查看更多>>摘要：Double perovskites Dy2CoMnO6 (DCMO) was synthesized by a sol-gel method and the structure and magnetic properties were systematically investigated. Both X-ray diffraction and Raman spectrum indicate that double pervoskite DCMO has a monoclinic structure with a space group P21/n. A Griffiths phase is confirmed to be existing in DCMO by the magnetic behaviors, which is significantly different from the behaviors of the non-Griffiths phase of Gd2CoMnO6 (GCMO) recently reported in reference. It is suggested that the origins of the different short-range magnetic orders of them can be attributed to the different 3d-4f exchange interactions in DCMO and GCMO, besides the effect of the unavoidable anti-site disorder, inter-rupting the long-range ferromagnetic (FM) order of Co2+-O-Mn4+, resulting in the formation of short-range FM order. The effects of A-site rare-earth Re3+ ions on the magnetism of double perovskite Re2Co(Ni)MnO6 are dominated by the combining and competing functions of the radius and the moments of rare earth ions (or the 3d-4f exchange interactions). The FM/AFM coupling is not only related to the most outer 4f electrons of the rare earth ions, but also to the inner 5d/6s orbital electrons. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Two-dimensional (2D) chromium tellurides have attracted considerable research interest for their high Curie temperatures. Their magnetic properties have been found diverse in various experiments, the understanding of which however remains limited. In this work, we report that the magnetic ordering of ultrathin chromium tellurides is structure dependent and can be tuned by external strain. Based on first-principles calculations and Monte Carlo simulations, we show long-range stable magnetism with high and low Curie temperature, and short-range magnetism in 2D Cr5Te8, CrTe2, and Cr2Te3 layers, respectively. We further find that ferromagnetic-to-antiferromagnetic transition can be realized by 2% compressive strain for CrTe2 and 2% tensile strain for Cr2Te3, and their magnetic easy axis is tuned from out-of-plane to in-plane by the medium tensile and compressive strain. This strain dependent magnetic coupling is found to be related to Cr-Cr direct exchange and the change of magnetic anisotropy is understood by the atom and orbital resolved magnetic anisotropy energy and second order perturbation theory. Our results reveal the important roles of the structure and strain in determining the magnetic ordering in 2D chromium telluride, shedding light on understanding of the diverse magnetic properties observed in experiments. (C) 2021 Elsevier B.V. All rights reserved.
Beladi, HosseinWang, JiangtingTari, VahidHodgson, Peter D....
12页
查看更多>>摘要：The complexity of interphase precipitation in a Fe-0.19C-1.54Mn-0.4Si-0.06Al-0.13Mo-0.06Ti (at%) high strength low-alloy (HSLA) steel at an early stage of the austenite-to-ferrite transformation was studied by analyzing the solute distribution across ferrite-austenite interfaces with Kurdjumov-Sachs (K-S) and non-K-S orientation relationships (OR). Structural characterization i.e. ferrite/austenite OR and habit plane characteristics was performed by electron backscatter diffraction (EBSD) and the clustering back-calculation approach, while solute distributions i.e. the solute concentration spikes in the interface regions were studied by atom probe tomography (APT) on the specimens specifically prepared across/near the ferrite/austenite interfaces. It was shown for the first time that interphase precipitation is promoted at both types of interface: (i) a K-S OR and habit plane deviated from ideal (110)(alpha)//(111)(gamma) and (ii) a non K-S OR. The key aspect of interphase precipitation is the distribution of solute atoms across the interface, which is pronounced Mn, Ti, Mo and C concentration spikes at the interphase boundary. In contrast, interphase precipitates were not formed at the coherent interface with a K-S OR and habit plane of (110)(alpha)//(111)(gamma). This was correlated with the interfacial condition, where the compositional ratio of substitutional solute and solvent elements remains almost constant across the interface, i.e. Mn and C spikes. Interface compositions in this study did not match with local equilibria (negligible partitioning local equilibrium and paraequilibrium) limits. In addition, it appeared that the interfaces with Mn, Ti, Mo and C concentration spikes form ledges leading to randomly redistributed interphase precipitates. (C) 2021 Elsevier B.V. All rights reserved.
Khan, BushraSingh, Manoj K.Kumar, AdityaPandey, Arushi...
