Electrostatic Energy Density Research Articles

Estimation of Hardness of Single-Phase Metallic Alloys

First, we discuss a common feature of single-phase pure metals and amorphous and high-entropy alloys: the maximum value of hardness corresponding to a valence electron count (VEC) value of around 6.5–7. This correlation is explained by the coincidence that by subtracting the number of sp valence electrons (Nsp = 2) from the VEC we obtain the maximal number of unpaired d electrons, Nd = 4.5–5 in the 3d, 4d, and 5d rows of transition elements. These unpaired d electrons form orbital overlap bonding, which is stronger than the isotropic metallic bonds of a delocalized electron cloud. The more unpaired d electrons there are, the higher the bonding strength. Second, we will discuss the hardness formulas derived from cohesion energy and shear modulus. We will demonstrate that both types of formulas originate in the electrostatic energy density of metallic bonds, expressing a 1/R4 dependence. Finally, we show that only two parameters are sufficient to estimate hardness: the atomic radius and the cohesion-based valence. In the case of alloys, our formula gives a lower bound on the hardness only. It is not suitable for calculation of the hardness increase caused by solid solution, grain size, precipitation, and phase mixture.

Probe on the pivotal role of green rust in improving the enzymatic activity and facilitating the formation of 1O2 in Fenton-like process for degradation of 4-chlorophenol

Iron-based materials have demonstrated significant efficacy in catalyzing hydrogen peroxide (H2O2) for the removal of antibiotics from aquatic environments. Green rust (GR), a hybrid valence state iron-based catalyst, was synthesized. By exploiting the catalytic properties of glucose oxidase (GOx) to generate H2O2 from glucose (Glu), a GR-GOx/Glu system for the removal of recalcitrant organic compound 4-chlorophenol (4-CP) was constructed. In terms of pollutant degradation efficiency, an increase of 30% was observed compared to Fe2+/H2O2 system. Utilizing density functional theory (DFT), we calculated the electrostatic potential energy and charge density distribution, demonstrating the existence of active electron transfer between GR and flavin adenine dinucleotide (FAD), which subsequently enhanced the activity of GOx. The enhancement was pivotal for the sustained generation of preferred oxidative species and rapid degradation of pollutants within the system. Furthermore, the acids and H2O2 generated during enzyme catalysis not only neutralized the alkalinity released by the Fenton-like reaction but also promoted the conversion of superoxide radical (·O2-) to singlet oxygen (1O2). Overall, this study elucidates the fundamental motivation underlying the enhancement of enzymatic activity and highlights the critical role of 1O2 within the system, providing valuable insights into the potential mechanisms by which metal hydroxides catalyze the H2O2 process.

Spherical image potentials for an N-charged particle system

The potential energy interaction between a system of N -charged particles and a spherical conducting surface is obtained by means of direct integration of the electrostatic energy density. Making use of the image charge method, we show that the full potential can be split into a sum of one-body central potentials and two-body contributions related to particle–particle and particle–sphere interactions. Analytical expressions are provided for all contributions. The spherical surface of radius R can be considered to correspond to a cavity inside a conductor or a metallic ball, with two different electric conditions, namely the grounded and isolated charged cases. By taking the limit R → ∞ of the spherical case, one recovers the image potential for an N -charged particle system interacting with a planar conductor. While the final results for the potential do not appear as unexpected, the provided analytical expressions should help in diverse physical applications modelled by a number of charged particles interacting close to a spherical surface.

Significantly Enhanced Electrostatic Energy Density of a PVDF-Based Film with [001]-Oriented Rutile TiO2 Fillers via Multilayer Interfacial Engineering

Significantly Enhanced Electrostatic Energy Density of a PVDF-Based Film with [001]-Oriented Rutile TiO₂ Fillers via Multilayer Interfacial Engineering

A supramolecular gel-elastomer system for soft iontronic adhesives

Electroadhesion provides a promising route to augment robotic functionalities with continuous, astrictive, and reversible adhesion force. However, the lack of suitable conductive/dielectric materials and processing capabilities have impeded the integration of electroadhesive modules into soft robots requiring both mechanical compliance and robustness. We present herein an iontronic adhesive based on a dynamically crosslinked gel-elastomer system, including an ionic organohydrogel as adhesive electrodes and a resilient polyurethane with high electrostatic energy density as dielectric layers. Through supramolecular design and synthesis, the dual-material system exhibits cohesive heterolayer bonding and autonomous self-healing from damages. Iontronic soft grippers that seamlessly integrate actuation, adhesive prehension, and exteroceptive sensation are devised via additive manufacturing. The grippers can capture soft and deformable items, bear high payload under reduced voltage input, and rapidly release foreign objects in contrast to electroadhesives. Our materials and iontronic mechanisms pave the way for future advancement in adhesive-enhanced multifunctional soft devices.

