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Temperature‐dependent adaptive CONDUCTIVITY coating for surface charge release and electric field control under electro‐thermal coupling field

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High Voltage 2023年第5期8卷 1082-1092页

作者： Jianyi Xue Zhu Zhang Binbin Li Yushun Zhao Lijian Ding School of Electrical Engineering and Automation Hefei University of TechnologyHefeiChina Electric Power Research Institute of State Grid Anhui Electric Power Co. Ltd.HefeiChina

Surface charge accumulation is the potential criminal for surface insulation failure on spacers under direct current(DC)voltages.The existence of thermal gradient posing the difficulty of surface charge regulation.This study proposes a temperature‐dependent adaptive CONDUCTIVITY coating technique for surppressing surface charge accumulation under electro‐thermal coupling field.A two‐dimensional axis‐symmetrical simulation model regrading surface charge computation is established.The effects of thermal gradients and coating CONDUCTIVITY on surface charge and electric field distribution are investigated.The results show that the thermal gradient increases the bulk conductive current,therefore aggravating surface charge accumulation.The effects of the coating condcutivity on surface charge and electric field contains three stages.The lower coating CONDUCTIVITY leads to aggravated homo‐polarity charge accumulation.By increasing the coating CONDUCTIVITY,the surface charge and electric field are significantly suppressed at the obtained optimal CONDUCTIVITY,where the bulk and surface conductive current reach a balance stage.Continuously increasing the coating CONDUCTIVITY results in aggravated hetero‐polarity charges.Besides,the increase of thermal gradient to an appropriate extent contributes to the further suppression of surface charge on coated spacers.It is hoped that this study could provide some references for designing highly reliable DC GIL under electro‐thermal coupling field.

关键词： coating charge CONDUCTIVITY

Non-linear electrical CONDUCTIVITY of ethylene-propylene-diene monomer-based composite dielectrics by tuning inorganic fillers

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High Voltage 2023年第4期8卷 781-790页

作者： Tiandong Zhang Hao Li Changhai Zhang Chao Tang Zhonghua Li Qingguo Chi School of Electrical and Electronic Engineering Harbin University of Science and TechnologyHarbinChina

In this study,three kinds of inorganic fillers are chosen and filled into ethylene-propylenediene monomer(EPDM)matrix,including silicon carbide,copper calcium titanate(CCTO),and vanadium dioxide(VO2).The electrical properties of the three modified composites at different temperatures have been systematically studied.The intrinsic conductance behaviours of different inorganic fillers on the direct current conductance and electric breakdown strength of the composite dielectrics are also analysed,and the possible mechanism for non-linear CONDUCTIVITY is revealed.The electrical CONDUCTIVITY increases with the increase of fillers content,where 30 wt.%CCTO/EPDM composite dielectric has a high non-linear coefficient of 5.71.The increase in temperature can further increase the CONDUCTIVITY of the composites,accompanying a lower breakdown strength.When the temperature rises to 70℃,the VO2/EPDM composite has a higher CONDUCTIVITY,but the electric breakdown strength degrades seriously.The simulation results show that the composites with non-linear electrical CONDUCTIVITY characteristics can effectively uniform the electric field and solve the problem of electric field concentration at the root of the stress cone,which is beneficial to improving the safe operation of the cable accessories.

关键词： composite composites CONDUCTIVITY

Large-scale plasma grafts voltage stabilizer on hexagonal boron nitride for improving electrical insulation and thermal CONDUCTIVITY of epoxy composite

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High Voltage 2023年第3期8卷 550-559页

作者： Penghao Zhang Chenguo Yao Liang Yu Xuetong Zhao Lisheng Zhao Linghan Lan Shoulong Dong State Key Laboratory of Power Transmission Equipment and System Security and New Technology School of Electrical EngineeringChongqing UniversityChongqingChina School of Energy and Power Engineering Chongqing UniversityChongqingChina