11页
查看更多>>摘要：KBiFe2O5 (KBFO) is an interesting multiferroic compound with the coexistence of ferroelectric and ferromagnetic phases with a narrow band gap. In this work, KBiFe2O5 (KBFO) is synthesized using a sol-gel technique, followed by calcination at 973 K. Rietveld refinement analysis of XRD data confirms the presence of monoclinic crystal structure with space group P2/c. The SEM micrograph of KBFO reflects the irregular shape of grains with slight agglomeration. The optical band gap measured by UV visible spectroscopy of KBFO is found to be 1.56 eV. The multiferroic behavior of KBFO has been confirmed by the electrical (dielectric) and magnetic (M-H loop) measurements. A weak ferromagnetic nature is observed due to canting of the magnetic moment of G-type anti-ferromagnetic ordering. The dielectric studies reveal the Maxwell Wagner type dispersion and an anomaly near magnetic phase transition temperature. KBFO shows negative magneto-dielectric (MD) coupling as both epsilon and tan delta decreases with the increasing magnetic field. Impedance spectroscopy is performed to analyze the intrinsic and extrinsic effects in MD coupling. The Nyquist plot shows positive magneto-resistance and negative magneto-capacitance which represent strong MD coupling in KBFO. It also reveals that the bulk property (intrinsic effect) dominates over the extrinsic effect in the sample. These results affirm that KBFO is a new candidate for room-temperature multiferroicity with a suitable bandgap and strong MD coupling for photovoltaic applications. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：It is greatly significant to remove organic dyes and antibiotics in water because they are extremely harmful for human health and environment. In this work, we successfully developed magnetic Fe3O4/GO/Ag com-posite microspheres, using Fe3O4 microspheres as cores to wrap graphene oxide (GO) interlayer and further in situ depositing silver nanoparticles onto GO layer. The microspheres were characterized by SEM, XRD, XPS and Raman spectroscopy. As compared to Fe3O4/Ag microspheres, Fe3O4/GO/Ag composite microspheres displayed higher activity for SERS detection, and also catalytic reaction due to the synergistic interaction of GO nanosheets and Ag nanoparticles. Subsequently, the Fe3O4/GO/Ag composite microspheres were employed to quantitatively detect aromatic molecules, methylene blue (MB) in aqueous solution, showing the limit of detection was low down to 10-9 M and the correlation coefficients (R2) of the linear relationship between SERS intensities and logarithmic concentrations was high up to 0.91. Moreover, the Fe3O4/GO/Ag composite microspheres as catalysts completely degraded methylene blue and ciprofloxacin in 12 min with the presence of NaBH4. Finally, Fe3O4/GO/Ag composite microspheres were utilized to effectively follow the degradation reaction process of MB by SERS. Taken together, Fe3O4/GO/Ag composite microspheres present SERS application potentials in terms of trace and quantitative detection of chemicals, and in-situ monitoring catalytic degradation of organic pollutants. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Due to the pressing need for electromagnetic interference and radar stealth, microwave absorbers have garnered considerable attention. Through chemical co-precipitation and in-situ polymerization, we synthesize a ternary composite containing reduced graphene oxide, Fe3O4 with flower-like nanostructures, and polyaniline (PANI). To fine-tune the impedance matching and corrosion resistance of composite materials, the conductive PANI was densely coated on the surface of reduced graphene oxide (rGO)/flower-like Fe3O4(f-Fe3O4). The ternary composite exhibits excellent microwave absorption performance. In comparison to rGO/f-Fe3O4(1:10), which has a minimum reflection loss (RLmin) of -32.81 dB at 10.61 GHz and a 5.15 GHz effective absorption bandwidth (EAB) (7.34-12.49 GHz), rGO/f-Fe3O4(1:10)@PANI has an RLmin of -46.49 dB at 9.93 GHz with a 2.5 mm thickness and an EAB of 4.25 (8.90-13.15 GHz). The results indicate that the addition of the PANI anticorrosion coating layer has no discernible effect on the final microwave absorption performance. This article also examines the effect of rGO weight ratio on microwave absorbing properties. When the rGO content is too high, the impedance will be mismatched, while the too low rGO content will affect the absorbing performance. This research work has contributed to our present understanding of the structure design and composition control of microwave absorbers. