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High Voltage 2024年第2期9卷 453-465页

作者： Mingzhe Li Bin Cao Fanghui Yin Hongwei Mei Liming Wang engineering laboratory of power equipment reliability in complicated coastal Environments Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhenChina

A key factor limiting the development of silicone rubber insulating materials is their short service life in harsh operating environments.The establishment of a self-healing system is desired to improve the long-term operational performance of silicone rubber and effectively extend its service life.In this study,poly(urea-formaldehyde)microcapsules containing polydimethylsiloxane healing agents are prepared and a dual-component microcapsule self-healing system for silicone rubber material is established and opti-mised.In addition,the key factors affecting the self-healing performance(such as microcapsule size,rupture rate,and microcapsule doping amount)are investigated.It is found that when SYLGARDTM 184 is used as the healing agent and matrix,with a 4:6(A:B)doping ratio of dual-component microcapsules and 20 phr doping amount,the self-healing efficiency is approximately 51%.Furthermore,increasing the microcapsule rupture rate and the interface strength between the healing agent and the matrix can effectively improve the self-healing performance.The relationships between key factors and self-healing performance are theoretically revealed.Based on the relationships,the microcapsule self-healing system can be appropriately designed.The results of this paper can provide a reference for the development of long-life silicone rubber insulating materials.

关键词： service rubber performance

Novel micro-capsule-doped insulating material with hydrophobicity transfer capability triggered by creepage discharge

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High Voltage 2022年第5期7卷 950-959页

作者： Mingzhe Li Bin Cao Yuhao Liu Liming Wang engineering laboratory of power equipment reliability in complicated coastal Environment Shenzhen International Graduate SchoolTsinghua UniversityShenzhenChina

The lack of hydrophobicity transfer capability has restricted the applications of insulating materials in environments with heavy contamination.In this study,an epoxy resin insulating composite was prepared using a micro-capsule system to achieve hydrophobicity transfer triggered by creepage discharge.The influence of the micro-capsules on the electrical properties of insulating materials and the hydrophobicity of the test samples before and after the creepage discharge test was analysed.The results show that the poly(urea-formaldehyde)micro-capsules,which contained hydrogen silicone oil,have good morphology and thermal stability characteristics at temperatures below 222℃.Microcapsules have minor effects on the electrical properties of epoxy insulating materials.Further,the hydrophobicity transfer capability of the test piece was improved considerably compared with that of the pure epoxy insulating material.This study expands the application of micro-capsule technology in the field of insulating materials and provides a reference for the development of next-generation insulating materials.

关键词： creepage transfer insulating

Interaction between plasma jet and silicone rubber covered by porous inorganic contaminants:Surface hydrophobicity or hydrophilicity?

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High Voltage 2022年第6期7卷 1023-1033页

作者： Shuang Li Jianjun Li Yongqiang Fu Ruobing Zhang engineering laboratory of power equipment reliability in complicated coastal Environments Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhenChina

The variation of surface hydrophobicity of silicone rubber materials covered with porous inorganic pollution layer under the action of atmospheric pressure plasma jet presents some new features,which have important engineering applications in the field of outdoor insulation of power systems.Interaction of the plasma with the polluted silicone rubber is studied and surface hydrophobicity is measured.Experimental results show that the exposure of plasma greatly accelerates the transfer of low molecular weight siloxanes(LMWs)in the pollution layer.However,the surface hydrophobicity is determined by the LMWs contents and the exposure time.Two acceleration effects of plasma during and after plasma exposure are proposed,their influence on surface hydrophobicity is analysed and related mechanisms are clarified.In addition,the competing influence of plasmainduced acceleration of the transfer of LMWs towards the surface and plasmaoxidation of LMWs on surface hydrophobicity is discussed.

关键词： rubber inorganic acceleration

Editorial for the Special Issue on Emerging Technology and Advanced Application of Nondestructive Detection for power equipment

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Chinese Journal of Electrical engineering 2024年第1期10卷 1-2页

作者： Li J. Mei H. Li S. Tianjin University China Tsinghua shenzhen International graduate school China Lanzhou Jiaotong University China

The rapid development of clean and renewable energy technologies represented by wind and solar energy,as well as the continuous growth of load demand,have put forward higher requirements for the safe operation of the power equipment.The performance of power equipment based on traditional dielectric materials is often limited by various defects generated during molding,transportation,assembly,and operation,which cannot meet the reliability requirements of power systems in the new situation.Nondestructive detection is an essential technical method in industrial development,which can detect and evaluate the defect and damage status of in-service equipment,key components,and materials without damaging the object.