Better electrical insulation and thermal management are both urgently required in integrated power semiconductors.Electrical insulation epoxy encapsulation suffers from poor heat conduction,which has increasingly become a bottleneck of power semiconductors integration.Although incorporating high thermal CONDUCTIVITY ceramics,such as hexagonal boron nitride(hBN),aluminium nitride etc.into epoxy promotes the thermal CONDUCTIVITY,the eco-friendly scalable fabrication of these composites with sufficient electrical breakdown strength remains a formidable challenge.Suitable voltage stabilizers are known to provide additional benefits to breakdown strength.Herein,a highthroughput approach combining plasma with roll-to-roll was developed.The voltage stabilizer(acetophenone)was grafted on interfaces between hBN and epoxy matrix through plasma.The high-energy electrons are consumed by the grafted interface,which leads to the significant suppression of partial discharge in Epoxy/hBN.Meanwhile,interfacial phonon scattering is repaired by grafting.Therefore,the epoxy composite concurrently exhibits improved breakdown strength(by 27.4%)and thermal CONDUCTIVITY(by 142.9%)at about 11.9 wt.%filler content,outperforming the pure epoxy.Consequently,a promising modification strategy for mass production is provided for the encapsulation materials in various high-power-density semiconductor devices.

关键词： composite CONDUCTIVITY insulation

Outstanding strength and CONDUCTIVITY of metallic glass composites with multiscale configuration

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Rare Metals 2023年第9期42卷 3099-3113页

作者： Wei-Zong Bao Jie Chen Jun-Zhi Li Bo-Hua Yu Chu-Yuan Liu Ping Jiang Zu-Jia Liu Kai-Tao Hu Dmitri V.Louzguine-Luzgin Guo-Qiang Xie School of Materials Science and Engineering Harbin Institute of Technology(Shenzhen)Shenzhen518055China Advanced Institute for Materials Research(WPI-AIMR) Tohoku UniversitySendai980-8577Japan MathAM-OIL National Institute of Advanced Industrial Science and Technology(AIST)Sendai980-8577Japan State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin150001China

Cu-based composites with multiscale configuration for electrical contact applications are fabricated via a ball milling(BM)-spark plasma sintering(SPS)-aging process.Synergistic strengthening of the Cu alloy matrix by micro-scale metallic glass particles and nanoscale intracrystalline precipitation phases is realized.The annealing technique achieves the decomposition of solute atoms in the Cu alloy,ensuring the excellent electrical properties of the matrix conductive network.The composite with multiscale configuration achieves an outstanding combination of ultimate compressive strength of(1114±15)MPa and electrical CONDUCTIVITY of 33.0%±1.1%International Annealed Copper Standard(IACS)after annealing at 400.C for 10.0 h.Investigation of the strengthening and CONDUCTIVITY mechanisms suggests that the precipitation of the Cr-rich phase within the matrix crystals is a critical contributor to the concerted enhancement of strength and CONDUCTIVITY.In addition,the positive role of nanocrystals precipitated at the edges of metallic glass particles on the interfacial bonding of composites is addressed.

关键词： Metallic glass composites Multiscale configuration Strength CONDUCTIVITY

Preparation,with graphene,of novel biomimetic selfhealing microcapsules with high thermal stability and CONDUCTIVITY

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Frontiers of Structural and Civil Engineering 2023年第8期17卷 1188-1198页

作者： Ying-Yuan WANG Yi-Qiu TAN School of Transportation Science and Engineering Harbin Institute of TechnologyHarbin 150090China State Key Laboratory of Urban Water Resource and Environment Harbin Institute of TechnologyHarbin 150090China

This paper reports a comparative study of microcapsules with enhanced thermal stability and electrical CONDUCTIVITY inspired by the bionic thermal insulation of birds’feathers for self-healing aged asphalt.The work is based on an in situ polymerization with composite shell components of graphene and hexamethoxymethylmelamine resin.By using graphene,microcapsules with rough surfaces are achieved,improving the interface between microcapsules and asphalt.In addition,the microcapsules’initial thermal decomposition temperature is appropriately high,so that the stability of the microcapsule in the asphalt highway system is protected.The proportion of graphene in the microcapsule shell can regulate the microcapsule’s heat resistance because graphene modifies the shell’s structural makeup.Additionally,the microcapsules’electrical CONDUCTIVITY is relatively high.The self-healing capability of bitumen sharply increases,providing benefit to the effect of microcapsules on the properties of aged asphalt.

