Graphene ribbons to the rescue

These ribbons can help melt ice on the blades of a chopper.

A new nanotech coating can melt ice on helicopter blades and might offer a new way to de-ice aircraft, wind turbines, and power lines.

In tests, the material melted centimetre-thick ice from a static helicopter rotor blade in a -200C environment. When a small voltage was applied, the coating delivered electrothermal heat —called Joule heating — to the surface, which melted the ice.

The coating is a mixture of graphene nanoribbons in epoxy. The nanoribbons, produced commercially by unzipping nanotubes, are highly conductive.

Rather than trying to produce large sheets of expensive graphene, scientists in the lab of chemist James Tour at Rice University determined 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 lab tests, nanoribbons were no more than five per cent of the composite. The researchers 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 930C. The team reported the findings in ACS Applied Materials and Interfaces.

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 says.

The lab reported that the composite remained robust in temperatures up to nearly 3150C.

As a bonus, Tour adds, the coating may also help protect aircraft from lightning strikes and provide an extra layer of electromagnetic shielding.

Scientists from Rice, the University of Akron, and the University of Ljubljana, Slovenia, collaborated on the project. The Air Force Office of Scientific Research and Carson Helicopter supported the research.