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Phase separation of polymer blends has attracted much interest in designing high-performance materials with specific mechanical and dielectric properties. To this end, three types of poly(methacrylic ester)s, including poly(methyl methacrylate) (PMMA), poly(butyl methacrylate) (PBMA), and poly(isobutyl methacrylate) [P(iBMA)], have been incorporated in the poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)] matrix, respectively. As exemplified in P(VDF-HFP)/P(iBMA) blended films, a conspicuous phase separation is experimentally observed and the blended film presents an enhanced Young's modulus and a one-fold increment in the elongation over the pristine P(VDF-HFP). The excellent plasticity is benefited from the interfacial regions between the two phases, which could effectively pin the cracks and retard the slippage under deformation. Simultaneously, an ultra-high Weibull breakdown strength (∼774 MV/m) is obtained in the blends, benefiting from the improved Young's modulus and excellent plasticity. The blends are endowed with an excellent energy storage density (∼21 J/cm3 at 830 MV/m), along with an impressive cycling stability. In contrary, P(VDF-HFP)/PMMA and P(VDF-HFP)/PBMA blended films sacrifice the plasticity due to the scarcity of phase separation; therefore, even though Young's moduli have been improved, there is no remarkable improvement for breakdown strengths and energy storage performances. The experimental results are augmented by molecular dynamics simulations. This contribution provides a facile approach to develop high-performance polymer dielectric materials through a phase separation design and emphasize the importance of plasticity for breakdown strength. [ABSTRACT FROM AUTHOR]

Plasmonic structure (PS) has recently been demonstrated to provide full control of dispersion characteristics by virtue of spoof surface plasmonic polariton (SSPP). In this paper, a comprehensive scheme is proposed, which develops the non-planar PS as a covering on the absorber to enhance the k-vector matching absorption in a wider frequency band. Owing to the dispersion engineering of SSPP, our theoretical investigation shows that the PS covering based on a straight wire array can not only enhance the k-vector matching absorption of the ground absorber at low frequency, but also achieve the broadband absorption at high frequency. As a proof, two hybrid plasmonic metamaterial absorbers (PMAs) based on the combinations of PS covering and various absorbers are proposed here. Simulations and experimental measurements demonstrate that two kinds of hybrid PMAs can simultaneously achieve broadband absorption enhancement, especially for the lower-frequency absorption. Our proposed strategy succeeds in the comprehensive utilization of dispersion engineering for broadband absorption enhancement, and a wide range of applications is expected to emerge from our design concept ranging from microwave to optical frequencies. [ABSTRACT FROM AUTHOR]

Naturally occurring water is a promising candidate for achieving broadband absorption. In this work, by virtue of the optically transparent character of the water, the water-based metamaterial absorbers (MAs) are proposed to achieve the broadband absorption at microwave frequencies and optical transparence simultaneously. For this purpose, the transparent indium tin oxide (ITO) and polymethyl methacrylate (PMMA) are chosen as the constitutive materials. The water is encapsulated between the ITO backed plate and PMMA, serving as the microwave loss as well as optically transparent material. Numerical simulations show that the broadband absorption with the efficiency over 90% in the frequency band of 6.4-30 GHz and highly optical transparency of about 85% in the visible region can be achieved and have been well demonstrated experimentally. Additionally, the proposed water-based MA displays a wide-angle absorption performance for both TE and TM waves and is also robust to the variations of the structure parameters, which is much desired in a practical application. [ABSTRACT FROM AUTHOR]

Voltage-modified Kerr magnetometer has been widely used to measure the voltage-modulated magnetic properties in multiferroic magnetic/ferroelectric heterostructures, where the Kerr signal change is considered to be in proportion to magnetization change, i.e., the magneto-optical Kerr effect. However, the total Kerr signal changes might also incorporate contribution from the electro-optical effect of the ferroelectric layer in the multiferroic heterostructure. Here, we evaluate quantitatively, by combining analytical calculations with experimental observations, such electro-optical contribution in the total voltage-induced Kerr signal changes with comparison to those from Kerr effect via converse magnetoelectric coupling. Influences of several parameters, including the magnetic film thickness on the Kerr signal changes, are also investigated. [ABSTRACT FROM AUTHOR]

The converse magnetoelectric (ME) effect was investigated in bi-layered Ni/Pb(Zr0.52Ti0.48)O3 (PZT) thin films grown on Si substrates, with different thicknesses of Ni thin layers. By using an AC-mode magneto-optical Kerr effect method, it was revealed that the electric-voltage induced magnetization variation was dependent on the thickness of the Ni thin layer. The results showed that the Ni/PZT bilayered films with thick (about 40 nm) Ni films presented a dominative strain mediated ME coupling, whereas an interface-charge and strain co-mediated ME coupling might coexist in the Ni/PZT bilayered films with decreasing thickness (e.g., about 10 nm) of Ni films. [ABSTRACT FROM AUTHOR]

