Good Insulation Performance Research Articles

Construction and Characterization of TiN/Si3N4 Composite Insulation Layer in TiN/Si3N4/Ni80Cr20 Thin Film Cutting Force Sensor.

The measurement of cutting force is an effective method for machining condition monitoring in intelligent manufacturing. Titanium nitride films and silicon nitride films were prepared on 304 stainless steel substrates by DC-reactive magnetron sputtering and plasma-enhanced chemical vapor deposition (PECVD). The effects of substrate negative bias and nitrogen flow on the surface microstructures of TiN film were investigated. The smoothness of the film is optimal when the bias voltage is −60 V. X-ray diffraction (XRD) analysis was performed on the samples with the optimal smoothness, and it was found that when the nitrogen flow rate was higher than 2 sccm, the titanium nitride film had a mixed phase of TiN(111) and (200). It is further revealed that the change of peak intensity of TiN(200) can be enhanced by nitrogen flow. Through atomic force microscopy (AFM), it is found that the stronger the intensity of the TiN (200) peak, the smoother the surface of the film is. Finally, the effect of different film thicknesses on the hardness and toughness of the TiN/Si3N4 film system was studied by nanoindentation experiments. The nanohardness (H) of the TiN/Si3N4 film can reach 39.2 GPa, the elastic modulus (E) is 480.4 GPa, the optimal toughness value (H3/E2) is 0.261 GPa, and the sample has good insulation performance. Linear fitting of the film’s toughness to nanohardness shows that TiN/Si3N4 films with higher hardness usually have a higher H3/E2 ratio.

Experimental study on low thermal conductive and flame retardant phase change composite material for mitigating battery thermal runaway propagation

Lithium-ion batteries (LIBs) have dominated the market in portable electronics, electric vehicles, and aerospace applications. However, safety issues greatly limit the further applications of LIBs. In this work, a low thermal conductive phase change composite material (CPCM) with flame retardant coating (FR-CPCM) is proposed, which is placed between batteries to prevent thermal runaway (TR) propagation. The CPCM with 40 wt.% paraffin (PA) and 60 wt.% silica aerogel (SA) achieves the lowest thermal conductivity of 0.051 W/(m•K) at the density of 424 kg/m3. After coated, the FR-CPCM performs the V-0 rating at UL-94 test and 56.31% of limiting oxygen index, as well as a good insulation performance under the nearly 700 °C side heating test. The thermal runaway (TR) tests of battery modules show that the addition of FR-CPCM between batteries can effectively prevent the propagation of battery TR, and keep the maximum external temperature of the adjacent battery below 182.6 °C. While TR in module without FR-CPCM propagated to its adjacent one in only 63 s. Moreover, FR-CPCM exhibits good compressive performance, which will not crack even under the pressure of 40 MPa. The above results indicate that FR-CPCM is promising in the application of safer battery systems.

Multi-physics Coupling Simulation of Heat Transfer and Structural Optimization for a Three-phase Gas Insulated Switchgear Busbar

Gas insulated switchgear (GIS) is one of the most important equipment in the power system. Excessive temperature of the GIS busbar conductor will lead to the loss of insulating gas performance and equipment life. In the present paper, based on the finite element method, the temperature distribution and power loss density of a 252 kV three-phase GIS busbar is numerically studied using electromagnetic-heat-flow coupling model, and the structure parameters of the rotation angle, center distance and conductor thickness of the busbar are optimized with Taguchi method. The results show that the conductor thickness has the greatest influence on the maximum temperature and power loss, and the influence proportion is more than 70 %. When the combination scheme of (A1, B5, C5) is adopted, the temperature rises and power loss performance of GIS has been optimized. The maximum temperature is reduced by 9.56 K and the power loss is reduced by 21.7 %. In addition, according to the analysis of the gas breakdown margin, it is found that the SF6 gas still has a good insulation performance after structure optimization. This study is of great significance to the heat transfer and optimization design of three-phase GIS busbar.

