Electric Field Loading Research Articles

Modulating the fracture behavior of interface cracks via electric field gradient in flexoelectric solids

Interface cracks seriously affect the performance and service life of layered electronic devices. At nanoscale, the electric field concentration can be generated at the tip of insulating cracks by solely applying a uniform electric field loading, resulting in a large electric field gradient and thus inducing a significant converse flexoelectric effect. The deformation generated by the converse flexoelectric effect is expected to achieve crack shielding, however, its mechanism is still not clear. In this paper, the role of electric field gradients on interface crack behavior is studied by the collocation mixed finite element method (MFEM) and the J-integral. The result shows that the electric field gradient generated by a uniform electric displacement loading can reduce the J-integral of crack tips, achieving crack shielding. The result provides new ideas for the study of failure assessment, nanoscale fracture experiment and others.

Thermal criticality and two-step diffusion-reaction of electromagnetic Casson-Williamson fluid flow along a vertical channel with convective cooling under bimolecular kinetic

The need to examine diverse conditions involving industrial working fluids and improving thermal transfer efficiency cannot be overstated. Every thermal system must monitor and control excessive heat production and propagation to avert disruptions in various engineering processes. Therefore, the study investigated the theoretical significance of thermal criticality and a two-step exothermic reaction on Casson-Williamson fluid dynamics behaviour through a fixed vertical channel driven by an electromagnetic field, axial pressure gradient, and heat buoyancy force under a generalized bimolecular chemical kinetic. The heat exchange at the convective wall surface is adhered to Newton’s law of cooling. The Galerkin weighted residual method (GWRM) was utilized to solve the dimensionless nonlinear equations governing the flow within the boundary layer, yielding graphical representations of momentum and energy distributions. The results show that higher values of the activation energy, Frank-Kamenetskii parameter, electric field loading, activation ratio term, Weissenberg number, and second step term led to better heat dispersion and, eventually, complete combustion of hydrocarbons in the Casson-Williamson fluid. To avoid system disruptions, the study underscores the crucial need for continuous monitoring of all factors that stimulate internal heat generation to prevent system failures, emphasizing the importance of vigilance in the field of thermal systems.

Analysis of electromagnetic and radiative heat source on tangential hyperbolic fluid under Arrhenius kinetic with convective cooling

The global threat of environmental degradation from harmful waste discharge is evident, leading to unusual diseases and natural disasters. Some of these toxic emissions result from human activities, such as the incomplete combustion of hydrocarbons. As such, this study aims to explore the analysis of electromagnetic and radiative heat sources on tangential hyperbolic fluid under Arrhenius kinetic with convective cooling. The transformed momentum and heat equations are solved using a rigorous computational approach called the Galerkin integration approximation with weighted residual method. This computational methodology ensures the reliability and accuracy of the results. Various graphs illustrate the results, showing parametric sensitivity profiles for the velocity, temperature, skin friction, thermal gradient, Bejan, and entropy generation. As noticed from the outcomes, electric field loading increases heat dispersion by about 3.25 % as heat source terms are enhanced. Increasing magnetic field, radiation, and electric field loading parameters strengthened thermodynamic equilibrium and minimized entropy generation. The tangential hyperbolic combustion process is 6.11 % increased with rising Brinkman number and electric field loading terms. The flow rate and temperature field are increased to the peak along the middle of the channel for increasing pressure gradient.

