查看更多>>摘要：? 2022 Elsevier B.V.Lead-free energy storage ceramics have attracted a large concentration for their significant role in pulsed power technology. Here, environmentally friendly (Sr0.7Ca0.3)1?1.5xBixTiO3 relaxor ferroelectric ceramics are systematically studied. The introduction of Bi2O3 can enhance polarization. As the Bi2O3 content increases, the dielectric constant rises from 300 to 774, while the dielectric loss is less than 0.5% under a measurement frequency of 1 kHz. For the Sr0.49Ca0.21Bi0.2TiO3 ceramic, an energy storage density (W) of 2.035 J cm?3 and a high energy storage efficiency (η) of 91.84% achieved under an electric field of 260 kV cm?1. The variation rate of the dielectric constant is less than 15% (compared with the capacitance at 25 °C) in the temperature range of ? 55–125 °C, meeting the requirement of the EIA X7R specification, and the W and discharge energy density (Wd) also exhibit desirable temperature stability in the temperature range of 30 °C to 150 °C. These results are related to the homogeneous phase transition and low concentration of oxygen vacancies. The thermal activation of polar nanoregions (PNRs) partially compensates for the reduction of polarization caused by lattice expansion, which also contributes to the temperature stability. Taken together, the results of this study indicate the Sr0.49Ca0.21Bi0.2TiO3 ceramics have potential as a target for developing high energy storage lead-free ceramic capacitors.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, the deformation behaviors of Mg-3Al-1Zn alloy with multi texture components have been investigated using a combined experimental measurement and crystal plasticity modeling. Six types of multi textured samples were successfully prepared by an easily operated processing containing cold rolling, compression loadings, and subsequent annealing. The corresponding processing parameters to control multi texture components were also proposed. The effect of multi texture distribution on macroscopic mechanical response, activation of deformation modes, texture evolution, as well as the 101?2 and 101?1 twin fractions were systematically investigated. It's a challenge work to model several texture components and random textures using EVPSC-TDT model for the first time. The simulation results generally match well with the experimental data. It has been found that the mechanical performance are strongly dependent on the multi texture components distribution and it was revealed by detailing the quantitative contribution of different deformation mechanisms to the plastic deformation. It's the more disperse (0002) distribution of hard orientations that matters in enhancing the yield strength and ductility of samples with a given fraction of soft orientations. The findings in the present study are crucial for enriching the texture engineering for Mg alloys and could assist in designing better materials in term of mechanical properties and material performance.
查看更多>>摘要：? 2022Microcomposite particles of aluminum (Al) dotted by ammonium dinitramide (ADN) (Al@ADN) are successfully prepared by an in-situ crystallization growth method. The morphologies, structures and thermal behavior of Al@ADN are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and simultaneous thermogravimetry and differential scanning calorimetry. The compositions and morphologies of Al@ADN after heating are characterized by X-ray photoelectron spectroscopy (XPS) and SEM. A high-speed camera is used to record the combustion performances of Al@ADN in a transparent quartz tube. Furthermore, the morphologies and structures of the residues are analyzed by SEM and XRD. The results show that ADN is deposited on the surface of Al to form Al@ADN. The decomposition of ADN increases the total oxidation degree of the Al particles. Under heating, the acids decomposed by ADN corrode the surficial alumina layer and the internal aluminum react with HNO3 to form Al(NO3)3, which makes the combustion of Al easier. Under an oxygen atmosphere, the pure Al could not be ignited. In contrast, Al@ADN could be ignited and Al@ADN 5:1 has a shorter ignition and burning time compared with Al@ADN 10:1. After burning, the Al@ADN composites are completely converted to α- and γ-Al2O3. For Al@ADN 10:1, the residues show a cube-like stacking, while a ribbon-like stacking is presented for Al@ADN 5:1.
