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Flash sintering of zinc oxide (ZnO) ceramics can be induced at room temperature (25 °C) by electrical breakdown at high electric field strength. However, a strong discharge may degrade the sample. This study investigated the effects of atmospheric pressure and composition on the onset electric field for the flash sintering of ZnO. The experimental results show that flash sintering of ZnO under a low electric field at room temperature can be achieved by adjusting the atmospheric conditions. Compared with the onset electric field strength under normal atmospheric conditions, the value for flash sintering of ZnO at 20 kPa in a mixture of 20% air +80% argon (Ar) can be reduced by 82% to approximately 700 V/cm. This method also applies to yttrium oxide (Y2O3) for a low electric field in flash sintering at room temperature, and is the first report on flash sintering of Y2O3 at room temperature.

Increasing the dielectric constant of polymer/sulfide ceramic composites by using wide-bandgap semiconducting sulfide ceramic fillers like ZnS is difficult because of their low interface polarization. To increase the dielectric constant, in this study, ternary polymer-based composite films were designed and fabricated using a hybrid filler consisting of shell-like ZnS particles and core-like V2C MXene particles. First, V2C MXene with a multi-layered structure was synthesized from the simplest raw materials followed by the in-situ hydrothermal growth of ZnS particles around the V2C particles. Then, binary polymer/ZnS and ternary polymer/V2C–ZnS composites were fabricated, and their dielectric, conductive, and electrical breakdown properties were investigated. Finally, the effect of interfacial bonding between the V2C and ZnS phases was investigated by density functional theory calculations, and the contribution of V2C/ZnS interfacial bonding to the higher dielectric constant of the ternary composites than that of the binary composites was explained. The ternary composites exhibited balanced electrical properties suitable for energy storage applications. The ternary composite with 10 wt% hybrid filler loading exhibited a high dielectric constant of ~52, a low dielectric loss of ~0.11 at 100 Hz, and a high electrical breakdown strength of ~202 MV m−1. This study paves the way for the facile fabrication of high-performance composite dielectrics for application in advanced capacitors.

The brittle fracture may occur in the application of piezoelectric ceramics, but the traditional research is still limited to the static fracture of the materials. Based on the improved Hopkinson pressure bar loading system and high-speed photography technology, the experimental study on the fracture behavior of piezoelectric ceramics under impact loading was carried out. The dynamic mechanical and electrical response of lead zirconate titanate (PZT) and the possible electric breakdown phenomenon were analyzed. The experimental results show that the output voltage is stable and the maximum output voltage is 889 V when the impact load does not cause the material to fracture. When the material breaks, its macroscopic output voltage fluctuates due to electric breakdown. Combined with the finite element simulation of the impact fracture process, the distribution characteristics of the stress field and electric field near the crack during the fracture process were analyzed. The results show that the sliding between grains formed the crack cavity parallel to the electric field during the impact process. Furthermore, based on the theory of dielectric breakdown, the possibility of electric breakdown in the initial defect and the elliptical cavity formed by the impact is analyzed.

Induction motors, acting as work house of industries, are affected by winding temperature due to poor insulation. In producing a sustainable polymer composite electrical insulator, this article gets into the investigative study of tensile strength, hydrophobicity, hardness and the electrical breakdown properties of silicone rubber (SR) reinforced with sugarcane bagasse ash (SCBA). In order to identify optimal proportion, various filler proportions are studied for mechanical, physical, tensile and electrical properties. For 7% optimal filler composition, the tensile and hardness tests on SR/SCBA composite manifested a maximum value of 78.48 × 10–3 MPa and 0.91496 MPa, respectively. The electrical breakdown was recorded with the maximum value of 108.65 kV/cm with 7% filler. For hydrophobicity, the 7% filler specimens had the lowest rate of rise in weight after the water absorption test. Scanning electron microscopy (SEM) analysis and particle size analysis were carried out to evaluate the molecular interaction and particle dispersion. SEM analysis confirmed the presence of fiber-adhesion in matrix composites. Finally, the superiority of the context is also compared with earlier works. This context investigates the properties of bio-resin composite derived from sugarcane ash and creating its properties with artificial polymers to come out with a reliable electrical insulator application.

High efficiency thermoelectric (TE) materials still require high thermopower for energy harvesting applications. A simple elemental metallic semiconductor, tellurium (Te), has been considered critical to realize highly efficient TE conversion due to having a large effective band valley degeneracy. This paper demonstrates a novel approach to directly probe the out-of-plane Seebeck coefficient for one-dimensional Te quantum wires (QWs) formed locally in the aluminum oxide layer by well-controlled electrical breakdown at 300 K. Surprisingly, the out-of-plane Seebeck coefficient for these Te QWs ≈ 0.8 mV/K at 300 K. This thermopower enhancement for Te QWs is due to Te intrinsic nested band structure and enhanced energy filtering at Te/AO interfaces. Theoretical calculations support the enhanced high Seebeck coefficient for elemental Te QWs in the oxide layer. The local-probed observation and detecting methodology used here offers a novel route to designing enhanced thermoelectric materials and devices in the future.

Fluorine doped tin dioxide (FTO) coatings were deposited on AISI 304 stainless steel (SS) substrates using ultrasonic spray pyrolysis (USP) technique. Four different candidate insulating intermediate layers of TiO2, MgO, Al2O3 and SiO2 were selected and coated on AISI 304 SS using USP and investigated in order to overcome dielectric breakdown of FTO layer due to conductive nature of stainless steel substrate under the applied voltage. After the optimization of the process parameters for the depositions, only TiO2 layer was successfully deposited while other oxides did not form continuous films on AISI-304 SS surface despite the efforts. SEM analysis, supported by back-scatter imaging, revealed thickness values of the layers for FTO and TiO2, individually. Heating performances of the samples with varying sheet resistance values were examined under different applied voltages. Heating experiments showed that 300 °C can be reached with 10 V of applied voltage without occurrence of an electrical breakdown of FTO coating having 160 nm thickness with TiO2 intermediate layer of 660 nm. 28.6% efficiency for the conversion of electrical energy into heat was calculated for FTO coating while bare stainless steel showed only 7.3% efficiency. Later, the heating experiments were repetitively conducted and the samples were tested under high relative humid environment to determine their resistance against moist conditions.

