Epoxy-glass-mica composite materials are widely used as electrical insulating materials in high-voltage rotating machinery due to their layered structure and excellent dielectric properties. Taking the F-class epoxy glass with a small amount of rubber powder mica tape commonly used as the main insulation of wind turbine stator coils as the research object, 7-day, 14-day, 21-day, and 28-day low-temperature treatment tests were conducted at -50 °C. The surface morphology and chemical structure changes of the materials were characterized by SEM and FTIR, and the influence laws of low-temperature treatment on the electrical properties of the mica tape insulation materials were systematically studied. The experimental results show that the low-temperature environment will induce microcracks and interface delamination and other structural damages, but no obvious change in the chemical structure of the mica tape was observed. With the extension of the low-temperature treatment time, the electrical properties of the mica tape show a deteriorating trend, and after 28 days of low-temperature treatment, the breakdown field strength of the F-class mica tape decreased by approximately 18.5%, and the volume conductivity overall increased by about two orders of magnitude. This indicates that the microcrack defects induced by low-temperature will lead to an enhanced electrical-thermal coupling effect in the insulation structure, thereby accelerating the degradation process of the insulation material. This reveals the degradation mechanism of wind turbine stator main insulation from "structural damage" to "performance degradation" and then to "insulation aging" under low-temperature conditions, providing a theoretical basis for the design and reliability assessment of insulation systems in wind turbine generators in cold regions.

The concentration of electric fields at the end region of stator bars in large generators can readily induce corona discharge. Under long-term operation, corona discharge may cause drift in the surface conductivity and nonlinear coefficient of anti-corona materials, thereby weakening their capability to homogenize the tangential electric field. In severe cases, this can lead to charring failure of the anti-corona material. To improve the electrical-parameter stability and surface morphological resistance to corona aging of silicon carbide (SiC)-based anti-corona materials under long-term corona exposure, epoxy-resin-based anti-corona materials were investigated in this study. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were first employed to analyze the effects of corona aging on the microstructure and chemical structure of the anti-corona layer, thereby revealing its failure mechanism. Subsequently, the evolution of surface conductivity, nonlinear coefficient, and surface morphology of bisphenol A epoxy resin (EP)- and hydrogenated bisphenol A epoxy resin (H-EP)-based anti-corona materials during 120 h of corona aging was comparatively investigated. On this basis, different mass fractions of organically modified montmorillonite (OMMT) were introduced into the H-EP-based anti-corona material for synergistic modification. The OMMT used in this study had a particle size of approximately 5 μm and an interlayer spacing of 2.6 nm, and its lamellar morphology and dispersion state in the epoxy matrix were characterized by cross-sectional SEM. Meanwhile, the trap-regulation mechanism of the OMMT-modified anti-corona materials was analyzed using isothermal surface potential decay (ISPD). The results show that erosion of the epoxy resin matrix by corona discharge is the primary cause of internal conductive-pathway disruption and anti-corona layer failure. Compared with the EP-based material, the H-EP-based material exhibited better conductivity and nonlinear stability during aging, although a certain degree of drift still occurred. The incorporation of an appropriate amount of OMMT further improved the corona resistance of the material. Among the investigated samples, the material containing 1 wt% OMMT showed the best performance, with its conductivity stabilized within the range of 10-13-10-11 S, the lowest variation rate of 104.76%, a relatively stable nonlinear coefficient, and slight surface damage. The ISPD results indicate that the interfaces introduced by OMMT increase the deep-trap density and suppress carrier migration, thereby stabilizing the conductive network. Overall, the synergistic effect of the H-EP matrix and 1 wt% OMMT can effectively enhance the corona resistance of SiC-based anti-corona materials.

