查看更多>>摘要：? 2022 Elsevier B.V.Recently, rare-earth doped phosphors have been newly developed and applied in hot issues such as phosphor-converted light-emitting diodes (pc-LEDs), anti-counterfeiting, and fingerprint visualization. Herein, an Eu3+-activated CaGdSbWO8 (CGSW) red phosphor was synthesized by a high-temperature solid-state reaction. The phosphors can exhibit narrow red-light emission at 614 nm due to the electric dipole transition 5D0→7F2 of Eu3+. Impressively, this phosphor has excellent thermal stability, its emission intensity of optimum sample doped with 0.30 Eu3+ remained 90.61% at 420 K and thermal quenching temperature exceeds 480 K. The Commission International del'Eclairage (CIE) chromaticity coordinates of CGSW:0.30Eu3+ are (0.662, 0.338) with a high color purity (98.5%). The fabricated white light diode (w-LED) has a high color rendering index (91.4) and a low correlated color temperature (4986 K) with CIE coordinates (0.343, 0.327). Further experimental results showed that the prepared security ink can be applied to anti-counterfeit labels and information encryption. The latent fingerprint developed by CGSW:0.30Eu3+ phosphor present the excellent selectivity and contrast. The level 1–3 structural characteristics of latent fingerprints could be well identified under ultraviolet irradiation. Therefore, the Eu3+-activated CGSW red-emitting phosphor has broad application prospects due to its excellent luminescence properties.
查看更多>>摘要：? 2022 Elsevier B.V.Strontium titanate (STO) is one of the important members of the perovskite family and has a wide range of applications in optoelectronics. In this study, the rectifying properties of the heterojunction produced by gold (Au) decorated STO were investigated. Morphological and structural characterization of Au-STO material coated as a thin film, such as SEM, TEM, XRD was performed and the results showed that this structure is a suitable material for heterojunction structures. Current-voltage (I-V) measurements of Ni/Au-STO/n-Si heterojunction devices obtained by coating the Si surface with the spin coating method of Au-STO were performed in the dark and between 60 and 400 K. Additionally, capacitance-voltage (C-V) measurements of the device were made under the same conditions and between 80 and 360 K. Basic diode parameters such as ideality factor (n), barrier height (Фb), series resistance (Rs) were determined from the I-V characteristic of the device using Thermionic emission (TE), Cheung and Norde functions. According to the TE method, the ideality factor of the device was calculated as 1.12 and the barrier height was 0.65 eV at 300 K. The obtained results showed that the Ni/Au-STO/n-Si heterojunction has rectifying properties. In all three calculation methods, as the application temperature increased, the ideality factor of the device decreased and on the other hand, the barrier height increased. This change showed the temperature sensitivity of the Au-STO/n-Si junction.
查看更多>>摘要：? 2022 Elsevier B.V.We report the synthesis, structural, magnetic, electrical transport, magnetoelectric and thermoelectric properties of ″112″-layered double perovskite Y1?xLnxCo2O5.5 (Ln = Sm, Eu and Gd; x = 0, 0.5 and 1) cobaltites. YBaCo2O5.50 exhibits simultaneous structural, magnetic and electrical transitions around 300 K. Whereas LnBaCo2O5.50 (Ln = Sm, Eu and Gd) exhibit well separated TC and TIM, respectively, below and above 300 K. It is expected from the chemical viewpoint that the substitution of Ln by Y in LnBaCo2O5.50 should result in proximity of TC and TIM. However, our investigation demonstrates that though TC shows significant upward shift, TIM exhibits robustness. This suggests that the electrical and magnetic transitions are decoupled. The large MR [(ρH-ρ0)/ρ0] values (~50%) at low temperatures are observed for Eu and Gd-phases. The low temperature electrical conduction mechanism is of variable range hopping (VRH) type and the thermoelectric properties suggest the p-type polaronic conductivity or hole like carriers in the samples. The observed results can be understood in the framework of electronic phase separation and the metal-insulator transition from viewpoint of structural transition instead of the spin state transition.
