Electric Strength Research Articles

Electric Strength of Dielectrics under Influence of Bipolar Voltage Pulses of Submicrosecond Duration

Electric Strength of Dielectrics under Influence of Bipolar Voltage Pulses of Submicrosecond Duration

Analytical analysis of inclined three-layered composite channel with cobalt ferrite nanoparticles and Hall current in Darcy medium

The present study explores the influence of electromagnetic effects on the flow of a nanofluid in a saturated permeable medium, confined between a clear viscous fluid in an inclined channel. The nanofluid consists of cobalt ferrite nanoparticles dispersed in ethylene glycol. The governing equations are derived considering Darcy's law for the permeable medium and Tiwari's model for fluids containing nano-sized particles. Additionally, radiation and dissipation effects are incorporated into the energy equation. The equations are transformed into dimensionless form and solved analytically using the perturbation technique. The results are analyzed through graphs and tables for different material parameters. The findings reveal that higher electric and magnetic strengths have a significant impact on the fluid velocity at the interface of the two fluids, resulting in reduced shear both at the clear fluid surface and the interface between them. This highlights the crucial role played by electric and magnetic strengths in modifying flow phenomena. Consequently, combining electric and magnetic strengths with nanofluids can be utilized to achieve desired qualities in multi-fluid flow and enhance heat transfer characteristics.

Synergistic effect of CaCu3Ti4O12 ceramic and Ti3C2Tx MXene nanoflakes on the dielectric properties of poly (vinylidene fluoride) composites

Polymer composites are popular multifunctional materials. Their effective use in elements of electronic devices is possible due to the optimal dielectric properties. In this work, a balance between a high dielectric constant and a low dielectric loss tangent was achieved by introducing two types of fillers into poly (vinylidene fluoride): ceramic CaCu3Ti4O12 (10, 20 and 30 vol%) and conductive Ti3C2Tx MXene (2.5–5 wt%). CCTO ceramics was synthesized by the solid-state method. Ti3C2Tx MXene was obtained by etching the Al layer from Ti3AlC2 MAX phase under hydrothermal conditions. The materials were studied by XRD, SEM, FTIR, laser diffraction, and impedance spectroscopy. Composites based on poly (vinylidene fluoride) with 30 vol% CaCu3Ti4O12 and 5 wt% Ti3C2Tx MXene demonstrated the most promising results when increasing the dielectric constant to 28 at a dielectric loss tangent value of 0.061 at a frequency of 10 kHz. At the same time, the electrical strength of the composites had values not lower than 100 MV∙m−1, which is extremely important for their practical application. The results obtained can be used in the development of modern polymer composite dielectrics for passive elements of flexible electronics.

Improved dielectric temperature stability and energy storage properties of BNT-BKT-based lead-free ceramics

The lead-free ceramics (1-x)(0.84Bi0.5Na0.5TiO3-0.16Bi0.5K0.5TiO3)-xBiMg2/3Nb1/3O3 (denoted as (1-x)BNKT-xBMN) and (1-y)(0.85BNKT-0.15BMN)-ySr0.7La0.2TiO3 with y = 0.3 (denoted as BNKMN-0.3SLT) were prepared by means of a conventional solid state sintering method. Effects of introduction of BiMg2/3Ni1/3O3 and Sr0.7La0.2TiO3 on phase structure, microstructure, and dielectric, ferroelectric and energy storage properties of the ceramics were studied in detail. The ceramics (1-x)BNKT-xBMN show pure perovskite structure, while BNKMN-0.3SLT appears a secondary phase. All ceramics exhibit dense microstructures with mean grain sizes between 0.56 μm and 1.36 μm. The introduction of SLT into BNKMN causes obvious decrease in dielectric constant around Curie temperature, inducing the widest temperature window of 263 °C from 29 °C to 292 °C for TCC≤±15 %. The ceramic BNKMN-0.3SLT shows high electric breakdown strength (Eb ∼ 300 kV/cm), large maximum polarization (Pm ∼ 36.48 μC/cm2), and low remanent polarization (Pr ∼ 1.70 μC/cm2), inducing high energy storage density of 4.03 J/cm3 as well as high energy storage efficiency of 85.2 %.

