By Sindya N. Bhanoo
January 3, 2011
De-icing aircraft with chemicals is expensive, environmentally unfriendly and time-consuming, as stranded passengers during winter blizzards may be well aware.
For the last decade researchers have been exploring the possibility of building planes with hydrophobic, or water-repellent, materials that would not require de-icing.
But now, researchers from M.I.T. report that this approach is flawed. Although a surface might be water-repellent, it may not be ice- or frost-repellent. Their findings appear in the journal Applied Physics Letters.
“Water can go directly from a vapor stage to a solid state,” said Kripa Varanasi the study’s lead author and a professor of mechanical engineering at M.I.T. “When ice forms this way – typically called frost – on a super hydrophobic surface it can pretty much coat up the entire surface.”
The result is a surface covered in frost that is no longer hydrophobic, but incredibly hydrophilic, or water-attracting, he said.
Dr. Varanasi believes that frost buildup can be better controlled by creating a surface with nanoscale texturing.
The technology would have applications outside aviation as well. Wind turbines tend to collect large amounts of ice, and aside from introducing significant drag and reducing performance, a spinning turbine can hurl out large chunks of ice that can cause serious damage.
The real challenge lies in creating an ideal texture that deflects unwanted frost formation and is also durable and scalable, Dr. Varanasi said.
http://www.nytimes.com/2011/01/04/science/04obplane.html?_r=1&src=twrhp
Source: THE NEW YORK TIMES
Date: 2011-01-03