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Blacker Than Black
An anonymous reader writes "British scientists at the National Physical Laboratory in London have invented the darkest material on Earth. 'It could revolutionise optical instruments because it reflects 10 to 20 times less light than the black paint currently used to reduce unwanted reflections. The key to the nickel and phosphorous coating's blackness is that its surface is pitted with microscopic craters.' Wonder how effective it would be as a solar heating surface ?"
I would say that the solar surface is hot enough as it is!
Enig? Det alt for hot det smor!
Goths just got scarier. "Black as night, faster than a shadow" -Judas Priest- "Hell Bent For Leather"
"Suburbia is where the developer bulldozes out the trees, then names the streets after them."
My high school physics teacher had a piece of "black," though not as black as this. He said he'd put it against walls and students sitting at the other end of the room would think there was a hole, he said. By the time I saw it, it was old and had gotten too dusty to be very impressive.
Whale
Why don't they name materials better today? What is interesting in the name "Super-black"? Nothing!
I suggest we call it Darkonium or something...
None.
None more black.
NIGEL: I think he's right, there is something about this, that's that's so black, it's like; "How much more black could this be?" and the answer is: "None, none... more black."
-Mark
Nigel Fox, who heads the optics group at NPL, said: "When you look at the black, it is an incredibly beautiful surface. It's like black velvet."
Who'll be the first schmuck to paint Jesus or Elvis onto this surface?
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The light that is neither transmitted nor reflected is absorbed. If it is totally opaque too it has to be also a good solar heating surface. That said, one might be a very good absorber at particular wavelengths, but transparent or reflective at others. The cavities should act as a blackbody and operate at a wide range of frequencies though.
Gentlemen, you can't fight in here, this is the War Room!
Wonder how effective it would be as a solar heating surface ?
It wouldn't make much difference, because changing from absorbing 97.5% of the sunlight to 99.65% isn't going to change the economics of your solar collector much.
However if you are building a telescope and you want to reduce the stray reflections, going from reflecting 2.5% to reflecting 0.35% is a huge improvement
I would love to see this used to coat the vanes that support the secondary mirrors of reflector type telescopes. Diffraction spikes (the little spikes on relatively bright stars) are really the reflection of light on these little supports. If you are into photographing nebulae, having a bright star in view can be a real photo killer.
The book 'The Hubble Wars' mentions a coating called 'Martin Black' developed by Lockheed-Martin for use in spy satellites - I wonder how this stuff compares. I found some info Here : The 'Martin Black' is not a paint at all, but a specially etched aluminum surface that acts like an anechoic chamber on a microscopic scale. The surface looks like an array of very steep pyramids a few wavelengths of light apart. It's extremely fragile & expensive to produce, but was never a classified process. Mostly used in aerospace optical hardware such as star trackers & imaging systems that have to work in direct sunlight. Ball Aerospace has a version of this process. It's considered to be a 'proprietary' process, ie they won't tell you how it's done for commercial reasons.
There's a little more detail and a few pictures at http://www.npl.co.uk/optical_radiation/superblack. html
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Scientists estimate this will be the blackest material ever manufactured, until they perfect the technique of mass-producing Hillary Rosen's soul.
Don't Touch It! It's Evil!
Well, now all those people wearing t-shirts saying "I'm only wearing black until they invent something darker" will be very happy! Any idea as to when we'll be able to get it in t-shirt form?
...this is a Good Thing for production instruments, but it won't matter much for research/labwork/prototypes; right now I'm working on laser detection of single atmospheric particles; we needed a *black* coating for the inside of the chamber, but it didn't need to be particularly robust, just dark - so we smoked it with a flame. Carbon black is the least reflective substance known, IIRC it absorbs something like 99.996% of incident radiation...anybody who's seen the inside of an old kerosene lamp chimney knows exactly what they mean in the article when they talk about the 'black velvet' appearance. We did have some problems with it 'popcorning' as we pumped the chamber down, but a staged evacuation with good degassing periods took care of that.
Oh, this would make a great solar heating material - somebody mentioned the specific heat of the material, but as long as you have a thin layer backed by a heatsink, the specific heat doesn't matter (it's just the amount of heat a material can contain per gram; if you have just just a tiny bit of black substance, it doesn't matter how much heat it stores); it's all about the absorbtion.