Mass production of carbon nanotube fibers and hybrid yarns for high-performance helical auxetic yarn strain sensors

With the spectacular physical properties of electrical conductivity, mechanical strength and thermal conductivity, carbon nanotube (CNT) fibers are favored in many fields such as energy storage devices, sensing, electromagnetic shielding and structural reinforcement, especially in flexible sensing devices. However, the lower tensile properties of CNT fibers limit their further application in stretchable strain sensors, especially when monitoring large deformation variables. Here, large-scale continuous production of CNT fibers has achieved through floating catalytic chemical vapor deposition (FCCVD) technology. In the meantime, the CNT fibers were hybrid with Kevlar fibers to obtain hybrid CNT yarns with the strength of 168.4 MPa and the electrical conductivity of 7.78 × 104 S m−1. The strength of the hybrid CNT yarns produced by this method is higher than that of 40 count cotton yarns, which is perfectly suited for the fabrication of textile devices. Through knitting with three-dimensional elastic fabrics, the textile-based sensors exhibit promising sensing ability, washability, weather tolerance and sweat resistance, owing to the excellent physical and chemical properties of the hybrid CNT yarns. Moreover, stretchable strain sensors exhibit fast response and cycle stability, which provides unique opportunities in designing smart textiles with fast response and environmental durability.

Antiferroelectric nano-heterostructures filler for improving energy storage performance of PVDF-based composite films

Incorporating high permittivity inorganic ferroelectric in polymer dielectrics is the most prevalent and straightforward approach to improve their energy storage capacity, which has an extensive application prospect in power electronic circuits owing to their higher power density. However, the discharged energy density attained with these materials are mainly restrained by the high remnant electric displacement of ferroelectric and the large discrepancy in permittivity between inorganic and organic substance. Herein, we proposed a novel antiferroelectric (Pb0.875La0.05Sr0.05)(Zr0.595Sn0.4Ti0.005)O3@Al2O3 (PLSZST@AO) nano-heterostructure as fillers to fabricate nanocomposite films, wherein the Al2O3 layer with wide band gap and dielectric constant close to that of the PVDF matrix was encapsulated onto the antiferroelectric nanoparticle PLSZST to alleviate the discrepancy in permittivity and enhance the breakdown strength. Especially, the experimental results and computational simulations confirmed that the presence of Al2O3 layer is capable of effectively enhancing the electric displacement and breakdown strength, while reducing the remnant displacement and impeding the formation of electrical trees. As a result, the nanocomposite films exhibited an impressive discharged energy density of 18.2 J/cm3 along with a remarkably enhanced energy storage efficiency of 70 % near the high electrical breakdown strength of 594.7 MV/m when the fillers content was 3 wt%, which was far surpassed the pristine PVDF (Ud = 5.34 J/cm3 and η = 51.8 %). Together with its excellent mechanical strength, the monolayer film was verified to be an outstanding performance dielectric material, outperforming the current PVDF-based composite dielectrics for high-power energy storage capacitors. This work allowed for more versatility in designing and manufacturing flexibility nanocomposite films, which can contribute to improving their performance and practicality.

Recent Advances in W–Cu Composites: A Review on the Fabrication, Application, Property, Densification, and Strengthening Mechanism

Tungsten–copper (W–Cu) composite is a pseudoalloy prepared by powder metallurgy method with tungsten and copper as the main components, which are widely used in electrical contacts, electrical discharge machining electrodes, electronic packaging, aerospace, and military fields due to its good conductivity, thermal conductivity, high melting point, high electrical breakdown strength, low contact resistance, high welding resistance, and high heat resistance. Herein, the recent advances of W–Cu composites are reviewed systematically. First, the preparative techniques of W–Cu composites are introduced in detail, and their advantages and disadvantages are evaluated objectively. Second, an introduction of the main application fields and corresponding characteristics advantages for W–Cu composites are provided. Subsequently, the densification techniques and strengthening mechanisms and their effects on microstructure, mechanical properties, and physical properties of W–Cu composites are mainly discussed. Finally, based on a comprehensive review of W–Cu composites, its future development trends and potential research challenges are summarized and prospected.

