查看更多>>摘要：? 2022 Elsevier B.V.A2W3O12-type (A=La, Sm, Eu, Gd, RE) rare earth tungstate high-entropy ceramic powder with a positively charged surface was fabricated by a high-temperature solid-phase method, and its antibacterial and antiviral properties were evaluated for the first time. Changes in the antibacterial and antiviral activity and ionic solubility of these compounds induced by changing the RE element at the A-position were investigated. The A2W3O12 high-entropy ceramic powder was a stable surface antibacterial material. Its antimicrobial properties are not affected by light and environmental acids and bases. The (La0.2Sm0.2Eu0.2Gd0.2Ho0.2)2W3O12 high-entropy ceramic powder had the best antibacterial performance in the absence of light, and the killing rate was more than 99.9% for both Staphylococcus aureus and Escherichia coli. On this basis, the animal viruses H1N1 influenza virus (enveloped) and EV71 enterovirus (nonenveloped) were selected for antiviral testing, and the survival rate of both viruses decreased by more than 99% within 2 h. The powder was evaluated for ion solubilization under acidic and alkaline service conditions, showing low ion solubilization and superior environmental suitability.
查看更多>>摘要：? 2022 Elsevier B.V.Phase equilibria of the Al-Co-Ta ternary system over the whole composition range at 1200 °C and 1300 °C were experimentally determined from the equilibrated alloys using electron probe microanalysis, scanning electron microscopy, and X-ray diffraction. The measured results indicate that, at 1200 °C, the addition of Al can stabilize the λ1-Co2Ta phase (Laves C14-type), which is absent in binary system, and forms a broad phase region parallel to the Al-Co axis in the Al-Co-Ta ternary isothermal sections. The ternary compound of the Heusler phase AlCo2Ta (L21-type) was confirmed at both investigated isothermal sections with the composition range about 49.7–55.7 at% Co and 14.7–23.6 at% Ta. In addition, a large solubility of Al was identified in the μ-Co6Ta7 phase. Based on the experimental results, the published data of the Al-Co and Al-Ta binary systems, and the reassessed Co-Ta parameters from the current work, a thermodynamic assessment of the Al-Co-Ta system was undertaken using the CALPHAD technique. A set of reliable thermodynamic parameters for the Al-Co-Ta system was obtained with a satisfactory agreement with the experimental data. The calculated liquidus projection and invariant reaction scheme in the Al-Co-Ta ternary system were presented. The present work can provide essential experimental and thermodynamic data for the establishment of the Co-based alloy database.
查看更多>>摘要：? 2022 Elsevier B.V.For biomedical titanium alloys, the reduction of their elastic modulus approximating that of human bone (~30 GPa) is highly required for using them as bone implant materials to reduce the risk of stress shielding. In this study, Ti-15Nb-(4-6)Sn (at%) shape memory alloys were developed to achieve the bone-like elastic modulus for biomedical applications by varying Sn content to adjust the factors such as transformation temperature, β stability, ω phase amount and texture component which are well known to affect the elastic modulus of titanium alloys. The elastic modulus of 68.8 GPa in the 4Sn specimen decreased to 41.5 GPa in the 5Sn specimen due to the suppression of α" martensite, achieving the least β stability and the decrease in the amount of athermal ω (ωath) phase. A good combination of low elastic modulus and room temperature superelasticity was obtained in the 5Sn specimen. Significantly, a bone-like elastic modulus of 31.5 GPa is achieved in the 5.5Sn specimen, which has not been reported yet in titanium alloy sheets. In this specimen, 110β001β (Goss texture) was developed as the dominant texture component and the ωath phase was completely suppressed. Also, the formation of the dominant Goss texture has not been reported previously in Ti–Nb–Sn alloy sheets. More detailly, along the rolling direction (RD), the [001]β//RD texture which effectively reduces elastic modulus along the RD was formed in 5Sn and 5.5Sn specimens and its intensity increased largely in the 5.5Sn specimen. Such a bone-like elastic modulus is attributed to the formation of a strong [001]β//RD texture as well as the absence of the ωath phase in β matrix.