Cross Linked Polyethylene (XLPE) has been widely used as an insulation material of a power cable due to its excellent electrical and mechanical properties. XLPE may cause an environmental devastation because it is not recyclable due to its thermosetting characteristics. Therefore, it is necessary to develop an insulation material which could be replaced with the conventional XLPE owing to its eco-friendly and good dielectric characteristics. In this paper, an analytic study on the comparison between conventional XLPE and six types of eco-friendly polypropylene (PP) samples developed by Hu-innovation Co. Ltd is conducted. As a result, the dielectric characteristics of PP according to manufacturing process are analyzed.

Aramid paper has been widely used in high-voltage motors and transformers due to its excellent insulation property and thermal durability. However, the smoothness and chemical inertness of aramid fibers lead to a loose structure (voids) of aramid paper, which limits its potential applications in harsh environments, such as high-frequency and high-voltage circuits. This work reports a simple and efficient method to improve the mechanical and insulation properties of meta-aramid paper via controllable dissolving and regeneration of aramid fibers. To obtain a dense and robust structure, the pristine meta-aramid paper was immersed in a dimethyl sulfoxide/potassium hydroxide (DMSO/KOH) mixture to make aramid fibers swelled and dissolved, followed by regeneration in water vapor, eventually generating densified aramid paper with fewer voids and enhanced insulation and mechanical performance. Optimum conditions resulted in aramid paper with the best comprehensive performance, and the tensile strength, Young's modulus, and electrical breakdown strength of the consolidated aramid paper were 22.85 MPa, 0.72 GPa, and 15.3 kV/mm, respectively, which were significantly higher than those of the pristine aramid paper (12.53 MPa, 0.41 GPa, and 8.36 kV/mm). Meanwhile, such treatment did not cause any chemical structure change, and thus it still retained the excellent thermal resistance (Td > 430 °C) of aramid fibers. This simple method can effectively regulate the surface porosity and the mechanical and breakdown strength of aramid paper, as well as provide a generic method for postprocessing and enhancing aramid paper.

The doped/alloyed HfO2 and ZrO2 thin films revolutionized not only the field of ferroelectric physics but also various ranges of device applications. Especially when the two oxides are combined in an 1:1 ratio, the ferroelectric polarization of the material became the most distinctive. Many researchers have investigated various different process conditions such as controlling Hf0.5Zr0.5O2 (HZO) film thickness and modifying different metal electrodes. Here, we explored the effect of additional Ar plasma treatment to the HZO film. The additional Ar plasma was exposed to the plasma-enhanced atomic layer deposition (PEALD) HZO for this study. Then, the sample was compared with a conventional PEALD and thermal ALD HZO films. By understanding the polarization–electric field (P–E), current–electric field (I–E), and electrical breakdown characteristics of the different samples, it was found that the Ar plasma treatment can control the degree of ferroelectric and antiferroelectric phases of HZO film.

The electrical breakdown strength of insulation material is very important for the design of a high-temperature superconducting (HTS) cable. This article investigates the breakdown characteristics of polypropylene laminated paper (PPLP) film samples, which are widely used in an HTS cable. Various test conditions, such as different modes of increasing voltage, voltage types, and ambient temperatures, are used. It is found that the breakdown strength of the PPLP film samples varies greatly with the aforementioned experimental conditions. Based on the existing research, the key reasons for the experimental phenomenon are analyzed. The experimental results provide the reference experimental data for the insulation design of the HTS cable.

Metal-aluminum oxide-metal structures are prepared by evaporation in vacuum on silicon wafers using Au, Cu or Pd on top and Al as bottom electrode. The aluminum oxide layer is deposited by electron beam evaporation with a thickness of 200 nm. The diameter of the top electrode is varied between 0.1 and 1.9 mm. Capacitance measurements reveal a relaxational dielectric permittivity as expected for aluminum oxide. Applying ramp voltages results in single breakdown spots on the electrode before the structure finally becomes conductive. The breakdown spots, as characterized with an AFM, are in the form a crater, reaching 500 nm into the silicon. However, for the smallest electrode, the calculated electrostatic energy stored in the capacitance is not high enough to form the craters.

Paschen curves were studied using different cathode materials such as magnesium, zinc, and carbon graphite by discharge in argon gas of a pressure range between 0.08 and 3 Torr using a parallel plates configuration. The first and second Townsend coefficients (α and γ, respectively) and the ionization efficiency (η) of different cathode materials were deduced from Paschen curves as a function of the reduced field (E/P). The minimum breakdown voltage was found to be about 242 V for Mg material, which has the lowest work function, while carbon graphite has a higher breakdown voltage of 283 V due to its higher work function. The second coefficient γ was increased as a function of E/P and has higher values for materials of lower work functions, and a similar trend of γ is obtained as a function of the ion mean energy. On the other hand, the first coefficient α has a reverse behavior with both E/P and the work function of the cathode materials compared with the second coefficient. The ionization efficiency of the three cathode materials is identical, as η depends only on the gas properties and not the cathode material. η has a maximum value of about 0.025 V−1 for an E/P of about 185 Vcm−1Torr−1, corresponding to the maximum ionizing ability of electrons. The validation of the breakdown results has been confirmed by conferring with other published experimental measurements.

In this study, XLPE electrical breakdown depending on insulation thickness is analyzed by simulations and experiments. The bipolar space charge and molecular chain displacement models are investigated to explain the experimental results. The results from experiments indicate that the electrical DC breakdown field decreases with increasing insulation thickness. For simulations, carrier mobility and trapping parameters are obtained from experiments. The simulation results of both models present an inverse power relationship between the DC breakdown strength and insulation thickness. The simulation results of molecular chain mobility model show consistency with experimental results as compared to a bipolar space charge model. The movement of polymer chain containing deep traps expands the free volume and this enlargement in free volume can be a major reason for the variation in the DC electrical breakdown strength of XLPE with insulation thickness.

