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High microwave absorption performance in Nd-substituted BaM/GO through sol-gel and high energy ball milling process
No full textIn this paper, a series of compound materials with different proportions of rare earth neodymium (Nd) doped M-type barium ferrite (BaM) and the mixture Nd-BaM with graphene oxide (GO) are prepared through the sol-gel method and high-energy ball milling route. The surface morphology, composition and electromagnetic properties of those materials are analyzed through XRD, SEM, TG, Raman and the vector network analyzer. It is found that the Nd-BaM particle is adhered on the surface of GO with the nanometer size. The electromagnetic performance can be severely affected by the doping amounts of Nd and the blending amounts of GO. Moreover, the microwave absorption performance of the compounds is studied in the frequency range of 2-18 GHz. For Nd-0.15-BaM/3%GO, the minimum reflection loss is - 82.07 dB at 12.65 GHz and the scope of the effective absorption band is 6.08 GHz with a thickness of 2 mm. Because of its good impedance matching, the interface polarization and electron polarization between Nd-BaM and GO, the electromagnetic wave occurs multiple reflection in this material. Compared with pure BaM or BaM/GO, the Nd substituted BaM/GO has excellent microwave absorption performance, which has a certain prospect in the microwave absorbing field. (C) 2021 Published by Elsevier B.V
Theoretical insights into the substitution effect of phenanthroline derivative ligands on the extraction of Mo (VI)
No full textWith the rapid development of nuclear medical imaging, the production of Mo-99 has attracted much attention, because the important medical isotope Tc-99m can be obtained from Mo-99. N,N'-diethyl-N,N'-ditolyl-2,9-diamidel,10-phenanthroline (Et-Tol-DAPhen) has been proven to be an excellent ligand for the extraction of U (VI), while there are still few reports on the extraction of Mo(VI) using this ligand. To investigate the coordination structures of MoO22+ with Et-Tol-DAPhen, we carried out theoretical calculations using scalar relativistic density functional theory (DFT). The analyses of Wiberg indices (WBIs), quantum theory of atoms in molecules (QTAIM) and natural orbitals of chemical valence (NOCV) indicate that the MoO22+ have stronger complexation ability with O atoms compared to N atoms. The bonds between MoO22+ ions and ligands are mainly ionic interactions. The analyses of EDA and the most negative binding energy indicates that complex [MoO2L(NO3)](+) is energetically favorable and Et-Tol-DAPhen has also good extraction ability for MoO22+. Moreover, although both the electron-donating and electron-withdrawing groups have slightly effect on the electronic structures of the [MoO2L(NO3)](+) complexes, Et-Tol-DAPhen modified by the electron-donating group can enhance the extraction ability of MoO22+. This study is helpful to understand the complexation behavior of Et-Tol-DAPhen with MoO22+ and provides useful structural and thermodynamic information for the MoO22+ extraction with phenanthroline derivative ligands
Converting thermally activated delayed fluorescence into hybridized local and charge-transfer via an addition acceptor moiety
No full textHigh-efficiency blue materials for Organic Light Emitting Diodes (OLEDs) are challenging but urgently needed, especially for solution-processed devices. Herein, based on a model compound of acridine-benzophenone, two blue materials were designed and synthesized, with the additional electron-withdrawing groups benzophenone and pentafluorobenzophenone connected to the acridine donor respectively to prepare BC and BC5F. The solution-processed OLED based on BC showed an emission peak at 486 nm, while the device with BC5F showed the electroluminescent peak at 478 nm. BC featured the thermally active delayed fluorescent (TADF) properties, but BC5F exhibited hybridized local and charge-transferring (HLCT) characteristics. This work showed that linking additional acceptors to the donor side could not only achieve deeper blue emission but also change the luminescent mechanism. Therefore, we provided a new strategy to manipulate the transition between TADF and HLCT
Designing a MOF-based slippery lubricant-infused porous surface with dual functional anti-fouling strategy
