Electrical Insulation Research Articles

SUSTAINABLE CONVERSION OF BANANA WASTE INTO ELECTRICAL INSULATION MATERIALS FOR HIGH VOLTAGE APPLICATIONS

<p style="text-align:justify;"><span style="font-family:"Times New Roman","serif";font-size:12.0pt;line-height:150%;text-justify:inter-ideograph;">The study examined the electrical characteristics of epoxy composites that were reinforced with fibers derived from banana leaves and pseudostems. Specifically, the study focused on analysing the dissipation factor, loss factor, and dielectric constant of these composites. The study found that composites containing banana leaf fibers demonstrated enhanced dielectric properties in comparison to pure epoxy composites. This improvement can be attributed to the effective interlocking between the fibers and the matrix, as well as the polarization effects. Enhancing the amount of fibre in the material resulted in greater dielectric constants, reaching a maximum at a critical volume of 17.2%. However, at higher frequencies, the dielectric constants fell due to decreasing polarization. Chemical treatments, such as alkali and peroxide solutions, improved the bonding between the fibers and the matrix, leading to higher resistance to water and greater electrical insulation. The results also showed that banana leaf fibers had superior dielectric performance compared to pseudostem fibers, mostly because of enhanced nanoparticle bonding. Using banana fibers is particularly noteworthy since it contributes to environmental sustainability by recycling agricultural waste, hence mitigating the ecological consequences of synthetic products.</span></p>

Enhanced Electrocaloric Effect of PVDF-based Polymer Composite with Surface Modified AlN.

Poly(vinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) relaxor ferroelectric polymer exhibits a modest electrocaloric effect (ECE) at a low electric field near room temperature and a low thermal conductivity. The low thermal conductivity causes poor heat transfer when the terpolymer is used as a cooling device, even when the ECE of the polymer is substantial. By incorporating aluminum nitride (AlN) nanoparticles, which possess high thermal conductivity and good electrical insulation properties, into polymer matrices, we can enhance both the thermal conductivity and the ECE. However, weak bonding at the AlN-polymer interface can lead to a reduced breakdown electric field. Therefore, surface modification of AlN nanoparticles is performed to strengthen the chemical bonding between AlN and the terpolymer, thereby increasing the breakdown electric field. Following the addition of surface-modified nanoparticles, the breakdown electric field of the composite films remained around 240 MV/m, which is comparable to that of the pristine polymer film. Furthermore, the ECE and thermal conductivity were improved by 44% and 55%, respectively. We found three factors influencing the ECE, including the interface effect, the change in ferroelectric-paraelectric phase transition behavior, and the Joule heating effect. To assess the interfacial effect on the ECE, composite films with AlN particles of four different sizes were prepared. It was found that as the size of the nanoparticles increased, which resulted in a decreased interface area, the ECE decreased correspondingly. This finding further confirms the significant impact of the interface area in the composites on the ECE.

Rapid In Situ Preparation of Conductive Graphite-like Films on Polymer Surfaces via Hydrogen Plasma Technology.

Many special polymer materials with high strength, low density, and high processability have been developed for the substitution of metal products in recent years; however, their electrical insulation properties sometimes limit their application in medicine, electronics, and aerospace fields. Constructing a conductive layer on polymers may be a promising strategy for conquering these problems, but simply obtaining a high-quality conductive layer remains a challenge. Here, we develop a universal strategy to in situ fabricate a conductive graphite-like film on various polymer surfaces based on a simple one-step gas plasma ion implantation method. Theoretical and experimental results confirm that the reducibility of free radicals and the electrophilicity of cations in plasma are critical for the formation of graphite-like films on polymer surfaces. Compared with argon and oxygen plasma, hydrogen plasma with strong reducing hydrogen radicals and weak electrophilic hydrogen cations can produce the highest degree of graphitization of graphite-like films. The as-prepared polymers treated by hydrogen plasma ion implantation presented good surface conductivity and reduced friction coefficient, which has great potential for application in medicine, electronics, and aerospace fields.

