Typical Hysteresis Loops Research Articles

Comparison on Hysteresis Loops and Dislocation Configurations in Fatigued Face-Centered Cubic Single Crystals

The aggregation and evolution of dislocations form different configurations, which are the preferred locations for fatigue crack initiation. To analyze the spatial distribution of the same dislocation configuration and the resulting configuration morphologies on different observation planes, several typical hysteresis loops and dislocation configurations in fatigued face-centered cubic single crystals with various orientations were compared. The crystal orientations of these specimens were determined by the electron back-scattering diffraction technique in a Cambridge S360 Scanning Electron Microscope. It is well known that dislocation ladder and wall structures, as well as patch and vein structures, are distributed on their respective observation planes, (12¯1) and (111). These correspond to the point defect direction and line defect direction of dislocations, respectively. Therefore, the wall structures on the (12¯1) and (111) planes consist of point defects and line defects, which can be defined as point walls and line walls, respectively. Furthermore, the walls on the (12¯1) plane consist of Persistent Slip Band ladders connected with each other, corresponding to the formation of deformation bands. The evolution of dislocation patterns follows a process from patch to ladder and from vein to wall. The formation of labyrinths and dislocation cells originates from the activation of different secondary slip systems. In one word, it can help us better understand the physical nature of metal fatigue and failure by studying the distribution and evolution of different configurations.

Component design for stabilizing P phase in NaNbO3-based ceramics and the energy storage performance

Antiferroelectric (AFE) ceramic dielectrics are widely recognized for their high potential in high-power pulse equipment applications. Lead-free NaNbO3 (NN) antiferroelectric ceramics have emerged as a prominent research topic in the field of energy storage due to their abundant phase structure, affordability, and moderate bandgap. The metastable ferroelectric Q phase results in a square hysteresis loop for NN at room temperature. However, 0.96NaNbO3-0.04 CaZrO3 (NNCZ) exhibits a typical double hysteresis loop at room temperature with the main crystalline phase being the antiferroelectric P phase, which has poor energy storage performance. In this study, Bi0.5Na0.5TiO3 (BNT) is used to optimize the energy storage performance and stabilize the P phase in NNCZ simultaneously. The dielectric constant and temperature-dependence XRD results that from −100 °C to 350 °C, x = 0.05 undergoes a phase transition from AFE P to AFE R and then to PE S. The solid solution of BNT decreased the sintering temperature of NN-based ceramics and decreased average grain size, thereby facilitating domain size reduction and improving the sample's energy storage efficiency from ∼30 % to ∼60 %, with an effective energy storage density reaching 1.51 J/cm3. The above results demonstrate that enhancing energy storage efficiency can be achieved through component design by reducing average grain size.

Modulated magnetostriction and multiferroic properties in the PVDF-based cobalt ferrite particulate composites

Multiferroic materials (MFM) have drawn substantial attention for developing smart magnetodielectric devices. Herein, cobalt ferrite CoFe2O4 (CFO) was synthesized by a glycine–nitrate sol-gel auto-combustion route and, PVDF-based particulate composite films embedded with CFO have been developed. A comprehensive investigation evaluated the effects of magnetostriction, initiated from the embedded CFO phase, on magnetodielectric characteristics of composite films. The structural, electrical, magnetostrictive and magnetodielectric properties were investigated. The embedded CFO particulate endows PVDF matrix at a higher β–phase forming ability, which enhances the ferroelectricity with a polarisation (Pmax∼1.09 μC/cm2@ 850 kV/cm), a higher dielectric constant (εr∼12.33) and lower dielectric loss. The typical magnetic hysteresis loop was obtained with saturation magnetization (MS∼4.96 emu/g) and coercivity (HC∼1.49 kOe), revealing the ferromagnetic ordering in composite films. The response of the magnetodielectric (MD) is observed at room temperature, that is, a large negative MD coefficient ∼2.1 % @ Hcr∼5.0 kOe is achieved for Co0.9Fe2.1O4/PVDF composite films, while MD∼0.65 %@ Hcr∼1.0 kOe is obtained for Co1.1Fe1.9O4/PVDF films, accompanied by a maximum MD∼4.35 % at resonance frequency. The variation in the MD performance reveals a close correlation to the modulated magnetostriction, such as the magnetocrystalline anisotropy, field-induced coefficient and magnetostrictive susceptibility, indicating the strain-mediated coupling MD effect. The multiferroic properties in CoxFe3–xO4/PVDF composites have potential for magneto-dielectric sensing applications. Furthermore, this work would be exploited to understand MD coupling mechanism and develop MFM for multifunctional devices.

