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Effect of pre-existing nuclei on crystallization during laser welding of Zr-based metallic glass
摘要： In this study, experiments are carried out in laser welding of a Zr-based (Zr52.5Ti5Al10Ni14Cu17.9) bulk metallic glass (BMG), pre-existing nuclei nucleus density has significant influence on its crystallization behavior. Based on the classical nucleation/growth theory, it is concluded that a small amount of pre-existing nuclei in a BMG can shift the time-temperature-transformation (TTT) curve from a well-known ‘C-shape’ to a ‘ε-shape.’ This result provides fundamental understanding on why the shape of the TTT curve for a heating process is different from that for a cooling process for the same BMG. Two quality factors were defined as a measure of the effect of pre-existing nucleus density. By integrating the classical nucleation/growth theory with the heat transfer model, the evolution of crystalline phase during laser welding for a BMG with pre-existing nuclei was studied, and the modeling predictions compared favorably with the experimental results.
关键词： Crystallization,Nucleation and growth,Laser processing,Metallic glasses,Amorphous alloys
更新于2025-11-28 14:24:20
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Ultrafine Cu2O/CuO nanosheet arrays integrated with NPC/BMG composite rod for photocatalytic degradation
摘要： A free-standing Cu2O/CuO@nanoporous copper/bulk metallic glass (Cu2O/CuO@NPC/BMG) composite rod with a multimodal hierarchical porous structure has been successfully prepared by a facile two-step synthesis strategy consisting of dealloying and anodizing. The NPC/BMG composite is first fabricated by dealloying of Cu50Zr45Al5 BMG rod. Then the ultrafine Cu2O/CuO nanosheet arrays are synthesized by anodizing of the NPC/BMG rod followed by heat treatment. The as-obtained Cu2O/CuO@NPC/BMG composite possesses a multimodal hierarchical porous structure comprising interconnected pores ranging from micro, meso to macro sizes. It is worth pointing out that there are several “barren lands” without nanosheets grown on the surface of the composite. Further analyses indicate that the microstructures of substrate materials not only dominate the sizes of Cu2O/CuO sheets, but also influence the nucleation and growth of Cu2O/CuO sheets. Meanwhile, the possible formation mechanism of the Cu2O/CuO nanosheets is proposed. Accordingly, the Cu2O/CuO@NPC/BMG composite shows remarkably high photocatalytic degradation performance and excellent cycling stability for RhB due to the multimodal hierarchical porous structure, ultrafine Cu2O/CuO nanosheets in the entire NPC and the integration design strategy.
关键词： Metallic glass,Dealloying,Nanoporous,Anodizing,Nanosheet
更新于2025-11-14 17:03:37
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Reactive Mechanism of Cu2ZnSnSe4 Thin Films Prepared by Reactive Annealing of the Cu/Zn Metal Layer in a SnSex + Se Atmosphere
摘要： Cu2ZnSnSe4 (CZTSe) thin films were prepared by a two-step process with the electrodeposition of a Cu/Zn metallic stack precursor followed by a reactive anneal under a Se + Sn containing atmosphere. We investigate the effect of the Sex and SnSex (x = 1,2) partial pressures and annealing temperature on the morphological, structural, and elemental distribution of the CZTSe thin films. Line scanning energy dispersive spectroscopy (EDS) measurements show the presence of a Zn-rich secondary phase at the back-absorber region of the CZTSe thin films processed with higher SnSex partial pressure and lower annealing temperatures. The Zn-rich phase can be reduced by lowering the SnSex partial pressure and by increasing the annealing temperature. A very thin MoSe2 film between the CZTSe and Mo interface is confirmed by X-ray diffraction (XRD) and grazing incidence X-ray diffraction (GIXRD) measurements. These measurements indicate a strong dependence of these process variations in secondary phase formation and accumulation. A possible reaction mechanism of CZTSe thin films was presented. In a preliminary optimization of both the SnSex partial pressure and the reactive annealing process, a solar cell with 7.26% efficiency has been fabricated.
关键词： Sex and SnSex (x = 1,2) partial pressures,annealing temperature,metallic stack precursor,Cu2ZnSnSe4 (CZTSe),electrodeposition
更新于2025-11-14 15:15:56
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The <i>h</i> -Sb <sub/>x</sub> WO <sub/> 3+2 <i>x</i> </sub> Oxygen Excess Antimony Tungsten Bronze
摘要： The previously unreported oxygen excess hexagonal antimony tungsten bronze is reported, with a composition of Sb0.5W3O10, in the following denoted as h-SbxWO3 + 2x with x = 0.167, to demonstrate its analogy to classical AxWO3 tungsten bronzes. This compound forms in a relatively narrow temperature range between 580 8C < T < 620 8C. It was obtained as a dark-blue polycrystalline powder, and as thin, needle-shaped, blue single crystals. h-SbxWO3 + 2x crystallizes in the hexagonal space group P6/mmm with the cell parameters a = 7.4369(4) (cid:2) and c = 3.7800(2) (cid:2). The antimony and excess oxygen occupy the hexagonal channels within the network of corner-sharing WO6 octahedra. h-SbxWO3 + 2x has a resistivity of 1300 K (cid:2) 1.28 mW cm at room temperature, with little if any temperature-dependence on cooling. DFT calculations on a simplified model for this compound find a metallic-like electronic structure with the Fermi level falling within rather flat bands, especially around the G point.