Rotation and transportation of liquid crystal droplets for visualizing electric properties of microstructured electrodes

The spatial resolution of typical sensor probes is sufficient for measuring the average electric properties of microelectrical devices, but they are unable to measure the distribution with a spatial precision. Liquid crystal droplets (LCDs) are promising candidate for visualizing the distribution. When voltage is applied, the LCDs show rotational and translational behaviors which depend on the location of LCDs within the devices. We demonstrate that by comparing the experimental and numerical results, the electric field and electrostatic energy distribution are visualized by rotating and transporting LCDs, with a spatial resolution of 10 µm and a detection accuracy of 5 µV/µm. In addition, we produced an array of LCDs by designing periodic modulation of the electrostatic energy density in the model device. These findings show that the LCDs serve as a periodic modulator of the refractive index as well as a sensor for the observation of electric properties of microelectrical devices.

Pseudopotential contributions to the quadrupole moment in charged periodic systems

There has been much interest over many years in studying charged systems after the artificial imposition of periodic boundary conditions, and correcting for the resulting divergence of the electrostatic energy density. A correction for cubic cells was derived by Makov and Payne in 1995, and its leading error term is of the form $L^{-5}$ for a cube of side $L$. Most modern Density Functional Theory codes use a different treatment of the `Z$\alpha$' energy term to that used by Makov and Payne, resulting in an error term of the form $L^{-3}$ if their correction is used unmodified. This paper shows how the Makov and Payne result can be made consistent with modern practice.

Enhanced breakdown strength and electrostatic energy density of polymer nanocomposite films realized by heterostructure ZnO-ZnS nanoparticles

We demonstrate that introduction of heterostructure nanoparticles into a polymer matrix is an effective strategy to substantially enhance dielectric breakdown strength (Eb) and thus a high electrostatic energy storage density (Ue) can be obtained, which is highly desired in modern electronic and electrical systems for energy storage and conversion. This is realized through the special “electrical rectification” effect of heterostructure nanoparticles on the charge transport, which stems from capturing and confining charge carriers in the nanocomposites by potential well and potential barrier formed at the heterojunction of ZnO-ZnS nanoparticles. The leakage current of the ZnO-ZnS/polyetherimide nanocomposites (ZnO-ZnS/PEI) is suppressed by the introduced heterojunction, which is accompanied with the simultaneous increase of dielectric displacement and charge–discharge efficiency, resulting in significant enhancement of Ue. Notably, the 1 wt% ZnO-ZnS/PEI nanocomposite films possess high discharged energy density at room temperature, i.e. 6.9 J cm−3 at 650 MV m−1, and even at 150 °C, the Ue still remains 3.6 J cm−3 at 500 MV m−1. Outstanding fatigue resistance over 50,000 charge–discharge cycles at 200 MV m−1 and 150 °C demonstrates high temperature cyclic stability of the heterostructure in confining charge carriers. This work provides a novel and scalable strategy to obtain polymer-based dielectrics with superior energy storage performance.

The Positronium and Mass-energy Equivalence

The positronium consists of two oppositely charged particles of the same mass m and intrinsic energy 'E'. A positron of charge +e and an electron of charge -e, revolve diametrically, under mutual attraction, at equal radius, round their center of mass. The revolution is in unclosed elliptic paths with radiation or a closed circular orbit without radiation. The positron or electron is considered to be an impregnable spherical shell of radius a and mass m as a constant equal to the rest mass 'M'. with electrostatic field Eo and energy density (ɛ/2)Eo^2, in space. The particles may combine, with centers 2a apart, without annihilating, emitting radiation of energy 'E', equivalent to m, to form a dipole, a neutral particle called ‘unitron’ of intrinsic energy 'E' and mass m. The ‘unitron’ has negative potential energy -'E', according to a mass-energy equivalence law. The positron, electron and ‘unitron’ are the basic building blocks of matter

Elaborately designed polymer dielectric films with low coefficient of thermal expansion demonstrating high and stable electrostatic energy density over a wide temperature range

