Aramid papers (AP), made of aramid fibers, demonstrate superiority in electrical insulation applications. Unfortunately, the strength and electrical insulating properties of AP remain suboptimal, primarily due to the ...Aramid papers (AP), made of aramid fibers, demonstrate superiority in electrical insulation applications. Unfortunately, the strength and electrical insulating properties of AP remain suboptimal, primarily due to the smooth surface and chemical inertness of aramid fibers. Herein, AP are modified via the nacre-mimetic structure composed of aramid nanofibers (ANF) and carbonylated basalt nanosheets (CBSNs). This is achieved by impregnating AP into an ANF-CBSNs (A-C) suspension containing a 3D ANF framework as the matrix and 2D CBSNs as fillers. The resultant biomimetic composite papers (AP/A-C composite papers) exhibit a layered “brick-and-mortar” structure, demonstrating superior mechanical and electrical insulating properties. Notably, the tensile strength and breakdown strength of AP/A-C5 composite papers reach 39.69 MPa and 22.04 kV mm^(−1), respectively, representing a 155 % and 85 % increase compared to those of the control AP. These impressive properties are accompanied with excellent volume resistivity, exceptional dielectric properties, impressive folding endurance, outstanding heat insulation, and remarkable flame retardance. The nacre-inspired strategy offers an effective approach for producing highly promising electrical insulating papers for advanced electrical equipment.展开更多
Thermally conductive papers with electrical insulation and mechanical robustness are essential for efficient thermal management in modern electronics.In this study,we introduced a metal ion-assisted interfacial crossl...Thermally conductive papers with electrical insulation and mechanical robustness are essential for efficient thermal management in modern electronics.In this study,we introduced a metal ion-assisted interfacial crosslinking strategy to strengthen sugarfunctionalized graphene fluoride(SGF)and cellulose nanofibers(CNF)by hydrogen bonding and metal ion crosslinking that leads to simultaneous enhancements in thermal conductivity and mechanical properties.The facile sugarassisted ball-milling exfoliation method was developed to achieve the exfoliation of graphite fluoride and hydroxyl group functionalization on the surface of graphene fluoride.Thanks to the good dispersibility of the SGF sheets in water,the flexible SGF/CNF composite papers with hydrogen bonding were prepared via vacuum-assisted filtration.We introduced hydrogen bonding and metal ion crosslinking into SGF/CNF papers to obtain densely packed composite papers.Ca^(2+)or Al^(3+)ion-crosslinked SGF/CNF papers exhibited superior thermal and mechanical properties owing to hydrogen bonding and metal ion crosslinking.SGF/CNF-Ca^(2+)and SGF/CNF-Al^(3+)papers at 50 wt%of SGF yield in-plane thermal conductivities of 72.93 and 75.02 W m^(-1) K^(-1),and tensile strengths of 121.5 and 135.7 MPa,respectively.A thermal percolation value was observed at 12.6 vol%of SGF filler content.In addition,the SGF/CNF papers exhibited electrical insulation properties.These remarkable characteristics of the metal ion-crosslinked SGF/CNF papers are attributed to the densely packed structures caused by the strong interfacial interactions from hydrogen bonding as well as metal ion-crosslinking that could promote phonon transport.High-performance metal ion-crosslinked SGF/CNF papers with these fascinating advantages offer great potential for the thermal management of flexible electronics.展开更多
While the enhancement of elastomer properties through nanofiller addition has been widely explored,developing high-performance elastomers for electrically insulating electromagnetic interference(EMI)shielding material...While the enhancement of elastomer properties through nanofiller addition has been widely explored,developing high-performance elastomers for electrically insulating electromagnetic interference(EMI)shielding materials using a simple approach remains crucial.In this study,high-performance composite silicone rubber(SR)elastomers were fabricated through a combination of straightforward physical mixing and chemical grafting approach.Specifically,the incorporation of components aluminum trioxide nanoparticles(n-Al_(2)O_(3))and reactive small molecule 2-isocyanoethyl acrylate(ICA)and 2-Amino-4-hydroxy-6-methylpyrimidine(UPY)into SR significantly improved both the mechanical strength and ther-mal resistance of the composites due to the synergistic effects of nanoparticles and hydrogen bonding.In addition,as flexible electronics become more complex and miniaturised,there is an increasing demand for stretchable electrically insulating EMI shielding materials.Liquid metal(LM)with extreme fluidity is ideal for the preparation of stretchable EMI shielding materials.By introducing LM,we prepared a stretchable electrically insulating EMI shielding material with a sandwich structure using a simple mechanical sintering and lamination process,and the EMI shielding properties of the material remained stable before and after stretching.The modified insulating layer has excellent elasticity and thermal stability,which en-sures the normal use of the composite EMI shielding material under high temperatures and mechanical deformation conditions.This research provides valuable insights into the development of shielding materials with high-performance electrical insulation and strain-invariant EMI shielding behavior.展开更多
Rare earth permanent magnetic materials are typical electrical conductor, and their magnetic properties will decrease because of the eddy current effect, so it is difficult to keep them stable for a long enough time u...Rare earth permanent magnetic materials are typical electrical conductor, and their magnetic properties will decrease because of the eddy current effect, so it is difficult to keep them stable for a long enough time under a high frequency AC field. In the present study, as far as rare earth permanent magnets are concerned, for the first time, rare earth permanent magnets with strong electrical insulation and high magnetic performance have been obtained through experiments, and their properties are as follows： （i） Sm1 TM17 ： Br=0. 62 T, jHc=803.7 kA/m, （BH）m= 58.97 kJ/m^3, p=7 Ω· m; （2） NdFeB： Br=0.485 T, jHc=766.33 kA/m, （BH）m=37.96 kJ/m^3, ρ=Ω · m. The magnetic properties of Sm2TM17 and NdFeB are obviously higher than those of ferrite permanent magnet, and the electric insulating characteristics of Sm2TM17 and NdFeB applied have in fact been approximately the same as those of ferrite. Therefore, Sm2TM17 and NdFeB will possess the ability to take the place of ferrite under a certain high frequency AC electric field.展开更多
The present work enhanced the thermal conductivity of poly（p-phenylene sulfide）/expanded graphites and poly（p-phenylene sulfide）/carbon nanotubes, by incorporating composites with hexagonal boron nitride, which si...The present work enhanced the thermal conductivity of poly（p-phenylene sulfide）/expanded graphites and poly（p-phenylene sulfide）/carbon nanotubes, by incorporating composites with hexagonal boron nitride, which simultaneously succeeded in raising the electrical conductivity of the systems. A two-step mechanical processing method which includes rotating solid-state premixing and inner mixing was adopted to improve dispersion of the hybrids, contributing to the formation of an interspered thermal conductive network. Similar synergic effect in thermal conductivity enhancement was discovered in the hybrid systems regardless of the dimension difference between the two carbon fillers. Such is postulated to be the one satisfying advantage generated by the afore-mentioned network; the other is the insulativity of the hybrid systems given by the effective blockage of hexagonal boron nitride as an insulating material in our network.展开更多