Using Fractal Theory to Study the Influence of Movable Oil on the Pore Structure of Different Types of Shale: A Case Study of the Fengcheng Formation Shale in Well X of Mahu Sag, Junggar Basin, China

This study investigated the influence of movable oil on the pore structure of various shale types, analyzing 19 shale samples from Well X in the Mahu Sag of the Junggar Basin. Initially, X-ray diffraction (XRD) analysis classified the shale samples. Subsequently, the geochemical properties and pore structures of the samples, both pre and post oil Soxhlet extraction, were comparatively analyzed through Total Organic Carbon (TOC) content measurement, Rock-Eval pyrolysis, and nitrogen adsorption experiments. Additionally, fractal theory quantitatively described the impact of movable oil on the pore structure of different shale types. Results indicated higher movable oil content in siliceous shale compared to calcareous shale. Oil extraction led to a significant increase in specific surface area and pore volume in all samples, particularly in siliceous shale. Calcareous shale predominantly displays H2–H3 type hysteresis loops, indicating a uniform pore structure with ink-bottle-shaped pores. Conversely, siliceous shale exhibited diverse hysteresis loops, reflecting its complex pore structure. The fractal dimension in calcareous shale correlated primarily with pore structure, exhibiting no significant correlation with TOC content before or after oil extraction. Conversely, the fractal dimension changes in siliceous shale samples do not have a clear correlation with either TOC content or pore structure, suggesting variations may result from both TOC and pore structure.

Endowing Ferroelectric Properties of Tetragonal Lysozyme Crystals through C60 Doping

The inherent nonpolarity of tetragonal lysozyme crystals excludes a ferroelectricity response. Herein, we present a demonstration of achieving measurable ferroelectricity in tetragonal lysozyme crystals through C60 doping. Ferroelectric characterizations revealed that C60-doped tetragonal lysozyme crystals exhibited typical characteristic ferroelectric hysteresis loops. Crystallographic structural analysis suggested that C60 doping may induce a reduction in the overall symmetry of tetragonal Lys@C60, leading to the observed ferroelectricity response. Moreover, the introduction of C60 facilitates efficient electron transport inside the crystal and influences the polarization of Lys@C60, further contributing to the observed ferroelectricity response. This work verifies that C60 doping can serve as a simple strategy to bestow novel ferroelectric properties to non-ferroelectric lysozyme crystals, potentially rendering them suitable for biocompatible and biodegradable application in implantable and wearable bioelectronics.

Magnetic suppression for a possible Fe-poor organic–inorganic hybrid superconductor Fe14Se16(tepa)0.8 (tepa = tetraethylenepentamine) with a superconducting transition at ∼42 K

