Breakdown Properties Research Articles

Tuning Dielectric Properties with Nanofiller Dimensionality in Polymer Nanocomposites.

Polymer nanocomposites hold great potential as dielectrics for energy storage devices and flexible electronics. The structural architecture of the nanofillers is expected to play a crucial role in the fundamental mechanisms governing the electrical breakdown and dielectric properties of the nanocomposites. However, the effect of nanofiller structure and dimensionality on these properties has not been studied thoroughly to date. This study explores the critical relationship between nanofiller dimensionality and dielectric properties in polymer nanocomposites. We fabricated polyvinylidene fluoride (PVDF) nanocomposites by incorporating a range of carbon-based nanofillers separately, including zero-dimensional (0D) carbon black (CB), one-dimensional (1D) multiwalled carbon nanotubes (MWCNT), 1D single-walled carbon nanotubes (SWCNT), two-dimensional (2D) reduced graphene oxide (rGO), and three-dimensional (3D) graphite. The frequency-dependent (1 kHz to 1 MHz) dielectric permittivity (k) of the nanocomposites at the same concentration of nanofillers demonstrated a hierarchical order, with MWCNT showing the highest permittivity (∼400%), succeeded by rGO (∼360%), CB (∼290%), SWCNT (∼230%), and graphite (∼70%), respectively. The temperature-dependent (50-150 °C) dielectric spectroscopy revealed high k with increasing temperature due to the enhanced dipole movement. However, their dielectric breakdown strength and energy densities were not correlated to k and exhibited the following order: SWCNT > MWCNT > CB > rGO > graphite. As the electrical breakdown depends upon the nanocomposites' mechanical strength, we correlated the mechanical properties with the nanofiller dimensionality, and Young's modulus followed the 1D ≈ 2D > 0D > 3D order. These findings will provide fundamental insights into designing tunable, conducive nanofiller-based nanocomposites in next-generation flexible electronics and capacitive energy storage devices.

Understanding of formation, gastrointestinal breakdown, and application of whey protein emulsion gels: Insights from intermolecular interactions.

Whey protein emulsion gel is an ideal model food for revealing how the multilength scale food structures affect food digestion, as their structure and mechanical properties can be precisely manipulated by controlling the type and intensity of intermolecular interactions between protein molecules. However, there are still significant understanding gaps among intermolecular interactions, protein aggregation and gelation, emulsion gel formation, gel breakdown in the gastrointestinal tract (GIT), and the practical use of whey protein emulsion gels, which limits their GIT-targeted applications. In this regard, the relationship between the structure and digestion behavior of heat-set whey protein emulsion gels is reviewed and discussed mainly from the following aspects: (1) structural characteristics of whey protein molecules; (2) how different types of intermolecular interactions influence heat-induced aggregation and gelation of whey protein in the aqueous solutions and the oil-in-water emulsions, and the mechanical properties of the final gels; (3) functions of the mouth, the stomach, and the small intestine in processing of solid foods, and how different types of intermolecular interactions influence the breakdown properties of heat-set whey protein emulsion gels in GIT (i.e., their respective role in controlling gel digestion). Finally, the implications of knowledge derived from the formation and gastrointestinal breakdown of heat-set whey protein emulsion gels for developing controlled delivery vehicles, human satiety enhancers, and sensory modifiers are highlighted.

Conductivity and Breakdown Properties of Epoxy Resin for HVDC Bushing by Multifunctional Modifier

Conductivity and Breakdown Properties of Epoxy Resin for HVDC Bushing by Multifunctional Modifier

Yielding optimal dielectric energy storage and breakdown properties of lead-free pyrochlore ceramics by grain refinement strategies

