What do you get when you stack carbon nanotubes on their ends and sandwich them together? A material that absorbs 99.9% of the light that touches it. The microscopic surface of the material is rough and uneven, which breaks up the light and makes it a poor reflector. Then add to that carbon nanotubes act as superconductors in certain arrangements, which makes them excellent light absorbers, and you have a perfect storm of black.
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