Ca and Mn co-doped BiFeO3 (BFO) thin films were fabricated on (111) Pt/Ti/SiO2/Si substrates via a simple solution approach. Enhanced ferroelectric properties were obtained in these Ca and Mn co-doped BFO films, e.g., large remnant polarization value (Pr ∼ 89 μC/cm2) and large remnant polarization to saturated polarization ratio (Pr/Ps ∼ 0.84) for Bi0.90Ca0.10Fe0.90Mn0.10O3 film. X-ray diffraction and Raman spectra of these films showed that B-site Mn doping causes substantial structural transition toward orthorhombic phase and A-site Ca doping facilitates an evolution to tetragonal phase with higher crystal symmetry. The structural transitions are in favor of enhanced ferroelectric properties in the BFO films. The approach of A and B site co-doping is proved to be effective in enhancing ferroelectric performance in multiferroic BFO films. [ABSTRACT FROM AUTHOR]

Switchable voltage modulation of the magnetic properties is reported in different multiferroic bilayers with magnetic films grown on pre-poled ferroelectric substrates, based on the magneto-optical Kerr effect observations. The dynamic voltage control of the magnetic coercive field (Hc) is dependent not only on the materials properties of each ferroic layer, but also on the bias voltage history. The Hc versus electric field behaviors essentially track the dependence of the piezostrains of the substrates on the bias voltage. The observations demonstrate that Hc in such multiferroic bilayers can be controlled by voltage via strain-mediated magnetoelectric coupling and that the Hc change is not an artifact due to a heating effect. [ABSTRACT FROM AUTHOR]

Carbon fibers filled low-density polyethylene matrix composites were prepared by means of the Hakke driver. The percolation of dielectric property occurs when the volume fraction of the CF in the composites is up to 0.20. The unexpected higher percolation threshold is explained according to the microstructure of the composites.

Ca-doped BiFeO3 nanofibres have been fabricated by electrospinning method. Our results indicate that phase transition from space group R3c to C222 can be observed by the Ca doping. These BiFeO3 nanofibres show obvious room temperature ferromagnetic behaviors, and saturation magnetization can be enhanced with the Ca-doping concentration increasing, which could be correlated with the variation of the ratio of Fe2+/Fe3+ valence state. The BiFeO3 nanofibres show obvious photocatalytic performance and can be improved by the Ca-doping. [ABSTRACT FROM AUTHOR]

A novel characterization method is presented to directly observe the pure converse magnetoelectric (ME) effect, i.e., the electric-field modification of magnetization, in composite magnetic/ferroelectric (FE) layered thin films. A low-frequency AC electric-voltage, rather than DC voltage bias, is applied to the FE thin films to minimize the leakage current, whereby the possible side effect of heating can be avoided. In particular, by synchronizing the frequency of the Kerr signal detector to the AC actuation voltage bias, the voltage-induced change of the magnetization in the magnetic films can be in situ recorded even under zero external magnetic fields. For illustration, this method is applied to two similar magnetic/FE composite thin films, with significant strain-mediated converse ME coupling being demonstrated in both cases. [ABSTRACT FROM AUTHOR]

Carbon fiber (CF) filled low-density polyethylene (LDPE) matrix composites was prepared by means of the Hakke driver. The dielectric properties of the CF/LDPE composites as a function of the frequency and the volume fraction of CF were studied. The dielectric constants decrease slowly with increasing the frequency and rise gradually with increasing the CF contents in the composites. As the volume fraction of the CF is up to 0.20, an abrupt increase in the dielectric constant occurs, and accordingly electrical conductivity measured at low frequency increases rapidly at this volume fraction. The percolation theory and the simple concept of polarization in the capacitors are employed to explain these experimental results. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

LixNi0.97-xFe0.03 nanofibers with different Li doping concentration have been synthesized by electrospinning method. The phase composition and microstructure analysis show that Fe and Li doping has no influence on the phase structure and morphology of NiO nanofibers, which reveal that the doped Fe and Li have been incorporated into the NiO host lattice. All the Li and Fe co-doped NiO nanofiber samples show obvious room-temperature ferromagnetic properties. The saturation magnetization can be enhanced with increase of the Li doping concentration. This phenomenon can be ascribed to the fact that the hole doping makes ferromagnetic coupling interactions between the holes and localized Fe 3d states more efficient. [ABSTRACT FROM AUTHOR]