Thermally Conductive Polydimethylsiloxane-Based Composite with Vertically Aligned Hexagonal Boron Nitride

The considerable heat generated in electronic devices, resulting from their high-power consumption and dense component integration, underscores the importance of developing effective thermal interface materials. While composite materials are ideal for this application, the random distribution of filling materials leads to numerous interfaces, limiting improvements in thermal transfer capabilities. An effective method to improve the thermal conductivity of composites is the alignment of anisotropic fillers, such as hexagonal boron nitride (BN). In this study, the repeat blade coating method was employed to horizontally align BN within a polydimethylsiloxane (PDMS) matrix, followed by flipping and cutting to prepare BN/PDMS composites with vertically aligned BN (V-BP). The V-BP composite with 30 wt.% BN exhibited an enhanced out-of-plane thermal conductivity of up to 1.24 W/mK. Compared to the PDMS, the V-BP composite exhibited outstanding heat dissipation capacities. In addition, its low density and exceptional electrical insulation properties showcase its potential for being used in electronic devices. The impact of coating velocity on the performance of the composites was further studied through computational fluid dynamics simulation. The results showed that increasing the coating velocity enhanced the out-of-plane thermal conductivity of the V-BP composite by approximately 40% compared to those prepared at slower coating velocities. This study provides a promising approach for producing thermal interface materials on a large scale to effectively dissipate the accumulated heat in densely integrated electronic devices.

Flexible silane‐functionalized boron nitride filled polymer composite with high thermal conductivity and electrical insulation

AbstractBoron nitride (BN) has excellent thermal conductivity (TC), however, it exhibits high surface energy, strong chemical inertness, poor interface compatibility with polymer matrices, and difficulty in even dispersion within‐polymer matrix, preventive effective construction of TC pathways. Four kinds of modified boron nitride/polyurethane composites (BTPUC) were prepared by different silane‐functionalized BN with polyurethane (TPU). Among them, 3‐trimethoxysilylpropylmethacrylate (TMSPMA)‐functionalized BN demonstrated better interface compatibility with TPU, significantly improving the mechanical properties and TC of the composites compared to the other three functionalized BN addition. The BN@TMSPMA/PU exhibited good TC and mechanical properties, with a TC of 0.865 W/mK, a tensile stress and a tensile strain of 9.65 ± 1.40 MPa and 759.88 ± 67.93%, respectively. It also showed good electrical insulation properties and mechanical durability. Therefore, the as‐prepared BN@TMSPMA/PU have broad prospects as flexible thermal‐management materials.Highlights The composites are constructed by TMSPMA‐modified BN and polyurethane by NIPS. The composites show good mechanical properties and cyclic failure resistance. The composites exhibit good thermal conductivity and electrical insulation.

Unlocking the Trade-off Between Intrinsic and Interfacial Thermal Transport of Boron Nitride Nanosheets by Surface Functionalization for Advanced Thermal Interface Materials.

The increasing computing power of AI presents a major challenge for high-power chip solution and heat dissipation. Boron nitride nanosheet-based thermal interface materials (BNNS-based TIMs) exhibit excellent electrical insulation property, ensuring the secure and stable operation of chips. However, the efficiency of micro/nano interfacial thermal transport is limited, impeding further enhancements in the thermal conductivity (TC) of BNNS-based TIMs. Here, a strategy of surface functionalization is reported to unlock the trade-off between the intrinsic and interfacial thermal transport of BNNS within TIMs. These results suggest that the surface functionalization maintains the intrinsic high TC of BNNS while significantly increasing binding energy between micro/nano interfaces in BNNS-based TIMs, effectively reducing interfacial thermal resistance of BNNS joint interfaces and interfaces between BNNSs and the matrix by 50% and 26.1%, respectively. The BNNS-based TIMs exhibit excellent TC (≈21-25W/(m·K)) and ultralow Young's modulus, which can promote the development of flexible high-performance chip cooling technology in the AI industry.

Substantial improvement of InGaN/GaN visible-light polarization-induced self-depletion phototransistor by thermally oxidized Al2O3

Atomic layer deposited (ALD) Al2O3 acting as gate dielectric and surface passivation is widely adopted in power electronics but seldom used in optoelectronic fields for its sophisticated and expensive technology. Herein, a simple but efficient Al2O3 passivation is used in the fabrication of InGaN/GaN visible-light (VL) polarization-induced self-depletion field effect phototransistors (FEPTs), for suppressing the surface leakage and recombination. The Al2O3 layer obtained by thermal oxidation (TO) of 2-nm-thick thermally evaporated metal Al shows high electrical insulation and even better passivation effect than the ALD-Al2O3. As a result, the dark current of TO-Al2O3 passivated device decreases by about 2 orders of magnitudes; meanwhile, the photoresponse increases by about 65%. Under a weak VL illumination of 6.8 μW/cm2, the InGaN/GaN FEPT exhibits a large photo-to-dark current ratio of 3.1 × 108 and an ultrahigh shot-noise-limited detectivity of 1.9 × 1018 jones. In addition, the FEPTs exhibit a strong wavelength selectivity with a 600 nm/400 nm spectral response rejection ratio exceeding 5 × 105. All these performances show huge potential in emerging VL applications that are limited by the insufficiencies of current Si photodetectors.

