IET Nanodielectrics最新文献

The fibrids in aramid insulation paper exhibit good adhesion ability. However, the effects of fibrids morphology on the mechanical and electrical properties of aramid insulation paper remains poorly understood. Aramid fibrids with different morphological structures were prepared by modifying the preparation process, and then they were used to fabricate aramid composite insulation paper under the same condition. The results showed that increasing the shear rate and aramid solution concentration affected the magnitude of the shear force and double diffusion process, thus affecting the average length, specific surface area, and crystallinity of the fibrids. When the rotor frequency is 25–30 Hz and the solution concentration is 15%, the fibrid has a large specific surface area while ensuring high crystallinity, which is beneficial to the improvement of breakdown strength. When the average length of fibrids is 0.8–1.4 mm, the fine content is 1.3%–2.3%, specific surface area is 57.5–62 m² g⁻¹, and crystallinity is 18.5%–27%, the aramid composite insulation paper has the optimal mechanical and electrical properties. Combined with the micromorphology test results, the influence mechanism of fibrids properties on the mechanical properties, dielectric properties, and AC and DC breakdown strength of aramid composite insulation paper was obtained. The result is of great theoretical significance and practical value for the preparation and application of high-performance aramid composite insulation paper.

Self-healing polyurethane diacrylate (PUDA) composites with outstanding thermal conductivity were prepared with variable boron nitride (BN) and a small number of graphene nanoplatelets (GNPs) (1 wt%). The thermal conductivity of PUDA composites containing 1 wt% GNPs and 29 wt% BN reached 1.73 W/(m·K), showing 27.2% increment compared to PUDA composites only with 30 wt% BN. BN and GNPs mutually promoted the dispersion in the PUDA matrix, and the small number of GNPs was enough to bridge the gaps between BN, so that GNPs and BN exerted a synergistic enhancement effect on the thermal conductivity of PUDA composites with a synergistic efficiency of 1.343. The PUDA composites maintained the tensile strength of 8.21 MPa with good electrical insulation (4.55 × 10⁹ Ω cm). The high degrees of recovery of mechanical strength (>90%) and thermal conductivities (>84%) were also realised by the healing effect of the reversible DA reaction. The PUDA composites with excellent comprehensive properties show broad application potential in the thermal management of electronic devices.

High conductivity loss and low breakdown strength of traditional polypropylene (PP) film in the high-temperature environment are the key factors limiting the application of metallised film capacitors (MFCs). The effect of cyclic olefin copolymers (COCs) with different glass transition temperatures (Tgs) on the dielectric performance of PP/COC composites at high temperature are studied. The results showed that the addition of COC enhanced the intermolecular interaction force, which led to the reduction of defects in the films. In addition, COC with high Tg inhibits the movement of molecular chains and enhances the thermal stability of the film, which limits the transport of carriers at high temperatures. The conductivity and breakdown strength of the modified films (with a Tg of 134°C for COC) at 125°C are 91.6% lower and 45.7% higher, respectively, than that of pure PP. This method shows great potential in improving the dielectric properties of PP at high temperatures.

Film capacitors are playing an increasingly important role in power-related fields, driven by the continuous development of dielectric materials and practical needs. Long-term accumulation has also led to an increasing wealth of data related to film capacitors. Sonification opens up a new way for people to make good use of data from film capacitors. A framework for sonifying film capacitors data based on TwoTone is presented. Based on the analysis and discussion, it is clear that the sonification results can easily represent the monotonic variation pattern of film capacitors data. What's more, the sonification results increase the possibility that people pay attention to the changing trend of film capacitors data when there is no significant difference in the visual perception of the data. In addition to providing a new way of music generation of electrical equipment, the method proposed is expected to contribute to theory reference in typical scenarios, such as factory calibration of film capacitors, monitoring of film capacitor operation status, and presentation of statistical data of film capacitors' dielectric materials, which will help us to better understand the distribution characteristics of polymer films.

Mechanical antennas have garnered considerable attention due to their ability to address the challenges posed by the significant size and high energy consumption associated with traditional electric antennas when operating at low frequencies. Here, a compact and structurally stable mechanical antenna design is presented. The proposed antenna is constructed using cylindrical piezoelectric ceramics, which have dimensions smaller than 1/1000 of the wavelength. The scrutiny of the influence exerted by the antenna feed area and material thickness on the radiation performance was undertaken, followed by an exhaustive discourse on these effects. Experimental measurements demonstrate the practical functionalities of signal coding, transmission, and reception in the low-frequency communication system. Notably, at a frequency of 288 kHz, a single proposed antenna achieves an effective information transmission distance of 60 m using binary information coding. This remarkable outcome underscores the potential of this design in facilitating the development of portable and cost-effective wireless communication equipment for low-frequency applications.