In general, the design of polymer dielectrics relies on the classical “band-gap criterion,” according to which a larger electronic band gap (Eg) is typically associated with a higher breakdown strength (Ebd). However, in hydrogen-bond-containing polypropylene-graft-maleic acid/poly(vinylidene fluoride) (PP-g-MA/PVDF) composites, this study identified a distinct phenomenon: as the number of hydrogen bonds increased, the electronic band gap decreased significantly from 4.76 to 3.86 eV, whereas the breakdown strength increased from 53.30 to 76.20 kV/mm, corresponding to an increase of 42.96

The growing demand for compact, high-power electronics in electric vehicles, renewable energy converters, and other harsh-environment platforms calls for dielectric films that can simultaneously deliver high energy density and high efficiency at elevated temperatures. However, the operating temperature ceiling of state-of-the-art BOPP films makes it difficult to satisfy the related requirements, motivating the exploration of alternative high-temperature polymer dielectrics. In this work, epoxy dielectric films are developed through a stepwise molecular design strategy that systematically balances thermal capability, polarization response, and high-field loss. A sulfone-containing curing agent is first introduced to improve high-temperature efficiency while maintaining strong polarization. Resin functionality is then tuned via progressive substitution with a tetrafunctional epoxy to extend the operating temperature window, revealing that high-field loss behavior, rather than Tg alone, governs efficiency at elevated temperatures. Finally, a small fraction of hydrogenated epoxy is incorporated to disrupt loss-active microstructural organization and concurrently suppress dielectric loss and leakage current. The final optimized film achieves 4.3 J/cm3 at 200 °C with efficiency above 90%. This study establishes a stepwise design framework that links molecular tuning to comprehensive performance, offering guidance for high-temperature dielectric energy storage films.

To establish the complex functional relationship between the stator bar end structure and the maximum electric field strength, and to optimize the anti-corona structure, an optimization model for the stator bar end based on the Seahorse Optimization algorithm—Radial Basis Function (SHO-RBF) neural network is proposed in this paper. The RBF neural network is employed to establish the complex relationship between the maximum electric field strength at the stator bar end and the anti-corona structure parameters. The SHO is introduced to find the optimal anti-corona structure at the stator bar end structure. A simulation model of the stator bar end is developed, and 30 sets of simulation data are collected for training and optimization purposes. The relationship between the stator bar end structure and the maximum electric field strength is established, and an optimized scheme comprising six groups of anti-corona structures is developed. The feasibility of the proposed design is validated through simulation calculations. Compared to manually adjusting parameters individually within the simulation model, this approach offers a significant advantage in terms of computational efficiency and speed.

This study successfully developed a high-performance thermal management composite material through innovative material design to address the heat dissipation demands of high-power electronic devices. Employing a hydrothermal synthesis method, the research achieved in-situ growth of one-dimensional zinc oxide (ZnO) nanorods on the surface of two-dimensional hexagonal boron nitride (h-BN) with excellent insulation properties, thereby constructing a unique "sea urchin-like" h-BN@ZnO hybrid filler. The filler was a composite with a thermoplastic polyurethane (TPU) matrix via a scrape coating process. Leveraging the bridging effect of onedimensional nanorods, this structure interconnects isolated three-dimensional thermal conduction pathways into a continuous network, thereby effectively mitigating the limitation of inferior out-of-plane thermal conductivity induced by the in-plane orientation of two-dimensional hexagonal boron nitride (h-BN).Processing shear forces induced orientated alignment of the filler particles, while the bridging effect of ZnO nanorods formed an efficient three-dimensional thermal conduction network within the polymer matrix. At a 60 wt% filler loading, the composite exhibits outstanding comprehensive properties: an out-of-plane thermal conductivity as high as 2.13 W/(m & sdot;K), representing a 61-fold improvement over pure TPU. It simultaneously maintains excellent electrical insulation and thermal stability, with minimal performance degradation after 120 thermal cycles. This composite material, combining high thermal conductivity, high insulation, and tunable flexibility, offers advanced thermal solutions for flexible electronics, aerospace, and other fields, presenting broad application prospects.