With the rapid development of 5G information technology,thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent.In this work,“high-temperature...With the rapid development of 5G information technology,thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent.In this work,“high-temperature solid-phase&diazonium salt decomposition”method is carried out to prepare benzidine-functionalized boron nitride(m-BN).Subsequently,m-BN/poly(pphenylene benzobisoxazole)nanofiber(PNF)nanocomposite paper with nacremimetic layered structures is prepared via sol–gel film transformation approach.The obtained m-BN/PNF nanocomposite paper with 50 wt%m-BN presents excellent thermal conductivity,incredible electrical insulation,outstanding mechanical properties and thermal stability,due to the construction of extensive hydrogen bonds andπ–πinteractions between m-BN and PNF,and stable nacre-mimetic layered structures.Itsλ∥andλ_(⊥)are 9.68 and 0.84 W m^(-1)K^(-1),and the volume resistivity and breakdown strength are as high as 2.3×10^(15)Ωcm and 324.2 kV mm^(-1),respectively.Besides,it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640°C,showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment.展开更多
Effect of electrode insulation on the electric field and the flow field of the machining gap during electrochemical drilling（ECD） is numerically studied. Electric field simulation shows that the current density alon...Effect of electrode insulation on the electric field and the flow field of the machining gap during electrochemical drilling（ECD） is numerically studied. Electric field simulation shows that the current density along the side gap decreases with increasing the thickness of electrode insulation. And the analysis of the electrolyte flow in the frontal gap shows that the insulation thickness has a remarkable influence on the pressure distributions. Ex- periments investigate the influence of the insulation thickness on the main characteristics of the machined hole, i.e. , radial overcut, entrance conicity, and current stability. The poor hole is observed and identified as most likely to occur with a combination of the low tool feed rate and the low insulation thickness. The appropriate thickness of the insulating layer leads to an improvement on hole accuracy and machining stability.展开更多
An online partial discharge(PD) measurement performed on a high voltage direct current(HVDC) wall bushing successfully identified the presence of internal discharges.The wall bushing is a sulfur hexafluoride gas-insul...An online partial discharge(PD) measurement performed on a high voltage direct current(HVDC) wall bushing successfully identified the presence of internal discharges.The wall bushing is a sulfur hexafluoride gas-insulated bushing,rated for 500 kV dc and terminated on a thyristor-controlled HVDC converter bridge.The measurement of PD within the HVDC station environment is particularly challenging due to the high levels of electromagnetic noise caused by thyristor switching events and external air-corona from the neighboring high-voltage equipment.An additional challenge is the""mixed"voltage stress on the bushing insulation,which has both ac and dc high-voltage components.There are also fast transients during the firing of thyristors in the HVDC conversion process that cause added stress to the insulation.As a result,the analysis and interpretation of PD data for HVDC equipment is more complex;PD pulses may occur in response to the ac,dc,or switching transient voltage stresses.In this paper,an online PD measurement strategy for noise filtering and isolation of PD sources within the bushing are discussed.The PD measurement data is plotted on a phase-resolved diagram where the line supply power cord voltage was used as a reference. The phase-resolved diagram appears to suggest that the fast transients,caused during switching,trigger some PD events.Measurements were also performed with the aid of a modern PD measurement instrument having noise separation capabilities.The findings from the online PD measurements are verified with physical evidence,found after the bushing was removed from service,suggested internal PD had occurred inside the bushing.展开更多
Given that graphene features high electrical conductivity,it is a kind of material with corrosion-promotion activity.This study aimed to inhibit the corrosion-promotion activity of graphene in coatings.Here,we report ...Given that graphene features high electrical conductivity,it is a kind of material with corrosion-promotion activity.This study aimed to inhibit the corrosion-promotion activity of graphene in coatings.Here,we report an exciting application of epoxy matrix(EP)/F-doped reduced graphene oxide(rGO)coatings for the long-term corrosion protection of steel.The synthesized F-doped rGO(FG)did not reduce the utilization of rGO by a wide margin and possessed distinctive electrically insulating nature.The electrical conductivity of rGO was approximately 1500 S/m,whereas those of FG-1,FG-2 and FG-3 were 1.17,5.217×10^−2 and 3.643×10^-11 S/m,respectively.FG and rGO were then dispersed into epoxy coatings.The chemical structures of rGO and FG were investigated by transmission electron microscopy(TEM),scanning probe microscopy(SPM),X-ray photoelectron spectroscopy(XPS),Fourier-transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD).EP/FG coatings exhibited outstanding corrosion protection in comparison with blank EP and EP/rGO coatings mainly because the corrosion-promotion effect of rGO was eliminated.The anticorrosion ability of EP/FG coatingswasimproved with increased F-doped degree of FG.In addition,electrochemical impendance spectroscopy(EIS)results indicated that the Rc values of EP/FG-2 and EP/FG-3 were four orders of magnitude higher than those of EP/rGO in diluent NaCl solution(3.5 wt.%)after immersion for 90 days.展开更多
BiFeO_(3)-BaTiO_(3)(BF-BT)lead-free piezoelectric ceramics have high piezoelectricity and high Curie temperature(T_(C)),but the mixed-valence Fe ions and Bi^(3+)volatilization would promote the formation of Bi_(25)FeO...BiFeO_(3)-BaTiO_(3)(BF-BT)lead-free piezoelectric ceramics have high piezoelectricity and high Curie temperature(T_(C)),but the mixed-valence Fe ions and Bi^(3+)volatilization would promote the formation of Bi_(25)FeO_(40)/Bi_(2)Fe_(4)O_9 and oxygen vacancy,which greatly degrade the insulation properties required for polarization.In this study,it was found that the modification of BiAlO_(3)(BA)in BF-BT ceramics could effectively solve these problems,reducing the leakage current to 1×10^(-9)A·cm^(-2)and transiting the space charge-limited conduction to ohmic conduction.Because of the enhanced insulation properties and appropriate rhombohedral-pseudocubic phase ratio(C_R/C_(PC)),BF-BT-xBA ceramics in an optimized composition obtain enhanced piezoelectric performance:piezoelectric charge coefficient(d_(33))=196 pC·N^(-1),planar electromechanical coupling coefficient(k_(p))=31.1%,T_(C)=487℃and depolarization temperature(T_d)=250°C;unipolar strain(S_(uni))=0.17%and piezoelectric strain coefficient(d_(33)^(*))=335 pm·V^(-1)at 100℃.Especially,d_(33)exceeds 283 pC·N^(-1)at 233℃and d_(33)^(*)is 335 pm·V^(-1)at100℃,showing an excellent high-temperature piezoelectricity and high depolarization temperature.The results are attributed to the domain structure of rhombohedral-pseudocubic phase coexistence and its high-temperature switching behavior.This work provides a feasible and effective approach to improve the high temperature piezoelectric properties of BF-BT-xBA ceramics,making them more suitable for high temperature applications.展开更多
