This week, US researchers announced that they had developed the darkest material on Earth, a substance that is more than 30 times darker than the carbon substance used by the US National Institute of Standards & Technology as the current benchmark of blackness. According to Reuters, the new substance, which absorbs 99.9% of light, is composed of carbon nanotubes standing on end. It has a total reflective index of 0.045%, compared to 5% to 10% for basic black paint.
Pulickel Ajayan, who led the research team at Rice University, said that the material gets its blackness from three factors:
It is composed of carbon nanotubes, tiny tubes of tightly rolled carbon that are 400 times smaller than the diameter of a strand of hair. The carbon helps absorb some of the light. These tubes are standing on end, much like a patch of grass. This arrangement traps light in the tiny gaps between the “blades.” The researchers have also made the surface of this carbon nanotube carpet irregular and rough to cut down on reflectivity.
Below is a photo of the new material. The nanotube material is in the center; at the left is the NIST’s reflectance standard; at the right is a piece of glassy carbon.
Photo: Shawn-Yu Lin, RPI via Reuters
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