Electric Displacement Research Articles

Emergent Inhomogeneity and Nonlocality in a Graphene Field-Effect Transistor on a Near-Parallel Moiré Superlattice of Transition Metal Dichalcogenides.

At near-parallel orientation, twisted bilayers of transition metal dichalcogenides exhibit interlayer charge transfer-driven out-of-plane ferroelectricity. Here, we report detailed electrical transport in a dual-gated graphene field-effect transistor placed on a 2.1° twisted bilayer WSe2. We observe hysteretic transfer characteristics and an emergent charge inhomogeneity with multiple local Dirac points evolving with an increasing electric displacement field (D). Concomitantly, we also observe a strong nonlocal voltage signal at D ∼ 0 V/nm that decreases rapidly with increasing D. A linear scaling of the nonlocal signal with longitudinal resistance suggests edge mode transport, which we attribute to the breaking of valley symmetry of graphene due to the spatially fluctuating electric field from the underlying polarized moiré domains. A quantitative analysis suggests the emergence of finite-size domains in graphene that modulate the charge and the valley currents simultaneously. This work underlines the impact of interfacial ferroelectricity that can trigger a new generation of devices.

Rayleigh waves in viscoelastic piezoelectric half-space with cladding structures: An analytic Legendre-Laguerre polynomial method

Piezoelectric materials are widely used in surface acoustic wave devices. Many piezoelectric materials themselves have viscoelastic properties, and their surface wave characteristics, especially the attenuation characteristics still needs to be explored. This article proposes a Legendre-Laguerre orthogonal polynomial method to solve the Rayleigh wave problems in a viscoelastic piezoelectric half space with a covering layer. The proposed method compensates for the inherent shortcomings of traditional Laguerre polynomials in solving layered half spaces: the normal stress and electric displacement are discontinuous. The correctness of the method was verified through literature comparison and finite element simulation. At the same time, by utilizing the orthogonality of the Legendre-Laguerre polynomial, the integral analytical formula encountered in the solution process is derived, which improves the computational efficiency by more than ten times. Through the analysis and discussion of the dispersion and attenuation curves, it is found that the piezoelectric effect can suppress the attenuation of Rayleigh waves; the piezoelectric and viscous properties of the covering layer mainly affect attenuation at high frequencies, while those of the half space layer mainly affect attenuation at low frequencies of high-order modes.

Quantifying Electric Charge on Cap-Pin Glass Insulator: Investigating the Impact of Pollution through Simulation and Experimental Approaches

The objective of this paper is to investigate the behavior of electric charges on cap-pin glass insulator under 50 Hz AC voltage. The study is conducted using COMSOL Multiphysics to understand the charge location, polarity, and parameters affecting their behavior. A 2D axisymmetric insulator design is used to visualize the overall charges on the insulating system (space charge) and along the insulating surface (surface charge density) under uniform and non-uniform pollution conditions. The research shows that the total charge accumulates over the surface area of the glass material. To quantify the amount of this charge, a simulation method based on using the surface integral of the electric displacement field over this area is introduced, which is supported by experimental tests. Comparing both simulation and experimental results provides insights into the simulation reliability and the parameters affinity used to those of the real model. Moreover, the simulation helps to identify the critical area where a high amount of charges is accumulated. The findings of this study are presented and examined.

Electroosmotic effect on the flow of hybrid nanofluid containing para and ferri-magnetic nanoparticles through the micro-channel implementing Darcy law

This study investigates the flow of an incompressible electroosmotic hybrid nanofluid through a micro-channel. The hybrid nanofluid consists of paramagnetic (Ta) and ferrimagnetic (Fe3O4) nanoparticles suspended in ethylene glycol. The Darcy model is applied to the porous media in the momentum equation, and its effects are also considered in the temperature equation, accounting for frictional and Joule heating effects. The micro-channel is influenced by both pressure and magnetic flux. The study derives an exact solution for the proposed model and evaluates key engineering parameters, such as the heat transfer rate. The findings show that a higher particle volume fraction reduces the velocity distribution, while an increased Darcy parameter decreases the rate of heat transfer. Additionally, the heat transfer rate diminishes with increasing Darcy parameter and electric flux. Notably, the ferrimagnetic nanofluid exhibits better thermal conductivity than the paramagnetic nanofluid.