Failure distribution and reliable analysis of ferroelectric ceramics under pulsed electric field

Dielectric breakdown at high electric field plays an important role in the application of ferroelectric ceramics. In this paper, the failure probability versus electric shock time of ferroelectric ceramics under positive pulse electric field is analyzed statistically. The failure probability distribution of ceramics after 10 electric shocks is studied. Piezoelectric constant, <i>P-E</i> loop of ferroelectric ceramics after 10 thousand electric shocks are measured and the breakdown mechanism is discussed. The results indicate that the relation between failure probability and electric shock number of ferroelectric ceramics is shown by a bath-tube curve and the failure probability of samples after 10 electric shocks decreases by 4 orders of magnitudes compared with that of origin sample. According to the results of piezoelectric constant and <i>P-E</i> loop, the samples subjected to positive pulse electric field many times do not show obvious fatigue or aging effect. So pulse electric field loading at 4.5 kV/mm is close to non-destructive condition. Considering the spread speed of cracks, it can be found that the rupture of ferroelectric ceramics under pulsed electric field roots from extension and connection of multi-cracks from multi-defects.

Mechanical behavior and microstructure of porcine brain tissues under pulsed electric fields.

Pulsed electric fields are extensively utilized in clinical treatments, such as subthalamic deep brain stimulation, where electric field loading is in direct contact with brain tissue. However, the alterations in brain tissue's mechanical properties and microstructure due to changes in electric field parameters have not received adequate attention. In this study, the mechanical properties and microstructure of the brain tissue under pulsed electric fields were focused on. Herein, a custom indentation device was equipped with a module for electric field loading. Parameters such as pulse amplitude and frequency were adjusted. The results demonstrated that following an indentation process lasting 5s and reaching a depth of 1000 μm, and a relaxation process of 175s, the average shear modulus of brain tissue was reduced, and viscosity decreased. At the same amplitude, high-frequency pulsed electric fields had a smaller effect on brain tissue than low-frequency ones. Furthermore, pulsed electric fields induced cell polarization and reduced the proteoglycan concentration in brain tissue. As pulse frequency increased, cell polarization diminished, and proteoglycan concentration decreased significantly. High-frequency pulsed electric fields applied to brain tissue were found to reduce impedance fluctuation amplitude. This study revealed the effect of pulsed electric fields on the mechanical properties and microstructure of ex vivo brain tissue, providing essential information to promote the advancement of brain tissue electrotherapy in clinical settings.

RF design of helical long-wire traveling wave antenna for helicon current drive in KSTAR

This paper presents the development, fabrication, and implementation of a state-of-the-art helical long-wire traveling wave antenna (LW-TWA) for the Korea Superconducting Tokamak Advanced Research (KSTAR) helicon wave current drive (HCD). A multi-stage design approach has been employed incorporating schematic and simplified radio frequency (RF) modeling, to fulfill critical antenna performance criteria, such as parallel refractive index, while maintaining low electric field properties and load resilience. The advanced design includes a Faraday shield and a structurally rigid support for mechanical stability and minimal RF performance distortion. The sophisticated design and megawatt (MW)-class RF power handling capability of the LW-TWA hold the potential to improve HCD performance in KSTAR plasma.

Entropy generation and current density of tangent hyperbolic [formula omitted]-[formula omitted] and [formula omitted]-[formula omitted] hybridized electromagnetic nanofluid: A thermal power application

Maintaining a continuous thermal convective power supply is very essential in many industries and thermal systems, this is because it helps in improving the efficiency of engineering machines and engines. Thus, hybridized electromagnetic nanoparticle in a heat supporting non-Newtonian fluid is a good platform to enhance thermal power energy. Based on its usefulness, this study focuses on the hybridization of zirconium dioxide (ZrO2) and copper (Cu) tangent hyperbolic nanofluid in ethylene-glycol(EG) (C2H6O2) solvent for thermal power optimization. With quadratic Boussinesq approximation, the fluid is influenced by electromagnetic induction and thermal convection. Via similarity quantities, an invariant derivative model is obtained. The model is completely solved using weighted residual method coupled with partition and one-third Simpson’s quadrature technique. The presented outputs revealed that entropy generation is minimized and thermodynamic equilibrium is achieved with rising values of the electric and magnetic field terms. Heat propagation is augmented with an enhanced electric field loading and nanoparticle volume fraction for hybrid nanofluid than unitary nanofluid. Also, current density is build-up for rising Williamson and thermal convection terms.

