Search Results (339)

Ultra-high voltage (UHV) power transmission has become a prerequisite for the development of clean energy. However, arcs generated by UHV circuit breakers can easily lead to safety incidents, and developing arc-extinguishing gases with low global warming potential (GWP) presents certain challenges. It is a fact that fluorolefins, as a class of fluorinated compounds with low GWP, show high application potential in replacing traditional arc-extinguishing agents. In this study, all six conjugated perfluorinated compounds, including C₆F₆ and C₆F_8, were calculated within the density functional theory (DFT) framework at the B3LYP/6-311+G(d,p) level. The dipole moments, HOMO/LUMO energy gaps, and the inherent aromaticity of annular molecules under external electric fields of these fluorinated molecules are investigated accordingly. By analyzing these results, it is found that the influence of the conjugated structure on the stability of arc-extinguishing gases under high-voltage conditions was partially elucidated, providing useful insights for the subsequent development of environmentally friendly and high-performance arc-extinguishing gases. Full article

Quantum dots (QDs) composed of the narrow-bandgap semiconductor PbTe were incorporated into the depletion region of p–n junctions based on wide-bandgap II–VI semiconductors (p-ZnTe/n-CdTe). The heterostructures were grown by molecular beam epitaxy (MBE) on semi-insulating GaAs (100) substrates. The depletion region was engineered by depositing 20 alternating thin layers of CdTe and PbTe, then thermal annealing under ultrahigh vacuum. As revealed by cross-sectional scanning electron microscopy (SEM), the initially continuous PbTe layers transformed into arrays of zero-dimensional nanostructures, namely PbTe QDs. The formation of PbTe QDs in a CdTe matrix arises from the structural mismatch between the zinc blende and rock-salt crystal structures of the two materials. Electron beam-induced current (EBIC) scans confirmed that the QDs are localized within the depleted charge region between the p-ZnTe and n-CdTe layers. The resulting wide-gap diodes containing narrow-band QDs show pronounced sensitivity to infrared radiation in the spectral range of 1–4.5 μm, with a peak responsivity of approximately 8 V/W at a wavelength of ~2.0 μm and a temperature of 200 K. A red-shift in the cutoff wavelength when temperature decreases indicates that the infrared (IR) response is governed by band-to-band optical transitions in the PbTe QDs. In addition, the devices show sensitivity to visible radiation, with a maximum responsivity of 20 V/W at 0.69 μm. These results demonstrate that wide-bandgap p–n junctions incorporating narrow-bandgap QDs can function as dual-wavelength (visible and infrared) photodetectors, with potential applications in two-color detection and infrared solar cells. Full article

Carbon aerogels (CAs) had been well applied in extreme condition thermal insulation, but achieving a balance between mechanical robustness and thermal insulation remains challenging. We present a novel strategy to fabricate carbon aerogels with tunable mechanical properties and thermal insulation properties by tailoring their skeleton architecture via molecular assembly. Carbon precursor aerogel with thick neck particle packing structure was obtained by strong hydrogen-bonding-induced self-assembly between polyurethane-urea oligomer (PUU) and phenolic resin (PF), and carbon aerogel retained robust interparticle connections after pyrolysis, resulting in excellent mechanical properties. The presence of PUU leads to denser packing of resin molecules, promotes graphitization of the carbon and formation of nanocrystalline structures at 1400 °C, resulting in optimized compression modulus and strength. The closed pore structure of carbon skeleton was further studied by Small-Angle X-ray Scattering (SAXS), while moderate pore width (0.4–0.6 nm) optimizes the balance between strength (110 MPa) and thermal conductivity (0.30 W/(m·K)). This work demonstrates that molecular-level assembly combined with pyrolysis control enables precise tuning of carbon aerogel structures and properties, providing new insights for high-temperature thermal insulation applications. Full article

Five types of fruit seed oils have been described from the perspective of their potential use in the synthesis of biopolyols. The overall goal is to increase the participation of biopolyurethanes in polymer production, aligning with the European Green Deal. Blackcurrant, cherry, grape, pomegranate, and watermelon seed oils were characterized by iodine value, acid value, density, average molecular weight, viscosity, and fatty acid profile. The thermal properties of the oils were also determined using thermogravimetry (TGA) and differential scanning calorimetry (DSC). In order to obtain reactive compounds for the synthesis of biopolyols, the vegetable oils were modified using the transesterification reaction with triethanolamine. The resulting biopolyols were characterized by their hydroxyl number, acid number, density, average molar mass, and viscosity. The biopolyols were then used to produce thermal-insulating polyurethane foams by completely replacing petrochemical polyols with counterparts derived from fruit seeds. The obtained foams were described by their closed cell content, apparent density, thermal conductivity coefficient, dimensional stability, maximum stress at 10% deformation, thermal stability, oxygen index, and water absorption. In addition, an analysis of the foaming process revealed that the properties of fruit seed oil after chemical modification had an impact on the properties of the open-cell polyurethane foams and the foaming process itself. Full article