Excellent energy storage properties with ultrahigh Wrec in lead-free relaxor ferroelectrics of ternary Bi0.5Na0.5TiO3-SrTiO3-Bi0.5Li0.5TiO3 via multiple synergistic optimization

Advanced energy storage capacitors play important roles in modern power systems and electronic devices. Next-generation high/pulsed power capacitors will rely heavily on eco-friendly dielectric ceramics with high energy storage density (Wrec), high efficiency (η), wide work temperature range and stable charge-discharge ability, etc. Lead-free Bi0.5Na0.5TiO3 (BNT) based relaxor ferroelectric (RFE) ceramics are considered as one of the most promising candidates for energy storage capacitors. However, the application fields of them are greatly limited by their relatively low Wrec (generally <5 J/cm3). In this paper, excellent energy storage properties characterized by a great breakthrough in Wrec are achieved in a novel BNT system, (1-x)BNT-x(0.7SrTiO3-0.3Bi0.5Li0.5TiO3)+0.5 at.%Nb2O5 (x = 0, 0.1, 0.2, 0.3, 0.4), by synergistically constructing highly dynamic polar nanoregions (PNRs) and nanodomains, ultrafine grains (submicron size) and intrinsic conduction. Of great importance, the x = 0.4 ceramic exhibits an ultrahigh Wrec of 8.63 J/cm3 as well as a high efficiency (ƞ) of 89.6 % under a giant electric field of 520 kV/cm, due to coexistence of ultrahigh polarization difference (ΔP=Pmax −Pr) and high dielectric breakdown electric strength (Eb). Furthermore, excellent temperature stability (20−180 °C), frequency stability (1 − 500 Hz), and cycling stability (1 − 105 times) with the variation of Wrec < ±4 % and η < ±3 % are also found in the x = 0.4 ceramic. These results demonstrate that it is a very promising lead-free dielectric capacitor with enormous energy storage applications.

Fully carboxy-functionalized polyhedral silsesquioxanes as polar fillers to enhance the performance of dielectric silicone elastomers

Octakis(2-carboxyethyl-thioethyl)silsesquioxane (T8-COOH), a structurally well-defined organo-functionalized nano-silica, was used as an addition in different percentages (up to 15 wt.%) to a high molecular mass PDMS, obtaining composites that were processed as films by solution casting and stabilized by condensation crosslinking. SEM images showed a common aggregation phenomenon within polymeric matrix at high filler concentration. The presence of T8-COOH pushed the main stage of thermal decomposition to higher temperatures, generally around 500 °C, as compared to 400 °C for pure PDMS. The mechanical strength of the obtained composites was also enhanced by increased addition of filler that acts as a reinforcing agent. Tensile toughness, strains at break, and Young's modulus increased with increasing filler content. The viscoelastic behavior of the silicone composites was evaluated in five cyclic stress-strain tests. All materials showed relatively large hysteresis loops for the first cycle due to Mullin's effect, while the subsequent hysteresis became smaller from the second cycle. The composites showed dielectric behavior with low loss (<10−1), relative permittivity superior to pure siloxane (4–5 vs. 3.4), and slightly increased electrical breakdown strength (30–36 V/μm vs. 27 V/μm). The applicative potential of these composites in electromechanical devices was estimated by calculated figures of merit, based on mechanical and dielectric parameters, which indicate their suitability for energy harvesting/capacitive sensors rather than for actuators. In addition, the composite with the highest ε′ was tested as capacitive pressure sensor, showing a high sensitivity at low pressure, with potential application in wearable devices.

