Excellent Dielectric Strength Research Articles

Synergistically Constructing High-Dielectric Poly(m-phenylene isophthalamide)/Silica/Cellulose Nanofiber Composite Insulation Paper through Dynamic Covalent Chemistry and Hydrogen Bonding.

The rapid advancement of modern power equipment and high-power devices has imposed increasingly stringent demands upon the mechanical and dielectric properties of electrical insulation materials. Herein, we report a poly(m-phenylene isophthalamide) (PMIA) composite insulating paper with excellent dielectric breakdown strength, reliable mechanical properties, and high thermal stability. Enhanced surface activity of PMIA is achieved through surface modification, facilitating the synergistic integration of modified PMIA (MPMIA), bovine serum albumin (BSA)/silica (SiO2), and cellulose nanofiber (CNF) into composite paper using dynamic covalent bonds and hydrogen bonding. The prepared MPMIA-BSA/SiO2-CNF composite paper exhibits a laminated stacked structure with high tensile strength (32.68 MPa) and strain at break (9.57%). Meanwhile, MPMIA-BSA/SiO2-CNF composites have excellent dielectric breakdown strength (24.75 kV/mm) and good temperature resistance. Therefore, the MPMIA-BSA/SiO2-CNF composite paper has a broad application prospect in the field of high-voltage and high-power electrical equipment insulation.

Current Trends in Liquid Crystal Polymers and Their Applications: A Review

Liquid crystal polymers (LCPs) are now highly focused by researchers due to their improved thermal properties, mechanical strength, excellent dielectric strength, resistance to solvents, better dimensional stability, and gas barrier properties. LCPs can be used in valuable widespread applications such as energy storage, high-performance polymer fibers, actuators, information technologies, surface modification, shape memory materials, data storage, fiber optics, the medical field, electrical or electronics devices, aircraft, chemical, domestic equipment, ultra-high-strength fibers, biosensing, advanced communication systems, satellite systems, biosensing, bio-oscillators, and bioprocess monitoring. LCPs can self-assemble into different liquid crystalline phases like nematic, cholesteric, smectic, and columnar phases. The self-assembling structures of LCPs can be affected by the chemical and structural structures of the backbone of the polymeric material, nearby alkyl tails, mesogenic units, flexible spacers, etc. Depending on the mesogenic units in their molecular architecture, LCPs are basically classified into various categories, such as crosslinked, main chain, and sidechain. Again, they are also classified as cholesteric, nematic, and smectic mesophases. This paper provides a fundamental understanding, an informative overview, and details of structural aspects, properties, classification, commercial aspects, and applications of LCPs.

Tungsten-bronze-type BaNd2Ti4O12 ceramics with high permittivity and ultra-low dielectric loss under low frequency

High dielectric constant and ultra-low dielectric loss are important for electronic device applications of dielectrics. In this work, the novel ceramic BaNd2Ti4O12, synthesized via solid-state reaction, exhibits remarkable dielectric stability, with excellent dielectric properties (ε′ = 117 and tanδ = 6.27 × 10−4, at 1 kHz) and high dielectric strength (Eb = 260 kV/cm). By exploring its polarization behavior and loss mechanisms at low frequencies for the first time, we found that the sustained high dielectric constant is attributed to the synergy of defect dipole polarization and interface polarization, while the observed exponential increase of dielectric loss is primarily caused by the conduction loss, with a minor contribution from the anelastic relaxation loss. In the low-temperature range of 50∼350 °C, the relaxation behavior is governed by the aggregation and subsequent thermal ionization of the oxygen vacancies, whereas at temperatures above 350 °C, it is predominated by the long-range motion of the doubly ionized oxygen vacancies. These findings provide valuable insights for the potential electronic device applications of BaNd2Ti4O12.