Combining good dispersion with tailored charge trapping in nanodielectrics by hybrid functionalization of silica

Abstract Fumed silica-filled polypropylene (PP)-based nanodielectrics were studied in this work. To not only improve the dispersion of the silica but also introduce deep charge traps into the polymeric matrix, five types of modified silicas were manufactured with different surface modifications. The modified silica surfaces comprise an inner and a surface layer. The inner layer contains a polar urethane group for tailoring the charge trap properties of the PP/propylene–ethylene copolymer nanocomposites, whereas the surface layer consists of hydrocarbons (ethyl-, tert-butyl-, cyclopentyl-, phenyl-, or naphthalenyl moieties) in order to gain a good dispersion of the silica in the unpolar polymer blend. Scanning electron microscopic pictures proved that these tailored silicas show a much better dispersion than the unmodified one. Thermally stimulated depolarization current measurements revealed the ability of the silica to introduce deep charge traps with low trap density. The trap depth distribution depends on the type of the unpolar surface layer consisting of the different hydrocarbons. Among these five differently modified silicas, the introduction of the one with a surface layer consisting of tert-butyl moieties resulted in the lowest charge injection and the lowest charge current in the nanocomposite, proving good dielectric performance. Additionally, this silica exhibits good dispersion in the polymeric matrix, indicating a promising performance for nanodielectric application.

Lightweight and multiscale needle quartz fiber felt reinforced siliconoxycarbide modified phenolic aerogel nanocomposite with enhanced mechanical, insulative and flame-resistant properties

Lightweight and multiscale nanocomposites are considered to be the most promising materials applied in the field of advanced aerospace and modern building industry, owing to their outstanding mechanical, thermal and flame-resistant properties served in high-temperature oxidizing environments. Herein, a novel siliconoxycarbide (SiOC) modified needle quartz fiber felt reinforced phenolic resin nanocomposite (SiQF/PR) with a hierarchical macro-/micro-/nano-scaled structure is reported. The as-prepared highly porous SiQF/PR nanocomposite exhibits a multiscale three-dimensional network and the micro-sized SiOC particles, derived from the hydrolysis of methyltrimethoxysilane (MTMS) and dimethyldiethoxysilane (DDS), are uniformly incorporated into the phenolic aerogel. The resultant nanocomposite has a bulk density of 0.30–0.35 g/cm3, and the maximum compressive strength reaches 4.20 MPa and 3.34 MPa in xy and z directions, respectively. Thermal stability and oxidation resistance experiments show that the SiQF/PR multiscale composite has a good ablation and heat insulation performance under oxyacetylene test condition, and the backside temperature of SiQF/PR is only 55.5 °C under 1.8mw/m2 for 120 s, and line ablation rate of SiQF/PR multiscale nanocomposite decreases by 20.1% at 1.8 MW/m2 and 59.5% at 0.4 MW/m2 compared to non-SiOC modified composite. These results indicate that the lightweight SiQF/PR nanocomposite fabricated by this method is very suitable for architectural or aerospace applications as high-performance insulation material.

Study on the thermal properties and insulation resistance of epoxy resin modified by hexagonal boron nitride

Abstract To study the effect of doping hexagonal boron nitride (h-BN) on the thermal properties and insulation resistance of epoxy resin (EP) and the mechanism of this effect, h-BN/epoxy composites with h-BN content of 0, 10, 20, 30, and 40 phr were prepared. Meanwhile, the corresponding molecular dynamics model of h-BN/epoxy composites was established, and the thermal conductivity, volume resistivity, glass transition temperature, and microstructure parameters of h-BN/epoxy composites were obtained. When the h-BN content is 40 phr, the thermal conductivity of h-BN/epoxy composite is increased by 138% compared to pure EP, and the glass transition temperature is increased by 76 K. At the same time, doping h-BN will reduce the insulation performance of EP. However, the lowest volume resistivity of h-BN/epoxy composite is still 1.43 × 1015 Ω·cm, and the EP composite still has good insulation performance. The fraction free volume and mean square displacement of EP decrease with the doping of h-BN, which indicates that h-BN can hinder the movement of molecular segments of EP, which is the reason for the increase in glass transition temperature.

