Surface Modification Of SCT Ceramics And Its Effect On Dielectric Properties Of PVDF Matrix Composites

Polymer based ceramic energy storage composite is composed of ceramic filler and polymer matrix,and has the advantages of both,with excellent dielectric properties,energy storage performance,breakdown performance,flexibility and processability,so it is widely used in capacitor field.However,the compatibility and dispersion of ceramic particles between ceramic filler and polymer matrix are poor due to the large performance difference between them.However,the ceramic surface modification can be improved to improve the dielectric properties of composites.In this paper,Sr_0.9Ce_0.1Ti O₃（SCT）ceramics were modified byγ-aminopropyl triethoxysilane coupling agent（KH550）and dopamine（DA）.Firstly,the effect of SCT ceramic filling amount on the dielectric properties of SCT/PVDF composites was studied.Then,the effect of surface modification of SCT ceramics on the microstructure and dielectric properties of composites was discussed,and the modification mechanism was studied.At the same time,the optimal modification amount was determined.The influence of surface modification of ceramic particles on the electrical properties of composites was simulated by Matlab and COMSOL.In the SCT/PVDF composites,the dielectric constant of the composites increases first and then decreases with the increase of ceramic filling amount.This is because the permittivity of SCT ceramics is greater than PVDF,but the maximum value will appear when the filling amount is certain.When the filling amount exceeds this,the pores and defects of composite materials will increase,but the permittivity decreases.On the other hand,the dielectric loss is stable first and then increases with the increase of ceramic filling.This is because the increase of ceramic filling amount will lead to more contact interfaces between ceramic and PVDF,which will lead to the accumulation of charge similar to defects at the interface,resulting in the increase of conductivity loss,thus increasing dielectric loss.The results show that the dielectric properties of the composites are the best when the filling amount of SCT ceramic is 20wt%.The surface of SCT ceramic particles was modified byγ-aminopropyl triethoxysilane coupling agent（KH550）.The effects of KH550 modification and its addition amount on the microstructure and dielectric properties of the composites were studied.The results show that when the additive amount of KH550 is 1wt%,the ceramic particle surface can be completely coated,which improves the dispersion and compatibility of ceramics in the polymer,so as to obtain the optimal modification value of dielectric properties of composites.SCT ceramic particles were surface modified by dopamine（DA）,and the effects of DA modification and addition amount on the microstructure and dielectric properties of the composites were investigated.The results show that,similar to KH550 modification,the dielectric properties of the composites are improved,and the optimal value of dielectric properties is obtained when the amount of DA is 1wt%.The composite model was established by Matlab,and COMSOL was used to simulate the electrical properties and electrical breakdown process of the composite before and after modification.The results show that the breakdown resistance of the composites can be improved by increasing the uniformity and dispersion of filler particles in the matrix.The results confirm the effectiveness of modification and provide guidance for future research.