Low-Temperature Deposition of Diamond Films by MPCVD with Graphite Paste Additive

Modern integrated circuits (ICs) take advantage of three-dimensional (3D) nanostructures in devices and interconnects to achieve high-speed and ultra-low-power performance. The choice of electrical insulation materials with excellent dielectric strength, electrical resistivity, strong mechanical strength, and high thermal conductivity becomes critical. Diamond possesses these properties and is recently recognized as a promising dielectric material for the fabrication of advanced ICs, which are sensitive to detrimental high-temperature processes. Therefore, a high-rate low-temperature deposition technique for large-grain, high-quality diamond films of the thickness of a few tens to a few hundred nanometers is desirable. The diamond growth rate by microwave plasma chemical vapor deposition (MPCVD) decreases rapidly with lowering substrate temperature. In addition, the thermal conductivity of non-diamond carbon is much lower than that of diamond. Furthermore, a small-grain diamond film suffers from poor thermal conductivity due to frequent phonon scattering at grain boundaries. This paper reports a novel MPCVD process aiming at high growth rate, large grain size, and high sp3/sp2 ratio for diamond films deposited on silicon. Graphite paste containing nanoscale graphite and oxy-hydrocarbon binder and solvent vaporizes and mixes with gas feeds of hydrogen, methane, and carbon dioxide to form plasma. Rapid diamond growth of diamond seeds at 450 °C by the plasma results in large-grained diamond films on silicon at a high deposition rate of 200 nm/h.

Trilayer structured ceramic/polymer nanocomposites with superior breakdown strength and discharged energy density

The excellent dielectric constant (εr) and breakdown strength (Eb) of dielectric nanocomposites are the necessary conditions for their excellent energy storage properties (ESPs) in microelectronics and power systems. In recent years, inorganic nanofillers and multilayer structure design have provided an efficient way to improve the ESPs of dielectric composites. Herein, we selected 0.8Bi0.5(Na0.82K0.18)0.5TiO3-0.2Sr(Sc0.5Nb0.5)O3 cecamic nanoparticles (BNKT-SSN NPs) with high εr and low loss as nanofillers, and prepare novel trilayer structured BNKT-SSN/P(VDF-HFP) nanocomposites to improve the εr and Eb. The investigated phenomena demonstrate that due to the contribution of BNKT-SSN NPs incorporation and interfacial polarization between neighboring layers, the εr and Eb of the trilayer structured BNKT-SSN/P(VDF-HFP) nanocomposites are enhanced while the dielectric loss (tanδ) and leakage current density are suppressed. It is worth noting that the Eb is measured up to 650 MV m−1 when the intermediate layer fillers BNKT-SSN NPs of the trilayer structured nanocomposite is 0.75 vol%, and the discharged energy density (Ud) and energy efficiency (η) are 25.79 J cm−3 and 70.07 %, respectively. In this work, it's demonstrates that the incorporation of inorganic ceramic fillers and the trilayer structured design provide a feasible approach of improving the ESPs of dielectric nanocomposites.

Mechanism of the effect of Al and Sr substitution on the electrical resistance in CaCu3Ti4O12 ceramics

To investigate the mechanism of Al and Sr substitution on grain resistance (Rg) and grain boundary resistance (Rgb) in CaCu3Ti4O12 (CCTO) ceramics, various compositions of Ca1-xSrxCu3Ti4-yAlyO12 (x = y = 0; x = 0, y = 0.04; x = 0.6, y = 0; x = 0.6, y = 0.04) ceramics were synthesized. All samples exhibited excellent dielectric loss and breakdown field strength performance. These improvements can be attributed to the substantial rise in Rgb and an unconventional boost in Rg. Activation energy tests and X-ray photoelectron spectroscopy analysis indicate that both Rgb and Rg are strongly influenced by oxygen vacancies (V•• O) and the mixed structures of Cu+/Cu2+ and Ti3+/Ti4+. This study explains the mechanism of Al and Sr substitution based on atomic electronegativity, with Al inhibiting the formation of Cu+ and Ti3+ but promoting the generation of V•• O, while Sr inhibiting the formation of Ti3+ and V•• O but promoting the generation of Cu+. This research offers valuable theoretical instructive for the design of high-resistivity CCTO ceramics.