Under the action of strong DC electric field, the resistance of the insulating cylinder of high-voltage DC voltage divider shows a nonlinear decrease with the increase in electric field strength, which leads to the decrease in measurement accuracy. It is shown that the effect can be suppressed to a certain extent by applying a semi-conductive coating on the surface of the insulating outer barrel. However, due to the inherent properties of the conductive nano-fillers, it is difficult to achieve uniform dispersion in the polymer matrix, which limits the electric field modulation ability of the coating and makes it difficult to fundamentally solve the nonlinear effect of the insulating outer barrel resistance. In this study, based on the multi-walled carbon nanotubes/polyaniline (MWCNTs/PANI) epoxy semiconducting coating system, the effects of dispersant type and dosage on the variation in the coating equivalent resistance with voltage were investigated. The semiconducting coatings with different dispersion states of conductive fillers were prepared by regulating the types and amounts of alkyl ammonium salt dispersants, polymer urethane dispersants, and low molecular weight unsaturated polycarboxylic acid polymer dispersants, and analyzed in combination with the equivalent resistance test, SEM microscopic morphology characterization, and coating adhesion test. The results show that the dispersion of the conductive filler has a significant effect on the suppression of the resistance nonlinear effect, and the polymer polyurethane dispersant can make the filler uniformly dispersed by virtue of the strong spatial site resistance, and the equivalent resistance change rate is lower than 28% under the additive amount of 0.5–1.5%, which has an excellent suppression of the nonlinear effect of the insulation resistance, and the adhesion of the coating is significantly improved to grade 0. The study provides theoretical basis and experimental support for the optimization of the preparation process of high-performance MWCNTs/PANI semiconducting coatings, which can help to improve the measurement accuracy and operational stability of high-voltage DC voltage dividers. Full article

Polyvinyl chloride (PVC), owing to its excellent electrical properties and low cost, is widely applied in the inner insulation and outer sheath of cables. To achieve early fault warning based on characteristic gases, this study integrates experimental testing with molecular simulations to systematically reveal the decomposition and gas generation characteristics of different PVC layers under electrical and thermal stresses. The results indicate that inner-layer PVC under electrical stress predominantly generates small-molecule olefins and halogenated hydrocarbons, while outer-layer PVC during thermal decomposition mainly produces hydrogen chloride, alkanes, and fragments of plasticizers. The surrounding atmosphere significantly regulates the gas generation pathways: air promotes the formation of CO₂ and H₂O, whereas electrical discharges accelerate the release of unsaturated hydrocarbons such as acetylene. By employing TG-FTIR, ReaxFF molecular dynamics, and DFT spectral calculations, a normalized infrared spectral library covering typical products was established and combined with the non-negative least squares method to realize quantitative deconvolution of mixed gases. Ultimately, a diagnostic system was constructed based on the concentration ratios of characteristic gases, which can effectively distinguish the failure modes of inner and outer PVC layers as well as different stress types. This provides a feasible approach for early detection of cable faults and supports intelligent maintenance strategies. Full article

Comprehending charge injection at the metal/epoxy interface is essential for designing and applying high-voltage electrical equipment. This study investigates surface charge accumulation in insulators used in high-voltage direct current (HVDC) gas-insulated switchgear (GIS), with a specific focus on the charge injection behavior at the metal/epoxy interface employing first-principles calculations. In this paper, two amine curing agents were selected to construct interface models of a Cu(111) slab and epoxy resin, with repeating fragments representing the crosslinked structure of the resin. Key parameters, including injection barriers, charge transfer, and vacuum energy level shifts (Δ), were evaluated. Notably, molecular structures containing -C₂F₆ bonds exhibited higher electron and hole injection barriers compared to those with -CH₂. Specifically, DDM induces reduced interfacial charge injection barriers and enhanced charge transport capabilities attributed to its low electronegativity and compact spatial configuration, whereas 6FDAM yields elevated barrier heights stemming from its strong electronegative character. The reliability of these findings was further validated through macroscopic charge injection experiments. The above study holds certain referential value for the development and application of high-voltage DC GIS equipment. Full article