Ultrahigh electrostrain with excellent fatigue resistance in textured Nb 5+-doped (Bi 0.5Na 0.5)TiO 3-based piezoceramics

(Bi_0.5Na_0.5)TiO₃ (BNT)-based lead-free piezoceramics exhibit excellent electric field-induced strain (electrostrain) properties, but often suffer from large hysteresis and poor fatigue resistance, which strongly limit their applications. Here, &lt;00<i>l</i>&gt; textured Nb⁵⁺-doped 0.8(Bi_0.5Na_0.5)TiO₃–0.2(Bi_0.5K_0.5)TiO₃ (0.8BNT–0.2BKT) ceramics with a high degree of texturing (~80%) were prepared by the reactive template grain growth (RTGG) method using Bi₄Ti₃O₁₂ as a template. By the combination of donor doping in the B-site and the RTGG method, the electrostrain performance achieves a significant enhancement. A high electrostrain of 0.65% and a piezoelectric coefficient (<inline-formula> <math display="inline" id="MA1"><mrow><msubsup><mi>d</mi><mrow><mn>33</mn></mrow><mo>*</mo></msubsup></mrow></math></inline-formula>) of 1083 pm/V with reduced hysteresis at an electric field of 6 kV/mm are obtained. No electrostrain performance degradation is observed after unipolar electric field loading of 10⁵ cycles, showing excellent fatigue endurance. These results indicate that the texturing BNT-based lead-free piezoceramics by the RTGG method is a useful approach to developing eco-friendly actuators.

Simultaneously achieving high energy storage performance and low electrostrictive strain in BT‐based ceramics

AbstractDielectric ceramics with high recoverable energy storage density (Wrec) and high energy storage efficiency (η) are urgently needed due to their potential application in pulse capacitor devices. However, the low η and breakdown strength (BDS) have produced a bottleneck for achieving high Wrec at high electric field. Here, we introduce Bi(Mg0.5Ti0.5)O3 (BMT) into Ba(Ti0.92Sn0.08)O3 (BTS) matrix to enhance the relaxor character of BTS–xBMT and reduce the electrostrictive strain generated during electric field loading. The enhanced relaxor character is beneficial for increasing the efficiency, whereas the reduced electrostrictive strain is profitable to increase the BDS. Furthermore, the BDS is significantly improved by the polymer viscous rolling process. Finally, the electrostrictive effect was considerably lowered in an optimized BTS–0.1BMT composition. More crucially, a high Wrec of 4.34 J/cm3 was attained accompanied by excellent temperature stability (variation ≤±5% between 30 and 120°C). The current results show that the developed dielectric ceramics can be used in pulse capacitor devices for energy storage.

TDDFT calculations of the PETN's ultraviolet absorption spectrum under the electric field loading.

The UV(ultraviolet) absorption spectrum of PETN under different electric field loading directions(X, Y, and Z) with the value of strength range from 0.001 a.u. to 0.006 a.u. was calculated with the TDDFT(Time-dependent density functional) in this work. With the increase of electric field strength, the absorbance of PETN in the ultraviolet band decreases. To explain the action mechanism of the electric field on PETN UV(ultraviolet) absorption spectrum, we analyzed and counted the contribution rate, oscillator strength, and vertical excitation energy of the main excitation process whose contribution rate to the UV absorption spectrum is greater than 10%. The contribution of PETN to the UV spectrum in all directions without an electric field was also listed to investigate the anisotropy of PETN in the excitation process under an electric field. The hole-electron analysis showed that the electric field will enhance the charge transfer characteristics in the excitation process of PETN. To investigate the anisotropy of the response under different electric field application directions, the contribution of the UV absorption spectrum in different directions was studied. Optimization and TDDFT calculation were performed at the level of M06-2X/def2-TZVP and PBE0/def2-TZVP respectively, with Gaussian09 program. The hole-electron analysis and UV absorption spectrum plotting were performed with Multiwfn3.8.

