Under certain weather conditions ice can form on antennas. Some antennas are equipped with electric heaters to keep the ice off the elements or radome. Satellite dishes can use large gas fired heaters that pump warm air over the reflector. James Tour and his colleagues at Rice University developed a deicing film for radar domes and have now refined the technology to allow it to work as a transparent coating for glass.
The film is made of graphene nanoribbons, atom-thick strips of carbon created by splitting nanotubes. Last year, the Rice group created films of overlapping nanoribbons and polyurethane paint to melt ice on sensitive military radar domes. The technology is designed to replace a bulky metal oxide framework.
Tour said the the graphene-infused paint worked well, but where it was thickest it would break down when exposed to high power radio signals. “At extremely high RF, the thicker portions were absorbing the signal. That caused degradation of the film. Those spots go so hot that they burned up.”
The solution was to make the films more consistent. The new films are between 50 and 200 nanometers thick, about a thousand times thinner than a human hair, but retain their ability to heat when a voltage is applied. The researchers were also able to preserve their transparency. The films are still useful for de-icing applications but can be used to coat glass and plastic as well as radar domes and antennas.
Tests with the film showed that when the material was applied onto glass slides that were iced, when voltage was applied to either side of the slide, the ice melted within minutes even when kept in a minus-20-degree Celsius environment.
Tour noted that future generations of long-range Wi-Fi may also benefit. “It's going to be important, as Wi-Fi becomes more ubiquitous, especially in cities. Signals can't get through anything that's metallic in nature, but these layers are so thin they won't have any trouble penetrating.”
Considering the problems the researchers had with RF heating the film, it seems to me that this technology could be applied to broadcast antennas, using a bit of the RF to heat film.
Additional information and images are available in the Rice University News Release.
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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