Composition/structure-dependent superconductivity for FeSe-based superconductors attracted great attention not only due to their high superconducting transition temperatures (TC), but also for understanding the origin of iron-based superconductivity. Here, we report a new Fe-poor organic-inorganic hybrid material Fe14Se16(tepa)0.8 with a paramagnetic-diamagnetic transition at ∼42 K grown by a high-temperature organic-solution-phase method with soluble iron/selenium sources in a tepa solution, alternative to previous intercalation strategies. The Fe14Se16(tepa)0.8 phase is in a tetragonal layered hybrid structure with a nanoplate shape. Composition analyses reveal a Fe-poor characteristic of the hybrid in contrast to previous FeSe-intercalated superconductor, and selected area electron diffraction pattern is featured by Fe3Se4 superstructures with a √2 × √2 of Fe vacancy order. Ab initio density functional calculations show that minus Fe3Se4 ions are stable in the hybrid and ∼0.25e−/Fe0.75Se is obviously larger than the reported values of approximately 0.2e−/FeSe in other FeSe-intercalated superconductors. Typical hysteresis loops and temperature dependence of dc/ac susceptibilities of the Fe14Se16(tepa)0.8 measured below ∼42 K suggest a presence of the Meissner effect in this material. Effects of synthesis conditions on structures and magnetic properties of the hybrids show a magnetic evolution from a long-range ferrimagnetic (FIM) order of Fe14Se16(tepa) to a coexistence of FIM and superconducting (SC) orders of Fe14Se16(tepa)0.9 and an SC order of Fe14Se16(tepa)0.8. X-ray absorption spectrum (XAS) confirms the presence of ferric/ferrous irons. Mössbauer studies reveal that the high-TC superconductivity originates from a suppression of the FIM order through tuning the spin states of irons from high-spin Fe3+ (S = 5/2) and Fe2+ (S = 2) in the Fe14Se16(tepa) to low-spin Fe3+ (S = 1/2) and Fe2+ (S = 0) in the Fe14Se16(tepa)0.8. Although no zero resistance is detected even at a temperature of 2 K, the resistivity at 2 K decreases by more than 1600 times compared to that in a normal state calculated by a variable range hopping (VRH) model, suggesting that the high-TC superconductivity of Fe14Se16(tepa)0.8 is possible.

Investigation of structural, dielectric and ferroelectric properties of nickel substituted BST ceramics

ABSTRACT The current study demonstrates the effect of Ni-substitution on the structural, dielectric and ferroelectric properties of Ba0.90Sr0.10Ti1-xNixO3 (where x = 0.000, 0.005, 0.015 and 0.025) ceramics, synthesized by solid-state reaction approach. A pure perovskite phase with tetragonal structure has been confirmed by X-ray diffraction (XRD) analysis. Scanning electron microscope (SEM) images revealed change in microstructure. The dielectric behavior of the prepared ceramics was investigated as a function of temperature (30–150°C) at different frequencies. The results indicate that there is an increase in dielectric constant (ϵRT) and low dielectric loss (tanδRT) were obtained at room temperature by substitution of Ni2+ ions in BST ceramics, offering a promising material for capacitor applications at room temperature. Room temperature P-E loops were recorded at different applied electric fields and typical hysteresis loops were obtained. Improvement in the values of Pr and Pmax was observed by substitution of Ni2+ ions.

An ultra-high-frequency memristor circuit model

In the context of sixth-generation (6G) wireless communications technology, advanced radio-frequency switches are required to accommodate high-frequency terahertz range and complex modulation techniques. This paper proposes a flexible charge-controlled memristor model specifically designed for ultra-high-frequency applications. It describes in detail the derivation of the behavior model of the proposed memristor circuit. The memristor circuit model is built around four inverters, two multipliers, one integrator, one adder, and one differentiator. Through PSPICE simulation, the typical hysteresis loop of the memristor is thoroughly analyzed, demonstrating its suitability for use in wireless communication systems. The model exhibits a good typical hysteresis loop that operates over a wide frequency range from 100 kHz to 20 THz, meeting the specific requirements of terahertz applications. Compared to existing memristor designs, it operates at a much higher frequency. However, the zero crossing of the typical hysteresis loop deviates when the operating frequency exceeds 20 THz. Furthermore, the proposed memristor model can be customized in terms of set/reset voltage, operating frequency and , and has been verified for use in high speed switches with switching speeds of 19.5 ps. Furthermore, this research fills the gap in ultra-high-frequency memristor modeling, offering valuable insights and guidance for the utilization of memristors in the 6G technology and ultra-high frequency fields.