This study provides a concise overview of the latest developments in multifunctional thermally conductive polymer composites(TCPCs).Drawing from the current state of research,the study elucidates the mechanisms that u...This study provides a concise overview of the latest developments in multifunctional thermally conductive polymer composites(TCPCs).Drawing from the current state of research,the study elucidates the mechanisms that underpin thermal conductivity in polymers and their composites.It further delineates the structure-property relationships of TCPCs,focusing on their modulus,resilience,and orientation.Concurrently,this work delves into the principles and structural design of TCPCs endowed with self-healing capabilities,electromagnetic interference(EMI)shielding,and electrical insulation characteristics.In particular,it outlines design strategies for imparting self-healing features to TCPCs and explores the interplay between thermal conductivity and self-healing efficacy.The principles of EMI shielding are clarified,along with the primary structural variants of TCPCs possessing EMI shielding attributes.Additionally,the paper addresses the insulative treatments applied to fillers within composites to enhance their electrical insulation.It concludes with a brief exposition of applications spanning electronic packaging,batteries,aerospace,LEDs,and flexible&stretchable electronics,to sensors.The aim of this review is to provide fresh insights for researchers intent on devising TCPCs with integrated self-healing,electromagnetic shielding,and electrical insulation functionalities,and to articulate strategies for optimizing the thermal conductivity coefficient(λ)alongside these attributes.展开更多
This study investigates the breakdown voltage characteristics in sulfur hexafluoride(SF6)circuit breakers,employing a novel approach that integrates both experimental investigations and finite element simulations.Util...This study investigates the breakdown voltage characteristics in sulfur hexafluoride(SF6)circuit breakers,employing a novel approach that integrates both experimental investigations and finite element simulations.Utilizing a sphere-sphere electrode configuration,we meticulously measured the relationship between breakdown voltage and electrode gap distances ranging from 1 cm to 4.5 cm.Subsequent simulations,conducted using COMSOL Multiphysics,mirrored the experimental setup to validate the model’s accuracy through a comparison of the breakdown voltage-electrode gap distance curves.The simulation results not only aligned closely with the experimental data but also allowed the extraction of detailed electric field strength,electric potential contours,and electric current flow curves at the breakdown voltage for gap distances extending from 1 to 4.5 cm.Extending the analysis,the study explored the electric field and potential distribution at a constant voltage of 72.5 kV for gap distances between 1 to 10 cm,identifying the maximum electric field strength.A comprehensive comparison of five different electrode configurations(sphere-sphere,sphere-rod,sphere-plane,rod-plane,rod-rod)at 72.5 kV and a gap distance of 1.84 cm underscored the significant influence of electrode geometry on the breakdown process.Moreover,the research contrasts the breakdown voltage in SF6 with that in air,emphasizing SF6’s superior insulating properties.This investigation not only elucidates the intricate dynamics of electrical breakdown in SF6 circuit breakers but also contributes valuable insights into the optimal electrode configurations and the potential for alternative insulating gases,steering future advancements in high-voltage circuit breaker technology.展开更多
Epoxy resin(EP)has been widely utilized in electrical equipment and electronic devices due to its fascinating electric,thermal,and mechanical properties.However,the complex insulation structures of modern power device...Epoxy resin(EP)has been widely utilized in electrical equipment and electronic devices due to its fascinating electric,thermal,and mechanical properties.However,the complex insulation structures of modern power devices in high-voltage direct current systems pose several challenges for EP-based dielectrics.The most significant among these challenges is the need for EP to stably operate under greater electric fields,requiring superior breakdown strength.This paper summarizes the key factors influencing the breakdown strength of EP and reviews reported methods for enhancing this property.Recognizing the limitations of existing approaches,we propose that the emerging technology of molecule design offers a potentially optimal solution for developing EP with enhanced breakdown strength.Furthermore,we anticipate the future development direction of EP with satisfactory insulation properties.We believe that enhancing the breakdown theory of solid dielectrics,exploring new research and development methodologies,and creating environmentally friendly EP with high performance are primary focus areas.We hope that this paper will offer guidance and support for the future development of EP with superior breakdown strength,proving valuable in advancing EP-based dielectrics.展开更多
Composite Li metal anodes based on three-dimensional(3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density.However,uneven Li deposition be...Composite Li metal anodes based on three-dimensional(3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density.However,uneven Li deposition behavior still occurs at the top of 3D frameworks owing to the local accumulation of Li ions.To promote uniform Li deposition without top dendrite growth,herein,a layered multifunctional framework based on oxidation-treated polyacrylonitrile(OPAN) and metal-organic framework(MOF) derivatives was proposed for rationally regulating the distribution of Li ions flux,nucleation sites,and electrical conductivity.Profiting from these merits,the OPAN/carbon nano fiber-MOF(CMOF) composite framework demonstrated a reversible Li plating/stripping behavior for 500 cycles with a stable Coulombic efficiency of around 99.0% at the current density of 2 mA/cm~2.Besides,such a Li composite anode exhibited a superior cycle lifespan of over 1300 h under a low polarized voltage of 18 mV in symmetrical cells.When the Li composite anode was paired with LiFePO_(4)(LFP) cathode,the obtained full cell exhibited a stable cycling over 500 cycles.Moreover,the COMSOL Multiphysics simulation was conducted to reveal the effects on homogeneous Li ions distribution derived from the above-mentioned OPAN/CMOF framework and electrical insulation/conduction design.These electrochemical and simulated results shed light on the difficulties of designing stable and safe Li metal anode via optimizing the 3D frameworks.展开更多
This work deals with the understanding of the degradation of the primary insulation (PEI/PAI) of rotating machines working temporarily under high-temperature. The main domain of application of these motors is the smok...This work deals with the understanding of the degradation of the primary insulation (PEI/PAI) of rotating machines working temporarily under high-temperature. The main domain of application of these motors is the smoke extraction either from tunnels or underground parking when a fire occurs. In such a critical situation, the internal temperature of the motor winding may reach temperatures up to 400°C. Under such very high thermal stresses, the behaviour of the electrical insulation is not well understood. This work proposes an analysis of the decomposition gases under very high temperatures and the corresponding degradation pathway. A simple method is proposed to identify whether the insulation of such motors has been strongly damaged during the working time at very high temperatures, thus allowing estimating if it can still continue to operate.展开更多
