A nanocomposite was developed that could be a superior high-temperature dielectric material for flexible electronics, energy storage, and electric devices. The nanocomposite combines one-dimensional polymer nanofibers and two-dimensional boron nitride nano-sheets. The nanofibers reinforce the self-assembling material while the white graphene nanosheets provide a thermally conductive network that allows it to withstand the heat that breaks down common dielectrics, the polarized insulators in batteries, and other devices that separate positive and negative electrodes.
A challenge posed by next-generation electronics is that dielectrics must be thin, tough, flexible, and able to withstand harsh environments. Ceramic is a very good dielectric but it is mechanically brittle; polymer is a good dielectric with good mechanical properties but its thermal tolerance is very low. Boron nitride is an electrical insulator but happily disperses heat. When the polymer nanofiber is combined with boron nitride, the resulting material is mechanically exceptional, and thermally and chemically very stable.
The 12- to 15-micron-thick material acts as an effective heat sink up to 250 °C (482 °F). Tests showed the polymer nanofibers-boron nitride combination dispersed heat four times better than the polymer alone. In its simplest form, a single layer of polyaramid nanofibers binds via van der Waals forces to a sprinkling of boron nitride flakes 10% by weight of the final product. The flakes are just dense enough to form a heat-dissipating network that still allows the composite to retain its flexibility, and even foldability, while maintaining its robustness. Layering polyaramid and boron nitride can make the material thicker while still retaining flexibility.