High-temperature electrostatic energy storage dielectric capacitors with the prominent advantage of ultrahigh power density have recently become a focal point in the field of power electric and electronic systems to adapt the harsh working environment. To reduce the decreasing degree of electric breakdown strength with the increase in temperature is the key to maintaining a high energy density at elevated temperature. Herein, we analyzed thermal and electric properties of a series of films and interpreted the relationship between the capability of dimensional deformation and electric breakdown strength in view of molecular dynamics. Based on the results, an empirical law, ln(Eb) = kln(1/α-n)+C, was proposed, which relates electrical and thermal performance of low thermal conductivity dielectric materials for achieving stabilized high-temperature energy storage density. Guided by this finding, the meticulously prepared silicon oxide/epoxy films with low thermal expansion coefficients present a high charge–discharge efficiency of 86% at 200 °C, resulting in a discharged energy density of 2.1 J/cm3. Designing polymer dielectrics with low thermal expansion coefficients in a wide temperature range proves effective to obtain excellent energy storage performance at ultrahigh temperatures.

Enhanced dielectric and electrostatic energy density of electronic conductive organic-metal oxide frameworks at ultra-high frequency

High-density energy materials comprise high dielectric strength, and rapid charge transport leads to improved microwave absorbance, maximum electromagnetic wave (EM) attenuation, and wideband characteristics. This work exhibits hierarchical polyaniline (PANI) functionalized polycrystalline hybrid units. Comprehensive band structures, increased electron conduction, high charge polarization, and definite EM wave absorption could be tuned by the featured morphologies. Filler material's (RGO/ZnO) intercalated structures have substantial free space volume. It could facilitate notable dielectric permittivity (∼2562 F m−1), give rise to higher charge polarization and excellent charge storage performance (∼112 F). This electrostatic charge proficiency could recognize with generous electron density corresponding to stimulated surface charge density (σs, ∼8.66×103 C m−2). Quality factor (Q) of 0.056 (∼ 7.1×106Hz) with minimized losses attributed to higher energy density (Ue, ∼1530 J cm−3) at low electric field strength ∼ 450 V m−1, which could resemble a variable Ue performance at lower to a higher percolation threshold voltage. Incorporated ZnO and RGO nanostructures are well organized, with the PANI matrix providing good interfacial adhesion. It significantly raises the EM wave losses (– 28 dB) of ∼0.300 mm thick specimen at ∼ 18.42 GHz. We envisioned that the multifunctional response of the PANI-RGO-ZnO 2:1 hybrid might manifest potential energy storage and microwave absorption as electrode materials that may be useful in solid-state devices used in modern communication systems.

Effects of Electrostatic Interaction on the Formation of a Particle Depletion Zone by Charged Nanoparticles during the Chemical Vapor Deposition of Si Processes

The electrostatic potential energy and surface charge density of charged nanoparticles (CNPs) were calculated via the finite element method (FEM). We combined the FEM results with kinetic Monte Carlo (kMC) simulations to study the dynamics of a nonclassical crystallization system comprising numerous small CNPs and a large CNP. Afterward, we investigated the evolution of a particle depletion zone around the large CNP during the low-temperature chemical vapor deposition of Si. The FEM calculation results showed that small and large CNPs having like charges attracted each other when they were in close proximity, because opposite charges were induced on the surfaces of particles adjacent to each other. The kMC simulation results showed that this attraction resulted in a relatively small particle depletion zone around the large CNP. During the formation of the depletion zone, charges accumulated on the large CNP. The accumulated charge resulted in repulsion between the small and large CNPs and a gradual expansion of the particle depletion zone. Further analysis indicated that the imbalance between the numbers of positively and negatively charged CNPs influenced the structural evolution of the particle depletion zone.

Controlling the crystallization of Nd-doped Bi4Ti3O12 thin-films for lead-free energy storage capacitors

Environmentally benign non-lead-based dielectric thin film capacitors with high electrostatic energy density, long-term stability, and fast charge/discharge capability are strongly demanded in advanced electrical and pulsed power devices. Here, we propose that insufficient crystallization is an effective method to achieve high energy storage performance. A high efficiency of 84.3%, together with a good energy density of 41.6J/cm3 and an excellent fatigue endurance, is obtained in a lead-free Nd-doped Bi4Ti3O12 film of low crystallization. An increase in the annealing temperature increases the crystallinity and grain size, which improves the ferroelectric polarization of a thin film. A narrow hysteresis loop with large maximum polarization and small remnant polarization is obtained in the insufficiently crystallized film, which is annealed in the intermediate temperature. This film also shows a lower leakage current compared with the fully crystallized counterpart due to the less defective microstructure. This work provides a straightforward and executable method to design ferroelectric materials for the applications of energy storage capacitors.