There is an extremely urgent demand in the realm of power equipment,including power transformers,motors,and cables.Specifically,there is a pressing need for cellulose-based composite insulating paper that can exhibit ...There is an extremely urgent demand in the realm of power equipment,including power transformers,motors,and cables.Specifically,there is a pressing need for cellulose-based composite insulating paper that can exhibit high thermal conductivity,superior mechanical properties,and robust insulation characteristics.In response to this demand,this study adopted a‘simulation-guided experimental research’methodology.Firstly,based on molecular dynamics(MD)simulations,nano-kaolin(KL)/cellulose composite models with different contents were constructed.Then,according to the simulation results,the corresponding proportions of nano-KL/cellulose insulating paper were prepared.The simulation and experimental findings further reveal a sig-nificant effect of nano-KL.To be more precise,nano-KL can effectively fill the microscopic defects and voids within the cellulose structure.Moreover,nano-KL forms an orderly and regular thermal conductivity network in conjunction with cellulose.As a result,this network structure elevates the paper's overall thermal conductivity.Owing to its low-dielectric-loss characteristics,nano-KL reduces the microscopic charge polar-isation phenomenon within the composite structure.It curbs the migration of elec-trons,alleviates the concentration of electric field stress,and ultimately improves the electrical insulation performance of the modified insulating paper.Notably,the 4 wt%nano-KL/cellulose insulating paper exhibits optimal performance,and its tensile strength,thermal conductivity,volume resistivity,dielectric loss,and breakdown strength are 55.81 MPa,0.201 W·m^(−1)⋅K^(−1),4.58×10^(15)Ω·m,0.25%,and 57.81 kV/mm.This study demonstrates MD simulations'feasibility and effectiveness in providing theories and protocols for experiments.展开更多
Sandwiched composites with a combination of electromagnetic interference(EMI)shielding performance,thermal conductivity,and electrical insulation show significant potential in electronic packaging.However,the fabricat...Sandwiched composites with a combination of electromagnetic interference(EMI)shielding performance,thermal conductivity,and electrical insulation show significant potential in electronic packaging.However,the fabrication of such composites using high-performance thermosets as matrices presents challenges due to their permanently crosslinked structures.Here,we relied on the dynamic covalent chemistry to propose an innovative interface-welding strategy to fabricate a sandwiched thermoset(covalent adaptable network)/carbon nanotubes/boron nitride(CAN/CNTs/BN)composite.To sustainability,theCANmatrixwas derived fromrenewable biobased resources,such as vanillin,glycerol triglycidyl ether,and 1,10-diaminodecane.The incorporation of CAN/BN composites as the outer layers bolstered thermal conductivity while maintaining electrical insulation,while the CAN/CNTs interlayer efficiently attenuated electromagnetic waves.With a BN and CNT content of 30 wt%,the CAN/CNTs/BN composite achieved a thermal conductivity of 1.79W⋅m^(−1)⋅K^(−1),an EMI shielding effectiveness exceeding 55 dB in the X-band,and an ultra-low electrical conductivity of 1.6×10^(−13)S⋅m^(−1).Leveraging dynamic covalent chemistry,the interface-welding technique fostered fully integrated interfaces,ensuring superior mechanical properties of CAN/CNTs/BN composite including a tensile modulus of 3837.8±196.9 MPa and tensile strength of 62.1±3.7 MPa.Additionally,its exceptional heat dissipation performance positions CAN/CNTs/BN composite as a promising contender for electronic packaging applications.展开更多
The multifrequency voltage(MFV)stress,including switching impulses and harmonics,commonly appearing in the modern power system will stimulate the multifrequency impedance dynamics behaviours of electrical insulation.T...The multifrequency voltage(MFV)stress,including switching impulses and harmonics,commonly appearing in the modern power system will stimulate the multifrequency impedance dynamics behaviours of electrical insulation.Therefore,this article presents a novel concept of insulation resilience response(IRR)by employing polymer insulation materials,which may be extended to electrical insulation resilience(EIR).The focus is on understanding reversible recovery performance and supporting physics-informed condition assessment for electrical insulation exposed to MFV.The underlying physical mechanisms and modelling methodologies are integrated to characterise the IRR behaviours of polymer insulation systems.The multifrequency dielectric/impedance properties of different resin dielectrics under diverse temperatures are comparatively investigated as proofofconcept cases.Furthermore,multidimensional sensitivity indicators are developed to quantify the electrical insulation resilience behaviour.A radar plot representation integrating resilience sensitivity indicators qualitatively assesses the IRR behaviours of polymer insulation systems.Additionally,a quantification methodology,including the resilience index(RI)and time-varied RI(TVRI),is proposed for the reversible recovery performance analysis for electrical insulation,respectively.Ultimately,an application-oriented framework derived from TVRI is provided to analyse the recovery performance evolution behaviours of electrical insulation under complex operating conditions.This offers a key theoretical foundation for insulation performance characterisation and condition analysis for high-voltage power equipment.展开更多
The tri-post insulator is a core component within the gas-insulated transmission lines(GIL),providing both electrical insulation and mechanical support.Typically,it is high-temperature cured through vacuum casting of ...The tri-post insulator is a core component within the gas-insulated transmission lines(GIL),providing both electrical insulation and mechanical support.Typically,it is high-temperature cured through vacuum casting of a mixture of epoxy resin,curing agent,and alumina fillers.In recent years,frequent incidents of mechanical cracking and breakdown of tri-post insulators have been reported,which are attributed to residual stress concentration.However,the formation mechanism and distribution characteristics of the residual stress remain unclear.This study focuses on the curing kinetics and re-sidual stress modelling of GIL tri-post insulators.It is verified that the epoxy resin/alumina reaction system follows the autocatalytic curing kinetic model by differential scanning calorimetry tests,and the model fitted by Malek's method corresponds well with the experimental results.Based on the Cure Hardening Instantaneously Linear Elastic model and the density inhomogeneity,it is found that a tensile stress concentration with a maximum value of 58.9 MPa at the edge of the insulator/sleeve interface,due to the mismatch of chemical and thermal shrinkage effects.Besides,the filler sedimentation can decrease the coefficient of thermal expansion and suppress the residual stress concen-tration.The investigation would help with the visualisation of the residual stress distri-bution in GIL tri-post insulators and provide some guidance for their processing treatments.展开更多
基金supported by the National Natural Science Foundation of China(No.22278260)the Open Foundation of Key Laboratory of Auxiliary Chemistry and Technology for Chemical Industry(No.KFKT2021-14)Shaanxi Collaborative Innovation Center of Industrial Auxiliary Chemistry and Technology(No.KFKT2021-14).
