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The minimal difference between the dielectric constant of graphite-phase g-C3N4 and that of PVDF significantly reduces the local electric field distortion, thus improving the breakdown strength and energy storage density of the composites. In addition, the low conductivity (10–12~−13 S/m) and wide band gap (2.7 eV) of g-C3N4 nanosheets are favorable for improving the breakdown strength of PVDF composites. In this study, g-C3N4/PVDF dielectric films were prepared by solution casting method using g-C3N4 as inorganic filler; the effects of g-C3N4 concentration on dielectric and energy storage properties of the composite films were discussed. The results show that the 3wt% g-C3N4 /PVDF composite film has the highest dielectric constant of 13 at room temperature because of its good dispersion and strong interfacial polarization. Additionally, the maximum discharge energy density is 6.85 J/cm3, which is twice that of PVDF (3.51 J/cm3) due to the formation of charge traps and enhanced mechanical properties. In this paper, a simple, low-cost and environmentally friendly method is proposed to prepare flexible composite dielectric films with high energy storage density using 2D filler g-C3N4. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) nanofillers can effectively improve the performance of nano‐dielectrics by having larger aspect ratios and larger electron‐scattering interfaces than one‐dimensional (1D) nanofillers and zero‐dimensional (0D) nanofillers; the formation of a large interfacial area in the polymer matrix effectively traps or scatters the mobile charges and increases the curvature of the propagation paths of the electric tree, thus effectively increasing the breakdown strength and the energy‐storage density of nanodielectrics. In this article, the intrinsic mechanism of 2D nanodielectrics is elaborated using percolation theory, microcapacitance theory, interfacial model, and ping‐pong racket model. Surface modification, oriented alignment, and multilayer structural design are reviewed to enhance the dielectric properties of nanodielectrics. Additionally, an outlook on the multiple challenges and potential opportunities in the process of preparing energy‐storage capacitors with excellent performance is provided. [ABSTRACT FROM AUTHOR]

The modification of BT ceramic particles was achieved using hydrogen peroxide and vinyltriethoxysilane, resulting in the production of core–shell-structured nano-materials (VTS@BT). Upon initiation, moderately cross-linked XL-VTS@BT/PVDF composites were prepared by reacting them with modified polyvinylidene fluoride (MDPVDF). As the amount of VTS@BT increased, the dielectric constant of the composite material increased from 7.89 to 19.1, while the dielectric loss increased only slightly from 0.058 to 0.075. Furthermore, as the filling amount of VTS@BT increased, the grain size gradually increased, the nucleation rate decreased, and the addition of crosslinking agents caused a minor transformation of the β-crystalline phase to the α-crystalline phase. The moderate cross-linking improved the breakdown strength and energy storage density of the composite material, with a cross-linked structure composite material at 10wt% addition achieving an energy storage density of 10.36 J/cm3 at an electric field strength of 340MV/m, which was nearly a 57% increase in energy storage density compared to PVDF. [ABSTRACT FROM AUTHOR]

The solution cast (SC) prepared polymer nanocomposite (PNC) films, based on poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) blend host matrix with varying amounts of barium titanate (BaTiO3) as nanofiller, were thermally treated through standardized hot pressed (HP) procedure at 160 °C under the pressure of 2 tons. The optical characterization including absorbance, reflectance, and percentage transmittance for UV–vis radiations of 200–800 nm, direct and indirect energy band gaps, Urbach energy, refractive index, extinction coefficient, optical range dielectric permittivity and optical conductivity as well as non-linear optical parameters of these solution cast-hot pressed (SC-HP) PNC films are performed and confirmed their dependency on the nanofiller concentrations. These SC-HP processed PNC films showed reduced UV–vis absorbance, direct energy band gap, and the degree of crystallinity of the PVDF crystalline phase whereas the crystallite melting temperature significantly enhanced in comparison to the same composition SC prepared PNC films. The dielectric permittivity and electrical conductivity values, at 27 °C, for these thermally treated PNC films are improved appreciably over the broadband radio frequency range of 1 MHz to 1 GHz. The technologically favoured changes in various optical and dielectric parameters establish the appropriateness of the thermal treatment process for envisaging applications of these PNCs in advances of high-performance flexible-type optoelectronic and radio electronic devices. [ABSTRACT FROM AUTHOR]

The long-term operation of motors induces substantial alterations in the surface conductivity and nonlinear coefficient of anti-corona paint, diminishing its efficacy and jeopardizing the longevity of large motors. Hence, the development of high-performance anti-corona paint holds paramount importance in ensuring motor safety. In this study, we integrate two nano-fillers, namely silicon carbide (SiC) and organic montmorillonite (O-MMT), into a composite matrix comprising micron silicon carbide and epoxy resin (SiC/EP). Subsequently, three distinct types of anti-corona paint are formulated: SiC/EP, Nano-SiC/EP, and O-MMT/SiC/EP. Remarkably, O-MMT/SiC/EP exhibits a glass transition temperature about 25 °C higher than that of SiC/EP, underscoring its superior thermal properties. Moreover, the introduction of nano-fillers markedly augments the surface conductivity of the anti-corona paint. Aging tests, conducted across varying temperatures, unveil a notable reduction in the fluctuation range of surface conductivity post-aging. Initially, the nonlinear coefficients exhibit a declining trend, succeeded by an ascending trajectory. The O-MMT/SiC/EP composite displays a maximum nonlinearity coefficient of 1.465 and a minimum of 1.382. Furthermore, the incorporation of nanofillers amplifies the dielectric thermal stability of epoxy resin composites, with O-MMT/SiC/EP showcasing the pinnacle of thermal endurance. Overall, our findings elucidate the efficacy of nano-fillers in enhancing the performance and longevity of anti-corona paint, particularly highlighting the exceptional attributes of the O-MMT/SiC/EP composite in bolstering motor safety through improved thermal stability and electrical properties. [ABSTRACT FROM AUTHOR]