Research progress and prospect of polymer dielectrics

With the increasing demand for energy, how to store and release energy efficiently and stably has become an urgent research topic. Polymer dielectrics have become a kind of ideal dielectric materials in electrostatic capacitors for energy storage due to their advantages of light weight, easy fabrication, low cost, and high breakdown strength. It has a wide application prospect in smart power grids, new energy vehicles, pulse power weapons, electromagnetic guns, and lasers. However, existing polymer dielectrics cannot simultaneously possess the characteristics of high energy density, high breakdown field intensity, high charge and discharge efficiency, and low dielectric loss, thus limiting the development of compact, efficient, and reliable electronic power technology. In addition, the inherent thermal/field charge injection, excitation, and transport phenomena of polymer dielectrics make the resistivity and dielectric energy storage properties of polymer dielectrics decrease sharply under the combined action of high temperature and high electric field. In order to optimize the energy storage performance of polymer dielectrics (including room temperature and high temperature dielectrics), it has been obtained excellent dielectric breakdown strength, energy storage density, energy storage charge, and discharge efficiency from polymer nanocomposites, polymer/small molecule composites, polymer/polymer blends, new synthetic polymers, multilayer polymers, and other material systems. Based on these material systems, this review summarizes and compares these material systems, points out their advantages and disadvantages including the key problems, and puts forward suggestions for the future research.

Azide-functionalized ligand enabling organic–inorganic hybrid dielectric for high-performance solution-processed oxide transistors

We propose a highly efficient crosslinking strategy for organic–inorganic hybrid dielectric layers using azide-functionalized acetylacetonate, which covalently connect inorganic particles to polymers, enabling highly efficient inter- and intra-crosslinking of organic and inorganic inclusions, resulting in a dense and defect-free thin-film morphology. From the optimized processing conditions, we obtained an excellent dielectric strength of over 4.0 MV cm−1, a high dielectric constant of ~14, and a low surface energy of 38 mN m−1. We demonstrated the fabrication of exceptionally high-performance, hysteresis-free n-type solution-processed oxide transistors comprising an In2O3/ZnO double layer as an active channel with an electron mobility of over 50 cm2 V−1 s−1, on/off ratio of ~107, subthreshold swing of 108 mV dec−1, and high bias-stress stability. From temperature-dependent I–V analyses combined with charge transport mechanism analyses, we demonstrated that the proposed hybrid dielectric layer provides percolation-limited charge transport for the In2O3/ZnO double layer under field-effect conditions.

Dielectric Properties of Refrigerant Fluids HFO-1336mzz-E, HFC-245fa, and HFE-7100

This article presents the comparison of the dielectric properties of three different refrigerant fluids, HFE-7100, HFC-245fa, and HFO-1336mzz(E) (R-1336E Opteon ME), the latter having a global warming potential of two orders of magnitude lower than the other two. Refrigerant fluids are used, among others, in generator circuit breaker applications where good thermal and chemical properties must be coupled with excellent dielectric strength and low electric conductivity. This article describes in detail the applied measurement techniques and the results obtained, as well as comparisons to previous measurements and literature. The comparison includes dielectric breakdown in liquid and vapor phase, dc conductivity, real permittivity, and dissipation factor.

Polarization-Induced Two-Dimensional electron gas at BeO/ZnO interface

Beryllium oxide (BeO) is a unique metal oxide with excellent thermal conductivity and dielectric strength. BeO tends to grow as wurtzite single crystals via atomic layer deposition, leading to the strong polarization of heterostructures with various substrates. We demonstrated the formation of a polarization-induced two-dimensional electron gas (2DEG) at a BeO/ZnO heterostructure interface. The polarity discontinuity induced by the c-axis-grown crystalline BeO film caused charges to accumulate on the ZnO substrate. The sheet carrier concentration and mobility of the BeO/ZnO heterostructure were 2.0 × 1014 cm−2 and 22 cm2·V−1·s−1 at room temperature, respectively, approximately 57 times and 11 times greater than those of bare ZnO, respectively. In addition, the carrier concentration was nearly constant over the temperature range of 150 K – 350 K. The 2DEG layers formed via ALD BeO films are possible channel materials for use in various electronic devices such as thin film transistors.

