Insulator Behavior Research Articles

Non-Combustible MLI Based Insulation Behavior Under Fire Condition - Experimental and Numerical Investigation

Non-Combustible MLI Based Insulation Behavior Under Fire Condition - Experimental and Numerical Investigation

Improving the ablative properties of silicone rubber by adding aluminum foil/expanded perlite

In this study, aluminum foil (AF) and expanded perlite (EP) were used as the reinforcing fillers to improve the ablation properties of phenyl methyl vinyl silicone rubber composites. The expansion and caramelization of char layer enhanced the ablation and thermal insulation performance of silicone rubber-based composites. The improved bonding of char layer provided a good basis for enhancing ablative properties. The presence of EP increased the emissivity of the char layer which improved the heat radiation properties during ablation process, and it was advantageous to lower surface temperature and reduce thermal erosion. The graphitic degree of char layer was increased which improved high-temperature and oxidative resistance. SEM observations revealed that the surface and cross-section of the char layer were densified, as characterized by the pore size distribution analysis. The above results indicated that the ablation and anti-erosion resistance as well as thermal insulation behavior of silicone rubbers were significantly improved by implementing the expansion and caramelization strategy, which exhibit promising applications as flexible anti-ablation materials for thermal protection purposes.

Engineering antiphase domain boundaries boosted tunable ferromagnetic insulation

Interface-engineered superlattices composed of perovskite PrCoO3 and brownmillerite CaCoO2.5 ([(PCO)n/(CCO)n]m) were designed and fabricated on (001) SrTiO3 substrates with integrated antiphase domain boundaries (APBs) for investigating ferromagnetic insulating phenomenon. The APBs were formed at the surface-step-terrace edges, and the densities of APBs can be regulated by the periods of the superlattices. In these superlattices, ferromagnetic insulating properties were found to be significantly modulated by the APBs. The room-temperature resistivity of the n = 1 superlattice increases by more than three orders of magnitude than that of the n = 5 superlattice and more than five orders of magnitude than that of the Pr0.5Ca0.5CoO3-δ alloy films. The insulation behavior is primarily derived from the charge carriers scattering at the APBs, which block the charge carriers transferring along the in-plane direction. These results could propel the advancement of multifunctional material genetics and provide a strategic approach for the development of artificial materials with tunable properties.

Explanation of puzzling FQHE at the filling fraction 3/4 in a band-hole 2D system in GaAs

A recent experiment revealed an unexpected FQHE at filling fraction 3/4 in a GaAs 2D hole system, which contradicts the composite fermion model prediction and the observation of a compressible Hall metal-type state in a twin 2D electron system in GaAs at the same filling fraction 3/4 at almost same other conditions. This finding challenges conventional effective single-quasiparticle model for FQHE exposing its limitations. We explain this experimental observation within a multiparticle approach based on a topological cyclotron commensurability criterion. This allows to generalize Laughlin function for filling fractions from the complete FQHE hierarchy including observable FQHE states at even denominator fractions. The topological multiparticle approach helps to decipher a structure of composite fermions and provides their generalization for so-called enigmatic states including even denominator filling fractions, and also for quantum fractional Hall-type behavior in Chern topological insulators without a magnetic field.

Experimental Investigation and Characterization of the Thermal Insulating Behavior of Municipal Solid Waste and its Constituents

Experimental Investigation and Characterization of the Thermal Insulating Behavior of Municipal Solid Waste and its Constituents

Novel high-entropy perovskite titanate: A potential thermal protective material with improved thermophysical properties

High-entropy oxides (HEOs) have attracted considerable attention as potential materials for thermal protective coatings, which are driven by the growing demand for critical high-temperature components. Solid-phase reaction was used in the successful synthesis of Nonisotropic high-entropy titanate (La0.3K0.1Ca0.2Sr0.2Ba0.2)TiO3+δ thermal protective coating (TPC) material, whose mechanical and thermal properties were investigated via combined first-principles calculations and experimental methods. Notably, the coating material exhibited a higher thermal expansion coefficient (TEC) of 12.2 × 10−6 K−1 compared with other HEOs reported in the TPC field. Meanwhile, the prepared TPC material presented a prominent thermal insulation behavior with a low thermal conductivity of 1.46W·m−1·K−1 at 1200 °C, and this condition was mainly attributed to multicomponent cation doping, which produces prevalent structural defects and lattice distortions that greatly enhance phonon scattering. First-principles calculations revealed the outstanding elastic anisotropy of (La0.3K0.1Ca0.2Sr0.2Ba0.2)TiO3+δ and its stronger resistance to microcrack extension compared with its single-component counterpart. The compound also showed good mechanical properties with a Vickers hardness of 11.5GPa. The extraordinary thermo-mechanical properties achieved serve as a strong motivation for the pursuit of high-entropy approaches for the development of promising high-temperature TPC.