In the quest to develop high-performance dielectrics suitable for high-power applications, its microstructure engineering and understanding the effect on the property have become crucial. However, the trade-off relationship between saturated polarization and breakdown strength with respect to the average grain size complicates defining the ideal microstructure for high-performance energy storage dielectrics. In this study, we investigates the impact of the microstructure of (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 (BZN) pyrochlore ceramics on their energy storage characteristics by adjusting sintering temperatures. Interestingly, dielectric properties, energy storage capabilities, and electrical fatigue characteristics exhibit minimal change, maintaining a high dielectric constant (∼160) and a low dielectric loss (< 10−4). Moreover, BZN ceramics demonstrate quasi-linear dielectric properties up to 250 kV cm−1, with slight fluctuation in energy density as the function of grain size (1.08–1.26 J cm−3). This weak dependence of energy storage on microstructure underscores that the enhancement of BZN ceramics for energy storage devices is more effectively achieved by improving breakdown strength through microstructural refinement rather than grain enlargement, which has limited impact on energy density in BZN systems. The findings from this study offer valuable insights into optimizing the microstructures of multilayer systems that are targeted at augmenting volumetric energy density, laying the groundwork for further advancements in dielectric materials.

Cracking the Pericellular Matrix Code: Exploring how MMP-2, -3, and -7 influence matrix breakdown and biomechanical properties

IntroductionThe intricate process of articular cartilage remodeling, pivotal for both physiological functions and osteoarthritis (OA) progression, is orchestrated through a balance of matrix synthesis and breakdown, which is mediated by matrix metalloproteinase enzymes (MMPs). At the heart of this remodeling lies the pericellular matrix (PCM), a specialized microenvironment encapsulating each chondrocyte and composed mainly of collagen type VI and perlecan. The aim of this study was to assess the impact of MMP-2, -3, and -7 on the structural integrity and biomechanical attributes of the PCM. MethodsHuman articular cartilage explants (N=10 patients) were incubated with activated MMP-2, -3, or -7, individually or in combination. Structural alterations in the PCM were evaluated by immunolabeling. The biomechanical properties of the PCM were measured using atomic force microscopy (AFM). ResultsCollagen type VI structural integrity and fluorescence intensity uniformly decreased across all enzyme groups, while perlecan was selectively affected by MMP-3 and -7. AFM measurements demonstrated decreased PCM stiffness after incubation with individual MMPs, leading to an overall ~31 % reduction in elastic modulus for each enzyme. Combinations of enzymes induced comparable significant biomechanical alterations (~35 %), except for MMP-2+MMP-7. DiscussionThis study highlights the significant influence of MMP-induced alterations in PCM composition on biomechanical properties, mirroring characteristics observed in early OA. Each MMP showed specificity in breaking down PCM, and an intriguing interplay, especially between MMP-2 and -7, indicated reduced efficacy in lowering PCM stiffness. Overall, MMP-2, -3, and -7 directly induce functional and structural PCM modifications.

Improved high temperature energy storage density and efficiency of polyimide nanocomposites via hindering charge and molecular motions

Electric vehicles and renewable energy consumption have huge demands for high-performance polymer dielectric capacitors. However, the resistivity and breakdown strength of existing polymer dielectrics deteriorate significantly at high temperatures, reducing the energy storage density and charge-discharge efficiency of capacitors below service requirements. The charge transport and molecular chain motion characteristics in linear polymers determine their conductivity, breakdown, and energy storage properties, but the quantitative relationship between them is not clear. An in-situ polymerization method was used to prepare polyimide/Al2O3 nanocomposites (PI/Al2O3 PNCs). Experimental results show that the resistivity, breakdown strength, energy storage density, and charge-discharge efficiency of PNCs increase initially and then decrease with increasing doping content, peaking at 3 wt%. The discharged energy density of PI/Al2O3-3 wt% PNCs at 180°C is 207.52 % higher than pure PI. A conductance-breakdown-energy storage co-simulation model based on charge transport and molecular chain displacement was used to simulate the voltage-current, breakdown, and energy storage characteristics of PNCs. The simulation results are consistent with the experiments. Comparative studies between simulation and experiments show that the independent interface zone between nanofillers and PI hinders charge transport and molecular chain movement, reducing electric field distortion and molecular chain spacing, thereby improving high-temperature breakdown and energy storage performance of PNCs.

Investigating the Impact of Hardness on Dielectric Breakdown Characteristics of Polyurethane.