Estimation of the Partial Discharge Inception Voltage of Electrical Asset Components at Variable Environmental Pressure: A Modelling Approach

Since partial discharges, PD, are a major accelerated degradation mechanism of organic electrical insulation systems, measuring partial discharge inception voltage, PDIV, of electrical asset components in aviation and aerospace is a fundamental tool to cope with life, safety, and reliability requirements. Partial discharge phenomenology and inception voltage depend on pressure, specifically, PDIV decreases with pressure. To avoid PD inception during aircraft or aerospace vehicle operation, the value of PDIV must be known at any pressure that electrical asset components will experience. However, a lack of experimental facilities adequate to test PD on real-size asset components might prevent from having PD-related information at pressures lower (or higher) than standard atmospheric pressure, SAP. This paper presents a heuristic approach, based on physics-derived PD field inception models, that allows the estimation of PDIV at low pressure to be carried out based on measurements made at SAP, when the typology of the defect causing partial discharge is known (from SAP PD measurements), but the precise type, size, and location of the PD-generating defect is unknown. It is shown that PDIV estimates obtained by the proposed models for internal and surface discharges are in good agreement with measured values in a range from SAP to 0.05 bar, testing simple insulation geometries but also real asset components, such as motors.

Enhanced energy storage performance of NaNbO3-based ceramics by modifying phase structures and electrical insulation

Enhanced energy storage performance of NaNbO3-based ceramics by modifying phase structures and electrical insulation

Bulletin Board: Get Your Work Published in IEEE Electrical Insulation Magazine

Bulletin Board: Get Your Work Published in IEEE Electrical Insulation Magazine

Comprehensive properties analysis of epoxy composites synergistically toughened with liquid nitrile rubber and polyethersulfone

In this paper , epoxy resin (EP) composites with different phase structures were prepared by introducing hydroxyl-terminated liquid nitrile rubber (HTBN) and hydroxyl-terminated polyethersulfone (PES) individually or simultaneously into the resin matrix. The results revealed that the rational distribution of phase structure of rigid PES and flexible HTBN can effectively contributed to the enhancement in their mechanical and electrical insulation strengths. The synergistic effect of the two reinforcing fillers granted the optimized ternary composite a tougher structural network, leading to significant improvements of 73.13% and 18.98% in mechanical impact strength and electrical breakdown strength, respectively, compared to the pristine EP. Furthermore, compared to HTBN, PES exhibited inhibited HTBN dielectric interfacial polarization and EP molecular chain segment relaxation, resulting in decreased dielectric constant and loss in the composites. This study provide insights into the dielectric properties and design strategies for the development of resin-based dielectric materials, ensuring their broader applicability.

Performance of sandwich type fire-resistant flexible composite phase change material PEE@EBF for battery thermal management and runaway protection

To mitigate the risks of overheating and thermal runaway in lithium-ion batteries, this study proposes a novel sandwich-type fire-resistant flexible composite phase change material (CPCM), referred to as PEE@EBF. The core material (PEE) was created by melt-blending paraffin wax (PW), expanded graphite (EG), and ethylene–vinyl acetate copolymer (EVA). The outer layer, a fire-resistant coating (EBF), was applied to the surface of PEE and consists of epoxy resin (EP), boron nitride (BN), and the composite flame retardant (CFR). Test results demonstrated that PEE@EBF maintained structural integrity, exhibiting no significant deformation or leakage after being heated at 80 °C for 5 h. PEE@EBF also displayed a high latent heat of 166.6 J/g, thermal conductivity of 0.8 W/(m∙K), and excellent electrical insulation properties. Furthermore, it achieved a UL94 V-0 flame retardant rating, with notable reductions in peak heat release rate (PHRR) and peak smoke production rate (PSPR) by 67.8 % and 81.8 %, respectively. During long-term cycling at 4C, the peak temperature (PT) and maximum temperature difference (MTD) of batteries in the module incorporating PEE@EBF were reduced by 11.8 °C and 4 °C, respectively, compared to natural convection cooling. In addition, the heat generated during the battery thermal runaway was efficiently absorbed and transferred by PEE@EBF, delaying the irreversible thermal runaway process by 633 s. This indicated that the sandwich-type PEE@EBF was suitable for thermal management and fire protection in lithium-ion batteries or energy storage devices.

IEEE Electrical Insulation Magazine, a Publication of DEIS

IEEE Electrical Insulation Magazine, a Publication of DEIS

Author's Guide for IEEE Electrical Insulation Magazine Technical Articles

Author's Guide for IEEE Electrical Insulation Magazine Technical Articles

Electrical and Dielectrical Properties of Composites Based on Alumina and Cyclic Olefin Copolymers.