No full textMaterial that resists biofouling adhesion is needed in a complex marine environment, but few of them can combine ultra-low fouling and environmental friendliness. Slippery lubricant-infused porous surface (SLIPS) is such a material, but it lacks the contact-killing ability, which limits its stability and anti-fouling efficiency. Here, we report a metal organic framework (MOF-based) Slippery ionic liquid-infused surface with excellent antifouling performance via synergistic release and contact-killing defense strategy. The dense needle-like MIL-110 array, grown in situ on the aluminum surface, is conducive to the stable stor -age of quaternary ammonium salt (QAS) ionic liquid. Compared to the control group with mature biofilm formed on the surface, SLIPS showed non-fouling performance in a 10-day test and another 21-day test under more challenging conditions. The adsorption amount of lipopolysaccharide (LPS) on SLIPS was 50% lower than that on the aluminum sheet and the aluminum sheet with MIL-110 grown on the surface as the control groups within three hours. The relationship between bacterial adhesion and LPS adsorption indicated that the anti-adhesion performance of SLIPS was mediated by the weak adhesion and easy release property of its surface to extracellular fouling molecules. This study provides the possibility to systematically reveal the antifouling mechanism of SLIPS on bacterial adhesion. (c) 2021 Elsevier Inc. All rights reserved
Correlation between dynamic magnetization process and dynamic domains of high saturation induction FeSiBNbCuMo nanocrystalline alloy with dual anisotropies
No full textImproving the high-frequency properties of the relatively high saturation induction alloys is significance for widening the frequency range of the noise suppression of common mode chokes. Herein, transverse magnetic field annealing after having been nano-crystallized (TA) was performed to the as-quenched Fe76Si13B8Nb1.5Cu1Mo0.5 alloy, and the dynamic properties, microstructure, and dynamic domains were in detail studied comparing with those annealed without magnetic field (NA). It was found that TA at 400 degrees C caused an increase in permeability at 50 kHz by 41% and a decrease in core loss at 0.2 T and 50 kHz by 30%, in comparison with those of NA. TA at 400 degrees C induced the ratio of field induced anisotropy constant K-u to average random anisotropy constant to be similar to 1.3 and inhomogeneous rotation, leading to the promoted domain refinement with increasing frequency and improved high-frequency properties, compared with that of NA bears only similar to 5.4 J/m(3). Moreover, the role of dual anisotropies on the magnetic domain structures, dynamic magnetization process and magnetic performances were obtained and its correlation model based on the experimental results was established. These results could provide a good guide for performance optimization to meet higher frequency requirements of common mode chokes application. (C) 2021 Elsevier B.V. All rights reserved
Surface modification on copper particles toward graphene reinforced copper matrix composites for electrical engineering application
No full textGraphene has been demonstrated as an effective reinforcement for metal matrix composites, due to its excellent mechanical properties, robust chemical inertness, thermal stability, and self-lubricating. Nevertheless, the limiting factor for its further use in metal matrix composites, is to realize the homogeneous dispersion of graphene for taking advantage of its exceptional and fascinating properties, because of the poor wettability and density contrast between metal matrix and graphene. Herein, we design a gel assisted route to synthesize high-quality graphene nanoplatelets modified monodispersed copper particles, followed by hot pressing to fabricate graphene reinforced copper matrix composites bulk. This simple route with high efficiency and low cost, offers a new solution for the mass-production of graphene reinforced copper matrix composites and other graphene-based composites on an industrial scale. Significantly enhanced tensile strength of 253 MPa, and yield strength of 145 MPa, accompanied by the low friction coefficient and improved wear resistance, can be simultaneously achieved in the composites. For the real electrical contact performance test, the service life of electrical contacts made of graphene reinforced copper matrix composites, is 10 times longer as that of the commercial pure copper electrical contacts and almost comparable to CuAg20 contacts, demonstrating its superior ability to solve the electrical contact issues in electrical engineering systems. (c) 2021 Elsevier B.V. All rights reserved
In-situ structural health self-monitoring and diagnosing of glass fiber reinforced plastics with embedded nickel coated carbon fiber
No full textIn this study, a nickel coated carbon fiber (Ni-CF) tow is used to enable glass fiber reinforced plastics (GFRPs) to exhibit multi-functional properties with self-diagnosing function. The experimental results indicate that the NiCF exhibits desirable interfacial compatibility with the matrix resin and has no negative effect on the performance of GFRPs, thereby the loading conditions can be effectively monitored without deterioration. The electromechanical response suggests that the changes in resistance can be further divided into two stages corresponding to the two different safety states based on the strain under uniaxial tensile loading. At the same time, the composites were examined under cyclic loading conditions to confirm the stability and robustness of the Ni-CF as a sensing element. Moreover, the safety factor and reliability of composites were calculated based on the stress corresponding to the transition point of the safety states and the ultimate stress of the composites. Consequently, the results show that the reliability is close to 100% when the maximum safety factor of Ni-CF/GFRP is 1.5. In addition, we also suggest two different solutions for manufacturing self-diagnosing composites which can be individually applied in the development of the structures with low failure risk or with high safety requirements