Polymeric materials play a vital role in high-voltage insulation, but their insulating properties can deteriorate over time, leading to insulation failures. The presence of voids resulting from manufacturing defects or external stresses can create a highly divergent field, further contributing to this issue. However, certain polymers, such as polyurethane (PU), possess self-healing properties that enable them to repair these voids and restore a uniform electric field distribution, thereby ensuring the reliability of the insulation. Surprisingly, the potential of PU as an insulating material in high-voltage applications remains unexplored. However, the self-healing capability of PU decreases with an increase in the hardness of the material. Therefore, in this study, the dielectric breakdown properties of PU with different levels of hardness, rated on the Shore scale as 40° (soft), 70° (medium), and 90° (hard), were investigated. The AC and DC dielectric breakdown characteristics of these PU variants and dielectric spectra were examined. Additionally, the study explores the relationship between the dielectric properties and the hardness of the material. Our findings revealed that the dielectric breakdown strength of PU increases as the material's hardness is increased under both AC and DC electric stress. However, this may come at the cost of reduced self-healing capabilities of PU. Therefore, there is a need to balance the hardness of the material with its ability to recover from breakdown events. The findings from this study can be useful for researchers and engineers, as they offer valuable insights into the dielectric properties of PU at various hardness levels.

A Study on Dielectric Breakdown Properties of Hot CO2/O2/C5F10O Gas Mixture: Focus on Concentration Rate of O2 Gas

A gaseous mixture of CO2 and C5F10O has been widely investigated as one of the alternative gases for SF6. Due to the better electron attachment ability of oxygen molecule O2, it is generally expected that adding of O2 gas would improve the dielectric strength of arc quenching and insulating gas for electric power equipment. Therefore, in this paper, the dielectric breakdown properties of hot CO2/O2/C5F10O gas mixture were numerically estimated. The calculation results revealed that the critical electric field strength of the CO2/C5F10O gas mixture is disappointingly decreased by the addition of O2 gas, especially in the temperature range of 3000 K to 1000 K. This is brought about by the increase of ionization reaction of CO2 molecules with an increase in the O2 concentration in the arc‐quenching gas of CO2/O2/C5F10O. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Characteristics of perfluoromethyl vinyl ether: A new eco‐friendly alternative gas for SF6

AbstractThe exploration of eco‐friendly insulating gas to substitute the most potent greenhouse gas sulphur hexafluoride (SF6) has consistently garnered significant attention. Herein, the authors evaluated the feasibility of utilising perfluoromethyl vinyl ether (PMVE, C3F6O) as a new branch of eco‐friendly insulating gas for the first time. The primary dielectric and stability characteristics of PMVE regarding AC breakdown, partial discharge, dielectric recovery, and decomposition properties were revealed under various gas pressure and electrical field conditions. It was found that PMVE demonstrated superior dielectric strength, with the AC breakdown and PD inception voltage (PDIV) 1.10 and 1.14 times that of pure SF6. Furthermore, the dielectric strength of PMVE exhibits stability even after undergoing 100 cycles of AC breakdowns, and there is no observable formation of solid precipitation on the electrode surface. The discharge decomposition of PMVE mainly generates fluorocarbon (CF4, C2F6, C3F6, C3F8, etc.) and CO. Overall, the exceptional insulation stability and no absence of solid precipitation features endow PMVE to be utilised as a new eco‐friendly gas for SF6‐free gas‐insulated equipment.

Effects of nanomagnesia and polypropylene-graft-maleic anhydride on the dielectric breakdown properties of polypropylene/ethylene propylene diene monomer blend

Thermoplastic polypropylene (PP) has garnered a significant attention in power cable insulation research because of its exceptional thermal tolerance and dielectric properties. Due to its poor impact strength at room temperature, PP has been blended with various elastomers, including ethylene-propylene-diene monomer (EPDM), to improve the mechanical stiffness of the final material. This, however, comes with compromised dielectric properties of the material. Recently, the addition of nanofillers to polymers has demonstrated promising properties that can be tailored for various dielectric applications, provided that nanofiller and polymer interactions are appropriately formulated. Nevertheless, the effect of nanostructuration in PP/elastomer blends, especially from the perspective of dielectrics, have yet to be systematically explored. In the current work, magnesia (MgO) nanofiller is added to a model PP/EPDM blend system to determine the effect of MgO on the breakdown properties of PP/EPDM. The results show that adding 0.5 wt% of MgO to PP/EPDM reduces the AC and DC breakdown strengths by 7% and 16%, respectively. As the amount of MgO increases to 3 wt%, the AC and DC breakdown strength reduces further by 25% and 29%, respectively. Significantly, appropriate modification of the nanocomposites with polypropylene-graft-maleic anhydride (PP-g-MAH) can result in 5% higher breakdown strength of the nanocomposites with respect to comparable nanocomposites without modification. The mechanisms surrounding these breakdown effects are discussed with the aid of materials structure interpretations. Overall, the results demonstrate that appropriate modification of nanocomposites with PP-g-MAH is crucial in tailoring breakdown properties of PP blend nanocomposites.