Multilayer heterogeneous dielectric films with simultaneously improved dielectric constant and breakdown strength

Due to the development of the microelectronics industry, there is a great demand for flexible polymer dielectrics with simultaneously excellent permittivity and dielectric breakdown strength, so as to realize the prominent dielectric energy storage capability. Here, we prepare sandwich-structure films with ferroelectric dielectric Polyvinylidene Fluoride (PVDF) acting as the top layer, 2D Boron Nitride nanosheets (BNNS) as the middle layer and linear dielectric Polyimide (PI) as the bottom layer. In the films the PVDF ferroelectric layer provides high polarization, the PI linear layer enhances the dielectric breakdown strength and decreases dielectric loss, and the 2D sheet BNNS layer further strengthens the dielectric breakdown insulation. The permittivity of the multilayer films is in the range of 5.0–6.3 and dielectric loss are all below 0.03 at 100 Hz. And the sandwich-structure film with 3 mg/mL BNNS can achieve a highest dielectric energy storage of 4.35 J/cm3 at 417.6 kV/mm, surpassing that of the currently commercial BOPP by about 360 % (≈1.2 J/ cm3 under the electric field of 640 kV/mm). In addition, the multilayer films exhibit satisfactory thermal stability and mechanical properties. The multicomponent heterogeneous layered materials with simultaneously enhanced permittivity and dielectric insulating strength demonstrate a wide application prospect in the field of dielectric energy storage.

Mechanically Strong Electrically Insulated Nanopapers with High UV Resistance Derived from Aramid Nanofibers and Cellulose Nanofibrils.

Aramid nanofibers (ANFs) have great potential for civil and military applications due to their remarkable mechanical modulus, excellent chemical reliability, and superior thermostability. Unfortunately, the weak combination of neighboring ANFs limits the mechanical properties of ANF-based materials owing to their inherent rigidity and chemical inertness. Herein, high-performance nanopapers are fabricated by introducing a tiny amount of cellulose nanofibrils (CNFs) to serve as reinforcing blocks via vacuum filtration. As a result of the formation of nanosized building blocks and hydrogen-bonding interaction of CNFs, the resultant ANF/CNF nanopaper yields a record-high tensile strength (406.43 ± 16.93 MPa) and toughness (86.13 ± 5.22 MJ m-3), which are 1.8 and 4.3 times higher than those of the pure ANF nanopaper, respectively. When normalized by weight, the specific tensile strength of the nanopaper is as high as 307.90 MPa·g-1·cm3, which is even significantly superior to that of titanium alloys (257 MPa·g-1·cm3). The ANF/CNF nanopaper also possesses excellent dielectric strength (53.42 kV mm-1), superior UV-shielding performance (≥99.999% absorption for ultraviolet radiation), and a favorable thermostability (Tonset = 530 °C). This study proposes a new design strategy for developing ultrathin ANF-based nanopapers combined with high reliability and thermostability for application in high-end electrical insulation fields, such as 5G communication, wearable electronics, and artificial intelligence.

Effect of cullet on firing temperature and dielectric properties of porcelain insulator

Porcelain insulators prepared from locally available ceramic materials, such as Hosaena clay, quartz, partially replaced feldspar by cullet (rich in alkaline materials). The physical and electrical properties, such as water absorption, apparent porosity, bulk density, linear shrinkage, and dielectric strength as a function of firing temperature, were evaluated. The XRD and AAS measurement results show Hosaenna clay mainly belongs to kaolinite minerals with a sufficient SiO2 (45.60wt. %), Al2O3 (35.52wt. %), and it possesses reasonable plasticity nature. The SEM and Electrical properties measurement shows the porcelain insulators fired at 1150 °C & 1200 °C showed homogenized primary and secondary mullite with optimum glassy phase and good dielectric strength for practical applications. The primary & secondary mullite and glassy phases were grown early at a firing temperature of 1150 and 1200 °C, due to the partial replacement of feldspar by cullet. The porcelain insulator prepared from the composition of 45%clay, 35%feldspar, 10%quartz and 10%cullet and fired at 1200 °C showed dielectric strength 8.9kv/mm, water absorption (0.459%), apparent porosity (1.530%), bulk density (4.29 g/cm3), and linear shrinkage (4.18%). Therefore, incorporating economic alkaline materials such as cullet to improve the alkalinity of the locally available clay materials, Hosaenna clay, Arero feldspar, and Arero quartz reduces the firing temperature with excellent dielectric strength.

