Slashdot Mirror
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 ?"
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
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