IET Nanodielectrics最新文献

Dielectric elastomers (DEs) could transduce electrical energy to mechanical energy, but their applications are currently limited by the elevated driving voltages. To obtain satisfactory actuated strains at low voltages, titanate oxide@tannic acid-ferric ion@silver (labelled as TiO₂@TA-Fe³⁺@Ag) satellite-structure nanoparticles were obtained in this study by in situ synthesis followed by incorporating the nanoparticles into natural rubber (NR) to prepare DE composites (denoted as TiO₂@TA-Fe³⁺@Ag/NR). The presence of surface coating of TA-Fe³⁺ and Ag nanoparticles improved the electromechanical performance of TiO₂@TA-Fe³⁺@Ag/NR composites. Among the samples, 30 wt% TiO₂@TA-Fe³⁺@Ag/NR composite displayed a relatively high actuated strain of 9.09% at a relatively low electric field of 22.78 kV/mm. In sum, the green, facile, and cost-effective surface modification method looks promising for improving the electromechanical properties of particulate-filled polymer composites.

Polymer-based dielectrics are extensively applied in various electrical and electronic devices such as capacitors, power transmission cables and microchips, in which a variety of distinct performances such as the dielectric and thermal properties are desired. To fulfil these properties, the emerging machine learning (ML) technique has been used to establish a surrogate model for the structure–property linkage analysis, which provides an effective tool for the rational design of the chemical and morphological structure of polymers/nanocomposites. In this article, the authors reviewed the recent progress in the ML algorithms and their applications in the rational design of polymer-based dielectrics. The main routes for collecting training data including online libraries, experiments and high-throughput computations are first summarized. The fingerprints charactering the microstructures of polymers/nanocomposites are presented, followed by the illustration of ML models to establish a mapping between the fingerprinted input and the target properties. Further, inverse design methods such as evolution searching strategies and generative models are described, which are exploited to accelerate the discovery of new polymer-based dielectrics. Moreover, structure–property linkage analysis techniques such as Pearson correlation calculation, decision-tree-based methods and interpretable neural networks are summarized to identify the key features affecting the target properties. The future development prospects of the ML-driven design method for polymer-based dielectrics are also presented in this review.

The importance of surface roughness with respect to the bulk properties of dielectric materials is often overlooked. Surface roughness or interfaces between different material layers often significantly affects the external properties of thin films. Surface roughness holds its commonalty and critical impact among many materials properties. This review summarises the recent work on the effect of surface roughness on the mechanical, thermal, physical, and dielectric properties of dielectric films. Appropriate roughness favours adhesion, filtration, biological fouling, tribological properties, and magnetic properties. Nevertheless, lower roughness generally benefits the dielectric properties of dielectric materials, with thicknesses ranging from a few nanometres to up to 50 μm. This review discusses surface roughness control and the techniques of measurement as well. It emphasises the importance and characterisation of sample surface roughness for a better understanding of the dielectric phenomenon, mechanisms, and electrical stress test setup for various dielectric films.

The polyaniline/graphite oxide (PANI/GO) nanocomposite was prepared by the in situ chemical polymerisation method. The synthesis involved the formation of dark green coloured polyaniline/graphite oxide composite. The crystalline structure and morphology of the composite were studied using UV-visible spectroscopy (UV), X-ray diffraction (XRD) and transmission electron microscopy (TEM).The characteristic peaks in XRD and UV-visible spectra confirmed the formation of the PANI/GO nanocomposite. DC conductivity measurements were performed using a two-probe method. Dielectric responses of the composites were investigated in the frequency range100 MHz to 3 GHz by the RF impedance analyser. The dielectric constant ϵ′(w) and dielectric loss ϵ′′(w) were investigated. It was observed that the dielectric constant ϵ′(w) and dielectric loss ϵ′′(w) decreased with an increase in frequencies (for different wt % of GO). The antibacterial activity of this composite was examined.