Structural and electrical properties of 0.98(KO\(_{0.5}\)NaO\(_{0.5}\)NbOO\(_{3}\))-0.02(BiO\(_{0.5}\)NaO\(_{0.5}\)TiOO\(_{3}\)) ceramics

In the present communication, lead-free ceramics having composition 0.98(K0.5Na0.5NbO3)-0.02(Bi0.5Na0.5TiO3) were synthesized by a high-temperature solid-state reaction route. The Rietveld refinement for the 0.98KNN-0.02BNT reveals an MPB with phase fraction Amm2 (87.76 %) and Pm-3m (12.27%). The SEM study predicted a mean diameter of 0.98KNN-0.02BNT grains as 0.52µm±0.19. The 0.98KNN-0.02BNTceramic displayed a typical hysteresis loop with a remnant polarisation(Pr) of 7.0 μC/cm2, saturation polarization (Ps) of 16 μC/cm2, and a coercive field (Ec) of 26 kV/mm. The electrical, Raman spectra, dielectric, and hysteresis loop study supported a morphotropic phase boundary. The synthesized KNN-BNT lead-free material can be an excellent material for designing new devices like ultrasonic transducers and piezo-actuators.

A novel technique for porous framework cordierite synthesis at room temperature and its catalytic cracking of waste polypropylene to produce motor oil and petrol

Conventional Cordierite is a non-framework metal oxide composite and is synthesized above 1000 °C. In our present investigation, Tetraethylenepentamine (TEPA) is a template for the synthesis of nanoporous tetrahedral framework cordierite (Aluminosilicate) at room temperature. Co2+ (non-isomorphous substitution) and Mn2+ (isomorphous substitution) are performed to produce α- cordierite and β-cordierite respectively. Both metal ions are in octahedral coordination by the direction of the template. Synthesized materials are characterized by FT-IR, XRD, BET and TEM are confirmed the framework, crystallinity, porosity and morphology respectively. BET analysis is shown that pore shapes for α- cordierite (13.5 nm) are H1 type and β-cordierite (11.9 nm) is H3 type hysteresis loop. Both cordierites are applied for the waste polypropylene cracking reaction. It is observed that α- cordierite has produced motor oil as a major product and β – cordierite has produced petrol as a major product.

Experimental investigation of a Wells turbine under dynamic stall conditions for wave energy conversion

Marine energy still plays a marginal role in the current global energy scenario, despite the incessant effort by research for more than thirty years in the exploitation of the so-called blue energy. Among the wide range of marine technologies, wave energy harvesting can play a significant role in view of its potential and Oscillating Water Column (OWC) systems, coupled with Wells turbines, can be considered among the most mature wave energy technology. Due to the oscillating nature of the flow rate in this kind of applications, Wells turbines are affected by dynamic stall, which has significant effects in terms of performance, fatigue, noise and structural integrity of the turbine.Actually, during dynamic stall, the Wells turbine experiences evident high frequency torque fluctuations which overlay on the typical hysteresis loop, mainly during flow deceleration. The amplitudes of these fluctuations are damped as the flow rate decreases toward reattachment. Often these fluctuations are not evident because hysteresis loops are usually provided with phase-averaged data, which can significantly smoothen or even conceal them. Indeed, it is difficult to find in the literature high frequency torque measurements able to show these fluctuations. With the aim to better investigate how the stall triggers this phenomenon, a monoplane Wells turbine has been manufactured in 3D printing and tested in the open wind tunnel of the Polytechnic University of Bari, Italy. The interest of the experimental campaign has been mainly focused on the effects of main parameters of the oscillating inlet flow rate (mean flow rate, amplitude and period of the oscillations, modifying the controlling parameters of the inverter driving the squirrel cage blower) on the performance of the machine. The machine has been firstly investigated under steady state inlet flow conditions, then under dynamic stall conditions. As a result, unsteady torque fluctuations occur during the flow deceleration till the flow reattachment. After the stall, the investigated Wells turbine experiences a drastic reduction of the torque coefficient of about 90%. Moreover, the torque coefficient shows a number of peaks during deceleration phases ranging from 2 to 4. Specifically, the case with the maximum period of the flow rate under investigation (i.e., T = 20 s) shows a greater number of peaks (4) than those related to the other cases (3). Moreover, it has been found that this unsteady behavior is due neither to the mass flow rate crossing the turbine, nor to the stagnation pressure drop, nor to the rotational speed control, which is correctly performed keeping the rotational speed within 1% of the target value. Hence, detecting these oscillations can be relevant in the turbine design phase to enhance the structural strength of the turbine.