Understanding the performance of polymer dielectrics at different temperatures is becoming increasingly important due to the rapid development of electric cars, electromagnetic devices, and new energy production solutions. Cyclic olefin copolymers (COCs) are an attractive material due to their low water absorption, good electrical insulation, long-term stability of surface treatments, and resistance to a wide range of acids and solvents. This work focused on the dielectric and electrical properties of cyclic olefin copolymer (COC)/Al2O3 composites over a wide range of temperature and frequency domains, from room temperature to cryogenic temperatures (around 125 K). Permittivity, electrical conductivity, and electrical modulus are given consideration. A composite of up to 50% Al2O3 mixed with COC was prepared via a conventional melt-blending method. The final samples were formed in sheets and processed using injection and extrusion moldings. It was found that formulations with Al2O3 concentrations ranging from 10 to 50% resulted in higher electrical conductivity while maintaining the viscosity of the composite at a level acceptable for polymer-processing machinery. Our data show that COC/alumina composites present substantial potential as materials for high-frequency applications, even at the regime of cryogenic temperatures.

General Approach to Hydrolysis Resistive Aluminum Nitride and Its High-Performance Thermal Interface Materials.

Aluminum nitride (AlN), noted for its excellent thermal conductivity and exceptional electrical insulation, presents a promising alternative to traditional ceramic particles in thermal interface materials (TIMs). However, its broader adoption in practical applications is limited by performance degradation due to the vulnerability of its crystal structure to ubiquitous moisture. This study introduces a dual solution, utilizing a mechanochemical method to design a dense outer layer of Galinstan liquid metal (LM) that simultaneously enhances AlN's resistance to hydrolysis and improves its thermal performance in TIM applications. The high surface free energy of the LM layer imparts hydrophobic properties to the AlN surface and, combined with outer metal oxides, forms a dual-layer protective barrier that prevents water penetration, significantly enhancing the TIM's long-term stability in high-humidity conditions. Additionally, the LM layer at the interface improves the thixotropic properties of the TIM and enhances interfacial heat transport through the bridging effect of the LM, resulting in improved rheological mobility and thermal conductivity of the composite material. This win-win surface modification strategy opens opportunities for the practical and durable application of AlN in widespread electronic thermal management.

Study on Mechanical Properties of Basalt Fiber and its Composite Materials

With the development of civil engineering industry, the use of new composite materials has become an inevitable trend. This paper mainly focuses on the mechanical properties and development status of Basalt Fiber (BF) and its fiber composites which is called Basalt Fiber Reinforced Polymer (BFRP). The raw material of BFRP, the basalt ore and the preparation of blast furnace are discussed. Then, the preparation method of BFRP is introduced. In the process of research, it is found that when the preparation of BFRP is completed, the types of BFRP can be roughly divided into mixed reinforcement type and basic profile type. Subsequently, the factors affecting the mechanical properties of blast furnace are studied, which are mainly divided into interface modification and interface aging. In the aspect of interface modification, four modification methods such as acid-base etching modification, plasma surface treatment, silane coupling agent treatment and nanoparticle modification are introduced in detail. Finally, comparing BF with carbon fiber (CF), polyester fiber (PF) and glass fiber (GF), it is found that BF has better plasticity, toughness, good electrical insulation and low thermal conductivity. However, there are still many difficulties to be solved in the production, preparation, modification and application of BF and BFRP

