Nanotubes Form The Darkest Material Yet Created 324
toxcspdrmn writes "Bad news for Spinal Tap fans. The BBC reports that researchers at Rensselaer Polytechnic Institute in Troy, New York, have produced the darkest known material by manufacturing "forests" of carbon nanotubes. This forms a surface that absorbs or scatters 99.9% of all incidental light."
Re:Where's my fuligin? (Score:2, Informative)
Re:wouldn't scattered light still be light? (Score:5, Informative)
Another article with a pic of the substance (Score:4, Informative)
Re:Black body radiation (Score:5, Informative)
Although Planck's formula predicts that a black body will radiate energy at all frequencies, the formula is only applicable when many photons are being measured. For example, a black body at room temperature (300 K) with one square meter of surface area will emit a photon in the visible range once every thousand years or so, meaning that for most practical purposes, the black body does not emit in the visible range.
My, possibly incorrect, interpretation (assumption?) of the article was "light" in the broad sense of all electromagnetic radiation. This, however, does not make your link less interesting; in fact, in makes it more interesting. Thank-you.
Re:Oh wow - an darker shade of black... (Score:3, Informative)
Here ya go. [ibiblio.org]
Re:Oh wow - an darker shade of black... (Score:5, Informative)
Re:Where to put it (Score:5, Informative)
Even if your brain couldn't handle pure blackness, the rods still fire randomly, ensuring that some form if input is always present. You can verify this by closing your eyes in a very dark room - you should see a color that is not black. This color is called eigengrau [wikipedia.org].
I think this will be of limited value for personal stealth measures - being that dark, you'd stand out even aginst regular dark surfaces. However, as another article pointed out, a stealth plane could profit from being able to absorb radar beams. Research into the absorption of non-visible wavelengths is already underway.
Comment removed (Score:2, Informative)
Re:Oh wow - an darker shade of black... (Score:5, Informative)
Pretty cool stuff. The sample on the left is carbon black, which is reasonably black, but the surface still texture stands out clearly with the flash. The sample of the new material looks like a black hole - which I guess it almost is. Except for the suckage.
Re:wouldn't scattered light still be light? (Score:3, Informative)
Light that is scattered on impact with the first tube stands a high chance of then ending up hitting a second tube, where it is absorbed. That is the reason this forest-of-nanotubes is blacker than say any other pile of nanotubes.
Re:Why wont this change the world? (Score:2, Informative)
No.
The "solar constant" is measured "on the outer surface of [the] atmosphere", most certainly NOT at ground level. Down here, you get around 100W/m2, during daylight, in the summer, with no cloud cover, etc.
Did you really think that our previous "blackest" materials were simply so highly reflective as to make such a scheme impossible? No, they absorb something like 95%+ of light. But with that, you simply need a huge area to get a useful amount of energy.
Re:Why wont this change the world? (Score:5, Informative)
You are wrong here. The 1366 W/m2 is indeed at the upper atmosphere. Lower in the atmosphere it is less, how much depends on the current state of the atmosphere. About 1000W/m2 is the right value.
The 100W/m2 is the energy output of a not so good photovoltaic module.
Nyh
Re:What happens with the absorbed photons? (Score:2, Informative)
Re:Absorbtion (Score:3, Informative)
However, this is not exactly a breakthrough, because the material, while darker than black paint, is not enough darker to make it worth considering the cost. For the price difference, you'd be better off simply build a bigger collector.
Re:Why wont this change the world? (Score:4, Informative)
Well, let us do some math on the trivial boiling of water with black containers.
Take a container with 1 kg of water. For ease of calculation we will take a 0.1 m x 0.1 m x 0.1 m container.
Let us assume one side of the container faces the sun. Area is 0.1 x 0.1 = 0.01 m2
The staring temperature is 20C, boiling temperature is 100C. Delta t is also 80 C. Specific heat of water is about 4200 J/K/kg.
To make the 1 kg of water boil you need 80 x 4200 = 336 kJ.
Energy received on the side of the container is 0.01 x 1366 = 13.66 W.
Time needed to get 336 kJ with this power is 336000/13.66 = 24597 s (=6 hours and 50 min).
Oops, not so trivial after all...
If you make a large area (1m2) container containing 1 kg water you need get a container of 1 m x 1 m x 0.001 m. This container would boil water in 336000/1366 = 245 s (about 4 min). Problem with such a container is a large area at the cool side of the container and the specific heat of the container is a lot higher than the specific heat of the water it contains. So you need to design a container with a very low specific heat compared to the specific heat of the water it contains, a large surface area to collect the solar energy and good isolation at the shade side to minimize heat losses. Welcome to the interesting world of designing solar collectors.
And for the very black material: going from 99% black to 99.9% black gives only (99.9-99)/99 = 0.9% increase of efficiency. The problem of solar collectors is not the black not being black enough. A new blacker black won't revolutionize solar collectors.
Nyh
Re:I was going to ask... (Score:3, Informative)
He said that when they first shined the laser upon it, their instruments could not detect the laser being reflected back. He said they knew two things when that happened:
1. They're on to something
2. They're going to need better equipment
He also said that they hope to make it even blacker by finding a way to produce nanotubes that are more perfectly straight.
Re:Paint (Score:3, Informative)
Re:Don't tell John Carmack! (Score:3, Informative)
I don't know about that. I'm something of a serious DNA fan, and when the radio show was on I always pictured Marvin as short with a big head, just like the one that was in the H2G2 movie.
When the TV show came out I was puzzled as to why a supposedly advanced and brainy robot would have a range of motion of only about four inches on each limb, it was only Stephen Moore's delivery of his lines that saved it for me. From what I understand Douglas himself wasn't happy with the TV Marvin either.
Stephen Moore was a better Marvin than Alan Rickman, but I guess they wanted someone better known to play him in the film.
Re:That's incident light, and asymptotic to boot (Score:5, Informative)