In-situ growth of homogeneous δ-MnO2 within lignin based porous carbon to reassemble uniform mesoporous crosslinked 3D-network structure for supercapacitors

In order to enhance the electrochemical performances of lignin based porous carbon (LPC), a feasible strategy is to incorporate homogeneous δ-MnO2 nanosheets within the LPC substrate via in-situ redox deposition. This work clarified the effects of different LPC supports and KMnO4 solution concentration on in-situ growth of MnO2 and the electrochemical performances of MnO2/LPC composite. The surface topography of δ-MnO2 significantly depends upon the pores feature of LPC. In-situ growth of δ-MnO2 embedded within LPC nanostructure also has a similar type of N2 adsorption-desorption isotherms of nanopores with the original LPC, belong to the type-IV isotherm with a hysteresis loop of H4 type. Moreover, as the KMnO4 solution concentration increases from 1 to 6 mM, the crystal form of δ-MnO2 within LPC maintains, while the electrochemical performances of MnO2/LPC can be improved. Such a uniform 3D-interlinked mesoporous nanostructure of Mn-4/LPC-CO composite electrode exhibits the highest specific capacitance of 198 F g−1 at 1 A g−1, much higher 190% than that of LPC (104 F g−1). Furthermore, the assembled symmetrical supercapacitor by using as-prepared Mn-4/LPC-CO composite exhibits a high energy density of 3.82 Wh kg−1 at the power density of 125 W kg−1 in voltage range of 0–1 V. This study offers a facile and low-cost approach for fabrication of biomass-based functional nanomaterials that can be used in energy storage devices.

Influence of transition metal-based activating agent on the properties and catalytic activity of sewage sludge-derived catalysts. Insights on mechanism, DFT calculation and degradation pathways

Research studies combining the detailed physicochemical properties' analysis, the catalytic activity in different real aqueous matrices, the proposal of degradation mechanisms and the stability of the intermediates/by-products by means of the Density-functional theory (DFT) are scarce. Therefore, this work gives a step forward in the field of circular economy and the removal of emerging pollutants such as the antibiotic ciprofloxacin, covering all the previously aspects mentioned, using four iron and nickel-based catalysts from two different sewage sludge.Experimental results revealed a significant influence of both the source of the sewage sludge and the activating agent used (iron chloride, nickel chloride and a mixture of both) on the physicochemical properties of the materials and, hence, on their catalytic activity. FTIR studies and chemical composition evidenced that the use of this biomass precursor leads to the generation of a wide variety of functional groups and heteroatoms in the synthesized catalyst structure. Moreover, they showed a combination of Type I-IV isotherms with H3-H4 type hysteresis loops, being mainly mesoporous materials and exhibiting a moderate microporosity except when nickel chloride was used solely as activating agent. The carbonaceous materials reached ciprofloxacin adsorption capacities in the range of 40.4–73.9 mg/g. The use of nickel chloride showed the lowest adsorption contribution and catalytic activity. The bimetallic catalyst (synthesized from a mixture of iron and nickel chloride) showed slightly higher catalytic activity than that found for the iron catalyst, but the metal leaching was also considerably higher. Consequently, the use of iron chloride solely as activating agent seems to be the better alternative, achieving a maximum ciprofloxacin removal around 99.7 % and an iron leaching concentration into the reaction medium of 0.48–0.61 mg/L. The main degradation pathways of ciprofloxacin were proposed according to the detection of LC-MS intermediates and DFT calculation, indicating the most likely areas of attack of reactive species on atoms with a high Fukui index (f0).