Effect of Li1.3Al0.3Ti1.7(PO4)3 on semiconductive composites: Positive temperature coefficient (PTC) performance and inhibition of space charge injection

The semiconductive layer located between the core and insulation layer of a high-voltage DC (HVDC) cable can inhibit the accumulation of space charge in the insulation layer. This helps increasing the electric field inside the cable, thus improving the stress distribution of the electric field on the inner and outer surfaces of the insulation layer and the electrical strength of the cable. An inevitable positive temperature coefficient effect (PTC) in the semiconductor layer leads to aging failure of the insulation layer. To improve this phenomenon, the semiconductive shielding layer was modified for suppressing its PTC effect and reducing the space charge injection into the insulation layer. Li1.3Al0.3Ti1.7(PO4)3(LATP) was prepared via a solid-phase reaction and added to a composite consisting of carbon black (CB), ethylene vinyl acetate copolymer (EVA), and low-density polyethylene (LDPE). Resistivity, thermally stimulated depolarization current (TSDC), and pulsed electroacoustic (PEA) measurements were performed on the modified sample. The results showed that when the LATP content was 4 wt%, the modification effect of the semiconductive shielding layer was most effective, the PTC effect was reduced by 11%, and the space charge injection into the insulating layer was improved significantly.

Electromagnetic properties of Λ hypernuclei with a beyond relativistic mean-field approach

We present a microscopic study of electromagnetic properties of the low-lying states of single-Λ hypernucleus Λ9Be using a quantum-number projected generator coordinate method (HyperGCM) based on covariant density functional theory. All the configurations are restricted to have axial symmetry, with the Λ hyperon in the lowest-energy state. The results are compared to the predictions of a simple particle-rotor model (PRM), for which analytic expressions are available. We show that the electromagnetic properties of Λ9Be from the HyperGCM calculation are close to those by the PRM. In particular, it is found that the magnetic moments and M1 transition strengths are less sensitive to the coupling strengths of the ΛN interaction than the electric quadrupole transition strengths. The latter may provide additional constraints on the ΛN interaction.

Modified (Ba,Sr)(Sn,Ti)O3 via hydrothermal synthesis for electrocaloric application

Electrocaloric cooling systems require components with large entropy change at the desired working temperature, high electric breakdown strength and low dielectric losses. We here report on hydrothermal synthesis (HTS) route for preparation of lead-free electrocaloric (EC) material Ba0.82Sr0.18Sn0.065Ti0.935O3 (BSSnT-18-6.5) with a median particle size of d50 = 150 nm. Influence of molar ratio (Ba,Sr):(Sn,Ti) on the purity and particle size of hydrothermally synthesized powders is investigated. The sintering behavior and the resulting microstructure of bulk ceramic samples prepared with HTS powders as well as their dielectric, ferroelectric, and electrocaloric properties are analyzed and discussed in detail. By using HTS powders we could significantly reduce sintering temperature from 1400 °C to 1275 °C. Samples prepared with a molar ratio (Ba,Sr):(Sn,Ti) of 1.6 show a maximum EC temperature change |ΔTEC| of 0.59 K around 30 °C with a broad peak of |ΔTEC| > 0.3 K in the temperature range from 5 °C to 65 °C under an applied electric field change of 5 V μm−1. Our results show that hydrothermal synthesis is well suited to produce starting powders of lead-free electrocaloric materials for future fabrication of multilayer ceramic (MLC) components.

Influence of the phthalimide on the process of electrical aging of the high-pressure polyethylene

Relevance. The use of polyolefins without additional processing methods, namely, the increase in their electrophysical characteristics, is an actual modern requirement. For this, it is necessary to use the mechanism of ionization ageing where the role of the modifying additive must be elucidated by the method of infrared spectroscopy in high-pressure polyethylene. Purpose. The research aims to study the effect of low molecular weight organic additives of phthalimide on molecular structural changes in polymers that occur under external action. Methodology. The impact of electrical discharges on polymer dielectrics was carried out in a test cell of an asymmetric type. Tested polymer film before and after pre-stretching was tightly stretched onto this plate following the research procedure. To create an air gap of constant thickness between the top electrode and the polymer film, 1.5 mm thick glass spacers were placed along the edges. Results. The electrical strength (lifetime) of high-pressure polyethene (LDPE) and its optimal modification before and after electrical ageing was investigated. Following experimental data, at the content of 0.05 wt. % LDPE its electrical strength reaches a maximum value compared to both the original LDPE and LDPE at other additive contents. The introduction of 0.05 wt.% phthalimide into high-pressure polyethene contributes to a noticeable decrease in the intensity of the formation of C=0 groups, which is the measure of the oxidative degradation of polymer chains. Conclusions. The optimal composition of the phthalimide was determined and their electrophysical properties were studied. It was found that composites with additions of 0.05 wt.% phthalimide significantly improve the electrophysical properties of LDPE.