Entanglement entropy of ( 2+1 )-dimensional SU(2) lattice gauge theory on plaquette chains

We study the entanglement entropy of Hamiltonian SU(2) lattice gauge theory in 2+1 dimensions on linear plaquette chains and show that the entanglement entropies of both ground and excited states follow Page curves. The transition of the subsystem size dependence of the entanglement entropy from the area law for the ground state to the volume law for highly excited states is found to be described by a universal crossover function. Quantum many-body scars in the middle of the spectrum, which are present in the electric flux truncated Hilbert space, where the gauge theory can be mapped onto an Ising model, disappear when higher electric field representations are included in the Hilbert space basis. This suggests the continuum (2+1)-dimensional SU(2) gauge theory does not have such scarred states. Published by the American Physical Society 2024

Influence of Nano-Silicon Dioxide in the Enhancement of Surface Structure of Public Filler and Properties of Recycled Mortar

This paper proposes a method of enhancing public filler (PF) with nano-SiO2 (NS) to prepare modified recycled aggregate mortar (RAM). The improvement effect of NS solution at different concentrations and immersion times on the macroscopic physical properties of recycled public fine aggregates (PFA) was investigated. Moreover, the effect of NS on the basic physical properties and durability of recycled mortar (RM) and the reinforcement mechanism of NS on recycled mortar was analyzed through various techniques. Results indicated that the modification effect of NS could remove loose cement mortar from the surface of PFA. It reacted with calcium hydroxide and calcite to generate nano-particles that could fill pores in PFA. The water absorption rate of PFA decreased to 9.3% when immersed in 2% NS solution for 72 h. There was no significant improvement in the mechanical properties of RM when the solution concentration and immersion time were increased. However, the compressive strength of RM prepared by modifying PFA with 2% NS was increased by about 21.9%, and the capillary water absorption and electric flux were reduced by 56.3% and 15.1%, respectively. Micro-analysis results showed that the volcanic ash effect of NS enabled it to react with Ca(OH)2 adhered to the surface of PFA, generating C-S-H and improving the interfacial bonding of PFA. Moreover, NS adsorbed on the surface of PFA dispersed into the freshly mixed cement slurry, which further enhanced the internal structure of PFA.

Enhancing chloride ion permeability resistance of recycled aggregate concrete through internal curing with glazed hollow beads

This study explores the effects of glazed hollow beads (GHB) dosage and additional water amount on the capillary negative pressure, mechanical properties, initial resistivity, and electric flux in conditions where recycled aggregate concrete (RAC) is subject to cracking. The chloride ion (Cl-) diffusion coefficient for RAC cured internally was evaluated using the resistivity method, which also looked at the relationship between the diffusion coefficient, GHB dosage, and additional water amount. This analysis advances our understanding of the functional mechanisms of pre-soaked GHB in RAC. The research reveals that incorporating pre-soaked GHB enhances RAC in two primary ways. Firstly, pre-soaked GHB acts as an internal curing agent that stimulates the formation of hydration products, thereby filling internal voids and mitigating micro-crack development. Secondly, it functions as an adsorbent. The differential in relative humidity and internal pressure between the unsaturated GHB and the cement stone matrix promotes the sequestration of corrosive agents in cracked RAC. Additionally, an internal curing impact factor has been introduced, forming the basis of a new model to calculate the Cl- diffusion coefficient that accounts for both GHB dosage and additional water intake. The established quantitative relationships between resistivity, electric flux, and Cl- diffusion coefficient in GHB-treated RAC (GHB-RAC) provide a methodological framework for quickly evaluating the durability of GHB-RAC against Cl- intrusion in practical engineering contexts.