Molybdenum temporary epicardial pacing wires: function and biodegradation

Abstract Cardiac pacing with temporary epicardial pacing wires (TEPW) is used to treat rhythm disturbances after cardiac surgery. Wires typically begin to fail around postoperative day four and are extracted. Occasionally, TEPW cannot be mechanically removed, have to stay in the thorax and may rarely cause serious complications like migration and infection. We aim to develop novel, bioresorbable TEPW which will dissolve over time, even if postoperative removal is unsuccessful. We manufactured prototypical braided molybdenum (Mo) leads (16 Mo wires of 40 µM diameter each, length 18 cm for ex vivo, 7.5 cm for in vivo experiments) coated with the biodegradable polymers poly(lactide-co-glycolic acid) (PLGA, inner coating) and polycaprolactone (PCL, outer coating) for shaping and electrical insulation. Mo electrodes showed similar pacing and sensing properties to conventional steel electrodes (Osypka) in Langendorff-perfused rat hearts, even with somewhat lower stimulation thresholds. In artificial body fluid at 37°C, the polymer-coated Mo electrodes dissolved at a rate of 1.6 ± 0.3 µg/cm2·d (n = 5) compared to uncoated electrodes with 30.3 ± 0.8 µg/cm2·d (n = 4, p < 0.001). Assessing apoptosis and necrosis in human cardiomyocytes and cardiac fibroblasts, we detected no toxicity at Mo concentrations up to 0.52 mM. To test the in vivo properties of Mo TEPW, we sutured them epicardially onto the anterior wall of the heart of female Wistar rats, led them out of the thorax through an intercostal space and placed them in a subcutaneous pocket. We tested electrophysiological properties directly after implantation and after different time periods. Mo TEPW showed similar pacing and sensing properties directly upon implantation and after 2 weeks, with only impedance and slew rate of the sensed R-wave decreasing time-dependently. After one month, all but one pair of Mo electrodes were mechanically broken at their exit from the thorax, the site of assumedly highest mechanical stress. Progressive Mo degradation led to multiple fragmentation of the Mo TEPW after 6 months. The conventional steel TEPW we used as control had similar electrical properties directly after implantation, after 2 weeks and one month without signs of broken electrodes. After 6 months, all but one pair of steel electrodes were mechanically broken at their thorax exit site. Comparing urinary Mo concentration of Mo TEPW treated rats to controls, we saw similar values of 1.9 ± 1.9 µM (n = 6) vs. 0.6 ± 0.2 µM (n = 5, n.s.) after one week. In contrast, we saw a significant increase of 12.1 ± 9.7 µM (n = 5) vs. 1.0 ± 0.9 µM (n = 5, p < 0.001) after 6 months, reflecting the degradation progress. We demonstrate that Mo TEPW are a feasible option for epicardial pacing in vivo for up to 2 weeks and observed the progress of Mo degradation up to 6 months. These findings represent an important step in the development of bioresorbable TEPW as a novel and even safer approach to temporary epicardial pacing.Graphical AbstractIn Vivo Degradation Progress

Effect and mechanism of phenyl content on the electrical insulation properties of silicone rubber

AbstractSilicone rubber is widely used in reinforced insulation of cable accessories due to its good electrical insulation and weather resistance. With the continuous improvement of high voltage transmission grade, higher requirements are put forward for the electrical insulation performance. The effect and mechanism of phenyl content on the electrical insulation properties of silicone rubber are investigated by the method of combination of experiments and molecular simulations. The experimental results show that the properties of silicone rubber are improved with the increase of phenyl content. Among them, the silicone rubber composite with phenyl content of 20 wt% has the best comprehensive performance. Compared with vinyl silicone rubber, the dielectric constant at 50 Hz decreases from 3.50 to 2.95, and the breakdown strength increases by 38.03%, from 56.59 to 78.11 kV/mm. In addition, the tensile strength and elongation at break are 5.44 MPa and 456%, respectively. The molecular simulation results show that with the increase of phenyl content, the glass transition temperature increases, the mean square displacement decreases, and the free volume decreases, which macroscopically leads to the change of electrical properties of the silicone rubber material. This work has a certain guiding significance for improving the electrical properties of silicone rubber for cable accessories.

Improving the Mechanical, Thermoelectric Insulations, and Wettability Properties of Acrylic Polymers: Effect of Silica or Cement Nanoparticles Loading and Plasma Treatment.

The acrylic polymer composites in this study are made up of various weight ratios of cement or silica nanoparticles (1, 3, 5, and 10 wt%) using the casting method. The effects of doping ratio/type on mechanical, dielectric, thermal, and hydrophobic properties were investigated. Acrylic polymer composites containing 5 wt% cement or silica nanoparticles had the lowest abrasion wear rates and the highest shore-D hardness and impact strength. The increase in the inclusion of cement or silica nanoparticles enhanced surface roughness, water contact angle (WCA), and thermal insulation. Acrylic/cement composites demonstrated higher mechanical, electrical, and thermal insulation properties than acrylic/silica composites because of their lower particle size and their low thermal/electrical conductivity. Furthermore, to improve the surface hydrophobic characteristics of acrylic composites, the surface was treated with a dielectric barrier discharge (DBD) plasma jet. The DBD plasma jet treatment significantly enhanced the hydrophobicity of acrylic polymer composites. For example, the WCA of acrylic composites containing 5 wt% silica or cement nanoparticles increased from 35.3° to 55° and 44.7° to 73°, respectively, by plasma treatment performed at an Ar flow rate of 5 L/min and for an exposure interval of 25 s. The DBD plasma jet treatment is an excellent and inexpensive technique for improving the hydrophobic properties of acrylic polymer composites. These findings offer important perspectives on the development of materials coating for technical applications.