查看更多>>摘要：? 2022 Elsevier B.V.A novel structure for Li/Na hybrid-ion batteries with unique two-stage electrochemical reactions is proposed, using nonstoichiometric Li2.7V2.1(PO4)3/C materials as the cathode and Na foil as the anode with a Li-ion electrolyte. A discharge specific capacity of 132.99 mAh·g?1 is delivered at a current density of 100 mA·g?1 in the range of 2.5–4.2 V. Besides, when the current density increases to 1000 mA·g?1, the specific density can reach a value of 108.50 mAh·g?1, which indicates superior rate performance. After 800 cycles, a discharge capacity of 87.11 mAh·g?1 is still observed at 1000 mA·g?1 in a voltage range of 3.0–4.3 V, maintaining a retention rate of 80.42%. This simple design strategy for Li/Na hybrid-ion batteries harvests the synergetic contribution of Li+ and Na+ ions and provides an efficient solution to further improve hybrid-ion battery performance.
查看更多>>摘要：? 2022 Elsevier B.V.Refractory high-entropy alloys (RHEAs), which exhibit excellent mechanical properties at room temperature and high temperature, have received widespread attention. The TiZrHfNbTa alloy is one of the few refractory high-entropy alloys with tensile ductility. Alloying means is a common method to optimize the special properties of alloys. Here, a series of TiZrHfNbTaWx (x = 0–1) RHEAs were synthesized by arc melting technique. It showed that the fracture plasticity of the RHEAs changed from ＞50% of the TiZrHfNbTa to 20.7% of the TiZrHfNbTaW, and the yield strength increased from 1064 MPa of the TiZrHfNbTa to 1726 MPa of the TiZrHfNbTaW. In addition, The TiZrHfNbTaWx RHEAs predominantly consisted of a single random solid solution phase with body-centered cubic (BCC) crystal structure. The present result indicated that W addition could effectively enhance the strength of the TiZrHfNbTa alloy, while maintaining high plasticity. Finally, a simple solid solution strengthening theoretical model was proposed to explain the high yield strength, and the experimental values were in good agreement with the theoretical values.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, a new grade of Inconel 718 alloy (IN718) strengthened by nano-oxides has been designed and produced. The alloy composition of 0.3 wt% Y2O3 – IN718 has been determined using CALPHAD-based thermochemical modeling approach. Designed ODS-IN718 alloy is produced by Selective Laser Melting (SLM) method with various power and velocity values to determine the best process parameters for this system. The SLM parameters are optimized for the production of ODS-IN718 alloy. To dissolve the non-equilibrium phases, which are detrimental to the mechanical properties, and maximize the number densities of nano-oxide and other strengthening phases of γ'/γ″, various heat treatment processes are applied based on the thermochemical calculations. The samples which are solutionized at 1050 °C for 1 h followed by aging at 650 °C for 5 h exhibit the best microstructural and mechanical properties. Tensile tests demonstrate that the strength and ductility of the solutionized and aged samples are much improved compared to the standard solutionized and double aged samples due to the fine and uniform microstructure, especially at elevated temperatures. It is observed that experimental results are consistent with the thermochemical modeling calculations. This clearly shows the promise of thermochemical calculations incorporating various databases for designing new alloy systems with nano-oxide strengthening.
查看更多>>摘要：? 2022 Elsevier B.V.As a development of an earlier attempt to determine the concentration of mobile carbon atoms in the ferrite phase in dual-phase (DP, ferrite + martensite) steels by means of mechanical loss measurements, which was made on binary Fe-C alloys [Honda et al., Solid State Phenom. 184 (2012) 87–91], we have investigated effects of Mn and Si on the mechanical loss profiles, aiming at establishing a method for quantitatively evaluating the distribution of carbon in practical DP steels. First we re-examined the effects of Mn and Si on the relation between the strength of the Snoek relaxation and the concentration of carbon in iron by measuring the mechanical loss of solution-treated, single-phase ferrite samples of dilute Fe-Mn-C and Fe-Si-C alloys. We then measured mechanical loss of ferrite + martensite two-phase alloys of various carbon contents, after equilibrating at a temperature where the material consists of ferrite and austenite, and then quenching. The concentrations of carbon in solution in the ferrite phase can be estimated from the observed magnitude of the Snoek relaxation peak, using the linear relation obtained in the first set of experiments, and correcting for the volume fraction of the ferrite phase. These estimates agree reasonably well with those expected from the compositions expected from the ternary phase diagrams, as in the previous case of simple Fe-C alloys. This renders the basis for determining the carbon concentration in the ferrite phase by measuring mechanical loss of DP steels with alloying elements. As another development, the properties of the characteristic mechanical loss due to the martensite phase have been studied. The mechanical loss, which steadily increase above room temperature, turned out to exhibit a maximum at 480–500 K. It is found to be a thermally activated relaxation, with the following parameters of the relaxation time: pre-exponential factor τ0 ? 10?14 s and activation energy E ? 1.2 eV. However, its magnitude does not show a simple linear relation with the carbon content, unlike the case of the Snoek relaxation in ferrite.