Numerical study of electrode permeability influence on planar SOFC performance

A solid oxide fuel cell (SOFC) is a clean and very efficient electrochemical conversion device, which generates electricity directly from fuel electrochemical oxidation. In this paper, a three dimensional numerical model has been developed in order to analyse the role of some thermophysical and morphological parameters on the performance of the SOFC cell. In particular, we studied the effect of the variation of permeability of the electrodes: fuel distribution, ionic and electric current density, pressure and diffusion flux are analyzed and compared. The volume fraction of the ionic and electronic phase in the electrodes is studied using a parametric study. It was shown that the current density enhanced by decreasing the permeability, up to a defined value, and it diminished with very small permeability. A remarkable influence of pressure and diffusion of species on the performance of the cell, with the variation of permeability, has been recognized. Varying the permeability in the active layer of electrodes has a large impact on the current density, connected to the volume fraction of ionic phase. This study permits to comprehend the relationship between the performance and microstructure of SOFCs. Meanwhile, it furnishes theoretical guidance for an optimum design of the electrode permeability.

Blueshift of the CN stretching vibration of acetonitrile in solution: computational and experimental study.

Acetonitrile, a polar molecule that cannot form hydrogen bonds on its own, interacts with solvent molecules mainly through the lone pair of its nitrogen atom and the π electrons of its CN triple bond [Correction added on 17 July 2024, after first online publication: Acetole has been changed to Acetonitrile in the preceeding sentence.]. Interestingly, acetonitrile exhibits an unexpected strengthening of the triple bond's force constant in an aqueous environment, leading to an upshift (blueshift) in the corresponding stretching vibration: this effect contrasts with the usual consequence of hydrogen bonding on the vibrational frequencies of the acceptor groups, that is, frequency redshift. This investigation elucidates this phenomenon using Raman spectroscopy to examine the behavior of acetonitrile in organic solvent, water, and silver ion aqueous solutions, where an even more pronounced upshift is observed. Raman spectroscopy is particularly well suited for analyzing aqueous solutions due to the minimal scattering effect of water molecules across most of the vibrational spectrum. Computational approaches, both static and dynamical, based on Density Functional Theory and hybrid functionals, are employed here to interpret these findings, and accurately reproduce the vibrational frequencies of acetonitrile in different environments. Our calculations also allow an explanation for this unique behavior in terms of electric charge displacements. On the other hand, the study of the interaction of acetonitrile with water molecules and metal ions is relevant for the use of this molecule as a solvent in both chemical and pharmaceutical applications.

Enhancing the circular dichroism of chiral dielectric nanostructure through the addition of a symmetric Au cylinder

Circular dichroism (CD) spectra play a crucial role in recognition, separation and detection of chiral molecules. Due to the inherent weak CD response of natural chiral molecules, researchers have endeavored to enhance CD signals through various artificial nanostructures. In this study, combining the advantages of both the dielectric and metal materials, we propose a hybrid dielectric-metal nanostructure consisting of a chiral Si nanorod dimer coupled with a symmetric Au cylinder to achieve robust CD responses. Owing to the plasmon resonance of the Au cylinder, the scattering-CD and absorption-CD of the hybrid system have been enhanced, which result in the enhanced extinction-CD response. Furthermore, the distributions of electric field, magnetic field and displacement current density of both the Si dimer and hybrid nanostructure have been meticulously crafted to elucidate the physical mechanisms underlying amplified CD signals. The synergistic coupling between the magnetic fields of dielectric materials and the electric fields of the Au cylinder leads to an increase in the electric field strength and the asymmetry of near-field distributions. Additionally, spatial overlaps between electric and magnetic fields occur. These factors contribute to the enhanced chiral response of the hybrid system. Meanwhile, the CD signal can be flexibly tuned by adjusting the size of the Au cylinder and Si nanorods. This design offers a versatile approach to enhancing the chiral response of dielectric nanostructures.

Nanobody and CuS Nanoflower-Au-Based Lateral Flow Immunoassay Strip to Enhance the Detection of Aflatoxin B1.

