Preparation And Modification Of Barium Titanate Nanowires And Research On Energy Storage Properties Of Polymer Matrix Composites

With the continuous development of information technology,energy storage dielectric materials are widely used in artificial intelligence,aerospace,integrated circuits and other fields.A single ceramic dielectric and polymer dielectric material can no longer meet the requirements of high energy storage applications for miniaturization,integration and light weight.In this paper,BTNWs/PVDF composites were prepared by using barium titanate nanowires（Ba Ti O₃ nanowires,BTNWs）as filler and polyvinylidene fluoride（PVDF）as the matrix.The effects of Ba Ti O₃ morphology,content and surface modification on the crystal structure,microscopic morphology,dielectric properties and energy storage properties of the composites were studied,in order to obtain composites with high energy storage performance.Ba Ti O₃ nanowires were prepared by hydrothermal method,and the effects of Na OH solution concentration and reaction time on the crystal structure and microscopic morphology of precursor Na₂Ti₃O₇ nanowires in the first hydrothermal reaction were studied.When the reaction temperature was 240℃,Na OH solution concentration was 14 mol/L and the reaction time was 12 h,smooth and slender Na₂Ti₃O₇ nanowires could be obtained.On this basis,the effects of reaction time and reaction temperature on the crystal structure and microstructure of Ba Ti O₃ nanowires in the second hydrothermal reaction were further studied.The results showed that under the reaction conditions of Ba:Ti molar ratio of 2:1,reaction time of 12 h,and reaction temperature of 150℃,Ba Ti O₃ nanowires with the lengths ranging from 1.8μm to 4.8μm,diameters ranging from 125 nm to 375 nm,and aspect ratios ranging from 4.8 to38.4 could be obtained.BTMPs/PVDF composites and BTNWs/PVDF composites were prepared by using Ba Ti O₃ nanowires and Ba Ti O₃ microparticles（BTMPs）as fillers with PVDF matrix,respectively.It was found that with the increase of BTNWs content,the dielectric constant of BTNWs/PVDF composites also increased,and the breakdown strength decreased slightly compared with pure PVDF.At the same filler content,using BTNWs as fillers is beneficial to enhance the dielectric constant,breakdown strength and energy storage density of BTNWs/PVDF composites.When the filler content is 30 vol%,the energy storage density of BTNWs/PVDF composites can reach 3.47 J/cm³,which is nearly 48.3%and 116.9%higher than that of PVDF and BTMPs/PVDF composites.In order to improve the breakdown strength and energy storage performance of BTNWs@PDA/PVDF composites,BTNWs@PDA was obtained by coating the surface of BTNWs with polydopamine（PDA）.The results showed that the coating and modification of BTNWs with one-dimensional structure can synergistically improve the dielectric properties,breakdown strength and energy storage properties of the composites.When the filler content is 30 vol%,the energy storage density of the BTNWs@PDA0.5/PVDF composites reaches5.48 J/cm³,and the breakdown strength of the composites is 192.1 k V/mm,compared with 30vol%BTNWs/PVDF composites,the energy storage density and breakdown strength of the composites were increased by 57.9%and 3.7%,respectively.