Facts do not cease to exist because they are ignored. - Aldous Huxley
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A pizza of radius z and thickness a has a volume of pi z z a
This will prove to be useful, for two reasons:
First, it is a better absorber then what we have now, which, as someone pointed out, would make an incremental improvement for things such as solar collectors.
Second, it may find some powerful uses as a black body emitter, which would have some applications for cooling. Specifically, there is a window in the atmosphere where energy can leave the atmosphere ( around one of the IR ammonia lines, IIRC) this may alleviate the greenhouse effect ... maybe ...
As one of my Professors used to say "Progress is measured by progress in Materials Science". He might have been biased, however...
I would be very interested to find out the wavelengths where this is effective.
There are three types of reflectance that I am aware of: mirrors; diffuse reflectors (lambertian surfaces) and a special case of reflectance as found on a dusty surface, such as the moon( which is an aggragation of spherical lambertian surfaces, with special properties). Anyone else know of any others?
This is progress?
offtopic, yes, but somewhat more in the vein of discussion, how does it do on reflecting, say, radar?
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The problem with solar power today isnt about efficiency since modern panels have about 70-80% efficiency in heating water. The incoming power is about 1000W per m2. A better absorber wouldnt make the panel that much more efficient.Chromium Oxide have an efficiency of about 92%. Much of the problems lie in how you transport the heat from the panel to the energy storage.Insulation of the panel is something that you have to take into consideration. Cost is also of utter importance since you often have a roof capable of housing more than 30 m2 of panels which in most houses is overkill. To generate water you typically would need about 5 m2 from mars to november.
If this material can make the total cost smaller then its good but if it makes it more expensive it isnt of any use. Robustness and price is what we should look into and not efficiency. A cheap solar panel that lasts for as long as it have to be functional to return the investment is possible today.
The main problem with solar power is that when you need the power most (night/winter) there arent much sun around. Solar Power can never be anything but a valuable complement to something else. All trials of storin the energy longer times have failed miserably so far.
Im not just rambling here, i was a partner in a company manufacturing solar panels some years ago.
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Blacker than the mood of a web master who just found out that his page was posted on slashdot.
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
Super-black
Technoli
If old stuff reflects X, and new stuff reflects 90% less, then new stuff reflects X-X*(90/100) = 0.1*X.
If old stuff reflects X, and new stuff reflects 100% less, then new stuff reflects zero.
With me still?
100% of X _is_ one times X.
Ten times X _is_ 1000% of X.
With me still?
Something that reflects 10 times less than the old stuff reflects 1000% less than the old stuff, and therefore reflects -9*X.
With me still?
The original wording is misleading. The original complaint against it was valid. Instead they should have put something more like:
The new material reflects 1/10th to 1/20th of the amount that the old material reflected.
The new material is 10 to 20 times less reflective than the old material.
YAW.
Your head of state is a corrupt weasel, I hope you're happy.
The F117A is called the Nighthawk. However, most pilots call it the "Wobblin' Gobblin" because it's aerodynamically unstable requiring computer-controlled corrections at a very high frequency while in-flight. Early tests didn't have the computer code particularly tweaked so the aircraft tended to shimmy around (wobble) quite a bit.
The shape of the aircraft is designed to reflect the majority of radio waves directly away from the source and the coating is designed to absorb the remaining radio frequencies, not light. But it does appear to be based on the same priciple as this super-black material. From what I understand of RAM (Radar Absorbing Material), there are small pockets on the surface that are designed to trap and scatter the radio waves until they've almost completely dissipated. The color of the material is rather arbitrary, as I've seen it painted in "desert-camo" in photos taken before it was made public (to hide it better against the sandy-colored ground in the desert where it was being tested). Just before being made public, it was painted black to hide better at night in the sky, which is it's intended primary operating time/environment. Making it even *more* black wouldn't make it much more "stealthy". If you're looking for IR signatures, the engine exhaust would probably be more of a giveaway even though it's cooled to about 800F or so. And because it's in the sky, a UV scan would probably be useless as space (the sky's background) is filled with UV. Blocking even more UV makes it a black mark on a light background.
I might have a use for this super-black material to coat the insides of my projection TV, as well as cover the windows during movie nights! Perhaps even using this on road signs in addition to the super-relective paint the DOT already uses can make road signs easier to see at night due to increased contrast and less glare. Oh, and telescopes, too. Kinda neat, overall.
My sources are unreliable, but their information is fascinating. -- Ashleigh Brilliant