Electrical breakdown voltage (VBD) and streamer propagation path characteristics in highly non-uniform electrode system were investigated to clarify the dielectric barrier effects. The experimental results showed that VBD is affected by both the barrier dimension and the barrier position. As the position of the dielectric barrier becomes closer to the needle electrode, the rising rate of VBD according to the barrier dimension increases. In addition, streamer propagation path could be identified into two categories, depending on the dielectric barrier position and the dimension. Finally, it is found that VBDs were determined by the electrical insulation structure, not the streamer propagation path or length.

Low density polyethylene (LDPE) film samples with the surface treatment by silver nanoparticles based on the biomimetic dopamine technology are obtained and the influence of the treatment on the space charge behavior as well as DC breakdown performance of the selected insulating system is studied. The results obtained by the energy dispersive spectrometer and the scanning electron microscope indicate that Ag particles with nanoscale or larger size form and distribute uniformly on the surface of LDPE modified in the dopamine solution, silver nitrate solution (AgNO3) and dopamine solution in sequence. Space charge profile measured by the pulsed electro-acoustic method shows that homo-charge injection is suppressed with proper surface treatment. DC breakdown strength increases initially and then decreases with the increase of the size of Ag particles. The electrical breakdown strength of the specimen D6-Ag1-D24 is the highest, which increases by 9.5% compared with that of untreated LDPE. Finally, it is considered that the treatment of LDPE based on the biomimetic dopamine technology changes the chemical and physical properties of the surface through forming a three-layer structure, which plays a similar role as the nano-dielectrics. Such treatment can impact the space charge injection and accumulation, and further the corresponding DC breakdown strength, which provides a novel method to optimize the dielectric strength of the polymeric insulating materials.

Film capacitor, one typical type of electrostatic capacitors, exhibits its unique advantages in the high-power energy storage devices operating at a high electric field due to the high electrical breakdown strength (Eb) of the polymeric films. However, the development of film capacitor towards high energy storage density is severely hindered by the low dielectric constant (e) and low charge-discharge efficiency (η) of the polymeric films. The film of polypropylene (PP), the most used polymeric film with a market share of 50%, owns a high η due to its low inherent hysteresis loss. Yet the low e (2.2 ​at 103 ​Hz) impedes the increase of its energy storage density (1–2 ​J/cm3). Here we demonstrate that the discharged energy density (Ue) of PP film could be largely increased from 1.40 ​J/cm3 of pure PP film to 3.86 ​J/cm3 of PP nanocomposite film by incorporating a small loading of core-shell structured PMMA@BaTiO3 (PMMA@BT) nanoparticles (2.27 ​vol%) into PP matrix. The obtained Ue of 3.86 ​J/cm3, to the best of our knowledge, is the highest reported value for the PP based films using commercial PP resin. Meanwhile, the η merely undergoes a slight decrease from 99.5% to 94.1%. Similarly, the obtained η of 94.1%, to the best of our knowledge, is also the highest value for the polymeric films reported in the previous works. The significant increase of Ue (175.7%) and negligible decrease of η (5.4%) are mainly attributed to the increases of e from 2.2 to 3.7 and Eb from 361 ​MV/m to 448 ​MV/m. Compared with the films of raw BT/PP nanocomposites, the Ue exhibits a significant increase of 365.1% from 0.83 ​J/cm3 to 3.86 ​J/cm3 and the η also displays an increase of 7.4% from 87.6% to 94.1%. The significant improvement of energy storage performance achieved in the film of PMMA@BT/PP nanocomposite suggests that the organic PMMA shell plays an important role in the amelioration of compatibility of BT nanoparticles and PP matrix and the alleviation of local electric field concentration. Moreover, the PMMA shell could also provide a robust scaffold to hinder the early breakdown failure of nanocomposites due to its high Eb (425 ​MV/m). Thus, high e, low loss and high Eb are simultaneously achieved. Specifically, the high hot stretch ratio (1:4) of nanocomposite film indicates the strong feasibility of industrialized film processing. Apart from the experimental analysis, theoretical analysis using the simulation of finite element is also carried out to figure out the influence of organic PMMA shell on the dielectric performance of PP nanocomposites films. These findings enable the development of film capacitor using non-polar PP based film towards high energy storage density.

MgO/LDPE nanocomposites with various nanofiller loadings are fabricated and the morphology and trap properties are characterized to investigate their effect on DC conductivity and electrical breakdown strength. It is found that DC conductivity depends on both shallow and deep traps. As the nanofiller loading increases, the density of shallow traps increases, leading to higher shallow trap-controlled hopping conductivity, while the deep traps increase firstly due to the formation of isolated interfacial regions and then decreases caused by the overlapping of interfacial regions, resulting in the variation in charge trapping-detrapping dynamics. An equation considers both the shallow trap-controlled hopping and the charge trapping-detrapping processes is derived to calculate the DC conductivity of MgO/LDPE nanocomposites, and the calculation results are consistent with experiments. The DC electrical breakdown strength is influenced by both the morphology and deep trap properties. At low nanofiller loadings, higher crystallinity and smaller crystallite size may block the motion of molecular chains in LDPE nanocomposites, and deep traps formed in interfacial regions hinder the charge transport. The synergetic effects of nano-doping on morphology structure and charge carrier transport enhances the DC electrical breakdown strength of MgO/LDPE nanocomposites.

Silver nanowire (Ag NW)-based flexible and transparent electrodes are a promising candidate for various electronic and optoelectronic applications. However, thermal and electrical instabilities of Ag NW networks during operation and post treatments need to be improved for practical applications. In this work, Ag NW/Graphene Oxide (GO) hybrid films with a multilayer structure were developed, in which transparent GO sheets were inserted between Ag NWs. For the pristine Ag NW networks, contacted NWs exhibited poorer thermal stability than individual NWs as faster Ag diffusion between NWs led to the breakage of the junctions at working temperatures, hence leading to the overall device failure. In contrast, the GO intermediate layers hindered the Ag diffusion between NWs in the Ag NW/Graphene Oxide hybrid films and maintained the junction structure, giving rise to enhanced thermal stability compared to the pristine networks and the GO-covered samples. For electrical tests, unlike the network degradation under annealing treatments, a local deterioration perpendicular to the current flow was directly observed after electrical breakdown, which was attributed to high local temperature under large applied voltage. The electrical failure of the devices was related to the network structure and defects. Furthermore, the pristine devices showed notable variation of failure voltage, which in the hybrid devices is more uniform and improved in general.