Dielectric Properties of Polypropylene Blended with Ethylene-Butene Elastomer for High Voltage Applications

In recent years, polypropylene (PP) has been tremendously explored in high voltage cable applications due to its outstanding thermal and electrical properties. Furthermore, PP is an environment-friendly material that can be recycled, thus making it a promising candidate to replace conventional crosslinked polyethylene. However, the stiffness and brittleness of PP need to be further modified so that it can be utilized for practical cable applications. Recently, elastomer blending has been one of the favorable methods used by the industry to modify PP flexibility. Unfortunately, different types of elastomers bring different compatibility in the PP matrix. In this paper, the dielectric performance of PP, when mixed with ethylene-butene elastomer (EBE), was investigated. The thermal behaviors and morphological analysis were identified by using a differential scanning calorimeter and scanning electron microscopy, respectively. Meanwhile, the direct current (DC) breakdown strength was set up referring to the ASTM D3755 standard. Based on the findings, EBE shows a certain degree of compatibility with PP, where uniformly distributed spots were observed. Although the addition of EBE slightly degraded the DC breakdown properties of PP, the performance of PP/EBE blends at low elastomer contents is still good enough compared to conventional XLPE.

Improved dielectric and breakdown traits of polymer composites filled with KH-550 encapsulated multilayer black phosphorus

Polymer/particles composites are attractive for dielectric energy-storage, but they express difficultly-reconcilable conflict in high dielectric constant and breakdown strength. Here, multilayer black phosphorus (BP) coated by γ-aminopropyl triethoxysilane (KH-550) as filler, and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) as matrix were used to prepare composite films. KH-550 encapsulation enhances BP/matrix interfacial compatibility. Dielectric constant of polymer/BP@KH-550 composite is ∼207 at 20 Hz when filler load is 10 wt% (dielectric loss ∼0.11), combined with direct-current breakdown strength of ∼288 MV m−1. This work is beneficial to facile preparation of dielectric composites with well-balanced dielectric and breakdown properties for capacitive energy-storage.

Performance limiting inhomogeneities of defect states in ampere-class Ga2O3 power diodes

Impacts of spatial charge inhomogeneities on carrier transport fluctuations and premature breakdown were investigated in Schottky ampere-class Ga2O3 power diodes. Three prominent electron traps were detected in Ga2O3 epilayers by a combination of the depth-resolved capacitance spectroscopy profiling and gradual dry etching. The near-surface trap occurring at 1.06 eV below the conduction band minimum (EC), named E3, was found to be confined within a 180 nm surface region of the Ga2O3 epilayers. Two bulk traps at EC − 0.75 eV (E2*) and at EC − 0.82 eV (E2) were identified and interconnected with the VGa- and FeGa-type defects, respectively. In the framework of the impact ionization model, employing the experimental trap parameters, the TCAD simulated breakdown characteristics matched the experimental breakdown properties well, consistently with inverse proportionality to the total trap densities. In particular, the shallowest distributed E3 trap with the deepest level is responsible for higher leakage and premature breakdown. In contrast, Ga2O3 Schottky diodes without E3 trap exhibit enhanced breakdown voltages, and the leakage mechanism evolves from variable range hopping at medium reverse voltages, to the space-charge-limited conduction at high reverse biases. This work bridges the fundamental gap between spatial charge inhomogeneities and diode breakdown features, paving the way for more reliable defect engineering in high-performance Ga2O3 power devices.