文摘Aramid papers (AP), made of aramid fibers, demonstrate superiority in electrical insulation applications. Unfortunately, the strength and electrical insulating properties of AP remain suboptimal, primarily due to the smooth surface and chemical inertness of aramid fibers. Herein, AP are modified via the nacre-mimetic structure composed of aramid nanofibers (ANF) and carbonylated basalt nanosheets (CBSNs). This is achieved by impregnating AP into an ANF-CBSNs (A-C) suspension containing a 3D ANF framework as the matrix and 2D CBSNs as fillers. The resultant biomimetic composite papers (AP/A-C composite papers) exhibit a layered “brick-and-mortar” structure, demonstrating superior mechanical and electrical insulating properties. Notably, the tensile strength and breakdown strength of AP/A-C5 composite papers reach 39.69 MPa and 22.04 kV mm^(−1), respectively, representing a 155 % and 85 % increase compared to those of the control AP. These impressive properties are accompanied with excellent volume resistivity, exceptional dielectric properties, impressive folding endurance, outstanding heat insulation, and remarkable flame retardance. The nacre-inspired strategy offers an effective approach for producing highly promising electrical insulating papers for advanced electrical equipment.
基金supported by the Basic Science Program(No.2022R1A2C2009700)through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICTthe Basic Science Research Capacity Enhancement Project(National Research Facilities and Equipment Center)through the Korea Ba-sic Science Institute funded by the Ministry of Education(No.2019R1A6C1010047)the Industrial Strategic Technology Development Program(No.20013248)through Korea Evaluation In-stitute of Industrial Technology funded by the Ministry of Trade,Industry&Energy(MOTIE,Korea).
文摘Thermally conductive papers with electrical insulation and mechanical robustness are essential for efficient thermal management in modern electronics.In this study,we introduced a metal ion-assisted interfacial crosslinking strategy to strengthen sugarfunctionalized graphene fluoride(SGF)and cellulose nanofibers(CNF)by hydrogen bonding and metal ion crosslinking that leads to simultaneous enhancements in thermal conductivity and mechanical properties.The facile sugarassisted ball-milling exfoliation method was developed to achieve the exfoliation of graphite fluoride and hydroxyl group functionalization on the surface of graphene fluoride.Thanks to the good dispersibility of the SGF sheets in water,the flexible SGF/CNF composite papers with hydrogen bonding were prepared via vacuum-assisted filtration.We introduced hydrogen bonding and metal ion crosslinking into SGF/CNF papers to obtain densely packed composite papers.Ca^(2+)or Al^(3+)ion-crosslinked SGF/CNF papers exhibited superior thermal and mechanical properties owing to hydrogen bonding and metal ion crosslinking.SGF/CNF-Ca^(2+)and SGF/CNF-Al^(3+)papers at 50 wt%of SGF yield in-plane thermal conductivities of 72.93 and 75.02 W m^(-1) K^(-1),and tensile strengths of 121.5 and 135.7 MPa,respectively.A thermal percolation value was observed at 12.6 vol%of SGF filler content.In addition,the SGF/CNF papers exhibited electrical insulation properties.These remarkable characteristics of the metal ion-crosslinked SGF/CNF papers are attributed to the densely packed structures caused by the strong interfacial interactions from hydrogen bonding as well as metal ion-crosslinking that could promote phonon transport.High-performance metal ion-crosslinked SGF/CNF papers with these fascinating advantages offer great potential for the thermal management of flexible electronics.
基金the financial support from the Director’s Fund of the Hefei Institute of Materials Research,Chinese Academy of Sciences(Nos.YZJJQY202405 and YZJJ2024QN36).
文摘While the enhancement of elastomer properties through nanofiller addition has been widely explored,developing high-performance elastomers for electrically insulating electromagnetic interference(EMI)shielding materials using a simple approach remains crucial.In this study,high-performance composite silicone rubber(SR)elastomers were fabricated through a combination of straightforward physical mixing and chemical grafting approach.Specifically,the incorporation of components aluminum trioxide nanoparticles(n-Al_(2)O_(3))and reactive small molecule 2-isocyanoethyl acrylate(ICA)and 2-Amino-4-hydroxy-6-methylpyrimidine(UPY)into SR significantly improved both the mechanical strength and ther-mal resistance of the composites due to the synergistic effects of nanoparticles and hydrogen bonding.In addition,as flexible electronics become more complex and miniaturised,there is an increasing demand for stretchable electrically insulating EMI shielding materials.Liquid metal(LM)with extreme fluidity is ideal for the preparation of stretchable EMI shielding materials.By introducing LM,we prepared a stretchable electrically insulating EMI shielding material with a sandwich structure using a simple mechanical sintering and lamination process,and the EMI shielding properties of the material remained stable before and after stretching.The modified insulating layer has excellent elasticity and thermal stability,which en-sures the normal use of the composite EMI shielding material under high temperatures and mechanical deformation conditions.This research provides valuable insights into the development of shielding materials with high-performance electrical insulation and strain-invariant EMI shielding behavior.
基金Item Sponsored by Liaoning Provincial Natural Science Foundation (20071090)
文摘Rare earth permanent magnetic materials are typical electrical conductor, and their magnetic properties will decrease because of the eddy current effect, so it is difficult to keep them stable for a long enough time under a high frequency AC field. In the present study, as far as rare earth permanent magnets are concerned, for the first time, rare earth permanent magnets with strong electrical insulation and high magnetic performance have been obtained through experiments, and their properties are as follows： （i） Sm1 TM17 ： Br=0. 62 T, jHc=803.7 kA/m, （BH）m= 58.97 kJ/m^3, p=7 Ω· m; （2） NdFeB： Br=0.485 T, jHc=766.33 kA/m, （BH）m=37.96 kJ/m^3, ρ=Ω · m. The magnetic properties of Sm2TM17 and NdFeB are obviously higher than those of ferrite permanent magnet, and the electric insulating characteristics of Sm2TM17 and NdFeB applied have in fact been approximately the same as those of ferrite. Therefore, Sm2TM17 and NdFeB will possess the ability to take the place of ferrite under a certain high frequency AC electric field.
基金Funded by the the National Natural Science Foundation of China(Nos.51173112,51121001)
文摘The present work enhanced the thermal conductivity of poly（p-phenylene sulfide）/expanded graphites and poly（p-phenylene sulfide）/carbon nanotubes, by incorporating composites with hexagonal boron nitride, which simultaneously succeeded in raising the electrical conductivity of the systems. A two-step mechanical processing method which includes rotating solid-state premixing and inner mixing was adopted to improve dispersion of the hybrids, contributing to the formation of an interspered thermal conductive network. Similar synergic effect in thermal conductivity enhancement was discovered in the hybrid systems regardless of the dimension difference between the two carbon fillers. Such is postulated to be the one satisfying advantage generated by the afore-mentioned network; the other is the insulativity of the hybrid systems given by the effective blockage of hexagonal boron nitride as an insulating material in our network.