Effect of Cullet on Firing Temperature and Dielectric Properties of Porcelain Insulator

In this study, porcelain insulators produced from locally available ceramic materials, Hosaena clay, Arero feldspar, and Arero quartz and cullet as alkaline materials. The chemical compositions of clay are determined using an atomic absorption spectrometer (AAS). The thermal response, mineralogy, morphology, and plasticity nature of the clay sample measured using TGA/DTA, XRD, SEM, and Atterberg test, respectively. Four test batches were prepared with progressive addition of cullet and sintered in the temperature range of 1100 ─1250°C at 50°C intervals. The physical and electrical properties of fired samples such as water absorption, apparent porosity, bulk density, and linear shrinkage; and dielectric strength as a function of firing temperature evaluated. The XRD and AAS results revealed that Hosaenna clay mainly belongs to kaolinite mineral with a sufficient SiO2 (45.60wt. %) and Al2O3 (35.52wt. %), and it possesses reasonable plasticity nature. The porcelain insulators fired at 1150°C & 1200°C showed homogenized primary and secondary mullets with optimum glassy phase and good dielectric strength for practical applications. The primary & secondary mullets and glassy phases were grown early at a firing temperature of 1150 and 1200°C, due to the partial replacement of feldspar by cullet. The porcelain insulators prepared from the composition of 45%clay, 35%feldspar, 10%quartz and 10%cullet and fired at 1200°C showed dielectric strength 8.9kv/mm, water absorption (0.459%), apparent porosity (1.530%), bulk density (4.29g/cm 3 ), and linear shrinkage (4.18%). Therefore, the addition of economic alkaline materials such as cullet in the locally available clay materials, Hosaenna clay, Arero feldspar, and Arero quartz reduces the firing temperature and with excellent dielectric strength.

Electro-mechanical characterization of alumina-based porcelain insulator doped with BaTiO3 at high temperature with frequency variation

In this article, the doping effect of BaTiO3 (0–2 wt%) on the physical, electro-mechanical and dielectric strength of prepared porcelain insulator were investigated. Green powder samples were sintered at 1350 °C with 2 h soaking time, applying uniaxial pressure techniques with a constant load of 160 MPa. The surface, morphological, elemental and phase analysis characterization was done by using scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD) to recognize the microstructure-surface property relationship of the insulator. Various characterization like physical, electro-mechanical and alternating current (AC) dielectric strength of prepared sintered porcelain composition at 1350 °C were investigated. AC dielectric behavior, conductivity, and resistivity were measured at frequencies ranging from 20 Hz to 1 MHz. AC Dielectric constant and loss value from 2 GHz to 20 GHz with frequency and temperature variation were measured. The highest recorded value of AC dielectric strength for a sample having BT (2 wt%) is 25.75 ± 0.5 kV/mm. The investigated composition having 0.5 wt% showed excellent electro-mechanical and high voltage dielectric strength as compared to the conventional porcelain insulators.

Dielectric properties and discharged energy density of poly(vinylidene fluoride) composites with dopamine-modified PMN-PT particles

Dielectric composites have been witnessed a surge of interest in the past few years for its potential application in energy storage due to their excellent dielectric properties and superior breakdown strength. In this work, PMN-PT particles were modified by dopamine and were used to prepare PMN-PT@Dopa /polyvinylidene fluoride (PVDF) composites. The maximum dielectric constant (er) of composites with PMN-PT particles was 19.25 (1 kHz). The dielectric loss (tanδ) of composites with different volume fraction of PMN-PT was all below 0.03. The discharged energy density (Udis) of composites with 3 vol% PMN-PT@Dopa particles reached 11.07 J/cm3 at 370 kV/mm. The energy efficiency (η) of composites remained 40% at 350 kV/mm. The composite with PMN-PT@Dopa particles exhibited good fatigue endurance after 106 cycles. The results demonstrated that composites with PMN-PT particles possessed potential application in dielectric property and energy storage.