This work presents the results of research on submicro- and nanocomposites with gradient properties, produced in a planned electrophoretic process. Epoxy-resin-based samples were filled with TiO2 particles of three different sizes (13 nm, 38 nm, and <1 µm) at four different values of average electric field Eav (0.0 Vmm−1, 125 Vmm−1, 250 Vmm−1, and 500 Vmm−1) for 1 h each. Changes in selected dielectric parameters (dielectric constant εr and dielectric loss factor tanδ) of the composites were analyzed using broadband dielectric spectroscopy (10−1 Hz to 105 Hz). The influence of the Eav and the current i(t) flowing through the sample material and the Joule heat generated in it on the resin curing process and the final gradient of dielectric parameters were investigated. The results show that the degree of modification of the εr gradient increases with increasing Eav and is more pronounced in the case of TiO2 nanoparticles. The largest modifications in the εr and tanδ were obtained for nanoparticles with a diameter of 13 nm at Eav = 500 Vmm−1, while the lowest for particles < 1 µm at Eav = 125 Vmm−1. The effect of electrophoresis on the dielectric parameters is significant, especially near the anode region. Increasing the concentration of TiO2 particles at the anode occurs at the expense of reducing their concentration in the remaining volume of the sample. The test results clearly demonstrate the importance of particle dimension and electric field strength for the gradient modification of the properties of the epoxy composite using electrophoresis. Numerical simulations of electric field stresses in the epoxy resin during the electrophoresis process, performed in the COMSOL program, revealed a significant increase in the E field strength in the areas close to the anode and cathode. [ABSTRACT FROM AUTHOR]

Polymeric epoxy-based nanocomposites have tremendously grown in electronic and indoor high-voltage insulation applications over the last two decades. The interface between the epoxy resin and inorganic fillers surprisingly improves the performance compared to neat epoxy and conventional ceramic insulators. However, several configurations, including the filler loading, filler size, and synthesis process, substantially impact performance. Dielectrics employed in power equipment are often exposed to corona discharges, causing surface erosion and may cause flashover due to prolonged exposure to the discharges. Also, dielectrics must continuously endure heat from leakage currents or surrounding temperatures. The present work examines various configurations of the epoxy/ZnO composites for the corona discharge resistance and thermal stability: the effect of filler loading, preparation method of nanocomposites, and co-filling of nano-micro fillers. The ZnO nanoparticles were disseminated in the epoxy resin using a probe and bath sonicator with and without solvent. It also includes the impact of heated nanoparticles. The corona discharge tests were performed using a set-up similar to CIGRE working group D1.24. The studies of surface degradation were conducted using surface roughness metrics obtained from an optical 3D profilometer. Differential scanning calorimetry (DSC) was used to perform the thermal analyses as per ASTM E1356. It was found that compared to all the filled specimens, the neat epoxy experienced more severe erosion. In addition, the specimen filled with ZnO nanoparticles endured positive corona discharges compared to negative and AC discharges. The specimen prepared with heated nanoparticles without solvent using a probe sonicator showed high heat energy and heat capacity leading to thermal instability. Besides, the interface between nano-micro particles and the host material increases corona discharge resistance and thermal stability. [ABSTRACT FROM AUTHOR]

Silver nanoparticles were synthesized via laser ablation in two different organic solvents (tetrahydrofuran and toluene). The influence of solvent choice on the production and behavior of silver nanoparticles dispersed in a polystyrene matrix was investigated. UV–Vis spectroscopy, ellipsometry and scanning probe microscopy techniques were used for characterization. The silver nanoparticles' optical properties were modified by the existence of a core-shell structure appearing in toluene-ablated particles. For both solvents and, in particular, for the toluene case, the particles showed good dispersion in the matrix. Additionally, the interphase behavior of the doped polymer films was influenced by the synthesis process, affecting the mechanical and optical (dielectric) properties. The observed results for the nanocomposite are attributed to the formation of a core-shell structure around the particles directly due to the ablation in organic solvents. These findings contribute to the understanding of silver/polystyrene nanocomposites and offer opportunities for developing tailored functional materials by using laser ablation in liquids. [ABSTRACT FROM AUTHOR]

Polyisobutyl methacrylate (PiBMA)/ferrous-ferric oxide (Fe3O4) polymer nanodielectric films with different wt% of Fe3O4 nanoparticles (from 0.2wt.% to 1.0wt.%) were prepared by solution casting technique. The effect of free volume on the dielectric properties of PiBMA/Fe3O4 polymer nanodielectrics is also explored. The free volume parameters and AC conductivity of PiBMA/Fe3O4 polymer nanodielectrics as a function of Fe3O4 nanoparticle wt% exhibit an increasing trend. The DSC results suggest weak interfacial interaction between agglomerated Fe3O4 nanoparticles and polymeric chains of PiBMA polymer. The dielectric constant ( ϵ ′ ) of PiBMA/Fe3O4 polymer nanodielectrics increased as a function of free volume hole size and Fe3O4 nanoparticle wt%. This is attributed to the increased interfacial polarization at the interface region and the orientation polarization effect of intrinsic dipoles. The increased electrochemical current of PiBMA/Fe3O4 polymer nanodielectrics for 0.8wt.% and 1.0wt.% of Fe3O4 nanofiller loading imply that the increased free volume favors the diffusion of electrolytic ions into PiBMA/Fe3O4 polymer nanodielectrics. [ABSTRACT FROM AUTHOR]