Ultra-thin composite underwater honeycomb-type acoustic metamaterial with broadband sound insulation and high hydrostatic pressure resistance

This research proposes a new type of composite underwater honeycomb-type acoustic metamaterial (AM) plate with the advantages of low-frequency broadband sound insulation and high hydrostatic pressure resistance. The proposed AM is composed of a thin plate (rubber-steel-rubber, RSR) clamped between two layers of honeycomb plate, and the thickness of the whole structure is 20.25 mm. The underwater sound insulation performance and mechanisms of the new type of AM were investigated numerically and experimentally. Wave propagation properties of the proposed AM were modeled using the finite element method (FEM). In addition, modal analysis of the eigenmode shapes were used to investigate the underwater sound transmission loss (STL) performance and local resonance bandgap formation. The results show that the honeycomb-type AM has good underwater sound insulation performance at low frequencies and the STL is more than 20 dB higher than that of homogeneous materials with the same area density. Furthermore, the theoretical STL of the proposed metamaterial was consistent with experimental values, thus verifying the STL performance and validating the theoretical modeling approach for the proposed AM. Moreover, the proposed AM structure can still achieve an average STL of 10 dB in the frequency range [2 kHz, 10 kHz] under the hydrostatic pressure of 3 MPa.

Large direct and inverse electrocaloric effects in lead-free Dy doped 0.975KNN-0.025NBT ceramics

Undoped and Dy3+ doped 0.975 K1/2Na1/2NbO3-0.025Na1/2Bi1/2TiO3 (0.975KNN-0.025NBT) ceramics were synthesized using the solid-state synthesis method. X-ray diffraction analysis revealed pure perovskite structure without any secondary phases. The dielectric investigations of both ceramics revealed low dielectric losses in the dysprosium doped ceramic, particularly for temperatures higher than 100 °C. The dielectric loss anomaly around room temperature corroborates the polymorphic phase boundary (PPB) between orthorhombic and tetragonal phases detected by XRD investigations. The electrocaloric effect (ECE) was investigated using the indirect method based on the Maxwell equation and thermal P–E hysteresis loops. The maximum ECE value was found equal to 0.63 K at 83 °C for KNNBT0.025. However, in Dy doped KNNBT0.025 ceramics, both direct and inverse ECE responses were found with values of 1.01 K at 118 °C and −1.79 K at 80 °C, respectively. Besides, yellow light emission was detected under an excitation wavelength of 350 nm. The simultaneous existence of high ECEs, good dielectric performance, and photoluminescence properties makes KNNBT-Dy a promising candidate for solid-state refrigeration and optoelectronic devices.

Research on Design and Mechanism of Sound Insulating Structure Based on Acoustic Metamaterials

In view of the difficult problems of low-frequency noise reduction, based on the clamping boundary-type acoustic metamaterial theory with negative effective mass density, a structure combining membrane-type and clamping boundary-type is designed, which can realize good sound insulation performance in the low-frequency region, and the theoretical calculation and numerical simulation are in good agreement. At the same time, the transmission property of the structure at zero refractive index and impedance matching is studied. The research suggests that the structure has good low-frequency broadband sound insulation performance, and can achieve high transmission performance of sound waves through structural regulation.

In situ growth of single crystal Si3N4 nanowire foam with good wave-transparency and heat insulation performance

The radome of high Mach number aircraft requires a bearing material that is light weight, capable of wave transmissivity, and has excellent high temperature stability. In this regard, silicon nitride (Si3N4) nanomaterials, especially porous macroscopic structures formed by them (such as Si3N4 nanowire foam), are promising candidates. However, there have been no studies on the various Si3N4 nanofoams. In this study, a carbon template was used with a simple and reliable in situ synthesis method to prepare Si3N4 single crystal nanowire foam with a cross-linking structure between nanowires. High purity Si3N4 nanowires have the characteristics of low density (8.9 mg/cm3) and high foam volume fraction (17.35%). The nanowires can be distributed spontaneously and uniformly in three-dimensional space. The elasticity of this foam is mainly a result of the high aspect ratio of the nanowires and the large amount of large size pores in the structure. In addition, the foam has an ultralow dielectric constant, good wave transmissivity, and excellent thermal insulation and high-temperature stability. All of these characteristics are related to the special pore structure and intrinsic single crystal structure of the nanowire foam. Thus, Si3N4 nanowire foam is a transparent material with heat insulation, wave-transparency, and high temperature resistance, and has special application prospects.

