Super black

Super black is a surface treatment developed at the National Physical Laboratory in the United Kingdom. It reflects much less light than the darkest conventional matte black paints available previously.

Conventional black paint reflects about 2.5% of the incident light. Super black absorbs approximately 99.6% of light at normal incidence, and only 0.4% is reflected. At other angles of incidence, super black is even more effective. At an angle of 45°, super black reflects 1/25 as much as black paint.

The technique used for super black is based upon chemically etching a nickel-phosphorus alloy.^[1][2]

Applications for super black are in specialist optical instruments to reduce unwanted reflections. The disadvantage of this material is its low optical thickness, as it is a surface treatment. As a result, infrared light of a wavelength longer than a few micrometres penetrates through the dark layer and has much higher reflectivity. The reported spectral dependence increases from about 1% at 3 µm to 50% at 20 µm.^[3]

In 2009, a competitor to the super black material was developed based on carbon nanotubes, that has a relatively flat reflectance in a wide spectral range.

See also

• Emissivity
• Black body

References

1. ^ New Scientist (6 February 2003). "Mini craters key to 'blackest ever black'". http://www.newscientist.com/article/dn3356-mini-craters-key-to-blackest-ever-black.html. 
2. ^ "Highly Absorbing Surfaces for Radiometry". January 2003. Archived from the original on 2005-06-27. http://web.archive.org/web/20050627082550/http://www.npl.co.uk/optical_radiation/superblack.html. 
3. ^ Brown, Richard J. C.; Brewer, Paul J.; Milton, Martin J. T. (2002). "The physical and chemical properties of electroless nickel???phosphorus alloys and low reflectance nickel???phosphorus black surfaces". Journal of Materials Chemistry 12: 2749. doi:10.1039/b204483h.