基金The authors are grateful for the support and funding from the Foundation of National Natural Science Foundation of China(52373089 and 51973173)Startup Foundation of Chongqing Normal University(23XLB011),Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN202300561)Fundamental Research Funds for the Central Universities。
文摘With the rapid development of 5G information technology,thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent.In this work,“high-temperature solid-phase&diazonium salt decomposition”method is carried out to prepare benzidine-functionalized boron nitride(m-BN).Subsequently,m-BN/poly(pphenylene benzobisoxazole)nanofiber(PNF)nanocomposite paper with nacremimetic layered structures is prepared via sol–gel film transformation approach.The obtained m-BN/PNF nanocomposite paper with 50 wt%m-BN presents excellent thermal conductivity,incredible electrical insulation,outstanding mechanical properties and thermal stability,due to the construction of extensive hydrogen bonds andπ–πinteractions between m-BN and PNF,and stable nacre-mimetic layered structures.Itsλ∥andλ_(⊥)are 9.68 and 0.84 W m^(-1)K^(-1),and the volume resistivity and breakdown strength are as high as 2.3×10^(15)Ωcm and 324.2 kV mm^(-1),respectively.Besides,it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640°C,showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment.
基金Supported by the National Natural Science Foundation of China(50635040)the National High Technology Research and Development Program of China("863"Program)(2006AA04Z321)the Natural Science Foundation of Jiangsu Province(BK2008043)~~
文摘Effect of electrode insulation on the electric field and the flow field of the machining gap during electrochemical drilling（ECD） is numerically studied. Electric field simulation shows that the current density along the side gap decreases with increasing the thickness of electrode insulation. And the analysis of the electrolyte flow in the frontal gap shows that the insulation thickness has a remarkable influence on the pressure distributions. Ex- periments investigate the influence of the insulation thickness on the main characteristics of the machined hole, i.e. , radial overcut, entrance conicity, and current stability. The poor hole is observed and identified as most likely to occur with a combination of the low tool feed rate and the low insulation thickness. The appropriate thickness of the insulating layer leads to an improvement on hole accuracy and machining stability.
基金Manitoba Hydro for funding and supporting this research
文摘An online partial discharge(PD) measurement performed on a high voltage direct current(HVDC) wall bushing successfully identified the presence of internal discharges.The wall bushing is a sulfur hexafluoride gas-insulated bushing,rated for 500 kV dc and terminated on a thyristor-controlled HVDC converter bridge.The measurement of PD within the HVDC station environment is particularly challenging due to the high levels of electromagnetic noise caused by thyristor switching events and external air-corona from the neighboring high-voltage equipment.An additional challenge is the""mixed"voltage stress on the bushing insulation,which has both ac and dc high-voltage components.There are also fast transients during the firing of thyristors in the HVDC conversion process that cause added stress to the insulation.As a result,the analysis and interpretation of PD data for HVDC equipment is more complex;PD pulses may occur in response to the ac,dc,or switching transient voltage stresses.In this paper,an online PD measurement strategy for noise filtering and isolation of PD sources within the bushing are discussed.The PD measurement data is plotted on a phase-resolved diagram where the line supply power cord voltage was used as a reference. The phase-resolved diagram appears to suggest that the fast transients,caused during switching,trigger some PD events.Measurements were also performed with the aid of a modern PD measurement instrument having noise separation capabilities.The findings from the online PD measurements are verified with physical evidence,found after the bushing was removed from service,suggested internal PD had occurred inside the bushing.
基金This work was financially supported by the National Natural Science Foundation of China(No.51775540)the Youth Innovation Promotion Association,CAS(No.2017338)+1 种基金the Nature Science Foundation of Zhejiang(No.LQ19E030007)the Natural Science Foundation of Ningbo(No.2018A610114).
文摘Given that graphene features high electrical conductivity,it is a kind of material with corrosion-promotion activity.This study aimed to inhibit the corrosion-promotion activity of graphene in coatings.Here,we report an exciting application of epoxy matrix(EP)/F-doped reduced graphene oxide(rGO)coatings for the long-term corrosion protection of steel.The synthesized F-doped rGO(FG)did not reduce the utilization of rGO by a wide margin and possessed distinctive electrically insulating nature.The electrical conductivity of rGO was approximately 1500 S/m,whereas those of FG-1,FG-2 and FG-3 were 1.17,5.217×10^−2 and 3.643×10^-11 S/m,respectively.FG and rGO were then dispersed into epoxy coatings.The chemical structures of rGO and FG were investigated by transmission electron microscopy(TEM),scanning probe microscopy(SPM),X-ray photoelectron spectroscopy(XPS),Fourier-transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD).EP/FG coatings exhibited outstanding corrosion protection in comparison with blank EP and EP/rGO coatings mainly because the corrosion-promotion effect of rGO was eliminated.The anticorrosion ability of EP/FG coatingswasimproved with increased F-doped degree of FG.In addition,electrochemical impendance spectroscopy(EIS)results indicated that the Rc values of EP/FG-2 and EP/FG-3 were four orders of magnitude higher than those of EP/rGO in diluent NaCl solution(3.5 wt.%)after immersion for 90 days.
基金financially supported by the National Natural Science Foundation of China (Nos.52072028 and52032007)National Key Research and Development Program (No.2022YFB3807400)。
文摘BiFeO_(3)-BaTiO_(3)(BF-BT)lead-free piezoelectric ceramics have high piezoelectricity and high Curie temperature(T_(C)),but the mixed-valence Fe ions and Bi^(3+)volatilization would promote the formation of Bi_(25)FeO_(40)/Bi_(2)Fe_(4)O_9 and oxygen vacancy,which greatly degrade the insulation properties required for polarization.In this study,it was found that the modification of BiAlO_(3)(BA)in BF-BT ceramics could effectively solve these problems,reducing the leakage current to 1×10^(-9)A·cm^(-2)and transiting the space charge-limited conduction to ohmic conduction.Because of the enhanced insulation properties and appropriate rhombohedral-pseudocubic phase ratio(C_R/C_(PC)),BF-BT-xBA ceramics in an optimized composition obtain enhanced piezoelectric performance:piezoelectric charge coefficient(d_(33))=196 pC·N^(-1),planar electromechanical coupling coefficient(k_(p))=31.1%,T_(C)=487℃and depolarization temperature(T_d)=250°C;unipolar strain(S_(uni))=0.17%and piezoelectric strain coefficient(d_(33)^(*))=335 pm·V^(-1)at 100℃.Especially,d_(33)exceeds 283 pC·N^(-1)at 233℃and d_(33)^(*)is 335 pm·V^(-1)at100℃,showing an excellent high-temperature piezoelectricity and high depolarization temperature.The results are attributed to the domain structure of rhombohedral-pseudocubic phase coexistence and its high-temperature switching behavior.This work provides a feasible and effective approach to improve the high temperature piezoelectric properties of BF-BT-xBA ceramics,making them more suitable for high temperature applications.
