Structural Design And Preparation Of High-dielectric Polymer Composites

Polymer composites with high dielectric constant are widely used in many fields such as microelectronics and communication.Normally,polymer/ceramic particle composites show a decreased breakdown strength owing to the excessive filler content.In this paper,the orientation structured composites were designed and the specification shaped fillers were prepared.The polymer-based composites with improved dielectric properties were obtained.The thesis is mainly divided into three parts:(1)The copper calcium titanate nanowires(CCTO NWs)with high aspect ratio were prepared by a two-step hydrothermal method.After the surface modification by using silane coupling agent,the CCTO NWs were added to polyvinylidene fluoride(PVDF)to prepare the composites,and the orientation of CCTO NWs in PVDF was realized by thermal stretching.When the CCTO NWs content was 0.2,the breakdown strength of the oriented composite was 84.59 kV/mm,which is higher than that of the randomly distributed composite by 21.26%.(2)The graphene with low content was added into the CCTO NWs/PVDF composite to obtain the ternary CCTO NWs/graphene/PVDF composite and the oriented structure was carried out through the same thermal stretching process.The maximum breakdown strength of the oriented composite reached 119.7 kV/mm(2.37 times higher than that of pure PVDF)when the amounts of CCTO NWs and graphene were 0.2 and 0.005,which was 14.5%higher than that of the composite with random distribution.(3)Layer structured CCTO nanosheets and boron nitride-loaded CCTO nanosheets were synthesized by hydrothermal method and high temperature calcination,respectively.And the boron nitride supported CCTO nanosheets/PVDF composites were prepared.When the filler content was 0.4,the dielectric constant of the composites was 12.5 at 1 kHz.