May 17, 2019 09:02 AM EDT
Scientists from the Rice University's Brown School of Engineering invented a nanocomposite that has great potential as a superior high-temperature dielectric material for energy storage, electric devices, and flexible electronics.
One-dimensional polymer nanofiber and two-dimensional boron nitride nanosheets comprise the nanocomposite. The "white graphene" nanosheets permit the self-assembling material to withstand heat that breaks down common dielectrics while the nanofibers strengthen the said material. These dielectrics separate positive and negative electrodes in devidces such as the polarized insulators in batteries.
Lead authors are M.M. Rahman and Anan Puthirath of the said institution. They answered to the challenge that dielectrics must be able to withstand harsh environments, flexible, tough and thin. Their invention was published in Advanced Functional Materials.
"Ceramic is a very good dielectric, but it is mechanically brittle," Rahman said of the common material. "On the other hand, polymer is a good dielectric with good mechanical properties, but its thermal tolerance is very low."
"When we combined the polymer nanofiber with boron nitride, we got a material that's mechanically exceptional, and thermally and chemically very stable," Rahman said.
The researchers showed that the 12-to-15 micron-thick material serves as an effective heat sink up to 250 degrees Celsisus. The results showed that the polymer nanofibers-boron nitride combination released heat four times better than the polymer.
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.
"The 1D polyaramid nanofiber has many interesting properties except thermal conductivity," Rahman said. "And boron nitride is a very interesting 2D material right now. They both have different independent properties, but when they are together, they make something very unique."
Rahman said the material is scalable and should be easy to incorporate into manufacturing.
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