查看更多>>摘要：? 2022 Elsevier B.V.The regulation of carriers by piezoelectric effect and plasmonic effect is considered to be the key to the efficient conversion of solar to chemical energy. In this work, we report a novel heterostructure piezoelectric photocatalyst by preparing MoS2 nanoflowers and AuNPs on Polyvinylidene Fluoride (PVDF) doped with BaTiO3 (BT). The piezoelectric properties of PVDF@BT composite fibers were greatly enhanced up to 4.5 times than that of pure PVDF by the dope of BT, which is much beneficial for the photocatalytic process. The enhanced piezoelectric properties can produce stronger regulation of photogenerated carriers caused by the plasmonic effect, resulting in higher photocatalytic activity. The optimized PVDF@BT/MoS2/Au active film exhibited significantly enhanced photocatalytic activity, the catalytic efficiency of methylene blue (MB) solution was as high as 99.7% within 10 min, and the pseudo-first-order kinetic constant (K) was as high as 0.3973 min?1, which is a 3.3-fold improvement over piezoelectric catalysis and an 11.9-fold improvement over photocatalysis. And oxytetracycline (OTC) degradation reached 97.6 % within 60 min, showing excellent versatility. This work provides an interesting solution for designing novel structures for efficient conversion of solar energy to chemical energy.
查看更多>>摘要：? 2022 Elsevier B.V.Gladiolus-like NiSe/CoSe/Ni3Se2 hierarchical nanocomposite supported by nickel foams (NF) was synthesized for the first time by the mixed solvothermal method. Structural characterizations show that the obtained hierarchical nanocomposite forms from the dense growth of NiSe and CoSe nanosheets around Ni3Se2 nanowires. This novel gladiolus-like nanostructure supported by NF possesses the remarkable synergistic structural advantages from 1D/2D nanostructures and porous metallic substrate. It makes the gladiolus-like NiSe/CoSe/Ni3Se2 hierarchical nanocomposite with the excellent electrochemical properties, i.e.: high mass specific capacitance of 1666 F g?1 at 0.5 A g?1, high rate performance of 56.7 % at 2.5 A g?1, and 85.19 % capacitance retention after 5000 cycles. These phenomena are ascribled to the hierarchical nanostructure, heterozygous mettalic atoms, high conductivity, and significant synergistic effect. Subsequently, solid-state asymmetric supercapacitors are built up by using gladiolus-like NiSe/CoSe/Ni3Se2 hierarchical nanocomposite and active carbon as the pair electrodes. This solid-state device has a high areal energy density of 0.33 mWh cm?2 at areal power density of 7 mW cm?2, 80.11 % capacitance retention after 10,000 cycles, and promising commercial value. Thus, the present work not only demonstrates that gladiolus-like NiSe/CoSe/Ni3Se2 hierarchical nanocomposite is the promising electrochemical materials, but also offers a new device for solid-state, small, and smart electronic products. The present groundbreaking work also offers a novel strategy for enhancing the electrochemical capability of supercapacitor electrodes by designing ingenious nanostructures.
