Thermally conductive nanostructured, aramid dielectric composite films with boron nitride nanosheets

The rapid development of modern electronics and high-frequency and high-speed circuits sets stringent requirements of low dielectric permittivity and efficient heat removal of thermal-management materials to reduce the time delay of signal propagation and ensure the long lifetime of the electronics. In this work, we report a novel thermally conductive and minimally dielectric nanocomposite film by vacuum filtering aramid nanofibers (ANFs) on nylon filter with boron nitride nanosheets (BNNSs). To obtain a continuous, uniform, freestanding composite film with both low dielectric permittivity and strong thermal conductivity, ANF suspensions were dialyzed and then absorbed into a BNNSs/Isopropanol (IPA) dispersion by bath-sonication. The advantage of the nanocomposite film lies in that it possesses an out-plane thermal conductivity up to 0.6156 (w·m−1·k−1) at BNNSs mass percent of 50 wt%, a conductivity that is almost 5 times that of the pure nano-aramid film. The nanocomposite film also boasts a low dielectric permittivity (∼2.4 at 108 Hz) along with excellent mechanical flexibility and strength (∼62 MPa).