查看更多>>摘要：? 2022 Elsevier B.V.Inspired by biological gradient structure, Ti basic gradient heterogeneous alloy component from TC11 alloy to TC4 alloy was fabricated by multi-wire arc additive manufacturing (MWAAM). The chemical mixing, phase and microstructure evolution, microhardness distribution and tensile property of Ti basic gradient heterogeneous alloy were investigated through EDS, XRD, SEM, hardness tester and tensile tester. The results indicated that the alloy elements formed a long-distance gradient concentration distribution during the transition between two different titanium alloys due to dilution, remelting, and convective mixing in the molten pool. The intensity of diffraction peaks of Ti basic gradient heterogeneous alloy in the gradient region had no obvious change. The microstructure of MWAAM Ti basic gradient heterogeneous alloy was mainly consisted of lamellar αP, acicular αS, equiaxed αS and β matrix. Different morphology of the αS phase was mainly attributed to the wetting state of the second solid phase and grain boundary. In addition, the microstructure of α phase in Ti basic gradient heterogeneous alloy was significantly changed by the gradient distribution of alloy composition. The gradient heterogeneous alloy component manufactured in this work had high bonding strength. The average UTS of MWAAM Ti basic gradient heterogeneous alloy was 793.14 MPa, which was close to MWAAM TC4 alloy and reached approximately 85% of MWAAM TC11 alloy.
查看更多>>摘要：? 2022 Elsevier B.V.Rational design of metal oxide-sulfide-based composite electrode materials with multi-functional nanoarchitectures, high electrochemical conductivity, and superior redox activity have attracted extensive attention in high-rate hybrid supercapacitors. Herein, the hierarchical binder-free copper-cobalt oxysulfide (Cu0.33Co0.67OxSy) nanoarchitectures with flower-like nanosheets and nanoplates are facilely synthesized on Ni-foam for hybrid supercapacitors using a simple and low-cost wet chemical method. The Cu0.33Co0.67OxSy-NFs demonstrated a high specific capacity of 193 mAh/cm2 (443.9 μAh/cm2) at current density of 3 mA cm? 2, with excellent cycling performance of 95 % even after 3000 charge-discharge cycles. In addition, an aqueous hybrid device was assembled using prepared Cu0.33Co0.67OxSy-NFs as positive and porous carbon as negative electrode, which demonstrated benchmark for energy storage properties. Specifically, the assembled device exhibited a high energy density of 0.33 mWh/cm2 and a power density of 2.1 mW/cm2 with high capacity retention (91 % after 5000 cycles at 20 mA cm?2). In view of practical applicability, the assembled hybrid devices can be able to power up a small wind fan for a long duration. The cost-effective single-step approach in designing high-performance cathode materials in this study provide a strategy for the design and manufacture of other ternary metal oxysulfides for high-performance energy storage devices.
查看更多>>摘要：? 2022 Elsevier B.V.Recently, various electroactive materials composed of binary transition metal oxides (TMOs), and conducting polymers have been extensively studied, with the materials demonstrating great potential in high-performing battery-type electrodes. Furthermore, the development of heterogeneous nanocomposites is a versatile approach because of their well-defined surface morphology and the significant synergistic effect of the various species. In this study, NiCo2O4 (NCO) combined with polyvinyl pyrrolidone (PVP) and polyaniline (PANI) hybrid nanocomposites of NCO/PVP/PANI are newly developed using a facile hydrothermal method. The NCO in combination with PVP and PANI species provides the interconnected hierarchical characteristics by offering large electroactive sites that facilitate the charge transfer. The NCO/PVP/PANI1.5 nanocomposites had a high areal capacity of 698.44 μAh cm?2 at a current density of 4 mA cm–2 and a remarkable capacitance retention of 86 % over 4,000 galvanostatic charge/discharge (GCD) cycles owing to its excellent synergistic effect of the rich faradaic redox reaction kinetics of metallic species, and highly conductive materials. Moreover, the proposed NCO/PVP/PANI1.5 battery-type positive electrode was successfully assembled with an activated carbon negative electrode, resulting a hybrid device with a high energy density of 27.60 Wh kg?1 at a power density of 874.9 W kg?1 and excellent cycling stability. This research holds the significant promise for advanced heterogeneous materials in energy storage systems by describing the newly developed nanocomposites.
