Researchers strike 'black gold' with metal-blackening laser
Last Updated: Wednesday, November 22, 2006 | 12:31 PM ET
CBC News
U.S. scientists have created a way to change the surface properties of most metals to render them pitch-black, which could lead to more efficient fuel cells, solar panels and sports cars as sleek as Batman's ride.
The process could one day be used to blacken everyday metal items — even wedding rings — as well as improve light detectors in space telescopes, said Chunlei Guo, assistant professor of optics at Rochester University and the project's lead researcher.
The process has captured the attention of automotive industry members, who are asking Guo about possible applications of the process in assembly lines of the future.
"I have been bombarded," Guo told CBC News Online on Wednesday.
Boosts surface area
The process uses an ultra-brief, ultra-intense beam of light called a femtosecond laser pulse.
The laser burst lasts only a few quadrillionths of a second. A femtosecond is to a second what a second is to about 32 million years.
During its brief burst, the laser unleashes as much power as the entire grid of North America onto a spot the size of a needlepoint, Guo said.
That intense blast forces the surface of the metal to form nanostructures — pits, globules and strands that dramatically increase the area of the surface and improve the metal's ability to capture radiation.
"We've been surprised by the number of possible applications for this," Guo said. "We wanted to see what would happen to a metal's properties under different laser conditions and we stumbled on this way to completely alter the reflective properties of metals."
Fuel cells utilize catalysis — or the acceleration of a chemical reaction by means of a substance — often by using metals such as platinum.
"The more surface area you have, basically the more catalysis area you have to promote fuel cells," Guo said.
Improves 'stealth' technology
The research team has tested the absorption capabilities for the black metal and confirmed that it can absorb virtually all the light that falls on it, making it pitch- black.
The huge increase in light absorption means nearly any metal becomes extremely useful whenever radiation gathering is needed. Guo said this could also be useful in improving so-called "stealth" technology, in which an object or vehicle is rendered invisible to radar by absorbing radiation waves sent to detect it.
The process has worked on every metal the team has tried, Guo said. Since it's a property of the metal itself, there's no worry about the black wearing off.
But he added people shouldn't expect to see home-blackening kits anytime soon.
"If you got your hand in the way of the focused laser beam, even though it's only firing for a few femtoseconds, it would drill a hole through your skin," Guo said. "I wouldn't recommend trying that."