关键词： graphene microcapsule bitumen heat insulation CONDUCTIVITY

Unexpected thermal CONDUCTIVITY enhancement in aperiodic superlattices discovered using active machine learning

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npj Computational Materials 2022年第1期8卷 99-105页

作者： Prabudhya Roy Chowdhury Xiulin Ruan School of Mechanical Engineering and the Birck Nanotechnology Center Purdue UniversityWest LafayetteIN47907-2088USA

While machine learning(ML)has shown increasing effectiveness in optimizing materials properties under known physics,its application in discovering new physics remains challenging due to its interpolative nature.In this work,we demonstrate a general-purpose adaptive ML-accelerated search process that can discover unexpected lattice thermal CONDUCTIVITY(κ_(l))enhancement in aperiodic superlattices(SLs)as compared to periodic superlattices,with implications for thermal management of multilayer-based electronic devices.We use molecular dynamics simulations for high-fidelity calculations ofκ_(l),along with a convolutional neural network(CNN)which can rapidly predictκ_(l)for a large number of structures.To ensure accurate prediction for the target unknown SLs,we iteratively identify aperiodic SLs with structural features leading to locally enhanced thermal transport and include them as additional training data for the CNN.The identified structures exhibit increased coherent phonon transport owing to the presence of closely spaced interfaces.

关键词： thermal CONDUCTIVITY transport

Optical and electrical CONDUCTIVITY properties of rare earth elements(Sm, Y, La, Er) co-doped CeO_(2)

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Journal of Rare Earths 2022年第10期40卷 1619-1627页

作者： Rabia Kιrkgecit Handan OzlüTorun Fatma Kιlc Dokan Esra Oztürk Institute of Science Material Science and EngineeringKahramanmaras Süt?üImam UniversityKahramanmaras46050Turkey Department of Energy System Engineering Kahramanmaras Istiklal UniversityKahramanmaras46300Turkey Department of Chemistry and Chemical Processing Technologies Kayseri UniversityKayseriTurkey Department of Metallurgical and Materials Engineering Karamanoglu Mehmetbey UniversityKaramanTurkey

In this research,un-doped CeO_(2) and Ce_(0.85)La_(0.10)MO_(0.05)O_(2)(M:Sm,Er,Y) compounds were synthesized by hydrothermal method and the multi-functional properties are reported.Oxygen defects were created with the additives of rare earth ions.The electrical and luminescence behaviors of the synthesized compounds were investigated in accord with the types of additives.The synthesized products were characterized by X-ray diffraction(XRD) analysis,Brunauer-Emmett-Teller(BET) measurement,UV-vis diffuse reflectance spectroscopy(DRS),scanning electron microscopy(SEM),photoluminescence(PL)spectroscopy and electrochemical impedance spectroscopic(EIS).All synthesized compounds are found to be nano-structured and have cubic phase.The total CONDUCTIVITY of all samples was calculated.Hence,the total CONDUCTIVITY of un-doped CeO_(2),Ce_(0.85)La_(0.10)Y_(0.05)O_(2),Ce_(0.85)La_(0.10)Er_(0.05)O_(2) and Ce_(0.85)La_(0.10)Sm_(0.05)O_(2) is found to be 2.07×10^(-10),5.70×10^(-4),1.0×10^(-3) and 0.0747 S/cm,respectively.Also,bandgap energy(E_(g)) of these samples calculated from UV visible absorption spectra is discussed,and the optical results show variation between 3.2 and 2.15 eV.Additionally,the luminescence properties of the compounds were investigated and different emissions occur depending on the additive type.Accordingly,photoluminescent emission spectra of Ce_(0.85)La_(0.10)Y_(0.05)O_(2),Ce_(0.85)La_(0.10)Er_(0.05)O_(2) and Ce_(0.85)La_(0.10)Sm_(0.05)O_(2) phosphors indicate that these phosphors have red,green and orange-red colors,respectively.