Nanoparticles with rationally designed isoelectronic traps as fillers significantly enhance breakdown strength and electrostatic energy density of polymer composites

Dielectric polymer nanocomposites with a high energy density and high charge-discharge efficiency are urgently in need which enable miniaturization of both electrical and electronic systems. One critical challenge for achieving a high energy density is the suppression of space charge movement in the composites which relates to the dielectric breakdown strength and thus energy density. Herein ZnS:O nanoparticles, in which a part of S in ZnS was substituted by O, were synthesized. The difference of electronegativity (ΔEN = 0.86) between S and O creates isoelectronic traps in the nanoparticles, which can to some extent bind space charges and suppress their movement. As a result, with ZnS:O as fillers and polyvinylidene fluoride (PVDF) as a host, the composites achieved a breakdown strength as high as 6000 kV/cm and an energy density of 14.4 J/cm3 with 2.5 vol% ZnS:O nanoparticles, which are nearly twice and over three times respectively of those of the pure PVDF (Eb ~3183 kV/cm, 4.6 J/cm3), and also much higher than those of ZnS filled PVDF. Moreover, the dielectric loss and leakage current were effectively suppressed, leading to a high charge-discharge efficiency of up to 97%. The present work provides an efficient approach of modulating the dielectric and electric performance of nanocomposites by confining charge carriers in the isoelectric traps. The effect was investigated by calculation of electric field threshold and electron hopping distance. Finite element simulation was employed to understand the mechanism which vividly interprets the above phenomenon.

Stationary Langmuir structures in a relativistic current carrying cold plasma

Nonlinear stationary structures formed in a cold plasma with immobile ions in the presence of a relativistic electron current beam have been investigated analytically in the collisionless limit. The structure profile is governed by the ratio of maximum electrostatic field energy density to the kinetic energy density of the electron beam, i.e., κ=Em/(4πn0m0v02)1/2, where Em is the maximum electric field associated with the nonlinear structure and v0 is the electron beam velocity. It is found that, in the linear limit, i.e., κ≪2γ0/(1+γ0), the fluid variables, viz., density, electric field, and velocity vary harmonically in space, where γ0 is the Lorentz factor associated with beam velocity (v0). In the range 0<κ≤κc(=2γ0/(1+γ0)), the fluid variables exhibit an-harmonic behavior. For values of κc<κ<+∞, the electric field shows finite discontinuities at specific spatial locations indicating the formation of negatively charged planes at these locations.

Separate spin evolution of electrostatic energy flow in a degenerate quantum plasma

We have discussed energy densities and energy flow speed in a spin polarized plasma when longitudinal waves [Spin electron acoustic wave (SEAW) and Langmuir wave] propagate through the plasma. Employing the separate spin evolution quantum hydrodynamic model, we have derived the expression for energy densities and energy flow speed. It is found that the spin polarization changes the profiles of various energy densities. Specifically, we find that the spin polarization broadens the profile of the electrostatic energy density retaining the same peak value. In the case of kinetic and quantum energy densities, the profiles become narrower with the decrease in the peak value for the former case and increase for the latter. On the other hand, in the case of Langmuir waves, the spin polarization effect is similar for electrostatic energy density but opposite to the peak values of kinetic and quantum energy densities. The corresponding profiles become narrower as in the case of SEAW. Furthermore, energy flow speed associated with the SEAW and Langmuir wave is reduced for higher values of spin polarization. It is also noted that the contribution of Bohm potential in the dispersion compensates the reduction of energy flow due to spin polarization. The results are graphically analyzed for the choice of solid state plasma parameters.

Optimal selection of coaxial ring systems in environmental electrostatic shielding

