This black coating almost makes the facets of a diamond disappear

In 2019, a yellow diamond underwent a paradoxical treatment. A layer of carbon nanotubes has covered its facets. Instead of multiplying the fragments, the stone appeared as a dark almost flat form. This work by Diemut Strebe accompanied research by the Massachusetts Institute of Technology.

The team had developed a microscopic forest of nanotubes on prepared aluminum. Measurements indicated at least 99.995% absorption of incident light in the reported trials. With so little light returned, variations in relief become difficult to distinguish. The object, however, retains its shape: it is the luminous clues of this form that disappear.

The researchers were considering uses to reduce stray light in optical instruments. They also recognized that the mechanism for such high absorption still needed to be studied. The result of 2019 does not need to be presented as an eternal record: almost removing reflections is already enough to upset the perception of an object.