High-temperature vulcanized silicone rubber (HTV-SR), widely used in composite insulators, experiences performance degradation when subjected to combined stresses such as corona discharge, humidity and temperature fluctuations. This degradation poses significant risks to the reliability of power grid operation. To investigate the aging behavior and mechanisms of HTV-SR under the combined influences of corona, moisture and thermal cycling, a series of multi-factor accelerated aging tests are conducted. Comprehensive characterizations of surface morphology, structural, mechanical and electrical properties are performed before and after aging. The results reveal that corona discharge induces molecular chain scission and promotes oxidative crosslinking, leading to surface degradation. Increased humidity accelerates water diffusion and hydrolysis, enhancing crosslink density but reducing material flexibility, thereby further deteriorating structural integrity and electrical performance. Compared with constant temperature aging, thermal cycling introduces repetitive thermal stress, which significantly aggravates filler migration and leads to more severe mechanical and dielectric degradation. These findings elucidate the multi-scale degradation mechanisms of HTV-SR under the coupling effects of corona discharge, humidity and temperature cycling, providing theoretical support for the design of corona- and humidity-resistant silicone rubber for composite insulator applications. Full article

Hydrogen serves as a key clean-energy carrier, with the main hurdles lying in safe, efficient transport and storage (gas or liquid) and in end-use energy conversion. Liquid hydrogen (LH), as a high-density method of storage and transportation, presents cryogenic insulation as its key technical issues. In LH storage tanks, the performance of high vacuum multilayer insulation (HVMLI) will decline due to hydrogen release and leakage from the microscopic pores of steel, which significantly destroy the vacuum layer. The accumulation of residual gases will accelerate thermal failure, shorten the service life of storage tanks and increase safety risks. Adsorption is the most effective strategy for removing residual gases. This review aims to elucidate materials, methods, and design approaches related to hydrogen storage. First, it summarizes adsorbents used in liquid hydrogen storage tanks, including cryogenic adsorbents, metal oxides, zeolite molecular sieves, and non-volatile compounds. Second, it explores experimental testing methods and applications of hydrogen adsorbents in storage tanks, analyzing key challenges faced in practical applications and corresponding countermeasures. Finally, it proposes research prospects for exploring novel adsorbents and developing integrated systems. Full article

In this study, benzophenone compounds substituted with electron-withdrawing groups (-NO₂, -F, and -Cl) and electron-donating groups (-OH, -CH₃, -NH₂, and -OCH₃) were employed as voltage stabilizers for crosslinked polyethylene (XLPE) insulation materials. At B3LYP/6-311+G(d,p) level, reaction Gibbs free potential energy data for eleven reaction channels and molecular characteristics, including electron affinity EA(s), ionization potential IP(s), and HOMO-LUMO gap (E_g) of benzophenone derivatives, were obtained. The effects of electron-donating and electron-withdrawing functional groups were systematically evaluated. The calculated results indicate that benzophenones exhibit the lowest Gibbs free energy barrier for grafting onto polyethylene among the investigated molecules. With the introduction of electron-donating groups, the reaction Gibbs free energy barrier increases. It is worth noting that 2-Nitrobenzophenone is considered to possess superior electrical resistivity, attributed to its highest electron affinity among the studied compounds. This investigation is expected to provide reliable insights for the development of modified polyethylene-based insulating materials for high-voltage cables. Full article

The wool of sheep consists of structurally intricate natural fibres that can be processed and manufactured into a range of products. It is prized for its insulation, moisture-buffering capability, flame resistance, and biodegradability. These features arise from its unique fibre architecture and specialised protein composition, which set it apart from most other natural and synthetic fibres. However, despite these novel characteristics, wool fibre variation hampers its uses and reduces its ability to compete with other fibres. This review summarises our current knowledge of wool fibre biology. It begins with a description of wool’s functional properties and performance attributes, then explores the structural foundations of these properties, the molecular basis of fibre trait variation, and prospects for improving fibre quality using genetic approaches. Particular attention is given to the wool keratin and keratin-associated protein genes, their spatiotemporal expression patterns, and genetic polymorphism that may influence fibre characteristics. Opportunities for the genetic improvement of sheep are discussed, including the use of genetic modification and marker-assisted selection. Challenges in interpreting gene–trait associations, particularly from high-throughput omics studies, are highlighted, along with the need for functionally validated genetic markers. Potential trade-offs between wool characteristics and other production and reproductive traits are considered, emphasising the need for balanced breeding approaches. By integrating insights from structural biology, molecular genetics, and breeding strategies, this review provides a foundation for wool fibre improvement. Full article