关键词： service Application operation

Review of flash sintering with strong electric field

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High Voltage 2022年第1期7卷 1-11页

作者： Hongyang Zhou Xiang Li Yuchen Zhu Jieming Liu Angxuan Wu Guoming Ma Xilin Wang Zhidong Jia Liming Wang Guangdong engineering Technology Research Centre of power equipment reliability in complicated coastal Environments Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhenGuangdongChina school of Electrical and Electronic engineering North China Electric Power UniversityBeijingChina

Flash sintering is a novel field‐assisted sintering technology for ceramics that allows a dramatic reduction in processing time and temperature.Since 2010,when flash sintering was first reported,it has been a focus of research interest in the field of materials science.Recent study results have confirmed that the sintering temperature decreases with the strength of the applied electric field;for some ceramics,the sintering temperature can be lowered even to room temperature.This represents an innovative breakthrough for ceramic sintering at ultra‐low temperatures.However,once the electric field strength in flash sintering is increased,new questions and challenges arise,such as whether or not partial discharge occurs in the green body if under electro‐thermal coupling stress,how to quantitatively analyse the impact of discharge on sintering,and,moreover,whether the sintering mechanism under a strong electric field is consistent with that under a weak electric field.These research questions require knowledge of partial discharge detection,dielectric theory,and other topics that are beyond the scope of materials science.To address this need,this review summarises the work carried out in flash sintering with a strong electric field from the perspective of high voltage and insulation technology.First,the flash sintering process and mechanism are briefly introduced.Then,the published literature on flash sintering with a strong electric field for various ceramic materials is summarised in depth.In addition,experimental phenomena that are observed in flash sintering with a strong electric field,such as flash and blackening,are discussed.Finally,some suggestions for future work are presented.It is anticipated that the knowledge gap between different areas of study can be filled by this review.

关键词： flash knowledge field

Cold sintering process for fabrication of a superhydrophobic ZnO-polytetrafluoroethylene(PTFE)ceramic composite

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Journal of Advanced Ceramics 2023年第9期12卷 1758-1766页

作者： Xuetong Zhao Yang Yang Li Cheng Jing Guo Shenglin Kang Yuchen Li Xilin Wang Lijun Yang Ruijin Liao State Key laboratory of power Transmission equipment&System Security and New Technology Chongqing UniversityChongqing 400044China State Key laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China engineering laboratory of power equipment reliability in complicated coastal Environments Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhen 518055China

Composite coatings or films with polytetrafluoroethylene(PTFE)are typically utilized to offer superhydrophobic surfaces.However,the superhydrophobic surfaces usually have limited durability and require complicated fabrication methods.Herein,we report the successful integration of PTFE with ZnO ceramics to achieve superhydrophobicity via a one-step sintering method,cold sintering process(CSP),at 300℃.(1–x)ZnO–x PTFE ceramic composites with x ranging from 0 to 70 vol%are densified with relative density of over 97%.Micro/nano-scale PTFE polymer is dispersed among ZnO grains forming polymer grain boundary phases,which modulate surface morphology and surface energy of the ZnO–PTFE ceramic composites.For the 60 vol%ZnO–40 vol%PTFE ceramic composite,superhydrophobic properties are optimized with static water contact angles(WCAs)and sliding angles(SAs)of 162°and 7°,respectively.After abrading into various thicknesses(2.52,2.26,and 1.99 mm)and contaminating with graphite powders on the surface,WCA and SA are still maintained with a high level of 157°–160°and 7°–9.3°,respectively.This work indicates that CSP provides a promising pathway to integrate polymers with ceramics to realize stable superhydrophobicity.

关键词： cold sintering process(CSP) ZnO-polytetrafluoroethylene(PTFE)ceramic composites contact angles sliding angles(SAs) superhydrophobicity

A versatile defect engineering strategy for room-temperature flash sintering

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Journal of Advanced Ceramics 2022年第7期11卷 1172-1178页

作者： Angxuan WU Ziyang YAN Xilin WANG Zhiyang YU Rongxia HUANG Nianping YAN Zhidong JIA engineering laboratory of power equipment reliability in complicated coastal Environments Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhen 518055China State Key laboratory of Photocatalysis on Energy and Environment College of ChemistryFuzhou UniversityFuzhou 350108China school of Electromechanical engineering Guangdong University of TechnologyGuangzhou 510006China State Grid Jiangxi Electric power Research Institute Nanchang 330096China

In this study,we reported that flash sintering(FS)could be efficiently triggered at room temperature(25℃)by manipulating the oxygen concentration within ZnO powders via a versatile defect engineering strategy,fully demonstrating a promising method for the repaid prototyping of ceramics.With a low concentration of oxygen defects,FS was only activated at a high onset electric field of~2.7 kV/cm,while arcs appearing on the surfaces of samples.Strikingly,the onset electric field was decreased to<0.51 kV/cm for the activation of FS initiated,which was associated with increased oxygen concentrations coupled with increased electrical conductivity.Thereby,a general room-temperature FS strategy by introducing intrinsic structural defect is suggested for a broad range of ceramics that are prone to form high concentration of point defects.