Numerical Simulation of Corona Discharge Plasma Affecting the Surface Behavior of Polymer Insulators

Corona discharge is a significant problem in the operation of high-voltage transmission and distribution systems, particularly for polymer insulators. Numerical simulation has become an effective tool for investigating the underlying physical mechanisms and optimizing the design of insulators. In this paper, we present a two-dimensional numerical simulation study on corona discharge plasma affecting the surface behavior of polymer insulators. The simulation was performed with the Comsol Multiphysic software and is based on the finite element method and the fluid plasma model, which considers ionization, recombination, and the transport of plasma species. The numerical results are analyzed to study the spatial and temporal characteristics of the corona discharge and its effect on the surface behavior of polymer insulators. The results show that the electric field is affected not only by the volume charge density but also by the surface charge density, which in turn depends on the densities of the charge carriers migrating on the insulator surface. However, the electric field drops drastically when one or two grading rings are installed. But one grading ring is not enough to limit the discharge.

Exploring the adsorption of 4,4’-[oxalylbis(imino)]bis(2-hydroxybenzoic acid) layer at steel/biogasoline interface by the combined electrical-optical-simulation approach

Reactions at the steel/biogasoline interface trigger the adsorption of 4,4’-[Oxalylbis(imino)]bis(2-hydroxybenzoic Acid) (ODA) layer on the steel surface, thereby activating a mechanism that inhibited the early reactions. Exploring the conditionally deposited ODA layer requires a combined approach, including electrical, optical, and simulation techniques to track the film development and coating characteristics over time, and with the assistance of atomic force microscopy, quantum chemistry (DFT), and molecular dynamics (MD) simulations to reveal the adsorption mechanism of the ODA layer at steel/biogasoline interface. The four experimental ODA concentrations were conducted, related to the simulated un-coverage, undersaturated-, saturated-, and oversaturated-coverage model of the adsorbate on the adsorbent. The EC-RS data examines surface compositions and their distribution, coating/solution interface, and coating/substrate adhesion by, respectively, Raman spectroscopy (RS), electrochemical impedance spectroscopy (EIS), and current density—potential (I-V) scan. Namely, RS pointed out that an organic layer was established when ODA was added to the simulated biogasoline. EIS results revealed insulator behaviors of the ODA layer at the solid–liquid interface, limiting the charge transfer between the steel substrate and the biogasoline. I-V results showed an increase in surface current density and a decrease in surface polarization resistance of the coating with the rise in ODA concentration. The AFM morphology profile verified the degradation of the sample’s surface when exposed to biogasoline and the minimization of surface damage by ODA addition through adsorption. The simulation findings revealed that the adsorption of ODA on steel preferred physisorption, reaching the most stable state at a specified temperature and ODA concentration. The adsorption mechanism follows the Generalized Langmuir isotherm. The adsorbate (ODA molecules) can produce a transition phase with the steel substrate surface, which modifies the surface thermodynamic characteristics. The combined electro-optical-simulation technique can be applied to investigate various surface phenomena (reactions, catalyzes, adsorption). It especially helps to understand the protective mechanism of inhibitors in different media.

Measurement and evaluation of the flashover voltage on polluted cap and pin insulator: An experimental and theoretical study

This study investigates the flashover voltage on high voltage insulators in polluted environments, employing a combination of experimental and theoretical approaches. Utilizing Analysis of Variance (ANOVA) and the Finite Element Method (FEM), the research aims to offer a thorough comprehension of the phenomenon. The experimental aspect of the study involves subjecting insulators to polluted environments, replicating real-world scenarios, and measuring the resulting flashover voltages. This experimental study focuses on investigating flashover pollution, where artificial pollution is introduced into an experimental model. An observational approach is employed to assess the impact of conductivity and pollution distribution on the 1512 L cap and pin insulator, as well as its proposed experimental model. Complementing the experimental approach, the theoretical aspect of the study employs the FEM method to simulate and model the insulator's behaviour under pollution. This computational technique enables a detailed analysis of the electrical field distribution, surface potential, and stress repartition across the surface of the insulator. Simulations further explore the impact of pollution on flashover voltage and leakage current. The FEM results are then compared with experimental findings to validate the model's accuracy and reliability. By analyzing the collected data, the ANOVA technique is applied to identify significant differences in flashover voltage under diverse pollution levels. This statistical approach allows for the determination of the most influential factors affecting insulator performance. This research offers valuable insights into the influence of flashover voltage on high-voltage insulators in polluted environments, contributing to the development of more robust and efficient insulation systems. The combination of ANOVA and FEM methods provides a robust framework for understanding and predicting insulator performance, ultimately benefiting the power industry and promoting energy sustainability.