High-performance energy storage in BaTiO3-based oxide ceramics achieved by high-entropy engineering

Dielectric energy-storage capacitors are of great importance for modern electronic technology and pulse power systems. However, the energy storage density (Wrec) of dielectric capacitors is much lower than lithium batteries or supercapacitors, limiting the development of dielectric materials in cutting-edge energy storage systems. This study presents a single-phase BaTiO3-based high-entropy (BT-H) ceramic, which is synthesized using a conventional solid-state reaction method. It is found that the BT-H ceramic exhibits a remarkable energy storage performance, with a Wrec of 5.18 J/cm3 and an ultrahigh η of 93.7% at 640 kV/cm electric field. Moreover, it also features wide temperature stability and excellent frequency stability. It is proposed that the introduction of high entropy enhances the random electric field and stress field, leading to lattice distortion and reduction of nanometer domain size, which in turn reduces remnant polarization and increases electric breakdown strength. This research provides a novel approach to improve the energy storage performance of ceramics through the high-entropy strategy.

Transition of Carbon Nanotube Sheets from Hydrophobicity to Hydrophilicity by Facile Electrochemical Wetting

The present study delves into the transformative effects of electrochemical oxidation on the hydrophobic-to-hydrophilic transition of carbon nanotube (CNT) sheets. The paper elucidates the inherent advantages of CNT sheets, such as high electrical conductivity and mechanical strength, and contrasts them with the limitations posed by their hydrophobic nature. A comprehensive investigation is conducted to demonstrate the efficacy of electrochemical oxidation treatment in modifying the surface properties of CNT sheets, thereby making them hydrophilic. The study reveals that the treatment not only is cost-effective and time-efficient compared to traditional plasma treatment methods but also results in a significant decrease in water contact angle. Mechanistic insights into the hydrophilic transition are provided, emphasizing the role of oxygen-containing functional groups introduced during the electrochemical oxidation process.

ANALISIS PENGGANTIAN RESISTOR DENGAN LAMPU PIJAR PADA RANGKAIAN DC MELALUI SIMULASI PhET

This study aims to analyze the ability of incandescent lamps to replace resistors in series circuits when given a DC voltage. The research method used uses a quantitative approach. The data collection technique is through virtual experimentation on the PhET interactive simulation. The experiment was carried out twice using different treatments. The first experiment uses two resistors with the same magnitude of each resistance. The second experiment uses a resistor and an incandescent lamp with the same resistance. An incandescent lamp has the same resistance as a resistor. Through each experiment, six data on the strength of electric currents with different DC voltages were obtained. Based on the two experiments, the increase in DC voltage causes the resulting electric current to be stronger. The data obtained is then visualized in graphical form, then analyzed by regression. Based on the research results, incandescent lamps cannot replace the role of resistors in an electric circuit. This was proven when one of the resistors was replaced with an incandescent lamp producing a different electric current strength. Even though the resistance on the resistor and the incandescent lamp are the same.