查看更多>>摘要：? 2022 Elsevier B.V.The effects of post-deposition oxygen annealing temperature on the physical, chemical, and optical properties of gallium oxide (Ga2O3) films were systematically studied in this work. First, Ga2O3 films were deposited on Si (100) substrates by atomic layer deposition (ALD) and then annealed at 500–900 ℃, respectively. Several standard surface analysis methods were used to characterize the Ga2O3 films before and after annealing. X-ray diffraction (XRD) patterns illustrated that the as-deposited amorphous film transitioned to β-phase after annealing at temperatures greater than 600 ℃. Atomic force microscopy (AFM) images showed that the grain size and roughness of the films significantly increased when annealed above 700 ℃. Transmission electron microscopy (TEM) tests presented that the interface microstructure was slightly affected by the annealing process. The effects of the annealing process on optical properties were performed using photoluminescence spectroscopy (PL) and spectroscopic ellipsometry (SE). Moreover, X-ray spectroscopy (XPS) was utilized to extract the oxygen vacancy (VO) concentration, bandgap, and the energy band alignment of Ga2O3. With increasing annealing temperature, it was found that the atomic ratio of O/Ga increased while VO decreased monotonically from 47.4 % to 27.0 %. Density functional theory (DFT) simulation further accounted for energy band shifts resulting from the variation of VO. This study provides a means to achieve high-quality β-Ga2O3 films, highly significant for applications of β-Ga2O3-based ultraviolet photodetectors and other relevant devices.
查看更多>>摘要：? 2022 Elsevier B.V.This study effectively succeeded in synthesizing CdSe QDs and CdSe- SiO2 nanocomposites with controllable tunable size and spectacular morphology by using a solvothermal technique. UV–visible spectroscopy was used to study the effect of the growth time of CdSe QDs on the optical properties of its nanocomposite with SiO2. The structure of the prepared nanocomposites of CdSe- SiO2 was studied through the measurements of X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy FTIR. The Effective Mass Approximation model (EMA), Simple Exponential Function (SEF), and Polynomial Fitting Functions (PFF) were employed to compute nanoparticle sizes, providing particle sizes of 3.86, 4.19, and 3.72 nm, respectively, for CdSe- SiO2 nanocomposites (2 min). For the same nanocomposite, these theoretical values were comparable to the experimental values of the particle sizes deduced from measurements of TEM (4.5 nm) and XRD (3.4 nm). The deduced optical parameters of CdSe-SiO2 nanocomposite, such as refractive index, dielectric constant, optical conductivity, electrical susceptibility, and some others, relied on the growth time of CdSe QDs. The absorption peaks of CdSe -SiO2 nanocomposites suffered from a bathochromic shift which increases as the growth time of CdSe QDs increases. Increasing the growth time of CdSe QDs resulted in increasing the reflection loss factor and decreasing the optical electronegativity. The values of the volume energy loss function (VELF) are greater than the values of the surface energy loss function (SELF) for the different nanocomposites. Consequently, the fast electrons miss their energies through their propagation within the studied materials more than through traveling on their surfaces. The enhancement of n values of nanocomposites of CdSe-SiO2 by increasing the growth time can candidate them to be usefully applied as antireflection coating for solar cells.
查看更多>>摘要：? 2022 Elsevier B.V.The effects of pre-strain on the continuous precipitation (CP) and discontinuous precipitation (DP) as well as mechanical properties of L12-strengthened HEAs were thoroughly studied. It is found that the pre-strain has a dual effect on the L12 precipitation behavior depending on the pre-strain level. At low pre-strains, the plastic deformation increases the dislocation density without significantly affecting the grain structure, which accelerates the CP reaction by promoting the CP nucleation and growth, leading to the CP-dominant microstructure. At high pre-strains, the server plastic deformation induces the formation of a high density of deformation bands and subgrains, the boundaries of which provide preferred nucleation sites for the DP reaction. In addition, the high stored energy induced by the cold deformation enhances the grain boundary migration, which promotes the DP growth and concurrent recrystallization. Mechanical tests further reveal that the pre-strain substantially improves the strength of the alloys without significantly deteriorating the ductility. The contributions of dislocations, grain boundaries, and precipitates to the strengthening of the pre-strained and aged alloys were quantitatively evaluated.
查看更多>>摘要：? 2022 Elsevier B.V.BHPC (biomass hierarchical porous carbon) is a new microwave absorption material with extraordinarily low density, excellent dielectric loss, and a low environmental impact. In this paper, a Ni/BHPC composite is introduced, which were fabricated using a simple electroless plating method. When the NiSO4 concentration is changed, the electromagnetic characteristics and absorption performance are optimized. The Ni/BHPC composite material exhibits excellent absorption characteristics at a NiSO4 concentration of 0.2 mol/L. With a thickness of 2.7 mm, the RLmin is ?58.504 dB at 10.741 GHz. In the frequency range 8.221–12.4 GHz, with a thickness of 2.9 mm, this reflection loss (RL) is less than ?10 dB. These results indicate that incorporating Ni particles into the BHPC enhances its wave absorption efficiency. The research contributes to develop high-performance porous carbon microwave absorption materials from biomass.