Polypropylene (PP) insulated cables are considered promising recyclable alternatives to conventional cross-linked polyethylene (XLPE) cables; however, their insulation performance under short-circuit and overload conditions remains insufficiently understood. In this study, 8.7/15 kV PP and XLPE insulated cables were subjected to short-circuit treatment for 1–7 s, overload aging at 130°C for 48 h, and thermal cycling for 400 h. Transient temperature-field simulations were performed to clarify the thermal distribution inside the cable insulation during short-circuit events. The chemical structure, crystallization behavior, microscopic morphology, dielectric properties, trap distribution, and AC breakdown strength of the insulation were systematically investigated. The results show that short-circuit thermal shock mainly induces localized thermal annealing and recrystallization, without causing obvious thermo-oxidative degradation or microscopic structural damage. Accordingly, both PP and XLPE maintain stable dielectric properties and breakdown strength after short-circuit treatment. Under overload conditions, XLPE exhibits significant increases in carbonyl index, low-frequency dielectric loss, and deep trap density, leading to greater deterioration in breakdown performance and a decrease in the Weibull shape parameter β. In contrast, PP shows smaller changes in carbonyl index, trap density, and dielectric parameters, indicating better resistance to overload-induced dielectric degradation. Under the tested conditions, PP insulation has good short-circuit withstand capability and superior overload stability compared with XLPE insulation.

This study presents a composite solution-based strategy for cellulose dissolution-regeneration, enabling the fabrication of a dual-crosslinked hydrogel through freeze-thaw cycling that integrates both physical and chemical networks. The resulting hydrogel serves as a flexible sensor and triboelectric nanogenerator (TENG). Carboxylated cellulose nanofibers (CNF-C) were dissolved in a mixed AlCl3/ZnCl2 solution and incorporated into a borax-crosslinked PVA matrix, yielding a conductive porous PVA-AlCl3/ZnCl2/CNF-C/Borax hydrogel. Combined with treatment using an anhydrous ethanol/water mixture, the carboxylated cellulose nanofibers were regenerated, forming a PVA-AlCl3/ZnCl2/CNF-B-E/W hydrogel. After treatment with anhydrous ethanol/water, the maximum stress of the hydrogel increased from 1.7 MPa to 1.9 MPa, and the maximum strain increased from 450 % to 455 %, with a high electrical conductivity (4.6 S/m). The hydrogel exhibited outstanding triboelectric performance and strain sensing capabilities (GF = 6.15, response time = 381 ms), demonstrating its applicability as a flexible strain sensor for motion detection and information transmission. Furthermore, the P-TENG based on this hydrogel enabled stable handwriting recognition. With its excellent electromechanical properties and operational stability, this material represents an ideal platform for intelligent sensing and self-powered energy systems, holding significant research and application value in flexible electronics.

This study employed a combination of molecular dynamics (MD) simulations and experimental tests to investigate the evolution of the electron mean free path (EMFP) of ethylene-tetrafluoroethylene (ETFE) copolymer under the synergistic effect of high temperature and low pressure. The intrinsic mechanisms by which temperature and pressure affect the breakdown strength were revealed, and a temperature-pressure coupled predictive model for electrical breakdown was constructed accordingly. The results indicate that the synergy of high temperature and low pressure enhances the thermal motion of ETFE molecular chains, leading to an expansion of intermolecular distances, an increase in fractional free volume (FFV), and a decrease in material density. This microstructural evolution prolongs the EMFP and increases the probability of impact ionization, resulting in a decline in breakdown strength. Specifically, the breakdown strength of ETFE decreased from 137.70 kV/mm at room temperature and atmospheric pressure to 63.23 kV/mm at 150.00 degrees C and 2.95 kPa, representing a reduction of 54.08%. Based on these findings, a temperature-pressure coupled electrical breakdown predictive model was derived and established based on the evolution law of the EMFP. The relative error between 80% of the predicted values and the experimental values is within 10%, indicating that the proposed model exhibits small relative errors and possesses high prediction accuracy.