The paper presents the effects of gradual temperature curing on the dielectric properties of epoxy nanocomposite samples. Samples were prepared based on Class H epoxy resin filled with nano-alumina (Al2O3) for different wt% loadings (0.5 wt% to 5.0 wt%) and two different filler sizes (13 nm and <50 nm), i.e., two different specific surface area values. During the research, specimen sets were cured gradually at increasingly higher temperatures (from 60 °C to 180 °C). Broadband dielectric spectroscopy (BDS) was used to determine the characteristics of the dielectric constant and the dielectric loss factor in the frequency range from 10−3 Hz to 105 Hz. As a result, it was possible to analyze the impact of the progressing polymer structure thermosetting processes on the observed dielectric parameters of the samples. The nano-Al2O3 addition with 0.5 wt%, 1.0 wt%, and 3.0 wt% resulted in a decrease in dielectric constant values compared to neat epoxy resin samples. The most significant reductions were recorded for samples filled with 0.5 wt% of 13 nm and <50 nm powders, by about 15% and 11%, respectively. For all tested samples, the curing process at a gradually higher temperature caused a slight decrease in the dielectric constant (approx. 2% to 9%) in the whole frequency range. Depending on the nanofiller content and the curing stage, the dielectric loss factor of the nanocomposite may be lower or higher than that of the neat resin. For all tested samples cured at 130 °C (and post-cured at 180 °C), the differences in the dielectric loss factor characteristics for frequencies greater than 100 Hz are low. For frequencies < 100 Hz, there are prominent differences in the characteristics related to the size of the nanoparticle and the individual wt% value. At a small nanofiller amount (0.5 wt%), a decrease in the dielectric constant and dielectric loss factor was observed for frequencies < 100 Hz for samples with nanofillers of both sizes. [ABSTRACT FROM AUTHOR]

The additional moisture can be easily introduced into dielectric materials with the nano-doping, which could have adverse impacts on the insulating properties. Herein, samples with different moisture absorption are tested using Terahertz (THz) waves. The relaxation resonance integrated polarization model is developed to illustrate the water absorption effect by the nano-filler on the THz spectrum, which is related to the hydrogen bond (HB) state of water molecular clusters. Detection of moisture content is realized by the polarized resonance intensity in the proposed model. The different HB states of free water and bound water are effectively distinguished using the Debye parameters in the model, and the formation process of water involved in the HB network is analyzed. Meanwhile, the proposed model is verified by molecular simulation. This work provides an application-worthy method to distinguish nuances in moisture contents and distribution in nano-dielectrics, with advantages of non-destructiveness, rapidity and 2D visualization.

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article walks the reader through the author's journey into the establishment of a high-voltage research laboratory in his university with almost nothing. The author introduces the challenges faced and the activities that revived research on natural esters. [ABSTRACT FROM AUTHOR]

In this study, hybrid boron nitride (BN)/titanium carbide (TiC)/epoxy resin composite nanodielectrics were manufactured and characterized. Their morphological and structural characterization was conducted via scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns, whereas the dielectric behavior was studied by means of broadband dielectric spectroscopy (BDS). Dielectric measurements were carried out from 30 to 160 °C and from 10−1 to 106 Hz, respectively. The dielectric results revealed the existence of three relaxation mechanisms, which from high to low frequencies, at constant temperature, refer to re-arrangement of polar-side groups (β-relaxation) of the macromolecular chains, transition from glassy to rubbery state of the amorphous polymer matrix (α-relaxation) and interfacial polarization (IP) between the polymer matrix and the nanofillers. It was found that, in general, nanodielectrics exhibited enhanced dielectric properties mainly due to the high dielectric permittivity of TiC and the fine dispersion of the fillers, confirmed also by the SEM images. Dynamic analysis conducted for the α-relaxation showed a Vogel–Fulcher–Tammann dependence on temperature. The ability of energy storing of the nanocomposites was examined via their energy density. Optimum performance is exhibited by the 5 phr TiC/1 phr BN/epoxy nanocomposite, reaching an energy storing ability nine times greater than the unfilled matrix. [ABSTRACT FROM AUTHOR]

Fumed silica-filled polypropylene (PP)-based nanodielectrics were studied in this work. To not only improve the dispersion of the silica but also introduce deep charge traps into the polymeric matrix, five types of modified silicas were manufactured with different surface modifications. The modified silica surfaces comprise an inner and a surface layer. The inner layer contains a polar urethane group for tailoring the charge trap properties of the PP/propylene–ethylene copolymer nanocomposites, whereas the surface layer consists of hydrocarbons (ethyl-, tert-butyl-, cyclopentyl-, phenyl-, or naphthalenyl moieties) in order to gain a good dispersion of the silica in the unpolar polymer blend. Scanning electron microscopic pictures proved that these tailored silicas show a much better dispersion than the unmodified one. Thermally stimulated depolarization current measurements revealed the ability of the silica to introduce deep charge traps with low trap density. The trap depth distribution depends on the type of the unpolar surface layer consisting of the different hydrocarbons. Among these five differently modified silicas, the introduction of the one with a surface layer consisting of tert-butyl moieties resulted in the lowest charge injection and the lowest charge current in the nanocomposite, proving good dielectric performance. Additionally, this silica exhibits good dispersion in the polymeric matrix, indicating a promising performance for nanodielectric application.

A structural model for the calculation of the equivalent permittivity of nanocomposites based on low-density polyethylene (LDPE) and epoxy resins (ERs) with inorganic fillers was developed. It was assumed that each nanoparticle was centered in an interfacial region composed of three layers in the case of LDPE-based nanocomposites, and of two layers in the case of ER-based nanocomposites. The model for the estimation of the permittivity was designed for flat samples of the height $g$ , divided into cubes with the side-length $l$ . Each of these cubes contains eight nanoparticles, which are separated from the polymer matrix by two or three layers. Based on the types and concentrations of dipoles present in the layers, the relative permittivity of each layer of the interface can be calculated. By the employment of a 3D numerical model in COMSOL, implemented by the finite element method associated with a cube, the distribution of the electric field inside a cube can be determined, which yields the values of the equivalent permittivity of the nanocomposites. In order to verify the numerical results, the permittivity of the nanocomposites based on LDPE and ERs with inorganic nanofillers (SiO2 or Al2O3) was determined in laboratory experiments. The results reveal congruent correlation between the computed and the experimentally determined values of the equivalent permittivity of the nanodielectrics.

