Graphene composite could be an effective wing de-icer
26 January 2016
A thin coating of graphene nanoribbons in epoxy developed at Rice University has proven effective at melting ice on a helicopter blade.
The coating, developed by the Rice lab of chemist James Tour, might be an effective real-time de-icer for aircraft, wind turbines, transmission lines and other surfaces exposed to winter weather, according to a report published in the journal, Applied Materials and Interfaces.
In tests, the lab melted centimetre-thick ice from a static helicopter rotor blade in a -20°C 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 some years ago that nanoribbons in composites would interconnect and conduct electricity across the material with much lower loadings than traditionally needed.
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," says Tour.
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 90°C.
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. The lab reported that the composite remained robust in temperatures up to nearly 315°C.
According to Tour, the coating offers an additional bonus protecting aircraft from lightning strikes and providing an extra layer of electromagnetic shielding.