Laia A.S.Brandao-Silva A.C.Gomes M.A.Macedo Z.S....
15页
查看更多>>摘要：? 2022 Elsevier B.V.The luminescent properties of three nanocrystalline samples of Y2O3:Er3+ produced via PVA-assisted sol-gel route, with mean particle diameter of 21, 44 and 86 nm, were investigated aiming their application as optical temperature sensors within the first and second biological windows. Luminescence spectra were analyzed using three different wavelengths (532 nm, 660 nm and 800 nm) as excitation sources. The three samples exhibited up to four emission bands centered at 660 nm, 800 nm, 860 nm and 1000 nm, which were related to the 4F9/2 → 4I15/2, 4I9/2 → 4I15/2, 4S3/2 → 4I13/2 and 4I11/2 → 4I15/2 transitions of Er3+, respectively. Three luminescence intensity ratio (LIR) schemes associated with thermally decoupled levels were proposed and their dependence on ambient temperature was investigated, two for excitation at 660 nm and one for excitation at 800 nm. In all the three cases, excitation and emission wavelengths were within the first or second biological window. Relative sensitivities of up to 2.02 ± 0.06% K?1 were obtained, with good repeatability and reproducibility and with temperature uncertainties below 1 K. The influence of particle size on luminescence intensity and sensor sensitivity was also presented and discussed, considering the potential applications. The results showed that particle size can affect the sensitivity of each LIR differently depending on the phonon-assisted processes involved.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, the effect of Co (0–5 wt%) on the mechanical properties of 718 alloy and its strengthening mechanism were studied to clarify the function of Co on the mechanical properties of 718 base alloy. The experimental results showed that the addition of Co refined the grain. After the heat treatment, the addition of Co promoted the precipitation of Laves phase and γ′ phase, but inhibited the precipitation of γ″ phase. With the increasing of the Co content, the tensile strength was increased first and then decreased. It was found that the increase in the tensile strength of the alloy was caused by refining the grains and promoting the intergranular precipitation of the Laves phase. Nevertheless, Co increased the volume fraction of intragranular γ′ phase, while suppressed the precipitation of intragranular precipitation of γ″, thus the intragranular strength of the alloy was reduced. Accordingly, the alloy with 3 wt% Co shows the highest yield strength among the experimental alloys. Besides, the Co content extent 3 wt% will show a yield plateau under room temperature tension, but not in the case of 650 °C tension. It was revealed by analyzing the TEM morphology of the Laves phase in the room-temperature tensile samples and 650 °C tensile samples that the dislocation could shear through the intergranular Laves phase under the 650 °C tensile test, but it was not the case under room temperature tensile test. Therefore, the yield plateau in the stress-strain curves is due to the intergranular Laves phase impeding the dislocation motion.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, tensile properties and relevant deformation mechanisms were investigated particularly in a novel low-cost second-generation nickel-based single crystal superalloy containing 1.5 wt% Re. The results showed that the experimental alloy exhibited an anomalous yielding phenomenon. The yield strength of alloy reached a peak value of 1120 MPa but the corresponding elongation was only 8.2% at 760 °C. Furthermore, the double yield phenomenon occurred at 900 °C and above whereas the strain softening behavior appeared at high temperatures. With increasing temperature, the main fracture mode gradually evolved from pure shear to microvoid accumulation fracture. The dislocations sheared into γ′ particles and led to the formation of stacking faults, which was the dominant deformation mechanism below 760 °C. Particularly, the formation of both K-W locks and L-C locks is closely related to the peak yield strength of the alloy at 760 °C. At 900 °C, the tensile deformation was controlled by the combination of APBs shearing and Orowan bypassing γ′ particles. As the temperature further increased to 1000 °C and 1100 °C, the dislocation networks formed on γ/γ′ interface could hinder the dislocations shearing into γ′ particles. Meanwhile, Orowan bypassing and dislocations climbing became the dominant deformation mechanisms. The results of this work could provide vital support for development and application of low-cost SX superalloys.