The purpose of this present study is to prepare a stable mineral-oil (MO)-based nanofluid (NF) for usage as a coolant in a transformer. Nanoparticles (NPs) such as hexagonal boron nitride (h-BN) and titanium oxide (TiO2) have superior thermal and electrical characteristics. Their dispersion into MO is likely to elevate the electrothermal properties of NFs. Therefore, different batches of NFs are prepared by uniformly dispersing the insulating h-BN and semiconducting TiO2 NP of different concentrations in MO. Bulk h-BN NP of size 1μm is exfoliated into 2D nanosheets of size 150–200 nm, subsequently enhancing the surface area of exfoliated h-BN (Eh-BN). However, from the zeta-potential analysis, NP concentration of 0.01 and 0.1 wt.% are chosen for further study. The thermal conductivity and ACBDV studies of the prepared NF are performed to investigate the cooling and insulation characteristics. The charging-dynamics study verifies the enhancement in ACBDV of the Eh-BN NF. Weibull statistical analysis is carried out to obtain the maximum probability of ACBDV failure, and it is observed that 0.01 wt.% based NF has superior cooling and insulation properties than MO and remaining batches of NFs. [ABSTRACT FROM AUTHOR]

In regards to the advances in hybrid polymer nanocomposite (HPNC) materials for high-frequency nanodielectric applications, herein we report the broadband radio frequency range (1 MHz to 1 GHz) dielectric permittivity and electrical conductivity of composites of poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blend matrices and oxide nanofillers (tin oxide (SnO2) and silica (SiO2)), in the form of PEO/PMMA/SnO2 and PEO/PMMA/SiO2 films at ambient temperature. The results confirmed that these HPNCs have low dielectric permittivity values which decrease slightly, from 3.4 to 2.8, with increasing nanofillers concentrations and the applied electric field frequency. The dependency of the dielectric permittivity on the different oxide nanoparticles sizes and their dielectric constant was explored. The dielectric loss tangent spectra of these hybrid materials indicated that they were reasonably low loss nanodielectrics having a dipolar orientation relaxation in the higher frequency region. The radiofrequency electrical conductivity of the HPNCs was found to increase linearly from ∼10−8 to 10−4 S/cm with the increase of frequency, and it was less dependent on the fillers concentrations. Considering the dielectric and electrical properties, it is proposed that these PEO/PMMA/SnO2 and PEO/PMMA/SiO2 composites could be highly useful materials for dielectric substrates and insulators in the development of radiofrequency operative flexible-type electrical and electronic components and devices. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper describes a polyimide (PI)/nanocomposite multilayer 3D model design on the basis of actual boundary conditions attained from SEM images of synthesized films. The impact of nanoparticle dispersion on the electric field enhancement is explicitly described in the model. The electrical properties of these synthesized multilayer PI/nanocomposite films are also measured through experimental results. The results expose that the chances of nanoparticles dispersion are improved by pasting a thin PI/nanocomposite layer on both sides of PI film as compared to the single layer of PI/nanocomposite film. In consequence, less space charge and low electrical fields are observed in multilayer films. Our methods will help to reliably predict the dielectric strength of polymer/nanocomposite insulating materials. Additionally, the new synthesized multilayer PI/nanocomposite insulating material will ensure reliable operation for electric motors and increase its lifespan. [ABSTRACT FROM AUTHOR]

The biodegradable hybrid polymer nanocomposite (PNC) films comprising silica (SiO2) and alumina (Al2O3) nanoparticles as inorganic nanofillers and the poly(vinyl pyrrolidone) (PVP) as organic host matrix (i.e., PVP-x wt% SiO2 and PVP-x wt% Al2O3 for x = 0, 1, 3 and 5) have been prepared by aqueous solution-casting method. X-ray diffraction (XRD) study reveals that these nanocomposite materials are highly amorphous. The dielectric spectroscopy of these different nanofiller concentrations PNC films has been carried out in the frequency range from 20 Hz to 1 MHz at a fixed temperature and also for 3 wt% nanofillers containing PNC films with the temperature variation. The results confirm that the complex dielectric permittivity of these hybrid films is influenced by the interfacial polarization in the low frequency range of 20 Hz to 1 kHz, whereas in the high frequency range up to 1 MHz permittivity is mainly governed by the molecular polarization and remains almost independent of the frequency. These SiO2 and Al2O3 nanofillers containing PNC films at fixed temperature display anomalous behaviour of dielectric permittivity and ac electrical conductivity with the increase of nanofiller concentration, but these parameters significantly enhance at low frequencies with the increase of temperature of the films. The electric modulus spectra of Al2O3 containing PNC film exhibit relaxation peaks below 100 Hz at higher temperatures which attribute to the interfacial polarization relaxation process. The frequency independent dielectric permittivity and significantly low loss of these PNC materials at radio frequencies confirm their suitability as polymeric nanodielectric (PND) substrate and insulator in the design and fabrication of biodegradable electronic devices and electrical components. [ABSTRACT FROM AUTHOR]

This paper proposes a method to analyze electric field distribution in the composite structure quantitatively based on statistical parameters through electric field simulations. A geometry of many nanoparticles each surrounded by interphase region in a random arrangement is modeled for simulation ensuring uniform distribution. General factorial design in design of experiments method is utilized in performing simulations to identify the significance of the factors considered. Volume fraction, permittivity, radius and interphase thickness of the nanoparticle inclusion are treated as the factors. Volume fraction is varied from 1% to 10% in ten steps to simulate the cases of particle interactions which include nanoparticles far apart, moderately apart, interphases of particles touching to each other and overlap of interphases. Particle permittivity is varied from 2 to 8 while keeping polymer permittivity constant. Conductivity of the nanoparticle is varied similar to permittivity variations. Radius and interphase thickness are varied from 20–50 nm and 20–40 nm respectively. Coefficient of variation as well as mean value of electric field intensity are chosen as output or response variables. Multiple linear regression is employed to formulate the relationship between the factors considered and the statistical parameters. Significance and effect of these factors on electric field distribution is discussed. Interparticle distance and interphase volume fraction are found to be the critical factors affecting variance and mean of electric field intensity in nanodielectrics. [ABSTRACT FROM AUTHOR]