Dielectric elastomer (DE) technology are used in several applications for example generator, sensor and actuator. One of the major factors that limits the DE performance is premature electrical breakdown. Compositing is the example that have been reported to increase the breakdown strength. In this study polydimethylsiloxane (PDMS) film will be incorporated with two different fillers which are titanium dioxide (TiO2) and zinc oxide (ZnO). Both metal oxides will be calcined up to 300°C before they are added to the PDMS elastomer as fillers. The results show that the calcined TiO2 and ZnO that incorporated in PDMS films show significant increase of breakdown strengths. Meanwhile, the calcined TiO2 PDMS film give higher breakdown strength as comparison to the calcined ZnO counterpart.

Flexible dielectric polymers and nanocomposites have attracted intensive attention owing to their high electrical breakdown strength, high power density and excellent cycle reliability which are highly demanded for electrostatic energy-storage systems and devices. However, achieving concurrently high discharged energy density (Ue) and discharge efficiency (η) without impairing polymer-endowed mechanical and processing advantages remains a great challenge. In this work, a strategy of doping diminutive CdSe/Cd1−xZnxS quantum dots (QDs) with a dual-ligand structure into a polymer is demonstrated, by which high Ue and η together with largely enhanced mechanical properties are obtained simultaneously. Contrary to conventional sense, a high dielectric constant (K, 17.8 at 1 kHz) is obtained by adding less than 1 volume percent of QDs into the polymer while both the polymer and QDs are intrinsically low-K materials (

Barium titanate (BaTiO 3 )-based lead-free relaxor ferroelectric ceramic Ba 0.65 Sr 0.245 Bi 0.07 TiO 3 was developed via a traditional electrocremic processing technique to obtain Pb-free dielectric bulk ceramics with enhanced energy storage performance that can be potentially used in pulsed power devices. The added CuO can broaden the phase transition peak, and move it to lower temperature, reinforcing the dielectric relaxor behavior. The microstructure evolution of the sample was investigated via Piezoforce microscopy, and the corresponding mechanism regarding the electric breakdown strength was studied. The solubility of solid CuO in the Ba 0.65 Sr 0.245 Bi 0.07 TiO 3 is approximately 0.02 mol. The ceramic sample with 0.005 mol CuO possesses 160 kV/cm electrical breakdown strength and an energy storage efficiency higher than 76%, which yields 1.28 J/cm 3 energy storage density. Moreover, the ceramic specimen with 0.005 CuO exhibits relatively good temperature stability, good frequency stability from 1 Hz to 200 Hz, and also good fatigue resistance up to 10 5 cycles, and can be a potential candidate for future energy storage applications.

Dielectric elastomer actuators (DEAs) are usually operated at high voltage to induce sufficient electric pressure between two compliant electrodes sandwiching the dielectric elastomer. However, a harsh environment (e.g. humid environment combined with high voltage) often induces electrical breakdown (EB) of the DEAs, which results in pinhole formation or even tearing of the device, followed by macroscopic failure. Therefore, it is ideal for DEAs to be self-healing to extend robustness and lifetime, such as observed for biological muscles, which can be healed from injuries by inherent biological processes. Herein, we prepared a soft (Young’s modulus: 187 kPa) polydimethylsiloxane (PDMS) thermoplastic elastomer (TPE) to demonstrate an autonomous self-healing ability. The system exploits hydrogen bonding (H-bonding) in two types of transient cross-linkers: urea group serves as a sacrificial bond under loading and ureidopyrimidone (UPy) serves as a strong, load-carrying crosslinker. The PDMS TPE shows a crossover of the elastic moduli at 119 °C and highly frequency dependent elastic modulus. The DEA is prepared with compliant, corrugated silver electrodes on both sides of a corrugated PDMS TPE film. A maximum actuation strain (6.8 % in longitudinal direction) is achieved at 18.8 V μm-1. A further increase in potential does not increase the actuation strain, but EBs are observed on the electrodes and the actuation is maintained without any detrimental effects to the film despite the previous breakdown. The EBs do not form permanent pinholes, nor do they cause tearing of films. Instead, only the removal of the silver electrode is observed, which is the so-called self-clearing effect commonly observed for metallic electrodes. In combination with the self-clearing effect, the heat generated by the EBs allows the PDMS TPE to soften. The polymer molecules are then capable of flowing into the voids that were created at the initiation of the EBs. As a result, further propagation of the EB is hindered, and instead, an instantaneous and autonomous self-healing of the DEA is observed.

In this paper, the Transport Coefficient of SO 2 gas are calculated from swarm model design using BOLSIG+ which is user-friendly open-source computer program based on numerical solution of Boltzman equation (BE) up to two-term approximations. To ensure close agreement of calculated transport coefficients for SO 2 gas with impending experimental works, first we calculate these coefficients for SF 6 , and CO 2 compared the results with reported values. Reasonable agreement is found between calculated and report transport coefficients. For realistic acceptance of SO2 gas as SF6 alternative in long-term for high voltage applications, we discussed the utilization of these coefficients in study of various electrical breakdown related phenomenon to understand its dielectric and electrical insulating behavior during electrostatic discharge. We also predict numerical values of insulating properties in uniform electric field under steady state conditions such as electric strength, breakdown voltage and ionization constant for SO 2 gas using transport coefficients. For SO 2 gas, some of these properties and values are being calculated for first time.

The insulation of high voltage power cables is aged due to the impact of water treeing. The voids created due to water treeing can be filled with the injection of nanofluids and restore the insulation of cables. In this work, cross-linked polyethylene (XLPE) cable insulation is restored with the help of tetraethyl orthosilicate (TEOS) rejuvenation nanofluid. The morphological changes in aged and rejuvenated samples are analyzed with the help of scanning electron microscopy (SEM). Moreover, the molecular changes in the aged and rejuvenated samples are detected using Fourier transform infrared (FTIR) spectroscopy. Both the samples are also tested with the help of electrical breakdown tests. The results indicate a positive recovery in the insulation of cables with the injection of TEOS nanofluid. The tanδ results showed a decrease in values after the injection of nanofluid in the aged sample. Moreover, the tanδ values of rejuvenated samples are even better than the unaged cables. SEM results also showed a recovery in the voids of the aged sample due to the injection of nanofluid. FTIR results confirmed that the nanofluid penetrated in the insulation of the cable and the peaks of silicone and alumina bonds are seen in the spectrographs.