Partial discharge characteristics from polymer insulator under various contaminant

The performance of polymer insulators can be significantly compromised by the presence of contaminants, resulting in damage, structural alterations, and accelerated aging. Hence, this research aimed to investigate the discharge behavior of polymer insulators when exposed to various types of contaminants. Three distinct contaminants, namely fly ash, salt, and algae, were prepared for the study. In order to assess the characteristics of these insulators, measurements of inception and surface breakdown voltages were conducted for each sample. Additionally, partial discharge measurements were performed at two different applied voltages to observe the patterns of partial discharge under different contaminants. To aid in distinguishing the characteristics of partial discharge, a statistical method based on graphical analysis was employed. Furthermore, visual inspection was carried out after the occurrence of partial discharge activity to provide an explanation for these phenomena. The findings of the study revealed that each contaminant produced a unique pattern, which was influenced by the specific elements present in the respective contaminant. It was observed that contaminants exhibit varying effects on partial discharge depending on their nature. Salt was found to induce faster stress propagation, fly ash inhibited stress propagation, and algae had a degrading effect on the surface of the polymer insulators.

Thermal-Insulation Fillers’ Influences on the Heating Resistance of PDMS-Based Aerogel Layer

PDMS-based aerogel layers were synthesized as insulation layers by adopting mullite fiber (MF), hollow glass microspheres (HGM) and silica aerogel (SA) as the main fillers, and their loading amounts and content ratios were checked to investigate their effects on the thermal insulation properties in PDMS composites by thermal conductivity, thermal stability, and thermal insulation. The loading amount of nanofillers can significantly influence the insulation-layer performance, and the best performance with the lowest thermal conductivity of 0.0568 W/(m·K) was obtained by 10 wt% loading in PDMS with MF:SA:HGM = 2:2:1, which can achieve a temperature difference (∆T) of 67 °C on a 200 °C hotplate. Moreover, the variation of the filler content ratios can also affect the thermal insulation behavior when the loading amount is fixed at 10 wt%, and the best thermal barrier performance can be found for the sample with more SA as the filler (MF:SA:HGM = 1:3:1). The formed sample had the best thermal stability and thermal insulation property, which can stand a 9 min flame test without burning by butane spray gun, and the backside of the sample showed ∆T > 500 °C for the whole test.

Thermal insulation and X-ray attenuation properties of fired clay-perlite composites

In this work, the expanded perlite (EP) was used as an additive in local Hang Dong (HDC) and San Kham Phang (SPC) clays from Chiang Mai province, Thailand, for wall tile manufacturing and its influence on various properties were investigated. All samples were fabricated by drying and sintering the mixtures at 1100 °C for 8 h. Fired bulk density, shrinkage, water absorption and modulus of rupture were measured. With increasing perlite content, the density showed a decreasing trend (2.16–1.62 g/cm3 for HDC clay and 2.13 to 1.37 g/cm3 for SPC clay) with the corresponding reduction in the modulus of rupture. Both types of clays showed higher water absorbability when more perlite was added, indicating the hygroscopic properties of porous perlite particles. Phase and chemical composition indicated the uniform distribution of pea-pod-like perlite structure in clay matrix with strong interfacial bonding due to chemical reaction between perlite additive and clay matrix. X-ray attenuation coefficient was found to decrease in correspondence with the decreasing trend in density values. The thermal conductivity of perlite-added Hang Dong clay exhibited at least 10 times reduction compared to pure clay, suggesting the excellent insulation behavior. The HDC with 100 and 200 cm3 perlite showed good performance in terms of rupture strength, water absorbability, X-ray attenuation with additional insulation properties. Based on this perlite-clay composite study, the sample could be further optimized for its X-ray shielding application by infiltration with elemental or alloy particles.