Hydrogen bonds, due to their directionality and reversibility, are often regarded as a key "dynamic bridge" connecting molecular-scale structural rearrangements with electrical behaviors. However, the stability evolution laws of hydrogen bond networks under temperature perturbations, and how they project onto electronic structures and charge trap energy levels through thermodynamic mechanisms, remain unclear. In this study, using polypropylene-graft-maleic anhydride/polyvinylidene fluoride (PP-g-MA/PVDF) composites as the research object, and combining molecular dynamics simulations with density functional theory calculations, we tracked the formation-breaking-rearrangement process of dynamic hydrogen bond networks and revealed the regulation mechanism of the entropy-enthalpy compensation (EEC) effect on these networks. The results indicate that at 403 K, the increase in conformational entropy and the change in bonding enthalpy reach an optimal balance; the dynamic hydrogen bond network exhibits the optimal geometric configuration (with an average bond length of 1.85 & Aring; and a bond angle of 166 degrees) and the highest stability, inducing stronger electron localization and deepening the charge trap energy level by 0.14 eV. Upon exceeding this temperature, entropy-driven disordering dominates, leading to the rapid disintegration of the hydrogen bond network, and the traps subsequently become shallower. Furthermore, a differential equation model describing the kinetics of hydrogen bond formation/breaking was established, and a physical model constructing the linear correlation between the variation of hydrogen bond interaction energy and the variation of trap energy levels was built. From a unified perspective of thermodynamics and kinetics, this study constructs a physical framework describing the regulation of polymer electronic states and charge trap energy levels by dynamic hydrogen bonds, thereby elucidating the influence mechanism of dynamic hydrogen bonds on polymer charge trap characteristics at a fundamental theoretical level, and providing a theoretical basis for subsequent research in related fields.

This study explores how molecular structures affect epoxy resin (EP) materials, focusing on space charge and electrical properties. Bisphenol A-type EP is used as the base material. Three curing agents are tested: low molecular weight polyamide (651), phenolic amine (T-31), and diethyl-diamino-diphenyl methane (ME-DDM). The research compares space charge distribution, conductivity current, and dc breakdown strength across these materials. Using space charge data, they analyze electric field distribution, charge carrier movement, and the distribution of charge traps. Results show that ME-DDM forms a conjugated system in the material. This system reduces space charge buildup significantly. It also creates a more uniform internal electric field. ME-DDM increases shallow charge traps, which improves charge mobility and helps charges move and disperse faster. In addition, ME-DDM enhances electron attraction, boosting dc breakdown strength and overall insulation performance.

As the demand for flexible, eco-friendly energy supplies in wearable electronic devices continues to escalate, triboelectric nanogenerators (TENGs) have evolved into a viable and prospective technology that is capable of scavenging low-frequency mechanical energy. This study presents a high-performance TENG based on an electrospun composite membrane of PVDF-TrFE/PMMA incorporated with bismuth tungstate (Bi2WO6) nanoparticles and silver nanowires (AgNWs). The synergistic interaction between Bi2WO6 and AgNWs formed a Schottky junction at the metal-semiconductor interface, significantly enhancing charge transfer and storage capabilities. The optimized composite membrane (TABA) exhibited outstanding mechanical properties, including a tensile strength of 21.38 MPa and an elongation at break of 247%, along with a high dielectric constant of 13.5. The resulting TABA-TENG demonstrated exceptional electrical output, achieving up to 410 V open-circuit voltage and 3.17 mu A short-circuit current, and maintained stable performance (similar to 400 V) throughout extended durability tests. Moreover, the fabricated device exhibited stable and efficient performance when operating under the optimized working parameters; it was successfully utilized as a self-powered sensing unit for monitoring various human body movements, including walking, arm swinging, and hand clapping. These results highlight the potential of the TABA-TENG as an efficient and durable energy solution for next-generation wearable electronics.

