Study On Properties Of Micron-CCTO/EPDM And Nano-CCTO/EPDM Composites

With the widespread use of power cables,cable accessories are becoming an increasingly important part of power cable systems.However,under DC voltage,the electric field distribution of the cable accessory is complicated,which is easy to accumulate space charge,accelerate the electrical aging of the material,and reduce the service life,and becoming the weakest part of the cable line.Therefore,cable accessories have become the weakest part of the cable lines.How to balance the internal electric field by adjusting the dielectric properties of materials,and prolong the service life of cable accessories have gradually become the focus of researches.CaCu₃Ti₄O₁₂(CCTO)has attracted wide attention for its remarkable dielectric properties,giant dielectric constant over a wide temperature range,and excellent nonlinear I-V characteristics.This paper mainly studies the influence of doping CCTO with micron and nanometer size on the properties of CCTO/EPDM composites,and the influence of CCTO with Cu non-stoichiometric ratio doping on the electrical properties of composites.Micron-CCTO ceramic powders were obtained by the solid-phase method in this project,and micron-CCTO/EPDM composites with different micron-CCTO contents were prepared by mechanical blending method.The phases of CCTO and EPDM were detected by XRD in the composites,and the size of micron-CCTO powders and the mixing degree of composites were observed by SEM.The phenomenon of increasing dielectric properties is explained based on the internal barrier capacitance model and effective dielectric enhancement model.At the same time,through the calculation of trap energy levels,the tendency of the breakdown field strength and surface charge decay is explained.Besides,the introduced traps lead to the declining conductivities initially,and with the increase of CCTO content,the field-dependent conductivity became more obvious.The nano-CCTO ceramic powders were prepared by the liquid-phase method and mixed as filler by mechanical blending with pure EPDM.When the addition amount is low,nano-CCTO can improve the dielectric constant more then composites with the same mass fraction micron-CCTO,which benefits to its larger specific surface area of nanoparticles.At the same time,based on the trap level calculation and the double-layer model of the nanoparticles,the reason for the higher breakdown field intensity and faster surface charge decay rate of nano-CCTO/EPDM is explained.In this paper,Cu non-stoichiometric powders were prepared in two ways and compounded with EPDM at 10wt%mass fraction,and the presence of CuO phase in Cu-rich powders was detected by XRD.And based on the IBLC model and the change of grain boundary potential barrier,we explained the phenomenon that the dielectric properties and breakdown strength of composites increase first and then decrease with Cu content.In addition,the trend of surface charge attenuation effect increasing first and then decreasing was analyzed by trap level calculation.