查看更多>>摘要：? 2022 Elsevier B.V.CoCrNi medium entropy alloys (MEAs) are promising candidates for high- temperature application, but their structural stability and mechanical properties during long-term service are still an open question. This work comprehensively investigated the microstructure and mechanical properties at both room and high temperatures of CoCrNi MEAs after being aged for 500 h at 850 °C. It has been shown that the long-term aged CoCrNi MEA has held a single γ phase, a nanoparticulate and discontinuous block γ′ phase, and η-Ni3(Ti,Ta) phase in acicular Widmanst?tten, cellular and rod-like shapes with the addition of Al, Ti, and Ta. Long-term aged CoCrNi MEAs hold same levels (or sometimes slightly weaker levels) of room- and high-temperature strengths as those MEAs under the standard heat treatment. Specifically, CoCrNi MEA with 2%Al, 2%Ti, and 1%Ta presents an ultimate strength of 1012 MPa at room temperature and a yield strength of 695 MPa at 700 °C. Surprisingly, all of the relevant long-term aged MEAs exhibit superior plasticity to that under standard heat treatment. The anomalous mechanical properties are firstly attributed to the γ' phase precipitation. Next, η phase plays an important role in strengthening, improving or at least harmless plasticizing effect since the η phase has the preferential orientation relationship of [011]γ//[2110]η, {111}γ//{0001}η with the γ matrix. It has been confirmed that the strengthening mechanisms are ascribed to the dislocation accumulation and proliferation, formation of stacking faults and nanotwinning in γ, γ' and η phase induced by the precipitation of γ′ and η phase.
查看更多>>摘要：? 2022 Elsevier B.V.The main challenge in the practical exploitation of lithium-sulfur (Li-S) batteries is to resolve the problems of the sluggish liquid-solid conversions and the diffusion loss of liquid polysulfides especially at high sulfur loading. Herein, a novel bio-inspired reactor with ant-nest like architecture was tailored for Li-S electrochemistry, which combines abundant active nickel nanoparticles with hierarchical porous carbon-nanosheets network (HPCN/Ni). The nanoreactor provides multiple functions including strong trapping efficiency with polysulfides, fast transfer of ions/electrons and liquid sulfur species, and sufficient catalytic activity. The cooperative effects could accelerate Li-S redox reactions and improve sulfur utilization. Enhanced by the highly efficient HPCN/Ni naonoreactor, Li-S cells demonstrate a high specific capacity of 1437.9 mAh g?1 at 0.1 C, remarkable rate performances such as 900 mAh g?1 at 2 C, and exellent cycling stability with a high capacity retention of 734.2 mAh g?1 after 300 cycles at 1 C. Even at a high sulfur area loading of 5.63 mg cm?2, a high area capacity of 4.75 mAh cm?2 could be achieved. This contribution affords a fesible approach to design and construct nanoreactors with high efficiency for Li-S batteries and the analogous applications.
查看更多>>摘要：? 2022 Elsevier B.V.Breath biomarker detection has the great potential to enhance clinical diagnostics by monitoring health factors in a non-invasive manner and facilitating referrals. Room temperature non-invasive metal oxide semiconductor-based sensors play a prominent role in ailment detection. In this background, this work presents the acetone sensing characteristics of ZnO/NiO nanocomposites of five different ratios (0/1, 0.25/0.75, 0.50/0.50, 0.75/0.25 & 1/0) prepared via the electrospinning process. The electrospun nanocomposite revealed multijunction morphological features with interconnected grains. The structural studies confirmed the hexagonal phase of ZnO and the cubic phase of NiO with predominant (0002) and (2000) planes, respectively. Among the various ratios of ZnO/NiO nanocomposites, the ratio of 0.25 Ni2+ and 0.75 Zn2+ heterostructures exhibited a maximum response of S = 6.06 towards 100 ppm of acetone (CH3-CO-CH3) at room temperature. Response/retrieval times were found to be 28 and 34 s towards 100 ppm of acetone. The limit of detection of 1 ppm with fast transient characteristics is an encouraging factor to be considered for using the same for exhaling analysis.
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