In the realm of analysis, the lateral flow immunoassay (LFIA) is frequently utilized due to its capability to be fast and immediate. However, the biggest challenge of the LFIA is its low detection sensitivity and tolerance to matrix interference, making it impossible to enable accurate, qualitative analyses. In this study, we developed a new LFIA with higher affinity and sensitivity, based on a nanobody (G8-DIG) and CuS nanoflowers-Au (CuS NFs-Au), for the detection of aflatoxin B1 (AFB1) in maize. We synthesized the immunoprobe G8-DIG@CuS NFs-Au, stimulated the in situ development of Au nanoparticles (Au NPs) on Cu NFs by electrical displacement, and obtained Cu NFs-Au for fixing the G8-DIG. G8-DIG@CuS NFs-Au probe-based LFIAs may, in ideal circumstances, use a strip chromatography reader to accomplish sensitive quantitative detection and qualitative visualization. AFB1 has a detection range of 2.82-89.56 µg/L and a detection limit of 0.87 µg/L. When compared with an LFIA based on CuS NFs, this sensitivity is increased by 2.76 times. The practical application of this method in corn flour demonstrated a recovery rate of 81.7% to 117%. Therefore, CuS NFs-Au show great potential for detecting analytes.

Study on durability of concrete under alternating positive and negative temperature curing in plateau area

In order to investigate the durability of concrete under alternating curing from −20℃ to 20℃, different antifreeze (JB-1 type/HD-type) and different dosages (1.5 wt%/2 wt%) were chosen to carry out the study. This study used a variety of tests such as rapid freeze-thaw test, freeze-thaw-sulfate coupling test, dry and wet cycle test, electrical flux test, and drying shrinkage test, combined with NMR techniques, to comprehensively evaluate the properties and pore structure of the concrete. The results show that adding antifreeze can optimize concrete durability and pore structure under alternating curing from −20°C to 20°C. This study showed that 1.5 wt% was the optimal dose to maximize the improvement of concrete durability. Comparative analysis revealed that JB-1 type antifreeze is superior to HD-type antifreeze in enhancing the frost resistance, the freeze-thaw-sulfate coupling resistance, and the chloride ion permeation resistance of concrete, which is manifested in the relative dynamic modulus of elasticity increase of 1.5 %, compressive strength increase of 1.5 MPa, mass loss decrease of 0.12 % and electric flux decrease of 86 C. In-depth investigation reveals that the JB-1 type antifreeze agent promotes the generation of C-S-H gel by accelerating the hydration process of concrete, fills and shrinks the micropores of concrete, reduces the porosity, and improves the microstructure. However, over-addition has a reverse effect, which enhances the content of tiny bubbles and leads to a 2.4 % decrease in the relative dynamic modulus of elasticity of concrete. Meanwhile, the increase in porosity leads to an increase in the electrical flux of concrete by 151 C and shrinkage by 17.2 μm.

Comparative study on the effect of crystalline agents for improving frost resistance of concrete from the perspective of reaction mechanism

The crystalline agents can be used to improve the concrete frost resistance by its densification effect on the microstructure of concrete, while the effect of which depends on the type and penetration process of the crystalline agents. This study, therefore, aimed to investigate the effect of two types of crystalline materials, in terms of organic and inorganic one, and two kinds of penetration methods including surface coating and soaking, in concrete. In addition to freeze-thaw test and electric flux test, the thermal gravity analysis, mercury intrusion porosimetry and scanning electron microscope were carried out. The results showed that after vacuum drying and soaking treatment, the material’s penetration depth has reached 7 mm. Deeper penetration depth shifted the freeze-thaw failure mode sudden to gradual, significantly enhancing frost resistance as a result. Among them, organic crystalline agent increased frost resistance by 2.5 times and decreased electrical flux by approximately 90 %, while inorganic crystalline agent only enhanced frost resistance by 1.5 times and reduced electrical flux by only about 37 %. From a reaction mechanism perspective, the hydrophobic layer within the pores formed by organic crystalline material has the most contribution, in which the needle-like substances generated by inorganic one filled the pores with limited effect to barrier water.