Zeolite/low-density-polyethylene (LDPE) nanocomposites with introduced high density traps to suppress space charge accumulation are achieved by filling 1 and 3 wt% NaY zeolite nanoparticles into LDPE. The conduction current and trap level distribution are analyzed by the isothermal discharge current method. The results indicate that the conduction current and trap level density is significantly higher in comparison with LDPE and increase with NaY-zeolite nanofiller concentration. The space charge tests demonstrate that the NaY-zeolite nanofillers can effectively reduce the conductivity and inhibit the space charge accumulation in zeolite/LDPE nanocomposites at high electrical field. A new method utilizing isothermal space charge decay measurement is proposed to calculate the trap characteristics, which can avoid measurement error in pA current. The calculated results suggest that trap level density of LDPE is improved by nanozeolite. The trap parameters obtained by the new method is consistent with the pA current test, which indicates that space charge distribution can efficiently applied to the analysis of charge trap characterization. In addition, the isothermal space charge decay method verifies the reliability of the space charge distribution test for LDPE nanodielectrics. [ABSTRACT FROM AUTHOR]

There is currently no reliable method for studying interfacial regions within dielectric nanocomposites. The aim of this work was to develop experimental protocols and signal analysis involving Electrostatic Force Microscopy (EFM). Model samples made of spherical nanoparticles deposited on a metallic substrate and covered by two shells were designed and fabricated to simulate the presence of an interphase between a particle and a matrix. EFM performed either with DC or AC gradients detection method proved good sensitivity to certain sample configurations. A quantification of the dielectric permittivity of the intermediate layer was possible, thanks to correlation with finite element numerical simulations. Interfacial states between stacked layers, which can be attributed to film deposition processes, were also evidenced. [ABSTRACT FROM AUTHOR]

Advancements in the field of very compact, high dielectric strength, nanodielectric material capacitors have continued to be made. The capacitors are constructed from a proprietary nanodielectric, MU100, which is a polymer-ceramic composite composed of barium titanate and a binding agent. The MU100 material exhibits several novel qualities-including high dielectric strength along with facile machining and assembly characteristics. Electrical property characterization data of MU100 has been collected at standard ambient temperature conditions. Assessing MU100's properties over a wide temperature range is necessary to verify its suitability for field application and for continued improvement of capacitor design. The dielectric constant and thermal expansion were measured for the MU100 material from −40°C to 120°C. The results demonstrate the nanodielectric has a strong stability both electrically and mechanically across the entire temperature test range. The maximum dielectric constant change of MU100 relevant to standard temperature was +/−9.8% occurring at 130°C. The maximum linear coefficient of thermal expansion found was 1.5 PPM/°C. These values suggest that the MU100 material is suitable for high voltage applications where harsh environmental conditions are expected. It combines the thermal stability of ceramic substrates with the ability to easily machine and assemble the material. [ABSTRACT FROM AUTHOR]

In this work was investigated the effect of the addition of barium titanate (BaTiO3) on electrical properties of two chemically recyclable thermosets, polyhemiaminal (PHA) and polyhexahydro‐s‐triazine (PHT), both fabricated from 4,4′‐oxydianiline (ODA), an ether derivative of aniline and paraformaldehyde. Thermal and mechanical properties as well as chemical recyclability of the two polymers and their nanocomposites/nanodielectrics were also investigated. In addition, a quantitative analysis was conducted of the nanoparticle dispersion in the PHA‐/PHT‐based BaTiO3‐containing nanocomposites using transmission electron microscopy imaging and the nearest‐neighbor distance index and this index was used to analyze the investigated properties in connection with the proper mechanisms. Regarding the electrical properties for both neat polymers, conductivity values of the order of 10−8 S m−1 at 100 Hz were observed and dielectric constant values close to 2.80 for both polymers at 1 kHz. The addition of 0.5 wt% of BaTiO3 ferroelectric nanoparticles increased by about 44% the dielectric constant (1 kHz) and conductivity (102 Hz) of the PHA‐based nanocomposite. PHA and PHT exhibited glass transition temperature (Tg) values in the range 125–180 °C. An increase of 7 °C in Tg was observed after the incorporation of 0.5 wt% of BaTiO3 into PHA. Concerning the mechanical properties, values in the range 4.00–4.45 GPa for reduced modulus and 0.30–0.43 GPa for nanohardness for PHA and PHT polymers were observed. Independently of filler content or polymer matrix, both mechanical properties were enhanced after the addition of BaTiO3. The chemical recycling of PHA/PHT and all nanocomposites in the initial ODA reagent after sulfuric acid treatment was successfully characterized using the NMR and Fourier transform infrared spectroscopic techniques. © 2018 Society of Chemical Industry The change of dielectric constant of BaTiO3 nanoparticles with temperature modified the dielectric properties of two nanocomposites. Better results for polyhemiaminal nanocomposites were observed due strong interactions with matrix and homogeneous dispersion. [ABSTRACT FROM AUTHOR]

Highlights • A linear-like dielectric polymer matrix with rather low U l is synthesized. • Exfoliated mica nanosheets are utilized to enhance the energy storage performance of the composite for the first time. • A high η of 74% under 450 MV/m among PVDF-based composites is achieved. Abstract Poly(vinylidene fluoride) (PVDF) based polymer/ceramic nanocomposites for high energy density dielectrics have long been plagued by their low discharging efficiency (40–60%), which originates from the matrix with high bulk ferroelectric relaxation and the high-k ceramics with large conduction loss. In this work, a linear-like PVDF-based polymer dielectric is synthesized through grafting poly(methyl methacrylate) (PMMA) onto main chains of poly(vinyl fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) terpolymer via an atom transfer radical polymerization (ATRP) process. PMMA grafted terpolymer (P(VDF-TrFE-CTFE)-g-PMMA) shows linear-like dielectric characteristics accompanied with greatly enhanced discharging efficiency of ∼80% under 250 MV/m, which is over 100% higher than that of pristine terpolymer. To further improve its breakdown strength and discharging efficiency, the grafted terpolymer are then compounded with ultrasonic-exfoliated mica nanosheets (e Mica) by solution-cast method. Thanks to the low hysteresis loss of linear-like dielectric matrix and the high insulating 2D mica nanosheets, the composite with the highest discharging efficiency of ∼78% under 250 MV/m is achieved. The maximum energy density of the optimized composite reaches 9.6 J/cm3, which is nearly 290% that of the pristine terpolymer. Besides, its discharging efficiency is about 74% under 450 MV/m, which is much more advantageous than the other PVDF-based polymer/ceramics composite dielectrics. This work suggests that utilizing polymer matrix with linear dielectric property and fillers with high insulating 2D structure might be a facile strategy to achieve composite dielectrics with simultaneously high energy density and high discharging efficiency. [ABSTRACT FROM AUTHOR]

