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."

Applications

[Jarjarthejedi]

Interesting applications listed, detectors, chemistry, etc. What I'm wondering is the question implied by the editor, can this blast be used to make the metal absorb radar waves? If they can made a laser pulse make the substance absorb all visible EM radiation, can they do the same for invisible? This could have significant applications for the military if it can, not just for better stealth aircraft, but think of it. An invisible to radar destroyer, aircraft carrier, tank even. This is defiantly worth keeping an eye on, for the many scientific applications as well as the military ones. If it's really as easy as creating a femptosecond pulse to make something stealth many other nations would be able to do it soon as well.

Re:anything special?

[biocute]

Low power (so low cost) makes it an ideal alternative to traditional coating/painting.

tag as "pigpile"

[Anonymous Coward]

As usual, tag as "pigpile" to warn others not to click on Roland Piquepaille's adwhore blog...

Comment removed

[account_deleted]

Comment removed based on user account deletion

Re:anything special?

[Tim C]

Surely if it absorbed all the light, it would be completely invisible, not black?

No, because if it was invisible you'd be able to see what was behind it; if it merely absorbs the light that falls on it, you'd see a black shape instead...

Obligatory Pigpile Rant

[RobertB-DC]

Since it's the holiday, the usual rants against the article submitter, Roland Piquepaille, have been rather muted. To sum up:

* He gets a lot of articles posted to the front page, which makes the rest of us jealous.

* His articles tend toward pseudoscience, or at least towards the sort of flashy, headline-inspiring science that does little to advance human knowledge.

* He used to link to his personal blog, which really irritated people who'd love to have their own blogs get Slashdotted on a regular basis.

* He now links to his zdnet blog, which really irritates people who'd love to have their own blogs get picked up by a big corporate website.

* To top it all off, he's French, so all the right-wing nutters hate him automatically.

My irritation comes mostly from the second point -- and, I'll confess, the first as well. But as his defenders (and even the Slashdot editors) have noted, it's not like he's got some inside line to CmdrTaco's desk. He just finds himself at the right place at the right time.

Nonetheless, I recommend continuing to tag his articles with "pigpile", just so's we can keep up.

Re:How black is it?

[TeknoHog]

An older New Scientist article [newscientist.com] on a related technique reports 7 to 25 times less light reflected, compared to optical black paint. NS also reports [newscientisttech.com] on the current laser-based technology.

Re:anything special?

[Ruff_ilb]

I sort of skimmed TFA and the abstract (GASP!), and they made it seem as if they could create nanostructures with different properties based on the frequency, intensity, and duration of a given pulse. While I find it unlikely that they've created something that effectively absorbs basically any sort of radiation, it's likely that with a little tweaking they can get it to absorb specific wavelengths.

Re:How black is it?

[P3NIS_CLEAVER]

Optically black paint is also problematic, as it chips off and gets into the optics. This would allow a black coating with zero contamination.

Re:Applications

[John Hasler]

> Whether it's also black to radio waves needs to be investigated.

No it doesn't. It is obvious that it is not. The process makes the metal black by creating an intricate surface structure on the scale of the wavelengths of visible light. It would look like a shiny metal surface at the centimeter or so wavelengths used by radar. The effect probably peters out somewhere in the infrared.

Re:Applications

[John Hasler]

> On the other side of the coin, back when there was an article about using
> lasers to take out missiles while they were in the air, someone suggested
> that they make them as shiny (in all spectrums) as possible to reflect rather
> than absorb the military laser.

Doesn't work. The electric field intensity at the surface of the target is so high it exceeds the work function of the material and rips electrons right off the atoms. This creates a plasma layer that efficiently absorbs the radiation.

Re:Obligatory Pigpile Rant

[RealGrouchy]

Actually, you missed one of the more important aspects of the fourth point:

He adds a link to his blog using "additional references and a picture" (or variants) as the text. This results in him getting higher google rankings for his blog, particularly for "additional references and a picture" (or variants). Note the Related Links at the top right of the Slashdot page for this article. In addition to a standard "slashvertisement", the effects also amount to a "googletisement".

While in ordinary circumstances this could potentially be acceptable, the contents of Roland's blog entries are usually redundant (including the picture) to the very articles he is reviewing in his blog. This amounts to an abuse of the trust provided by the Slashdot community.

Many people warn other slashdotters by adding the tag "pigpile" (for those who have tagging enabled). However, more people use the Greasemonkey script [userscripts.org] that will block Roland's pseudoscientific submissions, which brendandonhue [slashdot.org] posted in a previous Pigpile thread [slashdot.org]. That is why the Pigpile rants are low, not necessarily the holidays.