Recent Patents on EDM of Nonconductive Materials

Background: The non-conductive materials are widely applied in electronics, optics, instrumentation, aerospace, national defense and civil industry because of their strong wear resistance, high hardness and good insulation performance. However, it is difficult for traditional machine methods to process the non-conductive materials. Electrical Discharge Machining (EDM), as a nontraditional advanced processing technology, is an alternative method for machining the non-conductive materials. Therefore, the development trend of EDM of non-conductive materials has been paid more and more attention. Objective: To meet the growing processing requirement of processing efficiency and processing quality of EDM of nonconductive materials, the processing devices and processing methods of EDM of nonconductive materials such as high-voltage spark machining, auxiliary electrode spark machining and electrolysis spark discharge machining are being improved continuously. Methods: This paper retraces various current representative patents relative to high-voltage spark machining, auxiliary electrode spark machining and electrolysis spark discharge machining of nonconductive materials. Results: Through investigating a large number of patents on EDM of nonconductive materials, the main current existing problems such as low processing efficiency and poor processing quality are summarized and analyzed. Moreover, the development tendency of EDM of nonconductive materials in the future is also discussed. Conclusion: The optimization of processing devices and processing methods of EDM of nonconductive materials is conducive to improve processing efficiency and processing quality. More correlative patents will be invented in the future.

The effect of molding process on thermomechanical properties of feather nonwoven reinforced polyester composites

Composites reinforced with feather fibers have attracted the attention of scientists due to their low cost, availability, renewable character and low density. This experimental study emphasizes the effect of molding techniques on the mechanical, thermal and biodegradability properties of feathers nonwoven reinforced polyester composite (FP). The composites were prepared by three methods: resin transfer molding (RTM), infusion and vacuum molding techniques. The morphological analysis revealed excellent compatibility of feather fiber in the matrix. The FP composites made by the three methods showed good insulation performance with thermal conductivity values ranging from 37 mW/(m.K) to 39 mW/(m.K) at 10 °C and the lowest value was observed for the sample developed by the RTM technique. Moisture absorption and the effect of void content on the moisture absorption depend on a number of factors: type of reinforcement, matrix material, molding process and fiber content .The FP composites developed by the vacuum molding technique have shown higher water absorption due to the presence of a high void content. The tensile strength and young's modulus of the FP composites were also examined in this research; the mechanical results showed that the molding techniques clearly affected the performance of the composites. The results obtained in this study have potential applications where high environmental resistance, low cost and durable materials are required.

Research of Fluorescent Properties of a New Type of Phosphor with Mn2+-Doped Ca2SiO4.

Fluorescent optical fiber temperature sensors have attracted extensive attention due to their strong anti-electromagnetic interference ability, good high-voltage insulation performance, and fast response speed. The fluorescent material of the sensor probe directly determines the temperature measurement effect. In this paper, a new type of fluorescent material with a Mn2+-doped Ca2SiO4 phosphor (CSO:Mn2+) is synthesized via the solid-state reaction method at 1450 °C. The X-ray diffraction spectrum shows that the sintered sample has a pure phase structure, although the diffraction peaks show a slight shift when dopants are added. The temperature dependence of the fluorescence intensity and lifetime in the range from 290 to 450 K is explored with the help of a fluorescence spectrometer. Green emission bands peaking at 475 and 550 nm from Mn2+ are observed in the fluorescence spectra, and the intensity of emitted light decreases as the temperature rises. The average lifetime of CSO:Mn2+ is 17 ms, which is much higher than the commonly used fluorescent materials on the market. The fluorescence lifetime decreases with increasing temperature and shows a good linear relationship within a certain temperature range. The research results are of great significance to the development of a new generation of fluorescence sensors.