Covalently cross-linked CaCu3Ti4O12 and poly(arylene ether nitrile) hybrids with enhanced high temperature energy storage properties

Ensuring polymer dielectrics with stable high energy storage density at high temperatures via improving interfacial compatibility remains a challenge. Based on this principle, calcium copper titanate and poly(arylene ether nitrile) (CCTO-PEN) hybrids dielectrics are developed to exhibit improved high temperature energy storage properties through the interfacial cross-linked high-temperature resistant cyano. Herein, CCTO-PEN hybrid dielectrics are fabricated through the thermal induced self-crosslinking reaction of phthalonitrile between the phthalonitrile modified CCTO (CCTO-CN) and phthalonitrile end-capped PEN (PEN-CN). SEM, XPS, FTIR, mechanical, dielectric, and breakdown tests of the CCTO-PEN hybrids reveal that the phthalonitrile modified CCTO-CN possessed superior interfacial compatibility in PEN dielectrics, together with enhanced dielectric, breakdown, mechanical, and energy storage properties compared to CCTO directly doped PEN dielectrics. Benefitting from the improved interfacial compatibility and the appropriate distribution of CCTO-CN within PEN-CN matrix, the CCTO-PEN hybrids demonstrate stable dielectric properties from room temperature to 200 °C, and the energy storage density of CCTO-PEN hybrid reaches up to 0.785 J/cm3, suggesting that the CCTO-PEN hybrids can be utilized as high temperature dielectric materials.

Enhanced Dielectric Breakdown Property of Polypropylene Based on Mesoscopic Structure Modulation by Crystal Phase Transformation for High Voltage Power Cable Insulation

Enhanced Dielectric Breakdown Property of Polypropylene Based on Mesoscopic Structure Modulation by Crystal Phase Transformation for High Voltage Power Cable Insulation

Research progress of flexible energy storage dielectric materials with sandwiched structure

&lt;sec&gt;Polymer dielectric materials show wide applications in smart power grids, new energy vehicles, aerospace, and national defense technologies due to the ultra-high power density, large breakdown strength, flexibility, easy processing, and self-healing characteristics. With the rapid development of integration, miniaturization and lightweight production of electronic devices, it is required to develop such a storage and transportation dielectric system with larger energy storage density, higher charge and discharge efficiency, good thermostability and being environmentally friendly. However, the contradiction between dielectric constant and breakdown strength of dielectric materials is the key factor and bottleneck to obtain a high performance dielectric material. It is accepted that controlling charge distribution and inhibiting charge carrier injection are important to improve the energy storage characteristics of polymer dielectrics. In recent years, the materials with sandwiched or stacking structures have demonstrated outstanding advantages in inhibiting charge injection and promoting polarization, allowing polymer dielectrics to have increased permittivity and breakdown strength at the same time. Therefore, from the perspectives of material composition, structural design, and preparation methods, this study reviews the research progress of polymer dielectric films with sandwiched structure in improving the energy storage performance. The influence of dielectric polarization, charge distribution, charge injection, interfacial barrier and electrical dendrite growth on the energy storage performance and the synergistic enhancement mechanisms in such sandwich-structured dielectric materials are systematically summarized, showing good development and vast application prospects.&lt;/sec&gt;&lt;sec&gt;In brief, introducing easy polarization, wide-gap and deep-trap nanofillers has greater designability and regulation in the dielectric and breakdown properties. In addition, using the hard layer as the outer layer can reduce charge injection more effectively, resulting in a high breakdown resistance performance that is easy to achieve. The sandwiched structure design also possesses advantages over other methods in maintaining good flexibility and dielectric stability of dielectric materials, thus having become a hot-topic research area in recent years. In the future, it is necessary to combine low conductivity and high thermal conductivity of dielectric polymers to realize high temperature energy storage and efficiency. Researches on recyclable, self-repairing sandwiched insulating films are good for the service life and safety of electronic components and will further expand the application scope of dielectric polymers. Finally, effective evaluation of dielectric with sandwiched structure and energy storage performances through simulation and theoretical modeling is very helpful in revealing the breakdown mechanism and thermal failure mechanism, and also in theoretically guiding the design of polymer dielectric materials.&lt;/sec&gt;