- RG>

Re:Applications

[Jarjarthejedi]

Not so much. Perhaps I'm wrong, but as far as I know RADAR works by sending out a signal and picking up the reflected radiation. If nothing's reflected back it would be just like there was no object there at all. The only possible cause of the random noise you mention would be something to do with the ionosphere, and that would be so transient that it couldn't be used for accurate detection.

Re:anything special?

[MoxFulder]

Um, no. The energy is *drawn* from the outlet at a comparatively slow rate (say, over a period of a few seconds) and then *released* into the laser extraordinarily fast (10^-15 seconds).

The technical meaning of the word "power" is energy consumed or produced per unit time. So a fairly small amount of energy can result in a huge amount of power if it's produced or consumed quickly.

Re:Applications

[Anonymous Coward]

Stealth for aircraft if much more complicated than changing it's surface black.

If you're interested http://www.espionageinfo.com/Sp-Te/Stealth-Technol ogy.html [espionageinfo.com] this site gives a pretty good overview of stealth related issues and technology.

Hardly for car paintings

[Mr Europe]

This could hardly be used for car paintings, or any other big surfaces, since:
"For example, blackening a piece of metal the size of a little finger currently takes about 30 minutes."
And matt black hasn't ever been a favourite car color.

Nothing to see, move along.

[Sir Holo]

This "technology" is nothing new. Just a prof trying to make something mundane sound flashy.

Hit things with enough laser fluence and the surface atoms will move around, and may even be blasted off of the surface. This is the basis of a standard materials synthesis technique, pulsed laser deposition (PLD) [wikipedia.org]. Hit a target with a laser, and collect the ejected material on a nearby crystal.

Anyone who has done PLD knows that the surface of the target gets rough when you blast it. If the target is a metal, and the roughness is smaller than the wavelength of light (nanoscale), it will absorb light - it will be black.

In any case, the article asserts that the "blackness" is a material property and is therefore permanent. Nonsense. Touch it and the surface particles will rub off, leaving behind a shiny metal surface. Further, I'd be extremely surprised if there weren't tons of existing patents on surface modification by lasers. There are certainly tons of academic publications on the topic.

Re:Can it be used for long term archival

[Vegeta99]

That's just the reflective layer. If the laser in your CD-R had enough power to burn more than just the dye in FRONT of that reflective layer, you'd have some serious issues... ... dummy.

Re:anything special?

[fferreres]

I am sure he confused invisible, to invisible to radars and the type of systems that need a signal bounced back. You cannot use radars, but you can do motion detection and shape detection, etc. You can SEE the black thing for sure as almost nothing is pure black. It may be a good disguise in the sky though (unless you are between a start and your chaser) :-)

Re:Applications

[jon_joy_1999]

the reason that the stealth aircraft with the radar signature of a small bird isn't seen is because if the radar system could see the signature of the aircraft, then it could see the signature of every small bird within the range of the radar system, which is quite a lot. and a single radar pulse is not capable of detecting speed, you need multiple radar pulses to detect speed. it's like being in a dark room with a strobe light. you can tell how fast an object is moving by gauging the distance the object has moved between flashes. going back to seeing the signature of every small bird, on the radar screen it is impossible to tell where one bird has moved to, since there are 129,600 possible general directions it could have gone. not to mention that birds frequently drop below the radar level, while other birds rise into the radar, and, birds, somewhat like stealth aircraft, don't carry transponder systems

Re:Solar collectors

[aXis100]

That's why the collectors are covered in glass....

The black panels absorb and retransmits the light, but since their temperature is far lower than the sun the retransmitted light is lower wavelength (ie infra-red). The glass used (or all glass?) is opaque to infra-red, so the infra-red heat energy is re-absorbed and doesnt escape.

A double glass layer on top is even better for stopping the heat loss since it insulates the inner glass panel from convective currents.

Re:ethz

[cool_arrow]

There is a surface finish called parkerizing which is not too difficult to do and holds oil very well. It's the same finish they put on Glock handguns. I think you can get a kit and do it yourself.

Re:How black is it?

[sasdrtx]

I'd have to assume you made the jump to base 32, and therefore you've described a medium gray. In some freaky system with 5 bit nibbles.

Re:How black is it?

[TheCreeep]

You realize, of course, that #GGGGGG is basically whiter than white? Black is #000000