查看更多>>摘要：? 2022 Elsevier B.V.Annealing-induced hardening effect was studied in electro-deposited nanocrystalline Ni and NiFe thin films. Nanoindentation testing showed obvious hardening effect for all grain sizes in experiment, which were precisely controlled by adding Fe solutes. Contrast to the general trend in which the hardening effect monotonically increases with decreasing grain size, it enhanced firstly, peaking at a critical grain size (~ 16 nm) and then lowered. Based on the apparent inverse H-P trend and unusual enhancement of strain rate sensitivity after annealing, we attributed the weakened annealing-induced hardening phenomena, despite of the strongest grain boundary pinning effect resulted from the highest Fe solutes (up to 50 at%), mainly to the more pronounced grain-boundary mediated plasticity in extremely fine nanograins. This work contribute directly to understanding the distinct effect of alloying on mechanical properties of nanocrystalline metals.
查看更多>>摘要：? 2022 Elsevier B.V.The thermal stability and oxidation behavior of metastable W–Zr thin-film alloys with up to 83 at.% Zr were thoroughly investigated with a focus on the effect of gradual substitution of Zr for W. The films were prepared by dc magnetron co-sputtering of W and Zr targets in argon on unheated and unbiased substrates. The experiments showed that a supersaturated α-W(Zr) solid solution structure of as-deposited W-rich films with up to 19 at.% Zr is highly thermally stable up to 1200 °C in argon and the thermal stability of the W–Zr thin-film metallic glasses (33–83 at.% Zr) decreases with increasing Zr content. Nevertheless, the thermal stability of the W–Zr thin-film metallic glass with 33 at.% Zr reaches 1420 °C, which is very high value for binary metallic glass. The annealing of W-rich films (0–24 at.% Zr) in air leads to the formation of a protective surface oxide layer, which serves as a more effective oxygen diffusion barrier due to an increasing packing factor and amorphization with Zr addition. On the other hand, no protective surface oxide layer is grown during the annealing in air in the case of the W–Zr thin-film metallic glasses and the oxidation leads to the formation of compact, homogeneously oxidized substoichiometric W–Zr–O films with an amorphous structure and enhanced mechanical properties before reaching the final mass gain.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, five Ni-Co alloy catalysts (NiCo2-N, NiCo2-200, NiCo2-350, NiCo2-500, NiCo2-700) were prepared by the reduction of precursors, which came from different calcination temperatures. The catalyst characterization suggested that all these catalysts had different alloy structures. No calcination or calcination temperatures lower than 200 °C would generate Ni-Co alloy prone to collapse. However, catalysts would possess solid structures when these precursors were calcinated at 350, 500, or 700 °C. Moreover, the calcination temperature significantly affected the surface Ni/Co compositions on these catalysts and the H2 adsorption and activation capabilities of these Ni-Co alloy catalysts. Finally, when using benzene hydrogenation as a probe reaction, the catalyst activities were evaluated, and it's observed that NiCo2-350 catalyst, not only having a uniform Ni-Co alloy structure but pore structure on the surface of spherical particles, demonstrated the highest activity for benzene hydrogenation.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, the relationship between microstructural evolution and mechanical properties of a metastable β-ZrTiAlV alloy during compression was investigated. Microstructure characterization revealed that three different morphologies of α′ martensite, 101ˉ2 twinned α′ martensite, untwinned α′ martensite and α′ martensite paired were triggered at the initial deformation stage. With increasing deformation strain, these three kinds of α′ martensite undergo a process of widening and merging, and eventually form the 101ˉ2twin-related α′ domains, normal α′ domains and connected α′ domains, respectively. Mechanical properties test shows that the alloy exhibits a relatively high yield strength of 900 MPa and a high work hardening rate (about 6000 MPa) during compression. This high yield strength is attributed to the high triggering stress of deformation-induced β to α′ martensite transformation at initial deformation stage and the high solid solution strengthening effect of large amount Ti. The activation of α′ martensite and 101ˉ2 internal twins brings about the transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) effects, giving the alloy a substantial high work hardening rate, and their evolution with increasing strain leads to nonlinear evolution of the work hardening rate.