PurposeThe purpose of this paper is to present a new calculation method for increasing the shielded volume in which the external electromagnetic field is maximally reduced. In a space shielded in the way mentioned in this paper, it is possible to introduce measurement instruments and increase the accuracy of results obtained with them, as well as reduce the risk of unwanted electrostatic field influence on living organisms.Design/methodology/approachA new numerical procedure for the optimization of the coaxial ring conductor system for electrostatic shielding is developed in the paper. The optimization of the functional that consists of electrostatic energy density and a system of equations derived from the equipotential character of the conductor system is used. The system of nonlinear equations is obtained and then numerically solved by minimizing this functional. The first presented optimization procedure is based on the analytical optimization method using the Lagrange coefficients and gradient of the objective function.FindingsIt is possible to design a large number of protective ring formations. Applying the differential evolution optimization method, an optimal arrangement can be obtained for any specific number of rings. The differential evolution optimization method, which belongs to the class of evolutionary algorithms, is used for solving this very complex optimization problem. In combination with the above-mentioned method, excellent results in the elimination of the external electric field have been obtained. Although a larger number of rings provides more efficient protection, this number is limited from the economic point of view. Therefore, it is necessary to achieve a compromise between the number of rings, the size of volume shielded and the quality of protection.Research limitations/implicationsThere are few papers that address this problem, although the elimination of the influence of the external electromagnetic field has gained more importance lately. The presented method can be applied to increase the reliability of measured data, protection of the environment, in space research, etc. The main limiting factor for using a larger number of rings that provide better protection is the economical one.Originality/valueThe proposed method is suitable for the generalization of procedures, for the protection of the space where the external electric field needs to be reduced or eliminated.

A turbulent cascade model of bounce averaged gyrokinetics

A shell model is derived for the description of nonlinear bounce averaged gyrokinetics, which is one of the simplest kinetic descriptions in magnetized plasmas. In order to validate the numerical implementation, detailed linear evolution of the system is compared with a linear benchmark based on solving the linear dispersion relation numerically. The resulting wave number spectrum, which extends over 3–4 decades, is shown to have a robust general structure to model parameters, such as dissipation or the ratio of linear energy injection to nonlinear transfer. In a range of wave numbers where the nonlinear transfer term is dominant, a power law spectrum, roughly of the form k−4, is observed for the spectral electrostatic potential energy density. The model, being fully kinetic, can be used to obtain the free energy spectra for ion and electron distribution functions as functions of E. This model constitutes the first numerical implementation of a kinetic shell model.

Particle-in-cell simulation of Buneman instability beyond quasilinear saturation

Spatio-temporal evolution of Buneman instability has been followed numerically till its quasilinear quenching and beyond, using an in-house developed electrostatic 1D particle-in-cell (PIC) simulation code. For different initial drift velocities and for a wide range of electron to ion mass ratios, the growth rate obtained from simulation agrees well with the numerical solution of the fourth order dispersion relation. Quasi-linear saturation of Buneman instability occurs when the ratio of electrostatic field energy density to initial electron drift kinetic energy density reaches up to a constant value, which, as predicted by Hirose [Plasma Phys. 20, 481 (1978)], is independent of initial electron drift velocity but varies with the electron to ion mass ratio (m/M) as ≈(m/M)1/3. This result stands verified in our simulations. The growth of the instability beyond the first saturation (quasilinear saturation) till its final saturation [Ishihara et al., PRL 44, 1404 (1980)] follows an algebraic scaling with time. In contrast to the quasilinear saturation, the ratio of final saturated electrostatic field energy density to initial kinetic energy density is relatively independent of the electron to ion mass ratio and is found from simulation to depend only on the initial drift velocity. Beyond the final saturation, electron phase space holes coupled to large amplitude ion solitary waves, a state known as coupled hole-soliton, have been identified in our simulations. The propagation characteristics (amplitude–speed relation) of these coherent modes, as measured from present simulation, are found to be consistent with the theory of Saeki et al. [PRL 80, 1224 (1998)]. Our studies thus represent the first extensive quantitative comparison between PIC simulation and the fluid/kinetic model of Buneman instability.

Ultrahigh capacitive energy storage in highly oriented Ba(ZrxTi1-x)O3 thin films prepared by pulsed laser deposition

We report structural, optical, temperature and frequency dependent dielectric, and energy storage properties of pulsed laser deposited (100) highly textured BaZrxTi1−xO3 (x = 0.3, 0.4, and 0.5) relaxor ferroelectric thin films on La0.7Sr0.3MnO3/MgO substrates which make them potential lead-free capacitive energy storage materials for scalable electronic devices. A high dielectric constant of ∼1400–3500 and a low dielectric loss of <0.025 were achieved at 10 kHz for all three compositions at ambient conditions. Ultrahigh stored and recoverable electrostatic energy densities as high as 214 ± 1 and 156 ± 1 J/cm3, respectively, were demonstrated at a sustained high electric field of ∼3 MV/cm with an efficiency of 72.8 ± 0.6% in an optimum 30% Zr substituted BaTiO3 composition.