The Effects Of The Polarity And Shape Of Nano KTa_1-xNb_xO₃ On The Dielectric Performance Of PVDF Composite Films

With their superior flexibility,exceptional breakdown strength of polymer,and high dielectric constant of nanoparticles,polymer-based nanomaterials possess great potential for micro energy storage devices.which.This thesis investigates the dielectric modulation mechanism of the polarity and shape of nanoparticles on the polymer composites.Specifically,potassium tantalum niobate(KTa_1-xNb_xO₃)nanofillers with varied shape,interface and polarity were designed and fabricated,and their effects on the dielectric performance of polyvinylidene fluoride?PVDF?composites were examined.To synthesize KTa_1-xNb_xO₃nanoparticles of different shapes,initial experimens were performed to study the conditions of hydrothermal reaction that influence the resulting shape as well as to identify the optimal conditions of KTN nanorod synthesis.The effect of polarity on the dielectric performance of nanocomposites was investigated by engineering KTa_1-xNb_xO₃with different Ta/Nb ratios,which influence the KTa_1-xNb_xO₃nanostructures and Curie temperature.It was found that KTa_0.5Nb_0.5O₃possesses a relatively higher permittivity of 3780?1 k Hz?than those of others.As such,the permittivity of PVDF was improved from 10 to 19.5?1 k Hz?after 30 wt%KTa_0.5Nb_0.5O₃doping.The dielectric performance of polymer matrix composites with respective to the length of KTN nanorod fillers was also examined.Utilizing polyvinylpyrrolidone?PVP?as a surfactant for regulating the length of KTN nanorods,the average length was increased from 610 nm to 730 nm,and the corresponding dielectric performance was measured.The results demonstrated an improved relative permittivity??_r?of PVP-modified KTN/PVDF composite,which is 1.6 times higher than that of unmodified KTN/PVDF.In order to intensify the interface polarization of the nanocomposite,copper?Cu?nanoparticles were deposited on the surface of KTa_0.25Nb_0.75O₃nanorods via a chemical reduction method.The integration of Cu and KTN can achieve a composite with the high?_rof KTN,nanoscale dimensions and excellent conductivity of Cu nanoparticles,and high breakdown strength of the polymer.The microstructure,dielectric properties,and energy storage characteristics of the composites were analyzed.Compared to metal nanoparticle/polymer composites,Cu-deposited KTN was demonstrated to have enhanced interface polarization and reduced formation of conductive channels,increasing the permittivity and reducing the dielectric loss of the polymer composite.The Cu-KTN/PVDF possesses a greater dielectric constant,higher storage density,and lower dielectric loss compared to its counterpart,KTN/PVDF,providing a feasible approach for efficient energy storage in the realm of nanocomposite.