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Laser Turns All Metals Black
Roland Piquepaille writes "Researchers at the University of Rochester have found a way to change the properties of almost any metal by using a femtosecond laser pulse. This ultra-intense laser blast creates true 'black metal' from copper, gold or zinc by forming nanostructures at the surface of the metal. As these nanostructures capture radiation, the metals turn black. And as the process needs surprisingly low power, it could soon be used for a variety of applications, such as stealth planes, black jewels or car paintings. But read more for additional references and a picture of this femtosecond laser system."
Are we talking like optical black, suitable for coating the insides of instruments like telescopes and microscopes?
-jcr
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and his additional references
It is, but it also insulates a bit. If you paint something black, it emits and absorbs radiant heat with the properties of the paint, not the metal. This is about making the metal itself black so it absorbs/emits more efficiently.
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Seems like the perfect coating for solar panels for hot water. The search has always been for the best heat absorbing surface. This type of coating should be the most efficent coating for heat absorbsion.
For many, many years we've been able to use lasers to spot-anneal metals, which produces a very dark (though not totally black) mark on the metal while introducing no change at all dimensionally. One area where this process gets used quite a lot is in artificial limbs/implants where the foreign body to be introduced needs to be permanently marked for identification but can have absolutely no sharp edges or anything else that might irritate or damage the tissue. This new process sounds like something similar, although the femtosecond laser angle is kind of new. I'm curious to see how practical it turns out to be, as the few femtosecond lasers I've worked with were *extremely* sensitive to temperature changes.
For those having difficulty reconciling the "entire power output of the US from a standard AC outlet" thing, understand that you are radiating for a ridiculously short period of time, so you can get a very high peak power in that pulse while still having a very low average power usage if you can unload a decent percentage of the entire duty cycle's worth of power in that one pulse. The Nd:YAG machines that I worked with were only 90 watts or so CW (continuous wave), but when you cranked the Q-switch down to a low enough rate, you could get a peak power in excess of a quarter-million watts in each 10 microsecond pulse. 10 microseconds is 10 *billion* times longer than a femtosecond (same comparison: one second to 317 years), so you have the possibility of having staggeringly large peak powers in these really short pulses.
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Yes. The nanostructures formed by the laser give the metals much more surface area, thereby enabling a catalytic effect. Expect to see this played with much more in inorganic and organometallic labs very soon.
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