Since the proposal of the notion of nanodielectric, the space charge characteristics of nanodielectrics have been widely investigated. With the addition of nanoparticles, some nanodielectrics exhibit smaller space charge accumulation amount during the polarisation, and also faster charge decay during the depolarisation, which is believed to be related to the interfacial layer between the nanoparticle and the base material. In this study, the space charge measurement methods, theoretical models, and experimental results are reviewed in detail. Space charge measurement methods have been greatly improved after more than 20 years development. The nature of the interfacial layer between the nanoparticle and the base material has been investigated in detail, and based on that, several models are proposed to explain some electrical experimental results of nanodielectrics. Furthermore, the parameters of nanoparticle (such as the type, size, amount, shape, and the surface modification), the experimental conditions, and the base material properties can strongly affect the space charge characteristics of nanodielectrics. This study will provide useful research results and conclusions for researchers, and may also be an overview for recent study and an outlook for future investigation on space charge characteristics of nanodielectrics.

On-skin electronics require minimal thicknesses and decent transparency for conformal contact, imperceptible wearing, and visual aesthetics. It is challenging to search for advanced ultrathin dielectrics capable of supporting the active components while maintaining bending softness, easy handling, and wafer-scale processability. Here, self-delaminated aramid nanodielectrics (ANDs) are demonstrated, enabling any skin-like electronics easily exfoliated from the processing substrates after complicated nanofabrication. In addition, ANDs are mechanically strong, chemically and thermally stable, transparent and breathable, therefore are ideal substrates for soft electronics. As demonstrated, compliant epidermal electrodes comprising silver nanowires and ANDs can successfully record high-quality electromyogram signals with low motion artifacts and satisfying sweat and water resistance. Furthermore, ANDs can serve as both substrates and dielectrics in single-walled carbon nanotube field-effect transistors (FETs) with a merely 160-nm thickness, which can be operated within 4 V with on/off ratios of 1.4 ± 0.5 × 10 5 , mobilities of 39.9 ± 2.2 cm 2 V -1 s -1 , and negligible hysteresis. The ultraconformal FETs can function properly when wrapped around human hair without any degradation in performance., (© 2023 Wiley-VCH GmbH.)

From a novel empirical power law between the DC breakdown field and DC conductivity, an analysis of the trapping characteristics in polyimide/boron nitride (PI/BN) nanocomposites is presented based on space-charge-limited current (SCLC) measurements. The impact of the total trap density H t enhancement (increasing up to 1.1×1017 cm−3) induced by the BN nanoparticles on the space charge attenuation, the DC conductivity reduction and the DC breakdown field increase is clearly reported. This work proves that an efficient control of the trapping parameters allows huge enhancement of the insulating properties of PI nanocomposites. High temperature thermal breakdown can be delayed by free carrier reduction through deep trap formation caused by nanofiller addition. [ABSTRACT FROM AUTHOR]

This review highlights the research conducted on polymers, especially on polymer nanocomposites for electrical energy storage applications in power capacitors. State-of-the-art neat polymers are addressed as well as blends of polymers. Special emphasis is given to polymers filled with ceramic nanoparticles — polymer nanocomposites. The aim of this contribution is to overview the different approaches being made to improve the properties of dielectric polymer films for power capacitors. It concludes with an outlook on the research topics that should be addressed in the future. [ABSTRACT FROM AUTHOR]

Abstract This study proposes a new model for describing the electrical behaviour of nanocomposites. Unlike other models in the literature, this model has concentrated on the role of an interphase layer within the boundaries of nanoparticles. The experimental part investigates this role by filling an epoxy matrix with two types of surface-modified silicon nitride nanofiller: (a) the particles were dried at 200 °C, and (b) the particles were calcinated at 1050 °C. Electrical characterization showed that the epoxy which was filled with the calcinated particles has considerably better dielectric performance. Given that thermal and dielectric spectroscopy results demonstrate that the matrix molecular dynamics and polar content are comparable for all the investigated samples, the variations in the dielectric performance point to the particle interphase as an essential reason. As shown by infrared spectroscopy, the complex surface chemistry of the dried particles suggests a particle interphase with a high concentration of localized electronic states, which may enhance charge transport through hopping/tunnelling conduction. On the other hand, calcinating the particles results in a particle interphase with wider band gap, which may work as an energy barrier for charge movement. Consequently, this study highlights the paramount importance of particle interphase for designing dielectric properties of nanodielectrics. Graphical abstract Unlabelled Image Highlights • A new model has been proposed for describing and designing electrical behaviour of nanocomposites. • Unlike other models, this model has investigated the role of an interphase layer within the boundaries of nanoparticles. • Experimental results have demonstrated that particle interphase could have a critical influence on electrical properties. • The study highlights the critical role of particle interphase for designing nanodielectrics. [ABSTRACT FROM AUTHOR]

According to recent studies on electrical insulation systems, it was demonstrated that the nanocomposite (NC) organic/inorganic hybrid materials assure a distinct improvement of their high-temperature functioning and allow these systems to strengthen their dielectric properties. Recently, it was shown that some modifications of the electrical properties such as permittivity, dielectric breakdown, partial discharges resistance, or lifetime were often awarded to the properties of what it is called the interphase. This interphase represents the interaction zone between the matrix and nanoparticles and plays very often a leading part in the definition of the material macroscopic properties. However, the role of the interphase remains theoretical and a few experimental results exist to describe this phenomenon. In this paper, atomic force microscopy (AFM) is used to make at the same time qualitative and quantitative measurements of these interaction zones within polyimide/silicon nitride NC. For example, the peak force quantitative nano mechanical AFM mode reveals the presence of the interphase by measuring mechanical properties (Young modulus, deformation, and adhesion). As a result, this new and original study on the interphase measurement confronts experimental results with theoretical models. [ABSTRACT FROM AUTHOR]