A lightweight AuxHex zero Poisson's ratio pressure-resistant sandwich cylindrical shell and its load-bearing and sound insulation behaviors: Design, simulation and experiment

Pressure-resistant hulls are critical components in underwater vehicles and submersible systems. Exploring novel materials and structures has been a growing trend to overcome conventional structural limitations and achieve multifunctionality. Mechanical metamaterials with tunable physical properties can offer promise. Therefore, this study focuses on designing and fabricating a pressure-resistant sandwich cylindrical shell using AuxHex zero Poisson's ratio (ZPR) mechanical metamaterials. Structural optimization is employed to develop a lightweight AuxHex ZPR unit cell to withstand deep-sea pressure. Mechanical and acoustic experiments were then conducted on a 3D-printed Titanium alloy specimen, and the rationality of numerical modeling was validated by the experimental results. Load bearing and sound insulation properties of the designed ZPR sandwich cylindrical shell have been numerically analyzed and compared with its geometrically similar positive Poisson's ratio (PPR) and negative Poisson's ratio (NPR) shells. The designed ZPR structure that yields a mass density ratio of 0.569 g/cm³ can withstand hydrostatic pressure at 1000 m depths without strength or buckling damage, while adequate reserve buoyancy can be maintained. The submerged ZPR shell structure can provide superior protection for inner spaces and its average sound transmission loss (STL) is more than 5 dB higher than the PPR and NPR shells.

Ant‐Nest‐Inspired Biomimetic Composite for Self‐Cleaning, Heat‐Insulating, and Highly Efficient Electromagnetic Wave Absorption

AbstractThe pursuit of eco‐friendly electromagnetic wave absorption (EMWA) materials with multifunctional capabilities has garnered significant attention in practical applications. However, achieving these desired qualities simultaneously poses a significant challenge. This study introduces a single‐step calcination and chemical polymerization process to obtain an environmentally friendly ant‐nest‐inspired hybrid composite by optimizing conductive polypyrrole nanotubes (PNTs) within a 3D carbonaceous structure. The biomimetic composite forms a highly efficient conductive network, providing a pathway for free electrons within the carbonaceous barriers and enhancing the conduction loss. Remarkably, the EMWA performance of the composite achieves ultrathin (1.6 mm), wide effective absorption band (5.4 GHz), and strong absorption intensity (−67.6 dB) features. Moreover, due to the complex and intertwined 3D continuous network, the obtained samples exhibit excellent thermal insulation and superhydrophobic behavior by inhibiting heat transfer and preventing localized areas from being prone to water absorption. These findings not only offer a sustainable and low‐cost production route for biomimetic carbonaceous composites but also demonstrate a high‐efficiency absorber with great multifunctionality as a green alternative to traditional EMWA materials.

Tuning Interfacial Water Friction through Moiré Twist.

Foundations of nanofluidics can enable advances in diverse applications such as water desalination, energy harvesting, and biological analysis. Dynamically manipulating nanofluidic properties, such as diffusion and friction, is an area of great scientific interest. Twisted bilayer graphene, particularly at the magic angle, has garnered attention for its unconventional superconductivity and correlated insulator behavior due to strong electronic correlations. The impact of the electronic properties of moiré patterns in twisted bilayer graphene on structural and dynamic properties of water remains largely unexplored. Computational challenges, stemming from simulating large unit cells using density functional theory, have hindered progress. This study addresses this gap by investigating water behavior on twisted bilayer graphene, employing a deep neural network potential (DP) model trained with a data set from ab initio molecular dynamics simulations. It is found that as the twisted angle approaches the magic angle, interfacial water friction increases, leading to a reduced water diffusion. Notably, the analysis shows that at smaller twisted angles with larger moiré patterns, water is more likely to reside in AA stacking regions than AB (or BA) stacking regions, a distinction that diminishes with smaller moiré patterns. This study illustrates the potential for leveraging the distinctive properties of moiré systems to effectively control and optimize interfacial fluid behavior.

Influence of Thermal Aging on Space Charge Characteristics and Electrical Conduction Behavior of Cross-Linked Polyethylene Cable Insulation.

The aging of cable insulation presents a significant threat to the safe operation of cables, with space charge serving as a crucial factor influencing cable insulation degradation. However, the characteristics related to space charge and conduction current behavior during thermal aging remain unclear. This study focused on the thermal aging of cross-linked polyethylene (XLPE) material and utilizes a combined pulse electro-acoustic (PEA) and conduction current testing system to analyze the space charge and conduction current characteristics in the sample under varying electric fields and temperatures. The average charge density, short-circuit residual electric field, electric field distortion rate, and conduction current were studied. The findings indicate that the space charge in the samples following thermal aging is predominantly governed by the injected charge. The amorphous region of XLPE decreases, while the cross-linking degree increases after aging, thereby facilitating charge carrier migration within the sample and reducing the generation of charge carriers through thermal pyrolysis. The minimum temperature required for charge injection is reduced by thermal aging. Furthermore, modifications in conduction current, residual electric field, and average charge density indicate that thermal aging has the potential to alter the microstructure and trap characteristics of XLPE. This study provides empirical evidence to elucidate the underlying mechanism of cable insulation aging.

