These photos show a section of helicopter blade before (left) and after (right) applying Joule heating with the composite coating. Photos: Tour Group/Rice University.A thin coating of a composite material comprising graphene nanoribbons in epoxy, developed at Rice University, has proven highly effective at melting ice on a helicopter blade.
The coating by the Rice lab of chemist James Tour may be an effective real-time deicer for aircraft, wind turbines, transmission lines and other surfaces exposed to winter weather, according to a new paper in ACS Applied Materials and Interfaces.
Applying a small voltage to the coating generates electrothermal heat – a process known as Joule heating – causing any nearby ice to melt. In tests, the coating was able to melt centimeter-thick ice from a static helicopter rotor blade in a -4°F environment.
The nanoribbons are produced commercially by unzipping nanotubes, a process also invented at Rice, and are highly conductive. The Tour lab determined years ago that nanoribbons incorporated in composites would interconnect, allowing them to conduct electricity across the material. This kind of composite material would be much cheaper to produce than large sheets of pristine graphene.
Previous experiments showed how films containing the nanoribbons could be used to deice radar domes and even glass, since the films are transparent to the eye. "Applying this composite to wings could save time and money at airports where the glycol-based chemicals now used to deice aircraft are also an environmental concern," Tour said.
The graphene nanoribbons comprise no more than 5% of the composite used in this study. The researchers, led by Rice graduate student Abdul-Rahman Raji, spread a thin coat of the composite on a segment of a rotor blade supplied by a helicopter manufacturer, before replacing the thermally conductive nickel abrasion sleeve used as a leading edge on the blades. By applying a small voltage, they were then able to heat the composite to more than 200°F.
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 any ice and allow it to fall off without having to melt completely, Tour said. The lab also reported that the composite remained robust at temperatures up to nearly 600°F.
As an added bonus, Tour said, the coating may help to protect aircraft from lightning strikes and also provide an extra layer of electromagnetic shielding.
This story is adapted from material from Rice University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.