Nacre-like nanocomposite film with excellent dielectric insulation properties and mechanical strength based on montmorillonite nanosheet and aramid nanofiber

Unlike the mechanisms behind their enhanced mechanical properties, application of artificial nacre-like materials has attracted very little attention from scholars. In this study, we designed a unique artificial nacre-like material that integrated outstanding mechanical properties and dielectric insulation properties by assembling MTM nanosheet and aramid nanofiber (ANF) through vacuum-assisted filtration. Compared with other nanocomposite films, the layered ANF/MTM nanocomposite film displayed superior mechanical properties (the tensile strength of ~ 126.5 MPa and elongation at break of ~ 2.56%) and dielectric insulation performance (77.2 kV/mm). In addition, it exhibited good transparency and flexibility. Therefore, this nanocomposite film has great potential for application in flexible electronics and high-voltage electrical insulation.

Study of Compatibility Between Epoxy Resin and C4F7N/CO2 Based on Thermal Ageing

Fluorinated nitrile (C4F7N) is a potential SF6-alternative gas in Gas-Insulated Transmission Line (GIL) due to its lower impact to global warming and excellent dielectric strength. To ensure the long-term physical and chemical stability at the interface between C4F7N/CO2 gas and epoxy resin assembly in GIL, laboratory thermal ageing tests on the material compatibility were carried out. In order to evaluate the compatibility, the authors set up a gas-solid compatibility test platform in this paper. Thermal ageing tests of C4F7N/CO2 and epoxy resin were set up at different temperatures. Also, the groups of SF6 and He gas were adopted to evaluate the influence of temperature. The compatibility between the gas and solid insulating materials in contact was evaluated in terms of the changes of insulation performance after over long period of tests. The changes of gas compositions and solid contents were also assessed. Dielectric spectroscopy, surface flashover voltages, surface morphology, and chemical elements of epoxy resin and gas composition before and after the ageing tests were compared. The surface insulation of epoxy resin decreased only after ageing reached 160 °C, when a small amount of C3F6 and trimer of C4F7N were found. Under the normal operation of GIL (below 90 °C), the compatibility of epoxy resin with 9 % C4F7N/91 % CO2 is as good as epoxy resin with SF6.

Synthesis and Dielectric Properties of Trifluoromethanesulfonyl Fluoride: An Alternative Gas to SF6

Sulfur hexafluoride (SF6) gas has been used in large-scale electrical equipment, because of its excellent high-voltage dielectric strength. However, SF6 has been identified as a greenhouse gas, bec...

Electron-impact ionization cross sections of new SF6 replacements: A method of combining Binary-Encounter-Bethe (BEB) and Deutsch-Märk (DM) formalism

Recently, much attention has been paid to some new carbon-fluoride gases, such as C2F4H2 (R134), C3F4H2 (HFO1234ze), C4F8, C4F7N, C5F10O, and C6F12O. All these gases present excellent dielectric strength and very low values of global warming potential and thus have potential to replace sulfur hexafluoride (SF6) as an insulating medium. However, the electron-impact ionization cross sections (Qion), which are the necessary basic data for the investigation of plasma discharges in these gases, are still unavailable. This work is devoted to the calculation of Qion for the above new SF6 replacements with incident electron energy of up to 5000 eV. We propose a method of combining the Deutsch-Märk (DM) formalism at low electron energy and the Binary-Encounter-Bethe (BEB) formalism at high electron energy by using a dual sigmoid function. The comparison between the calculated and experimental Qion for various molecules indicates that this new combined method yields 49.41% and 61.24% improvement by the Euclidean metric on average compared with the BEB and DM methods, respectively. We also investigate the effects of molecular orbitals and atomic shells on the Qion of new SF6 replacements. It is found that the BEB method conforms to the law that higher molecular orbitals have larger effect on electron-impact ionization of a molecule, while the DM method does not. Generally, the 2p shells of carbon, nitrogen, or oxygen atoms in a molecule play a dominant role in electron-impact ionization, whereas the shells of fluorine atoms do not affect the ionization process very significantly.