Manufacturing of a new insulation material for power cables has become necessary in order to withstand electrical and mechanical stresses. The current study aims to enhance the dielectric and mechanical properties of Polyvinyl Chloride (PVC), one of the wide used power cable insulation, by the insertion of chemically modified silica (silicon dioxide, SiO 2 ) nanoparticles. The surface functionalization of the inserted SiO 2 nanoparticles was performed using amino silane coupling agent, and the PVC/SiO 2 nanocomposites were synthesized with different concentrations of nanoparticles. The surface morphology and chemical structure of the prepared samples were characterized by field emission scanning electron microscopy (FE-SEM) and Fourier transformation infrared spectroscopy (FT-IR). The mechanical properties of the obtained nanocomposites showed that the insertion of functionalized nanoparticles is able to increase the tensile strength and the Young’s modulus of samples, however it decreases their elongation. In addition, the dielectric properties of PVC/SiO 2 nanocomposites, such as relative permittivity ( ε r ) and dielectric loss ( tan δ ), were also measured in a frequency range of 20 Hz–1 MHz. Moreover, AC breakdown voltage of the prepared samples was measured under uniform and non-uniform field, and AC dielectric strength was evaluated using finite element method (FEM) for non-uniform and uniform field. For further evaluation, DC dielectric strength was also measured under uniform field. The obtained data revealed that PVC/SiO 2 nanocomposites with functionalized SiO 2 nanoparticles exhibited better dielectric properties compared to that with un-functionalized one or that of neat PVC. The physical mechanisms behind the obtained enhancements have been discussed. [ABSTRACT FROM AUTHOR]

Blends of polyethylene (PE) with nanocomposites of polystyrene- b -poly(ethylene- co -butylene)- b -polystyrene grafted maleic anhydride (SEBS-MA) thermoplastic elastomer filled with Zinc Oxide (ZnO) nanoparticles have been studied as potential candidates for applications in HV insulation systems including HVDC cables. In particular, the dielectric and mechanical properties of PE/SEBS-MA/ZnO blend nanocomposites have been evaluated and compared to those of PE/ZnO homopolymer nanocomposites prepared as a reference. PE/ZnO materials were characterized by homogeneous distribution of nanoparticles and presence of agglomerations attributed to insufficient compatibility between the metal oxide nanoparticles and the polyolefin matrix. However, nanoscale dispersion was achieved in SEBS-MA/ZnO and PE/SEBS-MA/ZnO nanocomposites due to improved compatibility between the nanoparticles and SEBS-MA. Besides, in PE/SEBS-MA/ZnO blend nanocomposites, ZnO nanoparticles remained exclusively confined in SEBS-MA or at the interface between PE and SEBS-MA. In terms of dielectric properties, the unfilled blend PE/SEBS-MA featured reduced breakdown strength and resistance to surface erosion by partial discharges in comparison with neat PE. However, upon addition of ZnO the blend PE/SEBS-MA presented higher performance when compared to PE. At 1 wt% ZnO loading, the resistance to surface erosion of PE/SEBS-MA increased by 45% higher than neat PE/SEBS-MA, 38% higher than unfilled PE and 30% higher PE/ZnO nanocomposite containing the same ZnO loading. Besides, blend nanocomposites exhibited dielectric losses lower than PE/ZnO nanocomposites at power frequencies and temperatures up to 80 °C. The breakdown strength of both sets of nanocomposites decreased compared to unfilled materials, at large loadings of nanoparticles. However, smaller reduction was observed in the case of PE/SEBS-MA/ZnO nanocomposites due to improved nanoparticles dispersion. Finally, PE/SEBS-MA/ZnO nanocomposites featured enhanced mechanical flexibility when compared to PE/ZnO nanocomposites. [ABSTRACT FROM AUTHOR]

• The BaFe 2 O 4 nanoparticles were synthesized by microwave hydrothermal technique. • The BaFe 2 O 4 nanoparticles were doped into the PiBMA polymer via solution casting. • The increased free volume suggests the reduced packing density of the PiBMA matrix. • The enhanced electrochemical peak current indicates porous pathways formation. Barium monoferrite (BaFe 2 O 4) nanoparticles of average size 60 nm were synthesized by microwave hydrothermal technique. The films of Poly(isobutyl methacrylate) (PiBMA)/ Barium monoferrite (BaFe 2 O 4) with different BaFe 2 O 4 nanoparticles wt.% are prepared by the solution casting technique. The increased free volume (V f) of PiBMA/BaFe 2 O 4 polymer nanodielectrics at lower wt.% of BaFe 2 O 4 nanoparticle loading suggests the reduction of overall packing density in the PiBMA polymer matrix. The XRD results suggest the weakening of crystallization of PiBMA polymer chains with BaFe 2 O 4 nanoparticles wt.%. The increased mobility of Ba2+, Fe2+and O2– ions are responsible for the enhancement of AC conductivity (σ ac) in PiBMA/BaFe 2 O 4 polymer nanodielectrics. The increased dielectric constant in PiBMA/BaFe 2 O 4 polymer nanodielectrics up to 0.6 wt% is attributed to the increased interfacial and orientation polarization. The enhanced electrochemical peak current and specific capacitance for 0.6 wt% of BaFe 2 O 4 nanofiller loading indicate the formation of porous pathways in PiBMA/BaFe 2 O 4 polymer nanodielectrics. [ABSTRACT FROM AUTHOR]

The performance of polymeric insulation will be distorted by the accumulation of space charge. This will lead to local electric field enhancement within the insulation material that can cause degradation and electrical breakdown. The introduction of nanofillers in the insulation material is expected to reduce the space charge effect. However, there is a need to analyze potential nanofillers to determine the best option. Therefore, the objective of this research work is to examine two types of nanofillers for Cross-Linked Polyethylene (XLPE); Zinc Oxide (ZnO) and Acrylic (PA40). The effects of these nanofillers were measured using the Pulsed-Electro Acoustic (PEA) method. The development of space charge is observed at three different DC voltage levels in room temperature. The results show that hetero charge distribution is dominant in pure XLPE materials. The use of both nanofiller types have significant effect in decreasing the space charge accumulation. With nanofillers, the charge profile changed to homo-charge distribution, suppressing the space charge formation. Comparison between both the nanofillers show that PA40 has better suppression performance than ZnO. [ABSTRACT FROM AUTHOR]