Reducing Threshold of Ferroelectric Domain Switching in Ultrathin Two-Dimensional CuInP2S6 Ferroelectrics via Electrical-Mechanical Coupling.

Room-temperature out-of-plane two-dimensional ferroelectrics have promising applications in miniaturized non-volatile memory appliances. The feasible manipulation of polarization switching significantly influences the memory performance of ferroelectrics. However, conventional high-voltage-induced polarization switching inevitably generates charge injection or electric breakdown, and large-mechanical-loading-induced polarization switching may damage the structure of ferroelectrics. Hence, decreasing critical voltage/loading for ferroelectric polarization reversal is highly required. Herein, using atomic force microscopy experiments, the ferroelectric domain switching via both electric field and mechanical loading was demonstrated for an ultrathin (∼4.1 nm) CuInP2S6 nanoflake. The relevant threshold voltage/loading for polarization switching was ∼ -5 V/1095 nN, resulting from the electric field and flexoelectric effect, respectively. Finally, the electrical-mechanical coupling was adopted to reduce the threshold voltage/loading of CuInP2S6 significantly. It can be explained by the Landau-Ginzburg-Devonshire double-well model. This effective way for easily tuning the polarization states of CuInP2S6 opens up new prospects for mechanically written and electrically erased memory devices.

An exploration for new strategy: Achieving both excellent temperature stability and good electrostrain in BiFeO3–BaTiO3-based relaxor ferroelectrics by domain engineering

In BiFeO3-xBaTiO3 (BF-xBT) ceramic systems, some of them exhibit good electrostrain, unfortunately, their electrostrain properties always fluctuate with temperature. To obtain good strain performance with excellent temperature stability, the BiFeO3–BaTiO3-xBi(Mg2/3Nb1/3)O3 (BF-0.4BT-xBMN) relaxor ferroelectrics were designed, and a new strategy of changing the temperature & electric field-dependent characteristics of nanodomains by doping was proposed for the first time. An excellent result (S = 0.27% @80 °C, fluctuating degree≈2% during 80 °C–180 °C) was achieved, much better than previously reported results, presenting great potential in the application of high-temperature devices. Temperature-dependent dielectric permitivity combined with piezo-response force microscopic (PFM) techniques demonstrated that the doping of Bi(Mg2/3Nb1/3)O3 (BMN) decreased the high maximum-dielectric-constant temperature (Tm) and freezing temperature (Tf) as well as the proportion of nanodomains with strong piezo-response. What's more, the temperature-dependent dS/dE curves combined with in-situ synchrotron X-Ray diffraction measurements during electric field loading revealed the transformation from nanodomain into macrodomain (n-m). The introduction of BMN resulted in an increase of the nanodomain-macrodomain transition electric field at room temperature together with the decrease of domain switching at high temperature, both of which were the key to improving the temperature stability of strain.

Fatigue crack growth mechanism in ferroelectric ceramics under alternating electric field: An investigation by digital image correlation technique

The deformation of crack tip in PZT ceramics under cyclic electric field loading was characterized by Digital Image Correlation (DIC) technique. Two other specimens without speckles were used to observe the physical processes during the crack propagation in-situ. The deformation of the region of interest is elucidated. Near the U-shaped notch, the DIC results directly reveal the existence of incompatible deformation. However, in the front of the newly formed crack, no incompatible deformation was observed. Additionally, in-situ observation reveals that, the crack growth occurs at the stage of crack closure when the crack propagates steadily. The observed pop-in behavior of the crack during the first cycle of electric field loading is rationalized by the interaction between the incompatible domain switching zones with and without U-shaped notch, which is consistent with the explanation of Westram et al. The subsequent crack propagation after the pop-in cannot be rationalized by the model exploited by Zhu and Yang, Westram et al., and Liu and Fang, which is thought to be related to three different factors – arcing, wedging and grain-to-grain interaction. The mechanism for the appearance and the disappearance of the incompatible domain switching zone near the U-shaped notch and around the tip of the newly formed crack is discussed based on the electrical boundary condition (EBC) of the crack surfaces we proposed recently.