Growing and controlling the c-axis orientation of the aluminium nitride (AlN) thin film on unheated Si (111) substrates using reactive magnetron sputtering are challenging. Sputtering parameters such as nitrogen concentration and sputtering power were effectively tuned to grow the c-axis oriented AlN thin film. The results show that a low concentration of (25%) N₂ is enough for forming AlN at a reduced flow rate, whereas a higher flow rate requires a higher concentration of N₂. Low concentration with a low flow rate is preferred to grow AlN at low temperature and power. The poor crystallinity of AlN with (100) orientation was improved by varying the power from 75 to 175 W. The X-ray diffraction results confirmed the improvisation of crystallinity of grown AlN films and indicated the strong dependence of preferred c-axis orientation on sputtering power. Also, the dependence of sputtering power on microstrain and stress was analysed. The surface morphology study by field emission scanning electron microscopy and topography measured by an atomic force microscope shows a dependence on sputtering power. The high c-axis orientation was observed at 175 W with low surface roughness, low leakage current density (2 × 10⁻⁹ A/cm²) and low dielectric constant (6.8).

Polyvinylidene fluoride-based ferroelectric polymers are favoured in the field of advanced high-energy-storage dielectric capacitors due to their strong spontaneous polarisation and high dielectric constant (ε_r). It has been confirmed that the ferroelectric behaviour and energy storage performance can be regulated by copolymerising polyvinylidene fluoride with bulky monomers such as chlorotrifluoroethylene, and hexafluoropropylene. Past research based on these copolymers mostly focused on the preparation of composites, yet with limited discussion on the effect of copolymer composition. In this work, a series of P(VDF-CTFE) films with different chlorotrifluoroethylene contents were fabricated through a solution-casting method. The introduction of bulky chlorotrifluoroethylene units can tune the polymer crystal structure and crystallinity, alter the state of polymer chains and the response of dipoles to electric fields, and lead to dramatic changes in dielectric properties, breakdown strength (E_b), and energy storage density (U_e). As a result, the copolymer with a chlorotrifluoroethylene content of 15 wt% obtained the best overall performance, and the U_e reached 16.73 J/cm³ at 650 kV/mm. This work provides a basis for the optimisation of the properties of polyvinylidene fluoride-based ferroelectric polymers and the development of high U_e dielectric.

A flexible smart coating with electroluminescence effect was designed and fabricated on the surface of gas insulated switch gear (GIS)/gas insulated transmission line (GIL) epoxy insulators based on two-step curing process. As the AC voltage increases, the luminous area on the insulator surface expands from the centre to the periphery, and the light intensity shows a linear relationship with the applied voltage. Besides, the flexible smart coating can effectively identify the location of metal particle defects and the degree of electric field distortion. The flexible smart coating enhances the surface flashover voltage due to its higher dielectric constant. Simultaneously, metal particle contamination can substantially reduce the insulation performance of epoxy insulators, particularly when they are located near the high-voltage side. It is hoped that this study can provide a reference for the smart detection of surface defects GIS/GIL basin insulators.

With an increasing demand for environmentally friendly refrigeration, the solid-state refrigeration based on the electrocaloric effect (ECE) has been drawn extensive attention. It is a challenge to maintain a large adiabatic temperature change (∆T) over a broad temperature span. Herein, the authors designed and synthesised (0.74-x) Na_0.5Bi_0.5TiO₃-0.06BaTiO₃-0.2SrTiO₃-xBi(Mg_0.5Zr_0.5)O₃ (abbreviated as NBT-xBMZ) (x = 0, 0.02, 0.04, 0.06 and 0.08) lead-free relaxor ferroelectrics. Their microstructures, dielectric properties, ferroelectric properties, ECEs and the structure-property relationships were investigated. Via doping with BMZ, an enhanced relaxor feature and a wider temperature range where multi-phases coexist were achieved. The relaxor ferroelectric characteristics were illustrated using the Vogel-Fulcher relation. The indirectly calculated ECE results showed that the optimal ΔT of 1.11 K was obtained for the x = 0.02 sample at 90°C and 70 kV/cm over a wide T_span of 120°C, providing a potential ECE material. The direct ECE results procured using thermocouple indicated that the maximal ∆T of 2.14 K and ∆T/∆E of 0.31 K m/MV were achieved in the same sample at 70°C and 7 MV/m and the variation trend of ECE results was consistent with the indirect results. Moreover, the multi-phases coexistent strategy can be extended to other materials system to generate a large ΔT over a wide temperature range.

The demand for innovative thermal management materials with superior thermal conductivity and electrical insulating properties has significantly increased with the development of portable and flexible electronic gadgets. Fluorinated graphene (FG) has recently attracted the attention of the scientific community because of its exceptional thermal conductivity and electrical insulating qualities. This work aims to provide a detailed analysis of the structure-property relationships inherent in FG, including both chemical and physical properties, and to explain the FG manufacturing process. Special attention should be paid to a thorough analysis of the thermodynamic conduction mechanism exhibited by FG, including the effects of corrugation size, fluorine coverage, and fluorine atom distribution on its thermal conductivity. The essay also examines in-depth the most current and cutting-edge developments addressing the utilisation of FG as a functional filler in composite-modified polyimide (PI) materials. Furthermore, it has been noted as a crucial component in answering the needs for possible applications by maximising thermal conductivity and mechanical qualities in FG/PI composites through particular FG structural engineering and increased FG-PI interaction. As a result, these elements serve as the main focus of ongoing research projects, highlighting important directions for development and investigation.