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Ni or Ga doping is well studied in literature. However, a Ga/Ni co-doped ZnO brings in complex competing mechanisms of electron mobility and electron localization. A sol-gel prepared solid solution of Ga/Ni codoped ZnO with hexagonal wurtzite structure (P63mc space group) is studied in detail to correlate the electronic properties to the structure of the materials. Lattice strain studies correlated to these changes in the electronic properties. The drastic reduction in native defects was detailed using the photoluminescence study of Ni/Ga co-doped ZnO. Lattice and phonon studies were used to explain the lattice strain in the ZnO lattice. The % Sensitivity of UV (290 nm), blue (450 nm), green (540 nm) and red (640 nm) wavelengths were tested and correlated with the defects. Additionally, the photo-catalytic dye degradation of toxic methylene blue was investigated and explained with changes in carrier concentration and mobility. The reason behind the conductive parameters was examined theoretically and a possible reason was found in terms of changes in electron localization due to increasing Ni/Ga concentration. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The performance of the electrode material for supercapacitor depends not only on its structure but also on the potential window. In this work, we have demonstrated a two-steps method to prepare the integrated electrode materials. Firstly, Ni@PES films are scribed at CO2 laser induction and Ni@PES-LIG is obtained. Secondly, the subsequent electrodeposition of FeOOH and MnO2 are carried out in three-electrode system. The MnO2/Ni@PES-LIG and FeOOH/Ni@PES-LIG electrodes exhibit high pseudocapacitances of 205 and 210 mF cm(-2), respectively. By using The MnO2/Ni@PES-LIG and FeOOH/Ni@PES-LIG electrodes as the anode and cathode, respectively, we have successfully fabricated the free-standing asymmetric supercapacitor (ASC) device, which has wider potential range over 2.0 V. The Ni@ASC device delivers high areal capacitance (110 mF cm(-2)), high areal energy density (41.6 mu Wh cm(-2)), and high areal power density (136 mW cm(-2)). Additionally, the Ni@ASC assembling with the integrated electrodes reveals a much higher capacitance and wider potential window than other single symmetric and asymmetric supercapacitors due to its multiple energy stored mechanisms. (C) 2021 Elsevier B.V. All rights reserved.
Wang, FeihongDong, BinbinKe, NianwangKhan, Noor Zamin...
8页
查看更多>>摘要：Membranes of ceramic foams exhibit excellent prospects for application in the field of high-temperature particulate matter (PM) capture. Production of ceramic membranes that can achieve good removal efficiency as well as low pressure drop in high-efficiency PM filtration represents a great challenge. This paper reports on the preparation of porous-foam mullite-bonded SiC-ceramic membranes (MSCMs) with a 3D interconnecting pore network by a direct foaming method combined with gel-tape casting. The produced MSCMs contained large pores with a diameter of 60-150 mu m, which were interconnected with abundant small functional (for filtering) pores of < 10 mu m. Increasing the amount of the foaming agent favored the increase of porosity of the MSCMs, which was tailored between 69.2% and 84.1%, while the bending strength decreased from 10.3 to 4.0 MPa, respectively. High PM filtration efficiency (70.2%, 90.1%, and 94.6% for PM0.3, PM2.5, and PM10, respectively) and ultra-low pressure drop (27 Pa) were also recorded. Hence, the produced MSCMs qualify for application as high-temperature PM filters. This work also aims at providing a new insight into developing high-efficiency air filters. (c) 2021 Published by Elsevier B.V.
查看更多>>摘要：Herein, we present an efficient and simple method to develop a 3D-Carbon /MnO2 (C/MnO2) composite active material for high-performance supercapacitors. MnO2 nanorods are synthesized by the hydrothermal process, and corresponding carbon composite is synthesized from table sugar precursors using the combustion process. MnO2 has rod-like morphologies and forms 3D electrode architectures with carbon, and contains about 5-10 nm of carbon coating. The charge storage behavior studied by galvanostatic chargedischarge cycling shows capacitance of 416 F g-1 at 1 A g-1 with capacitance retention of 90% after 5000 cycles. The superior electrochemical performance is attributed to the one-dimensional ion transport of Mn ion, the in-situ 3D electrode architecture, and carbon coating that enhances the conductivity and the surface area of MnO2. C/MnO2 composite exhibits an energy density of 60 Wh kg-1 with a power density of 201 W kg-1. The combined pseudocapacitive behavior of MnO2 and electric double-layer capacitors property of carbon exhibits significant electrochemical performance in the aqueous electrolyte. The synthesis approach uses environment benign active materials with the low cost of electrode fabrication provides an alternative route for the development of high-performance supercapacitors. (c) 2021 Elsevier B.V. All rights reserved.
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