Preparation And Properties Of Ag- TiO₂/P（VDF-HFP） Nanocomposite

Polymer matrix dielectric nanocomposites make full use of advantages of high dielectric permittivity from ceramic fillers and high dielectric strength from organic matrix and become a research hotspot to prepare new generation dielectric materials. What’s more, the three phase system consisted of ceramic/conductive fillers/polymer matrix achieves good dielectric properties while keep good processability in theory. However, the conductive particles connect easily and the ceramic phase cause electric field distortion, which limits the application. The purpose of this dissertation is to synthesize three phase composite with both of high dielectric perimittivity and low dielectric loss. Based on the P(VDF-HFP) matrix, studying the optimized method and process conditions of making different TiO2/Ag hybrid fillers in various structures and morphology. The effect mechanisms of fillers combination on the crystallization behavior and dielectric properties of the composite are revealed.According to the research, among several mathods to synthesize Ag@TiO2 core-shell nanoparticles, the vapor thermal method is optimiszed. By adjusting processing parameter, uniform and complete anatase TiO2 shell with thickness of 8-10nm was synthesized. Selecting anatase TiO2 powders as ingredient, adding alcohol as assistant, reacting at 180℃ for 48h, heat treating at 800℃ or 2h synthesized anatase TiO2 nanowires with great morpology, good dispersity, high crystallinity and good matrix combination. Ethylene glycol reduction method is available for preparing TiO2@Ag load nanoparticles. Moreover, ultra-small Ag nanoparticles were synthesized by controlling reaction time and reagent concentration.In the study of melt and crystallization behavior, high loading level of fillers will destroy the continunity of the matrix and promote its melt process. The strong interaction between fillers and matrix changes the crystallization temperature of the composite.In addition, nano-fillers show stronger effect for the melt and crystallization behavior than micro-fillers.The dielectric property research shows that the coated TiO2 layer of Ag@TiO2 separate Ag nanoparticle effectivly and keep the Ag@TiO2/P(VDF-HFP) composite low loss while permittivity increasing. As for TiO2NWs/Ag/P(VDF-HFP), the nanowires separate Ag nanoparticles well and suppress space charge. Avoiding the conduction of composite and improving the dielectric loss frequence dependence. TiO2 in the TiO2@Ag load nanoparticles can separate Ag nanoparticles form connecting to keep insulativity of the composite. The ultra-small Ag nanoparticles "trap" the carrier and decrease the loss and conductivity of the composite.