查看更多>>摘要：A series of LaFe11.6Si1.4/xwt%Pr2Co7 (x = 0, 5, 10) composites, with a range of particle size of LaFe11.6Si1.4 powders, were successfully fabricated by spark plasma sintering (SPS), followed by annealing. The influence of the particle size of the LaFe11.6Si1.4 powders and the Pr2Co7 binder content on the phase constitution, microstructure, thermal, mechanical, magnetic and magnetocaloric properties were studied. The Pr2Co7 binder content (10 wt%) and the particle size of LaFe11.6Si1.4 powders (100–200 μm) were chosen to be conducive to the formation of the desired 1:13 phase. The magnetic and magnetocaloric properties were influenced by the synergistic effects of Pr and Co atomic diffusion as well by the particle size of the LaFe11.6Si1.4 majority phase powders. The values of TC, ([sbnd]ΔSM)max and RC for the sample could be tuned in the range of 230–297 K, 1.90–3.70 J/kg·K and 84–149 J/kg (ΔH=2 T), respectively, by tuning the Pr2Co7 content and the particle size of the LaFe11.6Si1.4 powders. Significantly, this TC range covers a wide variety of near room temperature cooling applications. The excellent values of thermal conductivity, maximum compressive strength and strain were in the range of 14–20.90 W/m·K, 930–1405 MPa and 5.9–7.9%, respectively. These features make these materials very promising candidates for near room temperature magnetic cooling applications.
查看更多>>摘要：The proposed effort comprehends an extensive learning of the Ll, Lα2 and Lα1? X-ray emission lines of selected gadolinium materials, viz., Gd pure, GdCl3, GdF3, Gd2O3 and Gd2S3O12 by utilizing the encroachment in test-bed based wavelength-dispersive spectrometer. The examination of the energy shifts on the L shell peaks of elected Gd targets has been summarized in the current assessment which involves the proper understanding of the physical fundamental parameters and ligands effects. According to our investigation, no experimental and theoretical data associated to the Ll, Lα2 and Lα1? shell lines for Gd targets was conveyed previously. The obtained measured data reveals that the L shell lines emitted from different Gd targets exhibits the energy shifts of ~ (0.78–5.93) eV comparative to the Gd pure. Furthermore, the good agreement between the measured and theoretical data of radiative transition probabilities for L3M transitions and intensity ratio (I)Ll/Lαη values signifies the prospect of wide utilization of wavelength-dispersive spectrometer for other lanthanide materials. The promising correlation between the bond length, effective charge, intensity ratio and energy shifts for Gd L shell lines in Gd targets are also studied in the current article.
查看更多>>摘要：A built-in electric field generated at the p-n heterojunction will enhance charge transfer at the interface, which brings a new strategy for improving electrochemical energy storage. Herein, we construct a novel p-n heterojunction in a three-dimensional (3D) urchin-like CoNixSy/g-C3N4 (3D–2D) junction microsphere based on a one-step solvothermal method. The forming built-in electric field at the heterointerface of p-type semiconductor (CoNixSy) and n-type semiconductor (g-C3N4) ensure its high-efficiency charge transfer. Besides, the porous 3D urchin-like microsphere could facilitate the diffusion of electrolytes and enhance the stability and volumetric energy density. Benefiting from the synergistic advantages of the p-n heterojunction and the 3D urchin-like structure, the CoNixSy/g-C3N4 electrode displayed an ultrahigh battery-type specific capacity (1029 C g?1) in a three-electrode system. Furthermore, an asymmetric supercapacitor formed by positive electrode of CoNixSy/g-C3N4 and negative electrode of activated carbon (AC) obtains a high energy density of 71.9 Wh kg?1 and a retention of 72.2% after 5000 cycles.
查看更多>>摘要：Investigation on the basic properties and dielectric behavior of Bi2S3 nanorods will open up new areas of applicability of bismuth sulfide nanostructures. In this paper, Bi2S3 nanorods with good crystallinity have been synthesized using bismuth nitrate and thiourea by forced condensation method at 180 °C. The structural and morphological studies reveals the formation of distinct uniform nanorod like morphology, passing high aspect ratio, polycrystalline nature and growth along the orthorhombic (310) axis. The prepared Bi2S3 nanorod samples possess very good dielectric properties. The results obtained reveal that properly oriented nanorods exhibit a high dielectric constant and a small dielectric loss. The dispersion of relaxation time at higher temperature was investigated through the cole-cole analysis and reported here.
查看更多>>摘要：Low coercivity and poor thermal stability are still the main challenges for practical application of low-cost Nd-Ce-Fe-B magnet. To solve these challenging problems, a strategy to simultaneously improve the coercivity and thermal stability of Nd-Ce-Fe-B magnet through combining the nanocrystalline multi-main-phase (MMP) structure and grain boundary engineering is demonstrated. In this study, nanocrystalline MMP Nd-Ce-Fe-B magnet was grain boundary engineered by co-adding DyF3 and Cu powders. The results show that the intrinsic coercivity Hcj is significantly improved, and meanwhile optimum maximum energy product (BH)max is achieved at 2 wt% DyF3-Cu. Moreover, the superior reversible temperature coefficients of Hcj (β) and Br (α) are both achieved, implying the improved thermal stability for the DyF3-Cu added magnet. Microstructural and compositional characterizations indicate that the modified RE-rich phase, the inhibited abnormal grain growth near the flake boundary, and the diffused Dy towards main phase grains are the main reasons for simultaneously enhanced magnetic properties and thermal stability. Thus, combining the nanocrystalline MMP structure and grain boundary engineering will be a promising approach for preparing thermally-stable high-performance Nd-Ce-Fe-B magnet.
