有限元法研究填料形貌与介电常数对无机/有机介电复合材料介电性能的影响

Computational study of both morphologies and dielectric constant of fillers on dielectric properties of inorganic/organic dielectric composites by finite element method

为了开发高储能密度的无机/有机介电复合材料,本文采用有限元法分别研究了直径为100nm的球形填料与基体介电常数的比值(k)、球形填料在复合材料中的排列方式、球形填料尺寸(100~300nm)、纤维状填料长径比(α)和片状填料的球形度(β)对复合材料介电性能的影响。计算结果表明,当k值大于20时,复合材料的介电常数变化不明显;球形填料沿电场方向成链式排列时,复合材料有较大的介电常数,且材料中球形填料附近处存在较大的电位移和较大的电场,说明这种填料排列方式有利于材料介电常数的提高,但会削弱材料的耐击穿能力;当球形填料随机分布时,颗粒尺寸变化对复合材料介电常数的影响不明显。对于纤维状填料,其长径比α越大且长轴沿电场方向分布时,填料自身及周边会产生较大的电位移,表明这种情况有利于复合材料介电常数的提高。对于片状填料,其球形度β越小,填料与基体界面处高电场区域越小,表明材料的耐击穿能力越高。本研究可为高介高储能材料的实验研究提供理论指导。

In order to develop inorganic/organic dielectric composites with high energy storage density,the finite element method was adopt to study the effects of both morphologies and dielectric constant of fillers on the dielectric properties of inorganic/organic composites,including the ratio of dielectric constant of spherical filler to matrix(k),the size(100-300 nm)and the arrangement of spherical fillers,the aspect ratio of fiber fillers(α)and the sphericity of nanoplate fillers(β).The results show that the dielectric constant of composites doesn’t change significantly when kexceeds 20.The composites will get large dielectric constant when the spherical fillers are chained along the direction of the electric field.Large electric displacement and large electric field appear at the interface between the spherical fillers and matrix,indicating that this arrangement is beneficial to the improvement of the dielectric constant of the composites,but weakens the breakdown resistance.When the spherical fillers are randomly distributed in the matrix,the sizes of fillers have little effect on the dielectric constant of composites.Fiber fillers with largeαand the long axis along the direction of electric field will result in large electric displacement,which indicates this filler will improve dielectric constant of composites.The nanoplate fillers with smallβbring out lower electric field at the interface,indicating that the composites possess higher breakdown resistance.