantly improve the size and morphology of primary θ-Al2Cu, which was mainly attributed to the enrichment of Ca atoms in the front of solid-liquid interface during solidification. The enrichment of Ca can hinder the stacking of solute atoms, which impeded the radial growth, so as to make the θ-Al2Cu transform from angular planar grains into equiaxed grains with fine size. In addition, the enrichment of Ca also prevented the stacking of solute atoms at spiral dislocation steps during the axial growth. The decrease of eutectic spacing was mainly attributed to the increase in undercooling. Compared with the tensile strength of unmodified Al-40Cu alloy, the tensile strength of Al-40Cu alloy was enhanced by adding 0.6 wt% Ca which increased from 81.21 MPa to 144.80 MPa. In addition, the fracture elongation increased from 2.3% to 4.48%. The improvement of morphology of primary θ-Al2Cu phase was the basic reason for the enhancement of mechanical properties of Al-40Cu alloy.
查看更多>>摘要：? 2022Rechargeable magnesium batteries (RMBs) can meet the urgent demand for large-scale energy storage systems due to their high volumetric energy density, safety, and low cost. RMB development requires the exploitation of cathode materials with high specific capacities and potentials. Layered VO2 is a promising cathode material for RMBs due to its high capacity (>200 mAh g?1) and high voltage (>1.5 V). However, the diffusion kinetics of Mg2+ in the VO2 host are sluggish, which results in poor electrochemical performance. In this study, a VO2/graphene oxide (VO2/GO) composite was constructed via a facile ultrasonication method combined with freeze drying as a cathode material for rechargeable hybrid Mg2+/Li+ batteries (HMLBs). The VO2/GO cathode material has a high discharge capacity (261.7 mAh g?1 at 20 mA g?1), significant discharge platform (above 1.75 V), and satisfactory cycling capacity. The capacity retention of the cathode was maintained at 83% after 200 cycles at 100 mA g?1. Ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements were used to study the Mg2+ storage mechanism of the VO2/GO electrode during the charging and discharging processes.
查看更多>>摘要：? 2022 Elsevier B.V.Designing and fabricating outstanding electrocatalysts for anodic oxygen evolution reaction plays a key role in driving the earlier application of water splitting for large-scale hydrogen production. Surface/interface engineering is regarded as the most effective method for activating the active sites and modulating the electronic structure, which are two crucial factors determining the electrocatalytic performance. Herein, amorphous CoMn LDH ultrathin nanosheets doped by Ir are integrated with low-crystalline NiMoO4 nanorods (Ir-NiMoO4/Ir-CoMn LDH) to fabricate advanced hierarchical OER electrocatalysts. The optimized Ir-NiMoO4/Ir-Co3Mn2 LDH exhibits excellent OER performance as attested by an ultralow overpotential of 221 mV at the current density of 10 mA cm?2, as well as superb long-term durability. The intimate interface between NiMoO4 and Co LDH and modified electronic structure induced by Ir and Mn doping can greatly optimize the binding strength of between active sites and intermediated species, which improves the electrocatalytic OER performance. This study manifests how the synergistic surface/interface engineering design of nanomaterials boosts their catalytic activity.
查看更多>>摘要：? 2022 Elsevier B.V.We report a 220 keV Ag ion beam irradiation-induced modifications of thin films of fullerene C60 containing gold (Au) nanoparticles. Nanocomposite thin films of Au-C60 were synthesized using a thermal co-deposition technique on a glass substrate. The as-deposited (pristine) thin films were irradiated by 220 keV Ag ion beam at different fluences ranging from 1 × 1013 ions/cm2 to 3 × 1016 ions/cm2 utilizing a low energy ion accelerator. The optical properties of pristine and irradiated thin films of Au-C60 were investigated using UV–visible spectroscopy. A redshift in the Surface Plasmon Resonance (SPR) wavelength from ~ 598–775 nm was obtained with increasing fluence up to 1 × 1014 ions/cm2, which indicated the growth of Au nanoparticles in the fullerene matrix due to ion irradiation. It was further confirmed by High-Resolution Transmission Electron Microscopy (HRTEM). With further increase in fluence, a blue shift from ~ 775–570 nm was obtained at a fluence of 1 × 1016 ions/cm2. The transformation of fullerene C60 into amorphous carbon (a:C) with increasing fluence of Ag ion beam was the main cause of this blue shift which was further confirmed by Raman spectroscopy. An increase in surface grain size with ion fluence was observed by Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscope (FESEM). The X-ray Photoelectron Spectroscopy (XPS) measurements were used for the chemical state analysis of the nanocomposite thin films before and after irradiation. The current-voltage measurements confirm the increase in the conductivity of the nanocomposite films with the fluence due to its transformation in carbon at higher fluences. The control on the size of Au nanoparticles and tuning of SPR wavelength by low energy ion irradiation may enhance the applicability of Au-C60 nanocomposite in organic solar cell.