查看更多>>摘要：? 2022 Elsevier B.V.Flexible, transparent and conductive materials applied to the electromagnetic interference (EMI) shielding of foldable and wearable devices is urgently demanded in fifth-generation internet era. However, it is still a great challenge to realize excellent EMI shielding effectiveness (EMI SE) while maintaining high light transmittance. Herein, a double-layered structure strategy was proposed to prepare transparent and conductive silver nanowires (AgNWs) film with outstanding EMI SE. Specifically, the AgNWs network was partially embedded to hydroxy propyl methyl cellulose (HPMC) coating to enhance greatly its connectivity and integrity. As a result, the AgNWs/HPMC film showed a high transmittance of 90.55% at 550 nm and a sheet resistance of 11.62 Ω/sq, much better than other reported AgNW composite films so far. Meanwhile, the structural design also contributed to a high EMI SE of 45.79 dB. Meanwhile, it exhibited an enhanced conductive stability during bending test and harsh environment, such as full-oxygen, thermal and cold environment. Moreover, the multifunctional AgNWs/HPMC film presented remarkable thermal management performances including safe heating temperature (~ 71.3 °C) at high supplied voltages (7 V), ultra-rapid response time (~ 11 s), long-term heating stability and reliability. This work presented a facile and scalable approach to obtain the flexible AgNWs/HPMC film with high light transmittance and high EMI SE, promising for the EMI shielding foldable and homoiothermy wearable system for human.
查看更多>>摘要：? 2022The non-centrosymmetric hexagonal Ba2Ga8GeS16 (B2GGS) crystal is grown for the first time with good optical quality by the vertical Bridgman-Stockbarger technique. The linear (transmission, dispersion, and birefringence) and nonlinear (second order susceptibility) properties of this new uniaxial nonlinear crystal for the mid-IR part of the spectrum are studied.
查看更多>>摘要：? 2022BiFeO3–(Co/Ni)Fe2O4 (BFO–(C/N)FO) multiferroic nanofibers were synthesized using a self-assembly coaxial electrospinning technique. The structure, exchange bias effect, ferromagnetic, and ferroelectric properties were investigated using various physical and chemical characterization approaches. The coexistence of a spinel–perovskite mixed structure was verified in (BFO–(C/N)FO) nanofibers by X-ray diffraction and X-ray photoelectron spectroscopy. Raman spectra revealed a distorted crystal structure or more complex phase configurations with overlapping features. Compared to the pure BFO nanofibers, the magnetic properties showed a significantly increase after recombination. BFO–NFO nanofibers exhibited higher exchange coupling through switching field distribution analysis. The ferroelectric properties of the composite nanofibers were considerably changed compared to pure BFO nanofibers, which can be attributed to the presence of impurities (Bi2Fe4O9) and the asymmetrical spin in spinel ferrites. The BFO–CFO nanofibers exhibited larger leakage current and coercive electric field than the other two types of nanofibers. Hence, coupling of the structural distortion and crystal phases are important approaches in altering the ferroelectric and ferromagnetic properties. These results suggest that the BFO–(C/N)FO nanofibers have potential applications in multifunctional nanodevices.
查看更多>>摘要：? 2022 Elsevier B.V.From first principles computation, we propose hexagonal MnGe as a ferromagnetic Kagome candidate. As for three dimensional (3D) MnGe, the nearest, next-nearest and next-next-nearest magnetic exchange interaction parameters are respectively estimated to be 0.4 meV, 7.8 meV and 1.8 meV within the Heisenberg model while the calculated Curie temperature Tc is approaching 115 K based on Monte Carlo (MC) simulation. As for two dimensional (2D) MnGe monolayer, the spin-orbit coupling (SOC) would bring in a tiny gap (~ 1.9 meV) at the Dirac nodes and quantum anomalous Hall (QAH) effect, characterized by the chiral edge states and nonzero Chern number (C = 1). Moreover, the Dirac points can be tuned to the fermi level EF by 1.5 electrons doping or 3.3% compressive biaxial strain. Besides, possible synthetic scheme as well as the mechanical, dynamical and thermal stability are confirmed for both bulk and monolayer MnGe. Thus our work provides a promising Kagome ferromagnet to study intriguing topological physics associated with Dirac fermions towards spintronics application.
