Rice University
scientists embedded graphene nanoribbon-infused epoxy in a section of
helicopter
blade to test its
ability to remove ice through Joule heating. (Credit: Tour Group/Rice
University)
(January 25, 2016) Rice
University develops conductive material to heat surfaces, simplify ice removal
A thin coating of graphene nanoribbons in epoxy developed at
Rice University has proven effective at melting ice on a helicopter blade.
The coating by the Rice lab of chemist James Tour may be an
effective real-time de-icer for aircraft, wind turbines, transmission lines and
other surfaces exposed to winter weather, according to a new paper in the
American Chemical Society journal ACS Applied Materials and Interfaces.
In tests, the lab melted centimeter-thick ice from a static
helicopter rotor blade in a minus-4-degree Fahrenheit environment. When a small
voltage was applied, the coating delivered electrothermal heat – called Joule
heating – to the surface, which melted the ice.
The nanoribbons produced commercially by unzipping
nanotubes, a process also invented at Rice, are highly conductive. Rather than
trying to produce large sheets of expensive graphene, the lab determined years
ago that nanoribbons in composites would interconnect and conduct electricity across
the material with much lower loadings than traditionally needed.
Lab tests at Rice
University on a section of a helicopter rotor chilled to minus-4 degrees
Fahrenheit show
that a thin coat of nanoribbon-infused epoxy can be used as a de-icer.
The composite,
imbedded between an abrasion shield and the blade in the sample above,
heated when
electricity was applied, melting the ice. The material may be suitable for
keeping
aircraft, wind
turbines and transmission lines free of ice. (Credit: Tour Group/Rice University)
Previous experiments showed how the nanoribbons in films
could be used to de-ice radar domes and even glass, since the films can be
transparent to the eye.
“Applying this composite to wings could save time and money
at airports where the glycol-based chemicals now used to de-ice aircraft are
also an environmental concern,” Tour said.
In Rice’s lab tests, nanoribbons were no more than 5 percent
of the composite. The researchers led by Rice graduate student Abdul-Rahman
Raji spread a thin coat of the composite on a segment of rotor blade supplied
by a helicopter manufacturer; they then replaced the thermally conductive
nickel abrasion sleeve used as a leading edge on rotor blades. They were able
to heat the composite to more than 200 degrees Fahrenheit.
For wings or blades in motion, the thin layer of water that
forms first between the heated composite and the surface should be enough to
loosen ice and allow it to fall off without having to melt completely, Tour
said.