查看更多>>摘要：? 2022 Elsevier B.V.Photocatalytic CO2 reduction has attracted extensive attention because of its abilities to generate renewable clean fuels while immobilizing CO2. However, the widely used CO2 reduction photocatalysts generally have the problems of inadequate light absorption performance and insufficient photocatalytic reaction yield. Here we report 0D/2D CsPbBr3 quantum dot/CuCo2O4 nanosheet composites (CsPbBr3 QD/CuCo2O4 NS composites) synthesized by mechanical mixing method, which are applied for photocatalytic CO2 reduction. Thanks to the narrow bandgaps of CsPbBr3 QD and CuCo2O4 NS, CsPbBr3 QD/CuCo2O4 NS composites represent strong light absorption performance. The p-n heterojunction forms between CsPbBr3 QD and CuCo2O4 NS obviously boosts the charge separation, leading to the photocatalytic activity and stability of CsPbBr3 QD/CuCo2O4 NS composites significantly exceeding that of CsPbBr3 QD and CuCo2O4 NS. After 5 h of photocatalytic reaction, the generation rate for CH4 of CsPbBr3 QD/CuCo2O4 NS composites is 285.93 μmolg?1, which is about 3.2 times and 9.2 times higher than CsPbBr3 QD (88.08 μmolg?1) and CuCo2O4 NS (30.92 μmolg?1), respectively. This work provides a new insight to construct novel heterojunction photocatalysts based on lead halide perovskite QD, which shows the enhanced photocatalytic activity and light absorption performance.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, microstructural and mechanical response to hydrogen were investigated for CoCrFeMnNi high-entropy alloy (HEA) additively manufactured by selective laser melting (SLM) with and without heat treatment. Microstructural characterization, thermal desorption analyses, and slow-strain-rate tests were conducted to study the hydrogen trapping behavior and the effects of hydrogen on the deformation and fracture mechanism. The results showed that cell walls with high-density dislocations and Mn segregation provided hydrogen trapping and increased the high hydrogen capacity. This caused hydrogen embrittlement, accompanied by hydrogen-assisted intergranular cracking in as-built CoCrFeMnNi HEA. A heat treatment at 900 ℃ reduced dislocation density of the walls and eliminated the Mn segregation. Interestingly, hydrogen-induced ductilization was enabled in the heat-treated-SLM HEA. This is attributed to an appropriate twinability and twinning strain which greatly suppressed intergranular cracking in the surface layer. Therefore, tuning twinability through the control of microstructure is critical for a transition from hydrogen embrittlement to ductilization for SLM-built HEA.
查看更多>>摘要：? 2022Nanocrystalline soft magnetic composites (n-SMCs) with excellent soft magnetic properties are widely used in medium and high frequency electronic devices. However, the production of n-SMCs with high frequency stability and low core losses (Pc) remains a challenge. In this work, we balanced electromagnetic performances and frequency properties of Finemet n-SMCs by tuning the mass ratio of flake and spherical powders. The morphology, phase structures, electromagnetic performances or frequency characteristics of powders and n-SMCs were systematically investigated. Scanning electron microscope was employed to prove that the addition of spherical powders (SPs) can improve the matching degree of powders and density of n-SMCs. As the mass ratio of SPs increased, the Pc and the hysteresis losses (Ph) of magnetic powder cores first decreased and then increased, while the eddy current losses (Pe) showed the monotonic downward trend. What's more, owing to the excellent insulation coating performances of SPs, quality factor (Q), DC-bias characteristics and frequency stability were significantly improved after mixing SPs with FPs. The n-SMCs with the mass ratio of 2:3 between SPs and FPs exhibited the best comprehensive performances with the effective permeability of μe = 43 (f = 100 kHz), the quality factor of Q = 78, the core losses of Pc = 294 mW/cm3 (Bm = 50 mT, f = 100 kHz), and the DC-bias characteristics of 56%. This work endows Finemet n-SMCs with a potential application for inductance components at high frequency.
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