This paper investigates the effects of thermal aging on unfilled polypropylene (PP) and PP containing 1 wt% of magnesium aluminate (MgAl 2 O 4 ), calcium carbonate (CaCO 3 ), and surface modified calcium carbonate (CaCO 3 T) nanofillers. Two different aging conditions were considered, i.e., unaged (20 °C) and aged (140 °C). The structures of the evaluated samples before and after aging were observed using scanning electron microscopy (SEM). In addition, thermal stability and electrical properties were evaluated by means of thermogravimetric analysis (TGA) and DC breakdown testing. The results showed that the structure of all investigated samples was less susceptible to thermal aging. Meanwhile, the thermal stability of the unfilled PP has reduced significantly than that of nanocomposites. Besides that, the electrical breakdown strength of both the unfilled PP and PP nanocomposites containing 1 wt% of MgAl 2 O 4 , CaCO 3 , and CaCO 3 T nanofiller has reduced compared to the respective unaged samples. Of note, nanocomposites were less susceptible to changes in DC breakdown strength after thermal aging.

Low-dielectric constant (low-k) material is critical for advanced FinFET technology parasitic capacitance reduction to enable low-power and high-performance applications. Silicon Oxycarbonnitride (SiOCN) is one of the most promising low-k materials for FinFET gate sidewall spacer. The k value of SiOCN can be controlled in the range of 4.1–5.2 by modifying the chemical contents during the deposition process. However, the integration of SiOCN with k value lower than 5.2 for advanced FinFET technology faces substantial challenges associated with the material damage from subsequent manufacturing processes. Here, the authors demonstrate a hybrid low-k spacer scheme on a fully integrated 7 nm FinFET technology platform, in which SiOCN with k value of 4.5 was successfully integrated along the sidewalls of the gate electrode as spacer while retaining the structural integrity and dielectric properties. Device characterisation on the hybrid low-k spacer scheme (k = 4.5) demonstrated 12/11% reduction in P/NFET overlap capacitance (C OV) and 3% reduction in ring oscillator effective capacitance (C EFF) in comparison to the baseline reference using SiOCN with k value of 5.2 as spacer. Furthermore, reliability characterisation confirmed the dielectric breakdown voltage (V BD) and leakage current (I LKG) of the hybrid low-k spacer (k = 4.5) were comparable to the baseline reference (k = 5.2), meeting the technology requirements.

Sulfur hexafluoride (SF6), the most widely used insulating medium in power equipment, is a high-greenhouse effect gas. The use of alternative eco-friendly gases as an insulating medium is of great significance to the green development of the power industry. C5 perfluoroketone (1,1,1,3,4,4,4-heptafluoro-3-(trifluoromethyl)-2butanone; C5-PFK) mixtures have remarkable potential to replace SF6 in medium-voltage (MV) grade electrical equipment. This study constructs an experimental power–frequency breakdown platform to investigate the effect of O2 on the discharge decomposition products of environment-friendly C5-PFK/N2 mixtures and address the problem of generation of solid decomposition products due to insulation breakdown during engineering application. Studies have shown that the solid decomposition products produced by the insulation breakdown of C5-PFK/N2 mixtures mainly include simple C substances, CuF2, CuO, Cu2O, and fluorocarbons. The gas decomposition products mainly include CO, CF4, C2F4, C2F6, C3F6, C3F8, C4F10 and C3F7H. Addition of O2 to C5-PFK/N2 mixtures suppresses the formation of solid and gas decomposition products, such as C2F4, C3F8, and C3F6, but promotes the accumulation of gas decomposition products, such as CO and CF4. The recommended concentration of O2 to add to engineering applications is approximately 4% of the volume fraction; such a concentration can effectively avoid the generation of solid decomposition products due to insulation breakdown, and produce as few toxic decomposition products as possible. Addition of O2 to C5-PFK/N2 mixtures can prevent solid decomposition products from occurring during electrical breakdown of the gas-insulated medium.

Nanocomposite (NC) polymers are commonly employed because of their high breakdown strength, but the underlying mechanism of this phenomenon is not well understood. In the present study, specimens of polyethylene terephthalate (PET) films coated with epoxy resin (EP) and filled with nano-SiO 2 and Si 3 N 4 at concentrations of 0, 0.5, 1, 2, 5 and 10 wt % were subjected to DC and impulse voltages to breakdown. The effects of the types of nano-fillers and concentrations on the dielectric properties, crystallinity, and space charge trap characteristics were investigated on the breakdown strength. The experimental results show that improved DC breakdown strength of a sandwich structure of PET/nano-EP film is obtained even at 10 wt%, which is attributed to the effect of increased trap density for deep traps. In addition, to experimentally establish the dominant factors during impulse breakdown, a systematic theoretical model was used to account for the variations of impulse breakdown performance. It is concluded that the frequency-dependent dielectric characteristics plays an important role in determining the absorption of activation energy for trapped electrons, which affects the instantaneous insulating performance of NC polymers.

It is difficult to simultaneously achieve a high electrical breakdown strength, dielectric permittivity, discharged energy density and charge-discharge efficiency by simply blending electrically conductive nanoparticles with insulating polymers in large-scale preparations. In this work, a family of gradient sandwich-structured Si-based semiconducting nanoparticle/fluoropolymer nanocomposite films with a high breakdown and good energy storage performances was fabricated using a triple solution casting process by fine tuning the type and volume concentration of the Si-based nanofiller used in each layer of the sandwich films. Differing from traditional homogeneous composite films with mono-layered structures, novel inhomogeneous composite films with gradient sandwich structures were fabricated. This fabrication was achieved by implementing a gradient-design strategy used to produce high breakdown layer-by-layer composite dielectrics and the induced polarization tactics used to produce high-permittivity Si-based semiconductor/polymer composite dielectrics. Beta-Si 3 N 4 , alpha-SiC and monocrystalline Si nanoparticles (all ∼100 nm) were introduced into the upper, middle and bottom layers of the fluoropolymer matrices, respectively. The volume concentrations of the Si-based nanofillers in each of the three layers were controlled, and 1 vol% filler in each layer was found to be optimal. In this case, the preferred electric field applied to each layer due to the gradient design could result in the highest breakdown strength (360 MV m −1 ) of the composite. The interface blocking effect present between two adjacent layers might inhibit the electrical tree growth between the two electrodes, contributing to a significantly enhanced breakdown property. As a result, a discharged energy density of 13 J cm −3 and a charge-discharge efficiency of 67% at 350 MV m −1 were obtained. This work might pave the way for the large-scale preparation of high-performance nanocomposite dielectrics based on the interface blocking effect.

