The Preparation And Dielectric Properties Of Polymer-based Ceramic-nanorod-array Composites

With the rapid development of high-tech industries,the demand for dielectric capacitors with high energy density is becoming more and more urgent in the fields of energy,electronics,and national defense etc.The dielectric capacitor is the most commonly used energy storage device,and a passive device with largest amount as well.It has a simple structure with all solid state,having advantages of high working voltage,large power density,wide operating temperature,good safety performance,low loss,long life and low price.As a result,the dielectric capacitors have been widely used and studied.Both computational simulations and experimental results show that the 1-D ceramic nanofillers arranged along the direction of the external electric field could increase the polarization strength of the dielectric material,thereby increasing its dielectric constant and energy storage density.In this paper,a series of studies on ceramic nanorod arrays and their composite dielectric materials are carried out.First,three types of ceramic nanorod arrays were prepared by hydrothermal method,and the TiO₂ nanorod arrays with FTO as the substrate were selected for follow-up work.TiO₂-nanorod-array/polymer composite dielectric films were prepared in this paper,and their dielectric properties and energy storage properties were studied.The preparation of TiO₂-nanofiber/nanorod-array/polymer composite dielectric films was also attempted,and their dielectric properties were studied.The TiO₂-nanorod-array（TNA）/P（VDF-HFP）composite obtained in this paper can achieve a super high energy storage density of 17.5 J cm^-3 at a relatively high breakdown strength of 509 kV mm^-1.Moreover,the composite material can achieve very high charge and discharge efficiency（86%）at a high electric field(⁵00 kV mm^-1).In this work,the phase field simulation of the structure is also carried out.The simulation results not only confirm the large polarization inside the arrays,but reveal the great contribution the interface between the array-tips and the matrix made to the enhancement of energy density.The TiO₂-nanofiber（TNF）/P（VDF-HFP）composite films prepared in this work have a dielectric constant increase of 7.4%,14.8%,and 25.2%at 1 kHz with 1 vol.%,3 vol.%and 5 vol.%TNF adding respectively.For the TiO₂-nanofiber/TiO₂-nanorod-array/P（VDF-HFP）composite film（with the volume ratio of TNF 1.2 vol.%,the height ratio of TNA about 40%）,its dielectric constant at 1 kHz is 26.4,which is 95.6%higher than that of the polymer matrix.This work shows that ceramic nanorod arrays can be used as a special filler and polymer composite,and that the composite materials with excellent dielectric properties and energy storage properties,relatively low cost dielectric can be synthesized based on TiO₂ nanorod arrays.This lays the foundation for the future development of more complex topological structures based on ceramic nanorod arrays,and provides new ideas for the development of the research of dielectric materials.