查看更多>>摘要：? 2022 Elsevier B.V.The reinforced light-harvesting capability, suppressed photocarrier recombination and increased specific surface area represented a possibility of excellent photocatalytic performance for graphitic carbon nitride (g-C3N4)-based photocatalysts. Herein, the porous 1,3,5-Trihydroxybenzene substituted g-C3N4 (denoted as PTBCN) composites with superior visible-light-driven photocatalytic properties were rationally constructed via a two-step reaction combination of freeze-drying and thermal-polymerization. The optimal PTBCN-2 achieved the maximum photocatalytic Rhodamine B (Rh B) degradation and H2O2 evolution rate constants, nearly 6.56 and 3.17 times higher than that of bare g-C3N4. The outstanding performances of PTBCN-2 were probably attributed to the extended specific surface area, robust visible light response, adjusted electronic band structure, accelerated separation and transfer of photocarriers as well as good hydrophilicity. As a result, the above integrated merits were directly responsible for the huge superoxide anion (?O2?) generation, which dominated the efficient photocatalytic reactions. This work provided a new idea to design and construct high efficiency porous aromatic ring substituted g-C3N4-related photocatalysts for organic pollutants degradation and H2O2 production.
查看更多>>摘要：? 2022The search for new high-performance dielectric materials has attracted considerable research interest. Several mechanisms to achieve high permittivity have been proposed, such as BaTiO3-based perovskites or CaCu3Ti4O12. However, developing high-performance thin films remains a challenge. Here, we propose a new material design route to achieve high permittivity behavior in atomically thin films. We present a concrete example of Dion–Jacobson-type KSr2-xBixNb3O10 and its cation-exchanged form HSr2-xBixNb3O10, which exhibits a stable colossal permittivity and low dielectric loss. In addition, Sr2(1?x)Bi2xNb3O10-δ nanosheets were obtained by chemical exfoliation, with a high dielectric permittivity of over 500—the highest among all known dielectrics in ultrathin films (<20 nm). The Bi substitution of Sr2Nb3O10 led to a two-fold increase in the dielectric permittivity owing to the higher polarizability of Bi ions. Our proposed method provides a strategy for obtaining new high-k nanoscale dielectrics for use in nanoscaled electronics.
查看更多>>摘要：? 2022In the present work, we have synthesized Nickel selenide@Molybdenum diselenide (NiSe@MoSe2) heteronanostructured arrays by a one-step hydrothermal method. The structural and optical analysis of nanopowder is done through Field emission scanning electron microscopy (FESEM), elemental mapping, Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV–vis, and Photoluminescence (PL) spectroscopy. XRD reveals the formation of a hexagonal structured system with a crystallite size of 166 nm. The bandgap of NiSe@MoSe2 nanosheets is found to be 1.71 eV, calculated from UV–vis spectra. FESEM showed the homogenous growth of NiSe@MoSe2 nanosheets while electronic transitions are investigated through PL. Further, the polymer nanocomposites of NiSe@MoSe2/PVA are synthesized by the ex-situ method at six different NiSe@MoSe2 concentrations in the PVA matrix. XRD shows good interaction between NiSe@MoSe2 and PVA polymer. The crystallinity increases as concentrations of NiSe@MoSe2 in PVA increases. FESEM shows the uniform distribution of NiSe@MoSe2 nanosheets in the PVA matrix. The two-terminal Ag/NiSe@MoSe2-PVA/FTO devices have been fabricated and characterized electrically by I-V measurements. I-V shows hysteresis behavior and also, bipolar switching is observed with a maximum Ion/Ioff ratio of ~103 at 2 wt. % NiSe@MoSe2 concentration in the PVA matrix. The good stability and reliability are checked through endurance and write-read-erase-read cyclic sequences. The obtained results open up the possibility of a next-generation non-volatile resistive switching memory device.
查看更多>>摘要：? 2022 Elsevier B.V.Photocatalysis is a reliable technology to treat polluted wastewater. Herein, we report S-scheme photocatalyst namely ZnS/CdS nanocomposites (NCs) with S-vacancies and interstitial defect states, immobilised on the polymer matrix of cellulose and chitosan. It showed significant performance in photocatalytic degradation of Rhodamine B (RhB) dye. Defect sites present in ZnS facilitates charge separation and two-photon excitation concomitantly with a bandgap shift in ZnS/CdS NCs to 2.65 eV and promotes visible light harvesting. XRD analysis demonstrated the highly crystalline nature of the NCs. TEM and SEM were used to observe the crystal phases, particle morphology and defect sites. XPS and EDAX ensured the composition and purity of the synthesized NCs. FTIR displayed the peaks representing the bonds present in metal sulphides and chitosan/cellulose matrix. The photodegradation of RhB by ZnS/CdS NCs reached a maximum of 99.18% in 120 min which displayed 6.8 and 10.25 times higher rate than pure ZnS and CdS respectively. Further, ZnS/CdS NCs was able to achieve the TOC reduction of 86% after the photodegradation of RhB. Defect engineering played a vital role in enhancing the photocatalytic activity of NCs. PL spectra revealed the prolonged life time of photogenerated charge carriers and EIS analysis was used to investigate the charge mobility of the fabricated materials. Superoxide radical was found to be the major radical involved in photodegradation of RhB by NCs. The degradation pathway of RhB was elucidated based on GC-MS/MS analysis. The recyclability of NCs was tested for six consecutive cycles and remarkable stability was observed. The results of in vitro cytotoxicity assay, and cellular reactive oxygen species generation suggest that ZnS/CdS NCs are safety photocatalysts to environment and human being.
