IET Nanodielectrics最新文献

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.

A series of siloxane-containing polyimide films (PIS) were prepared by copolymerising with rigid aromatic dianhydride, siloxane diamines and six different aromatic diamines. The effects of siloxane structures, fluorine and imide content, rigid or flexible segment on the heat resistance, moisture absorption, dielectric performance, mechanical and bonding properties were systematically studied. The results show that PIS films maintain good heat resistance with T_g between 292 and 420°C and 5% weight loss temperature higher than 500°C. The moisture absorption and dielectric constant can be significantly reduced due to the presence of siloxanes and fluorinated groups, with the absorption rate as low as 1.2% and dielectric constant of 2.85 at 1 MHz. When measured at 10 GHz, the dielectric constant ranges from 3.10 to 3.50, and dielectric loss varies from 0.0059 to 0.0098. The PIS-6 film has the best comprehensive performance due to the low imide content, introduction of trifluoromethyl and ether bonds. The peeling strength of bonding PIS-6 film with a copper foil can reach 9.2 N/cm. It is proven that siloxane-containing PIS films with high heat resistance, low dielectric and outstanding adhesion are achieved, which can be applied for flexible integrated circuit boards, high-frequency electronics and microelectronics fields.

With a large number of film capacitors being deployed in critical locations in electrical and electronic systems, artificial intelligence (AI) technology is also expected to address the problems encountered in this process. According to our findings, AI applications can cover the entire lifecycle of film capacitors. However, the AI safety hazards in these applications have not received the attention they deserve. To meet this, the authors argue, with specific examples, risks that flawed, erratic, and unethical AI can introduce in the design, operation, and evaluation of film capacitors. Human-AI common impact and more multi-dimensional evaluation for AI are proposed to better cope with unknown, ambiguity, and known risks brought from AI in film capacitors now and in the future.

This article deals with the improvement of the dielectric properties of TUK cellulose paper by impregnation. The experiment was carried out using a nanofluid based on vegetable oil esters and iron nanoparticles (FeO₃). The insulating liquids used are palm kernel oil methyl ester (PKOME) and castor oil methyl ester (COME). The evaluation of the improvement is based on the analysis of the flashover voltage of the creeping discharges produced on the immersed paper. The tests were carried out under a positive lightning impulse voltage and for two electrode configurations. The concentrations of nanoparticles used in the experiment are 0.10 wt.%, 0.15 wt.% and 0.20 wt.%. The experimental results show that the 0.10 wt.% concentration gives the best improvement for the two electrode configurations used. The improvements are 53% for the inclined tip and 56.90% for the vertical tip in the case of COME + FeO₃. For PKOME + FeO₃, the results are 59.90% and 64.60%, respectively, for the two configurations.

Continuous three-dimensional BaTiO₃ (3DBT) ceramic network was prepared by the sol-gel method using cleanroom wipers as the template. Subsequently, flexible 3DBT/polyvinyl alcohol-boron nitride nanosheets (PVA-BNNS) composite dielectric films were facilely fabricated by inversely introducing different BNNS concentrations of PVA-BNNS solution into the 3DBT network. The results demonstrated that PVA solution effectively embedded into the 3DBT framework through an inverse infiltration process, thereby endowing the material with excellent flexibility. The content of 3DBT in the saturated 3DBT/PVA-BNNS composite was ∼27 wt% (6.9 vol%). In addition, the 3DBT/PVA-1.0%BNNS system exhibited an excellent dielectric constant of 17.4 (at 1 kHz), a high breakdown strength of 114.5 kV·mm⁻¹ and an energy density of 2.51 J·cm⁻³ (at 110 kV·mm⁻¹), being 1.67, 1.58 and 7.17 times higher than those of traditional fabricated 27 wt% nano-BT/PVA (at 70 kV·mm⁻¹) composite, respectively. What's more, the obtained 3DBT/PVA-BNNS dielectric film exhibited superior thermal and mechanical stability, indicating potential applications in harsh environments.