查看更多>>摘要：? 2022 Elsevier B.V.The equiatomic high-entropy alloy (HEA) CoCrFeMnNi not only has excellent mechanical properties but also good irradiation resistance. However, the mechanical properties of some equiatomic medium-entropy alloys (MEAs) are superior to those of CoCrFeMnNi HEA. In this study, the irradiation resistance and changes in composition due to irradiation in CoCrNi and CoCrFeNi MEAs and CoCrFeMnNi HEA are investigated. Thin film samples of the MEAs and HEA and Ni used for comparison were irradiated with up to 1.7 × 1019 ions/m2 of 2.4 MeV Cu ions at 673 and 873 K. The average damage in the observed area was 1 displacement per atom (dpa). No voids were observed in any of the MEA and HEA samples even after irradiation at 873 K; however, large voids were formed in Ni irradiated at 873 K. This indicates that the irradiation resistance of CoCrNi and CoCrFeNi MEAs and CoCrFeMnNi HEA was better than that of Ni. In addition, the formation of stacking fault tetrahedra (SFTs), a type of vacancy cluster, at 873 K was much more pronounced in CoCrNi and CoCrFeNi MEAs than in CoCrFeMnNi HEA. Therefore, the irradiation resistance of CoCrNi and CoCrFeNi MEAs is lower than that of CoCrFeMnNi HEA. Moreover, significant Cr segregation occurred in the CoCrNi and CoCrFeNi MEA samples irradiated at 873 K. In contrast, no segregation occurred in CoCrFeMnNi HEA. First-principles calculation results show that the formation rate of Cr-dumbbells is higher in CoCrNi and CoCrFeNi MEAs than in CoCrFeMnNi HEA, and that Cr interstitials are more stable in the MEAs. Therefore, Cr segregation is more likely to occur in the MEAs. Element segregation may affect the irradiation resistance of the alloys.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, a fully dense CoCrFeNi high entropy alloys (HEAs) coating with homogeneous microstructure was successfully prepared on AZ91 alloy by cold spray. It is innovative to cross-integrate HEAs with Mg alloys using cold spray to break through the “bottleneck” of Mg alloys. The average microhardness of the coating was 5 times higher than Mg alloys. The weight loss of the coating in wear test was 2 orders of magnitude lower than Mg alloys. The Ecorr of the coating was noticeably improved to be ~ ? 290 mVSCE and the icoor of the coating was significantly decreased by 4–5 orders of magnitude. The coating exhibited significantly spontaneous passivation due to the multi-layer passive film composed of FeO, Cr2O3 and NiO. The weight loss of CoCrFeNi coated AZ91 plates was below 1% after 28 days immersion. Lots of tiny micro-pits in size less than 1 μm were distributed on the corroded coating surface because the formation of large pitting pits was restricted. Unique corrosion mechanisms of the coatings were found: the repeatedly repassivation effect and the competing effect triggered by the rapid initiations of new pittings. The stable passive film and uniform microstructure of the coating resulted in the significant decrease of corrosion rate. The shielding effect of the coating can bring outstanding surface protection for Mg alloys.
查看更多>>摘要：? 2022 Elsevier B.V.Nonmagnetic Li+, Cu2+, In3+ and Ti4+ ions were employed to induce robust room temperature ferromagnetism in perovskite BaSnO3 for advanced spintronics applications. New BaSn0.96M0.04O3 (M = Li+, Cu2+, In3+ and Ti4+) compositions were synthesized by modified Pechini method. In all compositions, single phase of cubic BaSnO3 was detected in the XRD patterns without any impurities. The FTIR spectra displayed the distinctive vibrational absorption band of BaSnO3 and verified the absence of any impurities. The SEM images evidently showed a decrement of grain size alongside morphological changes for doped BaSnO3 compositions compared to the pure one. The band gap energy of BaSnO3 was considerably influenced by the incorporation of Li+, Cu2+, In3+ and Ti4+ dopants. BaSn0.96Cu0.04O3 sample exhibited the highest refractive index value and the minimum value was obtained for BaSn0.96Ti0.04O3. Remarkably, at equal concentration two of the used nonmagnetic elements showed the ability to induce room temperature ferromagnetism in BaSnO3 lattice. Herein, BaSn0.96Cu0.04O3 exhibits a robust and symmetrical ferromagnetic hysteresis loop with complete saturation magnetization (Ms) of 0.158 emu/g and coercivity (Hc) of 42 Oe. BaSn0.96Ti0.04O3 composition revealed a ferromagnetic behavior within magnetic field of± 5000 Oe and the trend was reversed for higher values to show a diamagnetic performance. The interaction between the 3d orbitals of Cu2+ (3d9) or Ti4+ (d0) with the trapped electrons in the oxygen vacancies encourage a ferromagnetic coupling in BaSnO3 structure. The outer shell orbitals of Cu2+ and Ti4+ dopants and the oxygen vacancies seem to play a significant role in the magnetic properties.