Two polyethylene and two polypropylene blends crystallized under non-isothermal conditions were compared to a crosslinked polyethylene (XLPE) reference material. Selected blends contained a gelation agent, which forms a network structure within the material. Compared to XLPE, the blends offered higher melting points, reduced electrical conductivity, increased electrical breakdown strength, improved space charge performance and enhanced thermo-mechanical stability. Additional improvements in space charge behavior were also noted in systems containing the DBS gelation agent. The ability to provide recyclable insulation materials capable of operating at much higher temperatures than XLPE, combined with enhanced dielectric properties, may prove advantageous to cable manufacturers, particularly in renewable energy applications.

The room temperature insulation breaks (RTIBs) for the International Thermonuclear Experimental Reactor (ITER) project insulate the helium (He) outlets of the High Temperature Superconducting (HTS) current leads in the feeders, which can be at up to 30 kV, from the grounded pipework returning the gas to the liquefier plant. Gaseous He at RT is particularly vulnerable to electrical breakdown, requiring an additional design effort as compared to that for cryogenic IBs with more than hundred times denser cryogenic He. To satisfy the working requirements, stainless steel (SS) pipes and glass fiber reinforced plastic (GFRP) were used to develop the RTIBs for the ITER Correction Coil (CC) feeders. Electrical and mechanical analyses of the RTIBs using finite element models were performed. In particular, the electric field distribution along the helium gas path and possible de-bonding or shear failure of the composite were investigated. In this paper, the results of the analysis are discussed. Further experiments indicate the designed RTIB can satisfy the functional require-ments.

Environmentally-friendly polymers which can be recycled and reused at the end of life are urgently needed for the development of advanced high-voltage direct current (HVDC) systems. Polymer nanocomposites have attracted considerable attention owing to their unique features arising from synergistic combination of inorganic fillers and polymer matrices. Here we describe thermoplastic poly(ether imide) (PEI) nanocomposites that contain boron nitride nanosheets (BNNSs). It is found that the polymer nanocomposites exhibit simultaneous improvements in multiple physical properties, such as the DC electrical breakdown strength, volume resistivity, mechanical strength and thermal stability, along with substantial reduction in loss tangent, compared with neat PEI. A great improvement in thermal conductivity has been attributed to the presence of BNNSs in the composites, which improves heat dissipation in comparison with neat polymers. The composite approach provides a promising solution for alleviating temperature-gradient distribution and addressing heat accumulation issues in HVDC equipment, and enables broader applications of insulation materials in HVDC systems operated under high voltages.

The superconducting gas insulated transmission line (S-GIL) is a new design being proposed for helium gas (GHe) cooled high temperature superconducting (HTS) power cables. The S-GIL design utilizes GHe as both cryogen and insulation medium for the HTS cable. This paper builds upon previous proof of concept measurements of the S-GIL. Through optimization of the S-GIL design parameters increase of 20–30% in electrical breakdown voltages was observed for the proof of concept measurements. The paper also contains details on a prototype S-GIL design which was adopted from a commercial coaxial air dielectric cable. The prototype S-GIL cable was successfully demonstrated at 77 K using both GHe and 4 mol% H2 balanced with GHe as the cryogen/insulation medium. The values obtained by the prototype S-GIL cable are higher than the voltage rating currently capable of other GHe cooled HTS cables which verifies the potential of the S-GIL design concept.

In this work, ultrafine-grained W-Cu composites without and with reinforcement of tungsten fibers (Wf) were prepared by successive processes of mechanical alloying, cold pressing, sintering and infiltration. For Wf reinforced W-Cu composite, the introduction of Wf coated with magnetron sputtered Cr, improved the sinterability and contiguity of Wf with the neighboring W powders, eliminating porosity between Wf and the matrix and improving the interfacial strength. Further compressive tests demonstrated that, compared with conventional commercial W-Cu composite made of micron-sized tungsten powders, for the ultrafine-grained W-Cu composite reinforced with Cr-coated Wf, the compressive strength increased dramatically by 122.9%, 43.6% and 91.3%, when deformed at room temperature, 300 °C and 500 °C, respectively. Besides, the electrical breakdown strength increased impressively by 118%, which can be ascribed to the arc dispersion from the increased fraction of grain boundaries in the ultrafine-grained structure free from blind holes.

Degradation of the silicone rubber in the composite insulators is usually caused by thermal and electrical stressing. The thermal conductivity of the composite insulator can be improved by adding a second phase with high thermal conductivity. Boron nitride is a new kind of two-dimentional (2D) materials, with a microstructure similar to the popular graphene but electrically insulating. Such unique properties make BN a promising candidate for increasing the thermal conductivity while maintaining the electrical insulating properties of the silicone rubber. In this report, we systematically studied the effects of BN nanoplates as a filler on the thermal diffusivity/conductivity, electrical breakdown strength, mechanical performance, dielectric behavior, as well as hydrophobicity properties of high temperature vulcanized silicone rubber. A series of samples were prepared with different BN filler loadings up to 32 wt% (∼25 vol%). We found that after adding BN nanoplates the sample's thermal conductivity can be increased by 30%. Surprisingly the electrical breakdown strength and hydrophobicity were also improved by the BN filler. However, the mechanical strength was deteriorated to some extent. Our results provide new thoughts in optimizing the performance of the silicone rubber for composite insulators. More studies need to be done in order to reveal the effects of BN additives in real composite insulators.