Signature of excitonic insulators in phosphorene nanoribbons

Phosphorene is a recently developed two-dimensional (2D) material that has attracted tremendous attention because of its unique anisotropic optical properties and quasi-one-dimensional (1D) excitons. We use first-principles calculations combined with the maximally localized Wannier function tight binding Hamiltonian and Bethe–Salpeter equation (BSE) formalism to investigate quasiparticle effects of 2D and quasi-1D blue and black phosphorene nanoribbons. Our electronic structure calculations shows that both blue and black monolayered phases are semiconductors. On the other hand black phosphorene zigzag nanoribbons are metallic. Similar behavior is found for very thin blue phosphorene zig-zag and armchair nanoribbon. As a general behavior, the exciton binding energy decreases as the ribbon width increases, which highlights the importance of quantum confinement effects. The solution of the BSE shows that the blue phosphorene monolayer has an exciton binding energy four times higher than that of the black phosphorene counterpart. Furthermore, both monolayers show a different linear optical response with respect to light polarization, as black phosphorene is highly anisotropic. We find a similar, but less pronounced, optical anisotropy for blue phosphorene monolayer, caused exclusively by the quasi-particle effects. Finally, we show that some of the investigated nanoribbons show a spin-triplet excitonic insulator behavior, thus revealing exciting features of these nanoribbons and therefore provides important advances in the understanding of quasi-one dimensional phosphorus-based materials.

The Effect of Radiant Heat on Polystyrene Thermal Insulation Materials

As a result of the increasingly stringent energy requirements of recent years, the issue of façade thermal insulation is gaining more and more prominence. Due to these requirements, layer thickness of insulation increases, or the use of materials with a better coefficient of thermal conductivity is preferred. These requirements are met by polystyrene insulation materials. Therefore, it is extremely important to know as much as possible the behaviour of polystyrene thermal insulation under the influence of fire and radiant heat. Its regulation is not coordinated in Europe, and the effect of radiant heat is not addressed by any country’s standard. In this paper, the behaviour of polystyrene thermal insulations, which are densely used in Hungary is examined, under the influence of radiant heat.

Investigation of the electronic band gap tuning by Si doping on BeO using UV–VIS spectroscopy and density functional theory

BeO with tissue equivalent features promising dosimetric properties, making BeO particularly suitable for being used in all dosimetry applications. In this work, BeO was synthesized and doped with Si using sol-gel and solid-state methods, respectively. To find the optical band gap of Si-doped BeO nanoparticles (BeO:Si) experimentally, the ultraviolet-visible (UV–Vis) spectroscopy was used. To simulate the electronic band structure of BeO and Si-doped BeO, we used the QUANTUM ESPRESSO code based on density functional theory (DFT). The calculated electronic band structure exhibited insulator behavior and the band gap decreased with Si doping in two potential types. Compared to BeO, a shift toward lower energies was determined from the UV–Vis absorption spectrum of BeO:Si, the simulated and the experimental band gaps were found to be in good agreement. These findings offer insights into the dopant syntheses of BeO and their widespread use for fundamental studies as well as their potential applications.

Examining electrical equivalent circuit models of insulators in transmission lines under pollution conditions: a comprehensive study and analysis

This research presents a comprehensive study investigating the behavior of insulators in transmission lines under various pollution conditions. Utilizing equivalent electrical circuits, the analysis aims to understand the impact of pollution on insulator performance, which is crucial for maintaining the reliability and efficiency of power transmission systems. By providing valuable insights into the relationship between pollution and insulator behavior, this study contributes to the development of improved strategies for mitigating the effects of pollution on transmission lines, ultimately enhancing the overall safety and stability of electrical power networks. The study focuses on a digital model that enables the visualization of potential and electric field distribution within a series of glass insulators utilized in Algerian electrical grids. Initially, a parallel RC network equivalent circuit was devised and its parameters were determined through finite element analysis using Comsol Multiphysics. This equivalent circuit was subsequently integrated into ATP/EMTP software to simulate leakage currents, yielding satisfactory outcomes. The model was then incorporated into the isolator's equivalent circuit. Results from various simulations indicate that the occurrence of discharge along the dry strip impacts leakage current. Furthermore, the re-initiation of discharge on the contaminated insulator's surface is influenced by the pollutant deposit's conductivity and distribution. Therefore, understanding the pollution level is vital for accurately evaluating and sizing the insulator chain at the installation site.