Electrical boundary condition at the crack surface in ferroelectrics

AbstractElectrical boundary condition (EBC) at the crack surface has significant influence on the fracture behavior of ferroelectrics. Here, we characterized the electrical displacement (ED) response of ferroelectrics specimens with through cracks under cyclic electric field. The physical processes occurred between the crack surfaces are in situ observed. It is found that when the distance between the crack surfaces was smaller than a critical value, significant ED was measured, which cannot be rationalized by the previous EBCs. The appearance of bubbles and arcing between the crack surfaces demonstrates that dielectric breakdown occurs during electric field loading. These results imply that the EBC of the crack surface is permeable, and the dielectric breakdown process should be taken into consideration.

Series Solution-Based Approach for the Interlaminar Stress Analysis of Smart Composites under Thermo-Electro-Mechanical Loading

This paper introduces a new loading condition considering the combined thermo-electro-mechanical coupling effect in a series solution-based approach to analyze the free-edge interlaminar stresses in smart composite laminates. The governing equations are developed using the principle of complementary virtual work. The assumed stress fields satisfy the traction-free and free-edge boundary conditions. The accurate stress states of the composite structures are acquired through the procedure of generalized eigenvalue problems. The uniform temperature is employed throughout the laminate, and the electric field loading is applied to the symmetric piezo-bonded actuators to examine the combined effect of thermal and electrical stresses on the overall deformation of smart composite laminates. It was observed that the magnitude of the peeling stresses generated by mechanical loading was reduced by the combined thermal and electric excitation loading (up to 25.3%), which in turn resulted in expanding the service life of the smart composite structures. The proposed approach is implemented on three different layup configurations. The efficiency of the current methodology is confirmed by comparing the results with the 3D finite element (FEM) solution computed by ABAQUS.

Crack propagation induced by incompatible domain switching in BaTiO3 crystal under electric field loading

Using a system composed of a polarized light microscopy and a charge coupled device (CCD), the crack propagation behavior in BaTiO3 (BTO) crystal under electric field was in situ investigated with the field direction parallel or perpendicular to the crack surface. In addition, the growth behavior of Vickers indentation surface cracks under alternating electric field was also in situ investigated. Three crack propagation modes induced by incompatible domain switching were proposed based on our observation. The electrical boundary condition of the crack surface was also characterized by measuring and comparing the hysteresis loop of a perfect BTO crystal without crack and a BTO crystal completely fractured in half. Results demonstrate that the electrical boundary condition of a fresh natural crack is permeable, and evolves from permeable to partial permeable during cyclic electric field loading.

Spin current distribution in antiferromagnetic zigzag graphene nanoribbons under transverse electric fields

The spin current transmission properties of narrow zigzag graphene nanoribbons (zGNRs) have been the focus of much computational research, investigating the potential application of zGNRs in spintronic devices. Doping, fuctionalization, edge modification, and external electric fields have been studied as methods for spin current control, and the performance of zGNRs initialized in both ferromagnetic and antiferromagnetic spin states has been modeled. Recent work has shown that precise fabrication of narrow zGNRs is possible, and has addressed long debated questions on their magnetic order and stability. This work has revived interest in the application of antiferromagnetic zGNR configurations in spintronics. A general ab initio analysis of narrow antiferromagnetic zGNR performance under a combination of bias voltage and transverse electric field loading shows that their current transmission characteristics differ sharply from those of their ferromagnetic counterparts. At relatively modest field strengths, both majority and minority spin currents react strongly to the applied field. Analysis of band gaps and current transmission pathways explains the presence of negative differential resistance effects and the development of spatially periodic electron transport structures in these nanoribbons.

