芳纶纳米纤维基夹芯结构耐高温复合电介质薄膜的制备及性能研究

Preparation and properties of sandwich structured aramid nanofiber composite dielectric films with high-temperature resistance

有机-无机复合电介质通常难以兼具高介电常数和高电气强度。本文选用芳纶纳米纤维(ANF)作为耐高温基体,以氮化硼纳米片(BNNS)为电击穿改性剂、钛酸钡颗粒(BT)为介电改性剂,采用分步抽滤-热压法制备具有夹芯结构的复合薄膜,并研究了夹芯结构和不同改性剂含量对复合薄膜微观结构和介电性能的影响。结果表明:夹芯结构复合薄膜具有良好的柔韧性和优异的高温稳定性。BT的加入使单层和夹芯结构复合薄膜的电气强度下降,而BNNS的加入使其电气强度提升;单独加入BT或BNNS均可提升复合薄膜低频区的介电常数,而两者同时添加可使介电常数在宽频域内提升。因此,通过调配夹芯结构及各层改性剂含量可获得介电性能和电气强度均衡的复合薄膜,当以BNNS质量分数为10%的ANF/BNNS薄膜为外层、BT质量分数为10%的ANF/BT薄膜为芯层时,所得复合薄膜的介电常数为1.41(1 kHz),介质损耗因数为0.013(1 kHz),电气强度为13.3 kV/mm。

Organic-inorganic composite dielectrics are often difficult to have both high dielectric constant and high electric strength.In this paper,a sandwich structured composite film was prepared by using aramid nanofibers(ANF)as high-temperature resistant matrix,boron nitride nanosheets(BNNS)as electrical breakdown enhancer,and barium titanate particles(BT)as dielectric modifier through step-by-step vacuum filtration and hot-pressing method,and the effects of sandwich structure and different modifier content on the microstructure and dielectric properties of the composite films were studied.The results show that the sandwich structured composite films have high flexibility and excellent high-temperature stability.The addition of BT decreases the electric strength of single layer and sandwich structured composite films,while the addition of BNNS increases the electric strength of the composite films.The individual addition of BT or BNNS can increase the dielectric constant of composite films at low frequency,while the simultaneous addition of BT and BNNS can increase the dielectric constant in wide frequency domain.Therefore,a composite film with balanced dielectric properties and electric strength can be obtained by adjusting the sandwich structure and modifier content in each layer.When taking the ANF/BNNS film with 10%mass fraction of BNNS as the outer layer and the ANF/BT film with 10%mass fraction of BT as the core layer,the dielectric constant,dielectric loss factor,and electric strength of the prepared composite film is 1.41(1 kHz),0.013(1 kHz),and 13.3 kV/mm,respectively.