High energy storage performance in AgNbO3 relaxor ferroelectric films induced by nanopillar structure

Inspired by the increasing demand for energy-storage capacitors in electrical and electronic systems, dielectrics with high energy-storage performance have attracted more and more attention. AgNbO3-based lead-free ceramics serve as one of the most promising environmental-friendly candidates. However, their energy storage optimization is seriously limited by the low breakdown strength. Fortunately, thin film as a form of AgNbO3 materials can effectively improve the breakdown strength. In this work, AgNbO3 film with ∼550 nm in thickness was deposited on SrRuO3/(001)SrTiO3 using pulsed laser deposition. The AgNbO3 film reveals typical relaxor ferroelectric hysteresis loops due to the new nanopillar structure, which contributes to high breakdown strength of up to 1200 kV cm–1. Benefiting from the high breakdown strength, a recoverable energy storage density of 10.3 J cm–3 and an energy efficiency of 72.2% are obtained in the AgNbO3 film, which demonstrates the promising prospect of AgNbO3 film for energy storage applications.

Magnetoelectric memory cell based on 0.5Ba(Zr0.2Ti0.8)O3-0.5Ba0.7Ca0·3TiO3/Fe65Co35 thin films

In this study, 0.5Ba(Zr0·2Ti0.8)O3-0.5Ba0·7Ca0·3TiO3(0.5BZT-0.5BCT) thin films were deposited on Pt/Ti/SiO2/Si substrate, and then small area Fe65Co35(FeCo) films were deposited on 0.5BZT-0.5BCT films. The hysteresis loops and piezoelectric curves of 0.5BZT-0.5BCT films were studied. The results show that the piezoelectric displacement of 0.5BZT-0.5BCT films is 63 Å, the residual polarization intensity is 2.76 μC/cm2 and the coercive field is 110 kV/cm. 0.5BZT-0.5BCT/FeCo composite films exhibit typical magnetic hysteresis loops and stripe-like domains, the in-plane and out-of-plane coercivities are 10 Oe and 94 Oe, respectively, which indicates that the thin films have good soft magnetic properties. The current-voltage (I–V) curves of FeCo films on 0.5BZT-0.5BCT films were studied, the I–V behaviors of the thin films could be modulated by applying bias voltage, resulting in a resistance switching behavior. The maximum resistance change is 94% at 10 V bias voltage and 1 V scan voltage.

Development of hysteretic model for LEM-filled CFS shear walls under cyclic loading

Lightweight EPS materials (LEM)-filled cold-formed steel (CFS) shear wall, as a novel-type CFS shear wall, is extensively used in low- and multi-storey rural residences. The previous experiments have revealed that this type of wall appeared significant load-bearing properties and elastic stiffness, and the hysteresis loop appeared obvious stiffness degeneration, slipping and pinching effect. This paper developed a hysteretic model for seismic analysis of these shear walls. Four feature points including elastic, yield, peak and ultimate point are put forward to determine the skeleton curve. Besides, the feature points are determined by considering the stress type of bending and shearing respectively. Through analyzing the typical hysteresis loop, four characteristic points were obtained to express the characteristic of the hysteretic loop. Through the combination of the skeleton curve and hysteretic rule, a multi-linear hysteretic model was established to represent the hysteretic curves. The representative characteristic points of the hysteretic loop were obtained based on test data and the existing literature. The generated skeleton and hysteretic curves were compared with test results and the comparison results showed great agreements in terms of feature points and hysteretic loops. The method would provide a meaningful theoretical basis to assessing the seismic response of the LEM-filled CFS shear wall.