Until now, development of conventional electronic devices has mainly focused on performance, and e-waste disposal has been neglected. To alleviate e-waste disposal problems, the use of naturally degradable materials as electronic components has been studied. While most research on such materials has focused on the substrate, other components such as dielectric insulators have not been widely studied. Here, we developed a poly-methacrylated tannic acid (PMTA) naturally degradable dielectric material with good electrical breakdown strength (5.4 MV cm−1), good long-term stability in ambient, and a stable surface. Pentacene thin-film transistors (TFTs) with a PMTA dielectric insulator layer showed reasonable field effect mobility of 0.2 cm2 V−1 s−1 at −20 V of gate voltage (Vg). In addition, the pentacene TFTs with a PMTA dielectric insulator layer and a polyvinyl alcohol substrate show a good degradability in natural; the TFTs were fully decomposed within 8 days in phosphate buffered saline (PBS buffer solution). Also, the TFTs with a PMTA dielectric insulator layer were fully decomposed within 19 days in 3.5 wt% sodium chloride solution, similar to seawater, which has a good potential for reduction of e-waste.

The influence of reduction temperature on the electromechanical properties and actuation behavior of polydimethylsiloxane (PDMS) dielectric elastomer containing the thermally reduced graphene oxide (rGO) with different surface chemistry has been systematically investigated. A set of rGO nanosheets was prepared by thermal reduction of graphene oxide (GO) at four temperatures (150, 200, 300, and 400 °C). The dielectric permittivity, dielectric loss, and elastic modulus of PDMS composites were increased, while the electrical breakdown strength of composites was decreased with an increase of the reduction temperature of GO. A thermodynamic model applied for studying the electromechanical deformation and stability of PDMS/GO(rGO-x) dielectric elastomer composites showed that the optimum value of the break-point was observed in PDMS/rGO-300. It is shown for the first time that the variation of electromechanical instability and recovery behavior are attributed to the surface chemistry of rGOs. A critical reducti...

In order to investigate the effects of additives on electrical breakdown strength of naphthenic transformer oil, three types of additives including N, N′-dimethyl aniline (DMA), trichloroethylene (TCE) and TiO2 nanoparticles were used to modify the oil with different concentrations. The breakdown strength and prebreakdown streamer propagation process in the pure and modified oils were investigated under positive lightning impulse voltage. The test results indicate that all additives can improve the breakdown strength of naphthenic transformer oil at certain concentrations, and TiO2 nanoparticles exhibit an optimal modification effect with an increase of 39.4%. Moreover, streamer propagation characteristics of modified oils are significantly affected by the type of additives. The presence of DMA increases the number of discharge branches, while TCE shortens the propagation length of branches without any obvious change in the shape. The positive streamers in the oil modified by TiO2 nanoparticles possess both denser branches and much slower velocities. Based on the analysis of molecule ionization and distribution characteristics of space charge, the improvement in breakdown strength and the change of prebreakdown process are mainly attributed to the significant influence of additives on the formation and transportation of charge carriers in the naphthenic transformer oil.

Graphene nanogaps are considered as essential building blocks of two-dimensional electronic circuits, as they offer the possibility to interconnect a broad range of atomic-scale objects. Here we provide an insight into the microscopic processes taking place during the formation of graphene nanogaps through the detailed analysis of their low-frequency noise properties. Following the evolution of the noise level, we identify the fundamentally different regimes throughout the nanogap formation. By modeling the resistance and bias dependence of the noise, we resolve the major noise-generating processes: atomic-scale junction-width fluctuations in the nanojunction regime and sub-atomic gap-size fluctuations in the nanogap regime. As a milestone toward graphene-based atomic electronics, our results facilitate the automation of an optimized electrical breakdown protocol for high yield graphene nanogap fabrication., npj 2D Materials and Applications, 5 (1), ISSN:2397-7132

Determining the metallicity and semiconductivity of a multi-walled carbon nanotube (MWCNT) bundle plays a particularly vital role in its interconnection with the metal electrode of an integrated circuit. In this paper, an effective method is proposed to determine the electrical transport properties of an MWCNT bundle using a current–voltage characteristic curve during its electrical breakdown. We established the reliable electrical nanoscale contact between the MWCNT bundle and metal electrode using a robotic manipulation system under scanning electron microscope (SEM) vacuum conditions. The experimental results show that the current–voltage curve appears as saw-tooth-like current changes including up and down steps, which signify the conductance and breakdown of carbon shells in the MWCNT bundle, respectively. Additionally, the power law nonlinear behavior of the current–voltage curve indicates that the MWCNT bundle is semiconducting. The molecular dynamics simulation explains that the electron transport between the inner carbon shells, between the outermost carbon shells and gold metal electrode and between the outermost carbons shells of two adjacent individual three-walled carbon nanotubes (TWCNTs) is through their radial deformation. Density functional theory (DFT) calculations elucidate the electron transport mechanism between the gold surface and double-wall carbon nanotube (DWCNT) and between the inner and outermost carbon shells of DWCNT using the charge density difference, electrostatic potential and partial density of states.

As a key accessory made from the crosslinked polyethylene (XLPE) in high-voltage (HV) insulated submarine cable, the EMJ joints represent unpredictable uncertainty in production reliability due to workmanship issues. Dielectric cracks in the size of tens of micrometers in insulation interfaces are identified as a string of voids to dominate insulation damages. The abnormal arrangements of XLPE lamellae observed by scanning electron microscope (SEM) imply that the structural micro-cracks will be formed under interface stresses. Electrical tree inception is facilitated to a faster propagation due to the poor dielectric property of the interface region, manifesting as 30% lower of tree inception voltage, which is attributed to the longer free-paths for accelerating charge carries in the cracks of interface region and will stimulate partial discharging from needle electrodes. The carbonized micro-discharging channels only arising in interface region suggest that the micro-discharging channels can be triggered by the voids in cracks and will finally develop into electrical breakdown of insulation damage. The mechanism of forming cracks in the fusion processes between the molten XLPE of cable and the molten XLPE of recovery insulation is elucidated.