关键词： flash sintering(FS) oxygen vacancies defect engineering ZnO powders electric discharge

Gas-discharge induced flash sintering of YSZ ceramics at room temperature

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Journal of Advanced Ceramics 2022年第4期11卷 603-614页

作者： Yuchen ZHU Hongyang ZHOU Rongxia HUANG Nianping YAN Xilin WANG Guanghua LIU Zhidong JIA engineering laboratory of power equipment reliability in complicated coastal Environments Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhen 518055China school of Electromechanical engineering Guangdong University of TechnologyGuangzhou 510006China State Grade Jiangxi Electric power Research Institute Nanchang 330000China State Key laboratory of New Ceramics and Fine Processing Tsinghua University School of Materials Science and TechnologyTsinghua UniversityBeijing 100084China

This is the first study to conduct the flash sintering of 3 mol%yttria-stabilized zirconia(3YSZ)ceramics at room temperature(25℃)under a strong electric field,larger than 1 kV/cm.At the standard atmospheric pressure(101 kPa),the probability of successful sintering is approximately half of that at low atmospheric pressure,lower than 80 kPa.The success of the proposed flash sintering process was determined based on the high electric arc performance at different atmospheric pressures ranging from 20 to 100 kPa.The 3YSZ samples achieved a maximum relative density of 99.5%with a grain size of~200 nm.The results showed that as the atmospheric pressure decreases,the onset electric field of flash sintering decreases,corresponding to the empirical formula of the flashover voltage.Moreover,flash sintering was found to be triggered by the surface flashover of ceramic samples,and the electric arc on the sample surfaces floated upward before complete flash sintering at overly high pressures,resulting in the failure of flash sintering.This study reveals a new method for the facile preparation of flash-sintered ceramics at room temperature,which will promote the application of flash sintering in the ceramic industry.

关键词： flash sintering yttria-stabilized zirconia(YSZ) room temperature flashover AC field low atmospheric pressure

Analytical model for the transient permittivity of uncured TiO_(2) whisker/liquid silicone rubber composites under an AC electric field

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High Voltage 2021年第3期6卷 470-479页

作者： Zikui Shen Zhenyu Xin Xilin Wang Xinyu Wei Zhidong Jia engineering laboratory of power equipment reliability in complicated coastal Environment Shenzhen International Graduate SchoolTsinghua UniversityShenzhenChina

The electric field grading of dielectric permittivity gradient devices is an effective way of enhancing their insulation properties.The in situ electric field‐driven as-sembly is an advanced method for the fabrication of insulation devices with adaptive permittivity gradients;however,there is no theoretical guidance for design.In this study,an analytical model with a time constant is developed to determine the transient permittivity of uncured composites under an applied AC electric field.This model is based on optical image and dielectric permittivity monitoring,which avoids the direct processing of complex electrodynamics.For a composite with given components,the increased filler content and electric field strength can accelerate the transient process.Compared with the finite element method based on differential equations,this statistical model is simple but efficient,and can be applied to any low‐viscosity uncured composites,which may contain multiple fillers.More importantly,when a voltage is applied to an uncured composite insulating device,the proposed model can be used to analyse the spatiotemporal permittivity characteristics of this device and optimise its permittivity gradient for electric field grading.

关键词： composites permittivity transient

Hydrophobicity changes of polluted silicone rubber introduced by spatial and dose distribution of plasma jet

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Plasma Science and Technology 2022年第4期24卷 53-60页

作者：李爽郭新正付永强李健俊张若兵 engineering laboratory of power equipment reliability in complicated coastal Environments Shenzhen International Graduate School(SIGS)Tsinghua UniversityShenzhen 518055People's Republic of China

The hydrophobicity of polluted silicone rubber was improved rapidly under plasma jet treatment.It is an important phenomenon of the interaction between the plasma jet and the porous surface,and shows a wide application prospect in the power system.In this process,the spatial characteristics and dose of plasma jet are very important.Therefore,the variation of hydrophobicity of polluted silicone rubber under plasma jet treatment was studied,and the spatial characteristics and dose of plasma jet on polluted silicone rubber were also investigated in the work.The results show that the surface property(hydrophilic or hydrophobic)depended on the dose of plasma applied to the surface.The effective treated area was a circle,and the contact angles changed along the radial direction of the circle.This was attributable to the diffusion of plasma bullets on the surface and the distribution of plasma species.The plasma dose could be characterized by the energy density of the plasma applied on the surface.With the increase of plasma dose,the surface contact angles first increased rapidly and then decreased gradually.

关键词： plasma jet polluted silicone rubber hydrophobicity plasma dose energy density spatial distribution