Effect Of Size On Dielectric Energy Storage In Polymer-based Barium Titanate Nanocomposites

As the new energy industry has gradually become a new engine of global economic growth,more and more new energy industries have entered people's vision.As an important factor restricting the development of new energy industry,energy storage technology has been widely studied in academia and industry worldwide.Dielectric capacitors have the advantages of high energy storage and small size,which have become the focus of current energy storage research.The internal dielectric materials are the core research content.Based on the above studies,it has been found that the composite of inorganic ceramic materials and polymers can effectively increase the dielectric constant of the composite material and maintain a small loss.This thesis focuses on the surface modification of ceramic particles and the effect of ceramic particle size on composite materials.The main research contents and results are as follows:(1).It has been studied that ceramic surface treatment can improve the dispersibility of inorganic ceramics in polymers.The modification of BT ceramic particles with DA and KH550 was used to verify the effect of surface modification on composite materials.The characterization method proves that the ceramic particles in the surface-treated composite material are more uniformly dispersed,so that the dielectric loss of the PVDF/BT@DA composite material at 1 k Hz is reduced by 42.1% compared with that before modification.Breakdown strength is as high as 497.5 MV/m,which had previously increased by 29.56%.The maximum releasable energy density is 16.78 J/cm3,and the energy storage efficiency is 67.21%.(2).The influence of BT mass fraction on composites was studied.With the increase of BT mass fraction,the dielectric constant and dielectric loss of composites increased.When the mass fraction is 3%,the PVDF/BT@DA composite material has the best energy storage performance.Under the test field of 500MV/m,the energy storage density can reach 24.96 J/cm3,which is 60.82% higher than the maximum energy storage density of pure PVDF polymers.(3).The influence of BT size on the dielectric properties and energy storage properties of composites was studied.1.In the non-linear material PVDF,as the size of BT ceramic particles decreases,the dielectric constant increases and the breakdown strength decreases.In this system,the PVDF/BT(500nm)composite material has the best energy storage performance,with a breakdown strength of 497.5 MV/m and a maximum releasable energy density of 16.78 J/cm3.2.In the linear material PMMA,as the BT ceramic particles increase in size,the dielectric constant decreases and the breakdown strength increases.The PMMA/BT(500nm)composite material has a breakdown strength of up to 629.8 MV/m and a releasable energy density of 9.5 J/cm3.3.In the linear-nonlinear mixed dielectric,the dielectric constant of P(VDFHFP)/PMMA/BT composite material increases with the decrease of BT size,and the breakdown strength decreases.The breakdown strength of P(VDF-HFP)/PMMA/BT(500nm)composite material is as high as 528.6MV/m,the energy storage density is 14.7 J/cm3,and the releasable energy density is 10.0J/cm3.The BT size effect maintains a certain law in nonlinear dielectrics,linear dielectrics,and linear-nonlinear mixtures.