Extruded polymeric HVDC cables have drawn great attention in modern power systems. This paper reviews the history and development of the polymeric HVDC cables and summarizes the key technical problems in extruded HVDC cables. It is pointed out that two key issues should be solved. One is the electric field inversion within HVDC cable insulation which is caused by the temperature and electric field dependent DC volume resistivity of the polymeric insulation materials. The other is the space charge behavior under multi-fields coupling, including charge injection, transportation, accumulation and dissipation characteristics. The following aspects need to be particularly concerned in the future: the interaction between temperature, electric field, space charge and DC volume resistivity under multi-fields coupling; mechanisms of nanoparticles doping on enhancing the properties of polymeric insulation material; the long-term operation characteristics of nanodielectrics; collaborative optimal regulation methods and theories on the properties of polymeric insulation material; and recyclable insulation materials for future HVDC cables. [ABSTRACT FROM PUBLISHER]

Zinc oxide nanoparticles (ZnO NPs), with wurtzite structure, were synthesized using sol-gel route. Both the microstructure and morphology of the synthesized ZnO NPs were examined using X-ray diffraction, Fourier transform infrared and high-resolution transmission electron microscopy. The synthesized ZnO NPs up to 5 wt% were introduced to high density polyethylene (HDPE) using melt blending technique. The dielectric properties of the fabricated HDPE/ZnO nanocomposites were studied by measuring the dc dielectric breakdown strength at constant 1 kV/s ramp. The dielectric strength values were showed ZnO nanofiller concentration dependency. Enhancement in breakdown strength has been observed with addition of ZnO NPs and reached to 17 ± 3.1 % (for HDPE/1 wt% ZnO) with respect to the pure HDPE sample. The real part of the permittivity ( $$\varepsilon^{\prime }$$ ) and the loss tangent ( $$\tan \delta$$ ) dependency on filler concentration was studied under different applied frequency values from 1 kHz to 1 MHz. As well as the variation of the dielectric parameters ( $$\varepsilon^{\prime }$$ and $$\tan \delta$$ ) was studied throughout temperature range from room temperature to 120 °C. Graphical Abstract: [ABSTRACT FROM AUTHOR]

In this report, we studied dielectric loss mechanisms in a 1–3 type of polymer nanocomposites, i.e., nanofibers or nanotubes in a polymer matrix. Sodium titanate nanotubes (TiNTs, 8–10 nm outer diameter and 300–500 nm long), which were synthesized by the hydrothermal method, were used as the fillers. The polymer matrix was a high permittivity relaxor ferroelectric polymer, poly(vinylidene fluoride- co -trifluoroethylene- co -chlorotrifluoroethylene). The nanocomposites were fabricated using solution-blending followed by hot-pressing above the melting temperature. Because of the high aspect ratio of TiNT fillers, the percolation threshold was found to be around 10–12.5 vol%. Below the percolation threshold, significant dielectric losses (both linear and nonlinear) were identified using bipolar and unipolar electric displacement – electric field (D-E) loop tests. For aggregated/percolated TiNTs, external electronic conduction was the major linear dielectric loss. For isolated TiNTs, internal electronic conduction contributed significantly to the nonlinear dielectric loss. From this study, we conclude that it is better to develop highly insulating nanofibers or nanotubes for the 1–3 type polymer nanodielectrics and the nanofillers content should be kept far below the percolation threshold in order to avoid significant dielectric losses. [ABSTRACT FROM AUTHOR]

The electrical conduction and dielectric breakdown of polyimide/boron nitride (PI/BN) are investigated in a large temperature range up to 350 °C. This work shows that BN nanofillers act as deep traps for mobile ions. Below 150 °C, the nanostructuration of PI slightly improves the DC conductivity and the breakdown field. On the contrary above 150 °C, while neat PI exhibits ionic space charge contribution on the charging currents, PI/BN nanocomposites show a return to normal polarization currents. In such combined high field and high temperature ranges, the nanostructuration of PI allows increasing the mean free path of ions by decreasing the ionic hopping distance. The consequence of the improvement of the total trap density is a huge decrease (5 orders of magnitude) in the steady state currents and an increase (factor 2) in the breakdown field of PI/BN. This study proves the possibility to extend both the electric field and temperature ranges of PI films thanks to an adequate nanostructuration. [ABSTRACT FROM PUBLISHER]

We use a recently developed scanning probe technique to image with high spatial resolution the injection and extraction of charge around individual surface-modified aluminum oxide nanoparticles embedded in a low-density polyethylene (LDPE) matrix. We find that the experimental results are consistent with a simple band structure model where localized electronic states are available in the band gap (trap states) in the vicinity of the nanoparticles. This work offers experimental support to a previously proposed mechanism for enhanced insulating properties of nanocomposite LDPE and provides a powerful experimental tool to further investigate such properties. [ABSTRACT FROM AUTHOR]

BaSrTiO 3 /epoxy resin nanocomposites were prepared in a wide range of filler concentrations. Electron microscopy images demonstrated fine dispersion of the nanoinclusions. Variation of glass transition temperature with particles concentration was determined via differential scanning calorimetry. Three relaxation processes were detected in the dielectric spectra, namely interfacial polarization, glass to rubber transition of the matrix (α-relaxation), and re-arrangement of polar side groups (β-relaxation). Nanofiller content affect the dielectric and thermal response of the composites via the particle-polymer and particle–particle interactions. At low filler content, reduction of the macromolecular mobility causes a decrease of permittivity and an enhancement of glass transition temperature. At intermediate filler content, interparticle interactions appear to dominate, leading to altered polymer flexibility, higher permittivity and lower glass transition temperature. At high filler loading, glass transition temperature increases in tandem with permittivity because of the limited macromolecular mobility, and the high permittivity of the particles. Systems’ performance can be interpreted by a three “filler load zones” model. [ABSTRACT FROM AUTHOR]