Designing a new KBT-based binary solid solution as a candidate for dielectric energy storage materials

Dielectric energy storage capacitors offer great potential in pulsed power devices due to the high power density and fast charging-discharging rate. Designing a host material with high field-induced polarization is of importance for developing dielectric energy storage materials via further composition modulation. In this paper, we compare the microstructure, dielectric, and ferroelectric properties as well as the energy storage performance of samples K1/2Bi1/2TiO3(KBT), 75KBT-25BiFeO3 (KBTF25), and 88KBT-12Bi0.85Nd0.15FeO3 (KBNTF12) in detail. It is found that, among three samples, sample KBNTF12 possesses the most complex local structure coexisting of a four-distortions with different polarities; meanwhile, sample KBNTF12 behaves as a strong relaxor, thus giving a high field-induced polarization. Besides, sample KBNTF12 realizes the highest electric breakdown strength Eb among three samples, which is resorted to the highest resistivity of grain boundary. Highest ΔP and Eb of sample KBNTF12 among three samples render it achieve ultrahigh stored energy density Ws of 6.94 J/cm3, high recoverable energy density Wr of 5.23 J/cm3, and high efficiency η of 75.4%. Our work suggests that 88KBT-12BNF binary composition be an optimal candidate for dielectric energy storage ceramics.

FeF3/(Acetylene Black and Multi-Walled Carbon Nanotube) Composite for Cathode Active Material of Thermal Battery through Formation of Conductive Network Channels.

Considerable research is being conducted on the use of FeF3 as a cathode replacement for FeS2 in thermal batteries. However, FeF3 alone is inefficient as a cathode active material because of its low electrical conductivity due to its wide bandgap (5.96 eV). Herein, acetylene black and multi-walled carbon nanotubes (MWCNTs) were combined with FeF3, and the ratio was optimized. When acetylene black and MWCNTs were added separately to FeF3, the electrical conductivity increased, but the mechanical strength decreased. When acetylene black and MWCNTs were both added to FeF3, the FeF3/M1AB4 sample (with 1 wt.% MWCNTs and 4% AB) afforded a discharge capacity of approximately 74% of the theoretical capacity (712 mAh/g) of FeF3. Considering the electrical conductivity and mechanical strength, this composition was confirmed to be the most suitable.

Optimizing Energy Efficiency of Dielectric Materials’ Electrodischarge Dispersion as One Sustainable Development Green Trend

Increasing the energy efficiency of production processes is closely related to minimizing the impact on the environment and is one of the priorities of the concept of sustainable development. Electric discharge is an effective tool for multilevel grinding of non-metallic materials in various working fluids and obtaining coarse and fine suspensions. We introduce the technique for calculating the electrotechnological parameters necessary for energy-efficient electric discharge dispersion. This technique considers the strength characteristics of the crushed material (dispersed phase) and the electrical conductivity of the working fluid (dispersed medium). It is also essential to consider the energy stored in the capacitor bank, the energy criterion, the critical value of the working fluid’s electrical strength, the radius of the high-voltage electrode point, and the distance from the discharge channel axis to the disintegration object. All this allows obtaining a given granulometric composition of the dispersed phase with minimal energy consumption. Experiments confirmed the validity of the proposed calculation technique. We obtained the water-brown coal suspension with a given dispersion two times faster and consumed four times less energy in comparison with the known methods that did not take into account the electrical conductivity of the working liquid and the mechanical strength of the crushed material.

A novel salt-barrier method of preparation flexible temperature resistant full-component nanocellulose membranes

With the simplification and diversification of separation technologies, nanocellulose membranes have become widely used as insulating materials. Recently, study of nanocellulose membrane modification has become a hot topic. However, the application of nanocellulose membrane has been limited due to their inadequate heat resistance and flexibility. Herein, based on the pyrolytic and thermoplastic properties of cellulose, we innovatively introduced a salt barrier scheme to regulate the degree of hydrogen bonding and thermoplastic bonding between fibers. This was achieved by adding a salt barrier agent, NaCl, in the middle of the nanocellulose to prepare and obtain flexible, high-temperature-resistant nanocellulose film materials. The full-component cellulose films thus prepared exhibited high tensile strength (8 MPa), excellent flexibility (105 mN), high electrical breakdown strength (67 KV/mm), and volume resistivity meeting the standard of insulation materials (3.23 × 1013 Ω·m). This scheme adheres to the principles of low cost, green, non-toxic and non-hazardous, providing a brand new approach for the research and development of high temperature resistant cellulose membrane materials, which is of significant commercial value and industrialization prospect.