查看更多>>摘要：? 2022 Elsevier B.V.For the first time we demonstrated the superiority of the mixture of monometallic compounds over the bimetallic ones for the use in luminescence thermometers in terms of temperature sensitivity. This was derived analytically and confirmed experimentally using a pair of composites 20[4Tb(Bz)3Phen+ 1Eu(Bz)3Phen]:80PS and 20Tb0.995Eu0.005(Bz)3Phen:80PS with identical spectra at the room temperature (Bz – benzoate, Phen – o-phenanthroline, PS – polystyrene). The tests within the range of 30–200 °C revealed that the temperature sensitivity of the 20[4Tb(Bz)3Phen+ 1Eu(Bz)3Phen]:80PS is higher at each temperature point than the sensitivity of the 20Tb0.995Eu0.005(Bz)3Phen:80PS, reaching Srmix=4.8%/℃ and Srbim=3.0%/℃, correspondingly, in accordance with the analytical description.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, we report the simple and cost-effective synthesis of α-MoO3 microbelts with side lengths on the centimeter or millimeter scale by one-step sintering using MoO3 powder. Transparent and flat microbelts revealing (0k0) plane facets cleaved preferentially along the [001] direction are formed without the use of supporting substances in air. Atomic force microscopy and high-resolution transmission electron microscopy analyses confirm that a single-crystal microbelt composed of stacked bunches of α-MoO3 sheets is synthesized. The effect of the synthesis conditions on the structure and size of the α-MoO3 microbelts is systematically investigated by varying the residual time during sintering and the amount of the source powder. Finally, we demonstrate the electrochemical properties of the single-crystal α-MoO3 microbelt in an acidic solution; the microbelt exhibits a variation in transmittance with the application of a potential, implying that it is electrochromic and possesses ion-storage capacity, making it promising for application in supercapacitors. Our study proposes a novel and facile method for the large-scale preparation of α-MoO3 microbelts, which will open up new avenues in the field of electrochemical devices.
查看更多>>摘要：? 2022 Elsevier B.V.The study describes a concise and eco-friendly approach for synthesising nano ZnO (nZnO) particles using raw Garcinia Cambogia fruit pulp extract. The remarkable crystallinity, purity, and hexagonal wurtzite structure of nZnO are established by X-ray diffraction (XRD) analysis. The formation of almost spherical nZnO with an average diameter of 32.8 nm is revealed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The Fourier Transform Infrared (FTIR) spectrum of nZnO outlines the synthesis mechanism. The recombinations of free excitons and oxygen vacancies are responsible for the peaks in the photoluminescence (PL) spectra. UV-Visible Diffuse reflectance spectroscopy (UV-Vis DRS) revealed that the optical bandgap of nZnO is 3.24 eV. nZnO exhibited excellent photocatalytic activity against the degradation of cationic and anionic dyes. The effects of process parameters on the extent of dye removal, such as photocatalyst quantity, solution pH, and time of irradiation, were investigated. The photocatalytic degradations of dyes were modelled by pseudo-first order kinetics, having a strong correlation coefficient (R2>0.95). Statistical assessments of dye degradation using Analysis of Variance (ANOVA) and Least Significant Difference (LSD) were conducted. Antibacterial studies show that nZnO has a substantial bactericidal effect against pathogenic bacteria. Consequently, the green synthesised nZnO might be utilised to eliminate dyes and bacteria from industrial effluent water in an environmentally benign and cost-effective way.
查看更多>>摘要：? 2022 Elsevier B.V.The tuned crystal structure and electrical properties of metal alloy nanoparticles can vary their catalytic capabilities. In the present study, hexagonal close-packed (hcp) ZnCo nanoalloy enclosed in N-doped carbon (hcp-ZnCo@NC) are created using a simple fabrication approach and are characterized via various complementary techniques. The fabricated hcp-ZnCo@NC shows remarkable oxygen evolution reaction (OER) performance in alkaline conditions (1 M KOH). The synthesized hcp-ZnCo@NC with Zn/Co ratio of ≈ 1:1 exhibits overpotentials of 282 mV at a current density of 10 mA cm?2 with a smaller tafel slope of 51.9 mV dec?1, and good stability of 30 h. These characteristics of the present material are better when compared with the state of the art. The enhanced efficiency of the hcp-ZnCo@NC is because of its favorable electron transfer characteristics and high conductivity. Hence, this study offers a new perception for future applications due to the unique crystal phase-linked electrical properties.
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