The cable production process plays a critical role in determining cable performance, with the cooling process having a particularly significant impact on the overall performance of polypropylene cables. To investigate the effects of bilateral asymmetric temperature cooling on the microcrystalline morphology and comprehensive performance of polypropylene-insulated cables, this study prepared four types of samples with different temperature differences between their two sides by controlling the cooling temperatures on each side. The research systematically examined the influence of asymmetric bilateral cooling on spherulite size distribution, crystallinity, thermal conductivity, electrical properties (volume resistivity, relative permittivity, dielectric loss, AC breakdown strength), and conductive activation energy. Special emphasis was placed on analyzing the directional differences in performance resulting from asymmetric cooling on the two sides. The experimental results indicate that an appropriate cooling temperature difference can optimize the crystalline morphology and significantly enhance the overall performance. When the high-voltage electrode is placed on the higher-temperature side for testing (forward testing), the material exhibits superior insulation properties (higher volume resistivity, higher breakdown field strength, and lower dielectric loss), higher thermal conductivity, and higher conductive activation energy. Among the samples, PP-70-20 demonstrated the optimal overall performance during forward testing. This study provides important theoretical guidance for the cooling process in the practical production of polypropylene.

New energy technologies such as solar energy, wind energy, and battery electric vehicles all rely on advanced energy storage systems for their efficient operation. However, conventional battery-based energy storage is highly susceptible to performance degradation under frequent high-current chargedischarge cycles. To enhance the performance of traditional energy storage devices, supercapacitors can be introduced to leverage their excellent fast charge-discharge capability, thereby improving the efficiency and safety of the energy storage system. This paper investigates the operating principles of supercapacitors and batteries and establishes their equivalent circuit models. A design scheme for a bidirectional DC/DC converter is proposed to optimize the energy conversion efficiency between the two types of energy storage devices. Meanwhile, a hybrid energy storage strategy is designed to realize reasonable power allocation between the battery and the supercapacitor.

Electronic and electrical equipment is gradually evolving towards miniaturization and higher power density. The heat accumulated during operation has become a primary factor affecting product reliability and service life. Therefore, it is imperative to solve the challenges faced by thermal management materials, including low through-plane thermal conductivity, poor insulation properties, and complex manufacturing processes. This study proposes a simple and low-cost approach to overcome these challenges, utilizing mechanical grinding to construct a brick-mud structure in which hexagonal boron nitride (h-BN) encapsulate epoxy resin microspheres (EMs). An easily processable hot-pressing technique is employed to form continuous thermally conductive pathways. During the hot-pressing process, the mechanical properties of the EMs ensure the orientation of h-BN at the through-plane. The introduction of liquid metal (LM) can fill the gaps between h-BN and EMs, thereby enhancing the continuity of the thermal conduction network. The composite material prepared in this work exhibits excellent formability, enabling it to conform more closely to the gaps in electronic chips. At 50 wt% h-BN loading, the thermal conductivity of EMs/BN50/LM10/EP reaches 2.008 W/(mK). The excellent dielectric properties of h-BN enable the composite material to maintain a low dielectric constant and dielectric loss. The volume resistivity of all tested samples exceeded the standard required for electrical insulation (>10(12) Omega cm), and they also had a relatively high breakdown field strength (>10 kV), meeting the application requirements for medium-low frequency electronic packaging.

Abstract To evaluate the reliability of stator main insulation in wind turbines operating in cold regions, typical F-grade and H-grade insulation materials were subjected to low-temperature treatments of varying durations at −50 °C. Their mechanical properties and microstructural evolution were then systematically analyzed. Mechanical testing showed that the flexural, tensile, and impact strengths of both insulation materials decreased progressively with increasing exposure time. SEM observations further revealed that low temperatures induce embrittlement of the insulation materials, accompanied by the initiation and growth of microcracks along interfacial regions. The degradation in mechanical performance corresponds closely with these microstructural damage features, which primarily result from the accumulation of interfacial residual stresses caused by mismatches in thermal expansion coefficients among the material constituents under cryogenic conditions. When the concentrated stresses exceed the local load-bearing capacity, microcracks nucleate and expand, ultimately compromising the overall structural integrity of the insulation.