关键词： hexagonal bipyramids,metallic oxide,tungsten,antimony,bronze
更新于2025-09-23 15:23:52
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Design and fabrication of the ultrathin metallic film based infrared selective radiator
摘要： Selective radiators have received considerable research attention and been extensively applied in many areas, such as thermophotovoltaic systems, infrared cloaking and sensing. Herein, the design of the infrared selective radiator based on ultrathin metallic films was fully demonstrated. From the discussions on the radiative characteristic and growth law of the metallic film, it has been concluded that a continuous ultrathin metallic film can behave as a thermal radiation enhancer. Taking the radiative cooling technology as the application background, a multilayered broadband selective radiator, consisting of an ultrathin Ag film and dielectric Ge films is designed and fabricated. The proposed radiator, which can radiate selectively in the 8–13 μm atmospheric transparency window (ε5–8 μm = 0.21; ε8–13 μm = 0.84; ε13–25 μm = 0.39), achieves an average temperature reduction of 3.5 °C under outdoor conditions and exhibits potential application in radiative cooling technology. Moreover, for our proposed selective radiator, flexible tuning of radiative characteristics can be achieved via structural design, which paves the way for its application in various areas. Unlike the common metamaterial based thermal radiator, our selective radiator with a planar structure is free from the complicated process of lithography or etching and is scalable to realize large-area fabrication and application.
关键词： Structural design,Radiative cooling,Selective radiator,Ultrathin metallic film
更新于2025-09-23 15:23:52
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Manipulation of Charge Transport by Metallic V <sub/>13</sub> O <sub/>16</sub> Decorated on Bismuth Vanadate Photoelectrochemical Catalyst
摘要： Conductive metal oxides represent a new category of functional material with vital importance for many modern applications. The present work introduces a new conductive metal oxide V13O16, which is synthesized via a simplified photoelectrochemical procedure and decorated onto the semiconducting photocatalyst BiVO4 in controlled mass percentages ranging from 25% to 37%. Owing to its excellent conductivity and good compatibility with oxide materials, the metallic V13O16-decorated BiVO4 hybrid catalyst shows a high photocurrent density of 2.2 ± 0.2 mA cm?2 at 1.23 V versus reversible hydrogen electrode (RHE). Both experimental characterization and density functional theory calculations indicate that the superior photocurrent derives from enhanced charge separation and transfer, resulting from ohmic contact at the interface of mixed phases and superior electrical conductivity from V13O16. A Co–Pi coating on BiVO4–V13O16 further increases the photocurrent to 5.0 ± 0.5 mA cm?2 at 1.23 V versus RHE, which is among the highest reported for BiVO4-based photoelectrodes. Surface photovoltage and transient photocurrent measurements suggest a charge-transfer model in which photocurrents are enhanced by improved surface passivation, although the barrier at the Co–Pi/electrolyte interface limits the charge transfer.
关键词： charge transport,bismuth vanadate,Co–Pi passivation,water oxidation,metallic V13O16
更新于2025-09-23 15:23:52
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Vacancy-Driven Robust Metallicity of Structurally Pinned Monoclinic Epitaxial VO <sub/>2</sub> Thin Films
摘要： Vanadium dioxide (VO2) is a strongly-correlated material with 3d-electrons, which exhibits temperature-driven insulator-to-metal transition with a concurrent change in the crystal symmetry. Interestingly, even modest changes in stoichiometry-induced orbital occupancy dramatically affect the electrical conductivity of the system. Here, we report a successful transformation of epitaxial monoclinic VO2 thin films from a conventionally insulating to permanently metallic behavior by manipulating the electron-correlations. These ultrathin (~10 nm) epitaxial VO2 films were grown on NiO (111)/Al2O3 (0001) pseudomorphically, where the large misfit between NiO and Al2O3 were fully relaxed by domain matching epitaxy. Complete conversion from an insulator to permanent metallic phase is achieved through injecting oxygen vacancies (x~0.20±0.02) into the VO2-x system via annealing under high vacuum (~5x10-7 Torr) and elevated temperature (450 oC). Systematic introduction of oxygen vacancies partially converts V4+ to V3+ and generates unpaired electron charges which result in the emergence of donor states near Fermi level. Through the detailed study of the vibrational modes by Raman spectroscopy, hardening of the V-V vibrational modes and stabilization of V-V dimers are observed in vacuum-annealed VO2 films providing conclusive evidence for stabilization of monoclinic phase. This ultimately leads to convenient free-electron transport through the oxygen-deficient VO2-x thin films resulting in the metallic character at room temperature. With these results, we propose a defect engineering driven pathway through the control of oxygen vacancies to tune electrical and optical properties in epitaxial monoclinic VO2.