Effect of quadratically varying electric potential on the multiple cracks in piezoelectric materials

A basic solution to the problem of three collinear equal cracks in a transversely isotropic piezoelectric material plate is obtained under the influence of electromechanical forces. Stroh formalism and complex variable methods are used to derive the mathematical expressions for SIF (stress intensity factor), COD (crack opening displacement), and COP (crack opening potential). The length of the saturation zones is investigated at each crack tip under the influence of quadratically varying electric displacement. Furthermore, a numerical study is carried out to discuss the effect of quadratically varying electrical potential on the saturation zone, COD, and COP. The results obtained numerically are reported graphically.

Homogenized moduli and local multiphysics fields of unidirectional piezoelectric nanocomposites with energetic surfaces

The study extends the locally-exact homogenization theory (LEHT) to determine the effective parameters and localized multiphysics fields of unidirectional piezoelectric nanocomposites with energetic surfaces. The interface is simulated using the generalized Gurtin-Murdoch model for piezoelectric nanocomposites, taking into account the discontinuities between surface stresses and electrical displacement. By characterizing hexagonal and square repeating unit cells (RUC), the interactions across a fiber's or pore's interface in piezoelectric nanocomposites with energetic surfaces have been analyzed. The extended LEHT possesses the advantages of fast convergence, excellent stability, and computational efficiency due to its avoidance of mesh discretization and pointwise satisfaction of interfacial conditions. To verify the validity of the present theory, this paper also derives the Eshelby solution for piezoelectric nanocomposite with energetic surfaces. The reliability and accuracy of the present theory are demonstrated by comparing the present results from the Eshelby solution and the finite element method (FEM) with generally good agreement. On this basis, the influence of microstructural effects, such as phase volume fractions and geometrical arrangement, on the effective and local responses of piezoelectric nanocomposites with energetic surfaces are investigated. The results show that effective piezoelectric/dielectric moduli and electric displacement field for piezoelectric nanocomposites are significantly affected by the size effect, along with several other parameters such as unit cell arrays and fiber/pore volume fractions. Those results highlight the significance of neighboring pore or fiber interactions for piezoelectric nanocomposites, which are often overlooked in traditional micromechanics models and are challenging to be captured using numerical methods.

Electric displacement modulation under internal field for high-performance mechanical-to-electrical energy generator

Electric displacement modulation under internal field for high-performance mechanical-to-electrical energy generator

Optimizing Capacitive Pressure Sensor Geometry: A Design of Experiments Approach with a Computer-Generated Model.

This study presents a comprehensive investigation into the design and optimization of capacitive pressure sensors (CPSs) for their integration into capacitive touch buttons in electronic applications. Using the Finite Element Method (FEM), various geometries of dielectric layers were meticulously modeled and analyzed for their capacitive and sensitivity parameters. The flexible elastomer polydimethylsiloxane (PDMS) is used as a diaphragm, and polyvinylidene fluoride (PVDF) is a flexible material that acts as a dielectric medium. The Design of Experiment (DoE) techniques, aided by statistical analysis, were employed to identify the optimal geometric shapes of the CPS model. From the prediction using the DoE approach, it is observed that the cylindrical-shaped dielectric medium has better sensitivity. Using this optimal configuration, the CPS was further examined across a range of dielectric layer thicknesses to determine the capacitance, stored electrical energy, displacement, and stress levels at uniform pressures ranging from 0 to 200 kPa. Employing a 0.1 mm dielectric layer thickness yields heightened sensitivity and capacitance values, which is consistent with theoretical efforts. At a pressure of 200 kPa, the sensor achieves a maximum capacitance of 33.3 pF, with a total stored electric energy of 15.9 × 10-12 J and 0.468 pF/Pa of sensitivity for 0.1 dielectric thickness. These findings underscore the efficacy of the proposed CPS model for integration into capacitive touch buttons in electronic devices and e-skin applications, thereby offering promising advancements in sensor technology.