Dielectric capacitors play an important role in advanced electronic and power systems such as portable electronic devices, hybrid electric vehicles and electronic weapon systems, and the improvement of energy storage density will have a positive effect on reducing the volume and weight of equipment. Here, a series of single-layer dielectrics with boron nitride nanosheets (BNNSs) uniformly dispersed and multilayer dielectrics with BNNSs showing a positive gradient distribution (PGD) and inverse gradient distribution (IGD) in the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P[VDF-TrFE-CTFE]) matrix were prepared by high-speed electrospinning and hot press technology. It is found that the best performance is observed inthe lowest interlayer gradient component in both PGD and IGD composite dielectrics. However, the performance of PGD is better than that of IGD, and the 3-5-3 multilayer dielectric in the positive gradient structure has the best electrical performance. Its maximum energy storage density of the 3-5-3 composite dielectrics is 12.93 J/cm³ at the applied electric field of 380 kV/mm. The above research results show that the gradient structure design plays an important role in optimising the breakdown strength and energy storage characteristics of composite dielectrics.

Integrated energy-generating and storage films are able to convert mechanical force into stored electrical energy, with the potential for use in self-powered wearable electronics and flexible energy supplies. The development of a transparent metal salt/polyvinylidene fluoride–hexafluoropropylene composite film is reported that possesses excellent piezoelectric and dielectric properties and has the potential to be employed as an energy-generating and preserving integrated film. The effects of the type of the metal salt and its content on the dielectric properties, d₃₃ value, open circuit voltage, and holding time of the composite films were investigated. Owing to the presence of pure water, the β-phase composition and polarization of the film are increased, leading to improved energy conversion properties. Most important, the prepared film exhibits excellent light transmittance. This film, which possesses both good electrical and transparent properties, has the potential for use as a flexible energy supplier, particularly for photovoltaic devices.

Polymer dielectrics have drawn great attentions for applications in advanced electronic devices and power grids because of their high breakdown strength, low dielectric loss, and excellent flexibility. However, the low energy density in polymer dielectric capacitors will hinder the continuous miniaturization of electrical systems. In this work, ultraviolet irradiation is demonstrated to greatly enhance the breakdown strength and energy density of polypropylene. Dramatically improved breakdown strength of 867 MV/m and discharged energy density of 8.0 J/cm³, together with the high energy efficiency of >90%, were simultaneously achieved in polypropylene after ultraviolet irradiation. Our research shows that proper ultraviolet irradiation can effectively improve the energy density of polypropylene without sacrificing its high charge-discharge efficiency, being potential for applications in power electronics and pulse electric systems.

Graphene has attracted scientific interest as a substrate or additive for developing high-performance stimuli-responsive materials. Research on graphene-based polymer dielectric composites has shown an enhanced electroresponsive electrorheological (ER) effect. However, the mechanism behind the enhanced electroresponse is still incompletely understood. Here, an investigation was performed into dielectric polarization and the ER effect of reduced graphene oxide-supported polyaniline nanoplates by comparing them with pure granular polyaniline and graphene oxide-supported polyaniline nanoplates based on dielectric spectroscopy and rheologic analysis. We discovered that both anisotropic morphology and electrical properties have dominant roles in the enhanced ER effect of reduced graphene oxide-supported polyaniline nanoplates, whereas only anisotropic morphology has a dominant role in the enhanced ER effect of graphene oxide-supported polyaniline nanoplates. The analysis also showed that reduced graphene oxide-supported polyaniline nanoplates have a good ER response to both DC and AC electric field actions in the wide shear rate region. This is highly desirable for practical engineering applications. Therefore, the analysis reveals the reason for the enhanced ER effect of reduced graphene oxide-supported polyaniline nanoplates and also may provide a guide for designing high-performance ER materials for practical engineering applications by combining the advantages of conducting a reduced graphene oxide core and ER active shell.