Toward high thermal conductive aramid nanofiber papers: Incorporating hexagonal boron nitride bridged by silver nanoparticles

AbstractIn this work, a novel thermal conductive and electrical insulation h‐BN@AgNPs/ANFs composite paper was fabricated by vacuum‐assisted filtration approach. Specifically, hexagonal boron nitride (h‐BN) was incorporated via polydopamine pretreatment and subsequent decoration by silver nanoparticles, which served as bridges to link neighboring h‐BN sheets. The results revealed that the thermal conductivity of as‐prepared composite paper increased to 1.032 W/m K with 40 wt% filler loading, about 464% higher than the pure ANFs paper, which was attributed to the efficient thermal conductive networks within the paper and strong interfacial combination through hydrogen bonding. Besides, the as‐prepared composite paper exhibited excellent mechanical property with the maximum tensile strength over 90 MPa, and good electrical insulation performance. More importantly, this work provided a promising strategy to achieve high thermal conductivity ANFs based composite paper by constructing efficient thermal conductive networks, which had potential to be used in the field of electronic packaging.

Research on the Sound Insulation Properties of Membrane-type Acoustic Metamaterials

Low- and medium-frequency noise from ship cabins is difficult to control effectively. Excessive noise can seriously affect the acoustic stealth performance of ships. A novel membrane-type acoustic metamaterial is proposed in this paper with light weight and good sound insulation performance at low frequencies. The sound insulation performance of the metamaterial structure is analysed by using the acoustic-solid coupling module in COMSOL software. Then, the ability to change the sound insulation performance of membrane-type acoustic metamaterials with cell structure and material parameters is obtained. The research results in this paper provide powerful technical support for noise control in ship cabins.

Development of Flame Spread Prevention Systems for Combustible Composite Panels Using Water Screen Technology

Composite panels are designed to be fabricated by adding Styrofoam, glass wool, and urethane into steel plates before integration with adhesive materials. As these panels exhibit good workability, cost efficiency, and heat insulation performance, they are widely used as building materials for plant or storage facilities. However, fire safety still needs to be addressed, because these panels can potentially cause large fires. As firewater cannot easily penetrate the material inside the panel, extinguishing any fires caused is difficult. Furthermore, the imperfect combustion of the core material tends to generate a large volume of toxic gas, resulting in serious damage to human life. In addition, the high risk of collapse makes fire-fighting activities more difficult. Flame spread prevention systems optimized for composite panels have been developed for more effective fire suppression based on accumulative research outcomes obtained thus far. Related test methods were reviewed before successfully demonstrating the performance of the developed systems. The existing composite panel structure—wherein the developed system was not applied-burned out after 5 min; however, when the developed system was applied to the composite panels, the structure was covered in soot after 15 min. The structure was designed by applying the developed system to a virtual factory building, and the construction standard was reviewed.

Regulating the Structural, Transmittance, Ferroelectric, and Energy Storage Properties of K0.5Na0.5NbO3 Ceramics Using Sr(Yb0.5Nb0.5)O3

Lead-free (1 − x)K0.5Na0.5NbO3–xSr(Yb0.5Nb0.5)O3 (KNN–xSYbN, x = 0.15, 0.175, 0.20, 0.225, 0.25, 0.30) ceramics have been fabricated using the traditional solid-phase sintering method. The effects of Sr(Yb0.5Nb0.5)O3 doping on the microstructure, phase transition, and optical and electrical properties were investigated in detail. X-ray diffraction analysis revealed that the ceramics had pseudocubic phase structure. At x = 0.175, the near-infrared light transmittance of the ceramic reached 43.5% and the optical bandgap Eg was 2.89 eV. After introduction of Sr(Yb0.5Nb0.5)O3, the crystal grains of the ceramic became fine dense small cubes. Excessive doping (x ≥ 0.20) reduced the density of the ceramic and melted the ceramic surface. The ceramic with x = 0.175 exhibited optimized energy storage properties with Wrec = 0.21 J/cm3 and η = 78.2%. The maximum dielectric constant of 1867.9 was obtained at x = 0.175, and its Tm peaks shifted toward lower temperature. The good insulation performance of the ceramics was confirmed by impedance spectroscopy.