Upon inclusion of collisions, the speed-limited particle-in-cell (SLPIC) simulation method successfully computed the Paschen curve for argon. The simulations modelled an electron cascade across an argon-filled capacitor, including electron-neutral ionization, electron-neutral elastic collisions, electron-neutral excitation, and ion-induced secondary-electron emission. In electrical breakdown, the timescale difference between ion and electron motion makes traditional particle-in-cell (PIC) methods computationally slow. To decrease this timescale difference and speed up computation, we used SLPIC, a time-domain algorithm that limits the speed of the fastest electrons in the simulation. The SLPIC algorithm facilitates a straightforward, fully-kinetic treatment of dynamics, secondary emission, and collisions. SLPIC was as accurate as PIC, but ran up to 200 times faster. SLPIC accurately computed the Paschen curve for argon over three orders of magnitude in pressure., 17 pages, 2 figures

The work is focused on the study of the dynamics of destruction of electrical insulation paper during electrical breakdown. Current and voltage waveforms were obtained experimentally during the breakdown of standard electrical insulation paper K120, castings of a composite of the nano-gel film of bacterial cellulose with filler in the form of nano-silicon dioxide, carbon nanotubes and without them. The characteristic parameters of electric breakdown development are evaluated. An explanation is given for physical phenomena at various stages of breakdown development.

Cross-linked polyethylene (XLPE) has been recognized as an outstanding insulator for high-voltage power cables due to its favorable structural integrity at high temperature, low moisture sensitivity, chemical resistance, and low rates of failure due to aging. However, the roles of by-products and amorphous regions generated during the XLPE production are not clearly known at the atomistic scale. In this study, we present an eReaxFF-based molecular dynamics simulation framework with an explicit electron description verified against density functional theory data to investigate the roles of XLPE by-products and processing variables such as density and voids on the time to dielectric breakdown (TDDB) of polyethylene (PE). Our simulation results indicate that an increase in density of PE increases the TDDB; however, adding a by-product with positive electron affinity such as acetophenone can reduce the TDDB. Furthermore, during the electrical breakdown in PE, electrons tend to migrate through voids when transferring from the anode to cathode. In comparison with neutral acetophenone, we find that the acetophenone radical anion can significantly reduce the energy barrier and the reaction energy of secondary chemical reactions.

When an ultrathin (

Flexible thin-film Electro-Adhesive Devices (EADs) represent a promising technology with great potential for gripper applications. Generally, the gripping action of an EAD is due to the electrostatic force induced by an electric field produced by applying a voltage across a couple of electrodes that are embedded between dielectric substrates. This paper presents a novel manufacturing process and the experimental characterization of a multilayer electro-adhesive gripper. The proposed device employs highly elastic silicone (PDMS) thin-film as the grasping layer, i.e., the dielectric layer that comes in contact with the grasped object, a carbon-black mixture in a silicone compound for the electrodes, and a rigid polyimide thin-film as the backing layer, i.e., the dielectric layer on the backside of the EAD. A fabrication methodology is illustrated, which starts from a casting of thin conductive electrodes on a polyimide film, followed by a laser-cutting operation to shape the electrodes and a blade casting process to encapsulate the overall system in a PDMS compound. Different prototypes obtained through this manufacturing procedure have been experimentally evaluated through a testing campaign conducted on three groups of specimens, each composed of five identical samples, with a different electrode thickness per group. Samples are tested for electrostatic shear stress and electrical breakdown during the grasping of paper substrates, identifying the best performing EAD group.

A dielectric film with a trilayer structure is fabricated to obtain both a high dielectric constant and superior electrical breakdown strength simultaneously. The outer layers of the trilayered composite film are composed of barium titanate (BTO) particles dispersed in poly(vinylidene fluoride) (PVDF) to ensure a relatively high dielectric constant, while the central layer of the composite film consists of exfoliated hexagonal boron nitride nanosheets (BNNS) dispersed in PVDF to provide high electrical breakdown strength. Compared with pristine PVDF, the dielectric constant and breakdown strength are simultaneously enhanced due to the sandwich structure, and the dielectric loss is maintained at a low level. Most important of all, positron annihilation lifetime spectroscopy (PALS) is applied to study the atomic-scale free volume holes of PVDF composite films and the effect of free volume holes on the dielectric constant and breakdown strength. Results show that the size of free volume holes of PVDF increased with the addition of BTO, but it decreased firstly and then increased with the BNNS loading. The correlation between dielectric properties and the size of free volume holes of the PVDF matrix was discussed in each layer. It is illustrated that the experimental dielectric constant of the PVDF/BTO single-layered film is consistent with the theoretical value at a lower BTO loading but smaller than the theoretical value at a higher BTO loading, which is probably ascribed to the increased size of free volume holes. The breakdown strength of the PVDF/BNNS film increased with the introduction of BNNS and the reduced size of free volume holes, which is ascribed to the reduced partial discharge phenomenon. The atomic-scale microstructure analysis based on free volume holes provides valuable ideas and new understanding for the study of the mechanism of the dielectric behaviour of polymer composites.

Crosslinked polyethylene is one of the main insulation materials in the high-voltage DC cables, which was produced from the low-density polyethylene crosslinked by the decomposed organic peroxide at elevated temperatures. The DC insulation performance of the polyethylene materials determines the insulation reliability of high-voltage DC cables. This chapter reviews the DC insulation performance of polyethylene, including DC electrical conductivity characteristics, space charge characteristics, as well as DC electrical breakdown characteristics. The morphology and physical-chemical defects of the polyethylene materials greatly affect the charge trap characteristics, thereby regulating the DC insulation performance.

This paper reports on the effects of aging on thermal, chemical, and dielectric properties of unfilled polypropylene and polypropylene nanocomposites containing 5 wt% of surface-modified calcium carbonate nanofiller. The evaluated samples were prepared using a melt blending technique. Then, a hydraulic laboratory press was used to obtain a thin film sample. Three different aging conditions were considered, namely, unaged (as reference), and aged at 110 °C and 140 °C. The evaluated samples were then characterized using differential scanning calorimetry and Fourier transform infrared spectroscopy for thermal and chemical analyses, respectively. Meanwhile, the dielectric strength was determined based on DC electrical breakdown tests. The experimental results show that aging the samples at 140 °C changed the thermal behavior of all evaluated samples. Specifically, the melting temperature increased when the sample was aged at 140 °C. Of note, the DC breakdown strength of unfilled polypropylene reduced significantly after aging at 140 °C when compared to polypropylene nanocomposites.