Researcher holds
flexible dielectric polymer. Insert shows boron nitride
nanosheets.
Image: Qing Wang/Penn State
(August 6, 2015) Easily
manufactured, low cost, lightweight, flexible dielectric polymers that can
operate at high temperatures may be the solution to energy storage and power
conversion in electric vehicles and other high temperature applications, according
to a team of Penn State engineers.
"Ceramics are usually the choice for energy storage
dielectrics for high temperature applications, but they are heavy, weight is a
consideration and they are often also brittle," said Qing Wang, professor
of materials science and engineering, Penn State. "Polymers have a low
working temperature and so you need to add a cooling system, increasing the
volume so system efficiency decreases and so does reliability."
Dielectrics are materials that do not conduct electricity,
but when exposed to an electric field, store electricity. They can release
energy very quickly to satisfy engine start-ups or to convert the direct
current in batteries to the alternating current needed to drive motors.
Applications like hybrid and electric vehicles, aerospace
power electronics and underground gas and oil exploration equipment require
materials to withstand high temperatures. The researchers developed a
cross-linked polymer nanocomposite containing boron nitride nanosheets. This
material has high-voltage capacity for energy storage at elevated temperatures
and can also be photo patterned and is flexible. The researchers report their
results in a recent issue of Nature.
This boron nitride polymer composite can withstand temperatures
of more than 480 degrees Fahrenheit under the application of high voltages. The
material is easily manufactured by mixing the polymer and the nanosheets and
then curing the polymer either with heat or light to create crosslinks. Because
the nanosheets are tiny -- about 2 nanometers in thickness and 400 nanometers
in lateral size, the material remains flexible, but the combination provides
unique dielectric properties, which include higher voltage capability, heat
resistance and bendability.