Study of the Protection of Aluminum Alloy Surfaces by a Graphene-Modified Fluorocarbon Anticorrosive Coating

Graphene-modified anticorrosion coatings have become a hot spot in the field of metal protection due to the large-scale promotion of aluminum alloys, which are prone to corrosion in marine and atmospheric environments. The protection of aluminum alloy surfaces by a graphene-modified anticorrosive coating was explored in this study by applying a graphene-modified anticorrosive coating to an aluminum alloy surface to test its resistance to corrosion. Dispersion-treated reduced graphene oxide (rGO) was used to modify the epoxy resin and fluorocarbon resin. It was found, by using a scanning electron microscopy (SEM) and the microstructure of the coating made by the Raman Spectroscopy Institute, that the addition of rGO could effectively improve the porosity of the epoxy primer, and the electrochemical workstation was able to resist the graphene-modified anticorrosive coating. The corrosion performance was quickly characterized, the polarization curve and the AC impedance curve were fitted, and it was found that the self-corrosion current density ( J corr ) of the graphene-modified anticorrosive coating was the smallest ( 1.190 × 10 − 7 A / c m 2 ) when 0.6% of rGO was added; the impedance modulus ( ∣ Z ∣ ) was the largest (104), the capacitive reactance arc radius was the largest, and the coating resistance was the largest after fitting (15517 Ω). When 0.8% of rGO was added, the dispersion coefficient was large, and it had a good physical insulation performance. The main reason for the reduction of the corrosion resistance was that the agglomeration of rGO made the aluminum alloy matrix and the external corrosive environment form a highly conductive circuit, thereby accelerating the corrosion of the aluminum alloy matrix.

Sintering characteristics and microwave dielectric properties of a new temperature-stable ceramic of Ce0.5Sm0.5O1.75

The novel temperature-stable microwave dielectric ceramics of Ce0.5Sm0.5O1.75 were fabricated via the mixed oxide reaction method, with the detail information including crystal phase, microstructure, sintering behavior and microwave dielectric properties being systematically investigated. For crystal phase, all the diffraction patterns were indexed as cubic fluorite-type structure with Fm-3m (225) space group and exhibited a single phase with no obvious peak position shift. The grain growth was analyzed by density and average grain size. For microwave dielectric properties of Ce0.5Sm0.5O1.75 ceramics, the dielectric constant value (er) was dependent on density. The quality factors (Q × f values) were investigated considered with average grain size. And the temperature coefficient of resonant frequency (τf value) had no significant change during the sintering temperature range, which was found consistent with the trend of the dielectric constant value. The Ce0.5Sm0.5O1.75 ceramics sintered at 1475 °C for 4 h exhibited good microwave dielectric performances with er = 18.21, Q × f = 70,500 GHz, and τf = − 16.4 ppm/°C.

A Contribution to Environmentally-Compatible Energy Conversion: Characterization of Nano Structured Natural Ester Oil Decorated with Carbon Quantum Dots

Performance of natural ester oils have not been investigated deeply yet, and concerns exist about their behavior under overstresses and partial discharges. The present work investigates the suitability of novel carbon quantum dots (CQD) decorated nanostructured natural ester based corn oil for transformer insulation applications, particularly focusing on collecting database for overstressed conditions due to lightning impulse (LI) and partial discharge (PD). CQD nanofluids prepared with SiO2 and TiO2 nanofillers are tested for its insulation properties such as PD, LI and AC power frequency breakdown voltage (BDV). The tests are carried out at different concentration of nanofillers with the mass fractions of 0.01, 0.05 and 0.1. Statistical analysis of test data is performed using two parameter Weibull distribution and the results are compared with and without CQD treatment. Results are also compared with conventional mineral oil. Addition of CQD treated insulative SiO2 nanofillers show good insulation performance than semiconductive TiO2 nanofillers. The overall results clearly indicate the positive influence of CQD treatment on SiO2/TiO2 nanoparticles at lower %wt (0.01%wt) concentration of nanofillers and clearly show the suitability for MV transformer insulation applications.