查看更多>>摘要：? 2022 Elsevier B.V.Recently, electrospinning technology has high-potential applications in the large-scale manufacturing of one-dimensional (1D) nano-catalytic functional materials. Herein, Ni nanoparticles embedded within highly N-doped carbon nanofibers (Ni@NCNFs) were fabricated using polyacrylamide (PAM) and nickel acetate (NiAc) aqueous solutions as precursors by electrospinning and subsequent carbonization for the first time. The as-prepared Ni@NCNFs were smoothly applied to the hydrogenation of quinoline toward 1,2,3,4-tetrahydroquinoline and manifested excellent catalytic performance with extremely high selectivity (99.0%) at full conversion (99.3%). The influence factors on the physicochemical properties were further studied, including the carbonization temperature, the PAM mass fractions and the mole ratios between PAM and NiAc (PMA/Ni). The present work demonstrated that electrospinning and carbonization could be potential technologies for manufacturing Ni@NCNFs as an outstanding catalyst for quinoline hydrogenation. Furthermore, PAM rich in nitrogen could serve as a new alternative electrospinning precursor for future applications.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, the Ni-Co-S nanosheets have been grown onto CoMoO4 nanorods by the electrodeposition method (CoMoO4 @NCS). The supercapacitor performance of the CoMoO4 @NCS composites can be greatly promoted due to the unique core-shell structure. The addition of amorphous Ni-Co-S nanosheets can provide much more electrochemical active sites, thereby enhancing the capacitive capability. The CoMoO4 @NCS composites show fairly high specific capacitance of 1276 F g?1 at 0.5 A g?1, which is twice that of pristine CoMoO4 nanorods (604 F g?1). The composites also present remarkable cycling characteristics. The specific capacitance retention reserves 98 % after 7000 cycles at 1 A g?1. Furthermore, the asymmetric supercapacitor (CoMoO4 @NCS//AC) device exhibits high energy density of 48.3 Wh kg?1. Notably, the fabricated device also presents outstanding stability with only 4% capacitance loss rate after 10000 cycles. The results indicate that the CoMoO4 @NCS composites have great potential for energy storage materials.
查看更多>>摘要：? 2022Efficient, stable, and environmentally friendly electrocatalysts urgently need to be explored for hydrogen evolution reaction (HER). A novel and facile nickel–selenium–dysprosium (Ni–Se–Dy) electrocatalyst was synthesized on Ni foam via simple and feasible one–step galvanostatic electrodeposition. The prepared Ni–Se–Dy electrodes showed excellent HER activity in alkaline medium with low overpotential values of 72 and 173 mV to deliver the current density values of 10 and 50 mA·cm?2. Tafel slope value (119.72 mV·dec?1) for Ni–Se–Dy electrode in 1.0 M KOH indicated that the Ni–Se–Dy catalyst followed a Volmer–Heyrovsky mechanism, and the rate–determining step of this reaction was a Volmer step. Electrochemical test and scanning electron microscopy results showed that the excellent HER performance of Ni–Se–Dy electrode can be attributed to surface morphology, better intrinsic activity, and high conductivity.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, by adding rare-earth (RE) elements to Fe89Zr7B4 ternary amorphous alloy, we obtained a series of Fe87Zr7B4RE2 (RE = Dy, Tb, Gd) amorphous ribbons to further improve the magnetic refrigeration capacity of the basic alloy. Through the heavy RE element substitutions, the glass-formability of the Fe89Zr7B4 alloy was improved effectively. Besides, the Curie temperature Tc of the alloy system increased from 275 K to 342 K, obtaining a roughly linear correlation between the de Gennes factor and Tc. Through the recombination of ribbons with different Tc values, we designed potential amorphous composites with a “table-like” magnetic entropy change curve under different temperatures. This research promises to deepen understanding of the effect of RE additions on the magneto-caloric properties and enhance the performance of Fe-Zr-B amorphous refrigerants around room temperature.
查看更多>>摘要：? 2022 Elsevier B.V.Continuous progress of piezoelectric coefficient (d33) and dielectric constant (εr) are obtained in (K, Na)NbO3 (KNN)-based lead-free piezoceramics by phase boundary formation, while usually accompanying by the poor temperature/thermal stability, which are not conductive to actual applications. In this work, the perovskite-type compound Bi(Ni2/3Nb1/3)O3 is designed and added into KNN ceramic. This additive can not only shift orthogonal-tetragonal (O-T) phase transition towards room temperature to enhance d33, but also make the O-T phase transition becoming diffusion in a broad temperature range. Furthermore, the piezoelectricity is further elevated by optimizing polarization via Ce3+ doping. Finally, the enhanced d33 is achieved with the excellent thermal stability from room temperature to> 350 °C. Besides, the high εr of ~ 1150 and low dielectric variation of ≤ ± 15 % can be obtained in a quite broad temperature span from room temperature to ~ 300 °C. These overall performances of this work show the potential multifunctional applications in high-temperature piezoelectric and dielectric devices.
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