The end of the stator bar of a high-voltage motor is prone to generating localized high electric fields due to electric field distortion, which triggers corona discharge, causing insulation damage and shortening the life of the motor. The effective countermeasure is to apply a nonlinear corona protection coating on the end, which can adaptively adjust its conductivity according to the change of electric field strength, thus suppressing the surface charge aggregation and achieving the purpose of corona protection. In this study, samples with different doping contents were prepared using silicon carbide (SiC) and boron nitride (BN), and the dispersion was observed by scanning electron microscopy (SEM) to systematically investigate the nonlinear conductivity characteristics of the composites. COMSOL Multiphysics software was used to simulate the electric and temperature field distributions of the stator wire rod. The results show that the addition of BN to SiC/EP composites can improve the thermal conductivity and nonlinear conductivity, and the nonlinear conductivity can reach up to 3.48, and the increase of thermal conductivity can slow down the influence of nonlinear conductivity by temperature. The simulation results show that the peak surface electric field is lowest at 70 phr SiC plus 2 phr BN, and the peak surface temperature is lowest at 4 phr BN, and the improvement of the nonlinear coefficient and thermal conductivity can help to optimize the electric field distribution and reduce the peak temperature.

Wearable strain sensor prepared with ionic conductive hydrogel holds great promises in a variety of engineering fields. In this work, we introduce sodium casein (SC) into a dual network hydrogel system made of polyvinyl alcohol (PVA) and polyacrylamide (PAM), to prepare an ionic hydrogel sensor. Compared to the PAM/PVA dual network hydrogel, the introduction of SC plays a significant synergistic role. Such dual network PAM/PVA/SC hydrogels exhibit excellent mechanical properties (a maximum strain of 719

With the emergence of the era of Internet of things, traditional batteries have been challenged by environmental pollution, replacement maintenance, and other problems, and the self-power technology of flexible electronic devices has received great attention. PVDF-TrFE is one of the commonly used materials for triboelectric nanogenerators (TENG) because of its high β-phase ratio and strong electron attraction ability. Electrospinning technology can further increase the proportion of β-phase in PVDF-TrFE by electric field polarization. However, the electrospun PVDF-TrFE fiber film has poor mechanical properties and is difficult to be used in electronic devices for a long time. The addition of PMMA can form hydrogen bonds in the fiber, which greatly optimizes the mechanical strength of the blended film. Therefore, in this work, PVDF-TrFE/PMMA electrospun film with mechanical and electrical stability was prepared by electrospinning method. After optimization of materials and working conditions, the optimal output performance of the hybrid membrane TA-TENG can reach 0.215 μA and 210 V. Over 2000 working cycles, the device offers excellent output stability and long-term durability. This study presents a novel approach to concurrently enhance both the electrical and mechanical properties of triboelectric materials, thereby broadening their applicability in everyday life.

In power equipment insulations subjected to prolonged high-field conditions, the formation of electrical trees is a common occurrence, significantly impacting the service life and operational reliability of the equipment. In this paper, PE composites were prepared by melt blending method using layered nano-MMT and spherical nano-SiO2 as fillers to enhance the suppression of electrical trees. The microscopic properties of PE composites were characterized by scanning electron microscopy (SEM), polarizing microscopy (PLM), (DSC). The electrical tree of composites was conducted by the electrical tree test system. Subsequently, the synergistic inhibition of PE by nanoparticles with different morphologies was investigated. Key insights derived from the experimental findings are as follows: first, when MMT is doped with PE, due to the layered structure characteristics, the electro-acoustic coupling effect, and the coulomb blockade effect, the complexity and complicacy of electron motion trajectory are increased, then the breakdown field strength E-B of MMT/PE is increased by 5.74% compared with PE. Thus, the length of electrical trees at the retardation stage decreased by 175 mu m, and their morphology changed from branch to bushy branch. Second, when layered MMT and spherical SiO2 are doped in PE simultaneously, the electron travel becomes more complex and tortuous due to the synergistic effect of nanoparticles. Compared with PE, E-B of MMT/SiO2/PE is increased by 9.95%, the length entering the retardation stage of electrical trees decreases by 240 mu m, and their morphology changes from branch to cluster like. Finally, microscopic and macroscopic results reveal that the combination of layered MMT and spherical SiO2 can effectively suppress the electrical tree growth in PE. These findings underscore the potential of utilizing nanostructured fillers to mitigate the development and expansion of electrical trees in polyethylene insulations, thereby enhancing the overall performance and reliability of power equipment.