Myelin is a lipid-rich membrane that insulates axons, providing support and ensuring efficient nerve impulse conduction. Disruption of this sheath, or demyelination, impairs neural transmission and underlies symptoms like vision loss and muscle weakness in multiple sclerosis (MS). Despite extensive studies using in vitro and in vivo models, the molecular mechanisms driving demyelination remain incompletely understood. To investigate the role of myelin basic protein (MBP) in membrane stability, we prepared model myelin membranes (MMMs) from lipids expectedly undergoing gel-to-fluid phase transition, mimicking both normal and altered myelin, with and without MBP. Differential scanning calorimetry (DSC) revealed that MBP suppresses the main phase transition in normal MMMs, unlike in modified MMMs. FTIR spectra showed strengthening of van der Waals interactions in normal MMMs with MBP upon heating and opposite effects in the analogous modified MMM system. Additionally, phosphate groups were identified as critical sites for MBP–lipid interactions. Circular dichroism (CD) spectroscopy suggests that MBP adopts helical structures that penetrate the bilayer of normal MMMs. These findings offer new insights into the molecular-level interactions between MBP and myelin membranes, with implications for understanding demyelination in diseases like MS. Full article

With the development of the new energy industry in high-altitude regions, epoxy resin insulating materials in electrical equipment face severe challenges from prolonged exposure to strong radiation environments. Strong ultraviolet irradiation induces the generation of free radicals such as alkyl (CH₂), alkoxy (CH₂O), and peroxyl (CH₂OO), which continuously attack the cross-linking structure of epoxy resin, leading to its degradation. This study employs molecular dynamics simulations to evaluate the enhancing effect of graphene quantum dots (GQDs) on the radiation resistance of epoxy resin (EP), proposing cross-linking structural integrity as an evaluation criterion. It compares and analyses pure EP (EP/neat), hydrogen-terminated GQDs (EP/GQD_C₅₄H₁₈), and carboxyl-terminated GQDs (EP/GQD_COOH) under three types of free radicals. The results indicate that the unique sp² hybrid structure and hydrogen-donating ability of GQDs can effectively inhibit the activity of free radicals, and improve the integrity of the cross-linked structure by 8% to 16% compared to EP/neat. While both types of GQDs demonstrate comparable behavior in response to alkyl free radicals, EP/GQD_COOH exhibits superior performance under the influence of oxygen-containing free radicals. This enhanced performance can be attributed to its augmented hydrogen-donating capacity and an increased number of active sites. This study investigates the extent to which GQDs with different structures enhance the radiation resistance of epoxy resins, providing an important theoretical basis for the modification of epoxy resins for applications in high-radiation environments. Full article

When the outer sheath of submarine cables is damaged, the degradation of cross-linked polyethylene (XLPE) insulation by anions in seawater becomes a critical factor affecting cable service life. This study investigates 500 kV three-core XLPE insulation and systematically reveals the differential and synergistic degradation mechanisms of major seawater anions (Cl⁻, SO₄²⁻, HCO₃⁻). Accelerated aging tests at 90 °C were conducted using solution systems simulating both single-ion and composite environments, combined with electrical performance evaluation, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Results show that seawater causes significantly greater deterioration of resistivity, breakdown strength, and molecular structure than any single-ion solution. Mechanistic analysis demonstrates that Cl⁻ induces nucleophilic substitution, SO₄²⁻ promotes oxidative chain scission, and HCO₃⁻ facilitates hydrolysis via pH regulation, while their coexistence produces nonlinear synergistic effects through oxidative reactions, electrochemical coupling, and ion transport. This work provides the first systematic comparison of individual and combined anion effects on XLPE, offering new mechanistic insights and quantitative evidence for understanding multi-ion degradation, with implications for insulation material design, protective strategies, and service life prediction of submarine cables. Full article

In high-humidity environments, the epoxy resin solid insulation materials of high-frequency transformers are prone to aging, resulting in varying degrees of deterioration in the material’s dielectric properties and other aspects. To enhance the adaptability of epoxy resin in high humidity environments, this paper, based on the molecular dynamics simulation method, establishes epoxy resin-based nanocomposites with doped nanofillers: a pure epoxy resin model and three epoxy resin models, respectively, doped with carbon nanotubes, graphene(GR), and SiO₂. Based on the above models, using LAMMPS-17Apr2024, the thermal diffusion coefficients (thermal conductivity and specific heat capacity), glass transition temperatures, and dielectric constants under different moisture contents are calculated. The results show that the various properties of the epoxy resin nanocomposites doped with nanofillers have been improved to varying degrees. Among them, the GR/epoxy resin composite model shows the most significant improvements in thermal conductivity, thermal diffusivity, and glass transition temperature, and the SiO₂/epoxy resin composite model has the best dielectric properties. Considering the high-temperature operation conditions and heat dissipation requirements of the high-frequency transformer, the GR-enhanced epoxy resin becomes the optimal filler choice. Full article