UV‐blocking performance and antibacterial activity of Cd, Ba co‐doped ZnO nanomaterials prepared by a facile wet chemical method

The utilization of highly efficient ultraviolet (UV)‐attenuating materials has inevitably signaled an ever‐increasing demand to mitigate the impending pessimistic impact of UV rays that consistently depletes the ozone atmosphere. In this context, a highly efficient Cd, Ba co‐doped ZnO nanomaterial has been prepared using a facile wet chemical approach. X‐ray diffractometer analysis indicates the evolution of wurtzite structure of ZnO with a slight peak shift towards the higher angle upon co‐doping which ascertains the impacted lattice contraction. N2 adsorption/desorption isotherms of the material supplement magnificently a typical type‐IV behavior displaying an H1 type hysteresis loop at high pressures whereby authorizing the open meso‐porous characteristics. The resulting Cd, Ba co‐doped ZnO nanorods disclose integrated performances of widespread polychromatic UV–visible luminescent emission, wide band gap, and enhanced UV absorbance. In particular, Cd, Ba co‐doped ZnO nanorods impart a positive UV‐blocking execution of 97% for UVA at 360 nm and 88% for UVB at 320 nm, which is found to be higher than most of the reported ZnO‐related materials. Besides these intriguing aforementioned properties, co‐doping is also appropriate for imparting better bacterial inhibition against the two tested strains (Escherichia coli and Staphylococcus aureus). Altogether, these results indicate that the co‐doped ZnO nanorods developed in the current investigation could potentially serve as a propitious alternative UV‐blocking material, especially for biomedical applications.

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Microstructure, magnetodielectric and multiferroic properties in PVDF-based sandwich-structured composites

The multiferroic thin films are promising candidates for applications in magnetic sensors, spintronics, information memory, and other multifunctional devices. In this work, BaTiO3-PVDF/CoFe2O4-PVDF/BaTiO3-PVDF sandwich-structured composites were designed and fabricated by a tape-casting method. The microstructure, dielectric, ferroelectric, magnetic and magnetodielectric properties were systematically investigated. An enhanced ferroelectricity is observed for the maximum polarization (Pmax~1.656 μC/cm2) and the high dielectric constant (εr) of 22 as well as a low dielectric loss for all BaTiO3 filler loading, much better than that of the pure PVDF matrix (εr∼8.26). A recoverable energy density of 0.648 J/cm3 is achieved at an electric field 950 kV/cm, along with a high efficiency (η∼71.0 %). The observed typical magnetic hysteresis loop reveals the presence of long-range ferromagnetic ordering in composites, accompanied by the significant magnetic properties with saturation magnetization (MS~0.507 emu/g), and coercivity (HC~2.3 kOe). Additionally, the response of the dielectric performance under the applied magnetic fields is obvious at RT, i.e., a large negative magnetodielectric coefficient of 2.85 % is obtained at a low magnetic field of 2 kOe, and is up to 6.53 % at 6 kOe for 5 vol% BaTiO3. Ultimately, it is anticipated that this work may provide an efficient method to develop flexible multiferroic composite for multifunctional devices.

Discrete Memristor and Discrete Memristive Systems.

In this paper, we investigate the mathematical models of discrete memristors based on Caputo fractional difference and G–L fractional difference. Specifically, the integer-order discrete memristor is a special model of those two cases. The “∞”-type hysteresis loop curves are observed when input is the bipolar periodic signal. Meanwhile, numerical analysis results show that the area of hysteresis decreases with the increase of frequency of input signal and the decrease of derivative order. Moreover, the memory effect, characteristics and physical realization of the discrete memristors are discussed, and a discrete memristor with short memory effects is designed. Furthermore, discrete memristive systems are designed by introducing the fractional-order discrete memristor and integer-order discrete memristor to the Sine map. Chaos is found in the systems, and complexity of the systems is controlled by the parameter of the memristor. Finally, FPGA digital circuit implementation is carried out for the integer-order and fractional-order discrete memristor and discrete memristive systems, which shows the potential application value of the discrete memristor in the engineering application field.