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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 ?"
OK, now we know what fuligin is made of.
Sheesh, evil *and* a jerk. -- Jade
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!
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
no llamas were harmed in the making of this sig
...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
Don't use your own shoes..
...and he grinned, like a fox eating shit out of a wire brush.
Say conventional black paint reflects 1% of the radiation. This stuff reflects, say, 0.1%. If you are building optical instruments then that is a 90% decrease in ambient reflections from internal surfaces, which is really useful.
But if you are interested in harvesting energy then the absorbancy has gone up from 99% to 99.9%, which is an increase of just 0.9% over what we had before. Gee.
Paul.
You are lost in a twisty maze of little standards, all different.
Gene Wolfe didn't coin it: Its from heraldry, and from latin terms for coal.
The opposite term is "argent"
this may alleviate the greenhouse effect ... maybe ...
I'd rather hope not
As my old Professor used to say "its the ENHANCED Greenhouse Effect thats the environmental problem, the normal Greenhouse Effect is what keeps us alive"
If our Atmosphere didn't 'trap' a certain amount of the incident energy from the sun, and the Oceans didn't transport this around the surface then out little planet would resemble a snowball.
This is what happens in an ice age when the Ocean/Atmosphere system flips into another metastable state and the large amount of ice and snow on the surface significantly changes the reflective properites of the planet and the whole system cools.
First we need to understand how this delicate balance actually works before we try and fix it. One thing we are learning is that the Ocean/Atmosphere system is not the safe stable thing we assumed it was, but its very dynamic with a number of metastable states. It can and has switched between states on a geologically quick (5000 years) timescale without much provocation. The bad news is that sustaining life is easy in the current state, it gets much harder in some of the others.
Like a pH buffered solution its quite possible that our environment can tolerate and compensate for all the stuff we chuck into it, and then suddenly flip to another state.
Oh, and the increment improvement in absorbtion will do very little to help solar collectors - the problem with solar collectors is doing something useful with the heat once you've got it, not getting it in the first place. Find me a material thats twice as good as a thermocouple than current technology and we may be on to something...
Fuligin.
(cf. Gene Wolfe's "Shadow of the Torturer" for details).
Is it? I was under the impression that the chromosphere kindof messed that up a little. Oh, and the Sun isn't in thermal equilibrium with anything. Actually, I suppose its own gravitational energy counts (over sufficiently short timescales)...executive decision? OTOH phenomena such as sunspots and other surface effects remove any homogeneity from the radiation, and don't forget the solar neutrino emission which is unlikely to be in thermal equilibrium.
Typically, black bodies are approximated by hollow ceramic ovens with a gold lining. The oven has a small hole in the side and is heated to the melting point of gold Thus you know exactly the temperature of the sides of the oven, you make the hole small enough that effusion doesn't upset the thermal equilibrium, et voila you have a blackbody standard.
Martin Marietta (now Lockheed Martin) has produced a proprietary "super black" coating for years now. I've seen it, and it is _very_ non-reflective. The coating mentioned in the article sounds similar.
"Martin Black" is proprietary though, so if you want a part coated you have to send it to Lockheed.
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.
There's an amusing story by Jack ("Call of the Wild") London entitled "The Shadow and the Flash." It's one of about a dozen stories he wrote that would be categorized as science fiction had the genre existed then.
Two competitive brothers both seek the secret of personal invisibility via divergent, and completely bogus methods. One of them finds some way to make his entire body perfectly transparent (!) in the belief the perfect transparency equals invisibility, and apparently gets his index of refraction close to unity but still has some dispersion, because although he is invisible, he produces telltale rainbow-colored flashes.
The other one searches for a perfect black, in the even stranger belief that an object covered in perfect black reflects no light and is therefore invisible. According to the story, this works except that, of course, he casts a shadow--and when he's present, even when not casting a shadow his presence creates an ill-defined sense of darkness or gloom.
"How to Do Nothing," kids activities, back in print!
"player 4 hit player 1 with 0 stroms"
A slightly more informative article is here.
They give the recipe.
Free book: Science Toys You Can Make
NPL Super Black In order to make accurate measurements in the UV, IR and visible regions, optical instruments and sensors need surfaces with very low reflectance. These black surfaces are used as efficient radiation detectors or may reduce stray light in an instrument. Highly efficient black surfaces allow smaller, lighter instruments to be made, which is an important advantage in aerospace applications. NPL has successfully developed a very high quality optical black ] known as NPL Super Black. The process uses an adapted nickel phosphorus electroless plating technique followed by finely controlled etching and gives probably the blackest surface known in the visible region. NPL has successfully and repeatedly produced the Super Black coating on a small-scale ecottage industryf basis for a number of years. It is now for upgrading and validating the process for plating much larger substrates with this high quality optical black. The upgrade has led to an opportunity to collaborate with CNES, Astrium and Sodern, the major space contractors for the European Space Agency, on the space evaluation of the black. If successful this will open up many new opportunities for supplying coated optics to the aerospace industry.