查看更多>>摘要：? 2022 Elsevier B.V.At 300 K, Y0.9Gd0.1Fe2Hx hydrides crystallize sequentially with increasing H concentration in various structures related to a lowering of the cubic MgCu2 type structure of the parent alloy: cubic C1, monoclinic M1, cubic C2, monoclinic M2, cubic C3, orthorhombic O. Above 300 K, they undergo a first-order transition at a TO-D temperature driven by order-disorder of hydrogen atoms into interstitial sites. Their magnetic, structural and magnetocaloric properties have been investigated through magnetic measurements, and high-resolution synchrotron diffraction experiments. The magnetization at 5 K decreases slightly from 4 to 3.8 μB for x = 3–3.9 H/f.u., then with a larger slope for higher H content. A discontinuous decrease of the magnetic transition temperature is observed: M1 and C2 hydrides are ferrimagnetic with TC near 300 K, M2 hydride displays a sharp ferromagnetic-antiferromagnetic transition at TFM-AFM = 144 K, whereas C3 and O hydrides present only a sharp increase of the magnetization below 15 K and a weak magnetization up to room temperature. Negative magnetic entropy variations (ΔSM) are measured near TC for the M1 and C2 phases, near TFM-AFM for the M2 phase, whereas positive ΔSM peaks due to inverse MCE effect are found near TO-D. A structural and magnetic phase diagram is proposed.
查看更多>>摘要：? 2022L10-MnGa alloy film is a kind of promising material for application of spintronics device and permanent magnet. In this paper, we prepare the Fe-doped L10-MnGa films on thermal MgO (100) substrates with different annealing temperatures and report magnetic regulation of the off-stoichiometric L10-MnGa thin film by tuning Fe doping amount and annealing temperature. It is found that the 4.6% Fe-doped L10-MnGa film has (001) orientation, large coercivity of 6.14 kOe, high effective anisotropy constant of 9.9 Merg/cc and low saturation magnetization of 482 emu/cc. The film annealed at 500 °C has a maximum magnetic energy product of 9.21 MGOe. The production of tensile strain and the change of interatomic exchange coupling state by Fe doping and annealing temperature enable the L10-MnGa film to apply in many fields. It is noteworthy that there are the different doping results compared to the Pt-doped L10-MnGa film in the previous work. These research results are valuable for the design and application of L10-MnGa film.
查看更多>>摘要：? 2022 Elsevier B.V.The nanohybrids of hematite (α–Fe2O3) nanoparticles and reduced graphene oxide (rGO) nanosheets were prepared by a facial two-step chemical method. The α[sbnd]Fe2O3 nanoparticles prepared by a sol-gel technique were hybridized with the pristine rGO nanosheets by ultra-sonication-assisted method. The rGO and α–Fe2O3 nanoparticles were dispersed in toluene to prepare (rGO)x/α–Fe2O3 nanohybrids. The crystal structure, vibrational modes, surface morphology, and elemental composition of these (rGO)x/α–Fe2O3 nanohybrids were investigated. The 3D nanostructure of α–Fe2O3 nanoparticles were randomly anchored on cross-linking rGO nanosheets. These rGO nanosheets functioned as mechanical support and an efficient electron conducting pathway in the (rGO)x/α–Fe2O3 nanohybrids. X-ray diffraction (XRD) spectra confirmed the crystal structure and phase purity while scanning electron microscopy (SEM) images showed the dispersion of α–Fe2O3 nanoparticles over rGO nanosheets. The hybridization of rGOs nanosheets with α–Fe2O3 nanoparticles significantly enhanced the electrochemical storage performance as anode material for LIBs. The first discharge capacity for the (rGO)x/α–Fe2O3 nanohybrids of 1469 mAh/gwas much better than that of the bare α–Fe2O3 nanoparticles of 895 mAh/g. Cyclic stability was enhanced as the discharge capacity was retained after 100 cycles for the (rGO)x/α–Fe2O3 nanohybrids. Moreover, the improved rate capability that was also observed for the (rGO)x/α–Fe2O3 nanohybrids further authenticates the use of these nanohybrids as anode materials for LIBs.
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