University Makes New Black from Tiny Carbon Tubes Rice University has developed the world's darkest material, made from millions of tiny vertical tubes of carbon. Pulickel Ajayan, who helped lead the project, says the material isn't perfect, but it's "pretty dark." It approaches the elusive ideal black, which would absorb all colors of light and reflect none.
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University Makes New Black from Tiny Carbon Tubes

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University Makes New Black from Tiny Carbon Tubes

University Makes New Black from Tiny Carbon Tubes

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We realize we should be paying more attention on this program to the journal Nano Letters. This month, there's a little gem described there - and we do mean little. It's a substance made of tiny tubes of carbon, said to be the darkest man-made material ever. It comes very, very close to approaching an ideal black object, a perfect absorber of light.

Pulickel Ajayan is a professor of engineering at Rice University in Houston. He helped create the material, which is not easy to describe.

Dr. PULICKEL AJAYAN (Engineering, Materials Science and Nanotechnology, Rice University, Houston): So it looks like a lot(ph) of gas, you know? It's a thick film, a several hundred microns thick, and it contains millions of carbon nanotubes, which are extremely tiny cylinders made of gracillic(ph) carbon. And the interesting thing about this particular material is that all the nanotubes in this film are all aligned vertically with respect to each other. So, it's almost like a bed of nails, where the nanotubes are standing up vertically to the substrate.

BLOCK: And those nanotubes would be how tiny?

Dr. AJAYAN: The nanotubes are a few nanometers in diameter.

BLOCK: I don't know what that means.

(Soundbite of laughter)

Dr. AJAYAN: Okay, so, it's a billionth of a meter.

BLOCK: Uh-huh.

Dr. AJAYAN: Typically, a strand of your hair would be 10 microns, and this would be about a million times smaller than a strand of hair or something like that.

BLOCK: So, invisible to the naked eye, fair to say?

Dr. AJAYAN: Absolutely invisible to the naked eye. You can only see a collection of these, and that's why you could see them.

BLOCK: How close to ideal black did you come?

Dr. AJAYAN: You know, an ideal black material is a material that absorbs light perfectly at all angles and at all wavelength. If you look at the man-made materials, the best you could find is in the "Guinness Book of World Records," and they say the total integrated reflectance from that material is about .16 percent. And what we have, if you compare it to the darkest reported before is about three times better dark.

BLOCK: So when you're saying .16 percent, that's the amount of light that is not absorbed, that's bouncing back?

Dr. AJAYAN: Right. That is coming out. So, any material, you will find some light that is, you know, reflected back or transmitted. Now, what we have here is - essentially, the light that is going into this material, almost 99.96 percent is taken up by this material and only about 0.045 percent is reflected.

BLOCK: So, that 0.045 percent that's coming back, is that part driving you crazy?

(Soundbite of laughter]

Dr. AJAYAN: Well, you know, you could actually get better if you make these carbon nanotubes maybe a little bit more straighter, more perfect, because there's always some defect in this material that, you know, creates a problem. But this is pretty dark.

BLOCK: I'm curious. When you look at the film that you've developed, does it look to you blacker than anything you've seen before? Is that a virtual thing or no?

Dr. AJAYAN: Well, certainly, it did look much blacker than the other carbon material that we're used to. And in fact, when we were trying to do some experiments with, you know, light and laser beams, we couldn't find the beam for a while because it is absorbing so much.

BLOCK: Well, that's when you knew you were really on to something.

Dr. AJAYAN: Right, right.

BLOCK: Dr. Ajayan, do you know the movie "Spinal Tap"?

Dr. AJAYAN: I'm afraid not.

BLOCK: You don't. Okay.

(Soundbite of laughter)

BLOCK: Well, the reason I asked is that there's a scene in that movie - one of our producers mentioned this today - where it's about a fictitious rock band, and they get their new album, and it's called "Smell the Glove," and I'm looking at the cover. The cover is pure black. And the guitarist, Nigel Tufnel, is very impressed. Here's what he says.

(Soundbite of movie "This is Spinal Tap")

Mr. CHRISTOPHER GUEST (Actor): (As Nigel Tufnel) Here's what he's talking about. This is so black, it's like, how much more black could this be? And the answer is, none, none more black.

BLOCK: None more black, he's saying.

Dr. AJAYAN: Well, I suppose he is not familiar with nanotechnology.

BLOCK: Yeah, probably not.

(Soundbite of laughter)

BOCK: Well, Pulickel Ajayan, it's nice to talk to you. Thanks so much.

Dr. AJAYAN: Absolutely. A pleasure. Thank you.

BLOCK: Pulickel Ajayan of Rice University helped lead the research that developed the blackest man-made material ever.


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