关键词： Cerium oxide Co-doping CONDUCTIVITY Luminescence Oxygen vacancy Rare earth elements

Abnormal thermal CONDUCTIVITY enhancement in covalently bonded bilayer borophene allotrope

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Nano Research 2022年第4期15卷 3818-3824页

作者： Yan Yin Yanxiao Hu Shichang Li Guangqian Ding Shifa Wang Dengfeng Li Gang Zhang School of Science Chongqing University of Posts and TelecommunicationsChongqing 400065China Chongqing Key Laboratory of Geological Environment Monitoring and Disaster Early-warning in Three Gorges Reservoir Area Chongqing Three Gorges UniversityChongqing 404000China Institute of High Performance Computing A*STARSingapore 138632Singapore

Thermal CONDUCTIVITY of two-dimensional(2D)materials has gained prominence due to the attractive applications in thermal management and thermoelectric devices.In this work,we present a new member of bilayer 2D boron allotropes,denoted as bilayerβ12 borophene,and study the thermal transport properties by solving phonon Boltzmann transport equation based on density functional theory.Based on quantitative chemical bonding analysis,we identify large degrees of covalent bonding of the interlayer interaction.In comparison to its monolayer counterpart,the bilayer exhibits much higher in-plane thermal CONDUCTIVITY despite the lower phonon group velocity and buckling structure,inferring a new physical mechanism.The thermal CONDUCTIVITY(κ)of bilayerβ_(12)borophene at 300 K is 140.5(86.3)W·m^(-1)·K^(-1)along armchair(zigzag)direction,andκ_(armchair)is about 52.7%higher than that of monolayerβ12 borophene.The abnormal enhancement is attributed to the suppressed phonon scattering possibility and elongation of phonon lifetime.More interesting,after forming bilayerβ12 borophene through interlayer covalent bonding,the dominated phonon branch to thermal CONDUCTIVITY changes to transverse acoustic phonons from out-of-plane flexural acoustic(ZA)phonons in the monolayer borophene.Our study elucidates the rich thermal transport characteristics in bilayer covalently bonded 2D materials,and injects fresh insights into the phonon engineering of 2D borophene relevant for emergent thermal management applications.

关键词： theory CONDUCTIVITY phonon

Realizing p-type performance in low-thermal-CONDUCTIVITY BiSbSe_(3) via lead doping

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Rare Metals 2023年第11期42卷 3601-3606页

作者： Si-Ning Wang Han-Chen Lu Du-Jiang Li Yang Jin Xing-Yi Li Yan Yan Kai Gu Yu-Ting Qiu Li-Dong Zhao School of Materials Science and Engineering Beihang UniversityBeijing100191China Flying College Beihang UniversityBeijing100191China School of Energy and Power Engineering Beihang UniversityBeijing100191China School of Mechanical Engineering and Automation Beihang UniversityBeijing100191China Beihang School Beihang UniversityBeijing100191China Key Laboratory of Intelligent Sensing Materials and Chip Integration Technology of Zhejiang Province(2021E10022) Hangzhou Innovation Institute of Beihang UniversityHangzhou310051China

BiSbSe_(3) is an intrinsic n-type thermoelectric material,which attracts a lot of research interest due to its low lattice thermal CONDUCTIVITY and multiple band structure,and it exhibits excellent thermoelectric properties in the midtemperature region.However,there is little research on p-type BiSbSe_(3).This work realized the successful preparation of p-type BiSbSe_(3) through Pb doping.The thermoelectric transport properties of Pb-doped p-type BiSbSe_(3)were investigated.Pb doping could further reduce the thermal CONDUCTIVITY of BiSbSe_(3).All Pb-doped samples exhibited and maintained stable p-type transmissionthroughout the working temperature range(300-723 K).This work proves that Pb can be successfully used as a p-type dopant for BiSbSe_(3).

关键词： dopant doping CONDUCTIVITY