查看更多>>摘要：It is essential but challenging to develop advanced electrocatalysts for oxygen evolution reaction (OER) under acidic conditions to break the activity-stability trade-off. In this work, through the controlled partial oxidation of Ru nanoparticles embedded in amorphous carbon, a robust Ru-RuO2 heterostructure with electronic cooperative interfaces was rationally designed and cleverly constructed. The rich heterogeneous interface between Ru and RuO2 creates a good electronic synergy and achieves high-performance OER electrocatalysis in acidic media. The best Ru-RuO2-NC heterostructure exhibits exceptionally excellent activity with an ultralow overpotential (η10) of 176 mV, a high specific mass activity of 1.37 A mgRu?1 (Jm@1.53 V), and an outstanding long-term durability over 80 h at 10 mA cm?2 in acidic environment. More importantly, the Ru-RuO2-NC heterostructure can further be utilized as a bifunctional electrocatalyst to drive acidic overall water splitting with a low cell voltage of 1.55 V and steady operation for at least 40 h at 10 mA cm2, which possesses potential for implementation in the proton exchange membrane water electrolysis.
查看更多>>摘要：To obtain more information and reduce false alarms during molecular identification, the Molybdenum disulfide (MoS2) spaced gold (Au)-silver (Ag) bimetal composite structure for surface-enhanced Raman scattering (SERS)-surface plasmon resonance (SPR) sensor is proposed. The sensor combines the advantages of D-shape plastic optical fiber (D-POF), MoS2-spaced Au and Ag bimetallic composite structure, showing excellent sensitivity. Compared with the Ag/Au bimetallic D-POF experiment (the sensitivity is 2163.57 nm/RIU), the sensitivity of proposed sensor was improved effectively and calculated as 2473.37 nm/RIU in a range of alcohol solution. To evaluate the SERS activity of the proposed sensor, Rhodamine 6 G (R6G) molecules has been successfully detected by Au/MoS2/Ag D-POF sensor with low limited of detection (LOD) of 10?9 M. Meanwhile, the proposed sensor successfully detected glucose with a concentration of 0.625~20% by observing the change of resonance wavelength and the characteristic peak of SERS signal. The highly sensitive spectral signals, richer and more comprehensive information can be obtained to reduce false positives in identification of biomolecules.
查看更多>>摘要：Donor-π bridge-acceptor (D-π-A) design principle has been widely employed to build functionalized materials with excellent optical properties, whereas its feasibility in electrocatalytic reactions is seldom investigated. We demonstrate the primary study of D-π-A rule in constructing electrocatalysts for oxygen reduction reaction (ORR) purpose by rationally designing three cobalt porphyrins EGZ1–3 with 9H-carbazole, triphenylamine and N,N-diphenyl-[1,1′-biphenyl]-4-amine as the donor substituents, respectively, cobalt porphyrin as the π bridge, and cyanoacrylic acid as the acceptor unit. The electronic properties of the molecules are calculated using the density functional theory and the composite catalysts EGZs/C are characterized by a series of spectroscopic approaches. The electrochemical measurements show that EGZ3/C attains a more positive reduction potential and a greater response current density than EGZ1/C and EGZ2/C, which is possibly due to the optimized electronic structure and the substituent effect. The electron transfer number as well as hydrogen peroxide generation yield values suggest slightly better selectivity of EGZ3/C and EGZ2/C than those of EGZ1/C (i.e., ~ 2.9, ~ 2.9 vs. ~ 2.7 and ~ 54%, ~ 53% vs. ~ 62%, respectively) towards full oxygen reduction. Our result reveals the feasibility of the D-π-A design rule and the importance of molecular electronic state and the substituent feature in constructing ORR electrocatalysts.
查看更多>>摘要：Nowadays, the scholars have studied many microwave absorbing materials (MAM) to solve the increasingly serious electromagnetic wave pollution, however, most of MAM are difficult to achieve the ultra-broad band absorption. In this work, we explored the practical applications of the inexpensive FeSiAl (FSA) by using the efficient electromagnetic simulation software, the Computer Simulation Technology (CST). Specifically, FeSiAl/silicon dioxide (FSA/SiO2) microwave absorbers were successfully prepared by a simple stirring method. The obtained FSA/SiO2 samples achieved a reflection loss (RL) of ? 46.6 dB at 9.71 GHz. In addition, a quadrilateral cone model was established by the CST, and the influence of angular cone parameters on absorption performance was investigated in detail through electromagnetic simulation. It is found that the model exhibited extraordinary absorption ability and the effective absorption bandwidth (EAB) reached 16.3 GHz covering 2–18 GHz when the height (H), thickness (t), length (L) were set as 1.9 cm, 0.2 cm, 1 cm, respectively. This work may solve the shortcoming of the narrow absorption band of the absorption powders.
查看更多>>摘要：In this work we have studied the effect of phase composition and microstructure of a rapidly solidified Ti2AlNb-based alloy containing hydrogen on deformation of the alloy during ball milling and production of a fine-dispersed powder. Hydrogen is introduced into the alloy up to a concentration of 2.0 wt%. The X-Ray diffraction (XRD) analysis and Scanning Electron Microscopy (SEM) show that the alloy has the following phase compositions depending on hydrogen content: β + O, β/β-hydride, β/β-hydride + intermetallic hydride (Ti2AlNbHx) or a single-phase intermetallic hydride. It is found that in the hydrogenated β + O alloy containing a small amount of hydrogen a strong decrease in ductility occurs, but this does not affect the ball milling and synthesis of the fine-dispersed powder. Efficient milling of the rapidly solidified alloy has been achieved when hydrogen content was 1.2 wt% and exceeding this value when a transformation from the H-saturated solid solution into a hydride phase is observed in the alloy or the formation of a single phase hydride occurs.
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Elsevier