Effect Of Particle Scale On Nonlinear Conductivity And Dielectric Properties Of Epoxy Resin-Based Composites

High-voltage generator stator rod ends and other structures often cause corona discharge problems due to the concentration of electric field,which directly affects the safe operation of the generator and the stability of the entire power system.Although the anti-corona layer structure prepared by a single silicon carbide filler can solve the electric field concentration problem at the stator rod end,it cannot meet the requirement of the anti-corona layer structure for breakdown strength;currently,for this kind of problem,we often choose to dope certain micro and nano fillers to improve the performance of the composite material and thus prepare a composite material with better performance.However,changing the filler content alone is not enough to fully determine the enhancement index of material performance,and studying the mechanism of the progressive change of particle size scale on the interparticle synergy is also important for the preparation of composites with better performance.In this paper,SiO₂/SiC/EP composites with different SiO₂particle sizes and contents were prepared based on composites with nonlinear electrical conductivity properties prepared from epoxy resin and micron SiO₂carbide,on which SiO₂particles with particle sizes of 60nm,2μm,and 25μm were added.Infrared spectroscopy was used to analyze the effect of surface treatment on the number of hydroxyl groups on the surface of SiO₂.The influence of the SiO₂carbide content and SiO₂dioxide particle size and content on the conductivity of the composites was investigated using a pico ammeter and a high resistance meter;the influence of the SiO₂carbide content and SiO₂dioxide particle size and content on the breakdown strength of the composites was analyzed using an AC breakdown test;the dielectric constant and loss of the composites were tested at different frequencies using a broadband dielectric spectrometer.The experimental results show that the hydroxyl absorption peak of the surface-treated SiO₂is significantly reduced;the particle size of the SiO₂is observed to be more average to meet the experimental needs,and after doping to the epoxy resin matrix blend,the different content and particle size of the SiO₂are observed to be more uniformly dispersed without obvious agglomeration problems.The addition of micron SiO₂carbide can significantly improve the conductivity of the composite,and with the increase of the field strength of the non-linear conductivity characteristics;and the addition of different content,the particle size of SiO₂can make the higher field strength of the composite conductivity decreases,the same doping amount of the composite conductivity with the increase of the added SiO₂particle size and decreases,nano-SiO2 doped composite non-linear The nonlinear coefficients of the nano silica-doped composites decreased,while the nonlinear coefficients of the composites doped with two types of micron SiO₂showed both increasing and decreasing trends.The breakdown field strength of the composites decreased significantly with the addition of micron silicon carbide,and the addition of SiO₂could improve the breakdown field strength of the composites and increase the breakdown strength of the composites decreased with the increase of the doping particle size;Except for the breakdown field strength of the composites doped with nano-SiO₂,which did not show a linear change with the increase of the doping amount,the breakdown field strength of the composites increased with the increase of the doping amount of SiO₂.Compared with the SiC/EP composites（EP:SiC=1:1）,the breakdown field strength of SiO₂/SiC/EP composites doped with 8 phr nano-SiO₂reached the maximum value,and the breakdown field strength increased by143.6%.The dielectric spectroscopy experiments showed that the addition of micron SiO₂carbide increased the dielectric constant as well as the loss angle tangent of the composites compared to the epoxy resin matrix;the effects of the three particle sizes of SiO₂on the dielectric constant and loss angle tangent of the composites were not identical:the dielectric constant of the composites decreased after the addition of nano-silica,while the dielectric constant of the composites after the doping of both micron-scale SiO₂The dielectric constants of the composites show both increasing and decreasing trends,and the SiO₂/SiC/EP dielectric constants are higher than those of the pure epoxy matrix;the addition of all three particle sizes of SiO₂causes the loss angle tangent values of the composites to decrease in the low frequency region,but with the increase of frequency,the loss angle tangent values of the composites with less SiO₂doping（1 phr doping）are higher than those of the SiC/EP composites（EP:SiC=1:1）.