基金supported by the National Natural Science Foundation of China(Nos.52303101,52327802,52173078,52130303,51973158,51803151)the China Postdoctoral Science Foundation(No.2023M732579)+1 种基金the Young Elite Scientists Spon-sorship Program by CAST(No.2022QNRC001)National Key R&D Program of China(No.2022YFB3805702).
文摘This study provides a concise overview of the latest developments in multifunctional thermally conductive polymer composites(TCPCs).Drawing from the current state of research,the study elucidates the mechanisms that underpin thermal conductivity in polymers and their composites.It further delineates the structure-property relationships of TCPCs,focusing on their modulus,resilience,and orientation.Concurrently,this work delves into the principles and structural design of TCPCs endowed with self-healing capabilities,electromagnetic interference(EMI)shielding,and electrical insulation characteristics.In particular,it outlines design strategies for imparting self-healing features to TCPCs and explores the interplay between thermal conductivity and self-healing efficacy.The principles of EMI shielding are clarified,along with the primary structural variants of TCPCs possessing EMI shielding attributes.Additionally,the paper addresses the insulative treatments applied to fillers within composites to enhance their electrical insulation.It concludes with a brief exposition of applications spanning electronic packaging,batteries,aerospace,LEDs,and flexible&stretchable electronics,to sensors.The aim of this review is to provide fresh insights for researchers intent on devising TCPCs with integrated self-healing,electromagnetic shielding,and electrical insulation functionalities,and to articulate strategies for optimizing the thermal conductivity coefficient(λ)alongside these attributes.
基金Ningbo Science and Technology Plan Project(Grant No.2023Z043)。
文摘This study investigates the breakdown voltage characteristics in sulfur hexafluoride(SF6)circuit breakers,employing a novel approach that integrates both experimental investigations and finite element simulations.Utilizing a sphere-sphere electrode configuration,we meticulously measured the relationship between breakdown voltage and electrode gap distances ranging from 1 cm to 4.5 cm.Subsequent simulations,conducted using COMSOL Multiphysics,mirrored the experimental setup to validate the model’s accuracy through a comparison of the breakdown voltage-electrode gap distance curves.The simulation results not only aligned closely with the experimental data but also allowed the extraction of detailed electric field strength,electric potential contours,and electric current flow curves at the breakdown voltage for gap distances extending from 1 to 4.5 cm.Extending the analysis,the study explored the electric field and potential distribution at a constant voltage of 72.5 kV for gap distances between 1 to 10 cm,identifying the maximum electric field strength.A comprehensive comparison of five different electrode configurations(sphere-sphere,sphere-rod,sphere-plane,rod-plane,rod-rod)at 72.5 kV and a gap distance of 1.84 cm underscored the significant influence of electrode geometry on the breakdown process.Moreover,the research contrasts the breakdown voltage in SF6 with that in air,emphasizing SF6’s superior insulating properties.This investigation not only elucidates the intricate dynamics of electrical breakdown in SF6 circuit breakers but also contributes valuable insights into the optimal electrode configurations and the potential for alternative insulating gases,steering future advancements in high-voltage circuit breaker technology.
文摘Epoxy resin(EP)has been widely utilized in electrical equipment and electronic devices due to its fascinating electric,thermal,and mechanical properties.However,the complex insulation structures of modern power devices in high-voltage direct current systems pose several challenges for EP-based dielectrics.The most significant among these challenges is the need for EP to stably operate under greater electric fields,requiring superior breakdown strength.This paper summarizes the key factors influencing the breakdown strength of EP and reviews reported methods for enhancing this property.Recognizing the limitations of existing approaches,we propose that the emerging technology of molecule design offers a potentially optimal solution for developing EP with enhanced breakdown strength.Furthermore,we anticipate the future development direction of EP with satisfactory insulation properties.We believe that enhancing the breakdown theory of solid dielectrics,exploring new research and development methodologies,and creating environmentally friendly EP with high performance are primary focus areas.We hope that this paper will offer guidance and support for the future development of EP with superior breakdown strength,proving valuable in advancing EP-based dielectrics.
基金supported by the National Natural Science Foundation of China (52302292, 52302058, 52302085)the China Postdoctoral Science Foundation (2021M702225)+1 种基金the Anhui Province University Natural Science Research Project (2023AH030093, 2023AH040301)the Startup Research Fund of Chaohu University (KYQD-2023005, KYQD-2023051)。
文摘Composite Li metal anodes based on three-dimensional(3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density.However,uneven Li deposition behavior still occurs at the top of 3D frameworks owing to the local accumulation of Li ions.To promote uniform Li deposition without top dendrite growth,herein,a layered multifunctional framework based on oxidation-treated polyacrylonitrile(OPAN) and metal-organic framework(MOF) derivatives was proposed for rationally regulating the distribution of Li ions flux,nucleation sites,and electrical conductivity.Profiting from these merits,the OPAN/carbon nano fiber-MOF(CMOF) composite framework demonstrated a reversible Li plating/stripping behavior for 500 cycles with a stable Coulombic efficiency of around 99.0% at the current density of 2 mA/cm~2.Besides,such a Li composite anode exhibited a superior cycle lifespan of over 1300 h under a low polarized voltage of 18 mV in symmetrical cells.When the Li composite anode was paired with LiFePO_(4)(LFP) cathode,the obtained full cell exhibited a stable cycling over 500 cycles.Moreover,the COMSOL Multiphysics simulation was conducted to reveal the effects on homogeneous Li ions distribution derived from the above-mentioned OPAN/CMOF framework and electrical insulation/conduction design.These electrochemical and simulated results shed light on the difficulties of designing stable and safe Li metal anode via optimizing the 3D frameworks.
文摘This work deals with the understanding of the degradation of the primary insulation (PEI/PAI) of rotating machines working temporarily under high-temperature. The main domain of application of these motors is the smoke extraction either from tunnels or underground parking when a fire occurs. In such a critical situation, the internal temperature of the motor winding may reach temperatures up to 400°C. Under such very high thermal stresses, the behaviour of the electrical insulation is not well understood. This work proposes an analysis of the decomposition gases under very high temperatures and the corresponding degradation pathway. A simple method is proposed to identify whether the insulation of such motors has been strongly damaged during the working time at very high temperatures, thus allowing estimating if it can still continue to operate.