Mechanistic insights into the thermal–mechanical aging of the interface of cross‐linked polyethylene/silicone rubber

AbstractCable accessory has the interface formed by cross‐linked polyethylene (XLPE)/silicone rubber (SiR), which is prone to surface discharge and thus causes the failure of cable system. This article conducts the simulated experiment of thermal–mechanical aging on the interface of XLPE/SiR. The interfacial breakdown and dielectric properties under different aging states are analyzed. It is found the interfacial aging process of XLPE can be divided into the recrystallization stage and the oxidation reaction stage. The former contributes to the interfacial roughness and thus the better insulating performance, whereas the latter leads to degradation of interface, and thus the worse insulating performance. In addition, combined with the established electric field model for the interface, the differences between thermal–mechanical aging and individual thermal aging on the interface are discussed. The sample under thermal–mechanical aging reaches the maximum interfacial breakdown voltage later than that under individual thermal aging, but their performance tends to be consistent in the later stage of aging.

Partial Discharge and Breakdown Properties in Dry Air, N, and CO Under Nonuniform Electric Field

Partial Discharge and Breakdown Properties in Dry Air, N, and CO Under Nonuniform Electric Field<sub /><sub />

Electron Impact Cross Sections and Transport Studies of C3F6O

Electron impact scattering from C3F6O is studied in this work. The R-matrix method was used for the calculations of elastic, momentum transfer, and excitation cross sections. The attachment cross section was obtained through a parametric estimator based on the R-matrix outputs. The Binary-Encounter-Bethe (BEB) method was used for computing the ionization cross section. The obtained cross section set was used for the transport studies using the BOLSIG+ code, which is a two-term Boltzmann equation solver. The present calculation was performed for steady-state Townsend experimental conditions for E/N, covering a range of 100–1000 Td. The critical dielectric strength of pure C3F6O was found to be 475 Td, which is much greater than that of SF6 (355 Td). The effect of the addition of different buffer gases, such as CO2, N2, and O2, was also examined. For the C3F6O–CO2, C3F6O–N2, and C3F6O–O2 mixtures with 65%, 55%, and 60% C3F6O, respectively, the critical dielectric strength was determined to be essentially the same as that of pure SF6. The presence of synergism was confirmed for these gas mixtures. We further derived the Paschen curve using a fitting method with the transport parameters as the basic inputs. The minimum breakdown voltage of C3F6O accounted for only 55% of that of SF6. The buffer gas mixture improved the condition; however, the performance of CO2 and O2 mixtures was not satisfactory. The addition of N2 as the buffer gas significantly improved the breakdown property of the gas. The mixture of ≥99% of N2 or ≤1% of C3F6O gave a better breakdown characteristic than SF6. Any proportion ≥90% of N2 or ≤10% of C3F6O was suitable in the higher pressure ranges. The present work demonstrates the potential of C3F6O as a substitute gas for SF6 with a negligible environmental threat.

A brief overview on iron oxide nanoparticle synthesis, characterization, and applications

Hematite (α-Fe2O3), magnetite (Fe3O4), and maghemite (γ-Fe2O3) are only a few of the polymorphic forms of iron oxide, a mineral component. Hematite and maghemite, solid propulsion technology nanoparticulate materials, perform exceptionally well during the thermal degradation of ammonium perchlorate. Due to their larger particle size, more active sites, and increased surface area, which encourages more gas adsorption during thermal oxidation reactions, metallic iron oxide nanoparticles have an enhanced catalytic impact. Currently, a variety of techniques, including co-precipitation, sol–gel, microemulsion, and thermal decomposition, can be used to create metallic iron nanoparticles. The literature contains information on these synthetic processes, but there is a dearth of information on nanoparticulate oxides and the methods used to characterise them. The methods for generating nanoparticulate iron oxides, the key features of the various characterization techniques, as well as information regarding the breakdown properties of these nanomaterials are presented in this concise review based on scientific papers, containing data from the last two decades. Transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy can all be used to describe the morphologies and structures of iron oxides. Physical adsorption techniques are typically used to determine the textural qualities.