Nonstoichiometric effect of A-site complex ions on structural, dielectric, ferroelectric, and electrostrain properties of bismuth sodium titanate ceramics

To investigate the nonstoichiometric effect of (Bi0.5Na0.5)TiO3 (BNT) ceramics on their properties, we propose a novel chemical expression, (Bi0.5+xNa0.5−3x)TiO3. The nonstoichiometric effect of BNT can be explored in compounds with this composition without being hampered by the charge imbalance problem. With x ranging from −0.02 to 0.02, we find that the morphological, dielectric, ferroelectric, and electrostrain properties differ considerably between Na-rich and Bi-rich ceramic samples. The average grain size (AGS) increased significantly in Na-rich samples compared to that in stoichiometric BNT, while it decreased slightly in Bi-rich samples. The dielectric characteristics measured from 30 °C to 500 °C indicate that conductivity is activated in Na-rich nonstoichiometric samples but is effectively suppressed in Bi-rich nonstoichiometric samples. The ferroelectric properties also show the same trend. In Na-rich samples, elliptical polarization against electric field (P-E) hysteresis loops were detected, indicating a conductive character induced by high electric field loading. However, saturated P-E loops are observed in Bi-rich samples with well-inhibited conductivity. Furthermore, compared to stoichiometric BNT and nonstoichiometric x = 0.02 Bi-rich samples, (Bi0.5+xNa0.5−3x)TiO3 samples with x = 0.01 exhibit higher electrostrain from 30 °C to 150 °C. Based on the assumption of charge balance, our findings indicated that the presence of 1 mol% excess Bi would facilitate significant improvement in the dielectric, ferroelectric, and electrostrain properties of BNT and BNT-based systems.

Understanding the correlation between intermediate monoclinic phase (Cc) and piezoelectric properties in NaNbO3-BaTiO3-CaZrO3 ternary system with octahedral tilt

Compared with traditional tetragonal (T) P4mm - rhombohedral (R) R3m morphotropic phase boundary (MPB) system, the structure-property relationship of MPB systems with octahedral tilt is still unclear. In this work, the phase structure evolution under composition and electric field modulations in lead-free (0.9-x)NaNbO3-0.1BaTiO3-xCaZrO3 (NN-BT-xCZ) close to the untilt P4mm-tilt R3c MPB was investigated in details by means of the ex- and in-situ x-ray diffraction and various electrical property measurements. Both P4 mm and R3c phases can irreversibly transform into a Cc phase under electric field loading, which should be considered as a result of the cooperative coupling between ferroelectric and antiferrodistortive instabilities. Quantitative analysis indicates that little composition dependent lattice strain and domain switching of P4 mm phase can be observed, and the variation of piezoelectric coefficient is closely related to Cc phase, which exhibits an enhancement of both lattice strain and domain switching within MPB. This suggests that lattice strain and domain switching of Cc phase are coupled. On the contrary, both of them are competed in P4 mm phase because the P4 mm phase is dominated by irreversible domain switching. The experimental results would benefit for deeply understanding the origin of piezoelectric response for many octahedral-tilt MPB piezoelectric systems.

Radiative thermal criticality and entropy generation of hydromagnetic reactive Powell-Eyring fluid in saturated porous media with variable conductivity

Theoretical study of inherent irreversibility and thermal runaway of an exothermic reactive Eyring-Powell fluid flow through a saturated porous fixed horizontal channel with thermal radiation and variable electrical conductivity is investigated. The reactive conducting fluid under bimolecular chemical rate law is propelled by pressure gradient. Ignoring the material assumptions, the governing dimensionless equations of the flow model are solved using semi discretization finite difference techniques coupled with weighted residual method. The results in terms of flow rate, temperature, thermal runaway, Bejan number and entropy generation are presented in graphical form. From the results, it is observed that parameter which argument the entropy production rate also enhances the Bejan number. Also, minimization of entropy generation is achieved at low values of thermal radiation, dissipation rate, electric field loading and viscosity variables.