基金National Natural Science Foundation of China,Grant/Award Number:52277138Guangxi Science Foundation for Outstanding Young Scholars,Grant/Award Number:202400489+1 种基金Guangxi Key R&D Programs,Grant/Award Numbers:Guike AB24010119,Guike AB25069468The Innovation Project of Guangxi Graduate Education,Grant/Award Number:YCBZ2024052。
文摘There is an extremely urgent demand in the realm of power equipment,including power transformers,motors,and cables.Specifically,there is a pressing need for cellulose-based composite insulating paper that can exhibit high thermal conductivity,superior mechanical properties,and robust insulation characteristics.In response to this demand,this study adopted a‘simulation-guided experimental research’methodology.Firstly,based on molecular dynamics(MD)simulations,nano-kaolin(KL)/cellulose composite models with different contents were constructed.Then,according to the simulation results,the corresponding proportions of nano-KL/cellulose insulating paper were prepared.The simulation and experimental findings further reveal a sig-nificant effect of nano-KL.To be more precise,nano-KL can effectively fill the microscopic defects and voids within the cellulose structure.Moreover,nano-KL forms an orderly and regular thermal conductivity network in conjunction with cellulose.As a result,this network structure elevates the paper's overall thermal conductivity.Owing to its low-dielectric-loss characteristics,nano-KL reduces the microscopic charge polar-isation phenomenon within the composite structure.It curbs the migration of elec-trons,alleviates the concentration of electric field stress,and ultimately improves the electrical insulation performance of the modified insulating paper.Notably,the 4 wt%nano-KL/cellulose insulating paper exhibits optimal performance,and its tensile strength,thermal conductivity,volume resistivity,dielectric loss,and breakdown strength are 55.81 MPa,0.201 W·m^(−1)⋅K^(−1),4.58×10^(15)Ω·m,0.25%,and 57.81 kV/mm.This study demonstrates MD simulations'feasibility and effectiveness in providing theories and protocols for experiments.
基金supported by the National Natural Science Foundation of China(Grant No.52273093)the Fundamental Research Funds for the Central Universities(Grant No.SWU-XDJH202314).
文摘Sandwiched composites with a combination of electromagnetic interference(EMI)shielding performance,thermal conductivity,and electrical insulation show significant potential in electronic packaging.However,the fabrication of such composites using high-performance thermosets as matrices presents challenges due to their permanently crosslinked structures.Here,we relied on the dynamic covalent chemistry to propose an innovative interface-welding strategy to fabricate a sandwiched thermoset(covalent adaptable network)/carbon nanotubes/boron nitride(CAN/CNTs/BN)composite.To sustainability,theCANmatrixwas derived fromrenewable biobased resources,such as vanillin,glycerol triglycidyl ether,and 1,10-diaminodecane.The incorporation of CAN/BN composites as the outer layers bolstered thermal conductivity while maintaining electrical insulation,while the CAN/CNTs interlayer efficiently attenuated electromagnetic waves.With a BN and CNT content of 30 wt%,the CAN/CNTs/BN composite achieved a thermal conductivity of 1.79W⋅m^(−1)⋅K^(−1),an EMI shielding effectiveness exceeding 55 dB in the X-band,and an ultra-low electrical conductivity of 1.6×10^(−13)S⋅m^(−1).Leveraging dynamic covalent chemistry,the interface-welding technique fostered fully integrated interfaces,ensuring superior mechanical properties of CAN/CNTs/BN composite including a tensile modulus of 3837.8±196.9 MPa and tensile strength of 62.1±3.7 MPa.Additionally,its exceptional heat dissipation performance positions CAN/CNTs/BN composite as a promising contender for electronic packaging applications.
基金supported by the Science and Technology Project of State Grid Corporation of China(Grant 5500-202455120A-1-1-ZN).
文摘The multifrequency voltage(MFV)stress,including switching impulses and harmonics,commonly appearing in the modern power system will stimulate the multifrequency impedance dynamics behaviours of electrical insulation.Therefore,this article presents a novel concept of insulation resilience response(IRR)by employing polymer insulation materials,which may be extended to electrical insulation resilience(EIR).The focus is on understanding reversible recovery performance and supporting physics-informed condition assessment for electrical insulation exposed to MFV.The underlying physical mechanisms and modelling methodologies are integrated to characterise the IRR behaviours of polymer insulation systems.The multifrequency dielectric/impedance properties of different resin dielectrics under diverse temperatures are comparatively investigated as proofofconcept cases.Furthermore,multidimensional sensitivity indicators are developed to quantify the electrical insulation resilience behaviour.A radar plot representation integrating resilience sensitivity indicators qualitatively assesses the IRR behaviours of polymer insulation systems.Additionally,a quantification methodology,including the resilience index(RI)and time-varied RI(TVRI),is proposed for the reversible recovery performance analysis for electrical insulation,respectively.Ultimately,an application-oriented framework derived from TVRI is provided to analyse the recovery performance evolution behaviours of electrical insulation under complex operating conditions.This offers a key theoretical foundation for insulation performance characterisation and condition analysis for high-voltage power equipment.
基金National Science and Technology Major Project,Grant/Award Number:2024ZD0802403National Natural Science Foundation of China,Grant/Award Number:52377153Measurement and Technology Key Project of Tianjin City,Grant/Award Number:2024TJMT011。
文摘The tri-post insulator is a core component within the gas-insulated transmission lines(GIL),providing both electrical insulation and mechanical support.Typically,it is high-temperature cured through vacuum casting of a mixture of epoxy resin,curing agent,and alumina fillers.In recent years,frequent incidents of mechanical cracking and breakdown of tri-post insulators have been reported,which are attributed to residual stress concentration.However,the formation mechanism and distribution characteristics of the residual stress remain unclear.This study focuses on the curing kinetics and re-sidual stress modelling of GIL tri-post insulators.It is verified that the epoxy resin/alumina reaction system follows the autocatalytic curing kinetic model by differential scanning calorimetry tests,and the model fitted by Malek's method corresponds well with the experimental results.Based on the Cure Hardening Instantaneously Linear Elastic model and the density inhomogeneity,it is found that a tensile stress concentration with a maximum value of 58.9 MPa at the edge of the insulator/sleeve interface,due to the mismatch of chemical and thermal shrinkage effects.Besides,the filler sedimentation can decrease the coefficient of thermal expansion and suppress the residual stress concen-tration.The investigation would help with the visualisation of the residual stress distri-bution in GIL tri-post insulators and provide some guidance for their processing treatments.