查看更多>>摘要：? 2022 Elsevier B.V.Among a family of the multi-principle-element alloys, a high-entropy Cantor alloy attracts much attention due to the striking temperature dependence of strength properties, strong grain boundary hardening and the excellent low-temperature ductility. Cantor alloy is a substitutional concentrated solid solution, thus, its strength properties and strain hardening could be additionally enhanced by interstitial hardening. Here we explore the effect of nitrogen alloying with atomic concentrations of 0.8%, 1.4% and 1.6% on a temperature dependence (temperature range from 77 to 473 K) of the microstructure, mechanical properties, and fracture micromechanisms of FeMnCrNiCo alloy with the focus on low-temperature deformation regime. Nitrogen-alloying promotes the expansion of a crystal lattice with a linear increase of a lattice parameter of the alloy with nitrogen content, ?a/?CN = 0.625 pm/at%. Nitrogen-bearing FeMnCrNiCo(N) alloys possess stronger temperature dependence of a yield strength relative to the Cantor alloy, and nitrogen forces both athermal and thermal components of the stress. The solid-solution strengthening of Cantor alloy is proportional to the nitrogen concentration Δτ ~ CN, and the value (ΔYS/ΔCN) for the coarse-grained FeMnCrNiCo(N) alloys is a temperature-dependent parameter (ΔYS/ΔCN = 97 MPa/at% at RT and ΔYS/ΔCN = 146 MPa/at% at 77 K). Dislocation slip is a dominating deformation mechanism of the nitrogen-alloyed alloys along the whole range of the deformation temperatures. A decrease in test temperature and nitrogen-alloying both force the tendency to the planar slip and facilitate strain hardening. Despite a weak effect of nitrogen on a stacking fault energy of the Cantor alloy and high deforming stresses in FeMnCrNiCo(N) alloys, nitrogen-containing alloys show low activity of the mechanical twinning. Opposite effects of the nitrogen-alloying on the elongation of the Cantor alloy were found for different deformation regimes: positive at T > 250 K (elongation increases with nitrogen-alloying) and negative at T < 250 K (it decreases in nitrogen-bearing alloys). For FeMnCrNiCo(N) alloys, the appearance of the ductile-to-brittle transition in low-temperature deformation regime is associated with the brittle intergranular fracture of the specimens alloyed with nitrogen CN ≥ 1.4 at%.
查看更多>>摘要：? 2022 Elsevier B.V.A dual-band terahertz (THz) perfect absorber (PA) based on the all-dielectric metamaterial (MM) composed of the vertical-square-split-ring (VSSR) structure InSb array was proposed and investigated numerically. Simulation results show that the absorbance of the proposed PA under room temperature T = 295 K is up to 99.9% and 99.8% at 1.265 THz and 1.436 THz, respectively, which is consistent well with the fitting results of coupling mode theory (CMT). According to the simulated electric field and power loss density distributions, the perfect absorption results from the excitation of the first- and second-order plasmonic resonance mode. Further results show that the designed PA is polarization-insensitive due to the high geometric rotational symmetry, and wide-angle absorption can be achieved for transverse magnetic (TM) waves. The geometric parameters of the VSSR structure InSb and the external environment temperature can be changed to adjust the resonance absorption properties of the designed dual-band PA. The dual-band PA can be functioned as a temperature sensor with a sensitivity of about 5.9 GHz/K and 6.4 GHz/K, respectively. Furthermore, the dual-band PA under T = 295 K also can be served as a refractive index sensor with a sensitivity of about 1.3 THz/RIU and 1.0 THz/RIU, respectively. Due to its excellent properties including simple design, easy fabrication, polarization-insensitive and perfect absorption, the proposed dual-band PA may find many potential applications in detecting, imaging, and sensing in the THz region.
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