Neel-type antiferromagnetic skyrmionic crystals on two-dimensional square lattices investigated with optimized quantum Monte Carlo method
No full textThe formations of individual antiferromagnetic (AF) skyrmions and AF skyrmionic lattices on two-dimensional (2D) magnets with square crystal structure are debatable in recent years, for only an isolated skyrmion can be generated in such systems if classical Monte Carlo (CMC) method is employed. For the sake, we apply here an optimized quantum Monte Carlo approach to a 2D square magnet where the AF Heisenberg exchange (HE) and Dzyaloshinskii-Moriya (DM) interactions co-exist. Consequently, the computing program converges to the equilibrium states with appreciable computational speed, and the results obtained in the last one iteration are able to accurately produce well symmetric and periodic AF skyrmionic lattices (SLs) at elevated temperatures when a considerably strong external magnetic field is exerted perpendicular to the 2D monolayer. Moreover, each of these AF SLs can be decomposed into two almost identical ferromagnetic (FM) SLs, and the distribution of topological charge density also forms symmetric lattice with the same periodicity as the AF SL, dividing the AF SL into several areas of distinct spin configurations. The reasons why the OQMC approach can work beyond CMC method are explained in the Discussion Section
Ultrathin nanofiltration membrane assembled by polyethyleneimine-grafted graphene quantum dots
No full textEmbedding nanofillers into the selective layer to creating moderate nanopores is a promising strategy to obtain high-performance nanofiltration membranes. Herein, we synthesized polyethyleneimine (PEI) functionalized graphene quantum dots (GQDs) as the water phase monomers and prepared an ultrathin desalination membrane through interfacial polymerization (IP). The in situ embedded GQDs with superiorly uniform dispersion generate abundant nanopores in the membrane, and PEI chains fill the introduced nanopores, avoiding the formation of overlarge nanopores. Besides, the PEI-grafted GQDs (NGQDs) display a reduced diffusion rate during IP, rendering an ultrathin selective layer. Benefiting from the ultrathin thickness (-6.5 nm), the abundant water pathways (specific surface area: 6.73 m(2)/g), and the increased pore size (-0.82 nm), the PA-NGQD600 membrane exhibits competitive pure water permeance (38.5 L m(-2) h(-1) bar(-1)) and inorganic salt rejection (95.5% for Na2SO4). The permeance exceeds those of the most desalination membranes reported so far and is-3 times higher than that of the reported GQD-based desalination membrane. This work provides a facile strategy for creating abundant nanopores in membranes with ultrathin thickness by interfacial polymerization
Designing strong interfacial adhesion between carbon fiber and epoxy resin via dopamine towards excellent protection ability under high hydrostatic pressure and severe erosion corrosion condition
No full textThe complex marine environment in the splash zone and the deep-sea area is always raising stern challenges for the steel structures served in the offshore facilitates. Compared with other coating fillers, the carbon fiber (CF), with outstanding mechanical strength, is a suitable candidate filler for coating reinforcement. However, CF has a poor compatibility with organic resin, which could cause defects inside the coating, and result in coating failure further. Hence, we used dopamine to modify CF surface (CF-PDA) and introduced CF-PDA into the epoxy coating as reinforced additive to improve the erosion wear resistance and anti-corrosion ability of coating. The interfacial shear strength (IFSS) of CF-PDA/epoxy was increased by 32.20%, compared with CF/epoxy. After 120 h immersion under 30 MPa pressure, the |Z|0.01 Hz of the CF-PDA/EP (1.04 x 108 omega cm2) was obviously higher than EP, and the interfaces of steel/coating and CF-PDA/resin were not failure evidently. Meantime, after the erosion wear test, compared with EP, the mass loss and the volume loss of CF-PDA/EP were decreased by 19.40% and 25.72%, respectively. Then, the failure process of coatings was discussed during erosion wear test, and we explained the relationship between the erosion wear resistance of coatings and interfacial strength of CF-PDA/ epoxy resin