关键词： Defect engineering,Oxygen Vacancy,Metallicity,Mott transition,Metallic monoclinic VO2,Charge doping
更新于2025-09-23 15:23:52
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Photocatalytic toluene degradation over Bi-decorated TiO2: Promoted O2 supply to catalyst’s surface by metallic Bi
摘要： In the photocatalytic volatile organic compounds (VOCs) degradation, the accumulation of intermediate products on the surface of catalysts could cause a decrease in activity through retarding reactant (e.g. O2) supply to surface active sites. Herein, Bi decorated TiO2 photocatalysts (Bi/TiO2) for photocatalytic toluene degradation were prepared and systematically studied. It is found that metallic Bi modification improves the ability of photocatalysts to capture O2. As a result, the activities of the Bi/TiO2 photocatalysts are obviously higher than that of the TiO2 for photocatalytic toluene degradation, and the productions of photogenerated reactive oxygen species (O2? and H2O2) over the Bi/TiO2 photocatalysts are almost equal to that over the TiO2 despite the fact that the separation efficiency of photoinduced charge carriers is decreased after the addition of Bi. Adsorbed benzaldehyde is the main surface intermediate on the surface of the Bi/TiO2 photocatalysts, whereas plenty of more readily oxidized aliphatic carboxylate species was monitored on the surface of the TiO2, which can be attributed to insufficient O2 supply to the TiO2 surface. This further indicates the positive role of the promoted O2 supply by Bi in the photocatalytic toluene degradation. The present work offers a new window for addressing the catalyst deactivation in the photocatalytic VOCs degradation.
关键词： The uptake of O2,Intermediate products,Metallic Bi,Photocatalytic VOCs degradation
更新于2025-09-23 15:22:29
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Metallic Nanostructures for Multispectral Filters
摘要： A metal-dielectric-metal structure with cross-shaped-hole array in metal thin films is studied for plasmonic multispectral filters, which covers visible to near-infrared wavelengths. Surface plasmons are induced from incident wave by a periodic array of nanostructures, then the localized surface plasmon polaritons oscillate in the cavity, which is formed by the two layers of metals through near-field excitation. The transmission spectrum of the metal-dielectric-metal structure with cross-shaped-hole array is investigated with the finite-difference time-domain method; our simulations show that the features of the hole, and the refractive index and the thickness of the dielectric layer all affect the optical spectral performance. This metal-dielectric-metal structure provides additional flexibility in tuning transmission spectrum due to its Fabry-Perot cavity property. Our study shows that it is possible to obtain desired multispectral filters by programming the refractive index and thickness of the dielectric layer, and these parameters of the metallic structures.
关键词： Surface Plasmon,Metallic Nanostructures,Multispectral Filters
更新于2025-09-23 15:22:29
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Multisegmented Metallic Nanorods: Sub-10 nm Growth, Nanoscale Manipulation, and Subwavelength Imaging
摘要： Multisegmented metallic nanorods (MS-M-NRs) have attracted increasing attention thanks to their integrated structures and complex functions. The integration of nanoscale segments in 1D enables maximum exposure of each segment and enhanced interaction between adjacent segments. Such structural integration will induce functional complexity in the nanorods, leading to superior properties for the individual components. Herein, recent progress on the development of MS-M-NRs is reviewed. Their precise fabrication, nanoscale manipulation, and subwavelength imaging, as well as simultaneous manipulation and imaging are discussed, respectively. Specifically, precise fabrication of MS-M-NRs focuses on porous anodic alumina (PAA) templated electrodeposition, which enables sub-10 nm growth of the segments and their interfaces/fronts. Nanoscale manipulation of MS-M-NRs introduces the fundamental methods that are employed for delicate movement control on the nanorods through internal or external stimulations. Subwavelength imaging of MS-M-NRs highlights the achievements on identification and location of constituent nanoscale segments/gaps based on their differences and interactions. Simultaneous manipulation and imaging of MS-M-NRs addresses the significance and potential applications of the nanorods with magnetic–plasmonic dual modulation. The development of MS-M-NRs will greatly contribute to materials science and nanoscience/nanotechnology.
关键词： metallic nanorods,porous anodic alumina (PAA),electrodeposition,imaging,manipulation
更新于2025-09-23 15:22:29