Lead‐Free High Permittivity Quasi‐Linear Dielectrics for Giant Energy Storage Multilayer Ceramic Capacitors with Broad Temperature Stability

AbstractElectrostatic energy storage capacitors are essential passive components for power electronics and prioritize dielectric ceramics over polymer counterparts due to their potential to operate more reliably at > 100 ˚C. Most work has focused on non‐linear dielectrics compositions in which polarization (P)/electric displacement (D) and maximum field (Emax) are optimized to give values of energy density, 6≤U≤21 J cm−3. In each case however, either saturation (dP/dE = 0, AFE) or “partial” saturation (dP/dE → 0, RFE) of P limits the value of U which can be achieved before breakdown. It is proposed that U can be further improved with respect to relaxors (RFEs) and anti‐ferroelectrics (AFEs) by designing high permittivity quasi‐linear dielectric (QLD) behaviour in which dP/dE remains constant up to ultrahigh Emax. QLD multilayer capacitor prototypes with dielectric layers composed of 0.88NaNb0.9Ta0.1O3‐0.10SrTiO3‐0.02La(Mg1/2Ti1/2)O3 deliver room temperature U ≈ 43.5 J cm−3, supporting an extremely‐large Emax ≈ 280 MV m−1, both of which exceed current state‐of‐art by a factor of two for devices based on powder, tape‐cast technology. Importantly QLD capacitors exhibit scant variation in U (≈15 J cm−3) up to > 200 ˚C and robust resistance to cyclic degradation, offering a promising new approach for the development of sustainable technology.

Development of a MATLAB‐based graphical user interface to illustrate Coulomb's law and Gauss's law

AbstractCoulomb's law and Gauss's law are two fundamental laws in electrostatics that involve electric charges and electric fields. These concepts that are not visible physically in real life can be challenging for students to understand, especially when it involves complex charge distributions. This paper presents a MATLAB‐based graphical user interface (GUI) to visualise the concept of Coulomb's law and Gauss's law as well as a serious snake game to reinforce users' knowledge. This MATLAB GUI features a diverse range of 3‐dimensional (3D) visualisations illustrating electric field attributes such as electric force, charge distribution and electric flux. These visualisations dynamically adapt to user‐defined parameters, offering a rich and varied exploration of the electric field's characteristics without confining the scope to a specific count of models. In Coulomb's law section, the GUI plots the electric forces in 3‐D for dipole, three‐point charges, and unlimited charge. The Gauss's law section consists of windows for illustration of the fundamentals of Gauss's law for the electric field, and the illustration for the application of Gauss's law in finding the electric field for a point charge, infinite line charge and infinite plane charge. The serious snake game developed in this work allows students to engage in quizzes related to Coulomb's law and Gauss's law to serve as a tool for reinforcing their learning outcomes. The MATLAB‐based GUI was chosen as the platform due to its excellent visualisation capabilities, ease of programming and capability to act as a powerful tool to enhance the learning of Coulomb's law and Gauss's law for students.

A novel double-gate trench SOI LDMOS with double-dielectric material by TCAD simulation study

In this paper, a novel double-gate trench silicon-on-insulator lateral double-diffused metal oxide semiconductor field-effect transistor (LDMOS) with double-dielectric material (DGDK-LDMOS) is proposed. DGDK-LDMOS has two dielectric materials: a reverse-L-shaped high-k (HK) thin film and an low-k (LK) buried oxide layer. The HK thin film optimizes the electric field distribution on the drift region surface, attracting electric flux, and the excellent withstand voltage of the LK buried oxide layer can significantly improve the breakdown voltage (BV) and reduce specific on-resistance (R on,sp) of the device. The modulation mechanism of LDMOS by HK thin film and LK buried oxide layer is analyzed. The results show that compared with conventional LDMOS, when the permittivity of HK thin film is 25 and the permittivity of LK buried oxide is 3, the BV of DGDK-LDMOS is increased by 89.6%, the R on,sp is decreased by 26.4%, and the figure of merit (FOM, FOM = BV2/R on,sp) is increased by 397.2% from 3.6 MW cm−2 to 17.9 MW cm−2. Meanwhile, the output characteristics, transfer characteristics, lattice temperature, AC characteristics and switching characteristics of DGDK-LDMOS are also discussed and compared.