Preparation And Properties Of Poly（Vinylidene Fluoride-hexafluoropropylene）/BaTiO₃ Nanowires Nanocomposites

Currently,energy storage materials are widely used in electronic devices such as capacitors,the dielectric ceramic and the polymer materials were difficult to meet the rapid development of electronic technology.In this paper,the barium titanate（BaTiO₃,BT）nanowires were prepared as filler by hydrothermal method,which were compound with P（VDF-HFP）polymer matrix to form composite films.To meet the energy storage requirements,the influences of BT power’s morphology changing and BT nanowires surface modification to the properties of the composite films were also studied.Obtaining the smooth and slender sodium titanate Na₂Ti₃O₇ precursors,the optimum conditions for the preparation were as follows:the alkaline concentration of the reaction solution was 10mol/L,the temperature was 180°C,and the time was 12 hours.Then in the second hydrothermal reaction,with the Ba（OH）₂·8H₂O powder as a barium source,BT nanowires with aspect ratio of 21 and 50⁸0nm in diameter were obtained through the replacement of barium ions and sodium ions.The change of BT powder’s morphology has a significant effect on optimizing the performance of the composite film.Under the 300MV/m electric field the discharged energy density of the 5 vol%BT nanoparticles/P（VDF-HFP）composite film was 6.26 J/cm³,and the discharged energy density of 5 vol%BT nanowires/P（VDF-HFP）composite film is 6.86 J/cm³,which is improved to 9.58%,also the breakdown strength increased from 306.87 MV/m to 321.8 5MV/m.The high filling amount of BT nanowires effectively improves the dielectric constant properties of the composite film material.However,the increasing amount of the filler made the compatibility of the filler and the matrix weakened,which would lead to the increasing of defects,such as voids and cracks,resulting in a significant drop in breakdown strength and energy efficiency.Therefore,the surface modification of BT nanowires by ethylenediamine or dopamine.5 vol%Dopa-BT nanowires/P（VDF-HFP）composite film has discharged energy density of 9.02 J/cm³ at 300 MV/m electric field,and the discharged efficiency of 46.39%.But ethylenediamine surface modification due to uniformity of coating and it’s functional groups are different,so the effect is slightly inferior.In 300 MV/m electric field has discharged energy density of 8.68 J/cm³,discharged efficiency of 44.54%with 5 vol%EDA-BT nanowires/P（VDF-HFP）composite film.