查看更多>>摘要：? 2022 Elsevier B.V.Rational construction of nanocomposites with special structure is still a considerable challenge in developing high-performance electromagnetic (EM) wave materials. In this work, NiO and multiwall carbon nanotubes(MWCNTs) intertwined as a new algae-like material is designed and fabricated by a facile and simple strategy to acquire high EM wave performances for the first time. Benefitting from the special nanostructures, which cause rich dipole polarization, interfacial polarization, multiple scattering centers, reduced specific gravity, three dimensional conductive networks, and proper impedance matching, the NiO/MWCNTs nanocomposites with S-6.5 wt% MWCNTs content display superior microwaves absorption capability. With 30 wt% filler loading, it possesses a strong absorption of ? 58.27 dB and a wide absorbing bandwidth of 5.25 GHz at a thickness of only 1.6 mm. Additionally, the broad absorption bandwidth of 16.2 GHz can be obtained in the thickness range of 1.5–5.0 mm. To deeply expose the inner EM wave absorption mechanism, the electronic properties of the hetero-interface (NiO and CNTs) are calculated by density functional theory (DFT). The electronic properties reveal the influence of the polarization on the absorption properties at the atomic level. The combination of experimental and theoretical research clarified the EM wave absorption mechanism of NiO/MWCNTs composites, indicating that NiO/MWCNTs composites can be a high-efficiency absorber with lightweight, ultrathin thickness, broad bandwidth, antioxidation, and strong absorption.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, gold (Au) and poly(3-hexylthiophene) (P3HT) composite nanoparticles (Au@P3HT) are synthesized and applied to modify the photoelectrodes of dye-sensitized solar cells (DSSCs). The modification is carried out by adsorption of Au@P3HT onto the electrode surface. The experimental results show that the Au@P3HT nanoparticles demonstrate a spherical shape with a mean diameter of 6 nm. The analysis of X-ray photoelectron spectroscopy indicates that the P3HT strongly interact with Au, protecting the Au particles from the corrosion of iodide electrolytes. Scanning electron microscope analysis reveals that the Au@P3HT nanoparticles adsorb strongly and uniformly on the mesoporous TiO2 photoelectrode. The UV–vis absorption spectrum shows that the Au@P3HT-modified photoelectrode can enhance the light absorption in the long wavelength region, attributed to the plasmon resonance effect of Au nanoparticles. It also demonstrates that the modification of Au@P3HT not only improves the incident photon to current conversion efficiency but also increases the recombination resistance at the photoelectrode/electrolyte interface. Therefore, the corresponding cell has higher current density and open-circuit voltage. By way of this method, the DSSC can achieve an energy conversion efficiency of 9.34%. The non-corrosive characteristics of the Au@P3HT-modified electrode against the iodide liquid electrolyte improve the durability of the DSSCs.
查看更多>>摘要：? 2022In this study, the effect of phase conditions on the tensile behaviors of Ti-Cu alloys with Cu contents of 0, 10, 20, and 30 wt% is investigated by controlling the annealing temperature. An in-depth characterization of the alloy microstructure is performed using scanning electron microscopy and transmission electron microscopy. The results suggest that the mechanical properties of the Ti-Cu alloys are strongly affected by the Cu content in α lath, which is dependent on the volume of Ti2Cu rather than Ti2Cu itself. A high volume of Ti2Cu reduces the Cu content in α lath, resulting in high elongation and low strength. Ti2Cu has superior antibacterial properties when compared with that of the Cu-supersaturated α lath. This study provides new insights into the design of Ti-Cu alloys for application as a biomaterial.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, we report on a micro-sensor employing two-dimensional (2D)- zero-dimensional (0D) heterostructure based on MOSe2/ZnO (fabricated by a novel Complementary Metal Oxide Semiconductor (CMOS) compatible microwave-irradiation-assisted solvothermal route) as a receptor. Density Functional Theory (DFT) calculations show that the heterostructure is more favorable to the adsorption of hydrogen sulfide (H2S) gas than the pristine 2D nanosheets. Experimentally, the device demonstrates sensitivity in the ultra-low concentration H2S range (i.e. 200 ppb – 6.1 ppm), and response of as high as 9.08% (200 ppb) - 186.91% (6.1 ppm) could be obtained repeatably with decent signal-to-noise ratio and response/recovery time (~600 sec). The device stands well on various sensor parameter tests including absolute response percentage, lower limit of detection (LOD), repeatability, reproducibility, hysteresis error, etc. A sensing mechanism based on Wolkentein's model is proposed to understand the detection behavior of the device.
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