Femtosecond lasers create true black metal

The process, using an incredibly intense burst of laser light, holds the promise of making everything from fuel cells to a space telescope’s detectors more efficient–not to mention turning your car into the blackest black around.

Guo is also quick to point out that the nanostructures’ remarkable increase in a metal’s surface area is a perfect way to catalyze chemical reactions. Along with one of his research group members, postdoctoral student Anatoliy Vorobyev, he hopes to learn how the metal can help derive more energy from fuel cell reactions. The new process has worked on every metal Guo has tried, and since it’s a property of the metal itself, there’s no worry of the black wearing off.

Currently, the process is slow. To alter a strip of metal the size of your little finger easily takes 30 minutes or more, but Guo is looking at how different burst lengths, different wavelengths, and different intensities affect metal’s properties. Fortunately, despite the incredible intensity involved, the femtosecond laser can be powered by a simple wall outlet, meaning that when the process is refined, implementing it should be relatively simple.

During its brief burst, Guo’s laser unleashes as much power as the entire grid of North America onto a spot the size of a needle point. That intense blast forces the surface of the metal to form and nanostructures–pits, globules, and strands that both dramatically increase the area of the surface and capture radiation. Some larger structures also form in subsequent blasts.

Guo’s research team has tested the absorption capabilities for the black metal and confirmed that it can absorb virtually all the light that fall on it, making it pitch black. The huge increase in light absorption enabled by Guo’s femtosecond laser processing means nearly any metal becomes extremely useful anytime radiation gathering is needed. For instance, detectors of all kinds, from space probes to light meters, could capture far more data than an ordinary metal-based detector could.

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