无机颗粒形状对高储能密度有机复合材料介电性能的影响

Effect of shape of inorganic particles on dielectric properties of polymer composites with high energy density

通过在有机基体内添加无机陶瓷颗粒形成二相复合材料是当前研究高储能密度的热点和难点,材料的静电储能特性由其内部电场分布决定。对于纯高聚物材料在均匀外电场环境中其内部电场分布均匀,但当填充无机颗粒形成复合材料时,材料局部电场会发生畸变,进而影响复合材料的介电性能。本文通过有限元方法系统研究了不同形状颗粒,包括球型、纤维状和圆片状颗粒及其空间分布的电响应特性,进而分析其对复合材料储能特性的影响。结果表明,颗粒形状及空间分布的不同均会产生不同的局部电场分布,对于球型颗粒其顶端和低端会出现明显的电场集中现象;对于纤维状颗粒,当其长径比较小时,其端部束缚电荷产生的电场畸变不能被忽略。最后,本文建立了不同形状颗粒填充复合材料三维有限元模型,计算结果表明,在相同填充浓度下,一维纤维状颗粒填充复合材料的介电常数最大,二维圆片状颗粒填充复合材料介电常数最小,而球型颗粒填充复合材料介于二者之间。本文对理解复合材料储能特性的微观机制具有重要的意义。

The formation of two-phase composite materials by adding inorganic ceramic particles in the organic matrix is a hot and difficult point in the current study of high energy storage density.The electrostatic energy storage characteristics of the material are determined by its internal electric field distribution.For pure polymer materials,the internal electric field is uniformly distributed in a uniform external electric field environment,but when the inorganic particles are filled to form a composite material,the local electric field of the material will be distorted,which will affect the dielectric properties of the composite material.In this paper,the electric response properties of particles with different shape,including sphere,fiber and disk and its special arrangement has been systematically studied.The results show that both the shape and the spatial arrangement of the particles in the polymer matrix affect the local distribution of electric field.For spherical particles,there will exist be field concentration up and below the particle.For fibers,the field caused by the terminal surface bound charge should not be neglected when the aspect ratio is not large enough.At last,three three-dimensional simulation models of composites with spherical,fiber and disk particles have been established.It is indicated that composites with fiber particle possess the highest effective permittivity,while the disk particle is the lowest under the same concentration.The investigation of this paper is of great significance to understand the microscopic mechanism of energy storage.